Treatment of azo dye-containing wastewater in a combined UASB-EMBR system: Performance evaluation and membrane fouling study.

This work investigated the treatment of azo dye-containing wastewater in an upflow anaerobic sludge blanket (UASB) reactor combined with an electro-membrane bioreactor (EMBR). Current densities of 20 A m-2 and electric current exposure mode of 6'ON/30'OFF were applied to compare the performance of the EMBR to a conventional membrane bioreactor (MBR). The results showed that dye (Drimaren Red CL-7B) removal occurred predominantly in the UASB reactor, which accounted for 57% of the total dye removal achieved by the combined system. When the MBR was assisted by electrocoagulation, the overall azo dye removal efficiency increased from 60.5 to 67.1%. Electrocoagulation batch tests revealed that higher decolorization rates could be obtained with a current density of 50 A m-2. Over the entire experimental period, the combined UASB-EMBR system exhibited excellent performance in terms of chemical oxygen demand (COD) and NH4+-N removal, with average efficiencies above 97%, while PO43--P was only consistently removed when the electrocoagulation was used. Likewise, a consistent reduction in the absorption spectrum of aromatic amines was observed when the MBR was electrochemically assisted. In addition to improving the pollutants removal, the use of electrocoagulation reduced the membrane fouling rate by 68% (0.25-0.08 kPa d-1), while requiring additional energy consumption and operational costs of 1.12 kWh m-3 and 0.32 USD m-3, respectively. Based on the results, it can be concluded that the combined UASB-EMBR system emerges as a promising technological approach for textile wastewater treatment.

Comparative study of the removal of sulfate by UASB in light and dark environment.

At present, the application of sewage treatment technologies is restricted by high sulfate concentrations. In the present work, the sulfate removal was biologically treated using an upflow anaerobic sludge blanket (UASB) in the absence/presence of light. First, the start-up of UASB for the sulfate removal was studied in terms of COD degradation, sulfate removal, and effluent pH. Second, the impacts of different operation parameters (i.e., COD/SO42- ratio, temperature and illumination time) on the UASB performance were explored. Third, the properties of sludge derived from the UASB at different time were analyzed. Results show that after 28 days of start-up, the COD removal efficiencies in both the photoreactor and non-photoreactor could reach a range of 85-90% while such reactors could achieve > 90% of sulfate being removed. Besides, higher illumination time could facilitate the removal of pollutants in the photoreactor. To sum up, the present study can provide technical support for the clean removal of sulfate from wastewater using photoreactors.

Microbiological insights into anaerobic phenol degradation mechanisms and bulking phenomenon in a mesophilic upflow anaerobic sludge blanket reactor in long-term operation.

In this study, a long-term operation of 2,747 days was conducted to evaluate the performance of the upflow anaerobic sludge blanket (UASB) reactor and investigated the degradation mechanisms of high-organic loading phenol wastewater. During the reactor operation, the maximum chemical oxygen demand (COD) removal rate of 6.1 ± 0.6 kg/m3/day under 1,680 mg/L phenol concentration was achieved in the mesophilic UASB reactor. After a significant change in the operating temperature from 24.0 ± 4.1 °C to 35.9 ± 0.6 °C, frequent observations of floating and washout of the bloated granular sludge (novel types of the bulking phenomenon) were made in the UASB reactor, suggesting that the change in operating temperature could be a trigger for the bulking phenomenon. Through the metagenomic analysis, phenol degradation mechanisms were predicted that phenol was converted to 4-hydroxybenzoate via two possible routes by Syntrophorhabdaceae and Pelotomaculaceae bacteria. Furthermore, the degradation of 4-hydroxybenzoate to benzoyl-CoA was carried out by members of Syntrophorhabdaceae and Smithellaceae. In the bulking sludge, a predominant presence of Nanobdellota, belonging to DPANN archaea, was detected. The metagenome-assembled genome of the Nanobdellota lacks many biosynthetic pathways and has several genes for the symbiotic lifestyle such as trimeric autotransporter adhesin-related protein. Furthermore, the Nanobdellota have significant correlations with several methanogenic archaea that are predominantly present in the UASB reactor. Considering the results of this study, the predominant Nanobdellota may negatively affect the growth of the methanogens through the parasitic lifestyle and change the balance of microbial interactions in the granular sludge ecosystem.

Variations in antibiotic resistance genes during long-term operation of an upflow anaerobic sludge blanket reactor.

