Aquaculture operators in one of Australia's premier oyster-producing regions say a proposed desalination plant could be "catastrophic" for the environment and shellfish.

Desalination is the process of removing salt and impurities from seawater to make it safe to drink.

After the purification process, the leftover salty brine or effluent usually gets put back into the ocean.

Western Australia's Water Corporation is considering desalination as part of a plan to future-proof the water supply of the state's Great Southern region.

This proposed desalination plant would mean the resulting hyper-saline brine is piped into Albany's Frenchman Bay, a concept opposed by people from a range of industries due to the potential negative impact on the marine environment.

The Water Corporation said a desalination plant, if approved, would not likely be online until 2030 with a plan to be finalised next year. 

Oyster production at risk

Albany shellfish hatchery manager Jonathon Bilton, who supplied baby oysters, or spat, to the majority of farms in WA, said shellfish larvae were "incredibly sensitive".

Mr Bilton said he was afraid that if anti-scale or biocide chemicals were used to clean the pipes leading into the bay, it could kill the spat.

"It might not kill them, but maybe it'll stop them from eating and if they don't eat, they die," he said.

The hatchery sits in King George Sound, considered one of Australia's premier aquaculture areas.

The mineral-rich seawater is used to make algae for the oyster spat, a meticulous process requiring strong biosecurity practices and clean water.

"We know from our experience that any contaminants in the system will cause catastrophic effects."

Lack of 'meaningful' consultation

The desalination proposal has also received criticism from recreational fishers, tourism operators, and environmental consultants.

Commercial fisherman Tony Westerberg relies on a healthy population of sardines in the sound for his business.

He was concerned the brine, which was "heavier" than salt water, would sink to the ocean floor and impact marine life.

"The two main fishing areas in the sound are deep holes, which are a lot deeper than the surrounding area, and the heavy salt water will flow into those holes and make it unsuitable for the fish," he said.

Up until recently, Mr Westerberg said he had no idea about the proposed desalination plant.

"I would have thought they would have approached all the users and had an around-the-table meeting beforehand so they can hear all the issues," he said.

"But it's all been through the grapevine, unfortunately."

New water source 'critical'

Almost half of Perth's water has been supplied by seawater desalination plants in the last five years.

It is considered a secure water source because it does not depend on rainfall.

However, a desalination plant would be a first for Albany, where the majority of local supply is sourced from groundwater.

Water Corporation Great Southern manager Adrian Stewart said all options for a secure water source for the future were being considered and thoroughly researched.

"This project started in 2021 and we've been talking to a whole range of community and stakeholder groups plus individual stakeholders," he said.

"We've looked at something like 40-plus individuals including environmental groups, community groups, and commercial fishing industry representation.

"This is obviously a really important project for the community — it's critical in terms of ensuring that we can provide long-term sustainable water for the community.