Most of the challenges in drinking water treatment arise out of contaminants that are present in extremely low concentrations and have properties that make them extremely difficult to be removed by conventional treatment methods. This study tries to look at the treatment of two such microcontaminants's serchlorate and MIB (Methyl Isoborneol)/ Geosmin.
Perchlorate (ClO4-) is a major inorganic contaminant in drinking water and has been detected in a number of public drinking water systems nationwide and has serious health impacts associated with it. A complete and critical review on this intriguing contaminant is presented including a detailed discussion on sources of contamination, the policy aspects including regulation and the available treatment technologies and their feasibility. It is clearly evident that it would not be possible to achieve compete removal of perchlorate with the direct application of a single technology and it is highly likely that a combination of these technologies would have to be employed to overcome this challenge.
Physical removal technologies such as ion exchange are effective for perchlorate but they also generate brines highly concentrated in perchlorate and suffer from selectivity issues. Hence a destruction technology that completely reduces perchlorate to harmless chloride is preferred. This study investigates the potential removal of perchlorate ion in drinking water by combining electrochemical reduction with zero-valent iron reduction and the effectiveness of this technology will serve as a basis to further develop the proposed methodology to purify surface or ground water in target zones at a larger scale.
Geosmin and MIB are organic semi-volatile chemicals that can seriously influence the finished quality of drinking water by imparting taste and odor to it even at extremely low concentrations. A critical review of these two taste and odor causing compounds in drinking water is presented with emphasis on the relevant treatment alternatives. Although some of these technologies are more effective and show more promise than the others, much work remains to be done in order to optimize these technologies for removal of MIB and geosmin while being effectively used for treatment of other common contaminants.
Studies have shown that activated carbon adsorption is the most effective technology currently available for treatment of these compounds. The impact of adsorbent pore size distribution (PSD) and presence of natural organic matter (NOM) on activated carbon adsorption of MIB and geosmin was evaluated through single solute and multicomponent adsorption of these compounds on three types of activated carbon fibers (ACFs) and one granular activated carbon (GAC). It was seen that the experimental data was well defined by single solute adsorption isotherms and both PSD and NOM were major factors influencing adsorption. The binary adsorption of MIB and geosmin on ACFs and GAC was well defined by the ideal adsorbed solute theory (IAST), which is a well established thermodynamic model for multicomponent adsorption. There were no significant differences in the binary isotherm between the oxic and anoxic conditions, indicating that adsorption was purely through physical adsorption and no oligomerization was taking place.