Water contamination scenarios involving potentially harmful pathogens can now be safely simulated to help prevent water contamination and waterborne disease outbreaks, using world-first ‘pathogen surrogate’ technology.
PHF Science researchers have created non-living particles that mimic pathogens, including Cryptosporidium, rotavirus and Legionella, but are made from harmless materials, and can be precisely tracked with unique synthetic DNA tracers.
Together, the new surrogate and DNA tracer technologies enable the assessment of water contamination scenarios without the risks of working with actual pathogens. This makes it safer, cheaper, and easier to predict and prevent drinking water contamination before it affects people.
Water treatment operators can spike systems with pathogen surrogates to simulate outbreaks and test emergency responses. Councils can use them to predict contamination pathways and design better protection systems. The research has already proven that turbidity (water clarity) isn't a reliable indicator of protozoan removal.
Unlike research involving live pathogens, which requires purpose-designed facilities and strict controls, PHF Science’s surrogates are safe to use in standard laboratory settings and in the field, expanding where and how this work can be undertaken, says Liping Pang, a Science Leader at PHF Science.
PHF Science’s second generation of pathogen surrogates are made from food-grade and biodegradable biopolymer materials. Made from tiny particles modified with biomolecules (such as vitamins, proteins and amino acids), surrogates can be created that mimic viruses, bacteria, and protozoa. Each surrogate mirrors the pathogen’s properties: size, shape, adhesion to soil and sand grains, and even DNA degradation.
By creating a new way to safely assess how pathogens behave in real water systems, PHF Science’s innovation helps us answer critical questions about how quickly, how far, and under what conditions pathogens travel through soils, aquifers, and water. Working with Environment Canterbury and Waikato Regional Council, PHF Science has tracked DNA-labelled particles up to one kilometre in a surface stream and through an aquifer in Burnham.
Understanding how pathogens move through groundwater is important because it supplies 40 per cent of New Zealand’s drinking water. Groundwater moves like traffic, flowing freely through gravel and sand ‘highways’ but getting bottlenecked between silt and clay layers. The DNA-labelled surrogates reveal the roads contaminants take, allowing risks to be predicted. This can help councils make decisions such as determining the safe distance needed between a drinking water well and a septic tank.
“Because the synthetic DNA tracers have their unique barcodes, there is no ambiguity about where they came from,” explains Theo Sarris, Water and Environment Group Manager at PHF Science. “You can detect minuscule quantities and link them directly to the specific contamination sources and pathways.”
Pathogen surrogates can also be introduced to water treatment systems to test the performance of treatment processes and help keep drinking water safe.
Invercargill City Council trialled the technology to test the removal of Cryptosporidium surrogates in its pilot treatment plant. “We tested how effective different rapid media filters were for the removal of Cryptosporidium surrogates at varying loads,” explains Adrian Cocker, three waters technical supervisor at Invercargill City Council.
“Recovering the Cryptosporidium surrogates after the pilot plant filter enabled us to determine the actual reduction, which enabled us to determine an appropriate filter media and optimise full-scale filter run times for effective removal of Cryptosporidium protozoa.”
The surrogates have also been used to test rotavirus removal by water filtration, and to show how chlorine destroys Legionella. Future applications could also be extended to include testing reticulated water systems in hospitals, aircraft and ships. Closer to home, PHF Science tested different commonly used domestic water filters and found varying effectiveness, with activated carbon filters the most effective for removing pathogens.
Climate change makes this research increasingly vital. “The only way to prepare is to experiment to anticipate contamination risks under extreme weather conditions, which are going to be more frequent and of greater magnitude," says Theo Sarris.
PHF Science’s safe, economical surrogates enable testing of different climate scenarios to predict how pathogens will behave under heavy rainfall and changing water supplies.
The approach can be extended to develop mimics for other important waterborne pathogens, says Liping. “With further development and validation, the new surrogate technology can be used as a tool to study pathogen mobility and persistence in freshwater systems, facilitating more accurate prediction and control of waterborne infection risk.”