Toxicokinetics of microplastics in Macrobrachium nipponense and their impact on the bioavailability of loaded pollutants.

Microplastics (MPs) have unique toxicokinetic (TK) processes that differ from those of soluble pollutants. This study investigated the ingestion, migration, accumulation, and clearance of environmental aging MPs in the Japanese swamp shrimp (Macrobrachium nipponense). The concentrations of plastic additives and personal care products adsorbed onto MPs in natural river water were determined, and TK models for MPs and MPs-loaded pollutants were developed. Results showed that the formation of surface biofilms and alterations in the distribution of MPs in waters caused by environmental aging affect MPs bioavailability, which is mainly related to the feeding habits of shrimp. The decrease in MPs particle size caused by biological digestion and the increase in the number of oxygen-containing functional groups caused by environmental aging affect the TK process of MPs. The TK model of MPs-loaded pollutants revealed the cleaning effect of shrimp on pollutants adsorbed onto MPs during swallowing and spitting MPs. This cleaning effect significantly increases the bioavailability of MPs-associated pollutants in aquatic environments. This study provides a new perspective for understanding the interactions between environmental MPs and their associated pollutants in aquatic ecosystems.

Adsorption and desorption of parachlormetaxylenol by aged microplastics and molecular mechanism.

The addition of active ingredients such as antibacterial agent and non-active ingredients such as plastic microspheres (MPs) in personal care products (PCPs) are the common pollutants in the aquatic environment, and their coexistence poses potential threat to the aquatic ecosystem. As a substitute for the traditional antibacterial ingredients triclosan and triclocarban, the usage of parachlormetaxylenol (PCMX) is on the rise and is widely used in PCPs. In this study, the adsorption and desorption behaviors of PCMX were investigated with two typical MPs, polyvinyl chloride (PVC) and polyethylene (PE), and the effects of different aging modes and molecular mechanisms were explored through batch experiments and density functional theory calculation. Both laboratory aging and field aging resulted in surface wrinkles of MPs, along with an increased proportion of oxygen-containing functional groups (CO, -OH). At the same aging time, the degree of laboratory aging was stronger than that of field aging, and the aging degree of PVC was greater that of PE. The aging process enhanced the adsorption capacity of MPs for PCMX. The equilibrium adsorption capacity of PVC increased from 3.713 mg/g (virgin) to 3.823 mg/g (field aging) and 3.969 mg/g (laboratory aging), while that of PE increased from 3.509 mg/g to 3.879 mg/g and 4.109 mg/g, respectively. Meanwhile, aging also resulted in an increase in the desorption capacity of PCMX from PVC and PE. Oxygen-containing functional groups in aged MPs could serve as adsorption sites for PCMX and improved the electrostatic adsorption capacity. Oxygen-containing groups generated on the surface of aged MPs formed hydrogen bonding with the phenolic hydroxyl groups of PCMX, which became the main driving force for adsorption. Our results reveal the potential impact and mechanism of aging on the adsorption of PCMX by MPs, which provides new insights for the interaction mechanism between environmental MPs and associated contaminants.

Decolorization and detoxification of Brilliant Crocein GR by a newly enriched thermophilic consortium.

