Landfills generate continuous purge of highly contaminated
leachate, containing many organic and inorganic (notably Ammonium) compounds.
Many landfill sites are subject to environmental regulations that require “Zero
Liquid Discharge” conditions, meaning that the leachate must be separated into
its water component, which water may be dischargeable to local water bodies,
and to a solid waste that can be returned to the landfill.
GEA Messo PT has
designed and supplied several plants for leachate treatment, with process
concepts suited to the individual application’s local conditions. The leachate
is typically concentrated to some degree by membrane filtration. The Permeate
may be subjected to secondary RO to meet the requirements for discharge to the
environment.
The leachate is concentrated further, depending on its
quantity, in a multistage evaporator to about 30%wt TDS and then fed to, or
(for smaller quantities) is directly fed to a thin-film evaporator that is also
the final drying step.
The condensate of the evaporator is usually
contaminated by NH3 and is recycled to the RO. A part of the alkalized
condensate is treated in a rectification column that produces aqueous ammonia
or in a stripping unit followed by an acidic or a catalytic oxidation of
NH3.