Academic literature on the topic 'Stormwater quality improvement devices (SQIDs)'

The treatment of stormwater using surface constructed wetlands has become common in the last decades. However, the use of constructed wetlands for stormwater management has not been thoroughly evaluated in their capacity to treat microbial loads. The case studies presented in this paper are situated at Lake Macquarie, a large estuarine lagoon located approximately 150 km north of Sydney, Australia. To protect the lake ecosystem from the impact of increasing urban development, the local Council constructed numerous stormwater quality improvement devices (SQIDs) at selected locations. The SQIDs typically consisted of trash racks, gross pollutant traps and surface constructed wetlands. To evaluate the effectiveness of three of these devices in reducing faecal contamination, water samples were collected for faecal coliforms (FC) during and following rainfall at inlets and outlets of the structures. Results indicated one of the SQIDs as the most efficient for bacterial reduction, while the other two provided low or non reduction of FC. Results also illustrated dependence of bacteria reduction on flow conditions. Comparison of devices suggested that hydraulic residence times and other design parameters strongly influenced the capacity of each device to reduce FC counts during different weather conditions.

Rising levels of impervious surfaces in densely populated cities and climate change-related weather extremes such as heavy rain events or long dry weather periods provide us with new challenges for sustainable stormwater management in urban areas. The Special Issue consists of nine articles and a review and focuses on a range of relevant issues: different aspects and findings of stormwater runoff quantity and quality, including strategies and techniques to mitigate the negative effects of such climate change impacts hydraulically, as well as lab-scale and long-term experience with pollutants from urban runoff and the efficiency of stormwater quality improvement devices (SQIDs) in removing them. Testing procedures and protocols for SQIDs are also considered. One paper analyses the clogging of porous media in the use of stormwater for managed aquifer recharge. The Special Issue demonstrates the importance and timeliness of the topic of sustainable rainwater management, especially with regard to growing cities and the challenges posed by climate change.

Stormwater runoff from metal roofs has been a significant subject of discussion, especially when it comes to its treatment and the target concentrations that need to be achieved prior to discharge into the aquatic environment. To raise further awareness on this issue, occurrence, characterization, and also mitigation measures for metal roof runoff were analyzed using the example of copper and zinc roofs. These stormwater runoffs were found to contain metals in significant concentrations, mainly due to the wash-off of corrosion products by precipitation. Factors influencing metal corrosion and runoff concentrations were compiled. As Cu and Zn mainly occur in dissolved and thus bioavailable forms in roof runoff, harmful effects on the environment were detected. Therefore, adequate treatment of the runoff before discharge to groundwater or surface water is necessary to protect the aquatic environment. Vegetated infiltration swales as an sustainable urban drainage system enable a reduction in pollution loads. However, especially in densely built-up urban areas, stormwater quality improvement devices (SQIDs) offer an attractive alternative for pre-treating metal roof runoff, as they are mostly located underground. There is not yet a uniform legal approval system for SQIDs in Germany, but the German state of Bavaria has approved four types of SQIDs according to its own developed test criteria.

Separation of particulate matter (PM) is the most important process to achieve a reduction of contaminants present in road runoff. To further improve knowledge about influencing factors on the settling of road-deposited sediment (RDS), samples from three sites were collected. Since particle size distribution (PSD) has the strongest effect on settling, the samples were sieved to achieve comparable PSDs so that the effects of particle density, shape, fluid temperature, and deicing salt concentration on settling could be assessed using settling experiments. Based on the experimental data, a previously proposed model that describes the settling of PM was further developed and validated. In addition, RDS samples were compared to a standard mineral material, which is currently in use to evaluate treatment efficiency of stormwater quality improvement devices. The main finding was that besides PSD, particle density is the most important influencing factor. Particle shape was thoroughly described but showed no significant improvement of the prediction of the settled mass. Temperature showed an effect on PM settling; deicing salts were negligible. The proposed models can sufficiently predict the settling of RDS in settling column experiments under varying boundary conditions and are easily applicable.

Stormwater quality improvement devices use sedimentation as a pre-treatment step to separate contaminant laden particulate matter (PM) from traffic area runoff. Multiple studies describe worse settling behavior during the cold season. This paper is written in response to a decreased PM retention that was observed in the cold season during a 20-month monitoring of a sedimentation tank. However, the data was insufficient to assess the two factors that influence sedimentation during the cold season—temperature and de-icing salt application. Therefore, simplified discrete particle settling models were used to determine the influence of temperature and de-icing salt. These influences were compared to other factors, like overflow rate, particle density, and particle size distribution. To calculate the effect of temperature and de-icing salt on density and viscosity, two empirical models were applied for the first time in this field. The calculations showed that de-icing salt (NaCl) had a negligible influence on the retention of PM. However, reducing the temperature from 20 °C to 5 °C was shown to decrease the total suspended solid removal efficiency by up to 8%. The order of influencing factors was found to be particle size distribution >> overflow rate > particle density > temperature.

