Since the completion of the R2-billion upgrade of the Zandvliet wastewater treatment works (WWTW) in October last year, municipality City of Cape Town (CoCT) reports a significant improvement in treated effluent quality.

The facility features an enhanced conventional activated sludge treatment module and a “state-of-the-art” membrane treatment module, increasing daily capacity from 72-million litres to 90-million litres. The facility treats incoming waste from the sewer network in Khayelitsha, Delft, Kuils River, Blue Downs, Blackheath and Eerste River.

These upgrades were crucial to ensuring that infrastructure development accommodates population growth, the city notes.

Prior to the upgrade, the plant struggled with ageing infrastructure and capacity overload, resulting in a compliance rate of about 50% with its licence conditions.

“Following the enhancements, compliance has surged to 90%, meeting the stringent standards set by the Department of Water and Sanitation,” says CoCT Water and Sanitation MMC Councillor Zahid Badroodien.

Key drivers of the improved effluent quality include the addition of primary sedimentation, membrane bioreactor system expansion and infrastructure refurbishment, ensuring cleaner, safer water for responsible discharge and potential water reuse.

To further bolster treatment capacity, a future expansion project at Zandvliet is in the planning stage and will add about 60-million litres a day of capacity, with improved sludge treatment processes and energy recovery. Construction is anticipated to begin in the 2034/35 financial year, Badroodien adds.

The Zandvliet WWTW forms a key part of the city’s New Water Programme. Its high-quality treated effluent will be transferred to the Faure New Water Scheme, where it will undergo advanced multi-barrier purification to bring it to drinking water standards before blending it with dam water. The water will then be further treated and blended into the water supply system for distribution.

“Introducing potable water reuse is essential for Cape Town’s long-term water security. Through this initiative, we will be able to augment the city’s drinking water supply by 70-million litres to 100-million litres a day, protecting us from unpredictable climate change and drought,” says Badroodien.

Water Reuse
The CoCT is also expanding its treated effluent network, helping to save up to 3.5-million litres of drinking water a day, for use in irrigation at recreational facilities. Treated effluent – wastewater purified for safe reuse – is supplied through a 283-km pipeline from nine WWTWs, including Athlone, Bellville, Cape Flats and Zandvliet.

Currently, 120 municipal facilities are connected to the treated effluent supply system, and more facilities are earmarked to be connected.

“Using treated effluent for irrigation and industrial purposes is an excellent way to help conserve Cape Town’s water supply, and to save on costs,” says the CoCT.