Performance Of Biotrickling Filters Packed With Polyurethane Sponges

Recently, volatile organic compounds (VOCs) present in waste gas streams emitted from large-scale industrial operations or chemicals process were able to result in environment pollution and jeopardize people health. Biological treatment is an emerging rapidly technology for treatment of the low concentration VOCs. In particularly, biofiltration is known as an efficient, economical and environmental friendly technology, and having no second pollutions.Synthetic media have advantages over many natural media, and polyurethane sponges have been applied in biotrickling filters (BTFs) and rotating drum biofilters. In this study, toluene was chosen as the model VOC, open-pore reticulated polyurethane sponges (10 pores per cm) were used as structured packing media in two identical bench-scale BTFs which were separately evaluated at various volatile organic compound loading rates and gas empty bed contact time (EBCT). These investigations are helpful for proper design of full-scale biofilters packed with polyurethane sponges.The BTFs packed with polyurethane sponges have a good performance for treating waste gas containing toluene. Both influent toluene concentration and EBCT have a great effect on performance of BTFs. Toluene removal efficiencies were over 99%, 65% and 50%, and the average elimimation capacity (EC) were 83, 37 and 22 g toluene/m~3·h when the EBCT were 30, 15, and 7.5 s, respectively, at a constant influent toluene concentration of 483 mg/m~3.The influent toluene concentration also influenced the performance of BTFs in a great extend. When the VOC average feed concentration were 713, 1130 and 2710 mg/m~3, correspondingly the organic loading rate of the BTF were 85, 135 and 322 g toluene/m~3·h, the EC increased rapidly to 84 g toluene/m~3·h during the first 15 days, then increased slowly and reached up to 98, 142 g toluene/m~3·h, and removal efficiency were over 99%, 74% and 44% respectively at an EBCT of 30 s.The activated sludge, from municipal wastewater treatment plant, has a good degradation performace for toluene after acclimated by toluene. Effect of inoculation of activated sludge on startup performance of a BTFs after backwashing was also investigated. Result showed that the BTF added activated sludge had a shorter startup period.The results indicated also that the removal efficiency or EC of the BTFs packed with structured polyurethane sponges will enhance with a incresing height of media at a certain infulent toluene concentration and EBCT. The pressure drop will increase with increasing influent gas flow rate and toluene concentration. Moreover, the BTF has a strong capacity of resisting shock loading when the influent organic loading had a wide fluctuation range as the biofilm on the media provide a great buffer capacity.In short, the biotrikling filter is reliabe, highly removal efficient and EC, and easy to be maintained. And meanwhile, the media in the biotrikling filter has a long service life. Therefore, it has a potential application area.