Features, Sewer, Water, Water treatment

Western Treatment Plant trials co-digestion

Melbourne Water recently commenced an 18-month co-digestion trial of organic wastes at its Western Treatment Plant in Werribee.

The trial is part of an investigation into the feasibility of implementing large scale co-digestion at the facility, which treats more than half of Melbourne’s sewage.

Co-digestion is the process of adding high strength organic wastes into the anaerobic section of the existing sewage treatment process, where organic materials are broken down by naturally occurring bacteria to produce methane-rich biogas.

At the Western Treatment Plant, biogas is captured from the anaerobic process (the treatment of sewage in the absence of any oxygen) and used to generate renewable electricity on site – enough to almost meet the electricity demand of the treatment process.

The organic wastes used in co-digestion are typically liquid and semi-liquid produced by the food industry, which cannot be disposed via sewers as they can cause odour and corrosion of sewers.

These wastes are often disposed to landfill, where the breakdown of the organic material and release of methane gas is often released into the atmosphere.

Harnessing the energy from these organic wastes through co-digestion offers both an energy source and sustainable alternative to waste disposal.

Melbourne Water’s Manager – Treatment and Resources Jenelle Watson said the trial is a great example of Melbourne Water’s drive for innovation in resource recovery.

“The co-digestion trial is the first step for Melbourne Water in providing a sustainable outlet for high strength organic wastes from the food industry,” Ms Watson said.

“It’s a great opportunity to work with our customers to create a new service offering that will benefit the environment.

“This initiative also has the potential to become a revenue generator for Melbourne Water, with profits going back into reducing costs for our customers.”

Co-digestion has successfully delivered multiple benefits at international sewerage treatment plants.

The benefits of providing this service at a larger scale at the Western Treatment Plant include:

  • An increase in renewable energy generated from biogas that can be used on site for treatment plant operations or exported to the grid
  • An alternative revenue source, the benefits of which will be passed onto customers
  • Reduced waste to landfill
  • Reduced travelling distance for waste transporters

The results of the current trial will inform the decision to progress to a large scale facility once the trial is completed in mid-2018.

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