Journal articles: 'Reactor recirculation'

1

Núñez, L. A., and B. Martínez. "Evaluation of an anaerobic/aerobic system for carbon and nitrogen removal in slaughterhouse wastewater." Water Science and Technology 44, no. 4 (August 1, 2001): 271–77. http://dx.doi.org/10.2166/wst.2001.0233.

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In this work the performance of an anaerobic UASB reactor coupled with an activated sludge reactor for carbon and nitrogen removal in slaughterhouse wastewater is investigated. Periods with and without recirculation of aerobic effluent over 165 days are analysed. Working with a recirculation ratio of 2, removal efficiencies up to 90% and 65% are obtained for DQO and total nitrogen (TN), respectively. Higher recirculation ratios caused severe washout of active biomass in both reactors due to the high hydraulic loading rates applied. Denitrification in the UASB reactor was complete, with no nitrite accumulation and mainly to nitrogen gas. Significant decreases in COD removal efficiencies in the UASB reactor were observed at recirculation ratio of 2. Sudden decreases in total nitrogen efficiencies were related to inhibition process of nitrifying microorganisms, especially at high recirculation ratios.

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Vistanty, Hanny, and Rizal Awaluddin Malik. "ENHANCED PERFORMANCE OF MULTI-STAGE ANAEROBIC DIGESTION OF TOFU WASTEWATER: ROLE OF RECIRCULATION." Jurnal Riset Teknologi Pencegahan Pencemaran Industri 10, no. 1 (August 19, 2019): 29–37. http://dx.doi.org/10.21771/jrtppi.2019.v10.no1.p29-37.

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Continuous three-stage anaerobic reactors with recirculation system were employed to treat real tofu wastewater. The system consists of 3 reactors connected in series and effluent of the last reactor was partly returned as feed of the first reactor along with fresh wastewater. The recirculation system was conducted on four variations of recirculation ratio (RR)s of 0, 1.0, 1.3, and 1.5 to evaluate the influence of recirculation on stability and performance of anaerobic system. Results showed that recirculation improved the performance of anaerobic digestion. COD was fluctuated without recirculation and gradually decreased to 373 and 298 mg/L at RR 1.3 and 1.5, respectively. Likewise, pH value was dropped to 6.5 at RR 0, and started to increase to approximately 8.0 upon employing recirculation. In addition, the system also showed excellent toleration against rise in ammonia loading, with effluent ammonia approximately 4.678 mg/L. The findings showed that the system employed had excellent efficiency and stability in treating tofu wastewater.

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Lepistö, Raghida, and Jukka Rintala. "The Removal of Chlorinated Phenolic Compounds from Chlorine Bleaching Effluents Using Thermophilic Anaerobic Processes." Water Science and Technology 29, no. 5-6 (March 1, 1994): 373–80. http://dx.doi.org/10.2166/wst.1994.0730.

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Thermophilic (55°C) anaerobic removal of chlorinated phenolic compounds (CPC) from softwood bleaching effluents was studied using four different types of anaerobic processes: an upflow anaerobic sludge blanket (UASB) reactor (R1); a UASB reactor enriched with sulfate (R2); a UASB reactor with recirculation (R3); and a fixed bed reactor with recirculation (R4). The concentrations of 16 CPCs were analyzed by gas Chromatography. In all processes most of the chlorinated phenols, catechols, guaiacols, and hydroquinons detected in the bleached kraft mill effluent (BKME) were either eliminated or reduced by as much as 80-95%. However, 2,4-DCP, 2,6-DCP, 4,5-DCG, 3,4,5-TCC, and TeCC were accumulated or only partially removed in all reactors, except in R4 where at high concentrations they were significantly reduced. All the reactors removed 30-70% of the COD and 25-67% of the adsorbable organic halides (AOX). The reactors with recirculation had slightly higher removal efficiencies than the other reactors, while the addition of sulfate had no apparent effect. High concentrations of BKME reduced the COD removal efficiency but not the CPC removal.

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Lukitawesa, Rachma Wikandari, Ria Millati, Mohammad J. Taherzadeh, and Claes Niklasson. "Effect of Effluent Recirculation on Biogas Production Using Two-stage Anaerobic Digestion of Citrus Waste." Molecules 23, no. 12 (December 19, 2018): 3380. http://dx.doi.org/10.3390/molecules23123380.

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Citrus waste is a promising potential feedstock for anaerobic digestion, yet the presence of inhibitors such as d-limonene is known to limit the process. Effluent recirculation has been proven to increase methane yield in a semi-continuous process for recalcitrant material, but it has never been applied to toxic materials. This study was aimed to investigate the effect of recirculation on biogas production from citrus waste as toxic feedstock in two-stage anaerobic digestion. The first digestion was carried out in a stirred tank reactor (STR). The effluent from the first-stage was filtered using a rotary drum filter to separate the solid and the liquid phase. The solid phase, rich in hydrophobic D-limonene, was discarded, and the liquid phase containing less D-limonene was fed into the second digester in an up-flow anaerobic sludge bed (UASB) reactor. A high organic loading rate (OLR 5 g VS/(L·day)) of citrus waste was fed into the first-stage reactor every day. The effluent of the first-stage was then fed into the second-stage reactor. This experiment was run for 120 days. A reactor configuration without recirculation was used as control. The result shows that the reactor with effluent recirculation produced a higher methane yield (160–203 NmL/g·VS) compared to that without recirculation (66–113 NmL/g·VS). More stable performance was also observed in the reactor with recirculation as shown by the pH of 5–6, while without recirculation the pH dropped to the range of 3.7–4.7. The VS reduction for the reactor with recirculation was 33–35% higher than that of the control without recirculation. Recirculation might affect the hydrolysis-acidogenesis process by regulating pH in the first-stage and removing most of the D-limonene content from the substrate through filtration.

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Yaya Beas, Rosa Elena, Katarzyna Kujawa-Roeleveld, Jules B. van Lier, and Grietje Zeeman. "A downflow hanging sponge (DHS) reactor for faecal coliform removal from an upflow anaerobic sludge blanket (UASB) effluent." Water Science and Technology 72, no. 11 (August 11, 2015): 2034–44. http://dx.doi.org/10.2166/wst.2015.427.

