Adsorption and biodegradation of 2-methylisoborneol and geosmin in drinking water granular activated carbon filters: A review and meta-analysis

Drinking water treatment plants often install granular activated carbon (GAC) to adsorb 2-methylisoborneol (MIB) and geosmin, which are associated with seasonal algal blooms. Biological degradation of MIB and geosmin can also occur in GAC filters, which might lengthen the GAC life compared to when removal is due to adsorption alone. In this review, we critically evaluated the effect of influent concentration, water background matrix, temperature, media characteristics, treated bed volumes (BV), empty bed contact time (EBCT), backwash protocol, and pretreatment on the adsorption and biodegradation of MIB and geosmin in GAC filters based on mathematical formulas and previously published experimental data (MIB, n = 225; geosmin, n = 195). A meta -analysis showed that the transition from GAC (adsorption) to BAC (biologically active carbon) may be complete by 40,000 BV, and an EBCT above 15 min is a robust threshold for effective MIB and geosmin removal. A multiple linear regression analysis showed that EBCT may be the most significant variable for effective MIB and geosmin removal. Future studies should further investigate the effect of natural organic matter character, GAC physicochemical properties, treated BV, the optimum backwash protocol, and ozone dosage on the MIB and geosmin adsorption and/or biodegradation in GAC filters.