In 2015, the town of El Port de la Selva in Spain implemented soil-aquifer treatment (SAT) using tertiary treated wastewater effluents to replenish the local potable aquifer. This study evaluated the initial phase of this indirect potable water reuse system including a characterization of hydraulic conditions in the aquifer and monitoring of microbial contaminants and 151 chemicals of emerging concern (CECs). The combined treatment resulted in very low abundances of indicator bacteria, enteric viruses and phages in the monitoring wells after three days of infiltration and a reduction of antibiotic microbial resistance to background levels of local groundwater. After tertiary treatment, 94 CECs were detected in the infiltration basin of which 15 chemicals exceeded drinking water thresholds or health-based monitoring trigger levels. Although SAT provided an effective barrier for many chemicals, 5 CECs were detected above health-based threshold levels in monitoring wells after short hydraulic retention times. However, additional attenuation is expected due to dilution prior to abstraction via downstream drinking water wells and during granular activated carbon (GAC) filtration, which was recently installed to mitigate residual CECs. Overall, the results demonstrate that indirect potable water reuse can be a reliable option for smaller communities, if related risks from microbial and chemical contaminants are adequately addressed by tertiary treatment and subsequent SAT, providing sufficient hydraulic retention times for pathogen decay and CEC removal.

Elevated levels of active pharmaceutical ingredients (API) have been detected in the Baltic Sea for many years. These APIs are often discharged from hospitals, households, pharmaceutical manufacturing plants, and animal farms, among other sources. As APIs are not completely degraded in municipal wastewater treatment plants (WWTP), they are then transported to the Baltic Sea. Although research on the effects of APIs in the Baltic Sea has been ongoing, the consequences of API discharges on the environment, in terms of potentially risky ecological effects, have not yet been fully evaluated. The European Union’s Interreg Baltic Sea Region programme funded the Clear Waters from Pharmaceuticals (CWPharma) project, which quantified API loading into the Baltic Sea from six river basin districts. Seven Baltic Sea Region (BSR) countries were involved as CWPharma partners (Denmark, Estonia, Finland, Germany, Latvia, Poland and Sweden). Surface water, soil, and sediment samples were collected from coastal, rural, and agricultural locations and analysed for up to 80 APIs. By comparing the API concentrations detected in rivers with predicted no-effect levels (PNEC), the environmental risk of individual APIs was quantified. A GIS-based model was developed which allowed illustration and assessment of API loads into the Baltic Sea coming from the project partner countries, as well as evaluation of the impacts of various emission reduction scenarios. Different types of emission reduction measures were proposed. Reductions of API emission from WWTPs through the application of advanced wastewater treatment (AWT) technologies were experimentally validated at full- and pilot-scale. AWT technologies tested in CWPharma included full-scale ozonation and various post-treatment technologies, such as moving bed bioreactors, constructed wetlands, deep bed filters using sand/anthracite, and granular activated carbon. Additionally, 21 recommendations for other reduction measures focused on improving collection and disposal of unused pharmaceuticals and pharmaceutical waste, targeting various groups and emitters, were also developed. By simulating the variety of API reduction methods within the API loading model, the most effective measures for reducing API emissions could be determined. Similarly, both the costs and global warming potential of upgrading various classes of WWTPs with AWT in the form of ozonation or activated carbon were calculated for each CWPharma project partner country. This report summarizes the most important recommendations elicited from the CWPharma project.

