Although odour complaints have declined significantly over time, we acknowledge that our operations, including our sewage treatment plants, may still cause odour from time to time. We aim to ensure local communities are not regularly affected by odour, and have a range of measures in place to do this.

What causes odour?

On any given day, there are multiple projects underway at the WTP to improve the way we treat and manage your sewage. The main source of odour is the plant’s sewage treatment lagoons – particularly when undergoing maintenance – although odour can also come from other areas of the plant. This is relatively minor and generally only occurs under specific wind and atmospheric conditions that impact odour distribution.

The lagoons are a key part of the sewage treatment process, creating ‘anaerobic’ (oxygen-less) treatment conditions that produce a methane-rich biogas. This has a high energy content and is used to generate electricity on site – but is also odorous. To manage odour and capture biogas, these lagoons are partially covered with engineered plastic.

The covered anaerobic lagoons need periodic maintenance, so every 5 to 7 years we remove and replace the covers, and remove residual solids that have built up during the sewage treatment process. Maintenance can take 3 to 6 months, during which time odour levels are much higher than normal and can be detected at or beyond the plant boundary.

  • Did you know?

    Between 85,000 and 100,000 megawatt hours of renewable electricity is generated from biogas every year, supplying more than 100% of the plant's electricity needs. This reduces the WTP’s greenhouse gas emissions by about 500,000 tonnes of carbon dioxide annually.

How to report odour

We want to make it easy for you to get in touch with us.

It’s important you report this at the time of smelling the odour, so we can investigate it in a timely way. Please do not log odour reports online, as there may be a delay in investigations.

To help our investigations, try and provide details such as:

  • when you smelt the odour
  • what it smelt like
  • how long you smelt it for.

Describing odours

EPA’s odour list can help you describe an odour – for example, odour from animals, chemicals, burning or cooking.

In general, we know that odour from our sewage treatment sites will often have a rotting/putrid smell due to the presence of hydrogen sulphide and similar odorous compounds.

Environment Protection Authority (EPA) odour wheel. A blue triangle is highlighting the type of smell our treatment plants may make.

Rotting or putrid

  • Garbage or rubbish
  • Rotten eggs
  • Decayed organics or compost
  • Sewage or septic
  • Milk or dairy (rancid)
  • Dead animal or rotten meat
  • Grease trap.

Burnt or smoky

  • Rubber
  • Plastic
  • Feathers or hair
  • Wood or woodsmoke
  • Waste or landfill

Chemical or solvent

  • Alcohol or medicinal
  • Paint thinners, spray paint (acetone)
  • Sour or acidic
  • Metallic or foundry
  • Sweet
  • Ammonia
  • Chlorine.

Vegetable origin

  • Compost or mulch
  • Garlic or onion
  • Yeast or fermented
  • Woody or resinous
  • Paper or pulp
  • Cabbage
  • Seaweed.

Hydrocarbon or fuel

  • Gas (mercaptan)
  • Petrol
  • Bitumen or tar
  • Diesel
  • Oil or grease.


  • Nutty or grain
  • Fried, oily or fatty
  • Coffee (burnt or roast)
  • Meaty (cooked or burnt).

Animal origin

  • Skin or hides
  • Urine (uric acid/ammonia)
  • Manure (faeces)
  • Chicken or poultry farm
  • Fishy (amines)
  • Livestock
  • Rendering.

What happens next

If Melbourne Water operations are confirmed as the source of your odour complaint, we’ll let you know and work to address any issues at the location that may be causing this.

We’ll also notify our environmental regulator, EPA Victoria, of any confirmed odour complaints.