Wintgens, Thomas
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Wintgens, Thomas
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- PublikationTradeoff between micropollutant abatement and bromate formation during ozonation of concentrates from nanofiltration and reverse osmosis processes(Elsevier, 2022) Wünsch, Robin; Hettich, Timm; Prahtel, Marlies; Thomann, Michael; Wintgens, Thomas; Von Gunten, Urs [in: Water Research]Water treatment with nanofiltration (NF) or reverse osmosis (RO) membranes results in a purified permeate and a retentate, where solutes are concentrated and have to be properly managed and discharged. To date, little is known on how the selection of a semi-permeable dense membrane impacts the dissolved organic matter in the concentrate and what the consequences are for micropollutant (MP) abatement and bromate formation during concentrate treatment with ozone. Laboratory ozonation experiments were performed with standardized concentrates produced by three membranes (two NFs and one low-pressure reverse osmosis (LPRO) membrane) from three water sources (two river waters and one lake water). The concentrates were standardized by adjustment of pH and concentrations of dissolved organic carbon, total inorganic carbon, selected micropollutants (MP) with a low to high ozone reactivity and bromide to exclude factors which are known to impact ozonation. NF membranes had a lower retention of bromide and MPs than the LPRO membrane, and if the permeate quality of the NF membrane meets the requirements, the selection of this membrane type is beneficial due to the lower bromate formation risks upon concentrate ozonation. The bromate formation was typically higher in standardized concentrates of LPRO than of NF membranes, but the tradeoff between MP abatement and bromate formation upon ozonation of the standardized concentrates was not affected by the membrane type. Furthermore, there was no difference for the different source waters. Overall, ozonation of concentrates is only feasible for abatement of MPs with a high to moderate ozone reactivity with limited bromate formation. Differences in the DOM composition between NF and LPRO membrane concentrates are less relevant than retention of MPs and bromide by the membrane and the required ozone dose to meet a treatment target.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationAnaerobic digestion of biowaste in Indian municipalities. Effects on energy, fertilizers, water and the local environment(Elsevier, 07/2021) Gross, Thomas; Breitenmoser, Lena; Hugi, Christoph; Wintgens, Thomas [in: Resources, Conservation and Recycling]Anaerobic digestion (AD) of biowaste seems promising to provide renewable energy (biogas) and organic fertilizers (digestate) and mitigate environmental pollution in India. Intersectoral analyses of biowaste management in municipalities are needed to reveal benefits and trade-offs of AD at the implementation-level. Therefore, we applied material flow analyses (MFAs) to quantify effects of potential AD treatment of biowaste on energy and fertilizer supply, water consumption and environmental pollution in two villages, two towns and two cities in Maharashtra. Results show that in villages AD of available manure and crop residues can cover over half of the energy consumption for cooking (EC) and reduce firewood dependency. In towns and cities, AD of municipal biowaste is more relevant for organic fertilizer supply and pollution control because digestate can provide up to several times the nutrient requirements for crop production, but can harm ecosystems when discharged to the environment. Hence, in addition to energy from municipal biowaste - which can supply 4-6% of EC - digestate valorisation seems vital but requires appropriate post-treatment, quality control and trust building with farmers. To minimize trade-offs, water-saving options should be considered because 2-20% of current groundwater abstraction in municipalities is required to treat all available biowaste with 'wet' AD systems compared to <3% with 'dry' AD systems. We conclude that biowaste management with AD requires contextualized solutions in the setting of energy, fertilizers and water at the implementation-level to conceive valorization strategies for all AD products, reduce environmental pollution and minimize trade-offs with water resources.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationMicropollutants as internal probe compounds to assess UV fluence and hydroxyl radical exposure in UV/H2O2 treatment(Elsevier, 18.02.2021) Wünsch, Robin; Mayer, Carina; Plattner, Julia; Eugster, Fabienne; Wülser, Richard; Gebhardt, Jens; Hübner, Uwe; Canonica, Silvio; von Gunten, Urs; Wintgens, Thomas [in: Water Research]Organic micropollutants (MPs) are increasingly detected in water resources, which can be a concern for human health and the aquatic environment. Ultraviolet (UV) radiation based advanced oxidation pro- cesses (AOP) such as low-pressure mercury vapor arc lamp UV/H2O2 can be applied to abate these MPs. During UV/H2O2 treatment, MPs are abated primarily by photolysis and reactions with hydroxyl radicals (•OH), which are produced in situ from H2O2 photolysis. Here, a model is presented that calculates the applied UV fluence (Hcalc) and the •OH exposure (CT•OH,calc) from the abatement of two selected MPs, which act as internal probe compounds. Quantification of the UV fluence and hydroxyl radical exposure was