Algae Power: A Low-Cost Wastewater Solution Transforms Rural South Africa.

Across many parts of rural Africa, access to effective wastewater treatment remains a major public health and environmental concern. Ageing infrastructure, underfunded facilities, and growing populations have pushed sanitation systems beyond their limits. In some communities, untreated sewage flows directly into rivers, damaging aquatic ecosystems and endangering lives.

For years, the global standard for wastewater management has involved large-scale treatment plants that use electricity, chemicals, and complex machinery to remove contaminants. However, these systems are costly, energy-intensive, and often unsustainable in low-income, rural settings.

Seeking a more viable alternative, a team of scientists led by environmental management expert Paul Oberholster tested an innovative solution in Motetema, a small town in South Africa’s Limpopo province. Their approach? Harness the cleaning power of algae.

The team introduced fast-growing microalgae into the town’s wastewater treatment ponds, targeting sewage from around 1,560 households. Remarkably, these microscopic organisms cleansed the water without requiring chemicals or mechanical systems that depend on electricity.

This nature-based method—known as phycoremediation—offers a low-tech, low-cost option for towns with limited resources and inconsistent power supplies. It works by leveraging a natural partnership: algae thrive on sunlight and absorb nutrients like nitrogen and phosphorus, while oxygen produced during this process supports aerobic bacteria that digest organic waste.

Though algae-based wastewater treatment is not a new concept, the Motetema project stood out by using two highly efficient species—Chlorella vulgaris and Chlorella protothecoides. These strains were selected from dozens tested for their exceptional capacity to remove nutrients from sewage.

To ensure a consistent supply of these algae, the team cultivated them in photobioreactors—specialized transparent tanks that control light, nutrients, and carbon dioxide for optimal growth. Once ready, the algae were introduced into the town’s wastewater ponds.

The results, recorded after a year, were impressive:

• Ammonia levels dropped by 99%

• Orthophosphate decreased by 83%

• Total nitrogen was reduced by 73%

These pollutants, particularly ammonia and phosphorus, can be toxic to aquatic life and contribute to harmful algal blooms. Thanks to phycoremediation, the treated water from Motetema’s ponds met environmental safety standards and could be safely released into the ecosystem.

Motetema, home to roughly 11,000 residents, uses a pond system comprising 12 large basins. One half operates while the other is cleaned. Originally designed to process about half of the 4.5 million liters of sewage it now receives daily, the system was under severe strain before the algae project began.

Similar challenges plague wastewater treatment systems across South Africa. Many facilities are outdated, too small to handle growing populations, and frequently suffer from power outages, poor maintenance, and lack of skilled operators. But algae need none of these resources—they simply require sunlight, water, and space.

Of course, phycoremediation has its own challenges. At Motetema, duckweed growth sometimes blocked sunlight, limiting algae effectiveness. Seasonal wildfires damaged equipment, and occasional sewage surges temporarily overwhelmed the ponds. Sludge buildup also reduced available space, slowing the cleaning process. Still, these issues were manageable through routine maintenance and periodic replenishment of healthy algae cultures.

Crucially, this model has the potential to be scaled across rural Africa. It only requires land—each pond can span up to 40,000 square meters—and time, as the algae need two to three weeks to purify wastewater fully. But the benefits are substantial: lower costs, reduced environmental harm, and improved public health.

For this solution to take hold more widely, it needs the backing of local municipalities and policymakers. As climate change continues to intensify water scarcity and energy costs, nature-based solutions like phycoremediation may be key to building resilient, sustainable sanitation systems.

Beyond just treating wastewater, this approach redefines it—as a valuable resource that can be cleaned and reused to support agriculture, aquaculture, or even replenish groundwater supplies. In Motetema, a green future may have begun with the humble algae.

Source:https://phys.org/news/2025-06-algae-sewage-electricity-chemicals-south.html

This is non-financial/medical advice and made using AI so could be wrong.