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Microbial contamination in surface waters has become a worldwide cause for concern. As efforts are made to reduce this contamination, monitoring is integral to documenting and evaluating water quality improvements. Autosamplers are beneficial in such monitoring efforts, as large data sets can be generated with minimized effort. The extent to which autosamplers can be utilized for microbial monitoring is largely unknown due to concerns over contamination. Strict sterilization regimes for components contacting the water being sampled are difficult, and sometimes logistically implausible, when utilizing autosamplers. Field experimentation showed contamination of fecal coliform in autosamplers to be more of a concern than that of Escherichia coli. Further study in a controlled laboratory environment suggested that tubing configuration has a significant effect on residual E. coli concentrations in sampler tubing. The amount of time that passed since the last sample was collected from a given sampler (antecedent dry weather period - DWP) tubing was also a significant factor. At a DWP of 7 days, little to no contamination was found. Thus, simple protocols such as providing positive drainage of tubing between sample events and programming samplers to include rinses will reduce concerns of contamination in autosamplers. [ABSTRACT FROM AUTHOR]

This study presents results on the assessment of the application of a Bayesian approach to evaluate the sensitivity and uncertainty associated with urban rainfall-runoff models. The software MICA was adopted, in which the prior information about the parameters is updated to generate the parameter posterior distribution. The likelihood function adopted in MICA assumes that the residuals between the measured and modelled values have a normal distribution. This is a trait of many uncertainty/ sensitivity procedures. This study compares the results from three different scenarios: (i) when normality of the residuals was checked but if they were not normal then nothing was done (unverified); (ii) normality assumption was checked, verified (using data transformations) and a weighting strategy was used that gives more importance to high flows; and (iii) normality assumption was checked and verified, but no weights were applied. The modelling implications of such scenarios were analysed in terms of model efficiency, sensitivity and uncertainty assessment. The overall results indicated that verifying the normality assumption required the models to fit a wider portion of the hydrograph, allowing a more detailed inspection of parameters and processes simulated in both models. Such an outcome provided important information about the advantages and limitations of the models' structure. [ABSTRACT FROM AUTHOR]

Stormwater biofilters are not currently optimised for pathogen removal since the behaviour of these pollutants within the stormwater biofilters is poorly understood. Modelling is a common way of optimising these systems, which also provides a better understanding of the major processes that govern the pathogen removal. This paper provides an overview of a laboratory-scale study that investigated how different design and operational conditions impact pathogen removal in the stormwater biofilters. These data were then used to develop a modelling tool that can be used to optimise the design and operation of the stormwater biofilters. The model uses continuous simulations where adsorption and desorption were dominant during wet weather periods and first order die-off kinetics were significant in dry periods between the wet weather events. Relatively high Nash Sutcliffe Efficiencies (>0.5) indicate that the calibrated model is in good agreement with observed data and the optimised model parameters were comparable with values reported in the literature. The model's sensitivity is highest towards the adsorption process parameter followed by the die-off and desorption rate parameters, which implies that adsorption is the governing process of the model. Vegetation is found to have an impact on the wet weather processes since the adsorption and desorption parameters vary significantly with the different plant configurations. The model is yet to be tested against field data and needs to be improved to represent the effect of some other biofilter design configurations, such as the inclusion of the submerged zone. [ABSTRACT FROM AUTHOR]

Understanding microorganism levels in urban runoff is essential for appropriate storm-water management, especially when storm-water is utilized by humans. An Escherichia coli monitoring program was conducted at four urban catchments in Melbourne, Australia. Simple and multiple correlation analyses were conducted that related climatic, rainfall, storm-water runoff, and other water-quality characteristics with the event mean concentrations (EMCs) of E. coli. Also, several existing and modified storm-water-quality models were tested against the measured storm-water E. coli levels to determine whether existing storm-water models could be used for prediction. The key findings are that source, growth, and removal of microorganisms are more important than wash-off and transport processes during wet weather since the most influential factors for E. coli EMC levels are (1) antecedent catchment conditions, such as vapor pressure prior to an event; (2) nutrient levels in storm water, such as ammonium, total phosphorus, and total nitrogen levels. However, rainfall intensity, which was found to be the most important transport-related variable (although less significant than the aforementioned build-up parameters), may also be considered in EMC prediction. [ABSTRACT FROM AUTHOR]