The environmental pollution caused by azo dyes at high temperatures has become an urgent problem. However, little attention has been paid to decolorizing azo dyes by thermophilic consortiums. In this study, a thermophilic bacterial consortium (BCGR-T) mainly composed of two genera, namely, Caldibacillus (70.90%) and Aeribacillus (17.63%) was first enriched, which can decolorize Brilliant Crocein GR (BCGR) at high temperatures (50-75 °C), pH values of 6∼8, dye concentrations (100-400 mg/L) and salinities (1-5%, w/v). The enzyme activity results showed that the azoreductase activity was nearly 8.8 times that of the control (p < 0.01), and the intracellular lignin peroxidase was also highly expressed with enzyme activity of 5.64 U (min-1 mg-1 protein) (p < 0.05), indicated that both azoreductase and intracellular lignin peroxidase played an important part in the decolorization process. Furthermore, seven new intermediate metabolic products, including aniline, phthalic acid, 2-carboxy benzaldehyde, phenylacetic acid, benzoic acid, toluene, and 4-methyl-hexanoic acid, were identified. In addition, functional genes related with the azo dye decolorization, such as those encoding the azoreductase, laccase, FMN reductase, NADPH-/NADH-quinone oxidoreductases and NADPH-/NADH dehydrogenases, catechol dioxygenase, homogentisate 1,2-dioxygenase, protocatechuate 3,4-dioxygenase, gentisate 1,2-dioxygenase, azobenzene reductase, naphthalene 1,2-dioxygenase, benzoate/toluate 1,2-dioxygenase, and anthranilate 1,2-dioxygenase and so on were found in the metagenome of the consortium BCGR-T. Finally, a new decolorization pathway of the thermophilic consortium BCGR-T was proposed. In addition, the phototoxicity of BCGR decreased after decolorization. Overall, the thermophilic consortium BCGR-T could be a promising candidate in the treatment of high concentration azo dye wastewater at high temperatures.

Meta-genome analysis of a newly enriched azo dyes detoxification halo-thermophilic bacterial consortium.

Treating textile wastewaters were always inhibited by its higher salt concentration and temperature. In this study, a halo-thermophilic bacterial consortium YM was enriched with ability to decolorize acid brilliant scarlet GR (ABS) at 55 °C and 10% salinity. Under optimum conditions of pH (8), temperature (55 °C), and salinity (10%), YM decolorized 97% of ABS under anaerobic conditions. Alteribacillus was identified to be the dominant genus in consortium YM. Consortium YM showed significant decolorization ability under a wide range of salinity (1%-10%), pH (7-9) and temperature (45 °C-60 °C). The degradation pathway of ABS was proposed by the combination of UV-vis spectral analysis, Fourier transform infrared (FTIR), gas chromatography mass spectrometric (GC-MS), and metagenomic analysis. Azoreductase, which was an important enzyme in decolorization process, was identified with great variation in the genome of consortium YM. Meanwhile, the metabolic intermediates after decolorization was identified with low biotoxicity by phytotoxicity tests. This study first identified that Alterbacillus play an important role in azo dye decolorization and degradation process under halo-thermophlic conditions and provided significant knowledge for azo dye decolorization and degradation process.

Effect of salinity on removal performance of anaerobic membrane bioreactor treating azo dye wastewater.

Membrane bioreactor (MBR) is an attractive option method for treating azo dye wastewater under extreme conditions. The present study assessed the effect of salinity on the performance of anaerobic MBR in treating azo dye wastewater. Increased salinity showed adverse effects on the decolorization efficiency and chemical oxygen demand (COD) removal efficiency. The decolorization efficiency decreased from 95.8% to 82.3% and 73.1% with a stepwise increasing of salinity from 0 to 3% and 5%, respectively. The COD removal efficiency decreased from 80.7% to 71.3% when the salinity increased from 0 to 3% and then decreased to 58.6% at 5% salinity. The volatile fatty acids (VFAs) concentration also increased as the salinity increased. Furthermore, increased salinity led to the elevated production of soluble microbial products (SMP) and extracellular polymeric substances (EPS), which can provide a protective barrier against harsh environments. More serious membrane fouling was observed as the SMP and EPS concentrations increased. The concentration of loosely bound EPS (LB-EPS), tightly bound EPS (TB-EPS), and the polysaccharide/protein (PS/PN) ratios in LB-EPS and TB-EPS all increased when the salinity was elevated. The production of SMP and EPS was caused by the generation of PS in response to the saline environment. Lactobacillus, Lactococcus, Anaerosporobacter, and Pectinatus were the dominant bacteria, and Lactobacillus and Lactococcus were the decolorization bacteria in the MBR. The lack of halophilic bacteria was the main reason for the decreased decolorization efficiency in the salinity environment.

Biodegradable Microplastics: A Review on the Interaction with Pollutants and Influence to Organisms.

