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1.
J Environ Manage ; 348: 119215, 2023 Dec 15.
Article in English | MEDLINE | ID: mdl-37827083

ABSTRACT

Anaerobic digestion has emerged as the most appealing waste management strategy in biorefineries. Particularly, recent studies have highlighted the energy advantages of waste co-digestion in industrial biorefineries and the use of two-stage systems. However, there are some concerns about moving the system from laboratory testing to industrial scale. One of them is the high level of investment that is required. Therefore, this study carried out a techno-economic analysis (scale-up and energy production, economic and risk analysis, and factorial design) to assess the feasibility of single- and two-stage systems in the treatment of cheese whey and glycerin for the production of hydrogen and methane. Scenarios (S1 to S9) considered thermophilic and mesophilic single and two-stage systems with different applied organic loading rates (OLRA). The analyses of scale-up and energy production revealed that S3 (a thermophilic single-stage system operated at high OLRA 17.3 kg-COD.m-3.d-1) and S9 (a thermophilic-mesophilic two-stage system operated at high OLRA 134.8 kg-COD.m-3.d-1 and 20.5 kg-COD.m-3.d-1, respectively) were more compact and required lower initial investment compared to other scenarios. The risk analysis performed by a Monte Carlo simulation showed low investment risks (10 and 11%) for S3 and S9, respectively, being the electricity sales price, the key determining factor to define whether the project in the baseline scenario will result in profit or loss. Lastly, the factorial design revealed that while the net present value (NPV) is positively impacted by rising inflation and electricity sales price, it is negatively impacted by rising capitalization rate. Such assessments assist in making decisions regarding which system can be fully implemented, the best market circumstances for the investment, and how market changes may favorably or unfavorably affect the NPV and the internal rate of return (IRR).


Subject(s)
Bioreactors , Methane , Anaerobiosis , Hydrogen , Risk Assessment
2.
Rev Port Cardiol ; 42(9): 759-769, 2023 09.
Article in English, Portuguese | MEDLINE | ID: mdl-36948457

ABSTRACT

INTRODUCTION: Current rates of permanent pacemaker implantation (PPMI) after transcatheter aortic valve implantation (TAVI) range between 3.4% and 25.9%. PPMI is associated with a worse prognosis. A lower valve implantation depth is associated with an increased risk of conduction disturbances. Theoretically, cusp-overlap projection (COP) has the potential to enable higher valve deployment. OBJECTIVE: To compare the 30-day PPMI incidence post-TAVI using self-expanding valves according to the fluoroscopic guidance technique. METHODS: This retrospective single-center study assessed consecutive patients undergoing TAVI with CoreValve™ valves between April 2019 and November 2021, grouped according to the fluoroscopic guidance technique (COP vs. coplanar implantation technique [CIT]). RESULTS: A total of 122 patients were included, predominantly women (52.5%), with a mean age of 81.6±5.5 years. COP was used in 49.2% of the sample. The CIT group had a significantly higher prevalence of previous beta-blocker use (p<0.01), lower baseline left ventricular ejection fraction (p=0.04) and a higher EuroSCORE II (p=0.02). The 30-day PPMI rate was 27.9% (n=34), with no significant difference between the COP and CIT groups (26.7% vs. 29.0%, p=0.77). Complete atrioventricular block was the main cause (38.5%). Likewise, mean fluoroscopy time (p=0.14) and contrast volume (p=0.35) used were similar between the two groups. Radiation dose was lower in the COP group (p=0.02). There was no significant difference between post-TAVI grades III and IV aortic valve regurgitation (p=0.27) and there were no cases of periprocedural acute coronary occlusion. CONCLUSIONS: This study shows that the COP technique, although safe and not associated with increased complexity, did not significantly reduce the 30-day PPMI rate compared to the traditional CIT view.


