Gatchina Wastewater Treatment

Gatchina is located 40 kilometers south of St Petersburg by the Izhora river which has its outflow in the Neva river which discharges to the Gulf of Finland. The water supply and wastewater treatment systems in Gatchina have improved over the past years. Investments have aimed at securing safe and reliable operation of pumping stations and sludge dewatering as well as for making forthcoming investments for enhanced treatment possible. The wastewater treatment plant has an average daily inflow of 49 000 m3. The reduction of organic material in the treatment plant is good but effluent concentrations of nitrogen and in particular phosphorous exceed the HELCOM recommendations.

Project Description

The proposed project involves improved nitrogen reduction in combination with biological and chemical phosphorous removal. The designs and cost estimates presented involves mechanical rehabilitation of two biological treatment lines, installing new membrane diffusers, mixers and instrumentation. A new dosing station for precipitation chemicals will be built with dosing equipment. There is also the introduction of a new SSH-reactor (Side Stream Hydrolyses) in one of the existing aeration lines. The effluent treatment requirements of the wastewater treatment plant after investments shall enable fulfilment of HELCOM requirements.

Environmental Benefits

The treatment plant will meet the HELCOM recommendations of (BSAP) and EU waste water treatment directives. Phosphorous reduction to the Baltic Sea will be some 25 t/a and nitrogen reduction 42 t/a.