Optimization of ammonia removal by ion exchange using clinoptilolite

The zeolite ion exchanger clinoptilolite was investigated with the objective of optimizing its application to ammonia removal from wastewaters. The study included multiple cycle pilot plant operations at three municipal sewage treatment plants. Particular attention was given to cation interference with exhaustion performance and with minimum cost regeneration. The ammonia capacity of clinoptilolite was found to be nearly constant over the pH range of 4 to 8, but diminished rapidly outside this range. In regeneration the pH was critical in determining the NaCl requirements, a higher pH favoring lesser amounts of salt. However, at a pH over 12.5 zeolite attrition became excessive and exchanger makeup contributed significantly to operating costs. An average ammonia removal of 95.7% was obtained in demonstration studies on three municipal wastes have an NH₃N content of about 20 mg/ℓ. The cost of ammonia removal using clinoptilolite for a 10-mgd plant operating under these conditions was estimated to be $0.082/1000 gal. Ammonia removal down to less than 0.5 mg/ℓ NH₃₋N is technically feasible, but only with shorter exhaustion runs and greater regenerant requirements.