Channah Rock

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Scholarly Contributions

Chapters

• Mclain, J. E., Rock, C. M., & Gerba, C. P. (2017). Environmental antibiotic resistance associated with land application of biosolids. In Antimicrobial Resistance in Wastewater Treatment Processes. Hoboken, NJ: Wiley-Blackwell.
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  Land application of biosolids derived from wastewater treatment processes has been increasing throughout the world, with more than 6.0 dry tons of biosolids now applied on an annual basis in the U.S. alone. For this reason, biosolids application has been proposed as a key point source for introducing antimicrobial resistant organisms, genetic elements of antimicrobial resistance, and antibiotic compounds as contaminants into agricultural soils. Recent studies cover a range of implications of land application of biosolids, with some studies suggesting minimal increased risk for development of antibiotic resistance, while other studies indicate significantly enhanced resistance development. It is becoming increasingly clear that results are dependent on composting treatments, land application methods and timing, and soil conditions prior to biosolids application. This chapter will present recent research examining the potential for transfer of antibiotic resistance from the wastewater treatment plant to the surrounding environment via biosolids application, with special emphasis on biosolids treatment and application methods that may enhance or reduce the presence of resistance determinants. The potential human health risk arising from transfer of resistance to agricultural soils will also be discussed.
• Rock, C. M. (2016). RAPID AND CONTINUOUS MONITORING OF PATHOGENS. In Potable Reuse Research Compilation: Synthesis of Findings(pp 85-98). Water Environment & Reuse Foundation.
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  The implementation of direct potable reuse (DPR), a strategy for augmenting public water supplies with advanced treated water, has been gaining traction in the water sector. Since 2012, more than US$20 million has been invested in research projects evaluating technical, operational, and managerial aspects related to DPR. By 2015, a significant body of research information was available as a result of these projects; however, the information was spread among them. Project 15-01 was undertaken in 2016 to summarize and synthesize the key issues and findings from this research to provide – in one comprehensive document – a clear understanding of the total state-of-the-art and state-of-the-science on DPR and to identify unknowns that may require further research.
• Rock, C. M., & Gerba, C. P. (2014). Water Quality. In PRODUCE CONTAMINATION PROBLEM: CAUSES AND SOLUTIONS, 2ND EDITION(pp 123 - 138). Elsevier.

