| As people’s environmental protection consciousness strengthens, the requirements of environmental quality is also higher and higher. At present, some petrochemical enterprises in large and medium cities have influenced their own survival and development because of its malodorous pollution. Biological filtration purification has been widely used. Packing is the core part of the filter. The performance of packing has a direct effect on the microbial growth and pollutants removal. In the process of biological treatment of waste gas, such as biofiltration of volatile organic compounds or odorous subs tances, the requirement of microbial nutrients is a key factor. The purpose of this work is to develop a new kind of packing material that can release nutrients slowly. It can provide microorganism more appropriate nutrients and make the biological filter more suitable for microbial growth.The new packing will be made by using a polymer adhesive to embed and fix an appropriate amount of nutrients on the surface of the skeleton. In the first part, the skeleton, adhesives and low soluble organic mineral were screened. Multi- faceted hollow ball is selected as filler skeleton because of its high porosity and strength. Lignite is selected as a nutritional powder, and it contains organic matter and abundant trace elements which can be used by microbes. Mixed adhesives are PU and PA which have good resistance to water. The mass ratio is 6: 4 for PU and PA by comparing performances of different ratios. A moderate amount of starch glue is added at the same time. Impregnation method is used to embed low-soluble organic nutrients and some nutrients to the skeleton. A certain amount of potassium dihydrogen phosphate and urea(N : P=5:1)are added, and Calcium carbonate is added as pH buffer. Finally a new type of packing is developed.The physicochemical properties of packing material was evaluated, especially the performance of nutrients release function. Experimentally obtained packing material has a porosity of 74%, a bulk density of 226 K g·m-3, pH 7.3, and surface area of 9.9×104 m2·m-3. There are creases and tiny holes on the packing surface, and these form the rough structure that is conductive to microbial adhesion. This packing material can maintain structural integrity in the water for a long time. The conductivity and the release of N, P, K and Ca can be determined through leaching experiments. Experimental data demonstrates that the packing can release nutrients in a long time. It contains abundant nutrients and has a slow-release property.In laboratory study period, This study used biological filter bed packing composite filler to treat toluene odorous gas. During start-up period, toluene degrading bacteria could quickly vaccinate on the complex organic packing, The start-up time is about 14 days. Research results show that this kind of composite packing could pro vide more favorable environment for the growth of toluene-degrading bacteria. When the inlet air flow rate is 100 m3·h-1, the inlet toluene concentration is 150 mg·m-3, the temperature of biological filter bed is between 20℃ and 30℃ and the humidity of packing is 50%, the removal efficiency is greater than 80% and gas concentration at the export conforms to the national standard. Electron micrograph of the packing surface and microscopy figure of the microbial suspension sho wed that microorganisms have a uniform distribution. Bacillus is superior in numbers in the biofilm. The selected efficient strain can breed and become abundant in the new packing filter. Biomass from the biofilm also continues to grow. Microorganisms can adapt to the environment and degrade toluene. |
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