Functional impact of natural organic matter on the adsorption of 2-methylisoborneol and geosmin to powdered activated carbon

Abstract

To remedy drinking water taste and odor outbreaks, municipalities commonly utilize powdered activated carbon (PAC) to reduce the concentration of the two of the most abundant odorants, 2-methylisoborneol (MIB) and geosmin (GSM), down to their low parts per trillion odor threshold limits. Natural organic matter (NOM), typically present at low parts per million concentrations, critically impedes PAC’s ability to adsorb these odorants. In order to further elucidate the leading mechanism of NOM interference on MIB and GSM adsorption, batch testing of odorant removal by three PAC products was conducted in a variety of synthetic and natural surface water sources. An analysis of the PAC dosages required to remove MIB and GSM down to their odor threshold limits in various NOM sources showed that for most waters, PAC adsorption performance was dependent only on NOM concentration and not NOM character. Subsequently, a simplified version of the ideal adsorbed solution theory-equivalent background component (IAST-EBC) model was adapted to successfully predict removal performance given odorant and NOM initial concentrations for a range of NOM sources. Finally, a comparison of removal performance between three mesoporous PACs highlighted combined micropore and mesopore volume to be the key activated carbon property that leads to enhanced resilience to NOM competition.