Direct Filtration with Horizontal Roughing Filter as Pretreatment

Abstract

Investigations were carried out to study the feasibility of direct filtration with horizontal roughing filter as pretreatment. With the roughing filter, tests were run at filtration rates of 5, 10 and 15 m/h. Suspended solids concentrations of up to 6000 mg/l were investigated. The tests performed on the down-flow rapid filters were also carried out at constant filtration rates of 5 m/h, 10 m/h and 15m/h; turbidities of up to 220 NTU were handled. Dosages of alum as low as 2,5 mg/l were tested and found satisfactory. Further, an attempt has been made to provide a rough guide for the design of the horizontal roughing filter including prediction of the filter length. The results of the investigations as well as the background literature review are of both practical and theoretical value. Direct filtration with horizontal roughing filter as pretreatment is proposed as a viable treatment method for the clarification of turbid surface waters. /Kir09