Application Study On Removal Of Odor And VOCs By Bio-trickling Filter

The actual chemical fiber wastewater treatment plant is used as a base to analyze the characteristics and laws of waste gas generation,which served as basic data for the biological treatment of industrial waste gas,and research the problems existing in the biological treatment of actual factory waste gas.Performance of bio-trickling filter(BTF),bio-filter and bio-scrubber in treating the actual chemical fiber exhaust gas were compared,results indicated that performance of the BTF in the treatment of chemical fiber exhaust gas is significantly better than the other two biological methods.This study further enhanced the performance of BTF in purifying VOCs by adding surfactants and replacing the fillers with good adsorption performance.The optimal conditions for enhancing the performance of BTFs were studied in several aspects.A vertical and a horizontal BTF with pilot-scale were started up and researches were carried out from different aspects including operational conditions and operating environment.Finally,the mechanism of microbial degradation of pollutants was preliminary investigated,and the basic model of microbial degradation of pollutants was summarized.The specific findings are as follows:The waste gas generated by four typical chemical fiber wastewater treatment pools was monitored and analysed for 40 continuous days,results showed that the main components of the chemical fiber exhaust gas are:methane,methanol,ethanol,methyl acetate,benzene,toluene,xylene,cyclohexane,trichloroethylene,styrene,etc.,as well as a small amount of NH3 and H2S.The effect of process on the concentration of each pollutant is greater than that of ambient temperature and humidity.Different wastewater treatment pools generate different characteristic pollutants.The maximum concentration of the total VOCs can reach 1705.37 mg/m3.The performance of BTF,bio-filter and bio-scrubber in treating exhaust gas generated from the actual chemical fiber waste water treatment plant were compared.Results showed that the BTF was the best biological method for purification of chemical fiber exhaust gas with higher removal efficiency and lower pressure drop under the EBRT of 172s and 86s.The average removal efficiency of different VOCs can reach more than 90%with the pressure drop below the detection limit.SEM images showed that the BTF was rich in types of microorganisms,had a strong metabolism,secreted a large number of extracellular polymers,and maintained a stable temperature and humidity environment.The rules of rhamnolipids in enhancing the degradation of VOCs were studied and compared with that of Tween-80.Results showed that when the concentration of rhamnolipid or Tween-80 was 0.8 mg/mL or 1.59 mg/mL,respectively,the purification performance of the BTF was significantly increased with the removal efficiency 10%higher than the BTF without adding rhamnolipid or Tween-80.The purification efficiency of more than 90%of toluene can be achieved under the condition that the toluene inlet concentration is lower than 800 mg/m3 and the residence time is 102s.However,when the concentrations of rhamnolipid or Tween-80 exceed 4 mg/ml or 7.95 mg/ml,respectively,the growth of microorganisms is inhibited,leading the reduction of purification performance of the BTF.Removal of n-butyl methacrylate from gas streams was studied in two parallel bio-trickling filters(BTFs),one packed with only ceramsite(BTFa)and the other with ceramsite coated with activated carbon fibre(BTFb).Results of the comparison experiments indicated that the use of activated carbon fibre could greatly shorten the start-up time of BTF.The removal efficiency of BTFb was 15.3%greater than that of BTFa under the EBRT of 44s and the inlet concentration of 500 mg/m,with the corresponding removal loading of 56.4 g/(m3 h)and 46.5 g/(m3 h),respectively.When the inlet loading of n-butyl methacrylate was lower than 34.0 g/(m3 h),a complete removal of n-butyl methacrylate could be achieved in BTFb.The biomass of BTFb was much higher than BTFa,but with the higher pressure drop.The maximum pressure drop of BTFb can reach as high as 380 Pa/m while that of BTFa was only 40Pa/m.The experiment showed that back washing proved a good way to reduce the pressure drop and biomass with no obvious changes in the removal efficiency.Two pilot-scale BTFs with counter-current and cross-current flow modes were constructed,and their performance tested,for purifying chemical fibre waste gas containing H2S,NH3 and VOCs with a maximum gas flow rate of 1008 m3/h.The start up time was only 14 days with the“stimulate biofilm growth by high concentration of nutrients and improve degradation ability by competition" method.The counter-current type BTF presented superior biodegradation results compared to the cross-current type one:it could start up quickly,tolerated high transient shock loadings,and possessed an average contaminant removal efficiency higher than 90%with an empty bed residence time of 59 s.The purified gas could reach the secondary standard value of the "integrated emission standard of air pollutants".The contaminant removal efficiency could be increased by 50%during winter due to insulation,with the total removal efficiency of 70%.The flow mode significantly influenced the distribution of microorganisms in the BTF.The abundance in the lower layer was greater than the upper layer in the vertical BTF while the abundance was high in both the phases in the horizontal one.The abundance and diversity from microorganism analysis showed that Dyella,Bacillus,Candidimonas,Pandoraea and Thiomonas were the main bacterial strains forming the community treating the pollutants.Through the broad-spectrum study of microbial degradation of the contaminants,it was found that the biodegradability of pollutants is not directly related to the complexity of molecular structure,but related to the specificity of microbial proteins.The research on the mechanism of microbial degradation of n-butyl methacrylate showed that the degradation of pollutants by microorganisms is the process of converting macromolecules into small molecules first,and then into CO2 and self proteins.Through analyzing the degradation ability of different microorganisms and the performance of the BTF,it was found that the relationship between the degradation performance of the microorganisms and the maximum degradation loading of BTF was:y=121.55x-61.86.This experiment is a further in-depth study on the basis of the pre-laboratory.It aims to improve the performance of the biotrickling filter for the purification of odor gas and VOCs,and apply bio-trickling method in the purification of odor gas in practical engineering.These results have certain practical significance on the enhancement of the performance of BTF and realizing its engineering applications.