Cape Town, South Africa, and its surrounding areas faced a dry year in 2018 after three consecutive years of dry weather from 2015 to 2017.

Capetonians were introduced to greywater almost overnight when municipalities implemented a series of water restrictions. Previously, many Capetonians had let untreated baths, showers, kitchen sinks, washing machines, and other water run down the drain. They now have storage tanks or carry buckets to water their lawns or flush toilets. The domestic graywater technologies were booming.

Day Zero was never reached thanks to the residents’ conservation of water and adoption of greywater. There are still some lessons that can be learned from this experience, particularly in terms of the use of greywater during both seasons of abundance and drought.

The dry spell is not over yet. Scientists warned repeatedly that water shortages are a risk due to climate change. Gqeberha, a city in South Africa, is also on the brink of its own Day Zero. The broader sub-Saharan area also faces dwindling access to water and a dwindling supply.

Researchers have long claimed that greywater can contribute to South Africa’s food safety if used to water food gardens.

The problem is that consumers are afraid greywater will not be safe to use in gardens. Together with colleagues, I conducted several studies in order to understand this hesitation better. In two of the studies conducted in South Africa’s Limpopo Province, we found that people did not believe household detergents made from greywater should be used to water food gardens. In addition to examining greywater quality in these areas, we found that the water is safe for domestic irrigation.

Global Examples

Greywater is used around the globe. Greywater is used all over the world.

In Australia, Cuba and, Bolivia, Jordan, and Tunisia, as well as the UK, US, Uganda, and as I studied with colleagues in Zimbabwe, greywater irrigation has been used safely in a variety of contexts.

Since 1925, the United States has used treated graywater to irrigate their crops. Greywater use is increasingly common in Spain: regulation mandates that greywater systems be installed on new buildings.

If South Africans want to use this valuable water source, they must address their concerns.

We wanted to know the objections of people living in Limpopo, a province of South Africa. Was chosen as the testing area due to its aridity and lack of water. Crop failure and food security are a result of high temperatures, droughts, and irregular rainfall. The greywater available there was also tested to see if it could be used safely in gardens in the home. Greywater that contains heavy pollutants should not be used continuously for irrigation.

Perceptions of reluctance

Limpopo has a large rural population. Subsistence farming is the foundation of many people’s lives. In the communities that we studied, crop production has been hampered by frequent droughts. People now have small gardens in their homes to compensate for crops lost in larger fields.

We asked residents of two Limpopo villages to share their opinions on reusing grey water for gardening. The respondents were concerned about water containing household detergents being used to water their gardens. Some respondents were worried that their plants might die and that the water could contaminate food. Others were concerned the greywater was poisonous or had unhealthy side effects. The greywater was not used when they had running water available, which was more convenient.

Residents from both villages that did use greywater said their gardens produced more than before. Others reported that greywater seemed to repel insects that eat plants.