The environmental conditions which cause blue-green algae (cyanobacteria) blooms vary according to location, the climate, and other attributes of aquatic ecosystems. This variety has made it difficult to develop one broadly applicable predictive model for cyanobacterial blooms. Water utilities monitor source waters to implement cyanobacterial risk management programmes but there are no standard protocols while limited information transfer between utilities has prevented the identification of management strategies that do or do not work. This research reviewed literature about early warning systems (Almuhtaram et al., 2021) and source control strategies, conducted a survey of 35 utilities in America and Canada (74%) and Australia (Kibuye et al., 2021) and evaluated selected control strategies. These different types of information were synthesised into decision trees within an overarching guidance document. It was concluded that a 3-tier framework to detect algal blooms which monitored biological activity, then confirmed the identification of cyanobacterial genes and associated metabolites gave sufficient early warning, while multi-barrier control strategies gave field-scale efficacy and enabled timely responses.

Membranes are used to remove viruses from treated wastewater to make it safe for discharge or recycling. It is important to monitor the integrity of membranes and check that viruses cannot break through. This creates a need for surrogates that are cheaper, safer and easier to use than the non-hazardous indicator virus currently applied to test membrane integrity. This research synthesised a series of fluorescent nanoparticles with similar dimensions to viruses, with the idea that the fluorescence would support continuous in situ monitoring in real time, but unfortunately the nanoparticles did not emit enough fluorescence and could not be detected in the product water.

Smaller and regional Wastewater Treatment Plants (WWTPs) have the capacity to recycle wastewater for agricultural use, but the cost of obtaining regulatory approval or ‘accreditation’ is prohibitive. One reason for this is that each WWTP must demonstrate that its processes and operations consistently remove pathogens that cause infectious diseases in humans. Operating conditions include flow rate through the WWTP, and temperature in the activated sludge component of the WWTPs. Although pathogen ‘log removal values (LVR)’ were obtained for a WWTP at 19-20°C in Part I of this project (WQRA project 2001), these values cannot also be attributed to summer temperatures of 26°C. This research determined LRVs for ‘new’ WWTP operating conditions and combined the data with data from Phase I (Project 2001) for analysis. One of the conclusions from Part II was that faster flow rates associated with increased rainfall reduced pathogen LRVs.

Ultrafiltration membranes are used to remove viruses from treated wastewater. This makes it safe for release to the environment or for recycling, but it is important to monitor integrity of the membrane to ensure there are no damaged sections that viruses can break through. This research demonstrated that a silver nanoparticle is a valid, safer alternative to using non-infectious bacteriophage viruses that are currently used to test membrane integrity. The silver nanoparticle was tested and validated in a laboratory-scale ultrafiltration membrane unit. It was concluded that work should proceed to full-scale validation and integrity-testing of ultrafiltration membranes in recycled water applications.

The Australian water industry uses a variety of membrane processes to remove unwanted pathogens or compounds, such as salt, from source waters. As membranes age their ability to fulfil these removal and filtering functions declines. The problem is that although there are recognised and validated tests for membrane integrity, they are usually performed only on new membranes, and information about the effect of membrane aging on pathogen removal is limited. This project reviewed published literature and identified four methods suitable for future development as Membrane Integrity Tests that may prove applicable to evaluate aging membranes during ongoing and long-term plant operation.

E. coli bacteria naturally populate the gastrointestinal tract of humans and animals; they are usually harmless and are commonly excreted. Faeces can also contain harmful microscopic pathogens, and this has led to the assumption that if harmless E. coli are found in water, that the drinking water has been contaminated with faeces that might also have contained pathogens that pose a risk to public health. Using E. coli as an indicator of faecal contamination was recently challenged by the finding that some E. coli strains live, grow and bloom in the environment, and their presence in water might not mean that the water has been contaminated with harmful pathogens. This research examined the environmental conditions associated with E. coli bloom formation in the context of climate-change adaptation and developed multiplex PCR tests which allow the identification of environmental and faecal E. coli. This information was added to a Utility Response Protocol.

Water treatment plant operators remove cyanobacteria and the toxins they produce from source waters but calculating the amount of treatment needed for effective removal is difficult, particularly in bloom conditions when cyanobacterial cell numbers and toxins change quickly. Current cell counting and toxin measurement can take hours or days to complete, and the results are not available quickly enough to help treatment plant operators respond to changing conditions. There is a need for a real-time method that gives instant results. This research examined the utility of fluorometers; probes that emit light that is ‘reflected’ back at different wavelengths by living cells and other matter in the water and is detected by the fluorometer. It was found that when only one species of cyanobacteria was present, there was a good correlation between the fluorescent signal and cell number, particularly when source waters were clear and not cloudy. Cell numbers did not relate well to levels of toxins or taste and odour compounds. When fluorometers were installed in 13 water treatment plants the correlation between cyanobacteria cell numbers and fluorometer signals was validated, and this led to the conclusion that fluorometers can give early warning of blue-green algae blooms.

‘Microbial source tracking’ (MST) is a technique that aims to identify the animal that excreted faeces and polluted water. There are a number of ways to do this, but the problem is that no one method accurately identifies the origins of faecal pollution in environmental water samples. This research found that faeces could be stored in a freezer or a laboratory -80°C cold-store for up to a month without changing the relative numbers of the different types of bacteria in the samples of faeces. Up to seven faeces samples from different animals were mixed together and examined using 17 techniques to identify the original animals. Three of the most accurate and reliable methods used mitochondrial DNA, the analysis of a bacterial enzyme sequence (beta-glucuronidase), and specific DNA sequences form bacteria known to come from humans, horses and cows. These three types of tests were selected for inclusion in a ‘Toolbox’ from which a combination of methods will allow accurate and reliable management of faecal contaminants in source waters.

Cryptosporidium, a microscopic pathogen, forms infectious oocysts which are removed by specific and targeted water treatments. Oocysts can only be seen by using a microscope but finding an infectious dose of 10 oocysts in a litre of water is like finding a needle in a haystack. Usually a larger volume of water, 1000mL, is filtered to recover all the oocysts into a small volume of 0.1 to 1 mL, because this is small enough to be examined under a microscope. It is scientific practice to add some dead, colour-dyed oocysts to the large volume of water. If all the coloured oocysts are counted on the filter, the recovery is 100%. From this it became clear that there was a problem with oocyst recovery. This research found that different elements reduced recovery from different types of water, for example, iron and silica reduced oocyst recovery from river or groundwaters. The approved method for quantifying the environmental occurrence of oocysts can now be modified to increase recovery, and this change improves analysis and consequent management which further reduces risks to public health.

Cryptosporidium, a microscopic single-cell parasite, forms an “oocyst” with a resistant outer layer analogous to an eggshell. Oocysts survive for a long time in the environment but UV in sunlight, and high temperatures that cause desiccation, kill them. If a mammal drinks water containing live oocysts, they embed in the gut wall and continue their lifecycle until eventually many more oocysts are excreted. There are 26 species of cryptosporidium but only five infect humans, and two; Cryptosporidium hominus and Cryptosporidium parvum, cause approximately 95% of all human infections. C. hominus occurs only in humans, but C. parvum is also found in cattle, sheep, and other animals. The problem is that human-infecting oocysts are excreted by animals in catchments and rain can wash live oocysts into water reservoirs. This research collated peer-reviewed published literature, and information and data collected by the water industry, then characterised the distribution of different Cryptosporidium species in Australian catchments. This led to recognition of a research need to track and predict live and dead oocyst transport during different weather events, and to model and evaluate catchment management initiatives such as excluding cattle from reservoir areas.