Treatability and Kinetic Study of Dairy Effluent Using Microalgae Spirulina platensis in a Laboratory Scale Batch Reactor

Abstract

Purpose of this research work is to evaluate the bio kinetic coefficients of a pretreated Dairy wastewater in a suspended growth batch reactor with the treatment of microalgae Spirulina platensis. The study was performed in a laboratory scale batch setup. Samples of dairy plant was collected and it was pretreated with a consortium of carbon oxidation and nitrification process with bacterial culture that was made as the feed of this purification process. Bacterial pretreatment was done in order to reduce its organic carbon and ammonium nitrogen content. Nitrate nitrogen which was formed during bacterial treatment process and most of the phosphate still remaining in the water was treated in this process with micro algal species to remove these nutrients in wastewater and consequently to meet with discharge standards of regulatory authorities like Central Pollution Control Board (CPCB) of India and World Health Organization (WHO). A simulated synthetic wastewater sample was prepared according to the concentration measured in the original pretreated-wastewater where average nitrate nitrogen concentration was found 54 mg/L and phosphate concentration was 16 mg/L. The maximum 99.00 and 90.38% of nitrate nitrogen (${\text{NO}}_{3}^{ - }$-N) and phosphorus (${\text{PO}}_{4}^{{3 - }}$-P) removal were achieved corresponding to initial nitrate nitrogen and phosphorus concentration of 54 and 16 mg/L respectively, with an initial inoculum concentration of microalgae Spirulina platensis of 0.8% v/v after 8 days of detention period in batch reactor. Kinetics study was also carried out to obtain bio-kinetic coefficient for nitrate nitrogen and phosphorus removal using microalgae Spirulina platensis in order to obtain kinetic constants (Y, K_s and k). The values of k, K_s and Y_N were found to be 21.74 per day, 1.61 mg/L and 0.011 g of biomass/mg of ${\text{NO}}_{3}^{ - }$-N as N for nitrate nitrogen removal. Values of k, K_s and Y_P were found to be 14.49 per day, 16.63 mg/L and 0.052 g of biomass/mg of ${\text{PO}}_{4}^{{3 - }}$-P as P for ${\text{PO}}_{4}^{{3 - }}$-P removal. Corresponding kinetic coefficients were compared to studies done by other researchers which corroborate the findings of this present investigation.