Ozonung von Kläranlagenablauf zur weitergehenden Abwasserreinigung

Literaturverzeichnis: Seite 116-13215

Effluent ozonation for advanced wastewater treatment

Zusammenfassung in englischer SpracheOrganische Spurenstoffe sind ubiquitär in der aquatischen Umwelt vorhanden. Da Kläranlagen für bestimmte Substanzgruppen, wie z. B. Arzneimittelwirkstoffe, einen relevanten Eintragspfad darstellen, wird die weitergehende Abwasserreinigung zur Spurenstoffentfernung mittlerweile in Wissenschaft, Technik und Politik diskutiert. Die Ozonung von Kläranlagenablauf und Aktivkohleanwendung sind zwei Verfahren, die aufgrund ihres Potentials zur Spurenstoffentfernung im Hinblick auf eine großtechnische Umsetzung untersucht werden. Im Rahmen des Projektes KomOzon wurden Pilotversuche zur Kläranlagenablaufozonung für nach dem Stand der Technik gereinigtes Abwasser (Nitrifikation/Denitrifikation) durchgeführt. Neben der Spurenstoffentfernung und der Inaktivierung von Bakterien, Viren und Protozoen wurde die Entstehung unerwünschter Transformations- bzw. Oxidationsnebenprodukte indirekt über Toxizitätstests untersucht und der Einfluss auf Abwasserparameter ermittelt. Dafür wurden Messkampagnen mit spezifischen Ozonzehrungen zwischen 0,6 und 1,1 g O3 g-1 DOC durchgeführt. Ergebnisse der Spurenstoffelimination zeigen, dass die Substanzen in Abhängigkeit von ihren Geschwindigkeitskonstanten oxidiert werden. Während Ozon selektiv mit Verbindungen reagiert, die eine hohe Elektronendichte aufweisen, reagieren parallel dazu gebildete OH-Radikale unselektiv mit Wasserinhaltsstoffen, weshalb sie für die Elimination von ozonrefraktären Substanzen relevant sind. Carbamazepin und Diclofenac sind Indikatorsubstanzen für die Erfolgskontrolle einer Ozonung mit hoher Ozonreaktivität. Beide wurden bei allen Kampagnen bis über 99 % entfernt. Bezafibrat als Indikator für moderat reagierende Substanzen wurde zwischen 76 und 87 % eliminiert. Dies ist in überwiegendem Maß (Literaturwerte - 75 %) auf OH-Radikalreaktionen zurückzuführen. Mittels standardisierter aquatischer Ökotoxizitätstests mit Grünalgen, Daphnien und Fischeiern konnte in keiner der untersuchten Proben eine toxische Wirkung detektiert werden. Die endokrine Wirkung wurde In vitro und In vivo (21-Tage-Fish-Screening-Assay) untersucht. Eine spezifische Ozonzehrung von 0,6 - 0,7 g O3 g-1 DOC resultierte in einem Rückgang der estrogenen Bindungsaktivität um ca. 97 %, während die androgene Wirkung weniger stark abnahm (51 ± 11 %). In vivo Tests konnten in exponierten Fischen weder vor noch nach der Ozonung eine hormonelle Wirkung bzw. eine induzierte Veränderung an Leber oder Gonaden nachweisen. In keiner Messkampagne wurde ein Anstieg der Gentoxizität durch die Ozonung detektiert. Viren waren am sensibelsten gegenüber Ozon (Reduktion um 5 Log-Stufen), gefolgt von E. coli (2,2 - 2,5 Log-Stufen) und Enterokokken (1,3 - 2,2 Log-Stufen). Durch die Reduktion der beiden Indikatororganismen der europäischen Badegewässerrichtlinie konnte die Einhaltung des ausgezeichneten Zustandes für Binnengewässer im Mittel eingehalten werden. Aerobe Sporen von Bacillus subtilis als Testsubstanz für Protozoen wurden nicht entfernt. Der Umbau der organischen Abwassermatrix hatte keinen Einfluss auf den DOC, führte jedoch zu einer Erhöhung der biologischen Abbaubarkeit, gemessen als BSB5. Im untersuchten Bereich (0,6 - 1,1 g O3 g-1 DOC) stieg der BSB5 linear an und bei 0,65 g O3 g-1 DOC betrug der Anstieg 13 %. Die Oxidation der Huminstofffraktion, die im Abwasser für die UV-Absorption und die gelbliche Färbung verantwortlich ist, führte bei 0,6 - 0,7 g O3 g-1 DOC zu einer mittleren Reduktion des SAK254 und SAK436 um 39 bzw. 58 %. Spezifische Betriebskosten wurden je nach Kläranlagengröße mit 1,7 bis 5,7 € pro EW