Urban farmers use wastewater to feed growing cities

Domestic and industrial effluent combined with domestic wastes in the urban watercourses of Nairobi are widely perceived as the causes of stench and disease, but not so for the thousands of urban farmers who have come to embrace the waste in urban farming, stocking grocery shops in the city with leafy vegetables, succulent oranges and large potatoes.

It is a blossoming market dominated by women from the informal settlements who transport their produce to the city centre to cash in on thousands of Nairobians who wish to buy groceries after leaving their place of work.

Food supply

Globally, urban farming is believed to produce roughly 20 per cent of the world’s food supply, with half of this food being grown using waste water, according to a 2009 survey of 53 cities conducted by the International Water Management Institute.

But in sub-Saharan Africa, urban and peri-urban farmers who depend on wastewater to grow their crops are producing 70–90 per cent of the perishable vegetables consumed in African cities.

The human and waste water contains significant nutrients for crop production that not only reduce the need for chemical fertilisers, but also increase crop yields.

Yet the health risks through microbial crop contamination, especially in foods consumed uncooked, are a reality.

Parasites and pathogens thrive in faeces, easily infecting those exposed through irrigation or consumption of unwashed produce.

Among wastewater-related infections, diarrhoeal diseases are the top cause of death among children in the developing world.

The problem is particularly acute in sub-Saharan Africa, where there are an estimated 1.2 billion incidence of diarrhoea a year, according to World Health Organisation, leading to the deaths of some 770,000 children less than five years old.

“While wastewater has the potential to serve as a hitherto untapped water and nutrient source for agriculture; where treatment is limited it also has the potential to affect human health and pollute large volumes of freshwater rendering them unfit for human uses,” the study Drivers and Characteristics of Waste Water Agriculture in Developing Countries states.

Yet waste water treatment remains minimal in Nairobi .Damaris Kinya from Mukuru kwa Njenga slum is one of the city’s vegetable street traders.

She belongs to a street-mothers’ self- help group that is responsible for feeding the city.

Besides selling indigenous vegetables and arrowroots, she also rears pigs, local chicken and a calf at her home.

Philemona Omondi, another seller owns a small plot in Kibera, which she has used to grow amaranthis, kale and spinach for the last 20 years, employing up to 11 casual labourers during peak periods.

These are the produces she sells to the over 100, 000 residents of Kibera with the day’s remainder finding their way to the city centre streets.

Damaris and Philemona represent many other urban farmers who have invested in untreated sewage water to irrigate their vegetable crops, a practice they continue without the use of protective clothing.

In this way they are able to maintain production throughout the year, except when there is a shortage of water in Nairobi and the middle income households do not flush their toilets or throw away waste water.

A water quality policy that guides the use of waste water for irrigation has been created, with National Environment Management Authority getting the legal mandate to enforce it, but implementation still remains a pipe dream with the Authority citing difficulties in ensuring that every farmer complies with the regulations.

Stakeholders involved in urban agriculture, marketing and wastewater treatment acknowledge that an urban agriculture policy framework based around market opportunities, value addition, livelihoods, and mitigation of health risks is important not only for the wastewater sector, but also for the future viability and competitiveness of urban agriculture and livestock keeping.

“There are very cheap and affordable ways that we can use to treat waste water and make it safe for urban farming because truth be told, urban farming is here to stay. There are many urban and peri-urban dwellers in Kenya who would like to benefit by harvesting closer to their kitchens, but are not sure how to go about it and fear legal prosecution. Other countries have long embraced them and they are working for them,” says Philip Mogeni an environmentalist.

Tunisia, in drought-fraught North Africa, integrates wastewater treatment into its national water resources management strategy.

More than 62 plants treat Tunisia’s wastewater, which is then re-used to irrigate agriculture.

The treated water costs more than conventional water, but the government subsidises it to ensure that farmers can afford it.