Journals/Publications

• Bakin, B. C., McGovern, C. J., Melendez, M., Kessler, C., Critzer, F., Rock, C. M., Buchanan, R. L., Schaffner, D. W., Danyluk, M. D., Kowalcyk, B. B., Morgan, K. M., Strawn, L. K., & Hamilton, A. M. (2023). Ranking Food Safety Priorities of the Fresh Produce Industry in the United States. Journal of food protection, 86(12), 100167.
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  A broad understanding of community member food safety priorities in the fresh produce supply chain does not currently exist. This information is essential to improve food safety knowledge and practices effectively and efficiently throughout the fresh produce industry; therefore, the goal of this study was to identify and rank community produce safety priorities in the United States. Survey questions were designed and approved by food safety experts for participants to rank 24 fresh produce safety priorities. The anonymous survey was distributed online via Qualtrics™ to fresh produce community members from November 2020 to May 2021. A score was calculated for each priority by summing weighted ranking scores across responses. Descriptive statistics and logistic regression were used to determine frequencies and distribution of response and identify factors (e.g., role in produce safety, size/location of organization/operation) that influenced rankings. A total of 281 respondents represented fourteen different roles in the fresh produce industry, with most identified as growers (39.5%). Produce operations were distributed across the U.S. and annual produce sales ranged from below $25,000 to over $5,000,000. Health and hygiene, training, postharvest sanitation, traceability, and harvest sanitation were ranked as the top five food safety priorities. These findings provide insight into community member priorities in fresh produce safety and can be used to inform intervention efforts, ranging from specialized training for produce growers and packers, industry-driven research projects, and gaps in risk communication strategies.
• Cooper, D. K., Sobolik, J. S., Kovacevic, J., Rock, C. M., Sajewski, E. T., Guest, J. L., Lopman, B. A., Jaykus, L. A., & Leon, J. S. (2023). Combined Infection Control Interventions Protect Essential Food Workers from Occupational Exposures to SARS-CoV-2 in the Agricultural Environment. Applied and environmental microbiology, 89(7), e0012823.
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  Essential food workers experience elevated risks of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection due to prolonged occupational exposures in food production and processing areas, shared transportation (car or bus), and employer-provided shared housing. Our goal was to quantify the daily cumulative risk of SARS-CoV-2 infection for healthy susceptible produce workers and to evaluate the relative reduction in risk attributable to food industry interventions and vaccination. We simulated daily SARS-CoV-2 exposures of indoor and outdoor produce workers through six linked quantitative microbial risk assessment (QMRA) model scenarios. For each scenario, the infectious viral dose emitted by a symptomatic worker was calculated across aerosol, droplet, and fomite-mediated transmission pathways. Standard industry interventions (2-m physical distancing, handwashing, surface disinfection, universal masking, ventilation) were simulated to assess relative risk reductions from baseline risk (no interventions, 1-m distance). Implementation of industry interventions reduced an indoor worker's relative infection risk by 98.0% (0.020; 95% uncertainty interval [UI], 0.005 to 0.104) from baseline risk (1.00; 95% UI, 0.995 to 1.00) and an outdoor worker's relative infection risk by 94.5% (0.027; 95% UI, 0.013 to 0.055) from baseline risk (0.487; 95% UI, 0.257 to 0.825). Integrating these interventions with two-dose mRNA vaccinations (86 to 99% efficacy), representing a worker's protective immunity to infection, reduced the relative infection risk from baseline for indoor workers by 99.9% (0.001; 95% UI, 0.0002 to 0.005) and outdoor workers by 99.6% (0.002; 95% UI, 0.0003 to 0.005). Consistent implementation of combined industry interventions, paired with vaccination, effectively mitigates the elevated risks from occupationally acquired SARS-CoV-2 infection faced by produce workers. This is the first study to estimate the daily risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection across a variety of indoor and outdoor environmental settings relevant to food workers (e.g., shared transportation [car or bus], enclosed produce processing facility and accompanying breakroom, outdoor produce harvesting field, shared housing facility) through a linked quantitative microbial risk assessment framework. Our model has demonstrated that the elevated daily SARS-CoV-2 infection risk experienced by indoor and outdoor produce workers can be reduced below 1% when vaccinations (optimal vaccine efficacy, 86 to 99%) are implemented with recommended infection control strategies (e.g., handwashing, surface disinfection, universal masking, physical distancing, and increased ventilation). Our novel findings provide scenario-specific infection risk estimates that can be utilized by food industry managers to target high-risk scenarios with effective infection mitigation strategies, which was informed through more realistic and context-driven modeling estimates of the infection risk faced by essential food workers daily. Bundled interventions, particularly if they include vaccination, yield significant reductions (>99%) in daily SARS-CoV-2 infection risk for essential food workers in enclosed and open-air environments.
• Murphy, C. M., Hamilton, A. M., Waterman, K., Rock, C., Schaffner, D. W., & Strawn, L. K. (2023). Efficacy of Peracetic Acid and Chlorine on the Reduction of Shiga Toxin-producing Escherichia coli and a Nonpathogenic E. coli Strain in Preharvest Agricultural Water. Journal of food protection, 86(11), 100172.
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  Produce-borne outbreaks of Shiga toxin-producing Escherichia coli (STEC) linked to preharvest water emphasize the need for efficacious water treatment options. This study quantified reductions of STEC and generic E. coli in preharvest agricultural water using commercially available sanitizers. Water was collected from two sources in Virginia (pond, river) and inoculated with either a seven-strain STEC panel or environmental generic E. coli strain TVS 353 (∼9 log CFU/100 mL). Triplicate inoculated water samples were equilibrated to 12 or 32°C and treated with peracetic acid (PAA) or chlorine (Cl) [low (PAA:6ppm, Cl:2-4 ppm) or high (PAA:10 ppm, Cl:10-12 ppm) residual concentrations] for an allotted contact time (1, 5, or 10 min). Strains were enumerated, and a log-linear model was used to characterize how treatment combinations influenced reductions. All Cl treatment combinations achieved a ≥3 log CFU/100 mL reduction, regardless of strain (3.43 ± 0.25 to 7.05 ± 0.00 log CFU/100 mL). Approximately 80% (19/24) and 67% (16/24) of PAA treatment combinations achieved a ≥3 log CFU/100 mL for STEC and E. coli TVS 353, respectively. The log-linear model showed contact time (10 > 5 > 1 min) and sanitizer type (Cl > PAA) had the greatest impact on STEC and E. coli TVS 353 reductions (p 
• Murphy, C. M., Hamilton, A. M., Waterman, K., Rock, C., Schaffner, D., & Strawn, L. K. (2023). Sanitizer Type and Contact Time Influence Salmonella Reductions in Preharvest Agricultural Water Used on Virginia Farms. Journal of food protection, 86(8), 100110.
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  No Environmental Protection Agency (EPA) chemical treatments for preharvest agricultural water are currently labeled to reduce human health pathogens. The goal of this study was to examine the efficacy of peracetic acid- (PAA) and chlorine (Cl)-based sanitizers against Salmonella in Virginia irrigation water. Water samples (100 mL) were collected at three time points during the growing season (May, July, September) and inoculated with either the 7-strain EPA/FDA-prescribed cocktail or a 5-strain Salmonella produce-borne outbreak cocktail. Experiments were conducted in triplicate for 288 unique combinations of time point, residual sanitizer concentration (low: PAA, 6 ppm; Cl, 2-4 ppm or high: PAA, 10 ppm; Cl, 10-12 ppm), water type (pond, river), water temperature (12°C, 32°C), and contact time (1, 5, 10 min). Salmonella were enumerated after each treatment combination and reductions were calculated. A log-linear model was used to characterize how treatment combinations influenced Salmonella reductions. Salmonella reductions by PAA and Cl ranged from 0.0 ± 0.1 to 5.6 ± 1.3 log CFU/100 mL and 2.1 ± 0.2 to 7.1 ± 0.2 log CFU/100 mL, respectively. Physicochemical parameters significantly varied by untreated water type; however, Salmonella reductions did not (p = 0.14), likely due to adjusting the sanitizer amounts needed to achieve the target residual concentrations regardless of source water quality. Significant differences (p  PAA) and contact time (10 > 5 > 1 min) having the greatest effects. The log-linear model also revealed that outbreak strains were more treatment-resistant. Results demonstrate that certain treatment combinations with PAA- and Cl-based sanitizers were effective at reducing Salmonella populations in preharvest agricultural water. Awareness and monitoring of water quality parameters are essential for ensuring adequate dosing for the effective treatment of preharvest agricultural water.
• Pecson, B. M., Darby, E., Danielson, R., Dearborn, Y., Giovanni, G. D., Jakubowski, W., Leddy, M., Lukasik, G., Mull, B., Nelson, K. L., Olivieri, A., Rock, C., & Slifko, T. (2022). Distributions of waterborne pathogens in raw wastewater based on a 14-month, multi-site monitoring campaign. Water research, 213, 118170.
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  The California State Water Resources Control Board is the first regulatory body in the United States to develop statewide regulations for direct potable reuse (DPR). To support this effort, a pathogen monitoring campaign was undertaken to develop and implement an optimized standard operating protocol to better characterize the concentration of human pathogens in raw wastewater. Methods to detect relevant viral and protozoan pathogens in raw wastewater were optimized and implemented during a 14-month monitoring campaign. Over 120 samples were collected from five wastewater treatment plants treating a quarter of California's population. Samples were analyzed for two protozoa (Cryptosporidium and Giardia) using microscopy methods, three enteric viruses (enterovirus, adenovirus, and norovirus) using culture and/or molecular methods, and male-specific coliphage using culture methods. The method recovery efficiency was measured in every protozoa sample and every other virus sample to confirm minimum recovery efficiencies were achieved and to correct the concentrations for pathogen losses during sample processing. The results from this study provide the industry with a large, high-quality dataset as demonstrated by the high degree of method sensitivity, method recovery, and QA/QC steps. Such high-quality data on pathogen concentrations in raw wastewater are critical for confirming the level of treatment needed to reduce pathogen concentrations down to acceptable levels for potable water in DPR projects.
• Valerisa, J., Carr, D., Woolfolk, C. M., Brassill, N., & Mclain, J. E. (2021). Evaluation of total Bacteroides sp. as an alternative indicator in agricultural water quality. Journal of Food: Microbiology, Safety, and Hygiene, 6(2), 148.
• Rebecca, M. L., Mclain, J. E., Woolfolk, C. M., Ellie, R., Ahmed, W., & Kerry, H. (2020). Comparing microbial risks from multiple sustainable waste streams applied for agricultural use: biosolids, manure, and diverted urine. Current Opinion in Environmental Science and Health, 14, 37-50. doi:10.1016/j.coesh.2020.01.003
• Weller, D., Brassill, N., Rock, C., Ivanek, R., Mudrak, E., Roof, S., Ganda, E., & Wiedmann, M. (2020). Complex Interactions Between Weather, and Microbial and Physicochemical Water Quality Impact the Likelihood of Detecting Foodborne Pathogens in Agricultural Water. Frontiers in microbiology, 11, 134.
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  Agricultural water is an important source of foodborne pathogens on produce farms. Managing water-associated risks does not lend itself to one-size-fits-all approaches due to the heterogeneous nature of freshwater environments. To improve our ability to develop location-specific risk management practices, a study was conducted in two produce-growing regions to (i) characterize the relationship between levels and pathogen presence in agricultural water, and (ii) identify environmental factors associated with pathogen detection. Three AZ and six NY waterways were sampled longitudinally using 10-L grab samples (GS) and 24-h Moore swabs (MS). Regression showed that the likelihood of detection (Odds Ratio [OR] = 2.18), and codetection (OR = 6.49) was significantly greater for MS compared to GS, while the likelihood of detecting was not. Regression also showed that codetection in AZ (OR = 50.2) and NY (OR = 18.4), and detection in AZ (OR = 4.4) were significantly associated with levels, while detection in NY was not. Random forest analysis indicated that interactions between environmental factors (e.g., rainfall, temperature, turbidity) (i) were associated with likelihood of pathogen detection and (ii) mediated the relationship between levels and likelihood of pathogen detection. Our findings suggest that (i) environmental heterogeneity, including interactions between factors, affects microbial water quality, and (ii) levels alone may not be a suitable indicator of food safety risks. Instead, targeted methods that utilize environmental and microbial data (e.g., models that use turbidity and levels to predict when there is a high or low risk of surface water being contaminated by pathogens) are needed to assess and mitigate the food safety risks associated with preharvest water use. By identifying environmental factors associated with an increased likelihood of detecting pathogens in agricultural water, this study provides information that (i) can be used to assess when pathogen contamination of agricultural water is likely to occur, and (ii) facilitate development of targeted interventions for individual water sources, providing an alternative to existing one-size-fits-all approaches.
• Woolfolk, C. M. (2020). Complex interactions between weather, and microbial and physicochemical water quality impact the likelihood of detecting foodborne pathogens in agricultural water used for produce production.. Frontiers in Microbiology, 124. doi:https://doi.org/10.3389/fmicb.2020.00134
• Dery, J. L., Rock, C. M., Goldstein, R. R., Onumajuru, C., Brassill, N., Zozaya, S., & Suri, M. R. (2018). Understanding grower perceptions and attitudes on the use of nontraditional water sources, including reclaimed or recycled water, in the semi-arid Southwest United States. Environmental research, 170, 500-509.
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  The use of nontraditional water sources, including reclaimed or recycled water, has become a desirable option to meet increasing demands in water stressed regions. In the Southwest United States, utilization of alternative water sources is becoming increasingly common, including use for landscape irrigation, environmental enhancement, cooling and power generation, potable reuse, and as a source water for agricultural irrigation. While much research has gone into identifying public perception towards water reuse schemes, little attention has been given to understanding grower attitudes, perceptions, and knowledge on the use of nontraditional water, including reclaimed water, in agriculture and how that may influence grower acceptance and production practices. This unique study utilized a needs assessment survey of growers (n = 521) within the Southwest region of the United States to gain an understanding of industry attitudes and needs regarding nontraditional water in agriculture. Results indicate that the majority of survey respondents were concerned with water availability (67.49%) yet less than half (48.30%) thought using a nontraditional water source in agriculture was 'very important'. Interestingly, respondents rated irrigation of 'food crops' third (42.20%) among agricultural activities for which they would be willing to use nontraditional water sources, behind irrigation of forage crops (61.60%) and dust control (61.60%). The importance of the use of nontraditional water sources in agriculture was influenced mostly by farm size (p = 0.007) and primary water source (p = 0.016), and the level of education was significant in respondent's level of concern over water availability (p = 0.021). Information on the quality of nontraditional water sources, showing that it is as good or better than respondents current sources, was found to shift rejection and uncertainty towards acceptance by 16.04%. The results of this study provide insight into perceived risks, willingness to use, drivers and constraints to grower adoption, and preferred methods of education regarding water reuse in agriculture. These findings can be used by water managers and planners to aid in the adoption of nontraditional waters, including reclaimed or recycled water, in agriculture thus extending water resources, securing food supplies, and protecting public health.
• Gerba, C. P., Bright, K. R., Mclain, J. E., Carr, D., Dery, J. L., Brassill, N., & Rock, C. M. (2019). Review of water quality criteria for water reuse and risk-based implications for irrigated produce under the FDA Food Safety Modernization Act, produce safety rule. ENVIRONMENTAL RESEARCH, 172, 616-629. doi:https://doi.org/10.1016/j.envres.2018.12.050
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  Questions related to the safety of alternative water sources, such as recycled water or reclaimed water (including grey water, produced water, return flows, and recycled wastewater), for produce production have been largely un-explored at the detail warranted for protection of public health. Additionally, recent outbreaks of Escherichia coli (E. coli) in fresh produce, in which agricultural water was suspected as the source, coupled with heightened media coverage, have elevated fruit and vegetable safety into the forefront of public attention. Exacerbating these concerns, new Federal regulations released by the U.S. Food and Drug Administration (FDA) as part of implementation of the FDA Food Safety Modernization Act (FSMA), require testing of agricultural water quality for generic E. coli. Here, we present a review of water quality criteria - including surface water, groundwater recreational water, and water reuse - in an attempt to better understand implications of new FDA regulations on irrigated produce. In addition, a Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate risks from pathogen contamination of food crops eaten fresh under the context of FDA regulations to provide perspective on current water reuse regulations across the country. Results indicate that irrigation water containing 126 CFU/100 mL of E. coli correspond to a risk of GI illness (diarrhea) of 9 cases in 100,000,000 persons (a 0.000009% risk) for subsurface irrigation, 1.1 cases in 100,000 persons (a 0.0011% risk) for furrow irrigation, and 1.1 cases in 1000 persons (a 0.11% risk) for sprinkler irrigation of lettuce. In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations. These findings, while limited to a one-time exposure event of lettuce irrigated with water meeting FSMA water quality regulations, highlight the need for additional assessments to determine if the scientific-basis of the regulation is protective of public health.
• Rock, C. M., Brassill, N., Dery, J. L., Carr, D., McLain, J. E., Bright, K. R., & Gerba, C. P. (2019). Review of water quality criteria for water reuse and risk-based implications for irrigated produce under the FDA Food Safety Modernization Act, produce safety rule. Environmental research, 172, 616-629.
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  Questions related to the safety of alternative water sources, such as recycled water or reclaimed water (including grey water, produced water, return flows, and recycled wastewater), for produce production have been largely un-explored at the detail warranted for protection of public health. Additionally, recent outbreaks of Escherichia coli (E. coli) in fresh produce, in which agricultural water was suspected as the source, coupled with heightened media coverage, have elevated fruit and vegetable safety into the forefront of public attention. Exacerbating these concerns, new Federal regulations released by the U.S. Food and Drug Administration (FDA) as part of implementation of the FDA Food Safety Modernization Act (FSMA), require testing of agricultural water quality for generic E. coli. Here, we present a review of water quality criteria - including surface water, groundwater recreational water, and water reuse - in an attempt to better understand implications of new FDA regulations on irrigated produce. In addition, a Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate risks from pathogen contamination of food crops eaten fresh under the context of FDA regulations to provide perspective on current water reuse regulations across the country. Results indicate that irrigation water containing 126 CFU/100 mL of E. coli correspond to a risk of GI illness (diarrhea) of 9 cases in 100,000,000 persons (a 0.000009% risk) for subsurface irrigation, 1.1 cases in 100,000 persons (a 0.0011% risk) for furrow irrigation, and 1.1 cases in 1000 persons (a 0.11% risk) for sprinkler irrigation of lettuce. In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations. These findings, while limited to a one-time exposure event of lettuce irrigated with water meeting FSMA water quality regulations, highlight the need for additional assessments to determine if the scientific-basis of the regulation is protective of public health.
• Rock, C. M., Dery, J., & Brassill, N. (2019). Minimizing Risks: Use of Surface Water in Pre-Harvest Agricultural Irrigation. Arizona Cooperative Extension.
• Rock, C. M., Dery, J., & Gerrity, D. (2019). Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS): What consumers need to know. Arizona Cooperative Extension.
• Rock, C. M., Vandegrift, J., Hooper, J., deSilva, A., Bell, K., & Snyder, S. (2019). Techniques to Evaluate Water Quality at Direct Potable Reuse (DPR) Treatment Facilities. JAWWA, 111(7), 12-23.
• Suri, M. R., Dery, J. L., Pérodin, J., Brassill, N., He, X., Ammons, S., Gerdes, M. E., Rock, C., & Goldstein, R. E. (2019). U.S. farmers' opinions on the use of nontraditional water sources for agricultural activities. Environmental research, 172, 345-357.
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  Water is a key resource for agricultural production in the United States. Due to projected changes in water availability across the country, long-term sustainability of agricultural production may rely on finding alternatives to traditional water sources. The aim of this study was to assess farmers' opinions on the use of nontraditional water sources (e.g., agricultural runoff, treated wastewater, recycled water, produced water, untreated surface water, and brackish surface and groundwater) for agricultural activities. A survey was distributed to farmers (n = 746) in the Mid-Atlantic and Southwest regions of the United States (U.S.) about water availability and nontraditional irrigation water perceptions. Chi-square, Fisher's exact tests, f-tests, and multinomial and ordinal logistic regression analyses were conducted. Of farmers surveyed, 80% (431/543) considered the use of nontraditional water sources to be at least moderately important and 61% (444/727) would use nontraditional water if given the option. Each of the following factors individually increased the likelihood that a farmer considered nontraditional water very important for agriculture: Farmers who lived in the Southwest region compared to the Mid-Atlantic, farmers who were concerned about water availability compared with those who were not, farmers with a graduate or professional degree compared to those with less education, farmers with access to nontraditional water, and farmers with some knowledge of nontraditional water compared to those with no reported knowledge. Concern about water availability and knowledge of nontraditional water sources were significantly associated with willingness to use these water sources (p 