Subject(s)
Aortic Valve Stenosis , Heart Valve Prosthesis , Pacemaker, Artificial , Transcatheter Aortic Valve Replacement , Humans , Female , Aged , Aged, 80 and over , Male , Transcatheter Aortic Valve Replacement/methods , Aortic Valve/surgery , Aortic Valve Stenosis/surgery , Stroke Volume , Incidence , Retrospective Studies , Treatment Outcome , Risk Factors , Ventricular Function, Left
3.
J Environ Manage ; 330: 117117, 2023 Mar 15.
Article in English | MEDLINE | ID: mdl-36584460

ABSTRACT

Anaerobic digestion for CH4 recovery in wastewater treatment has been carried out with different strategies to increase process efficiency, among which co-digestion and the two-stage process can be highlighted. In this context, this study aimed at evaluating the co-digestion of cheese whey and glycerol in a two-stage process using fluidized bed reactors, verifying the effect of increasing the organic loading rate (OLR) (2-20 g-COD.L-1.d-1) and temperature (thermophilic and mesophilic) in the second stage methanogenic reactor. The mesophilic methanogenic reactor (R-Meso) (mean temperature of 22 °C) was more tolerant to high OLR and its best performance was at 20 g-COD.L-1.d-1, resulting in methane yield (MY) and methane production (MPR) of 273 mL-CH4.g-COD-1 and 5.8 L-CH4.L-1.d-1 (with 67% of CH4), respectively. Through 16S rRNA gene massive sequencing analysis, a greater diversity of microorganisms was identified in R-Meso than in R-Thermo (second stage methanogenic reactor, 55 °C). Firmicutes was the phyla with higher relative abundance in R-Thermo, while in R-Meso the most abundant ones were Proteobacteria and Bacteroidetes. Regarding the Archaea domain, a predominance of hydrogenotrophic microorganisms could be observed, being the genera Methanothermobacter and Methanobacterium the most abundant in R-Thermo and R-Meso, respectively. The two-stage system composed with a thermophilic acidogenic reactor + R-Meso was more adequate for the co-digestion of cheese whey and glycerol than the single-stage process, promoting increases of up to 47% in the energetic yield (10.3 kJ.kg-COD-1) and 14% in organic matter removal (90.5%).


Subject(s)
Cheese , Euryarchaeota , Whey/chemistry , Anaerobiosis , Temperature , Glycerol , RNA, Ribosomal, 16S , Methane/analysis , Digestion , Bioreactors/microbiology
4.
Appl Biochem Biotechnol ; 189(4): 1039-1055, 2019 Dec.
Article in English | MEDLINE | ID: mdl-31165392

ABSTRACT

Stillage is an abundant wastewater from the sugarcane ethanol industry. It is rich in fermentable substrates and presents low-nutrient content, constituting a promising substrate for polyhydroxyalkanoate (PHA) production by mixed microbial cultures (MMC). This work assessed the enrichment of a PHA-accumulating MMC from acidified sugarcane stillage in a sequencing batch reactor under increasing organic loading rates (OLR) and no external nutrient supplementation. The OLR was increased from 1.0 to 7.1 kg COD m-3 day-1 in four steps. A PHA-producing MMC with high storage response was selected in all experimental conditions. The volumetric biomass productivity and the maximal PHA storage capacity increased continuously with the OLR, reaching 0.061 g VSS L-1 h-1 and 0.49 g PHA g VSS-1, respectively. The highest observed PHA storage yield (0.60 g CODPHA g COD.t-1) and specific PHA storage rate (0.169 g CODPHA g of CODX h-1) were obtained for the OLR of 4.5 kg COD m-3 day-1. The PHA produced was a co-polymer of 3-hydroxybutyrate (86-77%mol) and 3-hydroxyvalerate (14-23%mol). The performance of the biomass enrichment was comparable to those attained with other agro-industrial wastewaters, indicating the potential of acidified sugarcane stillage as a feedstock for MMC PHA production.


Subject(s)
Biomass , Microbial Consortia , Polyhydroxyalkanoates/metabolism , Saccharum , Wastewater/microbiology
5.
Waste Manag ; 82: 37-50, 2018 Dec.
Article in English | MEDLINE | ID: mdl-30509594

