Development And Assessment Of A Novel Composite Media For Biofiltration

Support medium is one of the most critical elements of a biofiltration system for waste gas, since its nature affects the removal performance of contamination directly. In this thesis, a novel composite media with a function of slow release was developed and was proved suitable as a support medium in the biofiltration process. Briefly, a proper amount of low-water-soluble organic mineral powder was embedded and fixed by a polymer adhesive, then homogeneously dispensed on the surface of a reticular fiber by means of impregnation. A determination method of the characteristic parameters was established to analyze the physicochemical properties of the media, and simulated waste gas with toluene was chosen to evaluate its performances for waste gas biofiltration.The support medium was mainly composed of polypropylene reticular fiber acting as a framework, 1# leonardite powder chosed as the major nutrients, and a mixed adhesive used as attaching and reinforcing agent, which was prepared by blending PU, 1# PA and 2# PA adhesives together. Then the optimal mass ratios of 30.7:38.6:30.7 for PU, 1# PA and 2# PA adhesives, 1:1.5 for organic mineral powder and mixed adhesive, and 1:1 for water and mineral powder were obtained.The results of performance evaluation of the novel composite media developed in this study showed that, the slow-release media presented a porosity of 0.88, bulk density of 164.3 kg·m-3, compressive strength of 22.4 kPa, surface area of 9.9×104 m2·m-3, and pH of 7.9. The organic matter, organic carbon, nitrogen and phosphor content of the media were 72.2%, 54.7%, 1.63% and 0.07%, respectively, which was similar to argillaceous media. The media could maintain good cohesive strength in moist environment, and nutrients could release in slow and stable way. The start-up time of slow-release media biofilter system was about 13 d. The average dry/wet biomass immobilized on the media bed were 11.6 kg·m-3 and 287.4 kg·m-3 respectively, and the resistance coefficient was 1.3×104 ~ 8.9×104 m-1. During the normal operation of biofilter experiment, the slow-release media biofilter showed a high adaptability to variable inlet gas flow rates and inlet loads. The removal efficiency gradually decreased from nearly 100% to 73% as the inlet air flow rate increased from 88 to 160 m3·h-1. An elimination capacity of about 103 g·m-3·h-1 with an average removal efficiency of 73% was observed for inlet loads up to 123.8 ~ 135.3 g·m-3·h-1. The non-use experimental results indicated that only 2 days were needed to recover biofiltration performance after a 12 day-shutdown.