Biodegradable plastics attract public attention as promising substitutes for traditional nondegradable plastics which have caused the serious white pollution problem due to their persistence. However, even for biodegradable plastics, natual conditions for the rapid and complete degradation are rare. Even more serious is that biodegradable plastics might be disintegrated into microplastics more rapidly than tranditional plastics, emerging as another threat to the environment. Similar to traditional microplastics, biodegradable microplastics could adsorb many pollutants by various physicochemical effects and release additives. Biodegradable microplastics have been confirmed to be toxic to the organisms as particle matter and the vector as pollutants. Under some conditions, biodegradable microplastics may pose more severe negative impacts on the organisms. With the fierely increasing trend to replace the nondegradable plastic commodities with biodegradable ones, it is necessary to evaluate whether biodegradable plastics and the generated microplastics would alleviate plastic pollution or induce greater ecological impacts.

Comparative Study of Algal Responses and Adaptation Capability to Ultraviolet Radiation with Different Nutrient Regimes.

Frequent outbreaks of harmful algal blooms (HABs) represent one of the most serious outcomes of eutrophication, and light radiation plays a critical role in the succession of species. Therefore, a better understanding of the impact of light radiation is essential for mitigating HABs. In this study, Chlorella pyrenoidosa and non-toxic and toxic Microcystis aeruginosa were mono-cultured and co-cultured to explore algal responses under different nutrient regimes. Comparisons were made according to photosynthetically active radiation (PAR), UV-B radiation exerted oxidative stresses, and negative effects on the photosynthesis and growth of three species under normal growth conditions, and algal adaptive responses included extracellular polymeric substance (EPS) production, the regulation of superoxide dismutase (SOD) activity, photosynthetic pigments synthesis, etc. Three species had strain-specific responses to UV-B radiation and toxic M. aeruginosa was more tolerant and showed a higher adaptation capability to UV-B in the mono-cultures, including the lower sensitivity and better self-repair efficiency. In addition to stable µmax in PAR ad UV-B treatments, higher EPS production and enhanced production of photosynthetic pigments under UV-B radiation, toxic M. aeruginosa showed a better recovery of its photosynthetic efficiency. Nutrient enrichment alleviated the negative effects of UV-B radiation on three species, and the growth of toxic M. aeruginosa was comparable between PAR and UV-B treatment. In the co-cultures with nutrient enrichment, M. aeruginosa gradually outcompeted C. pyrenoidosa in the PAR treatment and UV-B treatment enhanced the growth advantages of M. aeruginosa, when toxic M. aeruginosa showed a greater competitiveness. Overall, our study indicated the adaptation of typical algal species to ambient UV-B radiation and the stronger competitive ability of toxic M. aeruginosa in the UV-radiated waters with severer eutrophication.

Dioxin-like compounds formation mediated by Fe3+-montmorillonite: The substituent effects of halophenols.

Toxic dioxin or/and dioxin-like compounds could be naturally formed from the reaction of halophenols on Fe3+-montmorillonite minerals under ambient conditions. Given that the toxicities and productions of dioxin or/and dioxin-like compounds are largely determined by the number, species, and position of the carried halogen atoms, it is necessary to explore the substituent effects on the reaction of halophenols with Fe3+-montmorillonite. Herein, Fe3+-montmorillonite catalyzed polymerizations of six halophenols were examined in a wide range of relative humidity (10%∼80%) using combinations of mass spectrometry identifications and density functional theory calculations. Results show that both the position and species of the substituents substantially impact the reaction rate, product species, and transformation pathways. In general, regardless of humidity ortho-substituted chlorophenols are more reactive than meta-substituted chlorophenols, which is also supported by the density functional theory calculations indicating that the ortho positions are more likely to be attacked. Regarding substituent species, bromophenols are slightly more reactive and also more easily affected by humidities than chlorophenols, which is due to the weaker electron absorbing ability of the bromine atom than the chlorine atom. Hydroxylated polyhalogenated diphenyl ethers are more frequently detected polymerization products, although hydroxylated polyhalogenated biphenyls are greater quantity of products. Overall, this study provides useful information for understanding the natural formation of dioxin or/and dioxin-like compounds mediated by clay minerals and underlying reaction mechanisms.

