A community with a wastewater flow during the peak month of the year of 2.0 mgd at 15°C is...

A community with a wastewater flow during the peak month of the year of 2.0 mgd at 15°C is considering constructing a new treatment plant. The composition of the raw wastewater is as shown in Table 12.1, and the effluent limits are 30 mg/l of BOD, 30 mg/l of suspended solids, and fecal conform count of less than 200 per 100 ml. Sketch flow diagrams for the treatment systems listed below, showing the arrangement of unit processes (i.e.. tanks, pumping stations, and division boxes) and major pipelines (i.e., for wastewater, recycle, and sludge). Assume sludge stabilization is by anaerobic digestion and dewatering by belt filler presses. Duplication of treatment units is necessary, so if any unit is out of service for main­tenance the wastewater can still be processed through the plant, although the effluent qual­ity may be reduced. No pipelines are allowed to bypass raw or settled wastewater to the plant outlet. Standby generators arc provided for emergency operation during electrical power outage. (For examples of plant layouts, refer to Figures 9.5 and 9.7.) List numerical design guidelines for sizing each treatment unit, except pumps and sludge processing,

a) Preliminary treatment with constant speed pumps

(b) Preliminary treatment with variable speed pumps

(c) Two-stage trickling-filter plant with stone-media filters

(d) Trickling-filler plant with single stage biological tower.