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Highlights • UASB reactors were tested for total selenium (Se), Cd(II) and Zn(II) removal. • The presence of Cd(II) and Zn(II) enhanced the total Se removal. • Se(VI) removal efficiency (RE) was >99.6% under psychrophilic conditions. • The RE of Cd(II) and Zn(II) in the UASB reactors were 99.2 and 96.2%. • 64.8–79.5% of Se was entrapped in the anaerobic granular sludge. Abstract This study investigated the continuous biological removal of selenate [Se(VI)] in the presence of cadmium [Cd(II)] and zinc [Zn(II)] by anaerobic granular sludge in two upflow anaerobic sludge blanket (UASB) reactors operating under psychrophilic (17.5 ± 0.4 ℃) and mesophilic (30 ± 0.5 ℃) conditions for 42 and 74 days, respectively. Se(VI) and total selenium (Se) removal efficiencies reached, respectively, 99.6% and 95.0% in the UASB reactor operating at psychrophilic conditions. Cd(II) and Zn(II) removal efficiencies by the mesophilic UASB reactor reached, respectively, 99.2% and 96.2%. In the presence of Cd and/or Zn in the influent, both Se(VI) and total Se had a higher removal efficiency than when solely feeding Se(VI), both at 17.5 ℃ and 30 ℃. The lactate removal rates of the UASB reactors amounted to 1.0–1.2 mM/h. The mass balance showed 64.8%–79.5% of the supplied Se was entrapped in the biomass at the end of the experiment. The polysaccharides and protein concentrations of the extracellular polymeric substances (EPS) increased ∼3 to 5 times upon heavy metal exposure. A dramatic change in the microbial community occurred in the UASB reactors during long term operation. This study showed that UASB reactors have desirable Se(VI), Cd(II) and Zn(II) removal efficiencies both at 17.5 and 30 ℃. [ABSTRACT FROM AUTHOR]

Abstract In this study, a three-stage upflow anaerobic sludge blanket (UASB) system was developed and tested for hydrogen (H 2) and methane (CH 4) production from cassava wastewater with an emphasis on CH 4 production. The experiment was carried out at mesophilic temperature (37 °C) at different chemical oxygen demand (COD) loading rates from 5 to 18 kg/m3d (based on total liquid holding volume) with a recycle ratio of the final effluent to both the first and second bioreactors at a constant 1: 1 flow rate ratio of feed: final effluent. The first bioreactor was maintained pH at 5.5 while those of the other two bioreactors were not controlled. At an optimum COD loading rate of 15 kg/m3d, the system provided the highest COD removal level (92.5%) and the highest H 2 and CH 4 yields of 0.43 mL H 2 /g COD applied, and 328 mL CH 4 /g COD applied, respectively. The very high productivity of CH 4 with the very low H 2 productivity resulted from the recycled methanogen sludge from the third bioreactor to the first and second bioreactors. The process performance of the three-stage UASB system in terms of optimum COD loading rate and total energy yield was much higher than those of single and two-stage anaerobic processes. Graphical abstract Image Highlights • The three-stage UASB provided a high optimum COD loading rate with a high energy yield. • The high CH 4 yield with very low H 2 yield resulted from the recycled methanogenic sludge. • The recycled effluent could provide proper pH values in both first and second bioreactors with a minimum NaOH consumption. [ABSTRACT FROM AUTHOR]

This work investigates the anaerobic co-digestion of a mixture of food waste and domestic wastewater (0.09, v/v) using an upflow anaerobic sludge blanket (UASB) reactor to generate renewable energy in form of biogas. The reactor was operated under the conditions of mesophilic temperature (35 °C), pH 7.2, and 10 days of hydraulic retention time (HRT). The chemical oxygen demand (COD) removal efficiency and the methane content were 80 ± 1.3% and 56%, respectively, when the reactor was operated continuously at the organic loading rate of 2 g COD/L/d in 2 days of operation, while the COD removal efficiency started decreasing and reached 61 ± 1.7% after 10 days, with the methane content of 37%. The deterioration of reactor efficiency on converting organic matter to methane was attributed to the accumulation of long chain fatty acids (LCFAs) onto the sludge. To overcome the physical and metabolic inhibition by LCFAs, the application of intermittent feeding mode (48 h feed and 48 h feedless) was chosen and applied at different organic loading rates (OLRs; 2–4.5 g COD/L/d) to evaluate the reactor performance in terms of COD removal, methane content, accumulation of LCFAs and short chain fatty acids (SCFAs). The COD removal efficiency and methane content were 82 ± 1.1%, 75 ± 0.9%, and 62 ± 1.5% and 58%, 56%, and 51% at the OLR of 2, 3, and 4.5 g COD/L/d, respectively. The 48 h feed/48 h feedless cycle seemed a promising alternative to treat real food wastewater. However, further studies are still necessary to better evaluate the application of intermittent feeding to treat different mixtures of food waste and domestic wastewater at higher organic loading rates. [ABSTRACT FROM AUTHOR]

In this a, three-layered feedforward-backpropagation artificial neural network (BPANN) model was developed and employed to evaluate COD removal an upflow anaerobic sludge blanket (UASB) reactor treating industrial starch processing wastewater. At the end of UASB operation, microbial community characterization revealed satisfactory composition of microbes whereas morphology depicted rod-shaped archaea. pH, COD, NH 4 + , VFA, OLR and biogas yield were selected by principal component analysis and used as input variables. Whilst tangent sigmoid function ( tansig ) and linear function ( purelin ) were assigned as activation functions at the hidden-layer and output-layer, respectively, optimum BPANN architecture was achieved with Levenberg-Marquardt algorithm ( trainlm ) after eleven training algorithms had been tested. Based on performance indicators such the mean squared errors, fractional variance, index of agreement and coefficient of determination (R 2 ), the BPANN model demonstrated significant performance with R 2 reaching 87%. The study revealed that, control and optimization of an anaerobic digestion process with BPANN model was feasible. [ABSTRACT FROM AUTHOR]

In this study, the mass transfer, rheological behavior and fractal dimension of anaerobic ammonium oxidation (anammox) granules in upflow anaerobic sludge blanket reactors at various temperatures (8.5–34.5 °C) and upflow velocities (0.06, 0.18 m h −1 ) were investigated. The results demonstrated that a lower temperature increased the external mass transfer coefficient and apparent viscosity and impaired the performance of anammox granules. The external mass transfer coefficient was decreased, but efficient nitrogen removal of up to 96% was achieved under high upflow velocity, which also decreased the apparent viscosity. Furthermore, a fractal dimension of up to 2.93 achieved at low temperature was higher than the previously reported values for mesophilic anammox granules. A higher upflow velocity was associated with the lower fractal dimension. Because of the disturbance in granule flaking, the effectiveness factor was less suitable than the external mass transfer coefficient for characterization of mass transfer resistance. [ABSTRACT FROM AUTHOR]