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This research was conducted to study the faecal coliforms removal capacity of downflow hanging sponge (DHS) reactors as a post-treatment for an upflow anaerobic sludge blanket (UASB) reactor. Three long-term continuous laboratory-scale DHS reactors, i.e. a reactor with cube type sponges without recirculation, a similar one with recirculation and a reactor with curtain type sponges, were studied. The porosities of the applied medium were 91%, 87% and 47% respectively. The organic loading rates were 0.86 kgCOD m−3 d−1, 0.53 kgCOD m−3 d−1 and 0.24 kgCOD m−3 d−1 correspondingly at hydraulic loading rates of 1.92 m3 m−2 d−1, 2.97 m3 m−2 d−1 and 1.32 m3 m−2 d−1, respectively (COD: chemical oxygen demand). The corresponding averages for faecal coliform removal were 99.997%, 99.919% and 92.121% respectively. The 1989 WHO guidelines standards, in terms of faecal coliform content for unrestricted irrigation (category A), was achieved with the effluent of the cube type DHS (G1) without recirculation. Restricted irrigation, category B and C, is assigned to the effluent of the cube type with recirculation and the curtain type, respectively. Particularly for organic compounds, the effluent of evaluated DHS reactors complies with USEPA standards for irrigation of so called non-food crops like pasture for milking animals, fodder, fibre, and seed crops.

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Suna Erses, A., and T. T. Onay. "Accelerated landfill waste decomposition by external leachate recirculation from an old landfill cell." Water Science and Technology 47, no. 12 (June 1, 2003): 215–22. http://dx.doi.org/10.2166/wst.2003.0649.

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This research is focused on the management of moisture regime for a young landfill site in terms of leachate recirculation which entails the containment, collection and reinjection of leachate back into the landfill to promote in situ anaerobic biological treatment. Moreover, an innovative leachate management strategy was developed by using leachate recirculation from a mature landfill site into a young landfill site to provide accelerated waste stabilization. For this purpose, two reactors simulating young and old landfills were used in the laboratory. These reactors were loaded with shredded and compacted municipal solid waste with a typical composition determined for Istanbul Region. Both reactors were operated in a constant temperature room at 32°C to enhance the growth of anaerobic microorganisms. Moreover, water was added to the reactors in order to simulate the annual rainfall. The reactor having the properties of old landfills was used as a control reactor. The reactor which represented the characteristics of young landfill was operated under four operational stages to enhance the activity of methanogenic population and accelerate waste stabilization. Results of this study indicated that the utilization of leachate recirculation enhanced waste stabilization in the young landfill by increasing the uniformity, and providing additional substrate and nutrients. Additions of buffer solutions of KOH and Na2CO3 together with leachate recirculation enhanced further waste stabilization and prevented possible acid inhibition. The utilization of external leachate recycled from the old landfill having desired acclimated anaerobic microorganisms, low organic content and higher buffer capacity into a young landfill could be a promising leachate management strategy for faster and controlled waste stabilization.

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Bertolino, Sueli Moura, Lucas Antônio Melgaço, Nayara Carolina Quites, and Versiane Albis Leao. "Performance Evaluation of Two Anaerobic Reactors for Removing Sulphate from Industrial Effluents." Advanced Materials Research 825 (October 2013): 491–95. http://dx.doi.org/10.4028/www.scientific.net/amr.825.491.

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Reactors hydrodynamic condition and the choice of substrate are important factors for the optimization and implementation of this sulphate-reducing biological process. This study evaluated two continuous anaerobic reactors, UASB and fluidized bed. The maximum removal achieved by the UASB reactor when operated without recirculation was 65% for a substrate load applied to 3.55 kg/m3 d. When the mass transfer conditions of the reactor were improved by recirculating the biomass, the sulphate removal efficiency increased to 89%, representing a removal rate of 1.94 kg SO42-/m-3 .d-1. Glycerol was used with the carbon and electron source for SRB in the fluidized bed reactor and was compared to the performance with lactate. For the same sulphate load applied, a removal efficiency of 70%-90% was observed, resulting in a residual concentration average of 254 mg/L sulphate. Glycerol, which is a by-product from biodiesel production, is a potential choice as substrate for sulphate reduction.

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Dong, Chun Juan, Tian Tian Zhao, and Qing Ye Pan. "Treatment of Actual Coking Wastewater by Two-Stage EGSB System with Self-Recirculation and Crossed Recirculation." Advanced Materials Research 955-959 (June 2014): 2374–77. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.2374.

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To investigate the possibility of simultaneous high efficient removal of COD and NH3-N in the actual coking wastewater through micro-aerobic granular bio-film reactor, two-stage granular bio-film reactor system (EGSBI+ EGSBII) were continuously operated through two effluent recirculation ways for about 5 months: ERW1(24L.h-1 self-recirculation) and ERW2(15 L.h-1 self-recirculation +15 L.h-1 crossed recirculation). Compared with ERW1, through using ERW2, the two-stage EGSB reactor system could attain high COD and NH3-N removal efficiencies (86.7%-96.9% and 48.6%-80.4%) and low effluent NO2- and NO3- concentrations (0-25mg.L-1 and 7-71mg.L-1). Using ERW1, the two-stage EGSB reactor system melt with difficult of NO2- accumulation in the EGSBII (accompanied with low NH3-N removal of only 41.4%). Using ERW2, the difficult of accumulation in the EGSBII was solved and simultaneously high efficient removal of NH3-N and NO2- in the EGSBI was achieved.

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Hwang, Ping-Chih, and Sheng-Shung Cheng. "Treatment of p-Cresol with a Recirculating UASB Reactor Using the Concept of Kinetic Control." Water Science and Technology 24, no. 5 (September 1, 1991): 133–40. http://dx.doi.org/10.2166/wst.1991.0119.

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A series of batch Biochemical Methane Potential(BMP) tests and an Upflow Anaerobic Sludge Bed (UASB) bioreactor were conducted to investigate the biodegradability of p-cresol.The inhibition of microbes caused by substrate accumulation due to shock loading, recirculating pump turn-off and thermal shock were also studied. The results showed that the microbial activity was inhibited or even poisoned in the high concentration range(1000mg/L) of p-cresol. However, the volumetric loading of the reactor could be maintained relatively high at 8.0 kgCOD/m3·day, if the recirculation of effluent was used to maintain the substrate concentration in the reactor within a suitable range. The concept of so-called kinetic control was proved to be a critical strategy for the treatment of the inhibitory substrate. The results of shock loading, recirculation cessation and thermal shock tests all showed that the concentration control in the reactor would be of vital importance for the treatment of inhibitive compounds with biological processes, and the critical concentration of the highest degradation rate could be estimated with a modified Haldane equation derived from the batch BMP data.

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Donker, H. J. G. W., P. Opic, and H. P. de Vries. "P-Removal in Completely Mixed Systems." Water Science and Technology 17, no. 11-12 (November 1, 1985): 325–26. http://dx.doi.org/10.2166/wst.1985.0254.

