At the public meeting held about the quality of the water in Bombala and Delegate, Snowy Monaro Regional Council Water and Waste Water manager, Mark Rixon explained why some people in Bombala were getting dirty water through the town supply from the Bombala Water Treatment Plant (BWTP).
“Over the past years of operation at the BWTP there was an inability of the operators to adequately maintain a coagulant dose rate to appropriately treat the raw water source from the Coolumbooka Weir.
“Because of this, there has been an accumulation of a free aluminium residual in the reticulation network that has ‘seeded’ the biofilms and sludges that naturally occur in reticulation networks and build up over time.
“When these build ups are not managed effectively by flushing programs, the build-up of Aluminium hydroxide will result in delayed flocculation (flocking) when chlorine residuals and pH changes occur in the reticulation pipework.
“This flocking causes dirty water, sludge and taste and odour complaints in the reticulation network but it is not pathogenic (harmful to human health) but is of aesthetic concern and will cause laundry staining and other problems.
“The primary coagulant used at the BWTP was traditionally Aluminium Sulphate but has been recently replaced with Alchlor Gold, a Poly Aluminium Chlorohydrate product that gives improved treatment capacity.
“Other post treatment chemicals used at the BWTP include Soda Ash for pH adjustment, Chlorine gas for disinfection, Polyelectrolyte to assist colour removal and Fluoride, when Fluoride Dosing Plant is operational,” Mr Rixon said.
Scouring of the Bombala water pipes is scheduled to start on Wednesday April 4.