Getting to
Grips with…
landfi ll
leachate
Liquid that oozes from landfi lls can
be among the most challenging of
wastewaters to treat, but technology is
now available that can deal with it in an
energy-effi cient manner
The Knowledge
www.wwtonline.co.uk | WWT | OCTOBER 2018 | 23
BY MARK HARDIMAN,
DIRECTOR,
LAT WATER
Q: What is landfi ll
leachate and how is it
created?
A: Leachate is the liquid
that is formed in landfi lls
and drains or "leaches" to
the bottom of the landfi ll. It
is formed from the natural
rotting and decomposition
of the organic matter
that is buried combined
with water that enters
the landfi ll together with
dissolved material from
other solid matter. It is
always present in a landfi ll
and gradually seeps to the
bottom. Modern landfi lls
are sealed at the bottom
so the leachate has to be
extracted to prevent it from
saturating the landfi ll. The
make-up varies depending
on the composition of the
landfi ll but comprises in
general a mix of dissolved
Q&A
salts, organic compounds,
frequently quite high levels
of dissolved ammonia and
various levels of metal ions.
Basically anything that has
been buried in the landfi ll can
end up dissolving and being
present in the leachate. The
volume that is created varies
depending on the size and age
of the landfi ll but even a er
the landfi ll is closed and sealed
it remains biologically active,
hence producing leachate
that requires management for
decades a er being sealed.
Q: What particular
treatment challenges
does it present?
A: Leachate is one of the most
challenging contaminated
liquids to treat. Treatment at
the site creates problems for
conventional water treatment
methods as the volume
