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The purpose of this study is to determine the efficient hydrogen sulphide (H2S) adsorption system between fixed bed 1 to iron shavings pretreated with hydrochloric acid (HCl) and sodium hydroxide (NaOH) at 5,0% and hydrogen peroxide (H2O2) with sodium chloride (NaCl) fixed bed tower 2. Tests were performed on the Upflow Anaerobic Reactor (UASB); the measurements were made through direct monitoring (meter of monogas Tango X1) and indirect (measurement of weights). The results indicate that the highest adsorption of H2S occurred in the fixed bed tower 2 with an efficiency of 99, 58%. As for the weight variation, it increased 69,0 g compared to the one treated with HCl and NaOH, which had 28,6 g. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is among the most serious threats to water and the typical alkali-based treatment costs are high. This study's main objective was the establishment of a highly efficient biological process using an upflow anaerobic sludge blanket (UASB) reactor to treat AMD based on a shorter hydraulic retention time (HRT) and lower organic matter input. The process was evaluated for a long-term operation (739 days) in terms of the influence of HRT (14-24 h), metal addition, sulfate loading rate (0.5-2.6 g SO42− l−1 d−1), and the COD/SO42− ratio (0.67-1.0) using ethanol as the only electron donor at a pH of 4.0. Neutral effluent pH was achieved throughout the time apart from operational modifications. The reduction in HRT from 24 to 16 h and an increase in the sulfate loading rate (SLR) up to 2.25 g SO42− l−1 d−1 improved the sulfate removal to (92.1 ± 1.8)% with 80% chemical oxygen demand (COD) removal. However, the sulfate reduction was less than 80% when the HRT and SLR was changed to 14 h and 2.6 g SO42− l−1 d−1, respectively. The oxidation of organic matter by sulfate reduction was greater than 50% regardless of the conditions imposed but the use of ethanol to treat AMD was more efficient when either the HRT was 16 h (1.5 g SO42− l−1 d−1) in the presence of Fe, Zn, and Cu or the HRT was 14 h (2.6 g SO42− l−1 d−1) but the COD/SO42− ratio was reduced to 0.67. The fully optimized conditions of the UASB reactor were set at an HRT of 16 h, SLR of 1.5 g SO42− l−1 d−1, and a COD/SO42− ratio of 1.0. [ABSTRACT FROM AUTHOR]

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]

Different intermittent phases were introduced during the continuous operation of upflow anaerobic sludge blanket reactor treating simulated textile wastewater using single dye. The reactor was operated at an organic loading rate of 2 kg COD/m³ d and hydraulic retention time (HRT) of 24 h to optimize the non-feeding period of reactor for maximum chemical oxygen demand (COD) and color removal rates. The optimized combination was then operated for mixed dyes solution. Feeding period of 12 h and non-feeding period of 12 h (12F/12NF) gave COD and color removal of 57.5% and 71.0%, respectively. The similar cycle was operated using mixed dye feed with increase in dye concentration to 30 mg/L at same operating conditions. Maximum COD and color removal efficiency of 47.8% and 38.3% was achieved. The decreased removal rates for mixed dyes were due to the presence of intermediate metabolites produced by chromogenic breakdown of dyes. The above optimized condition was extended to 48 h HRT (12F/12NF/12F/12NF) with dyes concentration of 50 mg/L. Improved COD and color removal rates of 67.0% and 77.8% were achieved. [ABSTRACT FROM AUTHOR]

A variable-gain controller for anaerobic digestion of industrial winery wastewater is presented. A control law using both volatile fatty acids (VFA) and methane production rate as controlled variables and organic loading rate (OLR) as manipulated variable is defined. The process state is quantitatively estimated by an empirical function comparing VFA measurements against a setpoint value; then, it is modified with a second empirical function that compares the methane flow rate with a maximum capacity reference, and finally it is adjusted with a third factor considering the actual hydraulic retention time. The variable-gain function determines the extent of the OLR change applied to the system. The controller was successfully validated in a 95 L upflow-anaerobic-sludge-blanket (UASB) reactor, treating industrial wine wastewater at OLR ranged between 2.0 and 39.2 g COD/L d for 120 days at mesophilic conditions. Higher performance was achieved contrasted with a conventional strategy carried out in a parallel UASB unit. [ABSTRACT FROM AUTHOR]

