Remote communities have an issue with hardness levels in water supplies.  This project established the cost impact of hard water on household infrastructure in remote Indigenous communities.  The results of this project enabled Power and Water Corporation to form a business case to improve the water quality for the communities they support.

Honours Thesis completed by Heather Browett in November 2011.

This project investigated the preparation and stability of concentrated preformed monochloramine solutions, with the potential application of remote area redosing to maintain disinfectant residual. Various conditions (such as pH and temperature) were investigated for their affect on the formation and stability of high concentrated monochloramine solutions, and the optimum conditions determined. The effect of redosing with concentrated solutions on disinfection by product formation were investigated. Overall this project aimed to better understand the constraints on the stability of high concentrated monochloramine solutions.

Honours Thesis completed by Charlotte Andringa-Bate in November 2010.

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.

Reverse osmosis (RO) is used to desalinate seawater and brackish groundwater, and to remove microscopic pathogens from treated wastewater. The salty water is pressurised on one side of the RO membrane and this is part of the process that results in water molecules passing (diffusing) through the membrane to the lower pressure solution on the other side. Salts such as sodium chloride (table salt) and calcium sulphate and calcium carbonate (scale) do not diffuse easily across the RO membrane and build up on the high-pressure side. Eventually scale deposition on the membrane prevents the diffusion of water molecules and the production of freshwater declines. This research tested four commercial and three in-house antiscalent chemicals, and additionally developed a technique to monitor scale formation and RO membrane performance in real-time. It was concluded that the antiscalent ‘PC-191T’ was best and that adding an ‘Electrical Impedance Spectroscope’ to RO systems has the potential to deliver a sensitive in-situ, real-time monitoring method capable of detecting very early scale formation, well before membrane performance declines. This will enable optimisation of membrane scale removal and improve the efficiency of freshwater production.

Harmful pathogens and compounds must be removed from wastewater before it can be discharged to the environment or used for irrigation, and many source waters need salts removed to make them potable. Microfiltration and ultrafiltration membranes remove pathogens and unwanted chemicals but as they are used, they become fouled and blocked by particulates and compounds from the water being filtered, as well as by the formation of biofilm, and by chemical interactions between solutes and the membrane materials. Although the membranes are cleaned regularly, the cleaning chemicals themselves can cause a problem. This research characterised the damage that various cleaning regimens inflict on membranes made of different materials and examined the effects of progressive and consecutive stages of membrane aging and degradation on performance. It was concluded that the type of cleaning agent affects the mechanism of membrane degradation and the severity of membrane integrity loss. More information is needed regarding the cleaning protocols and agents used in industry. Information from this research can inform a generally applicable model to predict membrane aging and decline in performance.

In Australia, remote and regional communities frequently manage relatively small, isolated water treatment and waste management systems which have water quality and health risks characteristic of small-scale decentralised operations. Australian water utilities have a wealth of experience in addressing these issues, and this project gathered and documented a series of case studies from Victoria, Tasmania and the Northern Territory to form a knowledge base that can be referred to in the future.

The ADWG has methods for predicting risks to water quality, but these were not developed for managing extreme climate-change driven weather events such as bushfires or floods. This research developed a risk assessment tool for managing water-related health risks associated with extreme weather events. Real-world datasets and experience of water cloudiness (turbidity), colour and blue-green algae were used to create and validate environmental models which were developed further by applying Baysian network and System Dynamics concepts. This iteration of the model was not constrained by, and did not reflect existing risk profiles, but was judged to be flexible enough to provide a realistic representation of future hazards arising from extreme weather events.

The protection of sources of water and catchments is an important method for maintaining water quality; one that can mitigate cost and reliance on downstream water treatment and disinfection. Catchment protection requires risk assessment, but water quality management approaches were not originally developed for natural environments, and ecosystem-based methods (such as the Ecological Risk Assessment methodology), require complex data inputs often unavailable to water utilities.

This paper discusses various water quality risk management techniques and proposes a step-by-step catchment risk assessment methodology that is compatible with the Australian Drinking Water Guidelines.

Remote and regional Australian communities commonly produce potable water by removing salt from brackish groundwater. Existing desalination technologies, such as reverse osmosis (RO) have high electrical energy and technical requirements. Groundwaters often contain high levels of silica (quartz) which, together with the salts, form scale which blocks RO membrane and other components which are expensive to replace. This research examined an alternative desalination process: capacitive deionisation. Laboratory-scale experiments found that single-walled carbon nanotubes were the best material to use for electrodes, that membranes placed before the electrodes increased efficiency of salt removal and decreased energy usage, while silica, which lacks a charge that would bind it to either the positive or negative electrode, did not form scale deposits nor interfere with the desalination process. A full-scale version of this unit was tested onsite in the Northern Territory and described in WaterRA Project 1047.

This research has provided the most comprehensive account of the geographical distribution of blue-green algae (cyanobacteria), and the toxins they produce, in Australia. The blue-green algae cells were collected and stored. This collection now forms a valuable national asset which is particularly valuable for managing the complex array of factors that affect the accurate assessment of risk posed by any one algal bloom. Not all cyanobacteria produce toxins, and the identification of species and the presence of toxin is an important step in the decision-making process necessary to produce high quality, safe water. This research led to some notable conclusions; one being that a traditional method that uses cell-shape to identify algal species is unreliable, and also that the number of cyanobacterial cells does not necessarily correlate to the amount of toxin in source waters. Five laboratory tests were reviewed and it was found that tests for cylindrospermopsin were reliable, but tests for microcystin and saxitoxins differed as to the amount they measured, although they reliably identified the presence or absence of toxin. Problem cyanobacteria species are ubiquitous in Australia and if climatic events create favourable conditions, blooms can occur in unexpected locations.