Search

Aerobic granular sludge (AGS) in continuous-flow reactors (CFRs) has attracted significant interest, with notable progress in research and application over the past two decades. Cumulative studies have shown that AGS-CFRs exhibit comparable morphology, settleability, and pollutant removal efficiency to AGS cultivated in sequencing batch reactors, despite their smaller particle sizes. Shear force and selection pressure are the primary drivers of granulation. While not mandatory for granulation, feast/famine conditions play a crucial role in ensuring long-term stability and nutrient removal. Additionally, bioaugmentation can facilitate the granulation process. Furthermore, this paper comprehensively assesses the application of AGS-CFRs in full-scale wastewater treatment plants (WWTPs). Currently, AGS-CFRs have been implemented in nine WWTPs, encompassing two distinct processes. Hydrocyclone-based densified activated sludge significantly enhances sludge density, settleability, and biological phosphorus removal efficiency, thus increasing treatment capacity. The microaerobic-aerobic configuration with internal separators can induce granulation, ensuring long-term stability, eliminating the need for external clarifiers, and reducing land and energy requirements. This review demonstrates the high potential of AGS-CFRs for intensifying existing WWTPs with minimal retrofitting needs. However, further research is required in granulation mechanisms, long-term stability, and nutrient removal to promote the widespread adoption of AGS.

Aerobic granular sludge (AGS) has been successfully used in sequencing batch reactors. However, their application to existing continuous-flow systems remains challenging. In this study, a novel microaerobic-aerobic configuration with internal separators was implemented in a full-scale municipal wastewater treatment facility with a nominal capacity of 2.5 × 10 4 m 3 d -1 . Sludge characteristics, pollutant removal and associated pathways, shifts in the microbial community, and underlying granulation mechanisms were investigated. Following a two-month operation period, the transition from flocculent-activated sludge to well-defined AGS with distinct boundaries and compact structures was successfully achieved. The average size of sludge increased from 31.9 to 138.5 μm, with granules larger than 200 μm constituting 28.9 % of the total sludge and SVI 30 averaging 51.4 ± 8.2 mL g -1 . The 95th percentile effluent COD, NH 4 + -N, and TN concentrations were 35.0, 1.2, and 13.3 mg L -1 , respectively. The primary pathways for pollutant removal were identified as simultaneous nitrification, denitrification, and phosphorus removal within the microaerobic tanks. The enrichment of denitrifying phosphorus-accumulating organisms, including Hydrogenophaga, Accumulibacter, Azospira, Dechloromonas, and Pseudomonas, provides an essential microbial foundation. Furthermore, computational fluid dynamics modeling revealed that the incorporation of internal separators in aerobic tanks induced shifts in the flow pattern, transitioning from a single-circulation cell to multiple vortical cells. This alteration amplified the local velocity gradients, generating the required shear forces to drive granulation. Moreover, mass balance analysis revealed that the microaerobic and aerobic tanks operated under feast and famine conditions, respectively, creating a microbial selection pressure that favored granulation. This process eliminates the need for external clarifiers, resulting in a footprint reduction of 38.2 % and one-third energy savings for sludge reflux. This study offers valuable insights into the application of continuous-flow AGS to upgrade existing activated sludge systems with limited retrofitting requirements., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

This study investigated and evaluated the roles of acidic (pH 4.0), neutral (pH 7.0) and alkaline (pH 10.0) in anaerobic co-fermentation of sewage sludge and carbohydrate-type municipal waste. CO 2 , CH 4 and H 2 are produced in acidic, neutral and alkaline fermentation, respectively. The neutral co-fermentation contained the vast number of aqueous metabolites as total of 22.12 g/L, with the advantage of over 50 % biodegradable components in extracellular polymeric substance and over 80 % hydrolysis rate. Acidic and alkaline pH facilitated ammonia release, with the max concentration of 0.46 g/L and 0.44 g/L, respectively. Microbial analysis indicated that pH is the key parameter to impact microbial activity and drive microbial community transition. The high abundance of Lactobacillus, Bifidobacterium and Clostridium was associated with harvest of ethanol, lactic acid and acetate in acidic, neutral and alkaline fermentation. Meanwhile, the floc feature showed better dewaterability (zeta potential -8.48 mV) and poor nutrient convey (distribution spread index 1.03) in acidic fermentation. In summary, acidic and alkaline fermentation were prioritised for targeted spectrum. Neutral fermentation was prioritised for high production. This study presented an upgraded understanding of the pH role in fermentation performance, microbial structure and sludge behaviour, which benefits the development of fermentation processing unit., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

