Evaluation of A Novel Split-Feeding Anaerobic/Oxic Baffled Reactor (A/OBR) For Foodwaste Anaerobic Digestate: Performance, Modeling and Bacterial Community.

Shaojie Wang,Yixin Jiang,Liyu Peng,Haijia Su,Petros Gikas,Baoning Zhu

doi:10.1038/srep34640

Abstract

To enhance the treatment efficiency from an anaerobic digester, a novel six-compartment anaerobic/oxic baffled reactor (A/OBR) was employed. Two kinds of split-feeding A/OBRs R2 and R3, with influent fed in the 1st, 3rd and 5th compartment of the reactor simultaneously at the respective ratios of 6:3:1 and 6:2:2, were compared with the regular-feeding reactor R1 when all influent was fed in the 1st compartment (control). Three aspects, the COD removal, the hydraulic characteristics and the bacterial community, were systematically investigated, compared and evaluated. The results indicated that R2 and R3 had similar tolerance to loading shock, but the R2 had the highest COD removal of 91.6% with a final effluent of 345 mg/L. The mixing patterns in both split-feeding reactors were intermediate between plug-flow and completely-mixed, with dead spaces between 8.17% and 8.35% compared with a 31.9% dead space in R1. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis revealed that the split-feeding strategy provided a higher bacterial diversity and more stable bacterial community than that in the regular-feeding strategy. Further analysis indicated that Firmicutes, Bacteroidetes, and Proteobacteria were the dominant bacteria, among which Firmicutes and Bacteroidetes might be responsible for organic matter degradation and Proteobacteria for nitrification and denitrification.

Highlights

Various studies have been conducted on the biological treatment of sewage sludge to reduce organic contents, but few focused on the treatment of anaerobic digestate
The results showed that both two split-feeding reactors R2 and R3 could significantly improve the overall chemical oxygen demand (COD) removal of stage I, II, and III compared with regular-feeding reactor R1 (Table S1 in Supplementary Information)
Many literatures have demonstrated that the first two compartments (C1 and C2) were crucial for the degradation of macromolecular organics and accounted for more than 50% COD removal in a ABR37,38

Summary

Introduction

Various studies have been conducted on the biological treatment of sewage sludge to reduce organic contents, but few focused on the treatment of anaerobic digestate. Since the integration of multiple biological technologies shows positive effects on the degradation of digestate, a specific reactor layout should be designed to carry out such novel process. The anaerobic baffled reactor (ABR) shows the potential because it has already been successfully applied to many wastewater treatment plants due to its effective chemical oxygen demand (COD) removal, high tolerance towards loading shock, and capability to contain various biological metabolism phases[9,10,11]. The ABR is able to separate acidogenesis and methanogenesis horizontally along the reactor, thereby allowing the reactor to behave as a two-phase system[14] This multi-compartmental structure encourages different bacterial groups to develop under their most favorable conditions, and enables the ABR to maintain a high biomass concentration. Cloning and 16S rRNA gene analyses of the integrated system where the anaerobic and aerobic populations co-existed are still limited[25]

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Results

Conclusion