The steam produced by boiling a kettle of salty water can be collected, condensed and drunk. Membrane distillation is an analogous process to this, but in this study the salty feedwater forms a salt-free vapour at a lower temperature; 30 – 40°C. The warm feedwater and vapour are pumped past a thin, porous membrane which repels liquid water but allows vapour to pass through the pores into a cold stream of freshwater on the other side. The vapour condenses and increases the volume of fresh, salt-free water. In this project an operational pilot plant was built and installed at an electricity generating station which produces waste heat and a stream of salty effluent that is normally discarded. The pilot plant was equipped with a 0.67m2 membrane, ran continuously for 3 months, and produced an average of 2.2L freshwater per hour. This equates to 3.4L/h/m2. The membrane area can be scaled up to increase production. It was concluded that this is a viable treatment technology for industrial wastewater that emits minimal greenhouse gasses.

Some wastewater treatment plants (WWTPs) use membrane bioreactors (MBR). These contain a microporous membrane which clarifies treated wastewater by removing microbial organisms. Wastewater must also be treated to remove nitrogen and phosphorus, which can act like uncontrolled fertilisers if they are released to the environment. Iron or aluminium salts added to the wastewater react with phosphorus and make solid particles which can be ‘caught’ and separated in the MBR. The problem is that the amounts of iron salts commonly added to some WWTPs foul the membrane and reduce its performance. This research used a laboratory-scale MBR to discover that lower amounts of specific iron salts effectively reduce phosphorus to levels that are safe to discharge while also reducing fouling and increasing the operating life of the membrane. Another conclusion was that ascorbic acid (vitamin C) cleaned iron-associated foulants from membranes more effectively than the conventional cleaning agent, citric acid.

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.