Anaerobic Sequencing Batch Reactor Research Articles

Enhanced methane recovery from anaerobic membrane bioreactor coupled with cold plasma pretreatment for rapid hydrolysis and nitrogen removal

Research to increase biomethane recovery efficiency from thickened sewage sludge (TSWS) using sustainable anaerobic digestion (AD) in municipal wastewater treatment plants is ongoing. Pretreating substrates is known to increase organic biodegradation and biomethane conversion rates in AD. Cold plasma (CP), a recently adopted advanced oxidation processes (AOP) has emerged as an alternative to accelerate pretreatment times under different operation variables. This study assessed raw and CP-pretreated TSWS in an anaerobic sequencing batch reactor (ASBR) and anaerobic membrane bioreactor (AnMBR). The effects of incremental organic loading rates (OLR) and nitrogenous compounds concentration on enhanced CH4 bioconversion efficiency were evaluated. We found that the AnMBR outperformed the ASBR, with an overall chemical oxygen demand (COD) conversion rate of 67%, lower total nitrogen (T–N) accumulation (594 mg L−1), and an overall methane yield of 0.24 L CH4 g−1 COD. CP pretreatment improved TSWS AD, resulting in more efficient COD removal and methane recovery. This study suggests that CP technology is a promising pretreatment to improve AD when treating TSWS.

Azo Dye Decolorization in Sole Biocatalyzed Electrolysis System (BES) and Coupled with Anaerobic Sequencing Batch Reactor (ASBR-BES) in Operation with Ideal Synthetic Wastewater and Domestic Wastewater

Azo Dye Decolorization in Sole Biocatalyzed Electrolysis System (BES) and Coupled with Anaerobic Sequencing Batch Reactor (ASBR-BES) in Operation with Ideal Synthetic Wastewater and Domestic Wastewater

Integrated biological system for remediation and valorization of tannery wastewater: Focus on microbial communities responsible for methanogenesis and sulfidogenesis

Microbial communities in hybrid linear flow channel reactors and anaerobic sequencing batch reactors operated in series for remediation and beneficiation of tannery wastewater were assessed. Despite concurrent sulfidogenesis, more intensive pre-treatment in hybrid linear flow channel reactors reduced methanogenic inhibition usually associated with anaerobic digestion of tannery effluent and promoted efficiency (max 321 mLCH4/gCODconsumed, 59% biogas CH4). Nitrification and biological sulfate reduction were key metabolic pathways involved in overall and sulfate reducing bacterial community selection, respectively, during pre-treatment. Taxonomic selection could be explained by the proteinaceous and saline character of tannery effluent, with dominant genera being protein and/or amino acid degrading, halotolerant and/or ammonia tolerant. Complete oxidizers dominated the sulfidogenic populations during pre-treatment, while aceticlastic genera dominated the methanogenic populations during anaerobic digestion. With more intensive pre-treatment, the system shows promise for remediation and recovery of biogas and sulfur from tannery wastewater in support of a bio-circular economy.

Impact analysis of hydraulic residence time and dissolved oxygen on performance efficiency and microbial community in N, N-dimethylformamide wastewater treated by an AnSBR-ASBR

Suitable operating parameters are one of the key factors to efficient and stable biological wastewater treatment of N, N-dimethylformamide (DMF) wastewater. In this study, an improved AnSBR-ASBR reactor (anaerobic sequencing batch reactor, AnSBR, and aerobic SBR, ASBR, run in series) was used to investigated the effects of operating conditions such as hydraulic residence time (HRT), AnSBR stirring speed and ASBR dissolved oxygen (DO) for DMF wastewater treatment. When HRT decreased from 24 h to 12 h, the average removal rates of COD by the AnSBR were 34.59% and 39.54%, respectively. Meanwhile, the removal rate of NH4+-N by ASBR decreased from 88.38% to 62.81%. The DMF removal rate reached the best at 18 h and the expression of dehydrogenase was the highest in the AnSBR. The abundance of Megasphaera, the dominant sugar-degrading bacteria in the AnSBR, continued to decline due to the decrease of HRT. The relative abundance of Methanobacterium gradually increased to 80.2% with the decrease of HRT and that hydrotrophic methanogenesis dominated the methanogenic process. The HRT decrease promoted butyrate and pyruvate metabolism in anaerobic sludge, but the proportion of glycolysis and methane metabolism decreased. The AnSBR-ASBR reactor had the best operation performance when HRT was 18 h, AnSBR speed was 220 r/min, and ASBR DO content was 3–4 mg/L. This study provided an effective reference for the reasonable selection of operating parameters in the treatment of DMF-containing wastewater by the AnSBR-ASBR.