Antibiotic resistance genes (ARGs) have been widely detected in the environment. Anaerobic digestion (AD) has the potential ability to remove ARGs, and a comprehensive study is needed on the variations in ARGs during AD. In this study, variations in antibiotic resistance genes (ARGs) and microbial communities were investigated during the long-term operation of an upflow anaerobic sludge blanket (UASB) reactor. An antibiotic mixture of erythromycin, sulfamethoxazole and tetracycline was added to the UASB influent and the operation period was 360 days. The abundances of 11 ARGs and class 1 integron-integrase gene were detected in the UASB reactor, and the correlation between the ARGs and the microbial community was analyzed. The composition of ARGs indicated that the main ARGs in the effluent were sul1, sul2, and sul3, whereas the main ARG in the sludge was tetW. Correlation analysis indicated a negative correlation between microorganisms and ARGs in the UASB. In addition, most of ARGs showed a positive correlation with norank_f_Propionibacteriaceae and Clostridum_sensu_stricto_6, which were identified as potential hosts. These findings may help develop a feasible strategy for removing ARGs from aquatic environments during anaerobic digestion.

Study on the Treatment of Refined Sugar Wastewater by Electrodialysis Coupled with Upflow Anaerobic Sludge Blanket and Membrane Bioreactor.

In this paper, refined sugar wastewater (RSW) is treated by electrodialysis (ED) coupled with an upflow anaerobic sludge blanket (UASB) and membrane bioreactor (MBR). The salt in RSW was first removed by ED, and then the remaining organic components in RSW were degraded by a combined UASB and MBR system. In the batch operation of ED, the RSW was desalinated to a certain level (conductivity < 6 mS·cm-1) at different dilute to concentrated stream volume ratios (VD/VC). At the volume ratio of 5:1, the salt migration rate JR and COD migration rate JCOD were 283.9 g·h-1·m-2 and 13.84 g·h-1·m-2, respectively, and the separation factor α (defined as JCOD/JR) reached a minimum value of 0.0487. The ion exchange capacity (IEC) of ion exchange membranes (IEMs) after 5 months of usage showed a slight change from 2.3 mmol·g-1 to 1.8 mmol·g-1. After the ED treatment, the effluent from the tank of the dilute stream was introduced into the combined UASB-MBR system. In the stabilization stage, the average COD of UASB effluent was 2048 mg·L-1, and the effluent COD of MBR was maintained below 44-69 mg·L-1, which met the discharge standard of water contaminants for the sugar industry. The coupled method reported here provides a viable idea and an effective reference for treating RSW and other similar industrial wastewaters with high salinity and organic contents.

Upflow anaerobic sludge blanket reactor operation under high pressure for energy-rich biogas production.

Autogenerative high-pressure digestion has an advantage of producing CH4-rich biogas directly from the reactor. However, its continuous operation has rarely been reported, and has never been attempted in an upflow anaerobic sludge blanket reactor (UASB). Here, UASB was continuously operated at 10 g COD/L/d with increasing pressure from 1 to 8 bar. As the pressure increased, the CH4 content in the biogas increased gradually, reaching 96.7 ± 0.8% at 8 bar (309 MJ/m3 biogas). The pH was dropped from 8.2 to 7.2 with pressure increase, but COD removal efficiency was maintained > 90%. The high pressure up to 8 bar did not adversely impact the physicochemical properties of granules, which was due to the increased production of extracellular polymeric substances (EPS), particularly, tightly bound EPS (34% increase). With pressure increase, there was no changes in the microbial community and ATPase gene expression, but 41% increase in carbonic anhydrase gene expression was observed.

Microbial granules on reactors performance during organic butyrate digestion: clean production.

This critical review for anaerobic degradation of complex organic compounds like butyrate using reactors has been enormously applied for biogas production. Biogas production rate has a great impact on: reactor granulation methanogenesis, nutrient content, shear velocity, organic loading and loss of nutrients taking place in the reactor continuously. Various technologies have been applied to closed anaerobic reactors to improve biogas production and treatment efficiency. Recent reviews showed that the application of closed anaerobic reactors can accelerate the degradation of organics like volatile fatty acid-butyrate and affect microbial biofilm formation by increasing the number of methanogens and increase methane production 16.5 L-1 CH4 L-1 POME-1. The closed anaerobic reactors with stable microbial biofilm and established organic load were responsible for the improvement of the reactor and methane production. The technology mentioned in this review can be used to monitor biogas concentration, which directly correlates to organic concentrations. This review attempts to evaluate interactions among the: degradation of organics, closed anaerobic reactors system, and microbial granules. This article provides a useful picture for the improvement of the degradation of organic butyrate for COD removal, biogas and methane production in an anaerobic closed reactor.