Methane production in the upflow anaerobic bioelectrochemical reactor (UABE) treating acidic distillery wastewater was compared to the upflow anaerobic sludge blanket reactor (UASB), and the electron transfer pathways for methane production were also evaluated in the effluent recirculation. The methane productions from reactors were influenced by the low pH of influent wastewater. However, the methane production rate and yield of the UABE were 2.08 L/L.d and 320 mL/g COD r , which were higher than the UASB. The effluent recirculation containing alkalinity neutralized the acidic influent and increased the upflow velocity in both reactors, and improved the direct interspecies electron transfer more in the UABE. When the effluent recirculation ratio was 3.0 in the UABE, the methane production rate and yield were reached up to 3.88 L/L.d and 501.0 mL/g COD r , respectively. The UABE requires electrode installation and electrical energy for operation, but the benefits from increased methane production are much higher. [ABSTRACT FROM AUTHOR]

A novel reactor configuration for the enrichment of anammox bacteria from marine sediments was developed. Marine sediments were successfully kept inside the bioreactors during the enrichment process by strategically installing traps at different depths to prevent the wash-out of sediments. Three up-flow anaerobic sediment trapped (UAST) reactors were set up (α, β and ω supplied with 50, 150 and 300 mg Ca 2+ /L, respectively). Nitrogen removal rates (NRR) of up to 3.5 g N/L-d and removal efficiencies of >95% were reached. Calcium enhanced biomass production as evidenced by increased volatile suspended solids and extracellular polymeric substances. After the long-term operation, dominant families detected were Rhodobacteracea , Flavobacteracea , and Alteromonadacea , while the main anammox genera detected in the three reactors were Candidatus Kuenenia and Candidatus Anammoximicrobium . The UAST reactor is proposed as suitable technology for the enrichment of anammox bacteria applicable for the treatment of saline industrial wastewaters with high nitrogen content. [ABSTRACT FROM AUTHOR]

The dispersion of granules in upflow anaerobic sludge blanket (UASB) reactor represents a critical technical issue in methanolic wastewater treatment. In this study, the potentials of coupling a microbial electrolysis cell (MEC) into an UASB reactor for improving methanolic wastewater biodegradation, long-term process stability and biomethane recovery were evaluated. The results indicated that coupling a MEC system was capable of improving the overall performance of UASB reactor for methanolic wastewater treatment. The combined system maintained the comparatively higher methane yield and COD removal efficiency over the single UASB process through the entire process, with the methane production at the steady-state conditions approaching 1504.7 ± 92.2 mL-CH 4 L − 1 -reactor d − 1 , around 10.1% higher than the control UASB (i.e. 1366.4 ± 71.0 mL-CH 4 L − 1 -reactor d − 1 ). The further characterizations verified that the input of external power source could stimulate the metabolic activity of microbes and reinforced the EPS secretion. The produced EPS interacted with Fe 2+/3+ liberated during anodic corrosion of iron electrode to create a gel-like three-dimensional [-Fe-EPS-] n matrix, which promoted cell-cell cohesion and maintained the structural integrity of granules. Further observations via SEM and FISH analysis demonstrated that the use of bioelectrochemical stimulation promoted the growth and proliferation of microorganisms, which diversified the degradation routes of methanol, convert the wasted CO 2 into methane and accordingly increased the process stability and methane productivity. [ABSTRACT FROM AUTHOR]

The coupling of bioelectrochemical system (BES) with an up-flow anaerobic sludge blanket (UASB) was established for enhanced Fischer-Tropsch (F-T) wastewater treatment while the UASB (control group) was operated in parallel. The presence of electric field could offer system a more reductive micro-environment that lower the ORP values and maintain the appropriate pH range, resulting in the higher chemical oxygen demand (COD) removal efficiency and methane production for BES-UASB (86.8% and 2.31 ± 0.1 L/(L·d)) while those values in control group were 72.1% and 1.77 ± 0.08 L/(L·d). In addition, the coupled system could promote sludge granulation to perform a positive effect on maintaining stability of pollutants removal. The high-throughput 16S rRNA gene pyrosequencing in this study further confirmed that the promoting direct interspecies electron transfer (DIET) between Geobacter and Methanosarcina might be established in BES-UASB to improve the syntrophic degradation of propionate and butyrate, finally facilitated completely methane production. [ABSTRACT FROM AUTHOR]

Two-stage systems have been proposed to overcome the drawbacks associated to the implementation of the autotrophic biological nitrogen removal process in the mainstream of urban wastewater treatment plants. In this study, an upflow anammox sludge blanket (UAnSB) reactor was successfully operated for 325 days treating a low-strength synthetic influent mimicking mainstream conditions. A nitrogen loading rate of up to 1.8 ± 0.2 g N L −1 d −1 was achieved at 26 °C and the nitrogen removal rate obtained (1.7 ± 0.1 g N L −1 d −1 ) resulted considerably higher than most of the previously reported values for systems treating low-strength wastewater at similar temperatures. Fluorescence in situ hybridization analysis showed a high enrichment in the anammox specie Candidatus Brocadia anammoxidans during the whole operation. The evolution of the granule diameter was followed throughout the operation of the UAnSB reactor and a direct correlation of the average granule diameter with the liquid upflow velocity (V up ) was established, being the higher the V up , the bigger the granules. A stable granule diameter of 790 ± 40 μm was achieved by maintaining a V up of 1.0 ± 0.1 m h −1 . The low V upS applied avoid the use of effluent recirculation which would present a huge inconvenient to implement UAnSB reactors at real scale, however these low V upS led to external mass transfer problems in the reactor. In spite of the mass transfer limitations, not only a high specific anammox activity (0.26 ± 0.02 g N g −1 VS d −1 ) was achieved in the UASB reactor but also a high nitrogen removal (80 ± 3%). [ABSTRACT FROM AUTHOR]