Effect of decoupling hydraulic and solid retention times on carbohydrate-rich residue valorization into carboxylic acids

This research assessed the effect of decoupling hydraulic retention time (HRT) and solid retention time (SRT) on the production of volatile fatty acids (VFAs) via anaerobic fermentation of beet molasses. The performance of a continuous stirred tank reactor (CSTR, STR = HTR = 30 days) and two anaerobic sequencing batch reactors (AnSBR) with decoupled STR (30 days) and HRT (20 and 10 days) was compared. Previously, a temperature study in batch reactors (25, 35, and 55 °C) revealed 25 °C as the optimal temperature to maximize the VFAs yield and the long-chain VFAs (> C4) production, being selected for the continuous reactors operation. An HRT of 20 days in AnSBR led to an enhancement in bioconversion efficiency into VFAs (55.5% chemical oxygen demand basis) compared to the CSTR (34.9%). In contrast, the CSTR allowed the production of valuable caproic acid (25.4% vs 4.1% w/w of total VFAs in AnSBR). Decreasing further the HRT to 10 days in AnSBR was detrimental in terms of bioconversion efficiency (21.7%) due to primary intermediates (lactate) accumulation. By decoupling HRT and SRT, VFAs were maximized, revealing HRT as an effective tool to drive specific conversion routes (butyrate- or lactate-fermentation).

Use of soluble iron salt as an electron acceptor to provide Fe(III) for Feammox process: Ammonium removal performance and mechanism

Fe(III) reduction coupled with anaerobic ammonium oxidation (Feammox) is a newly discovered biological ammonium removal technology. Compared to anaerobic ammonium oxidation (anammox) process, Feammox does not require NO2−-N as a reaction substrate and is more tolerant to heavy metals. In this study, soluble iron salts FeCl3 was added to anaerobic sequencing batch reactor (ASBR) to start Feammox process. The effects of Fe/N, pH and temperature on the Feammox performance were investigated. Optimal working conditions were determined by combining the variation law of nitrogen and iron elements. The results showed that the best NH4+-N removal efficiency when Fe/N, pH and temperature were 0.15, 6.5 and 30 °C, respectively. The modified Boltzmann model fitted better in Feammox kinetic analysis (R2 = 0.9789), which could clearly explain that the degradation of substrate and the generation of product. Microbial analysis showed that in addition to the typical iron-reducing bacteria, the dominant genus Candidatus_Brocadia of anammox was also enriched in the system with relative abundance of 3.16 %, implying that both Feammox and anammox contributed to the transformation of NH4+-N. Overall, optimizing the operating conditions of Feammox is important significance to maintain the stability of NH4+-N removal performance and provide theoretical basis for constructing a novel wastewater treatment process.

Biological degradation of 2,4,6-trichlorophenol using anaerobic sequencing batch reactor equipped with a rotating biological bed

2, 4, 6-Triclorphenol is a halogenated aromatic compound with toxic, volatile, and odor properties. The anaerobic processes are superior to aerobic processes due to better dehalogenation of 2, 4, 6-Triclorphenol and easier control of releasing this toxic and odorous chemical compound into the air. However, anaerobic processes have lower reaction rates than aerobic processes. In this study, a rotating biological bed was used in an anaerobic sequencing batch reactor to increase the rate of anaerobic reactions. The anaerobic sequencing batch reactor equipped with a rotating biological bed removed more than 99% of the 2, 4, 6-Triclorphenol, 96% of total phenolic compounds, and more than 86% of its chemical oxidation demand in 2, 4, 6-Triclorphenol concentration of 430 mg/L and hydraulic retention time of 12 h. With the biological degradation of the 2, 4, 6-Triclorphenol by an anaerobic sequencing batch reactor Equipped with a rotating biological bed, more than 92% of the chlorine atoms in the structure of this compound were released into the effluent. Therefore, almost complete dehalogenation of 2, 4, 6-Triclorphenol is performed by this process. By removing the rotating biological bed from the anaerobic sequencing batch reactor equipped with a rotating biological bed, the bioreactor efficiency declined rapidly and progressed to failure. The role of rotating biological bed in dehalogenation (32%), biological degradation (10%), and mineralization (83%) of 2, 4, 6-Triclorphenol are very important. Therefore, a rotating biological bed has a significant role in promoting an anaerobic sequencing batch reactor. The anaerobic sequencing batch reactor equipped with a rotating biological bed can remove higher concentrations of 2, 4, 6-Triclorphenol at a lower hydraulic retention time than previously studied processes. Thus, the rotating biological bed can be an appropriate option for promoting anaerobic wastewater treatment plants that receive wastewater containing volatile, toxic, and complex organic compounds.

