Comparison of Continuous and Sequencing Batch Operated Biofilters for Treatment of Gas-Phase Methyl Ethyl Ketone

Although biofiltration has been used successfully to remove and biodegrade a wide variety of gas-phase organic contaminants generated by industrial facilities and environmental remediation efforts, the ability of conventional biofilters to maintain high removal efficiency during short-term, unsteady-state, elevated loading conditions is limited. A promising alternative for improving biofilter performance during transient elevated loading conditions while minimizing the disadvantages of conventional treatment technologies is utilization of adsorption packing media and implementation of sequencing batch operating strategies. In the studies described herein, a continuous-flow biofilter (CFB) and a sequencing batch biofilter (SBB) were operated for more than 300 days to treat a methyl ethyl ketone (MEK) contaminated gas stream. The packing medium for both biofilters consisted of activated carbon coated polyurethane foam cubes. Both biofilters exhibited stable long-term performance with greater than 99% removal of the influent 106?ppmv MEK concentration during “normal” loading conditions. To assess performance during transient loading conditions, on a regular basis the influent MEK concentration of each biofilter was temporarily increased by a factor of 10 to 1,060?ppmv MEK for a duration of either 45 or 60 min. Results are presented which demonstrate how the operational flexibility of SBB systems can be utilized to minimize or eliminate contaminant emissions from biofilters during unsteady-state loading conditions. The SBB was able to remove more than 99% of the influent MEK at a transient loading rate of 380?g?m?3?h?1 and 83% of the influent MEK at a transient loading rate of 760?g?m?3?h?1. In comparison, the CFB exhibited lower MEK removal efficiency.     

Biodegradation of Phenol with Wastewater as a Cosubstrate in Upflow Anaerobic Sludge Blanket

Anaerobic degradation of phenol mixed with a readily degradable synthetic wastewater (DSWW) as a cosubstrate was studied in a 12?L upflow anaerobic sludge blanket reactor at 30±2°C over a period of 632?days. DSWW was prepared by diluting sugar cane based molasses. The biomass was acclimatized to high phenol concentration by gradually decreasing the DSWW chemical oxygen demand (COD) of 4,000?mg/L. Feed made up of phenol COD and DSWW COD in the ratio of 7:3 (phenol concentration = 1,176?mg/L) was successfully treated at a hydraulic retention time (HRT) of 12?h and organic loading rate (OLR) of 8?g?COD/L?day. Phenol removal ranged from 99.9 to 84% at phenol COD varying from 10 to 70% in the feed. During the entire operation, COD removal varied from about 74 to 91.3%. The influent COD was distributed into CH4–COD ( ～ 72%), effluent COD ( ～ 17%), and sludge and unaccounted COD ( ～ 11%). The process failure occurred at 4:1 phenol COD: DSWW COD. Specific methanogenic activity of granular sludge exhibited uniform activity up to phenol COD of 70%. The performance of the reactor could not be maintained beyond 70% phenol COD even by reducing the sludge loading rate, increasing HRT, or decreasing OLR.     

Anaerobic Biodegradation of Polyhydroxybutyrate in Municipal Sewage Sludge

Anaerobic biodegradation in sewage sludge of polyhydroxybutyrate (PHB) was investigated. Evolved gaseous carbon was measured to assess biodegradability according to ASTM D5210. Mass-loss experiments were performed to determine degradation kinetics. Changes in the polymer properties were investigated. The impact of a natural plasticizer [tributyl citrate (TBC)] on biodegradation was determined. Polylactic acid was also biodegraded for comparison. Melt-pressed plates of PHB (with thicknesses of 0.24, 0.5, 1.2, 3.5, and 5.0 mm) were biodegraded to investigate the relationship between initial mass:initial surface area ratios and decay rates. Scanning electron microscopy micrographs of degraded specimens were recorded for visual illustration of the degradation process. A relationship between initial mass:initial surface area and degradation rates indicates that the thickness and surface area of the material affect its degradation. The degradation rates were impacted by the sewage sludge activity. TBC additive hindered PHB’s rate of degradation. Thermal properties, molecular bonding, and molecular weight measured by differential scanning calorimetry, Fourier transform infrared, and size exclusion chromatography, respectively, were only slightly affected by biodegradation, indicating that recycling PHB will not affect its performance.     

