Reduction of Toxic Products and Bioaerosol Emission of a Combined Ultraviolet-Biofilter Process for Chlorobenzene Treatment

摘要

A combined process involving ultraviolet (UV) photodeg-radation and biofiltration was developed to treat gaseouschlorobenzene. The toxicity of the photodegradationproducts and the bioaerosol emissions from the biofilterwere investigated. The experimental results showed that astandalone UV photodegradation of chlorobenzene canresult in products having significant acute toxicity andgenotoxicity, whereas a biofiltration process can producea high concentration of bioaerosols, which are a potentialhealth risk. In the combined process, the toxic productsproduced by the UV photodegradation were removed bythe subsequent biofilter. The acute toxicity of the prod-ucts was reduced from 0.042 to 0.005 mg zinc/mg totalorganic carbon (TOC). Also the genotoxicity was reducedfrom 0.76 to 0.16μg 4-nitroquinoline-N-oxide per milli-gram TOC. On the other hand, the bioaerosol concentra-tion emitted from the biofilter decreased from 1.38 x 10~3colony-forming units (CFU) · m~(-3)(without UV pretreat-ment) to 60 CFU · m~(-3)(with UV pretreatment), nearlythe same as the background level of 40 CFU · m~(-3).Thesignificant decrease in bioaerosol emission might be dueto a high concentration of ozone (50 mg · m~(-3)or 25 partsper million by volume produced by the UV pretreatment.Hence, the UV photodegradation and biofiltration pro-cess exhibited synergistic effects. Also, the combined UV-biofiltration process was ecologically safer and exhibited alower degree of infectivity as compared with standaloneUV or biofiltration processes.