A variety of challenging chemicals are often needed in order to meet treatment goals for drinking or wastewater operations. 

Polymers. These high viscosity fluids are used for flocculation and coagulation to aid in the removal of solid particles. It is crucial to use a metering pump that will precisely and gently dose long-chain polymers without causing damage to them. 

Caustics. The pH in both drinking water and wastewater must maintain certain levels to meet regulatory demands. pH is most often adjusted using chemicals such as sulfuric acid, hydrochloric acid, phosphoric acid, sodium hydroxide and calcium hydroxide. These chemicals can be caustic. 

Disinfection is often achieved using sodium-hypochlorite (chlorine) or peracetic acid. These are familiar chemicals to operators, but they bring their own challenges. Both chemicals are off-gassing which can lead to vapor lock and loss of prime. Peristaltic pumps are extremely effective when dosing fluids that contain trapped gasses; bubbles simply pass through the tube so there is no vapor lock or loss of prime.

Solutions to dosing challenging chemicals

Peristaltic Pumps, such as Blue-White’s FLEXFLO M3, are often considered the best choice for dosing caustic, abrasive and viscous liquids. The smooth, gentle peristaltic pumping motion gently moves delicate fluids through the pump tube without damage. 

Operators should check for material compatibility. It is important for peristaltic pump operators to choose a pump tube material that is compatible with the chemical being metered. Manufacturers generally offer a range of tube material options and should have a compatibility chart available. It pays to do the research and discuss the challenges in advance of installation and setup. 

It’s also important to choose the correct tubing size. Larger orifice tubes can often be the simple solution when dosing highly viscous or abrasive fluids. The larger diameter makes it easier for thicker fluids to flow through the tube and reduces resistance against the tube walls. 

Operators may consider installing a foot valve in their metering setup, or use a pump that has a foot valve strainer already built in, to help filter out excess particles in abrasive chemicals, and/or improve flow efficiency which is helpful for handling viscous fluids. 

Tube failure detection is also crucial. One of the most important advantages when choosing a peristaltic metering pump is the isolation of the chemical being dosed from the mechanical components. However, if the tube fails, this barrier could break down, causing damage to the pump mechanism and other equipment should the leak go undetected. 

For this reason, Blue-White FLEXFLO peristaltic pumps are equipped with a built-in tube failure detection feature which stops the pumping action when leaked fluid is detected in the pump head. Blue-White’s patented TFD System detects a wide range of conductive chemicals with no false triggering. If the TFD detects tube failure, the pump will automatically shut off and energize a relay switch. This permits communication with external equipment, such as a backup pump or alarm. Condensation and washdown procedures should not cause false triggering.

In conclusion, many abrasive, caustic and viscous fluids are critical to water treatment goals. However, correct dosing of these chemicals does not have to be difficult if the correct chemical feed pump is in use. Operators can effectively administer such chemicals without complication and with minimal downtime.