Zur Verminderung von Spurenstoffeinträgen in Oberflächengewässer wurden bereits einige Kläranlagen in Deutschland und der Schweiz um eine weitergehende Reinigungsstufe (Ozon oder Aktivkohle) erweitert. Zur Erzielung einer gleichbleibenden Spurenstoffelimination und einer gleichzeitigen Vermeidung von Fehldosierungen (Kosten, Rohstoffeinsatz) werden verlässliche Messverfahren und robuste MSR-Konzepte (Mess-, Regel- und Steuerung) benötigt. Im Rahmen des Projekts „MeReZon" (Schnelle und zuverlässige Messtechnik und Steuer-/Regelkonzepte für eine weitergehende Abwasserreinigung) wurde an einer Pilot-Ozonanlage zur Behandlung von gereinigtem Abwasser untersucht, unter welchen Randbedingungen eine verlässliche Onlinemessung möglich ist. Dabei wurde u.a. die Leistungsfähigkeit eines neu entwickelten Ultraschallreinigungsmoduls zur Vermeidung einer Messwertdrift durch Fouling untersucht und mit den Sonden bzw. Reinigungsmodulen anderer Hersteller in verschiedenen Konfigurationen verglichen. Dabei wurden deutliche Unterschiede festgestellt. Darauf aufbauend wurde das bestehende MSR-Konzept der Ozonanlage optimiert und ein alternierender Messbetrieb, d.h. abwechselnde Beschickung einer Messsonde mit Zu- bzw. Ablauf der Ozonung, implementiert. Die Ergebnisse zeigen, dass mit dem optimierten MSR-Konzept eine stabile Abnahme des SAK254 (<U+0394>SAK254) erzielt werden kann, welche mit der Spurenstoffelimination korreliert. Die erfolgreiche Umsetzung des alternierenden Messbetriebs ermöglicht die Ermittlung der SAK254 Abnahme mit nur einer Messsonde, was prinzipiell Vorteile bei einer Regelung der Ozondosis auf ein stabiles <U+0394>SAK254 mit sich bringt. Zudem konnte gezeigt werden, dass die Onlinemessung der Fluoreszenz eine praktikable Alternative zum <U+0394>SAK254 darstellt, da diese ebenfalls eine Änderung des Ozonbedarfs integral erfassen kann und mit der Spurenstoffelimination korreliert. Die gewonnenen Ergebnisse bieten Messgeräteherstellern wertvolle Anhaltspunkte wie sie ihre Onlinesonden und Reinigungsmodule weiter optimieren können. Das entwickelte MSR-Konzept bzw. der alternierende Messbetrieb kann von Betreibern von Ozonanlagen auf kommunalen Kläranlagen zur Optimierung bestehender oder zukünftiger Anlagen genutzt werden.

The overall aim of the CWPharma project is to reduce the load of active pharmaceutical ingredients (APIs) going into the aquatic environment and especially the Baltic Sea. Municipal wastewater treatment plants (WWTPs) are relevant point sources of APIs, as they treat the wastewater from public households, hospitals and industry of the connected catchment area. However, conventional "state-of-the-art" WWTPs can only remove some APIs, which are either easily biodegradable and/or absorbable to activated sludge, whereas other APIs can pass the WWTP with minor to no reduction. Therefore, reduction of a broad range of APIs can only be achieved by using targeted advanced treatment techniques such as ozonation or powdered and granular activated carbon, respectively, which have already been applied on full-scale for API removal in wastewater treatment in Germany and Switzerland and proven their practical and economical suitability. At the usual applied ozone doses, ozonation of secondary effluent does not mineralize (convert an organic substance into inorganic matter) but transforms organic compounds into smaller and (usually) more biodegradable compounds. Secondary effluent is a complex water matrix consisting of hundreds of different organic substances, and it is not feasible to determine all possible transformation products and oxidation by-products, which might be created by the ozonation process. Thus, utilities and water authorities sometimes struggle with the uncertainties of the ozonation process as they perceive difficulties to judge whether oxidation of the organic matrix is beneficial or if it is creating more problems. As chemical analysis of the water only provides quantitative data for known APIs and transformation products for which chemical standards are available, effect-based ecotoxicological test systems can be used to assess the integrated actual toxicity of the whole water matrix. Based on previous research compiled by Völker et al. (2019), ozonation has a positive impact on several toxicological endpoints. But there are also indications that ozonation can create negative effects for a few toxicological endpoints that can be reduced by a suitable post-treatment. However, only little knowledge is available regarding suitable post-treatments and which ecotoxicological test systems are appropriate to evaluate their impact. In addition, post-treatment options might also have beneficial impacts on water quality parameters, APIs and transformation products. Thus, this report will evaluate different aspects regarding the impact of ozonation and its posttreatment options on (i) water quality parameters, (ii) APIs and transformation products (TPs) and (iii) ecotoxicological effects. The evaluation was conducted at three WWTPs in Linköping (SE), Kalundborg (DK) and Berlin (DE) and different post-treatment options such as moving bed bioreactors (MBBR), deep-bed filters, and a constructed wetland.

