API: The Main Wastewater Treatment Plant (MWTP) of the Austrian capital ranks as one of the world’s most advanced and efficient largescale treatment plants, not only removing the bulk of organic pollutants but also nutrients such as nitrogen and phosphorus. This assures that Danube water leaves Vienna in the same good quality it has when it enters the city area. Have we reached the treatment efficiency ceiling?
Gantner: We certainly cannot afford to rest on our laurels, but need to cooperate closely with scientists and researchers to keep abreast of the latest technologies. What comes to mind in this respect is the recent debate about hormonally active substances and residues from medical drugs and personal care products in treatment plant outlets and receiving waters, of which today even trifling quantities can be evidenced much more efficiently thanks to the advances in chemical analysis. The sanitary conditions of water bodies, too, must meet increasingly stringent requirements. As to the aforementioned micro-pollutants, our MWTP staff is collaborating with TU Vienna on experiments with ozone. The last issue of aqua press reported in depth on our KomOzon project. Preliminary test results are quite encouraging, but it is still too early to raise expectations regarding a large-scale usability.
API: Nano-material residues are said to be turning into a problem for wastewater treatment because of their non-biodegradability. Is this really a problem, and if so, how is EbS coping with it?
Gantner: The environmental impact of nano-materials is still largely uninvestigated. Regarding the opportunities attributed to this new technology in terms of resource savings and eco-friendliness, we believe that laws should be set up that regulate the handling of these materials. But since all effluents end up in the MWTP, we will certainly deal with this issue, as we did with micro-pollutants, once the respective research results are available.
API: Entsorgungsbetriebe Simmering has decided to convert the MWTP into an energyautonomous facility. The integration of a small hydropower unit in the outlet channel of the plant, which is decribed in detail on the following pages, is a first step in this direction. Lyonnaise des Eaux, for instance, plans to use sewage gas for energy recovery. Is this also an option for EbS?
Gantner: In view of climate change, soaring power prices and dependence on foreign energy, it is important that we exploit and assess all available medium-term options. Last year a study was conducted and a catalogue of measures was developed, which shall help to enhance power supply and reduce power consumption by using alternative/renewable energies for hot service water. Based on these two accomplishments, a number of projects will be carried out in the years to come. As for the recovery of sewage sludge, we have concluded a medium-term agreement with Fernwärme Wien, so that this is not an issue of immediate priority. The next step towards energy autarky will therefore be the execution of a solar thermal project in keeping with our environment programme. Project evaluation and planning of a solar-powered hot water system for our social building and canteen is complete. A photovoltaics project is also scheduled for this year, and a wind power project is likely to be executed in 2010.
API: EbS has been EMAS-certified since 2007 and was honoured with the EMAS Award for its environmental declaration last year. The EMAS Directive is now under review. What do you think of the current proposals?
Gantner: As far as I know, only one substantial change has been added to the new draft, which I consider to be a positive development. It is the proposal to integrate some key indicators such as energy efficiency, water, waste and emissions, including the associated sector-specific best practice reference documents. In the light of the looming environmental challenges, this addition to the EMAS law is certainly the right approach and supports companies with a consistent eco-friendly management. Considering that EMAS also increases the bureaucratic burden, there should be more and better incentives for companies willing to take the burden.
API: The MWTP is designed to serve a population equivalent of four million. When will there be a need to further expand plant capacity? Are there any plans for a third cleaning stage?
Gantner: The MWTP is designed for a capacity that lasts until 2015. From a current viewpoint, the original underlying assumptions are still valid; based on these underlying parameters no further expansion will be necessary. As far as a third cleaning stage is concerned, this question cannot yet be answered. Last but not least, it also depends on the future legal requirements. But you can be certain that EbS will put continuing efforts into keeping its leadership position in wastewater management.
API: Thank you for this interview.
(Source: aqua press Int. 1/2009, Mag. Christof Hahn)