A model-based analysis of the reactive transport behaviour of 37 trace organic compounds during field-scale bank filtration.

Though bank filtration diminishes the loads of many trace organic compounds (TOrCs) present in the source water, still there is a wide uncertainty on the influence of local environmental conditions on biodegradation processes. This research addresses the fate and transport behaviour of 37 trace organic compounds at a bank filtration site in Germany over a relatively long-time span of six years. Using two-dimensional heat and reactive transport modelling in FEFLOW, TOrCs are classified according to their occurrence in bank filtration wells with a residence time of up to 4 months. We identify 12 persistent compounds, 20 reactive compounds and 5 transformation products formed during aquifer passage. Estimates of first-order biodegradation rate constants are given for six reactive compounds. Minimum biodegradation rate constants (i.e. maximum half-lives) are approximated for eight compounds only present in the surface water. For some compounds, a simple first-order degradation model did not yield satisfactory results and the behaviour appears to be more complex. Processes like sorption, redox- and/or temperature-dependent biodegradation and temperature-dependent desorption are suspected but incorporating these into the model was beyond the scope of this paper that provides an overview for many compounds. Results highlight the ability of the sub-surface to improve the water quality during bank filtration, yet at the same time show the persistence of several compounds in the aquifer.

Sorption behavior of 20 wastewater originated micropollutants in groundwater--column experiments with pharmaceutical residues and industrial agents.

Since sorption is an essential process with regard to attenuation of organic pollutants during subsurface flow, information on the sorption properties of each pollutant are essential for assessing their environmental fate and transport behavior. In the present study, the sorption behavior of 20 wastewater originated organic micropollutants was assessed by means of sediment column experiments, since experimentally determined data for these compounds are not or sparsely represented in the literature. Compounds investigated include various psychoactive drugs, phenazone-type pharmaceuticals and ß-blockers, as well as phenacetine, N-methylphenacetine, tolyltriazole and para-toluenesulfonamide. While for most of the compounds no or only a low sorption affinity was observed, an elevated tendency to sorb onto aquifer sand was obtained for the ß-blockers atenolol, propranolol and metoprolol. A comparison between experimental data and data estimated based on the octanol/water partition coefficient following the QSAR approach demonstrated the limitations of the latter to predict the adsorption behavior in natural systems for the studied compounds.

The effect of aeration on the removal of wastewater-derived pharmaceutical residues from groundwater - a laboratory study.

Several studies on waste- or drinking water treatment processes as well as on groundwater have recently shown that some pharmaceutical residues (PRs) are redox-sensitive. Hence, their (bio)degradation depends on the redox conditions prevalent in the aquifer. Groundwater, providing raw water for drinking water production, is often anoxic and aeration is a widespread treatment method applied mainly to eliminate unwanted iron and manganese from the water. As a side-effect, aeration may trigger the elimination of PRs. Within the present study the influence of aeration on the fate of a number of wastewater derived analgesics and their residues as well as several antimicrobial compounds was investigated. For this purpose, anoxic groundwater was transferred into stainless steel tanks, some of which were aerated while others were continuously kept anoxic. Results prove that the degradation of six phenazone type compounds is dependent on oxygen availability and compounds are efficiently removed under oxic conditions only. Concerning the antimicrobials, doxycycline and trimethoprim were better removed during aeration, whereas a slightly improved removal under anoxic conditions was observed for clindamycin, roxithromycin and clarithromycin. The study provides first laboratory proof of the redox-sensitivity of several organic trace pollutants. In addition, results demonstrate that aeration is an effective treatment for the elimination of a number of wastewater derived PRs.

Occurrence and distribution of psychoactive compounds and their metabolites in the urban water cycle of Berlin (Germany).

The occurrence and distribution of six psychoactive compounds (primidone, phenobarbital, oxazepam, diazepam, meprobamate, and pyrithyldione) and a metabolite of primidone (phenylethylmalonamide) were investigated in wastewater treatment plant (WWTP) effluents, surface water, groundwater of a bank filtration site, raw and final drinking water, and in groundwater affected by former sewage irrigation. Primidone and its metabolite phenylethylmalonamide were found to be ubiquitous in environmental water samples in Berlin. Maximum concentrations of 0.87 and 0.42 µg/L, respectively, were encountered in WWTP effluents. Both compounds are apparently not removed when passaging through the different compartments of the water cycle and concentrations are only reduced by dilution. Phenobarbital was present at nearly every stage of the Berlin water cycle with the exception of raw and final drinking water. The highest concentrations of phenobarbital (up to 0.96 µg/L) were measured in groundwater influenced by former sewage irrigation. Oxazepam was only present in WWTP effluents and surface waters (up to 0.18 µg/L), while diazepam was not detected in any matrix. Due to their withdrawal from the German market years ago, the pharmaceuticals meprobamate and pyrithyldione were only found in sewage farm groundwater (up to 0.50 and 0.04 µg/L, respectively) and, in case of meprobamate, also in decade old bank filtrate (0.03 µg/L). Our results indicate a high persistence of some of the investigated compounds in the aquatic system. As a consequence, these pollutants may potentially reach drinking water resources via bank filtration if present in WWTP effluents and/or surface waters in partly closed water cycles such as Berlin's.