Effect of Self-Made TiO2 Nanoparticle Size on the Performance of the PVDF Composite Membrane in MBR for Landfill Leachate Treatment.

The pollutant composition of landfill leachate is complex, and pollutant concentrations change greatly. Moreover, landfill leachates can easily penetrate into the soil and eventually pollute the ground water, which can cause environmental pollution and threaten human health. At present, landfill leachate treatment technology is still not mature. In this paper, the A/O-MBR (Anoxic-Aerobic Membrane Bioreactor) process is proposed to treat landfill leachate. To increase the hydrophilicity of the membranes and reduce the pollution of the membranes, the self-made TiO2 nanoparticles were used to modify the ultrafiltration membranes (PVDF-2). Meanwhile, PVDF-2 composite membranes showed the best separation performance. The optimum operating parameters were determined by changing the concentration of the pollutants in the reactor and selecting the dissolved oxygen, pH, and hydraulic residence time. The results show that the optimum operating conditions of MBR are mixed liquor suspended solids (MLSS) = 3200 mg/L, DO = 1.5-2.5 mg/L in a nitrifying tank, DO = 0-0.5 mg/L in a denitrifying tank, pH = 7-8, and a hydraulic retention time (HRT) = 5 h. To reach the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002), the effluent of the MBR system further enters into the RO system. This work presents an environmentally friendly synthesis of TiO2 nanoparticles and added into PVDF. The addition of self-made TiO2 in PVDF membrane has improved the antifouling performance significantly, which has the potential for the treatment of landfill leachate.

Efficient visible light driven degradation of antibiotic pollutants by oxygen-doped graphitic carbon nitride via the homogeneous supramolecular assembly of urea.

Graphitic carbon nitride (CN), as a non-metal material, has emerged as a promising photocatalyst to address environmental issues with the favorable band gap and chemical stability. The porous oxygen-doped CN nanosheets (CNO) were synthesized by an ecofriendly and efficient self-assembled approach using a sole urea as the precursor. The CNO photocatalysts were derived from the hydrogen-bonded cyanuric acid-urea supramolecular complex, which were obtained by pretreatment of urea at high temperature and pressure. The homogeneous supramolecular assembly was advantageous to the formation of uniform porous and oxygen-doped CN nanosheets. The formation process of the supramolecular intermediate and the CNO nanosheets were investigated. Moreover, doping amount of O in CNO could be controlled by the time of the high-pressure thermal polymerization of urea. The characterization results shown that the O atoms were successfully doped into the framework of CN by substitution the N atoms to form the C-O structures. The obtained CNO photocatalysts demonstrated the excellent visible-light photocatalytic performances for sulfamerazine (SMR) degradation, which was ascribed to synergistic interaction of porous structure and O doping. The degradation intermediates of SMR were identified and the degradation pathway were also proposed. Furthermore, density functional theory (DFT) calculations proved that O doping changed the electronic structure of CN, resulting in more easier to activate O2. This work provides a novel perceptive for the development of high-performance nonmetal photocatalysts by using the homogeneous supramolecular assembly, which exhibits great potential in the environmental treatment.

Processes and mechanisms of phosphorus mobility among sediment, water, and cyanobacteria under hydrodynamic conditions.

