Trichloromethane Formation Potential in Killing Algae with Chlorine Dioxide

Trichloromethane was detected by gas chromatography-mass spectrum- selected ion monitoring system during killing algae with chlorine dioxide. After oxidized by chlorine dioxide, the algal solution was filtered to removed algae, the filtrate was cultured with chlorine, and the trichloromethane was also analyzed. The results showed thattrichloromethane did not form during killing algae with chlorine dioxide, but the solution which was oxidized bychlorine dioxide and filtered to removed algae generated trichloromethane after cultured with chlorine. The concentration of trichloromethane formed was influenced by the dose of chlorine dioxide used to killing algae, initial algal number and chlorine concentration. When chlorine dioxide was below 3 mg L-1, the trichloromethane concentration fast increased with the dose of chlorine dioxide increasing, while chlorine dioxide was above 3 mg L-1, the trichloromethane concentration reached to a steady value. The trichloromethane concentration also increased with the increase of initial algal number and chlorine concentration. But even chlorine concentration was as high as 10 mg L-1, the trichloromethane concentration was not over 28 μg L-1, which was lower than the requirement for 0.06 mg L-1 trichloromethane in China Standards for Drinking Water Quality (GB5749-2006).