Department Environmental Chemistry

DEMEAU

Ozone reactor ARA Neugut

The Project Demeau (Demonstration of promising technologies to address emerging pollutants in water and wastewater) is a EU project within FP7 running from Sept. 2012 – August 2015. The overall objective of DEMEAU is to promote the uptake of knowledge, prototypes and practices from previous EU research enabling the water and wastewater sector to face emerging pollutants.

Eawag focuses on demonstrating the potential of ozonation for water and waste water application in full scale in a collaboration of the Departments of Environmental Chemistry, Process Engineering and Water Resources and Drinking Water as well as the Ecotox Center. Removal processes and the influence of the source water composition on the efficiency of eliminating micropollutants with ozone will be studied. Appropriate online control of the technologies to assure constant high water quality with minimal energy consumption is an important task to improve the long-term stability and robustness of the processes, a prerequisite for implementation. The up-scaling, controlling, and validation of ozonation will be demonstrated for waste water and drinking water treatment together with the wastewater treatment plant ARA Neugut (Dübendorf) and the waterworks of Zurich (WVZ).

Moreover, the removal processes in ozonation will be investigated in more details to close research gaps hampering the technology transfer to practice. The mitigation of transformation products from micropollutants by post-treatment will be studied and evaluated by theoretical concepts (including kinetics and mechanisms), chemical analysis and bioassays. The experiences and results will be used to develop a decision tool for the implementation of oxidation technologies based on a quantitative comparison of the different treatment technologies and on the framework requirements in different European regions.

Publications

Evaluation of a full-scale wastewater treatment plant with ozonation and different post-treatments using a broad range of in vitro and in vivo bioassays

Micropollutants present in the effluent of wastewater treatment plants (WWTPs) after biological treatment are largely eliminated by effective advanced technologies such as ozonation. Discharge of contaminants into freshwater ecosystems can thus be minimized, while simultaneously protecting drinking water resources. However, ozonation can lead to reactive and potentially toxic transformation products. To remove these, the Swiss Federal Office for the Environment recommends additional "post-treatment" of ozonated WWTP effluent using sand filtration, but other treatments may be similarly effective. In this study, 48 h composite wastewater samples were collected before and after full-scale ozonation, and after post-treatments (full-scale sand filtration, pilot-scale fresh and pre-loaded granular activated carbon, and fixed and moving beds). Ecotoxicological tests were performed to quantify the changes in water quality following different treatment steps. These included standard in vitro bioassays for the detection of endocrine, genotoxic and mutagenic effects, as well as toxicity to green algae and bacteria, and flow-through in vivo bioassays using oligochaetes and early life stages of rainbow trout.
Results show that ozonation reduced a number of ecotoxicological effects of biologically treated wastewater by 66 - 93%: It improved growth and photosynthesis of green algae, decreased toxicity to luminescent bacteria, reduced concentrations of hormonally active contaminants and significantly changed expression of biomarker genes in rainbow trout liver. Bioassay results showed that ozonation did not produce problematic levels of reaction products overall. Small increases in toxicity observed in a few samples were reduced or eliminated by post-treatments. However, only relatively fresh granular activated carbon (analyzed at 13,000 - 20,000 bed volumes) significantly reduced effects additionally (by up to 66%) compared to ozonation alone. Inhibition of algal photosynthesis, rainbow trout liver histopathology and biomarker gene expression proved to be sufficiently sensitive endpoints to detect the change in water quality achieved by post-treatment.
Kienle, C.; Werner, I.; Fischer, S.; Lüthi, C.; Schifferli, A.; Besselink, H.; Langer, M.; McArdell, C. S.; Vermeirssen, E. L. M. (2022) Evaluation of a full-scale wastewater treatment plant with ozonation and different post-treatments using a broad range of in vitro and in vivo bioassays, Water Research, 212, 118084 (13 pp.), doi:10.1016/j.watres.2022.118084, Institutional Repository

