Several Hyflux investors will be staging a protest at the Speakers' Corner in Hong Lim Park on Saturday to vent their anger over the state of affairs at the troubled water treatment company, The Straits Times has learnt.

They also intend to appeal for goodwill from national water agency PUB over what they see as a raw deal for investors.

PUB has said it will take control of Hyflux's Tuaspring desalination facility at zero dollars and waive any compensation claims PUB has against the company if the firm does not rectify its defaults.

The protest, which is planned for 3pm to 4pm, comes days before an important scheme meeting on April 5, where Hyflux creditors will vote on a rescue plan.

Protest organiser Alex Leong, 43, said he received approval from the police and the National Parks Board yesterday for the protest. He expects many people to turn up, based on an interest poll he put out to Hyflux investors several weeks ago.

Mr Leong invested around $100,000 in Hyflux preference shares as part of the group's fund-raising efforts in 2011 and reinvested all his dividends back into the company.

A restructuring plan offered by white knight Salim-Medco consortium, SM Investments (SMI), could potentially wipe out 97 per cent of what he has invested so far if creditors vote in favour of the plan.

The restructuring plan has to be approved by April 5 by at least 50 per cent in number and 75 per cent in value of each creditor class.

SMI has offered to bail out Hyflux with a $530 million lifeline for 60 per cent of the restructured company, but it has also threatened to leave the deal on April 1 unless the defaults were rectified.

Yesterday, Securities Investors Association Singapore (Sias) president David Gerald wrote to the Hyflux board stating that PUB's notice of default and SMI's threat to walk out have caused anxiety among investors. Sias told The Straits Times it was not aware of Saturday's protest.

Mr Leong is worried that if the original restructuring vote goes through, his investments, which make up a large portion of his savings, could vanish.

"Enough is enough. Many of us are fed up with the rubbish that we have been seeing about Hyflux," he said.

PUB's takeover of the desalination plant at Tuaspring without payment would not go down well with individual investors like him, said Mr Leong, especially as the plant is still operational and holds value.

Another investor, former polytechnic lecturer Raymond Koh, 47, said he, too, stands to lose around $100,000 from a 2011 investment.

Although the protest might not reap immediate change for investors, Mr Koh said, it is good enough that Hyflux, the authorities and other parties mired in the saga take notice.