Achieving Zero Effluent Phosphorus – The Membrane Treatment Solution

Googong Township is a new residential property development located near Queanbeyan, which is south east of Canberra, Australia. The Township has adopted an Integrated Water Cycle (IWC), with the primary objective being to ensure sustainable use of water. At the heart of the IWC strategy is the state-of-the-art Googong Water Recycling Plant (WRP).

The WRP has a relatively tight effluent phosphorus limit of 0.5 mg-P/L and also has a restriction on total dissolved solids (TDS) in the effluent of 700 mg/L. The semi-closed loop water cycle in the township leads to accumulation of non-biodegradable dissolved solid compounds which pose a challenge in achieving the licence limits, with traditional mechanisms for achieving very low phosphorus limits being reliant on chemical dosing which is inherently a source of additional TDS.

In order to meet this challenge a new approach was taken comprising 3 point dosing with sequential membrane separation processes in order to achieve low phosphorus, with minimal chemical addition. The plant has now been operational for over 1 year and operational data to date has demonstrated exceptionally low phosphorus limits may be achieved with average effluent concentrations less than 0.05 mg/L. In fact, the effluent quality is so low that one of the on-going tasks has been to optimise the plant to further reduce chemical consumption.

This technical paper outlines the design approach to achieving a low phosphorus effluent from the WRP which included network TDS modelling to optimise the usage of recycled water and the WRP plant design. The paper presents operational data from the first year of operation which demonstrated exceptionally low phosphorus levels without compromising the TDS quality and also explores the mechanisms for optimising chemical use whilst achieving ‘Zero Effluent Phosphorus’.