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Blaxland Free Surface Wetlands

Innovative Landfill Waste Water Treatment

Sydney Olympic Park Authority is responsible for the day-to-day and long-term management of ten engineered landfills and associated landfill leachate which were constructed between 1983 – 2001 to ensure the containment of waste, protection of human health and the environment. The landfills have been rehabilitated and transformed into open space and parklands where waste is contained within large mounds across the Park in safe storage. These waste mounds produce water that passes through the waste collecting contaminants from the waste body. This contaminated waste water, known as leachate, needs to be managed to prevent is from getting out and polluting the surrounding waterways.

Between 40,000,000 and 60,000,000 litres per year of contaminated liquid waste leachate is collected and, in the past, has been treated and disposed at an industrial waste treatment facility, an expensive process requiring leachate to be transported off-site for treatment.

The Sydney Olympic Park Authority has sought a sustainable and environmentally friendly alternative to off-site processing and a sustainable leachate management strategy moving away from the reliance on conventional off-site industrial treatment and disposal processes to more sustainable on-site treatment options while, ensuring Sydney Olympic Park Authority (SOPA) meets its statutory obligations in relation to the management of the remediated lands.

SOPA has accomplished pioneering works in promoting, building and operating sustainable landfill leachate treatment systems and operates three sustainable, on-site biological leachate treatment systems that allow clean, effective and environmentally sound treatment of these contaminants.

Since 2000, SOPA operates a biological leachate treatment system at Wilson Park. The NSW Environment Protection Authority (EPA) approved and regulates the bioremediation process. Leachate contaminated with petroleum and aromatic hydrocarbons resulting from the operation of the historical gas plant PACCAL (Petroleum and Chemical Corporation Australia Ltd) is treated in a series of treatment ponds. The achieved effluent quality is very high and meets the criteria for discharge to Parramatta River set out and regulated by NSW EPA.

A second biological leachate treatment system was constructed in 2013 treating leachate generated by the Blaxland Common landfill. The landfill comprises domestic, commercial and industrial waste. The treatment system created is one of the most innovative leachate treatment solutions in Australia. The main contaminant is ammonia which is a toxic product of waste degradation. Leachate ammonia is broken down by nitrifying and denitrifying bacteria in a system comprising a constructed vertical flow wetland and two constructed free surface wetlands.

The biological treatment system treats landfill leachate to a very high effluent quality that meets the NSW EPA’s environmental criteria for discharge to Parramatta River.

Top View
Leachate Diagram

A third biological on-site leachate treatment system was constructed in 2015 on the Former Golf Driving Range (FGDR) remediated landfill and commissioned in 2016. This treatment system provides an even higher level of sustainability. The treatment is also based on ammonia degradation to nitrogen gas by a sequence of nitrifying and denitrifying microbial activity. But this system allows irrigation of treated leachate back over the footprint of the landfill, reducing Sydney Olympic Park’s reliance on recycled or potable water for irrigation.


There are a lot of benefits of these projects:
All three constructed wetland systems treat landfill leachate biologically in very close proximity of the source and reduce the need to dispose leachate off-site. The treatment wetlands offer a more ecologically and economically sustainable solution to leachate treatment. The systems operate without using any chemicals or additives. The natural treatment process does not generate any wastes or by-products that require treatment and disposal. The treatment wetlands are easy to maintain and operate and the systems consume little energy. Both the Blaxland and Former Golf Driving Range constructed treatment wetlands rely on gravity as a force to transport leachate. The biological treatment wetlands do not cause odour, noise, air, land or water pollution and create new habitat for native flora and fauna. New indigenous plants species inhabit the wetland area. The treatment process provides a new source for irrigation helping to save potable and recycled water that would be otherwise used for irrigation.
Innovative processes such as the sustainable leachate treatment process make dealing with contaminated water from landfill sites a far cheaper, cleaner and environmentally safer option and offers greater opportunity to return remediated landfill sites to the community for safe recreational uses.