The Use of Chitin for the Removal of Nitrates and Orthophosphates from Greenhouse Wastewater

Abstract

The study investigated the possibility of using chitin flakes as an unconventional sorbent for the removal of orthophosphates and nitrates from greenhouse wastewater (GW). The effluent parameters were as follows: 66.2 mg P-PO4/L, 566.0 mg N-NO3/L, 456.0 mg S-SO4/L, 13.7 mg Cl−/L, 721 mg Ca2+/L, 230 mg Mg2+/L, hardness 11.3 °dH, and pH 5.4. The scope of the research included determinations of the influence of pH on GW composition and the efficiency of nutrient sorption, the kinetics of nutrient sorption, the influence of the dose of chitin flakes on the effectiveness of nutrient binding and the maximum sorption capacity of the sorbent. The sorption of P-PO4 on the tested sorbent was most effective at pH 4, and the sorption of N-NO3 at pH 2. The equilibrium time of sorption of both nutrients from GW to chitin depended on the sorbent dose and ranged from 150 to 180 min. The sorbent dose of 40 g/L enabled removing 90% of orthophosphates and 5.7% of nitrates from the wastewater. The maximum sorption capacity of CH towards P-PO4 and N-NO3 contained in the GW was 3.20 mg/g and 3.04 mg/g, respectively. In turn, the sorption of calcium and magnesium ions on chitin flakes was completely ineffective.