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We have developed poly(allyl amine hydrochloride) (PAA · HCl) polymer hydrogels, that efficiently remove nitrate (NO 3 − ), nitrite (NO 2 − ), and orthophosphate (PO 4 3− ) nutrient anions from the aquaculture wastewater. The hydrogels were prepared by chemically crosslinking linear PAA · HCl chains with epichlorohydrin (EPI). The anion binding capacity of the pH sensitive polymer gels was measured in standard solutions and studied as a function of gel synthesis parameters. Equilibrium NO 3 –N, NO 2 –N, and PO 4 –P loading of 15, 1.6, and 17 mg/g of dry gel, respectively, were calculated from the measurement of decrease in anion concentration in aqueous solutions using UV–vis spectrophotometry. Batch experiments showed that nutrient concentrations in aquaculture wastewater effluents decreased with regard to PO 4 –P by 98+%, NO 3 –N by 50+% and NO 2 –N by 85+% within 3 h of reaction. The regeneration of the hydrogels was demonstrated by the release of bound nutrient anions upon washing the gels with a 1 N NaOH solution. These results have demonstrated that the hydrogels are appropriate materials for treating aquaculture wastewater effluents, and reducing the nutrient anion concentrations to levels, less than 10 mg/l NO 3 –N, 0.08 mg/l NO 2 –N, and 0.3 mg/l PO 4 –P, suitable for discharge into natural surface waters.

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 (PO43-) 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 PO43- 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.