DNA Metabarcoding of the Leachate Microbiota from Sanitary Landfill: potential for bioremediation process

Microbial profile knowledge is essential to news alternatives and improvements in current treatments and destinations of landfill leachate that contains a variety of toxic compounds produced by municipal solid waste (MSW) disposal. Environmental DNA metabarcoding is an efficient, quick, and low-cost methodology for whole communities’ characterization. In this respect, the leachate from the Sanitary Landfill of Foz do Iguaçu City showed mixed characteristics from both acid and methanogenic phases, and 16S rDNA metabarcoding suggested the dominance of fermenting bacteria belonging to Firmicutes phylum, followed by Proteobacteria, Bacteroidetes and Synergistetes. The leachate acidogenic phase ended up being masked in the chemical and physical analyzes, however was evidenced in the metabarcoding methodology. On the other hand, no specifically methanogenic group was detected in significant abundance. To future application using culturomics approaches to bioremediation the leachate sample presented groups extensively studied, especially the Pseudomonas genus to heavy metals treatments, such as cadmium.

Two-stage anaerobic process benefits removal for azo dye Orange II with starch as primary co-substrate

Two-stage anaerobic system (S1: R1 (acidogenic phase) + R2 (methanogenic phase)) and the one-stage control (S0) were established to investigate the effect of phase separation on the removal of an azo dye orange II, i.e., Acid Orange 7 (AO7), with starch as the primary co-substrate. Although final AO7 removal from two systems showed no statistical differences, the first-order rate constants for AO7 removal (kAO7­) and sulfanilic acid (SA) formation (kSA) were higher in S1. Kinetic analysis showed that kAO7­ and kSA in S1 were 2.7-fold and 1.7-fold of those in S0, respectively, indicating the benefit of phase separation to the AO7 reduction. However, this benefit only appeared in the period with influent AO7 concentrations higher than 2.14 mM. Otherwise, this advantage would be hidden due to the longer HRT (5 d) and sufficient electron donor (1.0 g starch L−1). Within S1, R1 only contributed about 10% of the entire AO7 removal, and kAO7­ in R1 (0.172 h−1) was much lower than in R2 (0.503 h−1). The methanogenic phase rather than acidogenic phase was the main contribution to AO7 removal, because the influent of R2 had more available electron donors and suitable pH condition (pH 6.5–7.0) for the bio-reduction process.

Influence of Temperature on Biogas Production Efficiency and Microbial Community in a Two-Phase Anaerobic Digestion System

In this study, the influence of temperature on biogas production efficiency and the microbial community structure was investigated in a two-phase anaerobic digestion reactor for co-digestion of cow manure and corn straw. The results illustrated that the contents of solluted chemical oxygen demand (SCOD) and volatile fatty acid (VFA) in the acidogenic phase and biogas production in the methanogenic phase maintained relatively higher levels at temperatures ranging from 35–25 °C. The methane content of biogas production could be maintained higher than 50% at temperatures above 25 °C. The microbial community structure analysis indicated that the dominant functional bacteria were Acinetobacter, Acetitomaculum, and Bacillus in the acidogenic phase and Cenarchaeum in the methanogenic phase at 35–25 °C. However, the performances of the acidogenic phase and the methanogenic phase could be significantly decreased at a lower temperature of 20 °C, and microbial activity was inhibited obviously. Accordingly, a low temperature was adverse for the performance of the acidogenic and methanogenic phases, while moderate temperatures above 25 °C were more conducive to high biogas production efficiency.

Research on the Efficiency of Acid-Producing and Gas-Producing Based on the Enhancement of High-Performance Composite Strains

A batch test was carried out to investigate the effect of acid-producing fermentative characteristic of a new complex strains LZF-12 with high lignocellulose-degradation ability, which straw was the only carbon source in acidogenic phase. Simultaneity, the biogas-producing performance was also researched by shifting the liquid end products from acidongenic phase to methane phase, which fermentative substrate was the mixture of cow dung and kitchen waste. The results indicated that major fermentation products of acidogenic phase was acetic acid accounted for 70% of total volatile acid, which would be in favor of microorganisms growth of methanogenic phase. In two-phase anaerobic fermentation system, the straw degradation rate of composite strains LZF-12 reached the maximum at 72 hour, among which the degradation rate of cellulose, hemicellulose and lignin reached 55%, 67% and 13% respectively. The methane percentage of biogas-producing phase was more than 50% and 134.7mL/g VS of methane production rate was obtained.