Copyright notice We transcribed this article for reference purposes only.
'Louis Pasteur said 150 years ago that we drink 90 per cent of our illnesses'
In March this year, Jim Service, the chairman of water supply company Actew Corporation, and councillors from the Australian city of Canberra dutifully drank bottles of purified sewage water as they unveiled plans to recycle part of the city's waste-water into tapwater.
Within days, Professor Peter Collignon, director of infectious diseases and microbiology at the Canberra Hospital, wrote an open letter laying out his concerns about the health implications of the scheme.
What assurance could there be, he asked, that treatment would remove all disease-causing bacteria and viruses, as well as hormones and pharmaceutical compounds present in sewage?
It is a good question. As Atoine Frerot, chief executiveof Paris-based global water champion Veolia Water, observes: "Louis Pasteur said 150 years ago that we drink 90 per cent of our illnesses. That is why water reatment was created."
Around the world, Water companies and their equipment suppliers insist we have the technology to render sewage safe to drink - but they don't all guarantee they can pick up hormones or unexpected compounds. "This is an area in which we and others are doing a lot of research," says Roger Radke, chief executive of Warrendale, Pennsylvania-based Siemens Water Technologies.
Microfiltration through polymer membranes, followed by reverse osmosis through membranes can remove even viruses if a small enough pore size is specified, says Mr Radke, though to drink the water, you had better then pass it under ultra-violet light to be sure to kill microscopic parasites such as cryptosporidium and giardia.
But this adds expense. In reality, the level of treatment is dictated by standards that have been deemed necessary by regulators for the intended use. And when deployed, it typically comes at the back-end of the traditional waste-water treatment process.
In the case of Canberra, waste water would be treated in the conventional way with chemical and bacteriological processes to remove solids and create water of the quality that is typically released back into rivers around the world.
Actew says it is still investigating exactly which processes the water would then undergo before being pumped into the supply reservoir. It says it would expect to use a combination of micro-filtration and ultrafiltration to remove microscopic particles, contaminants and pathogens; reverse osmosis to remove salts, organic compounds and viruses; and ultra-violet disinfection/oxidation to additionally ensure any trace of organic material is destroyed. A final option is to let the water flow through an artificial marshland before joiniug the reservoir.
After that, the reservoir water would pass through an existing treatment plant before entering the tapwater distribution system.
Canberra, like many Australian towns, is short of water because of a drought that has proved longer, and more severe, than anyone forecast. Last year, residents of Toowoomba, Queensland, rejected proposals for a similar waste water-to-tapwater scheme in a referendum in which health concerns played a key role. The Canberra proposals could prove equally contentious.
Veolia's Mr Frerot says:
"To my knowledge, there are only two places in the world where treated waste water is gradually mixed into tapwater: the town of Windhoek, in Namibia, and Singapore."
In Windhoek, that is because the river is more polluted than the waste water, he says. In Siugapore, it is a political choice designed to reduce dependence on supplies from neighbouring Malaysia - and accounts for less than 1 per cent of water consumed.
Yet all around the world, city populations consume treated water drawn from rivers that receive treated wastewater from communities further upstream. Just as the citizens of Rouen, in France, drink the waste water of Parisians, the same is true in the River Thames in the UK, the Colorado in the US, and the Rhine in Germany and its neighbours. Without wastewater, these rivers would almost run dry.
Treatment prior to drinking is imperative: a 2003 study found the level of hormones in the River Seine sufficient to change the gender of some of its fish. And a study by the Netherlands government found that using Dutch rainwater even to flush toilets would pose a health risk.
If we are going to drink treated wastewater, says Mr Frerot, the best strategy, where geological conditions permit, is to reinject it into aquifers - as happens in Berlin and Adelaide. The soil acts as a natural filter, and the time-lag provides additional water for abstraction in periods of peak summer demand. Man is merely shortening the natural cycle.
Otherwise the most obvious and economically viable solution, he suggests, is to use treated waste water for industry and irrigation. Orange County, in California, adopted Siemens' microfiltration and reverse osmosis to treat waste water a decade ago, initially reinjecting it into aquifers, and subsequently selling additional supplies to farmers and industry - which covers the cost of the additional treatment, says Mr Radke.
In Australia and elsewhere, some towns have a second distribution system for "reticulated" water used by householders for garden watering and washing cars.
Meantime, treated sewage water is widely used to supply industry, farms and golf courses, freeing up "natural" supplies for tapwater. Veolia alone has 100 such facilities in France, and others scattered from Honolulu to Durban in South Africa.
Degremont, a Suez Environment subsidiary, cleans wastewater from Grasse, France's perfume capital, to bathing standards, says Degremont chief operating officer Remi Lantier, providing water quality guarantees for fish farms downstream.
