[Image: FMT]
South Africa’s Water Research Commission recently ran a study into using seawater to flush toilets in Cape Town.
According to the study, Capetonians are willing to pay up to 10% more on their water bills to use seawater to flush their toilets, as long as it doesn’t smell or stain their toilets.
UCT’s water engineering lecturer, Teboho Mofokeng, who researches water management and reuse in South Africa and co-authored the study, told The Conversation that there were three main issues with Cape Town’s flushing habit.
The biggest issue is that the city uses clean, treated drinking water for flushing toilets. In fact, around 20% to 30% of household potable water is used this way, which is an utterly inefficient use of a valuable resource.
After being used for bathing, cooking, cleaning, laundry, and flushing, this water flows down the drain and is treated at wastewater plants to remove harmful germs before being released into rivers.
The second concern is that in some parts of Cape Town – as well as in coastal cities like Durban and Gqeberha – wastewater is discharged into the ocean with minimal treatment. While this practice is legally permitted within certain limits, it still contributes to marine pollution.
Finally, as housing demand increases, so does the need for water and sanitation, meaning we are discharging growing volumes of wastewater into the sea, and instead of recycling and reusing this water within the urban system, it’s lost entirely.
Previous studies have shown that most households prefer using recycled water over clean, drinkable water for flushing, but this study is the first to explore the public’s attitude toward using seawater for this purpose.
Surveying 239 participants, they asked whether they’d be willing to flush with recycled water, seawater, or continue using drinking water – but at a higher cost.
While 90% of respondents were ‘open’ to alternatives to drinking water for flushing, the answers hinged on whether the water was clear, odorless, and did not stain people’s toilet bowls.
58% of the people who took part preferred using seawater to recycled water, but strangely, but this varied according to participants’ income, gender and household size.
About 45% of the people interviewed earned more than R12 800 per month, and they preferred using drinking water to flush toilets. Women with a higher education qualification were also more likely to pay extra for both seawater and recycled water options. Homes where more than three people lived were more likely to pay for recycled water than seawater.
With 10%-15% of Capetonians’ municipal bills going to paying for water, households who pay R350 to R900 per month for water were willing to pay 5%-10% more to use clean and clear alternative water. They were also willing to use water with a slight odour if they got a discount of up to 60% on their monthly water bills.
While the idea seems logical, there are several obstacles to incorporating seawater into our ageing water networks.
Firstly, a duplicate network would have to be set up. Cape Town’s ageing pipe network will not be able to handle this because seawater corrodes, so plastic pipes will be needed for the seawater flushing pipe network. Plastic manufacturing and the raw materials needed have a significant impact on the environment, which might just offset any environmental positives.
Secondly, storage facilities like reservoirs would need to be built to store the seawater and a new system set up to treat seawater before it is piped to homes.
Thirdly, the chemicals and electricity required to clean the water, the supply of water to consumers and eventually the disposal of the wastewater would add to the costs.
In the context of diminishing water supply and water security assurance, implementing dual systems may be favourable despite the significant increase in impact.
It is encouraging to see that people are at least open to the idea of using seawater – which is an obvious alternative to flushing drinking water down the drain – but the economic obstacles seem to outweigh public openness in this case.
At least UCT are looking at the problem, and who knows, some bright second year student may just come up with a plan that saves us flushing our way to another Day Zero.
[Source: UCT]
