The levels of human excrement and disease-causing pathogens in rivers around Stellenbosch are unacceptable and unsanitary. The water of the Eerste and Plankenbrug Rivers regularly do not meet international or national standards for the safe irrigation of fresh produce. People who use the rivers for sport and recreation stand a chance of contracting diseases such as diarrhoea, food poisoning and various types of infections.

These are the findings of the first thorough baseline study in more than a decade to quantify the extremely poor microbial state of the Eerste and Plankenbrug Rivers around Stellenbosch. The study, published in the Water SA journal, was led by food scientist Prof. Trevor Britz of Stellenbosch University (SU). It focused on the impacts that the polluted rivers have on food safety and human health.

Prof. Britz’s research team monitored the types of microbes and chemicals in the Plankenbrug and Eerste Rivers over more than three years across different seasons. The rivers pass through Stellenbosch and are used both upstream and downstream of the town to irrigate e.g. grapes, pears, citrus fruit, lettuce, strawberries, peppers, herbs and green beans especially during the summer months. Samples were taken once a month on a Monday morning for 42 months, from September 2007 to March 2011.

A high variety and extreme levels of waterborne faecal bacteria, protozoa and viruses were found in the water as well as on produce irrigated from the rivers. Various disease-causing pathogens are able to attach to plant tissue. These can be harmful to humans if the produce is eaten raw and untreated.

According to the South African Department of Water Affairs (DWA) and the World Health Organisation (WHO) levels of less than 1 000 faecal coliforms (bacteria that are present in the intestines of humans and animals) per 100ml sample of water is considered safe to use for irrigation. However, higher concentrations of faecal indicators in the Plankenbrug and Mosselbank were found in more than 70% of the samples, and to a lesser extent also in the Eerste and Berg Rivers.

“The Stellenbosch rivers clearly do not meet the minimum guidelines of the WHO or DWA, and are therefore not safe to use at all, not for irrigation, consumption, recreation nor sports,” project leader Prof. Britz of the SU Department of Food Science said unambiguously. “There is a high risk of exposure to human pathogens when water from these rivers is used to irrigate produce that is consumed raw or without any further processing steps.”

“Do not swim in them or drink untreated water, and if you are eating fruit or vegetables irrigated from these rivers make sure you wash it properly, preferably with a mild disinfectant like Miltons added to the water,” he further advised.

What was found?

• The researchers reported acceptable levels for irrigation purposes of physico-chemical properties such as temperature, acidity and alkalinity levels.
• However, microbial tests show that human excrement in particular is severely polluting the rivers.
• High concentrations of faecal indicators in the Plankenbrug and Mosselbank Rivers were present in more than 70% of the samples, and to a lesser extent in the Eerste and Berg Rivers.
• Concentrations of more than 1 000 000 microbes per 100 ml of water were often measured. Compared with the WHO and DWA guidelines, it points to severe unsanitary conditions.
• More than 30 types of bacteria and 180 phenotypic variations of the bacterium Escherichia coli (also known as E.coli) were found. E. coli an organism that is generally found in human and animal guts. Its presence in a sample means that there are human or animal faeces present in the water.
• Other potential pathogens such as Staphylococcus (food poisoning), Klebsiella (respiratory infections), Listeria (listeria infections) and Salmonella (food poisoning, diarrhoea or kidney failure) were also found.

The Kayamandi informal settlement, sewage pipe leaks and the Plankenbrug industrial areas were earmarked as continuous sources of pollution.

Even though the study showed slightly lower measurements than that of a 2004 community health study by Dr Jo Barnes, also of Stellenbosch University, the results are still extremely worrying.

“The high counts of Salmonella on their own pose a serious risk of potential food poisoning, since some residences on the banks of the Plankenbrug and Eerste Rivers draw water for gardening or household purposes,” Prof. Britz said.

Pollution levels were found to be constantly high throughout the year, irrespective of season or water temperature. Extremely high levels were even noted after heavy winter rainfalls. “This is probably because of increased run-off from the informal settlements or churning up by storm water of bacteria trapped in the river sediment,” he noted.

Certain human-based pathogens were also measured in boreholes, which might indicate that underground water sources have now also become contaminated because of seepage from the rivers.

“Based on the extremely high levels of contamination shown in the water and on irrigated produce, it is time to seriously put measures in place to prevent serious problems for our agricultural sector and the local population,” says Dr Gerhard Backeberg of the Water Research Commission.