Using Pilot-Scale Investigations to Estimate the Remaining Geosmin and MIB Removal Capacity of Full-Scale GAC-Capped Drinking Water Filters

Abstract

Pilot tests were conducted to investigate the removal of geosmin and 2-methylisoborneol (MIB) by new and semi-exhausted granular activated carbon (GAC) extracted from full-scale filters located in the City of Toronto's drinking water treatment facilities. Four pilot filters containing core-sampled GAC and new sand were fed with settled water from a full-scale plant and operated under conditions similar to those employed at full-scale. None of the pilot filters appeared to be capable of reducing geosmin and MIB concentrations to below the commonly cited threshold odour limits of 4 ng/L for geosmin and 9 ng/L for MIB at the influent levels tested. When operated at a 5-min empty bed contact time (EBCT) with geosmin influent concentrations in the range of about 70 to 110 ng/L, removals ranged from 10 to 38% in filters with 25 to 30 cm of used GAC. In the filter with 25 cm of new GAC, removal was 83%. When operated with a 7.5-min EBCT, the filter containing 95 cm of used bituminous GAC removed 78% of the geosmin present in the influent. For both geosmin and MIB, the effluent concentration and the amount removed increased as influent concentration increased, as was expected. In general, geosmin was better removed than MIB.

Fate of geosmin and 2-methylisoborneol in full-scale water treatment plants

“…Canada. Furthermore, Ndiongue et al (2006) demonstrated that an increase of GAC depth to 95 cm, and an increase of EBCT from 2.8 min to maximum 7.5 min, significantly increased geosmin removal efficiency of used GAC by around 35% which further supports the results of this study. Fig.…”

“…8a). The degree of removal was comparable with that reported by Ndiongue et al (2006), 61e75% and 24e47% geosmin removal using 25 cm of virgin and used (about 3 years), bituminous GAC at 2.8 min EBCT, respectively, at three full-scale WTPs located in southern Ontario, Table 1. Canada.…”

Impact of UV–H2O2 Advanced Oxidation and Aging Processes on GAC Capacity for the Removal of Cyanobacterial Taste and Odor Compounds

“…6) and without (data not shown) H 2 O 2 quenching. Ndiongue et al 45 demonstrated that an increase in GAC depth or EBCT would significantly improve the removal of geosmin and MIB from water. Furthermore, other studies have also observed better (minimum 13%) geosmin removal compared to MIB removal by GAC.…”