Isolation of a naphthalene-degrading strain from activated sludge and bioaugmentation with it in a MBR treating coal gasification wastewater

Advanced treatment of coking wastewater: Recent advances and prospects

Advanced treatment of refractory industrial wastewater is still a challenge. Coking wastewater is one of coal chemical wastewater, which contains various refractory organic pollutants. To meet the more and more rigorous discharge standard and increase the reuse ratio of coking wastewater, advanced treatment process must be set for treating the biologically treated coking wastewater. To date, several advanced oxidation processes (AOPs), including Fenton, ozone, persulfate-based oxidation, and iron-carbon micro-electrolysis, have been applied for the advanced treatment of coking wastewater. However, the performance of different advanced treatment processes changed greatly, depending on the components of coking wastewater and the unique characteristics of advanced treatment processes. In this review article, the state-of-the-art advanced treatment process of coking wastewater was systematically summarized and analyzed. Firstly, the major organic pollutants in the secondary effluents of coking wastewater was briefly introduced, to better understand the characteristics of the biologically treated coking wastewater. Then, the performance of various advanced treatment processes, including physiochemical methods, biological methods, advanced oxidation methods and combined methods were discussed for the advanced treatment of coking wastewater in detail. Finally, the conclusions and remarks were provided. This review will be helpful for the proper selection of advanced treatment processes and promote the development of advanced treatment processes for coking wastewater.

Overview of enhancing biological treatment of coal chemical wastewater: New strategies and future directions

Coal chemical wastewater (CCW) is a type of refractory industrial wastewater, and its treatment has become the main bottleneck restricting the sustainable development of novel coal chemical industry. Biological treatment is considered as an economical, effective and environmentally friendly technology for CCW treatment. However, conventional biological process is difficult to achieve the efficient removal of refractory organics because of CCW with the characteristics of composition complexity and high toxicity. Therefore, seeking the novel enhancement strategy appears to be a favorable solution for enhancing biological treatment efficiency of CCW. This review focuses on presenting a comprehensive picture about the exogenous enhancement strategies for CCW biological treatment. The performance and potential application of exogenous enhancement strategies, including co-metabolic substrate enhancement, biofilm filler enhancement, adsorption material enhancement and conductive mediator enhancement, were expounded. Meanwhile, the enhancing mechanisms of different strategies were comprehensively discussed from a biological perspective. Furthermore, the prospects of enhancement strategies based on the engineering performance, economic cost and environmental impact (3E) evaluation were introduced. And novel enhancement strategy based on "low carbon emissions", "resource recycling" and "water environment security" in the context of carbon neutrality was proposed. Taken together, this review provides technical reference and new direction to facilitate the regulation and optimization of typical industrial wastewater biological treatment.

Advantages of residual phenol in coal chemical wastewater as a co-metabolic substrate for naphthalene degradation by microbial electrolysis cell

The use of co-metabolic substrates is effective for polycyclic aromatic hydrocarbons (PAHs) removal, but the potential of the high phenol concentrations in coal chemical wastewater (CCW) as a co-metabolic substrate in microbial electrolysis cell (MEC) has been neglected. In this study, the efficacy of varying phenol concentrations in comparison to simple substrates for degrading naphthalene in MEC under comparable COD has been explored. Results showed that phenol as a co-metabolic substrate outperformed sodium acetate and glucose in facilitating naphthalene degradation efficiency at 50 mg-COD/L. The naphthalene removal efficiency from RP, RA, and RG was found to be 84.11 ± 0.44 %, 73.80 ± 0.27 % and 72.43 ± 0.34 %, respectively. Similarly, phenol not only enhanced microbial biomass more effectively, but also exhibited optimal COD metabolism capacity. The addition of phenol resulted in a stepwise reduction in the molecular weight of naphthalene, whereas sodium acetate and glucose led to more diverse degradation pathways. Some bacteria with the potential ability to degrade PAHs were detected in phenol-added MEC, including Alicycliphilus, Azospira, Stenotrophomonas, Pseudomonas, and Sedimentibacter. Besides, phenol enhanced the expression of ncrA and nmsA genes, leading to more efficient degradation of naphthalene, with ncrA responsible for mediating the reduction of the benzene ring in naphthalene and nmsA closely associated with the decarboxylation of naphthalene. This study provides guidance for the effective co-degradation of PAHs in CCW with MEC, demonstrating the effectiveness of using phenol as a co-substrate relative to simple substrates in the removal of naphthalene.