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Ca. 60 % of the Dutch activated sludge plants consist of completely mixed systems, experiments have been carried out in completely mixed pilot plants to study the biological P-removal. The research was carried out in two pilot plants. The pilot plants consisted of: anaerobic reactor, anoxic reactor, aerobic reactor and a clarifier. All the reactors were completely mixed. Both plants were fed with settled domestic waste water at a sludge loading of 400 and 250 g COD/kg sludge.day respectively. The results are given below:sludge loading (g COD/kg sludge.day)400400250ratio Anaerobic : Anoxic : Aerobic1: 1:2,71:1:4,11:1:2,7P-removal (%)802875N-removal (%)505065COD-removal (%)858585 It has been shown that there is no significant difference between the results at the two different sludge loadings. Remarkable is the difference between the ratio 1:1:2,7 in combination with the internal recirculation flow anoxic-anaerobic of 160 % and the ratio 1:1:4,1 with a recirculation flow of 30 %. During the start-up at a sludge loading of 250 g COD/kg sludge.day and an internal recirculation flow of 30 %, bulking sludge developed almost immediately. The Premoval was completely disturbed. Increasing the internal recirculation flow to 160% had a positive effect on settling properties and P-removal. This investigation has pointed out that a completely mixed system is suitable for biological P-removal, without negatively affecting the nitrification. Important factors in the process are the ratio anaerobic:anoxic:aerobic and the recirculation flows.

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Sanphoti, N., S. Towprayoon, P. Chaiprasert, and A. Nopharatana. "Enhancing waste decomposition and methane production in simulated landfill using combined anaerobic reactors." Water Science and Technology 53, no. 8 (April 1, 2006): 243–51. http://dx.doi.org/10.2166/wst.2006.255.

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The design of leachate recirculation to enhance municipal solid waste decomposition, methane production and microbial activities was taken into account in this study by using the combined anaerobic reactors of a simulated high organic content landfill reactor and a stabilized fixed film anaerobic reactor. The latter aimed to treat high strength leachate from the simulated landfill reactor before recirculation back to the former reactor. The results showed the possibility to apply this technique to high organic waste landfill where rapid and accumulative acids formed in the leachate were removed and treated by a fixed film anaerobic reactor. In addition, the treated leachate when circulated back to the simulated bioreactor landfill helps accelerate waste decomposition and methane production by providing buffer capacity as well as diluting organic content in the leachate to achieve the favourable conditions for acidogen and methanogen, respectively, to rapidly enter into the methanogenesis phase.

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Hudson, Adam D., David A. Sanders, Giles E. Tewkesbury, Howard Cawte, and John W. Hinks. "Simulation of a high recirculation airlift reactor for steady-state operation." Water Science and Technology 34, no. 5-6 (September 1, 1996): 59–66. http://dx.doi.org/10.2166/wst.1996.0535.

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This paper describes a new mathematical model of the fluid dynamic processes in a high recirculation airlift reactor. The model was created to provide information to assist in the design of a reactor, in particular considering the selection of parameters to adjust in order to achieve a steady state solution. The modelling of two phase-flow of air and water in small scale airlift bio-reactors is considered. This modelling was applied to the high recirculation airlift reactor process. A new computer simulation was created and a test program performed to evaluate the models used. The results of this evaluation are presented. The evaluation showed that variation of the superficial gas velocity or the simultaneous variation of the downcomer and riser diameters could be used to produce a steady-state design solution.

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Ikeda, N., T. Natori, T. Okubo, A. Sugo, M. Aoki, M. Kimura, T. Yamaguchi, H. Harada, A. Ohashi, and S. Uemura. "Enhancement of denitrification in a down-flow hanging sponge reactor by effluent recirculation." Water Science and Technology 68, no. 3 (August 1, 2013): 591–98. http://dx.doi.org/10.2166/wst.2013.235.

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A down-flow hanging sponge reactor, constructed by connecting three identical units in series, was applied to the treatment of artificial wastewater containing phenol and ammonia under high salinity conditions (10.9 g-Cl−/L). The theoretical hydraulic retention time (HRT) of each unit was 4 h (total HRT = 12 h). To enhance denitrification by effluent recirculation, the effluent recirculation ratio was increased in increments ranging from 0.0 to 2.0. The concentration of total ammonia nitrogen (TAN), NO2-N, and NO3-N in the final effluent as a proportion of the TAN in the influent was determined to calculate the unrecovered, or denitrification, proportion. The denitrification proportion of the reactor was equivalent to 19.1 ± 14.1% with no effluent recirculation; however, this was increased to 58.6 ± 6.2% when the effluent recirculation ratio was increased to 1.5. Further increasing the effluent recirculation ratio to 2.0 resulted in a decrease in the denitrification proportion to 50.9 ± 9.3%. Activity assays of nitrification and denitrification, as well as 16S rRNA gene sequence analysis, revealed that denitrification occurred primarily in the upper sections of the reactor, while nitrification increased in the lower sections of the reactor. Gene sequence analysis revealed that denitrification by Azoarcus-like species using phenol as an electron donor was dominant.

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Fdz.-Polanco, M., I. Díaz, S. I. Pérez, A. C. Lopes, and F. Fdz.-Polanco. "Hydrogen sulphide removal in the anaerobic digestion of sludge by micro-aerobic processes: pilot plant experience." Water Science and Technology 60, no. 12 (December 1, 2009): 3045–50. http://dx.doi.org/10.2166/wst.2009.738.

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H2S removal from biogas produced in anaerobic digestion of sludge through the introduction of oxygen under micro-aerobic conditions is studied. Research was carried out in two pilot plant reactors (working volume, 200 L each) treating sludge from WWTP with HRT of 20 days. Mixing was provided via sludge or biogas recirculation. Introduction of very low oxygen flow (0.013–0.024 L/Lreactor d) successfully removed H2S content in biogas with an efficiency above 99%. Reactor performance during micro-aerobic operation in terms of biogas production, methane yield and COD removal were not affected by the amount of oxygen supplied, remaining stable and similar to the anaerobic behaviour. Sludge recirculation (∼50 L/h) and biogas recirculation (∼3.5 L/min) as mixing methods were found not significant in H2S removal from biogas while biogas recirculation reduced by 10 times dissolved sulphide concentration compared to sludge recirculation.

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Beux, Simone, Ezequiel Nunes, and Ana Cláudia Barana. "Effect of temperature on two-phase anaerobic reactors treating slaughterhouse wastewater." Brazilian Archives of Biology and Technology 50, no. 6 (November 2007): 1061–72. http://dx.doi.org/10.1590/s1516-89132007000700017.