"Temperature Staging and Biological Phasing" (TSBP) is an improved two-phase anaerobic digestion (AD) technology. This technology hydrolyzes waste activated sludge (WAS) at 45 °C and converts methane at mesophilic temperature (35-38 °C), with hydraulic retention times of 3-5 d and 14-17 d, respectively. In this study, the performance and microbial community dynamics of full-scale TSBP-based sludge anaerobic digestion system were studied, and the technology was evaluated by energy balance and ecological benefit analysis. The stable operation for 390 d showed that the cumulative biogas yield was about 349,041 m 3 , the maximum biogas yield rate was 563.68 L/kg VS, and the VS degradation rate of organic matters in the sludge was 47.19%. Proteobacteria and Firmicutes were found to be the dominant bacteria in both thermophilic and mesophilic reactors. Methanobacterium and Methanosarcina were the two most abundant methanogenic genera in the AD samples. The aceticlastic methanogenesis was likely the predominant production pathway of methane in AD processes based on metagenomics. The TSBP system operated stably, and the recovered energy could achieve energy self-sufficiency, which provided technical reference for the anaerobic treatment of sludge., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This paper presents a potential process that can enhance H 2 transformation to CH 4 and simultaneously upgrading biogas by using hydrogenotrophic methanogens. For the first time, anaerobic granules were developed in upflow anaerobic sludge blanket (UASB) reactor feeding H 2 /CO 2 syngas as the sole substrate and the granule characterization was thoroughly investigated. The results from experiment revealed that the H 2 consumption rates of UASB reactor increased from 32.2 mmol L -1 ·d -1 at H 2 feeding rate 0.08 g L -1 ·d -1 to 132.0 mmol L -1 ·d -1 at 0.37 g L -1 ·d -1 , indicating that the hydrogenotrophic methanogenesis pathway was stimulated by injection of H 2 . Abundant cavities and cracks were observed on the surface and cross-section of granules, which greatly facilitated internally transferring H 2 /CO 2 synthesis gas and biogas escape. The abundance of hydrogenotrophic Methanobacterium increased, while Methanosaeta, Methanosarcina, and Methanomassiliicoccus decreased with increasing H 2 feeding rate. In general, this paper offers a feasible solution in terms of energy transformation and connecting power to fuel., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Low organic load while high fraction of particulates still challenging the application of aerobic granular sludge process in low-strength municipal wastewater treatment. The feasibility of adopting short cycle length to increase organic load and hydrolysis-acidification pretreatment to enhance anaerobic COD uptake was evaluated. As the cycle length decreased from 4 h to 2 h, the organic loading rate increased from 0.98 to 1.3 g L -1 d -1 and granulation appeared after two weeks. Moreover, with the hydrolysis-acidification pretreatment, the average effluent TN and TP concentrations decreased respectively from 17.8 to 13.7 mg L -1 and 0.76 to 0.41 mg L -1 , meeting the Grade IA of the effluent standards in China. Furthermore, cycle tests were conducted to reveal the underlying mechanism of the pretreatment effects. The results showed that the hydrolysis-acidification pretreatment enhanced the COD storage and phosphorus release in anaerobic phase, and improved the simultaneous nitrification-denitrification process, as well as the phosphorus uptake in aeration phase., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Chlorinated acetaldehydes (CALs) are typical chlorinated organic compounds that posing a great threat to biological wastewater treatment plants. In this study, volatile batch acid (VFA) tests were employed to investigate the acidification inhibition, biodechlorination, and biotransformation of high-strength CALs on hydrolytic acidification. The results indicated that the optimum parameters were 4 g/L sludge, pH = 8, and glucose as an electron donor. Moreover, the acidification inhibition and biodechlorination showed a strongly positive correlation with the degree of chlorination and CAL concentrations. Extracellular polymeric substances (EPS) decreased dramatically, while DNA increased sharply under higher CAL concentrations, which was the result of cell death caused by the toxicity of the CALs. Additionally, the relative toxicities of the CALs were as follows: trichloroacetaldehyde > dichloroacetaldehyde > chloroacetaldehyde. Furthermore, Excitation-Emission-Matrix (EEM) spectra of EPS revealed that aromatic protein-like substances I interacted with CALs to achieve a slight removal of CALs. The detected products revealed that some of the chlorine atoms and aldehyde groups in the CALs were removed by microbes to certain degree. Moreover, microbial community analysis indicated that the dominant phyla were Actinobacteria, Bacteroidetes, and Synergistetes, which had a stronger tolerance to CALs. Notably, biodechlorination was closely related to a remarkable increase in members of the genus Trichococcus., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Spontaneous anammox bacteria enrichment at mainstream conditions was reported in a full-scale Wastewater Treatment Plant (WWTP) in a temperate zone of China. The mainstream anammox was observed after WWTP process retrofit, which constructed a hybrid sludge retention time (SRT) system by providing moving carriers in the anaerobic/anoxic tank and was initially designed to enhance the denitrification process in a conventional anaerobic/anoxic/oxic process. The hybrid SRT system achieved 86.0 ± 4.6% total nitrogen (TN) removal via combined mainstream anammox and conventional denitrification. Autotrophic denitrification via mainstream anammox was confirmed by various shreds of evidence including high-throughput sequencing, specific anammox activity test, and 15 N isotopic tracing. Long-term anammox bacteria existence in the biofilm of the carrier in anoxic zones was detected in a much higher relative abundance compared with other spots. The contribution of anammox activity to TN removal was estimated at around 20%-30%. The reasons leading to spontaneous anammox enrichment were mainly attributed to the carriers for slow-growing bacteria growth and dissolved oxygen gradient in the anoxic tank (caused by intermittent aeration) for nitrite production. The insights of this full-scale case study provide important perspectives for future mainstream anammox application, and also the design of an energy-neutral WWTP process. PRACTITIONER POINTS: Spontaneous mainstream anammox in a full-scale WWTP after its retrofit in a temperate zone of China was reported. Anammox bacteria enrichment and long-term stability on moving carriers at mainstream conditions was achieved by modified hybrid SRT system. The hybrid SRT system achieve stable nitrogen removal even in cold winter and high BOD/N situation by combining mainstream anammox with conventional denitrification. Long term full-scale operation demonstrated excellent nitrogen removal with about 20%-30% contribution of mainstream anammox. This full-scale case study provided perspectives for future optimizing mainstream anammox application, and also energy-neutral WWTP process design., (© 2020 Water Environment Federation.)

