Waste Management In Action

Pump shafts and flow measurement: VEGA

VEGA level sensors are delivering reliable measured values to ensure Abwasserverband Aiz’s wastewater pumps operate efficiency.

In the extensive area covered by Austrian wastewater service provider Abwasserverband AIZ (AIZ), a large number of pumps are constantly at work moving wastewater into the right channels and ultimately to the sewage treatment plant.

Austria’s Tyrolean Valleys on the northern edge of the Alps are extremely popular with tourists. Countless hotels, guest houses and restaurants, as well as small businesses, do their best to make sure the guests have a completely enjoyable experience.

The local sewage treatment plants, however, face a special challenge.

Wastewater produced in the area has a high fat content.

Although cleaning out and processing this material is not a problem technologically, the process conditions are quite challenging for level sensors. The high fat content in the wastewater creates a lot of foam, which makes the liquid levels in the various basins and pump shafts difficult to detect.

Nevertheless, level measurement in wastewater treatment processes has to be exact and reliable.

Level data form, among other things, the basis for pump controls.

The sewage treatment plant treats not only the wastewater produced by visitors, but also that produced by the 53,000 permanent residents of the 32 local communities.

“All in all, we treat 10 million cubic meters of wastewater per year,” Josef Brandacher, who is responsible for measurement technology at AIZ, explains.

“The environment is our greatest asset, so it is incumbent upon AIZ to ensure that the collection and handling of wastewater, as well as its subsequent clarification, is environmentally compatible and economically viable.”

The wastewater is fed to the Strass sewage treatment plant via a 161 kilometre sewer network and 14 pumping stations distributed throughout the association’s territory.

“Thanks to the state-of-the-art process technology in our facilities, we’ve achieved absolute top performance in the entire pan-European wastewater sector,” Brandacher says.

As a result, the total energy consumption of the wastewater treatment plant has dropped noticeably since 2003, despite increasing loads.

This could only be achieved by means of reliable and accurate measured values.

For the process variables level and pressure, the association decided decades ago to use sensors from VEGA.

“We’ve been working with VEGA since 1989 and some of the pressure transmitters we installed back then still function perfectly,” Brandacher says.

“What we especially appreciate about the company is that when a problem does occur, we always get help immediately.”

There are about 100 pumping stations in AIZ’s network and a variety of level sensors are installed in each one.

These monitor the level – which can be from around 50 centimetres to one meter depending on the pumping station – and switch on the pumps according to the set limit value.

“The pumps sometimes start up only two or three times a day, but sometimes 50 to 60 times,” Brandacher says.

For reasons of explosion protection, VEGAPULS WL 61 is installed in many of these shafts.

The application spectrum of the radar sensor, which is designed specifically for water and wastewater measurement, ranges from level measurement in pump shafts and flow measurement in open flumes to river and lake gauging or level and discharge measurement at stormwater overflow basins.

The measurement is affected neither by changing medium properties nor by fluctuating process conditions such as temperature and pressure.

In addition, the flood-proof IP68 housing ensures continuous, maintenance-free operation.

Although AIZ very much appreciates VEGAPULS WL 61, it wanted to try out the new compact VEGAPULS C 21/C 22 radar sensors.

“We were just plain curious. The sensors are very interesting in terms of price, and in the wastewater sector, we increasingly need continuous level measurement, especially for simple applications.”

The sensors are intended for simple, non-contact level measurement where a high protection rating is required.

The sensor delivers exact measuring results without effect from the medium, the process or the ambient conditions, is maintenance free and ensures high plant availability.

The sensor has been in use since March 2020, delivering the required level data continuously without any problems – a development hat is entirely in the spirit of Brandacher’s philosophy.

“Sensors are there to measure and nothing else.”

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