Denitrifying granular sludge reactor holds better nitrogen removal efficiency than other kinds of denitrifying reactors, while this reactor commonly needs seeding anaerobic granular sludge and longer period for start-up in practice, which restricted the application of denitrifying granular sludge reactor. This study presented a rapid and stable start-up method for denitrifying granular sludge. An upflow sludge blanket (USB) reactor with packings was established with flocculent activated sludge for treatment of high concentration nitrite wastewater. Results showed mature denitrifying granular sludge appeared only after 15 days with highest nitrogen removal rate of 5.844 kg N/(m3 day), which was much higher than that of compared anoxic sequencing batch reactor (ASBR). No significant nitrite inhibition occurred in USB and denitrification performance was mainly influenced by hydraulic retention time, influent C/N ratio and internal reflux ratio. Hydraulic shear force created by upflow fluid, shearing of gaseous products and stable microorganisms adhesion on the packings might be the reasons for rapid achievement of granular sludge. Compared to inoculated sludge and ASBR, remarkable microbial communitiy variations were detected in USB. The dominance of Proteobacteria and Bacteroidetes and enrichment of species Pseudomonas_stutzeri should be responsible for the excellent denitrification performance, which further verified the feasibility of start-up method. [ABSTRACT FROM AUTHOR]

The redox-mediating capacity of magnetic reduced graphene oxide nanosacks (MNS) to promote the reductive biodegradation of the halogenated pollutant, iopromide (IOP), was tested. Experiments were performed using glucose as electron donor in an upflow anaerobic sludge blanket (UASB) reactor under methanogenic conditions. Higher removal efficiency of IOP in the UASB reactor supplied with MNS as redox mediator was observed as compared with the control reactor lacking MNS. Results showed 82% of IOP removal efficiency under steady state conditions in the UASB reactor enriched with MNS, while the reactor control showed IOP removal efficiency of 51%. The precise microbial transformation pathway of IOP was elucidated by high-performance liquid chromatography coupled to mass spectroscopy (HPLC-MS) analysis. Biotransformation by-products with lower molecular weight than IOP molecule were identified in the reactor supplied with MNS, which were not detected in the reactor control, indicating the contribution of these magnetic nano-carbon composites in the redox conversion of this halogenated pollutant. Reductive reactions of IOP favored by MNS led to complete dehalogenation of the benzene ring and partial rupture of side chains of this pollutant, which is the first step towards its complete biodegradation. Possible reductive mechanisms that took place in the biodegradation of IOP were stated. Finally, the novel and successful application of magnetic graphene composites in a continuous bioreactor to enhance the microbial transformation of IOP was demonstrated. [ABSTRACT FROM AUTHOR]

Upflow anaerobic sludge blanket (UASB) reactors have been used widely to treat high-strength wastewater. In this study, UASB reactor was operated in order to determine organic matter removal and methane production from low-strength synthetic and real wastewater. Also the optimum value of several parameters, specifically organic loading rates (OLRs) and hydraulic retention time (HRT), were investigated. While feeding synthetic wastewater, removal efficiencies of soluble chemical oxygen demand (SCOD) were around 97%, and methane production was around 0.2 L CH4/g SCOD removed. Its methane content was 73% at HRT of 6.1 h (OLR of 1.8 kg chemical oxygen demand [COD]/m³ d). With real domestic wastewater, removal efficiencies of SCOD were found to be 62%. Biogas production was 0.5 L/d, of which the methane content was 55%. At HRT of 5.7 h, methane gas yield was 0.19 L CH4/g SCOD removed, indicating that optimum HRT is around 6 h in synthetic and real wastewater condition. In both conditions, biogas and methane production decreased with the decrease of HRT. At all HRT conditions, the decrease of pH was not observed; however, washout of volatile fatty acid increased with decrease of HRT. Compared with UASB fed with high-strength wastewater, it was found that HRT was most important parameter for the operation of UASB fed with low-strength wastewater. In addition, utilization of COD for biogas production and for cell production accounted for 68% and 14% at HRT of 6.1 h for synthetic wastewater, respectively. [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]

Anaerobic sewage treatment systems, especially upflow anaerobic sludge blanket (UASB) reactors, have found wide application over the past decades, particularly in regions with a warm climate. A low sewage temperature is generally considered as a factor contributing to poor performance, characterized by an increase of the COD fractions in the effluent and the generated sludge, and decreasing the fraction that is transformed into methane. An experimental investigation was carried out at pilot scale to establish the values of the three COD fractions for different values of temperature and the applied organic load. The sludge age of the anaerobic treatment, together with temperature, was identified as the main operational variable that affects the efficiency of anaerobic treatment. An empirical expression was derived for the values of the three factions as a function of these two variables. From the results of the experimental investigation it was apparent that there is no point in applying a sludge age of more than 100 d, when the reactor is near its best performance. An expression was derived to establish the hydraulic retention time for maximum digestion efficiency as a function of temperature, concentration and composition of organic material and sludge mass. It was established that the main limit to the sludge hold-up in UASB reactors treating sewage is not the sludge settleability, but rather the break-up of flocs leading to loss of small, poorly-settling particles. [ABSTRACT FROM AUTHOR]

