Besides, as an economic and sustainable alternative water resource, Hong Kong has developed the world’s largest seawater supply system for toilet flushing since 1950s, which provides 750,000 m3 day-1 for 80 % of the inhabitants, saving 22 % of valuable freshwater imported from Guangdong Province of China and subsequently generates about 750,000 m3 day-1 of saline sewage (Lu et al. 2012).