I looked at how polluted Nairobi River is. What I found

Nairobi River flows through a low-income settlement. Tatsiana Hendzel/Shutterstock

A lot happens along the course of the Nairobi River as it makes its way from the north west to the south east of the city. It’s mainly used by residents of low-income settlements as a source of water for cleaning homes, bathing and for watering crops. But it’s also used to discard household and human waste as many homes don’t have toilets, and industrial waste is frequently dumped in the river.

I’ve done studies on the quality of water in Nairobi River focusing on the presence of metals in the water. I found that the levels of lead, copper, chromium, zinc and manganese were far beyond those allowed by the World Health Organisation (WHO) and Kenya’s National Environment Management Authority.

I also found harmful levels of bacteria. The levels of Escherichia coli (E. coli) were incredibly high – up to one million units in 100ml of water. There should be no E.coli in drinking water. It’s presence indicates faecal contamination, which could lead to periodic outbreaks of water-borne diseases like typhoid, cholera and dysentery.

There are major concerns about the state of the river, which runs through the heart of the country’s capital – Nairobi. And Kenya’s national environmental management agency is cracking down on industries accused of discharging pollutants into the river.

But there are huge holes in the governance of the river and the city’s waste, which have enabled the river’s poor condition. More needs to be done to address this, especially as the city continues to grow.

Waste management

There needs to be better management of industrial waste. Policies that govern waste water purification from industries aren’t strictly followed, often due to a lack of official monitoring. The heavy metals I found indicate industrial waste that comes from paint, leather and electroplating industries, among others.

Another problem is a lack of proper solid waste management. Kenya currently doesn’t have landfills, most solid waste is disposed of in uncontrolled, open dumpsites. An engineered landfill is deliberately constructed to handle waste. It’s lined at the bottom to prevent groundwater pollution and has a system to collect and treat leachates and capture biogas.

Human waste is also not treated properly. There are very few sanitation facilities in slums and other informal settlements, so residents will use the river to dispose of their waste. For those with sanitation facilities, there are just two sewage treatment plants that service Nairobi – Ruai and Kariobangi. But Ruai can’t process very much waste water and most of the equipment at the Kariobangi treatment plant has broken down.

Pollution impact

These pollutants can affect the health of those who rely on the river, or live close to it. For instance, farmers along the Nairobi River and its tributaries commonly use polluted water and raw sewage for irrigation. This exposes them, and consumers, to disease or infections.

Compounds from industries can have wide-ranging effects. For instance, lead is known to affect children’s mental development, cadmium can damage kidneys and some compounds, like chromium, are carcinogenic.

What needs to be done

A lot needs to be done.

First, the river itself needs to be cleaned. This can be done by diverting it as it enters the county into a dam. Then air can be pumped into the water to provide more oxygen to break down harmful chemicals – a process called aeration. Other processes of water purification can also be used such as introducing clay and charcoal, which can filter water. A monitoring plant will then need to be set up to return the water to the river course. It would be good to have several water treatment dams and monitoring sites along the course of the river.

While this is happening, the government must ensure that sewage units are efficient and that policies involving waste water disposal into the river are adhered to.

Mechanisms to prevent further pollution must also be put in place.

Companies must be held accountable for their waste. For instance, policies exist on how industries should manage their waste water. They must be enforced by the relevant government authorities, and tough penalties be imposed on defaulters.

Sanitation facilities need to be set up in informal settlements, and used properly. There are many systems to upgrade informal settlements, but these need to happen at a much larger scale. Investment is lacking because the settlements are only meant to be temporary.

Also, proper methods of dumping waste, such as well-engineered landfills, need to be put in place. The county government needs to do this so that solid waste doesn’t leach dangerous substances into the river.

Finally, waste water treatment plants to handle the waste produced in the county must be upgraded and expanded.

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