New insights of enhanced anaerobic degradation of refractory pollutants in coking wastewater: Role of zero-valent iron in metagenomic functions

Long-term evaluating the strengthening effects of iron-carbon mediator for coking wastewater treatment in EGSB reactor

Coking wastewater (CWW) treatment is difficult due to its complex composition and high biological toxicity. Iron-carbon mediators was used to enhance the treatment of CWW through iron-carbon microelectrolysis (ICME). The results indicated that the removal rate of COD and phenolic compounds were enhanced by 24.1 % and 23.5 %, while biogas production and methane content were promoted by 50 % and 7 %. Microbial community analysis indicated that iron-carbon mediators had a transformative impact on the reactor's performance and dependability by enriching microorganisms involved in direct and indirect electron transfer, such as Anaerolineae and Methanothrix. The mediator also produced noteworthy gains in LB-EPS and TB-EPS, increasing by roughly 109.3 % and 211.6 %, respectively. PICRISt analysis demonstrated that iron-carbon mediators effectively augment the abundance of functional genes associated with metabolism, Citrate cycle, and EET pathway. This study provides a new approach for CWW treatment.

Mechanism of self-supporting montmorillonite composite material for bio-enhanced degradation of chlorotetracycline: Electron transfer and microbial response

The efficient degradation of antibiotics holds significant implications for mitigating environmental pollution. This study synthesized a montmorillonite chitosan composite material (MMT-CS) using the gel template method. Subsequently, a bio-enhanced reactor was constructed to facilitate the degradation of chlorotetracycline (CTC). The addition of MMT-CS composite material enables the degradation of different concentrations of CTC. MMT-CS, a conductive carrier, effectively promotes microbial adhesion and boosts the metabolic activity of functional microorganisms. Additionally, it facilitates the maintenance of microbial activity under CTC pressure by promoting the secretion of extracellular polymeric substances, increasing critical enzyme activity, and enhancing the electron transfer capacity within the system. In this MMT-CS bio-enhanced process, Paracoccus (11.4%) and Bacillus (3.9%) are utilized as essential bacteria genes. The results of metabolic pathways prediction indicated significant enhancements in membrane-transport, nucleotide-metabolism, replication-repair, and lipid-metabolism. Thus, the developed self-supporting MMT-CS bio-enhanced process ensured the stability of the system during the removal of antibiotics.

Degradation of different wastewater by a biological sponge iron system: microbial growth and influencing factors

The bio-ZVI process has undergone widespread development in wastewater treatment in recent years. However, there has been limited examination of the growth and degradation characteristics of functional microorganisms within the system. In the present research, strains were isolated and identified from the bio-ZVI system constructed by sponge iron (encoded as SFe-M). The consistency of operating conditions in treating different wastewater was explored. Three SFe-acclimated microorganisms exhibiting characteristics of degrading organic pollutants and participating in the nitrogen removal process were isolated. The adaptation time of these microorganisms prolonged as the substrate toxicity increased, while the pollutant degradation was related to their metabolic rate in the logarithmic phase. All these functional bacteria exhibited the ability to treat wastewater in a wide pH range (5-8). However, the improper temperature (such as 10 °C and 40 °C) significantly inhibited their growth, and the optimal working temperature was identified as 30 °C. The iron dosage had a significant impact on these function bacteria, ranging from 1 g L-1 to 150 g L-1. It was inferred that the SFe-acclimated microorganisms are capable of resisting the poison of excessive iron, that is, they all have strong adaptability. The results provide compelling evidence for further understanding of the degradation mechanism involved in the bio-ZVI process.

Heterogeneous electro-Fenton treatment of coking wastewater using Fe/AC/Ni cathode: optimization of electrode and reactor organic loading

A self-developed iron-loaded activated carbon-based nickel foam electrode (Fe/AC/Ni cathode) was used to construct electro-Fenton reaction system to treat coking wastewater. To meet the gap between laboratory beaker experiments and field trials for practical applications, we proposed and validated a method for obtaining organic loads, the essential parameters used in the design of electrochemical systems for wastewater treatment. The three influencing factors most relevant to organic loading, the effective surface area of cathode, chemical oxygen demand (COD) concentration of influent, and treatment time, were selected and investigated for their effects on the COD removal rate of coking wastewater by single-factor experiments and further optimized by response surface method. The appropriate electrode area load (La) and reactor volume load (Lv) were calculated by their corresponding intrinsic relationships with the three factors. The optimum application conditions were effective surface area of cathode 28.5 cm2, COD concentration of influent 1.76 kg·m-3, and treatment time 160.43 min. Under these conditions, the maximum COD removal rate was 98.51%. The La and Lv were 8.905 mgCOD·cm-2·h-1 and 0.634 kgCOD·m-3·h-1, respectively. The characterization experiment results showed that the Fe/AC/Ni cathode had a significant effect on the treatment of refractory organic contaminants in coking wastewater.