Utilization of first-order mass action kinetic models to elucidate the mechanism of methane fermentation of glycerol

Knowledge-driven models can aid in understanding the underlying mechanism of methane fermentation, however, these models are often too complex. We proposed to utilize first-order mass action kinetic models as a simpler alternative to conventional knowledge-driven models for gaining some insights on the mechanism of methane fermentation. The data used for model fitting were obtained from a methane fermentation experiment using anaerobic sequencing batch reactor (ASBR) with glycerol as a substrate. Incorporation of substrate feeding profile into the model improved fitness to the data especially during the early stage of the feeding cycle. Model with the assumption that glycerol was metabolized into both propionic and acetic acid and methane was produced via both propionic and acetic acid showed the best fit (root-mean square error = 0.0012), which suggested that the mechanism of the glycerol methane fermentation might follow that particular path. The difference in the applicability of the models on several feed profiles used in this experiment suggested that the mechanism can be different for each feed profile, which was supported by the microbial consortium data. These findings showed the possibility to use first-order mass action kinetic models as a simpler alternative to study the mechanism of methane fermentation of glycerol.

Evaluation of the anaerobic digestion of winery wastewater: Effect of fly ash in anaerobic sequencing batch reactor

The addition of fly ash (FA) to an anaerobic reactor has been studied mainly in batch tests. Nevertheless, the FA effect on the continuous operation of an anaerobic bioreactor has not been addressed. Therefore, the present work shows the effect of FA on the continuous operation of anaerobic sequencing reactors (ASBRs) treating winery wastewater. Two ASBRs were used and operated continuously for 302 days under mesophilic conditions with a hydraulic retention time (HRT) of 3 days. The effect of the organic loading rate (ORL) on the operation was investigated for 204 days. After that, to evaluate the effect of FA as an anaerobic digestion (AD) enhancer, one of the reactors was dosed with 25 mg L−1 of FA for 98 days. The FA dosages allowed an increase in methane production and organic matter removal by 75% and 42%, respectively, concerning the system without FA. Furthermore, the importance of FA in the process was demonstrated by obtaining a yield of 334 NmL CH4 COD removed−1. This result represented a 12% increase compared to the yield previously obtained in the same reactor before adding the FA. Additionally, acetic acid and propionic acid were the predominant volatile fatty acids (VFAs) in the process. Finally, the metals present in the digested sludge after FA addition did not exceed the limits allowed by Chilean legislation.

Recovery of Energy and Carbon Dioxide from Craft Brewery Wastes for Onsite Use

Interest in craft beers is increasing worldwide due to their flavor and variety. However, craft breweries have high water, energy, and carbon dioxide (CO2) demands and generate large quantities of high-strength waste and greenhouse gases. While many large breweries recover energy using anaerobic digestion (AD) and recapture CO2 from beer fermentation, little is known about the economic feasibility of applying these technologies at the scale of small craft breweries. In addition, compounds in hops (Humulus lupulus), which are commonly added to craft beer to provide a bitter or “hoppy” flavor, have been shown to adversely affect anaerobic microbes in ruminant studies. In this study, biochemical methane potential (BMP) assays and anaerobic sequencing batch reactor (ASBR) studies were used to investigate biomethane production from high-strength craft brewery waste, with and without hop addition. A spreadsheet tool was developed to evaluate the economic feasibility of bioenergy and CO2 recovery depending on the brewery’s location, production volume, waste management, CO2 requirement, energy costs, and hop waste addition. The results showed that co-digestion of yeast waste with 20% hops (based on chemical oxygen demand (COD)) resulted in slightly lower methane yields compared with mono-digestion of yeast; however, it did not significantly impact the economic feasibility of AD in craft breweries. The use of AD and CO2 recovery was found to be economically feasible if the brewery’s annual beer production is >50,000 barrels/year.

