Showing papers on "Hydraulic retention time published in 2000"
TL;DR: In this paper, the effect of N2 sparging on hydrogen yield was investigated in non-sterile conditions using a hydrogen-producing mixed culture previously enriched from soya bean meal.
555 citations
TL;DR: Experimental results obtained emphasize that the response of metabolites was a more useful indicator than hydrogenic activity for obtaining efficient hydrogen production, and expressions of contour plots indicate that Response‐Surface Methodology may provide easily interpretable advice on the operation of a hydrogen‐producing bioprocess.
Abstract: The pH and hydraulic retention time (HRT) of a chemostat reactor were varied according to a central composite design methodology with the aim of modeling and optimizing the conversion of starch into hydrogen by microorganisms in an anaerobic digested sludge. Experimental results from 23 runs indicate that a maximum hydrogen production rate of 1600 L/m(3)/d under the organic loading rate of 6 kg starch m(3)/d obtained at pH = 5.2 and HRT = 17 h. Throughout this study, the hydrogen percentage in the biogas was approximately 60% and no methanogenesis was observed. while the reactor was operated with HRT of 17 h, hydrogen was produced within a pH range between 4.7 and 5.7. Alcohol production rate was greater than hydrogen production rate if the pH was lower than 4.3 or higher than 6.1. Supplementary experiments confirm that the optimum conditions evaluated in this study were highly reliable; while a hydrogen production yield of 1.29 l H(2)/g starch-COD was obtained. An examination of the response surfaces, including hydrogen, volatile fatty acids (VFA) and alcohols production, led us to the belief that clostridium sp. predominated in the anaerobic hydrogen-producing microorganisms in this study. Experiment results obtained emphasize that the response of metabolites was a more useful indicator than hydrogenic activity for obtaining efficient hydrogen production. Furthermore, expressions of contour plots indicate that Response-Surface Methodology may provide easily interpretable advice on the operation of a hydrogen-producing bioprocess.
475 citations
TL;DR: The membrane-bioreactor (MBR) is a modification of this conventional process, where the activated sludge is concentrated in a bioreactor which is connected to a cross-flow ultrafiltration membrane unit as discussed by the authors.
177 citations
TL;DR: The feasibility of sewage treatment by an upflow anaerobic sludge blanket (UASB) reactor was studied using actual sewage at a fixed hydraulic retention time (HRT) of 4.7 h, and at temperatures in the range of 25-13°C, for six months.
164 citations
TL;DR: In this article, a 162-day pilot-scale operation for reclamation of urban wastewater was studied by using an ultrafiltration membrane bioreactor (UMBR), with a sludge retention time of 5, 15, and 30 days, a hydraulic retention time (HRT) of 5 h, and membrane flux between 75 and 150 l m 2 h 1, respectively.
129 citations
TL;DR: The model suggests that a significant increase in the sulfate reduction capacity of the system is possible by increasing the volume of the bed relative to the total liquid volume of this reactors, and thus could be used in the design/scale-up of such reactors.
Abstract: A liquid-solid fluidized bed reactor was used to carry out sulfate reduction with a mixed culture of sulfate reducing bacteria. The bacteria were immobilized on porous glass beads. Stable fluidized bed operation with these biofilm-coated beads was possible. The low specific gravity of the hydrated beads allowed operation at low liquid recirculation rates. H 2 S level in the reactor was controlled by N 2 sparging, which also served as the location for liquid feed and removal. Ethanol was used as the electron donor/carbon source for the bacteria. Sulfate reduction rates up to 6.33 g sulfate L -1 day -1 were attained in the reactor at a hydraulic retention time of 5.1 h. The effect of hydraulic retention time and biomass loading on the beads, on reactor performance, and efficiency were examined. The efficiency of sulfate reduction increases considerably as the hydraulic retention increases, until the bacteria became very strongly substrate-limited at 55h HRT. The effect of bead biomass loading on bed expansion at various liquid superficial velocities was studied. A model for the reactor was developed. Simulations of the continuous flow experiments indicate that the model can describe the system well, and thus could be used in the design/scale-up of such reactors. The model suggests that a significant increase in the sulfate reduction capacity of the system is possible by increasing the volume of the bed relative to the total liquid volume of the system.