• Vandegrift, J., Hooper, J., da Silva, A., Bell, K., Snyder, S., & Rock, C. M. (2019). Overview of Monitoring Techniques for Evaluating Water Quality at Potable Reuse Treatment Facilities. Journal - American Water Works Association, 111(7), 12-23.
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  Needless to say, the safety of treated water for potable reuse must be definitively ensured. Numerous methods are available for assessing water quality; it's important to understand their challenges and limitations.
• Dery, J., Brassill, N. A., Rivadeneira, P., Mclain, J. E., & Rock, C. M. (2018). AZ1763: E. coli, Water Quality, Food Safety, and Human Health. Arizona Cooperative Extension Publication.
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  Preventing food contamination and human infection from E. coli requires control measures at all stages of the food production continuum: from agricultural production, to processing, manufacturing, transporting, storing, and preparation of foods in both commercial establishments like restaurants as well as domestic environments, such as your home (The Hartford Loss Control Department 1998). Although contaminated ground beef has been the most common cause of E. coli poisoning, contamination can also occur at any number of points along the food production continuum (CDC 2018). Fruits, vegetables, and water are other common sources of contamination. The focus of this publication is to inform readers about the impacts of E. coli bacteria in water on food safety and human health.
• Dery, J., Brassill, N. A., Rivadeneira, P., Mclain, J. E., & Rock, C. M. (2018). E. coli, Water Quality, Food Safety, and Human Health. Journal of Cooperative Extension, University of Arizona.
• Gerba, C. P., Betancourt, W. Q., Kitajima, M., & Rock, C. M. (2018). Reducing uncertainty in estimating virus reduction by advanced water treatment processes. Water research, 133, 282-288.
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  Treatment of wastewater for potable reuse requires the reduction of enteric viruses to levels that pose no significant risk to human health. Advanced water treatment trains (e.g., chemical clarification, reverse osmosis, ultrafiltration, advanced oxidation) have been developed to provide reductions of viruses to differing levels of regulatory control depending upon the levels of human exposure and associated health risks. Importance in any assessment is information on the concentration and types of viruses in the untreated wastewater, as well as the degree of removal by each treatment process. However, it is critical that the uncertainty associated with virus concentration and removal or inactivation by wastewater treatment be understood to improve these estimates and identifying research needs. We reviewed the critically literature to assess to identify uncertainty in these estimates. Biological diversity within families and genera of viruses (e.g. enteroviruses, rotaviruses, adenoviruses, reoviruses, noroviruses) and specific virus types (e.g. serotypes or genotypes) creates the greatest uncertainty. These aspects affect the methods for detection and quantification of viruses and anticipated removal efficiency by treatment processes. Approaches to reduce uncertainty may include; 1) inclusion of a virus indicator for assessing efficiency of virus concentration and detection by molecular methods for each sample, 2) use of viruses most resistant to individual treatment processes (e.g. adenoviruses for UV light disinfection and reoviruses for chlorination), 3) data on ratio of virion or genome copies to infectivity in untreated wastewater, and 4) assessment of virus removal at field scale treatment systems to verify laboratory and pilot plant data for virus removal.
• Gerrity, D., Rock, C. M., Robierto, E., Mclain, J. E., Dickenson, E., & Neyestani, M. (2017). Impacts of solids retention time on trace organic compound attenuation and bacterial resistance to trimethoprim and sulfamethoxazole. Chemosphere, 182, 149-158. doi:10.1016/j.chemosphere.2017.04.121
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  Abstract: The antibiotic trimethoprim acts by disrupting dihydrofolatereductase during nucleotide (thymine) synthesis. Bacteria can grow in thepresence of trimethoprim by expressing trimethoprim resistance genes orby acquiring thymine or thymidine from environmental reservoirs tofacilitate DNA synthesis. The purpose of this study was to evaluate theimpact of extracellular constituents of activated sludge from municipalwastewater treatment on the quantification of trimethoprim-resistantbacteria. The activated sludge process was modified to assess the impactsof varying solids retention time (SRT) on trimethoprim concentrations,culturable trimethoprim-resistant bacteria, and multi-drug resistantbacteria. This is significant because longer SRTs are often employed toimprove the quality of treated wastewater effluent. In the presence oftrimethoprim at standard clinical concentrations, up to 40% increases inthe relative prevalence of resistant bacteria were observed with (1)samples manually augmented with reagent-grade thymidine, (2) samplesmanually augmented with sonicated biomass (i.e., cell lysate), (3)samples manually augmented with activated sludge filtrate, and (4)activated sludge samples collected from reactors with longer SRTs. Theseobservations suggest that longer SRTs may select for trimethoprimresistantbacteria and/or result in false positives for trimethoprimresistance due to higher concentrations of free thymine, thymidine, orother extracellular constituents.
• Rock, C. M., & Mclain, J. E. (2018). Communicating research results to stakeholders: what scientists can learn from Cooperative Extension. University of Arizona Cooperative Extension Publication.
• Rock, C. M., & Mclain, J. E. (2018). Communicating research results to stakeholders: what we can learn from Cooperative Extension. Kachina News, 16.
• Rock, C. M., Brassill, N. A., Carr, D., Bright, K., Mclain, J. E., & Gerba, C. P. (2019). Review of the FDA Food Safety Modernization Act (FSMA) Agriculture Water Rule: implications for irrigated produce, water reuse, quantitative microbial risk assessment, and food safety. Environmental Research.
• Rock, C. M., Gerba, C. P., Walter, B., & Masaaki, K. (2018). Reducing uncertainty in estimating virus reduction by advanced water treatment processes.
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  Treatment of wastewater for potable reuse requires the reduction of enteric viruses to levels that pose nosignificant risk to human health. Advanced water treatment trains (e.g., chemical clarification, reverseosmosis, ultrafiltration, advanced oxidation) have been developed to provide reductions of viruses todiffering levels of regulatory control depending upon the levels of human exposure and associated healthrisks. Importance in any assessment is information on the concentration and types of viruses in theuntreated wastewater, as well as the degree of removal by each treatment process. However, it is criticalthat the uncertainty associated with virus concentration and removal or inactivation by wastewatertreatment be understood to improve these estimates and identifying research needs. We reviewed thecritically literature to assess to identify uncertainty in these estimates. Biological diversity within familiesand genera of viruses (e.g. enteroviruses, rotaviruses, adenoviruses, reoviruses, noroviruses) and specificvirus types (e.g. serotypes or genotypes) creates the greatest uncertainty. These aspects affect themethods for detection and quantification of viruses and anticipated removal efficiency by treatmentprocesses. Approaches to reduce uncertainty may include; 1) inclusion of a virus indicator for assessingefficiency of virus concentration and detection by molecular methods for each sample, 2) use of virusesmost resistant to individual treatment processes (e.g. adenoviruses for UV light disinfection and reovirusesfor chlorination), 3) data on ratio of virion or genome copies to infectivity in untreated wastewater,and 4) assessment of virus removal at field scale treatment systems to verify laboratory and pilot plantdata for virus removal.
• Urzua, R., Dery, J., Brassill, N. A., Mclain, J. E., Rock, C. M., & Rivadeneira, P. (2018). AZ1767: E. coli Prevention and Control in Fresh Produce from Farm-to-Fork. Arizona Cooperative Extension Publication.
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  Escherichia coli (E. coli) is a common bacterium found naturally in the digestive systems of warm blooded animals and soil and is not normally harmful. However, certain types of E. coli produce toxins, called Shiga Toxins, that are harmful. These Shiga toxin-producing E. coli, also called STEC, are significant foodborne pathogens that cause illness in approximately 265,000 people in the United States each year (Scallan, 2011). There are numerous steps along the farm-to fork continuum where growers, harvesters, shippers, and processors implement prevention and control methods to minimize risk from foodborne pathogens, with the goal of ensuring that only the safest fresh produce reaches consumers’ tables. Some of these measures are taken to comply with recent federal guidelines under the Food and Drug Administration (FDA) Food Safety Modernization Act (FSMA), which began to be implemented by the fresh produce industry in January 2018 (FDA 2017) Table 1., but for Arizona growers, the FSMA regulations are not burdensome. Since 2007, growers of fresh produce in our state have been voluntarily following equally strict, and even more specific, guidelines developed by the Arizona Leafy Greens Marketing Agreement (LGMA) as enforced by the Arizona Department of Agriculture (https://www.arizonaleafygreens.org). You may ask, “If guidelines are so strict and if growers are so cautious, why do people still get sick from outbreaks of E. coli and other foodborne pathogens?” This paper will provide a roadmap of how fresh produce travels from farmto-fork, identifying potential routes of contamination. We also describe the preventative controls that are implemented by the fresh produce industry at each stop to reduce the potential for microbial contamination, and how consumers can take simple steps to maintain safe foods eaten in their homes or in restaurants.
• Neyestani, M., Dickenson, E., McLain, J., Robleto, E., Rock, C., & Gerrity, D. (2017). Impacts of solids retention time on trace organic compound attenuation and bacterial resistance to trimethoprim and sulfamethoxazole. Chemosphere, 182, 149-158.
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  Bacteria can grow in the presence of trimethoprim and sulfamethoxazole by expressing antibiotic resistance genes or by acquiring thymine or thymidine from environmental reservoirs to facilitate DNA synthesis. The purpose of this study was to evaluate whether activated sludge serves as a reservoir for thymine or thymidine, potentially impacting the quantification of antibiotic resistant bacteria. This study also assessed the impacts of varying solids retention time (SRT) on trimethoprim and sulfamethoxazole removal during wastewater treatment and single and multi-drug resistance. When assayed in the presence of the antibiotics at standard clinical concentrations, up to 40% increases in the relative prevalence of resistant bacteria were observed with (1) samples manually augmented with reagent-grade thymidine, (2) samples manually augmented with sonicated biomass (i.e., cell lysate), (3) samples manually augmented with activated sludge filtrate, and (4) activated sludge samples collected from reactors with longer SRTs. These observations suggest that longer SRTs may select for antibiotic resistant bacteria and/or result in false positives for antibiotic resistance due to higher concentrations of free thymine, thymidine, or other extracellular constituents.
• Rock, C. M., Mclain, J. E., & Joe, V. M. (2017). Compost Tea 101: What Every Organic Gardener Should Know. University of Arizona, Cooperative Extension.
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  Growers of organic produce in the Southwestern United States face many challenges, including variation in water and temperature, and exposure to insects and disease. As a result, smallholder organic farmers are increasingly relying on soil additives such as compost tea that improve product quality, use less water, deter pests, and reduce reliance on chemical additives (Diver, 2002). But what exactly is compost tea? Do the benefits of using compost tea outweigh any concerns? For example, can it contain pathogens, and if so, do applicators have to worry about coming into contact with pathogens? This publication provides facts about making compost tea, and reviews both the benefits and potential disadvantages to help smallholder farmers to make educated decisions regarding the use of compost tea.
• Rock, C. M., Rivadeneira, P., Rock, C. M., Rivadeneira, P., Rock, C. M., Rivadeneira, P., Rock, C. M., & Rivadeneira, P. (2017). Food Safety Precautions Around Fresh Produce Fields. Arizona Cooperative Extension Fact Sheet AZ1753.
• Kabiri, L., Alum, A., Rock, C. M., Mclain, J. E., & Abbasaadegan, M. (2016). A tool box strategy using Bacteroides genetic markers to identify microbial sources in natural waters. Science of the Total Environment, 572, 897-905.
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  Bacteroides genetic markers have been widely used to identify fecal pollution of water originating from human and animal sources. Many of the assays currently used for detecting human-specific Bacteroides produce falsepositive results. The focus of this study was to develop a microbial source tracking (MST) tool box strategy for differentiating Bacteroides from human and animal sources. Bacteroides 16S rRNA gene sequences from fish and selected animals were aligned against human fecal Bacteroides isolates to compare and characterize the variable regions within the 16S rRNA gene sequence. Conserved sequences between 4 variable regions were deleted and the truncated sequences were combined to develop a hyper-variable genomic segment (HVGS). The cladogram created from truncated sequences show aclear separation of Bacteroides from human feces and those from animal sources. The proposed strategy was field tested by collecting water samples from central Arizona source waters and three different recreational ponds. PCR using HF134 and HF183 primer sets was performed and sequences from positive reactions were aligned against human Bacteroides sequences to identify the source of contamination. Based on PCR results, the source of fecal contamination was presumptively identified as either human or from another source. For samples testing positive using the HF183 primer set (8/13), fecal contamination was presumed to be from human sources,
• Kabiri, L., Alum, A., Rock, C., McLain, J. E., & Abbaszadegan, M. (2016). A tool box strategy using Bacteroides genetic markers to differentiate human from non-human sources of fecal contamination in natural water. The Science of the total environment, 572, 897-905.
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  Bacteroides genetic markers have been widely used to identify fecal pollution of water originating from human and animal sources. Many of the assays currently used for detecting human-specific Bacteroides produce false positive results. The focus of this study was to develop a microbial source tracking (MST) tool box strategy for differentiating Bacteroides from human and animal sources. Bacteroides 16S rRNA gene sequences from fish and selected animals were aligned against human fecal Bacteroides isolates to compare and characterize the variable regions within the 16S rRNA gene sequence. Conserved sequences between 4 variable regions were deleted and the truncated sequences were combined to develop a hyper-variable genomic segment (HVGS). The cladogram created from truncated sequences show a clear separation of Bacteroides from human feces and those from animal sources. The proposed strategy was field tested by collecting water samples from central Arizona source waters and three different recreational ponds. PCR using HF134 and HF183 primer sets was performed and sequences from positive reactions were aligned against human Bacteroides sequences to identify the source of contamination. Based on PCR results, the source of fecal contamination was presumptively identified as either human or from another source. For samples testing positive using the HF183 primer set (8/13), fecal contamination was presumed to be from human sources, but to confirm the results, PCR products were sequenced and aligned against the four variable regions and then incorporated within the truncated cladogram. As expected, the sequences from water samples with human fecal contamination grouped in a separate clade. A variability matrix, developed after exclusion of conserved sequences among the four regions, was utilized to establish discrete groupings for sequences within the truncated cladogram, generally differentiating Bacteroides isolates from varying host animals, but most importantly, separating Bacteroides from human feces from Bacteroides from other animals. The proposed strategy offers a new tool box method for MST and a step-wise methodology essential for identifying human sources of fecal pollution.
• Rock, C. M. (2016). The UA Wildcat Water Lab: Cats do like water!. Kachina News- AZ Water.
• Mclain, J. E., Cusimano, J., Rock, C. M., & Eden, S. (2015). Agricultural use of recycled water for crop production. University of Arizona Cooperative Extension Publications, az1670, 7.
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  Agriculture is by far the largest water-demanding sector in Arizona, accounting for 70% of water demand. Arizona’s agriculture industry is extremely diversified, producing many crops that can legally be irrigated with recycled water, including cotton, alfalfa, wheat, citrus, and vegetables. Throughout the State, farming communities are taking advantage of increasing supplies of recycled water. In many cases, this is a money-saving measure, as agricultural water transported over great distances (e.g., from the Colorado River) can require tremendous amounts of energy. While recycling water is also energetically intensive, performing wastewater recycling on site or nearby an agricultural field reduces the energy needed to move water longer distances or pump water from deep within an aquifer. In fact, the use of recycled water for agricultural irrigation is often limited by the distance of agricultural districts from large urban centers where water reclamation facilities are located.
• Alum, A., Rock, C., & Abbaszadegan, M. (2014). A unified method to process biosolids samples for the recovery of bacterial, viral, and helminths pathogens. Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering, 49(6), 679-684.
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  Abstract: For land application, biosolids are classified as Class A or Class B based on the levels of bacterial, viral, and helminths pathogens in residual biosolids. The current EPA methods for the detection of these groups of pathogens in biosolids include discrete steps. Therefore, a separate sample is processed independently to quantify the number of each group of the pathogens in biosolids. The aim of the study was to develop a unified method for simultaneous processing of a single biosolids sample to recover bacterial, viral, and helminths pathogens. At the first stage for developing a simultaneous method, nine eluents were compared for their efficiency to recover viruses from a 100 gm spiked biosolids sample. In the second stage, the three top performing eluents were thoroughly evaluated for the recovery of bacteria, viruses, and helminthes. For all three groups of pathogens, the glycine-based eluent provided higher recovery than the beef extract-based eluent. Additional experiments were performed to optimize performance of glycine-based eluent under various procedural factors such as, solids to eluent ratio, stir time, and centrifugation conditions. Last, the new method was directly compared with the EPA methods for the recovery of the three groups of pathogens spiked in duplicate samples of biosolids collected from different sources. For viruses, the new method yielded up to 10% higher recoveries than the EPA method. For bacteria and helminths, recoveries were 74% and 83% by the new method compared to 34% and 68% by the EPA method, respectively. The unified sample processing method significantly reduces the time required for processing biosolids samples for different groups of pathogens; it is less impacted by the intrinsic variability of samples, while providing higher yields (P = 0.05) and greater consistency than the current EPA methods. © 2014 Copyright Taylor and Francis Group, LLC.
• Alum, A., Rock, C., & Abbaszadegan, M. (2014). A unified method to process biosolids samples for the recovery of bacterial, viral, and helminths pathogens. Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering, 49(6), 679-84.
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  For land application, biosolids are classified as Class A or Class B based on the levels of bacterial, viral, and helminths pathogens in residual biosolids. The current EPA methods for the detection of these groups of pathogens in biosolids include discrete steps. Therefore, a separate sample is processed independently to quantify the number of each group of the pathogens in biosolids. The aim of the study was to develop a unified method for simultaneous processing of a single biosolids sample to recover bacterial, viral, and helminths pathogens. At the first stage for developing a simultaneous method, nine eluents were compared for their efficiency to recover viruses from a 100 gm spiked biosolids sample. In the second stage, the three top performing eluents were thoroughly evaluated for the recovery of bacteria, viruses, and helminthes. For all three groups of pathogens, the glycine-based eluent provided higher recovery than the beef extract-based eluent. Additional experiments were performed to optimize performance of glycine-based eluent under various procedural factors such as, solids to eluent ratio, stir time, and centrifugation conditions. Last, the new method was directly compared with the EPA methods for the recovery of the three groups of pathogens spiked in duplicate samples of biosolids collected from different sources. For viruses, the new method yielded up to 10% higher recoveries than the EPA method. For bacteria and helminths, recoveries were 74% and 83% by the new method compared to 34% and 68% by the EPA method, respectively. The unified sample processing method significantly reduces the time required for processing biosolids samples for different groups of pathogens; it is less impacted by the intrinsic variability of samples, while providing higher yields (P = 0.05) and greater consistency than the current EPA methods.
• Sima, L., Amador, J., da Silva, A. K., Miller, S. M., Morse, A. N., Pellegrin, M., Rock, C., & Wells, M. J. (2014). Emerging Pollutants - Part I: Occurrence, Fate and Transport. WATER ENVIRONMENT RESEARCH, 86(10), 1994-2035.