Anaerobic co-digestion of agro-industrial wastes using anaerobic sequencing batch reactor for bio-energy recovery: Focus on process performance and stability of the methanogenic step

Anaerobic co-digestion of tannery wastewater (TWW) with dairy wastewater (DWW) using a two-phase anaerobic sequencing batch reactor (ASBR) was evaluated. For this purpose, laboratory-scale anaerobic digesters, one for acidogenesis and the other for methanogenesis, with 0.4 and 0.6 L of working volume, respectively, operated in semi-continuous mode, were used. The results showed that a methanogenic reactor treating the effluent acidogenic reactor (50 % TWW and 50 % DWW) exhibits the best process performances in terms of daily biogas (64.7 mL/day), methane production (461 mL/day), specific methane yield (892 mL CH4/g COD), methane content (71.2 %), and total chemical oxygen demand (TCOD) removal efficiency (85.6 %) when operated at a hydraulic retention time (HRT) of 15 days. This indicated that the addition of DWW improves the anaerobic co-digestion process, increasing biogas production (64.7 mL/day) by about 41 % as compared with anaerobic co-digestion of 100 % TWW (27.4 mL/day). The process stability of the methanogenic stage of the two-stage anaerobic digestion process was also evaluated, and the obtained result showed suitable pH (6.70), no total volatile fatty acid (TVFA) accumulation (VFA/alkalinity: 0.363), alkalinity (3350 mg CaCO3/L), and ammonia (231 mg/L) within the optimum operating range. Furthermore, high overall performance efficiency in terms of TCOD reduction (88.8 %) in the two-phase (acidogenesis and methanogenesis) anaerobic digester of 50:50 (TWW:DWW) was obtained when operated at a HRT of 18 days (3 days for acidogenesis and 15 days for methanogenesis). Anaerobic co-digestion of TWW with DWW generally resulted in increased process stabilities and performances compared to mono-digestion of TWW.

Long-term influence of chloroxylenol on anaerobic microbial community: Performance, microbial interaction, and antibiotic resistance gene behaviors

The use of antibacterial and disinfection products is increasing in recent years. Para-chloro-meta-xylenol (PCMX), a widely used antimicrobial agent, has been detected in various environments. Herein, the impacts of PCMX with long-term exposure on anaerobic sequencing batch reactors were investigated. The high concentration (50 mg/L, GH group) PCMX severely inhibited the nutrient removal process, and the low concentration group (0.5 mg/L, GL group) slightly affected the removal efficiency which was recovered after 120 days of adaptation compared to the control group (0 mg/L, GC group). Cell viability tests indicated that PCMX inactivated the microbes. A significant reduction in bacterial α-diversity was observed in the GH but not the GL group. The microbial communities were shifted upon PCMX exposure, among which Olsenella, Novosphingobium, and Saccharibacteria genera incertae Sedis became the predominant genera in the GH groups. Network analyses showed that PCMX significantly reduced the complexity and interactions of the microbial communities, consistent with the negative impacts on bioreactor performance. Real-time PCR analysis indicated that PCMX affected the behavior of antibiotic resistance genes (ARGs), and the relationship between ARGs and bacterial genera gradually became complicated after long-term exposure. Most detected ARGs decreased on Day 60 but increased on Day 120 especially in the GL group, implying the potential risk of environment-relevant concentration of PCMX in the ecosystems. This study provides new insights into the understanding of the impacts and risks of PCMX on wastewater treatment processes.

Effect of operational parameters on the performance of an anaerobic sequencing batch reactor (AnSBR) treating protein-rich wastewater

Treating protein-rich wastewater using cost-effective and simple-structured single-stage reactors presents several challenges. In this study, we applied an anaerobic sequencing batch reactor (AnSBR) to treat protein-rich wastewater from a slaughterhouse. We focused on identifying the key factors influencing the removal of chemical oxygen demand (COD) and the settling performance of the sludge. The AnSBR achieved a maximum total COD removal of 90%, a protein degradation efficiency exceeding 80%, and a COD to methane conversion efficiency of over 70% at organic loading rates of up to 6.2 g COD L−1 d−1. We found that the variations in both the organic loading rate within the reactor and the hydraulic retention time in the buffer tank had a significant effect on COD removal. The hydraulic retention time in the buffer tank and the reactor, which determined the ammonification efficiencies and the residual carbohydrate concentrations in the reactor liquid, affected the sludge settleability. Furthermore, the genus Clostridium sensu stricto 1, known as protein- and lipids-degraders, was predominant in the reactor. Statistical analysis showed a significant correlation between the core microbiome and ammonification efficiency, highlighting the importance of protein degradation as the governing process in the treatment. Our results will provide valuable insights to optimise the design and operation of AnSBR for efficient treatment of protein-rich wastewater.