Recent reviews showed that the application of closed anaerobic reactors can accelerate the degradation of organic compounds, such as volatile fatty acid-butyrate, and affect microbial biofilm formation by increasing the number of methanogens, thus enhancing biogas production. The closed anaerobic reactors with stable microbial biofilm established the organic load and improved the performance of the reactor for methane production. The technology used involves monitoring biogas concentrations which correlates with organic concentrations. This review attempts to evaluate interactions among: the degradation of organics, closed anaerobic reactors system, and microbial granules. This review, therefore, provides a useful picture for the improvement of butyrate degradation for COD removal and methane production with the help of various anaerobic closed reactors. The performance of UASBR depends on granulation. The granulation process in UASB reactors can be divided into four steps: (1) Transport of cells to the surface of other cells; (2) Initial reversible adsorption by physicochemical forces; (3) Irreversible adhesion of the cells by microbial appendages and/or polymers; and (4) Multiplication of the cells and development of the granules. Any factor which can complement any one of the four steps will be able to accelerate the granulation process and shorten the startup time of UASB reactors.

Deciphering the spatial distribution along the upflow anammox reactor: Sludge characteristics and interspecies interactions.

Here, nitrogen conversion, granular characteristics and microbial dynamics were combined to reveal the longitudinal heterogeneity along anammox-UASB with nitrogen removal efficiency of 92.6%. The reactor was divided into Bottom-zone, Middle-zone, Upper-zone, and Top-zone with height increasing. Results indicated that particle size decreased from Bottom-zone to Upper-zone, while granular floatation caused an increase in Top-zone. Protein secondary structure in EPS was loose and hzsA transcription ratio was only 4.45% due to the limited mass-transfer and serious mineralization of ultra-large granules in Bottom-zone. Smaller granules in Middle-zone were more robust and active, with compact tryptophan- and aromatic-like protein in EPS and 23.71% hzsA transcription. Intriguingly, coexisting denitrification survived on EPS and/or microbial metabolites was observed. Transcription of narG was stimulated with height increasing, resulted in performance improvement through combining partial denitrification and anammox in Upper-zone. The findings deciphered stratification characteristics along the height-partitioned anammox-UASB, and reveal cross-feedings between denitrification and anammox bacteria.

Psychrophilic treatment of municipal wastewater with a combined UASB/ASD system, and perspectives for improving urban WWTP sustainability.

According to new paradigms of urban wastewater management, energy savings and resources and energy recovery from sewage will assume an ever-increasing importance. Anaerobic processes, aside from being more energy efficient than conventional aerobic ones, are particularly suited to recover embedded organic energy, improving the overall energy balance of treatment processes, however, their performance is limited by low temperatures and slower kinetics. In this study, a pilot Upflow Anaerobic Sludge Blanket (UASB) reactor was operated to treat municipal wastewater at low temperature regime (16.5-18.5 °C) for 22 weeks, both as standalone process and combined with a sidestream anaerobic sludge digester. Process performance highlighted good system robustness, as proved by stable pH and volatile fatty acid/total alkaline buffer capacity ratio, even though observed methane yield was low. Observed COD and TSS removal efficiencies were in the ranges of 60-69% and 63-73%, respectively. Methane production ranged between 0.106 and 0.132 Nm3CH4/kgCODrem. An economic assessment was carried out to evaluate the feasibility and benefits of implementing UASB pre-treatment of municipal wastewater in existing conventional facilities (activated sludge and anaerobic sludge digestion), showing that significant energy demand reduction could be achieved for both biological secondary treatment and sludge management, leading to considerable operational economies, and possible positive economic returns within a short pay-back period (3-4 yrs).

Impact of permeate flux and gas sparging rate on membrane performance and process economics of granular anaerobic membrane bioreactors.