Transcriptome analysis reveals self-redox mineralization mechanism of azo dyes and novel decolorizing hydrolases in Aspergillus tabacinus LZ-M

Bio-degradation is the most affordable method of azo dye decontamination, while its drawbacks such as aromatic amines accumulation and low degradation efficiency must be overcome. In this study, a novel mechanism of azo dye degradation by a fungus was discovered. At a concentration of 400 mg/L, the decolorization efficiency of Acid Red 73 (AR73) by Aspergillus tabacinus LZ-M was 90.28%. Metabolite analysis and transcriptome sequencing analysis revealed a self-redox process of AR73 degradation, where the electrons generated in carbon oxidation were transferred to the reduction of -C-N = and -NN. The metabolites, 2-hydroxynaphthalene and N-phenylnitrous amide were mineralized into CO₂ through catechol pathway and a glycolytic process. Furthermore, the mineralization ratio of dye was computed to be 31.8% by the carbon balance and electron balance. By using comparative transcriptome, a novel decoloring enzyme Ord95 was discovered in unknown genes through gene cloning. It hydrolyzed AR73 into 2-hydroxynaphthalene and N-phenylnitrous amide, containing a glutathione S-transferase domain with three arginines as key active sites. Here the new mechanism of azo dye degradation was discovered with identification of a novel enzyme in Aspergillus tabacinus LZ-M.

Salicylate or Phthalate: The Main Intermediates in the Bacterial Degradation of Naphthalene

Polycyclic aromatic hydrocarbons (PAHs) are widely presented in the environment and pose a serious environmental threat due to their toxicity. Among PAHs, naphthalene is the simplest compound. Nevertheless, due to its high toxicity and presence in the waste of chemical and oil processing industries, naphthalene is one of the most critical pollutants. Similar to other PAHs, naphthalene is released into the environment via the incomplete combustion of organic compounds, pyrolysis, oil spills, oil processing, household waste disposal, and use of fumigants and deodorants. One of the main ways to detoxify such compounds in the natural environment is through their microbial degradation. For the first time, the pathway of naphthalene degradation was investigated in pseudomonades. The salicylate was found to be a key intermediate. For some time, this pathway was considered the main, if not the only one, in the bacterial destruction of naphthalene. However, later, data emerged which indicated that gram-positive bacteria in the overwhelming majority of cases are not capable of the formation/destruction of salicylate. The obtained data made it possible to reveal that protocatechoate, phthalate, and cinnamic acids are predominant intermediates in the destruction of naphthalene by rhodococci. Pathways of naphthalene degradation, the key enzymes, and genetic regulation are the main subjects of the present review, representing an attempt to summarize the current knowledge about the mechanism of the microbial degradation of PAHs. Modern molecular methods are also discussed in the context of the development of “omics” approaches, namely genomic, metabolomic, and proteomic, used as tools for studying the mechanisms of microbial biodegradation. Lastly, a comprehensive understanding of the mechanisms of the formation of specific ecosystems is also provided.