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The effectiveness of the anaerobic treatment of effluent from a swine and bovine slaughterhouse was assessed in two sets of two-phase anaerobic digesters, operated with or without temperature control. Set A, consisting of an acidogenic reactor with recirculation and an upflow biological filter as the methanogenic phase, was operated at room temperature, while set B, consisting of an acidogenic reactor without recirculation and an upflow biological filter as the methanogenic phase, was maintained at 32°C. The methanogenic reactors showed COD (Chemical Demand of Oxygen) removal above 60% for HRT (Hydraulic Retention Time) values of 20, 15, 10, 8, 6, 4, and 2 days. When the HRT value in those reactors was changed to 1 day, the COD percentage removal decreased to 50%. The temperature variations did not have harmful effects on the performance of reactors in set A.

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Suchowska-Kisielewicz, Monika, Andrzej Jędrczak, and Zofia Sadecka. "Evaluation of Biodegradability of Waste Before and After Aerobic Treatment." Civil And Environmental Engineering Reports 13, no. 2 (December 10, 2014): 121–32. http://dx.doi.org/10.2478/ceer-2014-0020.

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Abstract An important advantage of use of an aerobic biostabilization of waste prior to its disposal is that it intensifies the decomposition of the organic fraction of waste into the form which is easily assimilable for methanogenic microorganisms involved in anaerobic decomposition of waste in the landfill. In this article it is presented the influence of aerobic pre-treatment of waste as well as leachate recirculation on susceptibility to biodegradation of waste in anaerobic laboratory reactors. The research has shown that in the reactor with aerobically treated waste stabilized with recilculation conversion of the organic carbon into the methane is about 45% higher than in the reactor with untreated waste stabilized without recirculation.

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Raghu, Aswathy K., and Niket S. Kaisare. "Analysis of the autothermal operability of the Sabatier reaction in a heat-recirculating microreactor using CFD." Reaction Chemistry & Engineering 4, no. 10 (2019): 1823–33. http://dx.doi.org/10.1039/c9re00183b.

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The Sabatier reaction in a U-bend micro-reactor benefits from a favourable temperature profile owing to heat recirculation, which improves methane yield and enables stable operation even with feed at ambient temperature.

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Giuliano, A., L. Zanetti, F. Micolucci, and C. Cavinato. "Thermophilic two-phase anaerobic digestion of source-sorted organic fraction of municipal solid waste for bio-hythane production: effect of recirculation sludge on process stability and microbiology over a long-term pilot-scale experience." Water Science and Technology 69, no. 11 (March 15, 2014): 2200–2209. http://dx.doi.org/10.2166/wst.2014.137.

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A two-stage thermophilic anaerobic digestion process for the concurrent production of hydrogen and methane through the treatment of the source-sorted organic fraction of municipal solid waste was carried out over a long-term pilot scale experience. Two continuously stirred tank reactors were operated for about 1 year. The results showed that stable production of bio-hythane without inoculum treatment could be obtained. The pH of the dark fermentation reactor was maintained in the optimal range for hydrogen-producing bacteria activity through sludge recirculation from a methanogenic reactor. An average specific bio-hythane production of 0.65 m3 per kg of volatile solids fed was achieved when the recirculation flow was controlled through an evaporation unit in order to avoid inhibition problems for both microbial communities. Microbial analysis indicated that dominant bacterial species in the dark fermentation reactor are related to the Lactobacillus family, while the population of the methanogenic reactor was mainly composed of Defluviitoga tunisiensis. The archaeal community of the methanogenic reactor shifted, moving from Methanothermobacter-like to Methanobacteriales and Methanosarcinales, the latter found also in the dark fermentation reactor when a considerable methane production was detected.

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Lizama, C., M. C. Yeber, J. Freer, and H. D. Mansilla. "Reactive dyes decolouration by TiO2 photo-assisted catalysis." Water Science and Technology 44, no. 5 (September 1, 2001): 197–200. http://dx.doi.org/10.2166/wst.2001.0285.

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The photocatalytic degradation of three reactive azo dyes (yellow-2, orange-16 and red-2) and one anthraquinone reactive dye (blue-19) was studied. The reactions were carried out in a reactor with recirculation using TiO2 immobilised on glass Raschig rings (system A) and compared with a batch system using the catalyst in aqueous suspension (system B). Both reaction systems were irradiated with a 125 W, l > 254 nm lamp. The suspended TiO2 system was also studied using a 125 W 360 nm lamp (system C). Kinetic studies indicated a rapid colour removal, following the order B > A > C. The same trend was observed in COD and TOC removal profiles. The energy consumption per order of magnitude of catalytic degradation of the dyes was lower in the batch reactor (system B) than in the reactor with recirculation and immobilised TiO2 (system A).

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Yoochatchaval, W., K. Nishiyama, M. Okawara, A. Ohashi, H. Harada, and K. Syutsubo. "Influence of effluent-recirculation condition on the process performance of expanded granular sludge bed reactor for treating low strength wastewater." Water Science and Technology 57, no. 6 (March 1, 2008): 869–73. http://dx.doi.org/10.2166/wst.2008.045.

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A 2.0 L volume of EGSB reactor was operated at 20°C for more than 500 days with 0.3–0.4 g COD/L of sucrose base wastewater to investigate the influence of effluent-recirculation on the process performance. At the start up period, the reactor was operated in EGSB mode with 5 m/h upflow velocity by continuous effluent recirculation. The COD loading was set to 7.2–9.6 kg COD/m3 day with HRT of 1 hour. However, in this mode, EGSB reactor exhibited insufficient COD removal efficiency, i.e., 50–60%. Therefore, UASB mode (without recirculation, 0.7 m/h upflow velocity) was used for 30 minutes in every 40 minutes cycle to increase the COD concentration in the sludge bed. As a result, an excellent process performance was shown. The COD removal efficiency increased from 65% to 91% and the reactor could maintain a good physical property of retained sludge (sludge concentration: 33.4 g VSS/L and SVI: 25 mL/g VSS). Furthermore, retained sludge possessed sufficient level of methanogenic activity at 20°C.

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Ouyang, C. F., and H. Y. Lin. "A Study of Controlled Recirculation of Anaerobic Activated Sludge Digestion Reactors." Water Science and Technology 26, no. 9-11 (November 1, 1992): 2449–52. http://dx.doi.org/10.2166/wst.1992.0759.

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A bench scale anaerobic activated sludge digestion (AASD) process was developed to study the effect of biomass recycling at different amounts of digested sludge recirculation and various solids concentrations in feed sludge. It was selected to observe how the anaerobic digestion can be improved and stabilized by using municipal wastewater sludge. The mathematical model of AASD process was developed.The positive effect of biomass recycling on the sludge concentration depends on the settling rate of the sludge. The performance parameters such as SRT, methane yield and DHA of the reactor with R= 0.5 were found best among those of the other recycle ratio reactors. With the reactor with sludge loading of 1.1 kg TVS/m3 day, SRT/HRT = 1.493 can be obtained.

