Subsurface passage as utilized during river bank filtration and artificial groundwater recharge has shown to be an effective barrier for multiple substances present in surface waters during drinking water production. Additionally it is widely used as polishing step after wastewater treatment. However, there are limitations concerning the removal of DOC and specific trace organics. The project ”OXIRED“ aims at assessing possibilities to overcome these limitations by combining subsurface passage with pre-oxidation by ozone. In the first phase of the project, laboratory-scale column experiments were conducted in order to quantify removal for different settings under varying conditions. In a previous study different combinations of advanced oxidation and subsurface passage were evaluated concerning their potential removal efficiency and practical implementation on the basis of existing, published experiences and theoretical considerations. Two different scenarios were identified as promising for experiments in laboratory-scale columns with surface water and sewage treatment plant effluent: (A) surface water - oxidation - groundwater recharge and (B) surface water - short bankfiltration - oxidation - groundwater recharge. The investigations were designed to lead to recommendations for the implementation of a combined system of subsurface passage and advanced oxidation in pilot scale experiments that will be carried out in the second phase of the project. Prior to column experiments, batch tests following the RCT-concept by Elovitz and von Gunten (1999) were carried out to characterize the reaction of ozone with the investigated water qualities [1]. Additional batch ozonation tests with subsequent analysis of biodegradable dissolved organic carbon (BDOC) were conducted in order to determine optimal ozone doses for DOC removal in column experiments. For laboratory-scale experiments a set of 8 soil columns (length: 1 m; diameter: 0.3 m) was operated at TUB to evaluate the effects of pre-ozonation of different source waters (secondary effluent, surface water, bank filtrate). Ozonation was conducted with gaseous ozone in a 13-L stirred tank reactor. Specific ozone doses of 0.7 mg O3/mg DOC0 and 0.9 mg O3/mg DOC0 were investigated. Trace organic compounds to be targeted were identified in a prior literature study on existing data on subsurface removal. Results from laboratory-scale soil column experiments led to recommend specific ozone doses (z) of 0.7 mg O3/mg DOC0 for the following technical- and pilot-scale applications. Removal of surface water DOC in the soil columns was increased from 22% without ozonation to 40% (z = 0.7) and 45% (z = 0.9) with preozonation and the DOC in the column effluent reached the level of tap water in Berlin within less than one week of retention time. At bank filtration and artificial recharge sites in Berlin similar removal rates were only observed within 3 - 6 months of retention [2]. The transformation of many trace compounds was efficient with specific ozone doses of 0.6-0.7 mg O3/mg DOC0. Realistic surface water concentrations of carbamazepine,sulfamethoxazole, diclofenac and bentazone were reduced below the limits of quantification (LOQ). The pesticides diuron and linuron were reduced close to LOQ. The substances MTBE, ETBE and atrazine were only partly transformed during ozonation. For efficient transformation of these substances, higher ozone doses or an optimisation of the oxidation process, for example as advanced oxidation process (AOP), should be considered. Operating a preceding bank filtration (scenario B) will enhance the transformation efficiency of MTBE and ETBE. With similar ozone consumption the transformation of MTBE and ETBE was increased by 27-31% and 28-33% of the original removal, respectively. Other investigated compounds were efficiently transformed during ozonation of surface water independently of the preceding bank filtration step. For the removal of bulk organic carbon only little improvement was observed for scenario B. Overall DOC removal increased from 45% with direct ozonation of surface water to up to 50% with a preceding soil column. Despite the presence of relevant bromide concentrations (~ 100 µg/L) formation of the oxidation by-product bromate was not observed (< 5 µg/L). However, this could also be a result of analytical problems, as later spiking tests showed. Formation of brominated organic compounds was also not observed. Adsorbable organic bromide (AOBr) even decreased by 50 - 60% for secondary effluent and 80 - 90% for surface water. The reduction of AOBr concentrations was accompanied by an increase of inorganic bromide by up to 40 µg/L during ozonation of surface water. In the two conducted in vitro genotoxicity tests (Ames test, micronucleus assay) no genotoxicity caused by ozonation of water samples was observed. Testing for cytotoxicity (glucose consumption rate, ROS generation) showed positive results in several samples. However, a systematic attribution of toxic effects to ozonation or subsequent soil passage was not possible. Reasons for cytotoxic effects were not evaluated within the scope of this project but it is assumed that they were caused by unknown cofactors. These results show that the objectives of enhanced removal of trace organics and DOC by combining ozonation and subsurface passage are well met. Further investigations need to confirm this for the pilot scale, especially taking into account the formation, retention and toxicity of oxidation by-products.