Performance and mechanisms of zero valent iron enhancing short-chain fatty acids production during thermophilic anaerobic fermentation of waste activated sludge

This work first explored the feasibility and possible mechanisms of zero valent iron (ZVI) pretreatment on the generation of short-chain fatty acids (SCFAs) during thermophilic anaerobic fermentation of waste activated sludge (WAS). Results showed that ZVI enhanced the quantity of SCFAs. On Day 6, the SCFAs production reached 455.84 ± 47.88 mg COD/g VSS at 5 g/L of ZVI addition, which increased by 63.80 % relative to control. The presence of ZVI can effectively promote butyric-based fermentation. ZVI accelerated the destruction of extracellular polymeric substances (EPS) and interior sludge cells, as well as improved biodegradation of soluble organics. Also, ZVI enhanced key enzyme activities (i.e., BK and CoA-), thus promoting degradation rates of acidogenesis (6.30 ± 0.84 mg/(gVSS·h) in glucose) and acetogenesis (74.63 ± 0.29 mg/(gVSS·h) in butyrate). Compared to Fe(III), the contribution of Fe(II) was higher among the decomposition products of ZVI. Besides, ZVI favored Proteobacteria and Actinobacteria, which enhanced acetate formation and organic compounds disassimilation of the process, respectively. The abundance of Tepidiphilus, Thermobrachium and Tepidimicrobium was increased, indicating promoting the system stability of SCFAs production in thermophilic anaerobic fermentation.

Electrocatalytic degradation of nitrogenous heterocycles on confined particle electrodes derived from ZIF-67

Nitrogen-containing heterocyclic compounds (NHCs) are hazardous, toxic, and persistent pollutants, thereby requiring urgent solutions. Herein, ZIF-67 was compounded with powder-activated carbon (PAC) to prepare Co/NC/PAC (NC i.e. nitrogen-doped carbon) particle electrodes for the electrocatalytic treatment of pyridine and diazines. Co/NC/PAC reflected the confinement of Co3O4/CoN/Co0 into the N-doped graphitic-carbon layer to generate both pyrrolic-N and graphitic-N active sites. Under the optimal conditions (0.3 A, 12 mL min-1, and initial pH 7.00), the degradation of four NHCs realized 90.2-93.7% efficiencies. The number and position of N atoms in NHCs directly affected the degradation efficiency. The following increasing order of facilitated degradation was recorded: pyridazine < pyrimidine < pyrazine < pyridine. The as-obtained Co/NC/PAC possessed the direct redox effect on NHCs, achieving fast electrocatalytic rate. Species like ·OH and H* were detected in Co/NC/PAC system with contributions to NHCs degradation estimated to 24% and 34%, respectively. Density functional theory (DFT) calculations revealed H* susceptible to attacking the N position, while the meta-position of C was subject to hydroxyl radical (·OH) addition. Overall, degradation of NHCs was achieved by hydro-reduction, oxidation, ring opening cleavage, hydroxylation, and mineralization. Ring-cleavage and mineralization of NHCs provided a novel electrochemical strategy to refractory wastewater treatment.

Efficient utilization of photoelectron-hole at semiconductor-microbe interface for pyridine degradation with assistance of external electric field

In this study, enhanced pyridine bio-photodegradation with assistance of electricity was achieved. Meanwhile, photoelectron-hole played a vital role in accelerating pyridine biomineralization. The significant separation of photoelectron-hole was achieved with an external electric field, which provided sufficient electron donors and acceptors for pyridine biodegradation. The enhanced electron transport system activity also revealed the full utilization of photoelectron-hole by microbes at semiconductor-microbe interface with assistance of electricity. Microbial community analysis confirmed the enrichment of functional species related to pyridine biodegradation and electron transfer. Microbial function analysis and microbial co-occurrence networks analysis indicated that upregulated functional genes and positive interactions of different species were the important reasons for enhanced pyridine bio-photodegradation with external electric field. A possible mechanism of enhanced pyridine biodegradation was proposed, i.e., more photoelectrons and holes of semiconductors were utilized by microbes to accelerate reduction and oxidation of pyridine with the assistance of electrical stimulation. The excellent performance of the photoelectrical biodegradation system showed a potential alternative for recalcitrant organic wastewater treatment.

