Isolation And Purification Of Phosphine-degrading Microorganisms And Microbial Characteristics

PH₃ is a highly toxic gas that is ubiquitous in nature and industrial processes.Phosphine not only harms human health and pollutes the environment;It is also a typical catalyst poison,which has a negative effect on the purification and utilization of industrial gases.At present,the industrial production process,high concentrations of phosphine tail gas can be purified by burning,adsorption and catalytic conversion,but low concentration phosphine(its concentration is usually lower than 20 mg.m^-3)produced by landfill and sewage treatment plant has not been effectively purified.The arbitrary discharge will pollute the surrounding environment and endanger human health.At present,the bio-purifying technology aroused more attention in the field of stench gas and organic waste gas treatment.In the early period,research group used the activated sludge to degrade the concentration of phosphine tail gas,which had a obvious good effect biodegradation degradation,but the issues,like which microbes to phosphine have purification effect and what are their the physic-chemical properties in the system,have not any further study.This study aimed to to isolate and purify functional microorganisms,investigated the main functional microorganisms and physicochemical characteristics of phosphine degradation,and then the low-concentration phosphine tail gas can have a degradation effect by coupling functional microorganisms with biochar.Five types of strains with typical characteristics were isolated by enrichment of the acclimated microorganisms in the early stage of culture,combined with the methords of dilution coating and plate marking.Under normal temperature and neutral conditions,two strains with high removal rate of phosphine were obtained by continuous testing of phosphine gas with under the condition of an inlet flow rate of100m L/min and a concentration of 15mg.m^-3 in the activated sludge system for 15d（no change of culture medium during the process）.Trains no.1 and no.2 had obvious distinctions between colony morphology and phosphine removal efficiency,but the high-throughput sequencing results showed that their genome sequences were no less than 96%similar to existing species of Clostridiu.Strain no.3 was gray and translucent,and its removal effect of phosphine was higher than that of strain no.1and strain no.2.The phosphine removal rate of strain no.4 was about 20%,and its similarity with existing bacterial species Pseudomonas was as high as 97%.The colony of strain no.5 is yellow,opaque and round.Its removal rate of phosphine is33%,its similarity with Streptococcus pentose was 97%.Pseudomonas and Streptococcus pentose are usually characterized by high environmental tolerance and the ability to degrade various toxic pollutants.After the proliferation and cultivation of strains no.4 and no.5,at normal temperature,the method of semi-continuous operation was used to test the physicochemical characteristics of microorganisms based on the activated sludge system.The best carbon source for microbial growth was odium lactate,and the appropriate p H value is 8.0～9.0.After continuous operation for 13 days under the condition of sodium lactate as the carbon source,PH₃as the only phosphorus source and p H value of 9.0,the main indicators of the bio-purification system gradually tended to be stable.The purification efficiency of phosphine in the activated sludge system formed by strains 4 and 5 was about 30%and 38%respectively.Microorganisms are more likely to utilize the high valence phosphorus compounds such as orthophosphate and phosphite in the system,and the purification efficiency of the system with phosphine as the only phosphorus source is slightly higher than the system with phosphate added.In order to improve the purification efficiency of phosphine in the biochemical system,phosphine should be used as the only phosphorus source in the purification system.Considering the purification efficiency of phosphine in the activated sludge system formed by a single strain is no more than 40%,carbon-based materials（bamboo charcoal,charcoal and coconut shell-based activated carbon）are added to the bioreactor to enhance the purification effect of phosphine in the biological system.When the microbial activity is completely inhibited（sodium azide is added）,the carbon base material and the microbial coupling system generally reach adsorption saturation within 180min,and the phosphine concentration in the export tail gas is basically close to the concentration in the import.After the continuous operation of the coupling system for a period of time,the purification efficiency of phosphine in the bioreactor was obviously improved.Coconut shell-based activated carbon was added to the activated sludge system of strain no.5,and the purification efficiency was up to 67.3%.After the addition of carbon-based materials in the bioreactor,The adsorption of the phosphine substrate material is enhanced,which reduced the gas-liquid mass transfer resistance of the insoluble gas,and the biological（or matrix）adsorption of the phosphine in the tail gas and the biological transformation is more smooth,thus promoting the phosphine purification effect of the coupling system.