Television has made us all familiar with the key tools of the Crime Scene Investigator: fingerprints, DNA testing, hair and fibre analysis, ballistics, CCTV (closed-circuit television) and a rocking soundtrack by The Who. But what happens when your crime scene is a drain, creek, wetland or river, and the crime isn't murder, it's pollution?

Send in the DSI – the Drain Scene Investigators.

Catching water polluters is notoriously difficult. Water doesn't stay still, and by the time pollution is reported it may already have moved downstream. Unlike many crime scenes, the fingerprints of water pollution are often liquidated before investigators arrive on the scene.

A team of researchers at the Centre for Aquatic Pollution Identification and Management (CAPIM) have developed some low-cost, high sensitivity, and mobile water quality probes for investigations into the source of pollutants.

Now the polluters (and pollution) have nowhere to hide.

Whether it's a café trying to save money by flushing their waste down an illegal connection to the stormwater drain, or a factory negligently leaching mercury into the stormwater network, CAPIM has the tools to track them down.

Continuous water quality samplers are the CCTV of water pollution detection; they constantly record a variety of pollution indicators and can capture the moment a spike in pollution goes past. However, it is way too expensive to install these samplers everywhere they might be useful.

This is why low-cost, sensitive and - most importantly - portable probes and samplers can be so effective at identifying the source of pollution.

Pollution can range from human or animal waste to pharmaceuticals, petroleum products, industrial chemicals, heavy metals, pesticides, herbicides and fungicides.

"Once we identify that pollution is present, we need to identify the source," said Associate Professor Vincent Pettigrove, CAPIM chief executive officer.

The team works its way upstream, and using probes, diagnostic tools and good old-fashioned deduction, they narrow in on the perpetrator.

"We can put one of our measurement probes in the water and get a host of water quality readings in a matter of minutes, then move up to the next site, using our knowledge of the hydrology of Melbourne's waterways and drains to narrow in on the source," said Dr Pettigrove.

When working at this pace, the CAPIM team can't necessarily run all of the measurements they would like to, so they will often use easy to measure proxies to follow the trail.

"Testing for faecal indicator bacteria takes a lot of time and money, but we know, for example, that an increase in ammonia is often related to the presence of sewage," said Dr Pettigrove.

"Dr Maria Ines Almeida from the School of Chemistry at the University of Melbourne has developed a rapid and sensitive ammonia passive sampler for the field, so we can follow the ammonia to track the bacteria."

If the concentration of a pollutant or proxy suddenly drops, they know they've probably gone the wrong way. A spike means they are getting close.

In 2013 EPA Victoria commenced a project to tackle its' commitment to improving Victoria's water quality with a round of targeted inspections of electroplaters, with the aim to reduce heavy metals entering soils, rivers and streams. Simultaneously, the CAPIM team looked at metals in stormwaters upstream and downstream of businesses before and after EPA's education and enforcement program.

"Our passive samplers enabled the EPA to assess pollution risks at each site and gauge the effectiveness of their program", said Simon Sharp, a research officer with CAPIM.

Cases of industrial pollution we identify are referred to the relevant authorities and can lead to fines, enforcement actions and education programs for the polluters.

"In serious incidents or breaches with severe environmental impacts, polluters may be pursued in court for heavy fines and criminal prosecutions."

Dr Pettigrove said that with the new technologies they have developed, they can locate pollution sources entering stormwater drains even when the pollution is intermittent.

"We are developing an array of sampling devices that will enable us to detect even more pollutants in these drains," said Dr Pettigrove.

CAPIM research fellow Dr Dave Sharley regularly deploys passive samplers in waterways as part of forensic investigations, monitoring programs or research studies.

"These passive samplers are a world first and we think there is a lot of potential for these to be used in other cities and countries worldwide," Dr Sharley said.

These investigations don't just find criminals; they can also ensure effective, and cost effective, management of waterways.

CAPIM has conducted several whole-of-catchment studies that demonstrate the importance of considering all potential factors in catchments impacted by multiple stressors, rather than solely focussing on single sources like sewage discharges.

The EPA recently found that an emergency relief structure, or ERS (which stops sewage spilling into residential properties by allowing emergency discharge to the storm water system), in the Upper Dandenong Creek catchment did not comply with their policy for wet weather spills.

Melbourne Water, who manages the structure, contracted CAPIM to investigate the potential effects of episodic sewage spills via the ERS on the aquatic animals. CAPIM then separated these effects from other sources of pollutants present within the catchment.

They wanted to know how much pollution could be traced back to the ERS. Not much as it turned out.

Dr Claudette Kellar, a researcher fellow with CAPIM and the School of BioSciences, University of Melbourne, who worked on this project, said: "The study clearly identified that pollutants from industry (metals and pesticides) were impacting the aquatic fauna rather than pollutants from the sewer. As a consequence, target areas and specific pollutants were identified for remediation instead of an expensive sewer upgrade."

Melbourne Water and the EPA used this information to implement the Enhancing Our Dandenong Creek program, a range of targeted improvements to the stormwater entering the creek.

Banner image: Stormwater drains in Dandenong Creek catchment. Credit: CAPIM