Simultaneous dissolved methane and nitrogen removal from low-strength wastewater using anaerobic granule-based sequencing batch reactor

Anaerobic treatment of mainstream wastewater has been proposed as a promising solution to enhance bioenergy recovery for wastewater treatment plants (WWTPs). However, the limited organics for downstream nitrogen removal and emissions of dissolved methane into the atmosphere are two major barriers to the broad application of anaerobic wastewater treatment. This study aims to develop a novel technology to overcome these two challenges by achieving simultaneous removal of dissolved methane and nitrogen, and unravel the microbial competitions underpinning the process from the microbial and kinetic perspectives. To this end, a laboratory granule-based sequencing batch reactor (GSBR) coupling anammox and nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) microorganisms was developed to treat wastewater mimicking effluent from mainstream anaerobic treatment. The GSBR achieved high-level nitrogen and dissolved methane removal rates (> 250 mg N/L/d and > 65 mg CH4/L/d) and efficiencies (> 99% total nitrogen removal and > 90% total methane removal) during the long-term demonstration. The availability of different electron acceptors (nitrite or nitrate) imposed significant effects on the removal of ammonium and dissolved methane, as well as on the microbial communities, and the abundance and expression of functional genes. The analysis of apparent microbial kinetics showed that anammox bacteria had a higher nitrite affinity than n-DAMO bacteria, while n-DAMO bacteria had a higher methane affinity than n-DAMO archaea. These kinetics underpin the observation that nitrite is a preferred electron acceptor for removing ammonium and dissolved methane than nitrate. The findings not only extend the applications of novel n-DAMO microorganisms in nitrogen and dissolved methane removal, but also provide insights into microbial cooperation and competition in granular systems.

Modeling and optimization of bioenergy production from co-digestion of poultry litter with wheat straw in anaerobic sequencing batch reactor: Response surface methodology and artificial neural network

This study investigated the sequencing batch co-digestion (Co-AD) of poultry litter (PL) and wheat straw (WS) for continuous methane production as a renewable bioenergy resource. Response surface methodology (RSM) and artificial neural network (ANN) were both used to model the methane content (MC, %) in the produced biogas and daily methane yield (DMY, mL CH4/g VS added) from the Co-AD process. The RSM models (R2 = 0.9554, RMSE = 0.813; R2 = 0.9618, RMSE = 4.940) were more accurate than the ANN models (R2 = 0.9163, RMSE = 1.114; R2 = 0.9037, RMSE = 7.847) in predicting MC and DMY, respectively. The optimal conditions for maximum DMY obtained by RSM were a C/N ratio of 22.73 (a mixing ratio of 0.46 g PL to 1.00 g WS on dry matter basis), total solids of 2.27%, and hydraulic retention time of 11.45 days, under which the validation trials showed MC of (58.37 ± 0.25)% and DMY of (184.36 ± 0.51) mL CH4/g VS added with the prediction errors by RSM (1.07% and 1.87%) being relatively lower than that by ANN (4.21% and 4.35%). The models and optimized parameters results could provide support for the operation and prediction of the continuous Co-AD of PL with WS for real bioenergy production applications.

