Management of Concentrated Waste Streams from High-Pressure Membrane Water Treatment Systems

Abstract

The sustainable management of concentrated waste streams from high-pressure membrane-based water treatment processes are commonly the greatest limitations to the implementation of such processes. This applies to seawater desalination, brackish water desalination, groundwater softening, surface water treatment, and municipal water reclamation. This review provides an analysis of the potential environmental implications of concentrate disposal to marine, freshwater, and terrestrial environments. Although high-pressure membrane treatment plants generate a number of other waste streams of similar content and effect on the environment (such as spent pre-treatment filter backwash and spent cleaning chemicals used during periodic cleaning of reverse osmosis membranes), these waste streams are not discussed in detail herein. The focus is on Australian circumstances, but the issues raised are universal. Established management practices are critically reviewed, and a number of alternative practices canvassed. Given that large-scale high-pressure membrane water treatment plants are relatively recent developments in Australia, a significant amount of work has been undertaken. However, a considerable number of knowledge gaps are revealed, preventing a complete understanding of the risks associated with existing practices and the development of potentially more economically and environmentally sustainable concentrate management practices. As such, the review provides insight to current research needs and priorities.

KEY WORDS:

• reverse osmosis
• desalination
• membrane concentrate
• brine disposal

ACKNOWLEDGMENTS

The undertaking of this review was supported by funding from Arup (Australia) and the Queensland Environmental Protection Agency. The authors appreciate additional advice from Richard Hough (Arup), Nicholas Swain (Arup), Paul Hochman (Arup), Paul Sherman (QLD EPA), Greg Leslie (UNSW), and Ron Cox (UNSW).