Treatment of ammonia in pilot-scale constructed wetland systems with clinoptilolite

•Clinoptilolite sorption was studied with batch experiments and constructed wetlands.•Both sorption and nitrification were enhanced in wetlands with clinoptilolite.•Clinoptilolite can improve ammonia treatment performance in constructed wetlands.

Clinoptilolite was investigated as a sorptive medium for use in constructed wetland treatment systems (CWTSs) based on its affinity for ammonia and high surface area for attachment of periphytic biofilms. Results from a batch sorption experiment indicate that the clinoptilolite studied has an affinity for ammonia described by the Freundlich equation q=0.72Ce0.57 for equilibrium ammonia-N concentrations from 0.07 to 30.1 mg/L. During a 10-day sampling period, a pilot-scale CWTS planted with Schoenoplectus californicus and containing 1000 g clinoptilolite removed significantly more (p-value = 8.8 × 10−3) ammonia-N (mean outflow 4.5 mg/L, standard deviation = 4.1) than a control system containing no clinoptilolite (mean outflow 8.6 mg/L, standard deviation = 2.7). Nitrification was detected in samples of clinoptilolite from the treated CWTS using nitrifying bacteria activity reaction tests (n-BARTs). Ammonia removal was not affected by addition of clinoptilolite to a pilot-scale CWTS planted with Typha latifolia, and nitrification activity was not detected in samples of clinoptilolite. These data illustrate that clinoptilolite can increase ammonia removal and nitrifying activity in CWTSs receiving ammonia concentrations equal to or greater than ∼6–10 mg/L when conditions required to support nitrification including hydrosoil redox are provided.