This paper analyses factors associated with bulking in 195 small scale wastewater treatment plant... 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...
This study evaluated the impact of socio-economic and lifestyle changes on nutrient loads and wat... more 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. The TP input decreased by approximately 45% due to the decrease in river and point source loads. Point sources contribute about one-third of the P load to the bay. An overall decreasing gradient from the rivers to the mouth of the bay was observed both for TP and TN concentrations indicating probable removal of these elements from the water column along the east-west transect. In order to keep the TN/TP ratio within the range that suppresses eutrophication in the bay, further efforts must be implemented to reduce point source phosphorus load.
Changes in the Nutrient Mass Balance of Haapsalu Bay, Baltic Sea, Estonia in Relation to the Esta... more Changes in the Nutrient Mass Balance of Haapsalu Bay, Baltic Sea, Estonia in Relation to the Establishment of a Sewage Treatment Plant
Implementation of the watershed management plans require consideration of multiple issues and inv... 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&#39;s P = -0.50, p-value &lt; 0.01) dependent on the dissolved oxygen concentration and is limited by photosynthesis and eutrophication
This paper analyses factors associated with bulking in 195 small scale wastewater treatment plant... 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...
This study evaluated the impact of socio-economic and lifestyle changes on nutrient loads and wat... more 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. The TP input decreased by approximately 45% due to the decrease in river and point source loads. Point sources contribute about one-third of the P load to the bay. An overall decreasing gradient from the rivers to the mouth of the bay was observed both for TP and TN concentrations indicating probable removal of these elements from the water column along the east-west transect. In order to keep the TN/TP ratio within the range that suppresses eutrophication in the bay, further efforts must be implemented to reduce point source phosphorus load.
Changes in the Nutrient Mass Balance of Haapsalu Bay, Baltic Sea, Estonia in Relation to the Esta... more Changes in the Nutrient Mass Balance of Haapsalu Bay, Baltic Sea, Estonia in Relation to the Establishment of a Sewage Treatment Plant
Implementation of the watershed management plans require consideration of multiple issues and inv... 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&#39;s P = -0.50, p-value &lt; 0.01) dependent on the dissolved oxygen concentration and is limited by photosynthesis and eutrophication
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