Saving the delicate balance of anaerobic organisms and biogas during an unexpected event

Rosedale Wastewater Treatment Plant Digester 3 Refurbishment

The four digesters at Watercare’s Rosedale Wastewater Treatment Plant (WWTP) needed upgrading. Digesters 1 and 2 relied on old tech constructed in the 1960s, not fit for purpose with rusting and redundant pipes. Digesters 3 and 4 were built in the early 2000s and needed refurbishing as well. There was a critical need for Rosedale WWTP to ensure robust and reliable treatment of biosolids, and our team was there to help.

After initially focusing on Digester 2, the lid on Digester 3 failed and we urgently changed course to fix it—the risk of exposing biogas to oxygen in the atmosphere can be explosive and environmentally detrimental. We developed a full set of design documentation for process and mechanical disciplines, including technical specification, datasheets, equipment and valve lists, and contract drawings. As well we reviewed the digesters’ gas mixing system and identified potential operational risks. We supported Watercare with construction queries and monitoring during the inspection, replacement, renewal, mechanical fitout, and instrumentation improvements for Digester 3 to ensure long-term health and safety of the facility.

This project had significant design challenges and our team was up to the task. Under urgency, problems arose quickly, however, we worked well with the contractor to react and find solutions quickly with the aim of full operational capacity.

Images attributed to Watercare.