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Nápoles-Armenta, Juan, Juan Antonio Vidales-Contreras, Luis Alonso Leyva-Soto, Edna Rosalba Meza-Escalante, Lourdes Mariana Díaz-Tenorio, Celestino García-Gómez, Edgardo Martínez-Orozco, Celia De La Mora-Orozco, Pablo Gortáres-Moroyoqui, and Lilian Alejandra Salcedo-Gastelum. "The Influence of the Configuration of Two Electrochemical Reactors on the Process of Removing Atrazine from Water." Sustainability 13, no. 9 (May 8, 2021): 5267. http://dx.doi.org/10.3390/su13095267.

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In Mexico, atrazine is widely used in agriculture to control broadleaf weeds. The objective of this research was to compare atrazine removal in water and energy consumption between an up-flow cylinder electro-oxidation reactor (UCER) and an up-flow rectangular electro-oxidation reactor (URER) using the response surface methodology. In each reactor, two titanium (Ti) mesh electrodes (cathodes) and one Titanium-Lead Dioxide (Ti-PbO2) mesh electrode (anode). Current intensity effects, electrolysis treatment time, and recirculation flow were evaluated. Synthetic water with 5 mg/L atrazine content was used. Optimum atrazine removal values were obtained at 2 A electric current, 180 min of treatment time, and 200 mL/min recirculation rate for both reactors: in these conditions an atrazine removal of 77.45% and 76.89% for URER and UCER respectively. However, energy consumption showed a significant difference of 137.45 kWh/m3 for URER and 73.63 kWh/m3 for UCER. Regarding energy efficiency, a 60% atrazine removal was reached in both reactors using less energy for UCER at (1.5 A–135 min–150 mL/min–25.8 kWh/m3) and for URER at (0.66 A–135 min–150 mL/min–20.12 kWh/m3).

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Shiraishi, Fumihide, Mayumi Nagano, and Shinpon Wang. "Characterization of a photocatalytic reaction in a continuous-flow recirculation reactor system." Journal of Chemical Technology & Biotechnology 81, no. 6 (2006): 1039–48. http://dx.doi.org/10.1002/jctb.1526.

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van Benthum, W. A. J., R. G. J. M. van der Lans, M. C. M. van Loosdrecht, and J. J. Heijnen. "Bubble recirculation regimes in an internal-loop airlift reactor." Chemical Engineering Science 54, no. 18 (September 1999): 3995–4006. http://dx.doi.org/10.1016/s0009-2509(99)00097-4.

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25

Takahashi, Shirou, Kenichi Nihei, Satoshi Kanno, Shoji Hayashi, Kouji Shiina, and Minoru Ootaka. "ICONE15-10244 DEVELOPMENT OF COOLING TECHNIQUES FOR INDUCTION HEATING STRESS IMPROVEMENT OF REACTOR RECIRCULATION INLET NOZZLE." Proceedings of the International Conference on Nuclear Engineering (ICONE) 2007.15 (2007): _ICONE1510. http://dx.doi.org/10.1299/jsmeicone.2007.15._icone1510_121.

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26

van Langerak, E. P. A., H. V. M. Hamelers, and G. Lettinga. "Influent calcium removal by crystallization reusing anaerobic effluent alkalinity." Water Science and Technology 36, no. 6-7 (September 1, 1997): 341–48. http://dx.doi.org/10.2166/wst.1997.0609.

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Waste waters from the waste paper industry and landfill leachates contain high calcium concentrations. Treatment of those waste waters in an anaerobic system will lead to extensive precipitation of calcium carbonates. Problems due to accumulation of calcium carbonate in anaerobic reactors can be avoided by applying a crystallization reactor to remove calcium from the influent. This solution, however, is expensive due to the need to dose alkalinity. In this paper, the possibility of reusing the produced alkalinity by recirculating anaerobic effluent was investigated. Calculations and experiments were carried out to investigate to what extent calcium could be removed from the influent. Experiments were carried out in a 4.5 1 UASB reactor and a 0.8 1 crystallization reactor, seeded with sand. The influent contained up to 1800 mg.l−1 calcium and the substrate was acetic acid. Removal of calcium from the influent could be successfully accomplished. Recirculation of the anaerobic effluent supplied sufficient bicarbonate alkalinity for crystallization. Consequently, no extra chemicals (i.e. Na2CO3 and/or NaOH) were needed. A chemical equilibrium model, with adapted pseudo solubility products, is a very useful tool to determine the proper recycle ratio of effluent for optimal performance.

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27

Gil, Iwona, and Piotr Mocek. "CFD analysis of mixing intensity in jet stirred reactors." Chemical and Process Engineering 33, no. 3 (October 1, 2012): 397–410. http://dx.doi.org/10.2478/v10176-012-0035-9.

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Abstract The homogeneous stirred reactor designed for kinetic studies of the combustion of hydrocarbons with intensive internal recirculation in high temperature combustion chamber is described. The originality of our reactor lies in its construction which allows to intensively mix fuel and flue gases, measure gas temperature as well as obtain samples which can be used to investigate diffusion flames. The cylindrical construction enables to use the reactor in laboratory cylindrical electrically heated ovens. The CFD analysis of the reactors, the mixing parameters (turbulent Peclet number and mixing level) and the volume average temperature in the reactors were elaborated on the basis of the typical dimensions of classical reactors to kinetics research as well as the own reactor design. The results of the analysis allow to reveal advantages of our construction.

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28

Dlabaja, T., and J. Malaťák. "Optimization of anaerobic fermentation of kitchen waste." Research in Agricultural Engineering 59, No. 1 (March 6, 2013): 1–8. http://dx.doi.org/10.17221/2/2012-rae.

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Anaerobic fermentation is a suitable method of energetic and material utilisation of waste coming from restaurants and canteens. Laboratory experiments of wet anaerobic fermentation were performed in a continuous reactor and in batch reactors under mesophilic conditions. Effects of hydraulic retention time, organic loading rate, period of feeding and recirculation of digestate were examined in the continuous reactor. Effects of substrate pre-treatment (crushing, heating, freezing) were examined in the batch reactors. Degree of substrate degradation ranged between 83–85% within hydraulic retention time of 2–30 days. Appropriate organic loading rate was found in the range 2–3 kg of volatile solids per m3/day. Recirculation of digestate (both an inoculum for fresh substrate and replacement of fresh water supply) caused an increase in ammonia concentration and led to immediate inhibition of the process. The results further showed a positive effect of substrate pre-treatment in the initial phase of fermentation. However, degree of degradation did not show a significant increase for the period of 20 days of fermentation.    

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29

Li, X. Z., and Y. G. Zhao. "On-site treatment of dyeing wastewater by a bio-photoreactor system." Water Science and Technology 36, no. 2-3 (July 1, 1997): 165–72. http://dx.doi.org/10.2166/wst.1997.0510.

