People, Africa, Natural Capital & The Environment

Using green technology to improve water quality

UN Environment | Feb 07, 2020


Image by Adrian Winther

This article was originally published by UNEP and is republished with permission.

“The smell alone when you cross the bridge tells you something’s wrong,” says Renison Ruwa, deputy director of the Kenya Marine and Fisheries Research Institute.

The bridge in question is Mtwapa bridge, which straddles Mtwapa Creek in Mombasa, Kenya. And the smell to which Ruwa is referring stems from this very creek, into which waste from the nearby Shimo la Tewa prison—and indeed many other places—is directly dumped.

The prison’s growing population has long overwhelmed the capacity of its septic system, causing excess raw sewage to be discharged into the creek for many years—dumping which can have grave long-term effects on the area.

The beautiful coral reefs of the nearby Mombasa Marine Park are very vulnerable to such pollution, as are local fish and crabs. Wastewater pollution not only has the potential of disrupting local ecosystems and biodiversity, but also potentially tourism revenue.

The prison has not been spared from the changes in Mtwapa Creek. “We’ve had to move prison officials out of some buildings,” acknowledges Kenrodgers Kyalo Mutemi, an officer at Shimo La Tewa—the structures were condemned as inhabitable because of the stench.

A low-cost and long-term solution to manage the prison’s wastewater in a sustainable, environmentally friendly way is sorely needed to safeguard the social, environmental, and economic benefits provided by the creek.

A new project involving the Kenya Marine and Fisheries Research Institute, Shimo la Tewa prison, the National Environment Management Authority and GreenWater aims to address this problem using constructed wetland technology to manage wastewater at the prison.

Constructed wetlands

Constructed wetlands, known as “green infrastructure”, mimic the functions of natural wetlands, namely water filtration. In other words, the prison’s wastewater will be directed towards a constructed wetland, which will have a plant, gravel or sand filter that mimics nature’s processes and removes harmful pollutants from the water.

“Once certified as suitable, the project will then redirect the treated water to grow food crops at the prison farm to improve food security and nutrition at the prison,” says United Nations Environment Programme’s (UNEP) Regional Seas project manager Jared Bosire. “The water will also be used for aquaculture by constructing, stocking and managing a fish pond at the prison,” he adds.

The Shimo La Tewa demonstration project is supported by the Implementation of the Strategic Action Programme for the Protection of the Western Indian Ocean from Land-Based Sources and Activities project, a Global Environment Facility-backed initiative working to support the Nairobi Convention. It reduces land-based stresses on this environment by protecting critical habitats, improving water quality and managing river flows.

The Convention, which forms part of UNEP’s Regional Seas programme, serves as a platform for governments, civil society and the private sector to work together for the sustainable management and use of the Western Indian Ocean’s marine and coastal environment.

National Environment Management Authority officials noted that the constructed wetland, if proven to be successful at the prison, could even be installed at other large buildings, like hotels, with similar wastewater management problems.

The outcomes of the project, which kicks off in early 2020, could also assist Kenya in achieving its commitments under Sustainable Development Goals 6 (Clean water and sanitation) and 14 (Life below water), by helping the country implement its water quality regulations.


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