Identification of metabolites from the biological transformation of the nonionic surfactant residue octylphenoxyacetic acid and its brominated analog

The aerobic biological transformation of octylphenoxyacetic acid (OP1EC) and its brominated analog (BrOP1EC) by groundwater enrichment cultures was studied, and persistent metabolites were identified by GC/MS. OP1EC is a representative of the class of alkylphenol ethoxycarboxylates (APEC), formed from alkylphenol polyethoxylate nonionic surfactants during sewage treatment. BrOP1EC is a byproduct formed during chlorine disinfection in the presence of bromide. The metabolite 2,4,4-trimethyl-2-pentanol was detected in stoichiometric quantities in OP1EC-metabolizing enrichment cultures, representing the intact alkyl side chain as a tertiary alcohol. BrOP1EC was transformed by the OP1EC-utilizing cultures only if OP1EC was simultaneously metabolized, suggesting a cometabolic mechanism of transformation. Brominated intermediates were also detected: brominated octylphenol and a compound tentatively identified as 2-aminomethoxy-3-bromo-5-(1,1,3,3-tetramethylbutyl)phenol.