120 citations
TL;DR: In this article, the authors investigated the biogas production from a slurry obtained by mixing finely ground olive pomace in water using anaerobic digesters of 1-l working volume at 37°C.
Abstract: Biogas production from a slurry obtained by mixing finely ground olive pomace in water was investigated using anaerobic digesters of 1-l working volume at 37°C. A start-up culture was obtained from a local landfill area and was adopted to the slurry within 10 days at this temperature. The biogas generation rates were determined by varying the total solids (TS) concentration in the slurry and the hydraulic retention time (HRT) during semi-continuous digestion. The maximum rate was found to be 0.70 l of biogas per l of digester volume per day, corresponding to a HRT of 20 days and 10% TS with a yield of 0.08 l biogas per g chemical oxygen demand (COD) added to the digester. The methane content of the biogas was in the range of 75–80% for both batch and semi-continuous runs, the remainder being principally carbon dioxide.
119 citations
TL;DR: In this article, the performance of an anaerobic baffled reactor (ABR, 10 l and eight compartments) treating a dilute wastewater (500 mg COD/l) was studied.
106 citations
TL;DR: In this article, the effect of hydraulic retention time (HRT) on the acidogenesis of dairy wastewater was studied using an upflow reactor at pH 5.5, 37°C, and six HRTs ranging from 4 to 24 hours.
Abstract: Effect of hydraulic retention time (HRT) on the acidogenesis of dairy wastewater was studied using an upflow reactor at pH 5.5, 37°C, and six HRTs ranging from 4 to 24 h. Results showed that the degree of acidification increased rapidly with HRT from 28.2% at 4 h to 54.1% at 12 h; further increase of HRT to 16 and 24 h only increased acidification slightly to 55.8 and 59.1%, respectively. The biodegradability of the three major constituents in dairy wastewater increased with HRT, following the order of carbohydrates > proteins > lipids. The predominant products were acetate, propionate, butyrate, lactate, and ethanol.
99 citations
TL;DR: COD (chemical oxygen demand) removal rate and efficiency of winery wastewater (WW) aerobic treatments were evaluated in an air-bubble column bioreactor using self-adapted microbial populations either free or immobilized on polyurethane particles and in a packed-bedBioreactor immobilized in Raschig rings.
94 citations
TL;DR: The start-up and performance of four anaerobic baffled reactors (ABR, each of 10 l and eight compartments) treating a complex dilute soluble or colloidal wastewater (milk and colloidal rice and dog food) was studied as discussed by the authors.
TL;DR: In this paper, the effect of cyanide on the anaerobic treatment of synthetic wastewater, containing starch and volatile fatty acids, was evaluated, and the results demonstrated the potential of anaerobatic treatment for COD removal in contaminated waste waters.
TL;DR: The results show that nitrification of anaerobically treated leachate is feasible at temperatures down to 5–10°C, and the nitrification rates were higher with than without carrier material, suggesting that a large fraction of nitrifying micro-organisms was attached on the surface of the carrier material.
TL;DR: The chemical composition, molecular weight distribution, and biodegradability of soluble microbial products (SMPs) in an anaerobic baffled reactor (ABR) treating low-strength wastewater were investigated in this paper.
Abstract: The chemical composition, molecular weight (MW) distribution, and biodegradability (both aerobic and anaerobic) of soluble microbial products (SMPs) in an anaerobic baffled reactor (ABR) treating low-strength wastewater were investigated. The effect of various process parameters on the production of SMPs was also examined. Results indicated that high MW (>300 kDa) compounds were produced in the middle compartments of the reactor and formed 22% of the effluent chemical oxygen demand (COD). This fraction was found to be 86% degradable under aerobic conditions but only 4% under anaerobic conditions. Low MW (<1 kDa) material represented the highest portion (36%) of the effluent COD and was mainly found in the first compartment of the ABR and in the effluent. This fraction was more easily degraded under anaerobic conditions (33%) than aerobic conditions (17%). Analysis of a hydrolyzed sample of the high MW fraction revealed the presence of several sugars and volatile fatty acids. Therefore, it was concluded that the high MW material contains heteropolysaccharides. Nuclear magnetic resonance analysis of the low MW fraction revealed the possible presence of alcohol, carboxylate, and aromatic chemical groups. SMP production increased with increasing hydraulic retention time (HRT), probably due to enhanced biomass decay at high HRTs, and also increased with decreasing temperature, probably due to increased stress on the biomass and a reduced metabolism of the SMP at low temperatures. Finally, SMP production in an ABR containing higher levels of initial biomass concentration was greater than for an ABR operating at the same conditions but with lower levels of initial biomass.
