ALICE SPRINGS SEWAGE PLANT DOSSIER
OUR SEWAGE MESS
ISSUE 0238, Oct 4, 1995
Report by Erwin Chlanda
While the NT Government is browbeating the public to save water, its own Power and Water Authority is wasting an estimated two billion litres a year in Alice Springs alone.
While around the nation state-of-the-art sewage treatment plants recycle water, Alice Springs' outdated system - serving the country's driest region - drains excess effluent into a swamp, creating a massive breeding area for mosquitoes.
They are potential carriers of a variety of diseases and a major irritation to residents in the Ilparpa Valley.
MacDonnell MLA Neil Bell says he's been trying "for years to get the government to honour its promise" of fixing the problem.
"I know of people who are leaving the area because of mosquitoes," says Mr Bell.
During heavy rains, only partially treated sewage, mixed with storm water, floods across Ilparpa Road, across the Stuart Highway, through the Department of Primary Industries complex and into the rural residential area along Col. Rose Drive.
Government promises to upgrade the facility remain unfulfilled.
Its mooted relocation to the Brewer Estate, about 20 km south of town, at a cost of some $30m, may be the wrong solution entirely as it will remove from the town a potentially vital source of water.
The water main from the present bore field runs past the sewage plant.
Furthermore, its close vicinity to the garbage dump may present an opportunity for an integrated waste system, according to Rural Areas Association president, Dr Alex Hope.
He says methane gas from the dump could be harnessed to fuel furnaces used in some water recycling plants.
Power and Water Authority Minister Denis Burke said last month that the level in the Mereenie Basin - where the town's water is pumped from - is dropping around a metre a year.
He said there may soon be a need for developing a new bore field south-east of The Alice, at a cost of $30m.
Jim Brown, a resident at White Gums since 1946, says the so-called Ilparpa Swamps - just behind the show grounds - were just clay pans, usually dry, until the government began to drain excess effluent there.
Mr Brown says if at least the swamp was deeper, fish could be bred there which could eat the mosquito larvae.
But its present depth, just a few centimetres in most places, is an ideal environment for breeding the insects, says Mr Brown.
The putrid area, some two kilometres, may well have been created by an illegal activity of the Power and Water Authority (PAWA). The Water Act 1992 says in part: "A person shall not, unless authorised to do so, cause, suffer or permit waste to come into contact with water."
Norm Watson, the Controller of Waters, a PAWA official himself, would not tell the Alice News whether or not the authority's release of effluent into water ways was being done under special authorisation.
There appear a variety of solutions to the problem - many of them Australian designed. They produce clean water as end result, take up a much smaller area than the present "plant", and cost less than moving the facility to Brewer Estate.
David Hickie, Principal Engineer of Gutteridge, Haskins & Davey Pty Ltd in Sydney, one of the nation's largest designers of sewage treatment plants, says a variety of treatment plants are now common in Australia.
Pond systems are used in many towns in the drier parts of Australia.
They have a deep first section where solids gather. From there the fluids move to shallower ponds, and then to the local water course.
Mr Hickie says "some smells" are inevitable with this type of plant, but mosquito breeding can be controlled by making the ponds at least around a metre deep: This means larvae are unable to move between bottom and surface, and they drown.
Another option is a "trickling filter plant": A giant sprinkler sprays the waste over a bed of stones, some two metres deep.
On its surface grows a "zoogleal film" which "chews up" biological matter in the waste.
As the film grows it is eventually washed from the stones and then removed into a settling tank.
The "activated sludge process" is used in about half the towns of Australia.
The sewage is channelled into a large concrete tank into which oxygen is forced, stimulating the growth of bacteria which degrade the waste.
"It's a living process," says Mr Hickie.v Remaining solids are transferred into a "secondary clarifier" to separate the sludge from the treated effluent.
Sludge settling in this vessel - still containing the active bacteria - is returned to the primary container where they stimulate the decomposition process.
Mr Hickie says these plants are referred to as secondary plants.
The effluent from these plants is as clear as drinking water, but still contain pathogens that are harmful to man.
These are removed by disinfection, either with chlorine or by exposing the water to the sun for 10 to 30 days.
All treatment processes produce sludge which must be stabilised before disposal.
In many plants the sludge is placed in a digester for 30 days.
Solid remains are placed on drying beds - depending on weather and temperature - for one to three months.
After this the solids can be used as soil "conditioner" - not actually a fertiliser but an additive that improved the soil by adding fibre.
