Friday, 12 March 2021

The Recycled Water Option !

 The New South Wales government is contemplating a major engineering project to raise the wall of Warragamba Dam by as much as seventeen metres.  The objective to be gained is to store more water for the ever growing city of Sydney and to provide flood protection for the Hawksbury/Nepean where it is planned to create new housing and commercial industries.

Raising the wall of the dam will inundate a large area of natural bush and this will include several World Heritage areas and some Indigenous sites.  Work estimates put the cost of raising the wall at about  $ 1.6 billion.

Perhaps that money would be better spent recycling the waste water we currently pump into the ocean and use it to preserve what is essentially " drinking quality water " stored in Warragamba dam. Science can now achieve the restoration of water containing sewage and this restored water could replace much of what we draw from Warragamba for non urban use.

It is hugely wasteful that we use drinking quality water to flush our toilets and water our gardens..  Immense quantities are used in industry for commercial cooling and with a law change we could progressively lower the amount we draw from Warragamba.

It would be too costly to re-pipe Sydney with a dual water system but piping recycled water to growth areas where new high rise office and apartment buildings in the planning stage would be required to plumb toilet water use to recycled water would progressively lower demand on Warragamba.

Water is a precious commodity and in the past we have been wasteful.  The one piped supply has been used for all and every purpose and that can not go on indefinitely.  As a continent, Australia experiences cyclical droughts and we are told that global warming will likely means less rainfall in the years ahead.

We need to plan for the next hundred years and estimate what will be the likely demand for water from an even bigger city.  Warragamba can be supplemented by converting salty sea water through desalination plants, but this is costly if we are still using drinking quality water in a multi purpose role.

Whenever it rains, millions of gallons of water are flushed down street drains and sewers and eventually get pumped out into the sea.  Stored and recycled, this can be reused to water the immense parks and gardens scattered around the city and preserve the flow from Warragamba, and we have the ability to restore that water to drinking quality if we so choose.

There is probably repugnance at the idea of drinking recycling water but we need to start replacing the use of drinking quality water in processes where that standard is not required, and obviously that is where growth areas provide the best opportunity., and that $ 1.6 billion would go a long way in getting the process started. 

It will not happen voluntarily.  It will take a law change to make it happen !


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