und Jahr abgeschätzt, was einem Anteil von 10 - 17 % der Betriebskosten für die Abwasserreinigung entspricht. Der zusätzliche Energieverbrauch für Ozonerzeugung und -eintrag liegt bei 18 - 20 %, kann sich durch die Zulaufbeschickung jedoch verdoppeln.Trace organic compounds (TrOCs) can be found ubiquitously in the aquatic environment. Wastewater treatment plants represent the major pathway to the aquatic ecosystem for specific compounds, as for example pharmaceuticals. This is a widely discussed issue in science, technology and politics. Ozonation and activated carbon application are two processes that have been investigated due to their high potential for TrOCs removal. The research project KomOzon dealt with pilot-scale ozonation of effluent from a wastewater treatment plant operated with nitrification and denitrification. The pilot study investigated TrOC removal, inactivation of bacteria, viruses and protozoa, the generation of unwanted transformation and oxidation by-products by the application of toxicity tests, and the impact on wastewater parameters. Sampling campaigns with specific ozone consumptions ranging from 0.6 to 1.1 g O3 g-1 DOC were conducted. Results on the TrOC removal revealed an elimination in accordance to the substancespecific rate constants. While ozone selectively reacts with compounds with a high electron density, OH-radicals are hardly selective towards their reaction partners, which makes them important for the oxidation of ozone refractory TrOCs. Carbamazepine and Diclofenac are indicator substances with a high reactivity, applied for the evaluation of effluent ozonation. Both were eliminated by more than 99 %. Bezafibrate is an indicator substance that moderately reacts with ozone. It was eliminated by 76 to 87 %, which can be attributed to the indirect reaction by - 75 % (literature value). Standardised ecotoxicity tests with green algae, daphnids and fish eggs revealed no toxic effects in the investigated samples. Endocrine activity was studied in vitro and in vivo (21-day fish screening assay). A specific ozone consumption of 0.6 - 0.7 g O3 g-1 DOC resulted in a decrease of estrogenic activity by approx. 97 % while androgenic activity decreased by 51 ± 11 %. Neither before nor after ozonation adverse effects on liver or gonads of fish were detected by in vivo testing. With regard to genotoxic activity no increase was observed after ozonation. Virus inactivation was most effective (5 log units), followed by E. coli (2.2 - 2.5 log units) and enterococci (1.3 - 2.2 log units). The reduction of the two bacteria indicator organisms of the European bathing water directive resulted in the compliance with the good quality for inland waters. Aerobic spores of Bacillus subtilis as surrogate parameter for protozoa, however, were not removed. The transformation of the effluent organic matter had no impact on the DOC while it resulted in an increase of the biological degradability, measured as BOD5. Between 0.6 and 1.1 g O3 g-1 DOC the BOD5 increased linearly amounting to 13 % at 0.65 g O3 g-1 DOC. Humic substances are responsible for the UV-absorption and the yellowish colour of effluent. The oxidation of humic substances lead to a 39 % reduction of the SAC254 and a 58 % reduction of the SAC436 at 0.6 - 0.7 g O3 g-1 DOC. Depending on the treatment plant size the yearly operating costs were estimated to be between 1.7 and 5.7 € per p. e. which is equivalent to an increase in the operating costs for conventional wastewater treatment (Austrian benchmarking data) by 10 - 17 %. The additional energy consumption for ozone generation and transfer amounted to 18 - 20 %. However, full-scale experiments demonstrated that the consumed energy can be doubled if energy is needed for influent pumping.11