A further water purification process is "nutrient removal": It takes out phosphorus and nitrogen which, if left in, would produce algae in water bodies, such as lakes, into which the effluent is channelled.
Mr Hickie says normal water discharge per person is 200 litres a day.
The approximate cost of primary and secondary plants is between $300 and $500 per head of population; if the third phase is added, achieving pure water, the total cost could go up to $1000 a head.
A plant serving a town of 25,000 would take up a mere 200 metre square plot.
With a 400 metre buffer zone all Ôround, the total amount of land needed is just one square kilometre, says Mr Hickie.
[Next week the Alice News will report about a filtration system developed by an Australian company, Memtec.
Last week we put 12 questions to the PAWA head in Alice Springs, John Baskerville.
We received no reply to these questions from him.]
FIGHT LOOMS OVER SEWAGE PLANT
ISSUE 0239, Oct 11, 1995
Report by Erwin Chlanda
MLA for MacDonnell Neil Bell says he intends "to take the fight" to the Government over the Alice Springs sewage treatment facilities during the current sittings of the Legislative Assembly.
"It is vital that the amenity of the Ilparpa valley be protected by the honouring by the CLP administration of its promise to relocate the sewerage ponds to the Brewer Industrial Estate," Mr Bell said.
"This promise was made during the mid-80s and it is high time that it was kept.
"As part of the relocation it is important that the best recycling technology be employed so that in the arid Centre we can make the best possible use of a scarce resource - water."
Meanwhile Memtec, an Australian company selling world-wide purification systems it has developed, says cost-effective options are available to turn effluent - now discarded in Alice Springs - into water suitable for irrigating lawns used by the public.
Memtec recently installed a "water mining" plant worth $2.4m in Canberra, capable of producing 600,000 litres of water a day from "typical household sewage".
It is filtered under pressure, subjected to biological reactions and finally treated with chlorine.
Recent rains may have led Ilparpa subdivision residents to recall that rain in early October in 1993 led to a sharp rise in mosquito numbers.
The rise led to complaints by residents and subsequent political interest which, in turn,was followed by increased mosquito control (fogging with chemicals), as well as a change in effluent management strategies, recommended by the Medical Entomology Branch of the then NT Department of Health and Community Services.
These measures resulted in a reported sharp drop in numbers.
Subsequent rain in December 1993 did not lead to a renewed increase in the pest population. The October rains of two years ago were heavier than those recently experienced (39 mm on October 2nd 1993 notably flooded out the Henley-on-Todd).
One year later an inspection of the Ilparpa Swamp area indicated considerably reduced areas of water.
At that time there was an area of approximately 15 hectares of surface water at the outlet of sewage pond B, with the remainder of the swamp described as dry.
The Typha bulrush was generally declining and dying except around the B outlet.
The report was optimistic that the Typha vegetation, where high concentrations of mosquito larvae were present, could be altered by "a combination of water and fire management.
"If all of the overflow currently being diverted to the Pond B outlet is contained within the new evaporation pond, there will be a dramatic reduction in mosquito problems in Alice Springs and hence ensure a relative freedom from mosquito borne diseases such as Ross River virus disease (epidemic polyarthritis)."
Earlier this year Chief Health Officer Dr Malcolm Dunjey responded to enquiries from the Alice Springs News: "It should be appreciated that Ilparpa Swamp is an ephemeral swamp that receives natural runoff after rainfall events and will continue to be a source of mosquitoes."
SEWAGE PONDS TO STAY, SAYS P.A.W.A.
ISSUE 0240, Oct 18, 1995
Report by Erwin Chlanda
The Power and Water Authority says relocation of the sewage ponds to the Brewer Estate - some 25 km further south along the Stuart Highway - is "not an economically viable alternative".
The authority told the Alice News: "The current ponds are designed as facultative ponds incorporating both anaerobic and aerobic processes.
"This treatment process is currently the most cost effective application for Alice Springs." The announcement follows repeated complaints from residents in the Ilparpa Valley about smell, mosquitoes, the absence of meaningful water recycling facilities, and the waste of potentially prime residential land.
Last week MLA for MacDonnell Neil Bell called on the NT Government to honour promises made in the 1980s to move the sewage facility to the Brewer Estate, an industrial complex near the Roe Creek rail yards.
The authority said: "The [present] treatment ponds have a design capacity of 41,500 equivalent population based on 260 litres per person per day and currently processes on average 2,100 megalitres per annum.
"Currently, treated effluent reused by Blatherskite Park and the Tree Farm averages 1,000 megalitres per annum.