Evaluation of a full-scale wastewater treatment plant upgraded with ozonation and biological post-treatments: abatement of micropollutants, formation of transformation products and oxidation by-products

To protect the ecosystem and drinking water resources in Switzerland and in the countries of the downstream catchments, a new Swiss water protection act entered into force in 2016 aiming to reduce the discharge of micropollutants from wastewater treatment plants (WWTPs). As a consequence, selected WWTPs must be upgraded by an advanced treatment for micropollutant abatement with suitable and economic options such as (powdered) activated carbon treatment or ozonation. WWTP Neugut (105′000 people equivalent) was the first WWTP in Switzerland to implement a long-term full-scale ozonation. Differing specific ozone doses in the range of 0.35–0.97 g O3/g DOC were applied to determine the adequate ozone dose to fulfill the requirements of the Swiss water protection act. Based on this assessment, a specific ozone dose of 0.55 g O3/g DOC is recommended at this plant to ensure an average abatement of the twelve selected indicator substances by ≥80% over the whole treatment. A monitoring of 550 substances confirmed that this dose was very efficient to abate a broad range of micropollutants by >79% on average. After ozonation, an additional biological post-treatment is required to eliminate possible negative ecotoxicological effects generated during ozonation caused by biodegradable ozonation transformation products (OTPs) and oxidation by-products (OBPs). Three biological treatments (sand filtration, moving bed, fixed bed) and granular activated carbon (GAC, fresh and pre-loaded) filtration were evaluated as post-treatments after ozonation. In parallel, a fresh GAC filter directly connected to the effluent of the secondary clarifier was assessed. Among the three purely biological post-treatments, the sand filtration performed best in terms of removal of dissolved organic carbon (DOC), assimilable organic carbon (AOC) and total suspended solids (TSS). The fresh activated carbon filtration ensured a significant additional micropollutants abatement after ozonation due to sorption. The relative abatement of the indicator substances ranged between 20 and 89% after 27′000 bed volumes (BV) and was still substantial at 50′000 BV. In an identical GAC filter running in parallel and being fed with the effluent of the secondary clarifier, the elimination was less efficient. Seven primary OTPs (chlorothiazide and six N-oxides) formed during ozonation could be quantified thanks to available reference standards. Their concentration decreased with increasing specific ozone doses with the concomitant formation of other OTPs. The seven OTPs were found to be stable compounds and were not abated in the biological post-treatments. They were sorbed in the fresh GAC filter, but less efficiently than the corresponding parent compounds. Two OBPs, bromate (BrO3−) and N-nitrosodimethylamine (NDMA), were formed during ozonation but did not exceeded 5 μg/L for bromate and 30 ng/L for NDMA at the recommended specific ozone dose of 0.55 g O3/g DOC. NDMA was well abated in all post-treatments (minimum 41% during fixed bed filtration, maximum 83% during fresh GAC filtration), while bromate was very stable as expected.
Bourgin, M.; Beck, B.; Boehler, M.; Borowska, E.; Fleiner, J.; Salhi, E.; Teichler, R.; von Gunten, U.; Siegrist, H.; McArdell, C. S. (2018) Evaluation of a full-scale wastewater treatment plant upgraded with ozonation and biological post-treatments: abatement of micropollutants, formation of transformation products and oxidation by-products, Water Research, 129, 486-498, doi:10.1016/j.watres.2017.10.036, Institutional Repository

Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O3/H2O2: kinetics of micropollutant abatement, transformation product and bromate formation in a surface water

