Full-scale Reactor Research Articles

Long-term performance evaluation of down-flow hanging sponge reactor regarding nitrification in a full-scale experiment in India

The first full-scale down-flow hanging sponge (DHS) reactor applied to post-treatment of effluent from an upflow anaerobic sludge blanket (UASB) reactor for the treatment of municipal sewage was evaluated, with emphasis on nitrification. The full-scale DHS reactor was successfully operated at a hydraulic retention time of 1.5h for over 1800days in India. The DHS reactor produced effluent with 6mgL−1 ammonium nitrogen, corresponding to 79% removal efficiency. The total nitrogen removal by the DHS reactor was 65%. The high process performance of the DHS reactor was supported by its distinctive characteristics of (1) high dissolved oxygen of 5.4mgL−1 in the DHS effluent without forced ventilation, (2) dense retained sludge in the range of 23–46gVSSLsponge−1, and (3) adequate sludge activity of 52mgNgVSS−1 day−1 for nitrification. The full-scale experiment has proven that the DHS reactor has practical applicability to developing countries.

Culture-Dependent and -Independent Identification of Polyphosphate-Accumulating Dechloromonas spp. Predominating in a Full-Scale Oxidation Ditch Wastewater Treatment Plant.

The oxidation ditch process is one of the most economical approaches currently used to simultaneously remove organic carbon, nitrogen, and also phosphorus (P) from wastewater. However, limited information is available on biological P removal in this process. In the present study, microorganisms contributing to P removal in a full-scale oxidation ditch reactor were investigated using culture-dependent and -independent approaches. A microbial community analysis based on 16S rRNA gene sequencing revealed that a phylotype closely related to Dechloromonas spp. in the family Rhodocyclaceae dominated in the oxidation ditch reactor. This dominant Dechloromonas sp. was successfully isolated and subjected to fluorescent staining for polyphosphate, followed by microscopic observations and a spectrofluorometric analysis, which clearly demonstrated that the Dechloromonas isolate exhibited a strong ability to accumulate polyphosphate within its cells. These results indicate the potential key role of Dechloromonas spp. in efficient P removal in the oxidation ditch wastewater treatment process.

Microbial Diversity of Ammonia Oxidizing Bacteria through Waste Water Genomics

Autotrophic ammonia-oxidizing bacteria are a critical factor of the microbial community in industrial wastewater treatment systems. We evaluated the diversity and community composition of β-proteobacterial ammonia-oxidizing bacteria in two full-scale treatment reactors - a sand filter and a biological aerated filter - receive an identical wastewater. Polymerase chain reaction of the 16S rRNA gene fragments of ammonia-oxidizing bacteria-selective primers was merged with denaturing gradient gel electrophoresis to allow the comparative analysis of the dominant ammonia-oxidizing bacteria populations. The phylogenetic affinities of the dominant ammonia-oxidizing bacteria were verified by cloning and sequencing of polymerase chain reaction-amplified 16S rRNA gene fragments. Denaturing gradient gel electrophoresis profiles were evaluated using a probability-based similarity index. An exploitation of a probabilistic index of similarity permitted us to consider the differences and similarities observed in ammonia-oxidizing bacteria community structure in different samples were statistically significant or could be accounted for random matching of bands in denaturing gradient gel electrophoresis profiles that would propose random colonization of the reactors at different ammonia-oxidizing bacteria. All Possibly-like sequences recognized, grouped within the Nitrosomonas genus. A greater diversity of ammonia-oxidizing bacteria were detected in trickling filters than the BAF on all samples analyzed were initiate to be dominated by ammonia oxidizing bacteria most closely linked to Nitrosococcus mobilis. Numerical investigation of the denaturing gradient gel electrophoresis profiles indicated that the ammonia-oxidizing bacteria community in depth profiles from the filter beds was selected in a non-random manner.

Comparative Analysis of Methanogenic Communities in Different Laboratory-Scale Anaerobic Digesters.

