Abstract After lengthy laboratory evaluation of resin selectivity towards the ionic species present in municipal sewage effluent (chloride, sulphate, phosphate, bicarbonate, ammonium, etc.), a process was developed for the recovery of nutrients by ion exchange. It comprises two exchange resin columns in series, containing Clinoptilolite and a porous type I quaternary anion resin with scavenger properties. Together, they remove eutrophic species to acceptable levels and filter residual suspended matter and partially adsorb non-biodegradable organic matter. The resins are regenerated by 0.6 M NaCl from which a slow release, economically valuable fertilizer, MgNH4PO4 · 6H2O, is recovered by stripping and precipitation. After minor corrections, the regenerant solutions can be recycled. The results of more than one year of uninterrupted operation of a fully automatic pilot plant, comprising one column for each resin and operated in a discontinuous mode, are described. Further results from a three column system, which provided the data for the design of a 240 m3/d demonstration plant, are also presented.
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