"An agreement has recently been reached with the Alice Springs Town Council to irrigate the dump area.
"The ponds are designed to store effluent for evaporation and overflows to the swamp [adjacent to the ponds] only occur when the design inflow rates are exceeded.
"Such events do not occur during rain through ingress of storm water into the sewer system.
"A new evaporation pond was constructed in 1994-95 as additional evaporation storage. Overflow to the swamp has also occurred as a result of flooding from adjacent land into the ponds. This event can cause partially treated sewage discharge into the swamp.
"Such an event occurred in February 1995.
"Ways to minimise the flooding events have been discussed with the Alice Springs Town Council.
"The authority does not support the suggestion that flooding extended to the rural area as suggested in a recent Alice Springs News article."
However, locals say that when the swamp overflows, water mixed with effluent crosses the Ilparpa Road, the Stuart Highway near St Mary's, proceeds through the Department of Primary Industry complex and floods across Col Rose Drive, the access to the Rangeview Estate rural area.
The Authority says it "works closely with the Alice Springs Council and the Territory Health Services to maintain the ponds environment to a level that minimises mosquito breeding. "Sampling by the Town Council and the Territory Health Services indicates that the ponds have minimal impact on mosquito breeding.
"Overflow into the swamp area caused by flooding does provide an environment conducive to mosquito breeding and as far as practical action is taken to reduce the breeding environment by burning and spraying.
"A number of additional enquiries have been considered by the Authority for effluent reuse for agriculture or horticulture purposes.
"To date, none have proceeded."
NEXT WEEK: OPTIONS FOR ALICE
WASTE WATER: MANY OPTIONS
ISSUE 0241, Oct 25, 1995
Report by Kieran Finnane
Water mining and aquifer recharge are practices well-established internationally but in their infancy in Australia although some of the leading technology being used was developed here and is readily available.
Sydney-based company Memtec has patented a continuous micro filtration (CMF) technology which allows for the reuse and purification of sewage, after it has been treated by conventional processes, as described in previous articles (Alice Springs News, Issues 38 and 39).
The technology is being used in Orange County, California to assist in the recharge of depleted water supply aquifers - a problem very similar to the one faced by Alice Springs.
The level in the Mereenie basin - the town's major source of water - is dropping around a metre a year, and the NT Government has indicated that draconian measures may be introduced if usage is not curbed.
In Orange County, at Water Factory 21, waste water is subjected to primary and secondary treatments and is then fed to CMF and reverse osmosis plants (for the removal of salts) and reinjected into the aquifer.
WF 21 has been reinjecting waste water into the aquifer since the 1970s.
"Memtec's technology has proven its ability to replace very expensive conventional chemical clarification techniques," says Memtec's Colin Nash.
"Alice Springs, with its potential shortages of ground water and its arid conditions make it not dissimilar to Southern California.
"The technology is available today to reuse the existing town's waste water with a much smaller footprint and without the problems now being encountered.
"Such reuse schemes can dramatically reduce the requirement for bore water and thus reduce the load on the underground basin," he says.
Mr Nash gives a ballpark figure of $600 per person or around $15 million for a tertiary treatment plant in Alice Springs, producing water suitable for reuse on parks, gardens, playing fields and for toilet flushing.
This figure does not include the infrastructure costs of laying new pipes for irrigation and domestic reuse.
By adding reverse osmosis, which would permit aquifer recharge, the total cost would grow to $20 million, says Mr Nash.
Once treated to this stage the water can also be used for selected industrial and commercial reuses such as cooling tower make-up and for boilers. Such water is currently being reused by Pacific Power in NSW.
"It's important for a town like Alice Springs, in considering its future, to build itself a water and waste water infrastructure that is capable of meeting future water requirements that will almost certainly have a much larger emphasis on conserving the scarce water resource," says Mr Nash.
Aquifer recharge is the subject of a mere handful of studies in Australia, despite its wide practice in the United States, Israel and the Netherlands, according to an article in the most recent issue of Ecos, a CSIRO magazine reporting on scientific research relating to the environment.
The article mentions in particular an experimental site at Andrews Farm on the North Adelaide Plains where CSIRO scientists Dr Peter Dillon and Paul Pavelic are working with the developer, Hickinbotham Homes, and with Mines and Energy SA hydrologists, to test a system treating storm water in a detention basin before injection into a limestone aquifer for reuse.
Injection well-clogging poses a problem for storm water reuse as storm waters are usually high in suspended solids content.
