Silica precipitation and silica scale formation on membrane surfaces in RO desalination present a significant operational challenge in water purification. Silica scale formation on the membrane surface leads to flux decline, RO system productivity lost, membrane degradation, and increased cost of chemicals. In spite of the apparent simplicity of silica’s composition and scale formation on the membrane surface, fundamental questions and empirical knowledge persist about the formation, solubility and behaviour of silica species during the silica polymerisation, precipitation and scale formation.
The broad objective of the present study was to define conditions and factors affecting silica polymerisation and precipitation in coal seam gas (CSG) waters in Australia. The scope of the problem was narrowed to focus on dissolved silica species studied by Si NMR spectroscopy, removal of silica by coagulation as pre-treatment step for RO desalination and silica fouling patterns in RO desalination for a range of salinities in both synthetic and CSG waters to develop a conceptual model of silica precipitation and deposition on the membrane surface.