A Review of Pollutant Concentrations in Urban Stormwater Across Eastern Australia, After 20 Years

Concerns about pollutants in urban stormwater were initially raised in the early 1970s. Australian investigations decades later, also found urban stormwater runoff contained elevated levels of sediment and nutrients, as well as heavy metals, that brought stormwater management to the forefront for regulators. Planning policies were implemented to integrate stormwater management into development in the form of water sensitive urban design (WSUD), also known internationally as low-impact design (LID) and Sustainable Urban Design solutions (SUDs). Since their introduction, comprehensive broad scale field research to verify their success in achieving load reduction targets (LRTs), has been limited. Paucity of field data on the performance of WSUD has prompted organisations to initiate their own locally-specific studies. Limited regulatory guidance on design of monitoring programs has resulted in various methodologies and meta-data recording. This research review collates urban stormwater data from 77 Australian studies, from geographic regions of east coast Australia. The raw dataset in this review included 2,836 events and 4,536 individual results, collected between 1993 and 2021 from local councils, research organisations and water authorities. The review examined total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN) concentrations, prior to any form of treatment measures as they are the focus of current guidelines and standards for stormwater management. Seminal research, used to inform stormwater guidelines and water quality modelling across Australia, is significantly different (p < 0.001), in this case approximately double the reviewed concentrations. International data is also >20% higher, on average. Geographic location of catchments had the greatest influence on pollutant concentrations, after accounting for the effects of land use and catchment urbanisation date (p < 0.001). Based on the findings of this review, generic load reduction targets (expressed as a percentage of annual inputs, e.g. 80% TSS reduction, 45% TN, 45% TP) typical in current Australian planning regulations, may be sub-optimal in achieving receiving water quality goals, particularly given the difficulty of removing pollutants when present in low concentrations. Alternately, place-based discharge targets which meet, or exceed, background water quality, or ecological and hydrological benchmarks may be a more appropriate tool to achieve environmental objectives

Case Studies of a Hydrocarbon Capture Technology for Stormwater Quality Class 1 Compliance against EN BS858.1-2002 and Subsequent Field Evaluation

Hydrocarbon spills and management in the marine environment are of significant environmental and public health concern and the subject of many research projects. In freshwater environments the treatment and management of hydrocarbons from point and diffuse sources appears less well investigated. For hydrocarbon treatment technologies introduced into the European market, they must be tested and comply with the requirements of the European Standard EN BS858-1-2002. This Standard requires laboratory testing of full-scale models. Testing of several models of a hydrocarbon capture technology was performed in accordance with EN BS858-1:2002 at the HR Wallingford, United Kingdom (UK) and repeated at the University of South Australia (UniSA) laboratories. The results of the laboratory testing demonstrated compliance with the Standard’s Class 1 criteria of less than 5 mg/L of hydrocarbons in the effluent. Field testing of several installations of the hydrocarbon capture device in Australia has also confirmed outlet concentrations conforming to the Class 1 requirement of <5 mg/L hydrocarbons

Removal of Nutrients, Sediment, and Heavy Metals by a Stormwater Treatment Train; a Medium-Density Residential Case Study in Southeast Queensland

Urban stormwater runoff from a medium-density residential development in southeast Queensland has been monitored in the field since November 2013. A treatment train installed on the site includes rainwater tanks collecting roofwater, 200-micron mesh baskets installed in grated gully pits, and two 850-mm-high media filtration cartridges installed in an underground 4-m3 vault. The site has been monitored over a 4.5-year period. Removal efficiencies were observed at this site for the regulated pollutants; the corresponding values for total suspended solids (TSS), total phosphorus (TP), and total nitrogen (TN) for the pit baskets were 61%, 28%, and 45%, respectively. The cartridge filters removed 78% of TSS, 59% of TP, 42% of TN, 40% of total copper, and 51% of total zinc. As the measured influent TSS and TP concentrations to the cartridge filters were low when compared to industry guidelines, the U.S. field dataset was truncated to anticipated guideline levels, confirming results at 90% for TSS and 76% for TP. The total gross pollutant generation rate from the medium-density residential catchment was observed to be 0.24 m3/Ha/year, with a corresponding air-dried mass of 142.5 kg/Ha/year. Less than 2% of the gross pollutant mass was anthropogenic. This paper concludes that the treatment train, and in particular the media filter, provides good removal of total copper and total zinc as well as TSS, TP, and TN from urban stormwater runoff, with higher inlet concentrations producing better performance. Field test data from 58 months of operation and standard maintenance suggests that breakthrough of TSS and TP has not occurred yet