4. Reinigungsstufe auf Kläranlagen zur weitergehenden Behandlung kommunaler Abwässer

Über die letzten Jahre entwickelten sich die Überlegungen zu einer über den derzeitigen Stand der Technik hinausgehenden Abwasserreinigung von reinen forschungsorientierten Ansätzen hin zu einer großtechnischen Implementierung, sodass es heute für die unterschiedlichen verfahrenstechnischen Varianten einer weitergehenden Abwasserreinigung zur Entfernung von organischen Spurenstoffe bereits großtechnische Umsetzungen gibt. Vor allem in der Schweiz hat aufgrund der gesetzlichen Rahmenbedingungen die Umsetzung einer 4. Reinigungsstufe bereits begonnen, wenngleich auch noch eine Reihe von Detailfragestellungen für eine technische Implementierung offen ist. Dieser Beitrag fasst die heute anerkannten Optionen für Verfahren zur weitergehenden Abwasserreinigung zusammen und ergänzt sie durch Erkenntnisse aus einem vom BMLFUW geförderten nationalen Forschungsprojekt „KomOzAk“, das dazu beiträgt, die Umsetzung einer 4. Reinigungsstufe technisch und betrieblich zu optimieren.Over the last years, considerations for an implementation of advanced treatment steps for the removal of organic trace pollutants shifted from a rather research oriented approach focusing on the removal potential of considered technologies towards a full-scale implementation. As an according legislation is put into place, especially in Switzerland full-scale units comprising different technologies and combinations of technologies already are realized and in place. This paper gives an overview on treatment technologies that proved to be suitable for tackling the topic of further removal of organic trace pollutants from municipal wastewater. This overview is supplemented by results of an Austrian research project looking into details on technical and operational optimization of ozonation and activated carbon application.Bundesministeriums für Land- und Forstwirtschaft, Umwelt und Wasserwirtschaft340345

Benchmarking of large municipal waste water treatment plants > 100,000 PE in Austria

The final publication is available via https://doi.org/10.2166/wst.2008.214.During a six-year period the Austrian Benchmarking System was developed. The main objectives of this benchmarking system are the development of process indicators, identification of best performance and determination of cost reduction potentials. Since 2004 this system is operated via an internet platform and automated to a large extent. Every year twenty to thirty treatment plants use the web-based access to this benchmarking platform. The benchmarking procedure comprises data acquisition, data evaluation including reporting and organised exchange of experience for the treatment plant managers. The process benchmarking method links the real costs with four defined main processes and two support processes. For wastewater treatment plants with a design capacity >100,000 PE these processes are further split up into sub-processes. For each (sub-) process the operating costs are attributed to six cost elements. The specific total yearly costs and the yearly operating costs of all (sub-)processes are related to the measured mean yearly pollution load of the plant expressed in population equivalents (PE110: 110 gCOD/d corresponding to 60 g BOD5/d)). The specific capital costs are related to the design capacity (PE). The paper shows the benchmarking results of 6 Austrian plants with a design capacity >100,000 PE representing approximately 30% of the Austrian municipal wastewater treatment plant capacity.14871493

Microorganism inactivation by an ozonation step optimized for micropollutant removal from tertiary effluent

The final publication is available via https://doi.org/10.2166/wst.2013.212.This paper demonstrates the additional benefit of the microbicidal efficacy of an ozonation plant implemented for micropollutant removal from tertiary effluent. Due to the low amount of viruses and protozoa in the tertiary effluent, bacteriophage MS2 and spores of Bacillus subtilis were dosed as surrogates. At specific ozone consumptions of 0.6 and 0.9 g O3/g dissolved organic carbon (DOC) a 2-log colony forming unit (CFU) reduction was achieved for indigenous Escherichia coli and enterococci, and the limits of the European bathing water directive for the excellent quality of inland waters were met. Higher removal was impeded by the shielding effect of suspended solids in the effluent, which implies the combination of ozonation with a preceding filtration step if higher microbicidal performances are required. The surrogate virus MS2 was reduced by 4–5 log while no significant inactivation was detected for B. subtilis spores. Additionally, the impact of ozonation on the biochemical oxygen demand (BOD) was studied. The BOD5 measurement was not adversely affected despite the reduced concentration of microorganisms after ozonation. The intrinsic increase in BOD5 averaged 15% at 0.6–0.7 g O3/g DOC. The impact of the projected increase on the surface water quality is generally not considered a problem but has to be assessed on a case-by-case approach