Investigations on the behavior of bulk organics and trace organic compounds in a temperated soil column system are reported. Objective of the research was to assess the importance of temperature for the degradation of bulk and trace organics. The analysis of the bulk organic behavior showed a fast mineralization of easy degradable organic carbon in the first few centimeters of the columns, which does not seem to be temperature-dependent. Along the further infiltration path an influence of the different temperatures on the bioactivity was clearly visible. However, a significant increase of mineralization potential of bulk organic compounds with increasing temperature was shown. The monitoring of the single organic pollutants Iopromide, Sulfamethoxazole and naphthalenedisulfonic acids showed that temperature has an influence on the degradation behavior of the monitored compounds. In most cases higher temperatures increased the mineralization potential.

Eine Forschungsgruppe derTechnischen Universität Berlin beschäftigt sich mit dem Verhalten von gelöstem organischen Kohlenstoff, DOC und organischen Einzelstoffen beider Uferfiltration. Die Ergebnisse zeigten, dass sowohl oxische als auch anoxisch/anaerobe Infiltrationsbedingungen zu einem ähnlich niedrigen DOC führen können. Unter oxischen Verhältnissen ist zur Mineralisierung des bioverfügbaren DOC (BDOC) nur eine einmonatige Bodenpassage notwendig, während es unter anoxisch/anaeroben Verhältnissen aufgrund der langsameren Abbauklnetik bis zu sechs Monate dauern kann. Bezüglich der Spurenstoffe konnte gezeigt werden, dass das Röntgenkontrastmittel lopromid in allen Felduntersuchr./ngen schnell entfernt wurde. Das Antibiotikum Sulfamethoxazol wurde unter anoxisch/anaeroben Verhältnissen effektiver entfernt (bis zu 80%), während unter oxischen Bedingungen maximal 50% der Ausgangskonzentration abgebaut wurden. Zusammenfassend kann die Uferfiltration als eine durchaus sehr.wirksame Stufe zur Entfernung von Organika bewertet werden.

Treated municipal wastewater may contain pathogenous micro-organisms and persistent trace organics leading to problems when being discharged into the surface waters. The investigations of the research project PILOTOX aimed at their elimination from treated municipal wastewater through subsequent oxidation by ozone. For this purpose, the TU Berlin (department of Water Quality Control) in cooperation with the Berliner Wasserbetriebe at the WWTP Berlin-Ruhleben, carried out several tests with a pilot plant by the company WEDECO aiming at the ozonation of the effluent. The results show that ozonation is a suitable procedure to remove and transform respectively, substantial quantities of the pharmaceutical residues detected in the effluent of the Ruhleben WWTP and, at the same time, to achieve a germ reduction complying with the threshold values stipulated in the European directive on bathing water. It was found that many trace organics such as the anti-epilepticum carbamazepin or the hormone estron can be removed at a very low ozone dosage to below their analytic detection limit. The X-ray contrast media however, turned out to be more resistant: even at a high ozone dosage, their concentrations could be reduced only partially. In this context, the tests detected that through the combination of H2O2 and ozone, an elevated elimination rate for the substances iopamidol and iohexol can be achieved. The elimination of the analysed trace organics correlated with the decrease of the water’s UV activity. Thus, it is advisable to use the rapidly and simply traceable parameter SAK254 as process control parameter to determine the necessary ozone dosage. In addition, it could be proven that ozonation increases the biological degradability of water components. Laboratory test looking at recontamination levels however, indicate that the threshold values stipulated in the EU directive on bathing water will not be exceeded if the ozone-treated effluent is mixed with water originating from the River Spree. A study regarding the water’s acute and chronic toxicity, to its gene toxicity and endocrine impacts, revealed that – compared to the untreated effluent - no eco-toxicological risk potential can be detected in the ozone-treated water samples.The specific treatment cost covering the large-scale application of ozone treatment at the WWTP Ruhleben range between 1,0 cent/m3 and 2,2 cent/m3, of which the investment costs account for a percentage of 20-30 %.

Recent research projects have shown a good suitability of the ozonation process to transform trace concentrations of most pharmaceuticals in wastewater treatment plant (WWTP) effluents. The concentrations of carbamazepine and 17a-ethinylestradiol, for instance, were reduced below their detection limits by use of ozone dosages resulting in a specific ozone consumption of 0.5 mg O3/ mg DOC0. At the same time a good disinfection performance was achieved. The given hygienic requirements of the EU bathing water directive (e.g. 2000 N / 100 ml faecal coliforms) are fulfilled without the formation of bromate (< 10 µg/L). As technical control parameter of the ozonation process usually the residual ozone in the liquid phase or in the off-gas are used. However, at very low specific ozone consumptions, ozone reacts instantaneously with dissolved compounds and can not be detected. Hence alternative parameters should be used for effective operation control. The present paper evaluates the relation between UVA decrease and the removal of different compounds (endocrine disrupting compounds, pharmaceuticals, iodinated Xray contrast media), microbial parameters and bromate formation. The results can be used as a guideline for the control of the oxidation performance at large scale ozonation units.

