Supply pressure and quality of water along distribution network of small supply scheme: a case of Mukono district, Uganda

Abstract

The main objective was to assess the variation of water quality with water pressure along the supply network in small water systems in Mukono District. To achieve this, an assessment of the variation of pressure was done, water quality along the supply chain was assessed, and the relationship between water pressure and quality variation was validated. A sample of 95 questionnaires were distributed. Water pressure and water quality samples were collected at the same points created on the network specifically at the production wells, transmission and distribution and at the customer meter points. Eight water quality Parameters were selected and tested during the study (i.e. Potential of Hydrogen, Dissolved Oxygen (PH), Total Dissolved Solids (TDS), Electrical Conductivity (EC), Total Coliforms (TC), Apparent color, Turbidity, and Residual Chlorine). The results showed that, all the water quality parameters indicated quality variation as water traveled into the supply system. However, some had significant increase, decrease and others had insignificant variation with water pressure. PH, DO, TDS, EC, TC, Apparent color, Turbidity and Residual Chlorine recorded; 0.765 & 0.255, 0.655 & 0.23, 0.577 & 0.492, 0.592 & 0.492, 0.53 & 0.08, 0.951 &0.0311, and 0.841 & 0.932 significant values in Nakifuma and KKN network systems respectively. PH, Total Dissolved Solids, Electrical Conductivity, and Total Coliforms recorded negative correlation with pressure (i.e.-0.184 & -0.63, -0.339 & -0.411, -0.327 & -0.411, and -0.327 & -0.411), whereas Dissolved Oxygen, Turbidity, and Apparent color showed positive correlation (i.e. 0.96 & 0.51, 0.038 & 0.912 and 0.402 & 0.964) in both Nakifuma and KKN) small water systems respectively varying with water pressure. Residual Chlorine recorded negative correlation in KKN (i.e. 0.125) and positive correlation in Nakifuma (i.e. -0.499). In order to attain an equilibrium of water residual pressure and safe quality water in small water system, water quality parameters should be maintained in the desired ranges, i.e. PH = (6.5-8.8)mg/l, Dissolved Oxygen = (6.5 – 8)mg/l, Total Dissolved Solids = < 300mg/l, Electrical Conductivity = < 400μs/cm, Turbidity = < 1NTU, Apparent Color = 5<15(PtCo), Total Coliforms = <0.0(Cfu/100m/l), residual chlorine = (0.2<0.5)mg/l. Water pressures supplied should be above 10<160m and maintained to prevent pressure variations causing intrusion of contamination into the water system due to occurrence of network failures. Key words: Water Pressure, Water quality, Variation, Mukono District, Nakifuma, Kabembe-Kalagi-Naggalama.