| This study is aimed to evaluate slow sand filtration as tertiary treatment of secondary wastewater effluents at pilot scale using different sizes of local sands. It was found that the percent removal for all the parameters analyzed were decreasing by decreasing the sand depth and/or by increasing the sand size.; The pilot scale filter was successfully able to achieve consistent results. The average percent removals of turbidity, BOD, COD, standard plate counts, and total coliform bacteria were 95, 89, 67, 93 and over 99%, respectively. It was found that efficiency of the filter at all sand depths and sizes with respect to the percent removal of bacterial contaminants were exceptional to an extent that the effluent would easily qualify for unrestricted irrigation. It may be suggested to use coarse sand with deeper bed compared to fine sand of shallow bed to get the desired efficiency.; It was also found that the presence of algal blooms are critical for the performance of the slow sand filter. (Abstract shortened by UMI.)... |
