Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Combating pollutants in wastewater with ozone

16.08.2007
Wastewater treatment plants are designed primarily to eliminate nutrients. However, attention is increasingly being focused on micropollutants, since even low concentrations of these substances can have adverse impacts on aquatic ecosystems. Ozonation of wastewater appears to be a promising option for removing micropollutants at treatment plants.

Thanks to the country’s well-equipped wastewater treatment plants (WWTPs), the state of Switzerland’s waters has improved significantly over the past 30 years. However, residues of chemicals in everyday use are still entering waterbodies, as these substances cannot be removed by conventional WWTP technology.

The Federal Office for the Environment (FOEN) is currently evaluating various ways of reducing inputs of such micropollutants from municipal wastewater into receiving waters. On behalf of the FOEN, Eawag – the Swiss Federal Institute of Aquatic Science and Technology – is conducting a pilot study at the Wüeri WWTP in Regensdorf (near Zurich) to investigate whether micropollutants can be eliminated with the aid of an additional treatment step involving ozonation of wastewater.

Ozonation followed by granular activated carbon filtration is already a standard method for the treatment of raw surface water to produce drinking water (see Box). Here, the main purpose is disinfection, but also the elimination of organic substances and odour compounds, and colour removal. The experience gained in the drinking water area can be used in applying the method to wastewater treatment. In addition, ozonation is a straightforward process involving only a small number of components, and it can be readily adapted to local conditions.

Laboratory tests with wastewater have shown that the ozonation method can be successfully used to eliminate a wide range of micropollutants. In the scaled-up process, ozone is added to the wastewater stream in a special reaction vessel, ensuring adequate mixing and contact time. Various options exist for technical implementation. A simple and reliable method – used at the Wüeri wastewater treatment plant (WWTP) in Regensdorf – is the injection of fine (gas) bubbles in a closed contact tank. Any remaining ozone not consumed in the process would be destroyed in the off-gas with the aid of a thermal catalytic unit.

At the Wüeri WWTP in Regensdorf, an ozone reactor connected to a sand filter is being installed after the biological treatment step. The sand filter, which includes a biofilm, is designed to permit further biological degradation of pollutants following the breakdown of complex compounds by ozonation. The planned studies will focus on measurement and ecotoxicological analysis of pollutants which it has not previously been possible to eliminate (at all or in full) at WWTPs. This is the case, for example, for benzotriazoles (used as anticorrosive additives, e.g. in dishwasher detergents), diclofenac (analgesic and anti-inflammatory agent) and carbamazepine (antiepileptic). To date, it has also only been possible for natural and synthetic hormones (estrone, estradiol) to be partly removed, under certain conditions (sufficiently high sludge age).

Box: What happens in the ozonation process?

Ozone, which consists of three oxygen atoms, is a reactive gas. It is a powerful oxidizing agent and forms hydroxyl radicals in contact with water. While ozone itself only oxidizes certain substances, the hydroxyl radicals attack a wide range of substances. Ozonation thus leads to the breakdown of various complex compounds, making substances much more susceptible to subsequent biological degradation. During this process, not only pollutants but also microorganisms are destroyed; for this reason, ozone is frequently used as a disinfectant.

Ozone is produced in ozone generators by electrical discharges from purified and dried air, or directly from industrial oxygen. It thus arises from oxygen and, over time, also decomposes into oxygen. A process of the same kind occurs naturally in thunderstorms.

Andri Bryner | alfa
Further information:
http://www.eawag.ch/index_EN

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling 'fast fashion' to reduce waste and pollution
03.04.2017 | American Chemical Society

nachricht Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>