Comparative analysis of methanogenic archaea compositions and dynamics in 11 laboratory-scale continuous stirred tank reactors fed with different agricultural materials (chicken manure, cattle manure, maize straw, maize silage, distillers grains, and Jatropha press cake) was carried out by analysis of the methyl coenzyme-M reductase α-subunit (mcrA) gene. Various taxa within Methanomicrobiales, Methanobacteriaceae, Methanosarcinaceae, Methanosaetaceae, and Methanomassiliicoccales were detected in the biogas reactors but in different proportions depending on the substrate type utilized as well as various process parameters. Improved coverage and higher taxonomic resolution of methanogens were obtained compared to a previous 16S rRNA gene based study of the same reactors. Some members of the genus Methanoculleus positively correlated with the relative methane content, whereas opposite correlations were found for Methanobacterium. Specific biogas production was found to be significantly correlating with Methanosarcinaceae. Statistical analysis also disclosed that some members of the genus Methanoculleus positively correlated with the ammonia level, whereas the prevalence of Methanocorpusculum, Methanobacterium, and Methanosaeta was negatively correlated with this parameter. These results suggest that the application of methanogenic archaea adapted to specific feedstock might enhance the anaerobic digestion of such waste materials in full-scale biogas reactors.

Proteolytic bacterial dominance in a full-scale municipal solid waste anaerobic reactor assessed by 454 pyrosequencing technology.

Biomethanization entails a good means to reduce the organic fraction (OF) derived from municipal solid wastes (MSW). The bacterial diversity of a full scale MSW anaerobic reactor located in Madrid (Spain) was investigated using high-throughput 454 pyrosequencing. Even though the proteolytic bacteria prevailed throughout all of the process, community shifts were observed from the start-up to the steady-state conditions, with an increasing biodiversity displayed over time. The Bacteroidetes and the Firmicutes were the majority phyla: 55.1 and 40.2% (start-up) and 18.7 and 78.7 (steady-state) of the total reads. The system's lack of evenness remains noteworthy as the sequences affiliated to the proteolytic non-saccharolytic Proteiniphylum, Gallicola and Fastidiosipila genera, together with the saccharolytic Saccharofermentans, were predominant on the system and this predominance appears to correlate with the presence of a high ammonium concentration. The 454 pyrosequencing revealed a great diversity of rare organisms which seemingly do not sustain any metabolic roles in the course of the OF-MSW degradation. However, this scarce and unique microbiota can confer great resilience to the system as a buffer against nutritional and environmental changing conditions, thus opening the door to increase the current knowledge about the bacterial community dynamics taking place during MSW treatment processes.

Isolation and characterization of Flexilinea flocculi gen. nov., sp. nov., a filamentous, anaerobic bacterium belonging to the class Anaerolineae in the phylum Chloroflexi.

A novel obligately anaerobic bacterium, designated strain TC1T, was isolated from methanogenic granular sludge in a full-scale mesophilic upflow anaerobic sludge blanket reactor treating high-strength starch-based wastewater. Cells had a multicellular filamentous morphology, stained Gram-negative and were non-motile. The filaments were flexible, generally >100 μm long and 0.3-0.4 μm wide. Growth of the isolate was observed at 25-43 °C (optimum 37 °C) and pH 6.0-8.5 (optimum pH 7.0). Strain TC1T grew chemo-organotrophically on a range of carbohydrates under anaerobic conditions. Yeast extract was required for growth. The major fermentative end products of glucose, supplemented with yeast extract, were acetate, lactate, succinate, propionate, formate and hydrogen. Co-cultivation with the hydrogenotrophic methanogen Methanospirillum hungatei DSM 864T enhanced growth of the isolate. The DNA G+C content was determined experimentally to be 42.1 mol%. The major cellular fatty acids were anteiso-C15 : 0, iso-C15 : 0 and iso-C17 : 0 3-OH. Based on 16S rRNA gene sequence analysis, strain TC1T belonged to the class Anaerolineae in the phylum Chloroflexi, in which Ornatilinea apprima P3M-1T was its closest phylogenetic relative (88.3 % nucleotide identity). Phylogenomic analyses using 38 and 83 single-copy marker genes also supported the novelty of strain TC1T at least at the genus level. Based on phylogenetic, genomic and phenotypic characteristics, we propose that strain TC1T represents a novel species of a new genus, for which we suggest the name Flexilinea flocculi gen. nov., sp. nov. The type strain of Flexilinea flocculi is strain TC1T ( = JCM 30897T = CGMCC 1.5202T).

