Full-scale Reactor Research Articles

Characteristics of retained biomass developed in a full-scale DHS reactor in Agra, India

Characteristics of retained biomass developed in a full-scale DHS reactor in Agra, India

Exploring anammox bacteria ecology to improve nitrogen removal in wastewater treatment

Exploring anammox bacteria ecology to improve nitrogen removal in wastewater treatment

Comparative analysis of common full scale reactors for dry anaerobic digestion process

Organic solid wastes are produced with large amount wherever there are human activities. However, improper treated organic wastes made them as sources of diseases. On the other hand, these fractions contain nutrients and energy, so they have also valuable resources. As a result, exploring their potential as an energy source can be accomplish via anaerobic digestion process, in which, organics converted into hydrogen, methane and/or ethanol. Therefore, this manuscript introduces an overview of the common applied types of reactor that can handle these types of wastes in their solid state and recover them in term of biogas, as well as, stabilize the produced digestate to bio-fertilizers by compositing approach. A comparison also listed to demonstrate the optimum operational conditions and expected amount of biogas from each type.

Effective Anaerobic Bio-Treatment of Fresh Leachate From Municipal Solid Waste Incineration Plant by Full-Scale Internal Circulation Reactor

This study aimed to investigate the effectiveness of the full-scale internal circulation (IC) reactor in biodegrading of municipal solid waste (MSW) fresh leachate under mesophilic conditions, where the anaerobic process stability, biogas yield, and sludge granulation were intensively investigated. The effects of operational parameters on the influent organic loading rate (OLR), chemical oxygen demand (COD) removal efficiency, alkalinity (ALK), pH, volatile fatty acids (VFAs) accumulation, and effluent recirculation were also studied. The results showed that the reactor operated stably and effectively. The COD removal efficiency and biogas yield could be maintained at (92.8 ± 2.0)% and (0.47 ± 0.05) m3/kg CODremoval, respectively, with the influent OLR (24.5 ± 0.9) kg COD/(m3 d) and hydraulic retention time (HRT) 2.7d during the stable operation phase. Meanwhile, this study demonstrated that 1.5–3.0 m/h would be the optimal Vup for the reactor, corresponding to the effluent recirculation of 32.5–78.0 m3/h. Moreover, it was found that the content of extracellular polymeric substances (EPS) in the anaerobic sludge increased from 50.3 to 140.7 mg/g volatile suspended solids (VSS), and the sludge had good granular performance during the reactor operation.

Full-Scale Processing by Anaerobic Baffle Reactor, Sequencing Batch Reactor, and Sand Filter for Treating High-Salinity Wastewater from Offshore Oil Rigs

High-salinity wastewater discharged from offshore oil rigs (WORS) is harmful to marine environments. Therefore, WORS should be properly treated before discharge. In this study, a full-scale anaerobic baffle reactor (ABR) + sequencing batch reactor (SBR) + sand filter (SF) process was used for the first time to treat WORS at an inshore treatment terminal. After seeding with residual sludge from a municipal wastewater treatment facility, the start-up of the ABR and SBR was accomplished in one month. During a steady running period, the ABR + SBR process showed stable performance in treating WORS. The results of microbial diversity indicated that Rhizobiales, Thermotogales, and Actinomycetales were the most abundant genera in the ABR sample, while Acidobacteria DRC31, Lactobacillales, and Bacillales prevailed in the SBR sample. The results showed that ABR + SBR is a reliable process for WORS treatment, with the treated WORS meeting the National Sewage Comprehensive Emission Standards (GB8978-1996).

High efficiency solar chemical-looping methane reforming with ceria in a fixed-bed reactor