This research investigated the impact of permeate flux and gas sparging rate on membrane permeability, dissolved and colloidal organic matter (DCOM) rejection and process economics of granular anaerobic membrane bioreactors (AnMBRs). The goal of the study was to understand how membrane fouling control strategies influence granular AnMBR economics. To this end, short- and long-term filtration tests were performed under different permeate flux and specific gas demand (SGD) conditions. The results showed that flux and SGD conditions had a direct impact on membrane fouling. At normalised fluxes (J20) of 4.4 and 8.7 L m-2 h-1 (LMH) the most favourable SGD condition was 0.5 m3 m-2 h-1, whereas at J20 of 13.0 and 16.7 LMH the most favourable SGD condition was 1.0 m3 m-2 h-1. The flux and the SGD did not have a direct impact on DCOM rejection, with values ranging between 31 and 44%. The three-dimensional excitation-emission matrix fluorescence (3DEEM) spectra showed that protein-like fluorophores were predominant in mixed liquor and permeate samples (67-79%) and were retained by the membrane (39-50%). This suggests that protein-like fluorophores could be an important foulant for these systems. The economic analysis showed that operating the membranes at moderate fluxes (J20 = 7.8 LMH) and SGD (0.5 m3 m-2 h-1) could be the most favourable alternative. Finally, a sensitivity analysis illustrated that electricity and membrane cost were the most sensitive economic parameters, which highlights the importance of reducing SGD requirements and improving membrane permeability to reduce costs of granular AnMBRs.

Effect of antibiotic mixtures on the characteristics of soluble microbial products and microbial communities in upflow anaerobic sludge blanket.

Two upflow anaerobic sludge blanket reactors (UASBs) were used to investigate the effects of three antibiotic mixtures (erythromycin, sulfamethoxazole, and tetracycline) on reactor performance, soluble microbial products (SMPs) composition and microbial community. One reactor (UASBantibiotics) was fed with antibiotic mixtures, whereas another reactor (UASBcontrol) was used as a control without the addition of antibiotic mixtures. Compared with those in UASBcontrol, UASBantibiotics show lower chemical oxygen demand removal efficiency and biogas content. A higher removal efficiency of antibiotic mixtures was obtained in first few stages in UASBantibiotics. The SMPs composition of effluent from the two reactors did not differ significantly, and the main components were protein-like substances, which produced higher fluorescence intensity in UASBantibiotics. Gas chromatography-mass spectrometry analysis revealed that the main compounds identified as SMPs (<580 Da) were alkanes, aromatics and esters, with only 20% similarity of SMPs between UASBantibiotics and UASBcontrol. Antibiotics had a significant effect on the microbial community structure. Notably, in UASBcontrol, hydrogenotrophic methanogens, key microorganisms in anaerobic digestion, had an obvious advantage at all stages compared with UASBantibiotics, whereas acetoclastic methanogen exhibited the opposite pattern. The above results demonstrated that antibiotic mixtures influenced the effluent quality during anaerobic treatment of synthetic wastewater, resulting in changes in the microbial community structure. This study clarified the effect of antibiotic mixtures on the operation of UASBs. It could contribute to identifying potential strategies for improving effluent quality in anaerobic treatment.

Calcium hypochlorite pretreatment improves thermophilic digestion of waste activated sludge in an upflow anaerobic sludge blanket reactor.

Anaerobic wasted activated sludge (WAS) digestion has been widely applied to reduce sludge volume and generate bioenergy in the form of methane. However, anaerobic WAS digestion performance is often challenged with poor hydrolysis of biomass cellular structures. In the present study, the feasibility of using calcium hypochlorite (Ca(ClO)2) to improve the thermophilic digestion of WAS was studied. Two thermophilic upflow anaerobic sludge bed (UASB) reactors (one with and one without Ca(ClO)2 pretreatment) were operated for 120 days under low and high organic loading rate (OLR) conditions, corresponding hydraulic retention time (HRT) of 10 days and 6 days, respectively. Both reactors achieved satisfied performance during the studied period. Under the low OLR condition, Ca(ClO)2 pretreatment significantly improved WAS total volatile solids (VS) removal efficiency (from 48.06 ± 2.63% to 57.34 ± 3.54%) and methane yield (from 289.2 ± 27.6 to 362.2 ± 36.7 N mL/g VS). However, no significant improvement was observed under the high OLR condition. g_S1 and g_Fervidobacterium were predominant bacteria in the thermophilic UASB reactor fed with Ca(ClO)2 pretreated WAS. Methanosarcina was dominant archaea in both reactors. The treatment mechanism and application potential of using Ca(ClO)2 to enhance the WAS digestibility were further discussed.

