Teboho Mofokeng, a lecturer in water engineering at the University of Cape Town (UCT), studied water management and reuse in South Africa and co-authored the study. She spoke to African conversations about her willingness to pay up to 10% for water bills to flush the toilet using seawater, unless the toilet smells or stains.
What is the problem with how toilets get flushed in Cape Town?
The first problem is that cities use clean, treated drinking water for toilet flushing. Generally, 20% to 30% of the city’s drinking water supply to households is used to flush toilets.
Water used for bathing, cooking, washing, cleaning and flushing toilets goes down the drain. Before being returned to the river, it is treated with wastewater plants to remove harmful bacteria.
The second problem is that in some Cape Town communities (and coastal cities in Durban and Gukeberha, South Africa), wastewater is expelled into the ocean with little treatment to remove harmful bacteria. The government allows for a certain amount of discharge, which is polluting the ocean.
The third problem is that as housing demand increases, so does water and sanitation. As more and more wastewater is discharged into the ocean, the opportunity to maintain and reuse water within urban water management systems is lost.
What is the alternative?
South Africa’s water supply network is aging and not well maintained and is scheduled for replacement or repair. If a new residential development is connected to a water supply network, there is an opportunity to come up with alternatives to flush the toilet with drinking water. One option is seawater.
The other is recycled water. Toilet water is treated to remove harmful bacteria and can be reused for cleaning. This requires a closed water system to flush the toilet. It eliminates current drinking water losses, flush the toilets and then drains them into the ocean.
How do people feel about using seawater instead?
Research shows that most households prefer to flush with recycled water rather than clean, easy to drink water. However, our study is the first to investigate how people feel about flushing in seawater.
We asked 239 people if they would be willing to wash them off with sea or recycled water or continue washing them with drinking water, but would pay more to do so. They also asked how they felt about toilet wastewater being discharged into the ocean.
Our study had a variety of findings. Overall, 90% of people were willing to stay away from using drinking water to flush their toilets, but only if the new water source did not dye the toilet bowl it was clear and odorless.
It was found that 58% of those surveyed prefer to use recycled water using seawater to flush toilets. However, preferences differed according to income, gender and household size. Approximately 45% of interviewees earned more than R12 800 (US$697) per month. They preferred to use drinking water to flush the toilet. However, women with higher education qualifications were more likely to pay extra for both seawater and recycled water options. A home where three or more people lived was more likely to pay for recycled water than seawater.
On average, between 10% and 15% of the Capetonian city bills are spent on water payments. We looked at the preferences of households paying R350 to R900 per month for water and found that they are willing to pay 5%-10% to use clean, clear alternative water. They were also willing to use water with a slight smell if they received a discount of up to 60% on their monthly water rates.
Treating wastewater before it is discharged into the ocean costs money. We discovered that people don’t want to make this bill. They were in favor of cities dealing with wastewater only if they cut their water bills by up to 7%.
What are the drawbacks of switching to seawater to flush out the toilet?
First, you need a duplicate network to set up. This is a network of water supply pipes for drinking water supply and a network for toilet flushing water supply. This means that both new and aging water systems will be replaced by systems using overlapping pipe networks.
Water supply networks typically use concrete, steel or plastic pipes. However, due to the corrosion of seawater, plastic pipes are required for the seawater flushing pipe network. Plastic production and the necessary raw materials have a major impact on the environment. On the other hand, steel or concrete pipes need to be replaced more frequently than plastic pipes.
Second, storage facilities such as reservoirs need to be built to store seawater, and new systems installed for seawater treatment before seawater is plumbed to the house.
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Third, the chemicals and electricity needed to clean water, the supply of water to consumers, and ultimately the disposal of wastewater will increase costs. Because South Africa’s energy is still electricity by burning coal, global warming can be greatly improved when more energy is used up in overlapping water systems. Therefore, you need to set up a renewable energy system.
Despite these drawbacks, replication systems work well in Hong Kong. Using less freshwater also benefits the environment.
What is the solution?
Climate change will become arid in Southwest Africa. Unpredictable rainfall and frequent droughts mean that there is less freshwater for people to drink. It is therefore important that coastal cities like Cape Town, which have an increasing population, now begin investing in water supplies from unconventional sources.
People need to be more aware that not all home activities require drinking water. Increased public awareness and education about the benefits of using alternative water helps people accept that toilets cannot be washed much longer with clean and easy-to-drink water.
This article was first featured in the conversation.
