Response of anaerobic membrane bioreactor to the presence of nano-Bi2WO6: reactor performance, supernatant characteristics, and microbial community

The Widespread Use of Nanomaterials: The Effects on the Function and Diversity of Environmental Microbial Communities

In recent years, as an emerging material, nanomaterials have rapidly expanded from laboratories to large-scale industrial productions. Along with people's productive activities, these nanomaterials can enter the natural environment of soil, water and atmosphere through various ways. At present, a large number of reports have proved that nanomaterials have certain toxic effects on bacteria, algae, plants, invertebrates, mammalian cell lines and mammals in these environments, but people still know little about the ecotoxicology of nanomaterials. Most relevant studies focus on the responses of model strains to nanomaterials in pure culture conditions, but these results do not fully represent the response of microbial communities to nanomaterials in natural environments. Over the years, the effect of nanomaterials infiltrated into the natural environment on the microbial communities has become a popular topic in the field of nano-ecological environment research. It was found that under different environmental conditions, nanomaterials have various effects on the microbial communities. The medium; the coexisting pollutants in the environment and the structure, particle size and surface modification of nanomaterials may cause changes in the structure and function of microbial communities. This paper systematically summarizes the impacts of different nanomaterials on microbial communities in various environments, which can provide a reference for us to evaluate the impacts of nanomaterials released into the environment on the microecology and has certain guiding significance for strengthening the emission control of nanomaterials pollutants.

Nanomaterials in membrane bioreactors: Recent progresses, challenges, and potentials

The use of nanomaterials (NMs) in the fabrication and modification of membranes as well as the coupling of nanomaterial-based processes with membrane processes have been attracted many researchers today. The NMs due to a wide range of types, different chemistry, the possibility of various kinds of functionality, different properties like antibacterial activity, hydrophilicity, and large surface area were applied to enhance the membrane properties. In the membrane bioreactors (MBRs) as a highly successful process of membrane technology in wastewater treatment, the NMs have been applied for improving the efficiency of MBR process. This review assessed the application of NMs both as the modifiers of membrane and as the effective part of hybrid techniques with MBR system for wastewater treatment. The efficiency of NMs blended membranes in the MBR process has been reviewed in terms of antifouling and antibacterial improvement and removal performance of the pollutants. Novel kinds of NMs were recognized and discussed based on their properties and advantages. The NMs-based photocatalytic and electrochemical processes integrated with MBR were reviewed with their benefits and drawbacks. In addition, the effect of the presence of mobilized NPs in the sludge on MBR performance was surveyed. As a result of this review, it can be concluded that nanomaterials generally improve MBR performance. The high flux and antifouling properties can be obtained by adding nanomaterials with hydrophilic and antibacterial properties to the membrane, and further studies are required for photocatalytic NMs applications. In addition, this review shows that the low amounts of NMs in the membrane structure could have an effective influence on the MBR process. Besides, since many studies in the literature are carried out at the laboratory scale, it is thought that pilot and real-scale studies should be carried out to obtain more reliable data.

Effects of salinity on the biological performance of anaerobic membrane bioreactor

The performance of anaerobic membrane bioreactor (AnMBR) was evaluated treating synthetic wastewater with various concentrations of NaCl (0-40 g/L), as well as the recovery phase. The effluent COD removal efficiency decreased from 96.4% to 95.0%, 91.4%, 86.7% and 77.7% with stepwise increasing of salt concentration from 0 to 5, 10, 20 and 40 g NaCl/L, respectively, then gradually increased to 94.1% during the recovery phase. Additionally, the significant changes in the content and composition of soluble microbial products (SMP) and extracellular polymer substance (EPS) were obtained under higher salt stress. GC-MS analyses were carried out for the effluent, and some new types of compounds, such as Dodecane, Undecane, and Ethyl Acetate, were found during salt exposure phases. The characterization of the microbial community was also investigated based on the analysis of genomic 16S rDNA, revealing the increasing salinity (5-40 g NaCl/L) could reduce the diversity of sludge microbial community in AnMBR. Meanwhile, the significant effects on the composition of dominate phyla (Proteobacteria, Bacteroidetes, Firmicutes and Chloroflexi) were found during the salt exposure phase.