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.

Settlement evaluation of municipal solid waste confined in lysimeters considering the phases of anaerobic biodegradation

This research evaluated the settlements occurring in the municipal solid waste mass, confined in three lysimeters, considering the influence of the biodegradation of these wastes, by physicochemical characterization of the leachate produced. The physicochemical variables studied were: Chemical Oxygen Demand (COD), Nitrogen-Ammonia, Hydrogen Potential (pH), Volatile Fatty Acids (VFA) and Total Alkalinity. The measured settlements were analyzed based on the biodegradation phases of the confined wastes. Currently, the MSW is in the methanogenic phase of anaerobic biodegradation.

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.

Variations in Microbial Flora in Different Phases of Refuse in Response to Dibutyl Phthalate

Simulated municipal solid waste (MSW) based on the actual proportional characteristics of MSW was loaded into a simulated leachate recirculation bioreactor landfill and the abundance of common and tolerant microbes exposed to dibutyl phthalate (DBP) were investigated in the initial, acidic and methanogenic phases. The results showed that the abundance of bacteria was greatest, while that of actinomycetes was smallest. The growth of microorganisms was not significantly inhibited by DBP during the initial phase; however, the growth of actinomycetes and fungi was inhibited during both the acidic and methanogenic phases, and the inhibition of actinomycetes was greater than that of fungi. When the DBP concentration was 5.0 g l-1, the inhibition ratio against actinomycetes was 89.5% and 80.9% in the refuse from the acidic phase and methanogenic phase, respectively, while it was 86.2% and 51.0%, respectively, against fungi during the same period. The toxic effects of DBP on microorganisms in refuse occurred in the order of actinomycetes > fungi > bacteria. In addition, the populations of bacteria, fungi and actinomycetes were significantly and positively correlated with dehydrogenase activity, but negatively correlated with the VSS and BDM of refuse (P<0.01).

Bio-methanization of organic fraction from municipal solid waste: temperature effects

The main objective of this study was to analyse the development of dry anaerobic digestion process of OFMSW in batch reactors under two temperature ranges, thermophilic (55°C) and mesophilic (35°C). The experimental results lead to the conclusion that the thermophilic range has a greater rate of hydrolysis and is therefore more effective to degrade wastes, shortening the overall operating time. For example, the hydrolytic step in the thermophilic (T) process lasted an average of 8 days versus 14 days in the mesophilic (M) range. The methanogenic phase lasted for 18 and 29 days in the T and M processes, respectively. The mesophilic range showed higher removal of the organic effluent but with greater uptime requirements. Moreover, the thermophilic range showed greater productivities than the mesophilic range, and the productivities were approximately doubled in terms of the produced biogas from a given amount of consumed organic matter.

The Characteristics of the Mixed Sludge Supernatant by Mesophilic Two-Phase Anaerobic Digestion Process

The mesophilic (35°C) two-phase anaerobic digestion ( TPAD) process was used to treat mixed sludge from primary sedimentation and secondary sedimentation tanks ( 1:3 ). The results show that when HRT is 10 days and organic loading rate is 1.5kgVS/ (m3•d), the upper-liquid COD of methanogenic phase and acidogenic phase increased along with time, but not obviously; The contents oSuperscript textf polysaccharides and proteins in upper-liquid multiplied increased with digestion time, polysaccharides and proteins in acidogenic phase upper-liquid were more than methanogenic phase; The value of CST became larger after being digested by mesophilic two-phase anaerobic digestion, but the dewaterability of sludge in methanogenic phase is better than acidogenic phase.

Experimental Study on Chinese Pharmacy Wastewater Treated by Two-Phase Anaerobic

The performance of two-phase anaerobic in a laboratory-scale operating on traditional Chinese pharmaceutical industry wastewater at various hydraulic retention times was investigated. The wastewater with high pollutant concentration in reactor designed based on two-phase anaerobic principles was analyzed with GC-MS. The effect of controlling the pH of the methanogonic phase of traditional Chinese pharmaceutical industry wastewater digestion on the biogas production rate and pollution potential reduction was also investigated. The reactor was designed to act as a liquid-solid separator, in order to maximize the microbial mass in it, and was operated at different hydraulic retention times. It operated as a two-phase reactor when the pH of the wastewater was controlled in the methanogenic phase. The results of experiment indicate that acidifier discomposes compounds composed of big molecule were degraded into small acid molecule which is more subject to biochemical treatment, and after the final treatment of reactor producing methane, species and contents of compound contained in treated wastewater are obviously reduced.