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Interview with Zalán Varvasovszki

Water Technology Expert at Fejérvíz:

The customer:

The county of Fejér, south-west of Budapest between Lake Balaton and the Danube, has been supplied with drinking water and had its wastewater treated by the Fejérviz Zrt waterworks since 1913. Messer’s PO system has enabled the municipal enterprise to increase the capacity of existing plants considerably without any new build.

“We were so impressed with the PO system that we commissioned a second one in Vértesacsa in May 2010.”

Gases for Life: What kind of diffi culties were you faced with at the wastewater treatment plant in Mezőszilas before trial operation of the PO system?

Zalán Varvasovszki: There is a nursing home in Mezőszilas which has grown considerably in the last few years. Roughly one third of the local wastewater comes from this home – much more than originally envisaged, and what’s more it is heavily polluted with ammonia. The conventional aeration system at the local wastewater treatment plant couldn’t cope. Even the installation of additional aeration capacity was not always able to ensure an appropriate supply of air and an adequate level of purifi cation in the activated sludge system. The activated sludge basin was putrefying before our eyes.

Gases for Life: So what did you do?

Zalán Varvasovszki: In 2007, we tried out a system for adding pure oxygen. The necessary infrastructure and oxygen was supplied by Messer. The three aeration nozzles were replaced and approximately fi ve cubic metres of oxygen per hour added to the activated sludge basin.

Gases for Life: What were the results?

Zalán Varvasovszki: After two and a half weeks we managed to return to optimum “living” operating conditions. The addition of pure oxygen ensures stable nitrification and favourable biological conditions. The system has also proved itself in periods of unusually large volumes of wastewater, for we have already experienced numerous shock loads lasting several days. In such cases, the oxygen content in the wastewater drops dramatically. Here the flexibility of partial oxygenation allowed us to respond effectively. We have also seen a marked decrease in the plant’s electricity consumption. We were so impressed with the PO system that we installed it as a reference system in September 2008. We also commissioned a second PO system in Vértesacsa in May 2010.

Gases for Life: What was the situation at Vértesacsa?

Zalán Varvasovszki: Here, too, the wastewater arriving at the treatment plant was heavily polluted. The PO system now provides an optimum oxygen supply for nitrification, even in periods of greatest demand. This has allowed us to reduce the aeration nozzle operating time by 15 to 20 per cent. The nitrogen content in the treated water is continuously below 20 milligrams per litre and thus well below the upper limit. In theory, the treatment plant could now even take 10 to 20 per cent more wastewater.

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