The efficiency of ozone-based processes under various conditions was studied for the treatment of a surface water (Lake Zürich water, Switzerland) spiked with 19 micropollutants (pharmaceuticals, pesticides, industrial chemical, X-ray contrast medium, sweetener) each at 1 μg L−1. Two pilot-scale ozonation reactors (4–5 m3 h−1), a 4-chamber reactor and a tubular reactor were investigated by either conventional ozonation and/or the advanced oxidation process (AOP) O3/H2O2. The effects of selected operational parameters, such as ozone dose (0.5–3 mg L−1) and H2O2 dose (O3:H2O2 = 1:3–3:1 (mass ratio)), and selected water quality parameters, such as pH (6.5–8.5) and initial bromide concentration (15–200 μg L−1), on micropollutant abatement and bromate formation were investigated. Under the studied conditions, compounds with high second-order rate constant kO3>104 M−1 s−1 for their reaction with ozone were well abated (>90%) even for the lowest ozone dose of 0.5 mg/L. Conversely, the abatement efficiency of sucralose, which only reacts with hydroxyl radicals (·OH), varied between 19 and 90%. Generally, the abatement efficiency increased with higher ozone doses and higher pH and lower bromide concentrations. H2O2 addition accelerated the ozone conversion to radical ·OH, which enables a faster abatement of ozone-resistant micropollutants. Interestingly, the abatement of micropollutants decreased with higher bromide concentrations during conventional ozonation due to competitive ozone-consuming reactions, except for lamotrigine, due to the suspected reaction of HOBr/OBr− with the primary amine moieties. In addition to the abatement of micropollutants, the evolution of the two main transformation products (TPs) of hydrochlorothiazide (HCTZ) and tramadol (TRA), chlorothiazide (CTZ) and tramadol N-oxide (TRA-NOX) respectively, was assessed by chemical analysis and kinetic modelling. Both selected TPs were quickly formed initially to reach a maximum concentration followed by a decrease of their concentrations for longer contact times. For the studied conditions, the TP's concentrations at the outlet of the reactors ranged from 0 to 61% of the initial parent compound concentration, CTZ being a more persistent TP than TRA-NOX. Finally, it was demonstrated in both reactors that the formation of bromate (BrO3−), a potentially carcinogenic oxidation by-product, could be controlled by H2O2 addition with a general improvement on micropollutant abatement. Post-treatment by granular activated carbon (GAC) filtration enabled the reduction of micropollutants and TPs concentrations but no changes in bromate were observed. The combined algae assays showed that water quality was significantly improved after oxidation and GAC post-treatment, driven by the abatement of the spiked pesticides (diuron and atrazine).
Bourgin, M.; Borowska, E.; Helbing, J.; Hollender, J.; Kaiser, H.-P.; Kienle, C.; McArdell, C. S.; Simon, E.; von Gunten, U. (2017) Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O3/H2O2: kinetics of micropollutant abatement, transformation product and bromate formation in a surface water, Water Research, 122, 234-245, doi:10.1016/j.watres.2017.05.018, Institutional Repository

Oxidation of cetirizine, fexofenadine and hydrochlorothiazide during ozonation: kinetics and formation of transformation products

The efficiency of wastewater ozonation for the abatement of three nitrogen-containing pharmaceuticals, two antihistamine drugs, cetirizine (CTR) and fexofenadine (FXF), and the diuretic drug, hydrochlorothiazide (HCTZ), was investigated. Species-specific second-order rate constants for the reactions of the molecular, protonated (CTR, FXF) or deprotonated (HCTZ) forms of these compounds with ozone were determined. All three compounds are very reactive with ozone (apparent second order rate constants at pH 7: kO3,pH7 = 1.7·105 M−1s−1, 8.5·104 M−1s−1 and 9.0·103 M−1s−1 for CTR, HCTZ and FXF, respectively). Transformation product (TP) structures were elucidated using liquid chromatography coupled with high-resolution tandem mass spectrometry, including isotope-labeled standards. For cetirizine and hydrochlorothiazide 8 TPs each and for fexofenadine 7 TPs were identified. The main TPs of cetirizine and fexofenadine are their respective N-oxides, whereas chlorothiazide forms to almost 100% from hydrochlorothiazide. In the bacteria bioluminescence assay the toxicity was slightly increased only during the ozonation of cetirizine at very high cetirizine concentrations. The main TPs detected in bench-scale experiments were also detected in full-scale ozonation of a municipal wastewater, for >90% elimination of the parent compounds.
Borowska, E.; Bourgin, M.; Hollender, J.; Kienle, C.; McArdell, C. S.; von Gunten, U. (2016) Oxidation of cetirizine, fexofenadine and hydrochlorothiazide during ozonation: kinetics and formation of transformation products, Water Research, 94, 350-362, doi:10.1016/j.watres.2016.02.020, Institutional Repository

