Small, organic, toxic compounds are not well eliminated by water-treatment systems and eventually become concentrated in the human body. In this study, liposomes are employed to house aptamers with their own binding buffer. When small, organic, toxic compounds in water pass through a liposome barrier, only the target molecules are captured by the DNA aptamers inside the liposomes. The capture efficiency is not high when DNA aptamers are used in tap water. When DNA aptamers in liposomes are used, the capture efficiency increases more than 80%. The simultaneous and selective elimination of target toxicants is successfully performed for tap-water samples containing toxicant mixtures.