Adam W. Olivieri

An analysis of the Milwaukee cryptosporidiosis outbreak based on a dynamic model of the infection process.

We combined information on the temporal pattern of disease incidence for the 1993 cryptosporidiosis outbreak in Milwaukee with information on oocyst levels to obtain insight into the epidemic process. We constructed a dynamic process model of the epidemic with continuous population compartments using reasonable ranges for the possible distribution of the model parameters. We then explored which combinations of parameters were consistent with the observations. A poor fit of the March 1–22 portion of the time series suggested that a smaller outbreak occurred before the March 23 treatment failure, beginning sometime on or before March 1. This finding suggests that had surveillance systems detected the earlier outbreak, up to 85% of the cases might have been prevented. The same conclusion was obtained independent of the model by transforming the incidence time series data of Mac Kenzie et al.1 This transformation is based on a background monthly incidence rate for watery diarrhea in the Milwaukee area of 0.5%.1 Further analysis using the incidence data from the onset of the major outbreak, March 23, through the end of April, resulted in three inferred properties of the infection process: (1) the mean incubation period was likely to have been between 3 and 7 days; (2) there was a necessary concurrent increase in Cryptosporidium oocyst influent concentration and a decrease in treatment efficiency of the water; and (3) the variability of the dose-response function in the model did not appreciably affect the simulated outbreaks. (Epidemiology 1998;9:255–263)

Water repurification via reverse osmosis

The City of San Diego in California, United States, (City) is developing new water sources to serve its arid region. Water repurification, in which reclaimed water receives additional advanced water treatment (AWT) prior to its discharge to a potable water supply reservoir, is one of the encouraging alternatives being implemented by the City to reduce the regions reliance on less dependable imported water. The City adopted the reverse osmosis (RO) process as the foundation for the AWT because RO has been shown to accomplish the best overall removal of organics, trace metals and total dissolved solids. In addition, RO has the potential for removal of all classes of pathogens. The California Department of Health Services (DHS) issued a conditional approval of the San Diego Water Repurification project in August, 1994. Several of the comments in the DHS conditional approval letter addressed the disinfection strategy and the reliability of the membrane processes in the AWT train. In response to the DHS comments, the City of San Diego initiated a major pilot testing program to evaluate the performance of various prequalified pretreatment and RO membranes. This program was initiated in 1995 and is still ongoing. Pursuant to the work performed at the Aqua2000 Research Center the DHS issued a letter on March 4, 1998, approving the Water Repurification System. The results of these studies demonstrated RO is a very effective and reliable process for water repurification. Minimal membrane fouling was observed for all of the polyamide RO membranes employed in the study. Significant contaminant rejection was achieved by all RO membrane purifying the reclaimed water to meet and exceed drinking water standards. Wide range of virus rejection was observed for the RO membranes which was dependent on the RO membrane type/manufacturer. The system consistently produces a product water that exceeds all drinking water standards.

Risk-Based Review of California’s Water-Recycling Criteria for Agricultural Irrigation

AbstractCalifornia currently recycles treated wastewater at a volume of approximately 8.0×108  m3 of water per year, with a potential to recycle an additional 1.9×109  m3 per year. A key challenge in promoting the expansion of water recycling for agricultural purposes was addressing the perceived concern about whether recycled water produced in conformance with California law is protective of public health. The California Department of Public Health (CDPH) established an expert panel to consider the concern. The panel found, based on quantitative microbial risk assessment (QMRA), that the annualized median risks of infection for full tertiary treatment ranges from 10−8 to 10−4 (for human enteric viruses Cryptosporidium parvum and Giardia lamblia, and Escherichia coli O157:H7) based on the assumption of daily exposure. The panel found that risk estimates are consistent with previous CDPH estimates and concluded that current agricultural water recycling regulations do not measurably increase public health risk.

