Articles & Case Studies

Wernert pumps provide Northumbrian Water with long term reliability in odour control

Posted: Wednesday 29th October 2008

For wastewater treatment companies, wet chemical scrubber circulation applications for odour control provide essential environmental control systems. To be truly effective they demand a high availability at all times, which means that the mechanical components must offer reliability and operating integrity.

At Northumbrian Water’s (NW) Howdon sewage treatment works, great reliance is placed on the efficiency and performance of the recirculated liquor pumps which handle Sodium Hydroxide (caustic) 25% dilution and Sodium Hypochlorite (Hypo) 17% dilution. The eight Wernert pumps supplied by AxFlow Limited were installed when the wet chemical scrubber plant entered service in 1998 and a decade on the same pumps are still giving the levels of service demanded by NW.

The plant was designed to remove H2s and sulphur based compounds through the use of a recirculated liquor made up of softened water. The Wernert NEPO pumps return the liquor from ground level to a height of around four metres to allow the liquor to dose the odorous air before it leaves the vessel stack. The chemicals are dosed directly into the liquors and are controlled and monitored using Prominent control technology.

The Wernert NEPO pump, fitted with a bellows-type axial face seal, has a long track record within the waste water and effluent treatment industry where it has to convey various chemicals. For NW, specification of the pumps back in 1998 was based on previous experience Wernert pumps on scrubber circulation operations.

Certified to ATEX 100a, the Wernert NEPO has thick-walled casing parts made from plastic, as well as the completely metal enclosure and together these ensure that the pump is safe for pressure rating PN16. The choice of plastic depends on the chemical, thermal, mechanical and abrasive loads. In the case of the pumps supplied to NWL, the pumps use an ultra-high molecular weight low pressure polyethylene. The pump design allows a quick exchange of the hydraulic side of the pump, without detaching the flanges or dismounting of the electric motor.

AxFlow reports that other than regular conditioning monitoring, the eight pumps used in the scrubber circulation application have performed well. In fact it has only been on four or five occasions that remedial work has been undertaken, which is not as frequent as similar pumps on other scrubber systems on the site.

Tel: 020 8579 2111

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