Three-layered feedforward backpropagation (BP) artificial neural networks (ANN) and multiple nonlinear regression (MnLR) models were developed to estimate biogas and methane yield in an upflow anaerobic sludge blanket (UASB) reactor treating potato starch processing wastewater (PSPW). Anaerobic process parameters were optimized to identify their importance on methanation. pH, total chemical oxygen demand, ammonium, alkalinity, total Kjeldahl nitrogen, total phosphorus, volatile fatty acids and hydraulic retention time selected based on principal component analysis were used as input variables, whiles biogas and methane yield were employed as target variables. Quasi-Newton method and conjugate gradient backpropagation algorithms were best among eleven training algorithms. Coefficient of determination ( R 2 ) of the BP-ANN reached 98.72% and 97.93% whiles MnLR model attained 93.9% and 91.08% for biogas and methane yield, respectively. Compared with the MnLR model, BP-ANN model demonstrated significant performance, suggesting possible control of the anaerobic digestion process with the BP-ANN model. [ABSTRACT FROM AUTHOR]

Bio-hydrogen, obtained by fermentation of organic residues, is considered a promising source of renewable energy. However, the industrial scale H 2 production from organic waste is far to be realized as technical and economical limitations have still to be solved. Low H 2 yields and lack of industrially robust microbes are the major limiting factors. To look for bacteria with both interesting hydrogen fermentative traits and proper robustness, granular sludge from a brewery full scale Upflow Anaerobic Sludge Blanket (UASB) digester was selected as trove of microbes processing complex substrates. One hundred and twenty bacterial strains, previously isolated from heat-treated granular sludge and genetically identified by 16S rDNA sequencing, were screened for extracellular hydrolytic enzymes on cellulose, hemicellulose, starch, pectin, lipids, protein. The most interesting hydrolytic strains were assessed for their H 2 production from glucose and soluble starch. Two Bacillus sp. strains, namely F2.5 and F2.8, exhibited high H 2 yields and were used as pure culture to convert Organic Fraction of Municipal Solid Waste (OFMSW) into hydrogen. The strains produced up to 61 mL of H 2 per grams of volatile solids and could be considered as good candidates towards the development of industrially relevant H 2 -producing inoculants. This is the first successful application of pure microbial cultures in bio-hydrogen production from OFMSW. [ABSTRACT FROM AUTHOR]

The effect of temperature on selenium (Se) removal by upflow anaerobic sludge blanket (UASB) reactors treating selenate and nitrate containing wastewater was investigated by comparing the performance of a thermophilic (55 °C) versus a mesophilic (30 °C) UASB reactor. When only selenate (50 μM) was fed to the UASB reactors (pH 7.3; hydraulic retention time 8 h) with excess electron donor (lactate at 1.38 mM corresponding to an organic loading rate of 0.5 g COD L −1 d −1 ), the thermophilic UASB reactor achieved a higher total Se removal efficiency (94.4 ± 2.4%) than the mesophilic UASB reactor (82.0 ± 3.8%). When 5000 μM nitrate was further added to the influent, total Se removal was again better under thermophilic (70.1 ± 6.6%) when compared to mesophilic (43.6 ± 8.8%) conditions. The higher total effluent Se concentration in the mesophilic UASB reactor was due to the higher concentrations of biogenic elemental Se nanoparticles (BioSeNPs). The shape of the BioSeNPs observed in both UASB reactors was different: nanospheres and nanorods, respectively, in the mesophilic and thermophilic UASB reactors. Microbial community analysis showed the presence of selenate respirers as well as denitrifying microorganisms. [ABSTRACT FROM AUTHOR]

The objective of this study was to produce hydrogen and methane from cassava wastewater using two steps of upflow anaerobic sludge blanket reactors (UASB), emphasizing maximum hydrogen production. For the first hydrogen production stage, the UASB system was operated at 37 °C and pH 5.5 at different COD loading rates. A maximum specific H 2 production rate of 0.39 l H 2 /l d and a maximum H 2 yield of 39.83 l H 2 /kg COD removed were found at a COD loading rate of 25 kg/m 3 d and the gas produced contained 36.4% H 2 , and 63.6% CO 2 without methane. For the second methane production stage, the UASB was fed by the effluent produced from the hydrogen production step operated at the optimum COD loading rate. A maximum specific CH 4 production rate of 0.91 l CH 4 /l d and a maximum CH 4 yield of 115.23 l CH 4 /kg COD removed were found at a COD loading rate of 8 kg/m 3 d. The inhibition levels of organic acids to acidogens and methanogens were found to be 10,000 and 400 mg/l as acetic acid, respectively. [ABSTRACT FROM AUTHOR]

In this study, two lab-scale UASB reactors were established to testify S 0 recovery efficiency, and one of which (M-UASB) was improved from the previous T-UASB by shortening reactor height once S 2− over oxidation was observed. After the height was shortened from 60 to 30 cm, S 0 recovery rate was improved from 7.4% to 78.8%, and while, complete removal of acetate, nitrate and S 2− was simultaneously maintained. Meanwhile, bacterial community distribution was homogenous throughout the reactor, with denitrifying sulfide oxidization bacteria predominant, such as Thauera and Azoarcus spp., indicating the optimized condition for S 0 recovery. The effective control of working height/volume in reactors plays important roles for the efficient regulation of S 0 recovery during DSR process. [ABSTRACT FROM AUTHOR]

Hydrodynamics and bio-dynamics are equally important in upflow anaerobic sludge blanket (UASB) reactors, but few studies have been conducted to consider both issues when developing a mathematical model. Therefore a novel ADM1-based dispersive model was developed in this study to provide a better description of UASB reactor performance by simultaneously taking into account the hydrodynamics and bio-dynamics of the reactor. Organic overloading shock experiments were carried out in a laboratory-scale UASB reactor to validate the developed model. The results of the simulation model were in good agreement with experimental data. Although considerable calculation time was required, the ADM1-based dispersive model showed obvious advantages in predicting reactor status, which may give an early warning of reactor abnormalities. The models developed here are expected to simulate UASB reactors more effectively and to provide useful information for their design and operation. [ABSTRACT FROM AUTHOR]

Oily bilge water is one of the major pollutants that threats marine environment due to its direct discharge from ships into sea. The aim of this paper is to investigate the possibility of dilute bilge water treatment by using hybrid up-flow anaerobic sludge blanket (HUASB) bio-reactor. The reactor operated at two hydraulic retention times (HRTs) of 10 h and 8 h. The organic loading rate (OLR) was gradually increased from 0.12 g to 0.6 g chemical oxygen demand (COD)/l day. After the immobilization of sludge on the surface of the support materials and 10 days of batch feeding of the reactor with the waste water as acclimation period (with COD removal of 59%), the continuous operation of the reactor started. At the end of the experiment, with the HRT of 8 h and OLR of 0.6 g COD/l day, the COD removal efficiency reached the amount of 75%. Furthermore, the bio-reactor showed a good performance in removing oil from the waste stream which was significantly lower than the standard value which has been laid down for the discharge of the bilge water from ships by the International Maritime Organization (IMO). The obtained data demonstrated that the HUASB reactor is an appropriate system for the treatment of a low-strength bilge water. [ABSTRACT FROM AUTHOR]

