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__VV_S!7f If a backwash is insufficient in removing foulants, the backwash efficiency can be enhanced by adding chemicals into the backwash (Chemically Enhanced Backwash). The CEB mode consists of a normal backwash procedure, a backwash with chemicals (these can be dosed after the backwash pump with a dosing unit), a soaking period and then a backwash to flush-out the chemicals. One 2-housing element OF membranes will be installed (with 100% redundancy) in the proposed WCMCRWWTP, along with the chemical enhanced backwash kits. Each element has a membrane area of 40 mz. The design net filtration flux is 48 L/mz/h and the recovery rate is 86.4%. The membranes have an average pore size of 0.025-0.028 pm and an absolute pore size of 0.03 pm. This ensures removal of all particulate matter larger than 0.03 pm, including colloids, solids and micro-organisms. There are two 500 micron strainers installed in the pipelines prior to entry to the membranes. 3.5 DISINFECTION The on-site chlorine-based disinfectant generation system is used for the WCMCRWWTP treated effluent disinfection. The disinfected water is discharged into the existing underground injection well. The most common chlorine contact tank configuration to use is a long plug-flow, around-the- end type of contact basins to assure a given percentage of the flow remains in the tank for a given period of time. To improve hydraulic performance, baffles are added in the chlorine contact tank. Figure 3 is a typical chlorine contact tank configuration. 1 T 1 T Figure 3 Schematic of typical chlorine contact tank configuration The theoretical contact time is 120 minutes and the model contact time is 90 minutes at the peak design flow (52 gpm). The operational volume of chorine contact tank is 6,336 gallons. The CT value shall be maintained at 450 mg-min/L, based upon Title 22 Disinfected Tertiary Recycling Water criteria. The MIOX system generates a chlorine-based disinfectant on-site as needed. The chlorine production capacity is designed to handle the peak demand for daily operations. One AE-4 unit shall be furnished and has 4 lbs/d chlorine generation capacity. A 24-hour reserve disinfectant supply is stored in an oxidant solution tank and injected into the water to be treated. Wine Cup Motor Coach Resort WWTP Page 8 of 10 8/22/2007 Preliminary Design Report