Compilation of kinetics and mechanisms for the oxidative transformation of organic substances

This deliverable aims at presenting the reactivity of selected compounds towards the oxidative treatments investigated in Work Area 3, i.e. ozonation and UV photolysis. Therefore , mechanisms of oxidation by molecular ozone and hydroxyl radicals on reactive moieties are first described for a better understanding of oxidants reactivity . Since the reactivity of compounds is finally quantified with kinetic laws and kinetic rate constants, protocols for the determination of reaction rate constants (k - values) are here described and discussed. Based on literature data or recent lab studies, k - values of selected compounds a re also compiled in this manuscript . These values are particularly useful since they can be implemented for prediction of their elimination during oxidative water treatment based on models presented here.
Bourgin, M.; von Gunten, U.; McArdell, C. S.; Hollender, J.; Hofman-Caris, R. (2015) Compilation of kinetics and mechanisms for the oxidative transformation of organic substances, 35 p, Institutional Repository

Decision basis for implementation of oxidation technologies

Oxidative treatment is one of the options to eliminate emerging pollutants (EPs) from drinking water or wastewater. For drinking water treatment, the ozonation technology is already implemented at many sites all around the world, so far mostly for disinfection purposes. However, in some countries such as the Netherlands surface water contains relatively high bromide concentrations, which leads upon reaction with ozone to the formation of bromate, a suspe cted carcinogen. In such a case, UV/H2O2 treatment is considered a useful alternative, despite the fact that energy requirements are substantially higher compared to treatment with ozone or O3/H2O2. Only in recent years, the oxidative treatment of wastewat er has been investigated to not only protect our water resources, but also the ecosystem from pollution with chemicals used in our daily life. In Switzerland, the first permanent full scale plant with ozonat ion, WWTP Neugut in Dübendorf, is running since March 2014. Its performance was investigated i n detail in the DEMEAU project.
The goal of this paper is to present a decision basis for the implementation of oxidation technologies to eliminate EPs. Depending on the composition of the water in different European regions, one or the other treatment is recommended. The different parameters that influence the efficiency of oxidation and the formation of by - products are discussed. A decision tool is presented to decide if oxidative treatment of wastewater is rec ommended and under which circumstances the treatment of drinking water with ozone, O3/H2O2, or UV/H2O2 may be the treatment of choice.
McArdell, C. S.; Bourgin, M.; von Gunten, U.; Hollender, J.; Kienle, C.; Hofman-Caris, R. (2015) Decision basis for implementation of oxidation technologies, 22 p, Institutional Repository

Contact

Dr. Christa McArdell Senior scientist / group leader Tel. +41 58 765 5483 Send Mail

Project team

Marc Böhler Application and Development Tel. +41 58 765 5379 Send Mail
Dr. Cornelia Kienle Ecotox Centre Tel. +41 58 765 5563 Send Mail
Prof. Dr. Urs Von Gunten Tel. +41 58 765 5270 Send Mail
Prof. Dr. Juliane Hollender Senior scientist / Group leader Tel. +41 58 765 5493 Send Mail

External collaborators

Wastewater treatment plant ARA Neugut (Dübendorf)  

Waterworks of Zurich (WVZ)  

Sigrist process-photometer  

Funding

EU within FP7 (ENV.2012.6.5-2)  

Duration

September 2012 – August 2015