Terry Lucke

The pollution removal and stormwater reduction performance of street-side bioretention basins after ten years in operation

This study evaluated the pollution removal and hydrologic performance of five, 10-year old street-side bioretention systems. The bioretention basins were subjected to a series of simulated rainfall events using synthetic stormwater. Four different pollution concentrations were tested on three of the bioretention basins. The four concentrations tested were: A) no pollution; B) typical Australian urban pollutant loads; C) double the typical pollution loads, and; D) five times the typical pollution loads. Tests were also undertaken to determine the levels of contaminant and heavy metals build-up that occurred in the filter media over the 10 year operational life of the bioretention systems. Although highly variable, the overall hydrological performance of the basins was found to be positive, with all basins attenuating flows, reducing both peak flow rates and total outflow volumes. Total suspended solids removal performance was variable for all tests and no correlation was found between performance and dosage. Total nitrogen (TN) removal was positive for Tests B, C and D. However, the TN removal results for Test A were found to be negative. Total phosphorus (TP) was the only pollutant to be effectively removed from all basins for all four synthetic stormwater tests. The study bioretention basins were found to export pollutants during tests where no pollutants were added to the simulated inflow water (Test A). Heavy metal and hydrocarbon testing undertaken on the bioretention systems found that the pollution levels of the filter media were still within acceptable limits after 10 years in operation. This field study has shown bioretention basin pollution removal performance to be highly variable and dependant on a range of factors including inflow pollution concentrations, filter media, construction methods and environmental factors. Further research is required in order to fully understand the potential stormwater management benefits of these systems.

The use of a Classroom Response System to more effectively flip the classroom

Classroom Response Systems (CRS) have been shown to improve student learning outcomes by encouraging student engagement with the course content, instructors and student peers. The systems ability to provide immediate and quality feedback to both students and instructors, particularly in large classes, is highly desirable. While CRS has been used for well over a decade and been shown to successfully improve student engagement and participation, a number of studies have also identified that its use could potentially mean that less material is able to be covered in lectures. Clearly, the approach of cramming CRS into already content-heavy class time does not embrace the potential for CRS to improve student engagement and student learning. The use of CRS should be planned as an integral component of the course which enhances and reinforces the learning outcomes. The effectiveness of CRS depends strongly on the quality and variety of the questions, and the design of the activities to encourage students to engage with the questions. This case study explores the use of a new, low-cost, state-ofthe-art CRS (Top Hat Monocle) which allows students to use their mobile devices (phones, tablets, laptops) to respond to a variety of numerical, multiple-choice, short-answer and open-ended discussion questions posed during face-to-face workshops. In order to allow sufficient time to fully engage with the workshop activities traditional lectures were revised and the classroom lecture was flipped. Students worked through narrated lecture material (hand-e-lectures) online, prior to attending the workshops. CRS was included as part of the e-lecture content and feedback from this was incorporated into the workshops. Workshops extended the e-lecture content by including a variety of carefully designed, engaging activities (many were group activities) that used CRS questions to facilitate discussions, problem solving and case study analysis to enhance student cognition. Overall, the new flipped lecture and CRS teaching format demonstrated a substantial increase in the level of student engagement, motivation and attendance compared to previous cohorts.

Do sediment type and test durations affect results of laboratory-based, accelerated testing studies of permeable pavement clogging?

Previous studies have attempted to quantify the clogging processes of Permeable Interlocking Concrete Pavers (PICPs) using accelerated testing methods. However, the results have been variable. This study investigated the effects that three different sediment types (natural and silica), and different simulated rainfall intensities, and testing durations had on the observed clogging processes (and measured surface infiltration rates) of laboratory-based, accelerated PICP testing studies. Results showed that accelerated simulated laboratory testing results are highly dependent on the type, and size of sediment used in the experiments. For example, when using real stormwater sediment up to 1.18 mm in size, the results showed that neither testing duration, nor stormwater application rate had any significant effect on PICP clogging. However, the study clearly showed that shorter testing durations generally increased clogging and reduced the surface infiltration rates of the models when artificial silica sediment was used. Longer testing durations also generally increased clogging of the models when using fine sediment (<300 μm). Results from this study will help researchers and designers better anticipate when and why PICPs are susceptible to clogging, reduce maintenance and extend the useful life of these increasingly common stormwater best management practices.

