Academic literature on the topic 'Stormwater treatment'

Due to high runoff volumes and peak flows, and significant contamination with (inter alia) sediment, metals, nutrients, polycyclic aromatic hydrocarbons and salt, urban stormwater is a major cause of degradation of urban water ways. Since current urban drainage systems, which heavily rely on piped sewer networks, may not be sustainable, attempts are being made to develop and refine sustainable urban drainage solutions, notably in Water Sensitive Urban Design (WSUD) and Low Impact Development (LID) concepts. Promising systems recommended for application in both WSUD and LID are stormwater biofilters (also known as bioretention systems or rain gardens) using vegetated filter media. Besides their capacity to attenuate flows and minimise runoff volumes, stormwater biofilters have proven efficacy for enhancing effluent water quality. Furthermore, they can be aesthetically pleasingly integrated even in dense urban environments. However, there are still gaps in our knowledge of the variability of biofilters' pollutant removal performance, and the factors that affect their performance.In the studies this thesis is based upon, the effects of various ambient factors, stormwater characteristics and modifications of filter design on the removal of metals, nutrients and total suspended solids (TSS) in biofilters, and pollutant pathways through them, have been investigated. For these purposes, standard biofilters and variants equipped with a submerged zone, a carbon source and different filter materials were exposed to varying temperatures and dry periods, dosed with stormwater and snowmelt, and the inflow and outflow concentrations of the pollutants were measured.Although removal percentages were consistently high (>70%), demonstrating that biofilters can reliably treat stormwater, the results show that metal outflow concentrations may vary widely depending on the biofilter design and the ambient conditions. Prolonged drying especially impaired their removal efficiency, but variations in temperature and filter media variations had little effect on metal removal rates. The adverse effects of drying could be mitigated by using a submerged zone, and thus providing a more constant moisture regime in the filters between storm events. Combined with embedded organic matter, the submerged zone especially significantly enhances Cu removal, helping to meet outflow target concentrations. Similarly, installing a mulch layer on top of the filter provides additional sorption capacity, hence metals do not ingress far into the filter and are mainly trapped on/in the top layer by sorption processes and/or mechanical trapping associated with TSS. This leads to significant metal accumulation, which facilitates biofilter maintenance since scraping off the top layer removes high proportions of previously accumulated metals, thus delaying the need to replace the whole filter media. However, removal of accumulated pollutants from the filter media is crucial for successful long-term performance of the filters to ensure that no pollutant breakthrough occurs.Nitrogen removal was found to be more variable than metal removal, and to be adversely affected by temperature increases, leading to high nitrogen leaching in warm temperatures. Phosphorus removal rates were consistently high, since most phosphorus was particle-bound and thus trapped together with TSS. However, in initial stages phosphorus was washed out from the filter media, indicating that filter media that do not have high levels of labile phosphorus should be used to avoid high effluent concentrations. Given that most outflow concentrations were far lower than those in the stormwater, biofilters are appropriate stormwater treatment systems. Dependent on the ambient conditions, the target pollutants and the sensitivity of the recipient, adaptation of the filter design is recommended. Further work is required to investigate the winter performance and improve the reliability of nitrogen removal, which is highly variable.<br>Dagvatten är en viktig orsak till ekologiska försämringar av urbana vattendrag p.g.a. stora avrinningsvolymer, och höga flöden samt en tillförsel av diverse föroreningar, t.ex. sediment, tungmetaller, näringsämnen, polycykliska aromatiska kolväten och salt. Dagvattenhanteringen har länge varit fokuserad enbart på att leda bort vattnet i rörledningar utan att hänsyn har tagits till retention av stora flöden eller till vattenkvalitén. På grund av dessa problem har utvecklingen av uthålliga dagvattensystem blivit allt viktigare och koncept som Lokalt Omhändertagande av Dagvatten (LOD), Water Sensitive Urban Design (WSUD) och Low Impact Development (LID) har utvecklats. En uthållig lösning inom dessa koncept är dagvattenbiofiltrering.Dagvattenbiofilter är infiltrationsbäddar med växter där dagvattnet infiltrerar och renas av växterna och filtermaterialet. De har en god förmåga att fördröja stora flöden samt att reducera föroreningar i dagvattnet innan det släpps ut till recipienten. Dessutom är det en estetisk och naturnära teknik som mycket väl kan integreras arkitektoniskt i både nya och befintliga stadsmiljöer. Dock saknas det fortfarande mycket kunskap om de processer som styr reningsförmågan samt hur de påverkas av varierande omgivningsförhållanden. I denna avhandling har därför effekterna av olika omgivningsfaktorer, dagvattenegenskaper