TL;DR: In this article, the performance of anaerobic fixed-film reactors with non-random support, for poultry slaughterhouse wastewater pre-treatment, including the influence of operating conditions, was investigated.
TL;DR: In this article, an image analysis of anaerobic biomass under both organic and hydraulic shocks was performed and the results indicated that filaments are predominantly acetoclastic bacteria, probably Methanosaeta.
TL;DR: A comparison with a one-phase system is carried out, showing that a two- phase system is much more appropriate for the digestion of this kind of highly biodegradable substrate in thermophilic conditions.
TL;DR: Chlorophenol degradation was studied by combined anaerobic–aerobic treatments as a single or multi-substrate system and was found to be sequential: 2-Ch chlorophenol (2-CP) and 4-CP were degraded first, followed by 2,4,6-Trichlorophenols (2,4-6-TCP) while the contrary was obtained inAnaerobic degradation.
Abstract: Chlorophenol degradation was studied by combined anaerobic–aerobic treatments as a single or multi-substrate system. 2,4-Dichlorophenol (2,4-DCP) was degraded to the extent of 52 and 78% in up-flow anaerobic sludge blanket (UASB) and aerobic suspended growth (ASG) reactors respectively, at organic loading rates of 0.18 kg/m3/day and hydraulic retention time of 26.4 h in the presence of glucose. The UASB represents the dominating facultative anaerobic microbial population. When the effluent from the anaerobic reactor (UASB) was subjected to aerobic treatment on the ASG reactor, 2,4-DCP and COD removals of 86 and 95% respectively were achieved. Aerobic degradation of chlorophenol by acclimated mixed bacterial isolates was found to be sequential: 2-Chlorophenol (2-CP) and 4-CP were degraded first, followed by 2,4-DCP and 2,4,6-Trichlorophenol (2,4,6-TCP) while the contrary was obtained in anaerobic degradation. In anaerobic degradation by acclimated mixed bacterial cells, 2,4-DCP and 2,4,6-TCP were degraded first followed by mono-chlorophenols. The anaerobic/aerobic bioreactors were most efficient when operated in sequence (series) rather than in parallel.
TL;DR: In this article, the authors investigated the start-up and treatment efficiency in anaerobic co-digestion of landfill leachate and septage by a UASB process.
TL;DR: Characterization and anaerobic treatability of leachate from Komurcuoda Sanitary Landfill located on the Asian part of Istanbul were investigated and it was quite interesting that such a dilution effect was not observed for ammonia.
TL;DR: In this paper, a column packed with clean sheets of reticulated polyurethane foam was fed with either raw sewage, synthetic sewage or skimmed milk for a short time to evaluate the mechanism of physical entrapment and filtration of particles.
TL;DR: Operational results of a co-digestion facility were assessed over a period of 18 months and the overall energy balance shows that the facility substitutes primary energy.
TL;DR: In this article, an expanded granular sludge bed (EGSB) was used to examine the anaerobic treatment of a mixture of maleic, oxalic, fumaric, acetic and formic acids.
TL;DR: Various immobilization methods were evaluated for the removal of ammonium-N from recirculating aquacultural water and nitrification showed the most effective nitrification while those immobilized in the carrageenan and agar beads showed reduced activities.
TL;DR: In this paper, a chemically enhanced primary sedimentation (CEPS) followed by an upflow anaerobic sludge blanket (UASB) reactor was used for 170 days.
Abstract: Raw domestic wastewater was treated continuously under laboratory conditions for 170 days by a chemically enhanced primary sedimentation (CEPS) followed by an upflow anaerobic sludge blanket (UASB) reactor. The CEPS was carried out with 70 mg FeCl3l−1 from day 1 to 82 and with 24 ml l−1 of the water extract of Moringa oleifera seeds from day 83 to 170. Compared to the natural primary sedimentation (NPS), the CEPS increased the ratio of soluble chemical oxygen demand to volatile suspended solids (CODs/VSS) of the supernatant by a factor 3 and 10 respectively. Although the FeCl3 increased the CODs/VSS ratio, it caused a decrease of the soluble content of the wastewater by a factor 1.4. This resulted in a low influent concentration supplied to the UASB reactor and consequently a low biogas production. However, the reactor achieved 54 % removal of total COD (CODt) at a hydraulic retention time (HRT) of 2 hours and a volumetric loading rate (Bv) of 1.4 g COD l−1 d−1. The Moringa oleifera seeds, besides the inc...