Sodium Inhibition of Thermophilic Methanogens

This study investigated the sodium inhibition of methanogens using two thermophilic (55°C) anaerobic sequencing batch reactors (ASBRs). The ASBRs were operated at a chemical oxygen demand (COD) loading of 4 g/L/day and a hydraulic retention time of 3 days. To evaluate the chronic toxicity of sodium to methanogens, the biomass in one of the ASBRs was acclimated to increasing sodium concentrations of 4.1, 7.1, and 12.0 g/L while the feed to the second ASBR was not supplemented with any additional sodium. The methanogenic activity (mL CH4/g volatile suspended solids/day) decreased by nearly 44% at an acclimation concentration of 12.0 g Na+/L, but the COD removal efficiency and methane production did not vary appreciably at the different acclimation concentrations studied. The acute toxicity of sodium to methanogens was determined by a series of batch anaerobic toxicity assays (ATAs). The biomass acclimated to different concentrations of sodium was collected from the ASBRs and used as inocula for the batch tests, and the sodium concentration was varied up to 17.7 g/L. The methanogens in the biomass acclimated to 0, 4.1, 7.1, and 12.0 g Na+/L were completely inhibited (100% inhibition) at predicted sodium concentrations of 10.6, 12.7, 18.0, and 22.8 g/L, respectively. To simulate the results of batch ATA in the ASBR, 7-day feeding with sodium concentrations in the influent measuring 6.2, 10.6, and 16.0 g/L were introduced into the reactor. Among each feeding, the reactor was operated with no additional sodium in the feed with 2–3 week intervals. Even though the methanogenic activity was not significantly affected at 6.2 and 10.6 g/L of sodium, there was a deterioration in methanogenic activity at 16.0 g/L dosage of sodium.     

Dynamic Growth Rates of Microbial Populations in Activated Sludge Systems

Results of mathematical modeling and whole cell 16S ribosomal RNA-targeted fluorescence in situ hybridizations challenge the widely held perception that microbial populations in “steady-state” activated sludge systems share a common net growth rate that is proportional to the inverse of the mean cell residence time. Our results are significant because they encourage bioprocess engineers to appreciate the differences in growth physiology among individual microbial populations in complex mixed microbial communities such as suspended growth activated sludge bioreactor systems.     

Using the Kinetics of Biological Flocculation and the Limiting Flux Theory for the Preliminary Design of Activated Sludge Systems. II: Experimental Verification

Current activated sludge models consider that the removal of biodegradable organics by suspended growth includes: rapid enmeshment of the organic particles in the microbial floc, hydrolysis of the complex organic molecules into readily biodegradable organic substances, and oxidation of dissolved organic substances. All of the models assume that hydrolysis is the rate-limiting step, but none considers the role that the kinetics of biological flocculation and the sludge-settling characteristics may play in defining the activated sludge operating parameters. Several researchers have studied the kinetics of biological flocculation, and have analyzed its role on the removal of particulate chemical oxygen demand in suspended growth reactors. It has been demonstrated that a large proportion of the organic matter present in sewage can be removed by biological flocculation using short hydraulic retention times and subsequent settling. The first paper demonstrates that the one-dimensional limiting flux theory may be useful for coupling the sludge-settling properties with the aeration tank behavior, and the second paper presents experimental evidence that the proposed model is a reasonable first approximation that can be used for activated sludge system design and operation.     

Use of a Sequencing Batch Reactor for Nitrogen and Phosphorus Removal from Municipal Wastewater

In this study, a suspended growth sequencing batch reactor (SBR) and an attached cum suspended growth SBR were used to investigate the performance characteristics of nitrogen and phosphorus (NP) removal from municipal sewage. The effects of three controlling factors, namely batch loading rate, feed pattern (initial feed or step feed), and mixing/aeration ratio, on NP removal were investigated under nine different experimental conditions. Owing to a large number of possible combinations among the controlling factors and different experimental conditions, it is very difficult to enumerate all the available combinations experimentally. In view of this, the Taguchi method, a cost-effective technique for design of experiments, was exploited for estimating the optimal operating condition. This study also evaluated the difference between the suspended growth SBR and the attached cum suspended growth SBR. The total nitrogen (TN), total phosphorus (TP), total biochemical oxygen demand (TBOD)5, and suspended solids (SS) removal efficiencies were 90.2, 83.9, 98.6, and 93.0%, respectively, for the suspended growth SBR. The corresponding values for the attached cum suspended growth SBR were 92.6, 82.1, 98.3, and 93.1%, respectively. It was observed that the batch loading rate influenced the efficiencies in terms of TN removal. It was also noted that step feed and mixing/aeration ratio had significant impact on TP removal performance. The optimal operating condition for the suspended growth SBR system in terms of batch loading rate, feed pattern, and mixing/aeration ratio were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 1-to-1, respectively. The associated TN, TP, TBOD5, and SS removal efficiencies for the suspended growth SBR were 93.8, 98.2, 99.6, and 98.5%, respectively. The corresponding results for the attached cum suspended growth SBR system were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 3-to-1, respectively. Similarly, the corresponding removal efficiencies for the attached cum suspended growth SBR were 94.7, 97.8, 99.3, and 98.8%, respectively.     

