In order to solve taste, odor and hardness problems of finished water from a water works in south Taiwan, a pilot-scale study was conducted. The taste and odor problems were probably cased by the metabolites of algae or other microorganisms as the raw water came from an eutrophicated lake. The conventional treatment processes with prechlorination currently employed in the full-scale plant were unable to completely remove them. Three treatment process trains were compared side by side in the pilot testing: a conventional process without prechlorination (Process 1), conventional process plus ozone, GAC, and pellet softening (Process 2), and integrated membrane process (UF plus NF) followed by the conventional process. Results show that membrane process produced water with the best quality measured by turbidity, dissolved organics, biostability or organoleptic parameters. The second best was Process 2, which produced water with high biostability and aesthetic quality. Even simply avoiding prechlorination could significantly improve the biostability of the finished water.