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Title: Laboratory and pilot scale evaluation of coagulation, clarification, and filtration for upgrading sewage lagoon effluents
Authors: Cullinane, M. John.
Shafer, Richard A.
Keywords: Effluent quality
Sewage lagoons
Publisher: Environmental Laboratory (U.S.)
U.S. Army Engineer Waterways Experiment Station.
Series/Report no.: Technical Report;EL-80-6
Abstract: Lagoons are recoginzed as an economical method for treating the wastewaters generated at recreation areas and other small flow-producing installations. Unfortunately, in many cases the algae-laden effluent from such lagoons may be objectionable. Various treatment techniques have been utilized in an effort to upgrade lagoon effluents to a water quality level acceptable to permitting authorities. The purpose of this study is to determine the technical feasibility of developing a mobile chemical-physical treatment facility to convert complete retention lagoons to controlled discharge systems, thus increasing design capacities. A truck-mounted chemical-physical treatment facility was designed and constructed for this study. Unit processes constituting the treatment facility included: coagulation, flocculation, sedimentation, and filtration. Analyses were performed to determine treatment efficiencies for biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), suspended solids, and orthophosphate. The algal genera present within the lagoon system being studied were also identified. The efficiency of several coagulants alone and in combination with coagulant aids was investigated. Optimum dosages of coagulant and/or coagulant aid were determined. Alum, lime, and ferrous sulfate were tested as coagulants, and cationic polyelectrolytes WT 2820, WT 2076, WT 2830, and Aqua-Floe 420 were studied as coagulant aids. The coagulation-flocculation-sedimentation system produced effluents with total suspended solids less than 15 mg/1 and orthophosphate concentrations less than 1.0 mg/l. Mean COD and BOD₅ concentrations of 37 and 6 mg/l, respectively, were obtained. Addition of a granular media filtration system further reduced COD, BOD₅ , total suspended solids, and orthophosphate concentrations to mean values of 30, 5.7, and 0.42 mg/l, respectively. Highest quality effluents were obtained at a pH ranging from 5.9 to 6.2, alum dosages between 200 and 300 mg/l, and addition of 1 to 2 mg/l of a cationic polyelectrolyte. Similar results were also obtained using a fill and draw rather than a continuous flow system. Removals of orthophosphate and suspended solids ranged from 90 to 95 percent for the coagulation-flocculation-sedimentation system operated in the fill and draw mode of operation.
Appears in Collections:Technical Report

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