Phosphate binding polymeric hydrogels for aquaculture wastewater remediation

Abstract

Methods that will remove conventional nutrient pollutants such as reactive phosphorus, even at extremely low concentrations, from wastewater effluents are a major need in the aquaculture industry. In this study, novel phosphate binding crosslinked poly(allylamine), PAA · HCl, polymeric hydrogel materials were developed, which efficiently bind phosphate anions in aquaculture wastewater effluents. The polymeric hydrogels were synthesized by chemically crosslinking linear PAA · HCl chains with epichlorohydrin. The phosphate binding capacity of the synthesized pH sensitive polymer gels was studied as a function of various gel processing parameters. Equilibrium orthophosphate (PO 4 3-) loadings of 47 mg g −1 polymer, were calculated from direct measurement of the decrease in phosphate concentration in aqueous solutions using UV spectroscopy. Experiments showed that pollutant concentrations in aquaculture wastewater effluents decreased with regard to PO 4 3- by more than 99%. The ability of the gels to bind phosphates was not fouled by particulate or dissolved complex organics and inorganics, or counterions which are present in aquaculture wastewater effluents. The hydrogels can be regenerated by release of the bound phosphates upon washing with a 1 N NaOH solution. Results demonstrated that the novel crosslinked polymeric hydrogels are appropriate materials for treating aquaculture wastewater effluents, and reducing the phosphorus concentrations to levels, less than 0.01 ppm, suitable for discharge to natural surface waters.