WATER CONSER VATION
Decentralised plants can take the pressure off our ageing water and wastewater treatment plants. Kirsten Kelly speaks to Herman Smit, managing director of Quality Filtration Systems (QFS), about the use of these systems in South Africa.
A case for decentralised wastewater treatment plants
O
ver the past 20 years, due to the skills shortage in South Africa, there has been a push towards centralised water and wastewater treatment plants (WWTPs), as these require fewer technical staff members like engineers, scientists and operators. However, when one looks at the types of problems within the water and wastewater treatment industry today, they tend to be network problems.
Herman Smit, managing director of QFS
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And centralised water and WWTPs have created a bigger dependency upon network maintenance. With municipalities reporting between 29% and 50% of non-revenue water, it is clear that network maintenance has failed. Water has to be pumped kilometres to its consumers and wastewater has to be pumped kilometres to WWTPs – placing huge pressure on network systems. These problems can be solved by decentralising water and wastewater treatment works,” explains Smit. Previously, there has been pushback against having WWTPs close to residential areas because of the smell. Presently, however, with the adoption of new technologies like membrane bioreactors (MBR), one finds wastewater treatment plants in the basements of high-rise buildings. These decentralised plants are compact, odour-free, highly automated and able to produce greywater that can be reused. They can also be deployed rapidly due to their modular structure.
Smit believes that decentralised WWTPs need to treat between 200 000 litres and 500 000 litres of wastewater a day. “If it is below 200 000 litres per day, the cost per kℓ is too high and if it is above 500 000 litres per day, its footprint will be huge and may be construed as an unwelcome, major WWTP in a suburb. “There will always be a case for centralised WWTPs; decentralised WWTPs are there to take the pressure off the existing infrastructure. Many centralised WWTPs are working over-capacity – there are instances where the plant is difficult to maintain, pumps are constantly breaking down or sewage is running down the streets. Upgrading these plants is extremely expensive compared to deploying a decentralised system, which is mostly built off-site and requires a tiny team on-site for its commissioning,” adds Smit. Smit mentions the recent report by the South African Human Rights Commission (SAHRC) on the spillage of raw sewage
