Stormwater runoff is a key pathway for diffuse pollutants to enter receiving waters. Mitigating measures include pollutant substitution, restricting their release into the urban technosphere and limiting the (re-)mobilisation of substances to minimise their negative impacts on receiving waters. Gully pots (GPs) are one of the most ubiquitous urban drainage infrastructure components, providing both a drainage function and limiting the onward transport of pollutants through in-pot sedimentation processes. In this study, sediments accumulated over a one-year period were collected from 26 GPs in catchments of four land-use types in Stockholm, Sweden. Sediments were analysed for 101 organic substances from eight substance groups (hydrocarbons, polycyclic aromatic hydrocarbons, alkylphenols, polychlorinated biphenyls, phthalates, organotins, per- and polyfluoroalkyl substances and brominated fire retardants) to inform an assessment of their occurrence and net accumulation rates over a typical unit operation period. A total of 63 substances were quantified in at least one GP, with aliphatic hydrocarbons, phthalates and organotins quantified in all GP sediments, highlighting their ubiquitous use. The identification of 14 and 21 organic substances in two pedestrian/bike path GPs emphasise the contribution of non-vehicular sources to diffuse pollutant loads. Significantly higher mass accumulation rates of 4-tert-octylphenol, 4-nonylphenols, formaldehyde, dioctyltin and dibutyltin are identified in commercial catchment GPs suggesting the need to enhance source-tracing and runoff quality-control measures within catchments of this land-use type. Sediments in 25 GPs were identified with at least one substance exceeding toxicology-based threshold values, highlighting the runoff quality-control function of GPs in reducing the potential ecotoxic impacts on recipients.

Bioretention systems are designed for quality treatment of stormwater. Particulate contaminants are commonly treated efficiently and accumulate mainly in the surface layer of the bioretention filter material. However, concerns exist that microplastic particles may not show equal accumulation behavior as other sediment particles. So far only two field and two laboratory studies are available on the fate of microplastics in few relatively newly built bioretention systems. Therefore, this study investigated the abundance and distribution of microplastics in nine 7–12 years old stormwater bioretention systems. It was found that microplastics generally accumulate on the surface of bioretention systems. Microplastic median particle concentrations decreased significantly from the surface layer (0–5 cm) of the filter material to the 10–15 cm depth layer from 448 to 136 particles/100 g, respectively. The distance to the inlet did not significantly affect the surface accumulation of microplastic particles, suggesting modest spatial variability in microplastics accumulation in older bioretention systems. Further, this study investigated the polymer composition in bioretention systems. It was shown that PP, EVA, PS and EPDM rubber are the most abundant polymer types in bioretention systems. Also, it was found that large percentages of microplastic particles are black particles (median percentage of black particles: 39%) which were found in 28 of the 33 investigated samples. This underlines the importance of including black particles in microplastic studies on stormwater, which has been overlooked in most previous studies.

Urban stormwater typically enters sewer networks through gully pots, which allow a primary sedimentation of solids upstream of the piped network. The regular removal and disposal of retained sediment are necessary, costly and can involve environmental risks due to the contamination of sediments with substances from the urban environment such as metals. The concentrations and speciation of Cd, Cr, Cu, Ni, Pb and Zn were analysed in sediments from 26 gully pots located in different land use areas in Stockholm, Sweden. In addition, accumulation rates of both sediment and metal masses were evaluated, providing a basis for optimising maintenance practices and better understanding of impacts of characteristic urban land use types. Metal concentrations varied by at most a factor of eight between samples and were always below Swedish polluted site guidelines for less sensitive land use, with only eight samples exceeding the guideline values for Cu and Zn for sensitive land use. Sequential extraction showed Pb and Zn to be the most mobile metals. Sediment accumulation rates varied from 0.003 to 0.197 kg/m2 impermeable surface/year. Metal accumulation rates were much more variable than metal concentrations, with a factor of up to 172 between the highest and lowest rates and the highest metal accumulation rates corresponding to the lower range of mass loads in road runoff. Differences in metal concentrations, sediment or metal mass accumulations could not be solely attributed to either traffic or catchment land use. In contrast, traction grit used for winter road maintenance, which has low (but detectable) metal concentrations, is identified as a major component of gully pot sediments, with a combined effect of both moderating metal concentrations and contributing to total mass.

Winter road salt applications are increasing chloride concentrations in many freshwater ecosystems. This trend is alarming, giv­en chloride’s potential to impair aquatic ecosystems. Short- and long-term exposure to salt could affect ecosystem metabolism and nutrient cycles. Here, we examine connections between chloride concentrations, water quality conditions, benthic respi­ration, and sediment-water nutrient flux throughout a large (722 km2) lake and its catchment. Aquatic locations experiencing high concentrations of chloride are indicators of anthropogenic activities and are often associated with additional pollutants. We used sediment core flow-through incubations under ambient and enriched chloride concentrations to determine the effects of road salt on benthic respiration and nutrient fluxes in stream, stormwater pond, and lake sites. Salt (as sodium chloride) ad­ditions caused a significant overall increase in benthic respiration. Acute exposure to road salt caused the strongest increase in benthic respiration when water was warm and at sites that had low (< 50 mg Cl-/L) or high (> 400 mg Cl-/L) ambient chloride concentrations or when water was cold and sites had intermediate (100-400 mg Cl-/L) ambient chloride concentrations. Nitrate flux responded less uniformly to salt additions. Depending on waterbody type and season, ambient nitrate flux into the sediment was similar, increased, or decreased post-chloride addition. Dissolved phosphorus flux was not significantly impacted by salt additions. Across lake and stream sites, our results supported the hypothesis that chloride causes increased respiration while nutrient cycles were weakly and inconsistently altered under experimental pulse road salt additions.

The Schuylkill River Watershed in southeastern PA provides essential ecosystem services, including drinking water, power generation, recreation, transportation, irrigation, and habitats for aquatic life. The impact of changing climate and land use on these resources could negatively affect the ability of the watershed to continually provide these services. This study applies a hydrologic model to assess the impact of climate and land use change on water resources in the Schuylkill River Basin. A hydrologic model was created within the Structural Thinking Experiential Learning Laboratory with Animation (STELLA) modeling environment. Downscaled future climate change scenarios were generated using Localized Constructed Analogs (LOCA) from 2020 to 2040 for Representative Concentration Pathways (RCP) 4.5 and RCP 8.5 emission scenarios. Three regional land use change scenarios were developed based on historical land use and land cover change trends. The calibrated model was then run under projected climate and land use scenarios to simulate daily streamflow, reservoir water levels, and investigate the availability of water resources in the basin. Historically, the streamflow objective for the Schuylkill was met 89.8% of the time. However, the model forecasts that this will drop to 67.2–76.9% of the time, depending on the climate models used. Streamflow forecasts varied little with changes in land use. The two greenhouse gas emission scenarios considered (high and medium emissions) also produced similar predictions for the frequency with which the streamflow target is met. Barring substantial changes in global greenhouse gas emissions, the region should prepare for substantially greater frequency of low flow conditions in the Schuylkill River.

