Assessing the potential use of cassava peel starch as a coagulant Aid; a case study of Ggaba III drinking water treatment plant.

Abstract

The agricultural industry is known to generate a significant portion of waste. Conversion of this waste into a useful end product would be beneficial not only to the economy but also the environment through reducing the solid waste disposed. In this study CPS was evaluated as both a sole coagulant and as an aid to alum based on the operational drawbacks identified at Ggaba III drinking water treatment plant which arise from the formation of light flocs during the coagulation stage in the water treatment train. Jar test experiments were done using raw water from Ggaba III treatment plant before the pre-chlorination stage that is intended to discontinue algal growth. The jar tests conditions were so as to simulate the operating conditions at Ggaba III treatment plant. Flash mixing was done at 200 rpm for 2 minutes and thereafter, gentle mixing with speed reduced to 30 rpm for 15 minutes. Setting was allowed for 30 minutes. A pH optimization study was also carried out to assess the effect of varying pH on the coagulating activity of CPS as both a sole coagulant and as an aid to alum. Raw water was characterized and the results compared with one year data records from the quality control department. Statistical analysis of raw water results showed a significant change (P<0.05) in water quality with respect to colour and turbidity. Jar test results showed that CPS did not present commendable coagulant properties achieving a maximum turbidity and colour removal of about 36% and 30% respectively but when used as an aid to alum, the blend was effective in removing turbidity and colour achieving less than 1FAU and 5 PtCo at optimum dosage of 50 mg/L of alum and 40 mg/L of CPS. CPS reduced the optimum alum dosage by 15 mg/L.