Towards Cleaner Water Flow in Valga – A Pilot Area for Improving River Water Quality
The pilot area in Valga, Estonia, is addressing water quality issues detected on a swimming beach by a river. As one measure, an active filter has been implemented to improve the river water quality.
The Estonian University of Life Sciences (EULS) and Valga Vesi AS are participating in the WSSP project which promotes a practical and resource-wise Watershed Safety Plan (WSSP) operational model that enables municipalities, water utilities and other relevant actors to reduce the amount of diffuse pollution from reaching the Baltic Sea. As the end user of the WSSP operational model, Valga Vesi water utility is piloting the WSSP operational model in the City of Valga with the support of the research partner EULS. EULS focuses on identifying the sources and pathways of bacterial contamination and on developing both experimental and practically applicable mitigation measures. In implementing the WSSP operational model, Valga Vesi contributes with its technical expertise and local knowledge.
Poor swimming water quality caused by diffuse pollution
For years, bacterial contamination at the Pedeli swimming beach in Valga has been a concern, occasionally resulting in a red flag being raised to warn the public about poor river water quality. The WSSP project offers support in addressing this issue by introducing various measures to reduce bacterial pollution as well as the amounts of nitrogen and phosphorus entering the Pedeli River.
The selected pilot area in Estonia is the Konnaoja River catchment area in the twin towns of Valga/Valka, located on the Estonian–Latvian border. The catchment area mainly consists of urban areas, agricultural land, pasture, and forest. Because the Konnaoja stream flows towards Estonia, water quality issues affect the downstream areas in Estonia, such as the Pedeli River swimming beach.
Microbial contamination in flowing surface waters rarely reaches levels that require restrictions on recreational use, like swimming. Such restrictions are more often associated with stagnant water bodies, such as lakes. However, in the case of the Pedeli River, bacterial pollution has emerged as a recurring public health concern. Monitoring data from multiple summer sampling campaigns have demonstrated elevated concentrations of Escherichia coli and intestinal enterococci, occasionally exceeding bathing water quality thresholds. High levels of bacterial pollution have especially been observed after heavy rainfall.
The contamination is likely associated with diffuse pollution sources within the catchment. This means that there are several potential contributing factors, such as households not connected to the municipal sewerage network, small-scale agricultural activities involving the application of organic fertilizers in close proximity to the Konnaoja River, stormwater-related inflow, and possible overflow events from wastewater treatment facilities. Heavy rainfall can further enhance the passage of pollution into the river.
The Konnaoja catchment area was selected as the Estonian pilot area to enable a systematic assessment of pollution sources and pathways, and to support the design and implementation of targeted mitigation measures aimed at improving microbial and nutrient water quality.
An active filter helps to remove microbial contamination and nutrient load
In the WSSP operational model, the process to manage diffuse pollution can be divided into five steps: 1) objectives and stakeholder engagement, 2) data collection, 3) risk assessment, 4) risk management, and 5) durability. The first four steps of the WSSP process have been piloted in the Valga pilot area.
Nature-based solutions, i.e. retention and treatment systems, are used to enhance year-round pollutant reduction through natural hydrological, physical, chemical, and biological processes. Such measures may include vegetated buffer strips, in-stream retention structures, and small-scale wetlands.
As part of step four, i.e. risk management, an active sand-biochar filter was constructed to enhance the removal of microbial contaminants and nutrients. This nature-based solution is particularly effective during the warm season when recreational water use is highest and microbial risk thresholds are most critical. The system enhances removal of faecal indicator bacteria through physical filtration, adsorption, and biofilm-mediated processes, while also supporting nutrient retention via adsorption and microbial transformation pathways.
Achieving measurable and sustainable improvements in stream water quality requires several different intervention strategies. The sand–biochar filtration system functions as a complementary component supporting both microbial risk reduction and nutrient load mitigation. Other interventions are, for example, source control and pathway-oriented management measures.
Source control and pathway-oriented management measures address pollutant generation and transport mechanisms within the catchment. In urban areas, these measures can be raising people’s awareness on the occurrence and prevention of pollution, upgrading and optimizing wastewater treatment plant performance, and mitigating combined sewer overflows during heavy rainfall, for example. In agricultural areas, measures focus on improving nutrient management planning, prevention of over-fertilization, and the establishment of protection zones adjacent to watercourses, for instance.
The work on the pilot area continues also by monitoring the effectiveness of the active filter.
About the project
Improving water management with a watershed-based operational model in the Central Baltic Sea area
The Baltic Sea is one of the world’s most sensitive and polluted seas. About half of the nutrient load in the Baltic Sea comes from diffuse pollution, which accumulates for example from urban areas, agriculture, and forestry. The WSSP project promotes a practical and resource-wise Watershed Safety Plan (WSSP) operational model that enables municipalities, water utilities and other relevant actors to reduce the amount of diffuse pollution from reaching the Baltic Sea.
