Thousands of plastic stems from cotton buds have been collected from Shelly Beach by Sea Shepherd Warrnambool representatives and others.

Wannon Water, which operates the Warrnambool Sewage Treatment Plant nearby, has said the buds did not come from the facility.

Sea Shepherd Warrnambool co-coordinator Andrew Holt said the problem had been going on for years, and the group’s recent focus was to find the source of the litter.

“We can go down there every week and clean them up, but that doesn’t stop the problem, so we started looking at the source,” Mr Holt said.

The volunteer said the number of cotton buds – some still intact – washing up on the small beach near Thunder Point was “phenomenal”.

“The flow-on effect down the line is just horrendous,” he said.

“These things take years to break down, and they just get smaller, they don’t disappear.”

Wannon Water branch general manager of service delivery Ian Bail said he was confident the plastic sticks did not come from the treatment plant.

“Although we constantly remind people not to flush foreign objects down the toilet or sink, Wannon Water has systems in place to deal with the large number of objects that enter our sewerage network each day, including cotton buds,” Mr Bail said.

“This ensures the objects are removed before the sewage is treated.

“The process includes fine screens to remove debris from the raw sewage entering the plant, curtains in our treatment tanks to capture any floating material and a final decanting process which selectively inhibits floating plastics.

“The equipment and assets at the plant are inspected and maintained on a daily basis.”

Mr Bail said treated water was released into the ocean under strict licence conditions set by the Environmental Protection Authority, and the organisation had been compliant with its licence for the Warrnambool plant for at least the past five years.