Sodium hypochlorite (or bleach) is a key component in thousands of production and disinfection processes in a variety of industries. It can be used to disinfect drinking water, prevent the growth of algae and shellfish, control odors in water and wastewater treatment plants, and much more.
Pumping sodium hypochlorite has frustrated maintenance personnel and operators throughout the years due to its high pH levels and difficulties with pumping. Anyone working with this chemical must take precautions every day to protect themselves and the environment. This article dives into the use of sodium hypochlorite as a disinfectant and odor controller in wastewater treatment facilities.
The most common issues with pumping this liquid:
- Off-gassing, which is the formation of gas in the piping system caused by heat, sunlight, low pumping rates, idle time, or a combination of these.
- Priming the pump is problematic when the pump is above the liquid supply container. Normally this occurs when the supply container is removed or changed, and air is allowed into the piping system.
- “Scaling” in the pump lines caused by a layer of reside from chemical imbalance forming around the pipe wall and in severe cases can actually block the line completely.
- Consistent and accurate pump rate delivery may be problematic because many pumps cannot pump "air entrained" liquids.
Best Practices:
- Store sodium hypochlorite away from heat and sunlight.
- Storage containers should normally contain a maximum of 30 days usage.
- The lower the concentration of sodium hypochlorite, the less chance for troubles.
- Maintain a flooded suction condition if possible. Suction lines should be 2-3 times larger than the pump inlet.
- If a suction “lift” is required, situate the pump as close to the suction source as possible and use a rigid suction line.
- Install an automatic “air-bleed" valve as close to the pump as possible and at the high point of the discharge line.
- Make sure all piping connections are tightly sealed to avoid air or vacuum leaks.
- Use a Peristaltic or “Hose” type pump (similar to the one below) since it can handle the air in the system better and prime and/or perform a suction lift if properly designed. **Please note: A diaphragm pump may be used. The selected diaphragm pump should include a 100% stroke length to enable smooth dosing of the degassing liquid.
Sodium hypochlorite is the most versatile cleaning and disinfecting liquid available. Finding the right pump technology is crucial when dealing with this chemical and its harsh effects on humans and the environment in high concentrations. With a properly designed pumping solution, the common issues associated with pumping this chemical can be avoided giving the operator many years of trouble free operation.
Tell us about your experience with pumping sodium hypochlorite or other difficult to pump chemical in the comments below!