High efficiency solar chemical-looping methane reforming is demonstrated in a prototype reactor operated in a high-flux solar simulator. The reactor includes six tube assemblies, which each comprise a fixed-bed of ceria particles and a gas-phase heat recuperator. The cycle was accomplished by alternating the flow to one tube assembly between CH4 and CO2. In the initial series of experiments, temperature, CH4 concentration, reduction flow rate, and cycle duration were varied to minimize carbon accumulation and maximize efficiency. In the second set of tests, the reactor was operated at optimized conditions for ten cycles at 1228 and 1274 K. Higher temperature favors better performance. At 1274 K, CH4 conversion is 0.36, H2 selectivity is 0.90, CO selectivity is 0.82, CO2 conversion is 0.69, and the energetic upgrade factor is 1.10. Heat recovery effectiveness is over 95%. Solar-to-fuel efficiency is 7% and the thermal efficiency is 25%. Projected solar-to-fuel and thermal efficiencies are 31 and 67% for the full-scale reactor and 56 and 85% for a commercial reactor with lower thermal losses. The demonstrated efficiencies are the highest reported to-date for this process. The projected scaled-up efficiencies suggest solar chemical-looping methane reforming could be a competitive approach for production of solar fuels.

Genomic insights into the metabolism of 'Candidatus Defluviicoccus seviourii', a member of Defluviicoccus cluster III abundant in industrial activated sludge.

Filamentous cluster III Defluviicoccus (DF3) are known to proliferate and cause bulking issues in industrial wastewater treatment plants. Members of the genus Defluviicoccus are also known to exhibit the glycogen accumulating organism (GAO) phenotype, which is suggested to be detrimental to enhanced biological phosphorus removal (EBPR). Despite the reported negative impact members of the DF3 have on activated sludge wastewater treatment systems, limited research has focused on understanding the physiological traits that allow them to compete in these environments. In this study, a near complete genome of an abundant filamentous DF3 named 'Candidatus Defluviicoccus seviourii' was obtained from a full-scale sequencing batch reactor (SBR) treating winery wastewater. Annotation of the 'Ca. D. seviourii' genome revealed interesting metabolic features that help to understand the abundance of this microorganism in industrial wastewater treatment plants. Their potential for the storage of polyhydroxyalkanoates (PHA) is suggested to favour these organisms with the intermittent availability of carbon in these systems. An ability to fix nitrogen and take up urea may provide them with an additional advantage with the characteristically high carbon to nitrogen content of industrial waste. The genome and preliminary findings of this study provide a foundation for further research into these biotechnologically relevant organisms.

The sustainable recovery of the organic fraction of municipal solid waste by integrated ozonation and anaerobic digestion

The organic fraction of municipal solid waste is commonly handled via biological processes, which enable the production of materials with potential fertilizer properties. When the biological process occurs under anaerobic conditions, the recovery of energy from biogas is also obtained. However, the sustainable recovery of organic solid waste implies the effective utilization of the biological treatment products, namely compost and digestate, which is often limited by the presence of organic contaminants. They enter the biological processes along with the organic waste and, due to their recalcitrance to the biodegradation, end up in either compost or digestate, posing the issue of their safe use on soil. The present study proposes ozonation as a possible strategy to reduce the presence of organic contaminants in the digestate originating from the organic fraction of municipal solid waste. In this view, digestate samples were collected from full-scale reactors operated at hydraulic retention time of 11 and 41 days and ozonated at 0.11 and 0.16 gO3/gTS. Experimental results, including the evaluation of the eco-toxicological potential of differently treated substrates, showed that the integration of ozone and anaerobic digestion can be pursued for the sustainable recovery of organic solid waste, but the identification of the combined process lay-out requires the evaluation of the digestate biological stabilization level.

Characterization of downflow hanging sponge reactors with regard to structure, process function, and microbial community compositions.

The activated sludge (AS) process has been the most widely used process for wastewater treatment despite it has several limitations for its further application and adoption worldwide, owing to unsustainable properties such as high-energy consumption and the production of large amount of excess sludge. To overcome the drawbacks of the AS process, the downflow hanging sponge (DHS) has been developed as an energy-saving and easy-to-maintain alternative. To date, six types of different sponge configurations have been developed and their performances have been evaluated in practical- to full-scale DHS reactors. A large number of studies have been carried out in order to enhance the performance and expand the application fields of the DHS. Transition of this process to the deployment and diffusion stage from the research and development phase is now ongoing in India and Egypt as well as in Japan. Under this situation, concise and state-of-the art review is important for enhancing DHS research and future applications. Herein, we summarize and present the DHS concerning the history of development, the mechanism of treatment, recent studies on its use in the field of wastewater treatment, and the features of microbial community structure.

