At an existing treatment plant, the practice of hauling away liquid digested sludge for spreading on farmland is being replaced by belt filter presses to dewater anaerobically digested sludge prior to stockpiling and spreading on agricultural land.The design sludge production, which is the average quantity during the maximum month of the year plus 25% for future plant expansion,equals 90,000 gpd with an average solids concentration of 5.0%.Using a trailer-mounted press,the performance data for dewatering the 5.0% sludge were a hydraulic loading of 45 gpm/m,cake solids content of 24%,polymer dosage of 4.0 gpm/m with a concentration of 0.20% powdered polymer,wash-water usage of 32 gpm/m, and wastewater production of 64 gpm/m containing 2200 mg/l of suspended solids.Calculate the following:solids loading,polymer dosage,wash-water usage and wastewater production per 1000 gal of sludge dewatered,solids recovery,and daily cake production.For a design operating schedule of 12 hr/day with two presses,recommend the size of the presses for installation.
