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Watson-Marlow hose pumps replace PC pumps at South African waterworks

A major waterworks in South Africa has replaced its old progressive cavity (PC) pumps with Bredel Apex15 hose pumps from Watson-Marlow Fluid Technology (WM).

The state-owned Umgeni Water is the largest supplier of bulk potable water in the Province of KwaZulu-Natal on the east coast of South Africa.

The organisation currently supplies 426 million m3 of potable water to its six municipal customers.

The Apex pumps have been chosen over PC pumps in an application that sees the metering of bentonite, a naturally occurring crystalline quartz, into the source water to help flocculation.

The abrasive nature of the substance can cause costly damage to the PC pumps, a factor that is not encountered when using Apex technology.

Conventional treatment methods for removal of suspended and colloidal material from water include chemical coagulation of small colloidal particles and flocculation of the small particles to form larger flocs or aggregates.

Bentonite is added when the water to be flocculated contains too few particles for effective flocculation.

Several Umgeni Water plants have experienced difficulties with their PC pumps as a result of bentonite metering, which is typically carried out around once a month on average.

Upon start-up, the PC pumps will immediately run dry due to the properties of bentonite, and suction lines can sometimes become blocked and the pump stator is subject to damage.

With this in mind, the introduction of bentonite metering processes at Umgeni Water’s Amanzimtoti waterworks, a short distance south of the coastal city of Durban, set the company thinking about alternative pump technology.

After a review of the market, the pump of choice proved to be a Bredel Apex15 hose pump from WM.

The application at Amanzimtoti sees bags of bentonite offloaded into a 3,000L holding tank and then mixed.

Using the Bredel Apex pump running at less than 3 bar, the abrasive liquid is then pumped so that the solids are kept in suspension.

Crucially, the two Apex pumps can be reversed if blockages are encountered and then run in the correct direction again once clear.

As a result, reliability has improved at the Amanzimtoti plant in the three years since the pumps have been installed.

Apex pumps are designed to suit all metering and transfer applications from 2.8 to 6,200L/h flow across a broad range of applications.