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  Part I: Occurrence, Fate, and Transport (this literature review) compiles research from 2013 investigating emerging pollutants in wastewater and environmental waters and the sources of emerging pollutants. The paper summarizes important findings on environmental aquatic occurrence, persistence and transport of emerging pollutants in the environment, monitoring approaches, modeling, and regulatory discussions. The paper further mentions updates in our understanding of the toxicological impacts of these compounds where relevant specifically to wastewater Finally, the paper speaks to the environmental sinks and degradation of pollutants. Part II: Treatment (the companion to this review) includes discussion of water and wastewater treatment technologies on emerging pollutants.
• Ajibode, A. M., Rock, C. M., Bright, K., Mclain, J. E., Gerba, C. P., Pepper, I. L., Ajibode, A. M., Rock, C. M., Bright, K., Mclain, J. E., Gerba, C. P., Pepper, I. L., Ajibode, A. M., Rock, C. M., Bright, K., Mclain, J. E., Gerba, C. P., & Pepper, I. L. (2013). Influence of residence time of reclaimed water within distribution systems on water quality. Journal of Water Reuse and Desalination, 12.
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  The abstract for the publication can be found at URL. My participation in this manuscript was to serve as a co-PI to procure funding for the project and to aid in microbiological analyses of samples and data analysis.
• Gold, A. J., Mcclaran, M. P., Parker, D., Gold, A. J., Waskom, R. M., Parker, D., Dobrowolski, J., Waskom, R. M., O'Neill, M., Dobrowolski, J., Groffman, P. M., O'Neill, M., Addy, K., Groffman, P. M., Barber, M., Addy, K., Batie, S., Barber, M., Benham, B., , Batie, S., et al. (2013). Advancing water resource management in agricultural, rural, and urbanizing watersheds: why land-grant universities matter. Journal of Soil and Water Conservation, 68(4), 337-348.
• Kabiri, L., Alum, A., Rock, C., McLain, J. E., & Abbaszadegan, M. (2013). Isolation of Bacteroides from fish and human fecal samples for identification of unique molecular markers. Canadian journal of microbiology, 59(12), 771-7.
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  Bacteroides molecular markers have been used to identify human fecal contamination in natural waters, but recent work in our laboratory confirmed cross-amplification of several human-specific Bacteroides spp. assays with fecal DNA from fish. For identification of unique molecular markers, Bacteroides from human (n = 4) and fish (n = 7) fecal samples were cultured and their identities were further confirmed using Rapid ID 32A API strips. The 16S rDNA from multiple isolates from each sample was PCR amplified, cloned, and sequenced to identify unique markers for development of more stringent human-specific assays. In human feces, Bacteroides vulgatus was the dominant species (75% of isolates), whereas in tilapia feces, Bacteroides eggerthii was dominant (66%). Bacteroides from grass carp, channel catfish, and blue catfish may include Bacteroides uniformis, Bacteroides ovatus, or Bacteroides stercoris. Phylogenic analyses of the 16S rRNA gene sequences showed distinct Bacteroides groupings from each fish species, while human sequences clustered with known B. vulgatus. None of the fish isolates showed significant similarity to Bacteroides sequences currently deposited in NCBI (National Center for Biotechnology Information). This study expands the current sequence database of cultured fish Bacteroides. Such data are essential for identification of unique molecular markers in human Bacteroides that can be utilized in differentiating fish and human fecal contamination in water samples.
• McLain, J. E., Rock, C. M., Kabiri, L., Alum, A., Abbaszadegan, M., McLain, J. E., Rock, C. M., Kabiri, L., Alum, A., & Abbaszadegan, M. (2013). Isolation of Bacteroides from fish and human fecal samples for identification of unique molecular markers. Canadian Journal of Microbiology, 59, 7.
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  The abstract for this publication can be found at URL. My role in this publication was to supervise all initial laboratory work in identification and quantification of Bacteroides using molecular methods. I aided in the supervision of a Ph.D. student, serving on her dissertation committee, and assisted in the development and editing of the final manuscript.
• Pepper, I. L., Gerba, C. P., Mclain, J. E., Bright, K. R., Rock, C. M., & Ajibode, O. M. (2013). Influence of residence time of reclaimed water within distribution systems on water quality. JOURNAL OF WATER REUSE AND DESALINATION, 3(3), 185-196. doi:https:/doi.org/10.2166/wrd.2013.088
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  The influence of residence time of reclaimed water within water distribution systems on microbial water quality was evaluated in two wastewater reclamation facilities in southern Arizona over a 15-month period. These utilities differed in age, geographic location, means of treatment, and disinfection (i.e. UV versus chlorine). At both facilities, samples were collected from the point of compliance (POC) directly after disinfection, and at discrete locations with increasing distance from the POC. Following entry into reclaimed water distribution systems, overall microbial water quality decreased rapidly due to microbial regrowth. However, following such regrowth, microbial concentrations remained relatively constant. Water-based opportunistic pathogens (Legionella, Mycobacterium, and Aeromonas) were frequently detected in both reclaimed water systems. In contrast, waterborne indicators such as Escherichia coli and Enterococcus were rarely detected, and only at low concentrations. These dates suggest the need for new indicators of water-based pathogens to be developed. Rechlorination in one of the distribution systems only reduced the concentration of bacteria temporarily due to rapid dissipation of chlorine, and subsequent regrowth of both water-based pathogens and indicators. Amoebic activity was detected in approximately one-third of all samples tested from both utilities, but was not correlated with either water-based pathogens or indicators.
• Rock, C. M. (2013). A unified Sample Processing Method for the Recovery of Bacterial, Viral and Helminth Pathogens from Biosolids. Journal of Microbiological Methods.
• Rock, C. M. (2013). Impact of Residence Time and Water Age on Microbial Growth and Re-Growth in Recycled Water Distribution Systems. Water Reuse and Desalination.
• Rock, C. M. (2013). Isolation of Bacteroides from Fish and Human Fecal Samples for Identification of Unique Molecular Markers. Canadian Journal of Microbiology.
• Ajibode, O., Rock, C., McLain, J., Pepper, I., & Gerba, C. (2012). Influence of Water Age on Recycled Water Quality in Distribution Systems. Journal of Water Reuse and Desalination.
• Rock, C., Solop, F. I., & Gerrity, D. (2012). Survey of statewide public perceptions regarding water reuse in Arizona. Journal of Water Supply: Research and Technology - AQUA, 61(8), 506-517.
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  Abstract: Increasing demands on water resources have made water reuse an attractive option for extending water supplies in the southwest. However, concerns remain about the potential risks of contact with recycled water. This study focused on perceptions regarding water reuse and how these may affect future utilization of the resource. This study, based on a telephone survey of 400 randomly-selected Arizona residents, was used to assess public opinion of water reuse in the state. Survey results indicated that residents feel it is important for their community to use recycled water. In fact, 76% of those surveyed support using 'consumer incentives for using recycled water', and over two-thirds of respondents support 'increasing water or sewer rates to treat water to higher standards'. Despite this support, the survey revealed that almost two-thirds of the respondents have concerns about recycled water. Those concerns can be alleviated by providing 'better information about recycled water'. Education level proved to be the most significant demographic affecting perception of terminology and recycled water uses. These results can be used by water agencies - even those outside Arizona - to address community concerns, effectively promote water reuse, and develop more sustainable and accepted alternatives to augment their water portfolios. © IWA Publishing 2012.
• Rock, C., Solop, F., & Gerrity, D. (2012). Survey of Statewide Public Perceptions Regarding Water Reuse in Arizona. Journal of Water Supply: Research and Technology - AQUA.
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  doi: 10.2166/aqua.2012.070
• McLain, J. E., Rock, C. M., Lohse, K., & Walworth, J. (2011). False-positive identification of Escherichia coli in treated municipal wastewater and wastewater-irrigated soils. Canadian journal of microbiology, 57(10), 775-84.
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  The increasing use of treated wastewater for irrigation heightens the importance of accurate monitoring of water quality. Chromogenic media, because they are easy to use and provide rapid results, are often used for detection of Escherichia coli in environmental samples, but unique levels of organic and inorganic compounds alter the chemistry of treated wastewater, potentially hindering the accurate performance of chromogenic media. We used MI agar and molecular confirmatory methods to assess false-positive identification of E. coli in treated wastewater samples collected from municipal utilities, an irrigation holding pond, irrigated soils, and in samples collected from storm flows destined for groundwater recharge. False-positive rates in storm flows (4.0%) agreed closely with USEPA technical literature but were higher in samples from the pond, soils, and treatment facilities (33.3%, 38.0%, and 48.8%, respectively). Sequencing of false-positive isolates confirmed that most were, like E. coli, of the family Enterobacteriaceae, and many of the false-positive isolates were reported to produce the β-D-glucuronidase enzyme targeted by MI agar. False-positive identification rates were inversely related to air temperature, suggesting that seasonal variations in water quality influence E. coli identification. Knowledge of factors contributing to failure of chromogenic media will lead to manufacturer enhancements in media quality and performance and will ultimately increase the accuracy of future water quality monitoring programs.
• McLain, J., Rock, C., Lohse, K., & Walworth, J. (2011). False positive identification of E. coli in treated municipal wastewater and wastewater-irrigated soils. Can. J. Microbiol, 57, 775-784.
• Rock, C., McLain, J., Pepper, I., Lansey, K., & Choi, C. (2011). Influence of Water Age on Recycled Water Quality in Distribution Systems, WRF-0804. Proceedings WateReuse Symposium, Las Vegas, NV.
• Rock, C., Alum, A., & Abbaszadegan, M. (2010). PCR inhibitor levels in concentrates of biosolid samples predicted by a new method based on excitation-emission matrix spectroscopy. Applied and Environmental Microbiology, 76(24), 8102-8109.
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  PMID: 20971866;PMCID: PMC3008220;Abstract: Biosolids contain a wide variety of organic contaminants that are known for their ability to inhibit PCR. During sample processing, these contaminants are coconcentrated with microorganisms. Elevated concentrations of these compounds in concentrates render samples unsuitable for molecular applications. Glycine-based elution and recovery methods have been shown to generate samples with fewer PCR inhibitory compounds than the current U.S. EPA-recommended method for pathogen recovery from biosolids. Even with glycine-based methods, PCR inhibitors still persist in concentrations that may interfere with nucleic acid amplification. This results in considerable loss of time and resources and increases the probability of false negatives. A method to estimate the degree of inhibition prior to application of molecular methods is desirable. Here we report fluorescence excitation-emission matrix (EEM) profiling as a tool for predicting levels of molecular inhibition in sample concentrates of biosolids.
• Rock, C., Alum, A., & Abbaszadegan, M. (2010). PCR inhibitor levels in concentrates of biosolid samples predicted by a new method based on excitation-emission matrix spectroscopy. Applied and environmental microbiology, 76(24), 8102-9.
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  Biosolids contain a wide variety of organic contaminants that are known for their ability to inhibit PCR. During sample processing, these contaminants are coconcentrated with microorganisms. Elevated concentrations of these compounds in concentrates render samples unsuitable for molecular applications. Glycine-based elution and recovery methods have been shown to generate samples with fewer PCR inhibitory compounds than the current U.S. EPA-recommended method for pathogen recovery from biosolids. Even with glycine-based methods, PCR inhibitors still persist in concentrations that may interfere with nucleic acid amplification. This results in considerable loss of time and resources and increases the probability of false negatives. A method to estimate the degree of inhibition prior to application of molecular methods is desirable. Here we report fluorescence excitation-emission matrix (EEM) profiling as a tool for predicting levels of molecular inhibition in sample concentrates of biosolids.
• McLain, J. E., Ryu, H., Kabiri-Badr, L., Rock, C. M., & Abbaszadegan, M. (2009). Lack of specificity for PCR assays targeting human Bacteroides 16S rRNA gene: cross-amplification with fish feces. FEMS microbiology letters, 299(1), 38-43.
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  Methods focused on members of the genus Bacteroides have been increasingly utilized in microbial source-tracking studies for identifying and quantifying sources of nonpoint fecal contamination. We present results using standard and real-time PCR to show cross-amplification of Bacteroides 16S rRNA gene molecular assays targeting human fecal pollution with fecal DNA from freshwater fish species. All except one of the presumptively human-specific assays amplified fecal DNA from at least one fish species, and one real-time PCR assay amplified DNA from all fish species tested. Sequencing of PCR amplicons generated from fish fecal DNA using primers from the real-time assay revealed no mismatches to the human-specific probe sequences, but the nucleotide sequences of clones from fish fecal samples differed markedly from those of human feces, suggesting that the fish-related bacteria may be different strains. Our results strongly demonstrate the potential for cross-amplification of human-specific PCR assays with fish feces, and may call into question the results of studies in which these Bacteroides-specific molecular markers are used to quantify human fecal contamination in waters where fish contribute to fecal inputs.
• Morales-Morales, H. A., Vidal, G., Olszewski, J., Rock, C. M., Dasgupta, D., Oshima, K. H., & Smith, G. B. (2003). Optimization of a reusable hollow-fiber ultrafilter for simultaneous concentration of enteric bacteria, protozoa, and viruses from water. Applied and Environmental Microbiology, 69(7), 4098-4102.
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  PMID: 12839786;PMCID: PMC165154;Abstract: The detection and identification of pathogens from water samples remain challenging due to variations in recovery rates and the cost of procedures. Ultrafiltration offers the possibility to concentrate viral, bacterial, and protozoan organisms in a single process by using size-exclusion-based filtration. In this study, two hollow-fiber ultrafilters with 50,000-molecular-weight cutoffs were evaluated to concentrate microorganisms from 2- and 10-liter water samples. When known quantities (105 to 106 CFU/liter) of two species of enteric bacteria were introduced and concentrated from 2 liters of sterile water, the addition of 0.1% Tween 80 increased Escherichia coli strain K-12 recoveries from 70 to 84% and Salmonella enterica serovar Enteritidis recoveries from 36 to 72%. An E. coli antibiotic-resistant strain, XL1-Blue, was recovered at a level (87%) similar to that for strain K-12 (96%) from 10 liters of sterile water. When E. coli XL1-Blue was introduced into 10 liters of nonsterile Rio Grande water with higher turbidity levels (23 to 29 nephelometric turbidity units) at two inoculum levels (9 × 105 and 2.4 × 103 per liter), the recovery efficiencies were 89 and 92%, respectively. The simultaneous addition of E. coli XL1-Blue (9 × 105 CFU/liter), Cryptosporidium parvum oocysts (10 oocysts/liter), phage T1 (105 PFU/liter), and phage PP7 (105 PFU/liter) to 10 liters of Rio Grande surface water resulted in mean recoveries of 96, 54, 59, and 46%, respectively. Using a variety of surface waters from around the United States, we obtained recovery efficiencies for bacteria and viruses that were similar to those observed with the Rio Grande samples, but recovery of Cryptosporidium oocysts was decreased, averaging 32% (the site of collection of these samples had previously been identified as problematic for oocyst recovery). Results indicate that the use of ultrafiltration for simultaneous recovery of bacterial, viral, and protozoan pathogens from variable surface waters is ready for field deployment.
• Morales-Morales, H. A., Vidal, G., Olszewski, J., Rock, C. M., Dasgupta, D., Oshima, K. H., & Smith, G. B. (2003). Optimization of a reusable hollow-fiber ultrafilter for simultaneous concentration of enteric bacteria, protozoa, and viruses from water. Applied and environmental microbiology, 69(7), 4098-102.
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  The detection and identification of pathogens from water samples remain challenging due to variations in recovery rates and the cost of procedures. Ultrafiltration offers the possibility to concentrate viral, bacterial, and protozoan organisms in a single process by using size-exclusion-based filtration. In this study, two hollow-fiber ultrafilters with 50,000-molecular-weight cutoffs were evaluated to concentrate microorganisms from 2- and 10-liter water samples. When known quantities (10(5) to 10(6) CFU/liter) of two species of enteric bacteria were introduced and concentrated from 2 liters of sterile water, the addition of 0.1% Tween 80 increased Escherichia coli strain K-12 recoveries from 70 to 84% and Salmonella enterica serovar Enteritidis recoveries from 36 to 72%. An E. coli antibiotic-resistant strain, XL1-Blue, was recovered at a level (87%) similar to that for strain K-12 (96%) from 10 liters of sterile water. When E. coli XL1-Blue was introduced into 10 liters of nonsterile Rio Grande water with higher turbidity levels (23 to 29 nephelometric turbidity units) at two inoculum levels (9 x 10(5) and 2.4 x 10(3) per liter), the recovery efficiencies were 89 and 92%, respectively. The simultaneous addition of E. coli XL1-Blue (9 x 10(5) CFU/liter), Cryptosporidium parvum oocysts (10 oocysts/liter), phage T1 (10(5) PFU/liter), and phage PP7 (10(5) PFU/liter) to 10 liters of Rio Grande surface water resulted in mean recoveries of 96, 54, 59, and 46%, respectively. Using a variety of surface waters from around the United States, we obtained recovery efficiencies for bacteria and viruses that were similar to those observed with the Rio Grande samples, but recovery of Cryptosporidium oocysts was decreased, averaging 32% (the site of collection of these samples had previously been identified as problematic for oocyst recovery). Results indicate that the use of ultrafiltration for simultaneous recovery of bacterial, viral, and protozoan pathogens from variable surface waters is ready for field deployment.
• Kuhn, R. C., Rock, C. M., & Oshima, K. H. (2002). Effects of pH and magnetic material on immunomagnetic separation of Cryptosporidium oocysts from concentrated water samples. Applied and Environmental Microbiology, 68(4), 2066-2070.
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  PMID: 11916735;PMCID: PMC123889;Abstract: In this study, we examined the effect that magnetic materials and pH have on the recoveries of Cryptosporidium oocysts by immunomagnetic separation (IMS). We determined that particles that were concentrated on a magnet during bead separation have no influence on oocyst recovery; however, removal of these particles did influence pH values. The optimal pH of the IMS was determined to be 7.0. The numbers of oocysts recovered from deionized water at pH 7.0 were 26.3% higher than those recovered from samples that were not at optimal pH. The results indicate that the buffers in the IMS kit did not adequately maintain an optimum pH in some water samples. By adjusting the pH of concentrated environmental water samples to 7.0, recoveries of oocysts increased by 26.4% compared to recoveries from samples where the pH was not adjusted.
• Kuhn, R. C., Rock, C. M., & Oshima, K. H. (2002). Effects of pH and magnetic material on immunomagnetic separation of Cryptosporidium oocysts from concentrated water samples. Applied and environmental microbiology, 68(4), 2066-70.
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  In this study, we examined the effect that magnetic materials and pH have on the recoveries of Cryptosporidium oocysts by immunomagnetic separation (IMS). We determined that particles that were concentrated on a magnet during bead separation have no influence on oocyst recovery; however, removal of these particles did influence pH values. The optimal pH of the IMS was determined to be 7.0. The numbers of oocysts recovered from deionized water at pH 7.0 were 26.3% higher than those recovered from samples that were not at optimal pH. The results indicate that the buffers in the IMS kit did not adequately maintain an optimum pH in some water samples. By adjusting the pH of concentrated environmental water samples to 7.0, recoveries of oocysts increased by 26.4% compared to recoveries from samples where the pH was not adjusted.
• Kuhn, R. C., Rock, C. M., & Oshima, K. H. (2002). Occurrence of Cryptosporidium and Giardia in wild ducks along the Rio Grande River valley in Southern New Mexico. Applied and Environmental Microbiology, 68(1), 161-165.
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  PMID: 11772622;PMCID: PMC126547;Abstract: Fecal samples were taken from wild ducks on the lower Rio Grande River around Las Cruces, N. Mex., from September 2000 to January 2001. Giardia cysts and Cryptosporidium oocysts were purified from 69 samples by sucrose enrichment followed by cesium chloride (CsCl) gradient centrifugation and were viewed via fluorescent-antibody (FA) staining. For some samples, recovered cysts and oocysts were further screened via PCR to determine the presence of Giardia lamblia and Crytosporidium parvum. The results of this study indicate that 49% of the ducks were carriers of Cryptosporidium, and the Cryptosporidium oocyst concentrations ranged from 0 to 2,182 oocysts per g of feces (mean ± standard deviation, 47.53 ± 270.3 oocysts per g); also, 28% of the ducks were positive for Giardia, and the Giardia cyst concentrations ranged from 0 to 29,293 cysts per g of feces (mean ± standard deviation, 436 ± 3,525.4 cysts per g). Of the 69 samples, only 14 had (oo)cyst concentrations that were above the PCR detection limit. Samples did test positive for Cryptosporidium sp. However, C. parvum and G. lamblia were not detected in any of the 14 samples tested by PCR. Ducks on their southern migration through southern New Mexico were positive for Cryptosporidium and Giardia as determined by FA staining, but C. parvum and G. lamblia were not detected.
• Kuhn, R. C., Rock, C. M., & Oshima, K. H. (2002). Occurrence of Cryptosporidium and Giardia in wild ducks along the Rio Grande River valley in southern New Mexico. Applied and environmental microbiology, 68(1), 161-5.
  More info

