Monday, July 11, 2005

Grey water.

Posted by AmishThrasher at 2:29 pm
Grey Water
Grey Water:
Is this the future?
Public transport is not the only infrastructure decision that we will have to face over the coming years. At the time of writing, Melbourne's water storages were 52.1% (click for source) full.

Before I go any further, a question that some of you will be asking around about now is "who cares" and "why does this stuff matter"? The truth is that the planning decisions we make today will have a tremendous impact on the kind of city that we will live in in 20 or 30 years time. Furthermore, the city that our children and grandchildren will inherrit depends on the decisions that we make today. With both public transport and water, there are clear choices to be made - with their consequences - as well consequences for inaction. Because of these, we need an informed, public debate over the choices to be made over the coming years. It's time to care.

Early in Melbourne's development, people with tremendous foresight had the vision of fencing off the Upper Yarra Valley, and preserving its forests, as a catchment for the growing city of Melbourne. Melburnians today benefit from this foresight every time we turn on a tap - we have some of the world's cleanest water. The problem for us is that the Upper Yarra is barely meeting our needs today, let alone our needs in the future. A simplistic answer I have heard is the suggestion that we need to build new reservoirs and boost our water storage capacity, but this answer fails to understand that doing so will fail to accomplish anything; the problem is not that we have insufficient capacity for storing water, but rather that we don't have the water to fill the capacity that we have already.

The State Government, while I have criticised them a number of times on the blog, deserves to be applauded for various initiatives it has put in place to cut Melbourne's water usage. But while this is a good short to medium term solution, it fails to address where our water will come from long term. It is a debate currently being played out in Sydney, where a choice will be made on whether money should be spent on desalinification facilities, or whether it would be better used building infrastructure for 'greywater'.

Here's some background on greywater from Wikipedia:
Greywater is wastewater generated by household processes such as washing dishes, laundry and bathing. Greywater is distinct from wastewater that has been contaminated with sewage, which is known as blackwater.

There are numerous processes such as using reedbed filter systems, the wetpark systems or the living wall that can be used to clean up greywater.

Recycled greywater from showers and bathtubs can be used for flushing toilets, which saves great amounts of water. Many attempts at this have been made in Germany.

In the water damage restoration industry, grey water is considered to be any water from the exterior of the home, or clean water that has been standing for more than 48 hours.
There are numerous processes that can be used to clean up waste waters depending on the type and extent of contamination. Most wastewater is treated in industrial-scale wastewater treatment plants (WWTPs) which may include physical, chemical and biological treament processes. The most important aerobic treatment system is the activated sludge process, based on the maintenance and recirculation of a complex biomass composed by micro-organisms able to degrade the organic matter carried in the wastewater. Anaerobic processes are widely applied in the treatment of industrial wastewaters and biological sludges. Some wastewater may be highly treated and reused as reclaimed water. For some waste waters ecological approaches using reedbed systems such as constructed wetlands may be appropriate. Modern systems include tertiary treatment by microfiltration or synthetic membranes. After membrane filtration, the treated wastewater is indistinguishible from waters of natural origin of drinking quality.

Treated wastewater can be reused as drinking water (Singapur), in industry (cooling towers), in artificial recharge of aquifers, in agriculture (70% of Israel's irrigated agriculture is based on highly purified wastewater) and in the rehabilitation of natural ecosystems (Florida's Everglades).

Some of the issues surrounding this debate has been raised in a recent press release by The Greens:

Sunday, 10 July 2005
Randwick's Greens Mayor tonight called for government owned effluent water and storm water recovery plants to bolster Sydney's long-neglected water supply.

NSW Premier Bob Carr is expected to tonight announce that a massive desalination plant will be constructed in the Randwick City Council area using private sector financing.

"Desalination is up to 5 times more expensive than a similar sized reclamation plant", Mayor Murray Matson said.

"Southern California is currently building a large scale water reclamation plant to utilize sewage.

"I think it to be a terrible idea that the private sector is to be given such a large amount of control over Sydney's water supply."

Randwick City Council recently considered the location of a desalination plant at Malabar Headland and rejected it.

"Desalination is simply too energy intensive and costly", Cr Matson said. "There are many other alternatives available and recognised both in Australia and overseas."

London recently rejected desalination and Singapore successfully utilises membrane technology to reclaim water for the island.

"Losses through leaks current account for 10% of Sydney's water use", Cr Matson said. "Just spending the money to fix our water pipes would make a lot more sense."

The Premier is ignoring authoritative advice from the NSW Auditor General who advocates better management and pricing of water, leakage reduction and re-use of water.

"450 billion litres of poorly treated sewage goes out through the ocean outfalls every year. Large scale water recycling is a viable option being used all around the world for quality reuse projects", Cr Matson said.

"Water reclamation is inherently more enviromently sound than desalination.

"Recycling water and treating in a reclamation plant has the additional beneficial side effect of reducing ocean pollution and creating fertiliser as the reusable waste product.

"A reclamation plant does not need to be built near the Sewer Treatment Plant and recycled water can simply be transferred back to the river system to restore environmental flows or used for other uses."

"The Greens believe that reusing water is acceptable to the community. Only a fraction of Sydney's water supply is actually used for drinking and this could still be meet by our supplies from dams.

"Large scale water recycling does note necessarily mean substitution of drinking water, that is a matter of community choice."

Before we move forward, there are some fundamental questions we have to address. The first is whether we want a key component of our water catchment system - either by way of water purification or desalinification - owned in private hands. Keep in mind that water was one area where not even the Kennett government chose privatization. Similarly, if this new infrastructure is to be publically funded, the question to answer is whether we want to plunge our governments into debt to pay for it; if the answer is no (as has often been the case in Australia), then it means the investment of surpluses over a longer period of time into water infrastructure.

If we chose reclaimed water / Greywater as a solution, there are further issues which need to be addressed. The Greens are seemingly advocating Greywater being mixed in with drinking water, but I personally doubt that this is a politically workable solution. My impression (and I may be wrong) is that more people who would support, say, their toilets being hooked up to reclaimed water, than those willing to drink the stuff.

Related to this point is the question of whether we want a centralized system for greywater, or whether it should be an individual choice. The hidden cost of greywater may be the need to implement a second pipe system in our streets to pump the reclaimed water into our toilets. However, this could be negated if the decision is made that water collection and treatment for toilets be done on-site. The question is whether there is a will amongst the general populace to spend money on such schemes. if the answer is no, or we decide that a centralized system is better, laying thousands of miles of pipes will take decades. The time to make the choice on whether we want to undertake such a massive project is now.

Melbourne's water system has treated us well for decades. The time has come to debate its future.