Ammonium removal from wastewaters using natural New Zealand zeolites

Ammoniacal nitrogen (ammonia and ammonium) in agricultural wastewaters can promote eutrophication of receiving waters and be potentially toxic to fish and other aquatic life. Zeolites, which are hydrated aluminum-silicate minerals, have an affinity for ammonium ions (NH4"") and are, therefore, potentially useful in removing this contaminant from wastewaters. The major objectives of this study were to evaluate the capacity of two natural New Zealand zeolites (clinoptilolite and mordenite) to remove NH4 from a range of wastewaters under both batch and flowthrough conditions. Effects of two zeolite particle size ranges (0.25-0.50 mm and 2.0-2.83 mm) on NH4"" removal performance were also investigated. Results obtained from the batch adsorption experiments indicated that both zeolites tested, regardless of their particle sizes, were equally effective (87-98%) atNtLt"" removal from domestic wastewaters or synthetic solutions containing NH4 + concentrations of up to 150 gNH4-N m~. However, mordenite showed more effective NH4 + removal than clinoptilolite for dairy and piggery wastewaters, and for synthetic solutions containing high NH4 + concentrations (350-750 g NH4-N m" ). At all equilibrium NH4"" concentrations tested (0.2-300 g NH4-N m" ), NH4"" removal by both mordenite and clinoptilolite was significantly (P < 0.0001) reduced by the presence of competing sodium (Na)