generally accurate when a UV susceptible and a UV resistant probe compound were selected, and both were abated at least by 50 %, e.g., iopamidol and 5-methyl-1H-benzotriazole. Based on these key parameters a model was developed to predict the abatement of other MPs. The prediction of abatement was verified in various waters (sand filtrates of rivers Rhine and Wiese, and a tertiary wastewater efflu- ent) and at different scales (laboratory experiments, pilot plant). The accuracy to predict the abatement of other MPs was typically within ±20 % of the respective measured abatement. The model was further as- sessed for its ability to estimate unknown rate constants for direct photolysis (kUV,MP) and reactions with •OH (k•OH,MP). In most cases, the estimated rate constants agreed well with published values, considering the uncertainty of kinetic data determined in laboratory experiments. A sensitivity analysis revealed that in typical water treatment applications, the precision of kinetic parameters (kUV,MP for UV susceptible and k•OH,MP for UV resistant probe compounds) have the strongest impact on the model’s accuracy01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationDeep-bed filters as post-treatment for ozonation in tertiary municipal wastewater treatment. Impact of design and operation on treatment goals(Royal Society of Chemistry, 2021) Wintgens, Thomas; Sauter, Daniel; Dabrowska, Agata; Bloch, Robert; Stapf, Michael; Miehe, Ulf; Sperlich, Alexander; Gnirss, Regina [in: Environmental Science. Water, Research & Technology]Ozonation followed by biological post-treatment is an established technology for abatement of organic micropollutants (OMP) from municipal wastewater. Although the necessity of biological post-treatment for oxidation by-product (OBP) removal is widely accepted, there is still discussion about the appropriate design and operation. The presented pilot-study investigates the impact of filter material and contact time on the removal efficiency of bulk organics, OMP, and OBP in three different deep-bed filters operated in parallel as post-treatment after ozonation (biological activated carbon (BAC) filter, dual-media filter sand/BAC and dual-media filter sand/anthracite). The use of BAC instead of non-adsorptive filter material resulted in higher removal of DOC and dissolved oxygen which indicates increased biological activity. Moreover, both BAC containing filters showed additional removal for a number of OMP even at high treated bed volumes of >50 000 whereas no removal was observed in the sand/anthracite filter. Analysis of N-nitrosodimethylamine (NDMA) and several carbonyl compounds revealed a clear formation of these biodegradable OBP during ozonation. A strong correlation was found between carbonyl formation and the specific ozone dose. Removal of OBP in the sand/BAC and the sand/anthracite filter was tested at different empty bed contact times (EBCT). While NDMA was efficiently removed independent of EBCT changes, there was a slightly negative impact of shorter EBCT on the reduction of carbonyl compounds. Furthermore, it was demonstrated that the integration of enhanced phosphorus removal into post-treatment is feasible with relatively low efforts by inline coagulant dosing (FeCl3) in the filter influent.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationSurface water treatment by UV/H2O2 with subsequent soil aquifer treatment. Impact on micropollutants, dissolved organic matter and biological activity(Royal Society of Chemistry, 2019) Wünsch, Robin; Plattner, Julia; Cayon, David; Eugster, Fabienne; Gebhardt, Jens; Wülser, Richard; von Gunten, Urs; Wintgens, Thomas [in: Environmental Science. Water, Research & Technology]Because organic micropollutants (MP) are frequently detected in river waters that are used as drinking water sources, combining a relatively cost-efficient natural treatment with upstream advanced oxidation processes (AOP) appears promising for their efficient abatement. Such a multi-barrier system can be integrated in drinking water production schemes to minimize risks from potentially hazardous MPs. This study investigates the impact of an UV/H2O2 AOP before soil aquifer treatment (SAT) on the abatement of selected MPs (EDTA, acesulfame, iopamidol, iomeprol, metformin, 1H-benzotriazole, iopromide), dissolved organic matter (DOM) (apparent molecular size distribution, specific UV absorbance at 254 nm – SUVA) and microbial parameters (intact cell count, cell-bound ATP). A pilot plant consisting of an AOP (0.5 m3 h−1, 4 mg L−1 H2O2, 6000 J m−2) and two parallel soil columns (filtration velocity: 1 m d−1, column height: 1 m) was continuously operated over a period of 15 months with Rhine river water pre-treated with rapid sand filtration. The investigations revealed a shift towards longer retention times of the humic substances peak in LC analysis of DOM, lower SUVA and higher biodegradability of DOM after UV/H2O2 treatment. In addition, an overall higher abatement of all investigated MPs by the combined treatment was observed (AOP with subsequent SAT) compared to either process alone. This observation could be explained by an addition of the single treatment effects. The strong primary disinfection effect of the AOP was detectable along the first meter of infiltration, but did not lead to any change in the column performance (i.e., similar abatement of dissolved organic matter).01A - Beitrag in wissenschaftlicher Zeitschrift