This work tried understanding aggregation preference of anammox bacteria from benefit-driven perspective. Aggregated anammox sludge (AGS) gained benefits in specific anammox activity (SAA) (increased by 40.47 ± 12.64%) and in toxicity resistance (enhanced by 65.41%) than scattered anammox sludge (SCS), which were verified by kinetics. The increased heme c content by 35.67 ± 5.77% and enhanced relative abundance of anammox bacteria by 9.29% supported the benefits in biological activity and improved EPS content by 1097.59 ± 43.06% (622.16 ± 61.73% for protein (PN), 2403.47 ± 162.75% for humic acid (HA) and 1145.34 ± 97.33% for polysaccharide (PS)) justified the benefits in toxicity resistance. The diverse microbial communities and organized spatial structures owned by AGS promoted interactions between species, as the intrinsic justification for obtaining the benefits. We expect our findings to provide theoretical guidance for promotions and applications of the anammox process with excellent nitrogen removal capacity and stability., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Anaerobic digestion, a recently hot technology to produce biogases especially methane generation for biofuel from wastewater, is considered an effective explanation for energy crisis and global pollution threat. A complex microbiome population is present in sludge, which plays an important role in the digestion of complex polymer into simple monomers. 16S rRNA approaches simply are not enough for amplification due to the involvement of extreme complex population. However, Illumina sequencing is a recent powerful technology to reveal the entire microbiome structure and methane generation pathways in anaerobic digestion. Metagenomic sequencing was tested to reveal the microbial structure of a digested sludge from a local wastewater treatment plant in Beijing. The Illumina HiSeq program was used to extract about 5 GB of data for metagenomic analysis. The classification investigation revealed about 97.64% dominancy of bacteria while 1.78% were detected to be archaea using MG-RAST server. The most abundant bacterial communities were reported to be Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria. Furthermore, the important microbiome involved in methane generation was revealed. The dominant methanogens were detected (Methanosaeta and Methanosarcina), with affiliation of dominant genes involved in acetoclastic methanogenesis in a digesting sludge. The metagenomic analysis showed that microbial structure and methane generation pathways were successfully dissected in an anaerobic digester.

