RESUMO
Due to the impacts of refractory organic pollutants and environment on the water treatment system, the sewage quality can not reach the standard. It is an effective measure to improve the efficiency of wastewater treatment by introducing exogenous engineering strains with relevant functional genes and the ability of horizontal gene transfer. In sewage treatment system, there are bacteria secreting signal molecules with quorum sensing. When population density reaches induction threshold, the bacteria would activate the related genes expression (such as biofilm formation, bioluminescent, antibiotics synthesis and virulence factor expression, etc.) through releasing signaling molecules, and thus trigger the behavior of other groups. Previously, researches about quorum sensing mainly concentrated on signal transduction, microbial social behavior, and medical microbiology. In recent years, stu-dies found that quorum sensing plays an important role in wastewater biological treatment and affects the colonization of the microorganism strain and pollutants degradation. Therefore, the regulation of quorum-sensing behavior is the key factor in the bioaugmentation performance. Here, we review the signaling molecules mechanism, the release of signaling molecules and its influence factors, the colonization of microbial community and the removal of pollutants. We further discussed the research from the perspective of quorum sensing biological process. The aim was to provide new idea for the effective implementation of bioaugmentation technology and the improvement of wastewater treatment efficiency, and to provide a theoretical reference for the in-depth understanding of quorum sensing regulation behavior in the process of bioaugmentation.
Assuntos
Poluentes Ambientais , Purificação da Água , Percepção de Quorum/fisiologia , Esgotos , Bactérias/genética , Poluentes Ambientais/metabolismoRESUMO
To evaluate the long-term performance of bioretention cell (BRC), a study was undertaken to assess the flow distribution and conductivity. Despite initial conductivity of the original medium being the common predictor of hydraulic performance, most of the BRCs are affected by conductivity variations during actual operation. This happen due to the fact that microbial behavior plays an important role in the conductivity variations. This linkage may occur when bacteria as inert colloids transports between particles and biodegrades dissolved pollutants, either promoting or retarding flow distribution and conductivity in BRC. Flow distribution was determined by numerical simulation and tracer test, and the correlation between conductivity and flow distribution was revealed by conductivity experiment coupled with flow distribution analysis. Results revealed a non-uniform flow distribution in BRC, and seepage flow in submerged zone was virtually impossible push flow. Conductivity had an inversely proportional relationship with hydraulic efficiency where hydraulic efficiency reached the highest value (0.297) under a low hydraulic conductivity (0.000107 m/s, approximately K/Kini = 0.79). Primary cause of hydraulic capacity reduction was the initial permeability decrease due to medium structure changes. Results revealed a sharp upward trend followed by a slight decrease, and then, stabilized to a stable infiltration stage. Permeation process of sewage influent was similar to the one of potable water where the permeability reduced to 0.000102 m/s after 450 h and declined continuously. Thus, it is clear that flow distribution and conductivity in bioretention must be estimated more accurately on a microscopic scale.
