Two stage treatment of dairy effluent using immobilized Chlorella pyrenoidosa

Background: dairy effluents contains high organic load and unscrupulous discharge of these effluents into aquaticbodies is a matter of serious concern besides deteriorating their water quality. whilst physico-chemical treatment isthe common mode of treatment, immobilized microalgae can be potentially employed to treat high organiccontent which offer numerous benefits along with waste water treatment.methods: a novel low cost two stage treatment was employed for the complete treatment of dairy effluent. thefirst stage consists of treating the diary effluent in a photobioreactor (1 l) using immobilized chlorella pyrenoidosawhile the second stage involves a two column sand bed filtration technique.results: whilst nh4+-n was completely removed, a 98% removal of po43?-p was achieved within 96 h of two stagepurification processes. the filtrate was tested for toxicity and no mortality was observed in the zebra fish which wasused as a model at the end of 96 h bioassay. moreover, a significant decrease in biological oxygen demand andchemical oxygen demand was achieved by this novel method. also the biomass separated was tested as abiofertilizer to the rice seeds and a 30% increase in terms of length of root and shoot was observed after theaddition of biomass to the rice plants.conclusions: we conclude that the two stage treatment of dairy effluent is highly effective in removal of bod andcod besides nutrients like nitrates and phosphates. the treatment also helps in discharging treated waste watersafely into the receiving water bodies since it is non toxic for aquatic life. further, the algal biomass separated afterfirst stage of treatment was highly capable of increasing the growth of rice plants because of nitrogen fixationability of the green alga and offers a great potential as a biofertilizer.