RESUMEN
The combined zero-valent iron (ZVI) and upflow anaerobic sludge blanket (UASB) process is established for the treatment of chloronitrobenzenes (ClNBs) wastewater, and the succession of microbial community and its enhanced mechanism are investigated in the study. Results showed that compared with the control UASB (R1), the stable COD removal, ClNBs transformation, and dechlorination occurred in the combined system (R2) when operated at influent COD and 3,4-Dichloronitrobenzene (3,4-DClNB) loading rates of 4200-7700 g m(-3) d(-1) and 6.0-70.0 g m(-3) d(-1), and R2 had the better shock resistance and buffering capacity for the anaerobic acidification. The dechlorination for the intermediate products of p-chloroanaline (p-ClAn) to analine (AN) occurred in R2 reactor after 45 days, whereas it did not occur in R1 after a long-term operation. The novel ZVI-based anaerobic granular sludge (ZVI-AGS) was successfully developed in the combined system, and higher microbial activities including ClNB transformation and H2/CH4 production were achieved simultaneously. The dominant bacteria were closely related to the groups of Megasphaera, Chloroflexi, and Clostridium, and the majority of archaea were correlated with the groups of Methanosarcinalesarchaeon, Methanosaetaconcilii, and Methanothrixsoehngenii, which are capable of reductively dechlorinating PCB, HCB, and TCE in anaerobic niche and EPS secretion.
Asunto(s)
Reactores Biológicos , Hierro/metabolismo , Nitrobencenos/metabolismo , Contaminantes Químicos del Agua/metabolismo , Anaerobiosis , Archaea/genética , Archaea/metabolismo , Bacterias/genética , Bacterias/metabolismo , ADN de Archaea/análisis , ADN Bacteriano/análisis , ARN Ribosómico 16S/genética , Aguas del Alcantarillado/microbiología , Eliminación de Residuos Líquidos , Aguas ResidualesRESUMEN
The zero-valent iron (ZVI) corrosion products and their functions were investigated in the combined ZVI and anaerobic sludge system. Results showed that ZVI corrosion occurred, and the reductive transformation and dechlorination of p-chloronitrobenzene (p-ClNB) by the anaerobic sludge were enhanced. In the combined systems with different types of ZVIs and mass ratios of anaerobic sludge to ZVI, a considerable amount of suspended iron compounds was produced and coated onto the microbial cells. However, the microbial cellular structure was damaged, and the p-ClNB reductive transformation was affected adversely after the long-term presence of nanoscale ZVI (NZVI) or reduced ZVI (RZVI) with a high concentration of 5 g L(-1). The oxidized products of FeOOH and Fe3O4 were found on the surface of ZVI, which are speculated to act as electron mediators and consequently facilitate the utilization of electron donors by the anaerobic microbes.
Asunto(s)
Hierro/química , Nitrobencenos/química , Nitrobencenos/metabolismo , Anaerobiosis , Corrosión , Halogenación , Oxidación-Reducción , Aguas del Alcantarillado/química , Aguas del Alcantarillado/microbiologíaRESUMEN
The combination of zero-valent iron (ZVI) with anaerobic sludge for enhancing reductive transformation and dechlorination of p-chloronitrobenzene (p-ClNB) was investigated in this study. p-ClNB was quickly reduced into p-chloroaniline (p-ClAn) and subsequently dechlorinated into aniline in the complex system, and the strengthening factor for pseudo-first-order transformation rate constant of p-ClNB (Q, k ZVI + sludge/(k sludge + k ZVI)) was above 3. The Q values for the different ZVI types with anaerobic sludge were as following: Reduced ZVI (RZVI) > Industrial ZVI > Nanoscale ZVI (NZVI). Thereinto, the aggregation of NZVI occurred, and its reaction activity declined. Furthermore, the increase of ZVI dosage promoted the p-ClNB transformation, but the p-ClAn dechlorination rate and Q value were not improved. With the anaerobic biomass increasing, the dechlorination rate of p-ClAn was significantly enhanced, and the Q value had positive relation with the mass ratio of anaerobic sludge to RZVI.
Asunto(s)
Hierro/química , Nitrobencenos/química , Aguas del Alcantarillado/química , Eliminación de Residuos Líquidos/métodos , Anaerobiosis , Factores de Tiempo , Purificación del Agua/métodosRESUMEN
Using a combined zero-valent iron (ZVI) and anaerobic sludge system as the platform, the hydrogen utilization and reductive mechanism of p-chloronitrobenzene (p-ClNB) were investigated in the study. Results showed that the corrosion of ZVI could be used as a source of electron donor for anaerobic microorganisms, and then enhanced reductive transformation of p-ClNB and production of methane. Thereinto, the transformation of p-ClNB was observed to have priority for the utilization of H(2). The enhancement factors (Q') for the reductive transformation of p-ClNB with exogenous H(2), reduced ZVI (RZVI), industrial ZVI (IZVI), and nanoscale ZVI (NZVI) as electron donors were 4.1-5.6, 14.8-35.1, 2.8-4.6, and 1.5-5.7, respectively. Results demonstrated that RZVI was the most effective type of electron donors, which was attributed to the production and utilization of H(2)/[H] simultaneously via the ZVI corrosion and microbial metabolism. It is hopeful for the application of ZVI to enhance the reductive transformation of analogous persistent organic pollutants in the anaerobic sludge system.