  Fecal samples were taken from wild ducks on the lower Rio Grande River around Las Cruces, N. Mex., from September 2000 to January 2001. Giardia cysts and Cryptosporidium oocysts were purified from 69 samples by sucrose enrichment followed by cesium chloride (CsCl) gradient centrifugation and were viewed via fluorescent-antibody (FA) staining. For some samples, recovered cysts and oocysts were further screened via PCR to determine the presence of Giardia lamblia and Crytosporidium parvum. The results of this study indicate that 49% of the ducks were carriers of Cryptosporidium, and the Cryptosporidium oocyst concentrations ranged from 0 to 2,182 oocysts per g of feces (mean +/- standard deviation, 47.53 +/- 270.3 oocysts per g); also, 28% of the ducks were positive for Giardia, and the Giardia cyst concentrations ranged from 0 to 29,293 cysts per g of feces (mean +/- standard deviation, 436 +/- 3,525.4 cysts per g). Of the 69 samples, only 14 had (oo)cyst concentrations that were above the PCR detection limit. Samples did test positive for Cryptosporidium sp. However, C. parvum and G. lamblia were not detected in any of the 14 samples tested by PCR. Ducks on their southern migration through southern New Mexico were positive for Cryptosporidium and Giardia as determined by FA staining, but C. parvum and G. lamblia were not detected.