Evaluation of Microbial Risk Assessment Techniques and Applications

This investigation reviewed and evaluated methodologies used for microbial risk assessment with respect to their applicability for reclaimed water applications. The investigation was comprised of five primary components: a comprehensive database of articles, reports and books describing microbial risk assessment methodologies was established and reviewed. Risk assessment techniques and models were identified for estimating the public health risk from exposure to microorganisms via reclaimed water applications. Two models were identified for further evaluation: a static (individual based) and a dynamic (population based).In the third component, the two models were evaluated to differentiate between the conditions under which models predict similar and substantially different estimations of risk. Through numerical simulation, exposure/pathogen combinations were identified when it may be appropriate to use the less complex, static model. Case study risk assessment scenarios demonstrated the model selection process for three realistic, yet hypothetical reclaimed water scenarios. The fourth component presents a constraint analysis for existing reuse regulations. The constraint analysis is carried out by documenting the existing reuse regulations. The constraint analysis is carried out by documenting the existing regs in three states for landscape irrigation and uses that comparison as a starting point to identify how microbial risk assessment may be useful within the context of existing and potential future water reuse regulations. The investigation concludes by identifying criteria for a computer interface that would allow regulatory and/or municipal agencies/utilities to take advantage of the analysis discussed in the report. This title belongs to WERF Research Report Series ISBN: 9781780404141 (eBook) ISBN: 9781843396840 (Print)

City of San Diego potable reuse of reclaimed water: Final results

Abstract Water reclamation is becoming a common component of water resource planning. In the past the driving motivation for water reuse was to provide a means of avoiding effluent disposal into surface waters. With continued drought and increased water demand reclaimed wastewater is now considered an important water resource. Nonpotable and potable use of reclaimed water can enable communities to maximize and extend the use of limited water resources. This paper summarizes results from the Health Effects Study (HES) portion of the City of San Diegos Total Resource Recovery Project, which includes study and implementation of an advanced wastewater treatment system. The HES represents the product of a substantial research effort to estimate the potential health risk associated with the reclaimed water relative to an existing raw water supply to the City.

Development of a Protocol for Risk Assessment of Microorganisms in Separate Stormwater Systems

Recent research has shown that the concentrations of microbial indicator organisms (e.g., fecal coliforms) in stormwater may be quite high. However, studies have not clearly established relationships between the concentrations of indicator organisms and microbial pathogens in stormwater, or between stormwater indicator organism concentrations and illness. Thus, it is difficult to interpret indicator data collected by local public agencies in the context of potential risk to human health. The primary objective of this investigation was to generate guidance to enable more accurate and defensible evaluations of stormwater microorganism data and the associated risks to human health from exposure to microbial pathogens in stormwater. The investigation consisted of three major tasks: reviewing and summarizing relevant published literature, conducting a web-based data questionnaire and developing a science-directed data collection plan. Topics discussed include: 1. waterborne pathogens that pose the greatest risk to human health, 2. concentrations of pathogens and indicator organisms observed in stormwater, 3. defensible relations between indicator organisms and pathogens of public health concern in stormwater, 4. the environmental fate of pathogens and indicator organisms in stormwater, 5. the use of microbial source tracking (MST) techniques to identify sources of fecal contamination, and 6. the effectiveness of stormwater microorganism control technologies and associated costs. Additionally, recommended next steps needed to enable defensible evaluations of stormwater microorganism data and the associated risk to human health from exposure to stormwater are presented. Next steps include the development of interim guidance for management prioritization, pathogens enumeration method development, and pilot and nation-wide data collection programs. This title belongs to WERF Research Report Series ISBN: 9781843397670 (Print) ISBN: 9781780403809 (eBook)

Aquatic biomonitoring of reclaimed water for potable use: The San Diego health effects study

Highly treated reclaimed wastewater was evaluated as a possible supplement to raw water sources required to meet San Diegos growing need for potable water. Biomonitoring experiments employing fathead minnows (Pimephales promelas) were used to compare reclaimed water with the citys current raw water supply. Juvenile fish were exposed in flow-through aquaria in field laboratories located at the reclamation plant (AQUA II) and at a municipal potable water treatment facility (Miramar). Biomonitoring measurements were survival and growth, swimming performance, and trace amounts of 68 base/neutral/acid extractable organics, 27 pesticides, and 27 inorganic chemicals found in fish tissues after exposure. Biomonitoring revealed differences in survival, growth, and swimming performance only after 90- and 180-d exposure. Reclaimed water and raw water were not readily distinguishable in 28-d chemical bioaccumulation tests in terms of organic chemical contaminants in fish tissue except for pesticide levels, which tended to be higher in raw water. Similar inorganic species were found in samples from both waters, although there was greater evidence of bioaccumulation of certain contaminants from raw water. Based on biomonitoring parameters included in these experiments, the use of reclaimed water to supplement raw water supplies would appear to pose no major public health threats. The results of these studies will be combined with additional health effects information before final conclusions are reached about the suitability of reclaimed water for human consumption.

