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The municipality of Arnhem has set up a monitoring program to investigate water quality in storm sewers as well as the efficiency of several end-of-pipe solutions for stormwater treatment. Four pilot installations have been set up: a sandfilter, a lamella-separator, a soil filter and a helophyte filter. Flow rates and water levels are real-time mea...
Citations
... However, there is uncertainty associated with monitoring stormwater runoff flows in urban areas. Stormwater runoff monitoring data in urban areas can contain high levels of noise from errors in data logger software and flow monitoring equipment as well as from unexpected disturbances of "experimental conditions" (Liefting and Langeveld, 2008). Before-and-after Control-Intervention (BACI) experimental designs are common in hydrological experiments but can be subject to disruptions (Shuster and Rhea, 2013). ...
Green infrastructure (GI) is increasingly being used in urban areas to supplement the function of conventional drainage infrastructure. GI relies on the “natural” hydrological processes of infiltration and evapotranspiration to treat surface runoff close to where it is generated, alleviating loading on the conventional infrastructure systems. This research addresses growing interest in identification and quantification of uncertainties with distributed, infiltration-based stormwater control measures, retrofitted on private and public properties and in right-of-ways in existing urban areas. We identify four major sources of variability and uncertainty in cumulative performance of systems that rely on extensive implementation of distributed GI: non-additive effects of individual best management practices (BMPs) at the catchment scale; the spatial configuration of fine-scale land use and land cover changes; performance changes due to climate change; and noise levels present in urban flow monitoring programs. Using a three-dimensional coupled surface-subsurface hydrological model of a residential sewershed in Washington DC, we find that prolonged, large-magnitude rain events affect various spatial configurations of GI networks differently. Runoff peaks and volumes can both be influenced by the spatial permutations of infiltration opportunities in addition to the absolute magnitude of treated area. However, the magnitude of the last source of uncertainty—noise levels in urban flow monitoring programs—may be larger than sources of variability associated with spatial changes in fine-scale land use and land cover. Changes associated with climate change– more frequent and larger rainfall events– will likely intensify performance differences between spatial configurations of GI but also increase noise levels in urban flow monitoring programs.
... The validation procedure applied to guarantee the quality of the measurement data obtained in the monitoring project in Arnhem is described in detail by Liefting and Langeveld (2008). Actuality and verifiability have been secured by keeping logbooks and archiving all relevant information digitally. ...
Stormwater runoff is a major contributor to the pollution of receiving waters. This study focuses at characterising stormwater in order to be able to determine the impact of stormwater on receiving waters and to be able to select the most appropriate stormwater handling strategy. The stormwater characterisation is based on determining site mean concentrations (SMCs) and their uncertainties as well as the treatability of stormwater by monitoring specific pollutants concentration levels (TSS, COD, BOD, TKN, TP, Pb, Cu, Zn, E.coli) at three full scale stormwater treatment facilities in Arnhem, the Netherlands. This has resulted in 106 storm events being monitored at the lamella settler, 59 at the high rate sand filter and 132 at the soil filter during the 2 year monitoring period. The stormwater characteristics in Arnhem in terms of SMCs for main pollutants TSS and COD and settling velocities differ from international data. This implies that decisions for stormwater handling made on international literature data will very likely be wrong due to assuming too high concentrations of pollutants and misjudgement of the treatability of stormwater. The removal rates monitored at the full scale treatment facilities are within the expected range, with the soil filter and the sand filter having higher removal rates than the lamella settler. The full scale pilots revealed the importance of incorporating gross solids removal in the design of stormwater treatment facilities, as the gross solids determine operation and maintenance requirements.
... The effort necessary to guarantee the quality of the measurement data obtained is described in detail by (Liefting and Langeveld, 2008). ...
The urban water systems of the municipality of Arnhem (Netherlands) are facing water quality problems that have to be addressed properly due to WFD. Therefore, the Municipality of Arnhem has set up an ambitious three year research project aiming to gain knowledge on the ecological status of receiving urban waters and the cost effectiveness of rehabilitation options of these receiving waters, such as development of natural banks or end-of-pipe treatment facilities for treating urban runoff discharged by storm sewers. This article describes the results of the monitoring campaign focussing on the emission from storm sewers and the removal efficiency of three full scale storm water treatment facilities, comprising a sand filter, a lamella separator and an infiltration (soil) filter. The results of monitoring over 150 storm events in 2006 and 2007 show that the emission from storm sewers is indeed significant with respect to nutrients and heavy metals and, in addition, storm water is unsafe from a microbiological point of view. The treatment efficiencies of all treatment facilities are in the range to be expected given the dominant treatment processes, with the sand filter and soil filter performing at a higher removal rate than the lamella settler.
... These results are confirmed by field observations in Arnhem, The Netherlands, where a 48 hours CSO event occurred during dry weather due to pump failure. (Liefting and Langeveld, 2008). ...
Although the majority of management authorities for wastewater systems has automatic systems for failure reporting, the reports are not uniform. Often they consist of a combination of real failures and interpreted operational data. Moreover, operational data are generally registered at a too low frequency. In order to enhance systematic process analysis, STOWA and the RIONED foundation have launched a uniform registration format, defining failures and operational data. At the moment, this format is being tested in three pilot projects for a period of one year. In these pilots different aspects of the implementation of the format are assessed, including availability of data, required changes of telemetry, added value of data. The results show that the required data is, or can easily be, registered in state of the art SCADA systems. However, extracting data for further analysis is not always possible. A first analysis shows that the level of pump failures varies between water authorities and between objects and that emergency stops of pumping stations due to operational problems at a downstream wwtp can occur even more frequently than pump failures. This indicates that the actual performance of wastewater systems may significantly deviate from the design level of performance.
Long-term and high-frequency in-sewer monitoring opens up a broad range of possibilities to study (influences on) water quantity and quality variations. Using data from the Eindhoven wastewater system in The Netherlands both dry weather flow and wet weather flow situations have been studied. For approximately 160 dry weather days mean diurnal variations of flow and pollutant concentrations have been derived. For wet weather situations (≈ 40 storm events) peak load factors have been studied. Generally, peak load factors for all considered pollutant parameters are larger than one. Peak load factors for particulate matter are larger than for dissolved constituents. Also, the smallest catchment area consistently shows the largest mean peak factors and vice versa.
In the Netherlands, lamella settlers are the most applied kind of end of pipe treatment to meet the
Dutch surface and water frame work directive water quality standards. Due to high expected removal
rates, low costs and a low spatial footprint, in a few years time this system has been implemented in
more than 50% of Dutch municipalities. However, not much research has been done on removal rates
of lamella settlers applied in storm sewers. This paper describes the results of a 2-year monitoring
campaign in Arnhem and the subsequent laboratory testing to explain and verify the observed results.
The results show that the emission from storm water sewers is indeed significant with respect to
nutrients and heavy metals. The removal efficiency of the lamella separator is less than expected and
to improve the hydraulic performance the system should be adjusted. Further monitoring of these
systems will take place in 2010-2011.