Formation and characterization of conductive magnetite-embedded granules in upflow anaerobic sludge blanket reactor treating dairy wastewater.

Promoting direct interspecies electron transfer (DIET) with conductive additives has proved effective in improving anaerobic digestion performance and stability. However, its application is limited by the need to replenish the washout loss of conductive materials. This study reports the formation of conductive magnetite-embedded granular sludge and its long-term influence on the performance of upflow anaerobic sludge blanket reactors treating dairy wastewater. The magnetite-supplemented reactor maintained better performance than the no-magnetite control, with greater sludge settling and electron transport activity, throughout the 192-d experiment at increasing organic loading rates (1.2-8.5 g chemical oxygen demand/L·d). The abundance of electroactive microbes also remained higher in the magnetite-supplemented reactor. The results suggest that DIET-based electric syntrophy was promoted in the magnetite-embedded granules. This study is the first to demonstrate the self-embedment of submicron conductive material into granular sludge and its benefits. These findings offer a new approach to enhancing anaerobic granular sludge systems.

Comparison of soluble microbial product (SMP) production in full-scale anaerobic/aerobic industrial wastewater treatment and a laboratory based synthetic feed anaerobic membrane system.

This study focused on the characterisation of soluble microbial products (SMPs) produced from a full-scale multi-stage (anaerobic/aerobic) industrial wastewater treatment plant, and contrasted them to the SMPs detected in the effluent of a lab-scale AnMBR treating synthetic wastewater to determine if there were any common solutes detected irrespective of the feed organics. Recently developed analytical methods using gas chromatography coupled mass spectrometry (GC-MS) and liquid chromatography coupled quadrupole-time-of-flight (LC-Q-ToF) for SMP characterisation in a wide molecular weight (MW) range of 30-2000 Da (Da) were applied. Samples collected from the Industrial Wastewater plant were the upflow anaerobic sludge blanket (UASB) influent and effluent, and aerobic membrane bioreactor (MBR) effluent before discharge. The GC-MS detected a spike in cyclooctasulphur in the UASB effluent, an indicator of shock-loading, which disappeared after the MBR process. Alkanes, acids and nitrogenous compounds were found to be the end-products from the GC-MS results, while LC-Q-ToF analysis revealed that eicosanoids, a group of cell-signalling molecules, were produced in the aerobic MBR, and made up 71% of its effluent. A comparison of the submerged anaerobic membrane bioreactor (SAMBR) and aerobic MBR effluents using GC-MS showed that there was only a small degree of similarity between the SMPs, comprising mainly long chain alkanes and phthalate. On the other hand, LC-Q-ToF showed a large contrast in compound composition, mostly having cell-signalling functions, which deepened our understanding of the different metabolic processes occurring in aerobic and anaerobic systems. These data could be useful for future work in various areas such as controlling quorum-sensing and biofilm formation, process optimisation and control, and microbial ecology.

Hydrolysis and Methanogenesis in UASB-AnMBR Treating Municipal Wastewater Under Psychrophilic Conditions: Importance of Reactor Configuration and Inoculum.

Three upflow anaerobic sludge blanket (UASB) pilot scale reactors with different configurations and inocula: flocculent biomass (F-UASB), flocculent biomass and membrane solids separation (F-AnMBR) and granular biomass and membrane solids separation (G-AnMBR) were operated to compare start-up, solids hydrolysis and effluent quality. The parallel operation of UASBs with these different configurations at low temperatures (9.7 ± 2.4°C) and the low COD content (sCOD 54.1 ± 10.3 mg/L and pCOD 84.1 ± 48.5 mg/L), was novel and not previously reported. A quick start-up was observed for the three reactors and could be attributed to the previous acclimation of the seed sludge to the settled wastewater and to low temperatures. The results obtained for the first 45 days of operation showed that solids management was critical to reach a high effluent quality. Overall, the F-AnMBR showed higher rates of hydrolysis per solid removed (38%) among the three different UASB configurations tested. Flocculent biomass promoted slightly higher hydrolysis than granular biomass. The effluent quality obtained in the F-AnMBR was 38.0 ± 5.9 mg pCOD/L, 0.4 ± 0.9 mg sCOD/L, 9.9 ± 1.3 mg BOD5/L and <1 mg TSS/L. The microbial diversity of the biomass was also assessed. Bacteroidales and Clostridiales were the major bacterial fermenter orders detected and a relative high abundance of syntrophic bacteria was also detected. Additionally, an elevated abundance of sulfate reducing bacteria (SRB) was also identified and was attributed to the low COD/SO4 2- ratio of the wastewater (0.5). Also, the coexistence of acetoclastic and hydrogenotrophic methanogenesis was suggested. Overall this study demonstrates the suitability of UASB reactors coupled with membrane can achieve a high effluent quality when treating municipal wastewater under psychrophilic temperatures with F-AnMBR promoting slightly higher hydrolysis rates.

