Peristaltic pumps from Watson-Marlow Bredel have been found suitable for water disinfection applications using sodium hypochlorite.
Sodium hypochlorite is a corrosive chemical that has disinfection and bleaching properties, and is used in the purification of wastewater as well as disinfection of drinking water.
However, its tendency to release gas bubbles and cause gas locking at the valves poses a major challenge to conventional pumping techniques.
South East Water has overcome this difficulty by opting for peristaltic pumping technology from Watson-Marlow Bredel.
Dealing with sodium hypochlorite can be difficult as it is toxic and emits chlorine when in contact with acids.
It naturally releases tiny bubbles of gas, which have a tendency to collect on the small ball valves found in conventional diaphragm dosing pumps. This can cause gas locks in the system, which prevent the pumps from functioning.
South East Water faced gas locking problems while using diaphragm pumps to dose sodium hypochlorite into drinking water. The gas locking problems necessitated maintenance on a regular basis.
The problem was eliminated when the pumps were replaced with 520U/R IP66 cased peristaltic pumps supplied by Watson-Marlow Bredel.
The peristaltic pumps from Watson-Marlow Bredel allowed the gas produced by sodium hypochlorite to pass straight through the tube without interrupting the dosing process, thereby reducing maintenance dramatically.
Having worked with Watson-Marlow for years, Ray Lawrence, Process Engineer at South East Water explained that they understood the value of their peristaltic technology, and decided to use it in an innovative way.
Since peristaltic pumps retain the fluid completely within the tube and have no valves that can leak or corrode, they can be used for the accurate metering of substances as challenging as sodium hypochlorite without the associated gas locking and maintenance problems.
Peristaltic technology has helped South East Water keep costly downtime to a minimum.
South East Water is also using the pumps for dosing sodium bisulphite in order to de-chlorinate the water after disinfection to remove the unpleasant taste.
The chemical is dosed in very small quantities, which requires a high degree of precision and accuracy from the pump.
The pump can be calibrated either by weight or volume, allowing very precise dosing and metering.
Key features of the 520 peristaltic pumps from Watson-Marlow Bredel:
- Generates a flow rate of between 4 microlitres and 3.5 litres per minute
- Ensures excellent levels of accuracy, reliability and control in harsh operating environments
- Rated to IP66, providing washdown protection for harsh conditions
- Delivers user feedback via the pump display
- Dual analogue input to control and scale speed
- ‘Drop-in’ alternative for diaphragm or piston pumps with variable stroke control