Pollutant loads stemming from anthropogenic activities conveyed in urban stormwater runoff contribute to the impairment of downstream water bodies. Cities and municipalities are increasingly turning toward green infrastructure stormwater control measures to treat pollutants at the source of runoff. One example of these technologies is bioretention, which is commonly applied for stormwater treatment in urban areas due to its demonstrated effectiveness in removing various pollutants from water, including sediment, nutrients (e.g., N and P), and metals. As metals are mainly removed by filtration or adsorption to soil particles, the filter media is important for metal removal in bioretention. However, the capacity to remove metals through adsorption by bioretention media is finite; thus, the media may need to be replaced and disposed of after maintenance or at the end of its operational lifespan. Pollutant accumulation in bioretention media has the potential to approach toxicity thresholds, which may introduce complexities for safe handling and disposal. To fully capture the potential challenges associated with metals accumulation in media over time, it is important to understand the accumulation processes and mobility of metals in bioretention facilities as they age. Although several studies have investigated metal accumulation and distribution in bioretention media, few have assessed metal mobility by fractionation using sequential extraction methods in older (i.e., >7 years) facilities. In November 2019, we conducted a comprehensive field study of older facilities in Ohio, Michigan, and Kentucky (USA) to improve the understanding of the accumulation processes and metal mobility in bioretention. In this study, concentrations of several metals (i.e., Cr, Cu, Ni, Pb, and Zn) were analyzed in samples of filter material from 29 bioretention sites in operation for 7–16 years. Except for Cd, all metals were found in all samples. Metals accumulation was clear with highest concentrations found in the top (0–5 cm) layer of the filter material, attributable to the filtration of particles percolating through the media profile. Lower concentrations were observed in deeper (i.e., >10 cm) layers of the bioretention media. The fractionation showed that the metals of interest were present at high levels with a risk of leaching over time, among which Cd, Zn, and Pb were suggested to be mobile from the filter material during precipitation. Thus, there is a potential risk of leakage from filter material or sediment removed from biofilters, e.g., during maintenance and disposal. The results of principal component analysis indicated specifically correlations between metal concentrations and the filter material soil texture including the organic matter content. These results contribute to improved design and operation and suggest regular maintenance to reduce long-term risks associated with the accumulation of metals in bioretention and similar urban stormwater treatment facilities. Since most metals are trapped in the top layer of the filter it may be enough to remove only the top layer. However, metal fractionation should be considered when handling the material.

Uppgifterna samlades in från ett reningståg för dagvatten i Sundsvall, Sverige. Anläggningen består av en grov föroreningsfälla (GPT) följd av tre parallella biofilterceller: ett vegeterat, kritomvandlat biofilter (BFC eller F1), ett icke-vegeterat sandfilter (SF eller F2) och ett vegeterat biofilter (BF eller F3).Ett av syftena med vårt forskningsprojekt var att bedöma och övervaka dagvattenkvaliteten från ett större vägavrinningsområde (inkl. motorvägsbro E4 i Sundsvall) och även utvärdera hur de olika sektionerna av reningståget presterar när det gäller att ta bort organiska mikroföroreningar från dagvattnet.

Filen med namnet "StormwaterRunoffQualityData_SND.csv" innehåller data för händelsemedelkoncentration (EMC) på dagvattenprover som samlats in från 8 regnhändelser (kodade av A till H) under ett år mellan september 2020 och september 2021. Proverna har analyserats för organiska mikroföroreningar och globala vattenkvalitetsparametrar (42 parametrar totalt). EMC:er har matematiskt genererats av en Monte-Carlo-simulering från uppmätta koncentrationer i delprover som samlats in under varje händelse. Datan utvecklar den genererade fördelningen för varje EMC med Q2.5, Q50 och Q97.5 percentiler och standardavvikelse från medelvärdet. Dessutom nämns antalet upptäckta och icke-upptäckta (censurerade) data för delprover. En lista med alla olika föroreningar och deras förkortningar finns inkluderade i dokumentationsfilen ”StormwaterRunoffQualityData_SND.docx”.

I filen med namnet "TreatmentTrainQualityData_SND.csv" presenteras inte bara händelsemedelkoncentrationen (EMC) för dagvattenavrinningens kvalitet, utan också för det behandlade dagvattnet i reningssystemet nedströms från avrinningsområdet, vilket inkluderar en försedimenteringsanläggning (GPT) och ett sandfilter. Förutom att dagvattenavrinningen utgör systemets inflöde (SW), har händelsemedelkoncentrationen (EMC) från fyra andra provtagningspunkter också presenterats: försedimenteringsanläggningens utflöde (GPT), växtbevuxet, kritomvandlat biofilterutflöde (BFC), icke-växtbevuxet sandfilter (SF) och växtbevuxet biofilterutflöde (BF). Den här delen av undersökningen täcker in 11 regnhändelser (kodade A till K) under perioden sep 2020 och sep 2021. Proverna har analyserats för organiska mikroföroreningar och globala vattenkvalitetsparametrar (42 parametrar totalt). EMC:er har matematiskt genererats av en Monte-Carlo-simulering från uppmätta koncentrationer i delprover som samlats in under varje händelse. Datan utvecklar den genererade fördelningen för varje EMC med Q2.5, Q50 och Q97.5 percentiler och standardavvikelse från medelvärdet. Dessutom nämns antalet upptäckta och icke-upptäckta (censurerade) data för delprover. En lista med alla olika föroreningar och deras förkortningar finns inkluderade i dokumentationsfilen ” TreatmentTrainQualityData_SND.docx”.

The effect of chemical cleaning and regular backwashing on the efficiency of an ultrafiltration membrane fouled during stormwater treatment was studied. Increasing backwash time from 30 to 60 s resulted in an increase in productivity by 20%. However, the productivity was highest when a backwash time of 45 s was used (3% higher than using 60 s). Chemical cleaning was carried out using an alkaline solution (NaOH with or without NaOCl) followed by acid washing with HCl. The addition of NaOCl to the cleaning chemical did not significantly increase the efficiency of chemical cleaning, and the average pure water permeability increase was 97 ± 13 LMH bar−1 after chemical cleaning with NaOH followed by HCl and 117 ± 15 LMH bar−1 after chemical cleaning with NaOH + NaOCl followed by HCl, on average. In addition, reversibility after chemical cleaning was 96 ± 67%, on average. The result from scanning electron microscopy showed that at the end of the experiments, inorganic foulants existed in both the inner layer (feed side) and the outer layer (permeate side) of the membrane.

Current gully pot maintenance strategies lack a robust evidence base and clear aims against which performance can be benchmarked. To facilitate discussions, questions on their long-term in-situ performance in trapping sediments and associated contaminants - and how they are impacted by various factors - require robust interrogation. As a contribution, this paper presents sediments data from 27 gully pots located at sites with various street layouts (roundabout; straight road; road crossing) and traffic intensities (<1000-23666 vehicles/day), over two accumulation periods: winter-spring and summer-autumn 2020-2021. On an annual basis, gully pots retained 0.54–44.2 (median: 10.95) kg (dry mass) over 151–189 days, corresponding to a solids accumulation rate of 2.5–1140.6 (median: 69.4) g/m2/year. Of the 27 gully pots, 18 gully pots showed significant seasonal variations in solids accumulation rates though the dominant season was not consistent. For example, roundabouts exhibited a significantly higher solids accumulation rate over the summer-autumn period in comparison to road crossing and straight road gully pots where accumulation was typically higher in the winter-spring season. Further, in contrast to the latter street layouts, a significant negative correlation between traffic intensity and solids accumulation rate was identified at roundabout gully pots, with the turning action of vehicles generating higher levels of sediment resuspension suggested as a possible contributing factor.

Due to large spatial and temporal variations of soil properties that govern swale infiltration capacities, traditional methods for estimating saturated hydraulic conductivity (ksat) values could potentially lead to erroneous estimation of the total system infiltration capacity. To increase the knowledge of grassed swale infiltration performance and the relationship between hydraulic properties related to the spatial variation within the swale, two methods were applied to estimate ksat values: 1) point measurements using the Modified Philip Dunne (MPD) Infiltrometer, and 2) a full-scale infiltration test (FSIT). A large variation in calculated ksat values was found, ranging from 22 to 1382 mm/hr, with lower/higher values at the swale bottom, and right swale slope respectively. Infiltration point measurements, with a geometric mean of 81 mm/hr, showed higher infiltration rates than those obtained from FSIT, which yielded 34 and 22 mm/hr (for test 1 and 2 respectively). Moreover, FSIT results showed an agreement with ksat values obtained from MPD infiltrometer at the swale bottom. In addition, infiltration rates are significantly reduced as the groundwater mound gets closer to the bottom of the grassed swale.