Proceedings Publications

• Rock, C., McLain, J., Thomure, T., Pepper, I., Lansey, K., & Choi, C. (2012, Fall). Approaches to Maintain Consistently High Quality Recycled Water in Storage and Distribution Systems. In WateReuse Association Research Conference.
• Kabiri-badr, L., McLain, J., Alum, A., Ryu, H., Rock, C., & Abbaszadegan, M. (2011, Fall). Searching for Unique Bacteroides 16S rRNA Genetic Markers in Human and Fish Feces Using Bacterial Culturing and Sequencing. In Not provided in APROL.
• Rock, C. (2011, Fall). Arizona Targeted Watershed Improvement Grant Program: Challenges and Opportunities for Volunteer Participation and Watershed Education. In USDA National Water Conference.
• Rock, C. (2011, Fall). Seasonal Reclaimed Water Quality; an Assessment of Nutrient, Chemical, and Biological Variability. In AZ Water.
• Rock, C. (2011, Fall). Survey of Public Perceptions Regarding Water Reuse in AZ: Challenges and Opportunities. In AZ Water.
• Rock, C. M., Ajibode, O., Riley, K., Quintanar, D., Symmonds, G., Gerba, D. C., Pepper, D. I., & Rock, D. C. (2011, Fall). Incidence of Water Based Pathogens in Reclaimed Water. In Not provided in APROL.
• Rock, C., McLain, J., Thomure, T., Pepper, I., Lansey, K., & Choi, C. (2011, Fall). Approaches to Maintain Consistently High Quality Recycled Water in Storage and Distribution Systems. In WateReuse Association Research Conference.
• Rock, C., Rupprecht, C., & Schwartz, K. (2011, Fall). Innovative Methods to Engage Local Stakeholders to Inform Future Statewide Water Planning Efforts: Arizona Water State Initiative. In USDA National Water Conference.

Presentations

• Teegerstrom, T., Ellsworth, P. C., Woolfolk, C. M., Weber, J. L., Nair, S., Ernst, K. C., Walker, K. R., Fournier, A. J., Gouge, D. H., & Li, S. (2021, October-November). Emergency Preparedness through Integrated Pest Management Education and Tribal Partnerships in Arizona. 2021 Entomological Society of America Annual Conference. October 31-November 3, 2021.
• Rock, C. M., & Rivadeneira, P. (2019, March). Investigation into the 2018 E. coli Outbreak in Yuma, Arizona. Northwest Horticulture Association Annual Conference. Yakima, Washington: Northwest Horticulture Association.
• Castaneda, D., DaSilva, A., Rock, C. M., & Mclain, J. E. (2018, September). Antibiotic resistance: state of the science of proliferation in water treatment and potable reuse implementation. 3rd Annual Water Reuse Symposium. Austin, Texas: WateReuse.
• DaSilva, A., Castaneda, D., Rock, C. M., & Mclain, J. E. (2018, July). Antibiotic resistance: state of the science of proliferation in wastewater treatment and water reuse implementation. Water Environment Federation Disinfection and Reuse Symposium. Portland, Oregon: Water Environment Federation.
• Rock, C. M., & Mclain, J. E. (2018, September). Minimal production of algal toxins in recycled water retention ponds. 33rd Annual Water Reuse Symposium. Austin, Texas: WateReuse.
• Rock, C. M., Rosenberg Goldstein, R., Suri, M., Dery, J., Brassill, N., Pee, D., & Goeringer, P. (2018, April/Spring). Agricultural Adaptations to Climate Change: Farmers Perceptions of Nontraditional Water Sources for Irrigation. Nexus 2018: Water, Food, Energy and Climate.. Chapel Hill, NC: University of North Carolina, Chapel Hill.
• Rock, C. M. (2017, September/Summer). Medical Health Initiative - WateReuse. National WateReuse Symposium. Phoenix, AZ: WateReuse Association.
• Rock, C. M. (2017, September/Summer). Public Perception - Public understanding and attitudes. Non-potable and potable. Tools and techniques to engage the public.. National WateReuse Symposium/ Reuse Boot Camp 2017. Phoenix, AZ: National WateResue Association.
• Rock, C. M., & Snyder, S. A. (2017, July/Summer). Assessment of Techniques to Evaluate and Demonstrate the Safety of Water from Direct Potable Reuse Treatment Facilities: Perception versus Reality. 11th IWA International Conference on Water Reclamation and Reuse. Long Beach Convention Center: WateReuse Association.
• Rock, C. M., Mclain, J. E., Gerrity, D., Mosher, J., Jakubowski, W., & Sapkota, A. (2017, July/Summer). Antibiotic Resistance: What Every Water Professional Needs to Know. 11th IWA International Conference on Water Reclamation and Reuse. Long Beach Convention Center: WateReuse Association.
• Rock, C. M., Prevatt, J., Kmiec, J., Thomure, T., Graf, C., Fullmer, R., & Saraiva, C. (2017, September/Summerr). Arizona Pure Water Brew Challenge - Panel. National WateReuse Symposium. Phoenix, AZ: WateReuse Association.
• Rock, C. M., Rosenberg Goldstein, R., Suri, M., Dery, J., Brassill, N., Pee, D., & Goeringer, P. (2017, December/Winter). Farmer Perceptions and Understanding of Irrigation Water from Nontraditional Sources. Society for Risk Analysis Conference. Arlington, VA: Society for Risk Analysis.
• Rock, C. M., Rosenberg Goldstein, R., Suri, M., Dery, J., Brassill, N., Pee, D., & Goeringer, P. (2017, December/Winter). Using Nontraditional Water on the Farm. 2017 Agricultural Outlook and Policy Conference. Annapolis, MD: University of Maryland, Cooperative Extension.
• Rock, C. M., Rosenberg Goldstein, R., Suri, M., Dery, J., Brassill, N., Pee, D., & Goeringer, P. (2017, February/Spring). Farmer Perceptions and Understanding of Irrigation Water from Nontraditional Sources. Southern Maryland Vegetable and Fruit Meeting. Gambrills, MD: University of Maryland, Cooperative Extension.
• Rock, C. M., Rosenberg Goldstein, R., Suri, M., Dery, J., Brassill, N., Pee, D., Goeringer, P., & Sapkota, A. (2017, January/Spring). Nontraditional Irrigation Water for Produce: Assessing Farmers’ Needs & Water Quality Results. Cultivate the Chesapeake Foodshed, Future Harvest Chesapeake Alliance for Sustainable Agriculture. College Park, MD: Chesapeake Alliance for Sustainable Agriculture.
• Rock, C. M., Sapkota, A., & Lipchin, C. (2017, July/Summer). "Moving Toward the Safe Use of Recycled Water for Crop Irrigation: A Sustainable Solution in an Era of Climate Variability?". IAFP Annual Meeting. Tampa, FL: International Association of Food Protection.
• Rock, C. M., Sapkota, A., & Lipchin, C. (2017, July/Summer). Moving Toward the Safe Use of Recycled Water for Crop Irrigation: A Sustainable Solution in an Era of Climate Variability?. International Water Association (IWA). Long Beach, CA: International Association of Food Protection.
• Rock, C. M., Sapkota, A., & Mosher, J. (2017, July/Summer). Recycled Water Use on Food Crops: How Safe is Safe?. 11th IWA International Conference on Water Reclamation and Reuse. Long Beach Convention Center: WateReuse Association.
• Mclain, J. E., & Rock, C. M. (2016, July). Recycled municipal wastewater and antibiotic resistance: is there a connection?. Arizona WateReuse 2016 Symposium. Flagstaff, Arizona: Arizona WateReuse.
• Rock, C. M. (2016, August). Extension Solutions to Agricultural Water Challenges. Arizona Cooperative Extension Water In-Service/Conference. Tempe: UACE.
• Rock, C. M. (2016, November). FSMA and the Ag Water Rule. Produce Safety Alliance. Irvine, CA: PSA and FDA.
• Rock, C. M. (2016, November). Public Health Issues in Potable Reuse. Clarke Prize Conference. Long Beach: NWRI.
• Rock, C. M. (2016, October). Microbiological Contaminants in Potable Reuse Applications. WateReuse Speciality Conference. Oklahoma City: WE&RF.
• Rock, C. M. (2016, September). Future of Potable Reuse. Water Reuse Symposium. Florida: WE&RF.
• Mclain, J. E., Burke, K., Engelthaler, D. M., Hart, R. J., Hill, B., Pruden, A., Rock, C. M., & Snyder, S. A. (2015, May). Separating science from emotion in perceptions of recycled water: a case study of Flagstaff, Arizona. 88th Annual Conference. Glendale, Arizona: Arizona Water Association.
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  Though water recycling is an attractive option for extending water supplies, concerns remain about potential public health risks. This case study examines the response of the City of Flagstaff to concerns raised after antibiotic resistance genes were detected in their municipal recycled water. An expert panel convened by Flagstaff’s City Manager and representing a diversity of expertise and opinions compiled a consensus report that data do not exist to suggest that recycled water poses known health risk. The panel noted gaps in scientific knowledge, and identified a critical need for research. Thus, Flagstaff successfully addressed a complex scientific problem in a charged political environment using scientific expertise, public engagement and strong leadership. Other communities following this model may realize an increase in public trust as they pursue answers to critical health-related questions.
• Mclain, J. E., Rock, C. M., & Farrell-Poe, K. L. (2014, January). Microbial indicators and onsite wastewater treatment systems: what do we really know?. 2014 Southwest On-site Wastewater Conference. Laughlin, Nevada: Arizona County Directors of Environmental Health Services Association.
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  Establishing onsite wastewater treatment system performance requirements has been a challenge nationwide. In many states with established standards, discharges under performance-based permit programs must meet treatment performance criteria for secondary, advanced secondary, or advanced wastewater treatment, depending on system location, unsaturated depth of natural soil, and the proximity of protected water resources. As might be expected, wastewater managers (including homeowners and business owners) might be confused by the complexities of landscape-dependent performance criteria, with microbial standards particularly problematic. This talk discussed current microbial standards andl served as an introduction to the challenges to be faced in developing methods to assess wastewater quality
• Rock, C. M. (2014, April). Complying with Irrigation Water Quality Criteria in Arid Regions: Lessons Learned from Imperial Valley, CA and Yuma Arizona. LGMA Water Workshop. Davis, CA.
• Rock, C. M. (2014, June). Emerging Issues in Recycled Water Public Perceptiopn. Reclaimed Water Conference - NAU. Presott, AZ.
• Rock, C. M. (2014, June). Evaluation of Risk-based Water Quality Sampling Strategies for the Fresh Produce Industry. 2014 CPS Produce Research Symposium.
• Rock, C. M. (2014, May). Evaluation of Risk-based Water Quality Sampling Strategies for the Fresh Produce Industry. Western Food Safety Summit.
• Rock, C. M. (2014, May). Risk Based Water Sampling Strategies for Direct Potable Reuse Safety. WateReuse Research Confrence. Las Vegas, NV.
• Rock, C. M., & Mclain, J. E. (2014, January). Does Increasing Solids Retention Time in the Wastewater Treatment Process Affect the Persistence of Antibiotic Resistance Genes?". 2014 Southwest Onsite Wastewater Management Conference. Laughlin, NV.
• Mclain, J. E., Rock, C. M., Nolte, K. D., & Obergh, V. (2013, September). Development of BMPs for assessment of irrigation water quality following routine maintenance of unlined canals: an interim report. Yuma Grower's Association Training Session. Yuma, Arizona: University of Arizona Cooperative Extension.
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  Presented to approximately 50 grower professionals. Presentation focused on results from Arizona Department of Agriculture Grant Award #SCBGP-FB12-19.
• Nolte, K. D., Nolte, K. D., Rock, C. M., & Rock, C. M. (2013, Summer, 2013). Good Agricultural and Good Safety Practices: Compliance by Everyone?. American Society for Horticultural Science Annual Conference. Palm Desert, California.
• Nolte, K. D., Nolte, K. D., Rock, C. M., & Rock, C. M. (2013, Summer, 2013). The Track and Scat Fresh Produce Safety. American Society for Horticultural Science Annual Conference. Palm Desert, California.
• Thomure, T., Rock, C. M., Lansey, K. E., & Mclain, J. E. (2013, June). Approaches to maintain consistently high quality recycled water in storage and distribution systems. Webinar. Tucson, Arizona: WateReuse Research Foundation.
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  Two hour webinar sponsored by the WateReuse Foundation and attended by more than 200 subscribers. Presented results of 2008-2010 study funded by the WateReuse Research Foundation.

