Authorities investigating mystery balls of debris that closed beaches in Sydney and the south coast in recent months have determined that they likely originated from Sydney Water’s land-based sewage treatment network, the NSW Environmental Protection Authority (EPA) said on Friday.
“The development comes after a comprehensive scientific and technical investigation found similarities between the makeup of the debris balls and samples taken from several of Sydney Water’s major wastewater treatment plants, including those at Malabar and Bondi,” the EPA said in a statement.
In November, Sydney Water had said “there have been no issues with the normal operations of the Bondi or Malabar wastewater treatment plants”.
EPA director of operations, Adam Gilligan, said on Friday the finding was “a significant step forward in our investigation but there is still work to do”.
“While we are yet to determine exactly what caused the pollution incidents to occur when they did, we can say the composition and the characteristics of the debris balls are consistent with a land-based sewage source,” Gilligan said.
The EPA issued an investigation notice to Sydney Water, requiring it to undertake oceanographic modelling of the dispersion of the debris balls; complete a sampling and analysis program at its sewage treatment plants; and assess its deep ocean outfall systems and sewerage pipe network to identify where in its systems the debris balls originated to prevent a recurrence.
Sydney Water’s acting executive general manager of water and environment services, Louise Beer, said in a Friday statement that an internal review had been implemented.
“It is important to note, all coastal treatment facilities are operating normally, and we are compliant with regulatory standards,” Beer said in a statement.
“As we could not find any faults with our system, we conducted widespread sampling and analysis of the debris balls at Sydney Water’s laboratories and appointed an independent oceanographer to determine the potential geographic origin of the debris balls.”
The investigation indicated the debris balls may have formed due to an increased load of fats, oils, and greases in the wastewater system over time, with unique oceanographic factors and weather conditions playing a role in why the debris balls appeared on beaches this summer, Sydney Water said.
It urged the city’s residents to keep fats, oils and greases out of drains.
More details soon …