Polar pollutants in municipal wastewater and the water cycle: occurrence and removal of benzotriazoles.

1H-benzo-1,2,3-triazole (BTri) and its methylated analogues (tolyltriazole, TTri) are corrosion inhibitors used in many industrial applications, but also in households in dishwashing agents and in deicing fluids at airports and elsewhere. BTri and one of the TTri-isomers (4-TTri) are typical examples of polar and poorly degradable trace pollutants. Benzotriazole elimination in four wastewater treatment plants (WWTP) in Berlin ranged from 20 to 70% for 5-TTRi over 30 to 55% for BTri to insignificant for 4-TTri. WWTP effluent concentrations were in the range of 7-18 microg/L of BTri, 1-5 microg/L of 4-TTri and 0.8-1.2 microg/L of 5-TTri. BTri and 4-TTri proved to be omnipresent in surface waters of the rivers Rhine and Elbe with concentrations increasing from <0.05 microg/L to around 0.5 microg/L of BTri and 0.2-0.5 microg/L of 4-TTri over 600-700 km. Bank filtration is an important process to generate raw water for drinking water production from surface waters. Even after residence times of several months BTri and 4-TTri were determined in concentrations of a few hundred ng/L in bank filtration water. Isotherm data from batch experiments indicate that activated carbon filtration should be suitable to avoid intrusion of TTri into drinking water in partially closed water cycles. For BTri, however, sorption to activated carbon appears to be too weak and ozonation may be mandatory to remove it from raw waters.

Investigation of the fate of sulfonamides downgradient of a decommissioned sewage farm near Berlin, Germany.

The drinking water production of a drinking water treatment plant in Berlin is affected by ambient contaminated groundwater. The three organic compounds para-toluenesulfonamide (p-TSA), ortho-toluenesulfonamide (o-TSA) and benzenesulfonamide (BSA) were identified in the catchment area of this plant. The groundwater pollution is a result of former sewage farm irrigation in the area, operating for almost 70 years until the 1980s. The distribution of the sulfonamides in the anoxic groundwater was investigated, and a large number of observation and production wells were sampled for this purpose. The contaminant plume is 25 m3000 m2000 m (depth, length, width) in size. The high concentrations of p-TSA, o-TSA and BSA in the groundwater show that the sulfonamides persist over decades in an anoxic aquifer environment. Groundwater quality assessment revealed that elevated concentrations of the analytes can be expected in the abstraction well galleries in the future. Therefore, sulfonamides should periodically be monitored in the drinking water (maximum allowed concentration of 0.30 microg/L of p-TSA and for o-TSA and BSA, a limit of 0.10 microg/L for unknown substances applies). Because of the widespread application and the persistence of the sulfonamides under anoxic conditions, our local investigations suggest that the substances may generally be present in groundwater under the influence of sewage irrigation. Incubation experiments were conducted under in situ hydrostatic pressure to study the behaviour of these trace organic compounds under different redox conditions (oxic and anoxic). Groundwater sampling equipment was either sterilised or not sterilised in order to distinguish between microbiological processes occurring in the aquifer and those representing sampling and storage artefacts (incubation experiments). Results showed that the addition of oxygen to the anoxic groundwater facilitates p-TSA and o-TSA degradation. Hence, while the substances are persistent under anoxic conditions, they are more degradable in the presence of oxygen. Results also illustrate that maintaining anoxic conditions or applying appropriate preservation techniques is necessary to ensure accurate analysis.

Investigation of the behavior and metabolism of pharmaceutical residues during purification of contaminated ground water used for drinking water supply.

