‘No human health risks’ from sea marine outfalls

Photographer Jean Tresfons aerial photograph that caused a stir last year.

A long-awaited study by the Centre for Scientific and Industrial Research (CSIR) suggests the city’s sea marine outfalls pose “no significant risk” to human health.

In addition, the two-year study commissioned by the City of Cape Town shows sewage outfalls at Hout Bay, Green Point and Camps Bay do not measurably affect inshore water quality or the wider environment.

The three outfalls discharge waste-water 1.7km from the shoreline at a depth of 28 metres.

The study follows widespread public concern over the state of the coastline.

Photographs of what were believed to be sewage plumes in the ocean taken by well-known Cape Town photographer Jean Tresfon were circulated on social media last year, sparking an outpouring of concern

However, the City says the findings confirm its position that the outfalls are not outstripping the ocean’s capacity to absorb them.

“It also found that there are no measurable risks to human health posed by the outfalls through either swimming at the beach or consumption of fish caught off our coastlines. In addition, near-shore pollution (when it occurs) is as a result of urban run-off. This is typical of all urban environments,” the City said in a statement.

The City will use this information to re-apply for a discharge permit for outfall pipes in the three areas.

The report says analysis showed most chemicals and compounds in effluents are diluted, within a small distance from discharge, to levels that are harmless to marine life.

Tissue of black mussels and West Coast rock lobsters collected at sites along the Atlantic Seaboard in 2016 also provided “no evidence” that mussels or rock lobsters collected inshore of the outfalls had accumulated chemicals to excessive concentrations in their tissue, the report says.

“Our society produces a lot of waste, and it is unavoidable that this waste eventually finds its way back to the environment in one form or another. There are over 84 000 synthetic chemicals that have been made by humans and no wastewater treatment plant is able to remove all of these components from effluent,” said Xanthea Limberg, mayoral committee member for informal settlements, water and waste services, and energy.

“This study confirms, however, that at current levels this waste can be safely assimilated by the ocean.”

Hout Bay resident Justin O’Riain, director of the Institute for Communities and Wildlife at UCT, said the report was “comprehensive”.

“It provides convincing evidence that despite our sewage being a potentially lethal cocktail of chemicals, heavy metals and bacteria, the effect on organisms living close to outfall sites is negligible. Hence health risks to people using the inshore region along the Atlantic seaboard from this source are clearly very low,” he said.

“Rather, as we have often experienced in Hout Bay, polluted run-off from urban areas contributes much higher levels of contaminants into our rivers, which then enter the sea via the coastline. Stormwater includes diverse sources of solid waste from plastic bottles to nappies and coliform bacteria that often exceed the acceptable levels for human contact.”

Consequently, the public were more at risk from the very catchment that they lived in and was actively polluted through poor waste management than they were from the sewer outfalls along the Atlantic seaboard, he said.

“Few would argue that we should aim to pollute neither ocean nor rivers with waste generating activities and all citizens are encouraged to do so with the products they use that enter the sewer system. Until we have the funding for treatment plants that can return clean water without synthetic chemicals into rivers or our reticulation system, the current practice seems to be the only affordable way forward that does not severely impact the health of people or wildlife.”

Mr Tresfon, however, remains unconvinced after studying the report.

In fact, he points out that one portion of the report states, “This does not mean there are no ecological impacts and human health risks associated with this practice, but rather that no major ecological impacts could be detected”.

He said from the outset the report continued in the same vein as certain officials from the City of Cape Town, which “isn’t surprising since the City commissioned, paid for and supplied much of the data for the report”.

“The report states that the Cape Town outfalls are comparable with those in other parts of the world and are common practice. What the report does not say is that in other parts of the world, such as Sydney, the effluent is treated to a primary and/or secondary level
before being pumped 3km out into the ocean,” he said.

“(But) in Cape Town we know better, and pump it straight into the sea, raw sewage and all. But surely it cannot be raw sewage? The report says it’s pre-treated, or is that preliminary treated? Or primary treated? What does it all mean?”

He said primary and secondary treatment were universal terms within the context of water treatment and meant very specific things in terms of treatment. However, he said Cape Town did neither.

“What happens here is that sand is removed and the effluent is passed through a 3mm screen to remove the bigger solids. Sometimes the effluent is also macerated. This is not treatment; at best it can be called screening. However in an attempt at obfuscation, the City refers to this practice as preliminary treatment or pre-treatment.”

He also questioned why the test results were based on the standards set out in the Department of Water Affairs’ Water Quality Guideline for Coastal Marine Waters 1995.

“Why are they using a 22-year-old water quality standard? Even then, in many instances, the test results did not comply with even the outdated water standard.”

Mr Tesfon said everyone in Cape Town was aware of the water crisis and plans were under way for desalination plants at Granger Bay, among other locations.

“Surely instead of trying to turn compromised sea water into fresh water, a far more practical solution would be to treat the wastewater from the outfalls first. We could recover a massive volume of water and reduce the toxic load of bacteria and chemicals reaching the sea.

“Although recycling wastewater has for many years been mooted as an im-
portant possible source for augmentation of the water supply, it is still not happening.”