Vom WasserVolume 120, Issue 2 p. 23-26 Kurzbeiträge Sinkgeschwindigkeiten von Mikroplastikfragmenten und -faserstücken S. Dittmar, Corresponding Author S. Dittmar stefan.dittmar@tu-berlin.de Berlin Stefan Dittmar, B. Sc., Technische Universität Berlin, Fachgebiet Wasserreinhaltung, Straße des 17. Juni 135, 10623 Berlin; E-Mail: stefan.dittmar@tu-berlin.deSearch for more papers by this authorA. S. Ruhl, A. S. Ruhl BerlinSearch for more papers by this authorM. Jekel, M. Jekel BerlinSearch for more papers by this author S. Dittmar, Corresponding Author S. Dittmar stefan.dittmar@tu-berlin.de Berlin Stefan Dittmar, B. Sc., Technische Universität Berlin, Fachgebiet Wasserreinhaltung, Straße des 17. Juni 135, 10623 Berlin; E-Mail: stefan.dittmar@tu-berlin.deSearch for more papers by this authorA. S. Ruhl, A. S. Ruhl BerlinSearch for more papers by this authorM. Jekel, M. Jekel BerlinSearch for more papers by this author First published: 01 June 2022 https://doi.org/10.1002/vomw.202200004AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume120, Issue2June 2022Pages 23-26 RelatedInformation

Im Vergleich zu gelösten Stoffen unterliegen partikuläre Substanzen wie Mikroplastik (MP) in aquatischen Systemen anderen Dynamiken. Die wirksamen Transportmechanismen wie Deposition und Resuspendierung sowie Flotation und Sedimentation sind dabei nicht nur von Charakteristiken des betrachteten Gewässers, sondern in höherem Maß auch von Eigenschaften der Partikel selbst abhängig. Da gängige Polymere sowohl geringere (zum Beispiel PE, PP) als auch höhere Dichten (zum Beispiel PS, PET, PVC) als Wasser aufweisen, flotieren einige MP‐Partikel, wohingegen andere sedimentieren. Partikeldichte, ‐größe und ‐form können potenziell wiederum durch Agglomeration, Fragmentierung sowie biologischen Bewuchs verändert werden [1].

Gravity-driven membrane (GDM) systems are promising for decentralized drinking water treatment at the point of use due to their treatment efficiency and low maintenance requirements. To further improve permeate quality in terms of dissolved organic carbon (DOC), adsorption onto activated carbon has been proposed as a pretreatment. In the present study, a novel GDM system with integrated granular activated carbon (GAC) was tested. The performances of polyvinylidene fluoride (PVDF) ultrafiltration membranes (0.45 m²) in combination with two different GAC were compared. The PVDF modules achieved a mean flux between 4.3 and 5.1 L/m²*h at 32.5 mbar. Flux stabilization in GAC/GDM systems was observed during long-term experiments over 272 days. pH increase caused by one GAC after start-up had a severe adverse effect on the flux due to CaCO3 precipitation resulting in a 34 % lower stable flux compared to the other GAC/GDM system. Permeate quality was substantially improved in terms of DOC and UVA254. The organic micropollutants carbamazepine and formylaminoantipyrine were effectively removed in both GAC/GDM systems by at least 88 % and 92 %, respectively. The GDM systems effectively retained Enterococcus faecalis and particles (1–200 μm) by 5.1 and 1.6 log units, respectively. Overall, a GDM system combined with GAC revealed the best performance producing approx. 50 L/d purified water. The GAC/GDM systems were operated without any maintenance measures and improved the permeate quality substantially. Thus, application of the studied GAC/GDM systems is a suitable option for decentralized drinking-water treatment.