The goal of this study was to develop a startup strategy for a high-rate anaerobic ammonium oxidation (anammox) reactor to treat waste brine with high concentrations of ammonium from a natural gas plant. An upflow anaerobic sludge blanket (UASB) anammox reactor with an effective volume of 294 L was fed continuously with waste brine with a salinity of 3% and a NH concentration of 180 mg-N/L, as well as a NaNO solution. By inoculating a methanogenic granular biomass as a biomass carrier, the reactor attained the maximum volumetric nitrogen removal rate (NRR) of 10.7 kg-N/m/day on day 209, which was 1.7 times higher than the highest reported NRR for wastewater of comparable salinity. High-throughput sequencing of 16S rRNA gene amplicons revealed that Candidatus Scalindua wagneri was enriched successfully in granules in the UASB, and it replaced Methanosaeta and became dominant in the granule. The inhibitory effect of NO on the anammox reaction in the granules was assessed by a N tracer method, and the results showed that anammox activity was maintained at 60% after exposure to 300 mg-N/L of NO for 24 h. Compared with previous studies of the susceptibilities of Candidatus Brocadia and Candidatus Kuenenia to NO , the enriched marine anammox bacteria were proven to have comparable or even higher tolerances for high NO concentrations after a long exposure. [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]

The setting-up of anammox granules reactor is time-consuming and highly sensitive to the environment. Metal ions were reported to facilitate granulation; however, there is no report of a practical guide to metal ion application in anammox, especially relative to the effects of different ions at different concentrations on granulation. Adding recycle to reactors is important in treating industrial wastewater with high levels of NH -N, but the optimum recycle ratio is still unclear. This study investigated the effect of Ca, Mg, Fe ions, their concentration, and recycle ratio of an upflow anaerobic sludge blanket reactor on anammox granulation as well as on reactor performance. The main physical properties of granules tested were sludge granulation rate, settling velocity, mixed liquor suspended solids (MLSS), mixed liquor volatile suspended solids/MLSS, and specific anammox activity (SAA)/nitrogen removal rate. The results demonstrated that introducing cations into cultivating mediums accelerates the anaerobic granulation process and improves specific anammox activity. In particular, Mg and Fe runs reached maximum SAAs with concentrations of 0.06 mmol/L and improved by ~ 25% of SAA compared with the control. SAAs of Ca runs were lower than those of Mg and Fe runs and showed a peak at a concentration of 0.03 mmol/L. In addition, recirculation enhanced the granulation. Granulation and retention of the anammox biomass were benefitted most when the recycle flow added was equal to the influent injection (noted as Q). Nitrogen removal also reached a maximum at Q, with removal efficiency of 97.3% with NH -N and 98% with NO -N. Thus, appropriately adding metal ions and recycle flow helped achieve quick setting-up and better performance. We also considered the relationship between four properties of granules tested and the performance of the reactor. [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 pilot-scale upflow anaerobic sludge blanket-moving bed biofilm (UASB-MBB) reactor followed by a high-rate algal pond (HRAP) was designed and operated to remove organic matter, nutrients and pathogens from sewage and to facilitate reuse. For an influent chemical oxygen demand (COD) concentration of 233±20 mg/L, final effluent COD was 50± 6 mg/L. Successful biomass granulation was observed in the sludge bed of the upflow anaerobic sludge blanket (UASB) reactor after 5 months of operation. Ammonia removal in HRAP was 85.1± 2.4% with average influent and effluent ammonia nitrogen concentrations of 20± 3 mg/L and 3 ±1 mg/L, respectively. Phosphate removal after treatment in the HRAP was 91±1%. There was a 2-3 log scale pathogen removal after treatment in HRAP with most probable number (MPN) of the final effluent being 600-800 per 100 mL, which is within acceptable standards for surface irrigation. The blackwater after treatment in UASBMBBR-HRAP is being reused for gardening and landscaping. This proper hydro-dynamically designed UASB reactor demonstrated successful granulation and moving bed media improved sludge retention in UASB reactor. This combination of UASB-MBB reactor followed by HRAP demonstrated successful sewage treatment for a year covering all seasons. [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]

This paper aims to present perspectives for energy (thermal and electric) and nutrient (N and S) recovery in domestic sewage treatment systems comprised of upflow anaerobic sludge blanket (UASB) reactors followed by sponge-bed trickling filters (SBTF) in developing countries. The resource recovery potential was characterized, taking into account 114 countries and a corresponding population of 968.9 million inhabitants living in the tropical world, which were grouped into three desired ranges in terms of cities' size. For each of these clusters, a technological arrangement flowsheet was proposed, depending on their technical and economic viability from our best experience. Considering the population living in cities over 100, 000 inhabitants, the potential of energy and nutrient recovery via the sewage treatment scheme would be sufficient to generate electricity for approximately 3.2 million residents, as well as thermal energy for drying purposes that could result in a 24% volume reduction of sludge to be transported and disposed of in landfills. The results show that UASB/SBTF systems can play a very important role in the sanitation and environmental sector towards more sustainable sewage treatment plants. [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]

