Wastewater treatment in Helsinki to become more energy efficient

Two new approaches will be employed by local authorities in a bid to save energy and further protect the environment

Helsinki Region Environmental Services HSY is starting two projects at Viikinmäki Wastewater Treatment Plant to promote energy efficiency in wastewater treatment. One of the projects focuses on heat recovery and heat utilization of digested sludge, the other on developing more efficient oxygen transfer of aeration used in wastewater treatment.

Saving energy wherever and whenever possible

Wastewater treatment consumes a lot of energy. The annual electricity consumption of the Viikinmäki wastewater treatment plant is approximately 40 GWh and the heat demand 34 GW. multiplied by HSY. The heat recovery solutions it develops do not produce emissions, which has a dampening effect on the climate.

Heat recovery from digested sludge utilizes the heat generated in the operation of the treatment plant. The heat recovered from the sludge is to be transferred to the treatment plant's own heat recovery network and raw sludge. The annual amount of thermal energy obtained is estimated to be about 2.8 GWh. This corresponds to the average total annual energy consumption of 140 detached houses or the heating energy needs of 215 detached houses.

When it comes to the other solution, aeration is part of the biological process of wastewater treatment. As a result, living bacteria begin to remove organic matter and nutrients from wastewater. The improvement in oxygen transmission efficiency to be implemented in the development project is estimated to reduce the air consumption of the lines to be modified by approximately three per cent and the total annual electricity consumption of Viikinmäki by approximately 240 MWh.

The Viikinmäki wastewater treatment plant is already about 97% self-sufficient in terms of electrical energy and completely self-sufficient in terms of thermal energy. The cleaning results are also at an excellent level.

The treatment plant serves the wastewater treatment of approximately 860,000 inhabitants and industrial area in the central and eastern metropolitan area of ​​Helsinki.