EFFECT OF UNDERDRAIN TYPES AND MEDIA SPECIFICATION ON FRICTION HEAD LOSSES OF MEDIA FILTER

Abstract

The main objective of this study was to assess the combination effect of media types, media bed depths, drain types and number of drains on friction head losses in media filter. An experimental study with scaled media filter prototype was conducted with three different media types basalt (1-2.8 mm), crushed marble (1.4-1.9 mm) and sand (1-1.4 mm), three media bed depths (30, 50 and 70 cm), and three commercial underdrain types referred as a single drain (SD1, SD2 and SD3) and double drain (DD1, DD2 and DD3) under three superficial velocities (50, 87.5 and 125 mh-1). Under single drains, The best operating combination i.e. minimum friction head losses HL was achieved using.. (SD2, 30 cm of basalt and 50 mh-1), which was 63.5 mbar. While the maximum HL was 991 mbar resulted by the following combination: SD3, 70 cm of sand and 125 mh-1. On the other hand, as expected the HL values under DD for the three underdrain types were lower than SD. the minimum HL value was 41 mbar under the following combination DD2, 30 cm basalt and 50 mh-1.While the maximum HL was 578.3 mbar for: DD3, 70 cm of sand and 125 mh-1. The results showed that the HL of basalt produced reliable results (p < 0.05; R2 = 0.865) in relation to values derived from the independent variables superficial velocity, underdrain type, number of drains and media bed depth. The results emphasized the role of proper selection of underdrain types and number as an impacting factor for saving power in comparison to the other mentioned variables.