title: Comprehensive microbial analysis of combined mesophilic anaerobic-thermophilic aerobic process treating high-strength food wastewater.
abstract: A combined mesophilic anaerobic-thermophilic aerobic process was used to treat high-strength food wastewater in this study. During the experimental period, most of solid residue from the mesophilic anaerobic reactor (R1) was separated by centrifugation and introduced into the thermophilic aerobic reactor (R2) for further digestion. Then, thermophilic aerobically-digested sludge was reintroduced into R1 to enhance reactor performance. The combined process was operated with two different Runs: Run I with hydraulic retention time (HRT) = 40 d (corresponding OLR = 3.5 kg COD/m(3) d) and Run II with HRT = 20 d (corresponding OLR = 7 kg COD/m(3)). For a comparison, a single-stage mesophilic anaerobic reactor (R3) was operated concurrently with same OLRs and HRTs as the combined process. During the overall digestion, all reactors showed high stability without pH control. The combined process demonstrated significantly higher organic matter removal efficiencies (over 90%) of TS, VS and COD and methane production than did R3. Quantitative real-time PCR (qPCR) results indicated that higher populations of both bacteria and archaea were maintained in R1 than in R3. Pyrosequencing analysis revealed relatively high abundance of phylum Actinobacteria in both R1 and R2, and a predominance of phyla Synergistetes and Firmicutes in R3 during Run II. Furthermore, R1 and R2 shared genera (Prevotella, Aminobacterium, Geobacillus and Unclassified Actinobacteria), which suggests synergy between mesophilic anaerobic digestion and thermophilic aerobic digestion. For archaea, in R1 methanogenic archaea shifted from genus Methanosaeta to Methanosarcina, whereas genera Methanosaeta, Methanobacterium and Methanoculleus were predominant in R3. The results demonstrated dynamics of key microbial populations that were highly consistent with an enhanced reactor performance of the combined process.
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology, 77, Cheongam-Ro, Pohang 790-784, Republic of Korea.
authors.forename: Hyun Min
authors.initials: HM
authors.lastname: Jang
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology, 77, Cheongam-Ro, Pohang 790-784, Republic of Korea; Department of Chemical Engineering, Pohang University of Science and Technology, 77, Cheongam-Ro, Pohang 790-784, Republic of Korea. Electronic address: jeonghha@postech.ac.kr.
authors.forename: Jeong Hyub
authors.initials: JH
authors.lastname: Ha
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology, 77, Cheongam-Ro, Pohang 790-784, Republic of Korea; Department of Chemical Engineering, Pohang University of Science and Technology, 77, Cheongam-Ro, Pohang 790-784, Republic of Korea; Division of Advanced Nuclear Engineering, Pohang University of Science and Technology, 77, Cheongam-Ro, Pohang 790-784, Republic of Korea. Electronic address: jmpark@postech.ac.kr.
authors.forename: Jong Moon
authors.initials: JM
authors.lastname: Park
authors.affiliation: Biomass and Waste Energy Laboratory, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Republic of Korea.
authors.forename: Mi-Sun
authors.initials: MS
authors.lastname: Kim
authors.affiliation: Institute of Chemical Engineering, Biotechnology and Environmental Technology, Faculty of Engineering, University of Southern Denmark, Niels Bohrs Allé 1, DK-5230 Odense M, Denmark.
authors.forename: Sven G
authors.initials: SG
authors.lastname: Sommer
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D005502:Food; D006358:Hot Temperature; D008697:Methane / Q000032:analysis; D064307:Microbiota; D060888:Real-Time Polymerase Chain Reaction; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000032:analysis* / Q000382:microbiology*
chemical_list: D008697:Methane; D062065:Wastewater
keywords: Combined biological process; High-strength food wastewater; Methane production; Pyrosequencing; Quantitative real-time PCR (qPCR)