Long-term performance of a lab-scale UASB reactor treating starch wastewater was investigated under different hydraulic retention times (HRT). Successful start-up could be achieved after 15 days’ operation. The optimal HRT was 6 h with organic loading rate (OLR) 4 g COD/L d at COD concentration 1000 mg/L, attaining 81.1–98.7% total COD removal with methane production rate of 0.33 L CH 4 /g COD removed . Specific methane activity tests demonstrated that methane formation via H 2 –CO 2 and acetate were the principal degradation pathways. Vertical characterizations revealed that main reactions including starch hydrolysis, acidification and methanogenesis occurred at the lower part of reactor (“main reaction zone”); comparatively, at the up converting acetate into methane predominated (“substrate-shortage zone”). Further reducing HRT to 3 h caused volatile fatty acids accumulation, sludge floating and performance deterioration. Sludge floating was ascribed to the excess polysaccharides in extracellular polymeric substances (EPS). More efforts are required to overcome sludge floating-related issues. [ABSTRACT FROM AUTHOR]

In this study the combination of an upflow anaerobic sludge blanket (UASB) reactor and a deammonification moving bed biofilm reactor (MBBR) for mainstream wastewater treatment was tested. The competition between aerobic ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) was studied during a 5 months period of transition from reject water to mainstream wastewater followed by a 16 months period of mainstream wastewater treatment. The decrease of influent ammonium concentration led to a wash-out of suspended biomass which had a major contribution to nitrite production. Influence of a dissolved oxygen concentration and a transient anoxia mechanism of NOB suppression were studied. It was shown that anoxic phase duration has no effect on NOB metabolism recovery and oxygen diffusion rather than affinities of AOB and NOB to oxygen determine the rate of nitrogen conversion in a biofilm system. Anammox activity remained on the level comparable to reject water treatment systems. [ABSTRACT FROM AUTHOR]

Volatile fatty acids (VFAs) are critical intermediates in anaerobic digestion. Temperature affects thermodynamics of syntrophic digestion of VFAs as well as solubilities and diffusion coefficients of intermediate metabolites. In this research interactive effects of propionic (HPr), butyric (HBu) and acetic (HAc) acids, hydraulic retention time (HRT) and methanogen to acetogen population ratios (M/A) were investigated as major microbiological and operating variables in syntrophic reactions at thermophilic temperature (55 °C). Experiments were carried out in upflow anaerobic sludge blanket (UASB) reactor inoculated with enriched acetogenic and methanogenic cultures. Central composite design (CCD) was used to design experiments and results were analyzed using response surface methodology (RSM). Corresponding to maximum VFA removals and biogas production rate (BPR), optimum conditions were found to be HPr = 1.9 g/L, HBu = 2.2 g/L, HAc = 2.5 g/L, HRT = 22 h and M/A = 2.5. Results of verification experiments and predicted values from fitted correlations were in close agreement at 95% confidence interval. Analysis of the results of thermophilic process showed that trends and interactive effects of different parameters as well as its optimum conditions were very similar and comparable with the previous study at mesophilic temperature (37 °C). [ABSTRACT FROM AUTHOR]

A new technology for in-situ biogas upgrading and recovery of CH 4 from the effluent of biogas reactors was proposed and demonstrated in this study. A vacuum degassing membrane module was used to desorb CO 2 from the liquid phase of a biogas reactor. The degassing membrane was submerged into a degassing unit (DU). The results from batch experiments showed that mixing intensity, transmembrane pressure, pH and inorganic carbon concentration affected the CO 2 desorption rate in the DU. Then, the DU was directly connected to an upflow anaerobic sludge blanket (UASB) reactor. The results showed the CH 4 content was only 51.7% without desorption of CO 2 , while it increased when the liquid of UASB was recycled through the DU. The CH 4 content increased to 71.6%, 90%, and 94% with liquid recirculation rate through the DU of 0.21, 0.42 and 0.63 L/h, respectively. The loss of methane due to dissolution in the effluent was reduced by directly pumping the reactor effluent through the DU. In this way, the dissolved CH 4 concentration in the effluent decreased from higher than 0.94 mM to around 0.13 mM, and thus efficient recovery of CH 4 from the anaerobic effluent was achieved. In the whole operational period, the COD removal efficiency and CH 4 yield were not obviously affected by the gas desorption. [ABSTRACT FROM AUTHOR]

This paper examines the impact of increasing organic loading in a two phase anaerobic digestion system treating commercial food waste. The first phase is a series of sequentially fed leach bed reactors (LBRs). The second phase is an upflow anaerobic sludge bed (UASB). Leachate from the leach beds, form the influent to the UASB. Effluent from the UASB is re-circulated over the leach beds. Flow rates corresponded to 1 volume of leachate per effective LBR volume per day. The theoretical organic loading rate (OLR) of the UASB is based on the conversion of volatile solids (VS) in the LBR to chemical oxygen demand (COD). The experiment was set up such that the theoretical OLR would rise from 7.1 to 8.8 to 11.8 kg COD m −3 day −1 . The system operated effectively at the lowest organic loading rate producing 384 L CH 4 kg VS −1 which corresponded to 72% of the value obtained in a BMP test. COD conversion efficiency was recorded at 75%. The accumulation of COD over the life of the experiment led to a situation whereby the volumetric OLR (product of COD concentration in the leachate by the flow rate) was over twice the theoretical OLR at the end of the experiment (24.3 kg VS m −3 day −1 versus 11.8 kg VS m −3 day −1 ). At the highest loading rate total ammonia nitrogen (TAN) reached levels of 4500 mg L −1 with pH levels of 8.15. This resulted in significant reduction of methane production. [ABSTRACT FROM AUTHOR]

