| | DECEMBER - JANUARY8IN MY OPINIONKristian Sahlstedt, Director of Wastewater Treatment, Helsingin seudun ympäristöpalvelut HSYByFact box: HSY·HSY (Helsinki Region Environmental Services) is a municipal federation, which provides water supply, sewerage, and waste management services for the Greater Helsinki region·Population served appr. 1.1M·Water supply and sewerage services funded 100 percent by customer fees·80 M m3/a of drinking water produced·130 M m3/a of wastewater treated·Turnover ~350 MEUR, investments ~180 MEUR/aHSY (Helsinki Region Environmental Services) is a municipal federation, which provides water supply, sewerage and waste management services for the Greater Helsinki region as well as information on the Helsinki metropolitan area and the environment.Improvement of energy efficiency is a long-time strategic goal of HSY. By 2030, our entire services shall be carbon neutral, and we shall produce an amount of renewable energy equal to no less than 100 percent of our own consumption. In addition to creating a positive climate impact, energy efficiency reduces our dependency on liquid fuels and electricity bought from the market, thus improving both the crisis resilience and economical performance of our services. In this article, we present some key features and results of the energy-related actions implemented at our wastewater treatment plants (WWTPs).Wastewater Treatment and EnergyAbout 60 percent of the energy consumed by HSY and 80 percent of the energy produced by HSY are attributed to wastewater treatment, making this service the key player in our energy balance. HSY owns two WWTPs, dimensioned for PE 1.5 M in total. Both plants are built inside bedrock and are based on biological-chemical removal of nitrogen and phosphorus by activated sludge and tertiary filtration. It include anaerobic digestion of biosolids, which produces biogas. Electricity is produced in biogas-powered combined heat and power (CHP) units and organic rankine cycle (ORC) exhaust gas turbines. In addition, electricity is produced by solar panels installed on top of the WWTPs and pumping stations. Heat is generated from CHPs, biogas boilers, and heat recovery from treatment processes and exhaust air. In addition, local energy companies utilize up to 125 MW of OPTIMISING THE ENERGY BALANCE OF WASTEWATER TREATMENTKristian Sahlstedt
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