Decentralized sanitation facilities serving single households to small communities can offer a more flexible way of improving global sanitation. In Nordic countries, on-site wastewater treatment systems (OWTS) are mostly used in sparsely populated areas and are regulated for the removal of phosphorus (Tot-P), organic matter (biological oxygen demand, (BOD7)) and total nitrogen (Tot-N). However, available reports, albeit commonly using small data sets, call attention to often low and variable treatment performance. In this work, a statistical analysis of 1301 samples from 395 units reported in 10 studies from Finland and Sweden was conducted. The objective was to increase knowledge regarding the effluent water quality of OWTS and their compliance with regulations. In addition, the goal was to identify possible factors affecting contaminant concentrations. Overall, compliance with base-level BOD7 removal requirements was met by most units while 10% of units exceeded Tot-N and >25% exceeded Tot-P limits. Non-compliance rates were high, especially for Tot-P, considering the studied data set was composed mostly of semi-new units (median 3.8 years). Neither weather (air temperature, precipitation, and snowmelt), age or load factors were found to strongly explain the data variability in either soil-based systems (SBS) or package plants (PP). Tot-N and Tot-P effluent concentrations of the two systems were not significantly different. Effluent BOD7 concentrations were lower in SBS (median 3.0 mg/L) when compared to PP (median 7.7 mg/L). Units with P-sorbing filters (median 0.69 mg/L) and chemical precipitation (median 1.54 mg/L), presented lower Tot-P effluent concentrations in contrast to traditional sand filters (median 4.0 mg/L). The biological process used in PP had a measurable effect on effluent BOD7 concentrations, with attached growth units presenting higher values (median 8.1 mg/L) than suspended growth units (median 7.1 mg/L). Although the data set utilized was large, its analysis revealed intrinsic bias in data collection, especially regarding system types and sampling seasonality with colder winter periods sampling underrepresented. There is a need for data collection to improve to allow conclusive treatment efficiency assessment including possible effects of climate and process-related factors.

Although Sweden pioneered in the development of resource-recovery sanitation solutions, and there has existed a political awareness of such solutions since the 1990s, their implementation has been slow. We adopt a historical (40-year) perspective and use the main journal of the Swedish sanitation sector as source material to go into depth why this has been the case. Central explanations emerge in terms of previously strong governmental control and continuously tightened environmental requirements that ceaselessly have expanded and strengthened the large-scale centralized sanitation system. In parallel, the sector has continuously been reminded of the shortcomings of alternative (and smaller) solutions and of the tension between recovery and treatment/risk management. The study highlights the possibility of achieving long-term and profound impacts from policy mixes, as well as the strong influence of the sum of challenges and choices over a long time, on today’s perspectives and propensity for change.

Green roofs have gained recognition and popularity globally for their potential to help mitigate the negative impacts of urbanization such as habitat loss and disruption of the water cycle caused by increased impervious surfaces. However, there is still a need to enhance our understanding of green roof vegetation dynamics and how they affect plant water use and hydrological function under varying environmental conditions. This doctoral thesis aims to address this knowledge gap by applying a wide range methods, including field surveys on full scale gren roofs, a laboratory scale water use experiment, and rainfall runoff monitoring from pilot scale green roofs.

Vegetation surveys on 41 green roofs of varying ages and designs in northern Sweden's cold climate revealed that substrate depth plays a crucial role in supporting greater plant abundance and more species-rich plant assemblages on these roofs. Of the originally intended speceis, 24% were found at the time of surveys whereas spontaneous unintended plant species frequently comprised a substantial proportion (69%) of the species richness on these roofs. No relationship was found between speceis richness and plant cover on the surveyed roofs.

Analysis of Scandinavian green roof vegetation in nine different locations with varying climates revealed that survival rates and covers of the intended vegetation were negatively influenced by low annual temperature. Contrary to the initial hypothesis, high annual precipitation was also negatively related to the survival and cover of intended vegetation. Conversely, spontaneous plants were favored by high mean annual precipitation, compensating for the loss of intended vegetation. Freeze-thaw cycles and longest dry period did not have any detectable effect on vegetation during the two year time period.

Additionally, the thesis explored the potential of spontaneous vegetation as a functional alternative to purposefully planted roofs. While unpredictable, spontaneous vegetation could significantly contribute to the overall ecological function of green roofs, as the spontaneous species found in a speceis survey had complementary life strategies and traits compared to the intended vegetation. The low abundance of most spontaneous species in plant surveys in northern Sweden however, questions their contribution to the hydrological function in that climate.

Growth, leaf traits, and life strategies related to species-specific water use of 10 green roof species was investigated under well-watered and water-deficit conditions in a controlled laboratory setting. Species classified with more competitive or ruderal life strategies were found to display higher water use as compared to stress-tolerant succulent species, and leaf dry matter content (LDMC) was a good indicator of water use for these species. The water use of typical succulent green roof plants (mostly classified as stress tolerators) was the same or lower than the evaporation from the bare substrate and the findings highlighted the potential of considering how species specific traits, life strategies affect plant water use to better understand plants contribution to green roof hydrological function.

Runoff from 34 pilot roof modules (size 2 m²) was measured from rains under natural weather conditions. The impact of four life strategy-based vegetation mixes on green roof hydrological function was assessed and compared to a standard succulent monoculture, non-vegetated bare substrate green roofs, and conventional roofs. All green roof modules, including bare substrates, showed significantly higher stormwater retention compared to conventional roofs. The effect of vegetation type increased with increasing rain volume, and the stress-tolerant strategy based vegetation generally outperformed bare substrates and succulent monocultures, having higher retention and peak flow attenuation.

Globally, water demands are increasing as a result of e.g., population growth and a warmer climate; at the same time freshwater supplies are becoming scarcer. Also in parts of Sweden where water shortage historically has not been a concern, the availability of freshwater for potable water use is declining, especially in the summer. As a result, alternative water management strategies are receiving increased attention in an effort to reduce the pressure on potable water sources. One strategy is the treatment, recirculation and re-use of greywater, a type of water that can be collected in source-separating wastewater systems. Hence, the aim of this literature review was to provide knowledge necessary to understand how greywater can be treated, recycled and re-used in the society, with an emphasis on reuse in Sweden. The review covers different aspects including greywater characteristics, greywater treatment processes, legal frameworks and guidelines on greywater re-use, global examples as well as summary of findings from sustainability analyses conducted on greywater re-use systems.

Greywater makes up 75–90% of the total domestic wastewater volume and thereby represents an important source for water reuse in systems with source-separating wastewater systems. Data of the quantity of greywater produced in households globally and in Sweden vary. According to Swedish studies, one person may produce between 66 to 150 l/d. Additionally, research indicates that greywater contains less pathogens and nutrients compared to mix wastewater due to the separation of greywater from blackwater, which in turn contains the human excreta. However, the concentrations of measured parameters vary significantly between different areas. Therefore, in order to ensure the quality of greywater, site-specific measures are necessary.

Studies have been conducted on different greywater treatment methods for non-potable re-use, with biological and filtration techniques receiving the most attention. However, it is challenging to make generalizations about the optimal treatment techniques based on the end-usage, due to the variation in greywater characteristics between sites. In addition, this review shows that there is a lack of legal guidance for greywater reuse, which makes it more challenging for practitioners to understand what levels of treatment that are required before the reclaimed water can be reused in used in society. The review also shows that further sustainability analyses should be conducted on greywater reuse systems, in order to understand their benefits more comprehensively.

