Leachate Treatment in the UK
"The services offered by international consultant IPPTS Associates placed in context"
In recent years leachate treatment has become an issue in many countries. In these countries
an increasing awareness exists about the fact that although at first sight, simply developing a properly engineered
sanitary landfill appeared to be largely the solution to adverse landfill impacts, it seldom is, unless leachate
treatment systems are also planned and installed at an early stage of site operation.
Leachate treatment issues are rarely easily solved without local specialist expertise and there is a wealth of
parallel expertise on offer worldwide which isn’t specifically skilled in leachate treatment, but all too ready to
claim to have the right skills to treat leachate. Biological leachate treatment design skills, which form the core
of so many UK leachate treatment plants don’t appear to exist outside the UK. The result has been a rash of
unsatisfactory leachate treatment plants built across the globe at high cost, by inexpert designers trying out
their leachate pant prototypes on innocent clients.
Is it therefore a surprise that landfill operators, once bitten, are casting their net wider to see what experience
is available in other countries? So, a question often asked, these days, is that of; “What is the situation for
leachate treatment in the UK”.
So, let me explain the position of leachate treatment in the UK to you. The United Kingdom is certainly a wet
country, especially on the west, so all but a few landfills in the drier east, notably in East Anglia, quite
rapidly start to produce leachate in significant quantities within 1 to 3 years of opening.
Most landfill operators very wisely don’t immediately take the initial leachate production off-site, unless they
are required to do so, for some reason by the waste regulator (which in England and Wales is the Environment Agency
(EA)). Instead, they re-circulate that leachate back onto the top of the open landfill cells, until volumes
build-up and that becomes unmanageable. That has big benefits in accelerating landfill gas production, due to
higher waste moisture content, and effectively provides the landfill operator with free anaerobic digestion
treatment of his/her leachate.
At that stage off-site disposal of leachate commences, either by tankerage to a sewage works (Waste Water Treatment
Works (WWTW)), or after on-site leachate pre-treatment to a WWTW via a pipeline (this being the EA’s normally
favoured option). If no sewer of adequate size and WWTW of adequate capacity is available locally the on-site
leachate treatment plant will be designed to discharge to a suitable (non-ephemeral) watercourse.
The UK has a sufficiently high rainfall and generally only short dry summer periods such that watercourses provide
good dilution of discharged leachate all year round, and against that background it is generally possible to
justify leachate discharges on the basis of “no detectable impact”, when the leachate when discharged still
contains some COD (the most part of which is hard refractive COD), raised nitrate, and the elevated salinity
typical of landfill leachate from modern sanitary EU Landfill Directive compliant landfills.
Against that background, which explains the UK’s long standing practice when setting discharge consent standards,
which is one of not setting prescriptive national discharge standards. This contrasts strongly with many other
nations where government departments have set national discharge water quality standards to watercourses which
appear to be based on “worst case” standards. As a result they require on most occasions where discharge is into a
reasonable sized watercourse, a highly unnecessary and very costly standard of treatment. Despite these standards
being high overseas, they nevertheless only need to be that high in a few “worst case” watercourse examples, and
won’t lead to better water quality watercourses where adequate dilution is available.
So, by setting discharge consents based upon good science, and a much more flexible regulatory framework than in
most countries, the UK has been able to develop a range of biological treatment plants which operate reliably, and
at low cost compared with leachate treatment plants in many other countries. In these other countries higher
technology processes are frequently forced upon all LTP specifiers and users, and that technology seldom operates
sustainably to, in any manner, flush organic and inert contaminants for the landfill. This will sadly prolong the
already very long period during which old closed landfills will remain a store of waste capable of causing
pollution, and put the local environment at more risk than necessary.
o, the situation for leachate treatment in the UK is one of extensive leachate generation
but its treatment is routine, and where it treatment is done on site, it is almost without exception carried out by
biological primary treatment, plus polishing by simple techniques, such as the use of reed beds.
The biological treatment plants of the types as offered by, for example, by leachate treatment plant designers
IPPTS Associates have been operating successfully and largely unaltered for up to 30 years.
Ask those landfill operators “what is the situation for leachate treatment in the UK”, and they will say it has
been “solved” by specialist UK skills in designing simple to operate biological leachate treatment plants. Plants
which don’t need skilled water treatment works operators or “black box” technology suppliers to maintain