In this study, the anaerobic treatment and microbial characteristics of high-concentration cephalosporin wastewater were studied. A pilot-scale expanded granular sludge bed (EGSB) reactor was designed to treat cephalosporin wastewater, whose diameter, height and effective volume were 0.5 m, 4.9 m, 0.92 m 3 , respectively. With mixed high-concentration cephalosporin wastewater and municipal wastewater as a substrate, the anaerobic reactor was started and operated 414 days. An average COD removal efficiency of 72% was achieved at an organic loading rate (OLR) of 9.96 kg COD/(m 3 ·d), with a hydraulic retention time (HRT) of 25 h. The average methane content reached 82%. Methanobacterium and Methanomassiliicoccus were predominant archaea in the granular sludge for each of the organic loading rates, and the predominant methane-producing pathway was hydrogenotroph and methylotroph. Those results demonstrated that the EGSB reactor could treat high-concentration cephalosporin wastewater with a unique methane-producing pathway., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The application of an enhanced membrane coagulation reactor (E-MCR) for sewage concentration and energy recovery through anaerobic digestion (AD) was investigated. The results show that the addition of powder-activated carbon (PAC) and polyaluminum chloride (PACl) enhanced the sewage concentration efficiency and minimized the membrane fouling. The reactor was operated for 100 d with 70 d without severe fouling. The flux of 6 L/(m 2  h) with sludge retention time of 2 d recorded a long-term stable performance and recovered concentrates with about 6000-9800 mg/L of chemical oxygen demand (COD) values. The concentrate was used as feed for AD using a continuous stirred tank reactor. The results show that at a thermophilic temperature of 35°C, a high biogas yield was achieved at 20 and 30 d hydraulic retention time (HRT). Meanwhile, biogas yields of 10, 220, and 295 mL/(gCOD) were achieved at 10, 20, and 30 d HRT, respectively. The addition of PAC/PACl and the low flux condition enhanced the concentration efficiency and minimized the membrane fouling during the long-term operation. Thus, with the optimization of the operation, E-MCR becomes a promising option for sewage concentration and energy recovery.

High solid anaerobic digestion (HSAD) is a rapidly developed anaerobic digestion technique for treating municipal sludge, and has been widely used in Europe and Asia. Recently, the enhanced HSAD process with thermal treatment showed its advantages in both methane production and VS reduction. However, the understanding of the microbial community is still poor. This study investigated microbial communities in a pilot enhanced two-stage HSAD system that degraded waste activated sludge at 9% solid content. The system employed process "thermal pre-treatment (TPT) at 70 °C, thermophilic anaerobic digestion (TAD), and mesophilic anaerobic digestion (MAD)". Hydrogenotrophic methanogens Methanothermobacter spp. dominated the system with relative abundance up to about 100% in both TAD and MAD. Syntrophic acetate oxidation (SAO) bacteria were discovered in TAD, and they converted acetate into H₂ and CO₂ to support hydrogenotrophic methanogenesis. The microbial composition and conversion route of this system are derived from the high solid content and protein content in raw sludge, as well as the operational conditions. This study could facilitate the understanding of the enhanced HSAD process, and is of academic and industrial importance., Competing Interests: The authors declare no conflict of interest.

