Sodium hypochlorite is a highly corrosive and toxic chemical with strong disinfecting properties, playing an important role in the water industry. 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 using peristaltic pumps from Watson-Marlow Bredel.
A highly corrosive chemical with disinfection and bleaching properties, sodium hypochlorite is used in the purification of wastewater and the disinfection of drinking water. When in contact with acids, the chemical turns toxic and emits chlorine.
Tiny bubbles of gas released during the process have a tendency to collect on the small ball valves found in conventional diaphragm dosing pumps, causing gas locks in the system and preventing the pumps from functioning.
South East Water had been using diaphragm pumps to dose sodium hypochlorite into drinking water, but found that gas locking problems necessitated maintenance on a regular basis.
Having worked with Watson-Marlow for years, the company decided to replace their existing pumps with 520U/R IP66 cased peristaltic pumps supplied by Watson-Marlow Bredel, successfully eliminating the problem.
The gas produced by sodium hypochlorite is able to pass straight through the tube of Watson-Marlow’s peristaltic pumps without interrupting the dosing process, thereby reducing maintenance dramatically.
Peristaltic pumps are designed to retain the fluid completely within the tube and do not have valves that can leak or corrode, making them ideal for 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.
Watson-Marlow’s peristaltic pumps are also being used by South East Water 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, requiring a high degree of precision and accuracy from the pump.
South East Water was previously diluting the chemical to control the dosage procedure accurately, which added an extra degree of complexity to the process, but the Watson-Marlow 520U/R IP66 peristaltic pump resolved the issue.
These peristaltic pumps can be calibrated either by weight or volume, allowing very precise dosing and metering. South East Water is now able to dose small amounts reliably even at low pressure, without the need for dilution.
Key features of Watson-Marlow 520U/R IP66 peristaltic pumps:
- Ideal as dosing pumps in water and wastewater treatment
- Generates a flow rate of between 4 microlitres, and 3.5 litres/min
- Superior accuracy, reliability and control in harsh operating environments
- Rated to IP66, providing washdown protection for arduous 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