Modeling and process optimization of a full-scale emulsion polymerization reactor

One of the most common but promising processes for the production of paints and coatings is the free radical emulsion polymerization reaction involving different types of monomers. As it is also demonstrated by statistics concerning accidents in chemical industries, polymerizations are one of the most frequent causes of thermal runaway; therefore such syntheses require a very high level of control of all the operating variables, especially at full plant scale where safety problems are of paramount importance.The main aims of this work were the modeling and the industrial scale optimization of a complex polymerization process. Since four different monomers are involved in different proportions in such a process, the pseudo-homopolymer approach together with available literature correlations for the estimation of the main constitutive parameters of the system were used to solve the mathematical model and simulate the dynamics of the synthesis at the full plant scale.The proposed model and all the constitutive parameters estimates were validated through the comparison with both laboratory and full-scale experimental data, demonstrating a good agreement. Finally, the results of the optimization procedure were validated at laboratory scale.

Overcoming floc formation limitations in high-rate activated sludge systems

High-rate activated sludge (HRAS) is an essential cornerstone of the pursuit towards energy positive sewage treatment through maximizing capture of organics. The capture efficiency heavily relies on the degree of solid separation achieved in the clarifiers. Limitations in the floc formation process commonly emerge in HRAS systems, with detrimental consequences for the capture of organics. This study pinpointed and overcame floc formation limitations present in full-scale HRAS reactors. Orthokinetic flocculation tests were performed with varying shear, sludge concentration, and coagulant or flocculant addition. These were analyzed with traditional and novel settling parameters and extracellular polymeric substances (EPS) measurements. HRAS was limited by insufficient collision efficiency and occurred because the solids retention time (SRT) was short and colloid loading was high. The limitation was predominantly caused by impaired flocculation rather than coagulation. In addition, the collision efficiency limitation was driven by EPS composition (low protein over polysaccharide ratio) instead of total EPS amount. Collision efficiency limitation was successfully overcome by bio-augmenting sludge from a biological nutrient removal reactor operating at long SRT which did not show any floc formation limitations. However, this action brought up a floc strength limitation. The latter was not correlated with EPS composition, but rather EPS amount and hindered settling parameters, which determined floc morphology. With this, an analysis toolkit was proposed that will enable design engineers and operators to tackle activated solid separation challenges found in HRAS systems and maximize the recovery potential of the process.

16s rRNA gene sequencing and radioisotopic analysis reveal the composition of ammonia acclimatized methanogenic consortia

Different mesophilic and thermophilic methanogenic consortia were acclimatised and enriched to extreme total ammonia (9.0 and 5.0 g NH4+-N L−1, respectively) and free ammonia (1.0 and 1.4 g NH3-N L−1, respectively) levels in this study. [2-14C] acetate radioisotopic analyses showed the dominance of aceticlastic methanogenesis in all enriched consortia. According to 16S rRNA gene sequencing result, in mesophilic consortia, methylotrophic Methanomassiliicoccus luminyensis was predominant, followed by aceticlastic Methanosarcina soligelidi. A possible scenario explaining the dominance of M. luminyensis includes the use of methylamine produced by Tissierella spp. and biomass build-up by metabolizing acetate. Nevertheless, further studies are needed to pinpoint the exact metabolic pathway of M. luminyensis. In thermophilic consortia, aceticlastic Methanosarcina thermophila was the sole dominant methanogen. Overall, results derived from this study demonstrated the efficient biomethanation ability of these ammonia-tolerant methanogenic consortia, indicating a potential application of these consortia to solve ammonia toxicity problems in future full-scale reactors.

Modified Anaerobic Digestion Model No. 1 for modeling methane production from food waste in batch and semi-continuous anaerobic digestions

A modified Anaerobic Digestion Model No. 1 (ADM1) with optimized kinetic parameters was presented to model methane production in the anaerobic digestion of food waste. Experimental data from batch and semi-continuous fermentations were used to calibrate and verify the model. Modified ADM1 simulation was carried out using AQUASIM 2.0 software. Sensitivity analysis was used to identify and evaluate the most sensitive kinetic parameters during biogas production. The decay constant of microorganisms, the disintegration constant, the hydrolysis constant of carbohydrates, the Monod maximum specific substrate uptake rate, and the half-saturation constants affected biogas production significantly. The optimized values of these parameters were 0.001, 0.16, 3, 1 and 0.23, respectively. Optimization results were validated using batch and semi-continuous experiments. The modified ADM1 well-predicted methane production, with R2 values for the validation experiments all above 90%. These results can be used as basic data to simulate methane production in full-scale reactors.

