Stormwater treatment technologies to manage runoff during rain events are primarily designed to reduce flood risks, settle suspended solids and concurrently immobilise metals and nutrients. Life Cycle Assessment (LCA) is scarcely documented for stormwater systems despite their ubiquitous imple- mentation. LCA modelling quantified the environmental impacts associated with the materials, con- struction, transport, operation and maintenance of different stormwater treatment systems. A pre- fabricated concrete vortex unit, a sub-surface sandfilter and a raingarden, all sized to treat a func- tional unit of 35 m3 of stormwater runoff per event, were evaluated. Eighteen environmental mid-point metrics and three end-point ‘damage assessment’ metrics were quantified for each system's lifecycle. Climate change (kg CO2 eq.) dominated net environmental impacts, with smaller contributions from human toxicity (kg 1,4-DB eq.), particulate matter formation (kg PM10 eq.) and fossil depletion (kg oil eq.). The concrete unit had the highest environmental impact of which 45% was attributed to its maintenance while impacts from the sandfilters and raingardens were dominated by their bulky ma- terials (57%) and transport (57%), respectively. On-site infiltrative raingardens, a component of green infrastructure (GI), had the lowest environmental impacts because they incurred lower maintenance and did not have any concrete which is high in embodied CO2. Smaller sized raingardens affording the same level of stormwater treatment had the lowest overall impacts reinforcing the principle that using fewer resources reduces environmental impacts. LCA modelling can serve as a guiding tool for practitioners making environmentally sustainable solutions for stormwater treatment.

We investigate water quality of a small urban river during dry and wet weather conditions, including both standard parameters and trace organics. The monitored river stretch receives both effluents from WWTP as well as (separate) stormwater runoff of an impervious area of 11 km2. Results show increases in concentrations in the river during rain events with a factor > 20 for zinc, polycyclic aromatic hydrocarbons, two herbicides and one flame retardant. Also, substances which are expected both in WWTP effluent and in stormwater effluents were detected at important concentrations in the river during wet weather, such as the corrosion inhibitor Benzotriazole (0.8 µg/L on average) and the plasticizer Diisodecyl phthalate (4.0 µg/L on average). The presented results are preliminary and will be complemented by more results and substances as well as an assessment of the relevance of the findings.

A study is conducted to determine the relevance of micropollutants in urban stormwater runoff. To evaluate for the first time city-wide annual loads of stormwater-based micropollutants entering urban surface waters, an event-based, one-year monitoring program was set up in separate storm sewers in Berlin. Monitoring points were selected in 5 catchments of different urban structures (old building areas <1930, newer building areas >1950, single houses with gardens, roads >7500 vehicles/day and commercial areas) to consider catchment-specific differences. Storm events of different characteristics were sampled up to four hours during different seasons by automatic samplers triggered by flow meters. Volume-proportional samples (one composite sample per event) were analysed for a set of 100 parameters including 85 organic micropollutants (e.g. flame retardants, phthalates, pesticides/biocides, PAH), heavy metals and standard parameters. So far (70/88 samples), 60 organic micropollutants were at least once detected in stormwater runoff of the investigated catchment types. Concentrations were highest for phthalates with average concentrations of 13 µg/L for diisodecyl phthalate. For heavy metals, concentrations were highest for zinc (average: 950 µg/L). Results also showed catchment-specific differences for many compounds as well as seasonal differences for selected pollutants which can be used to improve micropollutant strategies and potentially prevent loads at the source.

Diffuse nitrate (NO3) contamination from intense agriculture adversely impacts freshwater ecosystems, and can also result in nitrate concentrations exceeding limits set in drinking water regulation, when receiving surface waters are used for drinking water production. Implementation of near-natural mitigation zones such as reactive swales or wetlands have been proven to be promising measures to reduce nitrate loads in agricultural drainage waters. However, the behavior of these systems at low temperatures and its dependence on systemdesign has not beenwell known until now. In this study, the behavior of a full-scale (length: 45 m) reactive swale treating drainage water from an agricultural watershed in Brittany (France), with high nitrate concentrations in the receiving river, was monitored for one season (6 months). As flow in this full-size field system is usually restricted to winter and spring months (December–May), it usually operates at lowwater temperatures of 5–10 WC. Tracer tests revealed shorter than designed retention times due to high inflows and preferential flow in the swale. Results show a correlation between residence time and nitrate reduction with low removal (<10%) for short residence times (<0.1 day), increasing to >25% at residence times >10 h (0.4 day). Performance was compared to results of two technical-scale reactive swales (length: 8 m) operated for 1.5 yearswith two different residence times (0.4 and 2.5 days), situated at a test site of the German Federal Environmental Agency in Berlin (Germany). Similar nitrate reduction was observed for comparable temperature and residence time, showing that up-scaling is a suitable approach to transferring knowledge gathered from technical-scale experiments to field conditions. For the design of new mitigation systems, one recommendation is to investigate carefully the expected inflow volumes in advance to ensure a sufficient residence time for effective nitrate reduction at low temperatures.