The scientists are also investigating the fate of contaminants in ground water.
As well as being used to irrigate urban parks and gardens, storm water treated at Andrews Park could help to replenish ground water supplies for the nearby Virginia horticultural area, where 35 per cent of South Australia's vegetables are produced.
This industry uses 18 million cubic metres of ground water a year but its size is restricted by the natural rate of ground water replenishment.
Over-exploitation results in falling ground water pressures and increasing salinities, stabilised by restricting use.
To date the Andrews Farm experiment, focussing on feasibility and sustainability has recharged more than 100,000 cubic metres of fresh water to the aquifer that would otherwise have run off to the ocean.
[ED - The Ecos article was written by David Mussared and Bryony Bennett.]
According to one long-time resident, Jim Brown, the swamp was previously a clay pan similar to the ones further west, and only intermittently inundated.
According to Des Nelson, an Alice Springs resident for 42 years, the swamp pre-dates the sewage plant but used to dry out in times of drought.
Mr Nelson says the swamp was referred to by the Horn Expedition of 1894, and he himself remembers people shooting ducks there.
However, Mr Nelson says it is only since the establishment of the sewage ponds, and the effluent draining from them, that the swamp has turned into a large, permanent body of water, now a notorious mosquito breeding area.
Mr Neslon, a former resident of the AIB Farm just south of the present day race course, says the swamp is the head waters of the creek that crosses the Stuart Highway near St Mary's, and from there flows through the AIB Farm, ultimately running across Col Rose Drive in the Rangeview Estate rural subdivision.
The Alice News sought comment from the Power and Water Authority on its apparent breach, by disharging effluent into that creek, of the Water Act 1992 which says in part: "A person shall not, unlsess authorised to do so, cause, suffer or permit waste to come into contact with water."
The PAWA response was merely: "The Authority is of the view that the discharge of treated effluent into the swamp is not illegal."
The small square on the photo above indicates the comparatively minute amount of land required (just 200 by 200 metres) for state-of-the-art sewage plants described by consultants Gutteridge, Haskins & Davey (Alice News, Oct 4).
The larger square shows a 400 metre buffer zone suggested by GH&D.
This zone could be used for growing firewood, for example. There is a eucalyptus tree plantation (near the western ponds on the photo above).
However, despite several requests, NT Government sources have not told the Alice News whether any of these trees have been felled nor to what use they have been put, if any.
Just to the west of the area pictured is the Ilparpa rural subdivision, which makes the land now occupied by the sewage plant potentially prime real estate.
PLANS FOR SEWERAGE 'FARM'
ISSUE 0350, Dec 26, 1996
Alice Springs' sewerage system - a series of evaporation ponds spread over more than 2.7 square kilometres - is under review by the Power and Water Authority (PAWA).
MLA for Braitling Loraine Braham says among improvements being considered are "high tech" plants which could produce much more reusable water, and take up far less space.
At present, an estimated billion litres of water a year evaporates, while a further billion is used to irrigate a horse fodder plot on Blatherskite Park, and a tree plantation within the sprawling complex. That water is not considered suitable for direct contact with the public.
Mrs Braham says a discussion paper is being prepared, looking at possibilities of recycling water for a much greater range of users.
The Alice News understands that several consultants are currently looking options.
State-of-the-art recycling plants, capable of producing garden-quality or even drinking water, take up a fraction of the space occupied by the existing plant, and would eliminate the present smell and mosquito problems. Some produce fertiliser.
Modern sewerage plants are seen as a source of water, which would be a reason for not moving the facility to Brewer Industrial Estate, as has been suggested.
The only productive use of the area so far has been the fire wood plantation on 25 hectares, established abut 15 years ago.
No trees have yet been harvested.
However, PAWA says it is continuing looking at the option of having commercial operators undertake the work.
SEWAGE "FARM" - FUTURE HOUSING?
ISSUE 0402, Feb 12, 1997
Report by Erwin Chlanda
More than 2500 blocks of residential land, in a splendid valley, spread along the picturesque southern flank of the MacDonnell Ranges, just 10 minutes' drive from the Alice post office. A pipe dream? Not really, given the appropriate political will.
On the face of it, the site may sound an absurd choice for a suburb: The "sewerage farm" - now renamed the Water Quality Control Ponds, just south of The Gap.
However, a modern treatment plant would be odour free, take up a fraction of the 2.7 square kilometres occupied by the present facility and - a further bonus in this dry land - could recycle water for a range of uses.
