Removal of hazardous substances in municipal wastewater treatment plants.

Chemical pollution poses a threat to the aquatic environment and to human health. Wastewater treatment plants are the last defensive line between the aquatic environment and emissions of pollutants. This study focuses on identification of most relevant hazardous substances in Estonian municipal wastewater and their fate in the treatment process.

Evaluation of microalgae production coupled with wastewater treatment.

In the present study, the feasibility of microalgae production coupled with wastewater treatment was assessed. Continuous cultivation of Chlorella sorokiniana with wastewater was tested in lab-scale flat-panel photobioreactors. Nitrogen and phosphorus removals were found to be inversely proportional to the four dilution rates, while chemical oxygen demand removal was found to be 50% at all the tested conditions.

Impact of changes in nutrient inputs to the water quality of the shallow Haapsalu Bay, the Baltic Sea.

This study evaluated the impact of socio-economic and lifestyle changes on nutrient loads and water quality in Haapsalu Bay, the Baltic Sea between 1995-1996 and 2003-2004. Monthly monitoring data of water quality in four rivers discharging to the bay and seawater at five sea stations were used. External input of TN to the bay remained almost unchanged during the study period despite of the somewhat higher riverine load that was explained by intensified agriculture.

Recent trends in nutrient concentrations in Estonian rivers as a response to large-scale changes in land-use intensity and life-styles.

The aim of the study was assessment of changes in nutrient concentrations in Estonian rivers as a response to improved wastewater treatment and substantial reductions in the use of fertilisers and number of livestock during the past 15-20 years. A Mann-Kendall test and flow adjusted technique to assess recent trends have been used. Statistical analysis covered time series of 53 sampling sites on 40 rivers and streams in different hydro-geographical regions and varying human pressures.