In autumn 2011, the red-green coalition government - represented by Environment City Councillor Ulli Sima and Deputy Mayoress Maria Vassilakou - presented a new future-oriented climate protection project for ebswien hauptkläranlage: “E_OS - Energy_Optimisation Sludge Treatment”. Thanks to further investments into the primary sedimentation process, the first biological cleaning stage and the new construction of a sewage sludge treatment system, Vienna’s main wastewater treatment plant will achieve energy self-sufficiency by the year 2020.
To optimally clean all of Vienna’s wastewater, the treatment plant requires a lot of energy. Sima says: “ebswien has already started to build on the use of alternative fuels. Once the new sewage sludge treatment system is fully operational, the company can produce more energy from renewable sources than it needs and will become completely self-sufficient.“ This will enable substantial savings on operating costs. Vassilakou adds: “This project is another vital step towards eco-friendly power generation and climate protection in Vienna. And it leads to considerable cost reductions. E_OS demonstrates that investments into climate protection are also economically beneficial.“
Making room for climate protection
The primary sedimentation process and the first biological cleaning stage of Vienna’s main wastewater treatment plant have been continuously in operation since 1980. They will undergo a major upgrade starting in 2015. This reinvestment is necessary for the following reasons:
- The plant will continue to operate on the basis of state-of-the-art technology.
- Maintenance costs will decrease considerably.
- A higher level of operational safety can be guaranteed during revisions and during the increasing number of flood events (risk of “floating” tanks).
The concurrent new construction of a sludge treatment system will optimise synergies. The tanks will be built deeper to reduce the lateral extension of the first biological cleaning stage, which will create space for the newly constructed sludge treatment plant.
- Six digesters with a height of 30 m each will be erected.
- A co-generation plant converts the sewer gas into energy.
- 20 million m³ of methane result in 78 GWh of electricity and 82 GWh of heat. The system therefore produces gas as well as electricity or heat from renewable energy.
Energy self-sufficiency by 2020
ebswien hauptkläranlage currently needs 60 GWh of electricity per year for cleaning all of the city’s wastewater, equating to 1% of Vienna’s total electricity consumption. In accordance with Vienna’s climate protection programme KliP and energy efficiency programme SEP, ebswien has since 2008 undertaken consistent efforts towards increasing energy efficiency and using renewable sources of energy. A number of (waste)water, solar and wind energy utilisation goals have meanwhile been accomplished in the course of “SternE – Strom aus erneuerbarer Energie”, a project for electricity generation from renewable resources. This has already helped to cut energy consumption by 11%. The E_OS project goes even further:
- ebswien hauptkläranlage will become energy self-sufficient: by utilising 20 million m³ of methane from sewer gas per year (1% of the total amount of natural gas fed through Vienna’s system), ebswien hauptkläranlage will be able to produce all the energy needed for wastewater cleaning through its own system.
- The recovered sewer gas is acknowledged as an efficient renewable fuel which, unlike solar and wind power, is constantly and readily available. The proportion of renewable sources of energy used at ebswien will rise to over 100% once the new sludge treatment plant is fully operational.
- Vienna’s carbon footprint will benefit enormously: CO2 equivalent emission will decrease by 40,000 tonnes annually, equating to the greenhouse gas emissions of a town with 4,000 inhabitants or a car circumnavigating the globe 6,700 times.
Plant remains fully operational during construction
During the E_OS construction phase, the primary sedimentation process and the first biological cleaning stage of ebs hauptkläranlage have to remain in operation. This results in a construction period of more than five years. After the completion of the regulatory permitting and tender procedures, construction will begin in summer 2015. The E_OS project is scheduled to start operation by the end of 2020.