Optimised ozone process for the elimination of micropollutants
Efficient – Flexible – Space-saving
SIDEST, the regional waste water association, is researching the removal of micropollutants at a clarification plant in Grevenmacher, Luxembourg. ProMinent GmbH provides technological support with an ozone system as an additional purification stage in the clarification plant.
Degradation of various micropollutants
The composition of the waste water to be treated presents a particular challenge for this pilot project. The plant receives waste water from the Lower Moselle region, comprising six municipalities with a total population of around 47,000. The waste water comes not only from private households, but also from an industrial estate, regional wineries, motorway services and a passenger ship. It is, therefore, organically and chemically polluted. The clarification plant receives rinsing and washing water from the winemaking process, especially during the autumn grape harvest. It contains residues of cleaning agents, insecticides and medicines. These substances, known as micropollutants, can damage aquatic ecosystems even in the lowest concentrations. They are extremely difficult to remove using traditional clarification plant technologies. These micropollutants can only be significantly reduced in a subsequent treatment stage. In this project, the plant operator worked with ProMinent experts to determine the amount of ozone required to eliminate the micropollutants present. Particular attention was paid to both the ozone input and the response times.
Key data
- A research project on the degradation of micropollutants in waste water of different composition and origin in a fourth treatment stage
- A state-of-the-art ozone system produces 105 g O3/h from oxygen in the ambient air
- For future expansion: in combination with various contact tanks, load-independent flexibility thanks to redundant modules that can be switched on and off
Combined process to the test
Since March 2022, the regional waste water association SIDEST has been researching the degradability of micropollutants as part of a pilot study at the Grevenmacher clarification plant. ProMinent GmbH of Heidelberg, Germany, was chosen as the partner for the fourth purification stage of the waste water treatment and supplied a state-of-the-art ozone system for this process phase. The first step is to oxidise the pollutants into largely harmless substances using ozonisation. In addition, some substances are retained in the downstream activated carbon filter. The ozone system is a pressurised system in which the feed gas, oxygen, is fed into the ozone generator and metered under pressure. The mixing equipment, which includes a unique helical mixer, ensures effective ozone input and homogeneous dissolution. This is essential for successful treatment results with reduced response times.
Not just clean, but four times cleaner
The results in Grevenmacher show: effective mixing combined with on-demand ozone generation resulted in a significant reduction in contact time from 20-30 minutes to just 5 minutes while maintaining reduction performance. This also significantly reduces the size of the concrete and steel contact tanks required, reducing otherwise high construction costs and space requirements.
After the fourth treatment, more than 80% of the micropollutants are removed from the waste water. Two other points are important: Firstly, the amount of ozone fluctuates dramatically due to rapidly changing waste water volumes and pollutant loads – keyword: economic efficiency in ozone generation. The modular design of the ProMinent ozone system offers maximum flexibility. The ozone generator modules operate independently and can be switched on or off individually, depending on the ozone requirement. This allows the amount of ozone produced to be adjusted in response to fluctuations. At the same time, the output of the modules can be controlled, resulting in highly efficient operation. Secondly, the waste water from the industrial area contains bromide. Ozone treatment can produce potentially harmful bromate. However, the results so far suggest that bromate formation can be disregarded as a concern despite high bromide concentrations due to the effective control of the ozone system, the ozone injection system, and the existing water matrix.
- High efficiency reduces energy consumption
- Significant space savings of up to 70% compared to conventional systems
- Redundant modules that can be switched on and off ensure high operational reliability
- Extremely low oxygen requirement due to high concentrations of up to 15% by weight
- Low stress on electrical components for a reliable and resilient system
- Simple operation and process visualisation with a 10" colour touchscreen panel