Prime Disinfection Assured with Pump Switch

Progressive cavity pumps handle sodium hypochlorite metering challenges at California water agency.

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Progressive cavity pumps handle sodium hypochlorite metering challenges at California water agency.

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Typical seepex pump design for NaOCL feeding
Click here to enlarge image

The Zone 7 Water Resources Agency in Alameda County, California, USA, has been using progressive cavity pumps for several years to handle aqueous ammonia (NH3) and sodium hypochlorite (NaOCl) solutions. It recently added additional pumps when it began using on-site NaOCl generation to handle increased demand during months of high water use.

The Situation

Agency officials began the switch to progressive cavity pumps after experiencing repeated maintenance problems with the reciprocating pumps being used before, according to Dave Parola, Zone 7 water facilities supervisor. “Reciprocating pumps are prone to vapor lock, which can shut down a pump for hours. They are also very complicated, and repairs are labor intensive,” he said.

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Zone 7 Water Resources Agency service area
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Misco Pacific Water Treatment, a local water and wastewater treatment equipment represantative in Pleasanton, California, recommended several models of progressive cavity pumps manufactured by seepex.

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A seepex pumps for NaOCL feeding into the discharge line of a vertical turbine pump
Click here to enlarge image

After successfully switching to progressive cavity pumps for NaOCl pumping, Parola explored the possibility of using the pumps for metering a chloramine solution used at Zone 7’s wells. Chloramination enhances water quality by reducing potentially dangerous disinfection by-products such as trihalomethanes (THMs) and by stabilizing the NaOCl so its effect lasts longer. As ammonia can be a problem for metering equipment, Parola asked Misco if seepex could help.

The Solution

Misco recommended the seepex MD range pumps similar to the NaOCl pumps, designed with stainless steel internals and EPDM elastomers. Parola prefers the progressive cavity metering pumps because they can pump against high pressure without pulsation, a constant problem with reciprocating pumps. “The inline power train is so simple,” he added.

Another plus is the simplicity and ease of replacing parts when they’re needed. “These pumps are very easy to work on,” said Steve Yonkman, a member of Zone 7’s maintenance staff.

The Benefit

After three years in operation, the progressive cavity pumps used for NaOCl and NH3 metering have been virtually trouble-free. Zone 7 purchased additional seepex metering pumps to dose on-site generated 0.8% NaOCl solution. In all, the district now has 19 seepex metering pumps on location. In the near future further, installation of additional seepex pumps is planned.

seepex GmbH is based in Bottrop, Germany. It makes 27 ranges of progressive cavity pumps, macerators and control systems for the pulsation-free transfer of even viscous, aggressive and abrasive products. With manufacturing in Germany, China and the USA, it has a network of subsidiaries, branch offices and agencies in 50 countries. Created in 1981, its UK/Ireland head office is in Yeovil, Somerset, England. Contact: +44 (0) 1935 472 376, or

Range MD

  • Short, compact design with directly flange-mounted drive (block design)
  • Housing optionally in stainless steel or plastic
  • Conveying capacities: 0.2 L/h - 1,000 L/h | 0.053 USGPH - 264 USGPH
  • Pressures: up to 24 bar | 360 PSI

Apart from a stainless steel housing, pumps in this range are available with housing parts made of plastic and components that come into contact with fluids of Hastelloy C (2.4610) or Titan (3.7035), making them well suited for pumping and dosing chemically aggressive media.

Zone 7 supplies treated drinking water to retailers serving nearly 200,000 people in Pleasanton, Livermore, Dublin and, through special agreement with the Dublin San Ramon Services District, to the Dougherty Valley area. It also supplies agricultural water to 3,500 acres, primarily South Livermore Valley vineyards, and provides flood protection to all of eastern Alameda County.

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