ABSTRACT

This work used a pilot scale (with a total volume of 1300 L) Anaerobic Sequencing Batch Biofilm Reactor (AnSBBR) to treat landfill leachate from São Carlos-SP (Brazil) as well as to evaluate the biomass growth and its behavior. Biomass from the bottom of a landfill leachate stabilization pond was immobilized in polyurethane foam cubes as inoculum. The leachate characteristics varied during the experiment. Ethanol or volatile fatty acids were added as additional substrate when the leachate was temporarily recalcitrant. After acclimation, the AnSBBR presented efficiency over 70% (COD removal). A mass balance model, biomass sampling and temporal concentration profiles were performed to obtain a biomass yield coefficient of YX/S = 0.0251 ±â€¯0.0006 gTVS gCOD removed (r2 = 0.999). Additionally, it was observed that a variable fraction of the attached biomass may detach itself or present mobility during the batch time, however returning to fixed bed depending on the substrate type and concentration. This behavior has never been reported by the literature for attached biomass.


Subject(s)
Water Pollutants, Chemical , Anaerobiosis , Biofilms , Biomass , Bioreactors , Brazil
6.
Bioresour Technol ; 245(Pt A): 332-341, 2017 Dec.
Article in English | MEDLINE | ID: mdl-28898828

ABSTRACT

Biogas upgrading processes by in-situ hydrogen (H2) injection are still challenging and could benefit from a mathematical model to predict system performance. Therefore, a previous model on anaerobic digestion was updated and expanded to include the effect of H2 injection into the liquid phase of a fermenter with the aim of modeling and simulating these processes. This was done by including hydrogenotrophic methanogen kinetics for H2 consumption and inhibition effect on the acetogenic steps. Special attention was paid to gas to liquid transfer of H2. The final model was successfully validated considering a set of Case Studies. Biogas composition and H2 utilization were correctly predicted, with overall deviation below 10% compared to experimental measurements. Parameter sensitivity analysis revealed that the model is highly sensitive to the H2 injection rate and mass transfer coefficient. The model developed is an effective tool for predicting process performance in scenarios with biogas upgrading.


Subject(s)
Biofuels , Bioreactors , Euryarchaeota , Hydrogen , Methane
7.
J Environ Manage ; 145: 385-93, 2014 Dec 01.
Article in English | MEDLINE | ID: mdl-25127066

ABSTRACT

This paper reports the kinetics evaluation of landfill leachate anaerobic treatment in a pilot-scale Anaerobic Sequence Batch Biofilm Reactor (AnSBBR). The experiment was carried out at room temperature (23.8 ± 2.1 °C) in the landfill area in São Carlos-SP, Brazil. Biomass from the bottom of a local landfill leachate stabilization pond was used as inoculum. After acclimated and utilizing leachate directly from the landfill, the AnSBBR presented efficiency over 70%, in terms of COD removal, with influent COD ranging from 4825 mg L(-1) to 12,330 mg L(-1). To evaluate the kinetics of landfill leachate treatment, temporal profiles of CODFilt. concentration were performed and a first-order kinetics model was adjusted for substrate consumption, obtaining an average k1 = 4.40 × 10(-5) L mgTVS(-1) d(-1), corrected to 25 °C. Considering the temperature variations, a temperature-activity coefficient θ = 1.07 was obtained. Statistical "Randomness" and "F" tests were used to successfully validate the model considered. Thus, the results demonstrate that the first-order kinetic model is adequate to model the anaerobic treatment of the landfill leachate in the AnSBBR.


Subject(s)
Biofilms/growth & development , Bioreactors/microbiology , Water Pollutants, Chemical/analysis , Water Purification , Anaerobiosis , Biological Oxygen Demand Analysis , Biomass , Brazil , Kinetics , Methanosarcina/growth & development , Models, Theoretical , Pilot Projects , Temperature , Water Purification/instrumentation , Water Purification/methods
8.
Appl Biochem Biotechnol ; 165(1): 347-68, 2011 Sep.
Article in English | MEDLINE | ID: mdl-21494753

