A review on microbial contaminants in stormwater runoff and outfalls: Potential health risks and mitigation strategies.

Demands on global water supplies are increasing in response to the need to provide more food, water, and energy for a rapidly growing population. These water stressors are exacerbated by climate change, as well as the growth and urbanisation of industry and commerce. Consequently, urban water authorities around the globe are exploring alternative water sources to meet ever-increasing demands.

Nutrient Removal during Stormwater Aquifer Storage and Recovery in an Anoxic Carbonate Aquifer.

Stormwater harvesting coupled to managed aquifer recharge (MAR) provides a means to use the often wasted stormwater resource while also providing protection of the natural and built environment. Aquifers can act as a treatment barrier within a multiple-barrier approach to harvest and use urban stormwater. However, it remains challenging to assess the treatment performance of a MAR scheme due to the heterogeneity of aquifers and MAR operations, which in turn influences water treatment processes.

Biodegradation of pharmaceuticals and endocrine disruptors with oxygen, nitrate, manganese (IV), iron (III) and sulfate as electron acceptors.

Biodegradation of pharmaceuticals and endocrine disrupting compounds was examined in long term batch experiments for a period of two and a half years to obtain more insight into the effects of redox conditions. A mix including lipid lowering agents (e.g.

Unraveling the complexities of the velocity dependency of E. coli retention and release parameters in saturated porous media.

Escherichia coli transport and release experiments were conducted to investigate the pore-water velocity (v) dependency of the sticking efficiency (α), the fraction of the solid surface area that contributed to retention (S), the percentage of injected cells that were irreversibly retained (M), and cell release under different (10-300mM) ionic strength (IS) conditions. Values of α, S, and M increased with increasing IS and decreasing v, but the dependency on v was greatest at intermediate IS (30 and 50mM). Following the retention phase, successive increases in v up to 100 or 150mday and flow interruption of 24h produced negligible amounts of cell release.

Transport and retention of bacteria and viruses in biochar-amended sand.

The transport and retention of Escherichia coli and bacteriophages (PRD1, MS2 and ФX174), as surrogates for human pathogenic bacteria and viruses, respectively, were studied in the sand that was amended with several types of biochar produced from various feedstocks. Batch and column studies were conducted to distinguish between the role of attachment and straining in microbe retention during transport. Batch experiments conducted at various solution chemistries showed negligible attachment of viruses and bacteria to biochar before or after chemical activation.

Validation of stormwater biofilters using in-situ columns.

Stormwater harvesting biofilters need to be validated if the treatment is to be relied upon. Currently, full-scale challenge tests (FCTs), performed in the field, are required for their validation. This is impractical for stormwater biofilters because of their size and flow capacity.

Surrogates for herbicide removal in stormwater biofilters.

Real time monitoring of suitable surrogate parameters are critical to the validation of any water treatment processes, and is of particularly high importance for validation of natural stormwater treatment systems. In this study, potential surrogates for herbicide removal in stormwater biofilters (also known as stormwater bio-retention or rain-gardens) were assessed using field challenge tests and matched laboratory column experiments. Differential UV absorbance at 254mn (ΔUVA254), total phosphorus (ΔTP), dissolved phosphorus (ΔDP), total nitrogen (ΔTN), ammonia (ΔNH3), nitrate and nitrite (ΔNO3+NO2), dissolved organic carbon (ΔDOC) and total suspended solids (ΔTSS) were compared with glyphosate, atrazine, simazine and prometryn removal rates.

Methodologies for pre-validation of biofilters and wetlands for stormwater treatment.

Background: Water Sensitive Urban Design (WSUD) systems are frequently used as part of a stormwater harvesting treatment trains (e.g. biofilters (bio-retentions and rain-gardens) and wetlands).

Application of risk-based assessment and management to riverbank filtration sites in India.

This is the first reported study of a riverbank filtration (RBF) scheme to be assessed following the Australian Guidelines for Managed Aquifer Recharge. A comprehensive staged approach to assess the risks from 12 hazards to human health and the environment has been undertaken. Highest risks from untreated ground and Ganga River water were identified with pathogens, turbidity, iron, manganese, total dissolved solids and total hardness.

Determining treatment requirements for turbid river water to avoid clogging of aquifer storage and recovery wells in siliceous alluvium.

The success of Aquifer Storage and Recovery (ASR) schemes relies on defining appropriate design and operational parameters in order to maintain high rates of recharge over the long term. The main contribution of this study was to define the water quality criteria and hence minimum pre-treatment requirements to allow sustained recharge at an acceptable rate in a medium-coarse sand aquifer. The source water was turbid, natural water from the River Darling, Australia.

An explanation for differences in the process of colloid adsorption in batch and column studies.

