Prefiltration of Surface Waters with a Short Length Horizontal Flow Gravel Filter

Authors: Mehmet Emin AYDIN

Abstract: A 2.1 m long, 150 mm wide and 350 mm high horizontal-flow gravel filter (HFGF) was operated over an eight month period to improve the quality of a local stream water fed to slow sand filters. The media consisted principally of 5 to 6.3 mm gravel and the unit was operated at nominal flow rates of between 0.5 m/h and 5.0 m/h. Removals of suspended solids varied between a mean of 92 % at 1.0 m/h and 79 % at 5.0 m/h. The removal of total coliforms was as high as 91 % at flow rates of 0.50 and 0.65 m/h and reached a minimum of 77 % at 5.0 m/h. The fecal coliform percentage removals were varied between the 58 % and 87 %. Turbidity removals followed closely those of suspended solids. With a four parameters recorded the percentage removal fell from an initial high level at the lower flow rates to a minimum at 5.0 m/h.

Keywords: Horizontal-flow Gravel Filter, Pretreatment, Coliform Organisms, Suspended Solids, Turbidty.