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.

Fish, frogs, and other aquatic animals sometimes show signs of ‘endocrine disruption’; aberrant changes to their hormone or reproductive systems that are thought to be caused by chemicals in the water they inhabit. Very few of these chemicals have been identified, and this prevents the use of classical chemistry-based analytical methods. The other problem is that the levels of hormone-like chemicals which have endocrine-disrupting biological effects tend to be so low that standard chemical methods cannot detect them. This research developed a suite of biological tests sensitive enough to detect very low levels of chemicals associated with certain types of endocrine disruption. These tests were used to examine wastewater, surface water and drinking water collected from Australia, South Africa and four European countries. The water samples were also subjected to standard chemical analysis, and the datasets compared. It was concluded that some wastewater and surface water samples contained compounds that interacted with components of the estrogen, progesterone, androgen and mineralocorticoid hormone systems, but none of the biological tests detected endocrine disrupting activity in drinking water.

Sewage is delivered to wastewater treatment plants (WWTPs) where benign microbial organisms within ‘activated sludge’ vessels contribute to the removal of harmful pathogens from the sewage. The activity and pathogen-removing ability of these helpful organisms is affected by many factors including temperature, numbers of fine particles, pH, ammonia, and the time available to remove the pathogens. Regulatory authorities require at least 90% (one log removal value, LRV) of the pathogens to be removed, but as WWTP operating conditions vary, the LRVs change. This problem led to recognition of the need to develop models capable of predicting relationships between plant operating parameters (such as temperature) and pathogen removal. This research reviewed published reports and datasets, then set up and ran an experimental activated sludge pilot plant to generate data about a range of operating conditions and pathogen removals. These datasets were used to develop models which had only a ‘poor’ predictive value for clostridia but were ‘good’ for giardia and ‘very good to excellent’ for the removal of other pathogens. These models need to be extended with more operating conditions but have the potential to be used to attribute LRVs and for future integration into online real-time monitoring.

Burkholderia pseudomallei is a bacteria that is widespread in SE Asia and northern Australia, where there are an average of 16 cases per 100,000 people. This research found that water samples collected in and around Cairns from June to September did NOT contain Burkholderia pseudomallei and led to the conclusion that the risk of infection is much lower than in Darwin or Townsville.

Before treated wastewater can be discharged to the environment, utilities are required to perform a direct toxicity assessment (DTA), which usually requires that live aquatic animals, such as fish, swim in the clean discharge water for 4-10 days while their growth and activity are observed and measured. This preparatory research investigated the potential of in vitro cell culture assays for replacing whole animal tests. It was concluded that there are no legal or regulatory barriers, that in vitro cell culture has higher social and ethical acceptance than in vivo animal tests, and that three organisms (bacteria, algae and fish) could provide the cells needed to conduct seven toxicity tests that are good candidates for future development as alternatives to existing DTA methods.

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.

The management of blue-green algae (cyanobacteria), and the toxins and taste and odour compounds they produce, have been the focus of more than 30 years of research, but there is still a need for a suite of user-friendly tools to assess and manage aesthetic and toxin risks. This project conducted an extensive literature review about the ability of six treatment paradigms to remove MIB, geosmin, saxitoxins, microcystins and cylindrospermopsin. An empirical spreadsheet-base model was then built and used to simulate ‘whole-of-plant’ removal of cells and toxic metabolites. This model performed well when tested with two years of full-scale sampling data.

Water treatment plants (WTP) take in source waters then remove 95-99% of blue-green algae (cyanobacteria) cells and the toxins they produce. During this removal process waste sludge is generated and transferred from clarifier tanks in the treatment plant to lagoons. It was thought that confinement in the sludge killed the cyanobacteria, but this research found that when algal blooms have generated very high cell numbers, viable, toxin-producing cyanobacteria are retained in the sludge and can release toxins into the clarifier supernatant. It was concluded that timely removal to lagoons will avoid problems, and it is recommended that risk assessment for recycling lagoon supernatant back to the head of the WTP should incorporate extended times of 3 to 4 weeks after the end of algal blooms, to ensure cyanobacterial cell death and toxin degradation.

Cryptosporidium is a waterborne microscopic parasite with different forms at various stages of its lifecycle. One form, the spherical oocyst, is excreted by infected people and transported in rivers and surface waters. The problem is that it is not known if oocysts found in water are dead or are alive and infectious. This leads to an overestimation of the public health risk posed by oocysts found in source waters.

This research developed an in vitro cell culture test to differentiate between dead and infectious oocysts. The immortalised HCT-8 cell line was derived from cancerous human intestinal cells. When the cells are grown in a culture vessel, they display many characteristics of normal human gut cells. It was discovered that treating oocysts with acid to mimic stomach pH and using centrifugal force to ensure oocysts contact the HCT-8 cells, live (but not dead) oocysts react as though they are infecting a human host. The oocysts ‘hatch’ the next sporozoite form of the lifecycle, and these can be counted using a microscope. This ‘infectivity assay’ gives an improved, more accurate method for quantifying risks to human health presented by unidentified cryptosporidium oocysts in water.