och design av biofilter på reningen av metaller, näringsämnen och sediment undersökts. För att undersöka detta har biofilter, som delvis försetts med olika filtermaterial eller en vattenmättad zon, till dels kombinerad med en kolkälla, och utsatts för olika temperaturer och torra perioder. Biofiltren har bevattnats med dagvatten eller smältvatten. Prover har tagits på ingående och utgående vatten och föroreningskoncentrationerna har analyserats. Trots att reduktionsförmågan av metaller var hög (>70%), vilket bekräftar att biofiltren har förmågan att effektivt rena dagvattnet, visar resultaten att de utgående metallkoncentrationerna kan variera mycket beroende på utformningen av biofilter och varierande omgivningsfaktorer. Torra perioder som är längre än 3 till 4 veckor minskar metallavskiljningen i biofilter, medan växlande temperaturer och olika filtermaterial hade mindre betydelse för metallreningen. Dock kan en vattenmättad zon i filtermaterialet minimera (Cu och Zn) eller till och med avlägsna (Pb) den negativa effekten av torka med avseende på reningsförmågan. I kombination med en kolkälla kan en vattenmättad zon öka reningseffekten för framför allt Cu (som inte är lika bra i standardutförande av biofilter) på grund av en ökad komplexbildning och partikulärt organiskt material. Sediment, metaller och partikelbundna dagvattenföroreningar hålls tillbaka redan i det översta filterlagret vilket leder till en hög metallackumulation. Detta underlättar filterunderhållet: genom att skrapa och ersätta bara det översta jordlagret kan en hög andel ackumulerade föroreningar tas bort från filtret. Således kan utbyte av det hela filtermaterialet fördröjas.Kvävereningen var inte lika effektiv som metallreningen. I varma temperaturer (20°C) har kväveutlakning i stället for reduktion observerats. Fosforreningen var dock hög eftersom fosfor var mestadels partikelbunden och blev därför filtrerat tillsammans med sedimentet i det översta filterlagret. I början av biofilterdriften har dock fosforurlakning från filtermaterialet observerats vilket tyder på att det inte ska innehåller höga halter av fosfor för att undvika utlakning från filtret. Eftersom de flesta föroreningskoncentrationer i det utgående vattnet var betydligt lägre än i dagvattnet är biofilter en uthållig och tillförlitlig teknik för dagvattenrening. Beroende på olika omgivningsfaktorer samt de ekologiska förhållandena i recipienten rekommenderas dock anpassning av filterdesignen. Framtida forskning behövs för att undersöka biofiltrens reningsförmåga under vinterförhållanden och för att förbättra den varierande kvävereningen.<br>Godkänd; 2010; 20100812 (godble); DISPUTATION Ämnesområde: VA-teknik/Sanitary Engineering Opponent: Professor Jean-Luc Bertrand-Krajewski, INSA de Lyon, Frankrike Ordförande: Professor Maria Wiklander, Luleå tekniska universitet Tid: Fredag den 8 oktober 2010, kl 10.00 Plats: F1031, Luleå tekniska universitet

A floating treatment wetland (FTW) is an ecological approach which seeks to reduce point and nonpoint source pollution by installing substrate rooted plants grown on floating mats in open waters. While relatively novel, FTW use is increasing. A review of literature identified several research gaps, including: (1) assessments of the treatment performance of FTWs; (2) evaluations of FTWs in the U.S., particularly within wet ponds that receive urban runoff; and (3) plant temporal nutrient distribution, plant growth rate, and the long-term persistence of the FTWs in temperate regions with periodic ice encasement. An assessment model, i-FTW model, was developed, and its parameter s fitted based on data from 14 published FTW studies in the first research topic. The estimated median FTW apparent uptake velocity with 95% confidence interval were 0.048 (0.018 - 0.059) and 0.027 (0.016 - 0.040) m/day for total phosphorus (TP) and total nitrogen (TN), respectively. The i-FTW model provided a more accurate prediction in nutrient removal than two common performance metrics: removal rate (mg/m2/day) and removal efficiency (%). In the second research topic, the results of a mesocosm experiment indicated that FTWs with 61% coverage, planted with pickerelweed (Pontederia cordata L.) or softstem bulrush (Schoenoplectus tabernaemontani), significantly improved TP and TN removal efficiency of the control treatment by 8.2% and 18.2%, respectively. The pickerelweed exhibited significantly higher phosphorus and nitrogen removal than the softstem bulrush when water temperatures were greater than 25 deg C. Field observations in the third research topic found that pickerelweed demonstrated higher phosphorus removal performance (7.58 mg/plant) than softstem bulrush (1.62 mg/plant). Based on the observed seasonal changes in phosphorus distribution, harvest of above-ground vegetation is recommended to be conducted twice a year in June and September. Planted perennial macrophytes successfully adapted to stresses of the low dissolved oxygen (DO) concentrations (minimum: 1.2 mg/L), ice encasement, and relatively low nutrient concentrations in the water (median: 0.15 mg/L TP and 1.15 mg/L TN). Systematic observation of wildlife activities indicated eight classes of organisms inhabiting, foraging, breeding, nursing, or resting in the FTWs. Recommendations for FTW design and suggestions for further research are made based upon these findings.<br>Ph. D.

