Reclaiming sewage for industrial process water has been a routine practice since the Jurong Industrial Water Work was completed in 1965. The current water usage amounts to 45,000 m(3)/d. The quality of the reclaimed water in general meets with the quality requirements for general washing and process applications of industries such as paper and textile. As demand for ultrapure water for high pressure boilers in the petrochemical industry and process applications of the electronic industry increases, advanced treatment processes to reduce dissolved ions, silica, organic and inorganic particles and other impurities become necessary. This paper examines the various pretreatment methods used in ultrapure water production.