BACKGROUND Enriching hydrogen ( H2)-producing bacteria by suppressing methane- producing microorganisms is a critical step in continuous biological H2 production. Selective inhibition of methanogens can be achieved by varying the organic loading rate ( OLR) in continuous reactors. In this study, continuous H2 production was examined using mixed anaerobic cultures fed glucose in upflow anaerobic sludge blanket reactors ( UASBRs) operating at 37°C and at pH 5.0 by varying the OLR at a constant hydraulic retention time. RESULTS A stable H2 yield of 1.64 ± 0.04 mol mol−1 glucose was obtained at OLRs from 8.6 to 12.8 g COD L−1 d−1. Increasing the OLR increased the hydrogenase flux and suppressed methanogenesis. At high OLRs, high acetate and solvent production were associated with Clostridiaceae and Ruminococcaceae while at low OLRs, the presence of Synergistaceae and Propionibacteriaceae were related to the production of propionate and other reduced byproducts. CONCLUSION This study successfully demonstrated continuous H2 production using bench-scale UASBRs fed glucose. Understanding the OLR effect on H2 production and microbial interaction is important in the full-scale operation of H2 production facilities using low value feedstocks such as switch grass, corn stover and shorghum. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Direct anaerobic treatment in the main line of a wastewater treatment plant is a promising way of recovering chemical energy, even in moderate climates. Full-scale applications of upflow anaerobic sludge blanket (UASB) reactors are common in warm climates and have recently begun to appear in areas with colder climate. Several new types of reactors optimized for low temperature treatment were proposed such as UASB-Digester or anaerobic membrane bioreactor (AnMBR). However, long-term operation of such systems treating real wastewater at winter temperatures is needed to assess their suitability. The aim of this article is to evaluate the operation of a laboratory-scale UASB reactor (1.9 L) before and after the installation of ultrafiltration membrane for solids separation from the effluent. The laboratory model treated wastewater at 15°C for over 850 days. The organic loading rate of the UASB reactor and AnMBR was 1.4 and 1.6 g COD/[L·d], respectively, while the hydraulic retention time was around 9 and 10 h. Energy recovery from the wastewater in gaseous methane was 4% and 6% in the UASB reactor and AnMBR, respectively. The methane content was 63%±17% and 64%±2%, respectively. In the UASB reactor, 64% of the influent chemical oxygen demand (COD) was removed in long term. The AnMBR ran at average 85% COD removal. Results show that AnMBR can deliver more stable effluent quality for wastewater treatment even at low (15°C) temperature. However, even the AnMBR effluent requires further posttreatment. Thus, simpler and less energy demanding UASB appears more relevant for wastewater pretreatment under European conditions. [ABSTRACT FROM AUTHOR]

The influence of temperature in a range of 15–5°C, fluctuations in soluble chemical oxygen demand (sCOD) and suspended solids (SS) of the influent and also long hydraulic retention times (HRT) of 36 or 50 d on the performance of a laboratory septic tank were studied. A laboratory-scale septic tank with a volume of 20 L, started up at 15°C was fed with domestic wastewater from two settlements with sCOD up to 450 and up to 2,000 mg/L, respectively. The efficiency of the septic tank was assessed based on pollutant removal and biogas production. A stepwise decrease in temperature by 5°C in the range of 15–5°C halved the daily emission of biogas. Removal efficiencies for sCOD and SS were in the range of 74–86 and 86–88%, respectively. An increase in sCOD of influent from 450 to 4,000 mg/L resulted in a decreased performance of the septic tank (to ~25% less). The highest biogas emission was observed at 10°C and at retention time (36 d), owing to increased consumption of CO2and CH4by autotrophic microorganisms over the longer retention time (50 d). At the 15°C, biogas emission was lower than in case of lower temperatures applied. In the range of 15–5°C, operational temperature did not correlate significantly (p > 0.05) with the removal efficiency of sCOD or SS, assuming as a consequence of the long HRT. [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]