Preliminary investigation into the pollution reduction performance of swales used in a stormwater treatment train

Permeable pavements have been shown to be effective stormwater treatment devices that can greatly reduce surface runoff and significantly improve the quality of stormwater runoff in urban areas. However, the potential problems with sediment clogging and consequent maintenance requirements have been identified as the main barriers to more widespread adoption of permeable pavements in urban developments. This Australian study investigates the effectiveness of using grass swales as pre-treatment devices for permeable pavements in order to reduce clogging and extend the life span of these systems. The results of simulated runoff experiments demonstrated that between 50 and 75% of the total suspended sediment (TSS) was removed within the first 10 m of the swale length. This suggests swales of this length could potentially increase the effective life of permeable pavement systems by reducing clogging, and therefore maintenance. Nutrient removal was also tested in the study and the results indicated the tested swales were of limited effectiveness in the removal of these pollutants. However, in real runoff situations, reduction of TSS will have a direct influence on removing nutrients because a significant proportion of nutrients (and other pollutants) are attached to the sediments.

Air water flows in building drainage systems

This paper investigates the mechanisms of two-phase flows that occur in commercial and industrial roof drainage systems. Both traditional gravity-fed and siphonic roof drainage systems are examined. Air entrainment plays a fundamental role in the performance of siphonic roof drainage systems. In particular, air entrainment has a significant effect on: maximum system flowrate capacity; pipe friction losses; operational system pressures; operational gutter water depths; and ability of the system to prime.However, experimental results presented here demonstrate that the reduction in system capacity is not directly proportional to the increase in air content. One possible explanation for this is that water and air will be affected differently by sub-atmospheric pressures. The effect air entrainment has on roof drainage performance is investigated. The ways in which air is introduced into the system are identified and the effects of different air/water ratios are quantified. Finally methods for reducing air entrainment are described.

Activating learning in engineering education using ICT and the concept of ‘Flipping the classroom’

ABSTRACT This case study trialled the introduction of a student-response system (Top Hat) in a third-year engineering Fluid Mechanics course (n = 44) to improve student engagement, motivation and cognition. It was recognised that for the potential benefits of student-response systems (SRSs) to be fully realised, more time must be allocated for student engagement and the active learning components of the course. In order to allow sufficient time to fully engage with the SRSs and other classroom activities, traditional lectures were revised and the classroom format was flipped. This paper presents the initial case study results focusing on the use of SRSs. Overall, the new flipped lecture and SRS teaching format demonstrated a substantial increase in the level of student engagement, motivation, active learning and attendance compared to previous cohorts. However, the increased levels of engagement did not appear to reflect on any large increase in students’ individual grades.

EVALUATION OF THE LONG-TERM POLLUTION REMOVAL PERFORMANCE OF ESTABLISHED BIORETENTION CELLS

Over the last two decades bioretention (biofiltration) systems have been commonly constructed in urban areas to manage stormwater runoff by moderating peak flows and reducing downstream pollution loads. Bioretention systems are generally soil-plant based systems which typically include a filter medium above a drainage layer. They are often either lined with a geofabric to support infiltration, or with an impermeable membrane to prevent infiltration and/or to allow stormwater harvesting and reuse. Bioretention systems are known to treat a range of stormwater pollutants through physical, chemical and biological processes such as mechanical filtering, sedimentation, adsorption, and plant and microbial uptake. However, the long-term pollution removal performance, particularly of heavy metals, remains largely unknown. It is generally accepted that the filter media used in bioretention systems has a finite life span, after which time it should be replaced. However, there is only very limited information available on when this should occur, or how to assess this. It is also recognised that contaminated filter media may require regulated disposal. This study presents results from a series of controlled field experiments conducted over two years which evaluated the pollution removal performance of a series of 10 year old bioretention systems located in an industrial state in Australia.; ;

