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The City of Stockton, CA operates a wastewater treatment facility that discharges tertiary treated effluent during the summer and secondary treated effluent during the winter to the San Joaquin River. Investigations were carried out between 1996 and 2002 to provide insight regarding the potential public health benefit that may be provided by year-round tertiary treatment. A hydraulic model of the San Joaquin River and a dynamic disease transmission model integrated a wide array of disparate data to estimate the level of viral gastroenteritis in the population under the two treatment scenarios. The results of the investigation suggest that risk of viral gastroenteritis attributable to the treatment facility under the existing treatment scheme is several orders of magnitude below the 8-14 illnesses per 1000 recreation events considered tolerable by U.S. EPA, and winter tertiary treatment would further reduce the existing risk by approximately 15-50%. The methodologies employed herein are applicable to other watersheds where additional water treatment is being considered to address public health concerns from recreation in receiving waters.

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Given the pressures on the world's freshwater resources, recycled water is a valuable resource. Recycled water can increase the reliability of water supply because it is an independent source of water. Water recycling requires effective measures to protect public health and the environment. In the absence of comprehensive international guidelines, different countries have developed different approaches to managing water recycling depending on the understanding of the health risks, their individual economic circumstances, and affordability. Approaches vary between high technology/high cost/low risk and low technology/low cost/controlled risk. Furthermore, differences occur between countries and within individual countries. Inconsistencies can often be traced to lack of a unified scientific position on health effects. These inconsistencies increase public concerns about health risks and may give rise to conservative controls on responses to water recycling projects that some countries may be unable to afford. In this paper, an international panel of authors discusses how the different water recycling approaches might be linked together into international water recycling guidelines. These guidelines would incorporate a uniform approach to assessing hazards and risks while providing flexibility for individual countries to vary requirements to suit local circumstances of affordability and risk. The authors propose a framework of guidelines in which individual countries can progressively improve recycled water quality as lower risk levels become more affordable. The authors argue that a uniform international approach will result in a number of benefits including a better focus on risk management, better targeted research and development efforts and greater public confidence in water recycling. The authors invite discussion on the concepts put forward in the paper.

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