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Synthetic dyeing wastewater consisting of the three different commercial dyes with different strengths of COD (about 900 and 3000 mg/l respectively) was initially treated by an aerobic biological process, Intermittently Decanted Extended Aeration reactor (IDEA), for BOD removal, and then continuously treated by a TiO2 sensitised photoreactor for a further COD removal and decolorization. The catalysed photooxidation process can degrade those non-biodegradable organic substances in the effluent treated by the IDEA process and also decolorize the effluent completely. It is also found that some nonbiodegradable organic substances can be converted to biodegradable forms by the sensitized photo-oxidation reaction. A bio-photoreactor system was designed to combine this photocatalytic reactor with the IDEA reactor for the treatment of dyeing wastewater. The performance of this combined bio-photoreactor system with and without recirculation was investigated and compared. The system with recycled water has similar efficiency for decolorization and COD removal to that without recirculation, but has a high capacity to eliminate the effects caused by a shock loading, and also the system can treat dyeing wastewater with a higher organic concentration.

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30

Takai, T., A. Hirata, K. Yamauchi, and Y. Inamori. "Effects of temperature and volatile fatty acids on nitrification-denitrification activity in small-scale anaerobic-aerobic recirculation biofilm process." Water Science and Technology 35, no. 6 (March 1, 1997): 101–8. http://dx.doi.org/10.2166/wst.1997.0248.

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The purpose of this study is to clarify effects of temperature, volatile fatty acids (VFAs) and recirculation on nitrification-denitrification activity and biota such as nitrifying bacteria in a small-scale domestic wastewater treatment process. Effects of VFAs produced in anaerobic biofilm reactors under various flow-rates and recirculation ratios on nitrifying bacteria were also investigated with laboratory-scale plants on a long-term stable conditions. As a result, at a temperature of 10°C, nitrification activity could be increased about 65% by recirculation and nitrogen removal efficiency was also surely raised. Temperature coefficients of nitrification rate at recirculation ratios of 0 and 4.0 were 1.039 and 1.090, respectively, and that of denitrification was 1.065 at recirculation ratio of 4.0. High concentrations of VFAs were found in anaerobically treated effluent, especially at 10°C without recirculation, and inhibition of nitrite oxidation and nitrite accumulation were observed in the aerobic biofilm reactor. From batch experiments, VFAs' inhibition constants γ in nitrification activity of aerobic biofilm was calculated, and consumption rates of each VFA was investigated on the condition that denitrification was progressed or not. It was clarified that each VFA did not inhibit ammonium oxidation in observed concentration, but slightly inhibited nitrite oxidation. Acetic acid was used as a carbon source of denitrification at the rate of 17.3mg/mg-SS/hr. On the other hand, propionic acid was not used effectively and denitrification did not occur. It was concluded that the recirculation was indispensable to promote nitrification-denitrification activity and biodegradation of VFAs in the small-scale anaerobic-aerobic biofilm process.

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31

van Benthum, W. A. J., M. C. M. van Loosdrecht, and J. J. Heijnen. "Process design for nitrogen removal using nitrifying biofilm and denitrifying suspended growth in a biofilm airlift suspension reactor." Water Science and Technology 36, no. 1 (July 1, 1997): 119–28. http://dx.doi.org/10.2166/wst.1997.0027.

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Operation of a Biofilm Airlift Suspension (BAS) reactor was possible with nitrifying biofilm growth and heterotrophic suspended growth, simultaneously converting ammonium and acetate. Control of the location of heterotrophic growth, either in suspension or in layers over the nitrifying biofilms, was established by manipulation of the hydraulic retention time. Two process configurations (based on the BAS reactor) are identified, for nitrogen removal from wastewater by integration of nitrification in biofilms and denitrification in suspension. The first set-up consists of a conventional nitrifying BAS reactor, coupled with a suspended biomass reactor (without biomass retention). The second process configuration is a single BAS reactor which is sequentially aerated and non-aerated, by cyclically recirculating the offgas. Process design schemes for these configurations are presented and the design aspects are evaluated. Three limiting processes are identified: gas-liquid oxygen transfer, the hydraulic capacity of the settler and the minimal time needed for oxygen depletion of the gas phase during offgas recirculation. It was found that the two-reactor configuration is mainly suitable for pre-treatment of concentrated ammonia containing wastewaters. The one-reactor configuration can be applied to obtain low nitrogen concentrations in the effluent.

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32

Silva, A., C. Couras, I. Capela, L. Arroja, and H. Nadais. "Anaerobic Degradation of Dairy Wastewater in Intermittent UASB Reactors: Influence of Effluent Recirculation." International Journal of Systems Applications, Engineering & Development 15 (March 29, 2021): 1–6. http://dx.doi.org/10.46300/91015.2021.15.1.

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This work studied the influence of effluent recirculation upon the kinetics of anaerobic degradation of dairy wastewater in intermittent UASB (Upflow Anaerobic Sludge Bed) reactors. Several laboratory-scale tests were performed with different organic loads in a UASB reactor inoculated with flocculent sludge from an industrial wastewater treatment plant. The data obtained were used for determination of specific substrate removal rates and specific methane production rates and adjusted to kinetic models. A high initial substrate removal was observed in all tests due to adsorption of organic matter onto the anaerobic biomass which was not accompanied by biological substrate degradation as measured by methane production. Initial methane production was about 45% of initial soluble and colloidal substrate removal rate. This discrepancy was observed mainly in the first day of all experiments and was attenuated in the second day. Effluent recirculation raised significantly the rate of removal of soluble and colloidal substrate and methane productivity as compared to literature results for batch assays without recirculation.

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33

MOBINI, K., and R. W. BILGER. "IMPERFECTLY STIRRED REACTOR MODEL PREDICTIONS OF REACTION IN A BURNER WITH STRONG RECIRCULATION." Combustion Science and Technology 176, no. 1 (January 2004): 45–70. http://dx.doi.org/10.1080/00102200490255334.

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34

Bilgili, M. Sinan, Ahmet Demir, and Gamze Varank. "Effect of leachate recirculation and aeration on volatile fatty acid concentrations in aerobic and anaerobic landfill leachate." Waste Management & Research: The Journal for a Sustainable Circular Economy 30, no. 2 (September 18, 2011): 161–70. http://dx.doi.org/10.1177/0734242x11417983.

