Artificial swamps to deal with grey water

SMALL rectangular bathtubs filled with gravel and plants, designed to purify grey water.

That’s how Wits University’s Professor Craig Sheridan describes the constructed wetlands, or “artificial swamps”, that his international team will install in Alexandra township, as a feasible option to improve hygiene.

These constructed wetlands can act as a low cost, sustainable drainage system, treating wastewater in informal settlements that lack adequate sanitation infrastructure.

The R13m three-year project, Accessible Grey Water Solutions for Urban Informal Townships in South Africa, is being hosted in the Centre in Water Research and Development at Wits, where Sheridan is the director.

The project, with partners from Sweden and Germany, is one of eight awarded by the Council of the EU through the Water Joint Programme Initiative Grant, valued at €840 000.

“Constructed wetlands are like small rectangular bathtubs filled with gravel and plants, which the grey water would flow through. The plants grow in the gravel and there is a microbial community which lives with the plant.

“There are very complex interactions between the plants and the bacterial communities and the gravel. Basically these interactions destroy pathogens and remove the chemical impurities.”

As part of this project, his team will try to understand in detail how these interactions work, he said.

“The project aims to develop the idea of in situ, maintenance free systems for treating grey water, which will reduce the health risks to people as well reduce further impact to the environment as this water reaches the receiving environment (such as rivers).”

The project, too, will incorporate an existing constructed wetland project in Langrug township in Stellenbosch, where they have not been fully evaluated.

Sheridan said the grey water of an informal settlement is not the same as the grey water of a wealthy suburb. “In South Africa’s townships and informal settlements, rivers of untreated grey water – water that does not go down toilets – flows through streets.

“Untreated water can make people sick and sick people cannot work, raise their families or earn a living.

“Those who have to carry their tap water home may use it to wash fruit and children, then bath children, then wash textiles and then clean the floor.

“Only then is the water discarded. If shack dwellers feel unsafe to go outside at night, they amass night soil, which they may then add to grey water in the morning.

The disposal of this wastewater amid inadequate or non-existent drainage systems poses health and environmental risks. “Under these conditions, waterborne diseases such as cholera thrive and undermine health. Absenteeism from school and work can be expected.

“There is probably a lot of black water (containing faecal matter and carrying disease causing bacteria) in grey water in SA, which has implications for people’s health,” said Sheridan.

This week, planning for the multidisciplinary project kicked off in Paris at the International Co-operation for Water meeting of Funded Research, Development and Innovation.

“The partners to the project are all equal: we will all be participating in design, implementation and research.”

He said sites would be chosen following engagement with the local community. “Part of the project is to identify a suitable site, somewhere in an urban shanty environment.

“Projects such as these were historically designed and implemented by engineers and scientists with little interaction with the people that used them. A major part of this project is to understand the human interaction.

“How do people understand the systems? How do they interact with them? Do they want them?”