Study on utilization of spirulina platensis for treating wastewater from a soft-drink factory

Abstract

Spirulina platensis was cultivated in wastwater from a soft drink factory. It was found that Spirulina platensis yielded the best growth (900 mg/l cell dry weight) with wastewater from the 3rd pond. The maximum Biochemical Oxygen Demand (BOD) reducing capacity was found to be 82.55%. Wastewater from the 3rd pond was chosen for growing the organism in future experiments. To find the optimum condition for growth and BOD reducing capacity, certain salts present in Zarrouk medium were added at varying concentrations. Results showed that addition of NaHCO3, NaNO3 and K2HPO4, at 25% of that present in Zarrouk medium, yielded Spirulina platensis equal to that grown in the standard Zarrouk medium when cultivated for two weeks. Efficiency for removing total phosphorus (TP) and nitrate was found to be at 86.65% and 83.94%, respectively. When the algae were grown under the new condition of adding NaHCO3, NaNO3 and K2HPO4 at 25 % of that present in Zarrouk medium, BOD reducing capacity and other parameters in the hydraulic retention time (HRT) were determined. Reduction of BOD, NO3 N. TP and SS was found to be 85.00, 74.12, 79.28 and 75.92%, respectively in the first week and increased to 91.97, 90.48 and 91.67 %, respectively in the second week. This was coincided, with the high growth of the algae in the second week indicating a suitable growth condition.