Pumping treated waste water into marshlands and reed beds, where sunlight and plants complete' the purification, is an option too. But the outfall from even a small town would require a vast swamp to be effective.
The simplest solution for small communities, says Mr Radke, is to buy a Siemens skid-mounted modular unit the size of a small car - for a few thousand, or tens of thousands of dollars, and turn waste water into irrigation quality water by passing it through membranes.
Degremont's Mr Lantier says companies like his can produce ultra-pure water in which the only molecules are H2O. He likens the safety issue to that in the nuclear industry, standards are that stringent.
Globally, says Mr Lantier, only 45 per cent of the world's collected waste water is treated. The most urgent priority is to treat the 55 per cent released untreated. Of that treated, 20m m3 a day is recycled - about 2 per cent. He expects that proportion to triple in coming decades.
Ultimately, says Mr Frerot, the most cost-effective solution to water shortages developing in many towns and cities must surely be to supply such treated waste water for use in industry and irrigation, in place of the tapwater used today. "That would halve the demand for natural water," he says. "That is what we should do, before talking about drinking waste water."
Ironies stack up in sludge plant
The huge Seine Amont sewage treatment plant, on the south-western outskirts of Paris, is about as modern as any in the world.
It processes the waste water from the homes and offices of 2.4m Parisians, as well as the rainwater run-off from a quarter of the city and its outskirts, and is operated through a public-private partnership.
The public arm, SIMP, regroups the sewage treatment facilities of the Paris agglomeration: the private arm, Sequaris, involves two Suez Environment water companies, Degremont and Lyonnaise des
Eaux. The latest expansion and upgrade was completed, at a cost of &euro,500m, only 9 months ago. The plant draws 80 per cent of its energy from the 60,000 tonnes of sludge it extracts each year from the inflows. Much of the energy used helps make the remaining sludge, 30,000 tonnes a year into granules resembling instant coffee, or pellets that look like animal feed. These have a calorific content on a par with coal, and most are trucked to a cement works where they help fife the kilns.
Yet for all the modernity and efficiency of the stainless steel and concrete hardware spread across its 80 hectare site, you wouldn't' want to swim in, let alone drink, the water it releases into the Seine. The quality of that water, says Sequaris plant director Jean-Luc Ventura, pulling out his weekly testing reports, amply exceeds the standards laid down by European regulations and the Seine river authority. But the outflow can contain Coliform bacteria and other micro-pollutants.
But there are two other challenges that concern neighbours: smell, and sludge.
The Seine Amont plant at Valenton has been designed to resolve both issues. The nearest hl.lTlan neighbours, are half a kilometer away.
The plant receives its inputs of human waste water and storm run-off via pipes 30 metres below the surface. This water can total 600,000 m3 (cubic metres) a day of household and office waste, and 15m m3 of rain run-off. The household waste water contains up to 216 tonnes of solid matter each day, the run-off up to 317 tonnes after a dry spell, including dust and dog faeces.
The human waste enters sealed pre-treatment tanks, where biological activators encourage breakdown of the organic matter. Methane gas produced is collected. The residue is fed into covered sludge tanks, where the sediment collects. In the third phase, nitrate is added or removed, as necessary, to complete the biological breakdown of solids. Powerful extractor fans draw off air and pump it through three chemicals baths to remove any smell, leaving nitrogen to be released into the atmosphere. Does Seine Amont smell? Sporadically, as you walk round the site, you catch an odour. The inside of the sludge-drying plant smells like a cow-shed, without the acrid urine edge. If you poke your nose into one of the covered sludge concentration tanks, the smell is pretty overpowering.
Before the modemisation, says Mr Ventura, smells from the plant had become "a big issue for nearby residents". Since, he says with a broad smile: "We haven't had a single complaint for six months." Most sludge is pumped into a new drying plant, where it is heated in revolving drums using the methane drawn off earlier, together with previously dried sludge, as fuel. The resulting product can be burned as fuel or spread dry on fields as fertiliser. "Bringing together all the individual operations that are used elsewhere into a single plant is a world first," says Mr Ventura with a hint of pride.
Yet there is an irony. Existing regulations regard this treated sludge as a waste product. Suez sees it as a biofuel, but it doesn't attract any financial aid or benefit from inclusion in regimes that would qualify it as a renewable power source.
So the cement manufacturer that uses much of it declines to pay, saying it is doing Suez and the municipality a favour by getting rid of it. Mr Ventura and SIAPP site director Mr Renard reckon its calorific content alone merits a price of at least
€20 a tonne.
Ross Tieman
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