Phosphorus (P) has an important role in eutrophication and it is essential to explore the processes and mechanisms of P mobility in natural waters. In this study, laboratory experiments were conducted to simulate the SW system (sediment and water) and SAW system (sediment, algae, and water) under four hydrodynamic intensity conditions (static control, 50 rpm, 125 rpm, and 200 rpm treatments), to investigate P mobility. Results in SW system showed that sediment was an important source of P for overlying water, and the released total P (TP) increased with stronger hydrodynamic intensity, when P associated with metal pools (redox-sensitive P [BD-P] and meta-oxides bound P [NaOH-P]) were the most unstable and easier to migrate into the overlying water. Stronger hydrodynamic disturbances could enhance the processes including sediment resuspension, dissolution of particles, and release of P, when P mobility had a close relationship with redox conditions near sediment-water interface (SWI). Therefore, the release of TP, BD-P, and NaOH-P from sediment increased and decreased in the control and 50-200 rpm treatments over time. In SAW system, the release of TP significantly increased from sediment comparing to SW system, and the growth of Microcystis aeruginosa could selectively enhance the release of BD-P, NaOH-P, and organic P (OP). Meanwhile, the released P from sediment was quickly accumulated by algal cells. The maximum accumulation ability of P by cells, the highest photosynthetic efficiency, and the best growth of M. aeruginosa were observed in 125 rpm treatment. But with excessively strong hydrodynamic intensity (200 rpm treatment), the accumulation ability of P and alkaline phosphatase activity (APA) of M. aeruginosa was suppressed, which might hinder algal utilization of P and inhibit algal growth. Overall, our findings demonstrated the patterns of P mobility in natural ecosystems and could contribute to the understanding of P cycling.

Bioaugmentation treatment of polycyclic aromatic hydrocarbon-polluted soil in a slurry bioreactor with a bacterial consortium and hydroxypropyl-ß-cyclodextrin.

The aim of the study was to verify the effect of bioaugmentation by the bacterial consortium YS with hydroxypropyl-ß-cyclodextrin (HPCD) in a soil slurry. The bacterial consortium YS was enriched from a petroleum-polluted soil using pyrene as sole carbon resource. After 3 weeks, the degradation rate of phenanthrene in CK increased from 22.58% to 55.23 and 78.21% in bioaugmentation (B) and HPCD + bioaugmentation (MB) respectively. The degradation rate of pyrene in CK increased from 17.33% to 51.10% and 60.32% in B and MB respectively in the slurry. The augmented YS persisted in the slurry as monitored by 16S rRNA gene high-throughput sequencing and outcompeted some indigenous bacteria. Enhanced polycyclic aromatic hydrocarbon (PAH) degradation was observed in the addition of HPCD due to the enhanced bioavailability of phenanthrene and pyrene. Additionally, the amount of PAH-degrading bacteria and enzymatic activity in bioaugmentation with HPCD were higher than that in the CK group. The results indicated that bioaugmentation with a bacterial consortium and HPCD is an environmentally friendly method for the bioremediation of PAH-polluted soil.

Effect of iron nitrate modification on elimination of organic matter from landfill leachate by sludge-based activated carbon.

Sludge-based activated carbons (SACs) prepared from sewage sludge and corn straw, were modified by ferric nitrate, and the unmodified SAC and modified SAC were used as the adsorbing agent to treat the landfill leachate, the elimination capacity for chemical oxygen demand (COD) and organic matter in leachate were studied. Based on this, the physicochemical properties of SACs and the components changes in leachate were analyzed and characterized by X-ray photoelectron spectroscopy and three-dimensional fluorescence spectroscopy. The results showed that under optimal experimental conditions, the elimination capacities of SAC372 for COD, biological oxygen demand over 5 days, and NH4+-N in the leachate were 81.58%, 54.73%, and 69.08%, respectively; while the adsorption capacities of modified SAC for these three substances were 86.25%, 63.51%, and 79.15%, respectively. The ferric nitrate modification improved the ability of SAC to eliminate COD and organic matter from leachate slightly, and made the adsorption occurred easily. The adsorption process of unmodified SAC was dominated by multi-layer adsorption, while the adsorption process of modified SAC was dominated by monolayer adsorption. The mass fraction of Fe (2p) in modified SAC remarkably increased, from 0.70% to 26.01%, organic functional groups certain phase of Fe oxides with different valence states were generated in SAC, which provided a substrate for iron-carbon micro electrolysis. After adsorbed by unmodified SAC and modified SAC adsorption, the total fluorescence intensity of in the leachate increased by 17.01% and 116.84%, respectively. Both two SACs could decompose the humic acid-like substances into aromatic protein organic compounds, and modified SAC could further decompose the soluble microbial byproduct-like substances.

