What’s in our poo?



Sewer systems, the unsung heroes of modern society. We definitely take them for granted. But there are clues lurking in Sydney’s 27,000 kilometres of sewer pipes about what makes us tick. We remain a stimulant nation with the exception of cannabis.

By analysing what travels through these pipes, scientists can help government agencies figure out the recreational, drug and alcohol consumption rates of particular areas, or even identify where skills or diseases like polio and COVID might be spreading.

If we could develop a method to detect this virus in wastewater, it could potentially be used as an epidemiology tool. From tracking drug trends to the spread of viruses, there really is a lot more we could learn from looking under the hood. Now, before we dive in, we need to know what actually happens when you press the button. Let’s go for a drive. Here in Sydney, there are wastewater facilities dotted all over the city, treating 1.3 billion litres of wastewater every day.

But each treatment plant processes the wastewater to different levels. In short, close to the coast means less processing required. The primary level of treatment removes all solids and paper before pumping the wastewater out to sea. 2.2 kilometres and 63 metres deep if you’re looking at the Bondi plant. For plants that take treatment to the next level, the secondary level strips out the poo which results in a nutrient rich fertiliser.

Yup. Your poo is being used to grow crops! And there are ongoing trials to refine the gasses produced at the same time to inject them back into the natural gas network. The final tertiary level involves filtering and disinfecting the leftover water. Then it flows through to recycled water plants. So now that we’ve found out about how our sewer system works, it makes sense that by taking a look at samples along the way, we can understand a little bit more about us.

Wastewater based epidemiology is all about community or population testing. People get infections, they shed these pathogens when they take a shower or brush their teeth or pass urine or stools, they all these pathogens will end up in the wastewater. Back in 2020 February we thought if we could develop a method to detect this virus in wastewater, it could potentially be used as a epidemiology tool.

So I asked my manager and then she said, Yeah, let’s give it a go and see where we end up with. Traces of COVID 19 were found in wastewater in the city’s south west. Authorities say it’s another tool in the fight against the pandemic. The Wastewater Analysis Programme covered over 90% of the greater Sydney population and the findings gave rich data to support New South Wales Health’s COVID 19 response. So I asked Sudhi to walk us through the process.

So in a nutshell, we are separating the nucleic acid and purifying it from other debris. The nucleic acid contains genetic information like DNA and RNA. This is then analysed with a PCR machine to look for genetic markers of the COVID virus.

This current programme can apply for other pathogens as well. We have got a method for detecting monkeypox in wastewater and now we are working with the New South Wales Health to introduce a polio surveillance programme.

Aside from tracking the spread of illness, similar practises are being used by the Australian Criminal Intelligence Commission to track our drug use. We remain a stimulant nation with the exception of cannabis. Methylamphetamine remains the dominant illicit stimulant in Australia. What we are doing now is we’re triangulating the data even further by using our wastewater data, but also marrying that up with law enforcement, health and policy agencies. You can get a better idea by triangulating the data how many people are using?

How often? Whether they’re employed. All sorts of features of the community. So we can better understand types of areas that need to be targeted for treatment or enforcement action, etc..

It’s a fascinating field to help peel back the layers of our communities to better understand our trends and habits while assisting government agencies to more effectively allocate their resources to address national health and safety. So for Sydney’s wastewater scientists, the story of you starts with your poo.

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