The Mulden-Rigolen system, a new urban stormwater management system implemented in Germany, has been examined in this study. The aim of this new system is to replace traditional sewer system for urban road runoff, by infiltrating the incoming water locally through a dual underground system: an active top soil layer and a deeper trench of packed gravel. For each site using this system, the characteristics of the soils in terms of pH, texture, organic matter, infiltration rate as well as Heavy Metals (Cd, Cr, Cu, Pb, Zn) and Phosphorus soil concentrations were successfully determined. The measured values for the soil characteristics were still, after an operation time of up to 15 years for some sites, globally in the range of the recommendation of the German Association for Water, Wastewater and Waste, except for organic matter in some sites, suggesting the need for a more cautious maintenance. Concerning heavy metals and phosphorus content, no alarming soil contamination was observed indicating that the studied “Mulden-Rigolen” systems were still acceptable in terms of soil pollution after several years of use, according to the Danish standards. If this system seemed to have a good flexibility and adaptability to different urban land uses, its treatment efficiency still has to be fully assessed. Indeed, only a primary evaluation of its performance war carried out through a simplistic model which brought up some questions about pollutant retention (especially in case of Zn). Further research (intact soil columns experiments, sequential extractions, on-site runoff sampling) would be necessary to fully determine how well this system works in terms of water treatment.

Increases in impervious surfaces associated with urbanization change stream hydrology by increasing peak flow rates, storm-flow volumes and flood frequency, and degrade water quality through increases in sediment, nutrient, and bacteria concentrations. In response to water quality and quantity issues within the Stroubles Creek watershed, the Town of Blacksburg and Virginia Tech designed and constructed two innovative stormwater best management practices (BMPs). The goal of this project was to evaluate the effectiveness of a bioretention cell and a CU-Structural Soilâ ¢ infiltration trench. BMP construction was completed in July 2007. Twenty-nine precipitation events were monitored over a period of five months between October 2007 and March 2008. For each storm, inflow and outflow composite samples were collected for each BMP and analyzed for suspended sediment, total nitrogen, total phosphorus, fecal coliform bacteria and E-coli bacteria. The inflow and outflow concentrations and loads, as well as total inflow and outflow volumes and peak flow rates, were then compared to evaluate how well each BMP reduces stormwater flows, decrease peak runoff rates and improves water quality of stormwater runoff. Results for the bioretention cell indicate average reductions in stormwater quantity, sediment, total nitrogen, total phosphorus and fecal coliform bacteria that exceeded 99% by mass. The CU-Structural Soilâ ¢ infiltration trench produced reductions in stormwater quantity, total phosphorus and sediment that averaged 60%, 45% and 51%, respectively. Preliminary bacteria results indicated that both BMPs served as sources of E-coli, and the infiltration trench served as a source of fecal coliform bacteria.<br>Master of Science

Stormwater ponds for the treatment of urban runoff are being increasingly used as ‘treatment’ technologies in the management of urban stormwater world wide. Although stormwater ponds have been proven to be effective at reducing the concentration of nutrients from urban stormwater, the exact processes leading to this reduction remains largely unknown and unquantified. With stormwater management fast becoming a managed and mitigated water quality issue, the importance of our understanding on how these ecosystem function increases. A stormwater pond system designed and built for the treatment of urban runoff in 2001 was used as the study site for the PhD investigation. The primary goal of the PhD study was to investigate and quantify biological processes leading to N, P, and C load reduction within the inlet and outlet ponds at the Bridgewater Creek Stormwater Treatment System (BWC System) in Brisbane, Southeast Queensland Australia. The BWC System consists of 6 interconnected ponds spanning a total surface area of 0.8 ha, and draining 198 ha catchment consisting almost entirely of residential, single lot development. The initial sedimentation basin (Pond 1) and the final polishing pond (Pond 6) of the BWC System were the focus of the investigation. Based on rainfall runoff rates, 29.5% of the catchment feeding into the stormwater treatment pond system was classed as ‘directly connected impervious area’, with each storm event delivering a mean 18.3ML of urban runoff. Data showed