Plastic pipe pressures in siphonic roof drainage systems

Siphonic roof drainage is a highly efficient type of drainage system that is particularly suitable for large buildings and other structures over approximately 4 m in height. Although siphonic roof drainage systems are enjoying ever-increasing popularity with architects, there is still some uncertainty regarding the minimum pipe pressure class required for siphonic pipework, especially in tall buildings. This is particularly the case in warmer countries since higher temperatures can drastically decrease the strength of the pipework material used in siphonic systems – typically unplasticized polyvinylchloride (PVC-U) and high-density polyethylene (HDPE). However, there is very limited information available on how plastic pipes behave under the sub-atmospheric pressures that occur under operating conditions in siphonic systems. This paper describes experiments conducted to investigate sub-atmospheric pressures in siphonic systems and how they may be controlled by injecting air into vertical downpipes. Recommendations for minimum pipework pressure classes are provided together with methods for limiting the minimum pressures without significantly decreasing the system capacity. This paper will help engineers design siphonic systems with more confidence so that such systems will continue to perform adequately over their intended design life. L’évacuation siphonique des eaux de toit est un type de système d’évacuation des eaux hautement performant, qui est particulièrement adapté aux grands immeubles et autres structures dépassant 4 m de hauteur environ. Bien que les systèmes d’évacuation siphonique des eaux de toit bénéficient d’une popularité sans cesse croissante auprès des architectes, il existe encore quelque incertitude quant à la classe de pression minimale des tuyaux nécessaire pour les tuyauteries siphoniques, surtout dans les grands immeubles. Ceci est tout particulièrement le cas dans les pays plus chauds, dans la mesure où des températures plus élevées peuvent considérablement réduire la résistance du matériau utilisé pour les tuyauteries dans les systèmes siphoniques – généralement du polychlorure de vinyle non plastifié (PVC-U) et du polyéthylène haute densité (PEHD). Les informations disponibles sont cependant très limitées concernant la manière dont se comportent les tuyaux en plastique soumis aux pressions sub-atmosphériques qui se rencontrent dans les conditions de fonctionnement des systèmes siphoniques. Cet article décrit des expériences conduites afin d’étudier les pressions sub-atmosphériques dans les systèmes siphoniques et la façon dont elles peuvent être contrôlées en injectant de l’air dans les tuyaux de descente des eaux pluviales. Des recommandations concernant les classes de pression minimales des tuyauteries sont fournies, ainsi que des méthodes pour limiter les pressions minimales sans abaissement significatif de la capacité des systèmes. Cet article aidera les ingénieurs à concevoir avec plus d’assurance des systèmes siphoniques de façon à ce que ces systèmes puissent continuer à fonctionner convenablement tout au long de leur durée de vie nominale prévue. Mots clés: pression critique de flambage, pression négative, évacuation siphonique des eaux de toit

Urban stormwater characterisation and nitrogen composition from lot-scale catchments — New management implications

Stormwater runoff from urban areas has been shown to contain a variety of pollutants which are often linked to the specific land use of the catchment. This research program investigated the pollutant concentrations in stormwater runoff from several sites in South-east Queensland (SEQ), in Australia. The study sites are predominantly single development lots, under 7.5hectares (Ha) in area, with a single land-use classification that have been developed with stormwater treatment measures to manage pollutant loads as required by local regulations. The testing program also analysed the nitrogen composition in the catchment runoff samples (prior to treatment) during storm events and compared them to current Australian guidelines. The results to date (n=320) have shown pollutant concentrations to be significantly lower than those historically published as typical for Australian land uses (p<0.05). Ongoing application of out-dated influent values as part of development assessment processes could potentially provide inaccurate results, incorrectly sized and under-performing treatment measures. This current research also suggests that nitrogen in runoff from lot-scale, urban residential catchments has average nitrogen oxides (NOx) ~16% and ammonia ~9% as percentage of total nitrogen (TN). Total Kjeldahl nitrogen (TKN) forms on average ~84% of the total nitrogen concentration during events. Where it was previously recommended that to achieve water quality targets of 45% total nitrogen load reduction, treatment measures targeting NOx were required (e.g. Vegetated systems), this latest research indicates that solutions removing organic nitrogen also may be necessary, increasing the options available to designers.

Influence of channel geometry on water levels above siphonic roof outlets

This paper describes a full-scale experimental investigation into the effects of box gutter geometry on the open channel flow conditions above siphonic roofwater outlets. In particular, the effects of channel width (300, 400, 480 and 600 mm) and length (14.86 and 32.00 m) were investigated through measurements of flow rate, water depth and longitudinal velocity in the box gutter. The experimental results showed that for the same outlet flow rate, the depth of water in the gutter varied by up to 211% for the two different gutter lengths tested. Generally, the greatest water depths for the different flow rates were recorded in the 400-mm wide gutter and the lowest water depths were recorded in the 300-mm wide gutter. It was also found that the maximum flow rate through the single 110-mm diameter outlet varied depending on the width of the gutter. Practical application: The depth of water in the open channel box gutters above the outlets of siphonic drainage systems is an important design variable and it is imperative to be able to accurately estimate these water depths during all phases of operation to reduce flood damage risk. This research study has found that for the same flow rate, varying the length of gutter on either side of a siphonic outlet strongly influences the depth of water along the gutter and above the outlet. The results suggest that there may be an optimum gutter width and length for which different siphonic outlets may perform more efficiently.