The laboratory-scale upflow anaerobic sludge blanket (UASB) reactor equipped with a pair of bioelectrodes was established for the enhancement of p-chloronitrobenzene (p-ClNB) reductive transformation via the electrolysis. Results showed that a stable COD removal efficiency over 99% and high p-ClNB transformation rate of 0.328 h-1 were achieved in the bioelectrode-UASB coupled system with influent COD and p-ClNB loading rates of 2.1-4.2 kgCOD m-3 d-1 and 60 g m-3 d-1, respectively. The bioelectrodes were supplied with a voltage of 2.5-5.0 V and the effective current was above 2 mA, which resulted in a continuous supply of H2. Compared with the traditional UASB reactor (R1), the production of H2 was promoted in the bioelectrode-UASB coupled system (R2), and was consumed as an internal electron donor for p-ClNB reductive transformation by anaerobic microbes simultaneously. Furthermore, the cyclic voltammetry curve (CV) analysis of biocathodes showed a positive shift in the reductive peak potential and a dramatic increase in the reductive peak current, which demonstrated the catalytic reduction of p-ClNB by biocathode in the combined system. [ABSTRACT FROM AUTHOR]

This paper evaluated the occurrence and removal efficiency of four estrogenic hormones in five biological wastewater treatment plants (WWTPs), located in the State of Ceará, Brazil. The five WWTPs comprised: two systems consisted of one facultative pond followed by two maturation ponds, one facultative pond, one activated sludge (AS) system followed by a chlorination step, and one upflow anaerobic sludge blanket (UASB) reactor followed by a chlorination step. Estrogen occurrence showed a wide variation among the analyzed influent and effluent samples. Estrone (E1) showed the highest occurrence in the influent (76%), whereas both 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) presented a 52% occurrence, and the compound 17β-estradiol 17-acetate (E2-17A), a 32% one. The occurrence in the effluent samples was 48% for E1, 28% for E2, 12% for E2-17A, and 40% for EE2. The highest concentrations of E1 and EE2 hormones in the influent were 3050 and 3180 ng L − 1 , respectively, whereas E2 and E2-17A had maximum concentrations of 776 and 2300 ng L − 1 , respectively. The lowest efficiencies for the removal of estrogenic hormones were found in WWTP consisted of waste stabilization ponds, ranging from 54 to 79.9%. The high-rate systems (AS and UASB), which have chlorination as post-treatment, presented removal efficiencies of approximately 95%. [ABSTRACT FROM AUTHOR]

Abstract: Dense suspension upflow (DSU) regime in high-density circulating fluidized bed (CFB) risers, featuring no downward particle flux and high mean solid holdup, offers significant advantages over conventional fast fluidization, such as much less solid backmixing and higher solid holdup. While most of the previous CFD simulations are limited to the regime of fast fluidization in low-density CFB risers, it is difficult to reproduce the hydrodynamics of DSU regime using CFD simulation. In this study, a recently proposed EMMS-based two-fluid model (Wang et al., 2012. Chem. Eng. Sci. 75, 349–358), where the particle-rich dense phase and gas-rich dilute phase are treated as the two interpenetrating continua instead of treating gas and solid phases as interpenetrating continua as in standard two-fluid models, is first modified and then used to study the hydrodynamics of high-density CFB risers. Extensive simulations have been performed, and the comparison with experimental data indicated that the EMMS-based two-fluid model had the ability to correctly capture main features of the DSU regime. Therefore, present study not only provided further validation of the idea and feasibility of EMMS-based two-fluid model, but also offered new possibility to explore the hydrodynamic characteristics of DSU regime in high-density CFB risers. [Copyright &y& Elsevier]

Highlights: [•] A two-stage bioprocess was studied for anaerobic digestion of diluted cheese whey. [•] Acidifying biomass recirculation resulted in complete carbohydrate fermentation. [•] Optimum methane recovery and COD removal was achieved compared to single stage. [•] The methanogenic reactor was stable at organic loading rates up to 20kgm−3 d−1. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hydrodynamics plays a major role in improving the performance of upflow reactors. [•] Gas>solid>liquid can be ordered as for the circulation velocity. [•] Motion between bubbles and liquid is the key parameter affecting the shear rates. [•] Shear rate exerted on a sludge granule displays an optimum biogas production rate. [Copyright &y& Elsevier]

Abstract: Recovery of phosphorus from wastewater as calcium phosphate could diminish the need for mining of scarce phosphate rock resources. This study introduces a novel approach to phosphorus recovery by precipitation of calcium phosphate granules in anaerobic treatment of black water. The granules formed in the Upflow Anaerobic Sludge Blanket (UASB) reactor at lab- and demonstration-scale were analyzed for chemical composition and mineralogy by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), Electron microprobe (EMP), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and micro X-ray Diffraction (XRD). The granules had a diameter of 1–2 mm, organic content of 33 wt%, and phosphorus content of 11–13 wt%. Three calcium phosphate phases were identified in the granules: hydroxyapatite, calcium phosphate hydrate and carbonated hydroxyapatite. Without any addition of chemicals, 7 gP/person/year can be recovered with the calcium phosphate granules, representing 2% of the incoming phosphorus in the UASB reactor. As the heavy metal content was lower compared to other phosphorus recovery products, phosphate rock and phosphorus fertilizer, the calcium phosphate granules could be considered as a new phosphorus product. [Copyright &y& Elsevier]

Abstract: This study investigated the applicability of dynamic membrane technology in anaerobic membrane bioreactors for the treatment of high strength wastewaters. A monofilament woven fabric was used as support material for dynamic membrane formation. An anaerobic dynamic membrane bioreactor (AnDMBR) was operated under a variety of operational conditions, including different sludge retention times (SRTs) of 20 and 40 days in order to determine the effect of SRT on both biological performance and dynamic membrane filtration characteristics. High COD removal efficiencies exceeding 99% were achieved during the operation at both SRTs. Higher filtration resistances were measured during the operation at SRT of 40 days in comparison to SRT of 20 days, applying a stable flux of 2.6 L/m2 h. The higher filtration resistances coincided with lower extracellular polymeric substances concentration in the bulk sludge at SRT of 40 days, likely resulting in a decreased particle flocculation. Results showed that dynamic membrane technology achieved a stable and high quality permeate and AnDMBRs can be used as a reliable and satisfactory technology for treatment of high strength wastewaters. [Copyright &y& Elsevier]

Highlights: [•] We report for the first time the long-term removal of HMs in an UASB-CW system. [•] Reduced conditions in the UASB-CW system treating sewage allow a high HM removal. [•] Overall removals were in the following order: 94%>Sn>Cr>Cu>Pb>Zn>Fe>63%. [•] Removals of Sn, Cr, Cu, Zn and Ni were maintained at least for the first 5years. [Copyright &y& Elsevier]

Highlights: [•] Methanogens are the “key players” of anaerobic digestion under high ammonia levels. [•] Bioaugmentation of SAO co-culture was not possible in a UASB reactor. [•] M. bourgensis increased the maximum growth rate of SAO co-culture by 42%. [•] M. bourgensis reduced the incubation period of SAO co-culture by 33%. [•] Methanogens were the limiting factor of SAO co-culture bioaugmentation process. [Copyright &y& Elsevier]