Modelling aerobic granular sludge reactors through apparent half-saturation coefficients

During biological wastewater treatment, substrates undergo simultaneous diffusion and reactions inside microbial aggregates, creating microscale spatial substrate gradients and limiting the macroscale reaction rates. For flocculent and anaerobic granular sludge, this rate-limiting effect of diffusion is often lumped in model parameters, like the half-saturation coefficients of Monod kinetics in activated sludge models (ASM). Yet, an explicit description of the reaction-diffusion process with biofilm models is more common for aerobic granular sludge. This work investigates whether apparent half-saturation coefficients could have applications for aerobic granular sludge as well and examines the implications of this simplification. To this end, the macroscopic reaction rates predicted with a one-dimensional biofilm (1D) model were fitted with Monod kinetics. The results showed that the macroscale rates could indeed be described using apparent kinetics, at the very least over a time scale where the microbial population distribution stays fixed. However, the coefficients were sensitive to changes in the microbial population distribution, which can be affected by long-term changes in operating conditions. Also the activity of organisms that compete for the same substrates affect the parameter value. Be that as it may, apparent kinetics also depend on the operating conditions for flocculent and anaerobic granular sludge, but they have still been used successfully for design and optimization. Therefore, the last section of this work illustrates that they may also have applications for aerobic granular sludge. A simple model for ammonium removal using apparent half-saturation coefficients for oxygen and ammonium is applied to a full-scale reactor, taking advantage of the batch-wise operation and on-line monitoring data for regular recalibration.

Study of neutron-physical characteristics of VVER-1200 considering feedbacks using MCU Monte Carlo code

Abstract The purpose of the work is to calculate VVER-1200 neutron-physical characteristics that are important for safety using MCU Monte Carlo code for an independent verification of the accuracy of design calculations of the first fuel cycle. The calculations were carried out before the startup of the first VVER-1200 power unit. A full-scale computer model of VVER-1200 was developed using the design documentation of the fuel assemblies and the reactor facility. Special attention was given to the accurate specification of the geometry and material description of the core and its immediate environment. The full-scale VVER-1200 model allows performing Monte Carlo calculation of some safety-relevant characteristics for which it is impossible or extremely difficult to carry out full-scale reactor experiments. In total, more than 110 different states were calculated; five states were calculated taking feedbacks into account. For all calculations, the neutron-physical characteristics obtained by means of the MCU code were used to verify the BIPR-7A and the PERMAK-A codes.

Substrate and operational conditions as regulators of fluid properties in full-scale continuous stirred-tank biogas reactors - implications for rheology-driven power requirements.

Understanding fluid rheology is important for optimal design and operation of continuous stirred-tank biogas reactors (CSTBRs) and is the basis for power requirement estimates. Conflicting results have been reported regarding the applicability of total solid (TS) and/or total volatile solid (TVS) contents of CSTBR fluids as proxies for rheological properties. Thus, the present study investigates relationships between rheological properties of 12 full-scale CSTBR fluids, their substrate profiles, and major operational conditions, including pH, TS and TVS contents, organic loading rate, hydraulic retention time, and temperature. Rheology-driven power requirements based on various fluid characteristics were evaluated for a general biogas reactor setup. The results revealed a significant correlation only between the rheological fluid properties and TS or TVS contents for sewage sludge digesters and thermophilic co-digesters (CD), but not for mesophilic CD. Furthermore, the calculated power requirements for pumping and mixing, based on the various fluid characteristics of the studied CSTBRs, varied broadly irrespective of TS and TVS contents. Thus, this study shows that the TS and/or TVS contents of digester fluid are not reliable estimators of the rheological properties in CSTBRs digesting substrates other than sewage sludge.

