Wastewater treatment: low nitrate levels through precise dosing
In the Flanders region, more than 83% of the wastewater is treated using the most modern methods. The project has a positive effect on the water quality of the Schelde and Maas and makes a significant contribution to keeping the North Sea clean. Aquafin, which was founded by the Flemish government around 30 years ago, plays a key role in this.
Today the company is responsible for 323 sewage treatment plants and main sewers with a total length of around 6648 km. Dosing pumps play a major role in wastewater treatment.
One of the waterworks in Flanders uses peristaltic pumps to meter FeCl3 for phosphorus or phosphate precipitation and the addition of carbon sources (C-Sources) for denitrification. A certain proportion of easily biodegradable carbon compounds is a prerequisite for a functioning denitrification. If the denitrification process only takes place to a limited extent, increased nitrate formation occurs, which must be avoided.
Years ago the customer used diaphragm metering pumps for metering FeCl3 and PAC metering. Due to high pre-pressures in this specific installation there was a tendency to overfeeding. Since a peristaltic pump is less sensitive to pre-pressure Aquafin has tested conventional peristaltic pumps. However, these did not work as hoped. The peristaltic pumps with too small inner diameter clogged often due to contamination of the media/additives. Also the tube live of those conventional peristaltic pumps where very short and occasionally the tube just burst when facing higher pressure.
This experience led to a new trial.
- Simple and menu-guided hose change
- Chemical metering from 5.1 to 410 l/h at up to 8 bar back pressure
- Dosing of highly viscous, particle-containing media / polymer solutions
- Dosing of highly outgassing, abrasive or shear-sensitive fluids
Aquafin launched a tender for 20 new pumps to replace the existing c-source metering system. In the run-up, the water supplier tested various pumps. An ProMinent peristaltic pump was also considered: our DFYa peristaltic metering pump. It was tested in the sewage treatment plant at Genk. The tests began in June 2020 and lasted around two months. Our DFYa convinced with its benefits.
- The target and actual flow rate are displayed directly in digital form. The displayed flow rate corresponds exactly to the dosed quantity and can be set very easily and adjusted according to the given application.
- The maintenance is very straight forward. The pump has dedicated software assisted hose-change procedure. The user is guided through all necessary steps.
- Since the working chamber of the DFYa is not filled with glycerine, there is no need for time-consuming draining and filling.
- The pump can be connected via an external thread and not via a hose nozzle as is the case with conventional connections. This allows rigid pipelines to be permanently mounted.
- The dosing is currently time-controlled with preset quantities. As the ProMinent pump has also a 4-20 mA control option, the operator is considering switching from time-controlled dosing to mA-controlled dosing in the future.
- Another advantage of the DFYa is its large dosing range between 5.1 and 410 l/h. Due to this one pump version is suitable for all necessary flow rates.
- Last but not least is the DFYa using fabric reinforced hoses with a wide inner diameter. This wide inner diameter avoids blockings. The fabric reinforcement enables a long hose life.
After the test phase, the water supply company was convinced by the DFYa peristaltic metering pump: Since the start of the test phase in June 2020, it has been metering reliably, even in times of high ambient temperatures. Using an additional flow meter, it was possible to prove that at all times the pump metered the correct quantity of 50 l/h very stably - even independently of the product level in the storage tank. This was also confirmed by the operator. He was also impressed by the low noise level. Another advantage is that the pump is suitable for all pressure conditions and dosing quantities (up to 100 l/h) required in this plant. This greatly simplifies the spare parts inventory. In addition, the pump is easy to maintain as there is no glycerine in the hose chamber, the almost only wearing part - the hose - can be replaced fast and with the help of the pump.
As the revolutions of the pump are very slow at the required volume and due to the fabric reinforcement of the hose the service intervals of the DFYa are very long.
The installation and operation of the ProMinent DFYa is also easy. With the help of the display and the easy menu structure the operator can do adaptions within seconds.
Aquafin was not only very satisfied with the function and performance of the DFYa. The good cooperation and support of the Belgian ProMinent team was also convincing. 20 peristaltic pumps of the DFYa series were ordered. ProMinent is pleased to have the opportunity to work with Aquafin in the future.