The comparative advantages of ethanol and sucrose as co-substrates in the degradation of an anionic surfactant: microbial community selection

Microbial diversity and metabolic inference of diclofenac removal in optimised batch heterotrophic-denitrifying conditions by means of factorial design

Using the Response Surface Methodology (RSM) and Rotational Central Composite Design (RCCD), this study evaluated the removal of DCF under denitrifying conditions, with ethanol as cosubstrate, in batch reactors, being 1 L Erlenmeyer flasks (330 mL of reactional volume) containing Dofing medium and kept under agitation at 130 rpm and incubated at mesophilic temperature (30 °C). It considered the individual and multiple effects of the variables: nitrate (130 - 230 mg NO3- L-1), DCF (60-100 µg DCF L-1) and ethanol (130 - 230 mg EtOH L-1). The highest drug removal efficiency (17.5%) and total nitrate removal were obtained at 176.6 ± 4.3 mg NO3 -L-1, 76.8 ± 3.7 µg DCF L-1, and 180.0 ± 2.5 mg EtOH L-1. Under such conditions, the addition of ethanol and nitrate was significant for the additional removal of diclofenac (p > 0.05). The prevalence of Rhodanobacter, Haliangium and Terrimonas in the inoculum biomass (activated sludge systems) was identified through the 16S rRNA gene sequencing. The potential of these genera to remove nitrate and degrade diclofenac was inferred, and the main enzymes potentially involved in this process were α-methylacyl-CoA racemase, long-chain fatty acid-CoA ligase, catalases and pseudoperoxidases.

Microbial synergies drive simultaneous biodegradation of ethoxy and alkyl chains of Nonylphenol Ethoxylate in fluidized bed reactors

The widely-used surfactant Nonylphenol Ethoxylate (NPEO) produces endocrine-disrupting compounds during biodegradation, with these byproducts being more harmful than untreated NPEO. This study investigates the effectiveness of a Fluidized Bed Reactor (FBR) in reducing the production of 4-Nonylphenol (4-NP) during the biodegradation of NPEO. Two identical FBR filled with sand were used to assess the NPEO degradation and to enhance the microbial consortia capable of breaking down the complex byproducts, ethanol and fumarate were introduced as co-substrates. Our findings demonstrate the significant potential of the FBR, especially when coupled with fumarate, for enhancing the surfactant degradation. It outperforms the efficiency achieved with ethanol as the primary electron donor, albeit with a higher rate of byproduct production. Microbial community taxonomy and metabolic prediction revealed the high abundance of Geobacter (1.51-31.71%) and Methanobacterium (1.08-13.81%) in non-conductive sand. This may hint a new metabolic interaction and expand our understanding of Direct Interspecies Electron Transfer (DIET) in bioreactors applied to micropollutants degradation. Such an intricate relationship between facultative and anaerobes working together to simultaneously biodegrade the ethoxy and alkyl chains presents a new perspective on NPEO degradation and can potentially be extended to other micropollutants.

Removal of nonylphenol ethoxylate surfactant in batch reactors: emphasis on methanogenic potential and microbial community characterization under optimized conditions

ABSTRACTNonylphenol ethoxylate (NPE) is an endocrine-disrupting chemical that has bioaccumulative, persistent and toxic characteristics in different environmental matrices and is difficult to remove in sewage treatment plants. In this study, the effects of the initial concentration of NPE (0.2 ± 0.03 - 3.0 ± 0.02 mg. L-1) and ethanol (73.9 ± 5.0-218.6 ± 10.6 mg. L-1) were investigated using factorial design. Assays were carried out in anaerobic batch reactors, using the Zinder basal medium, yeast extract (200 mg. L-1), vitamin solution and sodium bicarbonate (10% v/v). The optimal conditions were 218.56 mg.L-1 of ethanol and 1596.51 µg.L-1 of NPE, with 92% and 88% of NPE and organic matter removal, respectively, and methane yield (1689.8 ± 59.6 mmol) after 450 h of operation. In this condition, bacteria potentially involved in the degradation of this surfactant were identified in greater relative abundance, such as Acetoanaerobium (1.68%), Smithella (1.52%), Aminivibrio (0.91%), Petrimonas (0.57%) and Enterobacter (0.47%), as well as archaea Methanobacterium and Methanoregula, mainly involved in hydrogenotrophic pathway.

