UV-assisted chlorination of algae-laden water: Cell lysis and disinfection byproducts formation

Abstract

Chlorination of algae-laden water under UV irradiation was studied in bench scale. An obvious synergistic effect between UV light (at 254 nm) and chlorine was obtained due to the formation of HO, which promoted the degradation of Microcystis aeruginosa. During this process, sequential UV/chlorine and UV irradiation were included, and UV/chlorine stage accounted for 86% of total algae removal with 50 mg/L chlorine. The removal performance was positively related to the chlorine dose in the range of 5–50 mg/L. The presence of chloride had little influence, whereas ammonia significantly inhibited the algae removal as chlorine was quickly transformed to chloramine. The integrity of algae cells was disrupted immediately, along with an instant release of algal organic matter which was synchronously degraded by UV/chlorine. The emission scanning electron microscopy results further confirm the occurrence of serious cell lysis. Moreover, a large amount of chlorinated disinfection byproducts (DBPs) produced during the UV/chlorine process. But the final yields of DBPs from chlorination of algae suspension over a period of 23 h storing in dark surpassed that after UV/chlorine treatment. This work suggests a promising technique for the treatment of algae-laden water by using UV/chlorine.