Rapid fabrication of nanoporous iron by atmospheric plasma for efficient wastewater treatment

Nanoporous (NP) iron with large surface area is highly desired for wastewater degradation catalysis. However, it remains a challenge for the fabrication of NP-Fe because the conventional aqueous dealloying or liquid metal dealloying are not applicable. Herein, a novel and universal plasma-assisted electro-dealloying technique was utilized to fabricate NP-Fe. The NP-Fe demonstrates evenly distributed pore structure. The pore density can be tuned by the variation of the ratio of Fe and Zn in the precursor, and the average pore size can be tuned by the processing time. Owing to its large specific surface area, the NP-Fe shows excellent wastewater degradation performance, which is 26 times better than that of commercial zero-valent iron catalysts. This study provides a useful approach to fabricate NP active metals with enhanced catalytic performance.

Effect of Addition of Zero-Valent Iron (Fe) and Magnetite (Fe3O4) on Methane Yield and Microbial Consortium in Anaerobic Digestion of Food Wastewater

Direct interspecies electron transfer (DIET), which does not involve mediation by electron carriers, is realized by the addition of conductive materials to an anaerobic digester, which then activates syntrophism between acetogenic and methanogenic microorganisms. This study aimed to investigate the effect of the addition of two conductive materials, zero-valent iron (ZVI) and magnetite, on the methane production and microbial consortium via DIET in the anaerobic digestion of food wastewater. The operation of a batch reactor for food wastewater without the addition of the conductive materials yielded a biochemical methane potential (Bu), maximum methane production rate (Rm), and lag phase time (λ) of 0.380 Nm3 kg−1-VSadded, 15.73 mL day−1, and 0.541 days, respectively. Upon the addition of 1.5% ZVI, Bu and Rm increased significantly to 0.434 Nm3 kg−1-VSadded and 19.63 mL day−1, respectively, and λ was shortened to 0.065 days. Simultaneously, Methanomicrobiales increased from 26.60% to 46.90% and Methanosarcinales decreased from 14.20% to 1.50% as the ZVI input increased from 0% to 1.50%. Magnetite, at an input concentration of 1.00%, significantly increased the Bu and Rm to 0.431 Nm3 kg−1-VSadded and 18.44 mL day−1, respectively. However, although magnetite improves the efficiency of methanogenesis via DIET, the effect thereof on the methanogen community remains unclear.

Carbon dot-based molecularly imprinted fluorescent nanopomegranate for selective detection of quinoline in coking wastewater

Quinoline, as a refractory and toxic organic pollutant in coking wastewater, causes great harm to the environment and human health even in trace amount. To realize the selective and sensitive detection of quinoline in coking wastewater, a novel molecularly imprinted fluorescent nanopomegranate with carbon dots (CDs) as seeds and fluorescence source (CD-MIP) was prepared, using quinoline as the template, and N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (KH792) as the monomer. The preparation and detection conditions of CD-MIP were systematically optimized. The structure and detection performance of CD-MIP were investigated in detail. The resulting CD-MIP exhibits excellent photoluminescence performance, high detection sensitivity, good selectivity and reproducibility towards quinoline. Under the optimized conditions, the fluorescence intensity of CD-MIP shows a satisfying linearity with quinoline concentration in the range of 20-200 mg/L with a detection limit of 6.7 mg/L. Owing to the existence of imprinted cavities that highly match with quinoline, a high imprinting factor (3.46) for CD-MIP was obtained. In addition, CD-MIP represents a greater affinity towards quinoline than towards other analogues, as well as an outstanding anti-interference capability. For trace analysis in real coking wastewater, CD-MIP also gives satisfactory results. Therefore, CD-MIP shows promising application in the selective detection of trace quinoline in wastewater.

