Across the past decade, increasing water demand has been identified in Sri Lanka. The National Water Supply and Drainage Board is responsible for supplying potable drinking water to Sri Lanka people. There having various rural, urban water supply schemes are operated under that. Apart from that, the private sector water supply systems are also there. Thus, this paper focuses on investigating Sri Lankan drinking water treatment’s operation procedure and optimizing its process by exemplifying the Kalu river basin as a case study.