No abstract

This paper reports the results of laboratory studies on the removal of ammonium from aqueous solutions using struvite pyrogenation residues. A series of experiments were conducted to examine the effects of the pyrogenation temperature (90-210 °C) and time (0.5-4 h) on the ammonium release of struvite. In addition, the pyrolysate of struvite produced at different pyrogenation temperatures and times was recycled for ammonium removal from aqueous solutions. The experimental results indicated that the ammonium release ratio of struvite increased with an increase in the pyrogenation temperature and time, and the struvite pyrolysate used as magnesium and phosphate source for ammonium removal was produced at the optimal condition of pyrogenation temperature of 150 °C for 1 h. Furthermore, experimental results showed that the optimum pH and pyrolysate dosage for ammonium removal from 100 ml synthetic wastewater (1,350 mg ammonium/L) were at pH 9 and 2.4 g of struvite pyrolysate, respectively, and initial ammonium concentration played a significant role in the ammonium removal by the struvite pyrolysate. In order to further reduce the cost of struvite precipitation, the struvite pyrolysate was repeatedly used for four cycles. The results of economic analysis showed that recycling struvite for three process cycles should be reasonable for ammonium removal, with ammonium removal efficiencies of over 50% and a reduction of 40% in the removal cost per kg NH(4)(+).

No abstract

This paper presents the full-scale treatment of nylon production wastewater in a wastewater treatment plant in Henan province, Central China. In this case, a 9600 m 3 /d capacity wastewater treatment plant was installed to treat the wastewater generated from the production of nylon-66 salt, based on the biological anaerobic filter (BAnF) combined with an anoxic/oxic (A/O) process. The performance of the biological combined system was monitored over a 75-day period. The results revealed that the main pollutants, expressed as chemical oxygen demand (COD), nitrate nitrogen (NO 3 -N), and ammonia nitrogen (NH 3 -N) could be removed satisfactorily. The average removals of COD, NO 3 -N, and NH 3 -N reached 95, 99, and 92%, respectively. The quality of the final effluent met with the required discharge standards for nylon production wastewater. The BAnF packed with volcanic scoria and porous polyurethane foam played a significant role in the combined system. About 50-60% of COD and about 90% of NO 3 -N were simultaneously removed by denitrification in the BAnF. An economic analysis indicated that the chemical and energy costs incurred during the wastewater treatment were low. The total cost amounted to $ 1567/d (i.e. $ 0.20 per m 3 nylon production wastewater).