Performance of Slow Sand Filters in Treating Secondary Effluent Using Different Sizes of Local Sand (M.Sc. Thesis)
Material type:
TextLanguage: English Publication details: Dhahran : The College of Graduate Studies King Fahd University of Petroleum and Minerals, c1990Description: xvi, 194 p. : illSubject(s): DDC classification: - 628.352378242 ALY
| Item type | Current library | Shelving location | Call number | Status | Date due | Barcode | Item holds |
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Reference Collection
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Government Document Section | Govt Publication Section | 628.352378242 ALY | Available | 64510 |
Abstract :
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. The wastewater was taken from extended aeration Treatment Plant of North Aramco. Two different sizes of local sand with effective sizes of 0.31 mm and 0.56 mm were used. In both cases, three different depths of sand bed, e.g., 135, 105 and 55 cm were investigated. This investigation was carried out over a period of about one year in order to include the seasonal variations in wastewater influent quality to the filter. 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 cruciform bacteria were 95, 89, 67, 93 and over 99%, respectively. In view of the results, 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 according to the standards employed in the Kingdom. Also, it was found that the filter could be operated until the sand depth is reduced to 55 cm due to cleaning purposes without any problem. The starting depth of the filter sand was 145 cm.
The average percent removals of turbidity, BOD, COD, Standard Plate Counts, and total coliform bacteria were 91, 83, 50, 88 and over 93%, respectively, in a sand bed of 55 cm. The effect of the sand size on percent removal was marginal. 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 as they resulted in decreasing the operational cycle about three folds. It was observed that the coarse sand resulted in longer duration of filter operation as compared to the fine sand i.e. 84 days against 26 days for almost similar quality of the influent.