Performance Evaluation of Cascade Separation for a Humic Substance and Nutrient Recovery from Piggery Wastewater toward a Circular Bioeconomy

Abstract

This study aims at developing adsorption-based cascade separation processes for recovering humic substances (i.e., humin, humic acid, and fulvic acid) and nutrients (i.e., nitrite and phosphate) from real piggery wastewater. The results indicated that both humin and humic acid in wastewater could be completely separated from wastewater by introducing alternate alkaline–acidic chemical extraction. Then, fulvic acid was recovered by ion-exchange adsorption, and the effect of resin-to-wastewater ratios and desorption stages on the recovery of fulvic acid was evaluated. The adsorbed fulvic acid could be almost completely recovered from resins after the fifth stage of desorption. The adsorption kinetics and isotherms for fulvic acid recovery were determined accordingly to obtain the key design parameters, such as rate constants and mass transfer coefficients. Moreover, the simultaneous adsorption of nitrite and phosphate (∼40%) by resins was found to occur, and the remaining nutrients in wastewater should be further recovered by other energy-efficient techniques. A preliminary analysis of economic potential was also conducted to evaluate the cost-effectiveness of the developed process. This study revealed that the developed adsorption-based cascade process exhibited a huge potential, in terms of technical feasibility and economic viability, in separating humic substances from piggery wastewater as biofertilizer products.