Hong Kong is the only place in the world that uses seawater to flush toilets in an extensive scale.

Hong Kong is an Asian city with nearly 7 million people. Because of the lack of natural resources, the local water supply is not adequate to meet the demand. Fresh water supply in Hong Kong relies on the cross border import of water from the East River in China. Therefore, to conserve fresh water, seawater has been used for toilet flushing since the 1950s.

Seawater is abstracted at the seafront pumping stations for treatment before supply, although it is not treated to the same standard as fresh water. About 80 percent of the population is provided with seawater for toilet flushing, thus effectively reducing the fresh water demand by as much as 20 percent.

Provided that fundamental precautions are taken, a seawater supply system is technically not much more difficult to construct, operate and maintain than any other reticulation systems. And seawater toilet flushing is found to be a considerably cheaper alternative to using. However, difficulties encountered in operating such a system include the generation of saline wastewater, which is more difficult to treat in sewage treatment works, and the corrosion of pipelines and equipment.

For those interested in finding out about the difficulties and solutions to these problems, Dr. S.L. Tang and Derek P.T. Yue of The Hong Kong Polytechnic University will be giving a presentation at Water & Environment 2010: CIWEM’s Annual Conference on the 29th April at the Olympia Conference Centre, London. For more information, go to