International air, water and effluent treatment specialist ACWA Services’ highly-successful Amtreat® high-rate ammonia removal process was in the spotlight at the recent European Biosolids & Organics Resources Conference, Europe’s premier biosolids and biowaste event.

The wide acceptance of the Amtreat® process is confirmed by the fact it is also going to be used as a key element in a number of new Anglian Water biosolids schemes - the popular, highly-robust technology is being installed at various Anglian Water wastewater treatment plant sites across its region. And with further significant contract wins shortly to be announced Amtreat is fast establishing itself as the industry’s ammonia removal process of choice.

ACWA process specialist Steve Bungay presented a paper at the European Biosolids & Organics Resources Conference on behalf of ACWA Services and Southern Water, focusing on a turnkey project that delivered a system to treat high-strength ammonia liquors at Southern Water’s sludge treatment centre in Ashford, Kent.

Mr Bungay’s paper detailed the plant’s operation from commissioning to the present, demonstrating its robust performance and discussing overall nitrification and denitrification, in particular the benefits and potential pitfalls of short-circuiting this process.

He explained that the robustness and flexibility of the Amtreat® process outweigh the alleged theoretical stoichiometric benefits of other more complex, fragile processes that short-cut the nitrification-denitrification cycle.

Amtreat® does not depend on a critical and complex operational balance between the solids retention time and the hydraulic retention time, influent ammonia concentration, dissolved oxygen concentration, reactor temperature and the performance of sensitive equipment.

The flexible, effective process can successfully treat liquors even when influent flows, temperatures and loads are highly variable. It does not require a pre-treatment stage to reduce COD - as the plant operates with a conventional biomass, it provides better removal of non-readily biodegradable COD and improved tolerance to ammonia or COD toxicity compared to alternative treatment processes.

Southern Water installed an Amtreat® plant at Ashford in 2008, replacing an existing SBR liquor treatment plant to treat liquors from pre-digestion thickening, post-digestion dewatering and condensate from a sludge dryer.

The overall process, which consists of a balance tank with mixing system, hot and cold liquor blending system and the Amtreat® plant, is configured for nitrification and  denitrification . A pre-anoxic tank delivers denitrification ahead of nitrification in the Amtreat® reactor, with final settlement to remove solids. Internal nitrate and RAS recycle systems optimise denitrification and alkalinity recovery, which in turn minimises caustic dosing.

Mr Bungay explained that regardless of the variability of the feed, the Ashford Amtreat® plant reliably produces a high-quality effluent, with long-term ammonia removal in excess of 99%, long-term BOD removal of over 96% and long term COD removal exceeding 88%.  

*The paper was co-authored by Steve Bungay, Process Specialist, ACWA Services and Technical Director at Helix ECL; Dr Sarah Collins, Wastewater Process Manager, ACWA Services; and Tim Baldock, Senior Process Scientist, Southern Water.

www.acwa.co.uk