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Recently, mass production of lipid along with heavy metal reduction is gaining momentum due to their cost-effective and greener approach towards waste water treatment. The purpose of this study is to investigate the small scale photo bioreactor treatment of tannery effluent using Chlorella sp. isolated form Yercaud lake, Tamil Nadu, India. The results showed a significant decrease in the heavy metals content in the tannery effluent after the treatment. Maximum reduction of the heavy metal Chromium (Cr) of 10.92 mg L−1 was recorded, followed by Cobalt (Co)-7.37 mg L−1, Nickel (Ni)-9.15 mg L−1, Cadmium (Cd)-8.48 mg L−1, Lead (Pb)-12.54 mg L−1, Zinc (Zn)-11.56 mg L−1 and Copper (Cu)-10.71 mg L−1 at the end of the 20th day of treatment. The microalgae, Chlorella sp. was analyzed for their biosorption ability and the maximum biosorption capacity (qmax) rate against heavy metals was 81.36, 70.53, 82.15, 63.29, 58.92, 83.43, 64.83 µg L−1 for Cr, Pb, Ni, Cd, Co, Zn, and Cu respectively. It matched with the Langmuir and Freundlich kinetics models. The maximum CO2 utilization was found to be 60.50% and maximum concentration of lipid, carbohydrate and protein was found to be 0.95 g L−1, 250 µg mL−1 and 160 µg mL−1, respectively. The presence of various groups such as hydroxyl, alkyl, carbonyl and carboxylic acids was confirmed using Fourier transform infrared analysis. Thus, the isolated microalgae showed good biosorption ability towards the various heavy metal pollutants from tannery waste water.

The present study focuses on treatment of tannery effluent samples using microalgae and isolated cyanobacteria. Different concentrations of both the effluent samples were treated with the algal isolates and a highest biomass of 0.295 g/l was attained in 50% of concentration on the 12th day in BHEL site. The biomass production in Walajapet site was found to be 0.387 g/l in the effluent treated with 50% of algae. The treated effluent was tested for growth and chlorophyll content was estimated, Chlorella sp. SRD3 showed higher chlorophyll content. The 50% treatment was processed at large-scale treatment in lab and biomass yield of 0.65 ± 0.04 g/l was achieved in BHEL site and 0.49 ± 0.028 g/l in Walajapet site. The treatment led to higher reduction rates in BOD and COD levels in treated effluents. The BOD in effluent from BHEL site was reduced to 83.41% and that from Walajapet site showed 87.46% reduction, whereas the COD values also showed 78% reduction. Based on the results, effluent sample serves as a medium for growth and bioremediation of tannery effluents by microalga, Chlorella sp. SRD3 revealed promising results which may prove efficient in the near future.