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The main aim of this study was to investigate the effect of leachate recirculation and aeration on volatile fatty acid (VFA) concentrations in aerobic and anaerobic landfill leachate samples. In this study, two aerobic (A1, A2) and two anaerobic (AN1, AN2) reactors with (A1, AN1) and without (A2, AN2) leachate recirculation were used in order to determine the change of volatile fatty acids components in landfill leachate. VFA degradation rate was almost 100% in each reactor but the degradation rate show notable differences. In aerobic landfill reactors, total VFA concentrations decreased below 1000 mg L−1 after 120 days of operation and only caproic and acetic acids were determined at this time. The stabilization of the VFA concentrations takes about 350 and 450 days for AN1 and AN2 reactors, respectively. VFA concentrations were higher than that of aerobic reactors because of the acidogenic phase occurred in anaerobic environment. According to the results of VFA components, the stabilization of the waste was achieved after 120 days of operation in aerobic landfills. At this time, anaerobic reactors were in the acidogenic phase which results with the high concentrations of VFA. The results also indicated that leachate recirculation does not affect the degradation rate in aerobic landfills as much as it does in anaerobic landfills

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35

Camacho-Rubio, F., E. Jurado-Alameda, P. González-Tello, and G. Luzón-González. "Kinetic study of fructose-glucose isomerization in a recirculation reactor." Canadian Journal of Chemical Engineering 73, no. 6 (December 1995): 935–40. http://dx.doi.org/10.1002/cjce.5450730618.

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36

Veeken, A. H. M., and B. V. M. Hamelers. "Effect of substrate-seed mixing and leachate recirculation on solid state digestion of biowaste." Water Science and Technology 41, no. 3 (February 1, 2000): 255–62. http://dx.doi.org/10.2166/wst.2000.0079.

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Lab-scale experiments were performed and a mechanistic model was developed to simulate the solid state digestion of biowaste in a batch reactor. Both experiments and model showed that the substrate-seed mixing degree and leachate recirculation rate have a strong effect on the reactor performance. This is due to mass transport limitations of volatile fatty acids (VFA) within the biowaste-seed bed. In that case two regions are developed in the digester, so-called acidogenic and methanogenic pockets. Limitations in mass transport will prevent irreversible acidification during start-up of the reactor because whereas high VFA concentration is met in the fresh waste pockets, the VFA concentration in the methanogenic pockets will remain low. However, accumulation of VFA in the acidogenic pockets will reduce the hydrolysis rate of biowaste due to inhibition by VFA. Moreover, experiments and simulations showed that the reactor performance can be improved by varying the leachate recirculation rate or applying sequential batch operation.

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37

Coulibaly, Gnougon Nina, Sungjun Bae, Joohyun Kim, Aymen Amin Assadi, and Khalil Hanna. "Enhanced removal of antibiotics in hospital wastewater by Fe–ZnO activated persulfate oxidation." Environmental Science: Water Research & Technology 5, no. 12 (2019): 2193–201. http://dx.doi.org/10.1039/c9ew00611g.

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38

Meinel, F., A. Sperlich, and M. Jekel. "Pilot-scale study of powdered activated carbon recirculation for micropollutant removal." Water Science and Technology 74, no. 4 (June 9, 2016): 927–34. http://dx.doi.org/10.2166/wst.2016.273.

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Adsorption onto powdered activated carbon (PAC) is a promising technique for the removal of organic micropollutants (OMPs) from treated wastewater. To enhance the adsorption efficiency, PAC is recycled back into the adsorption stage. This technique was examined in pilot scale in comparison to a reference without recirculation. Coagulation with Fe3+ was carried out simultaneously to adsorption. Extensive OMP measurements showed that recirculation significantly increased OMP eliminations. Thus, significant PAC savings were feasible. The PAC concentration in the contact reactor proved to be an important operating parameter that can be surrogated by the easily measurable total suspended solids (TSS) concentration. OMP eliminations increased with increasing TSS concentrations. At 20 mg PAC L−1 and 2.8 g TSS L−1 in the contact reactor, well-adsorbable carbamazepine was eliminated by 97%, moderately adsorbable diclofenac was eliminated by 92% and poorly-adsorbable acesulfame was eliminated by 54% in comparison to 49%, 35% and 18%, respectively, without recirculation. The recirculation system represents an efficient technique, as the PAC's adsorption capacity is practically completely used. Small PAC dosages yield high OMP eliminations. Poorly-adsorbable gabapentin was eliminated to an unexpectedly high degree. A laboratory-scale biomass inhibition study showed that aerobic biodegradation removed gabapentin in addition to adsorption.

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39

Farabegoli, G., A. Chiavola, and E. Rolle. "Remediation of chlorophenol- and phenol-contaminated groundwater by a sequencing batch biofilm reactor." Water Science and Technology 58, no. 2 (August 1, 2008): 295–301. http://dx.doi.org/10.2166/wst.2008.398.

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The paper describes the results of an investigation aimed at evaluating suitability of a lab-scale Sequencing Batch Biofilm Reactor (SBBR) for the remediation of groundwater contaminated by phenol (P) and 2-chlorophenol (2-CP). Kinetics of compound degradation was determined along the bed height in the absence and in presence of effluent recirculation, and with different influent composition (compounds fed separately or in combination in the same stream). SBBR performances with and without recirculation were very satisfactory for all the influent compositions: the system showed 99% removal efficiencies for both phenol and 2-CP and their complete removal was always achieved far before the end of react. In the presence of recirculation, the concentration gradient established during fill was rapidly eliminated and an even biomass distribution along the bed height was formed. Consequently, an acceleration of the elimination process was observed, particularly for phenol that was mostly removed in the first hour of the cycle. When the compounds were fed simultaneously, 2-CP removal kinetics improved probably due to cometabolism. The adsorption phenomena of the toxic compounds on the packing material were studied also, showing about 50% COD removal after 7 hours contact time.

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Cataldo-Hernández, Macarena A., Arman Bonakdarpour, Joseph T. English, Madjid Mohseni, and David P. Wilkinson. "A membrane-based electrochemical flow reactor for generation of ferrates at near neutral pH conditions." Reaction Chemistry & Engineering 4, no. 6 (2019): 1116–25. http://dx.doi.org/10.1039/c8re00306h.

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41

Kigel, M. Y., and J. F. Shultis. "Wastewater Treatment Technologies Accomplished in a Pseudofluidized Bed Reactor." Water Science and Technology 26, no. 9-11 (November 1, 1992): 2501–4. http://dx.doi.org/10.2166/wst.1992.0772.