Unlike the role of the membrane in a membrane bioreactor, which is designed to replace a sediment tank, direct sewage membrane filtration (DSMF), with the goal of concentrating organic matters, is proposed as a pretreatment process in a novel sewage treatment concept. The concept of membrane-based pretreatment is proposed to divide raw sewage into a concentrated part retaining most organics and a filtered part with less pollutant remaining, so that energy recovery and water reuse, respectively, could be realized by post-treatment. A pilot-scale experiment was carried out to verify the feasibility of coagulant/adsorbent addition for membrane fouling control, which has been the main issue during this DSMF process. The results showed that continuous coagulant addition successfully slowed down the increase in filtration resistance, with the resistance maintained below 1.0×10(13) m(-1) in the first 70 hr before a jump occurred. Furthermore, the adsorbent addition contributed to retarding the occurrence of the filtration resistance jump, achieving simultaneous fouling control and chemical oxygen demand (COD) concentration improvement. The final concentrated COD amounted to 7500 mg/L after 6 days of operation., (Copyright © 2015. Published by Elsevier B.V.)

The idea of sewage concentration is gradually being accepted as a promising and sustainable way of wastewater resource recovery. In this study, Hybrid coagulation microfiltration (HCM) with air backflushing (AB) was investigated to effectively concentrate organic matter. Compared to direct sewage microfiltration, the addition of coagulation process improved the filtration performance with less fouling trends and better concentration efficiency. The use of AB exhibited even better performance within the same 7-h preliminary concentration period by reducing to one tenth of the resistance and collecting around four times as much organic matter into the product concentrate as in direct sewage microfiltration. During 93-h lab-scale continuous concentration by HCM with AB, a product concentrate with the COD concentration over 15,000 mg/L was achieved and around 70% of total influent organic matter could be recovered. Compared to Direct Membrane Filtration (DMF) with Chemically Enhanced Backwash (CEB), HCM with AB achieved better concentration efficiency with higher concentration extent and concentration velocity along with less organic matter mineralization and the more concentrated product despite with lower organic matter retention. HCM with AB could be a promising effective sewage organic matter concentration for resource recovery under optimization., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The concept of temperature staged and biological phased (TSBP) was proposed to enhance the performance of waste-activated sludge anaerobic digestion. Semi-continuous experiments were used to investigate the effect of temperature (35 to 70 degrees C) as well as the hydraulic retention time (HRT) (2, 4 and 6 days) on the acidogenic phase. The results showed that the solubilization degree of waste-activated sludge increased from 14.7% to 30.1% with temperature increasing from 35 to 70 degrees C, while the acidification degree was highest at 45 degrees C (17.6%), and this was quite different from the temperature impact on hydrolysis. Compared with HRT of 2 and 6 days, 4 days was chosen as the appropriate HRT because of its relatively high solubilization degree (24.6%) and acidification degree (20.1%) at 45 degrees C. The TSBP system combined the acidogenic reactor (45 degrees C, 4 days) with the methanogenic reactor (35 degrees C, 16 days) and the results showed 84.8% and 11.4% higher methane yield and volatile solid reduction, respectively, compared with that of the single-stage anaerobic digestion system with HRT of 20 days at 35 degrees C. Moreover, different microbial morphologies were observed in the acidogenic- and methanogenic-phase reactors, which resulted from the temperature control and HRT adjustment. All the above results indicated that 45 degrees C was the optimum temperature to inhibit the activity of methanogenic bacteria in the acidogenic phase, and temperature staging and phase separation was thus accomplished. The advantages of the TSBP process were also confirmed by a full-scale waste-activated sludge anaerobic digestion project which was an energy self-sufficient system.

