title: Intimately coupling of photolysis accelerates nitrobenzene biodegradation, but sequential coupling slows biodegradation.
abstract: Photo(cata)lysis coupled with biodegradation is superior to photo(cata)lysis or biodegradation alone for removal of recalcitrant organic compounds. The two steps can be carried out sequentially or simultaneously via intimate coupling. We studied nitrobenzene (NB) removal and mineralization to evaluate why intimate coupling of photolysis with biodegradation was superior to sequential coupling. Employing an internal circulation baffled biofilm reactor, we compared direct biodegradation (B), biodegradation after photolysis (P+B), simultaneous photolysis and biodegradation (P&B), and biodegradation with nitrophenol (NP) and oxalic acid (OA) added individually and simultaneously (B+NP, B+OA, and B+NP+OA); NP and OA were NB's main UV-photolysis products. Compared with B, the biodegradation rate P+B was lower by 13-29%, but intimately coupling (P&B) had a removal rate that was 10-13% higher; mineralization showed similar trends. B+OA gave results similar to P&B, B+NP gave results similar to P+B, and B+OA+NP gave results between P+B and P&B, depending on the amount of OA and NP added. The photolysis product OA accelerated NB biodegradation through a co-substrate effect, but NP was inhibitory. Although decreasing the UV photolysis time could minimize the inhibition impact of NP in P+B, P&B gave the fastest removal of NB by accentuating the co-substrate effect of OA.
authors: Department of Environmental Science and Engineering, College of Life and Environmental Science, Shanghai Normal University, Shanghai 200234, PR China.
authors: Lihui
authors: L
authors: Yang
authors: Department of Environmental Science and Engineering, College of Life and Environmental Science, Shanghai Normal University, Shanghai 200234, PR China. Electronic address: zhym@shnu.edu.cn.
authors: Yongming
authors: Y
authors: Zhang
authors: Department of Environmental Science and Engineering, College of Life and Environmental Science, Shanghai Normal University, Shanghai 200234, PR China.
authors: Qi
authors: Q
authors: Bai
authors: Department of Environmental Science and Engineering, College of Life and Environmental Science, Shanghai Normal University, Shanghai 200234, PR China.
authors: Ning
authors: N
authors: Yan
authors: Department of Environmental Science and Engineering, College of Life and Environmental Science, Shanghai Normal University, Shanghai 200234, PR China.
authors: Hua
authors: H
authors: Xu
authors: Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, Tempe, AZ 85287-5701, USA.
authors: Bruce E
authors: BE
authors: Rittmann
mesh_terms: D019149:Bioreactors; D001711:Biotransformation; D009578:Nitrobenzenes / Q000378:metabolism* / Q000528:radiation effects*; D019815:Oxalic Acid / Q000737:chemistry; D010782:Photolysis; D014466:Ultraviolet Rays
chemical_list: D009578:Nitrobenzenes; D019815:Oxalic Acid; C036077:nitrobenzene
keywords: Biodegradation; Co-substrate; Intimate coupling; Nitrobenzene; Photolysis