Potential methanogenic and degradation of nonylphenol ethoxylate from domestic sewage: unravelling the essential roles of nutritional conditions and microbial community

Nonylphenol ethoxylathe (NPEO) is a non-ionic surfactant of increasing concern, used in the formulation of laundry detergents and is frequently found in aquatic environments. The purpose of this study was to evaluate the effects of yeast extract (YE) and sodium fumarate (SF) in NPEO removal from domestic sewage under anaerobic conditions via central composite rotatable design (CCRD) and response surface methodology (RSM). Experiments were designed by varying concentrations of NPEO (1.6-5.8 mg L^-1), YE (131.8-468.2 mg L^-1) and SF (97.7-602.3 mg L^-1) in batch reactors. SF and YE addition significantly influenced NPEO removal and CH₄ production. Optimal values of YE (400 mg L^-1) and SF (200 mg L^-1) result in removal efficiency of 97% for 5 mg L^-1 of NPEO, being mostly removed by biodegradation (86%). Meanwhile COD removal was 95% and methane yield was 134 ± 4 NmLCH₄ g^-¹COD_removed. The most abundant Bacteria genus identified were Macellibacteroides, Longilinea, Petrimonas and Proteiniphilum, while for Archaea, Methanosaeta and Methanoregula were the genera identified in higher relative abundances in optimized conditions.

Assessment of the aerobic and anaerobic biodegradation of contaminants of emerging concern in sludge using batch reactors

This work explores the degradation of xenobiotic compounds in aerobic and anaerobic batch reactors. Different inoculums were spiked with nine emerging contaminants at nominal concentrations ranging between 1 to 2 mg/L (ibuprofen, diclofenac, naproxen, acesulfame, sucralose, aspartame, cyclamate, linear alkylbenzene sulfonates, and secondary alkyl sulfonates). Ethanol was used as co-substrate in the anaerobic reactors. We found that the kinetic decay was faster in the aerobic reactors inoculated with a Spanish (S_pn) inoculum compared to a Brazilian (B_rz) inoculum, resulting in rection rates for LAS and SAS of 2.67 ± 3.6 h^-1 and 5.09 ± 6 h^-1 for the B_rz reactors, and 1.3 ± 0.1 h^-1 and 1.5 ± 0.2 h^-1 for the S_pn reactors, respectively. There was no evidence of LAS and SAS degradation under anaerobic conditions within 72 days; nonetheless, under aerobic conditions, these surfactants were removed by both the B_rz and S_pn inoculums (up to 86.2 ± 9.4% and 74.3 ± 0.7%, respectively) within 10 days. The artificial sweeteners were not removed under aerobic conditions, whereas we could observe a steady decrease in the anaerobic reactors containing the S_pn inoculum. Ethanol aided in the degradation of surfactants in anaerobic environments. Proteiniphilum, Paraclostridium, Arcobacter, Proteiniclasticum, Acinetobacter, Roseomonas, Aquamicrobium, Moheibacter, Leucobacter, Synergistes, Cyanobacteria, Serratia, and Desulfobulbus were the main microorganisms identified in this study.

How can ethanol enhance direct interspecies electron transfer in anaerobic digestion?

Anaerobic digestion (AD) of organic waste to produce biogas is a mature biotechnology commercialised for decades. However, the relatively recent discovery of direct interspecies electron transfer (DIET) brings a new opportunity to improve the efficiency of biogas technology. DIET may replace mediated interspecies electron transfer (MIET) by efficient electron transfer between exoelectrogens and electrotrophic methanogens, thereby enhancing yields and rates of biogas production. Ethanol, as the initial electron donor in the discovery of the DIET pathway, is now a "hot topic" in the literature. Recent studies have indicated that ethanol in AD functions not only as the substrate, but also as the precursor to stimulate DIET by enriching exoelectrogens and electrotrophic methanogens for co-digesting complex organic wastes. This review aims to highlight the state of the art and recent advances in ethanol-based DIET in AD. The DIET associated reactions of ethanol oxidation and carbon dioxide reduction are assessed by thermodynamic analysis to reveal the extent of the potential for improvement of the AD processes that utilizes DIET pathways. Three ethanol-based DIET strategies are discussed: (1) ethanol as the sole substrate supplemented with conductive materials in AD, (2) ethanol co-digestion with complex substrates and (3) ethanol-type fermentation prior to AD. This review aims to chart the pathways for improved AD performance by utilizing ethanol-based DIET in specific treatments of biological wastes.

