Improved wastewater treatment could create jobs, reduce health-care costs
WORLDWIDE, a huge proportion of people live in cities along the coastline. They cause daily wastewater discharge, with little or no treatment, into the marine coastal waters. Water polluted with sewage contains millions of pathogenic microorganisms – not just E coli.
A study initiated by the World Health Organisation estimated that the global burden of thalassogenic diseases (seawater-related illnesses caused by wastewater pollution) can result in as many as 120 million cases of gastrointestinal diseases, and more than 50 million cases of severe respiratory diseases.
In addition, seafood and shellfish are harvested along the coastline, and are often eaten raw as sushi, or lightly steamed, leading to nearly 4 million cases of infectious diseases such as Hepatitis A and E a year, with annually 40 000 deaths and 40 000 cases of chronic liver diseases. The worldwide costs of wastewater pollution of the sea is estimated to be about 3 million lost years of “healthy” life, with an estimated economic loss of more than $12 billion a year.
South Africa’s coastline attracts many bathers and surfers worldwide. Regular water surveys and recommendations for bathers are in existence for the EU and the US, but only few data are published regarding water quality and health hazards in South Africa. Swimmers and surfers swallow significant amounts of water.
Adult swimmers are prone to ingest 10-100ml of seawater, while children probably ingest larger quantities of water. Young children and people infected with HIV and TB are especially at risk of health hazards caused by ingesting sewagepolluted water. Although the HIV epidemic has stabilised in South Africa over the last four years, the number of people living with HIV is 5.6 million – meaning we are an immune-compromised population.
These people need to be informed about the health hazards of thalassogenic diseases. Bathing in cold water makes the body more susceptible to infections. Thirty-six beaches in South Africa have been awarded Blue Flag status for excellent bathing quality.
The Blue Flag is an internationally recognised eco-label, given to beaches on an annual basis that meet standard criteria for water quality, environmental education, environmental management, safety and services. No industrial wastewater or sewage-related discharges should affect the Blue Flag beach area.
As water pollution can also result from bathers themselves, the beach must be kept clean; no dogs are allowed and small particles such as cigarette butts must be removed on a regular basis. Analysis of water quality should be performed every two to four weeks. The Blue Flag Beaches in South Africa must comply with the water quality standards for E coli (100/100ml) and for Enterococci (50/100ml).
South African wastewater goes into the ocean often, with only one treatment. E coli is not removed with this treatment – only waste particles are filtered out. After storms and heavy rains, overflows are washed into the sea. Additionally, the deterioration of wetlands and rivers in the Western Cape progressively increases as one gets closer to the coast.
Sewage pipes are led into the ocean 1.7km offshore of Camps Bay beach and the water flows up the coastline of the Cape Peninsula, possibly polluting beaches there. During high tide, water from offshore is brought on to the beach area and coastline. Researchers have illustrated in a 3D ocean model that sewage treatment and wind conditions can cause faecal pollution as far as 20km downstream.
Escherichia coli ( E coli) is found in the intestines of humans and animals. It can survive for extended periods of time out of its host. It is recognised internationally as a marker for faecal water pollution. Up to now the degradation and inactivation of E coli in seawater has not been well established. Studies show it degrades more slowly in cold water, depending on exposure to sunlight. It seems seawater does not enhance the degradation of E coli.
In my study of Blue Flag beaches, Clifton was specifically selected as one of the most popular beaches on the Cape Peninsula, with easy access. The Blue Flag season ran from December 1, 2012 to March 31, 2013 at Clifton. It lies in proximity to the main shipping route. Several wastewater pipes are led offshore into the ocean and discharges from wastewater plants in Sea Point and rivers flow into the sea. The results are discussed in light of the high burden of HIV and tuberculosis (TB) within an immune compromised population.
In the examined study samples, E coli was always present. In 83 percent of samples, E coli counts exceeded 100/100ml. Values over 10 000/100ml were associated with signs of wastewater pollution, such as yellowish foam on the water and yellowish coloured sand.
Although Clifton is a Blue Flag Beach, there are times when the coastal water of the bathing area is affected by wastewater. During the study, only one time was the E coli content within the recommended range. There is an ongoing debate about whether to propose even lower limits for E coli for recreational bathing areas, as each individual reacts differently to exposure.
Even if a beach is awarded Blue Flag status, adults, children and especially immune compromised people are at risk for a thalassogenic disease when they swim in the sea.
The US Environmental Protection Agency recommends a 24-hour method for water testing at recreational bathing sites, to minimise the time between sample collection and swimmer exposure. Other countries have introduced real-time surveillance, enabling bathers to check the daily water quality on their smartphones. Meanwhile, it is advisable to look out for obvious signs of wastewater pollution, such as yellowish foam and sand on the beach.
Improved wastewater treatment in South Africa would create jobs, decrease the burden of diseases, reduce the costs for the health-care system and improve the sustainability of our oceans as a tourist attraction and for the fishing industry. It could serve as a model for many other countries worldwide.
Edda Weimann is a Professor of Paediatrics, a Medical Doctor and holds a Master’s degree of Public Health at the University of Cape Town