The biochemical methane potentials for typical fruit and vegetable waste (FVW) and food waste (FW) from a northern China city were investigated, which were 0.30, 0.56 m3 CH4/kgVS (volatile solids) with biodegradabilities of 59.3% and 83.6%, respectively. Individual anaerobic digestion testes of FVW and FW we re conducted at the organic loading rate (OLR) of 3 k g VS/(m3.day) using a lab-scale continuous stirred-tank reactor at 350C. FVW could b e digested stably with the biogas production rate of 2.17 m3/(m3 .day)and methane production yield of 0.42 m3 CH4/kg VS. However, anaerobic digestion process for FW was failed due to acids accumulation. The effects of FVW: FW ratio on co-digestion stability and performance were further investigated at the same OLR. At FVW and FW mixing ratios of 2:1 and 1:1, the performance and operation of the digester were maintained stable, with no accumulation of volatile fatty acids (VFA) and ammonia. Changing the feed to a higher FW content in a ratio of FVW to FW 1:2, resulted in an increase inVFAs concentration to 1100-1200 mg/L, and the methanogenesis was slightly inhibited. At the optimum mixture ratio 1:1 for co-digestion of FVW with FW, the methane production yield was 0.49 m3 CH4/kg VS, and the volatile solids and soluble chemical oxygen demand (sCOD) removal efficiencies were 74.9% and 96.1%, respectively.

Concentrating organic matter in sludge and converting it into methane through anaerobic bioconversion can improve resource recovery from domestic wastewater. Enhanced membrane coagulation (EMC) is highly efficient at concentrating organic matter, but residual coagulants (aluminum salts) can obstruct bioconversion by blocking microbial access. Limited research exists on evaluating EMC sludge bioconversion performance and addressing coagulant inhibition. This study proposes alkaline pre-fermentation to break down HO-Al-P backbones in coagulated sludge flocs, thereby improving hydrolysis and organic acid production for anaerobic digestion. Among the tested alkaline conditions (pH 9, pH 10, pH 11), pre-fermentation at pH 11 released the most organic matter (4710.0 mg/L SCOD), 20.4 times higher than without alkaline treatment. At pH 11, phosphate (61 mg/L PO43−–P) and organic acid production (2728.1 mg COD/L, with nearly 50% acetic acid) peaked, resulting in superior volatile solids removal (65.2%) and methane production (185.8 mL/g VS) during anaerobic digestion. Alkaline pre-fermentation favored alkali-tolerant bacteria such as Firmicutes and Actinobacteria, especially at pH 11, while neutrophilic Proteobacteria were suppressed. Trichococcus and Bifidobacterium, known acid producers, dominated under all conditions, with their abundance increasing at higher pH levels. Anaerobic digestion enriched fermentative bacteria like Chloroflexi and Synergistota (e.g., Thermovirga), especially in high pH reactors. Methanothrix, an acetoclastic methanogen, became the dominant methanogenic archaeon, indicating that methane production from EMC sludge primarily followed the acetoclastic methanogenesis pathway. Our findings demonstrate that alkaline pre-fermentation at pH 11 significantly enhances the hydrolysis efficiency of EMC sludge for methane recovery. [ABSTRACT FROM AUTHOR]

This work aimed to enrich a denitrifying bacterial community for economical denitrification via nitrite to provide the basic objects for enhancing nitrogen removal from wastewater. A sequencing batch reactor (SBR) with continuous nitrite and acetate feeding was operated by reasonably adjusting the supply rate based on the reaction rate, and at a temperature of 20 ± 2 °C, pH of 7.5 ± 0.2, and dissolved oxygen (DO) of 0 mg/L. The results revealed that the expected nitrite concentration can be achieved during the whole anoxic reaction period. The nitrite denitrification rate of nitrogen removal from synthetic wastewater gradually increased from approximately 10 mg/(L h) to 275.35 mg/(L h) over 12 days (the specific rate increased from 3.83 mg/(g h) to 51.80 mg/(g h)). Correspondingly, the chemical oxygen demand/nitrogen (COD/N) ratio of reaction decreased from 7.9 to 2.7. Both nitrite and nitrate can be used as electron acceptors for denitrification. The mechanism of this operational mode was determined via material balance analysis of substrates in a typical cycle. High-throughput sequencing showed that the main bacterial community was related to denitrification, which accounted for 84.26% in the cultivated sludge, and was significantly higher than the 2.16% in the seed sludge. [ABSTRACT FROM AUTHOR]

