Kinetic studies for phycoremediation and nutrient removal by Chorella sorokiniana of Palm oil mill effluent

Abstract

Palm Oil Mill Effluent (POME) is an untreated wastewater that is generated from palm oil industry containing high amount of nutrients such as nitrate, phosphate, ammonium and chemical oxygen demand (COD). Untreated effluent discharge into watercourse produce carcinogenic by-products in drinking water. In addition, eutrophication can cause oxygen deficiency in water thereby affecting the aquatic microorganisms. POME treatment using microalgae has been considered a more biofriendly system, however, high amount of nutrients affect the growth of microalgae. Hence, the present study investigates the effectiveness of robust Chlorella sorokiniana for pollutants removal in different dilutions of sterilized and raw POME. Standard and pyrosequencing methods were used in this study. The results for the former showed higher removal of nitrate, phosphate, ammonium and COD in raw POME than sterilized POME with the 80% (v/v) dilution been the best dilution accounting for higher growth and nutrients removal by C. sorokiniana. While results from the latter revealed the presence of Bacillaceae, Paenibacillaceae, Enterococcaceae, Clostridiaceae, Peptostreptococcaceae, Caulobacteraceae, Enterobacteriaceae, Moraxellaceae and Pseudomonadaceae bacterial families in raw POME. In addition, study of the biokinetic coefficients using Michaelis-Menten rate expression in optimal sterilized POME dilution showed that, the biokinetic coefficients of nitrate was; {k=9.2*10-3 mg NO3 - mg-1 dry cell weight (DCW), d-1, Km= 68.7 mg/L, YN=0.1 g DCW g-1 NO3 -}, for phosphate; {k=8*10-3 mg PO4 3- mg-1 DCW d-1 and Km=144.6 mg/L, YP= 0.12 g DCW g-1 PO4 3-}, for ammonium; {k=2.3*10-2 mg NH4 + mg-1 DCW d-1, Km= 113 mg/L, YN= , 0.08 g DCW g-1 NH4 +} and for COD {k= 0.15 mg COD mg-1 DCW d-1 and Km =1662 mg/L, YCOD= 0.02 g DCW g-1 COD for COD}. Transesterification reaction was also carried out on the biomass for fatty acid methyl ester (FAME) production. The gas chromatographymass spectrometer (GC-MS) conducted revealed the presence of saturated FAME in algae oil which includes tridecyclic acid, myristic acid, pentadecyclic, palmitic acid and stearic acid. Based on the effect of different nitrogen sources on biomass and lipid production, urea feed of 1 and 2 g/L was identified as the optimal concentration for maximum lipid and biomass production respectively. This study is the first report of the potential of C. sorokiniana for POME treatment with FAME production.