MechChem Africa November-December 2022

⎪ Water, wastewater and pumping solutions ⎪

Left: Tubular dewatering bags stacked at Phoenix wastewater treatment works. Right: Zebratube bags being used to build a berm to enable a processing plant to be moved closer to the shore.

“Areas along the Vaal near the wastewater plants arepitchblack, and this is clearlyvisible on Google Earth. Overwhelmed wastewater treatment plants are having to release raw sewage into the river and people from the surrounding communities are getting sick,” she adds. Dolamo says there is a hugeneed toempty out the accumulated sludge fromthese facili ties so the pumps can be fixed. “We've been supplying our large tubular ZebraTube bags to enable plants to take the sludge out of the bottom of their clarifiers for dewatering and storage nearby. “We are trying to provide a safe and en vironmentally friendly solution, and while using plastic is not ideal, it offersmuch better containment for sludge and is a far better solution than simply pumping it into a hole or allowing it to flow into the river. The tubes also help with odour control, because all the solids are contained,” she says. ZebraTube has quoted on similar sludge containment projects inCape Town aswell as Potchefstroom, but take up is still very slow. Also under discussion is a clean-up project for the Vaal river. “The next step of the Vaal project is to take a couple of metres of sludge fromthe contaminated areas of the river. Just aswe did inKwazulu-Natal, we can pump this sludge into geotextile tubes on the banks of the river. Once dewatered, the bags can be broken open and the dry solids safely trans ported to disposal sites,” explains Tshepang Dolamo. This will need to be done for several kilometres downstream of each contamina tion point, she adds. North of the border, ZebraTube is sup plying its high-flow geotextile bags for use in a mineral sands operation in Kenya. “Here we are using our small square bags, which

can contain about 1.0 m 3 of material. The operation was using regular bulk bags, but therewere complaints that theywere export ingwater. Once they realisedZebraTube bags were designed for dewatering, they could simply fill the bags, leave them to drain for a day or so before closing them up and loading them into a shipping container using a forklift truck. It makes the whole operation much more manageable and cost effective. “We have customised these bags for de watering, transportation and lifting purposes. It’s actually a little bit less than one cube in volume, but we have modified the stitching to double the amount of webbing on every corner. This makes the bags stronger and easier to handle during transportation,” says Dolamo. “This is typical of our fit-for-purpose ap proach. We are able to determine the real needs of anapplication then tryandmatch the

geotextilematerial and the stitching require ments to best suit that need. As well as the high-flow range of products for dewatering sludge and sand, ZebraTube can offer low-flowgeotextiles for dewatering fine slurrieswithparticle sizes down to10μm. “We have also recently patented ZebraTex, a composite-lined geotextile solution for retaining and dewatering slurries in the sub-10 μm range – without the need for floc culants,” she notes. “We are willing and able to develop cus tomised solutions for any dewatering task, be it for the reparation of the municipal wastewater infrastructure in South Africa, assisting in the clean up our contaminated rivers, assisting with emergency dredging of flooded slime dams or helping todewater and transport valuable minerals or waste solids,” Tshepang Dolamo concludes. zebratube.co.za

First layer of geotextile bags under passive drainage.

November-December 2022 • MechChem Africa ¦ 7