CO2 是生物法处理有机废气过程中的主要副产物之一，对其进行有效吸收可实现废气治理减污降碳协同的目标。该文以氯苯为模型污染物，在气升式细菌反应器中添加蛋白核小球藻(C。pyrenoidosa)，构建气升式藻-菌共生反应器，初步探究了藻-菌体系对废气去除、CO2吸收、微生物群落结构等关键指标的影响。结果表明在不同停留时间和氯苯进口浓度条件下，气升式藻-菌共生反应器对氯苯的去除率超过90%，与气升式细菌反应器无明显差异，然而气升式藻-菌共生反应器的出口CO2浓度显著低于气升式细菌反应器，75 天的运行周期内CO2累积排放量降低了约25%。
Removal of waste gas containing chlorobenzene and the simultaneous CO2 absorption by an airlift algae-bacteria symbiotic reactor
[Objective]Biological methods have emerged as a promising solution for the treatment of low-concentration waste gases containing volatile organic compounds(VOCs).These methods are distinguished by their low energy requirements,minimal secondary pollution,and reduced operational and maintenance costs.However,one of the drawbacks of VOC biodegradation is the inevitable emission of CO2,a normal intermediate product.Studies have shown that up to 60%or more of the carbon in VOCs can be converted into CO2,thereby increasing the carbon footprint of different bioreactors.In this context,microalgae,known for their photoautotrophic nature,have shown significant potential for biological carbon sequestration.This study explores the cultivation of microalgae alongside VOC-degrading bacteria within an algae-bacteria symbiotic reactor.The aim is to utilize the CO2 resulting from VOC biodegradation in situ by microalgae,therefore achieving simultaneous pollution control and carbon mitigation.[Methods]Chlorobenzene was selected as the model pollutant for this study.We established an airlift algae-bacteria reactor(ABR)using C.pyrenoidosa and Ralstonia sp.XZW-1 as the initial inoculum.For comparative purposes,a conventional airlift bacterial reactor(BR)inoculated with Ralstonia sp.XZW-1 was utilized.The exterior of the ABR reactor was equipped with four LED lights to provide constant illumination throughout the experiment,while the outer surface of the BR was entirely wrapped by aluminum foil to prevent light penetration and prevent unintended microalgae growth.Key performance metrics,such as gas removal efficiency,maximum elimination capacity,and microbial community structure,were investigated to evaluate the ABR's effectiveness in purifying waste gas containing chlorobenzene.Comparisons of CO2 production between ABR and BR highlighted the ABR's carbon mitigation potential.Additionally,chlorophyll-a concentration was measured as an indicator of microalgae growth,and other parameters such as dissolved oxygen concentration,chlorine ion generation,and microbial community structure were also analyzed to further assess the effects of algae-bacteria symbiosis.[Results]Preliminary results showed that the dissolved oxygen concentration in the ABR was significantly higher than that in BR.Under the different gas residence times(60 and 90 s)and inlet chlorobenzene concentrations(500 mg·m-3 and 1000 mg·m-3),the ABR achieved chlorobenzene efficiencies exceeding 90%,with a maximum elimination capacity of 44.08 g·m-3·h-1,comparable to that of the BR.However,the ABR exhibited a lower outlet CO2 concentration than that of the BR,resulting in a 25%reduction in cumulative emissions over the 75 d experiment.The increase in chlorophyll-a concentration confirmed stable growth of C.pyrenoidosa within the ABR.High-throughput sequencing demonstrated a high proportion of degradation bacteria related to chlorinated hydrocarbons and chlorinated aromatic hydrocarbons in the ABR,such as Rhodococcus and Acidophilus.[Conclusions]Although the introduction of an airlift algae-bacteria symbiotic reactor did not significantly enhance chlorobenzene removal compared to traditional methods,integrating microalgae into a conventional bacterial reactor increased the dissolved oxygen concentration,which likely supports the growth of chlorobenzene-degrading microorganisms.This symbiosis may prove beneficial for the bioreactor's long-term stability and efficiency.More importantly,the presence of microalgae plays a crucial role in utilizing CO2 resulting from VOC biodegradation.Therefore,the algae-bacteria symbiotic bioreactor emerges as an appropriate candidate to achieve simultaneous waste gas treatment and carbon reduction.Further research is still needed to further explore the synergistic effects between microalgae and VOC-degrading bacteria.
waste gas treatmentmicroalgaebiodegradationcarbon mitigation
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