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Ozonation-biofiltration for the production of drinking water from organic-rich groundwaters
Citation Link: https://doi.org/10.15480/882.5208
Publikationstyp
Doctoral Thesis
Date Issued
2023
Sprache
English
Author(s)
Kämmler, Jakob
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2022-12-20
TORE-DOI
Citation
Technische Universität Hamburg (2023)
Groundwater resources present a major reservoir for worldwide drinking water production that is used intensively due to its consistent quality and availability. Organic-rich groundwater resources with high concentration of natural organic matter (NOM) are not used to their full potential due to the negative impact of NOM on treatment processes and on water quality, particularly on water coloration.
This work examines the ozonation-biofiltration process to enhance NOM removal in drinking water production from organic-rich groundwater. Objects of research regarding the ozonation-biofiltration of organic-rich groundwater were (i) the transformation of groundwater NOM, (ii) by-product formation and its minimization and (iii) applicability and integration potential into groundwater treatment. An experimental approach was chosen to address these objects of research. Experiments included batch ozonation, small-scale pilot ozonation-biofiltration and membrane ozonation using different natural, organic-rich groundwaters.
Ozonation of organic-rich groundwater is characterized by rapid ozone (O3) consumption by NOM, normalized to the dissolved organic carbon (DOC) content of groundwater (approxi-mately 0.5 mgO3/mgDOC in the first 30 s of ozonation). This results in significant reduction of ultraviolet absorbance (UV254) and color (SAC436) but in low disintegration of NOM to smaller molecular size and therefore moderate formation of assimilable organic carbon (AOC). The simultaneous formation of bromate, a presumed human carcinogen, may exceed international drinking water limits under these conditions. This is due to high bromide contents of groundwaters and presumably enhanced by hydroxyl radicals formed by ozonation of phenolic NOM.
Biofiltration of ozonated groundwater by granular activated carbon and phonolithe results in significant reduction of AOC and minor reduction of UV254, SAC436 and DOC. Overall SAC436 removal potential by small-scale pilot ozonation-biofiltration was 40–50 % at bromate concentrations << 10 µg L-1, for two different groundwaters. For other groundwaters used in batch ozonation experiments, SAC436 removal potential may be up to 70 %. Decolorization performance of ozonation-biofiltration may be enhanced by the implementation of bromate minimization strategies. Process-oriented strategies (multi-stage ozonation and membrane ozonation) and pH reduction showed the highest potential to improve the trade-off between decolorization and bromate formation. Addition of ammonia or hydrogen peroxide reduced bromate concentration only at high ozone doses or compromised decolorization. Ozonation-biofiltration was performed with different feed water qualities including raw groundwater, aerated groundwater and finished groundwater, indicating high potential for integration into groundwater treatment.
Overall, it was shown that ozonation-biofiltration is applicable in different groundwater matrices, for different feed water qualities, at low ozone doses of < 0.5 mgO3/mgDOC. Its potential may be increased by the development of bromate minimization strategies particularly eligible for organic-rich groundwater treatment.
This work examines the ozonation-biofiltration process to enhance NOM removal in drinking water production from organic-rich groundwater. Objects of research regarding the ozonation-biofiltration of organic-rich groundwater were (i) the transformation of groundwater NOM, (ii) by-product formation and its minimization and (iii) applicability and integration potential into groundwater treatment. An experimental approach was chosen to address these objects of research. Experiments included batch ozonation, small-scale pilot ozonation-biofiltration and membrane ozonation using different natural, organic-rich groundwaters.
Ozonation of organic-rich groundwater is characterized by rapid ozone (O3) consumption by NOM, normalized to the dissolved organic carbon (DOC) content of groundwater (approxi-mately 0.5 mgO3/mgDOC in the first 30 s of ozonation). This results in significant reduction of ultraviolet absorbance (UV254) and color (SAC436) but in low disintegration of NOM to smaller molecular size and therefore moderate formation of assimilable organic carbon (AOC). The simultaneous formation of bromate, a presumed human carcinogen, may exceed international drinking water limits under these conditions. This is due to high bromide contents of groundwaters and presumably enhanced by hydroxyl radicals formed by ozonation of phenolic NOM.
Biofiltration of ozonated groundwater by granular activated carbon and phonolithe results in significant reduction of AOC and minor reduction of UV254, SAC436 and DOC. Overall SAC436 removal potential by small-scale pilot ozonation-biofiltration was 40–50 % at bromate concentrations << 10 µg L-1, for two different groundwaters. For other groundwaters used in batch ozonation experiments, SAC436 removal potential may be up to 70 %. Decolorization performance of ozonation-biofiltration may be enhanced by the implementation of bromate minimization strategies. Process-oriented strategies (multi-stage ozonation and membrane ozonation) and pH reduction showed the highest potential to improve the trade-off between decolorization and bromate formation. Addition of ammonia or hydrogen peroxide reduced bromate concentration only at high ozone doses or compromised decolorization. Ozonation-biofiltration was performed with different feed water qualities including raw groundwater, aerated groundwater and finished groundwater, indicating high potential for integration into groundwater treatment.
Overall, it was shown that ozonation-biofiltration is applicable in different groundwater matrices, for different feed water qualities, at low ozone doses of < 0.5 mgO3/mgDOC. Its potential may be increased by the development of bromate minimization strategies particularly eligible for organic-rich groundwater treatment.
Subjects
Ozonation
Natural organic matter (NOM)
Color
Groundwater
Drinking water
Bromate
DDC Class
620: Engineering
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