Nonionic surfactant Brij35 effects on toluene biodegradation in a composite bead biofilter

Nonionic surfactant effects on the toluene dissolved in the water phase and biodegradation kinetic behaviors of toluene in a composite bead biofilter were investigated. The toluene dissolved in the water phase was enhanced by the addition of surfactant into aqueous solution and the enhancing effect was more pronounced in the surfactant concentration less than critical micelle concentration. For the microbial growth process, the microbial growth rate was inhibited at higher surfactant content and the degree of inhibitive effect was more pronounced at lower inlet concentration. The microbial growth rate was inhibited at higher inlet concentration. Zero-order kinetic with the diffusion limitation could be regarded as the most adequate biochemical reaction model. For the biochemical reaction process, the biochemical reaction rate was also inhibited at higher surfactant content and the degree of inhibitive effect was more pronounced at lower inlet concentration. The biochemical reaction rate was also inhibited at higher inlet concentration. The maximum elimination capacity decreased with increasing surfactant content and it was in the range of 17.41 to 26.12 g C h-1 m-3 bed volume. The addition of surfactant into filter material was unfavorable for toluene degraded by the microbial.   Key words: Nonionic surfactant, toluene, biodegradation, composite bead biofilter.