Green walls in urban environments can be both an aesthetic feature and be of practical use in greywater treatment. This study evaluates the effect of different loading rates (4.5 l/d, 9 l/d, and 18 l/d) on the efficiency of treating actual greywater from a city district in a pilot-scale green wall with five different filter materials as substrates (biochar, pumice, hemp fiber, spent coffee grounds (SCG), and composted fiber soil (CFS)). Three cool climate plant species, Carex nigra, Juncus compressus, and Myosotis scorpioides, were chosen for the green wall. The following parameters were evaluated: biological oxygen demand (BOD), fractions of organic carbon, nutrients, indicator bacteria, surfactants, and salt. Three of the five materials investigated – biochar, pumice, and CFS - showed promising treatment efficiencies. The respective overall reduction efficiencies of BOD, total nitrogen (TN) and total phosphorus (TP) were 99%, 75%, and 57% for biochar; 96%, 58%, and 61% for pumice; and 99%, 82% and 85% for CFS. BOD was stable in the biochar filter material with effluent concentrations of 2 mg/l across all investigated loading rates. However, higher loading rates had a significantly negative effect on hemp and pumice for BOD. Interestingly, the highest loading rate (18 l/d) flowing over pumice removed the highest levels of TN (80%) and TP (86%). Biochar was the most effective material in removing indicator bacteria, with a 2.2–4.0 Log10 reduction for E. coli and enterococci. SCG was the least efficient material, giving a higher BOD in the effluent than in the influent. Therefore, this study presents the potential of natural and waste-derived filter materials to treat greywater effectively and the results can contribute to the future development of nature-based greywater treatment and management practices in urban areas.

The water quality implications of transferring stormwater through pipes composed of concrete (new and used), polyvinyl chloride (PVC), galvanized corrugated steel (GCS), high-density polyethylene (HDPE), and pipes subjected to cured in place pipe (CIPP) and spray in place pipe (SIPP) trenchless repair technologies on stormwater quality are reviewed. Studies involve either the use of flowing water or an immersion experimental design, with data showing contact with pipe materials can affect stormwater quality parameters including pH, electrical conductivity (EC), and concentrations of minerals, metals, and organic constituents, e.g. styrene. ‘In-transport’ changes in pH (1–3 units), EC (2–3-fold), bicarbonate (3–44-fold), and calcium (2–17-fold) in stormwaters were reported following exposure to concrete pipes. Differences between the use of synthetic and field-collected stormwater were identified, e.g. turbidity levels in field-collected stormwater reduced on passage through all pipe types, compared to synthetic water where levels of turbidity on exposure to concrete and cement-based SIPP increased slightly. Transfer through PVC and HDPE pipes had minimal effects on physicochemical parameters, whereas exposure to galvanized corrugated steel pipes led to increases in EC, Zn, and Pb. Though limited data was available, the use of CIPP repairs and associated waste condensate generated during thermal curing and/or incomplete curing of resins was identified to release organic contaminants of concerns (e.g. styrene, vinylic monomers, dibutyl phthalate (DBP), diethyl phthalate (DEP), and benzaldehyde). The implications of findings for both future research and stakeholders with responsibility for reducing diffuse pollution loads to receiving waters are considered.

Gully pots (GPs) are ubiquitously used in urban catchments, to direct surface runoff into piped sewer systems, reduce the risk of sediment-induced pipe blockages and the loading of solids and associated contaminants on the receiving waters. Over time, the build-up of sediments in GPs will lead to impaired hydraulic performance, putting the urban catchment at risk of flooding. However, GP maintenance strategies lack both a robust evidence base and clear aims against which their effectiveness can be benchmarked. An improved understanding of the factors influencing long-term in-situ solids accumulation in GPs is required for further assessment and optimisation of the GP maintenance scheme. As a contribution to addressing these knowledge gaps, sediments from 27 GPs located in urban catchments associated with three street feature types (roundabout; crossing; straight road) and varied traffic intensities were collected on two occasions, representing two distinct seasonal accumulation periods. Parameters including GP fullness levels, particle size distribution (PSD), and solids mass accumulation rates were evaluated with regards to the impacts of seasonal activities, traffic conditions as well as configuration and dimension of GPs. The results indicate impacts of seasonal activities on solids accumulation rates were not consistent across all GPs, with the magnitude of the difference larger following winter-spring catchment practices. Additionally, synergistic impacts of seasonal activities and traffic conditions on PSD and solids accumulation rates were observed. For example, the winter road safety measures may enhance the impacts of the characteristic vehicle turning motions at roundabouts, contributing to the negative correlation identified between traffic intensities and solids accumulation rates. The overall exhibited large variations in sump fullness levels (4 %–73 %) and solids dry mass (0.5–51 kg) directly challenged the commonly adopted generalised GP maintenance frequency without taking the catchment-specific activities into consideration.

Dagvatten från starkt förorenade ytor, såsom motorvägar och större vägkorsningar, leds ofta till dagvattendammar eller andra dagvattensystem. Reningseffekten hos dessa system har ett samband med deras area eftersom de har sedimentering som främsta reningsprocess. Urbaniserade områden bebyggs i dag allt tätare och de tillgängliga ytorna för dagvattenhantering är begränsade. Samtidigt blir miljökraven mer stringenta. Då kan det vara svårt att anlägga system som är dimensionerade för att avskilja föroreningarna tillräckligt effektivt. Flera studier har därför fokuserat på hur effekten hos befintliga system kan förstärkas. I rapporten beskrivs hur väl en reningsprocess med kemisk fällning fungerar på förorenat dagvatten.Kemisk fällning är en välkänd process i vattenverk och avloppsreningsverk där den används för att den är mycket effektiv när det gäller att avskilja både partiklar och fosfor. Många föroreningar i dagvatten förekommer i hög grad som partiklar eller är bundna till partiklar. Därför borde en process med kemisk fällning kunna åstadkomma hög avskiljning även för dagvatten. Men det har inte gjorts särskilt många studier på ämnet, och det har inte genomförts någon bredare undersökning av hur processen fungerar för dagvattenrening. Syftet med projektet var därför att undersöka vilka fällningskemikalier som lämpar sig för dagvatten, vad som bör beaktas i en sådan process och hur bra processen kan bli på att avskilja typiska dagvattenföroreningar. Insamlat dagvatten testades under kontrollerade förhållanden på laboratorium. För att utvärdera processen användes dels en snösmältblandning från en plogbank i Luleå, dels vägdagvatten. Det viktigaste resultatet var att reningsgraden blev mycket hög, över 90 procent, för merparten av metallföroreningar och organiska föroreningar. Reningsgraden hade även låg variation, motsvarande cirka en till fem procentenheter. De fällningskemikalier som presterade bäst var kommersiella förhydrolyserade fällningsprodukter. För att erhålla en kemisk fällning är parametrarna pH och alkalinitet viktiga, och vissa dagvatten kan behöva en pH-justering. Kemisk fällning hade även en tydlig effekt på avskiljning av mindre partiklar (<1μm). Vid enbart sedimentering avskildes inte den fraktionen utan hölls i suspension.Resultaten ska bidra till kunskap om kemisk fällning av dagvatten som kan ge verksamhetsutövare en bredare verktygslåda för effektiv dagvattenrenin

This study considered stormwater quality in terms of the environmental risk of micropollutants for receiving waterbodies and assessed the performance of a gross pollutant trap (GPT)-biofilter treatment train (TT) for a 4.7ha highway catchment in Sundsvall, Sweden, in reducing the risk of organic micropollutants (OMP), including 9phenolic substances, 16 polycyclic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH), and 4 TPH fractions. 229 intra-event samples were collected at 5 different sampling locations during 11 rain events overone year. Then, to identify and rank the potential risks of OMPs, risk indexes (RI) were calculated for 15 quantifiable OMPs using their event mean concentrations (EMC±Δ), occurrence probabilities, and environmental quality standards (EQS). Most of the 15 OMPs possessed a critical risk index (RI≥1) in the untreated stormwater, while the risks were reduced by the TT slightly to significantly, depending on OMPs and the type of treatment sections. Regarding the impact of sections on the risk reduction, a chalk-amended, vegetated biofilter (BFC) made the greatest impact followed by vegetated biofilter (BF) (like BFC but without chalk), non-vegetated sand filter(SF) with moderate, and lastly, GPT which had almost no impact. Besides, the whole TT performance in riskreduction at the TT outlet was robust for 6 PAHs (RI<<1), moderate for TSS, Octylphenol, and 5 other PAHs, but weak and unreliable for Bisphenol A and Nonylphenol.