Role of cycle duration on the formation of quinoline-degraded aerobic granules in the aspect of sludge characteristics, extracellular polymeric substances and microbial communities

This study investigated the culture and characteristics of quinoline-degraded aerobic granular sludge (AGS) under 8-h and 12-h cycle duration. According to results, the cultivation of an 8-h cycle duration enhanced the growth of quinoline-degraded AGS, as well as the settleability of sludge and the retention of biomass. Quinoline can be removed from mature AGS at a rate of more than 90%, but it is removed at a rate slightly higher when the AGS are cultured for 12-h. Compared to 12-h cycle duration, 8-h cycle duration result in a greater increase in the production of extracellular polymeric substances, particularly extracellular proteins. In these two systems, Acidovorax and Paracoccus dominated the quinoline degrading bacteria. In addition, analysis by non-metric multidimensional scaling (based on Bray-curtis distance) showed significant differences of community structure between the two reactors. Clostridia and Acidaminobacter are different bacteria with an 8-h cycle duration compared to 12 h. Relative abundance of nitrogen metabolism genes based on PICRUSt2 prediction, which explain the better total nitrogen removal for an 8-h cycle duration compared to a 12-h cycle duration. Finally, the KEGG pathway was analyzed in order to confirm the results of the microbial analysis.

Iron Compounds in Anaerobic Degradation of Petroleum Hydrocarbons: A Review

Waste and wastewater containing hydrocarbons are produced worldwide by various oil-based industries, whose activities also contribute to the occurrence of oil spills throughout the globe, causing severe environmental contamination. Anaerobic microorganisms with the ability to biodegrade petroleum hydrocarbons are important in the treatment of contaminated matrices, both in situ in deep subsurfaces, or ex situ in bioreactors. In the latter, part of the energetic value of these compounds can be recovered in the form of biogas. Anaerobic degradation of petroleum hydrocarbons can be improved by various iron compounds, but different iron species exert distinct effects. For example, Fe(III) can be used as an electron acceptor in microbial hydrocarbon degradation, zero-valent iron can donate electrons for enhanced methanogenesis, and conductive iron oxides may facilitate electron transfers in methanogenic processes. Iron compounds can also act as hydrocarbon adsorbents, or be involved in secondary abiotic reactions, overall promoting hydrocarbon biodegradation. These multiple roles of iron are comprehensively reviewed in this paper and linked to key functional microorganisms involved in these processes, to the underlying mechanisms, and to the main influential factors. Recent research progress, future perspectives, and remaining challenges on the application of iron-assisted anaerobic hydrocarbon degradation are highlighted.

Composition Characterization and Transformation Mechanism of Dissolved Organic Matters in a Full-Scale Membrane Bioreactor Treating Co-Digestion Wastewater of Food Waste and Sewage Sludge

The membrane bioreactor (MBR) serves as the most widely used technology in anaerobic digestion wastewater treatment, but the composition and transformation of the dissolved organic matters (DOMs) are vague. This study focused on the composition characterization and transformation mechanism of DOMs in real co-digestion wastewater of food waste and sewage sludge from a full-scale MBR via molecular weight cut-off, 3D-EEM, FT-IR, and SPME-GC/MS. The results indicated that the co-digestion wastewater mainly comprised organics with molecular weight (MW) lower than 1 kDa and dominated by tryptophane-protein-like substances. The hydrolytic/acidogenic process improved the biodegradability with the conversion of high-MW organics into low-MW organics, while the two-stage A/O process possessed the highest contribution to the organic removal with the consumption of most DOMs. However, the deficient removal of refractory organics (MW < 5 kDa) in the ultrafiltration unit led to the residual DOMs in the effluent. The potential functional bacteria in the biological processes have also been identified and were principally affiliated with Proteobacteria and Firmicutes. These findings could help to advance the understanding of the co-digestion wastewater and provide fundamental information for the optimization and development of MBR in anaerobic digestion wastewater treatment.

Insights into removal of sulfonamides in anaerobic activated sludge system: Mechanisms, degradation pathways and stress responses

The fate of antibiotics in activated sludge has attracted increasing interests. However, the focus needs to shift from concerning removal efficiencies to understanding mechanisms and sludge responding to antibiotic toxicity. Herein, we operated two anaerobic sequencing batch reactors (ASBRs) for 200 days with sulfadiazine (SDZ) and sulfamethoxazole (SMX) added. The removal efficiency of SMX was higher than that of SDZ. SDZ was removed via adsorption (9.91-21.18%) and biodegradation (10.20-16.00%), while biodegradation (65.44-86.26%) was dominant for SMX removal. The mechanisms involved in adsorption and biodegradation were investigated, including adsorption strength, adsorption sites and the roles of enzymes. Protein-like substance (tryptophan) functioned vitally in adsorption by forming complexes with sulfonamides. P450 enzymes may catalyze sulfonamides degradation via hydroxylation and desulfurization. Activated sludge showed distinct responses to different sulfonamides, reflected in the changes of microbial communities and functions. These responses were related to sulfonamides removal, corresponding to the stronger adsorption capacity of activated sludge in ASBR-SDZ and degradation capacity in ASBR-SMX. Furthermore, the reasons for different removal efficiencies of sulfonamides were analyzed according to steric and electronic effects. These findings propose insights into antibiotic removal and broaden the knowledge for self-protection mechanisms of activated sludge under chronic toxicities of antibiotics.