4-Nonylphenol degradation changes microbial community of scale-up Anaerobic Fluidized Bed Reactor

Nonylphenol Ethoxylate (NPe) is a nonionic surfactant widely applied in domestic and industrial uses and its degradation generates the endocrine disruptor 4-Nonylphenol (4-NP). The effects of this compound in biological sewage treatment are uncertain, especially in anaerobic systems. The aim of this study was to assess the 4-NP removal and degradation in scale-up (20 L) Anaerobic Fluidized Bed Reactor (AFBR) filled with sand as support material, operated with Hydraulic Retention Time (HRT) of 18 h, fed with synthetic sewage plus 4-NP, performed in four phases named Phase I (894 mg COD L^-1), Phase II (878 mg COD L^-1, 127 μg 4-NP L^-1), Phase III (940 mg COD L^-1, 270 μg 4-NP L^-1) and Phase IV (568 mg COD L^-1, 376 μg 4-NP L^-1). 4-NP did not affect reactor stability and organic matter removal remained stable at 94%. Highest 4-NP removal (78%) occurred for highest 4-NP influent (Phase IV), which resulted from biomass adaptation in the presence of ethanol. Through the 4-NP total mass balance, about 70% was biodegraded and 1% adsorbed on the sand bed. 4-NP addition promoted selection of microbial consortium strongly linked to aromatic compounds and surfactants degradation such as Geothrix, Holophaga, Aeromonas, Pelobacter, Pseudomonas, Delftia.

The influence of upflow velocity and hydraulic retention time changes on taxonomic and functional characterization in Fluidized Bed Reactor treating commercial laundry wastewater in co-digestion with domestic sewage

A large-scale (19.8L) Fluidized Bed Reactor (FBR) operated for 592 days was used to assess the removal performance of linear alkylbenzene sulfonate (LAS). Adjustments in hydraulic retention time (HRT) (18 and 30 h), ethanol (50, 100, 200 mg L^-1) and linear alkylbenzene sulfonate (LAS) concentration (6.3-24.7 mg L^-1) with taxonomic and functional characterization of biomass using Whole Genome Shotgun Metagenomic (WGSM) represented a major step forward for optimizing biological treatments of LAS. In addition, the variation of the upflow velocity (0.5, 0.7 and 0.9 cm s^-1) was investigated, which is a parameter that had not yet been correlated with the possibilities of LAS removal in FBR. Lower Vup (0.5 cm s^-1) allied to higher ethanol concentration (200 mg L^-1) resulted in lower LAS removal (29%) with predominance of methanogenic archaea and genes related to methanogenesis, while higher Vup (0.9 cm s^-1) led to aerobic organisms and oxidative phosphorylation genes. An intermediate Vup (0.7 cm s^-1) and higher HRT (30 h) favored sulfate reducing bacteria and genes related to sulfur metabolism, which resulted in the highest LAS (83%) and COD (77%) removal efficiency.

Laundry wastewater and domestic sewage pilot-scale anaerobic treatment: Microbial community resilience regarding sulfide production

In this study, the removal of anionic surfactant Linear Alkylbenzene Sulfonate (LAS) from laundry wastewater was evaluated in co-digestion with domestic sewage, using a pilot-scale Expanded Granular Sludge Bed reactor. Surfactant influent concentration was enhanced from 5 ± 3 mg LAS L^-1 (stage I) to 19 ± 10 mg LAS L^-1 (stage II) and 36 ± 19 mg LAS L^-1 (stage III) throughout reactor operation. Sulfide levels higher than 20 mg L^-1 influenced LAS removal efficiency, which decreased from 71% to 55% and 32% in stage I, II and III, respectively. Acclimation of microbial population was verified and higher relative abundance of the genera similar to Cytophaga, Bacteroides, Syntrophus and Syntrophobacter in the early stages (adaptation and stage I) was replaced by higher relative abundance of the genera Anaerophaga, Nitrosovibrio, Sulfurovum and Desulfovibrio in the last stages (stage II and III).

Microbial community assembly in detergent wastewater treatment bioreactors: Influent rather than inoculum source plays a more important role

In this study, three sequencing batch reactors Ra, Rb, Rc with different inoculum sources (activated sludge; activated sludge plus detergent degrading consortium; detergent degrading consortium) were used to treat detergent wastewater [consisting of sodium dodecyl sulfate, polyoxyethylene lauryl ether and tetrasodium ethylenediamine tetraacetate (Na₄EDTA)]. Fast start-up and highest performance in phase I and II (organic loading rate were 0.28, 0.39 kgCOD/kgMLSS/d, respectively) were observed in Rc. In contrast, Rb showed highest impact resistance to the increase of EDTA concentration in phase III. High-throughput sequencing analysis showed that inoculum sources led to significant differences on microbial community in phase I. However, regardless of the influent variation in phases II and III, the differences on microbial community among three SBRs were diminished along long-term operation. Pseudomonas, Sphingopyxis, Luteimonas, Pseudoxanthomonas and SM1A02 were found to be the core taxa, they might contribute to the excellent performance of detergent wastewater treatment.

