title: Production of mono- and di-carboxylated polyethylene glycols as a factor obstacle to the successful ozonation-assisted biodegradation of ethoxylated compounds.
abstract: Ozonation is believed to improve the biodegradability of organic compounds. In the present study, degradation of nonylphenol ethoxylates (NPEOs) was monitored in hybrid treatment systems consisting of ozonation and microbial degradation processes. We found that ozonation of NPEOs decreased, rather than increased, the biodegradability under certain conditions. The timing of ozonation was a definitive factor in determining whether ozonation increased or decreased the biodegradation rates of NPEOs. Initial ozonation of NPEOs prior to biodegradation reduced the rate of dissolved organic carbon (DOC) removal during the subsequent 14 d of biodegradation, whereas intermediate ozonation at the 9th day of biodegradation improved subsequent DOC removal during 14 d of NPEO biodegradation. Furthermore, reduction of DOC removal was also observed, when initial ozonation prior to biodegradation was subjected to cetyl alcohol ethoxylates. The production of less biodegradable intermediates, such as mono- and dicarboxylated polyethylene glycols (MCPEGs and DCPEGs), was responsible for the negative effect of ozonation on biodegradability of NPEOs. DCPEGs and MCPEGs were produced by biodegradation of polyethylene glycols (PEGs) that were ozonolysis products of the NPEOs, and the biodegradability of DCPEGs and MCPEGs was less than that of the precursor PEGs. The results indicate that, if the target chemicals contain ethoxy chains, production of PEGs may be one of the important factors when ozonation is considered.
authors.affiliation: Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan. Electronic address: sn4247621@hiroshima-u.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakai
authors.affiliation: Environmental Research Management Center, Hiroshima University, Higashi-Hiroshima 739-8513, Japan. Electronic address: okudaenv@hiroshima-u.ac.jp.
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Okuda
authors.affiliation: Environmental Research Management Center, Hiroshima University, Higashi-Hiroshima 739-8513, Japan. Electronic address: wataru@hiroshima-u.ac.jp.
authors.forename: Wataru
authors.initials: W
authors.lastname: Nishijima
authors.affiliation: Faculty of Liberal Arts, The Open University of Japan, Chiba 261-8586, Japan. Electronic address: okada.mitsumasa@ouj.ac.jp.
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Okada
mesh_terms: D001673:Biodegradation, Environmental; D002264:Carboxylic Acids; D004785:Environmental Pollutants / Q000737:chemistry / Q000378:metabolism*; D005026:Ethylene Glycols / Q000737:chemistry / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002264:Carboxylic Acids; D004785:Environmental Pollutants; D005026:Ethylene Glycols; C021754:terics; D011092:Polyethylene Glycols
keywords: Biodegradation; Carboxylated polyethylene glycol; Nonylphenol ethoxylate; Ozonation; Polyethylene glycol