Browsing by Author "Adebayo, Salau-deen Fatai"

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    Investigating the cause of sand loss in rapid sand filters: a case study of Upper Ruvu water treatment plant, Tanzania.
    (University of Dar es Salaam, 1997) Adebayo, Salau-deen Fatai
    The sand used in some water treatment filter plants has been progressively removed in a desperate attempt to maintain the output of production. To meet the quality requirement of potable water and also, water demand of the community served by such plants efforts is required to preserve the filtering media quality and granulometric characteristics. The purpose of this study was to examine the causes of sand loss problem in rapid sand filters of the Upper Ruvu water treatment plant. The various possible causes of sand loss in rapid sand filters was examined during the investigation at the Upper Ruvu treatment plant for a period of over a month. The plant site investigations revealed that the media loss in rapid sand filters occurred during the backwashing operations due to the filtering media material washout. Normally, media loss in rapid sand filters is related to improper design of washwater troughs or channel; media grain attrition; high backwash flow rate; high bed expansion; mode, sequence and duration of backwashing. However, results of tests conducted showed that the major causes of sand loss in Upper Ruvu filters are the mode and sequence of backwashing and the backwash time. A preliminary assessment of the impact of sequence of mode of backwashing and backwash time showed a reduction in the sand loss tendency (in terms of suspended solids concentration) of 71.23 %. Based on the outcomes of these studies, it was concluded that minimizing the backwashing time and prompt attention of the plant operator to strictly adhere to the backwashing procedures will greatly reduce the sand loss problem in rapid sand filters