Air Ammonia Stripping is a leachate treatment process which is now largely outdated and seldom used.
During the 1980s in the United Kingdom it was seen as a potential physico-chemical leachate treatment process which would be suitable for the treatment of leachate from sanitary (lined and capped) landfills, however, although a number of pilot scale leachate treatment plants using this process principle were set-up and experimented with, the users of the technology experienced significant problems with the process concept which in the end were thought to render the process obsolete.
There are, however, two Air Ammonia Stripping Technologies which have been used, one of which has been in long-term use on a landfill site in Hong Kong and may under some circumstances warrant further consideration for anyone seeking to install leachate a treatment on a municipal solid waste or C&I waste landfill site:
- pH adjusted air ammonia stripping using an strong alkali
- high temperature air ammonia stripping.
pH Adjusted Air Ammonia Stripping Using an Strong Alkali
This is not recommended due to the high cost of the alkali chemical used to raise the pH before the flow is passed through an ammonia stripping tower and then also of the acid used to lower the pH after ammonia stripping to a level suitable for a watercourse discharge, or additional on-site, or off-site treatment. Not only is the cost high but the high level of emitted ammonia which exited the flume caused corrosion of staff vehicles parked in the vicinity.
High Temperature Air Ammonia Stripping
This is by far the preferred method of air ammonia stripping for environmental and cost reasons, but the heat energy absorbed comes at a high cost in lost revenue. It has only been used where there was no incentive for the landfill owner to generate power and obtain CDM Carbon Credits, as the process demands the sacrificial use of landfill gas as the only available heat source. At most landfills substantial income could otherwise be obtained from the power from using that landfill gas to produce Energy from Waste, which could otherwise be exported off-site into the local power grid. It is this method which has been utilized at a landfill in Hong Kong and the company which developed that leachate treatment plant was a UK company named “Biogas”.