Debbie Fox
South Africa should clean up its act offshore or face unknown damage to the marine environment, says government scientist Lynn Jackson, deputy director of marine and aquatic pollution control in the Department of Environmental Affairs and Tourism.
Jackson says too little is being done to gauge the effects of sewage and industrial effluent channelled out to sea through the 60 or so licensed pipelines around the coast.
“While oil spills can be devastating, the impact is usually localised and short term. They get on to beaches, mess up holidays and capture the public imagination. But effluent discharge into the sea is a chronic and more insidious threat. I don’t believe we’re doing sufficient monitoring to pick up the problems at an early stage.”
About 66-million litres of domestic sewage, 230-million litres of industrial waste and 360-million litres of mixed effluent flow into the sea every day. Untreated sewage, often from informal settlements, is also channelled through pipes on to beaches. Cape Town alone has about 100 such stormwater drains.
With increasing urbanisation, says Jackson, waste is accumulating around cities like Durban and Cape Town. “The dilution of effluent depends on many factors, such as how open the coast is as well as wave and current action. Cities tend to develop around bays because of the sheltered waters. More and more people come to work and live there and the volume of sewage and industrial waste goes up. Because it’s a semi-enclosed area, the waste gets trapped close to shore.”
South of East London an effluent plume can be seen emerging from a pipeline metres from the beach. The main sewage treatment works at Port Elizabeth also discharges into the surf zone.
While pipeline owners are legally obliged to monitor the sea around their discharge, in some cases this is only required every three years. Consultants are hired to ensure there is no harmful build-up of contaminants such as heavy metals on the seabed. Jackson believes monitoring should be more frequent and extend around the whole coastline.
“In built-up areas we could start getting problems unless we cut down on the marine effluent. For example, mussels can concentrate heavy metals hundreds of thousands of times they then become toxic to humans.”
One report has found high mercury levels in the Durban area. There are also unproven suggestions that red tides natural, toxic occurrences of plankton could be exacerbated by high-nutrient discharges.
In the Western Cape the Department of Water Affairs analyses effluent at pump stations before it enters the pipeline every six weeks. While acknowledging the argument for increased monitoring, regional deputy director of water quality management Gareth McConkey says there are practical limits. “You have to be pragmatic monitoring is very costly to us and the industries and we have to ask: how much do you need to manage the situation?”
One way to relieve the pressure on marine monitoring, says Jackson, is to address the problem at source: using cleaner technology to reduce pollution. “Industries must find ways to eliminate completely the use of the more toxic contaminants, such as mercury in the manufacture of batteries. If you really have to use toxic substances, they should be converted on land into by-products which can be used in other industries. Failing that, toxins should be encapsulated into cement chambers.”
She also supports tax incentives for industries to clean up their act.
Steps towards cleaner technology are being taken under the 1998 Water Act. Companies must now pay to discharge into rivers, the fee depending on the quantity and quality of effluent. The use of untreated waste to irrigate land has also been curbed; increasingly effluents are being purified and returned to the source river.