Metagenomic Insight Reveals the Microbial Structure and Function of the Full-Scale Coking Wastewater Treatment System:Gene-Based Nitrogen Removal

Microbial communities play crucial roles in pollutant removal and system stability in biological systems for coking wastewater(CWW)treatment,but a comprehensive understanding of their structure and functions is still lacking.A five month survey of four sequential bioreactors,anoxic 1/oxic 1/anoxic 2/oxic 2(A1/O1/A2/O2),was carried out in a full-scale CWW treatment system in China to elucidate operational performance and microbial ecology.The results showed that A1/O1/A2/O2 had excellent and stable performance for nitrogen removal.Both total nitrogen(TN;(17.38±6.89)mgL1)and ammonium-nitrogen(NH4 t-N;(2.10±1.34)mg·L^(-1))in the final biological effluent satisfied the Chinese national standards for CWW.Integrated analysis of 16S ribosome RNA(rRNA)sequencing and metagenomic sequencing showed that the bacterial communities and metagenomic function profiles of A1 and O1 shared similar functional structures,while those of A2 significantly varied from those of other bioreactors(p<0.05).The results indicated that microbial activity was strongly connected with activated sludge function.Nitrosospira,Nitrosomonas,and SM1A02 were responsible for nitrification during the primary anoxic-oxic(AO)stage and Azoarcus and Thauera acted as important denitrifiers in A2.Nitrogen cycling-related enzymes and genes work in the A1/O1/A2/O2 system.Moreover,the hao genes catalyzing hydroxylamine dehydrogenase(EC 1.7.2.6)and the napA and napB genes catalyzing nitrate reductase(EC 1.9.6.1)played important roles in the nitrification and denitrification processes in the primary and secondary AO stages,respectively.The mixed liquor suspended solids(MLSS)/total solids(TS),TN removal rate(RR),total organic carbon(TOC)(RR),and NH_(4)^(+)t-N(RR)were the most important environmental factors for regulating the structure of core bacterial genera and nitrogen-cycling genes.Proteobacteria were the potential main participants in nitrogen metabolism in the A1/O1/A2/O2 system for CWW treatment.This study provides an original and comprehensive understanding of the microbial community and functions at the gene level,which is crucial for the efficient and stable operation of the full-scale biological process for CWW treatment.

A review of CFD simulation in pressure driven membrane with fouling model and anti-fouling strategy

Pressure-driven membrane filtration systems are widely utilized in wastewater treatment,desalination,and water reclamation and have received extensive attention from researchers.Computational fluid dynamics(CFD)offers a convenient approach for conducting mechanistic studies of flow and mass transfer characteristics in pressure-driven systems.As a signature phenomenon in membrane systems,the concentration polarization that accompanies the permeation process is a key factor in membrane performance degradation and membrane fouling intensification.Multiple fouling models(scaling,biofouling and colloidal particle fouling)based on CFD theory have been constructed,and considerable research has been conducted.Several representative antifouling strategies with special simulation methods,including patterned membranes,vibration membranes,rotation membranes,and pulsatile flows,have also been discussed.Future studies should focus on refining fouling models while considering local hydrodynamic characteristics;experimental observation tools focusing on the internal structure of inhomogeneous fouling layers;techno-economic model of antifouling strategies such as vibrational,rotational and pulsatile flows;and unfavorable hydraulic phenomena induced by rapidly changing flows in simulations.

Effect of solid particle erosion on fracture strength of low density polyethylene film

In this study,the infuence of solid particle erosion on the fracture strength of low density polyethylene(LDPE)film under con-trolled conditions is investigated through impact experiments.The variations in the residual fracture stress as well as the residual fracture strain of the LDPE flm after solid particle impact against the impact angle(α),impact velocity(νp)and impact duration(t)are analysed.The study revealed that the fracture stress and the fracture strain of the LDPE film decrease with an increase in the impact duration,and the degradation rate increases with the impact velocity and impact angle.Furthermore,the fracture stress and the fracture strain of LDPE film decrease exponentially against the impact energy under the same particle impact angle condition,and the reductions of fracture stress and fracture strain increase quasi-linearly with the sine-squared impact angle under the same impact energy.The study proposes empirical models to predict the attenuation of the fracture stress and the fracture strain of LDPE films due to the finite particle impact energy.