Evaluation of anionic surfactant removal by anaerobic degradation of commercial laundry wastewater and domestic sewage

An expanded granular sludge bed reactor was evaluated for the anaerobic digestion of commercial laundry wastewater and domestic sewage focused on the removal of linear alkylbenzene sulfonate (LAS). The reactor was operated in three stages, all under mesophilic conditions and with a hydraulic retention time of 36 h. At stage I, the laundry wastewater was diluted with tap water (influent: 15.3 ± 4.9 mg LAS/L); at stage II, 50% of the feed volume was domestic sewage and 50% was a mixture of tap water and laundry wastewater (influent: 15.8 ± 4.9 mg LAS/L); and at stage III, only domestic sewage was used as a diluent of the laundry wastewater (influent: 24.1 ± 4.1 mg LAS/L). Due to the addition of domestic sewage the organic compounds content and LAS in the influent increased. Under such conditions, it was observed that LAS removal rate decreased from 77.2 ± 14.9% (stage I) to 55.3 ± 18.4% (stage III). Statistical tests indicated that the decrease of the LAS removal rate was significant and indicated a correlation between the removal of LAS and specific organic loading rate. The analysis of 16S rRNA gene sequencing revealed genera similar to Geobacter, Desulfovibrio, Syntrophomonas, Syntrophus, Desulfobulbus, Desulfomonile, and Desulfomicrobium, which were related to the degradation of LAS.

Metabolic routes involved in the removal of linear alkylbenzene sulfonate (LAS) employing linear alcohol ethoxylated and ethanol as co-substrates in enlarged scale fluidized bed reactor

In this study, the microbial community characterization and metabolic pathway identification involved in the linear alkylbenzene sulfonated (LAS) degradation from commercial laundry wastewater in a fluidized bed reactor (FBR) on an increased scale were performed using the Illumina MiSeq platform. Ethanol and non-ionic surfactant (LAE, Genapol C-100) were used as co-substrates. The FBR was operated in five operational phases: (I) synthetic substrate for inoculation; (II) 7.9 ± 4.7 mg/L LAS and 11.7 ± 6.9 mg/L LAE; (III) 19.4 ± 12.9 mg/L LAS, 19.6 ± 9.2 mg/L LAE and 205 mg/L ethanol; (IV) 25.9 ± 11 mg/L LAS, 19.5 ± 9.1 mg/L LAE and 205 mg/L ethanol and (V) 43.9 ± 18 mg/L LAS, 25 ± 9.8 mg/L LAE and 205 mg/L ethanol. At all operation phases, organic matter was removed from 40.4 to 85.1% and LAS removal was from 24.7 to 56%. Sulfate-reducing bacteria (SRB) were identified in the biofilm of FBR in all operational phases. Although the LAS promoted a toxic effect on the microbiota, this effect can be reduced when using biodegradable co-substrates, such as ethanol and LAE, which was observed in Phase IV. In this phase, there was a greater microbial diversity (Shannon index) and higher microorganism richness (Chao 1 index), both for the Domain Bacteria, and for the Domain Archaea.

Microbial Community Structure and Function Indicate the Severity of Chromium Contamination of the Yellow River

The Yellow River is the most important water resource in northern China. In the recent past, heavy metal contamination has become severe due to industrial processes and other anthropogenic activities. In this study, riparian soil samples with varying levels of chromium (Cr) pollution severity were collected along the Gansu industrial reach of the Yellow River, including samples from uncontaminated sites (XC, XGU), slightly contaminated sites (LJX, XGD), and heavily contaminated sites (CG, XG). The Cr concentrations of these samples varied from 83.83 mg⋅kg^-1 (XGU) to 506.58 mg⋅kg^-1 (XG). The chromate [Cr (VI)] reducing ability in the soils collected in this study followed the sequence of the heavily contaminated > slightly contaminated > the un-contaminated. Common Cr remediation genes chrA and yieF were detected in the XG and CG samples. qRT-PCR results showed that the expression of chrA was up-regulated four and threefold in XG and CG samples, respectively, whereas the expression of yieF was up-regulated 66- and 7-fold in the same samples after 30 min treatment with Cr (VI). The copy numbers of chrA and yieF didn’t change after 35 days incubation with Cr (VI). The microbial communities in the Cr contaminated sampling sites were different from those in the uncontaminated samples. Especially, the relative abundances of Firmicutes and Bacteroidetes were higher while Actinobacteria was lower in the contaminated group than uncontaminated group. Further, potential indicator species, related to Cr such as Cr-remediation genera (Geobacter, PSB-M-3, Flavobacterium, and Methanosarcina); the Cr-sensitive genera (Skermanella, Iamia, Arthrobacter, and Candidatus Nitrososphaera) were also identified. These data revealed that Cr shifted microbial composition and function. Further, Cr (VI) reducing ability could be related with the expression of Cr remediation genes.

