Recovery of attached bacteria from GAC fines and implications for disinfection efficacy

A physical/chemical desorption technique was used to assess the impact of colonized granular activated carbon (GAC) fines released from biologically active carbon (BAC) contractors on disinfection performance. The procedure was found to be effective for the recovery of attached heterotrophic plate count (HPC) bacteria at GAC fines concentrations as low as 10 μg/l in experiments using fines colonized in the laboratory. Application of the desorption procedure to disinfected pilot plant process waters did not result in increased HPC recoveries. It was therefore concluded that after disinfection, attached bacteria in biologically treated waters have little impact on public health, either due to a low number of released fines or a low number of organisms attached to these fines.