Valorization of citric acid production wastewater as alternative carbon source for biological nutrients removal: A pilot-scale case study

Abstract A pilot-scale process for valorization of citric acid production wastewater as alternative carbon source was developed. Calcium oxide and polyaluminum chloride were used to precipitate phosphate and suspended solids. Concentrated liquor with high concentration organic matter was obtained through filtration and concentration processes, and could be used as an alternative carbon source for biological nutrients removal. The performance of alternative carbon source for biological nutrients removal was close to traditional external carbon source (e. g. sodium acetate). The carbon source utilization efficiency was observed as 5.41 and 4.92 mg chemical oxygen demand equivalent of alternative carbon source and sodium acetate, respectively, to remove per mg total nitrogen. The process for valorization of citric acid production wastewater as alternative carbon source was profitable (4.6 USD/m3) based on economic analysis. In summary, the process could relieve wastewater pollution issue while the product served as an efficient carbon source in biological treatment process of wastewater.