During a recent routine monitoring event, one of our environmental consultants discovered a bright orange algae-like formation, similar to the colouring on construction high-visibility vests, coating the substrate and surrounding plants and water surface of a small stream. Leading up to the sampling day there had been little rainfall in the area, moderate temperatures and evidence of a bushfire. What was interesting was the clear film with distinct large bubbles on the surface of the water. On closer inspection the whole surface was coated in a thick clear algae-like formation, which was trapping air from reaching the surface, hence the bubbles. The appearance of the algae-like formation was a rare occurrence as the site did not have any previous records of it in the past 10 years of monitoring. The presence of the algae-like formation can be attributed to multiple interacting factors leading up to the time of sampling, including a lack of rainfall, presence of iron-oxidising bacteria, and most importantly iron-rich landfill leachate run-off.
The stagnant anaerobic environment, due to an extended period of low rainfall, provided a suitable location for bacteria to accumulate without disturbance. This combined with the presence of iron deposited from landfill groundwater seepage and a recent fire in the area created the possibility for the organic slime to form. The iron-oxidising bacteria does not pose a human health risk, but can be an indicator of landfill leachate contamination and cause structural issues and blockages to drainage systems. This type of slime usually dissipates with heavy rainfall but other treatment methods include physical removal, pasteurisation, and chemical treatment of the water.
Landfill remediation is a growing issue across the world. As cities increase in size and landfills reach maximum capacity, under the current model it is necessary for landfills to be capped and disposal moved to a new location. Depending on the location, decommissioned landfills are monitored under individual state guidelines, such as: NSW EPA Environmental Guidelines for Solid Waste Landfills (2016); VIC EPA Siting, Design, Operation and Rehabilitation of Landfills (2015); QLD EPA Landfill Siting, Design, Operation and Rehabilitation (2013). This includes regular monitoring of the area for leachate migration, and conducting testing to ensure the landfill is properly contained and not damaging the surrounding environment. Depending on the wastes disposed to the site, landfill leachate can be high in various contaminants, ranging from heavy metals to nutrients, organic matter and persistent environmental pollutants such as PFAS and dioxins. Over time this can impact on biodiversity and ecosystem structure, as well as pose a risk to human health and infrastructure. Homebush Bay in Sydney is a key example of an area that has a history of illegal dumping and landfill usage, with wastes including toxic industrial waste, dredged sediments, acid sulphate soils, and broken ships being deposited prior to the 1980’s. Rehabilitation began in the 1980’s and has cost the NSW Government over $137 million, including ongoing monitoring of waterways, removal of contaminated materials and capping of landfills in the area. As a result of the contamination from the landfilled areas, fishing is prohibited in Homebush Bay and Sydney Harbour for health reasons related to elevated levels of dioxins.
SESL conducts routine monitoring at landfills across Australia to work with State and Federal guidelines aimed at reducing the environmental and anthropogenic impact of decommissioned landfills. Please feel free to get in contact with us if you would like to discuss how we can help manage the remediation of your site or landfill.