Investigation Of Toluene Vapor Elimination By Biofilter Packed With Functional Biological Fillers

Toluene is one of the typical pollutants of VOCs and is harmful to human health and ecological environment. Biological methods are low energy consumption, low cost, high removal efficiency and none secondary pollutants, which are extremely suitable for removing low concentration and large volume air pollutants.In this study, self-made functional biological fillers embedded with Pseudomonas putida were used as biofilter packing materials for treating toluene. Effects of spray intensity, inlet concentration, inlet loading rate and empty bed residence time to the capacity of biofilter were investigated. The recovery capacity was evaluated after different shut-down periods. Changes of micro-organisms in biofilter during different periods were also investigated.Results showed that:(1) The removal efficiency reached 93 % at the 8th day after biofilter set-up, under an empty bed residence time of 148.3 s and an inlet concentration of 300 mg/m3. The effect of 6 spray densities, 46, 92, 139, 185, 231 and 277 L/(min m2), to moisture content and removal efficiency, under 3 empty bed residence times of 148.3、74.2 and 49.4 s, was evaluated. Optimal spray density was 139 L/(min m2).(2) The results showed that: adaptable empty bed residence time was 74.2 s, and removal efficiency was higher than 88% when inlet concentration was under 900 mg/m3. The maximum elimination capacity was 16.97 g/(m3·h), occurred at an inlet loading rate of 22.11 g/(m3·h).(3) The contribution of lower layer was higher than other two layers, in biofilter layer contribution tests. The contributions of other two layers were increased with inlet loading rate. Maximum pressure drop was 76.5 Pa/m.(4) Shut-down periods affected the biofilter performance significantly. Initial removal efficiency changed largely at shut-down periods of 3, 7, and 30 d. Recovery time needed for achieving constant state, was also increased.