Im Rahmen des Projekte OgRe wurde das Ausmaß der Belastung von Regenablauf für Berlin durch ein einjähriges Monitoringprogramm in Regenwasserabfluss der Trennkanalisation unterschiedlicher Einzugsgebietstypen (Altbau, Neubau, Gewerbe, Einfamilienhäuser, Straßenablauf) untersucht. Ziel war, eine möglichst vollständige Erfassung organischer Spurenstoffe zu erreichen (einschließlich Identifizierung zusätzlicher Substanzen durch non-target-Analytik). Darüber hinaus sollte geklärt werden, inwieweit die unterschiedlichen Einzugsgebietstypen ein unterschiedliches Spektrum an Belastung durch Spurenstoffe aufweisen. Diese Informationen wurden dann genutzt, um eine Hochrechnung der über das Regenwasser in die Gewässer gelangenden Spurenstofffrachten für Gesamt-Berlin und einzelne Gewässerabschnitte zu ermöglichen. Die erhaltenen Frachten wurden verglichen mit modellierten Frachten abwasserbürtiger Spurenstoffe, die über Kläranlagenablauf in die Berliner Gewässer gelangen. Insgesamt wurden etwa 90 volumenproportionale Mischproben auf ein Set von etwa 100 Spurenstoffen analysiert. Zusätzlich wurden 12 Regenereignisse in der Panke beprobt, um Spitzenkonzentrationen regenwasserbürtiger Spurenstoffe im Gewässer zu ermitteln und ins Verhältnis zur Trockenwetterbelastung (5 Proben) zu setzen. Auch eine Untersuchung mikrobiologischer Parameter und der zeitlichen Dynamik konnten im Rahmen des Projektes durchgeführt werden.

Untreated stormwater runoff can be an important source of pollutants affecting urban surface waters. For example, in Berlin each year 78% or 54 million m³ of stormwater are discharged mostly untreated into receiving surface waters. Beside “classic” stormwater pollutants (e.g. suspended solids, COD, phosphorous or heavy metals), trace organic substances such as biocides, plasticizers, flame retardants and traffic related micropollutants (e.g. vulcanizing accelerators originating from tire wear or combustion by-products such as PAHs) started to come into focus in recent years (Zgheib et al. 2012, Gasperi et al. 2014). To evaluate for the first time city-wide annual loads of these trace organic substances entering urban surface waters through stormwater discharge, an event-based, one-year monitoring program was set up in the city of Berlin.

In recent years, the effect of urbanization on the quality of stormwater runoff gained increased attention including investigations on micropollutants. Especially in cities dominated by separated sewer systems, stormwater runoff containing micropollutants from anthropogenic origin is discharged mostly untreated into surface waters and therefore a potential source of high loads of pollutants. In a one year monitoring campaign stormwater runoff from five different catchments in Berlin is analyzed for major groups of micropollutants such as phthalates, organophosphates, organotin-compounds, biocides/pesticides, PAH’s, alkylphenols, polybrominated diphenylether, polychlorinated biphenyls and heavy metals. Sampling sites are equipped with automatic samplers, flow and water level meters in order to prepare flow proportional composite samples (recommended sampling strategy according to DIN ISO 5667-10). First results show that all groups of micropollutants were found in at least one catchment type in concentrations > 2 µg/L. Concentrations of the different micropollutant groups vary depending on the catchment types. So far, no organotin-compounds, polybrominated diphenylether or polychlorinated biphenyls were determined.

Micropollutant concentrations found in stormwater runoff were extrapolated to annual loads at the scale of the city of Berlin (impervious connected area of ~170 km2). Extrapolation was done by city structure, i.e., it was assumed that concentration patterns found in one of five specific city structure types is representative for every area of this structure type. Preliminary results show that micropollutants of several substance types can enter Berlin surface waters at loads in the order of kg/yr via stormwater runoff: plasticizers (e.g., sum of Di-iso-decylphthalate and Di-iso-nonylphthalate at 770 kg/yr), flame retardants (e.g., tris(2-butoxyethyl) phosphate (TBEP) at 89 kg/yr), biocides from different sources (e.g., Glyphosate at 17 kg/yr and Mecoprop at 30 kg/yr), vulcanizing accelerator benzothiazole (as sum of benzothiazole and metabolites methylthiobenzothiazole and hydroxybenzothiazole at 65 kg/yr) and combustion byproduct polycyclic aromatic hydrocarbons PAH 16 (sum of 16 EPA PAH at 107 kg/yr). These loads are in a similar order of magnitude as micropollutants that enter Berlin surface waters via (treated) sewage, such as pharmaceutical residues carbamazepine and ibuprofen with estimated annual loads of 436 kg/yr and 35 kg/yr, respectively.