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and those with densities less than water will float to the surface. To mitigate potential odors,the basins will be <br /> covered and odor control will be accomplished by routing foul air to a biofilter(City of Manteca 2007). <br /> Secondary Treatment <br /> Seven new aeration basins, each rated for an average flow rate of 2.5 mgd, are also proposed at the SSF. The <br /> proposed basins would include five zones separated by baffle walls. The baffle walls create a serpentine flow <br /> pattern,which reduces the potential for hydraulic short-circuiting. The basins would be operated in a plug flow <br /> fashion with an initial anoxic zone, followed by four aerated zones. Carbonaceous BOD removal and nitrification <br /> would be accomplished in the aerated zones.Nitrified wastewater would be recirculated back to the first anoxic <br /> zone for nitrate removal. Without aeration,the first zone in each basin would become anoxic. Under anoxic <br /> conditions,nitrate produced in the aerated zones would be reduced to nitrogen gas to achieve the required degree <br /> of total nitrogen removal. Internal recirculation pumps will be sized for a flow rate of 11.5 mgd for each aeration <br /> basin to accommodate peak flow rates. <br /> Mixed liquor from the aeration basins would be conveyed to seven new secondary clarifiers that are 110 feet in <br /> diameter for sludge separation before filtration and disinfection. The secondary clarifiers are sized based on <br /> recommended overflow rates and solids loading rates for nitrifying activated sludge systems. <br /> A RAS pumping station consisting of seven RAS pumps(six duty and one standby)would provide RAS <br /> pumping. The total design RAS flow of approximately 27 mgd is equal to 70%of the peak design flow of <br /> 38.4 mgd. If necessary,the standby RAS pump is available to increase the total RAS flow rate to 31.5 mgd. <br /> WAS would be conveyed to seven DAF units for thickening before anaerobic digestion. WAS would be directed <br /> to the DAF units from the discharge side of the RAS pumps. Under average conditions,the RAS pumps would <br /> provide sufficient pressure to convey WAS to the DAF units without supplemental pumping. However,under <br /> periods of increasing wasting,booster pumps would be required to convey the WAS to the DAF units. Six inline <br /> booster pumps will be used for this purpose, and a seventh would be in place for redundancy(City of Manteca <br /> 2007). <br /> Effluent Filtration, Disinfection, and Disposal <br /> Nine effluent filters would be installed to remove the remaining TSS in the secondary effluent. Filters would be of <br /> a cloth disk type designed to comply with the turbidity requirements of Title 22 wastewater reuse criteria. <br /> Filtration would increase the downstream disinfection efficiency by removing the suspended solid particles that <br /> are disinfection obstacles. <br /> To achieve Title 22 turbidity requirements, chemical addition before filtration may be necessary, especially <br /> during high solids loading conditions. Therefore, chemical addition facilities would be necessary to add <br /> coagulants and polymers to the effluent before the filters. Two rapid mixing tanks and six flocculation tanks <br /> would be constructed to provide efficient mixing of chemicals and to form larger sized flocs that are easily <br /> filterable. <br /> To comply with the Title 22 reuse criteria for unrestricted reuse, filtered effluent must also be disinfected. <br /> For reasons of worker safety, environmental protection,and operational flexibility, a low-pressure high-intensity <br /> UV light disinfection system, including four new UV channels,would be installed. The system would include <br /> effluent pumps to convey tertiary-treated wastewater through a new parallel outfall. <br /> The WQCF currently disposes of treated effluent via land application to City-owned property surrounding the <br /> WQCF or discharge to the San Joaquin River.At plant buildout,the City proposes to discharge treated effluent <br /> through a combination of on-site land application,urban landscape irrigation, and discharge to the San Joaquin <br /> River. On-site land application would involve the disposal of approximately 0.73 mgd of wastewater on 190 acres <br /> EDAW Manteca WQCF and Collection System Master Plans EIR <br /> Project Description 3-20 City of Manteca <br />