Numerical modelling and investigations on a full-scale zeolite 13X open heat storage for buildings

Abstract Thermal energy storage is a key technology for heat management and efficient use of renewable energy production. High-power and high-density heat storage in buildings can be achieved with physisorption. The present work presents a study of a full-scale zeolite 13X open reactor to be integrated in the ventilation system of a dwelling. An original numerical model of the system is developed and validated using various data obtained from eight sets of experiments. The analysis of the energy chain shows that approximately 70 % of absorbed energy is converted into useful heat released on discharge. However, approximately half of the total heat is also directly lost at the outlet of the adsorbent bed. The overall system efficiency is 36 % .

Pre-oxidation of ammonium using nanofiltration membranes for partial nitrification preceding Anammox

This study examined the pre-oxidation of ammonium using a nanofiltration (NF) hollow fiber membrane module to provide an alternative to conventional partial nitrification preceding Anammox. A permeability study showed that NF membranes were suitable for use in the pre-oxidation of ammonium due to high ammonium fluxes across the membrane (low rejection of ammonium), while most COD (in the form of glucose) was retained inside the bulk phase (high rejection of glucose-COD). In pre-oxidation, ammonium oxidizing bacteria (AOB) grown in the shell-side of the membrane module could oxidize the ammonium diffusing from the tube side mainly to nitrite, which then diffused back into the tube side, resulting in a mixture of ammonium and nitrite in the exit stream in an approximately equimolar ratio. This would meet the requirement for the Anammox process as suggested by previous reports. The application of a membrane process for the pre-oxidation of ammonium was found to be promising at a laboratory-scale, and practically viable at a scale similar to a full-scale reactor (Whitlingham STC, Norwich, UK) based on an estimate of the number of HF modules needed. However, a proper optimization study of the process is strongly recommended so that its feasibility could be further examined at a larger scale linking both nitritification and Anammox together.

Model-based design of a software sensor for real-time diagnosis of the stability conditions in high-rate anaerobic reactors – Full-scale application to Internal Circulation technology

Internal Circulation (IC) anaerobic systems are especially suitable when plant designs that involve both small footprints and high organic loading rates (>25 kg COD m−3 d−1) are required. However, given that operating anaerobic processes at high organic loads increases their vulnerability to external disturbances, real-time indicators of the stability conditions become particularly pertinent for IC reactors. This paper addresses the design and full-scale validation of a software sensor that uses only feeding flow-rate and biogas flow-rate measurements to classify the operating conditions of the reactor as “strongly”, “moderately” or “weakly” stable. A simulation-based procedure was used to design the software sensor and configure its parameters. Then, the performance of the software sensor was tested under real conditions in a full-scale IC reactor of 1679 m3 installed in a recycled paper mill (RPM).

A pressurized Gas Switching Combustion reactor: Autothermal operation with a CaMnO3−δ-based oxygen carrier

Gas Switching Combustion (GSC) promises greatly simplified scale-up of highly efficient gas-fuelled chemical looping combustion (CLC) technology. The GSC uses a single reactor alternating fuel and air feeds into a bed of oxygen carrier. Such a simple standalone reactor will be much easier to scale up and pressurize than the conventional interconnected CLC configuration. This paper presents results from autothermal GSC operation completed in a pressurized lab-scale reactor using a CaMnO3−δ-based oxygen carrier which are especially suited to GSC because they greatly reduce the temperature variation across the transient GSC cycle. The reactor showed perfect performance when H2 was used as fuel, but significant fuel slip occurs with CO after the oxygen carrier was only half way reduced. Higher temperatures improved fuel conversion, while higher pressures had a negative effect. It can be expected, however, that more oxygen carrier utilization would be possible in a full-scale reactor where the gas residence time would be much higher. In addition, 2–7% CO2 release was observed in the oxidation stage (from the total molar carbon fed in the fuel stage), increasing with the degree of oxygen carrier reduction. CH4 as fuel performs well only if the reduction stage is started on a fully oxidized CaMnO3−δ-based oxygen carrier. In summary, if the CO2 release in the oxidation stage can be efficiently dealt with, CaMnO3−δ-based materials appear to be very promising for use in future GSC-IGCC power plants.