Stress responses of partial denitrification system under long-term ciprofloxacin exposure in an anaerobic sequencing batch reactor

This study evaluated the stress response of partial denitrification (PD) sludge system under ciprofloxacin (CIP) exposure. The results showed that the nitrite accumulation rate (NAR) decreased from 77.41 % to 28.39 % under CIP stress of 200 µg/L, and after adapting to CIP stress, the NAR of PD system recovered to 61.56 % even the CIP increased to 1000 µg/L. The average COD removal efficiency increased from 69.08 ± 2.01 % to 73.33 ± 2.33 %, and the average removal efficiency of CIP increased from 9.83 % ± 0.71 % in phase II (CIP=50 µg /L) to 30.15 % ± 1.63 % in phase V (CIP=1000 µg /L). Under CIP stress, the protein (PN) in Tightly Bound-extracellular polymeric substances (TB-EPS) increased from 77.60 mg/(g-SS) in phase I to 135.58 mg/(g-SS) in phase Ⅲ (influent CIP=200 µg /L). FTIR revealed that functional groups (CO, C-H, C-O-C) in EPS of PD sludge could bind to CIP to protect microbial cells from damage. The results of principal co-ordinates analysis (PCoA) showed that the addition of CIP had a significant effect on the microbial community structure, CIP exposure led to an increase in biodiversity of PD system. At genus level, Thauera genus abundance decreased, while OLB12 and Denitratisoma genus abundances increased under CIP stress. This was consistent with the result that the conversion of NO3--N to NO2--N was inhibited while NO2--N reduction was promoted. The findings of this study provided insight into the stress-responses of PD system under long-term CIP exposure and provided useful guidance for the risk assessment and control strategy of wastewater treatment plants (WWTPs).

Efficient methane production from anaerobic co-digestion of poultry litter with wheat straw in sequencing batch reactor: Effects of carbon-to-nitrogen ratio, total solids, and hydraulic retention time

This study performed co-digestion of poultry litter (PL) with wheat straw in the daily anaerobic sequencing batch reactor considering operation parameters of carbon-to-nitrogen ratio (C/N, 11.6 to 28.4), total solids (TS, 2.6 to 9.4%), and hydraulic retention time (HRT, 7.6 to 24.4d). The inoculum with a diverse microbial community structure included 2% of methanogens (Methanosaeta) was chosen. Experimental performance by central composite design showed continuous methane production with the highest biogas production rate (BPR) obtained at C/N = 20, TS = 6%, and HRT = 7.6d, being (1.18 ± 0.14 L/LR/d). A significant modified quadratic model (p < 0.0001) for predicting BPR was built (R2 = 0.9724). The operation parameters and process stability both affected the release of nitrogen, phosphorus, and magnesium in the effluent. The results provided new support for the novel reactor operations for efficient bioenergy production from PL and agricultural wastes.

Quinone electron shuttle enhanced ammonium removal performance in anaerobic ammonium oxidation coupled with Fe(III) reduction

Anaerobic ammonium oxidation coupled with Fe(III) reduction (Feammox) is a newly discovered ammonium removal process, but the low ammonium removal efficiency restricts its application in practical wastewater treatment. In this study, iron compounds Fe2O3, Fe(OH)3 and Fe3O4 were added to anaerobic sequencing batch reactors (ASBR) to explore the effect of different iron sources for the Feammox reaction on ammonium removal performance. The removal efficiencies of ammonium in Fe2O3, Fe(OH)3 and Fe3O4 groups were 34.02%, 22.8% and 7.58%, respectively. Additionally, to investigate electron shuttle effect of the quinone compound anthraquinone-2,6-disulfonate (AQDS) between Fe2O3, Fe(OH)3, Fe3O4 and ammonium and whether AQDS can improve the efficiency of Feammox, batch experiments were carried out in 250 mL serum bottles. The ammonium removal efficiency of the AQDS-Fe2O3 group was 48.53%, while those of the AQDS-Fe(OH)3 and AQDS-Fe3O4 groups were 35.63% and 15.46%, respectively. This implied that AQDS enhanced the ammonium removal performance of Feammox, especially accelerating the electron shuttle rate between Fe2O3 and ammonium. X-ray diffraction showed new iron minerals appear in the system. Moreover, modified Boltzmann model was more suitable to describe the removal of NH4+-N and showed a good correlation(R2 >0.99). This study demonstrates the significant influence of AQDS on Feammox process, which provides a theoretical basis for the application of Feammox in practical sewage treatment.