In this study, the effect of seasonal variations on the performance of combined anaerobic–aerobic system for wastewater treatment was investigated. The pilot plant system consists of packed bed anaerobic sludge blanket, followed by a biological aerated filter. The packing material in both units was a non-woven polyester fabric. The system was operated for more than two years at ambient temperature. The results indicated that the performance of the pilot plant was very satisfactory during the whole seasons. However, in summer, slightly better results were achieved for chemical oxygen demand, biological oxygen demand, total suspended solids and total Kjeldahl nitrogen due to the increase in temperature. Their corresponding average removal values were 90, 91, 97, and 54%, respectively, compared with 88, 90, 91, and 46% in winter. Nitrogen removal was related to nitrification/denitrification and bacterial assimilation, where its activity increased in the summer. The quality of the treated effluent during the whole seasons complies with the National Regulatory Standards for reuse in irrigation. [ABSTRACT FROM PUBLISHER]

A modular diagnosis system (MDS), based on the framework of fuzzy logic, is proposed for upflow anaerobic sludge blanket (UASB) reactors treating sewage. In module 1, turbidity and rainfall information are used to estimate the influent organic content. In module 2, a dynamic fuzzy model is used to estimate the current biogas production from on-line measured variables, such as daily average temperature and the previous biogas flow rate, as well as the organic load. Finally, in module 3, all the information above and the residual value between the measured and estimated biogas production are used to provide diagnostic information about the operation status of the plant. The MDS was validated through its application to two pilot UASB reactors and the results showed that the tool can provide useful diagnoses to avoid plant failures. [ABSTRACT FROM AUTHOR]

A wastewater treatment system composed of an upflow anaerobic sludge blanket (UASB) reactor followed by a packed-bed reactor (PBR) filled with Sorbulite® and Polonite® filter material was tested in a laboratory bench-scale experiment. The system was operated for 50 weeks and achieved very efficient total phosphorus (P) removal (99%), 7-day biochemical oxygen demand removal (99%) and pathogenic bacteria reduction (99%). However, total nitrogen was only moderately reduced in the system (40%). A model focusing on simulation of organic material, solids and size of granules was then implemented and validated for the UASB reactor. Good agreement between the simulated and measured results demonstrated the capacity of the model to predict the behaviour of solids and chemical oxygen demand, which is critical for successful P removal and recovery in the PBR. [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]

The study explores the influence of physicochemical pretreatment on the performance of upflow anaerobic sludge blanket (UASB) reactors treating synthetic textile wastewater. Physicochemical pretreatment in this study utilized a new composite coagulant magnesium chloride added with aluminum chlorohydrate which produced nearly complete color removal and a partial chemical oxygen demand (COD) removal (~55%) efficiency. Various parameters such as volatile fatty acids (VFA), bicarbonate alkalinity (B-Alk.), gas production, total aromatic amines (TAAs) generation, COD, and color removal efficiency were monitored in the UASB reactors operated at different operating conditions. For the UASB reactor treating pretreated textile wastewater, a maximum of 99% COD removal was obtained at an organic loading rates (OLRs) of 1.2 kg COD m−3d−1and hydraulic retention time (HRT) of 20 h. Whereas in case of without pretreatment, a maximum of both 92% COD and color removal efficiency were achieved at an OLR of 2.4 kg COD m−3d−1and HRT of 20 h. However, in this case, highly toxic, carcinogenic, and mutagenic TAAs were observed to produce in the range of 6.9–8.1 mg L−1. VFA/B-Alk. ratios were found in the range of 0.05–0.15, indicating the sufficient buffering capacity for stability of the reactor. The study demonstrates the significance of physicochemical pretreatment on the performance of UASB reactor for the treatment of textile wastewater. Nevertheless, it also shows the importance of introducing pretreatment in order to avoid the production of harmful aromatic amines in the treated UASB effluent. [ABSTRACT FROM PUBLISHER]

In order to provide the comprehensive insight into the key microbial groups in anaerobic ammonium oxidation (anammox) process, high-throughput sequencing analysis has been used for the investigation of the bacterial communities of a lab-scale upflow anaerobic sludge bed (UASB) anammox bioreactor. Results revealed that 109 operational taxonomic units (OTUs; out of 14,820 reads) were identified and a domination of anammox bacteria of Candidatus Kuenenia stuttgartiensis (OTU474, 35.42 %), along with heterotrophs of Limnobacter sp . MED105 (OTU951, 14.98 %), Anerolinea thermophila UNI-1 (OTU465 and OTU833, 6.60 and 3.93 %), Azoarcus sp. B72 (OTU26, 9.47 %), and Ignavibacterium sp . JCM 16511 (OTU459, 8.33 %) were detected. Metabolic pathway analysis showed that Candidatus K. stuttgartiensis encountered gene defect in synthesizing a series of metabolic cofactors for growth, implying that K. stuttgartiensis is auxotrophic. Coincidentally, the other dominant species severally showed complete metabolic pathways with full set gene encoding to corresponding cofactors presented in the surrounding environment. Furthermore, it was likely that the survival of heterotrophs in the autotrophic system indicates the existence of a symbiotic and mutual relationship in anammox system. [ABSTRACT FROM AUTHOR]

