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.