Technical audits in PURE
In 2010, technical audits were conducted in the wastewater treatment plants of five PURE partner water utilities – Brest (Belarus), Jurmala (Latvia), Kohtla-Järve (Estonia), Gdansk and Szczecin (Poland). The technical audits considered the current technical processes, necessary technology to decrease the concentration of phosphorus in purified wastewater and the consequent additional investment and operation costs. Achieving HELCOM recommendation, the concentration of 0.5 mg/l phosphorus in outgoing wastewaters, significantly reduces the eutrophicating load to the Baltic Sea. The technical audits were carried out by Pöyry Finland Oy, hired by John Nurminen Foundation with PURE co-financing from the EU Baltic Sea Region Programme.
PURE technical audit reports showcase the diverse challenges that exist in efficient municipal wastewater treatment in the Baltic Sea Region and give proposals to improve the treatment efficiency at each audited WWTP.
Brest municipal wastewater treatment plant currently lacks capacity for efficient biological nutrient removal. Introducing chemical precipitation of phosphorus was found as the quickest and most cost-efficient way to reduce the phosphorus load to the Baltic Sea from Brest. As the incoming phosphorus load to the plant is high, chemical precipitation will be needed to reach the HELCOM recommendation even if the biological process would be refurbished in the future. PURE-financed chemical storing and dosing station will be built in old, unused pre-aeration basins. Also new on-line and laboratory analysis equipment of phosphate and total phosphorus will be purchased within PURE to optimize the treatment process.
Gdansk, Jurmala, Kohtla-Järve and Szczecin wastewater treatment plants are all quite new and achieve good results in nutrient removal, although occasionally exceed the limits for effluent concentrations. Common to these plants is large capacity with regards to the incoming wastewater load. Some of these audited plants are facing problems with bulking sludge, which can lead to escape of phosphorus with effluent solids. These problems can be minimized with sufficient process control.
At Jurmala wastewater treatment plant, the proposed PURE investment includes e.g. an additional polymer station to improve sludge thickening, and new online measurement equipment to improve the process control and balancing. This enables the plant operators to enhance nitrogen removal without jeopardizing phosphorus removal efficiency. The auditors gave several suggestions to further improve the performance of Kohtla-Järve wastewater treatment plant. These suggestions deal with e.g. improving sludge thickening and activated sludge mixing.
At Gdansk and Szczecin wastewater treatment plants, no new investments are needed to reach the level of 0.5 mg/l phosphorus. The biological processes remove nutrients efficiently and the plants already have the needed equipment for precipitation chemical storage and dosing to ensure efficient phosphorus removal. At the time of the audits, Gdansk Wschod WWTP aeration basins were undergoing major renovation with the aim to enhance nitrogen removal. The auditors, however, questioned the relevance of this renovation work in their report.
Partners technical report audits: