A. W. Olivieri – författare

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 Bay?s 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 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 publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below