Abstract
Granulated active carbon (GAC) is commonly used as a chemical barrier for the removal of organic micropollutants (OMPs) in drinking water treatment plants (DWTPs). However, little is known about the impact of dissolved organic carbon (DOC) and its long-term performance with regard to OMP removal efficiency. This study examined the performance of two GAC types (Norit 830W and Filtrasorb 400) in the removal of OMPs and DOC from natural lake water, in pilot-scale and full-scale tests run for almost one year. Potential early warning indicators of the exhaustion of GAC sorption capacity were also evaluated. The seven OMPs investigated (carbamazepine, lamotrigine, cetirizine, fexofenadine, oxazepam, fluconazole and N,N-diethyl-meta-toluamide (DEET)) all showed decreasing removal efficiencies after ~20,000 bed volumes (BV) in the pilot-scale Norit 830W and Filtrasorb 400 columns. However, columns with an 18-min empty bed contact time (EBCT) showed better performances than columns with 6-min EBCT. DEET was the OMP adsorbed most weakly. We found that DOC concentrations, methylene blue sorption kinetics, UV and fluorescence did not sufficiently explain the OMP breakthrough in the GAC columns. We concluded that carbamazepine, lamotrigine and fexofenadine can be used as indicators of decreasing GAC adsorption performance, due to their later breakthrough. Based on the results, UV and fluorescence removal could be used for the early detection of declining DOC removal, and online solid-phase extraction (SPE)–liquid chromatography–tandem mass spectrometry (SPE-LC-MS/MS) could be used for the early detection of OMPs in drinking water.
Highlights
Climate change and water scarcity, in combination with urbanization, will increase the need for water re-use in many regions of the world [1]
The highest sorption capacity was observed for cetirizine (16 and 22 ng g−1, for Norit 830W and Filtrasorb 400, respectively), while the lowest capacity was observed for DEET (3.7 and 4.6 ng g−1, respectively)
It has been have a differentstudies sorption mechanism than can interfere with the sorption of shown that granulated active carbon (GAC) capacities can be predicted for different waters if initial the organic micropollutants (OMPs), and the
Summary
Climate change and water scarcity, in combination with urbanization, will increase the need for water re-use in many regions of the world [1]. These often end up in environmental waters, as a consequence of incomplete removal by wastewater treatment plants (WWTPs) [5]. The increased detection of a wide range of OMPs in the aquatic environment demonstrates the limitations of conventional WWTPs in removing these compounds [3,4,5]. Conventional drinking water plants (DWTPs) feature multistage treatments, including coagulation/flocculation, clarification and filtration. These are followed by disinfection, which may be further augmented by advanced treatments such as activated carbon, membrane filtrations, ozone oxidation, or advanced oxidation processes [6,7,8,9,10]
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