Effects of reflux ratio on the anaerobic sludge and microbial social behaviors in an expanded granular sludge bed reactor: From the perspective of acyl-homoserine lactones-mediated quorum sensing

Performance of anaerobic sludge and microbial social behaviors in an expanded granular sludge bed (EGSB) were evaluated by increasing reflux ratio from 50% to 500% stage by stage, with a constant influent chemical oxygen demand (COD) of 5500 mg/L at hydraulic retention time 12 h. The results indicated that the reflux ratio of 100% - 200% was more favorable for the EGSB with a methane production of 2.4 m³/m³·d. It was found that acyl-homoserine lactones (AHLs)-mediated quorum sensing (QS) could balance various microbial populations in the anaerobic digestion process. C₄-HSL and C₈-HSL were identified as the specific AHLs in enhancing granulation of anaerobic sludge by stimulating protein secretion into extracellular polymeric substances (EPS). 3-oxo-C₆-HSL and 3-oxo-C₁₄-HSL were verified for the enhancement of methanogenesis. The present study showed a novel perspective on the performance of EGSB with reflux ratios based on the AHLs-mediated QS.

Deciphering the mechanism of medium size anammox granular sludge driving better nitrogen removal performance

In this study, an integrated investigation to the microbial activities, extracellular polymeric substance (EPS), microbial community and function of anammox granular sludge (AnGS) was performed.Results showed that AnGS at 0.5-1.0 mm had the highest average specific anammox activity (SAA) of 345.9 mg NH₄⁺-N·gVSS^-1·d^-1, but AnGS at 1.0-1.5 mm with higher SAA might lead to better nitrogen removal efficiency. The content of slime EPS and SAA achieved positively correlation with R² of 98.11%, while protein/polysaccharide ratio of slime EPS and sludge volume index achieved negatively correlation with R² of 99.13%. Cadidatus Broccadia and Denitratisoma were positive correlations and most abundant in AnGS 0.5-1.0 mm of 20% and AnGS 1.0-1.5 mm of 37%, respectively. AnGS at 0.5-1.0 mm exhibited higher energy metabolism which mostly contributed to produce protein. The study provides new insights into the mechanisms of AnGS about 1 mm playing more important role in nitrogen removal performance.

DNA metabarcoding of the leachate microbiota from sanitary landfill: potential for bioremediation process

Leachate generation contains a variety of toxic compounds, and is a major problem for municipal solid waste (MSW). Microbial profile knowledge is essential to new alternatives and improvements in current treatments of these effluents. In this respect, the microbial community in the leachate from the sanitary landfill of the city of Foz do Iguaçu was analyzed. The 16S rDNA metabarcoding suggested the dominance of fermenting bacteria belonging to Firmicutes phylum, followed by Proteobacteria, Bacteroidetes, and Synergistetes. The most abundant genera were Sedimentibacter, Vulcanibacillus, and Anaerovorax. However, 60% of amplicon sequence variants (ASVs) were not classified taxonomically. In addition, an expressive abundance was attributed to the superphylum known as PVC group, little studied and with unknown scientific potential. The leachate acidogenic phase was masked in the chemical and physical analyzes. Nevertheless, it was evidenced in the metabarcoding methodology. No specifically methanogenic group was detected in significant abundance. Therefore, from bacterial community identification, a bioremediation process can be designed. Enriched culture media can be developed and targeted to the recovery of specific groups which may be involved in leachate biodegradation. What is more, the results expand the knowledge of bacterial diversity, especially from the presence of unknown genera in this habitat.