Bank filtration and artificial groundwater recharge systems contribute to about 70 to 80% of Berlin's drinking water supplies. However, treated wastewater is discharged into Berlin's surface waters, and water cycles are partly closed. The behaviour of dissolved organic compounds (DOC), organic iodine compounds (AOI) derived from the use of X-ray contrast media, and aromatic sulfonamides prescribed against infections, were studied at a bank filtration site with considerable wastewater influences (Lake Tegel). This lake contains approximately 14 to 28 % of treated wastewater effluent. During bank filtration, DOC is reduced by 40–50 %. Mixing with background groundwater causes only negligible reduction of DOC. In drinking water, DOC concentrations are about 4.7 mg/L. AOI decreases only under anaerobic conditions, but only by 35 %. In drinking water, the mean concentration is 7 μg AOI/L. The dominant sulfonamide in the wastewater effluent, sulfmethoxazole, is biodegradable under both anaerobic and also under aerobic conditions after a lag phase for bacterial adaptation. Its concentration in drinking water wells is near the detection limit.

Adsorption onto powdered activated carbon (PAC) is a promising technique for the removal of organic micropollutants (OMPs) from treated wastewater. To enhance the adsorption efficiency, PAC is recycled back into the adsorption stage. This technique was examined in pilot scale in comparison to a reference without recirculation. Coagulation with Fe(3+) was carried out simultaneously to adsorption. Extensive OMP measurements showed that recirculation significantly increased OMP eliminations. Thus, significant PAC savings were feasible. The PAC concentration in the contact reactor proved to be an important operating parameter that can be surrogated by the easily measurable total suspended solids (TSS) concentration. OMP eliminations increased with increasing TSS concentrations. At 20 mg PAC L(-1) and 2.8 g TSS L(-1) in the contact reactor, well-adsorbable carbamazepine was eliminated by 97%, moderately adsorbable diclofenac was eliminated by 92% and poorly-adsorbable acesulfame was eliminated by 54% in comparison to 49%, 35% and 18%, respectively, without recirculation. The recirculation system represents an efficient technique, as the PAC's adsorption capacity is practically completely used. Small PAC dosages yield high OMP eliminations. Poorly-adsorbable gabapentin was eliminated to an unexpectedly high degree. A laboratory-scale biomass inhibition study showed that aerobic biodegradation removed gabapentin in addition to adsorption.

PAC adsorption is a widespread option for the removal of organic micropollutants (OMP) from secondary effluent. For an optimal exploitation of the adsorption capacity, PAC recirculation is nowadays a common practice, although the mechanistic interrelations of the complex recirculation process are not fully resolved. In this work, extensive multi-stage batch adsorption testing with repeated PAC and coagulant dosage was performed to evaluate the continuous-flow recirculation system. Partly loaded PAC showed a distinct amount of remaining capacity, as OMP and DOC removals considerably increased with each additional adsorption stage. At a low PAC dose of 10 mg PAC L−1, removals of benzotriazole and carbamazepine were shown to rise from <40% in the first stage up to >80% in the 11th stage at 30 min adsorption time per stage. At a high PAC dose of 30 mg PAC L−1, OMP and DOC removals were significantly higher and reached 98% (for benzotriazole and carbamazepine) after 11 stages. Coagulant dosage showed no influence on OMP removal, whereas a major part of DOC removal can be attributed to coagulation. Multi-stage adsorption is particularly beneficial for small PAC doses and significant PAC savings are feasible. A new model approach for predicting multi-stage OMP adsorption on the basis of a single-stage adsorption experiment was developed. It proved to predict OMP removals and PAC loadings accurately and thus contributes towards understanding the PAC recirculation process.

