Advancement in Ion Exchange Processes for Municipal Wastewater Nutrient Recovery

Interest in the recovery of nitrogen and phosphorus from wastewater has increased as it provides a way of securing nutrient supply for crops, reducing energy costs in obtaining raw nutrients, and reducing eutrophication in waterways resulting from discharge of nutrients. For mainstream recovery, alternative nutrient removal technologies such as ion exchange (IX) must be considered to concentrate the nutrients in order for recovery to be economical. Nutrients are concentrated in the regenerant of IX. Batch and column tests were conducted to optimize desorption of NH4+ and maintain IX capacity. During batch testing with clinoptilolite for NH4+ exchange, regeneration with 8% NaCl or 7.5% NaCl at pH=12 maintained 84% of initial IX capacity after 7 IX cycles. When operating an NH4+ IX column treating with secondary clarifier effluent dosed with nutrients, 120 bed volumes of sample was reduced from 32 mg/l to less than 1 mg/l NH4-N.