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Effect of biological activated carbon (BAC) filtration on the removal and biodegradation of natural organic matter (NOM) Black, Kerry Elizabeth

Abstract

Natural organic matter is a complex mixture of various organics including humic substances, carbohydrates, amino acids and carboxylic acids that exist in natural waters. Integrated treatment processes that combine oxidation processes and activated carbon biofilters have been shown to be effective at reducing natural organic matter (NOM) levels. The current research project investigated the effect of ozone and advanced oxidation at various doses on specific parameters including: biodegradability of NOM, formation of disinfection by-products (DBPs), change in apparent molecular weight (AMW) of NOM and dissolved organic carbon content (DOC). Overall, ozonation of the raw water at 2mg O₃/mg DOC resulted in significant reductions in aromatic material, resulting in lowered DBPFP. In addition, ozonation was successful at transforming NOM from high AMW to low AMW, rendering the organic material more biodegradable and preferentially removed during biofiltration. While the high-dose oxidants (ozonation at 25mg O₃/mg DOC and AOP treatment at 4000mJ/cm² and 10mg/L H₂0₂) were successful at reducing DOC, UVA, AMW and DBPFP, the elevated dose required make these options less realistic. Ozonation at 2mg O₃/mg DOC and AOP treatment at 2000mJ/cm² and 10mg/L H₂O₂ provide good reduction of UVA, AMW and DBPFP. The high dose oxidants are unsuitable as pre-treatment options for biofiltration given that they result in highly oxidized NOM that exhibited very little biodegradation during biofiltration. The lower dose oxidants are suitable pre-treatment options for biofiltration given the high reductions in UVA, AMW and DBPFP exhibited, and the similar biodegradation kinetics observed. Pre-oxidation prior to biofiltration is essential for removal of non-biodegradable DOC. The rate kinetics governing biodegradation were not sensitive to oxidant type or dose. Overall, this project provided beneficial insight into the operation of integrated treatment processes and the effect of these on several NOM characteristics including biodegradation.  

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Attribution-NonCommercial-NoDerivatives 4.0 International

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