Saving potable water for residential use

Upgraded wastewater recycling plant

The upgraded Dalby Wastewater Recycling Plant in southern Queensland was opened in June and now delivers Class A+ recycled water to a nearby business, which previously used drinking water for its industrial processes.

As Project Superintendent, Parsons Brinckerhoff (PB) assisted to deliver the $2.35 million project with the Western Downs Regional Council. The project has provided relief to a community previously faced with ongoing water restrictions and disruptions to potable water.

PB Senior Water and Process Engineer Thomas Mannhardt was the superintendent’s representative on the project. Thomas explains PB adapted the way in which water is delivered to Dalby residents by separating a dedicated recycled water pipeline at the Dalby Wastewater Treatment Plant, to deliver high-quality water to the industrial user. This user had previously used potable water to produce ethanol biofuel from grain.

The upgrade added tertiary treatment processes to the existing biological wastewater operation. The process is a sequential batch reactor operating in a continuous mode. Decanted liquor from the process is settled in two clarifiers, where clarified water is discharged to a nearby creek, via a chlorine contact channel. Prior to discharge, a flow diversion box was installed to redirect this outfall water to a balanced storage basin. From there a pair of submerged pumps lifts the water to the plant. Water passes through micron strainers before passing through a submerged ultrafiltration membrane, followed by ultraviolet disinfection and final chlorination to maintain water quality.

Construction began in July 2009 and the first Class A+ water was produced ahead of schedule in February 2010. The plant currently produces 1 ML of water per day, but the design allows for double this capacity with the installation of an extra ultrafiltration skid, if this is required in future.