Verifying Pump Output of Sodium Silicate In Water Treatment

The Rainier View Water Company treats Pierce County's drinking water supply in the state of Washington. The raw water in the area is more acidic than in other areas and therefore the pH needs to be increased to a state mandated level.

The choices for raising the pH in the water were using a caustic solution or using sodium silicate. Rainier View Water Company elected to use sodium silicate due to the fact that it is less expensive, offers other treatment advantages, is a much safer chemical to handle, and does not require a hazardous storage facility.

The state requires that the water maintain a level of sodium silicate of 20 mg/liter above the raw water. To do this, there is a flowmeter on each of the water mains' outputs, and an injection station is in place near each of these mains to insert the sodium silicate into the water. Each of the mains has a flowmeter that sends an output to a controller, which in turn sends a signal to a Milton Roy metering pump indicating how much chemical to pump down the line into the mains.

Rainier View Water needed to verify the output of the metering pump to ensure maintenance of proper levels of sodium silicate. To do this they first tried a tank level gauge, but the output was not accurate enough and proved to be unreliable. Next they tried an oval gear meter, but the viscosity was too high, and the meter either locked up or broke down in the line within a two-week period. At this point, they believed their remaining option was to go to a mass style flowmeter.

A representative of Badger Meter became aware of this situation and introduced them to the RESEARCH CONTROL® Mag meter (RCM). Considering the price difference (the RCM was about a third the price of a mass meter), Rainier View opted to give it a try. Badger sent one evaluation RCM40 to them to try out. The maximum flow rate that they were to see was 3.23 gph, and they appear to be averaging around .78 gph.

The meter was installed and has been operating effectively for about a month's time, and the customer has now agreed to place an order for 13 more RCM40s to fulfill his requirements at his other stations. He also informed Badger Meter that other counties in the area are considering moving to a different treatment solution since they are having trouble verifying their pump outputs.

Rainier View Water also is currently considering the use of the RCM series mag meters to monitor their chlorine injection and possibly fluoride.