Every day, 50,000 litres of polluted water flow from South Africa's Stiebeuel River into natural filter beds, where stones, sand and biochar clean it in 5 days, removing 99% of harmful bacteria and creating water for irrigation

Water pollution can place enormous pressure on communities that already face limited freshwater supplies and aging infrastructure. In South Africa, researchers are exploring whether nature itself can become part of the solution. At the Water Hub in Franschhoek, polluted water from the Stiebeuel River is being treated through a system that uses stones, sand, biochar, plants and naturally occurring microbes.

A River Facing Severe Pollution

The Stiebeuel River is situated in Franschhoek, around 75 kilometres east of Cape Town. Sewage and polluted rainwater enter the river because of inadequate sanitation and drainage systems serving the nearby Langrug informal settlement. Around 26,000 people live there, where densely populated housing places additional pressure on aging and overstretched infrastructure.

The river has become so polluted that local residents can no longer use it. It also carries extremely high levels of E. coli. As per the supplied research, levels can exceed 400,000 colony forming units per 100ml, while South African water quality guidelines state that people should not come into contact with water containing over 130 counts per 100ml.


The river also has ammonia, phosphorus, microplastics and traces of medicines. Ammonia and phosphorus can encourage algal blooms that turn lakes and slow-moving rivers green and reduce oxygen levels.

A Natural Approach to Water Treatment

Researchers at the University of Cape Town’s Future Water Institute are investigating nature-based techniques at the Water Hub, an off-campus research facility in Franschhoek. The site occupies an old, disused wastewater treatment plant and is being developed as a living laboratory.

In a recent research paper, the researchers explained how former sludge-drying beds were converted into natural filtration areas. The beds were filled with small stones, coarse sand and biochar, described in the supplied material as “a wood feedstock exposed to temperature of 800 degrees Celsius.”

Polluted river water slowly passes through these materials. During the process, bacteria and nutrients are removed. Naturally occurring microbes help break down pollution, while plants absorb excess ammonia and phosphorus.

50,000 Litres Treated Each Day

The large-scale biofiltration system pumps water from the Stiebeuel River into a 10,000 litre tank before sending it through two supply tanks and into a biofilter.

The design is based on the way healthy wetlands naturally cleanse water.

The research reports that the system removes 99% of harmful bacteria, reduces ammonia and phosphate concentrations by up to 90%, and achieves more than 90% removal of some pharmaceutical compounds and microplastics.

Approximately 50,000 litres of contaminated water are treated daily. Almost 3,000 litres per day are used to irrigate vegetable gardens managed by young women from the informal settlement. The gardens offer opportunities for skills development, food production and small-scale enterprise.

An Alternative for Water-Stressed Communities

Nature-based treatment cannot substitute properly functioning wastewater treatment facilities, particularly when dealing with the enormous quantities of wastewater produced by towns and cities. However, it could support municipalities facing high electricity costs, deteriorating infrastructure and limited technical skills.

The system can treat water close to where pollution happens rather than depending completely on large centralized treatment plants. Its basic operation requires relatively low maintenance costs and limited technical skills, although regular water-quality monitoring remains necessary.

The Stiebeuel River project illustrates how combining science, engineering and community participation can turn polluted water infrastructure into a productive resource. Instead of treating wastewater only as something to dispose of, the approach features how it can be recovered and reused to support irrigation, food production, livelihoods and water security.

Source: Infrastructure News (This article was originally posted on theconversation.com)

FAQs:

Q1. What is water pollution?

Water pollution occurs when harmful substances enter rivers, lakes or other water sources. It can affect water quality, ecosystems and people who depend on those resources.

Q2. Why is clean water important?

Clean water is essential for people, agriculture and natural ecosystems. Protecting available water supplies can also help communities facing shortages.