Occurrence, fates and potential treatment approaches for removal of viruses from wastewater: A review with emphasis on SARS-CoV-2.

The world is combating the emergence of Coronavirus disease 2019 (COVID-19) caused by novel coronavirus; severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Further, due to the presence of SARS-CoV-2 in sewage and stool samples, its transmission through water routes cannot be neglected. Thus, the efficient treatment of wastewater is a matter of utmost importance. The conventional wastewater treatment processes demonstrate a wide variability in absolute removal of viruses from wastewater, thereby posing a severe threat to human health and environment. The fate of SARS-CoV-2 in the wastewater treatment plants and its removal during various treatment stages remains unexplored and demands immediate attention; particularly, where treated effluent is utilised as reclaimed water. Consequently, understanding the prevalence of pathogenic viruses in untreated/treated waters and their removal techniques has become the topical issue of the scientific community. The key objective of the present study is to provide an insight into the distribution of viruses in wastewater, as well as the prevalence of SARS-CoV-2, and its possible transmission by the faecal-oral route. The review also gives a detailed account of the major waterborne and non-waterborne viruses, and environmental factors governing the survival of viruses. Furthermore, a comprehensive description of the potential methods (physical, chemical, and biological) for removal of viruses from wastewater has been presented. The present study also intends to analyse the research trends in microalgae-mediated virus removal and, inactivation. The review also addresses the UN SDG 'Clean Water and Sanitation' as it is aimed at providing pathogenically safe water for recycling purposes.

Simultaneous nitrogen and dissolved methane removal from an upflow anaerobic sludge blanket reactor effluent using an integrated fixed-film activated sludge system.

One of the main drawbacks of upflow anaerobic sludge blanket (UASB) reactors that treat low-strength sewage at room temperature is related to the low quality of their effluents in terms of dissolved methane, organic matter, and nitrogen content. The present study aims to evaluate the feasibility of using an integrated fixed-film activated sludge (IFAS) system as an alternative post-treatment technology to mitigate the environmental impact of such effluents. For this purpose, a pilot plant composed of a UASB (120 L) followed by an IFAS (66 L) system was operated for 407 days. Special attention was paid to the suspended biomass retention capacity and the dissolved methane and nitrogen removal potential of the IFAS post-treatment system. Furthermore, the role of carriers on denitrification and nitrification processes and the microbial communities present in the biofilm were also analyzed. Average total chemical oxygen demand (CODT) and ammonium removal efficiencies of 92 ± 3% and around 57 ± 16% were attained throughout the entire operation, respectively. During a first period in which biomass was maintained in both biofilms and suspension, and nitrite was the main electron acceptor, maximum nitrogen removal and methane removal efficiencies of 32.5 mg TN L-1 and 93% were observed in the IFAS system, respectively. However, throughout the second period, in which suspended biomass was completely washed out from the IFAS system, and nitrate became the main electron acceptor, these values decreased to 18 ± 4 mg TN Lfeed-1 and 77 ± 12%, respectively. Surprisingly, throughout the entire operation, it was observed that around 50 and 41% of the total nitrogen and methane removals observed in the IFAS system, respectively, were carried out in the aerobic compartment. Aerobic methane oxidizers and anammox were detected with significant relative abundances in the biofilm carriers used in the anoxic and aerobic compartments using 16S rRNA gene amplicon sequencing analysis. Therefore, the use of an IFAS system could be suited to diminish greenhouse gas emissions and nutrients concentration for those sewage treatment plants that used UASB systems, especially in countries with temperate and warm climates.

Blackwater biomethane recovery using a thermophilic upflow anaerobic sludge blanket reactor: Impacts of effluent recirculation on reactor performance.