Effect of Fe3O4 nanoparticles exposure on the treatment efficiency of phenol wastewater and community shifts in SBR system

Increasing magnetic Fe₃O₄ nanoparticles (Fe₃O₄ NPs) application has aroused concern about its potential environmental toxicity. During acute and chronic exposure, key enzymes involved in phenol biodegradation were promoted at 0-600 mg/L Fe₃O₄ NPs, while were inhibited at 800 mg/L Fe₃O₄ NPs, correspondingly affected phenol degradation efficiency. Lactic dehydrogenase (LDH) increased when Fe₃O₄ NPs exceeded 600 mg/L, indicated the more severe cell rupture at high Fe₃O₄ NPs concentration. At the same Fe₃O₄ NPs concentration, the removal of EPS further inhibited key enzymes, decreased phenol degradation, and increased LDH, indicating that the existence of EPS relieved the adverse effects on microorganisms. Spectroscopic analysis showed that protein and polysaccharide associated bonds in EPS decreased at 0-600 mg/L Fe₃O₄ NPs, while increased when Fe₃O₄ NPs exceeded 600 mg/L, which was in accordance with EPS content. Biopolymer-degrading and phenol-degrading genera increased at 0-600 mg/L Fe₃O₄ NPs, while decreased at Fe₃O₄ NPs exceeded 600 mg/L, which conformed to EPS content and phenol degradation efficiency.

Effects of anaerobic granular sludge towards the treatment of flowback water in an up-flow anaerobic sludge blanket bioreactor: Comparison between mesophilic and thermophilic conditions

Cost-effective treatment of flowback water remains a challenge for the sustainability of shale gas development. This study evaluated the efficiency of anaerobic granular sludge (AnGS) technology for flowback water treatment under mesophilic and thermophilic conditions. The granule characteristics and metagenomic characterization were also investigated. Thermophilic AnGS achieved 70.9% of COD removal and 362 NmL/d of methane production, higher than those for mesophilic AnGS (60.0% and 241 NmL/d). Thermophilic AnGS had higher extracellular polymeric substances content but low granular size and settleability. Metagenomic analysis revealed the genes related to hydrolysis acidification and carbohydrate metabolism were upregulated during thermophilic condition. Thermophilic condition most likely improved the hydrolysis of complex organics in the flowback water such as guar gum and hydrolyzed polyacrylamide, and led to higher COD removal and methane production. These results suggest that AnGS technology is a promising alternative for the treatment of flowback water, particularly when operated at thermophilic condition.

Performance prediction of ZVI-based anaerobic digestion reactor using machine learning algorithms

The use of zero-valent iron (ZVI) to enhance anaerobic digestion (AD) systems is widely advocated as it improves methane production and system stability. Accurate modeling of ZVI-based AD reactor is conducive to predicting methane production potential, optimizing operational strategy, and gathering reference information for industrial design in place of time-consuming and laborious tests. In this study, three machine learning (ML) algorithms, namely random forest (RF), extreme gradient boosting (XGBoost), and deep learning (DL), were evaluated for their feasibility of predicting the performance of ZVI-based AD reactors based on the operating parameters collected in 9 published articles. XGBoost demonstrated the highest accuracy in predicting total methane production, with a root mean squared error (RMSE) of 21.09, compared to 26.03 and 27.35 of RF and DL, respectively. The accuracy represented by mean absolute percentage error also showed the same trend, with 14.26%, 15.14% and 17.82% for XGBoost, RF and DL, respectively. Through the feature importance generated by XGBoost, the parameters of total solid of feedstock (TS_f), sCOD, ZVI dosage and particle size were identified as the dominant parameters that affect the methane production, with feature importance weights of 0.339, 0.238, 0.158, and 0.116, respectively. The digestion time was further introduced into the above-established model to predict the cumulative methane production. With the expansion of training dataset, DL outperformed XGBoost and RF to show the lowest RMSEs of 11.83 and 5.82 in the control and ZVI-added reactors, respectively. This study demonstrates the potential of using ML algorithms to model ZVI-based AD reactors.