Importance of abiotic hydroxylamine conversion on nitrous oxide emissions during nitritation of reject water

The spontaneous abiotic (or chemical) reaction of hydroxylamine (NH2OH) at low concentrations (<0.4mgN/L) with free nitrous acid (HNO2) was investigated at the conditions of partial nitritation of reject water. An abiotic batch reactor test was used to quantitatively assess the kinetics of the nitrous oxide (N2O) emission. The estimated chemical N2O emission rate was 0.16mgN/L/h. In addition, the concentration of NH2OH in a full scale nitritation reactor, Single reactor High Activity ammonium Removal over Nitrite (SHARON) was measured in the range ca. 0.03–0.11mgN/L. The presence of NH2OH in the SHARON reactor together with the abiotic N2O emissions rate (assessed in the abiotic batch reactor test) points towards a significant contribution of the abiotic N2O emission in the full scale reactor. An equivalent emission factor (N emitted as N2O/N oxidized in nitritation) of 1.1% was estimated to be linked to the abiotic pathway, which is around one third of the total measured N2O emission rate in the SHARON reactor.

Electrical resistivity tomography to quantify in situ liquid content in a full-scale dry anaerobic digestion reactor

The electrical resistivity tomography (ERT) method is a non-intrusive method widely used in landfills to detect and locate liquid content. An experimental set-up was performed on a dry batch anaerobic digestion reactor to investigate liquid repartition in process and to map spatial distribution of inoculum. Two array electrodes were used: pole–dipole and gradient arrays. A technical adaptation of ERT method was necessary. Measured resistivity data were inverted and modeled by RES2DINV software to get resistivity sections. Continuous calibration along resistivity section was necessary to understand data involving sampling and physicochemical analysis. Samples were analyzed performing both biochemical methane potential and fiber quantification. Correlations were established between the protocol of reactor preparation, resistivity values, liquid content, methane potential and fiber content representing liquid repartition, high methane potential zones and degradations zones. ERT method showed a strong relevance to monitor and to optimize the dry batch anaerobic digestion process.

The anaerobic baffled reactor (ABR) treating communal wastewater under mesophilic conditions: a review.

A review concerning the anaerobic baffled reactor (ABR) treating communal wastewater under mesophilic conditions is presented. Existing studies indicate strong resilience of the reactor towards loading variations and shock-loads. The compartmentalisation of the ABR is a strongly stabilising factor with feed fluctuations being evened out across reactor chambers. Significant chemical oxygen demand (COD) reduction occurs almost exclusively in the first three chambers. The hydraulic rather than the organic loading rate is treatment limiting. Laboratory-scale studies show high treatment efficiencies of above 80% COD removal. It was found that most laboratory-scale studies do not factor in important aspects of field operation, such as diurnal fluctuations of feed characteristics, adequate start-up periods and periods of constant loading and optimised chamber outlet design, and never studied the effect of loading on sludge digestion. Performance data on full-scale ABR implementations, however, are extremely scarce, and existing studies are without exception affected by site-specific treatment-limiting factors hindering the extrapolation of generally valid conclusions. In view of a large-scale roll-out, communal ABRs are not sufficiently understood. Current challenges concerning the optimisation of reactor design require numerous well-monitored long-term full-scale reactor investigations. Existing ABR investigations yield encouraging results, supporting that the ABR may be one of the solutions answering the global call for low-maintenance, robust treatment systems.

Identifying N2O formation and emissions from a full-scale partial nitritation reactor

In this study, N2O formation and emissions from a full-scale partial nitritation (SHARON) reactor were identified through a three-weeks monitoring campaign during which the off-gas was analysed for N2O, O2, CO2 and NO. The overall N2O emission was 3.7% of the incoming ammonium load. By fitting the N2O emission to a theoretical gas stripping profile, the N2O emissions could be assigned to aerobically formed N2O and N2O formed under anoxic conditions. This was further substantiated by liquid N2O measurements. Under standard operation, 70% of the N2O emission was attributed to anoxic N2O formation. Dedicated experiments revealed that low dissolved oxygen concentrations (<1.0 g O2·m−3) and longer anoxic periods resulted in an increased N2O emission. Minimising or avoiding anoxic conditions has the highest effect in lowering the N2O emissions. As an additional result, the use of the off-gas N2O concentration measurements to monitor the gas–liquid mass transfer rate coefficient (kLa) during dynamic reactor operation was demonstrated.

