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Untersuchung des CARIX™-Verfahrens zur Entfernung anthropogener Sulfat-Emissionen aus einem Trinkwasser mit erhöhter NOM-Konzentration
Citation Link: https://doi.org/10.15480/882.13613
Publikationstyp
Doctoral Thesis
Date Issued
2024
Sprache
German
Author(s)
Benne, Paul
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2023-12-08
TORE-DOI
Citation
Technische Universität Hamburg (2024)
Some water supply companies in Germany are observing increasing sulfate contamination in their raw water resources and are required to consider mitigation strategies due to the drinking water regulation limit of 250 mg/L sulfate. One method suitable for sulfate removal is the CO2-regenerated CARIX™ ion exchange process. This study investigated the performance, influencing factors, and limitations of the process at both pilot and laboratory scales using drinking water from Berlin-Friedrichshagen. Laboratory experiments were also conducted with drinking water from Hamburg.
During the twelve-month pilot testing at the Friedrichshagen waterworks, the process achieved sulfate removal of about 60–100 mg/L (34–59%) from the drinking water at yields of 70–84% without wastewater recovery. Additionally, 54–68% of water hardness, 62–75% of acid capacity, and 44–59% of DOC were removed. A reduction in acid capacity from 3.5 mmol/L to 2.9 mmol/L decreased sulfate removal from 100 mg/L (59%) to 60 mg/L (34%). The results indicate that while the yield influences the effluent water quality, the influent water quality, especially acid capacity, plays a crucial role.
In Berlin-Friedrichshagen, sulfate enters surface waters as sulfuric acid due to lignite mining in Lusatia. As the sulfate concentration increases, the acid capacity decreases. Under these conditions, the performance of the CARIX™ process significantly declines with increasing sulfate concentrations. A continuous accumulation of natural organic matter (NOM) on the anion exchanger was observed, leading to organic fouling of the material. After one year of pilot operation, approximately 45.6% of the anion exchanger's ion exchange capacity was no longer available for ion exchange processes.
Laboratory experiments showed that Berlin's humic substances and the organic fractions detected via UV254 exhibited a pronounced affinity for the anion exchanger, with ion exchange being their primary adsorption mechanism. For the first time, the displacement of anions by organic matter on the anion exchanger in the CARIX™ process was demonstrated. Carbonic acid proved unsuitable as a regenerant to reverse organic fouling due to its low concentration and pH levels. The operational behavior of the ion exchangers in the pilot plant was successfully reproduced in a laboratory setup.
Based on the results of ion removal in the pilot and laboratory systems, an empirical model was developed to estimate the CARIX™ effluent water quality using knowledge of acid capacity and carbonate hardness in the influent. Laboratory experiments and the empirical model can thus complement or replace time- and cost-intensive CARIX™ pilot testing. This work expands the understanding of the fundamental mechanisms of the CARIX™ process and provides guidance on its performance and design without relying on pilot trials.
During the twelve-month pilot testing at the Friedrichshagen waterworks, the process achieved sulfate removal of about 60–100 mg/L (34–59%) from the drinking water at yields of 70–84% without wastewater recovery. Additionally, 54–68% of water hardness, 62–75% of acid capacity, and 44–59% of DOC were removed. A reduction in acid capacity from 3.5 mmol/L to 2.9 mmol/L decreased sulfate removal from 100 mg/L (59%) to 60 mg/L (34%). The results indicate that while the yield influences the effluent water quality, the influent water quality, especially acid capacity, plays a crucial role.
In Berlin-Friedrichshagen, sulfate enters surface waters as sulfuric acid due to lignite mining in Lusatia. As the sulfate concentration increases, the acid capacity decreases. Under these conditions, the performance of the CARIX™ process significantly declines with increasing sulfate concentrations. A continuous accumulation of natural organic matter (NOM) on the anion exchanger was observed, leading to organic fouling of the material. After one year of pilot operation, approximately 45.6% of the anion exchanger's ion exchange capacity was no longer available for ion exchange processes.
Laboratory experiments showed that Berlin's humic substances and the organic fractions detected via UV254 exhibited a pronounced affinity for the anion exchanger, with ion exchange being their primary adsorption mechanism. For the first time, the displacement of anions by organic matter on the anion exchanger in the CARIX™ process was demonstrated. Carbonic acid proved unsuitable as a regenerant to reverse organic fouling due to its low concentration and pH levels. The operational behavior of the ion exchangers in the pilot plant was successfully reproduced in a laboratory setup.
Based on the results of ion removal in the pilot and laboratory systems, an empirical model was developed to estimate the CARIX™ effluent water quality using knowledge of acid capacity and carbonate hardness in the influent. Laboratory experiments and the empirical model can thus complement or replace time- and cost-intensive CARIX™ pilot testing. This work expands the understanding of the fundamental mechanisms of the CARIX™ process and provides guidance on its performance and design without relying on pilot trials.
Subjects
Ion Exchange
Sulphate removal
Drinking water
Natural organic matter (NOM)
CARIX
Carbon Dioxide Regenerated Ion Exchange
DDC Class
628: Sanitary; Municipal
572: Biochemistry
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