Better Than Running Out of Water – Desalination Plants in Australia

In earlier this year, Sydney’s desalination started in operation for the first time in seven years, should we worry about it?

You may hear that the desalination plant in Sydney will be doubled in capacity to beat drought. As the water supply in NSW reaches to dangerous level, a top bureaucrat from the state said they had launched the expansion plans.

 

What is desalination and why we need?

The desalination technology is a process that takes salt and other minerals out from the seawater to produce freshwater. The technology is becoming important to Australia because the water supply from rainfall is declining due to climate change.

Australian governments started to build desalination plants in related to the 2000s Australian drought. Currently, the water supply limitations of these desalination plants for main capital cities (Perth, Sydney, Melbourne, Adelaide, and Brisbane) are around 30% (Sydney was at 15% but is under expansion to 30%).

 

How is it working?

First, the instruments will take seawater to the filter to remove large particles.

Next, in contrast to natural way to separate water and salt through evaporation process, this newer method is called reverse osmosis.

Under extremely high pressure, the seawater goes into semi-permeable membrane, which is a kind of purifier used to purify salt and impurities out from the water. After that, the water is drinkable.

Partial Reverse Osmosis System inside of Carlsbad Desalination Plant in California. Credit: vanderhe1 from flickr

 

What the cost?

Unlike other ways to produce water, the reverse osmosis requires higher capital costs including constructions and further maintenance. For example, the desalination plant in Victoria cost $3.5 billion to build. The operation cost is expected to climb up to $649 million in 2019. For residents in Sydney, after the desalination plant turned on, their water bill will be added extra $25 – $35 a year.


People against desalination plant in Wonthaggi in 2009. Credit: Takver from flickr

 

Is it worth it?

One of the biggest problems people are worried about is the energy consumption. Comparing to traditional water treatment plans, the desalination plants is highly energy-intensive. The energy consumption for reverse osmosis is around 1-kilowatt-hours per 400 litres.

If we take the “Target 155” as an example (a water efficiency campaign to encourage Melbournians using up to 155 litres per individual per day), the amount of energy can support to filter water for a person 3 days’ consumption. According to the Victoria State Government website, the plant in Wonthaggi normally uses about 90 megawatts (MW).

As stated by the government, “all the power used to operate the desalination plant and transfer pipeline is offset by Renewable Energy Certificates (RECs)”. That means we are not using fossil fuels to drive the plant in Victoria, which is good for the environment.

 

Victorian Desalination Plant near Wonthaggi. Credit: PressReleaseFinder from flickr

I used to think renewable energy is not enough to contribute to the increasing usage of desalination plants. But after checking the electricity generation report from the DELWP, I realise it is a small portion of the energy. The installed renewable energy capacity in Victoria was 5,345 MW in 2018 and there were 1707 MW projects under construction or tests.

How about the direct pollution to the ocean? Since the desalination plant can generate only half a litre of drinking water from every litre of seawater extracted, there are long-term concerns that the extra salty water discharging into the ocean may have large-scale ecological impacts to the environment.

But interestingly, a newer finding from the University of New South Wales shows only 100 metres of surrounding area will be impacted and the high-concentrate salt water is not toxic to marine life.

The maximum production capacity of the Victorian desalination plant is 150 gigalitres (GL, billion litres) and can be expanded to 200 gigalitres if needed. The Victorian Government has ordered 125 GL water from the plant. It is unsure whether there will be extra orders during this summer, but it is sure the water price will be higher.

As long as there is no impact to the environment, I would like to pay more on water. You may don’t like your water bill to be increased, but that’s better than running out of water.