The overall aim of the "Clear Waters from Pharmaceuticals" (CWPharma) project is to provide guidance on how to reduce the load of active pharmaceutical ingredients (APIs) entering the aquatic environment and especially the Baltic Sea. Even though different methods for reducing the amount of APIs entering the wastewater exist and, thus, "end-of-pipe" measures are also necessary. API usage cannot be completely avoided. Municipal wastewater treatment plants (WWTPs) are relevant point sources of APIs as they treat the wastewater from public households, hospitals, and industry of the connected catchment area. However, conventional "state-of-the-art" WWTPs can only remove APIs that are either easily biodegradable and/or absorbable to activated sludge, whereas others can pass the treatment process with no or only minor reductions. Therefore, reduction of a broad range of APIs can only be achieved by using targeted advanced wastewater treatment (AWT) techniques, such as ozonation or application of powdered and granular activated carbon. All of these technologies for API removal are already used at full-scale WWTPs and have proven their practical and economical suitability. This guideline is meant to provide an overview on how to plan, start, and operate AWT technologies for API elimination. The recommendations are based on the experiences and results from the CWPharma project, but also on the available knowledge from Germany and Switzerland, which is collected and distributed by competence centres such as the German Micropollutants Competence Centre Baden-Württemberg (KomS) Verfahrenstechnik Mikroverunreiniungen and the Swiss Plattform as well as by expert groups from the related water associations. Membrane separation via dense membrane such as nanofiltration (NF) or reverse osmosis (RO) was not considered in this guideline, as both technologies produce a brine with high API concentrations. At coastal WWTPs, this brine might be discharged directly to the sea in order to protect fresh water ecosystems, but this would not reduce the API load to the Baltic Sea. Thus, the brine also requires treatment, which makes this approach less economical in comparison to the other established API removal technologies.

In this report, the treatment efficacy of four demonstration sites combining constructed wetlands with engineered pre- or post-treatment processes for wastewater treatment is evaluated focusing on the achievement of effluent quality suitable for water reuse. Special focus is given on the performance of disinfection processes and their combination with constructed wetlands targeting water reuse applications for treatment of primary effluent and polishing of secondary effluent. Monitoring results of the demonstration sites are compared to five existing legally binding national water reuse regulations of European countries, highlighting similarities and differences between these regulations. Results are furthermore compared to the EU-level water reuse standards proposed by the European Commission in May 2018: “Proposal for a Regulation of the European Parliament and of the Council on minimum requirements for water reuse” (COM337, 2018). The first part of this report focuses on the comparison of the application of water reuse in the EU and the different national regulations in Cyprus, France, Greece, Italy and Spain – countries, which incorporated water reuse standards into their national laws. Water reuse legislations vary significantly among the EU member states. Different reclaimed water uses associated with different water quality classes and varying levels of detail in definitions are considered in each regulation. The number of classes defined in the regulations varies from 1 class including 3 categories of reuse purposes in Italy to 12 classes including 24 categories of reuse purposes in Spain. The allocation of a reuse purpose to the relevant class in the different regulations may change when looking at the level of definition of the regarded reuse purpose. For example, differences in individual definitions for use types of agricultural products, such as irrigation of a “crop consumed processed” and a “vegetable consumed cooked”, may lead to the inclusion or exclusion of the same reuse purpose into different classes in some of the regulations. The same is true for restrictions of irrigation types, which can differ regarding temporal or spatial restrictions. The number of water quality parameters which are restricted by each national regulation also differs considerably, ranging from six parameters regulated by the French water reuse legislation to 55 parameters regulated in Italy. In certain cases, the number of restricted parameters can increase up to 80 (Greek reuse regulation for WWTP > 100,000 p.e.) or even 90 in Spain (when requested by regional government depending on external regulations concerning the protection of the receiving environment). Apart from defined water reuse classes, regulated parameters and relevant limit values, the national reuse regulations also differ with regard to compliance requirements, which further complicates evaluations. While some regulations specify a percentile of samples required