It is postulated that up-flow anaerobic sludge blanket (UASB) reactor efficiency can be enhanced by a membrane immersed in the reactor to operate it as an anaerobic membrane bioreactor (AnMBR) for low-strength wastewater treatment. This postulate was tested by comparing the performance with and without a hollow fiber microfiltration membrane module immersed in UASB reactors operated at two specific organic loading rates (SOLR). Results showed that membrane filtration enhanced process performance and stability, with over 90% total organic carbon (TOC) removal consistently achieved. More than 91% of the TOC removal was achieved by suspended biomass, while less than 6% was removed by membrane filtration and digestion in the membrane attached biofilm during stable AnMBRs operation. Although the membrane and its biofilm played an important role in initial stage of the high SOLR test, linear increased TOC removal by bulk sludge mainly accounted for the enhanced process performance, implying that membrane led to enhanced biological activity of the suspended sludge. The high retention of active fine sludge particles in suspension was the main reason for this significant improvement of performance and biological activity, which led to decreased SOLR with time to a theoretical optimal level around 2 g COD/g MLVSS·d and the establishment of a microbial community dominated by Methanothrix-like microbes. It was concluded that UASB process performance can be enhanced by transforming such to AnMBR operation when the loading rate is too high for sufficient sludge retention, and/or when the effluent water quality demands are especially stringent. [ABSTRACT FROM AUTHOR]

Highlights: [•] Combined UASB–MBR is feasible for dairy wastewater treatment at ambient temperatures. [•] The system presented a high tolerance to loading changes and temperature fluctuations. [•] High biogas production with more than 70% methane content was obtained. [•] Overall biomass yield similar to anaerobic systems was obtained. [•] Permeability values similar to those reported for aerobic MBR systems were obtained. [ABSTRACT FROM AUTHOR]

Abstract: Application of an up-flow anaerobic sludge blanket (UASB) reactor to dark fermentative H2 production greatly improves H2 productivity due to the maintenance of high biomass concentration. However, a long start-up HRT and start-up period are required to develop the H2-producing granules (HPGs) and to avoid washing out the suspended sludge at the start of the process. In the present work, a novel strategy to rapidly form HPGs was developed in UASB reactor. To induce highly active mass transfer in the UASB reactor, a high recirculation rate (15 times the influent) was adopted over 10 days, then recirculation was stopped. As the operation progressed, self-flocculation took place and HPGs developed after 90 h of operation. A stable production of H2 was observed after 20 days of operation. The thickness of the HPGs layer in the sole UASB reactor increased progressively, and consequently the average HPG diameter and concentration were 1.86 mm (0.1–3.9 mm) and 52 g/L, respectively, after 60 days of operation. These findings seem to suggest that high-rate recirculation plays a crucial role in accelerating the formation of HPGs in such UASB reactors through high up-flow velocity, providing active mass transfer. [Copyright &y& Elsevier]

Abstract: The major objective of dark fermentative H2 production (DFHP) is the significant enhancement of the H2 production performance from economic and engineering perspectives. An up-flow anaerobic sludge blanket (UASB) reactor based on H2-producing granules (HPGs) has been introduced, which results in the efficiency of the H2 production being improved significantly. However, the long start-up period remains a substantial obstacle in the stable operation of the UASB reactor. In the present study, a newly proposed operational strategy was employed to form the HPG using xylose as the feedstock, and this resulted in a successful reduction of the start-up period of the UASB reactor. After the mixed liquor in the continuously stirred tank reactor was transferred to the UASB reactor as a seeding source, the height of the HPG in the UASB reactor was progressively increased. In the UASB reactor, a maximum H2 yield of 2.98 mol H2/mol xylose and a stable H2 production rate of 9.98 L H2/L/h were observed at a hydraulic retention time of 6 h and a substrate concentration of 30 g COD/L. In this novel method, HPGs with an average particle size of 2.32 mm (0.1–4.7 mm) were successfully developed after 120 days and this is the first report documenting the successful formation of HPGs using xylose as feedstock in a UASB reactor. [Copyright &y& Elsevier]

Abstract: The effect of substrate concentration on continuous H2 production from a sucrose-rich synthetic wastewater was investigated in this work. The maximum H2 production rate of 2.89 m3 H2/m3/d achieved at 7000 mg COD/L while the peak ethanol concentration of 2840 mg/L was observed at 5000 mg COD/L. The H2-producing granules with ethanol-type fermentation were successfully cultivated in an upflow anaerobic sludge blanket (UASB) reactor. Denaturing gradient gel electrophoresis analysis demonstrates that the substrate concentration had a considerable effect on the microbial community. After the mature H2-producing granules were formed, the microbial community structure in the UASB reactor tends to stabilize. The dominant bacterium in the mature H2-producing granules were composed of Janthinobacterium sp. WPCB148, Clostridium sp. HPB-4, Variovorax paradoxus strain SJ100, Variovorax sp. CN3b and Uncultured bacterium clone C2. [Copyright &y& Elsevier]

Abstract: Polyethylene glycol (PEG) gel was used to immobilize hydrogen producing Clostridium LS2 bacteria for hydrogen production in an upflow anaerobic sludge blanket (UASB) reactor. The UASB reactor with a PEG-immobilized cell packing ratio of 10% weight to volume ratio (w/v) was optimal for dark hydrogen production. The performance of the UASB reactor fed with palm oil mill effluent (POME) as a carbon source was examined under various hydraulic retention time (HRT) and POME concentration. The best volumetric hydrogen production rate of 365 mL H2/L/h (or 16.2 mmol/L/h) with a hydrogen yield of 0.38 L H2/g CODadded was obtained at POME concentration of 30 g COD/L and HRT of 16 h. The average hydrogen content of biogas and COD reduction were 68% and 65%, respectively. The primary soluble metabolites were butyric acid and acetic acid with smaller quantities of other volatile fatty acid and alcohols formed during hydrogen fermentation. More importantly, the feasibility of PEG-immobilized cell UASB reactor for the enhancement of the dark-hydrogen production and treatment of wastewater is demonstrated. [Copyright &y& Elsevier]

