The introduction of the Resource Management Act in 1991 in New Zealand enforces statutory requirements for the disposal of farm and industrial wastewaters in ways that minimize environmental impacts. Wastewaters often contain high concentrations of ammonium ( ), phosphate ( ) and potassium (K+) ions, and in some cases heavy metals. Zeolite is a naturally occurring, porous and electrically-charged alumino–silicate mineral, which can be used to adsorb cation and anion contaminants from wastewater. Zeolites of New Zealand origin were obtained from New Zealand Resource Refineries Ltd. and evaluated for their effectiveness to remove ions from a fellmongery wastewater stream. The natural zeolites were of clinoptilolite species and had high cation exchange capacity (CEC) (>100 cmol kg−1), which after treatment with alkali solutions increased by up to 74%. The CEC of the zeolites indicated that these samples can hold a potential maximum of 18.7 to 20.1 g zeolite. The adsorption of ions by the zeolites increased w...