Stadtwerke Heppenheim is the municipal utility company managing wastewater in the city of Heppenheim, south of Frankfurt in Germany. The wastewater treatment plant (WWTP) at Heppenheim handles the wastewater of approximately 30,000 people (the 25,000 inhabitants of Heppenheim plus parts of the Odenwald district). The WWTP, which has the capacity to treat wastewater from 80,000 citizens and currently treats 1.2 million cubic metres of wastewater per year, also handles industrial wastewater from e.g. an ice cream factory, a winery, and a non-alcoholic beverage factory.
The WWTP at Heppenheim is a sequencing batch reactor (SBR) system which does not treat wastewater continuously but works in batches using four basins. Until recently, the plant only dosed aluminium sulphate to achieve particle reduction in the wastewater, but a new dosing station was added in order to reduce phosphate levels in the water.
Like many other WWTPs, the Heppenheim plant needs to save on operating costs, and optimising chemical consumption is a good place to look for savings. "Chemical reduction is very important for cost savings", says Kai Kühn, Wastewater Treatment Manager at Stadtwerke Heppenheim. The company already kept an eye on chemical consumption, measuring consumption using tank level meters, but when the new dosing station was installed, the WWTP discovered new ways of monitoring plant performance.
The Grundfos solution
The new dosing station relies on two Grundfos SMART Digital XL DDA-FCM 60-10 diaphragm dosing pumps that reduce phosphate levels in the wastewater by dosing iron (II) chloride (FeCl2). The first pump doses FeCl2 while the treatment basin is being filled; the other pump is in standby mode for back-up in case of issues. The permanent magnet synchronous motor and diaphragm dosing technology means that the pumps dose the chemicals with unbeatable accuracy, saving on chemical costs while ensuring consistent treatment performance.
The process monitoring and online communication features of the SMART Digital XL DDA-FCM add value during everyday operation. With the built-in flow meter and pressure monitor, the pumps are able to monitor FeCl2 consumption with great precision. This provides more accurate measurements than checking the tank level and makes external measuring equipment superfluous. "We use the integrated flow meter of the SMART Digital XL. For the old aluminium sulphate dosing setup, we need an external flow meter and a pulsation damper", comments Oliver Schranz, Electrical Department Manager at Stadtwerke Heppenheim.
Accurate flow information also allows the SMART Digital XL DDA to adjust dosing volumes to match actual operating conditions. The pump continuously ensures that the amount of iron chloride is just right without operator interference, and it raises the alarm in case of issues such as pipe bursts or clogged pipes: Through a Grundfos CIU 150 communication interface unit, each pump is able to communicate via the Profibus DP protocol, alerting WWTP operations staff. "All issues and disturbances are identified and communicated to the plant control room via fieldbus", explains Oliver Schranz. "In the case of faults or warnings, the pump performs self-analysis to detect the reason and then transmits the information to the operator on duty at night or on weekends".
Automatic operation and timely alerts make the operator’s job a lot easier at Heppenheim. The built-in intelligence of the pump minimises the need for operator intervention, and when the operator does need to get involved, the easy use and handling of the pump means that no manual is required. The WWTP staff is very satisfied with the user friendliness of the SMART Digital XL DDA.
The SMART Digital pumps have helped Stadtwerke Heppenheim achieve reliable, low-cost dosing in a user-friendly solution. "We like the easy operation of the SMART Digital XL and the possibility to integrate fieldbus options", says Oliver Schranz. "Fieldbus integration is very important in wastewater treatment. The dosing is highly accurate, and we may use the option to connect the SMART Digital XL to a phosphate measuring device in a next step".
Overall, using the SMART Digital XL pumps has been a good experience for the municipal company which is also very satisfied with the support it has received from Grundfos. "Support was excellent with very fast answers. When a Profibus description was not available, we called support and immediately got the documentation in German", says Oliver Schranz.
Stadtwerke Heppenheim first heard of the Grundfos SMART Digital range when a chemical company testing H2O2 in wastewater treatment for the WWTP was using SMART Digital S units. The company was therefore familiar with the range when the new phosphate dosing station was installed by local engineering company TDL Dosiertechnik. Oliver Schranz and his colleagues are happy with the solution and see many applications for the SMART Digital range, even outside the WWTP. "It could be a good solution for water treatment in other places in the city, such as the swimming pool", concludes Oliver Schranz.
The WWTP at Heppenheim is a four-tank SBR system that handles wastewater from approx. 35,000 residents and several industries.