that storm events generating greater than 9.89 mm of rainfall produced runoff volumes greater than the storage capacity of the BWC System, thus triggering the high flow bypass channel. During the study period (2003-2005), 56.9% of all generated stormwater bypassed the BWC System, attributed to the small size of the pond system compared to its catchment drainage area. Within Ponds 2-6 of the treatment system, stormwater was retained for up to 9 days. Nutrient load reduction within the pond system was calculated at 50%, and 16% for TN and DOC respectively, but TP loads increased by 30% within the pond system. The export of TP loads greater than input for the given events within the BWC System was attributed, in part, to sediment resuspension and transportation due to the lack of significant macrophyte stands to stabilize sediment within the system. Possibly a result of this, the BWC System rarely achieved TP water quality objectives, set by the Brisbane City Council, but TN, Org-N, NH4, NOx and PO4 objectives where achieved more than 40% of the time.m Using Principal Component Analysis, three factors where found to significantly influence the variability of water quality within the pond system on a temporal scale. That being, ‘storm events’, ‘phosphorus dynamics’, and/or ‘DIN dynamics’. These factors effectively describe the abiotic or biotic variables driving water quality within the ponds at any given point in time. Key physicochemical parameters driving water quality in the ponds included pH, redox potential and DO. Water quality was similar between pelagic and littoral zones of both ponds within the BWC System. The phytoplankton community within the BWC System was characteristic of polluted freshwaters, dominated by mixotrophic green algae. Cyanobacteria blooms within the ponds was minimal, with one bloom of Anabaena spp. occurring in Apr-04. Phytoplankton production rates were indicative of eutrophic freshwater environments (0.6-20 gC m?² day?¹), with production limited by light. Bacterioplankton production far exceeded that of phytoplankton production (8-210 gC m?² day?¹) during all incubations, defining the pond system as net heterotrophic. These high rates of bacterioplankton production coupled with the phytoplankton production suggested that the mineralsation of gross particulate organic matter entering the system during stormevents may be providing the nutrients nessasary to fuel such high production rates. Within Pond 1, nutrient movement across the benthic/water column interface were calculated at 0.73, 0.37 and 0.47 mg m?² day?¹ for TN, TP and DOC. In Pond 6, there was a gross loss of nutrients from the water column to the sediment zone for TN and TP (0.24 and 0.03 mg m?² day?¹) but not for DOC (sediment to water movement, 0.17 mg m?² day?¹). As in Pond 6, if sunlight can penetrate the benthos and gross particulate matter is low, Benthic Macro Algae can inhabit the benthos and enhace nutrient loss from the water column. During the mesocosom experiments the Ceratophyllum/epiphyton complex exhausted ammonia concentrations within the incubation jars and reduced PO4-P to background concentrations. Attached epiphyton and phytoplankton community displayed similar characteristics in PO4-P concentration reduction from the water column, with biotic uptake within the incubation jars limited to 0.03 and 0.02 mg L?¹ day?¹ respectively (0.14 mg L?¹ day?¹ for Ceratophyllum/epiphyton complex). From these incubation experiments, the important role of submerged macrophyte communities in nutrient reduction from the water coloumn was proven. The research presented in this thesis justifies the use of stormwater ponds for urban stormwater management. The ability of submerged macrophytes at enhancing nutrient removal from stormwater was demonstrated. Phytoplankton and Bacterioplankton production and associated inorganic N and P uptake within the pond system did not correspond to measured and calculated storm flow inputs, indicating a large ‘unmeasured source’ – assumed to be the input of large particulate organic matter into the system during storm events.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>Griffith School of Engineering<br>Full Text

The full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate

