Research Interests:
Implementation of the watershed management plans require consideration of multiple issues and involvement of major stakeholders. This paper focuses on the wickedness of water management issues with an aid of a pilot study. Soolikaoja is a... more
Implementation of the watershed management plans require consideration of multiple issues and involvement of major stakeholders. This paper focuses on the wickedness of water management issues with an aid of a pilot study. Soolikaoja is a small stream located in Nitrate Vulnerable Zone and fed mainly by groundwater. 48.8% of the land use of the catchment area is related to agriculture. Mitigating non-point source pollution in urban area is by itself a wicked issue and limited by negligible possibilities to induce substantial land use changes in a short-term period. In order to reduce nitrate concentrations in the surface water a pilot scale in-stream woodchip reactor was installed in June 2021. Preliminary results show that an average NO3-N removal rate was 43.7 gN m-3 d-1, but it varies between 9.5 and 99.3 gN m-3 d-1. An average removal efficiency was 43.6 ± 18.8 %. The nitrate removal efficiency is strongly (Pearson's P = -0.50, p-value < 0.01) dependent on the dissolved oxygen concentration and is limited by photosynthesis and eutrophication
Research Interests:
Research Interests:
This paper analyses factors associated with bulking in 195 small scale wastewater treatment plants (WWTPs) in Estonia. Operational data from each plant were collected and analysed statistically. The key factors associated with bulking... more
This paper analyses factors associated with bulking in 195 small scale wastewater treatment plants (WWTPs) in Estonia. Operational data from each plant were collected and analysed statistically. The key factors associated with bulking were infiltration into sewage pipes, the type and purpose of process reactor, operational practices and influent characteristics. Both anaerobic fraction and volumetric fraction of the anaerobic reactor compared to the aerobic reactor resulted in a positive correlation with sludge volume index (SVI) <150 ml/g values. Good operation and maintenance practice as well as an operator's competence play a crucial role in bulking prevention. Using the 30 minute settling test (V30) as the single process control parameter can mislead an operator's judgement in process control strategies and cause effluent violations. Misjudgements in process control decisions can lead to unwanted conditions in small WWTPs (e.g. excessive chemical addition favoured bul...
Research Interests:
Research Interests:
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... more
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. During this study, seasonal wastewater and sewage sludge samples were collected from nine municipal wastewater treatment plants and analyzed for 282 hazardous substances, including EU (n = 45) and Estonian (n = 31) priority substances. Results of this study show that several substances that are subject to international restrictions (e.g. Stockholm Convention) are still present in untreated sewage. Wastewater treatment systems that had a greater level of complexity (TEC >5) were more successful in removing hazardous substances. Statistical analyses showed that removal efficiency of organic hazardous substances had significant (p-value <...