Council trialling new way of disposing treated sewage sludge

THE Toowoomba Regional Council has agreed to run a short trial to test the "thermal treatment" of some of the region's 13,000 annual tonnes of biosolids.

Aerial photograph TRC's Wetalla Sewage Treatment Plant at Mt Kynoch, Thursday, January 05, 2012. Photo Kevin Farmer / The Chronicle Helicopter services courtesy of Heliwest Group. Picture: Kevin Farmer

THE Toowoomba Regional Council has agreed to run a short trial to test the "thermal treatment" of some of the region's 13,000 annual tonnes of biosolids.

The councillors today voted to let Downer Engineering, in partnership with Toowoomba firm Pyrocal, develop a six-month trial for the "innovative" process as an alternative means to disposing of it.

Currently the council uses a contractor to transport and spread the waste at land near Cecil Plains.

But waste services manager Troy Uren told the councillors at the committee meeting that potential issues with this practice were being highlighted by regulators, and it could be phased out.

"There is growing concern with regards to the disposal of biosolids to land related to the potential presence of PFAS and other chemicals," his report said.

"If the current path of disposal was constrained, it would require alternative and investment options assessment to manage biosolids including potential storage (space, liquid phase containment), transport and disposal."

But Downer Engineering and Pyrocal put forward the trial, at no cost to council, that would essentially recover some of the waste and create char.

Water and waste general manager Damian Platts said the aim of the trial was only to test the concept, rather than give Downer and Pyrocal an advantage if the council adopted the idea and took it to tender.

"The trial will treat some of the biosolids, not all of them, and the aim of this trial is to prove the concept and  to understand the financial, commercial and technical aspects of the thermal treatment, as well as the opportunities for the char that will be generated," he said.

"The intent of the trial should not be to advantage the vendor, but to prove the concept (and) the relationship should not involve the sale or purchase of any material to the vendor."

Cr Geoff McDonald praised the idea, calling it a "positive step".

Diagram of thermal treatment process used by Pyrocal in Toowoomba. Picture: Pyrocal

HOW 'THERMAL TREATMENT' WORKS

ACCORDING to Pyrocal's website, its continuous carbonisation technology rapidly heats, dries and thermally decomposes the material through a rotary hearth.

This process also creates volatile gases that, mixed with the air, can partially combust to create heat that continues the thermal process.

"The flaming off-gases travel up through the hearth and then to the thermal oxidiser, where they are mixed with more air and oxidised completely through to water and carbon dioxide," the company said.

"The biomass is transported through a number of chambers before dropping out into a screw conveyor where it is quenched and discharged as a char product."

Originally published as Council trialling new way of disposing treated sewage sludge