Getting benefits from water many times over

These and the results of similar projects in other parts of Europe (including the UK) are leading researchers towards the view that PWNT may have created the first economically viable ceramic membrane system to treat drinking water in the world.

PWN is a Dutch water supply company. Owned by the province of North Holland, it is a social enterprise operating on a non profit basis. Since it opened its first pilot plant in 1966, PWN has developed innovative treatment technologies in order to guarantee top quality drinking water where existing treatment proved to be insufficient.

PWN Technologies was founded to make these innovations available to other water companies. What makes this company different and unique is that its revenues are invested in new R&D programmes. The key to its success has been the innovative adaptation of existing technologies to produce the best possible water quality with almost no waste (zero liquid discharge) at the lowest possible energy demand.

The company has successfully developed a suspended resin system capable of using various types of recyclable resins, not dependent on magnetic resin, for the removal of organic material for the first time. Given the inherent weaknesses of coagulants, especially for the removal of organics, PWNT has developed a more efficient system that uses resin to remove a high percentage of organics and serves as a robust pre-treatment system for membranes and UV treatment. The SIX (Suspended Ion Exchange) process removes organics that can foul membranes, allowing much higher membrane operation efficiency than is possible with coagulation.

Ceramic membranes, which are well known to be very sustainable because they can last 20+ years and are not susceptible to fibre breakage, have until now been considered too expensive for the municipal drinking water market. PWNT's breakthrough has been to create a new ceramic membrane system that reduces the footprint and material by more than 90% and improves overall efficiency. The key design feature of the CeraMac (advanced ceramic membrane technology) system is that, rather than having ceramic membrane modules in individual stainless steel casings, up to 192 ceramic elements can now be housed in a single stainless steel vessel. This greatly reduces the costs of the ceramic membrane system to a level which makes the system cost competitive with polymeric membranes.

The water industry has struggled for many years to find an appropriate and robust form of pre-treatment for membranes. An important aspect of PWNT's achievement has beenthe successful integration of two robust technologies.

What is at stake in the Australian trials is the feasibility of ceramic membranes in the context of wastewater recycling. Human and industrial wastes and pharmaceuticals present a tough water treatment challenge, hence the interest of a bevy of international researchers.

The high organic content of the ETP secondary wastewater, which presents a potential fouling issue for polymeric membranes, is one type of wastewater where ceramic membranes are expected to outperform alternative applications. To date the results show that the membrane operation is efficient despite the high organic levels. The ozone stabilises the operation greatly.

When these research results satisfy Australia's regulatory standards for pathogen removal it has the potential to open the door for further investments in reuse by Australian water utilities.

An economic assessment of the ETP project is expected to be completed by mid-2013. This will demonstrate the performance of the ceramic membrane system under local conditions. Assuming it is successful this project will provide true incentives for water recycling compared with other technologies that aim to achieve at least the same water quality. It is applicable to major municipal and industry water recycling nationally.

In addition to meeting efficiency targets when building or refurbishing water infrastructure, the resilience of these systems is also critical. They operate under a wide range of conditions, which can change dramatically from one season to the next and which are becoming more demanding with a changing climate. Building resilience into a system will ensure it has the capacity to deliver services effectively under stress. Balancing efficiency, which is largely a measure of cost, with resilience is an ongoing challenge for the water industry.