Case study: kudos to Qdos
7 Mar 2016
Peristaltic pumps have made maintenance simpler at German effluent plant.
The local authority effluent plant in Selters, West Germany has the capacity to purify wastewater and treat slurry from nine local communities with a combined population of 11,500.
“Wastewater is purified and [then] discharged into a nearby stream – the Saynbach,” says plant manager Achim Linder.
Linder says an important stage in the purification process is the elimination of phosphates.
“Most of which come from domestic washing and cleaning products,” Linder says.
While the phosphate content of the water inflow is usually around 5-6 mg/l, the concentration after purification must not exceed 1.6 mg/l.
Measuring up
In order to avoid excessive phosphate content, a measured amount of precipitant is added – before the water enters the aeration tank – as soon as the concentration of phosphates in the wastewater reaches a concentration of 1.0 mg/l.
Specifically, the plant adds ferric chloride to eliminate the phosphate.
The addition of the precipitant converts the phosphate solution into insoluble phosphate compounds, which can then be isolated.
The introduction of the ferric chloride from a large tank takes place at the precipitant metering station.
Depending on the phosphate content of the inflow water, delivery is between 60 and 250 ml of ferric chloride per minute.
According to the plant’s wastewater manager Bernd Schenkelberg, until recently, diaphragm metering pumps were used, but proved insufficiently robust as the ferric chloride attacked the pumps, meaning they had to be changed every three to four months.
The simple but effective functioning principle did not take long to convince us of its suitability. Qdos is also intuitive to use and easy to operate.
Bernd Schenkelberg, wastewater manager at the effluent plant in Selters, West Germany
“This took one of our technicians at least an hour every time and, because of the subsequent leakage of ferric chloride, almost as long again to clean the metering station,” Schenkelberg says.
To help find an alternative pump and alleviate the plant’s issues, automation experts from German company Jonas Schaltanlagenbau were brought in.
Benjamin Bullert, project manager at Jonas Schaltanlagenbau, says in view of the susceptibility of diaphragm pumps, an alternative functioning principle had to be considered.
“[This] brought us quickly to peristaltic pumps and Watson-Marlow, who recommended their Qdos pump,” Bullert says.
Minimal maintenance
To test its capabilities, the effluent plant installed a Qdos 30 metering pump in the precipitant metering station.
“The simple but effective functioning principle did not take long to convince us of its suitability. Qdos is also intuitive to use and easy to operate,” says Schenkelberg.
“Previously, we always had to factor in a time slot of 1.5 hours for changing a pump diaphragm.
“In contrast to this, the pump head on the Qdos can be changed as a complete component in just a few simple steps. It takes five minutes at most.”
Not only can the pump head be changed within minutes without the use of tools but, unlike changing a diaphragm, it can also be done without mess, Watson-Marlow says. The flow direction on the pump can also be reversed easily, and the precipitant chemical fed back into the storage vessel from the pipe system.
This means that hardly any fluid escapes while the pump head is being changed – making maintenance simpler and safer.