Long-term performance study applying a tandem AnSBR-ASBR to treat wastewater containing N, N-dimethylformamide: Sludge physicochemical properties, microecology, and functional genes

The effective treatment of industrial pollutant N, N-dimethylformamide (DMF) containing wastewater is a matter of worldwide concern. This study investigated the performance and microecology of anaerobic granular sludge (AGS) and aerobic sludge (AS) in treating DMF wastewater. It was also explored the degradation pathways of DMF in an anaerobic sequencing batch reactor series aerobic sequencing batch reactor (AnSBR-ASBR). Results showed that 5 mg/L DMF facilitated the degradation of chemical oxygen demand (COD) by AGS with AS, while 100 mg/L DMF reduced the efficiency of AS. The physicochemical properties of the sludge showed that the polysaccharide and protein levels in extracellular polymeric substances and key enzyme activity (acetate kinase, coenzyme F420) deteriorated when DMF increased from 25 to 100 mg/L. As the DMF dose increased (0–100 mg/L), the Euryarchaeota abundance in the AGS decreased from 28.41% to 11.06%, and the predominant methanogenic pathway shifted from a combination of aceticlastic methanogenesis (AM) and hydrogenotrophic methanogenesis (HM) to HM. The metabolic pathway to effectively remove DMF was as follows: hydrolysis of DMF to dimethylamine, methylamine, and finally mineralisation to CO2. The abundance of dmd-tmd, a functional gene encoding dimethylamine/trimethylamine dehydrogenase, increased as the DMF increased in the AS. This study systematically examined the operating efficiency and stability of the AnSBR-ASBR, and summarized the AGS and AS stress response, microbial community evolution, key metabolic pathways to DMF, also provided useful information for the treatment of industrial wastewater containing DMF.

Starting-up performances and microbial community shifts in the coupling process (SAPD-A) with sulfide autotrophic partial denitrification (SAPD) and anammox treating nitrate and ammonium contained wastewater

A novel coupling process (SAPD-A) with sulfide autotrophic partial denitrification (SAPD) (NO3−-N→NO2−-N) and anaerobic ammonium oxidation (Anammox) was developed using anaerobic sequencing batch reactor (ASBR) in this work. The integrated process comprised two stages. Firstly, the starting-up of SAPD process succeeded by gradually increasing the influent nitrate and sulfide in 95 days. The average nitrate removal efficiency (NRE) and NO2−-N accumulation rates were 71.24% ± 0.21% and 46.44% ± 0.53% at SAPD process (days 75–95). Then, successful coupling process (SAPD-A) was implemented in two stages (stage I and stage II of SAPD-A). In stage I, it is feasible to promote the successful construction of SAPD-A process by elevating influent ammonium only based on SAPD system, making the NRE increased from 44.45% ± 0.46% (day 95) to 64.62% ± 0.12% at the end of stage I in SAPD-A system (day 126). Meanwhile, the ammonium nitrogen removal efficiency (ARE) and total nitrogen removal efficiency (TN-RE) also rose up to 42.46% ± 2.02% and 63.28% ± 0.54% respectively. Furthermore, the average ARE, NRE and TN-RE during the stage II in the bioreactor could reach 65.17% ± 1.45%, 74.50% ± 0.81% and 77.81% ± 0.37% by loading some biofilters (with of approximate 10% of the volume of the bioreactor) attached anaerobic ammonium oxidation bacteria (AnAOB). High-throughput sequencing results showed that the dominant genera concerning nitrogen removal were norank_f_norank_o_Fimbriimonadates (with the abundance of 2.88–8.54%), norank_ o_ norank _ c_ OM190 (2.48–4.41%), norank_f_norank_o_norank_c_WWE3 (11.01–17.69%), subgroup_10 (1.97–3.81%), Limnobacter（2.17–3.49%）, norank_f_n orank_ o_norank_ c_OLB14 (2.03–5.23%), norank-f-PHOS-HE36 (2.18–5.5%), Ellin6067 (1.34–2.24%) and Candidatus_ Brocadia (1.95–2.42%) during the whole starting-up period of coupling SAPD-A process. Batch experiments revealed that the sulfide was fully oxidized within 2 h, with the maximum reaction rate of 38.30 ± 1.53 mg (L h)−1 in the first 1 h. Simultaneously, the concentration of nitrate sharply decreased from 53.08 ± 0.23 mg L−1 to 24.16 ± 0.42 mg L−1 with the reaction rate of 66.41 ± 2.12 mg (L h)−1 in 0.5 h. Also, the ammonium concentration significantly declined from 47.88 ± 0.34 mg L−1 to 10.98 ± 0.39 mg L−1 in 8 h. Anammox process was responsible for the dominant nitrogen removal in the coupling SAPD-A system.