ISOLATION OF ALGAL SPECiES FROM WATER BODIES USING DIFFERENT STRESS CONDITIONS AND THEIR USE FOR NUTRIENT REMOVAL

Abstract

This study was undertaken to find suitable algal strains which could remove nutrients from wastewater. For this purpose, raw samples were collected from Lakkarghat (Rishikesh, Uttarakhand) oxidation ditches. For enrichment and isolation of desired algal species, pH was maintained at 7, 9 and 11. For algal growth, solid and liquid BG 11 media was used. For checking the morphology of enriched, isolated algae and also to check contamination in the media, light microscopy was used. It was observed that after three consecutive transfers, algal colony grown on the petri dishes (pH 7, 9 and 11) had similar morphological structure. Therefore, algal colonies grown after three consecutive transfers were transferred to the liquid media to check their suitability for nutrient (nitrate) removal. For nutrient removal studies, algae grown on pH 7 was grown on modified BG 11 media which had increased amount of inorganic carbon for enhanced algal growth. For nutrient removal studies at pH 9 and 11, original BG 11 media was used. CO2 was used occasionally to maintain pH of the media It was observed that low biomass production was achieved in all the algal culture media. Maximum biomass concentration was observed for pH 7 after 3 weeks of incubation at a light intensity of 2300 - 2500 lux. The growth of biomass was low as compared to the values reported in the literature. Inorganic and organic carbons were estimated in a regular interval to know that sufficient inorganic carbon was present in the media. Due to low growth nitrate removal efficiencies were also low. During the studied period (2 to 4 weeks) NO3 removal efficiencies were as follows 17 %, 21% (pH 7)13% (pH 9) and 3 1 % (pH 11). The maximum ratios of total suspended solids to total organic carbon came out to be high as 7.92, 5.7, 8.13 and 6.19.