Abstract
Two labscale aerobic moving bed biofilm reactor (MBBR) systems, with a different type of biocarrier in each (K3 and Mutag BioChip), were operated in parallel for the treatment of real saline bilge water. During the operation, different stress conditions were applied in order to evaluate the performance of the systems: organic/hydraulic load shock (chemical oxygen demand (COD): 9 g L−1; hydraulic retention time (HRT): 48–72 h) and salinity shock (salinity: 40 ppt). At the same time, the microbiome in the biofilm and suspended biomass was monitored through 16S rRNA gene analysis in order to describe the changes in the microbial community. The dominant classes were Alphaproteobacteria (families Rhodospirillaceae and Rhodobacteraceae) and Bacteroidia (family Lentimicrobiaceae), being recorded at high relative abundance in all MBBRs. The structure of the biofilm was examined and visualized with scanning electron microscopy (SEM) analysis. Both systems exhibited competent performance, reaching up to 86% removal of COD under high organic loading conditions (COD: 9 g L−1). In the system in which K3 biocarriers were used, the attached and suspended biomass demonstrated a similar trend regarding the changes observed in the microbial communities. In the bioreactor filled with K3 biocarriers, higher concentration of biomass was observed. Biofilm developed on Mutag BioChip biocarriers presented lower biodiversity, while the few species identified in the raw wastewater were not dominant in the bioreactors. Through energy-dispersive X-ray (EDX) analysis of the biofilm, the presence of calcium carbonate was discovered, indicating that biomineralization occurred.
Highlights
Industrial wastewater has always been a challenge for biological treatment processes.Wastewater produced by industrial applications usually contains hazardous substances, which directly affect microbial growth [1]
The aim of this study was to investigate the potential of lab-scale moving bed biofilm reactor (MBBR) to treat real, high-strength saline bilge water, as well as to determine the microbial communities involved in the process
The removal observed in the first and second reactors (R1a and R1b) was 56.5 ± 10.9% and 47.6 ± 16.0% COD removal, respectively. The contribution of both bioreactors was important in preserving the outflow COD of the system at a concentration of 1908 ± 240 mg L−1
Summary
Wastewater produced by industrial applications usually contains hazardous substances, which directly affect microbial growth [1]. As the next-generation sequencing (NGS) analysis of environmental samples has become more accessible, it is possible to identify the microbial groups involved in a treatment process [4]. With this tool available, the potential of biological processes can be further explored. The performance of the bioprocess and the response of the microbial community to inflow wastewater changes can be monitored [5] at a small scale, where real industrial conditions can be simulated. By determining the microbial diversity and monitoring adaptation, we can consolidate our understanding of the bioprocess and guarantee that the core mechanisms for biodegradation exist in our process
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