[Chemical removal of excess biomass from biofilters]

Biomass control techniques are very important for biofilters treating volatile organic compounds (VOCs) to enhance their long-term operation performance. In this study, four paralleled biofilters were set up treating toluene gas. The chemical removal of excess biomass and its impact on biofilter operation were investigated. The experimental results of circulating wash showed that the optimal washing time for biomass removal was 2 - 3 hours by NaOH ranging from 0.2% to 0.8%. Among the four experimental concentrations, the NaOH solution of 0.4% was more effective to remove the biomass from the biofilter and biomass shearing was the main process of the biomass removal under this circumstance. According to the comparison results of three washing mode, circulating washing was found to be the most suitable mode for biomass removal. The monitoring results of the toluene removal performance demonstrated that the impacts of NaOH solutions with different concentrations had little difference and the toluene removal capacities could be recovered after 3 - 4 days.