High Rate Filtration Of Combined Sewer Overflows PDF Download

Pilot plant studies were conducted to develop and demonstrate the capabilities of the deep bed, dual media, high rate filtrate treatment process for storm caused combined sewer overflows. The treatment system is comprised of a drum screen with a 40 mesh screening element (420 microns opening) followed by a deep bed, dual media, high rate filter of five feet of No. 3 anthracite (effective size 4 mm) over three feet of No. 612 Sand (effective size 2 mm). The results show suspended solids removals of 93 percent, with polyelectrolyte addition, at a filtration rate of 24 gpm/sq ft at an average influent suspended solids of 411 mg/l. Reductions in biochemical oxygen demand averaged 65 percent. Capital costs and operating costs for a high rate filtration plant are given. Principal advantages of the proposed system are: high treatment efficiencies, automated operation, and limited space requirements as compared with alternate flotation or sedimentation systems.