Optimized ozone process for eliminating micropollutants
Efficient – Flexible – Space-saving
The regional waste water association SIDEST is conducting research into the breakdown of micropollutants at a sewage plant in Grevenmacher, Luxembourg. ProMinent GmbH provides technological support with an ozone system that is used as an additional purification stage in the sewage plant.
Breakdown of various micropollutants
The particular challenge in this pilot project arises from the composition of the waste water to be treated. The waste water from the Lower Moselle region, comprising six municipalities with around 47,000 inhabitants, is fed into the sewage plant. However, the waste water not only originates from private households but also from an industrial park, regional winegrowers, a highway rest area and a passenger boat. Therefore, it is contaminated both organically and chemically. Rinsing and wash water from the wine-making process is fed into the sewage plant, primarily during the grape harvest in the fall. It contains the residue of cleaning agents, pesticides and pharmaceuticals. These substances, known as micropollutants, can damage aquatic ecosystems even in the smallest concentrations. They are almost impossible to eliminate using conventional technology in sewage plants. An additional purification stage is required to eliminate these trace substances as far as possible. In this project, the system operator worked with ProMinent experts to determine the amount of ozone required to eliminate the existing micropollutants. Particular attention was paid to ozone input and reaction times.
Key data
- Research project on the breakdown of micropollutants in waste water of different composition and origin in a fourth treatment stage
- Generation of 105 g O3/h from oxygen in the ambient air with a state-of-the-art ozone system
- For later expansion: in combination with several contact basins, load-independent flexibility thanks to modules that can be redundantly switched on and off
Combined procedure under test
Since March 2022, the regional waste water association SIDEST has been researching the degradability of micropollutants as part of a pilot project at the sewage plant in Grevenmacher. ProMinent GmbH from Heidelberg was chosen as the partner for the fourth purification stage in waste water treatment, who supplied a state-of-the-art ozone system for this process step: First, the pollutants are oxidized into largely unproblematic substances by means of ozonation. In addition, other substances are retained in the downstream activated carbon filter. The ozone system is a pressurized system in which the feed gas, oxygen, is fed into the ozone generator and dosed in under pressure. The mixing system with a special swirl mixer ensures efficient ozone input and homogeneous dissolving. This is crucial for effective treatment success with shortened reaction times.
Not just clean, but fourfold pure
The results in Grevenmacher show: The combined process of efficient mixing and demand-controlled ozone generation allows a significant reduction in the contact time from the usual 20-30 minutes to just 5 minutes, while maintaining the same reduction performance. This also significantly reduces the required size of the concrete and steel contact tanks, which in turn reduces the otherwise high construction costs and the enormous space requirements.
After the fourth treatment, more than 80 percent of micropollutants are removed from the waste water. Two further points are important: For one, the ozone quantity also changes dramatically due to the strongly fluctuating waste water volumes and pollutant load – keyword: economic efficiency in ozone generation. Thanks to its modular construction, the ozone system from ProMinent offers the greatest possible flexibility in this regard. The ozone generator modules work independently and can be switched on or off individually, depending on the ozone requirement. This allows the amount of ozone produced to be adapted to fluctuations. At the same time, the modules’ capacity can be regulated, resulting in extremely efficient operation. Secondly, the waste water from the industrial park contains bromide. Treatment with ozone can produce potentially harmful bromate. However, the results to date show that the proper control of the ozone system in conjunction with the ozone input system and the existing water matrix render the bromate formation negligible despite high bromide concentrations.
- An extremely high level of efficiency ensures minimal energy consumption
- Significant space savings of up to 70 percent compared to conventional systems
- Modules that can be switched on and off redundantly ensure high operational safety
- Extremely low oxygen requirement due to high concentration of up to 15 percent by weight
- Reliable and robust system thanks to the low load on the electrical components
- Simple operation and process visualization via a 10" color touch screen panel