Urban areas play a key role in the production of microplastics (MPs) and their entry into water bodies. This article reviews the literature on the sources, transport, and control of MPs in urban environments with the aim of clarifying the mechanisms underlying these processes. Major MP sources include atmospheric deposition, micro-litter, and tire and road wear particles (TRWPs). MPs deposited from the atmosphere are mostly fibers and may be particularly important in catchments without traffic. Littering and attrition of textiles and plastic products is another important MP source. However, the quantities of MPs originating from this source may be hard to estimate. TRWPs are a significant source of MPs in urban areas and are arguably the best quantified source. The mobilization of MPs in urban catchments is poorly understood but it appears that dry unconsolidated sediments and MP deposits are most readily mobilized. Sequestration of MPs occurs in green areas and is poorly understood. Consequently, some authors consider green/pervious parts of urban catchments to be MP sinks. Field studies have shown that appreciable MP removal occurs in stormwater quality control facilities. Street cleaning and snow removal also remove MPs (particularly TRWPs), but the efficacy of these measures is unknown. Among stormwater management facilities, biofiltration/retention units seem to remove MPs more effectively than facilities relying on stormwater settling. However, knowledge of MP removal in stormwater facilities remains incomplete. Finally, although 13 research papers reported MP concentrations in stormwater, the total number of field samples examined in these studies was only 189. Moreover, the results of these studies are not necessarily comparable because they are based on relatively small numbers of samples and differ widely in terms of their objectives, sites, analytical methods, size fractions, examined polymers, and even terminology. This area of research can thus be considered “data-poor” and offers great opportunities for further research in many areas.

Due to structural and hydraulic deterioration, urban water pipe networks have annual rehabilitation needs. Worldwide, these needs are often significantly larger than the actual amount of rehabilitation being performed, leading to increased risks of serious failures, lower performance and a growing techno-financial burden for future generations. It is well accepted that, in order to limit the multiple impacts of utility works in the urban environment, rehabilitation projects should be coordinated between water, transport, energy and telecommunication infrastructures. In practice, such coordination means that public utilities must rehabilitate assets earlier or later than technically needed, in order to engage in joint projects in which digging and resurfacing expenditures are shared. Hence, at the municipal scale, such coordination influences two variables that are key to strategic decision support: average costs (€/metre) for asset rehabilitation, and the service lifetimes of those assets. However, current models for strategic asset management do not enable practitioners to estimate how changes in the coordination process may influence the long-term financial and environmental impacts of infrastructure rehabilitation. The present study aimed at addressing this methodological gap by introducing the concept of a coordination window that quantifies to what extent utilities compromise asset rehabilitation times in order to join multi-utility projects. An algorithm for modelling the influence of the coordination window size on long-term sustainability costs is presented and applied to one Swedish municipality. The results suggested that total capital costs and carbon emissions can be lowered by 34% and 16% with a coordination window of 35 and 25 year, in comparison to the no-coordination case.

This study investigated how urban stormwater runoff, known to contain various chemical substances, alters pollutant concentrations in the receiving water bodies. Samples were collected under dry and wet weather conditions at 4 sampling stations along the Fyrisån, a river that passes along the city of Uppsala, Sweden. Samples were analyzed for 80 organic substances, 19 metals (total and dissolved phase), and conventional physicochemical parameters. 19 of 80 organic substances were qualified above the limit of quantification (LOQ) in at least one sampling event. The most detected substance family was poly-fluoroalkyl substances (PFAS). The concentrations of detected organic substances and metals increased in wet weather conditions. Organic substance and metal concentrations showed similar spatial variation with higher concentrations measured at sampling locations close to urbanized areas.

This study details the occurrence and concentrations of organic micropollutants (OMPs) in stormwater collected from a highway bridge catchment in Sweden. The prioritized OMPs were bisphenol-A (BPA), eight alkylphenols, sixteen polycyclic aromatic hydrocarbons (PAHs), and four fractions of petroleum hydrocarbons (PHCs), along with other global parameters, namely, total organic carbon (TOC), total suspended solids (TSS), turbidity, and conductivity (EC). A Monte Carlo (MC) simulation was applied to estimate the event mean concentrations (EMC) of OMPs based on intra-event subsamples during eight rain events, and analyze the associated uncertainties. Assessing the occurrence of all OMPs in the catchment and comparing the EMC values with corresponding environmental quality standards (EQSs) revealed that BPA, octylphenol (OP), nonylphenol (NP), five carcinogenic and four non-carcinogenic PAHs, and C16-C40 fractions of PHCs can be problematic for freshwater. On the other hand, alkylphenol ethoxylates (OPnEO and NPnEO), six low molecule weight PAHs, and lighter fractions of PHCs (C10-C16) do not occur at levels that are expected to pose an environmental risk. Our data analysis revealed that turbidity has a strong correlation with PAHs, PHCs, and TSS; and TOC and EC highly associated with BPA concentrations. Furthermore, the EMC error analysis showed that high uncertainty in OMP data can influence the final interpretation of EMC values. As such, some of the challenges that were experienced in the presented research yielded suggestions for future monitoring programs to obtain more reliable data acquisition and analysis.

Datasammanställningen som presenteras här innehåller rådata från provtagningar som utfördes vid åtta enskilda anläggningar för behandling av bad-, disk- och tvättvatten (BDT) i Södertälje kommun. Prover togs från tre typer av minireningsverk och en markbädd för BDT rening. Stickprover togs från inkommande och utgående vatten mellan augusti 2020 och december 2021 och analyserades på organisk substans, näringsämnen, indikatorbakterier, anjoniska tensider, salt och (för två av anläggningar) mikroplast. Mätningar på andra parametrar såsom pH och suspenderat material är inkluderade. För mikroplast inkluderas dessutom resultat på blankprover.

Detta dataset har använts för att utvärdera reningseffektiviteten av de enskilda BDT-vattenanläggningarna och för att bedöma om det renade vattnet skulle kunna återanvändas.

The studies which this thesis is based on assessed the stormwater quality in a highway catchment located in Sundsvall, Sweden, and examined the performance of a gross pollutant trap (GPT)-biofilter stormwater treatment train (TT) downstream of the catchment, in terms of removal efficiency, intra-event variability, and environmental risk reduction of organic micropollutants (OMPs) for the receiving water body. Assessing the occurrence and event mean concentrations (EMCs) of all OMPs in the catchment revealed that bisphenol A (BPA), octylphenol (OP), nonylphenol (NP), five carcinogenic and four non-carcinogenic polycyclic aromatic hydrocarbons (PAHs), and C16-C40 fractions of petroleum hydrocarbons (PHCs) all potentially pose an environmental risk to freshwater (EMCs >PNEC: predicted non-effect concentration), while alkylphenolethoxylates, six low- molecular weight PAHs, and lighter fractions of PHCs (C10-C16) do not occur at problematic levels.

