In Estonian landfills, in addition to waste sorting and depositing, most biodegradable waste is composted. Stormwater and snowmelt samples collected from compost fields have shown a high content of pollutants. Furthermore, the flow rate of landfill wastewater can vary greatly. This has a significant influence on the options for and efficiency of treatment methods.
Different technologies for landfill wastewater treatment were tested, and the operation of several treatment plants was observed from 2007 to 2014. On the basis of the present research, the wastewater treatment system at Väätsa was redesigned and reconstructed. The treatment system consists of a landfill wastewater collection system, an equalizing tank, physical/chemical (i.e. reverse osmosis) treatment after biological activated sludge treatment and oxidation in pond, and stabilization of the pumping and distribution systems for concentrate discharge from reverse osmosis back to the landfill. Since April 2012, the parameters in the effluent from the treatment plant have been in compliance with the permitted limit values. The composting of biodegradable waste needs to cease for an efficient and stabilized treatment of landfill wastewater. Methane fermentation is considered to be the most effective method for biodegradable waste treatment, and it generates biogas as a by-product.
The rearrangement of composting and depositing of biodegradable waste in combination with anaerobic fermentation would facilitate the production of up to 23.1 million m3 of biomethane per year, which is equal to about 226 MWh heat and electric energy. The digestate that is produced during methane fermentation contains a significant amount of plant nutrients, which could be used for fertilizing certain cultivated areas.
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