Field Evaluation of a Stormwater Treatment Train with Pit Baskets and Filter Media Cartridges in Southeast Queensland

Field monitoring of a stormwater treatment train has been underway between November 2013 and May 2015 at a townhouse development located at Ormiston, southeast Queensland. The research was undertaken to evaluate the effectiveness of a 200 micron mesh pit basket in a 900 square format and an 850 mm high media filtration cartridge system for removing total suspended solids and nutrients from stormwater runoff. The monitoring protocol was developed with Queensland University of Technology (QUT), reflecting the Auckland Regional Council Proprietary Device Evaluation Protocol (PDEP) and United States Urban Stormwater BMP Performance Monitoring Manual with some minor improvements reflecting local conditions. During the 18 month period, more than 30 rain events have occurred, of which nine comply with the protocol. The Efficiency Ratio (ER) observed for the treatment devices are 32% total suspended solids (TSS), 37% for total phosphorus (TP) and 38% total nitrogen (TN) for the pit basket, and an Efficiency Ratio of 87% TSS, 55% TP and 42% TN for the cartridge filter. The performance results on nine events have been observed to be significantly different statistically (p < 0.05) for the filters but not the pit baskets. The research has also identified the significant influence of analytical variability on performance results, specifically when influent concentrations are near the limits of detection

Field and Evaluation Methods Used to Test the Performance of a Stormceptor® Class 1 Stormwater Treatment Device in Australia

Field testing of a proprietary stormwater treatment device was undertaken over 14 months at a site located in Nambour, South East Queensland. Testing was undertaken to evaluate the pollution removal performance of a Stormceptor® treatment train for removing total suspended solids (TSS), total nitrogen (TN) and total phosphorous (TP) from stormwater runoff. Water quality sampling was undertaken using natural rainfall events complying with an a priori sampling protocol. More than 59 rain events were monitored, of which 18 were found to comply with the accepted sampling protocol. The efficiency ratios (ER) observed for the treatment device were found to be 83% for TSS, 11% for TP and 23% for TN. Although adequately removing TSS, additional system components, such as engineered filters, would be required to satisfy minimum local pollution removal regulations. The results of dry weather sampling tests did not conclusively demonstrate that pollutants were exported between storm events or that pollution concentrations increased significantly over time

Performance Evaluation of a Floating Treatment Wetland in an Urban Catchment

Floating Treatment Wetland (FTW) systems are purpose-built devices designed to replicate the water treatment processes that occur in and around naturally occurring floating vegetated islands. FTWs can be used to improve the water quality of water storage ponds by contributing to water treatment processes through adhesion, filtration, nutrient uptake (direct use by plants), and sequestration. This paper presents the results of a twelve-month investigation into the pollution removal performance of a FTW receiving stormwater runoff from a 7.46 ha urban residential catchment. As anticipated, there was a high degree of variation in FTW treatment performance between individual rainfall events. Overall pollution removal performance was calculated to be 80% for Total Suspended Solids (TSS), 53% for Total Phosphorous (TP), and 17% for Total Nitrogen (TN) for a FTW footprint of 0.14% of the contributing catchment. TSS and TP concentrations were found to be significantly reduced after FTW treatment. The minimum FTW footprint to catchment size ratio required to achieve regulated nutrient removal rates was calculated to be 0.37%. Sum of loads calculations based on flow resulted in pollution load reductions of TSS 76%, TP 55%, and TN 17%. Pollution treatment performance (particularly for TN) was found to be affected by low influent concentrations, and highly-variable inflow concentrations. The study demonstrated that FTWs are an effective treatment solution for the removal of pollution from urban stormwater runoff