Treatment of high-strength ammonia liquors using Amtreat process as Ashford STC, Southern
Bungay, S.1,2, Collins, S.2, Baldock,T.3, 1Helix ECL, 2ACWA Services, 3Southern Water, UK
(free)
Abstract:
The Amtreat process is a high-rate activated sludge plant for treating high-strength ammonia liquors. The compact, high-rate ammonia treatment system has a relatively small footprint compared to conventional activated sludge treatment processes, and full nitrification of high-strength ammonia effluent can be achieved, with typical ammonia removal rates in excess of 97%.
In 2008 Southern Water installed an Amtreat sludge liquor treatment plant at their sludge treatment centre at Ashford. The plant replaced an existing SBR liquor treatment plant, and treats liquors arising from pre-digestion thickening, post-digestion dewatering, and condensate from a sludge dryer. The plant comprises a balance tank with mixing system, hot and cold liquor blending system and the Amtreat plant. The Amtreat plant is configured for nitrification, denitrification, and alkalinity recovery; with a pre-anoxic tank for denitrification; the Amtreat reactor for nitrification; and final settlement for solids removal. The plant includes an internal nitrate recycle and RAS recycle to optimise denitrification and alkalinity recovery, which in turn minimises caustic dosing.
This paper discusses the operation of the Amtreat plant at Ashford STC since initial commissioning in 2008, up to the present day.
Key words
Ammonia Removal, Amtreat, Liquor Treatment, Nitrification, Denitrification, Alkalinity Recovery.
Introduction
The Amtreat process is a high-rate activated sludge plant for treating high-strength ammonia liquors. The compact, high-rate ammonia treatment system has a relatively small footprint compared to conventional activated sludge treatment processes, and full nitrification of high-strength ammonia effluent can be achieved, with typical ammonia removal rates in excess of 97%. The Amtreat process was initially developed in 1992 with funding from a consortium of 3 Water Authorities looking for a solution to the problem of nitrifying high strength digested sludge liquors. There were initial pilot-plants located at Manor Farm and Wargrave WwTWs. In 1995 further research by a 4th Water Authority ratified the process as being a very stable and robust system for the reduction of ammonia in sludge liquors. The first full-scale plant was installed in 1998 at Cliff Quay STW, Anglian Water. Cliff Quay was designed to treat digested sludge dewatering liquors with an ammonia concentration of 1,400 mg/l. The plant achieves complete nitrification of this liquor, producing an effluent less than 5mg/l NH3-N. Cliff Quay following construction is shown in Figure 1 below.
