Sustainability of roughing filters in Sri Lanka

Roughing filters of various types and shapes, such as Up flow, Down flow and Horizontal flow are operated in Sri lanka. Performance of some the filters was evaluated to assess the sustainability of filters and find out what improvements are needed for efficient operation of the filters in future. The recent observations show that rectangular type Up flow & Down flow filters have been sustainably managed for several years of operation where a proper maintenance schedule is used with a trained care taker. The circular filters of large diameter have some operational problems due to short-circuiting and inefficient hydraulic cleaning. The major problems affecting the sustainability are due to the design problems associated with filtration velocity, scouring velocity, uniform distribution of inflows and some operational problems such as operation manuals, training and operator’s commitments. Even though roughing filtration is a simple technology which can be simply managed, it needs constant care and monitoring for efficient operation and sustainability.