In order to assess the impact of the downstream TT in mitigating the risks of the studied OMPs, the performance of the TT compartments (a GPT followed by three filter cells) was analyzed and then compared with each other to identify the importance of each design feature (i.e. pre-treatment GPT, sand-based filter media, vegetation, and chalk amendment). Overall, the TT removed most OMPs from highway runoff effectively. The GTP did not contribute to this treatment, thus, the filter sections were responsible for most of the OMP removal. The results showed that, although the non-vegetated sandfilter (SF) could moderately (<50% removal for phenolic substances) to substantially (50–80% removal for PAHs and PHCs) treat the OMPs, the vegetated biofilters (BF and BFC) considerably improved the removal performance, especially for BPA, OP, and suspended solids (TSS). This observation was explained by additional filtration processes provided by the vegetation topsoil layer, which not only enhanced the particulate/particle-bound OMP physical retention but also physiochemical adsorption of colloidal and soluble substances/fractions (such as BPA and OP).

Further analysis of intra-event concentration (IEC) variations of OMPs and TSS showed that the IECs in the highway stormwater and GPT outflow varied considerably without any particular patterns over the course of the events, but first flush rarely occurred. The IEC variations were attenuated by the SF and BFC cells so that more even pollutant load discharge with no first flush was observed during the filter cells’ outflow events. Yet, the IECs for the SF cell revealed that the IECs often peak at the beginning of the effluent events (within the first 100 m3 out of maximum record of ⁓600 m3) and then decrease and become stabilized towards the end of the event. The early-phase concentration peaks exceeded the PNECs for TSS, five PAHs, BPA, and OP, a fact that was not shown by the EMC-based analysis, thus highlighted the advantage of the IEC analysis.

This field study assessed the occurrence, event mean concentrations (EMCs), and removal of selected organic micro-pollutants (OMPs), namely, polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), nonylphenol (NP), 4-t-octylphenol (OP), and bisphenol A (BPA), in a gross pollutant trap (GPT)-biofilter/sand filter stormwater treatment train in Sundsvall, Sweden. The effects of design features of each treatment unit, including pre-sedimentation (GPT), sand filter medium, vegetation, and chalk amendment, were investigated by comparing the units' removal performances. Overall, the treatment train removed most OMPs from highway runoff effectively. The results showed that although the sand filter provided moderate (<50 % for phenolic substances) to high (50–80 % for PAHs and PHCs) removal of OMPs, adding a vegetated soil layer on top of the sand filter considerably improved the removal performance (by at least 30 %), especially for BPA, OP, and suspended solids. Moreover, GTP did not contribute to the treatment significantly. Uncertainties in the removal efficiencies of PAHs and PHCs by the filter cells increased substantially when the ratio of the influent concentration to the limit of quantification decreased. Thus, accounting for such uncertainties due to the low OMP concentrations should be considered when evaluating the removal performance of biofilters.

Greywater contains inorganic and organic substances, nutrients, pathogens, micropollutants and microplastics. Source-separated greywater using decentralized systems can potentially provide energy-efficient and low-maintenance treatment. If effectively treated, greywater could be a source for non-potable water use in for instance urban landscaping or agricultural irrigation. The overall aim of this thesis was to investigate the treatment efficiencies of two different types of decentralized greywater treatment systems: a) on-site package plants and b) a nature-based solution (NBS) - green wall. These two different treatment systems were assessed based on their removal efficiency of organic matter (BOD, COD, TOC), nutrients (nitrogen (N) and phosphorus (P)), surfactants, indicator bacteria (E. coli and enterococci) as well as microplastics.

The study of the on-site package plants investigated eight on-site greywater treatment facilities of four different types (A, B, C and D). Systems types A-C were commercially available and type D was an onsite built sand filter. The treatment unit of type A consisted of a trickling filter fitted with geotextile resting on a sand filter bed. The treatment unit of type B included a fibrous mineral wool filter material while type C contained a series of fine-meshed plastic filters. Prior to types A, B and D, septic tanks were located to contribute with pre-treatment, whereas type C, the smallest system investigated, included a septic tank within the treatment unit. >90% removal of organic matter (BOD and COD) was achieved by types A and D, but the N removal was comparatively higher by type B (44-68%). Effective P removal was only observed in type D (56%). However, the effluent concentration from all the systems was <3mg/l. The treatment efficiency of type C was found to be relatively low.

In the green wall study, the efficiency of five filter materials (pumice, biochar, hemp fiber, spent coffee ground (SCG) and compost fiber soil) were evaluated with regards to hydraulic loading rates (HLRs) (4.5, 9, and 18 l/d). The treatment efficiency varied significantly with materials and HLRs. Biochar consistently removed 99% of BOD for all HLRs. High N removal (>80%) was observed by pumice and biochar during the high HLR (18 l/d). However, P removal by hemp was comparatively higher (75-85%) than by biochar and pumice. SCG and compost soil was tested with only 4.5 l/d, where compost soil showed effective treatment of BOD (99%), N (82%) and P (85%). SCG was the least effective material releasing more organics and nutrients in the effluent. 

Both the studies showed high concentration (>105 cfu/100 ml) of E. coli and enterococci in the influent and effluent greywater. The treatment systems were in general not effective in removing E.coli and enterococci. The most efficient system was the sand filter (D), achieving 1.4-3.8 log10  E.coli reduction and 2.3-3.3 log10 reduction for enterococci. Biochar achieved similar removal at HRL 4.5 l/d. Using thermal extraction desorption gas chromatography-mass spectrometry (TED-GCMS) technique, polyvinylchloride, polystyrene, poly-ethylene-terephthalate, polyethylene, polypropylene, and polyamide 6 were detected in the influent and effluent greywater in both studies. Even though there was variability in the influent concentrations, low concentrations were observed in the effluents, suggesting the systems were effective in retaining the microplastics.

The vegetation layer contributes to multiple functions of green roofs including their hydrological function as plants remove water from substrates between rainfall events through evapotranspiration, restoring the green roofs storage capacity for rainfall retention. While individual traits have been related to water use strategies of green roof plants, these traits are inconsistent, suggesting the importance of trait combinations which may be reflected in CSR (competitor, stress tolerator, ruderal) strategies. Therefore, relating plant water use to leaf traits and CSR strategies could help facilitate green roof plant selection into new geographical regions where green roof technology is developing. For example, in high latitude northern European regions with long daylight during the growing season. Growth (shoot biomass, relative growth rate and leaf area), leaf traits (leaf dry matter content, specific leaf area and succulence) and CSR strategies were determined of 10 common European green roof plants and related to their water use under well-watered (WW) and water-deficit (WD) conditions. All three succulent species included in the experiment showed mostly stress tolerant traits and their water loss was less than the bare unplanted substrate, likely due to mulching of the substrate surface. Plants with greater water use under WW conditions had more ruderal and competitive strategies, and greater leaf area and shoot biomass, than species with lower WW water use. However, the four species with the highest water use under WW conditions were able to downregulate their water use under WD, indicating that they could both retain rainfall and survive periods of water limitations. This study indicates that, for optimal stormwater retention, green roof plant selection in high latitude regions like northern Europe, should focus on selecting non-succulent plants with predominantly competitive or ruderal strategies to make the most of the long daylight during the short growing season.

