Biological degradation of soluble microbial products in a combined system of anaerobic packed-bed reactors and a down-flow hanging sponge reactor

Soluble microbial product;Biodegradation;Anaerobic packed-bed reactor;Down-flow hanging sponge reactor;Microbial diversity;Metagenomics;Metatranscriptomics

Kim, Na Kyung

关键词: Soluble microbial product;    Biodegradation;    Anaerobic packed-bed reactor;    Down-flow hanging sponge reactor;    Microbial diversity;    Metagenomics;    Metatranscriptomics;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/99454/KIM-DISSERTATION-2017.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Anaerobic biological processes are a reliable alternative to the conventional activated sludge process for the treatment of high-strength industrial wastewater, offering various advantages. Such advantages include, for example, less sludge generation, less operational cost, greater energy recovery, and a smaller footprint. An anaerobic up-flow packed-bed reactor maximizes the advantages by retaining a high concentration of biomass in the system, providing sufficient sludge retention time to slow growing anaerobic microorganisms. The inherent configuration of the reactor, however, is prone to increasing soluble microbial products (SMP). SMP are soluble organic cellular components that are released from biomass metabolisms in mixed culture biotechnology, which often result in a hindrance to efficient performance, lower effluent quality, and toxicity and a precursor of disinfectant by-products in discharged water. Despite several attempts to reduce SMP through coagulation and adsorption, a long-term treatment of SMP has not been achieved. In this study, a combined process of anaerobic packed-bed reactors and a down-flow hanging sponge (DHS) reactor is proposed. As a matter of post-treatment, the DHS reactor further degraded SMP produced from the anaerobic methanogenic reactors, using selectively enriched microbial consortia-utilizing SMP. As such, the primary research aims of this project are as follows: (1) to understand the microbial community structure and ecology treating high-strength organic wastewater in the anaerobic packed-bed reactors; (2) to investigate biological SMP degradation in the DHS reactor; and (3) to explore phylogenetic characteristics and the metabolic functionality of the enriched microbial community involved in SMP degradation. This study discussed the diversity and dynamics of microbial communities in anaerobic packed-bed reactors in the process of optimizing operational parameters. The communities were influenced by an increasing organic loading rate, which indicated a strong association with the abundance of Bacteroidetes and Chloroflexi among the dominant populations. These populations may take charge of initiating the degradation of organic compounds in the system. Next, the biological degradation of SMP, with respect to the selective enrichment of the microbial community in the DHS reactor, was demonstrated. SMP produced from the anaerobic reactors originated primarily from biomass metabolisms, exhibiting a bimodal MW distribution with 14-20 kDa and <4 kDa. The sub-fractions of SMP indicated different degradation fates in the DHS reactor with an overall stable removal (>70%) of the total SMP. Spatial and temporal variability of the DHS microbial communities was significantly influenced by operational parameters. In particular, Saprospiraceae was the most correlated population in the community for increasing SMP loading, which indicated positive co-occurrences with neighboring bacterial populations. Different microbial diversity, along with the vertical depth of the reactor, suggested that stratified microbial communities might participate in the SMP degradation. Lastly, the genetic functional potential and expression of the DHS microbial community, with regard to SMP degradation, were explored. Despite the disparate microbial communities with the increase of SMP loading, a functional convergence for the SMP degradation was observed. The gene expression of the dominant draft genomes, based on carbohydrate-active enzymes, indicated that Bacteroidetes-related draft genomes actively represented cell associated enzyme-related genes, which were specific to the polysaccharide components of peptidoglycan. This finding led to speculation that the majority of SMP herein may be composed of detrital cell structural components released from peptidoglycan.Ultimately, the findings from this study suggest a possible application of the biological SMP degradation, using a DHS reactor, to improve treatment performance and efficiency in bioprocesses. It also broadens current understanding of SMP, which are produced from mixed culture biotechnology, and their microbial utilization.