BACKGROUND The aim of this study was to investigate the feasibility of utilizing a continuous-flow anaerobic granular sludge bed ( UASB) reactor for the removal of palladium ( II) from aqueous streams and the recovery of this precious metal as biogenic Pd(0). Anaerobic methanogenic granular sludge has been recently shown to reduce Pd( II) in the presence of a suitable electron donor leading to the formation of biomass-associated Pd(0). RESULTS Two laboratory-scale UASB reactors were fed with ethanol or acetate, in order to compare their performance in terms of Pd removal and reduction. Pd( II) was added in two periods of increasing concentration, 5 mg Pd( II) L−1 and then 15 mg Pd( II) L−1. Extensive removal of Pd (up to 99%), was attained in both reactors. X-ray diffraction ( XRD) and energy-dispersive X-ray spectroscopy ( EDS) analysis confirmed significant differences in the content of Pd(0) in the biomass, depending on the electron donor used. The main mechanisms of Pd( II) removal when acetate and ethanol were used as electron donor were biosorption and reduction to Pd(0) by biogenic H2 released as fermentation product, respectively. CONCLUSIONS The results obtained demonstrate that it is possible to apply a continuous process for Pd reduction and recovery using a methanogenic consortium. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The treatment of high-strength wastewater from distillery was studied in a bench-scale upflow anaerobic sludge blanket (UASB) reactor. Reactor was operated at different organic loading rates (OLRs) and constant hydraulic retention time for 2 d at mesophilic temperature of 37°C for a period of about two years (635 d). The maximum COD and BOD removals achieved were 68.35 and 89.11%, respectively, at optimum OLR of 15.34 kg COD/m3 d. UASB reactor performance was also evaluated in terms of hydrolysis, acidification, and methanogenesis, and the performance values were found to be 33.88, 52.16, and 48.07%, respectively. Total and soluble biodegradability of the high-strength wastewater were 48.09 and 78.06%, respectively, that represents good conversion of soluble substrate to biogas. The average biogas produced was 0.38 m3/kg COD removed. The COD mass balance of the reactor showed that 51.32, 0.24, 9.46, 1.75, and 37.22% COD was converted into methane (gaseous phase), methane (aqueous phase), sludge, sulfate reduction, and effluent, respectively. The characteristics of the port sludge elaborate the sludge profile in the reactor. FEG-SEM shows the morphology of the sludge granules, showing various colonies of cocci and rods grown on granules surface. ICP-AES indicates that Ca was utilized for the formation of granules and FTIR shows IR spectrum of an alcohol. [ABSTRACT FROM PUBLISHER]

Natural rubber processing wastewater contains high concentrations of organic compounds, nitrogen, and other contaminants. In this study, a treatment system composed of a baffled reactor (BR), an upflow anaerobic sludge blanket (UASB) reactor, and a downflow hanging sponge (DHS) reactor was used to treat natural rubber processing wastewater in Vietnam. The BR showed good total suspended solids (TSS) removal of 47.6%, as well as acidification of wastewater. The UASB reactor achieved a high chemical oxygen demand (COD) removal efficiency of 92.7 ± 2.3% and energy recovery in the form of methane with an organic loading rate of 12.2 ± 6.6 kg-COD m−3 day−1. The DHS reactor showed high performance in residual organic matter removal from UASB effluent. In total, the system achieved high-level total COD removal of 98.6% ± 1.2% and TSS removal of 98.0% ± 1.4%. Massive parallel 16S rRNA gene sequencing of the retained sludge in the UASB reactor showed the predominant microbial phyla to beBacteroidetes,Firmicutes,Proteobacteria, WWE1, andEuryarchaeota. Uncultured bacteria belonging to the phylumBacteroidetesand Phylum WWE1 were predominant in the UASB reactor. This microbial assemblage utilizes the organic compounds contained in natural rubber processing wastewater. In addition, the methane-producing archaeaMethanosaetasp. andMethanolineasp. were detected. [ABSTRACT FROM AUTHOR]

