Biodegradation of high concentration of nitrobenzene by Pseudomonas corrugata embedded in peat-phosphate esterified polyvinyl alcohol

An in-situ bio-remediation of nitrobenzene in stimulated aquifer using emulsified vegetable oil

Widespread nitrobenzene (NB) contamination in groundwater requires an economical and effective remediation technology. In situ microbial reactive zone enhanced by injecting emulsified vegetable oil (EVO) is an effective method for remediating NB-contaminated groundwater, which can be reduced to aniline (AN) effectively in the reactive zone. However, the bio-mechanism of NB remediation in a real contaminated site is still unclear. Thus, a 3-D tank was established to conduct a pilot-scale experiment and the bacterial communities in the tank were analyzed by 16S rDNA high-throughput sequencing. The results suggested that the injection of EVO can stimulate some certain microorganisms to grow, and reduce NB though biological and biochemical processes. There were three degradation pathways of NB: (1) direct oxidation by Pseudomonas; (2) direct mineralization by Clostridium sensu stricto; and (3) coupled reduction of NB through microbial dissimilatory iron reduction by Geobacter and Arthrobacter. Among these pathways, the coupled reduction process is the main degradation pathway.

Isolation of two iron-reducing facultative anaerobic electricigens and probing the application performance in eutrophication water

Purpose

Sediment microbial fuel cell (SMFC) is a promising bioremediation technology in which microbes play an important role. Electricigens as the bio-catalysts have effect on pollution control and electricity generation. It is of great significance to screen the microorganisms with the ability of generating electricity.

Methods

The SMFC anode biofilm was used as microbiological source to study the feasibility of electricigens with iron-reducing property for eutrophication water treatment. Preliminarily, we isolated 20 facultative anaerobic pure bacteria and evaluated their cyclic voltammogram (CV) through the three-electrode system and electrochemical workstation. The power generation performance of strains was verified by air-cathode microbial fuel cells (AC-MFCs) under different single carbon sources.

Result

According to its morphological, physiological, and biochemical characteristics, along with phylogenetic analysis, the two strains (SMFC-7 and SMFC-17) with electrical characteristics were identified as Bacillus cereus. Compared with SMFC-7, SMFC-17 exhibited efficient NH4+-N and NO3−-N removal and PO43−-P accumulation from eutrophic solution with a removal rate of 79.91 ± 6.34% and 81.26 ± 1.11% and accumulation rate of 57.68 ± 4.36%, respectively.

Conclusion

The isolated bacteria SMFC-17 showed a good performance in eutrophic solution, and it might be a useful biocatalyst to enable the industrialized application of SMFC in eutrophic water treatment.

Microbial Community in a Biofilter for Removal of Low Load Nitrobenzene Waste Gas

To improve biofilter performance, the microbial community of a biofilter must be clearly defined. In this study, the performance of a lab-scale polyurethane biofilter for treating waste gas with low loads of nitrobenzene (NB) (< 20 g m-3 h-1) was investigated when using different empty bed residence times (EBRT) (64, 55.4 and 34 s, respectively). In addition, the variations of the bacterial community in the biofilm on the longitudinal distribution of the biofilters were analysed by using Illumina MiSeq high-throughput sequencing. The results showed that NB waste gas was successfully degraded in the biofilter. High-throughput sequencing data suggested that the phylum Actinobacteria and genus Rhodococcus played important roles in the degradation of NB. The variations of the microbial community were attributed to the different intermediate degradation products of NB in each layer. The strains identified in this study were potential candidates for purifying waste gas effluents containing NB.

A bench-scale assessment for phosphorus release control of sediment by an oxygen-releasing compound (ORC)

The effects of oxygen-releasing compound (ORC) on the control of phosphorus (P) release as well as the spatial and temporal distribution of P fractions in sediment were studied through a bench-scale test. An ORC with an extended oxygen-releasing capacity was prepared. The results of the oxygen-releasing test showed that the ORC provided a prolonged period of oxygen release with a highly effective oxygen content of 60.6% when compared with powdery CaO2. In the bench-scale test, an ORC dose of 180 g·m(-2) provided a higher inhibition efficiency for P release within 50 days. With the application of the ORC, the dissolved oxygen (DO) concentration and redox potential (ORP) of the overlying water were notably improved, and the dissolved total phosphorus (DTP) was maintained below 0.689 mg·L(-1) compared to 2.906 mg·L(-1) without the ORC treatment. According to the P fractions distribution, the summation of all detectable P fractions in each sediment layer exhibited an enhanced accumulation tendency with the application of ORC. Higher phosphorus retention efficiencies were observed in the second and third layers of sediment from days 10 to 20 with the ORC. Phosphorus was trapped mainly in the form of iron bound P (Fe-P) and organically bound P (O-P) in sediment with the ORC, whereas the effects of the ORC on exchangeable P (EX-P), apatite-associated P (A-P) and detrital P (De-P) in the sediment sample were not significant. The microbial activities of the sediment samples demonstrated that both the dehydrogenase activity (DHA) and alkaline phosphatase activity (APA) in the upper sediment layer increased with the ORC treatment, which indicated that the mineralization of P was accelerated and the microbial biomass was increased. As the accumulation of P suppressed the release of P, the sediment exhibited an increased P retention efficiency with the application of the ORC.

Toxicity and Microbial Degradation of Nitrobenzene, Monochloronitrobenzenes, Polynitrobenzenes, and Pentachloronitrobenzene

Nitrobenzene and its derivatives (NBDs) are highly toxic compounds that have been released into the environment by anthropogenic activities. Many bacteria and fungi have been well-characterized for their ability to degrade NBDs. The biochemical and molecular characterization of the microbial degradation of NBDs has also been studied. In this review, we have summarized the toxicity and degradation profiles of nitrobenzene, monochloronitrobenzenes, polynitrobenzenes, and pentachloronitrobenzene. This review will increase our current understanding of toxicity and microbial degradation of NBDs.