Hydraulic dredging of stormwater ponds may include on-site dewatering of dredged materials using polymersand geotextile filtration. The choice of polymer and its preparation affect the overall operational effectivenessand the quality of the reject water (filtrate) returned to the stormwater pond. This study examined the resultingparticle content as well as nutrient and metal concentrations in the filtrate conducted on hydraulically dredgedstormwater sediment that was chemically conditioned and filtered through geotextile. This study investigateshow polymer choice and preparation affects the outcome. In total, three types of polymers were tested (powder,emulsion commercial cationic polymers and chitosan), the water (tap water or reclaimed) the polymer wasprepared in, and the aging time of the polymer solution. Deviations from manufacturer's instructions on thepolymer preparation increased the amount of polymer needed for an optimal conditioning process. In terms ofpollutant retention, there was no difference between polymer preparations. In the filter cake there was nodiscernable difference between conditioned and unconditioned sediment, rather the difference was noticeable onthe filtrate. Conditioned stormwater sediment produced a geotextile filtrate with considerably less metal andnutrient content than the unconditioned stormwater sediment.

Datauppsättningen som presenteras här består av rådata med avseende på kvaliteten på inkommande bad-, disk- och tvättvatten (BDT-vatten), som genereras från en stadsdel med 800 PE (population equivalent), och kvaliteten på BDT-vattnet efter rening i en grön vägg. Fem naturliga filtermaterial (pimpsten, biokol, hampafiber, kaffesump och komposterad fibermull) användes i den gröna väggen och testades för tre hydrauliska belastningshastigheter (54, 108 och 216 l/m2/d). Inflödesproverna och proverna efter behandling i den gröna väggen togs manuellt mellan november 2021 och mars 2022. De analyserades med avseende på innehåll av organiskt material, näringsämnen, patogener, anjoniska tensider, salt och mikroplaster. Stödparametrar, t.ex. suspenderade fasta partiklar och pH, ingår också i datasetet. Vidare, för mikroplaster, ingår resultat från blankprover. Denna datauppsättning användes för att utvärdera behandlingseffektiviteten hos de olika filtermaterialen vid olika hydrauliska belastningshastigheter.

Building surface materials, exposed to wash-off by rainwater or snowmelt, are recognised as one of the significant urban diffuse pollution sources contributing to the impairment of stormwater quality. The pollution conveyed by roof runoff originates from two potential sources, migration of surface material constituents, or wash-off of pollutants deposited on the surface by atmospheric deposition. This study investigated the releases of metals and several groups of contaminants of emerging concern: alkylphenols, alkylphenol ethoxylates, and phthalates, from commercially available materials, which are commonly used on buildings and structure surfaces in the urban environment. The materials tested included the following: metal sheets of stainless steel, copper, zinc, galvanised steel, corten steel, corrugated and coated steel, coated zinc; and bitumen-based roofing felt and shingles, as well as polyvinyl chloride (PVC) from two manufacturers. The stainless steel was considered a control material serving to estimate pollutant contributions deposited on the pilot panels from the surrounding environment. Moreover, this study presents novel data on roof snowmelt induced runoff quality, not reported in the previous literature. The experimental setup consisted of 2-m2 rectangular panels mounted in triplicates of each material and placed in an open-air setting on the campus of Luleå University of Technology, Sweden. Runoff leaving the gently sloping material panels was collected during 11 rain and three snowmelt driven runoff events occurring over a five-year period. The results showed that, in general, the micropollutant concentrations and loads were lower in snowmelt than rain induced runoff, and no decreasing trend was detected in the releases of phthalates or metals during the study period. Moreover, on a yearly basis, copper sheets were estimated to release 0.6 g/m2 Cu to runoff, zinc and galvanised sheets 1.3 and 0.7 g/m2 Zn, respectively, and, PVC sheets were estimated to release up to 78 mg/m2 of diisononyl phthalate (DINP).

Rapid development of new materials and technologies in the automotive sector and urban growth cause changes in emissions of certain pollutants to the environment and introduction of new ones. This can cause changes in the pollutants signature and content in urban snow. Thus, it is important to revisit the reported data on urban snow quality periodically to ensure that snow management planning is based on up-to-date information. In this paper, the concentrations of TSS and ubiquitous urban metals (Zn, Cu, Cr and Pb) in urban snow, sampled at six sites in the City of Luleå during the winter 2020-21, were compared with previous data (from 1995 and 2002) to examine historical changes in snow quality in Luleå during the period 1995-2021. The results show that the pollutant concentrations in snow are influenced by measured air temperatures and precipitation, and such influences bring uncertainties into data comparisons.

A polymeric ultrafiltration (UF) membrane was used for stormwater treatment, with the focus on evaluating the increase in the membrane process productivity by adding pulsatile fluid flow to UF membrane treatment. Sedimentation and sieving were used as pre-treatment. The result showed that increasing the pulse frequency from 0 to 4 Hz increased productivity from -6.6 to 82 LMH. UF membrane removed suspended solids, oil and turbidity below detection limit. The UF membrane also separated total coliforms, E. coli and P. aeruginosa below detection limit. Total organic carbon (TOC) was reduced by between 70 and 91%. In addition, the UF membrane was able to reduce BOD7 and COD to below 7 mg/L in the permeate. According to the US EPA, WHO, and national regulations in Canada,  Japan, and South Korea, treated stormwater can be used for flushing toilets and streets irrigation and agricultural use. 

Backwash water is an integral part of membrane treatment, normally making up between 2 and 10 % of the clean water production which constitutes a large volume on an industrial scale. To identify suitable treatment or disposal methods for backwash water, it is important to understand the characteristics of the backwash water and what contaminants it contains. In this study, the backwash water from an ultrafiltration membrane process for stormwater treatment was analysed. Concentrations of TSS and TOC were 2.4 and 24 times higher in the backwash water than the influent stormwater. The concentration of particulate and dissolved (<0.45µm) metals in the backwash water was high, for example, the average concentration of total Cu and Cr was 742 ± 215 and 737 ± 243 µg/L. In addition, the average concentration factors for Cu and Cr were 29 ± 9 and 41 ± 15.9. Methods such as coagulation, electrocoagulation and evaporation could be used to further treat backwash water. The residue fraction would contain high concentrations of metals that need to be disposed or could potentially be a good resource for metal recovery in the future.

Bioretention systems for urban drainage are one type of blue-green infrastructure that have gained more attention in recent decades. There are numerous design options for these systems, including various construction components, filter material mixtures, and plants. However, the research focus on the impacts of these many design options has mainly been technical, i.e., how different bioretention designs affect runoff pollution treatment and hydraulic control. Knowledge of the effects of various design elements on other sustainability criteria, such as economic, social, and environmental aspects, needs to be developed. This research aimed to evaluate and compare various design elements and bioretention types to gain a better understanding of the relative sustainability of various bioretention systems. This was accomplished by identifying relevant criteria and sub-criteria, covering social, economic, and technical-environmental indicators, in a multicriteria analysis. To evaluate the sustainability performance of various bioretention designs, 12 sub-criteria were allotted −100 to 100 points in a scoring process. The main finding was that while design features had a major impact on bioretention performance, no single design configuration excelled in all criteria. High scores in the social criteria were correlated with the use of trees and smaller volumes of pumice in the filter material mixture. In the economic criteria, extensive use of concrete and a complex mixture of filter material increased the costs. The system with a water-saturated zone and a variety of plant species outperformed the other systems in the technical-environmental criteria. The results can be utilized as a reference to assess design configurations that best satisfy specific needs for each unique bioretention implementation.

Synthetic stormwater was tested to determine the ageing effects on dissolved metal concentrations and used in a column experiment to determine efficiency of four different filter materials (milkweed, bark, peat, polypropylene) in removing total and dissolved metals. Synthetic stormwater was created by adding metal salts, oil and collected stormwater sediment to tap water. Two ageing experiments were performed to determine the change of synthetic stormwater quality over time. One experiment lasted for 11 days and another focused on rapid concentration changes one day after preparation. The one-day ageing experiment showed rapid decrease in dissolved concentration of certain metals, specifically Cu. To consider this change, correction coefficients for each metal were developed and used to estimate the average dissolved metal concentration in the synthetic stormwater during the experiment to determine filter treatment efficiency. During the 11-day experiment on metal concentrations, no noticeable quality changes were observed for at least six days after the preparation of synthetic stormwater. Furthermore, a column experiment was run with duplicate filter columns. Inflow and outflow samples were analysed for total and dissolved metals, turbidity, particle size distribution, and pH. High removal of total metal concentrations was noticed in all tested filter media (58-94%). Dissolved metal concentration removal varied among different filter media. In general, columns with bark and peat media were able to treat dissolved metals better than polypropylene and milkweed. The level of treatment of dissolved metals between the different filter media columns were bark > peat > milkweed > polypropylene.