The capacity of anaerobic granular sludge to reduce Pd(II), using ethanol as electron donor, in an upflow anaerobic sludge blanket (UASB) reactor was demonstrated. Results confirmed complete reduction of Pd(II) and immobilization as Pd(0) in the granular sludge. The Pd-enriched sludge was further evaluated regarding biotransformation of two recalcitrant halogenated pollutants: 3-chloro-nitrobenzene (3-CNB) and iopromide (IOP) in batch and continuous operation in UASB reactors. The superior removal capacity of the Pd-enriched biomass when compared with the control (not exposed to Pd) was demonstrated in both cases. Results revealed 80 % of IOP removal efficiency after 100 h of incubation in batch experiments performed with Pd-enriched biomass whereas only 28 % of removal efficiency was achieved in incubations with biomass lacking Pd. The UASB reactor operated with the Pd-enriched biomass achieved 81 ± 9.5 % removal efficiency of IOP and only 61 ± 8.3 % occurred in the control reactor lacking Pd. Regarding 3-CNB, it was demonstrated that biogenic Pd(0) promoted both nitro-reduction and dehalogenation resulting in the complete conversion of 3-CNB to aniline while in the control experiment only nitro-reduction was documented. The complete biotransformation pathway of both contaminants was proposed by high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis evidencing a higher degree of nitro-reduction and dehalogenation of both contaminants in the experiments with Pd-enriched anaerobic sludge as compared with the control. A biotechnological process is proposed to recover Pd(II) from industrial streams and to immobilize it in anaerobic granular sludge. The Pd-enriched biomass is also proposed as a biocatalyst to achieve the biotransformation of recalcitrant compounds in UASB reactors. [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]

This paper assesses a wastewater treatment plant (WWTP) regarding the technology used, as well as organic matter and nutrient removal efficiencies aiming to optimize the treatment processes involved and wastewater reclamation. The WWTP consists of a dissolved air flotation (DAF) system, an upflow anaerobic sludge blanket (UASB) reactor, an aerated-facultative pond (AFP) and a chemical-DAF system. The removal efficiencies of chemical oxygen demand (COD) (97.9± 1.0%), biochemical oxygen demand (BOD) (98.6±1.0%) and oil and grease (O&G) (91.1±5.2%) at the WWTP, the nitrogen concentration of 17±11 mgN-NH3 and phosphorus concentration of 1.34± 0.93 mgPO4-3/L in the final effluent indicate that the processes used are suitable to comply with discharge standards in water bodies. Nitrification and denitrification tests conducted using biomass collected at three AFP points indicated that nitrification and denitrification could take place in the pond. [ABSTRACT FROM AUTHOR]

An anoxic sewage treatment process, an upflow anaerobic sludge blanket (UASB) followed by an aerated bio-filter (ABF), was investigated for the reduction of oxygen demand and the separation efficiency of the organic matter. After recycling the nitrified effluent, complete denitrification occurred in the UASB, with an enhancement in both turbidity characteristics and TCOD removal rates. Low turbidity and COD in the effluent of the UASB reduced the oxygen demand and improved the nitrification efficiency in the subsequent ABF. Both with and without the recycling of the nitrified effluent in the UASB, 95 and 63% of the TCOD values, respectively, were removed. Compared with a conventional activated sludge system, approximately 11.74% of the TCOD was converted to CO2in both the UASB and the ABF, generating an approximately 60% reduction in the amount of CO2. After accumulation in the UASB, 84% of the influent TCOD could be sequestered for use as a marginal energy source in a subsequent anaerobic digester. [ABSTRACT FROM PUBLISHER]

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]

The main problem linked to the stability of upflow anaerobic sludge blanket (UASB) reactors during the treatment of Tequila vinasse is the high acidity and the null alkalinity present in this effluent. This research evaluates the effect of alkalinity and volatile fatty acids (VFAs) concentration on the performance of an UASB reactor with recirculation of the effluent for removing organic matter and biogas production from Tequila vinasses. Recirculation of the effluent reduces the impact of VFAs and organic matter concentration present in the influent, inducing the stability of the reactor. The UASB reactor was operated during 235 days at organic loading rates from 2.5 to 20.0 kg m−3 d−1, attaining a removal efficiency of COD greater than 75% with a methane yield of 335 ml CH4g−1COD at SPT, maintaining a ratio of VFAs/Alk ≤ 0.5. Therefore, an optimal ratio of VFAs/Alk was established for the system operating in stable conditions for the treatment of Tequila vinasses. Under these conditions, the alkalinity was recuperated by the system itself, without the addition of external alkalinity. [ABSTRACT FROM PUBLISHER]

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]

