Bioremediation of tannery wastewater by a salt-tolerant strain of Chlorella vulgaris

Phycoremediation is the use of algae for removal or reduction of inorganic nutrients and xenobiotics from wastewaters. It is a reliable process for biotransformation and detoxification of a variety of pollutants. This study focused on the potential of a strain of the green microalga, Chlorella vulgaris, to reduce various pollutants in tannery wastewater (TW). The microalga was grown in TW for a culture period of 21 days and the resultant removal/reduction/biotransformation of biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrates (NO3-N), phosphates (PO4-P), sulphates (SO4-S), dissolved solids and chromium (Cr) was monitored. The isolate was efficient in the removal of excess nutrients in wastewater. Most notably, complete removal (100 % reduction) of NO3-N and Cr was observed by the 6th and 12th day of culture period, respectively. Removal of phosphates was as high as 91.73 % by day 6 and over 99 % by day 21. This strain also reduced sulphate concentrations to 67.4 % by day 21. Levels of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in TW were reduced by 94.74 and 95.93 %, respectively, after 21 days. Our results are useful to suggest that this isolate of C. vulgaris is promising for bioremediating and detoxifying tannery wastewater to improve its quality to meet up recommended effluent discharge limits.