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A pseudofluidized bed reactor has been developed and successfully used with the purpose of water and wastewater treatment based on both biological and physical-chemical processes. The reactor was tested in a full-scale industrial facility for the treatment of petrochemical wastewater. Major reactor's process and hydraulic components were also investigated for the removal of chromium from ground water. Combined simultaneous biological and chemical treatment was tested to remove organic as well as inorganic contaminants. The reactor provides accomplishment of several process phases proceeding in one apparatus unit including oxygen transfer to water, mixing, gas bubbles removal, creation of pseudofluidized beds, internal recirculation, and liquid/solid phase separation. Hydraulic conditions for the pseudofluidization regime were investigated in a three-column pilot-scale unit then checked in a 1-gpm (0.0631 L/s) reactor prototype. Treatment process parameters were investigated in continuous operation of a 1.5-gpm (0.1 L/s) full-scale facility based on a symbiotic (algae and activated sludge) biological treatment process modification. The obtained results allowed 40 - 50% decrease in total residence time of reaction and phase separation processes.

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42

Thijs, Barbara, Jan Rongé, and Johan A. Martens. "Selective electrochemical reduction of CO2 to formic acid in a gas phase reactor with by-product recirculation." Sustainable Energy & Fuels 5, no. 6 (2021): 1867–73. http://dx.doi.org/10.1039/d1se00218j.

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43

Sharma, K. R., and J. C. Huang. "High rate treatment by aerobic upflow sludge blanket (AUSB) with external oxygenation." Water Science and Technology 50, no. 8 (October 1, 2004): 193–200. http://dx.doi.org/10.2166/wst.2004.0515.

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A 3-year study was conducted using an aerobic upflow sludge blanket (AUSB) reactor to achieve high-rate biological treatment through maintenance of a high biomass concentration (7–10 g VSS/L) together with a high oxygen flux. The AUSB reactor was not aerated directly; instead, oxygenation was provided in an external chamber with flow recirculation. The oxygenation was provided at four different ressurizations: 0, 15, 20 and 25 psig. The AUSB reactor was also pressurized to avoid the flotation of biomass. The flow recirculation rate was varied from 400% to 1,500% in order to ensure adequate oxygen supply. It was found that the AUSB system was able to handle a volumetric loading of as high as 10 kg COD/m3-day with a removal efficiency of 92%. Despite a high upflow velocity through AUSB, the effluent suspended solid concentration was mostly below 60 mg/L. The active fraction of biomass in the AUSB sludge was about 3 times higher than that of the regular activated sludge. This was indicated by a very high specific oxygen uptake rate (SOUR), up to 180-250 mg O2/g VSS-hr. The sludge yield in the entire system was only 0.09 to 0.13 g VSS/g COD removed. This was mainly caused by additional auto-oxidation of biosolids in the oxygenation chamber due to flow recirculation.

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44

Wang, Rong Chang, Shuang Lin Dai, Yun Fei Tang, and Jian Fu Zhao. "Hydrodynamic Characteristics Assessment and Modeling of a Novel Membrane-Aerated Reactor." Advanced Materials Research 516-517 (May 2012): 763–68. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.763.

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The research study is aimed at the characterization of the hydrodynamics of a novel membrane-aerated reactor. Hydrodynamics was determined by means of impulse tracer trials in clean reactor and calculating residence time distribution (RTD) curves at different recirculation flow rates and hydraulic retention time. Thus the typical RTD curves were analyzed to calculate the average residence time, the dimensionless variance, the number of stirred tank reactors in series, and the dispersion number.The results showed that the hydraulic characteristics in the membrane-aerated reactor was essentially correlated with circulation rate. With the circulation velocity increasing, the number of stirred tank reactors in series decreased gradually, approaching to 1, while the dispersion number increased up to 0.2. It was concluded that the flow patterns within the membrane-aerated reactor are perfectly mixed under all the conditions tested. A simple correlation between the Reynolds number and the mixing was developed which can be used for design and scale-up purposes.

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45

Li, Nian, Yunyun Ning, Xiaopeng Wu, Jin Xie, Weipeng Li, and Chengjian Zhu. "A highly selective decarboxylative deuteration of carboxylic acids." Chemical Science 12, no. 15 (2021): 5505–10. http://dx.doi.org/10.1039/d1sc00528f.

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A scalable, practical and general method for precise deuteration of aliphatic carboxylic acids via synergistic photoredox and HAT catalysis has been developed. The use of recirculation reactor achieved the preparative scale deuteration.

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46

Srisuddee, Sura, Malinee Sriariyanun, Chanin Panjapornpon, and Atthasit Tawai. "Input/output Linearization Control Technique for Anaerobic Digestion Reactor with Recirculation." E3S Web of Conferences 141 (2020): 01007. http://dx.doi.org/10.1051/e3sconf/202014101007.

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Anaerobic digestion (AD) process has been generally applied in factories for wastewater treatment and energy recovery. For the AD processes, the continuously stirred tank reactor (CSTR) with recirculation are typically applied in industries for methane production from wastewater treatment. Since the recycle stream affects the inlet concentration of the reactor, the control performance of traditional PI and PID controllers used to manipulate control actuators may be limited. Additionally, the process control loops related to biochemical reactions are generally employed the operational experiences without process dynamic consideration. A control system based on input/output (I/O) linearization control technique for an anaerobic digestion (AD) process was developed in this work. The control system applied the concept of the I/O linearization technique, which followed dynamic behaviors of the reactor with a two-step (acidogenesis-methanogenesis) kinetic model. The volatile fatty acid (VFA) concentration was regulated by manipulation of the dilution rate to achieve the requested trajectories. Control performances of the closed-loop system were investigated by a simulation under servo and regulatory problems. The simulation results showed that the developed control scheme successfully forced the controlled output to achieve the desired set points and handled the introduced control problems.

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Lee, Hansaem, Daeju Lee, Seongwan Hong, Geum Hee Yun, Sungpyo Kim, Jung Ki Hwang, Woojae Lee, and Zuwhan Yun. "Anoxic gas recirculation system for fouling control in anoxic membrane reactor." Journal of Environmental Sciences 26, no. 6 (June 2014): 1289–93. http://dx.doi.org/10.1016/s1001-0742(13)60601-4.

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48

Choi, Hyeoksun, and JoAnn Silverstein. "Effluent recirculation to improve perchlorate reduction in a fixed biofilm reactor." Biotechnology and Bioengineering 98, no. 1 (2007): 132–40. http://dx.doi.org/10.1002/bit.21425.

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49

Director, L. B., O. A. Ivanin, and V. A. Sinelshchikov. "Numerical analysis of biomass torrefaction reactor with recirculation of heat carrier." Journal of Physics: Conference Series 946 (January 2018): 012037. http://dx.doi.org/10.1088/1742-6596/946/1/012037.

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50

Chen, Wei-Hsin, Shih-Cheng Lin, and Teng Chien Chen. "Biogas partial oxidation in a heat recirculation reactor for syngas production." Energy Procedia 142 (December 2017): 125–30. http://dx.doi.org/10.1016/j.egypro.2017.12.020.

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Journal articles on the topic 'Reactor recirculation'

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