The use of high-rate nitrification for the pretreatment of ammoniacal digested sludge liquors

Anaerobic sludge digestion reduces most of the organic nitrogen in raw sludge to ammonia. Where the digested sludge is dewatered, the ammonia in the liquors can represent up to 25% of the total ammonia load on the receiving wastewater-treatment plant. This can cause problems with compliance and also limit the throughput of the digestion plant. The paper describes how Anglian Water addressed this problem at Cliff Quay wastewater-treatment plant, Ipswich by installing the Amtreat(TM) high-rate nitrifying process. The reasons for the necessity to reduce the ammonia load to the plant are presented and the rationale behind the selection of this solution is outlined. The Amtreat(TM) plant is described and its performance is evaluated. The Cliff Quay site is the first application of this process to a municipal wastewater-treatment plant in the UK, although there are several installations operating with industrial effluents.