Dosing trial helps Veolia WTS produce ultrapure water

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Dosing trial helps Veolia WTS produce ultrapure water

The long-life of the innovative Qdos Conveying Wave Technology (CWT) chemical metering pump is benefitting an industrial water purification facility operated by Veolia WTS in Italy as Andrea Rossi , sales engineer at WMFTS, explains. 

A close partnership between global water management company Veolia WTS and Watson-Marlow Fluid Technology Solutions (WMFTS) is tapping into the performance benefits of the innovative Qdos CWT chemical metering pump at an industrial water purification plant in Italy.  

The pump is dosing inlet river water with sodium hypochlorite (NaCIO) as part of a process to produce ultrapure water to incredibly tight resistivity requirements. The plant produces ultrapure water for steam generation, which feeds into a turbine producing energy for a chemical production facility. It is situated in the city of Ferrara in northern Italy and water is sourced directly from the River Po.  

Veolia WTS runs the plant on a build-own-operate contract, where the end-user pays only for the treated water. The comprehensive treatment process at the plant is underscored by careful water quality monitoring to deliver water that meets the specific requirements of the end client.  

Veolia WTS’s plant maintenance manager, Davide Spinola, says: “We are producing ultrapure water with a resistivity of 17 ohm-meters per centimetre (Ω⋅m/cm). The process begins by treating water coming from the River Po and involves dosing controlled quantities of NaCIO to optimise the functionality of the reverse osmosis plant. 

“We dose sodium hypochlorite upstream for water disinfection, then perform double-pass reverse osmosis, followed by electro-deionisation," says Spinola. “Reverse osmosis involves a semi-permeable membrane that removes unwanted contaminants and molecules, while electro-deionisation is a continuous, chemical-free process that removes ionised and ionisable species from feedwater using DC power.” 

Several Qdos pumps are already installed at the Ferrara site, dosing in different applications. It was this experience of the efficiency of Qdos that led to the decision to work closely with engineers from WMFTS to trial the ground-breaking Conveying Wave Technology (CWT) model. 

Spinola says, “We were already co-operating with WMFTS on other projects on site and thought this application was ideal for the Qdos CWT. We know from experience that Watson-Marlow’s peristaltic pumps are very reliable and robust. 

“We have several on site, including a Qdos model with ReNu PU pumphead for polymer dosing. When we heard about the innovative operating principle of the Qdos CWT, we were keen to try it in place of our existing diaphragm pump.” 

Ongoing trial 

Installation of the Qdos CWT at the Veolia WTS plant took place in November 2020 and it has continued to perform beyond the initial trial. The pump doses sodium hypochlorite with the range of 4-20mA input signal at a flow rate of 3 litres/hour (l/h) in winter, rising to approximately 15l/h in summer. 

The capability of Qdos CWT in managing this seasonal variability was an important factor in deciding to use the pump at this site. Absolute consistency is required in the production of ultrapure water, which is used in numerous industries, including food and beverage, chemical processing, microelectronics, mining, pharmaceuticals life sciences, pulp and paper, energy, and textiles. 

Rossi says, “Many industries require ultrapure water for their processes, but this was a particularly demanding application, which is one of the reasons we were keen to trial Qdos CWT at the Ferrara site. Consistency is key to producing ultrapure water, but here there was the additional challenge of the seasonable variability of the river water entering the plant, with changing quantities of soluble and non-soluble contaminants. 

“We already had a strong relationship with Veolia WTS and we hugely appreciate their willingness to work closely with our team to test the performance of the Qdos CWT in the field. Together we have demonstrated that the pump was able to meet the stringent process requirements and adjust according to the seasonal fluctuations in contaminants and flow rate.  

“The long-life of the pumphead, which far exceeds that of the legacy equipment, has also made a major impression on the client.” 

Precise metering  

Qdos CWT offers all the advantages of a peristaltic pump, but with a significantly longer service life than typical peristaltic designs.  

Rollers or shoes in a peristaltic pump compress a tube or hose. The innovation within the Qdos CWT is that the CWT pumphead incorporates an EPDM element instead of a tube.  

This element is elastically compressed against a PEEK track, reducing material stress and fatigue and providing longer service life, reduced maintenance and less plant disruption. In addition, Qdos CWT pumps allow the dosing of chemicals, including sodium hypochlorite, with high precision and regularity over the entire life of the pump, thus avoiding the overdosing practices often required by other technologies to achieve a constant level of accuracy. 

Reflecting on the success of the Qdos CWT installation, Spinola says, “We’ve not had a single issue since day one. Nothing has been replaced and no service needed; it has been a fit and forget solution.  

“However, this is nothing more than I was expecting based on past experiences with Watson-Marlow. It is clear to me that the Qdos CWT is a really good pump.”