Reactive nitrogen and phosphorus removal from aquaculture wastewater effluents using polymer hydrogels

We have developed poly(allyl amine hydrochloride) (PAA · HCl) polymer hydrogels, that efficiently remove nitrate (NO3 ), nitrite (NO2 ), and orthophosphate (PO4 ) 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 NO3–N, NO2–N, and PO4–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 PO4–P by 98+%, NO3–N by 50+% and NO2–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 NO3–N, 0.08 mg/l NO2–N, and 0.3 mg/l PO4–P, suitable for discharge into natural surface waters. © 2000 Elsevier Science B.V. All rights reserved. www.elsevier.nl/locate/aqua-online * Corresponding author. Tel.: +1-301-4057335; fax: +1-301-3142029. E-mail address: [email protected] (P. Kofinas). 0144-8609/00/$ see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S0144 -8609 (00 )00058 -3 316 D.R. Kioussis et al. / Aquacultural Engineering 23 (2000) 315–332