Abstract: Berberine is a broad-spectrum antibiotic extensively used in personal medication. The production of berberine results in the generation of wastewater containing concentrated residual berberine. However, few related studies up to date focus on berberine removal from wastewaters. In this study, a lab-scale upflow anaerobic sludge blanket (UASB)–membrane bioreactor (MBR) process was developed for berberine removal from synthetic wastewater. The performance of the UASB–MBR system on berberine, COD and NH4 + was investigated at different berberine loadings. And the effects of berberine on bacterial communities were evaluated using polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE). Results showed that, as the increase of berberine loadings, UASB performance was affected remarkably, whereas, efficient and stable performance of MBR ensured the overall removal rates of berberine, COD and NH4 + ently reached up to 99%, 98% and 98%, respectively. Significant shifts of bacterial community structures were detected in both UASB and MBR, especially in the initial operations. Along with the increase of berberine loadings, high antibiotic resisting species and some functional species, i.e. Acinetobacter sp., Clostridium sp., Propionibacterium sp., and Sphingomonas sp. in UASB, as well as Sphingomonas sp., Methylocystis sp., Hydrogenophaga sp. and Flavobacterium sp. in MBR were enriched in succession. [Copyright &y& Elsevier]

Abstract: A novel polyethylene glycol (PEG) gel was fabricated and used as a carrier to immobilize Clostridium sp. LS2 for continuous hydrogen production in an upflow anaerobic sludge blanket (UASB) reactor. Palm oil mill effluent (POME) was used as the substrate carbon source. The optimal amount of PEG-immobilized cells for anaerobic hydrogen production was 12% (w/v) in the UASB reactor. The UASB reactor containing immobilized cells was operated at varying hydraulic retention times (HRT) that ranged from 24 to 6h at 3.3g chemical oxygen demand (COD)/L/h organic loading rate (OLR), or at OLRs that ranged from 1.6 to 6.6 at 12h HRT. The best volumetric hydrogen production rate of 336mL H2/L/h (or 15.0mmol/L/h) with a hydrogen yield of 0.35L H2/g CODremoved was obtained at a HRT of 12h and an OLR of 5.0g COD/L/h. The average hydrogen content of biogas and COD reduction were 52% and 62%, respectively. The major soluble metabolites during hydrogen fermentation were butyric acid followed by acetic acid. It is concluded that the PEG-immobilized cell system developed in this work has great potential for continuous hydrogen production from real wastewater (POME) using the UASB reactor. [Copyright &y& Elsevier]

Abstract: Three Upflow Anaerobic Sludge Blanket (UASB) reactors were compared for Anammox enrichment using synthetic wastewater with Spherical Plastic (SP) and Bamboo Charcoal (BC) addition, and without carrier (CK). After four months of operation, the Anammox activity occurred in all reactors allowing continuous removal of ammonium and nitrite. Ammonium and nitrite removal efficiencies were all higher than 98% in steady phase with the effluent concentrations below 1mgL−1. The start-up time could be shortened from 117 to 97d in CK and SP reactor to 85d in BC amendment reactor. Quantitative PCR (q-PCR) analyses indicated a significant increase in the number of Anammox bacteria in BC amended reactor as compared with CK and SP during the entire start-up periods. The copy numbers of Anammox of 16SrRNA gene in the reactor with BC amendment could reach up to 6×109 copiesg−1 Volatile Suspended Solids, around 22.5times and 12.3times greater than that in CK and SP reactor, respectively. BC addition could accelerate the start-up of Anammox and significantly increase the Anammox bacteria number. [Copyright &y& Elsevier]

Alternative fuel sources have been extensively studied. Hydrogen gas has gained attention because its combustion releases only water, and it can be produced by microorganisms using organic acids as substrates. The aim of this study was to enrich a microbial consortium of photosynthetic purple non-sulfur bacteria from an Upflow Anaerobic Sludge Blanket reactor (UASB) using malate as carbon source. After the enrichment phase, other carbon sources were tested, such as acetate (30 mmol l −1 ), butyrate (17 mmol l −1 ), citrate (11 mmol l −1 ), lactate (23 mmol l −1 ) and malate (14.5 mmol l −1 ). The reactors were incubated at 30 °C under constant illumination by 3 fluorescent lamps (81 μmol m −2 s −1 ). The cumulative hydrogen production was 7.8, 9.0, 7.9, 5.6 and 13.9 mmol H 2 l −1 culture for acetate, butyrate, citrate, lactate and malate, respectively. The maximum hydrogen yield was 0.6, 1.4, 0.7, 0.5 and 0.9 mmol H 2 mmol −1 substrate for acetate, butyrate, citrate, lactate and malate, respectively. The consumption of substrates was 43% for acetate, 37% for butyrate, 100% for citrate, 49% for lactate and 100% for malate. Approximately 26% of the clones obtained from the Phototrophic Hydrogen-Producing Bacterial Consortium (PHPBC) were similar to Rhodobacter , Rhodospirillum and Rhodopseudomonas , which have been widely cited in studies of photobiological hydrogen production. Clones similar to the genus Sulfurospirillum (29% of the total) were also found in the microbial consortium. [ABSTRACT FROM AUTHOR]

Abstract: Nowadays, carbon emission and therefore carbon footprint of water utilities is an important issue. In this respect, we should consider the opportunities to reduce carbon footprint for small and large wastewater treatment plants. The use of anaerobic rather than aerobic treatment processes would achieve this aim because no aeration is required and the generation of methane can be used within the plant. High-rate anaerobic digesters receive great interests due to their high loading capacity and low sludge production. Among them, the upflow anaerobic sludge blanket (UASB) reactors have been most widely used. However, there are still unresolved issues inhibiting the widespread of this technology in developing countries or countries with climate temperature fluctuations (such as subtropical regions). A large number of studies have been carried out in order to enhance the performance of UASB reactors but there is a lack of updated documentation. In face of the existing limitations and the increasing importance of this technology, the authors present an up-to-date review on the performance enhancements of UASB reactors over the last decade. The important aspects of this article are: (i) enhancing the start-up and granulation in UASB reactors, (ii) coupling with post-treatment unit to overcome the temperature constraint, and (iii) improving the removal efficiencies of the organic matter, nutrients and pathogens in the final effluent. Finally the authors have highlighted future research direction based on their critical analysis. [Copyright &y& Elsevier]

