Toxic cyanobacteria, notably Anabaena and Microcystis, are increasingly prevalent in South Africa’s freshwater systems, contributing to severe eutrophication and posing serious health risks.
Cyanotoxins and Their Dangers
- Anabaena produces anatoxins, a group of neurotoxins known for their fast-acting nerve toxicity.
- Microcystis generates microcystins, which are more widespread and chemically complex. Once denatured, their breakdown products can become even more toxic than the intact molecule.
Microcystin Safety Thresholds vs. South African Realities
- The World Health Organization (WHO) has set a maximum safe limit of 1.0 microgram per litre for microcystins in drinking water.
- However, microcystin levels in South African rivers have been recorded at 10,000 to 18,000 μg/L, far exceeding safe thresholds (Oberholster et al., 2004).
- Approximately two-thirds of South Africa’s major dams are now classified as eutrophic (Matthews and Barnard, 2015), providing ideal conditions for harmful algal blooms.
- Even treated municipal tap water may contain microcystin concentrations near 10 μg/L, ten times higher than WHO guidelines.
Activated Carbon: An Effective and Scalable Water Purification Solution
Activated carbon is a powerful and increasingly accessible solution for improving water quality in both municipal and household settings. Through a process of activation, the carbon develops a highly porous structure that maximizes its surface area, allowing it to effectively adsorb organic toxins, heavy metals, and microbial contaminants from water.
Municipal Use: Retrofitting Water Treatment Plants in South Africa
In large-scale bulk water treatment plants, activated carbon is used in the final stage of purification. Water is passed through large contact chambers filled with activated carbon, where remaining contaminants such as microcystin—a toxic byproduct of cyanobacterial blooms—are adsorbed.
- After uranium, lead, and other heavy metals are removed through precipitation and become part of the sludge, activated carbon filtration is used to polish and detoxify drinking water.
- This system can be easily retrofitted into existing South African potable water treatment infrastructure, offering a cost-effective upgrade to meet public health standards.
- Household Solutions: Activated Carbon Tap Filters