Sludge Watch ==> Purified sewage is unpalatable

[Maureen Reilly]

hdr.undp.org/hdr2006/press/responding/Purified%20Sewage%20is%20Unpalatable.pdf

Water: Purified sewage is unpalatable
by Ross Tieman
18 April 2007


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 wastewater
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 Antoine Frerot, chief executive of 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 treatment 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
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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 ultra-filtration 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 joining 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
Singapore, 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
Page 3
Siemens' micro-filtration 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 H20. 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."
Case study: Ross Tieman: 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
Page 4
public-private partnership. The public arm, SIAAP, 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 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 fire 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
human 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 1.5m 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 modernisation, 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
Page 5
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.
LOAD-DATE: 19 April 2007
The Financial Times Ltd