The use of granular activated carbon (GAC) in fixed bed filters is a promising option for the removal of organic micropollutants (OMP) from wastewater treatment plant effluents. Frequent backwashing of the filter bed is inevitable, but its effect on potential filter stratification is not well understood yet and thus has been evaluated in the present study for two commercial GAC products. Backwashing of GAC filters was simulated with 10 or 100 filter bed expansions of 20 or 100% at backwash velocities of 12 and 40 m/h, respectively. Five vertical fractions were extracted and revealed a vertical stratification according to grain sizes and material densities. Sieve analyses indicated increasing grain sizes towards the bottom for one GAC while grain sizes of the other GAC were more homogeneously distributed throughout the filter bed. The apparent densities of the top sections were significantly lower than that of the bottom sections of both products. Comparative long term fixed bed adsorption experiments with the top and bottom sections of the stratified GAC showed remarkable differences in breakthrough curves of dissolved organic carbon, UV light absorption at 254 nm wavelength (UVA254) and OMP. GAC from the upper section showed constantly better removal efficiencies than GAC from the bottom section, especially for weakly adsorbing OMP such as sulfamethoxazole. Furthermore correlations between UVA254 reductions and OMP removals were found.

This study investigates if ozonation of wastewater treatment plant (WWTP) effluent can reduce the negative impacts of effluent organic matter (EfOM) on the adsorption of organic micro-pollutants (OMP) onto powdered activated carbon (PAC). Pre-treatment of the water included membrane filtration for the removal of suspended/colloidal organics, ozonation with various specific ozone consumptions, and subsequent OMP spiking to comparable initial concentrations in all of the ozonated waters. This approach allowed for comparative PAC adsorption tests. Adsorption analyses show that the adsorbability of EfOM decreases with increasing specific ozone consumptions. This is also reflected by liquid chromatography with online carbon and UV254 detection (LC-OCD) which shows the ozone-induced disintegration of large EfOM into smaller fragments. Also, small organic neutrals are decreased while the small organic acids peak continuously increases with rising specific ozone consumptions. UV254 demonstrates that the aromaticity of all LC-OCD fractions continuously declines together with increasing specific O3 consumptions. This explains the varying EfOM adsorbabilities that occur due to ozonation. The ozone-induced decrease of EfOM adsorbability directly translates into reduced adsorption competition against the adsorption of OMP. With higher specific ozone consumptions, OMP removal and OMP loadings increase. The reduced adsorption competition is reflected in the outputs from equivalent background compound (EBC) modeling. In each of the ozonated waters, correlations between the OMP removals and the UV254 removal were found.

Multi-stage reuse of powdered activated carbon (PAC) is often applied in practice for a more efficient exploitation of the PAC capacity to remove organic micro-pollutants (OMP). However, the adsorption mechanisms in multi-stage PAC reuse are rarely investigated, as large-scale experiments do not allow for systematic tests. In this study, a laboratory method for the separation of PAC/water suspensions and the subsequent reuse of the PAC and the water was developed. The method was tested on wastewater treatment plant (WWTP) effluent in a setup with up to 7 PAC reuse stages. The tests show that the overall OMP removal from WWTP effluent can be increased when reusing PAC. The reason is that a repeated adsorption in multi-stage PAC reuse results in similar equilibrium concentrations as a single-stage adsorption. Thus, a single relationship between solid and liquid phase OMP concentrations appears valid throughout all stages. This also means that the adsorption efficiency of multi-stage PAC reuse setups can be estimated from the data of a single-stage setup. Furthermore, the overall OMP removals in multi-stage setups coincide with the overall UV254 removals, and for each respective OMP one relationship to UV254 removal is valid throughout all stages. The results were modeled by a simple modification of the equivalent background compound model (EBCM) which was also used to simulate the additional OMP removals in multi-stage setups with up to 50 reuse stages.

