NUISANCE ALGAE IN WATER SUPPLY PROJECTS IN SRI LANKA

Sri Lanka is a tropical continental island which consists of 103 rivers and about ten thousand man made tanks. There are over 250 water supply systems constructed using these water bodies since later part of the nineteenth century, reservoirs which are used extensively for domestic and agricultural practices. It is reported that most of these water sources are constantly becoming contaminated with different types of algae making the water unsuitable for human consumption. The present study was carried out to identify toxin producing, filter clogging, taste and odor forming nuisance algae and some physico-chemical parameters in some selected water bodies namely Labugama, Kalatuwawa, Parakramasamudra, Kondawatuwana, Mahaweli intake at Neelapola and Kantale. Sampling for algae and physico cemical parameters were carried out for a period of one year from April 2009 to April 2010. The results of the present study showed that all physico-chemical parameters in the water bodies were within the drinking water quality standards recommended for Sri Lanka. However Species diversity and density of phytoplankton was different in the water bodies. In Labugama and Kalatuwawa, total algae population consisted 10 % of cyanotoxin producing Microcystis aeruginosa, 10%, 20 % and 60 % of taste and odor forming Peridinium sp., Microcystis sp. and Staurastrum species respectively. In contrast, 89 % of cyanotoxin producing cyanobacteria in Kondawatuwana tank, 50 % in Parakramasamudra, 40 % in Neelapol