Theoretical And Experimental Research On The Biodegradation Of Indoor Gaseous Chemical Pollutant

Clean air is considered to be a basic requirement of human health and well-being. However, air pollution continues to pose a significant threat to health worldwide, and air pollution in indoor environment has been one of the key threats. Despite there have been many improvement or emerging technologies come forth to improve indoor air quality (IAQ), there still has not one technology of air pollution control can remove gaseous chemical pollutants from indoor environment absolutely and meet various IAQ requirements in all dimensions, in respect to the particularity of those pollutants in physical or chemical properties, and deficiencies in these existing technologies.This research aiming at removal of low-concentrations gaseous organic chemical pollutants, which exist widely in indoor environment, through introduction of biodegradation technology into application of indoor air pollution control, and the feasibility of this suggestion has been discussed in depth. The focus of this research is on the potential impacts of inlet gas temperatures, which are tent to be involved in HVAC system of buildings, on long-term performance of biodegradation system for air purification.Formaldehyde was selected as the objective and typical gaseous chemical pollutant in this research. Based on the characteristic of immobilized-microorganisms packing and kinetic analysis about biodegradation process of gaseous chemicals in the trickling biofilters, a mathematical model was developed to predict the operational performance of the trickling biofilter with the effects of different inlet temperature. The inlet temperature influence the operation of biofiltration indirectly with the paths of Henry's constant H(T) and bacterial specific grow rateμ(T). According to the predicted results, operational performance of the trickling biofilter represented negative correlations with inlet gas, less gaseous formaldehyde were removed by trickling biofilter when the inlet temperature was increased. Especially for the state that inlet temperature was higher than 30℃, degradation of operation performance was intensified. It is analyzed that decrease of gas solubility in circulating liquid caused by increase of temperature was the main reason.At the same time, through the method that continuous monitoring the periodical run of one trickling biofilter packed with immobilized-microorganisms packing under different inlet conditions, a series of systematic studies were carried out about the effect of inlet temperature on biofiltration. Experimental data presented that, the best biofiltration results, more than 90% of average removal efficiency, appeared if the inlet temperature were around 30℃, and the removal efficiency reduced as soon as temperature deviate from 30℃neither higher nor lower, but it still keep in acceptable range of 75~80%. Additionally, trickling biofilter would operate more stable at relatively higher inlet temperature from the long term. Furthermore when inlet cons of formaldehyde was under 0.6ppmv, that the cons of outlet were not exceeded the healthy limits stated by GB/T18883-2002 (0.1mg/m3) was achieved under every kind of operational condition. It was found that the trickling biofilter ceased to be effective after 48h run, because lack of substantive removal process by biodegradation, and the bottom packing stage was appeared to failure in filtration of formaldehyde at first.For the sake of validating action of biodegradation in trickling biofilters, the same trickling biofilter, of which packing was replaced by blank beads without bacterium, was investigated again for 5 days under the same experimental conditions with previous ones.