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Solids Thickening and Digestion <br /> Sludge removed in the secondary treatment process is thickened in two DAF units,where air is injected into the <br /> activated sludge to separate the solids from the liquid. The sludge is then sent to two anaerobic digesters where <br /> organic constituents within the solids are broken down("digested")in the absence of oxygen(anaerobic). <br /> The purpose of the anaerobic digestion process is to reduce the mass of solids, stabilize the organic material, <br /> reduce the pathogen content of the solids, and produce a combustible gas that can be used for sludge heating and <br /> electricity generation. <br /> Solids Dewatering and Disposal <br /> A high-solids sludge centrifuge is then used to dewater the sludge. Dewatered"cake"from the centrifuge is <br /> discharged at a solids content of approximately 30-50%onto a solids handling conveyor and then discharged to a <br /> biosolids composting and storage area,where it is then trucked off-site to a local landfill for disposal. The <br /> conveyor discharge is located at a height that can accommodate truck loading.No biosolids are land-applied on- <br /> site. <br /> SUPPORT WASTEWATER QUALITY CONTROL FACILITIES <br /> Odor Control <br /> A control system for wastewater odors was recently installed next to the influent pump station. The soil filter, or <br /> biofilter,uses bacteria to remove the majority of odor compounds without needing to use large quantities of <br /> chemicals. Foul air is blown through the bottom of the soil filter through a distribution system or perforated pipe, <br /> and as the air comes in contact with the bacteria,the bacteria consumes the hydrogen sulfide and other odor <br /> compounds. <br /> Electrical Service and Power Distribution <br /> The plant's normal power supply is provided by Pacific Gas and Electric Company(PG&E). Power is distributed <br /> throughout the plant via a 17-kilovolt(W)feeder circuit that links all major unit processes. <br /> Other Support Facilities <br /> Operation of the Manteca WQCF is accomplished by 23 full-time personnel. The plant also serves as a staging <br /> location for two staff members dedicated to maintenance of the wastewater collection system. Two buildings at <br /> the WQCF house staff functions: the Operations and Maintenance Building and the Administration Building. <br /> WASTEWATER COLLECTION SYSTEM OVERVIEW <br /> The existing wastewater collection system consists of gravity flow pipes that are 6-60 inches in diameter, force <br /> mains that are 6-24 inches in diameter, and 13 wastewater pump stations. The majority of the collection system <br /> serves the core of the City(i.e.,the central trunk sewer shed). The majority of the collection system within the <br /> central trunk sewer shed flows by gravity to the Union Road pump station(located at the intersection of Union <br /> Road and Center Street). Downstream of the Union Road pump station,wastewater flows to the WQCF by gravity <br /> via a 36-inch diameter sewer. The existing collection system alignment is shown on Exhibit 3-2. <br /> 3.7 PROPOSED WQCF AND COLLECTION SYSTEM MASTER PLAN <br /> CHARACTERISTICS <br /> The proposed project would expand WQCF capacity from 9.87 to 27 mgd ADWF and construct new trunk sewers <br /> to accommodate growth planned for in the City general plan(2003), and construct a new recycled water <br /> Manteca WQCF and Collection System Master Plans EIR EDAW <br /> City of Manteca 3-15 Project Description <br />