Performance and mechanism of hydrogen sulfide removal by sludge-based activated carbons prepared by recommended modification methods.

The sludge-based activated carbons (SACs) were prepared by sewage sludge and corn straw and modified by ferric nitrate. The H2S removal performance and the desulfurization mechanism of the modified SAC were studied. Results showed that breakthrough sulfur capacity and saturation sulfur capacity of the SAC prepared by recommended modification were 27.209 mg/g and 48.098 mg/g, which were as 4.68 times and 7.02 times larger as those before modification, respectively. Additionally, results showed that the desulfurization products of unmodified SAC were mainly sulfur, while that of modified SAC were mainly sulfate. These results indicated that ferric nitrate modification changed the way of hydrogen sulfide removal by SAC: the desulfurization process of unmodified SAC can be expressed as S2- → S0 → S4+ → S6+, and the oxidative active component was dominated by O*, while that of modified SAC can be expressed as S2- → S0 → S6+, and the oxidative active components are both Fe3+ and O*.

Development and characterization of a halo-thermophilic bacterial consortium for decolorization of azo dye.

Textile wastewater is characterized by high salinity and high temperature, and azo dye decolorization by mixed cultures under extreme salinity and thermophilic environments has received little attention. High salinity and temperature inhibit the biodecolorization efficiency in textile wastewater. In the present study, a halo-thermophilic bacterial consortium (HT1) that can decolorize azo dye at 10% salinity and 50 °C was enriched. Bacillus was the dominant genus, and this genus may play a key role in the decolorization process. HT1 can decolorize metanil yellow G (MYG) at a wide range of pH values (6-8), temperatures (40-60 °C), dye concentrations (100-200 mg/L) and salinities (1-15%). Laccase, manganese peroxidase, lignin peroxidase and azoreductase are involved in the decolorization process of MYG. In addition, the decolorization pathway of MYG was proposed based on GC-MS and FTIR results. The toxicity of MYG decreased after decolorization by HT1. A metagenomic sequencing approach was applied to identify the functional genes involved in degradation. Overall, this halo-thermophilic bacterial consortium could be a promising candidate for the treatment of textile wastewater under elevated temperature and salinity conditions.

Enhanced azo dye biodegradation at high salinity by a halophilic bacterial consortium.

The aim of this work was to study the bioaugmentation of hydrolysis acidification (HA) by a halophilic bacterial consortium. A bacterial consortium was enriched at 5% salinity, and it decolorized metanil yellow G (MYG) at salinities of 1%-15% and dye concentrations of 100-400 mg/L under static conditions. A HA system was constructed to assess the effectiveness of bioaugmentation by the halophilic bacterial consortium. The HA system showed obviously better performance for decolorization and CODMn removal and presented higher the 5-day biological oxygen demand (BOD5)/CODMn (B/C) ratio after bioaugmentation. MiSeq sequencing results indicated that the bacterial communities remarkably shifted and that the bacterial diversity was increased after bioaugmentation. Marinobacterium invaded the native microbe community and became the dominant bacterial genus in the bioaugmented HA, and it played a key role in azo dye decolorization. Therefore, bioaugmentation with a halophilic bacterial consortium improved the HA system for decolorization of azo compounds.

Decolorization of Metanil Yellow G by a halophilic alkalithermophilic bacterial consortium.

