While reducing wastewater is good, it can lead to problems
LOWER water levels from prolonged drought in South Africa as well as municipal water restrictions in cities such as Joburg, Cape Town and eThekwini could strain old wastewater treatment infrastructure and cause the build-up of harmful bacteria and algae.
Dr John Zvimba, the research manager responsible for sustainable municipal wastewater treatment management at the Water Research Commission, said this week that the commission was to commission a study to investigate the impact of reduced flows resulting from drought incidents and water restrictions on wastewater treatment works.
“We’re in a drought situation, where people are con- cerned about the likely impacts of reduced water flows going to wastewater treatment works… If you look at our wastewater treatment environment, many of these operations battle with overloads whereby they handle the excess flow, so if they receive reduced flows that should be a piece of cake for them.
“But that doesn’t mean there won’t be problems from reduced flows. Remember, wastewater has to be conveyed through a system of piping that transfers the water. Imagine, with reduced flows, what sort of mess it would create in this network of pipes. The most likely impact is the growth of undesirable impacts in the environment, creating conditions for bacteria. You are likely to get algal growth and there’s even the potential for methane gas to cause accidental fires.
“The conveyance system starts from the toilet up to the point it’s introduced at the treatment plant. If you can’t flush the system, you create a localised environment where bacteria can multiply and that can be problematic for the environment and human beings. But this is why we’re com- missioning this study, because we just don’t know what will happen in the system.”
The planned WRC study, he said, would be completed by the middle of 2017.
Anthony Turton, a water scientist, said despite the threats of water shedding, sewage contamination remained the biggest risk “as this is volumetrically the lar- gest, with the biggest footprint, likely to be exacerbated by high water temperatures and reduced natural flows as the El Niño drought intensifies across the country”.