Immobilized nitrifiers gel was used to remove high levels of ammonium nitrogen from the exhaust gas scrubber wastewater of a municipal sludge drying facility. Prior to full-scale application, the effects of temperature and pH on characteristics of immobilized gel pellets and the removal of ammonium nitrogen were investigated. The activated sludge was entrapped in polyethylene glycol gel, and elastic pellets containing activated sludge were obtained. The lifespan of the pellets in terms of compressive strength was estimated using Arrhenius equation. The results indicated that the lifespan of the pellets was at least five years at pH between 6 and 9, and at a temperature of 40 °C. The pilot plant study showed that wastewater containing 95-260 mg/l of ammonium nitrogen could be treated by immobilized pellets within a retention time of 6 hours and the removal of ammonium nitrogen was 98%. The 480 m3/d full-scale plant was constructed and has been operated successfully.

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