ABSTRACT

Currently, there is an increasing demand for the production of biodiesel and, consequently, there will be an increasing need to treat wastewaters resulting from the production process of this biofuel. The main objective of this work was, therefore, to investigate the effect of applied volumetric organic load (AVOL) on the efficiency, stability, and methane production of an anaerobic sequencing batch biofilm reactor applied to the treatment of effluent from biodiesel production. As inert support, polyurethane foam cubes were used in the reactor and mixing was accomplished by recirculating the liquid phase. Increase in AVOL resulted in a drop in organic matter removal efficiency and increase in total volatile acids in the effluent. AVOLs of 1.5, 3.0, 4.5 and 6.0 g COD L(-1) day(-1) resulted in removal efficiencies of 92%, 81%, 67%, and 50%, for effluent filtered samples, and 91%, 80%, 63%, and 47%, for non-filtered samples, respectively, whereas total volatile acids concentrations in the effluent amounted to 42, 145, 386 and 729 mg HAc L(-1), respectively. Moreover, on increasing AVOL from 1.5 to 4.5 g COD L(-1) day(-1) methane production increased from 29.5 to 55.5 N mL CH(4) g COD(-1). However, this production dropped to 36.0 N mL CH(4) g COD(-1) when AVOL was increased to 6.0 g COD L(-1) day(-1), likely due to the higher concentration of volatile acids in the reactor. Despite the higher concentration of volatile acids at the highest AVOL, alkalinity supplementation to the influent, in the form of sodium bicarbonate, at a ratio of 0.5-1.3 g NaHCO(3) g COD (fed) (-1) , was sufficient to maintain the pH near neutral and guarantee process stability during reactor operation.


Subject(s)
Biofuels , Methane/metabolism , Organic Chemicals/metabolism , Bioreactors , Hydrogen-Ion Concentration
9.
Rev Port Cardiol ; 30(1): 65-72, 2011 Jan.
Article in English, Portuguese | MEDLINE | ID: mdl-21425744

ABSTRACT

Left main coronary aneurysm is extremely uncommon and its precise pathogenesis remains poorly understood. They are associated with serious complications and treatment is still the subject of disagreement. The authors present the case of a 42-year-old man admitted for a coronary syndrome, whose coronary angiogram revealed a large left main coronary aneurysm. The echocardiogram and multi-row detector CT angiography confirmed the abnormalities observed. No positive findings resulted from etiological evaluation. We decided to maintain the patient under oral anticoagulation and he remains clinically stable after two years of follow-up.


Subject(s)
Coronary Aneurysm/diagnostic imaging , Adult , Coronary Aneurysm/drug therapy , Echocardiography, Transesophageal/methods , Humans , Male , Tomography, X-Ray Computed/methods
10.
Bioresour Technol ; 102(2): 889-93, 2011 Jan.
Article in English | MEDLINE | ID: mdl-20888757

ABSTRACT

The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR--Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 °C. Experiments were performed with four impeller types, i.e., helical, flat-blade, inclined-blade and curved-blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530±37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the flat-blade turbine impeller.


Subject(s)
Bioreactors/microbiology , Waste Disposal, Fluid/instrumentation , Water Purification/instrumentation , Anaerobiosis , Biodegradation, Environmental , Biofilms , Kinetics
11.
Appl Biochem Biotechnol ; 163(1): 127-42, 2011 Jan.
Article in English | MEDLINE | ID: mdl-21153450

ABSTRACT

A study was performed regarding the effect of the relation between fill time, volume treated per cycle, and influent concentration at different applied organic loadings on the stability and efficiency of an anaerobic sequencing batch reactor containing immobilized biomass on polyurethane foam with recirculation of the liquid phase (AnSBBR) applied to the treatment of wastewater from a personal care industry. Total cycle length of the reactor was 8 h (480 min). Fill times were 10 min in the batch operation, 4 h in the fed-batch operation, and a 10-min batch followed by a 4-h fed batch in the mixed operation. Settling time was not necessary since the biomass was immobilized and decant time was 10 min. Volume of liquid medium in the reactor was 2.5 L, whereas volume treated per cycle ranged from 0.88 to 2.5 L in accordance with fill time. Influent concentration varied from 300 to 1,425 mg COD/L, resulting in an applied volumetric organic load of 0.9 and 1.5 g COD/L.d. Recirculation flow rate was 20 L/h, and the reactor was maintained at 30 °C. Values of organic matter removal efficiency of filtered effluent samples were below 71% in the batch operations and above 74% in the operations of fed batch followed by batch. Feeding wastewater during part of the operational cycle was beneficial to the system, as it resulted in indirect control over the conversion of substrate into intermediates that would negatively interfere with the biochemical reactions regarding the degradation of organic matter. As a result, the average substrate consumption increased, leading to higher organic removal efficiencies in the fed-batch operations.


