Application of air stripping to powdered activated carbon adsorption of geosmin and 2-methylisoborneol
Removal of odor-causing compounds (OCCs) including geosmin and 2-methylisoborneol (2-MIB), well known to cause the musty and earthy odor in drinking water, was investigated using powdered activated carbon (PAC) adsorption and air stripping processes. Removal by air stripping was mainly affected by aeration flow rates with volumetric mass-transfer rates of 0.002–0.005 min−1. Aeration also proved efficient for marginal removal of geosmin and 2-MIB in conjunction with PAC adsorption. Removal efficiencies increased depending on both PAC dose and aeration time in the aerated PAC contactor. PAC adsorption with aeration reduced the required PAC dose and contact time for removal of these compounds, compared with PAC adsorption alone. Removal efficiency of geosmin above 93% was improved by simultaneous PAC adsorption and air stripping under the same conditions. 2-MIB was relatively less amenable to removal and removal efficiency was about 58% by PAC adsorption at a dose of 15 mg l−1, 14% by air stripping at aeration flow rate of 15 l min−1 with 60 min aeration and 74% by simultaneous PAC adsorption and air stripping, respectively. Aeration flow rate, contact time and PAC dose were the critical factors in PAC adsorption with aeration for OCC removal and optimum conditions are suggested.
Keywords: air stripping, geosmin, odor causing compounds, PAC adsorption, 2-methylisoborneol