Metagenomic analysis of the microbiome in three different bioreactor configurations applied to commercial laundry wastewater treatment

The taxonomic and functional diversity of three different biological reactors (fluidized bed reactor, FBR; up-flow anaerobic sludge blanket reactor, UASB; and expanded granular sludge bed reactor, EGSB) used for commercial laundry wastewater treatment was investigated using metagenome shotgun sequencing. Metagenomes were sequenced on the Illumina Hiseq platform and were analyzed using MG-RAST, STAMP and PAST software. The EGSB and UASB reactors were more closely related based on taxonomic and functional profiles, likely due to similar granular sludge and procedures adopted to ensure anaerobic conditions. The EGSB and UASB reactors showed a predominance of methanogens and genes related to methanogenesis, with a prevalence of the acetoclastic pathway, in addition to the peripheral and central O₂-independent pathways for aromatic compound degradation. By contrast, FBR showed a dominance of aerobic microbiota and pathways for O₂-dependent aromatic compound degradation. Therefore, although the reactors showed similar surfactant removal levels, the microbial composition, functional diversity and aromatic compound degradation pathways were significantly distinct.

Simultaneous determination of anionic and nonionic surfactants in commercial laundry wastewater and anaerobic fluidized bed reactor effluent by online column-switching liquid chromatography/tandem mass spectrometry

This study presents a new method developed for the simultaneous determination of anionic surfactant (linear alkylbenzene sulfonate - LAS, 4 homologs) and nonionic surfactant (linear alcohol ethoxylate - LAE) in commercial laundry wastewater. The surfactants were identified and quantified using online column-switching solid-phase extraction (SPE) coupled with liquid chromatography/tandem mass spectrometry (LC-MS/MS). Ten and three transitions (m/z) were identified for LAS and LAE, respectively. The detection and quantification limits were 75 and 200μg/L for LAS, respectively, and 75μg/L for LAE. This method was applied to the determination of the surfactants in the influent and effluent of an anaerobic fluidized bed reactor that was used for the treatment of commercial laundry wastewater. After 480days of operation with a hydraulic retention time (HRT) of 18h, the removal of 45.9±5.6% LAS and 99.2±4.3% LAE from an influent with surfactant concentrations of 26.1±12.9mg/L and 23.8±6.8mg/L, respectively, was obtained. Under these conditions, the breakage of longer-chain LAS homologs with the release of carbon units was observed with an increase in the number of shorter homolog chains. This SPE online sample treatment method is simple, fast and effective for the analysis of both surfactants. This technique is pioneering in its simultaneous measurement of two surfactant categories in anaerobic fluidized bed reactors.

Effects of hydraulic retention time, co-substrate and nitrogen source on laundry wastewater anionic surfactant degradation in fluidized bed reactors

The aim of this study was to evaluate the influence of hydraulic retention time (HRT) on linear alkylbenzene sulfonate (LAS) removal in fluidized bed reactors (FBRs). FBR1 (HRT of 8h) and FBR2 (HRT of 12h) were fed laundry wastewater with 18.6±4.1 to 27.1±5.6mg/L of LAS in the following conditions: ethanol and nitrate addition (Phases I, II and III), nitrate (Phase IV), ethanol (Phase V) and laundry wastewater (Phase VI). LAS removal was 93±12% (FBR1) and 99±2% (FBR2). In FBR1, nitrate influenced significantly on LAS removal (99±3% - Phase IV) compared to the phase without nitrate (90±15% - Phase V). In FBR1 the absence of ethanol was more favourable for LAS removal (99±3% - Phase IV) compared to ethanol addition (87±16% - Phase II). In FBR2, 99±2% LAS removal was found up to 436days. By microbial characterization were identified bacteria as Acinetobacter, Dechloromonas, Pseudomonas and Zoogloea.