Microalgae-Based Meat Processing Wastewater Treatment for Nutrients Recovery and Water Reconditioning

Food processing generates large amount of wastewater containing high concentration of biodegradable organics and nutrients which can cause serious water pollution without proper treatment. The purpose of this study was to reduce food processors’ environmental impact by evaluating microalgae as a treatment option for high-strength meat processing wastewater. Results showed that acclimation in artificial wastewater improved resistance of microalgae to harsh environment and selected consortium of Scenedesmus obliquus, Chlorella vulgaris and Chlorella sorokiniana removed 91% chemical oxygen demand (COD), 67% total nitrogen (TN) and 69% total phosphate (PO43-) from raw meat processing wastewater. To address the challenge of algal biomass harvesting, microalgae were co-immobilized with sludge bacteria using alginate gel. With seven days treatment under optimized operational conditions, algal biomass reached 3,191 mg/L wastewater (dry weight, DW) with simultaneous removal of 83% COD, 85% TN and 89% total PO43- from raw wastewater. Despite of this substantial removal, treated wastewater contained 417 mg/L COD, 25 mg/L TN and 12 mg/L total PO43- which were still above the regulated dischargeable limit (COD\u3c125 mg/L; TN\u3c8-10 mg/L; total PO43-\u3c3 mg/L). To improve wastewater treatment efficiency, effect of chlorine and ozone pretreatment were determined. Results indicated that chlorine disinfection did not enhance the efficiency of wastewater treatment while ozonation of 0.5 minute was most effective and COD, TN and total PO43- were reduced to 342 (60% removal), 29 (80% removal) and 10 mg/L (92% removal), respectively. Finally, harvested microalgae were used to cultivate Saccharophagus degradans to produce biopolymer. Results showed that algal biomass obtained from wastewater treatment contained 34.0% total carbohydrate and 45.7% protein, 6.5% lipid. S. degradans could effectively digest alginate immobilized microalgae and produced 64.9 mg/L polyhydroxybutyrate (PHB) biopolymer after 72 h cultivation. This research firstly applied microalgae in the treatment of high strength food processing wastewater aiming for large-scale application and by addressing the major technical challenges, this research provided information to promote sustainable water utilization in food processing industry