Expert insights from Phindile Mahlangu of Magalies Water on managing polluted catchments, rising treatment costs, and ensuring safe, compliant drinking water in South Africa.
Phindile Mahlangu, scientific services manager, Magalies Water
“This has resulted in partially treated effluent being discharged into our systems.”
Hartbeespoort Dam
The effects of upstream pollution are precisely what Magalies Water is working to address through its appointment by the Department of Water and Sanitation (DWS) as the implementing agent for the Hartbeespoort Dam remediation programme, which forms part of the broader Crocodile West Catchment Water Resource Management Project. This work is not limited to the dam itself but extends across the entire upstream catchment.“Any gains from upstream interventions ultimately flow back to us downstream, where we abstract the water, allowing us to clearly see both the impact of our efforts and the value of investing in the catchment,” explains Mahlangu.At a catchment level, Magalies Water is undertaking water quality monitoring, pollution profiling and source tracking. This involves analysing water quality data to identify pollution hotspots and trace contaminants back to their origin, enabling the regulator to take enforcement action. Within the dam itself, interventions focus on restoring ecological balance and improving water quality. This includes removing invasive aquatic vegetation, which thrives in nutrient-rich conditions driven by excessive nitrogen and phosphorus loads. These nutrients, largely from wastewater effluent, drive eutrophication, resulting in algal blooms, invasive plant proliferation and deteriorated water quality. Magalies Water has also implemented in-lake treatment technologies, including nanobubble and bioremediation interventions, to increase dissolved oxygen levels and reduce nutrient concentrations. This technology is designed to improve water quality within the dam, although its effectiveness is constrained by the continuous inflow of polluted water from upstream. Importantly, the organisation recognises that in-dam interventions alone are not enough. While remediation efforts can improve conditions locally, the long-term solution lies in reducing pollution at source, particularly by improving wastewater treatment performance in upstream municipalities and strengthening regulatory enforcement. Without this, the dam remains heavily polluted.
Integrated water resource management
At Hartbeespoort Dam, Magalies Water is not just monitoring water quality, it is leading a full-scale catchment remediation effort on behalf of the Department of Water and Sanitation
“Water boards can no longer operate in isolation,” says Mahlangu. “We need an integrated approach across the entire water supply value chain, from source to tap.”As a water board with strong research, development and innovation capacity, Magalies Water is well positioned to support municipalities with technical expertise, data-driven interventions and fit-for-purpose solutions to improve water quality and system performance. “Magalies Water is increasingly involved in catchment management and remediation as well as municipal support. We aim to help resuscitate water systems at the water service provider or water services authority level. Magalies Water is assisting municipalities with Blue Drop compliance, process audits and the development of water safety plans and Incident Management Protocols. These systems take a holistic view of the entire water value chain, from abstraction and storage to pipelines and the consumer tap, identifying risks and interventions across the system. Bulk water supply is essentially at the beginning of the water value chain for municipalities, and we can help them identify further risks along the chain and optimise their operations,” adds Mahlangu. Magalies Water regularly partners with municipalities and holds community engagement forums on water conservation and demand management, pollution and water quality. They also promote digitisation, smart metering and non-revenue water reduction, recognising that operational inefficiencies and water losses further strain already limited resources.
The rise of emerging risks
The Roodeplaat Dam is part of the Magalies Water supply network, and is primarily used to supply bulk potable water to the City of Tshwane
For a sector already under financial and operational strain, this adds another layer of complexity.
In effect, drinking water treatment plants are increasingly being forced to compensate for upstream failures, taking on a role they were never designed to fulfil. This has a cascading effect. Higher contamination levels drive up operational costs, increase energy consumption, and accelerate infrastructure wear through intensified strain. Treatment becomes less efficient, more complex and expensive. “At Magalies Water, the output per unit, specifically energy and chemical spend, is increasing due to deteriorating raw water quality, which is forcing the plants to work harder while producing less. Previously, the same amount of energy and chemicals could reliably produce, for example, 50 Mℓ/day, but now, with higher nutrient, metal, and microbial loads, that same input may yield only a fraction of the original quantity of compliant treated water. Increased chemical dosages are required for treatment, maintenance is more frequent (due to source water eutrophication and system inefficiencies due to invasive plants), and yet the throughput must be reduced to safeguard water quality,” explains Mahlangu. In simple terms, the cost per litre treated is rising because the system must use more energy and chemicals more often to maintain safe drinking water standards amid worsening raw water conditions. Mahlangu gives an example: “Ammonia enters rivers and dams through partially treated sewage, industrial discharge and agricultural runoff. Many wastewater treatment plants are failing to effectively remove ammonia, and conventional water treatment works are not traditionally designed to remove it, so many systems are struggling. As a result, water treatment plants are forced to adapt, adjusting processes and, in some cases, introducing advanced treatment technologies just to keep water within safe limits.” At the same time, ammonia interferes with disinfection processes. When chlorine is added to water containing ammonia, it forms chloramines, which are weaker disinfectants. If not carefully managed, this can compromise the system’s ability to control microbial contamination effectively. Beyond the treatment works, ammonia plays another role, one that is visible to the public. As a nutrient, it fuels the growth of algae and cyanobacteria in dams and reservoirs. This process, known as eutrophication, leads to the familiar problems of green water, unpleasant tastes and odours, and, in some cases, the production of toxins. Systems like Hartbeespoort Dam have become well-known examples of how nutrient loading, including ammonia, can transform a water body into a highly degraded ecosystem. The proliferation of alien invasive species in nutrient-rich water presents additional problems to bulk water suppliers. “At raw water abstraction points, these plants accumulate at inlet screens, which are designed to prevent debris from entering the treatment works. Historically, these screens dealt with occasional natural debris, such as branches. Today, they are increasingly overwhelmed by dense mats of invasive vegetation. These screens constantly must be removed, cleared and put back,” says Mahlangu.Managing the costs of water treatment
The Elands River forms part of the broader Crocodile West Catchment and supplies water to the Vaalkop Water Treatment Works
Compliance
Magalies Water operates an advanced, SANAS-accredited laboratory with extensive analytical capacity, capable of performing a wide range of physicochemical and microbiological tests to support regulatory compliance and ensure the consistent delivery of potable water
Source water protection
The Cullinan Water Treatment Plant
“The improvement of water quality at an impoundment level, but at the same time, more contaminants are entering the system.”“Water is not just a commodity”, Mahlangu concludes. “It is a shared resource that underpins our health, our economic development and our future. Protecting it is everyone’s responsibility. People need to understand that what is discharged into the environment does not disappear. It returns, often in a different form, and often at a higher cost. What is done to water resources will ultimately be returned, in this instance, in the form of consumer costs and ecological disruptions.”