This project provided an on-line monitoring protocol utilizing fluorescence to aid utilities in their provision of safe drinking water thus addressing the National Research Priority Goal “Water – A critical resource”

PhD Thesis completed by Yulia Shutova in October 2014.

Raw source water contains parts of plants, blue-green algae and their toxins, and many other types of organic matter. Identifying the types and amounts of organic matter helps treatment plant operators make informed decisions about the most efficient and cost-effective methods for treating and removing unwanted substances from source waters. The problem is that many of the tests for identifying organic compounds can take hours to days to deliver results. This research developed a test that gives information immediately. It uses three commercially available fluorescent probes that each emit fluorescent light at a specific wavelength. Certain compounds within organic matter, such as proteins, “reflect” the fluorescent light, but at different wavelengths which can be detected by the probes. These patterns of “reflected” fluorescence were related to traditional tests for organic compounds. This on-line fluorescence monitoring was then trialled at real-world treatment plants. The patterns gave reliable information about broad categories of organic compounds and there was a linear correlation between dissolved organic carbon and fluorescent intensity in both raw and treated waters. This research has provided a valuable addition to the suite of tools available for producing safe, high quality drinking water.

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.

Natural organic matter (NOM) and bromide in source waters react with disinfectants to produce disinfection by-products (DBPs) in drinking water. This research quantified NOM and bromine in raw water and after coagulation treatment with alum. Neither raw nor alum-treated water were toxic in two laboratory tests. This research used a new site to confirm previous findings (Project 1041) that coagulation reduces DBP formation and toxicity after chlorination.

Source waters are disinfected to remove harmful pathogens, but chlorine reacts with organic matter and bromides to form disinfection by-products (DBPs) which can affect health. Water treatment reduces DBPs to safe levels by using alum to remove organic matter before disinfection but some water sources, particularly those with high bromine levels, are still difficult to treat. This research aimed to compile the best protocols for alum coagulation and disinfection when source waters contain different levels of organic matter and bromides, and to relate these to health risks. When organic matter was removed with 125 mg/L alum, and this treated source water was disinfected twice, and the first dose was calculated to generate chlorine levels of 0.5 mg / L for two days before administering the second dose, then DBP levels in drinking water were minimised. Neither alum-treated nor disinfected water caused toxicity in two laboratory tests used to examine risks to health.

Components of dissolved organic matter (DOM) and dissolved organic nitrogen (DON) in source waters can react with disinfecting chlorine or chloramine to form nitrogenous disinfection byproducts (n-DBPs) which might be toxic and hazardous to health. In this research, water samples were collected from nine water treatment plants and found to contain 28 n-DBPs. Total n-DBP formation, and particularly brominated n-DBP formation, was affected more by the levels of bromine in raw water than the different forms of nitrogen, and this led to the recommendation that it could be beneficial to monitor raw waters with high bromine concentrations. Although chloramination caused formation of more n-DBPs than chlorination, coagulation treatment decreased total DBP levels. Further research was recommended to characterise the toxicity of n-DBPs and to optimise the removal of DOM, DON and other n-DBP precursors by using GAC Acticarb in the treatment train.

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.

Water is disinfected to remove harmful microbes and pathogens such as cholera and typhoid. The problem is that disinfection of certain types of waters, such as those containing naturally high levels of bromide or iodide, can cause the formation of disinfection by-products (DBPs). Some DBPs have been linked to cancer although this association is relatively weak because many other factors have a much stronger influence on the development of cancer than drinking water. Nevertheless, the water industry aspires to minimise this risk and conducted this research to measure the levels of bromide, iodide and other substances in Australian source waters. A number of treatments with potential to remove bromide were examined, and it was found that chlorination reduced the risk posed by iodo-DPBs.