MechChem Africa May-June 2021

⎪ Water and wastewater processing ⎪

Pumping responsibly the only way to conserve groundwater

“As South Africa increases its use of boreholes to meet growing water needs, users must pay more attention to monitoring and controlling how much groundwater they pump or these resources could be rapidly depleted,” says Stephan Venter, Grundfos product manager for water utilities.

rising cost of the electricity required to pump water. Fortunately, solar power generation technologyhas improved in leaps andbounds, says Venter, and has been well leveraged by borehole pump manufacturers. “Solar power now allows water to keep flowing even when mains power goes down,” he says. “The development of high-efficiency pumps – combined with technology such as permanent magnet motors and variable speed drives – can reduce pumping costs and ensure constant supply.” He says that specialised software devel- oped byGrundfos – one of theworld’s largest pump manufacturers – even allows users to go online and select the ideal pump model to suit their borehole specifications, helping to make the most responsible use of the coun- try’s scarce groundwater resources. www.grundfos.com/za

groundwater source to be lost altogether.” There is no substitute for constant moni- toring, however, and Venter emphasises the value of digital technology in collecting and transmitting data to keep users informed. Many users still use a manual inspection method to check the level of theborehole and the condition of the pump, but the most ef- fective way is through electronic equipment linked to an online platform. “This provides updated information at the click of a button, either through a SCADA system for larger users, on a standard com- puter or even on a mobile phone,” he says. “Monitoring andmeasuring our groundwater resources is vital in a dry country like South Africa, especially aswework towards becom- ing more responsible water users.” Further challenges for borehole users include the unreliable power supply and the

A ccording toStephanVenter,Grund- fos product manager water utili- ties for India, the Middle East and Africa, borehole users must pay more attention tomonitoring and controlling how much groundwater they pump or these resources could be rapidly depleted. “The main risk when municipalities, busi- nesses or households make use of ground- water resources is that their extraction from boreholes could exceed the recharge rate of the aquifer,” says Venter. “To avoid this, users need to gather a great deal of information from the start – it’s more than just drilling and pumping.” An important aspect of ensuring the sustainability of a borehole, he says, is the correct sizing of the pumping infrastructure. This requires data, including the borehole’s safe yield, the dynamic water level, the re- quired lift above the ground, the discharge ratios, the friction loss in piping, flowdemand and well size. He notes that while larger water projects will usually employ the services of a qualified hydrogeologist to generate the necessary data on the aquifer, many smaller users simply proceed with minimal information. “This makes it difficult to put the borehole on a sustainable footing,” he says. “Lack of investment in themonitoring equipment also creates challenges in controlling the water abstraction adequately.” He highlights the importance of taking a conservative view on what levels of extrac- tion the aquifer can accommodate. Even when yield testing is conducted, for instance, there could be other users of that particular aquifer who are not pumping at the time of the tests, leading to an over-estimation of yield capacity. “Just to be safe, I tend to advise users to size their pumping equipment at only 50 to 60% of the borehole’s safe yield,” he says. “This reduces the risk of over-pumping, which could possibly cause the valuable

The installation of a Grundfos SP submersible pump in a groundwater application.

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