What's more, the entire land is freehold, and as such unaffected by the present native title uncertainties.
Just west of the "farm" there's already a rural subdivision, Ilparpa.
Power and Water Authority (PAWA) engineers, with the help of consultants, are looking at options of improving the facility.
Their brief, of course, doesn't include the wider issues of land use policies, but these could flow from the work under way.
Currently, raw sewage is piped to the "farm" where it travels through three sets of ponds. In the first one, some 2.5 metres deep, bulky matter is allowed to settle and bacteria, crucial to the decomposition process, are encouraged to grow.
The next stop is an "aerobic" pond, much shallower, where wind generated water movement slowly injects oxygen into the effluent.
In the third type of pond the effluent "matures" - and the fluid evaporates, around a billion litres a year.
That's as far as the process goes at present: The result, in part, is water suitable for limited purposes.
At present, for example, a stock fodder plantation at Blatherskite Park is being irrigated, but under strict conditions.
The National Health and Medical Research Council term is "municipal use - controlled access". The area is fenced and off limits to humans for at least four hours after each watering, because bacteria and algae are still present in the water.
Paul Heaton, a hydraulics engineer with overseas experience - including in arid Israel - says PAWA wants to take the process at least one step further.
If the algae and bacteria could be removed, the much cleaner effluent could be used for watering parks and playing fields without restrictions to human access.
It could also be injected into an underground basin beneath Blatherskite Park and the Todd River, known as the palaeochannel.
This is separate from the Mereenie Basin, not far from Pine Gap, where the town's water is pumped from at present.
Form the palaeochannel water could be retrieved, as required, for uses other than drinking. That kind of storage itself would have further filtered the water, allowing it to seep through sand. Storing effluent in that underground water basin - some two million years old - could alleviate the need for some of the present surface storage ponds which take up the bulk of the present "sewerage farm" land.
Injecting treated effluent is a method used world wide, turning waste into a source of water. This process would require "tertiary" treatment not used in The Alice at present, namely additional mechanical and chemical treatment.
Algae would float to the surface and be skimmed off. The cost of the hardware for this is still being looked at, according to Mr Heaton.
He says recycling water to drinking standard is a long way off, and not done anywhere in Australia at this stage.
However, the drop by a metre a year of the water level in the basin from which the town now gets its water provides a strong motive for saving effluent.
Once it's gone through the "tertiary" process the water is well suited for the garden, the destination of 60 to 70 per cent of household water in Alice Springs.
(In the southern states that percentage is between 40 and 50, but heat and evaporation are less severe there, says Mr Heaton. Home occupancy is lower, 2.6 persons per household as compared to 3.3 in The Alice. Also, blocks of land here are generally bigger.)
Water recycled in that way would, of course, need its own pipe system.
While this would be a major expense in existing suburbs, in new ones it could be installed more cheaply.
(Yulara -the Ayers Rock Resort - for example, has three pipe systems: one for treated bore water for drinking; one for untreated bore water for showers and toilets for example; and the third, recycled effluent, for watering lawns and drip irrigation.)
The present "farm" includes a eucalyptus plantation, established in the late 70s and irrigated with "stage one" effluent.
There are now some 20,000 mature trees on some 25 hectares. This area is closed to the public at present, because of the relatively unsafe watering method.
It is a stunning forest where horses and cattle, agisted under contract, are grazing on lush meadows.
Clearly, turning the "farm" into residential land would be expensive - as would a state of the art treatment plant.
Its price tag, for a town the size of The Alice, is around $35m.
However, the present shortage of residential land, and its huge price, suggest any costs may be more than offset by the sales of blocks.
Say, if PAWA could reduce the size of the sewerage plant to one square kilometre, it would free up 1.7 square kilometres.
As a rule of thumb, some 20 per cent of subdivision land is needed for roads and other public facilities.
That would leave 1,360,000 square metres - or 2720 blocks, each 500 square metres in size. At a cost of $50,000 each, that would yield $136m.
There would be further benefits: although it's rare, some effluent from storage ponds flows into the nearby swamp, where mosquitoes breed, creating a health hazard.
(The ponds themselves are mosquito free, says Mr Heaton: air movement across them causes ripples and flows which inhibit breeding.)
The rubbish dump - already being managed with other future uses in mind - could be moved.
And - best of all - the town would reclaim one of its most scenic areas, partly wasted, partly marred by indiscriminately dumped rubbish, and carved up by off-road bike riders and four-wheel drivers.
Return to Alice Springs News Webpage.