It is essential to understand the mechanisms that control virus and bacteria removal in the subsurface environment to assess the risk of groundwater contamination with fecal microorganisms. This study was conducted to explicitly provide a critical and systematic comparison between batch and column experiments. The aim was to investigate the underlying factors causing the commonly observed discrepancies in colloid adsorption process in column and batch systems.

Environmental monitoring of selected pesticides and organic chemicals in urban stormwater recycling systems using passive sampling techniques.

Water recycling via aquifers has become a valuable tool to augment urban water supplies in many countries. This study reports the first use of passive samplers for monitoring of organic micropollutants in Managed Aquifer Recharge (MAR). Five different configurations of passive samplers were deployed in a stormwater treatment wetland, groundwater monitoring wells and a recovery tank to capture a range of polar and non-polar micropollutants present in the system.

Application of a probabilistic modelling approach for evaluation of nitrogen, phosphorus and organic carbon removal efficiency during four successive cycles of aquifer storage and recovery (ASR) in an anoxic carbonate aquifer.

Aquifer storage is increasingly being recognised in its role as a treatment process barrier within a multiple barrier approach to water reuse. Aquifers are postulated to have the ability to provide sustainable treatment for removal of nitrogen, phosphorus and organic carbon, the dominant nutrient hazards in water recycling, but, to date this treatment performance has remained difficult to validate in field studies. This study applied a statistical method, proposed for validation of the performance of advanced water treatment processes, to evaluate nutrient removal during aquifer storage and recovery (ASR) with recycled water.

Water quality requirements for sustaining aquifer storage and recovery operations in a low permeability fractured rock aquifer.

A changing climate and increasing urbanisation has driven interest in the use of aquifer storage and recovery (ASR) schemes as an environmental management tool to supplement conventional water resources. This study focuses on ASR with stormwater in a low permeability fractured rock aquifer and the selection of water treatment methods to prevent well clogging. In this study two different injection and recovery phases were trialed.

Risk assessment of aquifer storage transfer and recovery with urban stormwater for producing water of a potable quality.

The objective of the Parafield Aquifer Storage Transfer and Recovery research project in South Australia is to determine whether stormwater from an urban catchment that is treated in a constructed wetland and stored in an initially brackish aquifer before recovery can meet potable water standards. The water produced by the stormwater harvesting system, which included a constructed wetland, was found to be near potable quality. Parameters exceeding the drinking water guidelines before recharge included small numbers of fecal indicator bacteria and elevated iron concentrations and associated color.

Quantification of herbicide removal in a constructed wetland using passive samplers and composite water quality monitoring.

Constructed wetlands used as treatment for urban stormwater have the potential to improve water quality. This study aimed to estimate the removal of selected herbicides in stormwater by a constructed wetland using composite water quality monitoring and passive samplers. For the four week duration of the study the wetland was effective in reducing the concentrations of diuron, simazine and atrazine.

Valuing the subsurface pathogen treatment barrier in water recycling via aquifers for drinking supplies.

A quantitative microbial risk assessment (QMRA) was performed at four managed aquifer recharge (MAR) sites (Australia, South Africa, Belgium, Mexico) where reclaimed wastewater and stormwater is recycled via aquifers for drinking water supplies, using the same risk-based approach that is used for public water supplies. For each of the sites, the aquifer treatment barrier was assessed for its log(10) removal capacity much like for other water treatment technologies. This information was then integrated into a broader risk assessment to determine the human health burden from the four MAR sites.

Use of static Quantitative Microbial Risk Assessment to determine pathogen risks in an unconfined carbonate aquifer used for Managed Aquifer Recharge.

Managed Aquifer Recharge (MAR) is becoming a mechanism used for recycling treated wastewater and captured urban stormwater and is being used as a treatment barrier to remove contaminants such as pathogens from the recharged water. There is still a need, however, to demonstrate the effectiveness of MAR to reduce any residual risk of pathogens in the recovered water. A MAR research site recharging secondary treated wastewater in an unconfined carbonate aquifer was used in conjunction with a static Quantitative Microbial Risk Assessment (QMRA) to assess the microbial pathogen risk in the recovered water following infiltration and aquifer passage.

A new method to evaluate polydisperse kaolinite clay particle removal in roughing filtration using colloid filtration theory.

Previous application of colloid filtration theory to roughing filtration has not considered a reliable method for determining a representative attachment factor for a polydisperse suspension (of constant particle density). Establishment of such a method would broaden the application of trajectory modelling in roughing filtration, and progress the development of a comprehensive database of attachment factors and surface charge potentials for various particle and fluid types. This study establishes a methodology for the application of colloid filtration theory to roughing filtration and incorporates recent advancements in theoretical single-collector efficiency.