Tallinn University of Technology

Aare Kuusik defended his doctoral thesis "Intensifying the wastewater and biodegradable waste treatment in Estonia" at the Department of Environmental Engineering of Tallinn University of Technology.

The continuously increasing requirements for environmental protection create problems in treating landfill wastewater in many countries. In the doctoral thesis defended by Aare Kuusik, the results of studies on the chemical composition and treatment possibilities of landfill wastewater and leachate at five Estonian landfills are presented.

The research carried out at the Department of Environmental Engineering of Tallinn University of Technology in the years 2007-2013 showed that after equalisation of the flow rate and pollutant concentration of the landfill wastewater in an equalising tank (either preceded or not preceded by biological treatment), the most suitable treatment method proved to be two-stage reverse osmosis (with DT filters). Based on the research the wastewater treatement system of the Väätsa landfill was reconstructed. (The landfill wastewater treatment system at Väätsa consists of the landfill wastewater collection system, reverse osmosis following the equalisation tank and biological treatment and pumping concentrate from the reverse osmosis back to the landfill).

The defended doctoral thesis relied on the fact that at Estonian landfills, in addition to sorting and landfilling of wastes, biodegradable waste is composted. The concentration of pollutants in rain and snowmelt water collected at composting areas is high, while the flow rates of landfill wastewater are highly variable. This in turn complicates landfill wastewater treatment.

One of the supervisors of the doctoral thesis, Professor at the Department of Environmental Engineering of Tallinn University of Technology, Karin Pachel says: "In order to obtain maximum and stable efficiency in the treatment of landfill wastewater, composting of biodegradable waste should be terminated and substituted with methane fermentation. Methane fermentation is a much more efficient way of biodegradable waste treatment, in the course of which useful biogas is generated. The digestate that is generated in methane fermentation contains a large amount of plant nutrients, such as phosphorus and nitrogen, and it can be used successfully in agriculture (the quality must comply with the legislation in force). Landfill wastewater, including leachate, must be collected and treated in such a way that environmentally hazardous emissions were controlled as much as possible, which would also minimize environmental contamination."

Supervisors: Professor Enn Loigu, Professor Karin Pachel (TTU) and Visiting Professor Walter Z. Tang (Florida International University, USA).
Opponents: PhD Peeter Ennet (Estonian Environmental Agency) and PhD Pekka E. Pietilä (Tampere University of Technology, Finland).

The doctoral thesis has been published in the digital collection of TTU library: http://digi.lib.ttu.ee/i/?5954