The Shafdan reclamation project facility (Tel Aviv, Israel) practices soil aquifer treatment (SAT) of secondary effluent with hydraulic retention times (HRTs) of a few months to a year for unrestricted agricultural irrigation. During the SAT, the high oxygen demand (>40 mg L-1) of the infiltrated effluent causes anoxic conditions and mobilization of dissolved manganese from the soil. An additional emerging problem is the occurrence of persistent trace organic compounds (TrOCs) in reclaimed water that should be removed prior to reuse. An innovative hybrid process based on biofiltration, ozonation and short SAT with similar to 22 d HRT is proposed for treatment of the Shafdan secondary effluent to overcome limitations of the existing system and to reduce the SAT's physical footprint. Besides efficient removal of particulate matter to minimize clogging, coagulation/flocculation and filtration (5-6 m h(-1)) operated with the addition of hydrogen peroxide as an oxygen source efficiently removed dissolved organic carbon (DOC, to 17-22%), ammonium and nitrite. This resulted in reduced effluent oxygen demand during infiltration and oxidant (ozone) demand during ozonation by 23 mg L-1 and 1.5 mg L-1, respectively. Ozonation (1.0 -1.2 mg O-3 mg DOC-1) efficiently reduced concentrations of persistent TrOCs and supplied sufficient dissolved oxygen (>30 mg L-1) for fully oxic operation of the short SAT with negligible Mn2+ mobilization (<50 mu g L-1). Overall, the examined hybrid process provided DOC reduction of 88% to a value of 1.2 mg L-1, similar to conventional SAT, while improving the removal of TrOCs and efficiently preventing manganese dissolution. (C) 2015 Elsevier Ltd. All rights reserved.

Long-term column studies with ozonated secondary effluent were conducted to evaluate the removal of dissolved organic carbon (DOC) and to assess formation and stability of the oxidation by-product bromate in combined ozonation and managed aquifer recharge (MAR) systems. DOC removal during simulated MAR was continuously increased from approximately 20 to 40% by pretreatment with ozone indicating the high potential of this combination to remove disinfection by-product (DBP) precursors. This improvement in DOC removal was likely caused by transforming DOC into fractions that are more amenable to biodegradation, as well as the supply of dissolved oxygen favouring aerobic degradation processes. Bromate formation during ozonation of secondary effluent from the Berlin-Ruhleben WWTP exceeded the limit of the EU Drinking Water Directive at a specific ozone consumption of >0.9–1.0 mg O 3 /mg DOC 0 . During oxic infiltration, no significant removal of bromate could be observed. Under anoxic conditions, bromate concentration was efficiently reduced. Additional biodegradation tests in small-scale columns indicated a simultaneous consumption of nitrate and bromate as electron acceptors.

The oxidation of secondary effluent with ozone and O3/H2O2 (peroxone) was evaluated in batch experiments as pre-treatment for soil aquifer treatment for non-potable reuse purposes. The addition of hydrogen peroxide improved the reduction of ozone-resistant compounds with an optimized radical formation at 0.5 mol H2O2/mol O3. However, the improvement of radical formation was shown to be limited to approximately 30–40% independent from ozone dosage. Also a preozonation step did not accelerate efficiency of subsequent peroxone treatment. Thus, other treatment options, such as an increase of ozone dosages, need to be considered for more efficient removal of ozone-resistant compounds. However, the peroxone process might still be a promising option for oxidation of bromide containing effluents, since a reduction of bromate formation can allow the application of higher ozone dosages.

Activated carbon is investigated as adsorptive barrier for organic micropollutants (OMP) within the Berlin water cycle. In a pilot plant using granular activated carbon (GAC) as upper layer in dual-media filtration, OMP concentrations in treated wastewater could be reduced without any negative impact on filtration efficiency. OMP breakthroughs occurred after shorter runtimes than estimated according to isotherm experiments with powdered activated carbon (PAC). Batch adsorption tests comparing the used GAC to new GAC showed that the capacity of the used GAC was not exhausted, indicating that besides direct site competition, pore blocking is also responsible for the poor GAC performance. A pilot plant application of PAC of the same type as GAC showed significantly higher OMP removals at lower dosages, taking advantage of immobilization of PAC particles in the filters. Both PAC and GAC applications can be integrated into tertiary wastewater treatment without significant constructional changes.

