Pretreatment of poultry waste anaerobic digested effluents by chitosan flocculation for Chlorella pyrenoidosa growth and pollutants removal

Abstract

Poultry waste anaerobic digested effluents are biorefractory for microalgal cultivation. Hence, proper pretreatment is required to improve the conditions of digested effluent and enable the microalgal cultivation. This study evaluated the efficiency of nutrient removal in the digested effluents by pretreatment of chitosan flocculation and determined the potential of pretreated effluents to cultivate Chlorella pyrenoidosa. Approximately 82.1% of chemical oxygen demand, 91.6% of turbidity, and 99.3% of color in the digested effluents (without pH adjustment) were removed by chitosan flocculation (dis-solved in hydrochloric acid) at an optimum chitosan concentration of 1.65 g/L. The maximum biomass production of 0.719 g/L and chlorophyll-a content of 13.71 mg/L were obtained from C. pyrenoidosa Y3 cultured for 20 d in the flocculated effluent at the optimum chitosan concentration. NH4-N in the pretreated effluent decreased significantly by 77.2%. However, total phosphorus was reduced by algae to a certain extent (19.5%). Overall, the results indicate that chitosan flocculation is a feasible pretreatment to improve decontamination and algal biomass yield.