Structures of microbial communities found in anaerobic batch runs that produce methane from propionic acid—Seeded from full-scale anaerobic digesters above a certain threshold

The volatile fatty acid propionate inhibits anaerobic digestion during organic waste treatments. To examine potential microbial interactions that accelerate propionate oxidation, anaerobic digestion systems seeded with various types of anaerobic sludge were analyzed. Seed samples were collected from 10 different full-scale anaerobic reactors in South Korea. Propionate oxidation was estimated as the methane production rate per gram of propionate used per day. Two domestic sewage sludge showed the highest methane production rate values, 109.1±4.2 and 74.5±8.6mL CH4/(g propionate∙d). A food waste recycling wastewater source exhibited the lowest methane production rate, 33.2±2.6mL CH4/(g propionate∙d). To investigate how the microbial community structure affected propionate oxidation, qualitative molecular analyses were carried out using denaturing gradient gel electrophoresis. Methanosaeta concilii, an aceticlastic methanogen, was detected in most batch runs. Smithella propionica, a unique propionate oxidizer and simultaneous producer of acetate, was found in domestic sewage sludge sources showing the highest methane production rate; in contrast, Desulfobulbus rhabdoformis, a sulfate reducer coupled with the consumption of acetate to be used as a precursor of methane, was observed in food waste recycling wastewater sludge source showing the lowest methane production rate. Thus, we propose that S. propionica, a syntrophic acetate producer using propionate, might cooperate with aceticlastic methanogens for high methane production during anaerobic digestion that included propionate.

NMR and MALDI-TOF MS based characterization of exopolysaccharides in anaerobic microbial aggregates from full-scale reactors.

Anaerobic granular sludge is composed of multispecies microbial aggregates embedded in a matrix of extracellular polymeric substances (EPS). Here we characterized the chemical fingerprint of the polysaccharide fraction of EPS in anaerobic granules obtained from full-scale reactors treating different types of wastewater. Nuclear magnetic resonance (NMR) signals of the polysaccharide region from the granules were very complex, likely as a result of the diverse microbial population in the granules. Using nonmetric multidimensional scaling (NMDS), the 1H NMR signals of reference polysaccharides (gellan, xanthan, alginate) and those of the anaerobic granules revealed that there were similarities between the polysaccharides extracted from granules and the reference polysaccharide alginate. Further analysis of the exopolysaccharides from anaerobic granules, and reference polysaccharides using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) revealed that exopolysaccharides from two of the anaerobic granular sludges studied exhibited spectra similar to that of alginate. The presence of sequences related to the synthesis of alginate was confirmed in the metagenomes of the granules. Collectively these results suggest that alginate-like exopolysaccharides are constituents of the EPS matrix in anaerobic granular sludge treating different industrial wastewater. This finding expands the engineered environments where alginate has been found as EPS constituent of microbial aggregates.

Impact of heat and mass dispersion and thermal effects on the scale-up of monolith reactors

Monolith reactors used in catalytic after-treatment systems (e.g. TWC, DOC, LNT and SCR) are often studied in laboratory experiments using monolith samples of the same cell density, washcoat thickness, and catalyst loading but with a smaller length compared to the full-scale reactor. The flow rate in the laboratory scale operation is selected so that the same space velocity is maintained as in the full-scale system. However, matching space velocity between the laboratory-scale and full-scale reactor leads to similar performance only under ideal conditions such as isothermal or adiabatic operation with negligible heat and mass dispersion (i.e. plug flow conditions) and small adiabatic temperature rise. In this work, it is shown that when thermal effects are significant (or adiabatic temperature rise is large) and heat and mass transfer and dispersion effects are not negligible, similarity may not exist and the ignition/extinction behavior of the two systems can be qualitatively different. Further, when laboratory-scale data is used for kinetic parameter estimation, failure to consider these effects in the reactor model can lead to false kinetic parameters and inaccurate prediction of reactor performances. Another major reason for possible discrepancy between laboratory-scale and full-scale reactors, external heat exchange with furnace (surroundings), is also investigated. We present analysis, simulations, and analytical results quantifying the impact of these effects on the scale-up of monolith reactors.

