|October 04, 2013|
From Toilet to Tap Water
|In a few years, residents of the eThekwini municipality in the port city of Durban in South Africa could be drinking water that was once flushed down their toilets, as authorities are planning to recycle some of the municipality's sewage and purify it to drinking quality standards.|
"We're going through a crucial water shortage, which is increased by the water demand of eThekwini," Speedy Moodliar, the municipality's senior manager of planning for water and sanitation, told IPS.
The municipality relies on the Umgeni river system for water. But demand on the system, which supplies drinking water to about five million people and fuels industry in the economic hubs of Durban and Pietermaritzburg, a town 66 kilometres from the coast, has outstripped supply for the past seven years.
To boost supply in future, the South African government has proposed building a dam with a capacity of 250 million cubic metres on the uMkhomazi river, the third-largest river in KwaZulu-Natal, and transferring water to the Umgeni system.
But this scheme will only be operational by 2024 at the earliest, said Moodliar. "Between now and when the uMkhomazi project comes online, wastewater re-use will be our mitigation measure."
In dry countries like Israel, Egypt, and Australia treated wastewater is used for industry, landscaping and agriculture. But worldwide few countries put it directly into their drinking water supplies.
Singapore uses purified wastewater to meet 30 percent of its water needs, although just a small percentage goes to drinking water and the majority is used by industry. Citizens of Windhoek, the capital of South Africa's arid northwestern neighbour Namibia, have been drinking recycled wastewater for over 40 years.
In 2011 the Beaufort West municipality, which serves close to 50,000 people, began treating its sewage for use as drinking water after a vicious drought, making it the first in South Africa to do so. According to a 2012 World Bank report "The future of water in African cities: why waste water?" few cities in Africa have functioning wastewater treatment plants and "only a small proportion of wastewater is collected, and an even smaller fraction is treated."
eThekwini municipality plans to upgrade two of its existing, and underperforming, wastewater treatment plants -- the KwaMashu and Northern treatment works, Moodliar explained.
To remove contaminants and clean the water to drinking quality standard, a three-stage system that treats effluent through ultra-filtration and reverse osmosis, as well as disinfection by ultraviolet light and chlorine would be used. The treated water would also be stored and tested before being released.
The purified water will be mixed with conventional drinking water at a ratio of 30 percent re-used water to 70 percent conventional, said Moodliar. It will feed the municipality's northern regions, including Umhlanga, Durban North, Reservoir Hills, and KwaMashu.
Re-using wastewater in this way will add 116 megalitres of tap water to the municipality's supply daily. This is enough to fill just more than 46 Olympic-size swimming pools. It is roughly 13 percent of the municipality's current daily consumption, and will provide an estimated seven years of water security.
While it will cost more to produce drinking water through wastewater recycling -- about 75 cents per kilolitre compared to 50 cents per kilolitre for conventional treatment -- the municipality sees it as "the best fit," said Moodliar.
The municipality has touted the effectiveness and safety of the proposed system, but there has been opposition to the plan, including the submission of a 5,000-signature petition during the public participation process last year.
Citizens have raised concerns about the safety of drinking the re-used water. "Recycling of toilet water to drinking water is a death sentence to the general public because of health implications," wrote Jennifer Bohus in an email to Golder Associates, the firm that produced the basic assessment report for the wastewater recycling proposal.
The municipality, however, maintains that the water will be fit to drink.
"The technology is advanced enough that the quality of the water being returned is high," Graham Jewitt, director of the Centre for Water Resources Research at the University of KwaZulu-Natal, and chair of water resources management for state-owned Umgeni Water, told IPS. "Many cities all round the world use recycled water."
"About 14 percent of water use in South Africa is actually water that's being re-used, most of it indirectly," Niel van Wyk, chief engineer with the Department of Water Affairs, responsible for strategic water resource planning in KwaZulu-Natal, told IPS.
Citizens opposing the plan also said the municipality, which loses 36 percent of its water annually, largely through leaks and illegal connections, should focus on fixing leaking pipes. Others proposed investment in seawater desalination plants, instead.
The potential for sucking seawater from the Indian Ocean and converting it to freshwater for the region is currently under investigation. But the process of seawater desalination, which involves pumping saltwater at high-pressure through a semi-permeable membrane that retains the salt, and allows water to pass through, remains costly.
Umgeni Water, the state-owned company that is the largest supplier of bulk potable water in KwaZulu-Natal, is doing a feasibility study for two desalination plants: one on the south coast, adjacent to the Lovu River, and one on the north coast near Tongaat, Shami Harichunder, corporate stakeholder manager for Umgeni Water, told IPS.
If built, these plants would be the largest desalination operations in the country, each capable of producing 150 megalitres of water a day. By comparison, the largest desalination plant in South Africa, in Mossel Bay in the Southern Cape, produces a tenth of that amount.
The cost to build one of the proposed plants is as much as 300 million dollars, according to Harichunder. The required technological components, like high-pressure pumps, are expensive, he said.
Desalination plants, however, can be built more quickly than large dams and transfer infrastructure, and also scaled up in future if needed, said the Department of Water Affairs' van Wyk.
Umgeni Water's feasibility study is to be completed in December this year. And the feasibility of building desalination plants will be compared to that of the proposal to dam the uMkhomazi river, said Harichunder.