There is a need to develop effective stormwater filters for passive (without any addition of chemicals or energy) and effective removal of pathogens in order to mainstream stormwater harvesting. This study focuses on the development of coated granular activated carbon (GAC) filtration material in order to develop filters for effective removal of pathogens from urban stormwater. Several laboratory trials were performed to gauge the effectiveness of the filters, which use a mixture of the zinc- sulphate-heptahydrate coated GAC and sand, on the removal of Escherichia coli (E. coli) from semi- natural stormwater. On average, a 98% removal of the inflow concentration of E. coli was achieved. Furthermore, there was also an improvement of approximately 25% in the removal of phosphorous. However, it was found that the treated material was leaching zinc. It was important to determine whether the observed removal of E. coli was indirectly caused by the sampling methodology. The results showed that the inactivation of the E. coli in the collected sample was small compared with the inactivation which actually occurred within the filter. This provides much promise to the filter, but the presence of zinc in the outflow demonstrates the need for further investigation into the stabilisation of the coating process. [ABSTRACT FROM AUTHOR]

Biofilters are common, low energy technologies used for the treatment of urban stormwater. While they have shown promising results for the removal of stormwater microorganisms, certain factors affect their performance. Hence, this study investigated the effects of particle-microbial interaction, inflow concentration, antecedent microbial levels and plant species on microbial removal capacity. A biofilter column study was set up to evaluate removal performance and a sequential filtration procedure was used to estimate microbial partitioning. The columns were dosed with different concentrations of free phase Escherichia coil only End E. coil mixed with stormwater sediment. Results indicate that the microbial removal is significantly affected by inflow concentration and antecedent microbial levels. Leaching was only observed when a relatively low inflow concentration event occurred within a short period after a very high inflow concentration event. Finally, Lomandra iongifoiia showed better removal compared with Carex appressa. [ABSTRACT FROM AUTHOR]

An experimental study was undertaken by Monash University to develop and test enviss™ stormwater treatment and harvesting technologies - non-vegetated filtration systems with an extremely low footprint. This paper focuses on the water quality and hydraulic performance of two systems tested over a 'year' of operation in a Melbourne climate: (1) REUSE enviss™ filters, designed for stormwater harvesting systems for non-potable supply substitution, and (2) WSUD enviss™filters, developed to treat urban stormwater prior to discharge to downstream systems. The presence of chlorine as a disinfection agent proved to be very efficient for the removal of microorganisms in REUSE enviss™ filters. WSUD enviss™ filters had the benefit of providing an elevated nutrient treatment performance, due to an extended depth of filter media. However, nutrient outflow concentrations (total nitrogen (TN) in particular) were found to increase during the testing period. Also, extended dry weather periods were found to have a detrimental effect on the treatment performance of almost all pollutants for both filters (nutrients, Escherichia coli and heavy metals). Although hydraulic conductivity results indicated two or three sediment trap replacements per year are required to maintain filtration rates, it is expected that the compressed loading rate schedule overestimated this maintenance frequency. [ABSTRACT FROM AUTHOR]

Model calibration and sensitivity analysis of stormwater models are required to assess model performance; it is very unlikely that non-calibrated models will lead to reasonable results. The aim of this paper is to present results of the calibration and sensitivity analysis of the key parameters used in flow modelling by MUSIC and parameters of a simple stormwater quality model. The assessment of the models is undertaken using a Monte Carlo Markov Chain approach. We describe the models' performance, provide information on their sensitivity to parameters and also discuss the correlation between these parameters. This work will help practitioners to understand importance of the MUSIC parameters that they usually use without calibration. The information reported in the results will also help to guide future development of stormwater quality models and the data needed to support it. [ABSTRACT FROM AUTHOR]