Implemented for decades as part of the ‘best management practices (BMPs)’ for controlling urban runoff impacts on receiving waters, stormwater management ponds (SMPs) have been increasingly viewed as potential habitats for urban wildlife. However, since SMPs are subject to a lot of environmental constraints, research toward assessing their ecological quality and their actual benefits as habitats for biota is needed. In this study, the sediment toxicity of eight SMPs located in Southern Ontario, Canada was assessed using the sediment quality triad (SQT) approach. Sediment samples were collected for chemical, ecotoxicological and biological analyses. An oligochaete-based index approach (Oligochaete Index of Lake Bioindication and percentage of pollution-sensitive species) was used as the biological endpoint and integrated into a weight-of-evidence approach to assessing the general sediment quality of the ponds. Our results showed that (i) heavy metals in the sediment and (ii) chloride concentrations in the sediment interstitial water caused detrimental effects on the ecological quality of the sediments in the ponds studied. The oligochaete indices applied in this study showed value as biological endpoints to be integrated into the SQT and used for setting up sediment ecological quality goals.

Three commonly used drainage system components, with considerably different characteristics and roles in stormwater management, were studied and reported on in this thesis: (i) grass swales, (ii) gully pots (GPs), and (iii) stormwater management ponds. With time, solids and associated pollutants accumulate in these components, and regular maintenance is needed to ensure that their design functions, including protection of the environment, are sustained.

Trace metals and their concentrations, loads and speciation were investigated within and among the individual types of components. The study program started with a critical review of processes enhancing the quality of stormwater passing over grass filter strips and through swales, and continued with field research of swale soils, and sediments from GPs and ponds.

The swales studied in the thesis served for stormwater drainage and storage of snow cleared from adjacent trafficked areas during winter months. Results suggest that both stormwater runoff and snow stored in the swale were transport vectors of metals originating from traffic. Other sources of metals were native soils and traction material used in winter road maintenance.

Moreover, the speciation results showed that across components, Zn and Pb were the metals with the highest share in the most mobile fraction, followed by Cu, while Ba, Cr,V, Co, and Ni were found in a higher share in the less mobile fractions.

GP and pond sediments showed similar organic matter content, whereas swales soils showed relatively low organic content, further decreasing with the soil depth. Results suggested that higher organic matter content corresponded to higher concentrations of certain metals in the case of ponds and, to some extent, swales. In the case of GPs, a positive relationship between metals and the proportion of fine particles was detected.

The highest concentrations of Cu and Zn were observed in sediments from ponds and reached 319 and 1380 mg/kg DW, respectively. The highest concentration of Pb (188mg/kg DW) was observed in swale, operating for 57 years located next to a road with the traffic intensity of 11,650 v/day.

The large variation in the accumulated dry mass of solids in GPs (2-91 kg) questions the current practice of emptying all GPs at the same regular intervals. Moreover, of the 26 GP samples, Swedish thresholds for soils with the sensitive (S) land use were exceeded for Cu in five samples and Zn in six samples. Of 32 pond samples, the S threshold was exceeded for Cu in nine samples and Zn in 12 samples; of these, three and eight of the pond samples also exceeded the less sensitive (LS) threshold. Of 96 swale samples, 25 samples exceeded the S threshold for Pb, with one sample also exceeding the LS threshold.

Trafikrelaterade föroreningar som partiklar, metaller, klorid, organiska föroreningar och mikroplaster (MP) lagras tillfälligt i plogvallar längs gator och vägar i urbana områden. När snön smälter frigörs de ackumulerade föroreningarna och smältvattnet som innehåller olika föroreningar kommer infiltrera marken eller avledas via dagvattenledningar och så småningom släppas ut i, och påverka, recipienter. För att kunna hantera utsläppen till miljön som uppstår som en följd av detta är det viktigt att få en mer omfattande förståelse av (i) förekomst, distribution och tidsvariation av konventionella (TSS, Cu, Zn, Pb, Cd, klorid och PAH:er) samt ”nya” föroreningar (däck- och vägslitagepartiklar (T&RWP), platinagruppelement (PGE), volfram (W) och antimon (Sb)) i urban snö, (ii) storleksfraktionering av föroreningar i snö, (iii) spridning av föroreningarna vid snösmältning samt (iv) hur metoder och tillvägagångssätt för snöprovtagning i fält påverkar osäkerheten i mätdata. Därför utgör dessa fyra punkter fokus för denna doktorsavhandling.

Arbetet som presenteras i avhandlingen inkluderar en litteraturstudie av föroreningar såsom metaller i urban snö, fältprovtagning av plogvallar och snöhögar samt smältningsexperiment i laboratorieskala. Fältprovtagningen genomfördes på tre platser i Sverige – Frihamnen (en av Stockholms hamnar), samt Luleå och Umeå kommuner i norra Sverige, och användes till studier av variationer i snökvalitet med avseende på suspenderade partiklar, metaller, klorider, PAH:er och mikroplast partiklar. Ett urval av fältproverna användes också i laboratorieexperiment för att studera hur olika föroreningar påverkas under snösmältningsprocessen.

En litteraturöversikt identifierade Zn, Cu, Pb, Cd och Ni som de mest frekvent studerade metallerna i urban snö. Sb, W och PGEs har studerats mer sällan och benämns därför här som "nya föroreningar”. Koncentrationerna av dessa föroreningar i de analyserade snöproverna skiljde sig tydligt på grund av skillnader mellan provtagningsplatserna såsom meteorologiska förhållanden, trafikintensitet och -sammansättning, vintervägunderhåll samt snöns ålder (SCA). Undersökningar av mätnoggrannhet för bestämning av föroreningsmängder lagrade i snöhögar påverkades av hur proverna togs. Enstaka prover genom hela snödjupet hade en tendens att underskatta eller överskatta föroreningsbelastningen i snöhögarna, med variationer på upp till 400%, vilket observerades i prover som togs i Frihamnen. Det understryker vikten av att samla in och analysera flera prover för att kunna göra pålitliga bedömningar av den faktiska föroreningsbelastningen.

Jämförande analys av snökvalitet under tre vintersäsonger (1994-95, 2002-03 och 2020-21) visade en statistiskt signifikant minskning av Pb- och Cd-koncentrationerna i snöprover från 1995 till 2021. Denna minskning kan tillskrivas lagar och föreskrifter om minskad användning av dessa ämnen under årens gång.

I laboratorieexperiment med snösmältning följde endast 10% av totala metaller (Cu, Zn och Cd) och PAH:er med det avrinnande smältvatten, medan resten stannade kvar (immobiliserade) som sediment på platsen för snöhögen. De lösta (<0,45 µm) och sant lösta (<3000 MWCO) storleksfraktionerna av metallerna samt klorider frigjordes tidigt under smältförloppet (preferential elution), medan TSS och PAH:er uppvisade en fördröjd frisättning (delayed release).

Sammanfattningsvis bidrar avhandlingen till att utveckla en övergripande förståelse för dynamiken av föroreningar i urban snö och lyfter fram betydelsen, och behovet, av effektiv snöhantering för att minska miljöpåverkan av föroreningar som förekommer i urban snö.