A new-generation dosing pump is playing a key role in alleviating waterborne diseases in rural Africa.

Watson-Marlow Bredel’s SPX 10 dosing pump is at the heart of onsite diluted sodium hypochlor-ite plants being built by Pretoria-based Aquarius Chlorination to overcome sanitation problems across the continent.

The pump recently overcame a problem at a plant being built in Algiers. Aquarius Chlorination’s Hans Coetzee explains: “the 36,4% salt solution in the saturation plant is too strong to process and has to be diluted down to an ideal consistency of 3%.

“To pump the salt solution to a mixing pipe has, in the past, created problems due to the salt crystal- lising and preventing the nonreturn valves from functioning properly. “Watson-Marlow Bredel’s SPX 10 peristaltic pump was the obvious choice to solve this problem as there is no need for a nonreturn valve as the pump has a nonreturn function, so there is no chance of permanent crystallisation.” The pump was installed with a variable-speed drive to allow accurate dosing and with a digital display to ensure the accuracy of the saturated salt solution supplied.

“Maintenance on the peristaltic pump is child’s play,” says Coetzee. “Only the tube, when expired, has to be replaced – which can be done well within 30 minutes and involves a cost of around R700, possibly once a year.” Explaining the process at the plant, Coetzee adds that the salt-saturation tank manufactures a maximum of 196 litres of diluted sodium hypochlorite an hour at a strength of 0,8%. “This solution is then mixed by pressure into the normal water supply line which is fed through a rotameter and a diaphragm valve, which allows an accurate flow.” Flow rates are calculated and then set to an end result of three per cent salt solution, which is pumped through the cells and converted into sodium hypochlorite.

“The solution then overflows to a dosing tank where it is used for potable water, sewage plants, swimming pools, or disinfectants for hotels and hospitals.” According to Coetzee, the benefits of a sodium hypochlorite plant are that it is user-friendly and cost-effective. “This system of producing potable water is 85% cheaper than any other method of using chlorine,” he explains.

“We are striving towards installing as many plants as possible into Africa, especially the rural areas. Most islands can also benefit from this system as seawater, being in the region of 3,4% salt solution, is already the raw material required for the manufacture of sodium hypochlorite.”