to comply with the set limit values (e.g. 80% of annual samples need to meet the limit), others require the annual mean to comply with the limits. In addition, sometimes maximum allowed deviation limits for samples exceeding the limit values are defined. As these specifications may not only vary among different regulations but also for different parameters in the same regulation, as well as among different quality classes for the same parameter in the same regulation, an evaluation of monitoring results of the different demonstration sites in regard to the national water reuse regulations is challenging and might become confusing. The proposal of the European Commission for an EU-level regulation on water reuse includes 4 water quality classes and 4 restricted quality parameters (with two additional for certain reuse purposes). However, water reuse in this proposal is only limited to agricultural irrigation. In contrast to national regulations, the EC proposal includes performance criteria for unrestricted irrigation on top of effluent quality limits. The variability of standards and definitions for water reuse across European countries poses a barrier for the wide application of reclaimed water, resulting in an underdevelopment of the water reuse sector in Europe. The second part of the report provides a comparison of the monitoring results of four AquaNES constructed wetlands (CW) demonstration sites in Greece and Germany with European water reuse regulations. Because of the regulatory heterogeneity described above, a direct comparison of the different European water reuse regulations with monitoring data of the demonstration sites is only possible for well-defined cases, as the allocation to the relevant class in the different regulations may change when looking at the level of definition of the regarded reuse purpose. Therefore, three specific reuse cases have been defined (for details see 3.1): - restricted irrigation (irrigation of beans using drip irrigation), - unrestricted irrigation (irrigation of tomatoes using any irrigation methods) and - urban irrigation (irrigation of a public park). For both Greek sites, monitoring results were evaluated regarding respective water reuse classes of these use cases for all national legislations, while for both German sites, evaluation was only done in respect to the standards proposed by the European Commission. The two Greek sites, Antiparos and Thirasia wastewater treatment plants (WWTP), are both located on the Cyclades island group of the Aegean Sea, and are full-scale WWTPs subjected to significant season fluctuations in the hydraulic and pollution loads between summer and winter periods. The combination of a two-stage CW with chlorination-disinfection realized at Antiparos WWTP results in water quality suitable for “restricted irrigation” according to the French and Greek regulation as well as to the EU-level proposed regulation (COM337, 2018). TSS and electrical conductivity (E.C.) have been identified as the two main parameters limiting possible reuse options. Before implementation of reconstruction measures in clogged wetland beds and pond, and managerial changes for optimization of plant performance (restriction of sewage trucks per day during peak season) some limits for “restricted irrigation” were exceeded. This was mainly due to elevated TSS concentrations and temporarily due to elevated concentrations of E. coli resulting from insufficient chlorination at peak flows that exceeded the design capacity of the plant. Different constructional and managerial improvements in this plant were found to improve and equalize the performance of the plant under peak and low flow conditions in summer and winter periods. However, high values for E.C. in WWTP effluent would prevent application in countries with reuse legislations that include this parameter (i.e. Cyprus, Italy, Spain). The Thirasia WWTP combines primary treatment and photocatalysis before horizontal subsurface flow (HSSF) CWs with subsequent ultrafiltration and chlorination. The quality of treated effluent meets the requirements for the defined case of “restricted irrigation” only according to the French regulation and the EU-level proposal. Parameters limiting the effluent’s suitability for reuse are more variable among the three defined reuse purposes and among the different reuse regulations compared to the Antiparos WWTP. The only parameter exceeding the Greek limits for “restricted irrigation” is total nitrogen. Performance of the HSSF CW regarding total nitrogen (TN) removal is not optimal, thus, the average concentration of total nitrogen in WWTP effluent (50 mg/L, n=24) exceeds the limit of class 3 of the Greek reuse regulation (45 mg/L). However, values since August 2018 show an improved removal of TN that always meets the limit (mean: 34 mg/L, n=11). Further analyses are suggested to ensure the sufficient removal of TN to reliably meet the Greek limit for water reuse. Testing different dosages of titanium dioxide (TiO2) in the photocatalysis stage led to the conclusion that adding the catalyst does not considerably improve the removal of relevant parameters, and therefore is economically