Optimization of Ozonation and Peroxone Process for Simultaneous Control of Micropollutants and Bromate in Wastewater

The final publication is available via https://doi.org/10.2166/wst.2018.170.The study aims to simultaneously control micropollutants and bromate formations by using ozonation and peroxone process. The batch experiments were run with variations in specific ozone dose (SOD) and hydrogen peroxide-to-ozone (H2O2/O3) ratio. Based on the removal by ozonation and peroxone, micropollutants were categorized into three groups: non-reactive compounds (i.e. amidotrizoate), moderately reactive compounds (i.e. metoprolol, acesulfame potassium, bezafibrate, and benzotriazole), and highly reactive compounds (i.e. carbamazepine and diclofenac). For ozonation and peroxone process, the removals for highly reactive compounds and moderately reactive compounds were 82–99% and 29–99%, respectively. The removal of amidotrizoate was not observed in this study. The effect of ozonation on micropollutant removals was similar to the peroxone process. However, differences in bromate formation were observed. Bromate formation depended on the SOD, while addition of hydrogen peroxide suppressed the bromate formation. The peroxone process at the H2O2/O3 ratio of 0.3 was recommended to bromide-containing water below 100 µg·L−1 for simultaneous control of micropollutants and bromate. Enhancement in micropollutant removals, except for the non-reactive groups, was achieved with either higher SOD or the addition of hydrogen peroxide to ozonation. The micropollutant removal predicted from the second-order kinetic reaction with ozone and •OH exposures was higher than the observed data

Effect of ozonation on the biodegradability of urban wastewater treatment plant effluent

The present work aimed to study the effect of ozonation on the organic sum parameters linked to enhanced biodegradability. Laboratory experiments were conducted with the effluent of four Austrian urban wastewater treatment plants with low food to microorganism ratios and different matrix characteristics. Biochemical oxygen demand over 5 days (BOD5) was measured before ozonation and after application of different specific ozone doses (Dspec) (0.4, 0.6 and 0.8 g O3/g DOC). Other investigated organic parameters comprised chemical oxygen demand (COD), dissolved organic carbon (DOC), UV absorption at 254 nm (UV254), which are parameters that are applied in routine wastewater analysis. Carbamazepine and benzotriazole were measured as reference micropollutants. The results showed a dose-dependent increase in biological activity after ozonation; this increase was linked to the enhanced biodegradability of substances that are recalcitrant to biodegradation in conventional activated sludge treatment. The highest relative change was determined for BOD5, which already occurred between 0 and 0.4 g O3/g DOC for all samples. Increasing the Dspec to 0.6 and 0.8 g O3/g DOC resulted in a less pronounced increase. DOC was not substantially decreased after ozonation, which was consistent with a low reported degree of mineralization, while partial oxidation led to a quantifiable decrease in COD (7 to 17%). Delta UV254 and the decline in specific UV absorption after ozonation clearly correlated with Dspec. In contrast, for COD and biodegradable DOC (BDOC), a clear dose-response pattern was identified only after exposure to BOD5 measurement. Indications for improved biodegradability were further supported by the rise in the BOD5/COD ratio. The results indicated that subsequent biological processes have a higher degradation potential after ozonation. The further reduction in biodegradable organic carbon emission by the combination of ozonation and biological post treatment represents another step towards sustainable water resource management in addition to micropollutant abatement.19

Ozone as oxidizing agent for the total oxidizable precursor (TOP) assay and as a preceding step for activated carbon treatments concerning per- and polyfluoroalkyl substance removal

