Theoretical Analysis And Experimental Research On The Biodegradation Of Indoor Formaldehyde Pollutant

As the rapid economic development in China, the residential conditions of people have been greatly improved. There are a lot of decoration materials are used widely in buildings, it makes sick building syndrome (SBS) become one of the most important environmental problems to numerous occupants. Formaldehyde, as the top one killer in the indoor chemical pollutants, has been identified as carcinogenic and teratogenic substances by the World Health Organization (WHO). With the higher demand of good indoor air quality, people pay more attention on the removal of indoor formaldehyde.Through theoretical analysis and experiments, this study has conducted a deep research to the entrapped microbial degradation of indoor formaldehyde pollutant. The analysis of biochemical mechanism in formaldehyde degradation indicates that the formaldehyde is metabolized and assimilated by two pathways: oxidation and assimilation. Where, formaldehyde dehydrogenase and formaldehyde dismutase play important roles in oxidation way, while 3-hexulose-6-phosphate synthase and serine transhydroxymethylase catalyse the formaldehyde metabolism via the ribulose-monophosphate and serine pathway separately.Experimental studies show that the calcium alginate gels with Pseudomonas putida (P. putida) entrapped in them have the ability of formaldehyde degradation, which can make with biofilter unified with the stuffing. The entrapped microorganisms can maintain their vitality extended when the biological filter resistance controlled within 120Pa. The immobilized cells are entrapped substantially without leakage, which will be harmless to human beings. In experiments, formaldehyde removal efficiency and biochemical elimination amount have been detected in different conditions, such as liquid flow rate, formaldehyde concentration in the upstream and air flow rate. The microbial removal efficiency of formaldehyde reaches 86%-91% and the biochemical elimination amount maintains 1.62-1.75mg per day on the experimental condition of air flow rate 1.5L/min, formaldehyde concentration 0.8mg/m3 in the upstream and liquid flow rate 34ml/h.Through the dynamical analysis of formaldehyde biodegradation, combining the related principles in heat and mass transfer and in physical chemistry, a formaldehyde biodegradation model of P. putida entrapped in calcium alginate gel has been established, and based on this a theoretical elimination model of the biofilter under an ideal densely covered condition has been promoted. The results of the theoretical models can match case with the experimental values in certain range of experimental conditions.The attenuation experiment carrying out in a chamber ascertains the effect of microorganism in the process of degradation. In the circulation flow rate of about 25 L/min, the biofilter can purify the formaldehyde in the chamber within nine hours, whose concentration was as 10 times high as China's standard at the beginning. The unit purification of the bio-filter is about 0.0640mg/h and the Clean Air Delivery Rate (CADR) is 0.0561m3/h.In summary, the technology of microbial entrapment helps treating the indoor formaldehyde pollutant efficiently without secondary pollution and some other problems especially the interaction of indoor humidification and the biofilter would be further researched.