Advanced treatment of wastewater is currently being discussed throughout Europe in an effort to reduce emissions to surface waters and protect drinking water resources. In this study the combination of adsorption onto powdered activated carbon (PAC) and coagulation/filtration was investigated as a single advanced treatment step for simultaneous removal of organic micropollutants (OMPs) and phosphorus from domestic secondary effluent. Two pilot-scale dual-media filters were operated in parallel for a period of 4 months to investigate the influence of PAC addition on filtration parameters and determine removal of 14 selected OMPs. OMP abatement in the PAC filter was compared to batch tests and correlated with relative removal of UV254 absorption (UVA254). Stable operation with an average PAC dose of 8 mg/L and a removal >90% of total suspended solids was possible for filtration cycles of 24 h. The results show that PAC dosing does not negatively affect either filtration resistance or removal of phosphorus by precipitation. Concentrations of benzotriazole and carbamazepine were reduced by >70%, while sulfamethoxazole and diclofenac were removed to the extent of 40–60% (median values). Relative OMP removal showed only minor fluctuations despite occasionally strong changes of influent concentrations. Moreover, the results indicate that contact times were not sufficient for complete PAC exhaustion before separation and that further adsorption onto embedded PAC in the filter significantly contributes to overall OMP removal.

Ozonation is known as an efficient treatment to reduce the concentration of many trace organic compounds from WWTP effluents, but the formation of unknown and possibly persistent and toxic transformation products has to be considered. In this paper tertiary treatment of wastewater by the combination of ozone and soil aquifer treatment was investigated with respect to the removal of the antiepileptic drug carbamazepine (CBZ, 10 mu g/L) and its transformation products. Batch tests and pilot experiments confirmed efficient removal of carbamazepine from secondary effluent by ozone. With typical ozone consumption of 0.7 mg O-3/mg DOC0, approx. 50% of the transformed CBZ was detected as its primary product 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM). Structure proposals and a formation pathway were elaborated for a total of 13 ozonation products of CBZ. In subsequent biological treatment BQM turned out to be more effectively biodegraded than CBZ. Its aldehyde group was quickly oxidized to a carboxylic acid (BaQM which was removed in sand column experiments. Most of the minor ozonation products of CBZ persisted in sand column experiments with residence times of 5-6 days. Non-target screening of column effluent revealed no formation of persistent biotransformation products. (C) 2013 Elsevier Ltd. All rights reserved.

This study investigates the applicability of the rapid small-scale column test (RSSCT) concept for testing of granular activated carbon (GAC) for organic micro-pollutants (OMPs) removal from wastewater treatment plant (WWTP) effluent. The chosen experimental setup was checked using pure water, WWTP effluent, different GAC products, and variable hydrodynamic conditions with different flow velocities and differently sized GAC, as well as different empty bed contact times (EBCTs). The setup results in satisfying reproducibility and robustness. RSSCTs in combination with WWTP effluent are effective when comparing the OMP removal potentials of different GAC products and are a useful tool for the estimation of larger filters. Due to the potentially high competition between OMPs and bulk organics, breakthrough curves are likely to have unfavorable shapes when treating WWTP effluent. This effect can be counteracted by extending the EBCT. With respect to the strong competition observed in GAC treatment of WWTP effluent, the small organic acid and neutral substances are retained longer in the RSSCT filters and are likely to cause the majority of the observed adsorption competition with OMPs.

To cope with occurring traces of organic contaminants in the effluent of waste water treatment plants, ozonation is a suitable technical treatment method. However, there is an ongoing discussion about the necessity of a post-treatment of ozonation effluents to remove possible toxic ozonation by-products. This study compares a dual media filter (DMF) and a biological activated carbon filter (BAC), which were used for ozonation post-treatment, and were also designed as coagulation filters for tertiary phosphor removal. The results of this study demonstrate that both rapid filters performed similarly in respect to DOC reduction and oxygen demand, and could also be used for tertiary phosphorus removal without any impairments. A comparison of a serial mode of the DMF and the BAC with a slow sand filter, which was used as a surrogate for an infiltration pond, showed that this two-stage process could increase the degradation of the DOC, but was not able to remove the entire biodegradable DOC.