Subject(s)
Organic Chemicals/analysis , Sewage/analysis , Waste Disposal, Fluid/methods , Bacteria/metabolism , Bioreactors/microbiology , Sewage/microbiology , Time Factors , Waste Disposal, Fluid/instrumentation
12.
J Environ Manage ; 91(12): 2499-504, 2010 Dec.
Article in English | MEDLINE | ID: mdl-20675039

ABSTRACT

A mechanically stirred anaerobic sequencing batch reactor (ASBR) containing granular biomass was applied to the treatment of a wastewater simulating the effluent from a personal care industry. The ASBR was operated with cycle lengths (t(C)) of 8, 12 and 24 h and applied volumetric organic loads (AVOL) of 0.75, 0.50 and 0.25 gCOD/L.d, treating 2.0 L liquid medium per cycle. Stirring frequency was 150 rpm and the reactor was kept in an isothermal chamber at 30 °C. Increase in t(C) resulted in efficiency increase at constant AVOL, reaching 77% at t(C) of 24 h versus 69% at t(C) of 8 h. However, efficiency decreased when AVOL decreased as a function of increasing t(C), due to the lack of substrate in the reaction medium. Moreover, replacing part of the wastewater by a chemically balanced synthetic one did not yield the expected effect and system efficiency dropped.


Subject(s)
Bioreactors , Sodium Dodecyl Sulfate/chemistry , Waste Management/methods , Water Pollutants, Chemical/chemistry , Anaerobiosis , Hair Preparations , Industrial Waste
13.
J Environ Manage ; 91(8): 1647-56, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20363066

ABSTRACT

The objective of this work was to assess the effect of agitation rate and impeller type in two mechanically stirred sequencing batch reactors: one containing granulated biomass (denominated ASBR) and the other immobilized biomass on polyurethane foam (denominated AnSBBR). Each configuration, with total volume of 1 m(3), treated 0.65 m(3) sanitary wastewater at ambient temperature in 8-h cycles. Three impeller types were assessed for each reactor configuration: flat-blade turbine impeller, 45 degrees -inclined-blade turbine impeller and helix impeller, as well as two agitation rates: 40 and 80 rpm, resulting in a combination of six experimental conditions. In addition, the ASBR was also operated at 20 rpm with a flat-blade turbine impeller and the AnSBBR was operated with a draft tube and helix impeller at 80 and 120 rpm. To quantify how impeller type and agitation rate relate to substrate consumption rate, results obtained during monitoring at the end of the cycle, as well as the time profiles during a cycle were analyzed. Increasing agitation rate from 40 rpm to 80 rpm in the AnSBBR improved substrate consumption rate whereas in the ASBR this increase destabilized the system, likely due to granule rupture caused by the higher agitation. The AnSBBR showed highest solids and substrate removal, highest kinetic constant and highest alkalinity production when using a helix impeller, 80 rpm, and no draft tube. The best condition for the ASBR was achieved with a flat-blade turbine impeller at 20 rpm. The presence of the draft tube in the AnSBBR did not show significant improvement in reactor efficiency. Furthermore, power consumption studies in these pilot scale reactors showed that power transfer required to improve mass transfer might be technically and economically feasible.


Subject(s)
Bioreactors , Sanitation/methods , Waste Disposal, Fluid/instrumentation , Waste Disposal, Fluid/methods , Anaerobiosis , Bioreactors/microbiology , Brazil , Polyurethanes , Sewage
14.
Appl Biochem Biotechnol ; 162(3): 885-99, 2010 Oct.
Article in English | MEDLINE | ID: mdl-19812910