TL;DR: A moving bed biofilm reactor (MBBR) pilot plant, using Kaldnes type K1 biofilm carriers, was tested for nitrogen removal at the FREVAR wastewater treatment plant as mentioned in this paper.
TL;DR: In this article, three configurations for a dual digestion system were examined, and the first stage was operated at 55°C with a hydraulic retention time of 4 h and the second stage at 35°C using a mixture of sewage sludge and strong confectionery waste.
TL;DR: In this article, the results from lab-scale reactors were used for designing and operating an industrial scale activated sludge unit, being the efficiency attained at full-scale similar to the laboratory unit.
TL;DR: With the consideration of its better capability for destructing fecal bacteria in animal manure, the thermophilic-mesophilic ASBR system is more advantageous than the mesophilic (35°C) mesophobic-mesophile AsBR system for treating animal manure; however, the higher energy requirement for heating the reactors in the former system needs to be considered.
Abstract: Anaerobic treatment of screened swine and dairy manure was studied in the laboratory with two-stage anaerobic sequencing batch reactor (ASBR) systems. The effects of anaerobic treatment on odor control in subsequent manure storage units were evaluated. One thermophilic (55°C) mesophilic (35°C) system (II) was evaluated against one mesophilic (35°C) mesophilic (35°C) system (I) at a system hydraulic retention time (HRT) of six days and four volatile solid (VS) loading rates (1, 2, 3, 4 g/L/day). Generally, anaerobic digestion under all the test conditions resulted in higher solids reduction in swine manure than in dairy manure. The thermophilic-mesophilic system had a better performance in treating dairy and swine manure with 6 to 15% more VS removal than the mesophilic-mesophilic system. The headspace gas analysis results using manure storage jars showed that both systems were effective in reducing the generation of odorous sulfur gases during storage. The untreated dairy and swine manure exhibited strong offensive odors with high hydrogen sulfide (H 2 S) and mercaptan concentrations detected in the headspaces of storage jars. The anaerobically treated manure, however, showed minimal residual odors while in many cases, H 2 S and mercaptans were not detectable. With the consideration of its better capability for destructing fecal bacteria in animal manure, the thermophilic-mesophilic ASBR system is more advantageous than the mesophilic-mesophilic ASBR system for treating animal manure. However, the higher energy requirement for heating the reactors in the former system needs to be considered when selecting thermophilic vs. mesophilic anaerobic digestion systems. Keywords. Anaerobic digestion, Anaerobic sequencing batch reactors, Odor control, Dairy, Swine, Manure.
TL;DR: In this paper, the influence of phytoplankton species composition on biomass removal from high-rate oxidation ponds or lagoons (HROPs) by means of sedimentation with spontaneous flocculation was analyzed.
Abstract: The objective of this study is to analyze the influence of phytoplankton species composition on biomass removal from high-rate oxidation ponds or lagoons (HROPs) by means of sedimentation with spontaneous flocculation. Two experimental systems each consisting of an HROP (with a surface area of 1.54 m 2 and depth of 0.3 m) with a clarifier (surface area = 0.025 m 2 ) for phytoplankton biomass removal were operated with different hydraulic retention time criteria over a period of a year. Phytoplankton biomass removal rates reached a yearly average of 70 to 80% in both HROPs. During periods with large amounts of the algal species Scenedesmus acutus, which was present as discrete, unflocculated particles, both systems operated unsatisfactorily, with effluent total suspended solids (TSS) concentrations greater than 30 mg/L. Phytoplankton biomass removal from HROPs by means of sedimentation and spontaneous flocculation is unreliable for year-round use (at least for 6 months of the year) if TSS effluent concentration is required to be less than 30 mg/L. Additional treatment, such as pH or chemical augmentation, is needed to reduce TSS and improve the effluent quality of HROPs with clarifiers.