This paper presents the sensitivity analysis of a newly developed model which predicts microorganism concentrations in urban stormwater (MOPUS-MicroOrganism Prediction in Urban Stormwater). The analysis used Escherichia coli data collected from four urban catchments in Melbourne, Australia. The MICA program (Model Independent Markov Chain Monte Carlo Analysis), used to conduct this analysis, applies a carefully constructed Markov Chain Monte Carlo procedure, based on the Metropolis-Hastings algorithm, to explore the model's posterior parameter distribution. It was determined that the majority of parameters in the MOPUS model were well defined, with the data from the MCMC procedure indicating that the parameters were largely independent. However, a sporadic correlation found between two parameters indicates that some improvements may be possible in the MOPUS model. This paper identifies the parameters which are the most important during model calibration; it was shown, for example, that parameters associated with the deposition of microorganisms in the catchment were more influential than those related to microorganism survival processes. These findings will help users calibrate the MOPUS model, and will help the model developer to improve the model, with efforts currently being made to reduce the number of model parameters, whilst also reducing the slight interaction identified. [ABSTRACT FROM AUTHOR]

The complex nature of pollutant accumulation and washoff, along with high temporal and spatial variations, pose challenges for the development and establishment of accurate and reliable models of the pollution generation process in urban environments. Therefore, the search for reliable stormwater quality models remains an important area of research. Model calibration and sensitivity analysis of such models are essential in order to evaluate model performance; it is very unlikely that non-calibrated models will lead to reasonable results. This paper reports on the testing of three models which aim to represent pollutant generation from urban catchments. Assessment of the models was undertaken using a simplified Monte Carlo Markov Chain (MCMC) method. Results are presented in terms of performance, sensitivity to the parameters and correlation between these parameters. In general, it was suggested that the tested models poorly represent reality and result in a high level of uncertainty. The conclusions provide useful information for the improvement of existing models and insights for the development of new model formulations. [ABSTRACT FROM AUTHOR]

The management of stormwater pollution has placed particular emphasis on the first flush phenomenon. However, definition and current methods of analyses of the phenomena contain serious limitations, the most important being their inability to capture a possible impact of the event size (total event volume) on the first flush. This paper presents the development of a novel approach in defining and assessing the first flush that should overcome these problems. The phenomenon is present in a catchment if the decrease in pollution concentration with the absolute cumulative volume of runoff from the catchment is statistically significant. Using data from seven diverse catchments around Melbourne, Australia, changes in pollutant concentrations for Total Suspended Solids (TSS) and Total Nitrogen (TN) were calculated over the absolute cumulative runoff and aggregated from a collection of different storm events. Due to the discrete nature of the water quality data, each concentration was calculated as a flow-weighted average at 2mm runoff volume increments. The aggregated concentrations recorded in each increment (termed as a 'slice' of runoff) were statistically compared to each other across the absolute cumulative runoff volume. A first flush is then defined as the volume at which concentrations reach the 'background concentration' (i.e. the statistically significant minimum). Initial results clearly highlight first flush and background concentrations in all but one catchment supporting the validity of this new approach. Future work will need to address factors, which will help assess the first flush's magnitude and volume. Sensitivity testing and correlation with catchment characteristics should also be undertaken. [ABSTRACT FROM AUTHOR]