More than two years of monitoring data from a bank filtration site in Berlin, Germany, and a long retention soil column system (30 m) were analyzed to study the influence of redox conditions on the degradation of bulk organics. Dissolved organic carbon (DOC), UV-absorption at 254 nm (UVA254) and liquid chromatography with online carbon detection (LC-OCD) was employed to receive qualitative and quantitative information about the fate of different fractions of DOC. It was found that the kinetics of DOC-degradation depend significantly on the dominant redox conditions during infiltration. A faster mineralization of biodegradable DOC was observed during oxic soil passage (~1 month). Anoxic infiltration led to a comparable residual DOC-concentration, but 3-6 months were required for complete removal of biodegradable DOC (BDOC). LC-OCD measurements revealed that the fraction of polysaccharides (PS) is removed very fast during infiltration in the field. Under strictly anoxic conditions the PS were more stable. The fractions of humic substances, building blocks and low molecular weight acids were degraded partially, independently from the redox potential, while the change in aromaticity of the residual DOC was influenced by the dominant redox conditions.

Die TU-Forschungsgruppe beschäftigt sich mit dem Verhalten von DOC und organischen Einzelstoffen bei der Uferfiltration. Die Forschung soll Einblick in die Vielzahl von Einflussfaktoren geben, die das Verhalten der Organik in der Bodenpassage beeinflussen. Unterschiedliche Redoxverhältnisse, Aufenthaltszeiten und Bodenbeschaffenheiten beeinflussen den Abbau der Organik. Die Forschung im Rahmen des NASRIProjektes konzentrierte sich in der ersten Phase auf ein umfangreiches Feldmonitoring, welches im Zeitraum Mai 2002August 2005 durchgeführt wurde. Dazu wurden drei Feldstandorte in Berlin ausgewählt, an welchen ein deutlicher Einfluss von behandeltem Abwasser auf das Oberflächenwasser vorliegt. Zusätzlich wurde eine Vielzahl von Experimenten an Bodensäulenanlagen durchgeführt. Neben einem 30 mBodensäulensystem in Berlin- Marienfelde, wurden eine redoxgeregelte Bodensäulenanlage und eine temperaturgeregelte Bodensäulenanlage für die Untersuchungen aufgebaut. Die Feldund Bodensäulenproben wurden mittels DOC, SAK, LC-OCD, differenziertem AOX und Spurenstoffanalytik (HPLC-FLD und HPLC-MS/MS) untersucht. Die Ergebnisse zeigten, dass sowohl oxische als auch anoxisch/anaerobe Infiltrationsbedingungen zu einem ähnlich niedrigen DOC führen können. Unter oxischen Verhältnissen ist zur Mineralisierung des BDOC nur eine einmonatige Bodenpassage notwendig, während es unter anoxisch/anaeroben Verhältnissen aufgrund der langsameren Abbaukinetik bis zu 6 Monate dauern kann. Die Ergebnisse der DOCFraktionierung mittels LC-OCD zeigten, dass die Fraktion der Polysaccharide unter allen Bedingungen sehr schnell abgebaut wurde. Dagegen wurde für die anderen Fraktionen (Huminstoffe, Building Blocks etc.) nur eine partielle Entfernung beobachtet. Bezüglich der Spurenstoffe konnte gezeigt werden, dass das Röntgenkontrastmittel Iopromid in allen Felduntersuchungen schnell entfernt wurde. In den Bodensäulenexperimenten zeigte sich, dass die Entfernung durch Metabolisierung und nicht durch Mineralisierung zustande kam. Das Antibiotikum Sulfamethoxazole wurde unter anoxisch/anaeroben Verhältnissen effektiver entfernt (bis zu 80%), während unter oxischen Bedingungen maximal 50% der Ausgangskonzentration abgebaut wurden.

Investigations on the behaviour of different trace organic compounds at a bank filtration site at Lake Wannsee in the city of Berlin, Germany are reported. More than two years of monitoring for the bulk parameter differentiated adsorbable organic halogens (AOX) revealed a more efficient degradation of adsorbable organic iodine (AOI) and adsorbable organic bromine (AOBr) under anoxic/anaerobic conditions. 64% of AOI were removed under reducing condition, whereas under oxic conditions only ~35% were dehalogenated. One year of monitoring of the single organic pollutants Iopromide (X-ray contrast agent), Sulfamethoxazole (bacteriostatica) and naphthalenesulfonic acid (industrial chemical) showed that the redox conditions have a strong influence on the degradation behaviour of some of the monitored compounds. Iopromide was efficiently removed under oxic conditions, but no evidence for a dehalogenation under oxic conditions was found. Sulfamethoxazole showed a better removal under anoxic/anaerobic conditions (97% in 0.5 month retention time). Oxic infiltration only led to a removal of 62%, even with longer retention times of 2.8 months. The very stable 1.5-naphthalenesulfonic acid was not removed under either redox conditions.