Removal of Taste and Odour Compounds by Conventional Granular Activated Carbon Filtration

Abstract

In recent years, musty-earthy tastes in drinking water have become a seasonal problem (September to November) for communities that draw their water from the upper St. Lawrence River. The source of the problem is attributed to the presence of geosmin and 2-methylisoborneol (MIB) at concentrations ranging from 5 to 60 ng/L. In 1997 and 1998, the Cornwall Water Purification Plant added granular activated carbon (GAC) to conventional gravity filters to control taste and odour compounds. We report on a study to test the efficiency of these conventional GAC-capped filters to reduce geosmin and MIB concentrations in finished water as a function of filter age, initial chlorine residual and contact time. GAC–capped filters removed on average 60% of the MIB and 80% of the geosmin from the source water after 2 and 12 months of filter operation. However, testing after 24 months operation showed reduced efficiency. Amounts removed ranged between 13 and 20% (15% average) for MIB and 50 to 57% (54% average) for geosmin in these filters. Testing also suggested that filter efficiency was greater with longer contact times and with higher chlorine residuals (in the range 0.1 to 0.6 mg free Cl2/L). In addition to carbon age, chlorine residual and contact time, flow channelization and slow release of the taste and odour compound load (particularly MIB) from the GAC bed may affect apparent filter efficiency.

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

“…8b). These results are also in accordance with previous publications (Kim et al, 1997;Ridal et al, 2001) observing better (over 13%) geosmin removal using GAC compared to MIB removal. Notably, ATP measurements demonstrate no significant biological activity was detected on GAC samples from the full-scale contactors.…”

“…Dissolved geosmin and MIB are detectable by humans in very low concentration, 10 ng/L (Hobson et al, 2010); hence, the presence of these compounds in water is one of the major causes of customer complaints to water utilities worldwide (Ridal et al, 2001;Rao et al, 2003;Smith, 2011;Hobson et al, 2010) requiring proper management strategies including tight operation of water treatment plants (WTPs). Furthermore, the intracellular to extracellular ratio of these metabolites varies (a) between water bodies, (b) within the water profile, (c) depending on the bloom age and the producers present, and (d) the compounds present (Hobson et al, 2010;Su et al, 2015).…”

“…Water utilities have invested heavily in capital and operational costs to enable the application of granular and powdered activated carbon (GAC and PAC, respectively) for the removal of geosmin and MIB from water. Despite the proven performance of virgin GAC for removal of these compounds, several questions still remain unanswered concerning the effectiveness of aged GAC for the removal of geosmin and MIB concentrations to below 10 ng/L, including the impact of ageing on carbon surface characteristics and adsorption capacity, biofilm formation and biodegradation, particularly under different operational and water quality conditions (Lalezary et al, 1988;Ridal et al, 2001;Newcombe et al, 2002aNewcombe et al, , 2002bHo, 2004;Persson et al, 2007). These questions are especially pertinent for the maintenance of operational GAC contactors.…”

Simultaneous determination of eight common odors in natural water body using automatic purge and trap coupled to gas chromatography with mass spectrometry

“…Asides from the well-known earthy-musty offflavors MIB, GSM, IPMP and IBMP [7], attention is also drawn to DMS, DMTS, ␤-cyclocitral and ␤-ionone [6,[8][9][10][11] which are associated with decomposition of algal blooms [6,12,13]. Because these T&O compounds often simultaneously break out in natural waters [6,7,14], the origin, biotransformation, and removal in/from aquatic environments have been gaining attention in the field of water science [5,[15][16][17][18]. An effective method for the determination of these compounds would be the key step for such efforts.…”

Specific and non-specific interactions of procaine with activated carbon surfaces

“…It can have a variety of surface properties to meet the requirements of different applications. It has been widely used for many years as a very cost effective technique for water and gas/air purification [3][4][5][6] as well as for catalyst supports [7][8][9]. In pharmaceutical applications, it has been used as a very effective adsorbent for the treatment of drug overdose [10][11][12][13].…”