Don M. Eisenberg

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.

A Dynamic Model to Assess Microbial Health Risks Associated with Beneficial Uses of Biosolids - Phase 1

There is increasing interest in the development of a microbial risk assessment methodology for regulatory and operational decision making. This document presents a methodology for assessing risks to human health from pathogen exposure using a population-based model that explicitly accounts for properties unique to an infectious disease process, specifically secondary transmission and immunity. To demonstrate the applicability of this risk-based method, numerical simulations were carried out for a case study example in which the route of exposure was direct consumption of biosolids-amended soil and the pathogen present in the soil was enterovirus. The output from the case study yielded a decision tree that differentiates between conditions in which the relative risk from biosolids exposure is high and those conditions in which the relative risk from biosolids is low. This decision tree illustrates the interaction among the important factors in quantifying risk. For the case study example, these factors include biosolids treatment processes, the pathogen shedding rate of infectious individuals, secondary transmission, and immunity. Further refinement in methods for determining biosolids exposures under field conditions would certainly increase the utility of these approaches.

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.

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...