The behaviour of microorganisms in urban stormwater should be thoroughly investigated and understood to (a) design treatment technologies that can reduce the human health risks of utilising stormwater and (b) develop models which can accurately predict the levels of microorganisms in urban stormwater to aid in health risk assessments. A crucial part of understanding the behaviour of pollutants in urban stormwater is to determine whether the pollutant experiences higher levels in certain portions of the event (e.g. does the pollutant experience a first flush?). The aim of this paper is twofold: (a) determine if the first flush phenomenon exists for a commonly used microbial indicator, Escherichia coli, and (b) determine whether the presence of a first flush is dependent on antecedent climatic and/or hydrologic characteristics. E. coli data collected from the wet weather flows of four urban catchments in Melbourne was used in the paper. Cumulative mass versus volume curves were used in conjunction with standard statistical inferences to determine that the first flush phenomenon was not consistently present, and that the presence and magnitude of a first flush varied considerably between each site. Regression analyses were used to determine that this variation was probably not caused by the same governing processes for all four sites, with different explanatory variables significantly explaining the first flush at each site. [ABSTRACT FROM AUTHOR]

The development of a model that predicts the levels of microorganisms in urban stormwater will aid in the assessment of health risks when using stormwater for both recreational uses and as an alternate water resource. However, the development of such a model requires an understanding of the dominant processes that influence the behaviour of microorganisms in urban systems. Using simple and multiple regression analyses this paper determines the dominant processes which affect the inter-event variability of the microbial indicator Escherichia coli (E. coli ) in four urbanised catchments. The results reveal that a number of antecedent climatic conditions, together with rainfall intensity, can significantly explain the inter-event variation in wet weather E. coli levels. [ABSTRACT FROM AUTHOR]

As the concept of integrated urban water management is incorporated into the practice of urban water servicing, new options, such as stormwater harvesting, which can have multiple benefits, are of increasing interest. The multi-functional benefits of stormwater harvesting include the potential to enhance urban stream health through improvements to the flow regime as well as providing a valuable water supply source. This paper synthesises a current research programme being undertaken to assess the viability of, and develop recommendations for, stormwater harvesting. The design of the collection, treatment, storage, flood protection, and distribution components of an integrated system are each discussed, along with the environmental flow consequences of urban stormwater harvesting. The incorporation of swales and biofilters into the collection system was not found to lead to significant exfiltration and evaporation losses in most circumstances and so can be employed as part of the treatment train. Further treatment can be provided by WSUD-type biophysical measures such as ponds, wetlands or horsily designed biofilters or physio-chemical treatment processes. Depending on the design, the stormwater storage component may or may not provide flood protection. In many circumstances, the storage capacity requirements are not considered to be a barrier to stormwater harvesting. [ABSTRACT FROM AUTHOR]

Biological clogging of filtration and infiltration systems has been acknowledged as a significant problem in the case of wastewater systems. However, scant research has been conducted on biological clogging in storm water filtration and infiltration systems, with the main hypothesis being that biological clogging is insignificant due to the low level of organics present in storm water. This article tested that hypothesis, using a laboratory-based approach. Five replicates of each zeolite-based filter design were dosed with storm water manifesting the following forms: (1) typical storm water (base case); (2) storm water containing very high nutrient concentrations to accelerate biological clogging; (3) typical storm water that was sterilized to suppress biological clogging; and (4) typical storm water with the addition of chlorine to suppress biological activity. The hydraulic performances of these four configurations were monitored over time until the systems were fully clogged. Loss on ignition (LoI) and microscopic analysis of accumulated material within the top layers of the filters were undertaken in an attempt to assess the level of organic matter present in clogging layers of the filters. It was found that all configurations performed differently in comparison to the base case, which represents the most likely set of operational conditions in the field. For instance, the chlorinated filters treated about 30% more storm water compared with the base case. Columns dosed with sterilized storm water treated almost the same volume of storm water but removed a greater quantity of sediment with higher treatment efficiency. Columns dosed with a high level of nutrients clogged more quickly than in the base case. Results of loss on ignition partially confirmed these findings. However, results of microbial cell counts provided tenuous evidence of biological clogging being present. Although the evidence was not overpowering, the variations observed in this study suggest that biological clogging in storm water filters warrants greater attention, which is mostly ignored at present. [ABSTRACT FROM AUTHOR]