EPA Victoria

Passive samplers and networked sensors in urban stormwater

Industrial pollution is a major problem across Australia. The nature of the business activity increases the risk of toxicants making their way down to local rivers and creeks. By identifying areas that are most at risk of generating stormwater pollution, more targeted education and enforcement programs can be implemented.

Introduction

Point source pollution continues to be one of the main drivers of ecological stress on urban waterways. Heavy metals, hydrocarbons and pesticides from urban catchments make their way through stormwater networks into waterways. These pollutants can flush into receiving waterways and can accumulate in sediments where they can persist and cause toxicity to benthic fauna. Stress and toxicity from pollutants can have major consequences for the long-term health of aquatic ecosystems.

As part of EPA Victoria's (EPA) Research and Development Program in 2020-2021, new real-time wireless water quality sensors and stormwater passive samplers were trialled to detect pollutants flowing from the catchment into Merlynston Creek. This catchment was chosen because of its history of poor water quality associated with several industrial fires, including SKM in 2017 and Campbellfield Industrial Services in 2019.

Currently, most water quality monitoring programs involves the collection of discrete grab samples, which are reflective of pollution concentrations at that point of time. Further sampling based on laboratory analysis requires field staff to collect water from a single point in time. While EPA also receives pollution reports from the community, these pollution events have often already passed before EPA can respond and attend a site.

Passive sampling and in-situ monitoring allows for sampling to occur over a longer time-scale providing more data points over time across the catchment. These new technologies use real-time sensors to track concentrations of pollutants (including ammonia, copper and hydrocarbons) to identify pulse pollution events, trends and potential sources. Automatic alarms triggered via the visualisation dashboard will enable responsive actions based on 24/7 real-time pollution data.

Isolating high risk areas within a catchment using Stormscout^TM technology will allow EPA to develop targeted programs focusing on high-risk sub-catchments and allow local management authorities to deliver programs more efficiently or to initiate more intensive monitoring. This type of surveillance may be critical to EPA's regulatory response, allowing for problem sites to be identified and for pollution to be tracked to the source.

Passive sampling

StormScout samplers

Bio2Lab deployed StormScout^TM samplers^# into stormwater drains at 10 locations for five weeks (Figure 1). Samplers were always deployed for one week, constituting a sampling event. After each sampling event, media from the sampler was collected, processed and analysed for common persistent contaminants*, and a new sampler deployed.

All chemical analysis was performed by consulting laboratories accredited by the National Association of Testing Laboratories Australia (NATA). We converted contaminant concentrations into a simple colour-coded pollution risk rating for ease of interpretation, with colour ratings for each pollutant based on concentrations detected. The site risk score was determined by average pollutant concentrations across the five weeks of sampling. Pollution risk ratings used in this report are based on summary statistics derived from stormwater pollutant concentrations detected in StormScout^TM samplers over a 12-year period (see links to the interactive dashboard below). For each site, measured concentrations were compared to the summary statistics and grouped accordingly.

Real-time stormwater pollution sensors

Real-time pollution sensors were deployed at seven locations in the Merlynston Creek catchment. Data was continually streamed via the 4G network every 15 minutes to a data visualisation dashboard (see links to the interactive dashboard below). Ammonia, pH and copper were monitored from 12th October 2020 - 12th March 2021 at three locations along Merylnston Creek. Water was collected periodically for spot-checking purposes. Volatile organic compounds (VOCs)and water level were monitored in real-time at four locations in the stormwater network across the catchment (Figure 3).

*Note: mercury was not included in the analysis. This was due to a change in the type of StormScoutTM sampler used from “StormScout - Collect” to “StormScout- Adsorb”. As this sampler is not effective at accumulating mercury, it was decided to omit it from the list of parameters to be analysed.

^{# StormScouts use a artifical media comprised of organic carbon and other media specifically designed to adsorb pollutrants in stormwater over time (7-14 days).}

Ammonia Passive Samplers

Ammonia passive samplers were deployed for ten weeks at three key sites in Merlynston Creek (Link Drive, Maffra St and Fawkner). Fabrication and analysis of ammonia passive samplers was completed at the University of Melbourne, School of Chemistry. Samplers were deployed over a 7-day period. Analysis was done by flow system with a limit of detection (LOD) for NH₄⁺ of 0.08 mg/L to 0.13 mg/L. Quality control included multiple sample (trip and field) blanks and the mean concentration blank was subtracted from the passive samplers that were deployed into the creek. Measurement uncertainty was estimated between 0.8 – 7.1% against quality control standards (0.5 and 2 NH₄⁺ mg/L). The total ammonium (NH₄⁺) in each sampler was converted to a time weighted average concentration (C_TWA) (see Almeida et al. 2016; based on equation C_TWA = C_RS/0.618). This value is reflective of the amount of ammonia accumulated in the device during the deployment time and gives us a better understanding of pollutant concentrations over large temporal scales when compared to grab sampling techniques. The final concentrations (C_TWA) were reported as ammonia-N (NH₃-N mg/L).

Almeida, M.I.G., Silva, A.M., Coleman, R.A., Pettigrove, V.J., Cattrall, R.W. and Kolev, S.D., 2016. Development of a passive sampler based on a polymer inclusion membrane for total ammonia monitoring in freshwaters. Analytical and bioanalytical chemistry, 408(12), pp.3213-3222.

Šraj, L.O.C., Almeida, M.I.G., McKelvie, I.D. and Kolev, S.D., 2017. Determination of trace levels of ammonia in marine waters using a simple environmentally-friendly ammonia (SEA) analyser. Marine Chemistry, 194, pp.133-145.

Summary

This research and development project showed how coupling real-time pollution sensors to a visualisation dashboard with alerts enabled EPA to take quicker action to control flows, investigate pollution events and find pollution sources. The sensors were able to detect increases in contaminants and inform EPA Victoria through automatic alerts generated from the dashboard. This informed EPA's inspection strategy and improved response times to pollution events. The sensors were also used to monitor water quality following the 2020 MRI fire, which allowed EPA to better assess site clean-up actions.

Future directions

Operationalising certain components and continuation of trials to better understand how real-time pollution sensors can improve areas of EPA's core business is recommended. For instance, installation of real-time VOC and level sensors into high-risk industrial sites would provide 24/7 monitoring capability. Configuring alerts to better predict the type of pollution event is also achievable. Improvement in data analytics will allow triggers to better predict the magnitude of pollution events. For instance, the signature of an industrial fire would be different to a small dumping event. Triggers could be configured to alert EPA to different types of pollution events.

This EPA Research and Development project showed clearly how sensors could enable EPA to quickly respond to pollution events and inform inspection strategy. It also showed how deploying passive sampling technology into high-risk catchments can prioritise risks and trace pollutants back to their source, thereby reducing contaminants and improving the health of waterways across Victoria.

EPA Victoria

Passive samplers and networked sensors in urban stormwater

Introduction

Aims

Methodology

Passive sampling

StormScout samplers

Real-time stormwater pollution sensors

Ammonia Passive Samplers

Results and discussion

StormScout technology

Figure 1 - Site locations for the StormScout sampler program

Ammonia passive sampling

Figure 2 - Bar plot showing ammonia concentrations from the ammonia passive samplers

Real-time water quality monitoring

Figure 3 - Site locations for the real-time pollution monitoring sites in Merlynston Creek and stormwater drains situated in the Coolaroo industrial estate

Click on the image below to view the interactive pollution profiling dashboard

Click on the image below to view the real-time monitoring visualisation dashboard

Summary

Future directions

Acknowledgement of Country

Contributing Authors

Acknowledgements

Contact details