Improve of chemical dosing tools at a wastewater therapy plant in Germany is delivering excessive efficiency on phosphorus elimination, says Thomas Klobuczynski, industrial gross sales engineer, Watson-Marlow Fluid Expertise Options.
The wastewater therapy plant (WwTP) serving the city of Hessisch-Lichtenau in Germany is taking an modern strategy to chemical metering in a phosphorus elimination software.
Two diaphragm pumps, initially used to dose ferric chloride to remove phosphate, are being changed with a single Qdos CWT peristaltic pump from Watson-Marlow Fluid Expertise Options (WMFTS), in a primary for the nation. The Fürstenhagen wastewater therapy plant serves an 18,500 population-equivalent (PE) within the Werra-Meissner district of Hessen state.
The first wastewater processing system features a mechanical pre-cleaning system with grill and sand lure and an aeration tank with upstream de-nitrification and downstream nitrification, with recirculation. There are two secondary clarification basins and a sludge therapy unit.
Chemical dosing with the precipitating agent, ferric chloride sulphate (FeClSO4), is required on the organic therapy stage for constant phosphorus discount, as a result of the phosphorus load on the plant inlet is extremely variable. Environmental rules imply discharge of handled effluent to the river Losse is strictly restricted to 0.70 milligrams per litre (mg/l) whole phosphate.
Single-point dosing is used to ship the precipitate, with the chemical metering pump drawing the ferric chloride from a 25m3 holding tank. It’s then transferred to the dosing level, which is a few 30 metres away.
In accordance with the operator, it’s important that dosing is carried out persistently 24/7, however the two legacy diaphragm pumps performing this activity, working alternately, have been unreliable and required frequent servicing.
Wastewater operations supervisor Marco Quehl mentioned, “We’d like a continuing primary quantity of precipitant to be dosed, and the amount wants to extend robotically consistent with the phosphorous load on the inlet.”
In accordance with Quehl, the largest downside with the diaphragm pumps was that the corrosive ferric chloride sulphate left iron residues on the pump valves, leading to poor sealing in opposition to the valve seats and fixed minor leaks.
“This required frequent minor upkeep work, and after a mean working time of round 12 months, by which the 2 diaphragm pumps ran alternately, we needed to exchange the pumphead, and even all the pump,” he mentioned. “When the required cleansing operations have been additionally thought-about, this turned out to be time-consuming and costly in the long term.”
Most chemical dosing pumps want common upkeep to stay operational. This may take a pump out of service for hours, usually needing a back-up pump to offer course of continuity. It additionally takes the complete consideration of a minimum of one expert onsite technician.
Pumpheads throughout Watson-Marlow’s whole Qdos vary don’t must be taken aside. As a substitute, the pumphead is solely eliminated as a single unit and a brand new one clicked in place. It takes one operative lower than a minute, providing substantial advantages when it comes to time saving and onsite well being and security, as upkeep workers don’t have any chemical contact.
“We’d already had optimistic expertise with utilizing Watson-Marlow Qdos tube pumps for dosing ferric chloride sulphate and different chemical compounds,” Quehl mentioned, “which is why we agreed to testing the CWT pump at our website.”
The brand new Qdos CWT is the world’s first peristaltic pump with no tube, which represents a step-change within the mechanics of peristaltic pump design. The pump underwent its first discipline trial at Fürstenhagen WwTP as a part of a long-term check interval.
Whereas a standard peristaltic tube is compressed flat by way of plastic deformation, the Qdos CWT pumphead incorporates an EPDM ingredient, which is elastically compressed in opposition to a PEEK observe. This reduces materials stress and fatigue, offering considerably longer service life, diminished upkeep, and fewer plant disruption.
The pump is self-priming and there’s no fluid again movement, even when the pump just isn’t in operation. This additionally prevents fuel locks, so there is no such thing as a threat of interruption and no want for extra tools reminiscent of pressure-sustaining valves, air-discharge valves or holding pumps.
Operations supervisor Bernd Sennhenn mentioned, “The Qdos CWT was put in 12 months in the past, and it has been working faultlessly since then. It was doable to put in this pump as a direct substitute for a diaphragm pump.”
Reflecting on the trial at Fürstenhagen WWTP, Quehl mentioned, “The Qdos CWT has been in operation for greater than 8,000 hours and dosed a complete of just about 90,000 litres of precipitating agent and hasn’t wanted any upkeep.
“As compared with diaphragm pumps, the Qdos CWT additionally doses extra evenly and with decrease pulsation, which protects the pipework and connectors. There’s no want for pulsation dampers.”
The dosing pumps improve has saved the plant appreciable outlay in time and value. The Qdos CWT has been working at a mean of 75% of its most capability, demonstrating its functionality and reliability at greater efficiency ranges.
This reliability of the Qdos CWT lies within the design of the expertise. The fluid contact ingredient is subjected to low stress ranges, and though a second metering pump is stored in reserve at Fürstenhagen, to make sure operational availability, it’s virtually by no means wanted.
Because of the total reliability and performance of the Qdos CWT pumphead, the Fürstenhagen plant has achieved a 97.5% discount in phosphorus load over the yr.
“The brand new Qdos CWT expertise is solely one of the best in the case of dosing precipitating agent at our plant. There’s no want for anybody else to return to me with different options,” concluded Quehl.