Kenya prison goes green to fix sewage problems and protect the sea

MOMBASA, KENYA (AFP) – Heading north from Mombasa, the unmistakable smell of a foul stench in the air was as reliable as any mile marker for motorists using the highway along the coast Kenyan.

“You would always know you were near Shimo la Tewa prison,” said government scientist Stephen Mwangi, who has lived for decades in the coastal region where thousands of inmates are held in a maximum-security prison.

The smell did not come from the prison itself but from its septic system, which had collapsed from overuse.

Every day, a small sewage river descended into the Mtwapa stream, which emptied into the Indian Ocean.

The contamination threatened fishing grounds, waterfront hotels and restaurants and the tropical reefs of the Mombasa Protected Marine Park, a gem of the tourist industry just offshore.

Motorists pinched their noses as they passed over the creek, but on the prison grounds the stench was unavoidable.

Government housing used by prison guards and hospital staff was deemed uninhabitable and abandoned for public health reasons.

Stephen Mwangi, a researcher at the Kenya Marine and Fisheries Institute, unclogs the inlet to the baffled anaerobic reactor at the sewage treatment construction site of Shimo la Tewa Maximum Prison in Mombasa. PHOTOS: AFP
Construction workers building sewage treatment

“Those who lived in the wards were really affected by the smell,” said Shimo la Tewa Prison Deputy Officer in Charge Erick Ochieng.

“It was not good.”

In an effort to address the perennial threat, a low cost “green technology” approach is being adopted to treat wastewater.

An artificial wetland is being built on the prison grounds – a simple but effective system that mimics the way nature cleans pollutants from the water using vegetation, soil and microbes.

Once fully operational – expected by the end of April – sewage will first pass through an improved septic tank where solids are separated. From there, the semi-treated water seeps through underground beds of sand and gravel, filtering out pathogens and other impurities.

The end result should be safe not only for the stream, but also for irrigation of farms or fish ponds around the prison, said scientist Mwangi from the Kenya Marine and Fisheries Research Institute, who is involved in the project.

Reeds planted on the surface of the wetland help with filtration and absorb nutrients from below, attracting birds and other wildlife, and beautifying a space few dared to linger in the past.

“There will be no smell. We will actually have a very good environment,” Mwangi said.

The United Nations Environment Program (UNEP), which is sponsoring the project, said the constructed wetlands provide an affordable and versatile solution for sanitation, while also storing carbon and helping to cool the planet.

Technology champions said big savings are possible with relatively inexpensive materials that filter waste by simple gravity.

Traditional sewage systems require huge volumes of concrete to create retention basins for the waste, and pumps and other electricity-consuming machinery to process it.

GreenWater, the Kenya-based company building the Shimo la Tewa system, has built sustainable wetland systems for schools, homes, businesses and farms.

The prison complex houses up to 6,000 people – convicts but also prison guards, hospital staff and courthouse officials – and the project serves as a model for other built-up areas on waterways and beaches. .

Home to 40% of the world’s population, coastal areas are among the most densely populated regions on earth, UNEP said.

Streams and creeks along the Kenyan coast are self-cleaning by evacuating water with the ebb and flow of the tides, said conservationist David Obura.

“The problem now is with so many people and so much pressure…that the cleaning function has been overwhelmed,” said Obura, director of CORDIO East Africa, an ocean research institute based in Kenya. ” It does not work anymore. And you can see it on the
Kenyan coast.

Sewage dumped into creeks around Mombasa – Kenya’s oldest and second largest city – drifts north on winds and currents, browning beaches and damaging coral reefs, seagrass beds and fisheries.

Obura said it was too late for a major overhaul of sewage systems in overcrowded cities like Mombasa, but engineered wetlands were a “key tool” for policymakers trying to tackle the pollution crisis .

“We need local treatment using natural systems, and then I think we can really start to solve some of these challenges.”

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