Biodegradation of Nitroaromatics and RDX by Isolated Rhodococcus Opacus

Identification of bacteria that can utilize a wide range of nitroaromatic compounds will allow development of more effective biological treatment methods in industrial wastewater treatment processes and environmental remediation efforts. A new strain of Rhodococcus opacus capable of mineralizing or transforming nitroaromatic and nitramine compounds of importance was isolated. Specifically, the bacterium were found to utilize 2,4,6-trinitrophenol (TNP) as a sole carbon and nitrogen source and have a yield coefficient of 0.16 g cells-N/g TNP-N. The Edwards model was found to provide the best fit to the data and the estimated inhibited growth parameters μmax, KS, and KI were 0.58?h?1, 25, and 112?mg/L, respectively. It was found that the TNP-degraders could degrade 2,4-dinitrophenol as the sole carbon and nitrogen source and utilize 1,3,5-trinitrobenzene as the sole nitrogen source. Additionally, the results show that the isolates are able to cometabolize 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 4-nitrophenol (4-NP), and 2,4- and 2,6-dinitrotoluene (2,4 and 2,6-DNT) to some extent when TNP is also present.     

Isotopic Fractionation of Tetrachloroethene Undergoing Biodegradation Supported by Endogenous Decay

A long term column study of the anaerobic biodegradation and associated isotopic fractionation of tetrachloroethene and transformation products was conducted. The column, initially fed with tetrachloroethene, ethanol, and yeast extract, was operated for one year with input of dissolved tetrachloroethene only to examine reductive dehalogenation and isotopic fractionation under endogenous decay conditions. A one-dimensional, inverse, multispecies, reactive transport model was employed to estimate the degradation rate constants and enrichment factors of the chlorinated ethenes at different times and under different column conditions. The inverse method combined a genetic algorithm with a gradient-based method for efficient parameter estimation. The trichloroethene and cis-1,2-dichloroethene first-order degradation rate constants decreased with time as endogenous decay progressed in the absence of ethanol and yeast extract. Temporal trends in tetrachloroethene degradation rate constants were not significant. The enrichment factors did not change significantly with time, biodegradation rates, or readdition of ethanol at the end of the study. This is encouraging with respect to using isotope enrichment factors in reactive transport models to estimate the extent of biodegradation in the field.     

Adsorption of Methylene Blue and Phenol by Wood Waste Derived Activated Carbon

The phosphoric acid activated carbon (PAC) was derived from waste wooden pallets by a two-step chemical activation technique, carbonization and phosphoric acid activation in sequence. A widely used commercial activated carbon, Calgon Filtrasorb 400 (F400), was studied in parallel for comparison. The physical properties and surface chemistry of the activated carbons were characterized using BET-N2 adsorption, elemental analysis, Boehm’s titration, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. PAC possessed physical properties (surface area and pore volume) that were comparable to those of F400, but displayed distinct surface chemistry in terms of pHPZC, surface acidity and basicity, and surface functional groups. Batch studies were conducted to evaluate the methylene blue (MB) and phenol adsorption capacity of PAC and F400 and their dependence on pH, contact time, and initial adsorbate concentration. Experimental results showed that the solution pH slightly influenced the adsorption of MB and phenol on F400, whereas it had no effect on their adsorption on PAC. Equilibrium adsorption data were fitted with an Langmuir isotherm equation. In comparison with F400, PAC showed a higher adsorption capacity for MB but lower for phenol. Given the comparable physical properties of PAC and F400 and the polar nature of MB and phenol, surface chemistry of the two carbons appeared to determine the adsorption mechanism and capacity. The strongly negative surface of PAC, due to phosphoric acid activation, facilitated the adsorption of positively charged MB, whereas the presence of oxygen-containing functional groups on PAC inhibited phenol adsorption.     

Biodegradation of Tetrachloroethene by Chitin Fermentation Products in a Continuous Flow Column System

The ability of chitin fermentation products to promote tetrachloroethene (PCE) reduction was evaluated in a continuous-flow column system to identify how different electron donors affect reductive dechlorination. Natural chitin fermentation products were initially used to support PCE reduction. Acetate (3.5?mM) was the dominant fermentation product, followed by propionate (0.1?mM), butyrate (0.1?mM), and hydrogen (100?nM). After chlorinated ethene concentration profiles reached pseudo steady state, the ability of individual fermentation products (acetate, acetate+propionate, propionate, or formate) to support PCE reduction was evaluated. None of the fermentation products tested stimulated dechlorination as well as the suite generated from chitin (kPCE = 6.9?day?1); however, acetate-stimulated PCE dechlorination the best (kPCE = 5.3?day?1), followed by formate (kPCE = 2.4?day?1), acetate+propionate (kPCE = 1.8?day?1), and propionate (kPCE = 1.2?day?1). Similar trends were observed for the PCE daughter products trichloroethene and dichloroethene. Free energies of individual fatty acid reactions were calculated and shown to be useful predictors of dechlorination performance, except for the case of acetate+propionate. Hence, acetate is the dominant fatty acid controlling dechlorination in the chitin-enhanced system, propionate appears to have an inhibitory effect when present with acetate alone, and other unidentified nutrients produced during chitin fermentation likely contribute to dechlorination activity as well.     