A quantitative microbial risk assessment of wastewater treatment plant blending: case study in San Francisco Bay

An investigation was carried out to evaluate the impacts of blending practices (i.e., a practice used to manage wet weather flows) on the effluent from the East Bay Municipal Utility Districts (EBMUD) wastewater treatment plant in Oakland, California and water quality in the receiving water (San Francisco Bay). A static based quantitative microbial risk assessment (QMRA) was used to estimate the incremental risk to public health from recreational exposure to adenovirus and the protozoan Giardia spp. in San Francisco Bay for wet season (generally between October and March) blending and non-blending events. The mean risks of infection per recreational exposure event during the wet season for all of the modeled scenarios were more than an order-of-magnitude below the USEPAs illness level (36 illnesses per 1000 contact events) associated with recreational water quality. While the QMRA results showed discernible differences in per event estimated risks between blending and non-blending scenarios, the estimated incremental increase in the annual number of infections due to blending (based on median estimates) resulted in an estimated combined increase of less than one infection annually. These estimates are subject to various uncertainties, including the potential for secondary transmission, assumptions on the extent of exposures, and the number of blending days required in the future due to climate change, which are discussed in this paper.

Development of a Water Quality Model to Support a Pathogen TMDL (Newport Bay, California, USA)

Newport Bay (Orange County, California) is listed by the California State Water Resources Control Board (SWRCB) as a water quality limited receiving water body because of sporadic exceedances of the fecal coliform water quality objectives for body contact recreation. Consistent with federal and state requirements, a Total Maximum Daily Load (TMDL) is being implemented in the watershed. The fecal coliform TMDL in Newport Bay is a phased approach for understanding and controlling the microbiological water quality in the to ensure the reasonable protection of the Bays beneficial uses. An important initial step within that TMDL was to assess the impairment of the body contact recreation beneficial use (REC-1) of Newport Bay receiving waters through characterizing the risk of illness associated with REC-1 exposure. A health risk assessment investigation was developed to characterize that risk. The health risk assessment investigation involved the integration of a population based model of disease transmission, a water quality modeling component necessary for estimating pathogen dose as part of the exposure assessment, and site-specific population use and receiving water data collection. The Water Environment Research Foundation funded the water quality modeling component of the health risk assessment investigation, which is the focus of this report. Also provided within this report is an overview of the health risk assessment methodology, a summary of the major findings from the risk assessment investigation, and a discussion of how the health risk methodology may be applied to other watersheds where impairment of the REC-1 beneficial use is in question. The major findings of the health risk assessment investigation indicated that (1) the risk of illness from REC-1 use in Newport Bay, estimated using two separate methods was generally below levels considered tolerable by US EPA, and (2) the reduction of controllable sources of pollution would not appreciably reduce the existing risk. Based on the collection of site-specific exposure data and the health risk characterization, it was determined that evaluating the impairment of the REC-1 beneficial use requires a more rigorous and comprehensive health based approach than that prescribed by the current regulations for recreational waters. This title belongs to WERF Research Report Series ISBN: 9781843396642 (Print) ISBN: 9781780403137 (eBook)

INVESTIGATION AND CLEANUP OF FUEL TANK LEAKS IN THE SAN FRANCISCO BAY AREA—A REGULATORY STRATEGY

ABSTRACT During the past few years, contamination associated with underground chemical storage has been found to have caused extensive degradation of otherwise usable groundwater in many locations. In response, many cities within the San Francisco Bay area are presently implementing ordinances that require monitoring of underground tanks including fuel tanks. In addition, recently enacted state laws will require some form of rigorous monitoring for fuel tanks throughout California. Implementation of fuel leak monitoring programs will result in the discovery of a significant number of additional fuel leak sites. The authors project that 200 to 300 reports of subsurface fuel contamination will be generated during the next year in the San Francisco Bay area. To deal with this overwhelming increase in regulatory workload it is likely that some level of initial response to fuel leaks may be delegated to local governments. For the above reasons, the California Regional Water Quality Control Board, San Francisco...