Bioaugmentation of Biological Activated Carbon Filters for Enhanced Micropollutant Removal

Granular activated carbon (GAC) filtration is an important technology for micropollutant removal from water. In GAC filters, micropollutants adsorb onto the activated carbon and can also be biodegraded, prolonging the filter lifetime. Biodegradation can be enhanced by introducing micropollutants degrading microorganisms to the filters, that is, through bioaugmentation. We assessed pyrazole adsorption to activated carbon and biodegradation in GAC filters inoculated with pyrazole degrading biomass originating from a drinking water plant. Pyrazole was chosen as a model micropollutant because it was detected at high levels in 2015 in Dutch surface water, and little is known about its removal mechanism in water treatment. GAC filters without inoculation and inoculated at different moments were operated, and breakthrough curves were fit to an adsorption and biodegradation model based on surface diffusion and Monod kinetics. Pyrazole biodegradation was successfully transferred from a sand filter to GAC filters and contributed to decreasing pyrazole concentrations below 10 μg/L in the GAC filter effluent. Pyrazole degradation was a stable process that could be maintained despite the lack of pyrazole in the filter influent for up to 30 days. Achieving a combination of adsorption and biodegradation in GAC filters is essential to sustain high micropollutant removals in the long term.