Low-dosage ozonation in gas-phase biofilter promotes community diversity and robustness

Marvin Yeung,Prakit Saingam,Jinying Xi,Yang Xu

doi:10.1186/s40168-020-00944-4

Abstract

BackgroundThe ozonation of biofilters is known to alleviate clogging and pressure drop issues while maintaining removal performances in biofiltration systems treating gaseous volatile organic compounds (VOCs). The effects of ozone on the biofilter microbiome in terms of biodiversity, community structure, metabolic abilities, and dominant taxa correlated with performance remain largely unknown.MethodsThis study investigated two biofilters treating high-concentration toluene operating in parallel, with one acting as control and the other exposed to low-dosage (200 mg/m3) ozonation. The microbial community diversity, metabolic rates of different carbon sources, functional predictions, and microbial co-occurrence networks of both communities were examined.ResultsConsistently higher biodiversity of over 30% was observed in the microbiome after ozonation, with increased overall metabolic abilities for amino acids and carboxylic acids. The relative abundance of species with reported stress-tolerant and biofilm-forming abilities significantly increased, with a consortium of changes in predicted biological pathways, including shifts in degradation pathways of intermediate compounds, while the correlation of top ASVs and genus with performance indicators showed diversifications in microbiota responsible for toluene degradation. A co-occurrence network of the community showed a decrease in average path distance and average betweenness with ozonation.ConclusionMajor degrading species highly correlated with performance shifted after ozonation. Increases in microbial biodiversity, coupled with improvements in metabolizing performances of multiple carbon sources including organic acids could explain the consistent performance commonly seen in the ozonation of biofilters despite the decrease in biomass, while avoiding acid buildup in long-term operation. The increased presence of stress-tolerant microbes in the microbiome coupled with the decentralization of the co-occurrence network suggest that ozonation could not only ameliorate clogging issues but also provide a microbiome more robust to loading shock seen in full-scale biofilters.CGvAG3YimbbyXNa59zcaAyVideo abstract

Highlights

Biofiltration is a technology widely applied in the abatement of a wide range of gaseous pollutants [1]
A persistent issue present in the application of biofilters is the excessive growth of biomass, resulting in clogging, increased pressure drop, and decreased removal performance [7, 8]
One technique of ozone injection was previously reported [10], complemented by another study examining the metabolic activities of the microbiome in biofilters under O3 exposure, which concluded that O3 exposure led to an increase in the metabolism of numerous carbon sources of lower biodegradability, such as γhydroxybutyric acid, D-galactonic acid γ-lactone, D-mannitol, D-cellobiose, and γ-methyl-d-glucoside [11]

Summary

Introduction

Biofiltration is a technology widely applied in the abatement of a wide range of gaseous pollutants [1]. It was shown that despite the decrease in biomass, microbial activity for the metabolism of multiple carbon sources increased in the biofilter, implying an inherent change at the microbial level. It is well-known that the microbiome of a biofilter is crucial for effective pollutant abatement [15], yet the exact microbiome and functional changes that occur allowing for increased microbial activity while maintaining system performance with a decrease in biomass remain intriguing and unknown. The ozonation of biofilters is known to alleviate clogging and pressure drop issues while maintaining removal performances in biofiltration systems treating gaseous volatile organic compounds (VOCs). The effects of ozone on the biofilter microbiome in terms of biodiversity, community structure, metabolic abilities, and dominant taxa correlated with performance remain largely unknown

Results

Discussion

Conclusion