To preconcentrate domestic sewage and control membrane fouling, this study proposed a novel anaerobic membrane-based preconcentration (AnMPC) system and controlled fouling by coagulation-adsorption assisted biogas sparging. The effect of polyaluminium chloride (PACl) dosage on membrane fouling control and methane potential of preconcentrated domestic sewage was also investigated. Membrane fouling control was realized by the increase of particle-size (6.03%–40.65%) and the decline of soluble microbial product (11.10%–33.14%) with the rise of PACl addition. The minimum membrane filtration resistance of 1.15 × 1013 m−1 was obtained at the group with 10 mg/L PACl, which was 7.96%–28.20% lower than other groups. More than 75% of chemical oxygen demand (COD) could be preconcentrated, and the preconcentrated ratio increased by 4.22%–9.70% with the rise of PACl addition. Methane potential decreased by 5.40%–40.56% due to the inhibition of accumulated PACl. The pre-hydrolysis of domestic sewage during AnMPC could shorten fermentation time by 0.8–3.2 d. The group with 10 mg/L PACl addition was the optimal due to the excellent anti-fouling performance and the promising energy balance. This study could provide a promising membrane-based preconcentration method with high COD recovery and mild membrane fouling for sustainable treatment of domestic sewage. [Display omitted] • Anaerobic membrane-based preconcentration was firstly proposed to treat sewage. • 10 mg/L PACl reduced the filtration resistance by 8%–28% and got 1.15 × 1013 m−1. • Over 75% of COD was preconcentrated and the ratio increased by 4%–10% with PACl. • Methane potential and fermentation time reduced by 5%–41% and 0.8–3.2 d with PACl. • 10 mg/L PACl was the optimal with promising fouling control and energy balance. [ABSTRACT FROM AUTHOR]

This study proposes the recovery of organics and nitrogen from sewage through membrane-based pre-concentration (MPC) combined with ion exchange (IE) process. Unlike conventional activated sludge process, MPC–IE redesigned organic carbon flow to increase chemical oxygen demand (COD) conversion for energy recovery via anaerobic digestion (AD). This process also achieved nitrogen recovery instead of destruction. Membrane-based pre-concentration of COD was conducted using actual sewage for one month. As high as 65% COD was recovered. Batch IE adsorption and regeneration experiments were conducted. However, these experiments recovered only 37.5% NH 4 -N because of the selectivity of IE for hard ions over ammonium. Despite the low rate of recovery, the process could achieve a total of 0.38 kWh/m 3 energy recovery by combining energy production with anaerobic digestion of pre-concentrated organics (0.26 kWh/m 3 ) and energy saving via nitrogen reuse (0.12 kWh/m 3 ). Highly efficient energy and nitrogen recovery from sewage via MPC–IE process was expected after optimization. [ABSTRACT FROM AUTHOR]