Abstract: The granulation process in palm oil mill effluent using calcium oxide-cement kiln dust (CaO–CKD) provides an attractive and cost effective treatment option. In this study the efficiency of CaO–CKD at doses of 1.5–20g/l was tested in batch experiments and found that 10g of CaO/l caused the greatest degradation of VFA, butyrate and acetate. An upflow anaerobic sludge blanket (UASB) reactor was operated continuously at 35°C for 150 days to investigate the effect of CaO–CKD on sludge granulation and methanogenesis during start-up. The treatment of POME emphasized the influence of varying organic loading rates (OLR). Up to 94.9% of COD was removed when the reactor was fed with the 15.5–65.5g-CODg/l at an OLR of 4.5–12.5kg-COD/m3 d, suggesting the feasibility of using CaO in an UASB process to treat POME. The ratio of volatile solids/total solids (VS/TS) and volatile fatty acids in the anaerobic sludge in the UASB reactor decreased significantly after long-term operation due to the precipitation of calcium carbonate in the granules. Granulation and methanogenesis decreased with an increase in the influent CaO–CKD concentration. [Copyright &y& Elsevier]

Abstract: The feasibility of treating low-strength wastewater with an up-flow anaerobic sludge blanket (UASB) reactor, using a poly(vinyl alcohol)-gel carrier, at various temperatures and hydraulic retention times (HRTs) was examined. The temperature was decreased from 35°C to 25°C and then to 15°C. The HRT was reduced from 2.0h to 0.22h. The COD removal rate reached 28kg-CODm−3 d−1 at 35°C, 16kg-CODm−3 d−1 at 25°C, and 6kg-CODm−3 d−1 at 15°C. The COD removal rate was reduced by half for each temperature reduction of 10°C. [Copyright &y& Elsevier]

Abstract: An upflow anaerobic sludge blanket (UASB) bioreactor was successfully used for the treatment of petroleum refinery effluent. Before optimization, chemical oxygen demand (COD) removal was 81% at a constant organic loading rate (OLR) of 0.4kg/m3 d and a hydraulic retention time (HRT) of 48h. The rate of biogas production was 559mL/h at an HRT of 40h and an influent COD of 1000mg/L. Response surface methodology (RSM) was applied to predict the behaviors of influent COD, upflow velocity (V up) and HRT in the bioreactor. RSM showed that the best models for COD removal and biogas production rate were the reduced quadratic and cubic models, respectively. The optimum region, identified based on two critical responses, was an influent COD of 630mg/L, a V up of 0.27m/h, and an HRT of 21.4h. This resulted in a 76.3% COD removal efficiency and a 0.25Lbiogas/Lfeedd biogas production rate. [Copyright &y& Elsevier]

Abstract: The effect of starch addition on the microbial composition and the biological conversion was investigated using two upflow anaerobic sludge bracket (UASB) reactors treating methanolic wastewater: one reactor was operated with starch addition, and another reactor was operated without starch addition. Approximately 300days of operation were performed at 30kg COD/m3/d, and then, the organic load of the reactors was gradually increased to 120kg COD/m3/d. Successful operation was achieved at 30kg COD/m3/d in both reactors; however, the methanol-fed reactor did not perform well at 120kg COD/m3/d while the methanol–starch-fed reactor did. The granule analysis revealed the granule developed further only in the methanol–starch-fed reactor. The results of the microbial community analysis revealed more Methanosaeta cells were present in the methanol–starch-fed reactor, suggesting the degradation of starch produced acetate as an intermediate, which stimulated the growth of Methanosaeta cells responsible for the extension of granules. [Copyright &y& Elsevier]

Abstract: Wastewater discharged from tannery industries is highly complex, concentrated, and toxic. In view of the varying nature of discharged wastewater and the numerous small industries in Egypt, there is a need for highly efficient treatment processes that are simple to operate and have low/reasonable construction and operation costs. This study investigated the possibility of applying innovative low cost biological treatment using upflow anaerobic sludge blanket (UASB) in providing adequate treatment for tannery wastewater. The anaerobic treatment application was thus evaluated through using two stage UASB reactors connecting in series, each with volume of 94l. Five hydraulic retention times (HRT) were used along the experimental works, which lasted for a year, starting by HRT of 24h then 18, 12, 8 and finally 5h for each UASB reactor. The proposed process at 12h HRTs could pre-treat the tannery wastewater to be disposed to the municipality sewers. The study created best fit equations to predict the efficiency of the system. [Copyright &y& Elsevier]

Abstract: The present study reports kinetic characteristics of Anammox (anaerobic ammonium oxidation) EGSB (Expanded Granular Sludge Bed) reactor after feeding with strong ammonium-containing synthetic wastewater. The microbial communities were analysed based on their 16S rRNA gene sequences. The results showed that the volumetric nitrogen loading rate (NLR) and volumetric nitrogen removal rate (NRR) reached up to 22.87kgN/(m3 d) and 18.65kgN/(m3 d), respectively, when the influent nitrogen concentrations were 1429.1mg N/L. Monod and Haldane models both proved to be suitable in characterizing the kinetic behavior of the reactor. Based on Haldane model, the relationships among the ammonium, nitrite, nitrogen conversion rates and substrate concentrations were established with corresponding correlation coefficients of 0.992, 0.993 and 0.993, respectively. The maximum ammonium, nitrite and nitrogen conversion rates (q max) by the granular sludge were 381.2, 304.7 and 731.7mg N/(gVSSd), half saturation constants (K s ) were 36.75, 0.657 and 29.26mg N/L and inhibition constants (K i ) were 887.1, 13,942.1 and 1779.6mg N/L, respectively. Anammox-EGSB reactor was found tolerant to substrate and capable of treating strong ammonium-containing wastewater. The dominant microbial population of the granular sludge in the reactor was Candidatus Kuenenia stuttgartiensis. [Copyright &y& Elsevier]

Abstract: A laboratory study using expanded granular sludge bed (EGSB) reactors was undertaken to explore the kinetic behavior of sulfate reducers and methanogens in treating sulfate-containing wastewater. A kinetic model was also formulated in a way that accounted for mass fractions of sulfate reducers and methanogens (f SR, f M) and an inhibiting effect of unionized H2S on microbial groups. When the EGSB reactor was maintained at the influent COD/SO4 2− ratio of 0.5 (i.e., acetate was growth-limiting and sulfate was in excess), sulfate reducers kinetically prevailed for acetate over methanogens. In contrast, when the EGSB reactor was maintained at the influent COD/SO4 2− ratio of 0.8–3.0 (i.e., acetate was in excess and sulfate was growth-limiting), methanogens can utilize the excess acetate and may prevail over sulfate reducers. The values of f SR, f M evaluated at the influent COD/SO4 2− ratio of 0.5–3.0 and the obtained kinetic parameter values of sulfate reducers and methanogens (k SR, K I,SR, K sa, K s,SR; k M, K I,M, K s,M) together with the validated kinetic model are of help in predicting the performance of the EGSB reactor treating sulfate-containing wastewater. [Copyright &y& Elsevier]