ABSTRACT

Many lab-scale studies have been carried out regarding the effect of feed strategy on the performance of anaerobic sequencing batch reactors (ASBR); however, more detailed pilot-scale studies should be performed to assess the real applicability of this type of operation. Therefore, the objective of this work was to assess the effect of feed strategy or fill time in a 1-m(3) mechanically stirred pilot-scale sequencing batch reactor, treating 0.65 m(3) sanitary wastewater in 8-h cycles at ambient temperature. Two reactor configurations were used: one containing granular biomass (denominated ASBR) and the other immobilized biomass on polyurethane foam as inert support (denominated anaerobic sequencing batch biofilm reactor (AnSBBR)). The reactors were operated under five distinct feed strategies, namely: typical batch and fed-batch for 25%, 50%, 75%, and 100% of the cycle length. Stirring frequency in the ASBR was 40 rpm with two flat-blade turbine impellers and 80 rpm in the AnSBBR with two helix impellers. The results showed that both the ASBR and AnSBBR when operated under typical batch, fed-batch for 50% and 75% of the cycle length, presented improved organic matter removal efficiencies, without significant differences in performance, thus showing important operational flexibility. In addition, the reactors presented operation stability under all conditions.


Subject(s)
Bioreactors/microbiology , Waste Disposal, Fluid/methods , Anaerobiosis , Biofilms/growth & development , Biomass
15.
J Environ Manage ; 90(10): 3070-81, 2009 Jul.
Article in English | MEDLINE | ID: mdl-19497659

ABSTRACT

The objective of this work was to study the technological feasibility of treating wastewater from a personal care industry (PCI-WW) in a mechanically stirred anaerobic sequencing batch biofilm reactor (AnSBBR) containing immobilized biomass on polyurethane foam. An assessment was made on how system efficiency and stability would be affected by: increasing organic load; supplementation of nutrients and alkalinity; and different feed strategies. The AnSBBR operated with 8-h cycles, stirring speed of 400 rpm, temperature of 30 degrees C, and treated with 2.0 L wastewater per cycle. First the efficiency and stability of the AnSBBR were studied when submitted to an organic loading rate (OLR) of 3.1-9.4 gCOD/(L d), and when the PCI-WW was supplemented with nutrients (sucrose, urea, trace metals) and alkalinity. The AnSBBR was shown to be robust and presented stability and removal efficiency exceeding 90%. At an OLR of 12.0 gCOD/(L d) efficiency became difficult to maintain due to the presence of commercial cleansers and disinfectants in the wastewater lots. In a subsequent stage the AnSBBR treated the wastewater supplemented with alkalinity, but with no nutrients at varying feed strategies and maintaining an OLR of approximately 9.0 gCOD/(L d). The first strategy consists of feeding 2.0 L of the influent batchwise [OLR of 9.4 gCOD/(L d)]. In the second 1.0 L of influent was fed-batchwise and an additional 1.0 L was fed fed-batchwise [OLR of 9.2 gCOD/(L d)], i.e., in relation to the first strategy the feed volume was maintained but supplied in different periods. In the third strategy 1.0 L of treated effluent was maintained in the reactor and 1.0 L of influent was fed fed-batchwise [OLR of 9.0 gCOD/(L d)], i.e., in relation to the first strategy the feed volume was different but the feed period was the same and the OLR was maintained by increasing the influent concentration. Comparison of the first and second strategies revealed that organic matter removal efficiency was unaffected (exceeding 90%). The third strategy resulted in a reduction in average removal efficiency from 91 to 83% when compared to the first one. A kinetic study resulted in first order kinetic parameters ranges from 0.42 to 1.46 h(-1) at OLRs from 3.1 to 12.0 gCOD/(L d), respectively, and the second feed strategy [OLR of 9.2 gCOD/(L d)] was shown to be the most favorable.


Subject(s)
Bioreactors , Industrial Waste , Waste Disposal, Fluid/methods , Anaerobiosis , Biodegradation, Environmental , Biofilms
16.
Bioresour Technol ; 99(8): 3256-66, 2008 May.
Article in English | MEDLINE | ID: mdl-17669646