Poster Presentations

• Rock, C. M., Mclain, J. E., Brassill, N. A., & Joe, V. (2018, May). Quantifying and evaluating qPCR and ddPCR effectiveness on an impaired river using molecular source markers. Water Microbiology Conference. Chapel Hill, North Carolina: University of North Carolina.
• Rock, C. M., Mclain, J. E., Chief, K., Rivadeneira, P., Brassill, N. A., Joe, V., Rock, C. M., Mclain, J. E., Chief, K., Rivadeneira, P., Brassill, N. A., & Joe, V. (2018, February). Development of Native American-tailored produce and agricultural water safety trainings. University of Arizona Water Resources Research Center 2018 Annual Conference. Tucson, Arizona: University of Arizona Water Resources Research Center.
• Gerrity, D., Rock, C. M., Obergh, V., Dickenson, E., Neyestani, M., & Mclain, J. E. (2017, July). Impacts of free DNA on quantitative analysis of resistance genes through wastewater treatment. 4th International Symposium on the Environmental Dimension of Antibiotic Resistance. Lansing, Michigan.
• Joe, V., Mclain, J. E., Brassill, N., Carr, D., Suslow, T., & Rock, C. M. (2017, January/Spring). Evaluation of total Bacteroides as an alternative irrigation water quality indicator. AZ Water - Building our Sustainable Water Future Workshop. Tempe, Arizona: AZ Water.
• Joe, V., Mclain, J. E., Brassill, N., Carr, D., Suslow, T., & Rock, C. M. (2017, March). Evaluation of total Bacteroides as an alternative irrigation water quality indicator. SWESx Student Research Symposium. Tucson, Arizona: University of Arizona.
• Mclain, J. E., Batista, J., Dickenson, E., Rock, C. M., Gerrity, D., & Obergh, V. (2017, March). Occurrence, proliferation, and persistence of antibiotics and antibiotic resistance during wastewater treatment. Water Resources Research Center Annual Conference. Tucson, Arizona: WRRC.
• Mclain, J. E., Nolte, K., Rock, C. M., & Simons, J. (2017, March). Self-sterilizing harvesting tools. Water Resources Research Center Annual Conference. Tucson, Arizona: WRRC.
• Rock, C. M., Rosenberg Goldstein, R., Suri, M., Dery, J., Brassill, N., Pee, D., & Goeringer, P. (2017, December/Fall). Farmer Perceptions and Understanding of Irrigation Water from Nontraditional Sources. Ag Water Summit. Loveland, CO: Colorado Ag water Alliance.
• Rock, C. M., Rosenberg Goldstein, R., Suri, M., Dery, J., Brassill, N., Pee, D., & Goeringer, P. (2017, February/Spring). Farmer Perceptions and Understanding of Irrigation Water from Nontraditional Sources. Western Maryland Fruit Meeting. Keedysville, MD: University of Maryland Cooperative Extension.
• Rock, C. M., Rosenberg Goldstein, R., Suri, M., Dery, J., Brassill, N., Pee, D., & Goeringer, P. (2017, September/Fall). "Farmer Perceptions and Understanding of Irrigation Water from Nontraditional Sources ". Annual WateReuse Symposium. Phoenix, AZ: WateReuse Association.
• Rock, C. M., Suslow, T., Carr, D., Brassill, N., Mclain, J. E., & Joe, V. (2017, March). Evaluation of total Bacteroides as an alternative irrigation water quality indicator. Water Resources Research Center Annual Conference. Tucson, Arizona: WRRC.
• Rock, C. M., Zozaya, S., Dery, J., & Brassill, N. (2017, August/Summer). Would you CONSERVE?. CONSERVE Scholar Internship. Phoenix, AZ: USDA.
• Joe, V., Mclain, J. E., Brassill, N., Carr, D., Dalton, J., Suslow, T., & Rock, C. M. (2016, November). Evaluation of total Bacteroides as an alternative irrigation water quality indicator. 2016 ASA-CSSA-SSSA International Annual Meetings. Phoenix, Arizona: ASA-CSSA-SSSA.
• Simons, J., Mclain, J. E., Nolte, K. D., & Rock, C. M. (2016, November). Self-sterilizing harvesting tools and irrigation pipeline. 2016 ASA-CSSA-SSSA International Annual Meetings. Phoenix, Arizona: ASA-CSSA-SSSA.
• Malott, E., Rock, C. M., Mclain, J. E., Nolte, K. D., Rivadeneira, P., Rivadeneira, P., Nolte, K. D., Mclain, J. E., Malott, E., & Rock, C. M. (2015, June). Pathogen transmission to crops from animals. Western Food Safety Summit. Hartnell College of Agricultural Business, Salinas, California.
• Elissa, M., Nolte, K. D., Mclain, J. E., & Rock, C. M. (2014, March). Animal intrusion in crop fields analysis. WRRC 2014 Annual Conference. Tucson, Arizona: Water Resources Research Center.
• Elissa, M., Nolte, K. D., Mclain, J. E., Rivadeneira, P., & Rock, C. M. (2014, October). Pathogen transmission to crops from animals. Food Safety Consortium Annual Conference. Tucson, Arizona: University of Arizona Food Safety Consortium.
• Gudvangen, E., Brown, K., Walston, S., Rock, C. M., & Mclain, J. E. (2014, October). The critical challenge of antibiotic resistance: are wastewater treatment plants a concern?. Food Safety Consortium Annual Conference. Tucson, Arizona: University of Arizona Food Safety Consortium.
• Malott, E., Nolte, K. D., Mclain, J. E., & Rock, C. M. (2014, April). Animal intrusion in crop fields analysis. SWESx Earth Day Poster Presentation. Tucson, Arizona: Department of Soil, Water and Environmental Science.
• McOmber, T. C., Mclain, J. E., & Rock, C. M. (2014, April). Is treated wastewater effluent improving the water quality of the Upper Santa Cruz River?. SWESx Earth Day Poster Presentations. Tucson, Arizona: Department of Soil, Water and Environmental Science.
• McOmber, T. C., Rock, C. M., Mclain, J. E., & Curry, J. E. (2014, January). Water quality improvements for Southern Arizona on the Upper Santa Cruz River. Arizona Water Association Research Workshop. Tempe, Arizona.
• McOmber, T. C., Rock, C. M., Mclain, J. E., & Rivera, B. (2014, May). Water quality improvements for Southern Arizona on the Upper Santa Cruz River. Water and Health Conference. Chapel Hill, North Carolina: University of North Carolina School of Public Health.
• Mclain, J. E., & Rock, C. M. (2014, May). Recycled municipal wastewater and antibiotic resistance: is there a link?. CALS Poster Forum. Tucson, Arizona: College of Agriculture and Life Sciences.
• Mclain, J. E., Malott, E., McOmber, T., Obergh, V., & Rock, C. M. (2014, April). Posters (3) on subject matter related to water quality and the environment. Science of the Environment Earth Day Poster Presentation. Tucson, Arizona: Department of Soil, Water and Environmental Science.
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  Three posters were presented by students working in the McLain laboratory: Animal Intrusion in Crop Fields (Elissa Malott, presenter); Is Treated Wastewater Effluent Improving the Water Quality of the Upper Santa Cruz River? (Todd McOmber, presenter); Canal Maintenance Effects on Irrigation Water Quality (Victoria Obergh, presenter). Of note is that poster judges awarded Elissa Malott an honorable mention for her poster presentation.
• Mclain, J. E., Obergh, V., Malott, E., Willis, R., Joe, V., Gudvangen, E., & Rock, C. M. (2014, October). Posters (5) on subject matter related to food safety. 5th Annual University of Arizona Food Safety Conference. Tucson, Arizona: University of Arizona Food Safety Conference.
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  Students from the McLain laboratory presented five posters: The Critical Challenge of Antibiotic Resistance: Are Wastewater Treatment Plants a Concern? (Emily Gudvangen, presenter); Food Safety Impacts of Compost Teas in Organic Agriculture (Valerisa Joe, presenter); Pathogen Transmission to Crops From Animals (Elissa Malott, presenter); Canal Maintenance Effects on Irrigation Water Quality (Victoria Obergh, presenter); Abundance of Antibiotic-Resistant E. coli in Recycled vs. Potable Water Systems (Rachael Willis, presenter). Note: Elissa Malott won a second place poster prize; Victoria Obergh won a third place poster prize.
• Mclain, J. E., Obergh, V., McOmber, T., Malott, E., Joe, V., & Rock, C. M. (2014, April). Posters (4) on subject matter related to water quality. University of Arizona Water Resources Research Center Annual Conference. Tucson, Arizona: University of Arizona WRRC.
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  Four students working in the McLain lab were poster authors: Identifying Chicken Fecal Contamination in the Chesapeake Bay Using Quantitative PCR Assays (Valerisa Joe, presenter); Animal Intrusion in Crop Fields (Elissa Malott, presenter); Is Treated Wastewater Effluent Improving the Water Quality of the Upper Santa Cruz River? (Todd McOmber, presenter); Canal Maintenance Effects on Irrigation Water Quality (Victoria Obergh, presenter). Of note is that Todd McOmber won a second place prize for most effective poster presentation (out of 24 posters displayed).
• Mclain, J. E., Rock, C. M., & Brown, K. (2014, July). The critical challenge of antibiotic resistance: are wastewater treatment plants a concern?. Arizona Partners in Science Summer Poster Presentation. University of Arizona: Arizona Partners in Science.
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  Kourtney Brown, a teacher-intern through Arizona Partners in Science (mentored by Jean McLain) presented first year of summer research.
• Obergh, V., Nolte, K. D., Rock, C. M., & Mclain, J. E. (2014, October). Canal maintenance effects on irrigation water quality. Food Safety Consortium Annual Conference. Tucson, Arizona: University of Arizona Food Safety Consortium.
• Obergh, V., Rock, C. M., Nolte, K. D., & Mclain, J. E. (2014, April). Canal maintenance effects on irrigation water quality. SWESx Earth Day Poster Presentation. Tucson, Arizona: Department of Soil, Water and Environmental Science.
• Obergh, V., Rock, C. M., Nolte, K. D., & Mclain, J. E. (2014, March). Canal maintenance effects on irrigation water quality. WRRC 2014 Annual Conference. Tucson, Arizona: Water Resources Research Center.
• Rock, C. M. (2014, Spring). Complying with Irrigation Water Quality Criteria in Arid Regions: Lessons Learned from Imperial Valley, CA and Yuma Arizona. Western Food Safety Summit. Dav.
• Rock, C. M., & Gerba, C. P. (2014, 08/2014). The Assessment of Escherichia coli as an Indicator of Microbial Quality of Irrigation Waters Used for Produce. IAFP 2014. Indianapolis, IN.
• Russell, M. J., Nolte, K. D., Atwill, R., Bond, R., & Rock, C. M. (2014, 08/2014). Evaluation of Indicator Escherichia coli, Fecal Coliforms, E coli O157 and Salmonella spp. in Surface Waters of the Southwest Desert Canal Network. IAFP 2014. Indianapolis, IN.
• Todd, M. C., Mclain, J. E., & Rock, C. M. (2014, March). Is treated wastewater effluent improving the water quality of the Upper Santa Cruz River?. WRRC 2014 Annual Conference. Tucson, Arizona: Water Resources Research Center.
• Brassil, N., Rock, C. M., Mclain, J. E., & Nolte, K. D. (2013, June). Assessment of Escherichia coli as an indicator of microbial quality of irrigation waters used for produce. 113th Annual Conference of the American Society for Microbiology. Denver, Colorado: American Society for Microbiology.
• Mclain, J. E., Rock, C. M., Curry, J. E., & McOmber, T. (2013, October). Water quality improvements for Southern Arizona on the Upper Santa Cruz River. University of Arizona Food Safety Consortium Annual Meeting. Tucson, Arizona: UA-Food Safety Consortium.
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  Poster presentation of Master's Level Research.
• Walston, S., Mclain, J. E., Abrell, L. M., Gerrity, D., & Rock, C. M. (2013, May). Does increasing solids retention time in the wastewater treatment process affect the persistence of antibiotic resistance genes?. 86th Annual AZWater Conference. Glendale, Arizona: AZWater.
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  Poster presentation of Master's Research.
• Walston, S., Rock, C. M., Mclain, J. E., Abrell, L. M., & Gerrity, D. (2013, March). Does increasing solids retention time in the wastewater treatment process affect the persistence of antibiotic resistance genes?. Water Resources Research Center Annual Conference. Tucson, Arizona: UA-WRRC.
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  Poster Presentation of Master's Level Research.
• Walston, S., Rock, C. M., Mclain, J. E., Gerrity, D., & Abrell, L. (2013, April). Does increasing solids retention time in the wastewater treatment process affect the persistence of antibiotic resistance genes?. SWESx Earth Day Poster Presentation. Tucson, Arizona: Department of Soil, Water and Environmental Science.