A case for aerobic sludge granulation: from pilot to full scale

A pilot-scale sequencing batch reactor (SBR) treating 120 m3/d of a town's wastewater was set up in 2009 and aerobic granules with a mean diameter of 0.28 mm, mixed liquor suspended solids (MLSS) of 7,500 mg/L and sludge volume index (SVI)30 of 43 mL/g were achieved. A full-scale SBR with 50,000 m3/d for treating a town's wastewater was operated in 2010 and aerobic granules with a mean MLSS of 2,285 mg/L and SVI30 of 52.5 mL/g were obtained. Aerobic granules had excellent performances of chemical oxygen demand (COD) and NH4+-N removal and remained stable for a long time. Raw wastewater and SBR operating mode had a positive effect on aerobic granule formation. Therefore, aerobic granular technology could be successfully applied in the full-scale bioreactor under specific conditions. Future development of aerobic granular technology is the application in full-scale continuous-flow reactors.

The efficiency of shredded and briquetted wheat straw in anaerobic co-digestion with dairy cattle manure

Anaerobic co-digestion of cattle manure (CM) with shredded or briquetted wheat straw (SS and BS, respectively) was evaluated in thermophilic continuously stirred tank reactors (CSTR) in two experiments (lab and full-scale). Three lab-scale CSTR (15 l) were used with 20 days hydraulic retention time (HRT); one was fed with CM and the other two with mixtures of CM (95% of fresh matter, FM) and SS or BS (5% FM). In the second experiment, two full-scale CSTR (30 m3) were operated with 25 days HRT; one reactor was fed with CM and the other with CM + BS (9% FM). Ultimate CH4 yield was analysed from each substrate. Biochemical CH4 potential at 21 days for CM, SS and BS were 128; 187 and 200 lSTP [CH4] kg−1 [VS]. Anaerobic digestion of CM, CM + SS and CM + BS in lab-scale reactors yielded 165; 214 and 217 lSTP [CH4] kg−1 [VS]. In full scale-reactors, CM and CM + BS yielded 264 and 351 lSTP [CH4] kg−1 [VS]. Increments of 31 and 33% on CH4 yield were achieved in CM + BS compared to CM in lab and full-scale reactors, respectively. Regarding the energy balance, the energy yields were the same for both reactors using straw as co-substrate (CM + SS and CM + BS) after subtracting the energy consumption of the pretreatment, corresponding to 1100 kWh of net energy output. However, briquetting technology could be advantageous for biogas plants where the straw might be transported over longer distances, due to reduction of the transportation costs.

Online monitoring of stable carbon isotopes of methane in anaerobic digestion as a new tool for early warning of process instability

Effective control of anaerobic digestion in biogas plants requires the monitoring of process sensitive and rapid response parameters in order to ensure efficient biogas production and to prevent potential process failure. In this study, stable carbon isotopes of methane (δ13CCH4) produced in a full-scale continuous stirred-tank reactor were investigated as a potential new monitoring tool for this purpose. Over a six-month period with variable organic loading rates, δ13CCH4-values were measured online by a portable high-precision laser absorption spectrometer. During a stress period of consecutive high organic loading, δ13CCH4-values early indicated process changes in contrast to traditionally monitored parameters where a change was observed some five to ten days later. Comparison of the stable isotope values with data from microbial analyses showed a distinct relationship between the quantity of potentially acetoclastic methanogens and δ13CCH4-values. This finding indicates an association between dominant methanogenic pathways and carbon isotope values.

