Supervisor: Professor Ülo Mander
Opponent: Professor Otto R. Stein, Montana State University, PhD
Constructed wetland approach to wastewater treatment has become widespread throughout the world as an ecological alternative to conventional wastewater treatment systems (activated sludge plants, biofilters etc.). At that the purification efficiency is highly dependent on the availability of dissolved oxygen in the treatment system. Therefore, in order to reduce the area and the costs needed for wastewater treatment, it is of great importance to develop methods to enhance oxygen supply in the constructed wetland.
This PhD dissertation focuses on the methods used to enhance oxygen supply in CWs. The main objective of the PhD dissertation is to study and discuss different aspects of advanced management of constructed wetlands and to compare the performance of novel batch-operated constructed wetland to that of typical flow-through systems.
During the PhD study, two experimental filter systems were established, first of them treating municipal wastewater and second treating household greywater. Batch-operated filter system showed high purification efficiencies treating low-strength communal wastewater. Although, the aeration capacity of the experimental filter system was somewhat lower than for example reported for well-studied vertical-flow filter systems, we believe that performance indicators of batch-operated filter system are expected to improve substantially when more concentrated wastewater and/or higher hydraulic loading rates are applied.
The highly-loaded compact filter systems for greywater treatment demonstrated very good performance. The results provide encouragement for the application of similar full-scale systems in places where space for the establishment of CWs is limited, in areas that are far from central sewage systems and/or where there is a lack of potable water. The system's effluent can be reused for toilet flushing and/or irrigation.