The water recycling plant takes sewage from the International Terminal and treats it using mechanical, chemical and microbiological processes. The water is then recycled through a dedicated pipe network for use in toilet flushing and cooling towers for the air-conditioning system.
Actual water savings fluctuate according to demand and in 2009 the plant was saving an average of 350 kilolitres of fresh drinking water each day. In 2010 and 2011, this increased to an average of 580 kilolitres per day and is expected to increase up to a maximum of one megalitre per day over the next 20 years.
The use of recycled water means that each day the plant avoids the consumption of fresh drinking water and reduces the amount of waste that needs to be disposed.
The water recycling plant has two components: the plant to treat the sewage and the reticulation network to pipe the recycled water to where it can be used.
The total construction cost was $10.05 million supported with $3 million from the NSW Government’s Climate Change Fund.
The water treatment plant processes raw sewage from the International Terminal and surrounds including the multi-storey car park, Ulm Building (Sydney Airport’s Corporate Office) and Customs House.
The treatment plant produces two streams of recycled water:
Recycled water piped to the International Terminal to be used for toilet flushing. There are 526 toilets and 212 urinals connected that will be flushed using recycled water.
Reverse osmosis water is piped to the Central Services Building and used in air-conditioning cooling towers.
The benefits of the project include:
Environmental – reducing the amount of sewage that has to be disposed
Sustainable – reducing the amount of fresh drinking water consumed
Commercial – saving on water costs
The plant is located at the southern end of the International Terminal precinct.
How it works
Step A: Sewer line – Flow balance tank
Sewer is harvested from the existing pump station. The harvested sewage passes through inlet screens where foreign objects are screened before it enters the flow balance tank.
Step B: Flow balance tank
The flow balance tank provides an initial mixing of the sewage buffering the peaks and lows of the sewage flows and allows a constant flow of sewage into the biological reactor. The volume of sewage within the flow balance tank governs the harvesting cycle.
Step C: Biological reactor
The sewage passes through the anoxic tank and aerobic tank. The anoxic tank removes nitrogen from the waste prior to entering the aerobic zone. Within the anoxic tank there are submersible pumps that ensure there is no settlement of solids whilst not introducing excessive mixing that will hinder the denitrification process.
The aerobic tank is essentially a complexly mixed reactor, where biological mass or biomass is allowed to grow and consume biodegradable matter in the wastewater. Oxygen required for biomass is supplied by air blowers. Aerobic zone removes the organic and nitrogen components of wastewater by oxidising them and absorbing to their cell tissues. In the process, biomass population grows and is referred to as the mixed liquor suspended solids (MLSS). The mixed liquor is continuously fed to the membrane tank via overflow from the outlet box and re-circulated back into the anoxic zone by return activated sludge (RAS).
Step D: Membrane
The MLSS is gravity fed from the aerobic tank to the membrane tank. Within the membrane tank is a membrane cassette containing hollow fibre membrane manufactured from oxidant resistant material. The mixed liquor from the bioreactor flows past the surface of the membrane fibre. As required a slight suction is applied to the inside of the fibre sufficient to draw through treated water and leave behind contaminants such as solids and pathogens.
By-products of the membrane include the waste activated sludge which is returned to the sewage pumping station and the return activated sludge which is recirculated into the biological reactor.
Step E: Filtrate tank
The filtrate tank collects and stores water passing through the membrane process and allows the creation of the two recycled water streams.
Stream 1 – Recycled water
Removes colour from the recycled water and will also contribute to disinfection of the water.
There are two independent contact tanks having a combined capacity of 350kl. The contact tanks provide a final water storage point and contact time for the chlorine dosing to allow recycled water disinfection.
Deliver the recycled water to the International Terminal to be used in flushing toilets and urinals.
Stream 2 – Reverse osmosis water
Reverse osmosis membranes
The recycled water is pumped through the reversed osmosis membranes. The process removes the dissolved salt, organic compounds, inorganic compounds and nutrients from the recycled water. The process also provides an additional barrier against microbiological contaminants such as E.coli, viruses and protozoa.
The reverse osmosis water flows through a calcite filter for re-mineralisation. The re-mineralisation process limits the potential for corrosion of the cooling tower infrastructure.
Deliver the recycled water to the Central Services Building to be used in air-conditioning cooling towers.