Climate change, e.g. more intense rainfall events, will affect urban drainage systems, and cause problems in cities. There is a need to understand and assess these impacts and consequences better; therefore, a strategy and possible tools are suggested in this paper. The recommended tools are Urban Drainage Simulations, Risk Analysis, and Geographic Information Systems (GIS). Since the impacts of climate change on urban drainage concerns several different disciplines, the assessment should be performed in cooperation with, e.g. urban drainage experts, climate change experts, practitioners, politicians, etc
The changes in climate were of a growing concern in the last decade, and will be even more so in the coming years. When investigating impacts on urban drainage systems due to changes in the climate, two challenges are (1) what type of input rainfall data to use, and (2) what parameters to measure the impacts. The overall objective of this study is to investigate the hydraulic performances ofurban drainage systems related to changes in rainfall, and through these hydraulic parameters describe impacts of climate change. Input rainfall data represents today's climate, as well as three future time periods (2011-2040, 2041-2070, and 2071-2100). The hydraulic parameters used were water levels in nodes (e.g. as the number of floods, frequency and duration of floods), and pipe flow ratio. For the study area, the number of flooded nodes and the geographical distribution of floods will increase in the future, as will both the flooding frequency and the duration of floods.
Fat oil and grease (FOG) from food preparation can cause severeproblems if it is discharged to the municipal sewer network. A surveyamong Swedish and Norwegian municipalities has shown that nearlyall respondents experience FOG-related problems. The most commonproblem is FOG accumulation connected to the sewer pipes whichdecreases the pipe pipe capacity and may lead to sewer overflows. FOGaccumulation occurs especially at lift stations and depressions. FOGdeposits are often made up of saponised FOG. The fatty acids promotefurthermore corrosion of concrete pipes. FOG can even impact wastewater treatment and might cause severer working conditions.The aim for the water suppliers has thus to be an effective FOGsource control before FOG is discharged to the sewer network. Sourcesare both commercial establishments and residential sewer customers.In this report different source control measures are discussed. Greaseinterceptors are commonly used for commercial FOG sources. However,a number of them lack a grease interceptor and quite often operationand maintenance is deficient. An insufficient frequency ofemptying and a lack of supervision have been identified as a commonproblem. FOG collection systems for commercial FOG producers existin both Sweden and Norway. Collection systems for private householdsare currently in a test phase and experiences from among others Austriaare promising. Even the collected amount of FOG could presumablybe increased. Collected FOG and FOG slurry from interceptors is avaluable resource which can be used as raw material in the chemicalindustry or as an energy source (combustion, biodiesel, fermentation).Threshold values for FOG discharges are set up commonly by municipalities.However, even here supervision is often insufficient. Often, thethreshold values are inadequately low and a value of at least 150 mg/lis recommended. All those measures have to be supported by informationcampaigns which aim on both commercial and private customers.
Matfett och -olja som släpps ut till avloppsnätet kan orsaka driftproblem. Denna enkätstudie har visat att nästan alla kommuner i Norge och Sverige upplever problem på grund av fettet.
Detta projekt har genomförts av Luleå Tekniska Universitet i samarbete med 5 kommuner; Arvika, Skellefteå, Sundsvall, Trelleborg samt Växjö. Projektets syfte har varit att studera hur olika metoder kan användas för att utvärdera dagvattensystemets påverkan av extrema regnhändelser. Rapporten har skrivits i syfte att ge en övergripande bild av olika metoder och de osäkerheter som finns när de olika metoderna används. Materialet i rapporten är hämtat från aktuellt projekt samt från parallella studier vid forskningsgruppen Stadens vatten, LTU och från internationella och nationella studier för att ge ett så brett perspektiv på olika metoder som möjligt. De metoder som beskrivs i rapporten går från en väldigt enkel analys baserat på vanliga dimensioneringsekvationer som kan utföras i ett excelark eller för hand till analyser som kräver komplexa modeller som simulerar vattenföringen i ledningsnätet samt ytavrinning kopplat till infiltration. Alla metoder kräver någon form av nederbördsinformation och därför inkluderas i rapporten ett avsnitt om regn och framtida regn kopplat till klimatförändring. För att genomföra en analys krävs även parametrar att studera effekterna av olika körningar och i slutet presenteras ett kort avsnitt om indikationer som är lämpliga att använda vid utvärdering av dagvattensystemet. När en metod ska väljas är det viktigt att syfte med undersökning och resurser i form av tid, existerande data och pengar ställs mot varandra. En avancerad modell har ett större krav på indata, datakapacitet och på mätdata som den kan verifieras mot. I vissa fall är det bättre att använda en enklare modell med kontinuerligt, historiskt regndata medan i andra fall krävs en komplex modell som inkluderar t.ex. infiltration i permeabla ytor och att då använda sig av designregn för att klara av de begränsningar som ev. finns i datakapacitet och simuleringstid. Innan beslut tas om modell eller metod bör det noggrant funderas över varför modellen ska tas fram, hur den ska användas samt vilka data som finns tillgängliga eller kan tas fram med nya mätningar. Om metoderna beskrivna i rapporten används på korrekt sätt och verifieras med tillräckligt data kan dessa utvärderingar av dagvattensystemet ge en bra bild av hur systemet fungerar samt hur det påverkas av olika scenarier.
The water and wastewater transport systems faces severe challenges due to climate change, resource constrain and an aging infrastructure. In cold regions the challenges are also related to general conditions societies have in common, e.g. sparsely populated, depopulation, long distances between populated areas and difficulties with recruiting right competence, beside the influence of the harsh climate on the technical system. In Sweden, municipal water services are financed by fees paid by the water utility users in a specific municipality. This means that water utilities in sparsely populated cold regions with on-going depopulation have limited economical resources to operate and maintain the transport and treatment systems for water and wastewater. The objectives of this paper are to illustrate the challenges for managing the transport system by comparing benchmark values for municipalities in cold regions with the Swedish averages, suggest possible measures to meet the challenges and give examples of on-going research in Stormwater&Sewers related to these questions.
Ageing drinking water, stormwater and sewer pipe networks imply an increased degree of rehabilitation. The need for rehabilitation can be predicted using lifetime distribution functions together with current network age and material distribution. In Sweden, current age and material distribution is neither documented on a national level, nor for many water utilities on a local level. In this study, current network age and material distribution was provided through a questionnaire sent to Swedish water and wastewater utilities and the data provided were extrapolated to cover the whole of Sweden. The data were then combined with lifetime distribution functions to provide predictions. One limitation is that for newer materials the lifetime is still uncertain. Predictions were made for different scenarios to reflect local differences and the medium scenario shows that while the Swedish rehabilitation rate is stable, investments in monetary terms need to double in the next 60 years. The rehabilitation rate is also dependent on the extent to which the network is expanded. This method can be used to calculate national investment needs, and the results can also provide a basis for estimates for Swedish utilities with data scarcity
In this paper, a simple conceptual model is presented to describe the dynamics of total suspended solid (TSS) transport during snowmelt- and rainfall-induced road runoff from a small urban runoff plot in northern Sweden. The study period (28 March to 28 May 2000) included both snowmelt and rainfall. A temperature-index method is used to describe snowmelt and the accumulation and transport of TSS is described by a linear build-up function and a wash-off model. The model was verified through measurements taken from 22 March to 22 May 2001. The simulation results showed that the simple model concept was capable of describing the dynamics of road runoff and TSS well, based on the continuous course of events for the whole modelling period. However, if the model was used for simulating a snowmelt period, or single events during snowmelt, the model approach would be too simple.