Sewage stench lingers at Milnerton Lagoon

A stench of sewage from the Milnerton Lagoon in Cape Town is nothing new, but it has been nauseating over the past weeks, say residents. This is despite the provincial government having issued the City a directive to rehabilitate the highly polluted lagoon more than four years ago.

Residents living near the lagoon say the stench, which has emanated from the lagoon in the past is “eye-watering” and nauseating since late last month.

Asked about the source of the sewage pollution in the lagoon, mayco member for water and sanitation Zahid Badroodien referred GroundUp to a letter sent to Milnerton residents and councillors setting out sewerage infrastructure failures since July, and the City’s interventions to address the resultant pollution.

The letter, dated 29 November, states that the City had been receiving complaints about the “foul odour” at Milnerton for the “past few weeks”. This was due to “a series of events” having “compromised the integrity of the sewer system”, which were being addressed.

The letter describes sewer line collapses in July, August, and September, all of which contributed to sewage flowing into the lagoon via stormwater channels.

Rehabilitation work in October also resulted in sewage overflows into stormwater channels flowing to the lagoon.

The City described the repairs being undertaken and efforts to contain the sewage flows, while apologising for the “extended inconvenience”, and stating that it was “working tirelessly to address the root causes of the pollution and prevent future occurrences”.

Sewage treatment failures

The Potsdam wastewater treatment works (WWTW) releases more than 40-million litres of sewage effluent per day into the Diep River, just 5km upstream of the lagoon. This is the main flow of freshwater into the lagoon in summer. It would not result in pollution if the Potsdam WWTW was properly treating the sewage it receives before releasing it into the river.

Among other pollutants, sewage contains E. coli and enterococcus, which are bacteria known as faecal coliforms, found in the human gut. National guidelines state treated effluent should have fewer than 1,000 colony forming units (cfu) of faecal coliforms per 100ml. This is the same at the City’s “target” range for intermediate contact in its rivers, vleis, and estuaries. In other words, one should be able to canoe and kite surf in properly treated effluent released from a sewage treatment plant, without any ill effects.

Badroodien said the pollution was not caused by the the Potsdam WWTW.

But the Department of Water and Sanitation’s (DWS) regulatory information system shows that Potsdam WWTW has met the minimum effluent quality guideline for just 3% of its monthly effluent quality tests over the past year.

Additionally, Potsdam achieved chemical compliance in only 48% of effluent quality tests so far this year. This is a measurement of elements such as nitrogen, phosphates, and ammonia. It also achieved just 31% for physical compliance, which measures aspects such as suspended solids, pH, and electrical conductivity. Currently, the DWS system lists Potsdam’s effluent quality as ‘bad’.

The City has been conducting a R5.2-billion upgrade of the Potsdam WWTW for the past 20 months, with completion set for the end of 2027.

Asked about the poor effluent quality, Badroodien said the final results of upgrade would only be evident “once all components have been constructed”.

“To address current challenges, some infrastructure components have been fast-tracked and are expected to be completed by approximately mid-2025, leading to a marked improvement in treated effluent quality,” he said.

He said the effluent compliance had “already improved to 75%”.

Yet the DWS information system reveals nine “high level failures” this year, the most recent being on 29 October.

Water quality results

To the City’s credit, it makes its inland water quality test results publicly available through the Public Inland Quality Dashboard. The results also point to the main source of sewage pollution in the lagoon coming from the Potsdam WWTW.

According to the City’s water quality data, the results at the testing point immediately downstream of the Potsdam WWTW have on average been worse than the water quality results upstream of the sewage works. The latest water quality test results (19 November) show an E. coli count of 29,100cfu/100ml above the Potsdam WWTW, which is more than 11 times the acceptable limit for intermediate contact. But the count downstream of Potsdam WWTW was 7.3-million cfu/100ml. This indicates a serious pollution source most likely emanating from the sewage treatment works.

Environmental activist and Milnerton resident Caroline Marx, who is included on the mayoral advisory committee for inland water quality, said the results show that significant sewage pollution either comes from Potsdam WWTW or a sewerage pipe that runs to Potsdam.

Marx said on 27 November the stench from the lagoon was so bad it made her eyes burn. When GroundUp spoke to her on 3 December, she said the lagoon still stank.

She said at this time of year, when there was little to no rain, most of the flow into the lagoon came from the sewage works.

Compared to the 40-million litres a day of effluent released from Potsdam, there would need to be “an enormous volume” of sewage coming from other sources for it to pollute the lagoon to this extent.

But whatever the source, she said whatever measures the City was taking to prevent pollution of the lagoon seemed to be insufficient.

Green Scorpions directive

Following warnings to stop pollution of the Milnerton Lagoon – which a study found was an important nursery area for fish on the west coast, including Cape stumpnose and white steenbras – provincial environmental compliance officials, known as the Green Scorpions, issued a directive to the City in September 2020 ordering it to clean up the lagoon.

A directive is an enforceable notice issued in terms of the National Environmental Management Act.

The City’s Inland Water Quality Dashboard shows significant pollution in the lagoon in 2019, with improvement in late 2020 and 2021, but worsening from 2022 to the present. The 2024 results are worse on average than those of 2019, which led to the directive being issued.

Western Cape Department of Environmental Affairs and Development Planning spokesperson Rudolf van Jaarsveldt said the directive was being enforced, and the City was engaging with the provincial government on several conditions in the directive.

“Some of the conditions [of the directive] are subject to future-dated timeframes as well as lengthy procurement processes, and the City has communicated this to the Western Cape government,” stated van Jaarsveldt.

He said the upgrades of the Potsdam WWTW and the Koeberg pump station would “prevent further pollution from these facilities”.

He said compliance with the directive, and the City’s reports on the matter continued to be monitored.

But chairperson of the Milnerton Canoe Club, Richard Allen, said the state of the lagoon seems to have deteriorated. While more experienced canoe club members used to paddle on the lagoon four years ago when the provincial department issued its directive, Allen said they have since halted all paddling on the lagoon. He said the club members now paddle along the canals at Century City about 5km away. He said they are battling to keep the canoe club alive.

He said the water quality in the lagoon had gotten “progressively worse”.

“It’s toxic and stinks to hell,” he said.

He said the smell from the water had been “ghastly” at the end of November.

Some functions had been organised at the clubhouse on the bank of the lagoon but the water was “really foul”. “I was almost hurling.”

Speaking to GroundUp on 10 December, Marx said the stench had reduced due to higher tides flushing the lagoon and “everyone suddenly jumping to fix the problems”.

This article was first published on GroundUp