Methanosaeta strains are frequently involved in the granule formation during methanogenic wastewater treatment. To investigate the impact of Methanosaeta on granulation and performance of upflow anaerobic sludge blanket (UASB) reactors, three 1-L working volume reactors noted as R1, R2, and R3 were operated fed with a synthetic wastewater containing sodium acetate and glucose. R1 was inoculated with 1-L activated sludge, while R2 and R3 were inoculated with 200-mL concentrated pre-grown Methanosaeta harundinacea 6Ac culture and 800 mL of activated sludge. Additionally, R3 was daily dosed with 0.5 mL/L of acetyl ether extract of 6Ac spent culture containing its quorum sensing signal carboxyl acyl homoserine lactone (AHL). Compared to R1, R2 and R3 had a higher and more constant chemical oxygen demand (COD) removal efficiency and alkaline pH (8.2) during the granulation phase, particularly, R3 maintained approximately 90 % COD removal. Moreover, R3 formed the best granules, and microscopic images showed fluorescent Methanosaeta-like filaments dominating in the R3 granules, but rod cells dominating in the R2 granules. Analysis of 16S rRNA gene libraries showed increased diversity of methanogen species like Methanosarcina and Methanospirillum in R2 and R3, and increased bacteria diversity in R3 that included the syntrophic propionate degrader Syntrophobacter. Quantitative PCR determined that 6Ac made up more than 22 % of the total prokaryotes in R3, but only 3.6 % in R2. The carboxyl AHL was detected in R3. This work indicates that AHL-facilitated filaments of Methanosaeta contribute to the granulation and performance of UASB reactors, likely through immobilizing other functional microorganisms. [ABSTRACT FROM AUTHOR]

In this study, methanotrophic microorganisms were enriched from a municipal wastewater sludge taken from an Upflow Anaerobic Sludge Blanket reactor. The enrichment was performed in a sequencing batch reactor (SBR) with an autotrophic medium containing nitrite and nitrate. The microbial community composition of the inoculum and of the enrichment culture after 100 days of SBR operation was investigated and compared with the help of data obtained from 454 pyrosequencing analyses. The nitrite and nitrate removal efficiencies were 68% and 53%, respectively, probably due to heterotrophic denitrification. Archaeal cells of the anaerobic methanotrophicArchaic(ANME)-I and ANME-II groups were detected by polymerase chain reaction throughout the whole cultivation period. Pyrosequencing analysis showed that community composition was different among the two samples analysed. The dominant phyla found in the inoculum wereSynergistestes,FirmicutesandEuryarchaeota, whilePlanctomycetes,Verrucomicrobia,ChloroflexiandProteobacteriaprevailed in the enriched biomass. The cultivation conditions decreasedMethanobacteriumabundance from 8% to 1%, and enriched for methanotrophic bacteria such asMethylocaldum,MethylocistisandMethylosinus. Sequences ofMethylocaldumsp. accounted for 2.5% of the total reads. The presence and high predominance ofVerrucomicrobiain the enriched biomass suggested that other unknown methanotrophic species related to that phylum might also have occurred in the reactor. Anaerobic methane oxidation activity was measured for both samples, and showed that the activity of the enrichment culture was nearly three times higher than the activity of the inoculum. Taken together, these results showed that the inoculum type and cultivation conditions were properly suited for methanotrophic enrichment. [ABSTRACT FROM AUTHOR]

Anaerobic digestion of alkaline kraft elemental chlorine-free bleaching wastewater in two mesophilic, lab-scale upflow anaerobic sludge bed reactors resulted in significantly higher biogas production (250 ± 50 vs. 120 ± 30 NmL g) and reduction of filtered total organic carbon (fTOC) (60 ± 5 vs. 43 ± 6%) for wastewater from processing of hardwood (HW) compared with softwood (SW). In all cases, the gas production was likely underestimated due to poor gas separation in the reactors. Despite changes in wastewater characteristics, a stable anaerobic process was maintained with hydraulic retention times (HRTs) between 7 and 14 h. Lowering the HRT (from 13.5 to 8.5 h) did not significantly affect the process, and the stable performance at 8.5 h leaves room for further decreases in HRT. The results show that this type of wastewater is suitable for a full-scale implementation, but the difference in methane potential between SW and HW is important to consider both regarding process dimensioning and biogas yield optimization. [ABSTRACT FROM AUTHOR]

In the present study, physico-chemically pre-treated textile wastewater with a residual chemical oxygen demand (COD) of 780 ± 10 mg L−1was treated using a lab-scale upflow anaerobic sludge blanket (UASB) reactor at variable HRTs of 30.8 to 8 h, and organic loading rates (OLRs) of 0.62–2.4 kg COD m−3 d−1. Using a new composite coagulant at dosage of 800 mg L−1for pre-treatment, more than 99% of colour was removed from the feeding influent to UASB reactor. The optimum OLR was found as 0.95 kg COD m−3 d−1at which maximum COD reduction (98%) was achieved. Modified Stover-Kincannon, Grau second-order, Monod, Haldane and Contois models were applied to evaluate the carbonaceous substrate removal kinetics inside the UASB reactor. The experimental results of this analysis revealed that modified Stover-Kincannon and Grau second-order kinetics were suitable for predicting the performance and to estimate the kinetic coefficients of UASB reactor. [ABSTRACT FROM PUBLISHER]

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]