ABSTRACT

Safe application of the anaerobic sequencing biofilm batch reactor (ASBBR) still depends on deeper insight into its behavior when faced with common operational problems in wastewater treatments such as tolerance to abrupt variations in influent concentration, so called shock loads. To this end the current work shows the effect of organic shock loads on the performance of an ASBBR, with a useful volume of 5L, containing 0.5-cm polyurethane cubes and operating at 30 degrees C with mechanical stirring of 500 rpm. In the assays 2L of two types of synthetic wastewater were treated in 8-h cycles. Synthetic wastewater I was based on sucrose-amide-cellulose with concentration of 500 mg COD/L and synthetic wastewater II was based on volatile acids with concentration ranging from 500 to 2000 mg COD/L. Organic shock loads of 2-4 times the operation concentration were applied during one and two cycles. System efficiency was monitored before and after application of the perturbation. When operating with concentrations from 500 to 1000 mg COD/L and shock loads of 2-4 times the influent concentration during one or two cycles the system was able to regain stability after one cycle and the values of organic matter, total and intermediate volatile acids, bicarbonate alkalinity and pH were similar to those prior to the perturbations. At a concentration of 2000 mg COD/L the reactor appeared to be robust, regaining removal efficiencies similar to those prior to perturbation at shock loads twice the operation concentration lasting one cycle and stability was recovered after two cycles. However, for shock loads twice the operation concentration during two cycles and shock loads four times the operation concentration during one or two cycles filtered sample removal efficiency decreased to levels different from those prior to perturbation, on an average of 90-80%, approximately, yet the system managed to attain stability within two cycles after shock application. Therefore, this investigation envisions the potential of full scale application of this type of bioreactor which showed robustness to organic shock loads, despite discontinuous operation and the short times available for treating total wastewater volume.


Subject(s)
Bioreactors , Organic Chemicals , Waste Disposal, Fluid/methods , Water Purification/methods , Biofilms , Biomass , Calcium Carbonate , Hydrogen-Ion Concentration , Industrial Waste
17.
Bioresour Technol ; 99(3): 644-54, 2008 Feb.
Article in English | MEDLINE | ID: mdl-17336516

ABSTRACT

An investigation was performed on the biological removal of ammonium nitrogen from synthetic wastewater by the simultaneous nitrification/denitrification (SND) process, using a sequencing batch biofilm reactor (SBBR). System behavior was analyzed as to the effects of sludge type used as inoculum (autotrophic/heterotrophic), wastewater feed strategy (batch/fed-batch) and aeration strategy (continuous/intermittent). The presence of an autotrophic aerobic sludge showed to be essential for nitrification startup, despite publications stating the existence of heterotrophic organisms capable of nitrifying organic and inorganic nitrogen compounds at low dissolved oxygen concentrations. As to feed strategy, batch operation (synthetic wastewater containing 100 mg COD/L and 50 mg N-NH(4)(+)/L) followed by fed-batch (synthetic wastewater with 100 mg COD/L) during a whole cycle seemed to be the most adequate, mainly during the denitrification phase. Regarding aeration strategy, an intermittent mode, with dissolved oxygen concentration of 2.0mg/L in the aeration phase, showed the best results. Under these optimal conditions, 97% of influent ammonium nitrogen (80% of total nitrogen) was removed at a rate of 86.5 mg N-NH(4)(+)/Ld. In the treated effluent only 0.2 mg N-NO(2)(-)/L,4.6 mg N-NO(3)(-)/L and 1.0 mg N-NH(4)(+)/L remained, demonstrating the potential viability of this process in post-treatment of wastewaters containing ammonium nitrogen.


Subject(s)
Biofilms , Bioreactors , Nitrogen/isolation & purification , Water Purification/methods , Aerobiosis , Ammonium Sulfate/metabolism , Bicarbonates/analysis , Feasibility Studies , Filtration , Nitrates/analysis , Nitrites/analysis , Nitrogen/analysis , Organic Chemicals/analysis , Sewage , Volatilization
18.
Appl Biochem Biotechnol ; 136(2): 193-206, 2007 Feb.
Article in English | MEDLINE | ID: mdl-17496340

ABSTRACT

The effect of temperature on the performance of an anaerobic sequencing biofilm batch reactor (ASBBR) with liquid-phase recirculation was assessed. Assays were performed using a recirculation velocity of 0.20 cm/s, 8-h cycles, and an average treated synthetic wastewater volume of 2 L/cycle with a concentration of 500 mg of Chemical Oxygen Demand (COD)/L. Operation temperatures were 15, 20, 25, 30, and 35 degrees C. At 25, 30, and 35 degrees C, organic matter removal efficiencies for filtered samples ranged from 81 to 83%. At lower temperatures, namely 15 and 20 degrees C, removal efficiency decreased significantly to 61 and 65%, respectively. A first-order model could be fitted to the experimental concentration profile values. The first-order kinetic parameter value of this model varied from 0.46 to 0.81 h-1 considering the lowest and highest temperature studied. Moreover, analysis of the removal profile values allowed fitting of an Arrhenius-type equation with an activation energy of 5715 cal/mol.


