Biological Processes for Dissolved Organic Carbon Removal

Christopher Pipe-martin (2011). Biological Processes for Dissolved Organic Carbon Removal MPhil Thesis, School of Chemical Engineering, The University of Queensland.

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s4137431_mphil_thesis_abstract.pdf Abstract for Mphil thesis application/pdf 8.56KB 2
s4137431_mphil_thesis_final_4Oct2011.pdf Approved final Mphil thesis with corrected date application/pdf 1.29MB 8
Author Christopher Pipe-martin
Thesis Title Biological Processes for Dissolved Organic Carbon Removal
School, Centre or Institute School of Chemical Engineering
Institution The University of Queensland
Publication date 2011-11
Thesis type MPhil Thesis
Supervisor Professor Jurg Keller
Dr Damien Batstone
Total pages 98
Total colour pages 19
Total black and white pages 79
Language eng
Subjects 09 Engineering
Abstract/Summary Biological water treatment has the potential to be a readily available, robust, effective and low energy intensity treatment technology. This report investigates the application of biological treatment processes for the removal of remaining organic compounds from a domestic wastewater treatment plant effluent. Biologically activated carbon (BAC) was found to be the preferred media for biological filtration, with removal of dissolved organic compounds by activated carbon being more than three times higher than in comparable sand filters. A two-stage sand-BAC filter was effective in achieving high DOC removal and had advantages during filter cleaning, as well as being compatible with the preferred configuration of the large slow rate filters required for high DOC removal. Methods for enhancing the filtration process were investigated. Pretreatment with alum coagulation and Dissolved Air Flotation/Filtration removed up to 40% of DOC and achieved excellent solids removal, leading to stable biological activity in BAC filters over long periods with surface skimming as the only maintenance and without the need for backwashing . Ozonation increased the DOC removal by BAC filtration. The DOC removal by BAC at low flow rates without ozonation exceeded that for ozone/BAC treatment at typical (higher) flow rates, meaning that the use of ozone may not be necessary to significantly reduce DOC in all cases. In the absence of ozonation, aeration was essential to achieve high DOC removal as the oxygen consumption in the filters was very high. It was found that longer contact times than are typically used for BAC filtration are required for high DOC removal, although the contact time is dependent on the level of pretreatment. Longer treatment time implies larger filter sizes, and a bigger footprint for the treatment plant. This increase in size and cost can be offset by the fact that equipment for ozone treatment may not be required. Coagulation/filtration removed 40% of DOC from secondary treated effluent, BAC filtration removed a further 22% with an EBCT of 140±30 minutes to give a total DOC reduction of 62%. Ozone/BAC treatment was able to achieve a 30% reduction (relative to influent) of the DOC remaining after coagulation/ filtration at an EBCT of 140±30 minutes to give a total DOC reduction of 70%. The effectiveness of biological treatment on the different components of the DOC was also explored. Very hydrophobic and slightly hydrophobic acids combined made up about 80% of the identified DOC fractions in the feed water, and also after alum pretreatment. BAC filters were able to remove 40% of this fraction, while ozone/BAC treatment removed over 50%. There was some variability in the effectiveness of BAC (with or without ozone) for removing hydrophilic compounds. It was also found that BAC, with or without ozone, was able to remove a wide range of pharmaceutical compounds and other micropollutants to below detection limits, with the two exceptions of caffeine and the pharmaceutical gabapentin, which were more than 90% removed in both treatment trains. The toxicity of the BAC treated water (again with or without ozone pretreatment) was significantly lower than that of the feedstock, and was comparable with that of pure water used as blank control. As measured by IC50, the toxicity was reduced to approximately 30% of that of the feed water. The estrogenic effect after treatment, with or without ozone, was below the detection limit. Slow flow BAC treatment appears to be an extremely effective means of removing micropollutants from water, even without the ozone pretreatment. The use of the UV Excitation Emission Matrix (EEM) technique as a rapid method for evaluating DOC removal was explored. It proved to be a useful analytical tool, able to distinguish the proportion of the different fractions such as neutral hydrophilic compounds, charged hydrophilic compounds and hydrophobic compounds (in combination with resin treatments) as well as the total residual DOC after treatment.
Keyword water
Additional Notes 27,33,37,54,55,57,58,62,63,65,68,70,73,74,75,76,78,79,81

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Created: Fri, 04 Nov 2011, 18:33:33 EST by Mr Christopher Pipe-martin on behalf of Library - Information Access Service