Expression, purification, and characterization of a metagenomic thioesterase from activated sludge involved in the degradation of acylCoA-derivatives

Metagenomic libraries are a novel and powerful approach to seek for pathways involved in xenobiotic degradation, since this technique abolishes the need for cultivating microorganisms that otherwise would be overlooked if they cannot grow on standard laboratory media and conditions. In this paper, we describe the expression, purification and characterization of a novel metagenomic thioesterase which was described to be involved in phenylacetic acid degradation (A. Sánchez-Reyes, R. Batista-García, G. Valdés-García E. Ortiz, L. Perezgasga, A. Zárate-Romero, N. Pastor, J. L. Folch-Mallol, A Family 13 thioesterase isolated from an activated sludge metagenome: insights into aromatic compounds metabolism, Proteins 85 (2017) 1222-1237). According to similarity and phylogenetic analyses, the enzyme seems to belong to an Actinobacterium. Nevertheless, after a process of denaturation and refolding, the protein expressed in E. coli was obtained in an active form. New data concerning the substrate preferences for this enzyme are presented which suggest that this thioesterase could be involved in breaking the ester bond in the CoA-linear acyl derivatives of the phenylacetic acetic pathway.

Current Status of the Degradation of Aliphatic and Aromatic Petroleum Hydrocarbons by Thermophilic Microbes and Future Perspectives

Contamination of the environment by petroleum products is a growing concern worldwide, and strategies to remove these contaminants have been evaluated. One of these strategies is biodegradation, which consists of the use of microorganisms. Biodegradation is significantly improved by increasing the temperature of the medium, thus, the use of thermophiles, microbes that thrive in high-temperature environments, will render this process more efficient. For instance, various thermophilic enzymes have been used in industrial biotechnology because of their unique catalytic properties. Biodegradation has been extensively studied in the context of mesophilic microbes, and the mechanisms of biodegradation of aliphatic and aromatic petroleum hydrocarbons have been elucidated. However, in comparison, little work has been carried out on the biodegradation of petroleum hydrocarbons by thermophiles. In this paper, a detailed review of the degradation of petroleum hydrocarbons (both aliphatic and aromatic) by thermophiles was carried out. This work has identified the characteristics of thermophiles, and unraveled specific catabolic pathways of petroleum products that are only found with thermophiles. Gaps that limit our understanding of the activity of these microbes have also been highlighted, and, finally, different strategies that can be used to improve the efficiency of degradation of petroleum hydrocarbons by thermophiles were proposed.

Isolation and characterization of organic matter-degrading bacteria from coking wastewater treatment plant

As a step toward bioaugmentation of coking wastewater treatment 45 bacteria strains were isolated from the activated sludge of a coking wastewater treatment plant (WWTP). Three strains identified as Bacillus cereus, Pseudomonas synxantha, and Pseudomonas pseudoaligenes exhibited high dehydrogenase activity which indicates a strong ability to degrade organic matter. Subsequently all three strains showed high naphthalene degradation abilities. Naphthalene is a refractory compound often found in coking wastewater. For B. cereus and P. synxantha the maximum naphthalene removal rates were 60.4% and 79.8%, respectively, at an initial naphthalene concentration of 80 mg/L, temperature of 30 °C, pH of 7, a bacteria concentration of 15% (V/V), and shaking speed of 160 r/min. For P. pseudoaligenes, the maximum naphthalene removal rate was 77.4% under similar conditions but at 35 °C.

A review: Driving factors and regulation strategies of microbial community structure and dynamics in wastewater treatment systems

The performance and stabilization of biological wastewater treatment systems ¹are closely related to the microbial community structure and dynamics. In this paper, the effects and mechanisms of influent composition, process configuration, operating parameters (dissolved oxygen [DO], pH, hydraulic retention time [HRT] and sludge retention time [SRT]) and environmental condition (temperature) to the change of microbial community structure and process performance (nitrification, denitrification, biological phosphorus removal, organics mineralization and utilization, etc.) are critically reviewed. Furthermore, some strategies for microbial community structure regulation, mainly bioaugmentation, process adjustment and operating parameters optimization, applied in the current wastewater treatment systems are also discussed. Although the recent studies have strengthened our understanding on the relationship between microbial community structure and wastewater treatment process performance, how to fully tap the microbial information, optimize the microbial community structure and maintain the process performance in wastewater treatment systems are still full of challenges.