Subject(s)
Bacteria, Anaerobic/metabolism , Biofilms/growth & development , Bioreactors , Waste Disposal, Fluid/methods , Temperature , Water Movements , Water Purification
19.
Appl Biochem Biotechnol ; 133(2): 171-88, 2006 May.
Article in English | MEDLINE | ID: mdl-16702609

ABSTRACT

The performance of an anaerobic sequencing batch reactor (ASBR) was assessed when submitted to increasing organic load with different influent concentrations and cycle lengths. The 5-L mechanically stirred (75 rpm) ASBR contained 2 L of granular biomass and treated 2 L of synthetic wastewater per cycle. Volumetric organic loads (VOLs) from 0.66 to 2.88 g of chemical oxygen demand (COD)/(L x d) were applied by using influent concentrations from 550 to 3,600 mg of COD/L in 8- and 12-h cycles. Reactor stability was maintained for VOLs from 0.66 to 2.36 g of COD/(L x d), with organic matter removal efficiencies for filtered samples (epsilonF) between 84 and 88%. For VOLs from 0.78 to 2.36 g of COD/(L x d) at an influent concentration of 2,000 mg of COD/L, when cycle length was reduced from 12 to 8 h, epsilonF did not vary, yet showed a very distinct behavior from the other conditions. In addition, two operation strategies were studied for VOLs with approximately similar values of 2.36 and 2.08 g of COD/(L x d). One involved operation with an influent concentration of 2,000 mg of COD/L and an 8-h cycle, whereas the other involved an influent concentration of 2,600 mg of COD/L and a 12-h cycle. Only the former resulted in system stability and efficiency. These results indicate that besides organic load, influent concentration and cycle length play a significant role in ASBR systems.


Subject(s)
Bioreactors , Sewage/microbiology , Anaerobiosis , Biomass , Sewage/chemistry
20.
Water Res ; 39(11): 2376-84, 2005 Jun.
Article in English | MEDLINE | ID: mdl-15922400

ABSTRACT

The main objectives of this study were to evaluate the performance of an anaerobic sequencing batch reactor when subjected to a progressive increase of influent glucose concentration and to estimate the kinetic parameters of glucose degradation. The reactor was initially operated in 8-h cycles, treating glucose in concentrations of 500, 1000 and 2000 mg l(-1). No glucose was detected in the effluent under these three conditions. The reactor showed operating stability when treating a glucose concentration of approximately 500 mg l(-1), with filtered chemical oxygen demand (COD) removal efficiencies varying from 93% to 97%. Operational instability occurred in the operation with glucose concentrations of approximately 1000 and 2000 mg l(-1), caused mainly by a production of extracellular polymeric substances (EPS), which led to hydrodynamic and mass transfer problems in the reactor. The mean volatile acid concentration values in the effluent were approximately 159+/-72 and 374+/-92 mg l(-1), respectively. A first-order model was adjusted to glucose concentration profiles and a modified model, including a residual concentration of substrate, was adjusted to COD temporal profiles. To check the formation of EPS, the reactor was operated in 3-h cycles with concentrations of 500 and 1000 mg l(-1). The purpose of this step was to discover if the production of EPS resulted from the biomass's exposure to a low concentration of substrate over a long period of time. Thus, it was hypothesized that a reduction of the time cycle would also reduce the exposure to low concentrations. However, this hypothesis could not be confirmed because large amounts of EPS were formed already under the first operational condition, using approximately 500 mg l(-1) of glucose in the influent, thus indicating the fallacy of the hypothesis. The production of EPS proved to depend on the organic volumetric load applied to the reactor.


Subject(s)
Anaerobiosis , Biofilms , Bioreactors , Sewage , Bacteria, Anaerobic/metabolism , Glucose/metabolism , Time Factors , Water Purification
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