Asunto(s)
Hidrógeno/metabolismo , Hierro/metabolismo , Nitrobencenos/química , Aguas del Alcantarillado/microbiología , Eliminación de Residuos Líquidos/métodos , Anaerobiosis , Biodegradación Ambiental , Corrosión , Hierro/química , Metano/química , Metano/metabolismo , Nitrobencenos/metabolismo , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/metabolismoRESUMEN
Lake and reservoir' s eutrophication and its produced microcystins (MCs) have enormous threats to ecological environment and human health. Because the conventional water pollution control techniques have definite limitations, it' s quite urgent to develop new technique to remove the MCs from water environment. MCs can be effectively degraded by specific microbes, and its intermediate and terminal products are non-toxic or low-toxic. This paper summarized the MCs-degrading microbial strains, biodegradation processes, mechanisms, and affecting factors, degraded products and their structural characteristics, and the applications of MCs-degrading microbial strains in water environment restoration. The further research directions were also proposed. It was hoped that this review could provide technical ideas for restoring MCs-polluted lakes and reservoirs and ensuring drinking water safety in China.
Asunto(s)
Fenómenos Fisiológicos Bacterianos , Eutrofización , Microcistinas/aislamiento & purificación , Contaminación del Agua/prevención & control , Purificación del Agua/métodos , Biodegradación Ambiental , Burkholderia/fisiología , Agua Dulce , Microcistinas/análisis , Microcistinas/metabolismo , Pseudomonas/fisiología , Sphingomonas/fisiología , Contaminación del Agua/análisisRESUMEN
The formation and characterization of the aerobic 4-chloroaniline-degrading granules in the three column-type sequencing batch reactors were investigated in this paper. The granular sludge was observed since 15 days after start-up in R2 and R3 which had the high ratio of height to diameter (H/D). Since then and within the subsequent 75 days, the granulation of aerobic sludge was apparently developed by the decreased settling time and gradually increased 4-chloroaniline (4-ClA) concentration to above 400 mg.L(-1) in R1 to R3. The aerobic granules tended to be mature in all reactors continuously operated with 4-ClA loading rates of around 800 g.m(-3).d(-1), and the removal efficiencies of chemical oxygen demand, total nitrogen, and 4-ClA were maintained above 93%, 70%, and 99.9%, respectively. Mature aerobic granules in R1 to R3 featured with the average diameter of 0.78, 1.68, and 1.25 mm, minimal settling velocity of 20.5, 70.1 and 66.6 m.h(-1), specific 4-ClA degradation rates of 0.14, 0.21, and 0.27 g.gVSS(-1).d(-1), and the ratio of proteins to polysaccharides of 8.2, 10.8, and 13.7 mg.mg(-1), respectively. This study demonstrates that the reactor with a high H/D ratio and internal circulation favors the granulation and stabilization of aerobic sludge.
Asunto(s)
Compuestos de Anilina/metabolismo , Bacterias/metabolismo , Reactores Biológicos/microbiología , Aguas del Alcantarillado/química , Aerobiosis , Biodegradación Ambiental , Tamaño de la Partícula , Aguas del Alcantarillado/microbiologíaRESUMEN
The interactions of 2-nitroaniline (2-NA), 3-nitroaniline (3-NA) and 4-nitroaniline (4-NA) with bovine serum albumin (BSA) have been investigated by means of fluorescence spectrometry, synchronous fluorescence spectrometry and UV absorption spectrometry under the simulative physiological conditions. Association constants (K(A)) were estimated by the remarkable static quenching effect of 2-NA, 3-NA and 4-NA to the intrinsic fluorescence of BSA, and thermodynamic parameters such as enthalpy change (DeltaH) and entropy change (DeltaS) were calculated according to van't Hoff equation. The results show that hydrophobic force plays a main role in the interaction of nitroanilines to BSA, nitroanilines have high affinity to BSA and the affinity order is as follows: 4-NA > 2-NA > 3-NA. On the basis of this study, it is found that percents of the binding of nitroanilines to BSA are almost no relative to the concentrations of nitroanilines, and correlation between K(A) and logK (ow) is disclosed. In the meantime, relationships between the combination of nitroanilines with BSA and toxicological implications were also discussed. In addition, synchronous fluorescence method was used to study the interaction mechanisms between nitroanilines and BSA, and energy transfer distances from BSA to nitroanilines were estimated based on the Förster's non-radiation energy transfer theory. The results suggest that the binding site for nitroanilines on BSA is close to the sub-domain IIA where Trp 214 is located.