Saving Melbourne beaches from faecal pollution

By Cameron Amos

This ammonia test kit assists in detecting microbial pollution.

Port Phillip Bay and Melbourne’s beaches are very popular with visitors during warm and dry weather. Last summer saw an unusual number of beach closures following water quality testing by the EPA Victoria. Storm events were primarily responsible for these closures, primarily due to litter, faecal matter, contaminants and debris being flushed into stormwater drains, creeks, rivers and eventually the bay.

The EPA monitors the water quality at 36 beaches around Port Phillip Bay, and issues advice and forecasts about recreational water quality. The forecasts are based on observed and predicted rainfall, water quality history, sunlight, weekly sampling results and local pollution reports. The weekly samples are analysed for Enterococci, an estuarine and marine-tolerant human gut bacterium known to be pathogenic to humans. Following heavy rainfall, on January 20th 2017 all 36 Port Phillip beaches were closed due to high Enterococci levels.

On January 20th 2017 all 36 Port Phillip beaches were closed due to high Enterococci levels.

Microbial pollution (such as Enterococci) can result from heavy rainfall or faulty sewer infrastructure. In storm events, faecal matter can wash off surfaces and enter nearby stormwater drains, creeks, rivers and bay ecosystems. Damaged or blocked sewerage pipes and accidental cross-connections can also cause microbial contamination of stormwater. While this can happen in any type of weather, it presents a higher risk to human health on dry and warm days, when the beach is most attractive to visitors.

In 2014 and 2016, EPA Victoria commissioned CAPIM to locate areas where sewage was discharging into stormwater drains. This investigation aimed to identify defective drains for repair and reduce the number of dry weather beach closures. To this end, CAPIM used three tools developed to detect and track microbial pollution sources in stormwater networks: ammonia passive samplers, ammonia test-kits, and Bacteroides analysis.

CAPIM uses ammonia passive samplers, ammonia test-kits, and Bacteroides analysis to track faecal pollution.

Ammonia passive samplers rely on the positive relationship between ammonia and the freshwater bacterium Escherichia coli, commonly used to detect faecal pollution. The passive samplers absorb ammonia molecules over a period of time through a matrix and provide data as a time-weighted average. The samplers, which are robust and inexpensive to build, are used at the beginning of faecal sourcing projects to indicate catchments of concern. The next stage consists in using ammonia test-kits to pinpoint sewage discharges into stormwater.

The ammonia test-kits enable instant detection of pathogens. The kits are inexpensive, robust, efficient and readily available from commercial pet stores and aquarists. A five millilitre sample is mixed with two reactive chemicals. After five minutes, the colour of the mix indicates the ammonia concentration (see photo, showing a potentially high concentration of sewage).

Ammonia is an indirect and non-specific indicator for faecal pollution. CAPIM uses Bacteroides analyses to identify the microbial source, e.g. human, dog, bird or cow. Bacteroides are a group of bacteria that originate from the gut and are present in faeces. Their DNA is analysed and matched against species-specific DNA signatures. Using this method in addition to ammonia testing helps refine water quality assessments and subsequent health warnings.

Bacteroides DNA is analysed and matched against species-specific DNA signatures.

In 2016, a CAPIM investigation tracked a large volume of sewage that was entering a creek via a stormwater drain. This tracking was initially conducted using the ammonia test-kit. Bacteroides analysis confirmed that microbial pollution was coming from a large, damaged sewerage pipe. The EPA and the regional water authority were alerted and the pipe was repaired immediately. This intervention reduced dry weather beach closures in the area and minimised threats to both the health of beachgoers and their hopes to cool down on hot days.

For more information about faecal pollution tracking, contact Daniel Macmahon macmahon@unimelb.edu.au.

References

EPA 2016-2017 Beach Report: http://yarraandbay.vic.gov.au/beach-report/2016-17-summer-highlights-report

http://www.abc.net.au/news/2017-01-20/poor-water-quality-forecast-at-all-beaches-in-port-phillip-bay/8197404