lA multiple PAHs-degrading Shinella sp. strain and its potential bioremediation in wastewater

Characteristics of polycyclic aromatic hydrocarbons (PAHs) removal by nanofiltration with and without coexisting organics

Polycyclic aromatic hydrocarbons (PAHs) are contaminants of great concern owing to their persistence, toxicity, and bioaccumulation in aquatic environments. In this study, nanofiltration (NF) was used to investigate the removal of naphthalene (NAP) and phenanthrene (PHE) using three membranes of NF270, NF90, and DK. Subsequently, we examined the effects of coexisting organics on PAHs removal. Based on the results, DK was determined to be the optimal membrane for removing PAHs by comparing the membrane flux and pollutant rejection. The membrane flux reached 34.32 L/m2·h, and the NAP and PHE rejections were 92.21% and 97.85%, respectively, at transmembrane pressure (TMP) of 5 bar using DK. Coexisting organics decreased the membrane fluxes of NF270 and DK in the following order: protein > glucose > humic acid. The NAP and PHE rejections were obviously improved using NF270 in the following order: humic acid > protein > glucose. The PHE rejection was slightly improved using DK. A low concentration of organics could reduce the NAP rejection using DK; however, the NAP rejection could be restored at high concentrations of organics, except for humic acid. Coexisting organics could cause severe membrane fouling. The order of the effect of different coexisting organics on membrane fouling was protein > humic acid > glucose. The total investment and operating costs were about 1.47 and 0.187 million dollars, respectively, for treating PAHs solution using DK when the feed flow was 300 m3/d.

Degradation of polycyclic aromatic hydrocarbons in aquatic environments by a symbiotic system consisting of algae and bacteria: green and sustainable technology

Polycyclic aromatic hydrocarbons (PAHs) are genotoxic, carcinogenic, and persistent in the environment and are therefore of great concern in the environmental protection field. Due to the inherent recalcitrance, persistence and nonreactivity of PAHs, they are difficult to remediate via traditional water treatment methods. In recent years, microbial remediation has been widely used as an economical and environmentally friendly degradation technology for the treatment of PAH-contaminated water. Various bacterial and microalgal strains are capable of potentially degrading or transforming PAHs through intrinsic metabolic pathways. However, their biodegradation potential is limited by the cytotoxic effects of petroleum hydrocarbons, unfavourable environmental conditions, and biometabolic limitations. To address this limitation, microbial communities, biochemical pathways, enzyme systems, gene organization, and genetic regulation related to PAH degradation have been intensively investigated. The advantages of algal-bacterial cocultivation have been explored, and the limitations of PAHs degradation by monocultures of algae or bacteria have been overcome by algal-bacterial interactions. Therefore, a new model consisting of a "microalgal-bacterial consortium" is becoming a new management strategy for the effective degradation and removal of PAHs. This review first describes PAH pollution control technologies (physical remediation, chemical remediation, bioremediation, etc.) and proposes an algal-bacterial symbiotic system for the degradation of PAHs by analysing the advantages, disadvantages, and PAH degradation performance in this system to fill existing research gaps. Additionally, an algal-bacterial system is systematically developed, and the effects of environmental conditions are explored to optimize the degradation process and improve its technical feasibility. The aim of this paper is to provide readers with an effective green and sustainable remediation technology for removing PAHs from aquatic environments.

Determining the degradation mechanism and application potential of benzopyrene-degrading bacterium Acinetobacter XS-4 by screening

In industrial wastewater treatment, organic pollutants are usually removed by in-situ microorganisms and exogenous bactericides. Benzo [a] pyrene (BaP) is a typical persistent organic pollutant and difficult to be removed. In this study, a new strain of BaP degrading bacteria Acinetobacter XS-4 was obtained and the degradation rate was optimized by response surface method. The results showed that the degradation rate of BaP was 62.73% when pH= 8, substrate concentration was 10 mg/L, temperature was 25 °C, inoculation amount was 15% and culture rate was 180 r/min. Its degradation rate was better than that of the reported degrading bacteria. XS-4 is active in the degradation of BaP. BaP is degraded into phenanthrene by 3, 4-dioxygenase (α subunit and β subunit) in pathway Ⅰ and rapidly forms aldehydes, esters and alkanes. The pathway Ⅱ is realized by the action of salicylic acid hydroxylase. When sodium alginate and polyvinyl alcohol were added to the actual coking wastewater to immobilize XS-4, the degradation rate of BaP was 72.68% after 7 days, and the removal effect was better than that of single BaP wastewater (62.36%), which has the application potential. This study provides theoretical and technical support for microbial degradation of BaP in industrial wastewater.