• A pilot-scale enhanced magnetic separation equipment (300 m3/d) was proposed for up-concentration. • Adsorption further enhanced the ability to capture soluble organics of magnetic separation. • Over 60% of organics were removed within 10 min with satisfactory energy consumption. • The energy potential of the produced sludge was competitive. The up-concentration process has been demonstrated as an attractive approach to carbon-neutral wastewater treatment. Innovation in the separation processes can help eliminate the current heavy dependence on gravity, and credible pilot-scale verification is crucial for application promotion. We hereby proposed a pilot-scale enhanced magnetic separation (EMS) system as an up-concentration step to maximize energy recovery from municipal wastewater. The design of EMS was based on the hypothesis that magnetic-driven separation could be a breakthrough in separation speed, and adsorption could further enhance the separation efficiency by capturing soluble substances. Jar tests confirmed the feasibility of activated carbon adsorption, which could also roughen the surface of aggregates. Further, over one-year operation of a 300 m3/d EMS equipment provided optimum operation strategies and evidence of system effectiveness. More than 80% of particulate organics and 60% of soluble organics were removed within 10 min at an energy consumption of only 0.036 kWh/m3. The characteristics of sludge were clarified in terms of organic concentration, extracellular polymeric substances composition, and micro-community analysis. The anaerobic experiments further demonstrated the potential value of the concentrated products. Surprisingly, the developed EMS system exhibited significant advantages in time consumption and space occupation, with competitive operating cost and energy consumption. Overall, the results of this study posed the EMS process for up-concentration as a potential approach to organics recovery from municipal wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A pilot-scale MCDI system was designed for ammonia recovery from municipal wastewater. • Different working conditions were optimized for ammonia recovery. • Competitive adsorption between Ca2+, Mg2+ and NH 4 + were discussed. • The MCDI system showed high stability in long-term operation. • MCDI showed preferential electrosorption of NH 4 + in short adsorption periods. With the depletion of energy, renovation of wastewater has attracted wide attention around the world, among which the recovery of ammonia has also been an ongoing topic. Membrane capacitive deionization (MCDI) has emerged as a promising technology for nutrient removal and recovery. However, limitations of both scale-up and treatment of practical wastewater still restrict its real application. This study aims to investigate the feasibility of ammonia removal from real wastewater by MCDI on a pilot scale. The MCDI module used in this study was expanded to a 2-unit facility (15 pairs of electrodes per unit). Firstly, synthetic wastewater was used as feed water to optimize different kinds of operating parameters, including applied voltage (0–2.5 V), flow rate (7–30 L/h), and initial concentration (20–100 mg/L). Further experiments investigated the competitive adsorption performance under complex inflow conditions. Results indicated that the presence of co-existing cations significantly reduced the removal efficiency and adsorption capacity of ammonia. With the same inflow concentration, the removal efficiency of NH 4 +, Mg2+, and Ca2+ was 39.12 ± 5.31%, 47.56 ± 2.68%, and 33.33 ± 1.90% respectively. The interplay of initial ion concentration, charge valence, and hydrated radii led to the different electro-sorption performances. Subsequently, practical municipal wastewater after the up-concentration of organics was used as feed water to evaluate the feasibility of the pilot-scale MCDI. Under the optimized condition, a long-term experiment was carried out for 15-day to deal with actual wastewater. Besides, ion removal performance, the energy consumption, and desorption efficiency were also analyzed. The system maintains a stable removal efficiency for all cations, with low energy consumption (1.16 kWh/m3) and high desorption efficiency (around 90%). Overall, the results of this study posed the MCDI process as a potential approach to ammonia removal and recovery from municipal wastewater. [ABSTRACT FROM AUTHOR]

The technical and economic feasibility of sewage-pre-concentration-based resource recovery for cleaner production (CP) subject to scaling up remains unknown. A pilot-scale ultrafiltration (UF) pre-concentration system, which optimizes the use of UF, enhanced coagulation process (ECP) and air-backflushing (AB), is established coupling with anaerobic digestion (AD) in this study to demonstrate its scaled-up performance of CP-oriented integrated resource recovery. Results show that 90% of organic matter recovery is achievable with only 2–3% of mineralization under optimized AB during over 100d operation. The efficient and stable concentration performance mainly results from cake layer induced by optimized AB with minimal carbon loss and maximal productivity. AD of the optimized concentrate obtained a methanisation of 61.3% and a digestate with improved dewaterability and pathogens limitation for efficient nutrient recovery. Energy balance of the whole system in different working scenarios reveals that the optimized net energy production was 0.2537 kWh/m3. Considering integrated permeate reclamation and energy and nutrient recovery with similar case study, the whole system in optimized scenario could achieve a net operational profit of 0.9188 CNY/m3 with a minimized payback time of approximately 6 years, which is a moderate and acceptable value. Above results demonstrate the promise of implementation of UF pre-concentration for sustainable CP-oriented integrated resource recovery. [ABSTRACT FROM AUTHOR]