Getting benefits from water many times over

Australia's foremost public science organisation, CSIRO says, "Projections indicate that by 2030, southern Australia may receive up to 10 per cent less rainfall ... By 2050, southern areas may get up to 20 per cent less rainfall...

"Water security problems are projected to intensify by 2030 in southern and eastern Australia as a result of reduced rainfall and higher evaporation... The frequency and extent of droughts is projected to increase over most of southern Australia."

In other words Australia's most populous region – the south-eastern corner – will have a lot less naturally available water and many more people demanding it. Over Melbourne there is a big red mark showing the highest level of water risk.

The enduring lesson from the decade long drought, which prompted the hurried spending of billions of dollars on desalination plants and recycling projects, is that next time we need to be ready with cost effective supply systems that are resilient enough to deliver sufficient water during prolonged dry periods.

As a regular visitor to Australia, having contributed to the design of the advanced water treatment plant at Bundamba in south-east Queensland, I am impressed by the extent to which water utilities are doing their best, under today's economically constrained conditions, to prepare Australia's major cities for the inevitable next dry period.

Water recycling is a vital solution for water scarce countries such as Australia. In times of drought it is one of the few available water resources.

There are major challenges in converting wastewater to potable drinking water, the first being public perception, an obstacle Australia has yet to tackle convincingly. Further, there is a significant technological challenge in removing high levels of contaminants, which one hopes will go some way towards convincing the Australian public of the safety of recycled water.

To deal with both challenges a high level treatment system is required. The treatment that has been generally accepted to date is a combination of multiple treatment technologies. This in most case has included three steps: membrane microfiltration and reverse osmosis followed by advanced oxidation. This multiple barrier approach is rather costly when treatment of most surface water can be achieved with membrane filtration alone.

An international team of experts led by Victoria University, and funded jointly by the Australian Water Recycling Centre of Excellence and PWN Technologies, is currently undertaking research to determine if water recycling can be more affordable and sustainable. This novel approach, which is being trialed for the first time in Australia at Melbourne's Eastern Treatment Plant, could be a major breakthrough as it combines the treatment into one single step and uses a very resilient and robust ceramic membrane system, developed in the Netherlands by PWN Technologies, the R&D arm of a public water utility. Ozone, an oxidant that destroys micro-contaminants can be applied directly on the membrane. The ozone has a catalytic reaction on the membrane, which keeps the membrane very clean. The end result is that the system can work at a very high rate (flux) with very little water loss.

This unusual combination of effects - micro-contaminant destruction with simultaneous enhanced membrane operation - could be the key to more economical water reuse for Australia. Preliminary trial results show that the membrane operation is efficient despite the high organic levels.

PWNT's technology is considered to be a 'gamechanger' for recycling. In Singapore an 18 month trial of a fully operational demonstration plant treating surface water, has produced not just superior treatment outcomes but also savings of up to 40% on comparable polymeric systems.

In Holland the ceramic membrane technology treats water from the polluted Rhine to drinking water standard at 30% lower cost than comparable polymeric membranes, producing a lower environmental load and consuming considerably less energy.