Development of cities, new buildings and other impervious surfaces entails increased stormwater flows, volumes and pollutant loads. Heavy metals, nutrients, sediments and salt are common pollutants in stormwater. The conventional way to managestormwater, which is by discharge to the receiving water body via asewage network, will not be sufficient for mitigating high flows, flood risks and pollution export. Thus,Low Impact Development (LID) stormwater facilities, such as stormwater biofilters, are built in an increasing rate in Swedenand worldwide.The main function of a stormwater biofilter is water quality treatment, which is achieved when stormwater percolates through a vegetated filter media. Sometimes a pre-treatment facility is installed before the biofilter to reduce thesedimentload on the biofilter and extend its life-length. However, there are knowledge gaps regarding pollutant removal in biofilters and the role of associated pre-treatment facilities. In this study the impact of a pre-treatmentfacility, calcium carbonateas amendment in the filter media and vegetation wasinvestigated regardingtreatment of heavy metals (Cd(cadmium),Cu(copper), Pb (lead)and Zn (zinc)), phosphorus and total suspended solids. To do this, influent and effluent stormwater samples from an existing biofilter in Sundsvall were analysed and evaluated regarding removal performance of the above-mentionedpollutants. In general, the stormwaterbiofilter facility (including pre-treatment) removed total metals well while the removal of the dissolved fraction showed higher variations. Influent concentrations of TP were always higher than effluentconcentrations. Leaching of phosphate repeatedly occurred from the filter sections.The mean removalof TSS was high (96.9%). CaCO3as amendmentin the filter material had a beneficial effect on the overall metal removal of the stormwater facility. Although leaching of phosphate occurred from all filter sections, the leaching was lowest from the section with CaCO3, indicating possible benefits of CaCO3as amendment. CaCO3 did not seem to affect the mean total phosphorusremoval significantly.Removal of total metals seemed to be improved by vegetation, but the removal of dissolved metals, total phosphorusand phosphate did not seem to be enhanced by vegetation. The filter section with vegetation and without CaCO3 amendment contributed with the highest effluent concentrations of total phosphorusand phosphate (leaching), considering that vegetation released more phosphate that it captured. The main treatment of the stormwater pollutants occurred within the biofilter and both positive and negative removal of all pollutants was observed by the pre-treatment facility. The result showed that the pre-treatment facility was most beneficial for removal of dissolved metals.<br>Utvecklingen av städer, nya byggnader och andra hårdgjorda ytor ökar både mängden dagvatten och föroreningshalterna. Vanligt förekommande föroreningar i dagvatten är tungmetaller, näringsämnen, sediment och salt.Det traditionella sättet att hantera dagvatten är genom avledning via avloppsnätet till närliggande recipient, men med den förändrade kvalitén och kvantitet på dagvatten blir kapaciteten i det befintliga ledningsnätet otillräckligtför de ökadeflödenaoch föroreningsinnehållet.Därför byggs bland annat dagvattenbiofilter, som är en typ av Low Impact Development (LID), i en ökande takt i Sverigeoch globalt. Huvudsyftet med dagvattenbiofilter är dagvattenrening, vilket uppnås när dagvattnet filtreras genom en filterbädd med växter. För att minska (sediment)belastningenoch förlänga livslängden på biofiltret kan ibland en förbehandlingsanläggning placeras i före biofiltret. Dock finns det fortfarande kunskapsluckor om reningspotentialen i biofilter och betydelsen av en förbehandlingsanläggning. I den här studien undersöktes betydelsen av en förbehandlingsanläggning, kalciumkarbonat som tillsatsi filter materialet och växter på biofiltret för reningen av tungmetaller (Cd (kadmium), Cu (koppar),Pb(bly)ochZn(zink)), fosfor och totalt suspenderat material. För att undersöka detta analyserades och utvärderades dagvattenprover på inkommande och utgående vattenfrån ett biofilter i Sundsvall, med avseende på reningsprestation av ovan nämnda föroreningar. Resultatet visade att biofiltret (med förbehandlingsanläggningen inkluderad), renade totala metaller bra medanreningen av lösta metaller varierade mer. Inkommande koncentrationer av totalfosforvar alltid högre än utgåendekoncentrationeroch fosfat lakades kontinuerligt ut från filtersektionerna. Den genomsnittliga reningen av TSS var hög (96,9%).CaCO3 som tillsats i filtermaterialet hade en positiv effekt på reningen av totala och lösta metaller i biofiltret. Fosfat lakades ut från alla filtersektioner,men urlakningen var lägst från filtersektionen med CaCO3, vilket tyder på möjliga positiva effekterdet som tillsats i filtermaterialet.CaCO3 verkade inte öka genomsnittliga reningen av totalfosfor signifikant. Vegetationenverkade öka reningen av totala metallermen inte reningen av lösta metaller, totalfosfor eller fosfat. Filtersektionen med vegetation men utan CaCO3genererade de högstautgående koncentrationernaav totalfosfor och fosfat (urlakning), vilket tyder på att vegetation avgav mer fosfor än den tog upp. Den dominerande reningenav dagvattenföroreningarnaskedde inuti biofiltret och både högre och lägre koncentrationer av samtliga föroreningar observerades efter förbehandlingsanläggningen.Resultatetvisade attförbehandlingsanläggningen var mest effektiv för reningen av lösta metaller.