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The City of Eagan in Minnesota, US has bought a Verderflex VF10 peristaltic hose pump to accurately dose 15 per cent sodium hypochlorite (’hypo’) for its new wastewater-treatment plant.

Hypo is used in wastewater treatment, to kill off bacteria before being discharged back into the environment and as one of the primary methods of drinking-water disinfection.

It is also a challenging product to pump.

This is because hypo tends to off-gas, causing some types of pump to vapour lock.

Diaphragm pumps are particularly prone to this.

Ten Verderflex VF10 peristaltic hose pumps will be put to immediate use in the treatment plant.

Each Verderflex VF10 pump is capable of flow rates up to 48 US GPH and at pressures up to 175psi.

Verderflex pumps can pump both gas and liquid, ensuring the liquid stream receives a consistent dose.

Peristaltic pumps are the pump choice for dosing sodium hypochlorite and Verderflex pumps can be found in wastewater treatment plants worldwide.

The fluid being dosed is kept totally enclosed within the rubber hose, which is then compressed by a rotating shoe that forces along the liquid inside.

Upon restitution of the hose, the resulting vacuum draws in more liquid.

This process is known as peristalsis and is what makes the peristaltic pump the first choice for liquid metering.

Variations in hose type allow for low strength and even high-strength hypo dosing.

The City of Eagan was impressed with the long life given by the Verderflex hose and the ease of maintenance when the hose needed to be changed.

The nature of the pumping process used by peristaltic pumps results in only the hose coming into contact with the fluid being pumped.

This means the pump is hygienic and leak free and also means there are no moving parts to become clogged or damaged.

The only maintenance required is changing the hose, which is done quickly and efficiently, keeping downtime to an absolute minimum.

Ultimately this saves costs and increases profits.

Several other applications in water and wastewater industries are ideal for Verderflex peristaltic pumps.

Lime, Kalic or Kalkmilch are ideally dosed by these products.

The chemicals are used to rectify the pH of wastewater discharges and are particularly abrasive, creating continual wear problems for progressing cavity pumps.

This leads to high stator replacement costs and frequent maintenance downtime.

Lime is also relatively viscous, generally too viscous for diaphragm pumps, causing them to clog up and become highly maintenance dependent.

Verderflex pumps are abrasion resistant and ensure the smooth passage of the liquid regardless of its viscosity.

Their design also presents no opportunity for the product to settle, as the peristaltic action keeps the product in suspension.

Furthermore the product can be mixed on site, as solids in the liquid stream do not present a problem for the pumps.

They also have a linear flow-speed characteristic that is ideal for feedback-control systems, allowing precise control of the chemicals being dosed, minimising chemical usage.

Ferric and polymer dosing is another common application for Verderflex.

These additives are used in clean-water plants to remove peat, suspended solids and residual colours from clean water streams.

In wastewater treatment, sophisticated polymers maximise plant throughput by increasing the solid-separation rate, allowing greater primary waste volumes to be treated.

Most polymers are highly shear sensitive but this is not a problem for Verderflex.

The gentle pumping action its products employ ensures that shear-sensitive solids and liquids are not damaged or altered, a common problem with other designs.

All water-treatment plants produce waste that has to be prepared for disposal.

Usually a filter press minimises volumes and constrains the waste-processing costs.

Such equipment presents a challenge to traditional pumping solutions as the water is abrasive, resulting in reduced flow.

To address the problem, pump speed is often increased and the pump is operated with the gland seals pressurised.

The result is increased leakage, exposing the press mechanism to abrasive wastes.

Variable suction performance is the inevitable consequence and as suction-pressure increases, ’rat holes’ appear in the filter press feed as water is pulled from above the top of the sludge blanket.

This increases the water content and the volume of the pressed waste, increasing operation costs.

By contrast, Verderflex pumps give consistent suction performance and do not incur significant wear.

For this reason they have also become an industry standard to optimise filter press operation in treatment plants.

Verderflex® peristaltic hose pumps and tube pumps are the ideal solution for pumping liquids and dosing chemicals. Ranging from smaller Original Equipment Manufacture (OEM) pumps to the world’s largest hose pumps used in very heavy industrial applications.

Verderflex® peristaltic hose and tube pumps are used in many industries including: water and wastewater, mining, food & beverage, chemical, pharmaceutical, printing and packaging.

Verder’s peristaltic tube and hose pumps can pump abrasive, highly corrosive, viscous, high density and shear sensitive products.

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