Options to deal with Cape Town’s ocean-bound sewage unveiled

Cape Town has been pumping sewage from the Atlantic seaboard into the sea for decades, but the practice has come under increasing scrutiny and public opposition since photos of the sewage floating along the ocean surface were published in 2016.

At least 32 million litres of untreated sewage is pumped into Cape Town’s marine protected areas every day through marine outfalls at Greenpoint, Sea Point and Hout Bay.

According to a new feasibility study, it will cost up to R8 billion to build wastewater treatment works to treat it first, or pump it to existing wastewater plants.

There has been renewed public scrutiny of the marine outfalls over the past year after Forestry, Fisheries and the Environment Minister Barbara Creecy ordered the city to undertake a public participation process relating to the required discharge permits for the outfalls.

The process ended on 21 November, with 1 979 comments submitted, according to consulting firm Zutari, which managed the process for the city.

Zutari was also commissioned early last year to determine the feasibility of treating the sewage released at Greenpoint – which includes all sewage from the city centre extending to Salt River, Camps Bay and Hout Bay – before releasing it through the outfalls.

The study was presented at a workshop on 31 January attended by the city’s water and sanitation directorate, the water and sanitation portfolio committee, and the mayoral advisory committee for inland water quality.

The presentation, provided to GroundUp, states that in the short-term, upgrades to the marine outfall pump stations and present infrastructure will cost R100 million.

Zutari said the Hout Bay outfall failed to comply with its Coastal Water Discharge Permit issued by the department of forestry, fisheries and the environment in respect of total Kjeldahl nitrogen – a measurement of organic nitrogen and ammonia nitrogen contained in sewage. It met the requirements just 41% of the time.

When it came to the release of heavy metals into the marine environment, the Greenpoint outfall met the requirement for zinc levels just 34% of the time, with the Camps Bay outfall compliance being 46% overall.

However, overall compliance since 2020 has improved.

As designated marine outfalls, all three areas are exempt from measurements of faecal bacteria – such as E.coli – and chemical components.

The study provides mediumand long-term solutions for treating the sewage.

Within the medium-term, the study offers options to extend the existing marine outfall pipelines, which are between 1.35km and 2.1km long, although in Camps Bay and Hout Bay, the discharge is only about 700m from land due to the shape of the bays.

Offering no treatment options but extending the pipelines by 10km for Camps Bay, 15.3km for Greenpoint, and 11.6km for Hout Bay, would cost between R2.2 billion and R2.6 billion, depending on whether the pipelines were anchored to the sea bed, or buried beneath it.

Building a new wastewater treatment works for the three areas would cost between R2.2 billion and R3.4 billion, depending on the extent of the treatment.

The long-term scenario presents options for pumping the sewage from the three areas to various existing wastewater treatment works, via new ocean or land-based sewage pipelines.

These options vary in price from R2.2 billion to R7.3 billion, with the land-based piping options being generally less expensive than ocean pipelines.

Mayoral committee member for water and sanitation Zahid Badroodien said a more in-depth report was being finalised.