ABSTRACT Current knowledge about the microbial communities that occur in urban road runoff is scarce. Road runoff of trafficked roads can be heavily polluted and is treated by stormwater quality improvement devices (SQIDs). However, microbes may influence the treatment process of these devices or could lead to stress resistant opportunistic microbial strains. In this study, the microbial community in the influent, effluent and the filter materials used to remove dissolved heavy metals from two different SQIDs were analyzed to determine microbial load, retention, composition, and mobile resistance genes. Although the microbes were replaced by new taxa in the effluent, there was no major retention of microbial genera. Further, the bacterial abundance of the SQIDs effluent was relatively stable over time. The heavy metal content correlated with intl1 and with microbial genera. The filter media itself was enriched with Intl1 gene cassettes, carrying several heavy metal and multidrug resistance genes (e.g. czrA, czcA, silP, mexW and mexI), indicating that this is a hot spot for horizontal gene transfer. Overall, the results shed light on road runoff microbial communities, and pointed to distinct bacterial communities within the SQIDs, which subsequently influence the microbial community and the genes released with the treated water.

Developing methods to recycle and reuse stormwater and effluent/waste water has become an important and urgent issue. In order to manage water resources in a sustainable manner and to help reduce national water restrictions, treated stormwater can play a significant role. Before reusing, treatment is mandatory to remove the different types of pollutants from the stormwater. To reduce the extent of pollutants, stormwater quality improvement devices (SQIDs) are introduced that filter run-off before it enters the waterways. SQIDs are used to help protect the creeks, rivers and beaches by trapping or collecting rubbish and pollutants that end up in our stormwater drains. The Green Gully is one of the new concepts to remove gross pollutants from stormwater. The main purpose of the Green Gully is to remove pollutants from stormwater as quickly and effectively as possible and divert the water for reuse, especially for watering roadside plants and gardens. This study aims to determine the performance in terms of efficiency of the Green Gully using a laboratory model. To achieve the goal, an extensive literature review relevant to the research such as stormwater reuse, stormwater quality improvement devises, numerical simulation and water-quality for stormwater were done. The Green Gully was designed, developed and installed in the existing flume in Fluid Mechanics laboratory of CQUniversity. Efficiency, defined as the amount of water flow passed through the Gully screen with respect to the total inflow (in percentage), was determined for three types of gully screen (cross-diagonal, perpendicular and square screens) and for three different angles of flume base (0º-horizontal level, 1º and 2º- inclined). Each experiment was conducted using only water flow and water flow with mixed litter. Mixed litter consisted of leaves, cigarette-butts, bottle-caps, plastics and papers. It was found from the experimental results that the cross-diagonal screen at the flume base angle of 0º achieved the highest efficiency overall, while the perpendicular screen performed well when no litter was mixed with the water flow. A three dimensional Computational Fluid Dynamics (CFD) model was developed to validate the experimental measurement using CFD code FLUENT (6.3.26). Geometry creation and mesh generation was done using GAMBIT (2.3.16). Experimentally determined efficiency of the cross-diagonal screen at flume base angles of 0º, 1º and 2º (using only water flow) was compared with CFD simulated efficiency. It was found that the experimentally determined efficiencies are in good agreement (within 3% to 10% for flume base angle of 0º and 1% to 16% for flume base angle of 1º) with simulated efficiencies. For flume angle of 2º, simulated efficiency varies from 20% to 36%. Futhermore, stormwater road runoff quality parameters were tested in the laboratory to determine the level of treatment required for road runoff to reuse for watering roadside plants or gardens. American Public Health Association (APHA) standard methods for examination of the water and waste water were followed for water quality tests. Laboratory test results were compared with the results of other study available in the literature and with Australian and New Zealand Environment and Conservation Council (ANZECC) standards. Significantly different (higher or lower depending on the parameters) water quality data were found compared to that of the ANZECC standard. It is identified from the test results that a tertiary level of treatment arrangement should be added to the Green Gully facility for purifying and reusing stormwater. Simple laboratory chemical reactors, known as plug flow reactor (PFR) or continuous-flow stirred-tank reactors (CSTR) can be designed and installed for a tertiary level of treatment to attain stormwater quality suitable for roadside plants or gardens. This study contributed to the understanding of the new SQID 'Green Gully', its performance investigation and types of gully screen in relation to fresh water flow and water flow with mixed litter. This study developed a method to improve the resilience of Australian irrigation to drought and climate change -- Abstract.