Bioremediation techniques-classification based on site of application: principles, advantages, limitations and prospects

Environmental pollution has been on the rise in the past few decades owing to increased human activities on energy reservoirs, unsafe agricultural practices and rapid industrialization. Amongst the pollutants that are of environmental and public health concerns due to their toxicities are: heavy metals, nuclear wastes, pesticides, green house gases, and hydrocarbons. Remediation of polluted sites using microbial process (bioremediation) has proven effective and reliable due to its eco-friendly features. Bioremediation can either be carried out ex situ or in situ, depending on several factors, which include but not limited to cost, site characteristics, type and concentration of pollutants. Generally, ex situ techniques apparently are more expensive compared to in situ techniques as a result of additional cost attributable to excavation. However, cost of on-site installation of equipment, and inability to effectively visualize and control the subsurface of polluted sites are of major concerns when carrying out in situ bioremediation. Therefore, choosing appropriate bioremediation technique, which will effectively reduce pollutant concentrations to an innocuous state, is crucial for a successful bioremediation project. Furthermore, the two major approaches to enhance bioremediation are biostimulation and bioaugmentation provided that environmental factors, which determine the success of bioremediation, are maintained at optimal range. This review provides more insight into the two major bioremediation techniques, their principles, advantages, limitations and prospects.

Bioaugmentation: An Emerging Strategy of Industrial Wastewater Treatment for Reuse and Discharge

A promising long-term and sustainable solution to the growing scarcity of water worldwide is to recycle and reuse wastewater. In wastewater treatment plants, the biodegradation of contaminants or pollutants by harnessing microorganisms present in activated sludge is one of the most important strategies to remove organic contaminants from wastewater. However, this approach has limitations because many pollutants are not efficiently eliminated. To counterbalance the limitations, bioaugmentation has been developed and consists of adding specific and efficient pollutant-biodegrading microorganisms into a microbial community in an effort to enhance the ability of this microbial community to biodegrade contaminants. This approach has been tested for wastewater cleaning with encouraging results, but failure has also been reported, especially during scale-up. In this review, work on the bioaugmentation in the context of removal of important pollutants from industrial wastewater is summarized, with an emphasis on recalcitrant compounds, and strategies that can be used to improve the efficiency of bioaugmentation are also discussed. This review also initiates a discussion regarding new research areas, such as nanotechnology and quorum sensing, that should be investigated to improve the efficiency of wastewater bioaugmentation.

Pseudomonas sp. LZ-Q continuously degrades phenanthrene under hypersaline and hyperalkaline condition in a membrane bioreactor system

Graphical Abstract

Abstract

Phenanthrene is one of the most recalcitrant components of crude oil-contaminated wastewater. An efficient phenanthrene-degrading bacterium Pseudomonas sp. strain named LZ-Q was isolated from oil-contaminated soil near the sewage outlet of a petrochemical company. Pseudomonas sp. LZ-Q is able to degrade 1000 mg/L phenanthrene in Bushnell-Hass mineral salt medium. It also degrades other polycyclic aromatic hydrocarbons such as naphthalene, anthracene, pyrene, petrol, and diesel at broad ranges of salinities of 5 g/L to 75 g/L, pHs of 5.0–10.0, and temperatures of 10–42 °C. Therefore, Pseudomonas sp. LZ-Q could be a good candidate for remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated wastewater. A membrane bioreactor (MBR) was applied to investigate the remediation ability of the strain LZ-Q. Wastewater containing phenanthrene with pH of 8, salinity of 35 g/L, and COD of 500 mg/L was continuously added to the system (HRT = 3 h). Results showed that Pseudomonas sp. LZ-Q is capable of degrading 96% of 20 mg/L phenanthrene and 94% of 500 mg/L COD for 60 days in a continuous mode. These results showed that the MBR system with strain LZ-Q might be a good approach for PAHs’ remediation in industrial wastewaters.