Ratmalana Waste Water Treatment Plant, Colombo Sri Lanka

Project Features

Ratmalana Waste Water Treatment Plant was commissioned in February 2014, as the second high-tech activated sludge plant in Sri Lanka. With a process designed for removal of BOD, nitrogen and phosphorous, the plant receives industrial and municipal wastewater from Ratmalana Moratuwa area, 15 km south of Colombo. The implementation of Ratmalana WWTP is part of the Sri Lankan National Water Supply and Drainage Board’s ongoing programme; The Ratmalana/Moratuwa and Ja-Ela/Ekala wastewater disposal project, which was initiated in 2007. The project was financed by the Swedish International Development Agency (SIDA) and the treatment plants, dimensioned for 36 000 (Ja-Ela) and 100 000 (Ratmalana) person equivalents were designed by Purac. The total project also included 7 Pumping Stations and a Sewerage Network. Ratmalana, a southern suburb of Colombo, is a major industrial area, including textile/garments, chemical, metal finishing, food and asbestos factories. Prior to the commissioning of Ratmalana WWTP, households in the area disposed domestic wastewater into septic tanks polluting the ground water and most industrial process and cooling water streams was directed straight into ditches. Due to the lack of sewage infrastructure several water bodies were found to be heavily contaminated. The project was implemented in co-operation with, Pihl & Søn AS, a Danish civil contractor up to the installation stage and the commissioning with 12 month operation has been done by Purac directly under a separate contract.



Technical data

• Mean value:  3 mg/l
• Required value: <25 mg/l
• Mean value: 40 mg/l
• Required value: <120 mg/l
Total N
• Mean value: 7.2 mg/l
• Required value: <30 mg/l
Total P
• Mean value: 1.2 mg/l
• Required value: <5 mg/l