Improving Biological Treatment of Real Bilge Wastewater With Zero Valent Iron and Activated Charcoal Addition

From the ships engine rooms a recalcitrant wastewater is produced called “bilge” which contains oil, metal working fluids, surfactants, and salinity. This study investigated the treatment of real bilge wastewater in short experiments using the following processes: (i) anaerobic digestion with granular sludge and ZVI addition for enhancement of methane production, (ii) activated charcoal addition to biological treatment (aerobic and anaerobic) for Chemical Oxygen Demand (COD) significant reduction and (iii) combination of ZVI and anaerobic charcoal addition for high performance treatment. The addition of ZVI in anaerobic sludge resulted in higher performance mostly in cumulative CH₄ production. The microbial profile of anaerobic granular sludge exposed to ZVI was determined and Acetobacterium and Arcobacter were the most dominant bacteria genera. Activated charcoal achieved higher COD removal, compared to biological degradation (aerobic and anaerobic). The combination of the two mechanisms, activated charcoal and biomass, had higher COD removal only for aerobic biomass. The combination of ZVI and activated charcoal to anaerobic digestion resulted in higher CH₄ production and significant COD removal in short contact time.

The effects of temperature shock on the treatment of high-concentration organic wastewater by an Fe0/GO-anaerobic system

Temperature changes are inevitable during the actual operation of anaerobic systems. Adding an Fe⁰/GO composite is shown to improve microbial activity and alleviate the adverse effects caused by temperature shock.

Impact of high phenol loading on aerobic granules from two different kinds of industrial sludge along with thiocyanate and ammonium

Two sequencing batch reactors inoculated with two different kinds of industrial sludge; refinery sludge (R1) and brewery sludge (R2), were operated to observe the impact of high phenol loading (5.71 kg COD m^-3 day^-1) along with 100 mg L^-1 of ammonia-nitrogen and thiocyanate on the granular stability and performance. R2 granules were stable and degraded all the pollutants up to an organic loading of 5.71 kg COD m^-3 day^-1 with the large size and high extracellular polymeric substances of 2769.94 ± 62.26 µm and 114.83 ± 1.33 mg gVSS^-1, respectively, whereas R1 granules disintegrated at an organic loading of more than 3.32 kg COD m^-3 day^-1. At higher phenol loading, granular biomass activity was 3.43 and 16.35 mg COD removed mgVSS^-1 day^-1 in R1 and R2, respectively, from the initial sludge activities of 8.01 (refinery sludge) and 6.56 (brewery sludge) mg COD removed mgVSS^-1 day^-1.

Construction of a new lipase- and xylanase-producing oleaginous yeast consortium capable of reactive azo dye degradation and detoxification

A new oleaginous yeast consortium Y-BC-SH which stands for molecularly identified species Yarrowia sp., Barnettozyma californica and Sterigmatomyces halophilus was successfully constructed in this study. This multipurpose oleaginous yeast consortium was developed based on its higher ability to accumulate large amounts of lipids in the form of triacylglycerol, grow on xylose, produce lipase and xylanase and it could rapidly decolorize and degrade commonly-used textile reactive azo dyes. The specific enzyme activities of lipase, xylanase, xylan esterase, β-xylosidase, CMCase, β-glucosidase and cellobiohydrolase produced by Y-BC-SH were significantly higher than that of individual strains. As chemical oxygen demand reduction had occurred in the dye mixture solutions, it was evidence of their color removal and mineralization by Y-BC-SH. The significant induction of oxidoreductive enzymes by Y-BC-SH was probably due to the coordinated metabolic interactions of the individual strains. Phytotoxicity assay confirmed that metabolites generated after dye degradation by Y-BC-SH are non-toxic.

One-step green preparation of magnetic seaweed biochar/sulfidated Fe0 composite with strengthen adsorptive removal of tetrabromobisphenol A through in situ reduction

Rare information is available on the facile preparation of biochar/sulfidated Fe⁰ composite. A facile one-step green method was established for the synthesis of magnetic seaweed (Ulva prolifera) biochar/sulfidated Fe⁰ composite (S-Fe⁰/BC) to use excessive seaweed biomass. Removal efficiency of tetrabromobisphenol A (TBBPA) reached up to 88% in iron-sulfur treatment. Two major products were identified as bisphenol A and monobromobisphenol A, confirming the in-situ reductive debromination of TBBPA. Batch experiments showed that the removal of TBBPA was facilitated with S/Fe molar ratio of 0.2 and acidic conditions (pH = 3-7). The S-Fe⁰/BC composite had good stability and reusability based on the cycle experiments. The removal process of TBBPA by S-Fe⁰/BC composite might include chemical adsorption by S-Fe⁰/BC composite, reduction debromination by S-Fe⁰ and enhanced electron transfer. The environmentally-friendly S-Fe⁰/BC composite synthesized by one-step facile procedure showed novel potential applications in terms of pollution control of halogenated xenobiotic compounds such as TBBPA.