Study Of Removal Of M-dichlorobenzene With Enhancing Biotricking Technology

Emissions of volatile organic compounds（VOCs）have become one of important environmental problems.At present,although the biological trickling filter can effectively remove some VOCs,the removal efficiency is not high for the hydrophobic organic compounds treatment.Enhancing of predominant bacteria and co-strengthening of metal ions and surfactant both are effective method to strengthing the removal efficiency of biotricking technology for the hydrophobic organic compounds.In this study,m-dichlorobenzene as one of hydrophobic organic compounds was chosen as the research object.The strain with capability of m-dichlorobenzene removal was isolated and purified using enrichment culture method and sterile filter paper plate method.The preponderantly strains were identified by morphological observing,physiological and biochemical identification and biochemical analysis of 16 S rRNA.The results showed that five m-dichlorobenzene preponderantly degrading strains（DH-1、DH-2、DH-3、DH-4 和 DH-5）were obtained in the enrichment culture and their removal efficiency（RE）were 75.4%,74.8%,70.1%,67.5% and 50.7% respectively after 48 h cultivation.Morphological observing,physiological and biochemical identification was studied for DH-1 and DH-2,and it showed that they have flagella,spores and capsule,and they are gram positive,making gelatin liquefaction,having starch hydrolysis.Phylogenetic analysis based on 16 S rRNA gene showed the similarity of 94% between strain DH-1（DH-2）and Brevibacillus agri.The degradation characteristics of DH-1 having the highest removal efficiency was studied in the next experiment and it showed that the best time,initial concentration,inoculation、pH and temperature was 2 d,130 mg /L,10%,7 and 30 ℃ respectively.The strain of Brevibacillus agri DH-1 was used to study the impact of rhamnolipid,Fe³⁺ and Mg²⁺ on the degradation of m-dichlorobenzene as the sole carbon and energy source,and the growth and integrity of the cells.The optimal condition was obtained using Response Surface Optimization.The results showed that the rhamnolipid,Fe³⁺,and Mg²⁺ have obvious influence on the microbial growth and the removal of m-dichlorobenzene and its optimal condition is 150 mg/L,5 mg/L,2 mg/L respectively.the microorganism have higher density and become cenobium in the environment of optimal condition after 2 days.In addition,the removal efficiency of m-dichlorobenzene is 98.94% after 3 days（increased 25.32 %）.The effects of three additives(rhamnolipid,Fe³⁺ and Mg²⁺)on microbial growth and removal efficiency for m-dichlorobenzene were studied in three biotricking filters（BTF1,2 and 3）.The optimal concentrations of three additives were obtained in BTF1,2 and 3 that were 170 mg/L,4 mg/L and 2 mg/L respectively.Interactions between three additives presented that they can be improved each other for m-dichlorobenzene removal.In order to study composite effects of rhamnolipid,Fe³⁺ and Mg²⁺,the optimal concentrations of three additives was applied in BTF2 and BTF1 as a control group.The effects of EBRTs for RE at different inlet concentration was studied using the BTF1 not feed with rhamnolipid and Fe³⁺ and Mg²⁺ and BTF2 feed with rhamnolipid and Fe³⁺ and Mg²⁺.The application of rhamnolipid and Fe³⁺ and Mg²⁺ had promoted m-dichlorobenzene removal using biotricking filter.In addition,dissolved oxygen（DO）throughout entire period was analyzed indicating that three additives promoted oxygen transfer and operational condition.