In Australia, around 1.4 million tonnes of biosolids were produced in 2021. Land application of biosolids can promote environmental benefits such as: improve soil structure, carbon sequestration, cycling of nutrients as well as realising economic benefits through conserved landfill space, increased crop production and reduced demand for fertilizers. However, biosolids can have negative impacts on the environment if not properly managed.  Currently there is a lack of data on volatile emissions from biosolids when applied to land in Australia. Volatile emissions as well as impacting the environment can contribute to odours which reduce the community acceptance. Variations in volatile emissions can occur due to wastewater origins, biosolids processing, application methods and local conditions. This project aims to 1) identify and collate data from literature and industry on biosolids land application practices in Australia, and 2) measure volatile emissions from different biosolids, biosolids-amended soils and land application methods to inform best practice.

PhD Thesis underway by Thais Nunes Guerrero.

Biosolids odour impacts communities and public perception of water utilities. This project will explore how microbial community mediates variability of biosolids odour and GHG emissions using new approaches. The project aims to:
1. Develop methods to characterise microbial community structure and function with metabolomics and flow cytometry.
2. Explain the role of microbial community in regulating emissions during anaerobic incubation.
3. Investigate how the microbial community mediates emissions variability under environmental gradients.

PhD Thesis underway by Andreas Pfeifle.

Biosolids, the main by product from wastewater treatment plants, have a high potential in agricultural applications because they contain important plant nutrients and they can function as soil amendments. However, there are limitations to direct soil application of biosolids due to odour, pathogens, PFAS, micro-plastics, pharmaceuticals, and high heavy metal concentration present biosolids. This project proposes co-pyrolysis of biosolids with other waste types as a technique to overcome these limitations. In co-pyrolysis process, biosolids are mixed with other types of waste feedstocks and then are transformed thermochemically to biochar, pyro-oil, and pyro-gas in oxygen free atmosphere. This process is expected to overcome existing barriers in biosolids management and soil applications by transforming biosolids into high quality biochar with low heavy metal content and destroy PFAS components present in biosolids. In addition, co-pyrolysis also evidently improves qualities of oil and gas products due to the synergetic effects between the feedstock materials.

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.

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.

Blue-green algae (cyanobacteria) reduce water quality especially when they bloom and form high numbers of cells which produce toxins, and taste and odour compounds. Most cyanobacteria photosynthesise and tend to grow and float at depths which optimise their exposure to sunlight, but an increase in unexplained occurrences of taste and odour compounds in reservoirs, and a bloom of benthic (bottom-living) cyanobacteria, forced the closure of a water supply. This research examined the role that bottom-living benthic cyanobacteria play in the production of toxins or taste and odour compounds. Seven DNA-based PCR tests were developed to identify benthic species of cyanobacteria and their capacity for producing toxins. A taste and odour compound, and two toxins were found in winter and spring in an SA reservoir, whereas a different taste and odour compound and toxin assemblage were found in summer and autumn in a reservoir in NSW. These results will help water suppliers to anticipate and manage future aesthetic or toxin issues related to benthic cyanobacteria.

Blue-green algae (cyanobacteria) blooms decrease water quality by releasing toxins and unpalatable taste and odour compounds. The problem is that it is difficult to rapidly and accurately identify toxic cyanobacteria in drinking, recycled or recreational waters. This research developed a reliable and sensitive DNA-based PCR test which used robotic equipment to carry out the laboratory component of the test. The speed and accuracy of this diagnostic test has the potential to improve management of blooms and contribute to the maintenance of water quality.

Cyanobacterial blooms in surface waters are a source of cells, taste and odour compounds, and a range of toxins. This research optimised treatment processes for the removal and control of cyanobacteria and their metabolites from a range of source waters. It was concluded that pre-chlorination is not advisable when cyanobacteria are present, but that in some situation’s potassium permanganate is a viable alternative. Although all three tested coagulants; ferric chloride, aluminium chlorohydrate and aluminium sulphate (alum) removed 90 to 95% of cells, alum at pH 6.3 was the most cost-effective. Maintaining pH > 6 reduced cell lysis and metabolite release. Since cyanobacteria in sludge remained viable for 2-3 weeks it was recommended that sludge detention in the clarifiers should be minimised.

Cyanobacterial blooms are a major problem for reservoir managers because of the large numbers of cells and the toxins they contain. These blue-green algae blooms have traditionally been treated with the algaecide copper sulphate, but this was expensive and unsustainable because it killed non-target species and left residual contaminants. This research examined and rejected alternatives: other copper-based algaecides, hydrogen peroxide, substances that trap cyanobacterial-growth supporting nutrients on the floor of the reservoir, and mechanical surface mixers. Laboratory experiments that tested the ability of ultrasound to prevent the photosynthetic cyanobacteria from floating at the depth that optimises light absorption were initially promising because the ultrasound reduced photosynthesis and metabolism and the blue-green algae died. Unfortunately, when an ultrasound system was deployed in a reservoir, the much larger volume of water attenuated and ‘absorbed’ the low-power ultrasound and led to the conclusion that sustainable, environmentally friendly levels of ultrasound do not provide effective control of blue-green algae. This rigorously conducted scientific study has generated useful information about methods which do not work, and resources can now be directed to promising new innovations.

This project developed analytical methods sensitive enough to detect the very low levels of compounds that leach out of old coal tar enamel-lined pipes, then catalogued the chemicals and the levels they were found at in a problematic pipeline. One of the chemicals leaching out of the old lining is probably acted on by microbes to produce another substance with an earthy, musty flavour. None of these were toxic in tests and they are therefore unlikely to pose a risk to human health.