Increased temperature, salinity and alkalinity restrict the biodecolorization rate of textile wastewater. In the present study, the halophilic alkalithermophilic bacterial consortium ZSY, which can decolorize azo dyes under 10% salinity, pH 10 and 50 °C, was enriched. It can decolorize Metanil Yellow G (MYG) under a wide range of pH values (8-10), temperatures (40-50 °C), dye concentrations (100-400 mg/L) and salinity levels (1%-10%). Laccase (Lac), lignin peroxidase (Lip), nicotinamide adenine dinucleotide-dichlorophenol indophenol reductase (NADH-DCIP) and azoreductase are involved in the decolorization process. A decolorization pathway of MYG was proposed via gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR). The toxicity of MYG decreased after decolorization by ZSY consortium. A metagenomic sequencing approach was subsequently applied to identify the functional genes involved in decolorization. Overall, this halophilic alkalithermophilic bacterial consortium could be a promising candidate for the treatment of textile wastewater in environments with increased temperature, salinity and alkalinity.

Decolorization and detoxification of azo dye by halo-alkaliphilic bacterial consortium: Systematic investigations of performance, pathway and metagenome.

The high pH and salinity of textile wastewater is a major hindrance to azo dye decolorization. In this study, a mixed bacterial consortium ZW1 was enriched under saline (10% salinity) and alkaline (pH 10.0) conditions to decolorize Methanil Yellow G (MY-G). Consortium ZW1 was mainly composed of Halomonas (49.8%), Marinobacter (30.7%) and Clostridiisalibacter (19.2%). The effects of physicochemical factors were systematically investigated, along with the degradation pathway and metagenome analysis. The co-carbon source was found to be necessary, and the addition of yeast extract led to 93.3% decolorization of 100 mg/L MY-G within 16 h (compared with 1.12% for control). The optimum pH, salinity, temperature and initial dye concentration were 8.0, 5-10%, 40 °C and 100 mg/L, respectively. The typical dye-related degradation enzymes were most effective at 10% salinity. Consortium ZW1 was also able to differentially decolorize five other direct and acidic dyes in a short period. Phototoxicity tests revealed the detoxification of MY-G degradation products. Combining UV-vis, FTIR and GC-MS detection, the MY-G degradation pathway by consortium ZW1 was proposed. Furthermore, metagenomic approach was used to elucidate the functional potential of genes in MY-G biodegradation. These results signify the broad potential application of halo-alkaliphilic consortia in the bioremediation of dyeing wastewater.

Effect of salinity on removal performance in hydrolysis acidification reactors treating textile wastewater.

Hydrolysis acidification (HA) is a classical method for synthetic textile wastewater treatment. However, the salinity effect on the functional mechanism of the microorganisms carrying out HA has rarely been researched. In the present study, the salinity effect on the dye removal efficiency was investigated, and the soluble microbial products (SMP), extracellular polymeric substances (EPS), and microbial community were analyzed at different salinities. The dye and COD removal rates in the HA reactor decreased with increasing salinity. Volatile fatty acids (VFAs) accumulated. The remarkable increases in SMP and EPS were found at high salinity, mainly because more polysaccharides were synthesized than protein. In addition, sequencing analysis showed that high salinity altered the microbial community structure, and Lactococcus, Raoultella and Enterococcus were the decolorizing bacteria at high salinity. This work will improve the understanding of the influence of salinity on the removal efficiency and microbial community during HA.

Azo dye decolorization by a halotolerant consortium under microaerophilic conditions.

As a result of the use of a large amount of salt in dye industries, azo dye decolorization is often needed under hypersaline environments and low dissolved oxygen. Consortium GG-1, which is able to decolorize azo dyes in high salt concentrations and microaerophilic conditions, can be enriched using Metanil Yellow. Consortium GG-1 is mainly composed of Zobellella (62.25%), Rheinheimera (12.4%) and Marinobacterium (9.44%) and is able to decolorize azo dyes under 1%-10% salinity. The activities of azoreductase, laccase and lignin peroxidase were also measured. Together with the detected intermediates and the results obtained from FTIR, the decolorization process of Metanil Yellow was proposed. The influences of pH, initial concentration of azo dyes and concentration of yeast extract on the decolorization rate were also detected. Meanwhile, consortium GG-1 was identified with wide substrate specificity to dyes such as Direct Blue B, Acid Black ATT, and Acid Violet 7. Therefore, consortium GG-1 was identified with potential use in azo dye elimination.