Reviews

• Rock, C. M., Gerba, C. P., Walter, B., & Masaaki, K. (2018. Reducing uncertainty in estimating virus reduction by advanced water treatment processes(pp 282 - 288).
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  Treatment of wastewater for potable reuse requires the reduction of enteric viruses to levels that pose nosignificant risk to human health. Advanced water treatment trains (e.g., chemical clarification, reverseosmosis, ultrafiltration, advanced oxidation) have been developed to provide reductions of viruses todiffering levels of regulatory control depending upon the levels of human exposure and associated healthrisks. Importance in any assessment is information on the concentration and types of viruses in theuntreated wastewater, as well as the degree of removal by each treatment process. However, it is criticalthat the uncertainty associated with virus concentration and removal or inactivation by wastewatertreatment be understood to improve these estimates and identifying research needs. We reviewed thecritically literature to assess to identify uncertainty in these estimates. Biological diversity within familiesand genera of viruses (e.g. enteroviruses, rotaviruses, adenoviruses, reoviruses, noroviruses) and specificvirus types (e.g. serotypes or genotypes) creates the greatest uncertainty. These aspects affect themethods for detection and quantification of viruses and anticipated removal efficiency by treatmentprocesses. Approaches to reduce uncertainty may include; 1) inclusion of a virus indicator for assessingefficiency of virus concentration and detection by molecular methods for each sample, 2) use of virusesmost resistant to individual treatment processes (e.g. adenoviruses for UV light disinfection and reovirusesfor chlorination), 3) data on ratio of virion or genome copies to infectivity in untreated wastewater,and 4) assessment of virus removal at field scale treatment systems to verify laboratory and pilot plantdata for virus removal.

Creative Productions

• Rock, C. M., & Rivadeneira, P. (2017. Food Safety Precautions Around Fresh Produce Fields (Fact Sheet). Cooperative Extension publicationUniversity of Arizona Cooperative Extension.

Creative Performances

• Brassill, N. A., Rock, C. M., Rivadeneira, P., Lopez, T., Barnett, N., Brown, M., & Funk, A. (2019. Field Demonstration: Food Safety Modernization Act Produce Safety Rule On-Farm Readiness Review. Grower Orientation. Yuma Agricultural Center, Yuma, Arizona: Arizona Department of Agriculture.

Case Studies

• Rock, C. M., & Thomure, T. (2017. Guidance Framework for Direct Potable Reuse in Arizona(pp 1-118).
• Rock, C. M., Cotruvo, J., Dadakis, J., Haber, L., Nelson, K., & Thrupp, G. (2017. Final Panel Report - Independent Advisory Panel for Soquel Creek Water District’s Pure Water Soquel Groundwater Replenishment Project(pp 1-43).

Other Teaching Materials

• Rivadeneira, P., Mclain, J. E., Carr, D., Rock, C. M., Nolte, K. D., & Renick, K. (2015. Scat and Track Guidebook for the Southwest. University of Arizona.
• Rock, C. M., & Carr, D. (2015. Español: Educación en Seguridad Alimentaria - Microbiología. University of Arizona.
• Rock, C. M., & Carr, D. (2015. Microbiology and Biofilm Intervention Food Safety Course. University of Arizona.
• Rock, C. M., Carr, D., Gerba, C. P., Bright, K., & Tamimi, A. (2015. AgWater App. University of Arizona.

Others

• Cooper, M. A., Li, S., Woolfolk, C. M., Cooper, M. A., Li, S., & Woolfolk, C. M. (2022, November). Keeping Food Safe at Home. IPM Newsletter.
• Brassill, N. A., Rock, C. M., Li, S., & Gouge, D. H. (2019, January). IPM for Microorganisms with a Focus on Influenza Viruses. Online distribution network and distribution list. https://cals.arizona.edu/apmc/docs/2019JanuaryAZschoolandhomeIPMNewletter.pdf
• Gouge, D. H., Li, S., Rock, C. M., & Brassill, N. A. (2019, January). IPM for Microorganisms with a Focus on Influenza Viruses. Online network and distribution list. https://cals.arizona.edu/apmc/docs/2019JanuaryAZschoolandhomeIPMNewletter.pdf
• Li, S., Rock, C. M., & Gouge, D. H. (2018, February). IPM for Microorganisms – Focus on Flu Part 2. School & Home IPM Newsletter. https://cals.arizona.edu/apmc/docs/2018FebruaryAZschoolandhomeIPMNewletter.pdf
• Li, S., Rock, C. M., Brassill, N. A., & Gouge, D. H. (2018, January). IPM for Microorganisms: Cleaning, Disinfecting, and Sanitizing. School & Home IPM Newsletter. https://cals.arizona.edu/apmc/docs/2018JanuaryAZschoolandhomeIPMNewletter.pdf
• Rock, C. M., & Rivadeneira, P. (2017, March). AZ1753: Food Safety Precautions Around Fresh Produce Fields. Arizona Cooperative Extension. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1753-2017.pdf
  More info

  Food safety is a high priority for fresh produce growers, not only because of new regulations related to the Food Safety Modernization Act, but because they care about the health and safety of their customers. Most fresh produce, like lettuce and other leafy greens, is eaten raw so growers have to be particularly diligent in following food safety protocols that will help to prevent foodborne pathogen contamination in their fields. Trained professionals conduct assessments of agricultural fields throughout the growing season to ensure that pathogens like Salmonella and E. coli do not contaminate the food we are going to eat. Salmonella and E. coli cause gastrointestinal distress, and in some cases, may even lead to kidney failure and death. If you find yourself near a fresh produce field during the growing season, whether you are working in the field or just visiting the area, adhering to the following guidelines will help prevent the introduction of pathogens into fresh produce fields.
• Artiola, J. F., Chief, K., Beamer, P., Wilkinson, S. T., Maier, R. M., Rock, C. M., & Sanchez, C. A. (2016, April). The Gold King Mine Spill: Can it Impact Water Users below Lake Powell Reservoir and Yuma Farmers?. University of Arizona, College of Agriculture & Life Sciences, Cooperative Extension. http://arizona.openrepository.com/arizona/bitstream/10150/607717/1/az1698-2016.pdf
• Chief, K., Artiola, J. F., Beamer, P., Wilkinson, S. T., Maier, R. M., Rock, C. M., Sanchez, C. A., Chief, K., Artiola, J. F., Beamer, P., Wilkinson, S. T., Maier, R. M., Rock, C. M., & Sanchez, C. A. (2015, August). Understanding the Gold King Mine Spill. CALS publications Website. http://superfund.pharmacy.arizona.edu/info-material/gold-king-mine
  More info

  This bulletin was produced in response to questions arising about the Gold King Mine spill.
• Chief, K., Chief, K., Chief, K., Artiola, J. F., Artiola, J. F., Artiola, J. F., Beamer, P., Beamer, P., Beamer, P., Wilkinson, S. T., Wilkinson, S. T., Wilkinson, S. T., Maier, R. M., Maier, R. M., Maier, R. M., Rock, C. M., Rock, C. M., Rock, C. M., Sanchez, C. A., , Sanchez, C. A., et al. (2015, August). Understanding the Gold King Mine Spill. web. http://superfund.pharmacy.arizona.edu/info-material/gold-king-mine
  More info

  This bulletin was produced in response to questions arising about the Gold King Mine spill.
• Mclain, J. E., Rock, C. M., Eden, S., & Cusimano, J. (2015, June). Agricultural use of recycled water for crop production in Arizona. Arizona Cooperative Extension Publications.
• Mclain, J. E., Rock, C. M., & Anderson, H. (2014, August). Testing water for antibiotic-resistant bacteria. University of Arizona News. http://uanews.org/story/testing-water-for-antibiotic-resistant-bacteria
  More info

  News story written by University undergraduate Haley Anderson and edited by Jean McLain and Channah Rock, focused on research in the McLain and Rock labs.
• Artiola, J., Rock, C., & Hix, G. (2012, Fall). Water Storage Tank Disinfection, Testing, and Maintenance. Arizona Cooperative Extension..
• Rock, C. M. (2012, Fall). Water State Initiative 4. Arizona Cooperative Extension; Water State Initiative.
• Rock, C., McLain, J., & Gerrity, D. (2012, Fall). Common Terminology of Water Recycling. Arizona Cooperative Extension.
• Rock, C., McLain, J., & Gerrity, D. (2012, Fall). WateRecycling FAQs. Arizona Cooperative Extension.
• Rock, C., McLain, J., Scott, C., Graf, C., & Megdal, S. (2011, Fall). Arizona Blue Ribbon Panel on Water Sustainability. UA Extension Publication.
• Rock, C., McLain, J., Scott, C., Graf, C., & Megdal, S. (2012, Fall). Arizona Blue Ribbon Panel on Water Sustainability. UA Extension Publication.
• Rock, C., McLain, J., Scott, C., Graf, C., & Megdal, S. (2012, Fall). EPA WateReuse Guidelines. Arizona Blue Ribbon Panel on Water Sustainability.
• Uhlman, K., Eden, S., Rock, C., Westfall, E., & Sprouse, T. (2012, Fall). Effluent Dependent Streams of Arizona. Arizona Cooperative Extension.
• Riveria, B., & Rock, C. (2011, Fall). Microbial Source Tracking: Watershed Characterization and Source Identification. Arizona Cooperative Extension.
• Rock, C. M. (2011, Fall). Sources of Bacteria in Drinking Water. Drinking Water and Human Health eXtension Community of Practice.
• Rock, C. M. (2011, Fall). Sources of Pharmaceuticals and Personal Care Products (PPCPs) in Drinking Water. Drinking Water and Human Health eXtension Community of Practice.
• Rock, C. M. (2011, Fall). Sources of Protozoa and Amoeba in Drinking Water. Drinking Water and Human Health eXtension Community of Practice.
• Rock, C. M. (2011, Fall). Water State Initiative 3. Arizona Cooperative Extension; Water State Initiative.
• Sifuentes, L., Gerba, C., & Rock, C. (2011, Fall). Playing Safe in Natural Waters: How to Protect Yourself from Naegleria fowleri When You Go Swimming. Arizona Cooperative Extension.
  More info

  #AZ1545
• Rock, C. M. (2010, Fall). Molecular Source Tracking of Bacterial Pathogens in Surface Waters of Arizona. Arizona Department of Environmental Quality.
• Rock, C. M., & Rock, C. M. (2010, Fall). Arizona Cooperative Extension Water Website. http://ace.clover.cals.arizona.edu/water-portal/-your-watershed