Several thousands of highly persistent per- and polyfluoroalkyl substances (PFAS) exist and it is therefore challenging to analytically determine a larger spectrum of these compounds simultaneously in one sample. It is even more difficult to efficiently remove mobile PFAS in wastewater treatment plants (WWTPs) to protect the receiving waters. The total oxidizable precursor (TOP) assay is an approach that enables the detection of the total PFAS content in a sample via oxidation of precursors, followed by subsequent analysis of the perfluoroalkyl acid (PFAA) concentration before and after oxidative processes. Activated carbon combined with a preceding ozonation step is considered a promising tool for the removal of micropollutants but considering PFAS removal efficiencies in effluents for this process combination more information is required. The focus of the study was to implement and assess the TOP assay with ozone as oxidizing agent to estimate the total PFAS content in a WWTP effluent. Additionally, granular activated carbon (GAC) and powdered activated carbon (PAC) with a preceding ozonation step was tested for the removal efficiencies for 22 PFAS. For the TOP assay the obtained accordance in molarity using spiked tap water as quality control was 95.2% (15 mg O3/L) and 99.1% (6 mg O3/L). Applying the TOP assay, an estimated total PFAS content of 840 ng/L was determined in the respective effluent, which was 91.1% higher than obtained by target PFAS analysis, implying the presence of unknown precursors not included in common monitoring. While all treatment techniques that included ozone or a preceding ozonation step solely transformed precursors and long-chain perfluoroalkyl acids (PFAA, i.e., >C9) to shorter congeners, PAC was the only tested water treatment application that was able to remove 19.3% of the total PFAS molarity.1343

Desorption of Organic Micropollutants from Loaded Granular Activated Carbon

©2020 by the authors.The loading of granular activated carbon (GAC) is influenced by the amount of water treated and the concentrations of adsorbates present in the water matrix. Through extraction experiments, we aimed to investigate the total adsorbed mass of eight organic micropollutants by using ethanol as solvent and the maximum possible concentrations, due to the desorption of organic micropollutants, in water. Three different drying methods and the impact of the contact time, GAC particle size, and GAC/solvent ratio were investigated. Although no significant differences between the drying methods could be observed, the chosen contact time and particle size had a significant impact on the amount of organic micropollutants extracted. Lower GAC/solvent ratios positively affected the extraction yield. The masses extracted in ethanol were compared with the cumulated masses calculated from 72 feed and effluent samples, collected during filter operation, resulting in extraction yields between 0.5% and 30%. The composition of extracted micropollutants in ethanol reflected the concentrations in feed water of the pilot-scale filter. Desorption in water was mostly influenced by the solubility of the investigated micropollutants. The same substances found in the supernatants inf the experiments could also be identified in the backwash water of the filter.1202

Long-Term Toxicological Monitoring of a Multibarrier Advanced Wastewater Treatment Plant Comprising Ozonation and Granular Activated Carbon with In Vitro Bioassays

A set of CALUX in vitro bioassays was applied for long-term toxicity monitoring at an advanced wastewater treatment plant comprising ozonation and granular activated carbon filtration for the abatement of contaminants of emerging concern (CEC). During the 13-month monitoring, eight reporter gene assays targeting different modes of action along the cellular toxicity pathway were accessed to evaluate the suitability and robustness of the technologies. Two approaches were followed: on the one hand, signal reduction during advanced treatment was monitored; on the other hand, results were compared to currently available effect-based trigger values (EBTs). A decrease of the corresponding biological equivalent concentrations after the multibarrier system could be observed for all modes of action; while the estrogenic activity decreased below the EBT already during ozonation, the potencies of oxidative stress-like and toxic PAH-like compounds still exceeded the discussed EBT after advanced treatment. Overall, the long-term monitoring confirmed the positive effect of the multibarrier system, commonly evaluated only by CEC abatement based on chemical analysis. It could be demonstrated that advanced WWTPs designed for CEC abatement are suitable to significantly decrease toxicity responses not only in the frame of pilot studies but under real-world conditions as well.11616Austrian Federal Ministry of Agriculture, Regions and TourismFederal Government of Burgenlan