Application of nanoparticles to increase biological hydrogen production: the difference in metabolic pathways in batch and continuous reactors.

An alternative to improve the production of biorefinery products, such as biohydrogen (H2) and volatile fatty acids (VFA), is the combination of nanotechnology and biological processes. In order to compare the use of both processes in two different reactor configurations, batch reactors and continuous anaerobic fluidized bed reactors (AFBR) were studied under the same conditions (37°C, pH 6.8, Clostridium butyricum as an inoculum and glucose as a substrate) to evaluate the influence of zero valence iron and nickel nanoparticles (NPs) on H2 and VFA production. There was a shift in the production of acetic and butyric acids to produce mainly valeric acid when NPs were added in batch reactors. Meanwhile, in AFBR the change was from lactic acid to butyric and acetic acids with the addition of NPs. It showed that the effect of NPs on the fermentation process was different when the configuration of batch and continuous reactors was compared. The H2 yield in both reactor configurations increased with the addition of NPs. In batch reactors from 6.6 to 8.0 mmol H2 g-1 of COD and in AFBR from 4.9 to 6.2 mmol of H2 g-1 of COD. Therefore, given the simplicity and low cost of the synthesis of metallic NPs, it is a promising additive to optimize the fermentation process in different reactor configurations.

4-Nonylphenol degradation changes microbial community of scale-up Anaerobic Fluidized Bed Reactor.

Nonylphenol Ethoxylate (NPe) is a nonionic surfactant widely applied in domestic and industrial uses and its degradation generates the endocrine disruptor 4-Nonylphenol (4-NP). The effects of this compound in biological sewage treatment are uncertain, especially in anaerobic systems. The aim of this study was to assess the 4-NP removal and degradation in scale-up (20 L) Anaerobic Fluidized Bed Reactor (AFBR) filled with sand as support material, operated with Hydraulic Retention Time (HRT) of 18 h, fed with synthetic sewage plus 4-NP, performed in four phases named Phase I (894 mg COD L-1), Phase II (878 mg COD L-1, 127 µg 4-NP L-1), Phase III (940 mg COD L-1, 270 µg 4-NP L-1) and Phase IV (568 mg COD L-1, 376 µg 4-NP L-1). 4-NP did not affect reactor stability and organic matter removal remained stable at 94%. Highest 4-NP removal (78%) occurred for highest 4-NP influent (Phase IV), which resulted from biomass adaptation in the presence of ethanol. Through the 4-NP total mass balance, about 70% was biodegraded and 1% adsorbed on the sand bed. 4-NP addition promoted selection of microbial consortium strongly linked to aromatic compounds and surfactants degradation such as Geothrix, Holophaga, Aeromonas, Pelobacter, Pseudomonas, Delftia.

An integrated anaerobic system for on-site treatment of wastewater from food waste disposer.

In this study, an integrated system of siphon-driven self-agitated anaerobic reactor (SDSAR) and anaerobic fixed bed reactor (AFBR) was conducted for the treatment of wastewater from food waste disposer (FWD), and the effect of influent total solids (TS) concentration on the process performance was evaluated. When the influent TS concentration increased from 7.04 to 15.5 g/L, the methane gas production rate increased from 0.45 to 0.92 L-CH4/L/day. However, with the influent TS concentration of food waste (FW) further increased to 23.5 g/L, a large amount of scum formed and accumulated in the SDSAR. According to the result of chemical oxygen demand (COD) recovery, the proportion of COD remained in the effluent at different TS concentrations was only around 2%. On the other hand, with an increase in TS concentration, the proportion of COD remained in the reactors increased significantly. Our results demonstrated that effluent from the integrated system can meet the water quality requirements recommended by Japan Sewage Works Association (JSWA) for wastewater from FWD. In addition, to enhance the process stability, the influent TS concentration should be maintained below 15.5 g/L.

Optimized 1,3-propanediol production from crude glycerol using mixed cultures in batch and continuous reactors.

The production of 1,3-propanediol from crude glycerol and mixed anaerobic sludge was investigated in batch experiments and continuous reactors. Using a 23 complete factorial design, the effects of the concentration of glycerol (22-30 g L-1), KH2PO4 (1.50-2.00 g L-1), and vitamin B12 (7-8 mg L-1) were examined in batch reactors. As an evaluated response, the highest 1,3-PD yields occurred for high concentrations of vitamin B12 and low levels of KH2PO4, reaching 0.57 g g-1 glycerol consumed. The variable glycerol concentration was not significant in the studied range. In addition, the condition that provided the best 1,3-PD yield was applied to an anaerobic fluidized bed reactor fed with crude glycerol (26.0 g L-1), which was monitored as the hydraulic retention time (HRT) decreased from 36 to 12 h. The greatest 1,3-PD yield, of 0.31 g g-1 glycerol, was obtained with an HRT of 28 h.

Production of biohythane from food waste via an integrated system of continuously stirred tank and anaerobic fixed bed reactors.

The continuous production of biohythane (mixture of biohydrogen and methane) from food waste using an integrated system of a continuously stirred tank reactor (CSTR) and anaerobic fixed bed reactor (AFBR) was carried out in this study. The system performance was evaluated for an operation period of 200days, by stepwise shortening the hydraulic retention time (HRT). An increasing trend of biohydrogen in the CSTR and methane production rate in the AFBR was observed regardless of the HRT shortening. The highest biohydrogen yield in the CSTR and methane yield in the AFBR were 115.2 (±5.3)L H2/kgVSadded and 334.7 (±18.6)L CH4/kgCODadded, respectively. The AFBR presented a stable operation and excellent performance, indicated by the increased methane production rate at each shortened HRT. Besides, recirculation of the AFBR effluent to the CSTR was effective in providing alkalinity, maintaining the pH in optimal ranges (5.0-5.3) for the hydrogen producing bacteria.