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Wastewater treatment plants step on the gas

Pure oxygen speeds up wastewater treatment

From the outside, wastewater treatment plants look like places where nothing happens in a hurry; not that much seems to be going on in the large basins. But this impression is misleading. The physical, chemical and biological wastewater treatment processes literally take place below the surface. And here the speed of the processes definitely matters: the quicker the purification process, the greater the plant’s efficiency. Biological clarification can be greatly speeded up through the targeted addition of oxygen. In Hungary, the experience with this process has been good, and has helped to keep investment costs down.

The Hungarian wastewater industry has received a considerable development boost over the past decade. As part of Hungary’s EU accession in 2004, the infrastructure was modernised across large parts of the country, bringing it into line with EU standards. At the same time, however, the demands on the system have changed considerably. Hungarians are much more economical with their drinking water today – consumption has dropped by a quarter since the early 1990s, from around 125 litres to approximately 95 litres per head. While there has also been a corresponding drop in the quantity of wastewater, its relative pollutant load has increased significantly. Furthermore, the wastewater treatment plants are often faced with considerable load fluctuations. Varying amounts of wastewater, often containing a high concentration of pollutants, have to be treated as and when the need arises while at the same time complying with strict limits. Increasing the capacity by means of conventional technology is time-consuming and expensive. A cost-effective alternative is to speed up the purification process. The partial oxygenation process (PO) developed by Messer boosts the efficiency of existing plants while keeping capital expenditure low. The process involves injecting pure oxygen instead of normal air into the activated sludge basins. This has the effect of boosting aerobic bacterial activity, resulting in a much faster biodegradation process. This also applies to the very important process of nitrification, the bacterial oxidation of ammonia to nitrate.

The aeration hoses, injectors and oxidators used in the PO process can be precisely calibrated in accordance with the treatment plant’s parameters. “The choice of system or system combination is largely determined by the application and the local conditions,” says András Paszera, an environmental technology specialist at Messer. Important parameters include the basin geometry and the availability and cost of electricity.

Thick-walled hoses with a large number of tiny pores or a pump-Venturi injector are used to inject the oxygen into the activated sludge basin, where it is dispersed in the form of very fine bubbles. This allows a particularly large amount of oxygen to be added with a correspondingly high degree of efficiency, as well as precise dosing in line with requirements. “Partial oxygenation is especially suitable for industrial plants with heavily fluctuating loads and for wastewater treatment plants with campaign operation,” András Paszera explains. “This means that it is no longer necessary to have large, capital-intensive basin volumes available – physical capacity is replaced by biological efficiency.”

Partial Oxygenation

The PO process can be used in a wide range of industries, including the chemical, leather, textile and food industries as well as the pulp and paper industry and municipal wastewater treatment plants.



The strengths of partial oxygenation:

  • Increased cleaning capacity
  • Reliable nitrification
  • Flexible response to shock loads
  • Marked reduction in odour emissions
  • Silent oxygen injection
  • Increased operational reliability
  • No need to expand treatment plant, low investment costs
  • Emergency use possible in event of aerator failure
  • Suitable as interim solution

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