Thermophilic anaerobic digestion is a promising process for high-solid blackwater (BW) treatment due to improved hydrolysis rates, high methanogenesis efficiency, and pathogen removal, when compared with mesophilic treatment. In the present work, the effects of effluent recirculation (i.e., mixing) on thermophilic blackwater treatment were studied. A laboratory-scale thermophilic upflow anaerobic sludge blanket reactor was operated with and without effluent recirculation. The methanogenesis efficiency of the BW treatment increased from 45.0 ± 2.9% when effluent recirculation was applied to 56.7 ± 5.5% without effluent recirculation. Without effluent recirculation, the COD accumulation in the bioreactor was reduced from 17.2 to 3.8% and the effluent volatile fatty acids (VFA) concentration was reduced from 0.64 ± 0.18 to 0.15 ± 0.10 g/L. Further, both acetoclastic and hydrogenotrophic methanogenic activity increased from 101.3 ± 10.8 and 93.9 ± 6.1 to 120.4 ± 9.4 and 118.2 ± 13.2 mg CH4-COD/(gVSS⋅d), respectively, after effluent recirculation was discontinued. The predominant methanogens changed from Methanothermobacter (67%) with effluent recirculation to Methanosarcina (62%) without effluent recirculation. As compared to the effluent recirculation conditions, the enhanced biomethane recovery and treatment performance without effluent recirculation can be attributed to the close proximity of bacteria and archaea groups and the reduced VFA accumulation. Predicted functional gene comparison showed higher prevalence of function for intermediate metabolite transportation (transporters, ATP-binding cassette (ABC) transporters, and two-component system) after discontinuing effluent circulation, which contributed to improved syntrophic propionate oxidation and syntrophic acetate oxidization and enhanced hydrogenotrophic methanogenesis.

Phosphorous recovery from a novel recirculating aquaculture system followed by its sustainable reuse as a fertilizer.

Phosphorus (P) is an essential element for life that is introduced through feed in modern aquaculture-the fastest growing food production sector. P can also be a source of environmental contamination and eutrophication if mistreated. Fish assimilate only 20-40% of the applied P; the rest is released into the water. The goals of this research were to study the fate of P in a novel intensive near-zero discharge (<1%) recirculating aquaculture system (RAS). We also tested means to recover and reuse the removed P. Water, sludge and the microbial communities in the different treatment units of the system were analyzed. The treated sludge was tested as a potential substitute for P fertilization in a planter experiment. Of the applied P, 29.5% was recovered by fish, 69.8% was found in the fish sludge and 3.8% was released into the water as soluble reactive P. The P concentration in the fish tank remained stable, likely due to its uptake by denitrifying polyphosphate-accumulating organisms and its precipitation in the RAS's anaerobic reactor. Thus, only 1.5% of the applied P was discharged as effluent, and 69% recovered. The dominant minerals were from the apatite group, followed by the struvite family. Differences in mineral abundance between thermodynamic prediction and actual findings were most probably due to biomineralization by bacteria. Similar plant biomass was recorded for the commercial and digested-sludge fertilization treatments. Biological P removal and recovery from RAS was successfully studied and demonstrated.

Anaerobic treatment of glutamate-rich wastewater in a continuous UASB reactor: Effect of hydraulic retention time and methanogenic degradation pathway.

To investigate the anaerobic treatment efficiency and degradation pathways of glutamate-rich wastewater under various hydraulic retention times (HRTs), a lab-scale upflow anaerobic sludge blanket (UASB) reactor was operated continuously for 180 days. Results showed that high chemical oxygen demand (COD) removal efficiencies of 95.5%-96.5% were achieved at HRTs of 4.5 h-6 h with a maximum methane yield of 0.31 L-CH4/g-COD. When the HRT was shortened to less than 3 h, the removal performance of the reactor declined. There also was an excessive accumulation of volatile fatty acids, which implies that an appropriately small HRT is applicable to the UASB reactor treating glutamate-rich wastewater. Methanogenic degradation of glutamate in the UASB reactor depended on the HRT applied, and the typical methane-producing capability of the sludge at an HRT of 3 h, in descending order, was acetate > glutamate > butyrate > H2/CO2 > valerate > propionate. Clostridium and Methanosaeta were predominant in the glutamate-degrading sludge. At least three degradation pathways most likely existed in the UASB reactor, and the pathway via 3-methlaspartate by Clostridium pascui was expected to be dominant.