2021 : Comparison of investment costs for the construction of pre-sedimentation basins to reduce surface water turbidity

Ali Masduqi S.T., M.T.



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There is an important problem in the process of operating a water treatment plant in areas that use raw water, whose turbidity varies during the rainy and dry seasons. The turbidity of raw water in the dry season is very low compared to the turbidity in the rainy season. To answer this problem, a study has been conducted at a Regional Drinking Water Company (PDAM) in Indonesia. There are two alternatives to reduce this turbidity, i.e. setting the dose of coagulant and building a pre-sedimentation basin as a pretreatment. Coagulant dose setting is intended to determine the appropriate coagulant dose according to varying turbidity values. Meanwhile, the development of pre-sedimentation is intended to reduce turbidity physically, so that less coagulants are needed. The results showed that 80 mg/L of coagulant was required at high turbidity. If the turbidity is reduced by 65% by pre-sedimentation, the coagulant required is 50 mg/L. Furthermore, the costs required to implement the two alternatives are calculated in order to compare which alternative is more economical. The cost comparison of these two alternatives is calculated for the 20 years of treatment plan operation. The results show that the pre-sedimentation development is more advantageous than the coagulant dose setting.