The State of California's WastewaterReclamationCriteria is under review and will be revised and expanded to include several new regulations on the use of reclaimed municipal wastewater. To provide a scientific basis for the evaluation of the existing and proposed Criteria, enteric virus monitoring data from secondary and tertiary effluents were evaluated. These virus data were obtained from special studies and monitoring reports, covering the period from 1975 to 1989, including ten municipal wastewater treatment facilities in California. Based on the enteric virus data from these reports, and using the current Criteria as a guide, four exposure scenarios were developed to determine the risk of waterborne enteric virus infection to humans as a consequence of wastewater reclamation and reuse. The exposure assessments included food crop irrigation, landscape irrigation for golf courses, recreational impoundments, and ground water recharge. The virus enumeration and the resulting risk assessments described in this paper provide a comparative basis for addressing the treatment and fate of enteric viruses in wastewater reclamation and reuse. The analyses show that annual risk of infection from exposure to chlorinated tertiary effluent containing 1 viral unit/100 L in recreational activities such as swimming or golfing is in the range of 10−2 to 10−7, while exposures resulting from food-crop irrigation or groundwater recharge with reclaimed municipal wastewater is in the range of 10−6 to 10−11. The risk analyses are also used to demonstrate that the probability of infection can be further mitigated by controlling exposure to reclaimed wastewater in the use area.

Evaluating the reliability of treatment processes and treatment facilities should be an important part of the planning and design process for water resource, wastewater treatment, and particularly wastewater reuse projects. With the recent developments in technology, particularly the development of membrane processes and alternative disinfection processes for water and wastewater treatment, there is an increasing need for a common methodology to evaluate the reliability of alternative processes and treatment facilities that utilize different combinations of those processes. To assess the reliability of a treatment facility, several aspects of treatment must be considered including a methodical evaluation of both mechanical reliability and plant performance. A straightforward method for conducting these types of analyses is described herein along with a description of applications of this methodology. A discussion is provided highlighting the value of such a methodology for both the water quality engineer and the risk manager.

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A hypochlorite ion degradation model helps utilities using liquid bleach to develop control strategies to minimize formation of chlorate ion. Studies have led to an understanding of how chlorate ion (ClO3–) formation in the pH 6–13 region from decomposing bleach is affected by pH, temperature, NaOCl concentration, chloride ion concentration (by means of an ionic strength effect), and transition metal ion impurities. The hypochlorite ion degradation model developed by Gordon and Adam predicts free available chlorine decomposition, ClO3– formation, and oxygen generation. Thus, a utility applying liquid bleach can use this newly developed model to predict the time‐dependent changes that occur in stored liquid bleach and to develop chemical specifications and control strategies to minimize the formation of ClO3– during the storage of sodium hypochlorite. The field studies reported here provide verification of the model showing a strong correlation between the model predictions and the measured data taken in the field.