unfeasible. Similar and relevant removal for BOD5 and COD (~60%). and TN (~30%) were found regardless of TiO2 dosage, even without addition of the catalyst and associated chemicals. Thus, it is recommended to run this stage as aeration stage with sedimentation. In the two German sites (Schönerlinde and Erftverband), polishing stages were tested at pilot scale after full-size WWTPs. Effluent quality was evaluated for compliance with the proposed EU-level water reuse quality standards. In Schönerlinde, the combination of ozonation with two CWs differing in substrate composition (sand or lava gravel with biochar) was demonstrated. Regarding E. coli, most of the removal was accomplished during ozonation (>2 log units), which also achieved removal of various micropollutants (see D3.2). The subsequent removal in both wetland types was similar, reaching a further reduction of E. coli by about 0.5 log units and resulting in effluent quality that meets class B limits according to the proposed limits of COM337. When ozonation was not in operation, the conventional wetland (with sand as substrate) still achieved a similar effluent concentration for E. coli (2.7 logreduction), demonstrating the robustness of this combination for water reuse purposes. TSS and turbidity were well removed by CWs reaching the best class A limit for these parameters. Overall, the combination of ozonation with CWs for polishing of WWTP effluent is a good option to achieve a very good effluent quality suitable for water reuse, with the potential to reach class A quality suitable for irrigation of crop that is consumed raw with further reduction of E. coli by about 0.5-1 log units. At Erftverband, a full-scale system is built at WWTP Rheinbach for flexible treatment of combined sewer overflow (CSO) during storm events, and polishing of WWTP effluent during dry weather. Three pilot-scale retention soil filters (RSF, specific form of vertical flow CWs for the treatment of rain water and/or wastewater) were tested for >3 years with one system containing an additional layer of activated carbon, and one RSF being subjected to simulated CSO events. Regarding E. coli, only class C limit is achieved (mean log removal in wetlands about 1.5). During CSO events with high peaks of E. coli in the influent of the RSF, effluent quality does not meet the requirements for any reuse purpose defined in the EC proposal, even though a log removal of about 2.5 is achieved. A temporary disinfection during heavy rain events would be necessary in order to provide effluent suitable for water reuse. BOD5 and TSS do not limit water reuse according to the EC proposal, thus, a sufficient disinfection would allow water reuse even for class A reuse purposes. Overall, systems, which include a combination of CWs with some sort of technical system with disinfection capabilities, achieved class B effluent quality according to the proposed EU-level standards. The Erftverband site containing a natural treatment stage without an additional disinfection achieved class C quality when not subjected to CSO events. Thus, effluents of all sites would be suitable for the following reuse purposes defined in the EC proposal: (a) food crops consumed raw, where the edible portion is produced above ground and is not in direct contact with reclaimed water; (b) processed food crops and (3) non-food crops including crops to feed milk- or meat-producing animals. Whereas in class B the irrigation method is unrestricted, in class C only drip irrigation is allowed. The combination of CWs with disinfection treatment processes for wastewater treatment in small communities is a promising option for the wider application of water reuse, at least for restricted irrigation purposes.

Upgrading wastewater treatment plants (WWTPs) with advanced technologies is one key strategy to reduce micropollutant emissions. Given the complex chemical composition of wastewater, toxicity removal is an integral parameter to assess the performance of WWTPs. Thus, the goal of this systematic review is to evaluate how effectively ozonation and activated carbon remove in vitro and in vivo toxicity. Out of 2464 publications, we extracted 46 relevant studies conducted at 22 pilot or full-scale WWTPs. We performed a quantitative and qualitative evaluation of in vitro (100 assays) and in vivo data (20 species), respectively. Data is more abundant on ozonation (573 data points) than on an activated carbon treatment (162 data points), and certain in vitro end points (especially estrogenicity) and in vivo models (e.g., daphnids) dominate. The literature shows that while a conventional treatment effectively reduces toxicity, residual effects in the effluents may represent a risk to the receiving ecosystem on the basis of effect-based trigger values. In general, an upgrade to ozonation or activated carbon treatment will significantly increase toxicity removal with similar performance. Nevertheless, ozonation generates toxic transformation products that can be removed by a post-treatment. By assessing the growing body of effect-based studies, we identify sensitive and underrepresented end points and species and provide guidance for future research.