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WASTE DISCHARGE REQUOMENTS ORDER NO. R5-2004-002* -24- CITY OF MANTECA, CITY OF LATHROP AND DUTRA FARMS WASTEWATER QUALITY CONTROL FACILITY SAN JOAQUINCOUNTY Filtration is an effective means of reducing viruses and parasites from the waste stream. Filtration is also necessary prior to UV disinfection to prevent any solids from interfering with the performance of the UV disinfection system. The wastewater must be treated to tertiary standards(filtered)to protect contact recreation and food crop irrigation uses and to assure the reliability and effectiveness of UV disinfection. The California Department of Health Services (DHS) has developed reclamation criteria, CCR, Title 22, Division 4, Chapter 3 (Title 22), for the reuse of wastewater. Title 22 requires that for spray irrigation of food crops, parks,playgrounds, schoolyards, and other areas of similar public access,wastewater be adequately disinfected, oxidized, coagulated, clarified, and filtered, and that the effluent total coliform levels not exceed 2.2 MPN/100 ml as a 7-day median. Title 22 is not directly applicable to surface waters;however, the Regional Board finds that it is appropriate to apply DHS' reclamation criteria because the San Joaquin River is used for irrigation of agricultural land and for contact recreational purposes. The stringent disinfection criteria of Title 22 are appropriate since the relatively undiluted effluent may be used for the irrigation of food crops. Coliform organisms are intended as an indicator of the effectiveness of the entire treatment train and the effectiveness of removing other pathogens. The method of treatment is not prescribed by this Order; however, wastewater must be treated to a level equivalent to that recommended by DHS. In addition to coliform testing, a turbidity effluent limitation has been included as a second indicator of the effectiveness of the treatment process and to assure compliance with the required level of treatment. The tertiary treatment process, or equivalent, is capable of reliably meeting a turbidity limitation of 2 nephelometric turbidity units (NTU) as a daily average. Failure of the filtration system such that virus removal is impaired would normally result in increased particles in the effluent,which would result in higher effluent turbidity. Turbidity has a major advantage for monitoring filter performance, allowing immediate detection of filter failure and rapid corrective action. Coliform testing,by comparison, is not conducted continuously and requires several hours, to days,to identify high coliform concentrations. The establishment of tertiary limitations has not been previously required for this discharge; therefore, a schedule for compliance with the tertiary treatment requirements is included as a Provision in this Order. This Order provides interim effluent limitations for BOD, TSS, and total coliform,which the Discharger is currently capable of meeting. Full compliance with the final effluent limitations for BOD, TSS, total coliform, and turbidity are not required by this Order until completion of tertiary treatment facilities, or 1 February 2009,whichever is first. Adequate time is provided for the Discharger to propose alternatives that are still protective of public health and irrigation uses, but at a reduced cost. The permit may be reopened at such time as the Discharger proposes an alternative that is protective of public health and irrigation uses. Alternatives to tertiary treatment, such as expanded land disposal, would require modification of the permit. 58. This Order contains Effluent Limitations and a tertiary level of treatment, or equivalent, necessary to protect the beneficial uses of the receiving water. In accordance with California Water Code, Section 13241, the Regional Board has considered the following: