Algal blooms

The particular species of algal bloom occurring along the coastline was identified by the National Department of Agriculture Forestry and Fisheries (DAFF) as Lepidodimium chloroforum and has no known toxins. DAFF holds the mandate to monitor the occurrence of algal blooms as well as for issuing any consumer warnings in the event of a toxic bloom (red tide).

Algal blooms are a normal and common occurrence off the coastline of Cape Town, and South Africa more broadly. The phenomenon is mostly caused by ocean upwelling events that brings colder, nutrient-rich water, and the accompanying dinoflagellate cells, into warmer surface waters. The combination of nutrients, warmth and sunlight causes the cells to bloom.

Alarmist stories have been carried by some news outlets after an article was released by a UCT scientist about water quality matters. The City has not seen the findings of the research first-hand but understands that the scientist has requested certain news outlets to print corrections to their stories to more accurately reflect the true state of affairs. The City welcomes this call as inaccurate reporting does a disservice to readers and the broader community.

As a matter of record, the City also has the highest number of Blue Flag beaches in the country, 10 of which five are in False Bay between Fish Hoek in the west and Bikini Beach in the east. As part of the Blue Flag criteria, water quality at these sites is independently analysed by the South African Bureau of Standards.  

Impact of the algal blooms on the Strandfontein and Monwabisi desalination plants

It must also be noted that there are organisations who are creating the impression that the City’s desalination plants have not been working at all due to some functional failure or cover-up by the City. This is simply not true.

The operations of the desalination plants in Strandfontein and Monwabisi have at times been affected by algal blooms and the high turbidity of the sea water. The algal blooms occur naturally and the high turbidity in the ocean is normally caused by bad weather and sea conditions (strong winds and big swells). Algal blooms cause damage to the sensitive membrane filtration systems of the desalination plants, while the high turbidity affects the pre-treatment processes of the desalination plants, which can result in reduced production by the plant. Halting operations temporarily is thus a precautionary approach while ongoing monitor and technical assessments continue to ensure the optimal functioning of the plants.

The Strandfontein plant was producing little to no water over the period 1 to 7 November 2018 due to the high turbidity of the sea water. The Monwabisi plant could not operate for four days during the same period. After resuming the production, both plants again stopped producing drinking water on 16 November 2018 due to the occurrence of the algal bloom but are fully functional otherwise.

The algal bloom has dissipated in the False Bay area and the Strandfontein plant is in production again while the Monwabisi plant will be in production again soon. It must be noted that the City only pays for water that is actually injected into the reticulation system, hence the temporary suspension is not for the City’s account, as claimed.

The contractors who have been appointed to run the desalination plants as part of the City’s Water Emergency Water Augmentation Scheme are contractually required to deliver water that meets South African National Standards (SANS 241:2015) requirements. These are the standards set nationally for drinking water quality. The City has a proud record of always meeting these standards. The desalination plants have online monitoring equipment to check the quality of the desalination process and adherence to the SANS standard.

Desalination, at this stage, is a relatively small component of our augmentation programme and as such temporary drops in production are not expected to have a very significant impact on the overall water supply.

Zandvliet Waste Water Treatment Plant (WWTP) upgrade to benefit Sandvlei community and surrounds

The inland wastewater treatment upgrades for the Zandvliet plant have also been conflated with the algal bloom situation. It thus bears no correlation with the water quality issue discussed above.

The City has started to undertake measures to mitigate environmental impact. Currently, 8 million litres of flow per day that is currently going to the Zandvliet WWTP is being diverted to the Bellville WWTP (completion of diversion expected in early 2019). Furthermore a R1,5 billion upgrade to the Zandvliet WWTP is planned to cater for rapid ongoing development in the Khayelitsha, Delft, Blackheath and Eerste River areas.

The City has for several years been attempting to upgrade the plant but this has been delayed by five tender appeals, including a High Court appeal, and a land claim.

Encouragingly, most of the upgrade work has been approved by Council in the past few months, and it is expected that work will begin in the first half of 2019. We still, however, require residents to obey the laws which state that nothing should be flushed down the toilet or thrown into manholes which could interfere with the free flow of sewage, such as rags, litter, rubble, cooking oil and fat, and anything other than greywater and toilet paper.

The commissioning of the new plant is anticipated by December 2023. Soon thereafter, a further expansion will be implemented to cater for continuing urban growth in the area. Work will see construction of a membrane bioreactor (MBR), sludge dewatering facilities, new inlet works, pump stations, primary settling tanks and maturation ponds where effluent is purified before discharge.

Importantly, it must be noted that the City does not discharge untreated sewage into the river. The plant currently operates within the design capacity in term of flow rates. However, it is over its capacity in terms of nutrient load due to the population growth in the area which is serviced by the plant. The City is implementing a number of initiatives such as the addition of polymers for treatment to settle the nutrients while the expansion is under way.

The City’s sampling and testing frequency has been increased to a weekly schedule, and will include input from the community on agreed sampling locations. These results are being shared with the National Department of Water and Sanitation, and with the CSIR.

Humans produce waste

There are over 84 000 synthetic chemicals in common use and no wastewater treatment plant in the world is able to remove all of these components from effluent. They will continue to be present in the environment so long as we continue to use them as a society. Our understanding is that further research into the long-term effects of these various chemicals on public health and the environment is necessary, as the effects of these chemicals in aquatic ecosystems are largely unknown. 

In general, the treated effluent discharged from the City’s WWTPs achieve a compliance rate of more than 80% with the standards required by the Regulator; and the plants operate in accordance with ISO standards. The City is committed to ensuring that it continues to evolve its processes to manage waste and to ensure that it does absolutely everything in its power to put in place enhanced processes for sustainable urban management.

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