Molecular level characterisation of ion-exchange water treatment coupled to ceramic membrane filtration

FT-ICR MS, NMR and ATR-FTIR were used to gain insight into the dissolved organic matter (DOM) removal process throughout a pilot water treatment system. The pilot plant under study utilises suspended ion exchange (SIX) followed by in-line coagulation with (ILCA) polyaluminium chloride and ceramic membrane filtration (CMF). MS results indicate that the SIX treatment is removing DOM irrespective of the compound type (>90% formulae similarity between SIX treated and raw water). However, the ILCA-CMF treatment substantially altered the chemical composition of the DOM by removing a high proportion of the aromatic and phenolic compounds. This was also confirmed by NMR and ATR-FTIR. An adjoining WTW plant which uses the same coagulant as the pilot plant, flocculation mixers for inline flocculation and filtration via MEMCOR (R) hydrophilic membranes did not show any selectivity when processing the same inlet water. Removal of aromatics/polyphenols in the pilot plant can therefore be attributed to the CMF step. Removal of aromatic/phenolic compounds is important, as these are known to react more readily with chlorine, potentially producing trihalomethanes - substances regulated in potable water.