In the extensive area covered by the ‘AIZ’ Wastewater Management Association, a large number of pumps are constantly at work moving wastewater into the right channels and ultimately to the sewage treatment plant. VEGA level sensors deliver reliable measured values that ensure that the pumps switch on and off at the right time and save energy.

Achental, Inntal, Zillertal (AIZ) – are Tyrolean valleys on the northern edge of the Alps – extremely popular with tourists in both winter and summer, attracting around 8.5 million visitors every year. Hotels, guest houses, bars and restaurants, as well as their world-renowned alpine dairies and yoghurt producers, make sure the guests have a very enjoyable experience.

The local sewage treatment faces a special challenge. There are large variations in the wastewater produced in the area with different tourist (and weather) seasons, and it also has a higher than normal fat content. Technologically, this makes the process conditions quite challenging for level sensors: the high fat content in the wastewater means lots of foam – this makes detection and control of the sewage levels in the various points of the network difficult to control.

At one with nature

The network treats not only the wastewater produced by the visitors, but also that produced by the approx. 53,000 permanent residents of the 32 local communities. connected to the AIZ. “All in all, we treat 10 million cubic meters of wastewater per year,” explains Josef Brandacher, who is responsible for the measurement technology at AIZ. “The local environment is our greatest asset, so it is vital that the collection and handling of wastewater as well as its subsequent treatment is both environmentally compatible and economically viable.”

The wastewater feeds into the Strass sewage treatment plant via a 161 km-long sewer network 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.” adds Brandacher, with great pride. As a result, the total energy consumption of the wastewater treatment systems has dropped noticeably since 2003, despite the increasing loads. The specific energy consumption in kWh per inhabitant and year has been reduced from an initial 30 kWh to approximately 20 kWh.

This could only be achieved by utilisation of reliable, and above all accurate, measured values and data. For the level and pressure process variables, the association decided decades ago to standardise on sensors from VEGA. “We’ve been working together since 1989 and some of the pressure transmitters we installed back then still function perfectly,” continues Brandacher, “What we especially appreciate about the company is that, if a problem does occur, we always get help and support straight away.”

On the way to the sewage treatment plant

The wastewater is collected via a sewer network and then directed to the Strass sewage treatment plant. Because of the terrain, there are about 100 pumping stations in the network with level and pressure sensors installed in each one. These monitor the level – which can be from around 50 cm to 1 meter depending on the pumping station – and control the pump sets. “Sometimes the pumps start up only 2 or 3 times a day, but sometimes it is 50 to 60 times,” explains Brandacher. The 26GHz VEGAPULS radar WL 61 is installed in many of these shafts. This sensor is considered an all-rounder in the water and wastewater sector, proving its robustness and adaptability to virtually any process and environmental conditions.

New sensor in use

In early 2020, AIZ wanted to test the new range of compact VEGAPULS radar sensors. “We were just plain curious. The new sensors are very interesting in terms of price and performance. In wastewater we increasingly need affordable, reliable level measurements – even for the simple applications, to get better data and control.”

The new non-contact radar series are designed for the water sector, where a combination of high performance and protection is required. The application spectrum ranges from level measurement in pump shafts and flow measurement in open flumes, to river and lake gauging or event duration monitoring at stormwater overflows, and even bulk solids like lime and sludge cake. It is based on VEGA’s latest 80-GHz FMCW radar technology, which has been revolutionising level measurement for several years now. This is thanks to the extremely narrow beam angle, and high sensor sensitivity, which makes it possible to operate even in cramped, narrow measuring situations, with many internal installations or in extremely dirty environments or foaming surfaces.

A great example of this exists in the two pump shafts in Hart and Buch in Zillertal. “All the adversities one can imagine are present in the pump shafts. Aerosols, moisture, cold, dirt, etc. and of course the huge quantities of fatty material,” explains Brandacher further.

In Hart, the pump shaft has a cross-section of about 3 x 2.5 metres and a depth of 4 metres. In Buch the shaft is round, with a diameter of 2 metres and a depth of 5.5 metres. The situation here is particularly difficult because of the low level of water level impoundment. This means the pump is effectively in continuous operation, switching on and off up to 100 times a day. An ideal application site for the new VEGAPULS radar sensor series. The sensors work reliably, even with foam, of which there is plenty in the AIZ network, and with the fatty build-up on the shaft walls.

Since March 2020, both sensors have been delivering the required level data continuously without any problems. A development that is entirely in the spirit of Brandacher’s philosophy: “Sensors are there to measure and perform, and nothing else.”

Their installation and set-up is very simple and straightforward. The sensors delivered the required measured values right from the start. “The new sensor is of course particularly interesting because of its simplicity and user-friendly App based Bluetooth set up. Since we don’t have to worry about level measurement any more, we can concentrate on other tasks,” says Brandacher in conclusion. “VEGA has always understood this aspect very well and expertly demonstrates it in this measurement technology.”