Development of V2UP (V&V plus uncertainty quantification and prediction) procedure for high cycle thermal fatigue in fast reactor—Framework for V&V and numerical prediction

High cycle thermal fatigue on a structure caused by thermal striping phenomena is one of the most important issues in the design of fast breeder reactors (FBRs). In development of numerical simulation codes and in plant design and estimation by using the numerical estimation code, implementation of verification and validation (V&V) is indispensable process and also scaling issue from the subscale experiments to the full scale reactor should be considered. Therefore, a procedure called as V2UP (verification and validation plus uncertainty quantification and prediction) was made by referring to the existing guidelines on V&V (ASME V&V-10 and 20) and the methodologies of the safety assessment (CSAU, ISTIR, EMDAP). The V2UP consisted of five components as follows: (1) phenomena analysis with the Phenomena Identification and Ranking Table (PIRT) method, (2) implementation of the V&V, (3) design and rearrangement of experiments for the V&V, (4) uncertainty quantification in each problem and integration of uncertainties and (5) numerical prediction (estimation) for the target issue. Although the complete application of the procedure has not been performed at this moment, a flow chart of the V2UP procedure was described in this paper with recent results of the examinations.

Nitrogen removal performance and microbial distribution in pilot- and full-scale integrated fixed-biofilm activated sludge reactors based on nitritation-anammox process

Nitritation–anammox process was successfully established in pilot- and full-scale integrated fixed-film activated sludge (IFAS) reactors. An average nitrogen removal efficiency of 80% was achieved under ammonium loading rate of 0.7–1.3kgN/(m3d) in the pilot-scale reactor (12m3). Moreover, molecular analysis showed that ammonium oxidizing bacteria (AOB) were more abundant in the activated sludge while anammox bacteria were primarily located in the biofilm. The segregation of AOB and anammox bacteria enhanced the nitrogen removal rate and operational stability. Furthermore, a full-scale IFAS reactor of 500m3 was set-up to treat sludge dewatering liquors. An average nitrogen removal efficiency of 85% and a nitrogen removal rate of 0.48kgN/(m3d) were achieved after inoculation. It was noted that high influent suspended solids would seriously affect the performance of the IFAS system. Therefore, a pre-treatment was proposed to reduce suspended solid in the full-scale application.

On-site evaluation of the performance of a full-scale down-flow hanging sponge reactor as a post-treatment process of an up-flow anaerobic sludge blanket reactor for treating sewage in India

A down-flow hanging sponge (DHS) reactor is a novel, unaerated, aerobic, biofilm reactor that is used to polish effluent received from an up-flow anaerobic sludge blanket (UASB) reactor for treating municipal sewage. A full-scale DHS reactor was constructed for post-treatment of a full-scale UASB reactor at a municipal sewage treatment plant in India. Performance of the DHS reactor was evaluated with respect to organic removal over 1800days of continuous operation. The UASB+DHS system consistently produced effluent with chemical oxygen demand (COD), biochemical oxygen demand (BOD), and suspended solids (SS) values of 37, 6.0 and 19mgL−1, on average, respectively. The sludge yield of the DHS reactor was estimated to be 0.04kgSSkg−1 COD removed or 0.12kgSSkg−1 BOD removed, which is considerably lower than other aerobic treatment methods that have been employed for polishing UASB effluent.

Evaluation of functional microbial community’s difference in full-scale and lab-scale anaerobic digesters feeding with different organic solid waste: Effects of substrate and operation factors

Samples taken from the full-scale and lab-scale anaerobic digesters feeding with different organic solid waste were investigated with assessment of the substrate effects. To understand the substrate effects on the microbial community diversity, heterogeneity, and functional structure, twelve samples were analyzed by constructing 16S rRNA gene clone libraries and statistical analysis. Microbial diversity varied according to substrate types and operating parameters. With acetoclastic methanogen of genus Methanosaeta predominated in full scale and Methanosarcina predominated in the lab-scale digesters, a significant difference archaeal communities were found. Principal component analysis clearly indicates that both bacterial and archaeal communities create independent clusters according to substrate types. However, the relationship between acetogenic bacteria and the acetoclastic methanogens had a similar variation tends in most of full-scale and lab-scale reactors. Canonical correlation analysis and variance partitioning analysis implied that bacterial and archaeal community variations were significantly affected by substrate and the operation conditions.