Residues of phenazone-type pharmaceuticals originating from spills of a former pharmaceutical production plant have recently been detected in ground water in Berlin, Germany. The degradation pathways of phenazone, propyphenazone, and dimethylaminophenazone (DMAA) during water purification were enlightened in batch experiments with groundwater and filter material obtained from operating waterworks. For phenazone and propyphenazone a complete biological transformation into their respective metabolites 1,5-dimethyl-1,2-dehydro-3-pyrazolone (DP) and 4-(2-methylethyl)-1,5-dimethyl-1,2-dehydro-3-pyrazolone (PDP) was observed. Generally, removal of phenazone-type pharmaceutical residues during rapid sand filtration was almost exclusively caused by microorganisms only present in polluted raw water. DMAA applied to fresh filter materials was rapidly degraded into its metabolites 1-acetyl-1-methyl-2-phenylhydrazide (AMPH), acetoaminoantipyrine (AAA), formylaminoantipyrine (FAA), and 1-acetyl-1-methyl-2-dimethyloxamoyl-2-phenylhydrazide (AMDOPH). DMAA, AAA, and FAA were, however, only detected at low levels in a few samples of purified water from an operating water works. Whereas, the metabolites AMDOPH and DP were detected up to 1 microg l(-1). Propyphenazone was rapidly removed and AMPH, phenazone, and PDP were only measured with concentrations in the low ng l(-1) range. The concentrations of the metabolites DP and PDP are even higher in the purified water than in the raw water caused by their formation during degradation of phenazone and propyphenazone. Reduction of filtration velocity on an experimental filter from 5 m h(-1) down to 2 m h(-1) resulted in improved removal of phenazone, propyphenazone and their metabolites DP and PDP, respectively. AMDOPH, however, was highly persistent in all experiments independent from filtration velocities and contact times.

Determination of estrogenic steroids in surface water and wastewater by liquid chromatography-electrospray tandem mass spectrometry.

An analytical method is presented which permits trace level determination of 17alpha-ethynylestradiol (EE2), 17beta-estradiol (E2), and estrone (E1). Using this method, the estrogenic steroids were analyzed in drinking water, surface water, and wastewater (sewage influents and effluents) at concentrations down to 0.1 ng/L. Sample volumes between 100 and 500 mL are concentrated using automated solid-phase extraction. Analysis is performed by liquid chromatography with detection by tandem mass spectrometry. Applying simple clean-up procedures and internal standard calibration, recovery losses resulting from matrix-dependent ion suppression during electrospray ionization could be compensated for all of the investigated compounds. Recoveries around 100% were obtained for all analytes after correction using the internal standards. Limits of quantification (LOQ) were between 0.1 and 0.4 ng/L for purified sewage, surface, ground, and drinking water and between 1 and 2 ng/L in the case of raw sewage. Water treatment by wastewater treatment plants (WWTPs) or by a surface water treatment plant affected the removal of all estrogenic steroids. Thus, E1, E2, and EE2 were removed in the municipal WWTPs to the extent of 93%, 93%, and 80%, respectively. In the effluents of the WWTP in Ruhleben (Berlin, Germany), E1, E2, and EE2 were detected at the low ng/L level. E2 and EE2 were, however, not present in the Berlin surface water above the LOQ (0.2 ng/L). E1 was the only compound that could be detected in surface water samples. After additional surface water treatment it was still detectable but only at trace-level concentrations with a mean value of 0.16 ng/L.

Determination of polar drug residues in sewage and surface water applying liquid chromatography-tandem mass spectrometry.

A simple and rapid method is presented for the trace-level analysis of 10 polar pharmaceutical residues in various types of water samples from the aquatic environment. Using this method, the pharmaceuticals and several drug metabolites can be analyzed in drinking and surface waters and in wastewater (treated and untreated sewage) at concentrations down to 0.01 microg/L. Samples are prepared by a simple in situ derivatization enabling the preconcentration of very polar metabolites by automated solid-phase extraction. The analytes were separated by liquid chromatography with tandem mass spectrometric detection and quantified by comparison with an internal standard. Limits of quantification were between 0.01 and 0.02 microg/L for three phenazone-type pharmaceuticals, six of their metabolites, and the antiepileptic drug carbamazepine. Except for dimethylaminophenazone, recoveries for all analytes were between 87 and 117% for raw and purified sewage, groundwater, and surface and drinking water. Investigations of some environmental samples revealed that sewage and surface water treatment causes a slight reduction of the concentrations of some analytes whereas other compounds were persistent during water treatment. Thus, some compounds were detected at the low-microgram per liter level in sewage effluents of wastewater treatment plants in Berlin (Germany) and were also found at high-nanogram per liter concentrations in Berlin surface water samples.