Characterization of Fines Produced by Sand Crushing

Sand particle crushing generates coarse fragments with size d ≥ 75?μm and fine fragments, i.e., “fines,” with size d<75?μm. Yet, postcrushing fines are seldom characterized due to testing constraints. An experimental study was conducted to examine the size distribution evolution of fine fragments generated by crushing two uniform sands with contrasting degrees of mineral composition heterogeneity, in one-dimensional compression. The determination of fine fragment sizes was made possible by using a particle size analyzer that employs a small sample. The results indicate that the degree of mineral composition heterogeneity affects the load–deformation behavior of crushing sands and the resulting amounts and size distribution evolutions of the produced coarse and fine fragments. In particular, the trends gathered suggest that fines generation occurs by abrasion of parent particles, coarse fragment breakage, and subsequent breakage of fine fragments with sizes larger than the comminution limit.     

Enhancement of Aromatic Hydrocarbon Biodegradation by Toluene and Naphthalene Degrading Bacteria Obtained from Lake Sediment: The Effects of Cosubstrates and Cocultures

Toluene and naphthalene degrading (ND) bacteria, obtained from contaminated lake sediment, were used to degrade both monoaromatics and polycyclic aromatic hydrocarbons (PAHs) and the effects of cosubstrates and cocultures were examined. When toluene and naphthalene enrichments were used, the effect of the substrate interaction on their metabolism was found to be inhibitory and yet the cocultures were stimulatory, especially for toluene enrichment degradation of naphthalene (with toluene). Pseudomonas putida M2T14, a toluene degrading isolate, could efficiently degrade benzene and toluene but not naphthalene. Nonetheless, when toluene was present, this monoaromatic degrader became capable of degrading PAHs, among which the methyl substituted PAHs (mPAHs) were preferred to their corresponding unsubstituted PAHs (uPAHs). Pseudomonas azelaica ND isolate could degrade benzene, toluene, and all test PAHs. Although the uPAHs were preferred, the degradation rates of mPAHs were greatly increased via substrate interactions with naphthalene. The interaction modes of dual aromatic hydrocarbons (AHs) degraded by P. putida M2T14 and P. azelaica ND were cometabolism, synergism, no effect, inhibition, and antagonism. However, when a negative effect of biodegradation from the interaction of these AHs was found on one isolate, a positive effect would be found on the other. When benzene was present, it exhibited inhibitory effects on aromatic hydrocarbon biodegradation by M2T14 and ND isolates. A study of the biodegradation of the ternary mixture of benzene, toluene, and naphthalene by both isolates together illustrated that not only was inhibition relieved but that degradation of each compound was also greatly enhanced. Degradation by the toluene and the ND bacteria could be facilitated by complementary substrate interactions between monoaromatics and PAHs and by bacterial association. These model organisms may be very useful for the study of complex aromatic hydrocarbon degradation and for bioremediation purposes.     

In Situ Microscale Analyses of Activated Sludge Flocs in the Enhanced Biological Phosphate Removal Process by the Use of Microelectrodes and Fluorescent In Situ Hybridization

Phosphate concentration microprofiles were measured within activated sludge flocs in the enhanced biological phosphate removal (EBPR) process, and a fluorescent in situ hybridization and clone library analysis were conducted to indentify polyphosphate accumulating organisms (PAOs). The center of the flocs had the highest phosphate concentrations, and the stratification of the flocs found by microprofiling indicated that the PAOs were probably distributed evenly throughout the flocs. Under the assumption that the phosphate, which was generated because of phosphate release by microbial activity, was not consumed by microbes and was only transferred from the flocs to the bulk by diffusion during anaerobic conditions, the effective diffusion coefficient (Df) for phosphate release within the flocs was calculated to be 3.33×10?7?cm2/s at the end of the anaerobic phase of the EBPR process. These results provide a better understanding of the phosphate removal mechanism, and this understanding of the internal function of flocs can lead to improvement in the modeling, design, and operation of the biological phosphorus removal process.     

An Overview of the Studies about Heavy Metal Adsorption Process by Microorganisms on the Lab. Scale in Turkey

Abstract

Heavy metal ions, Cr(VI), Pb(II), Cu(II), Fe(III) and Ni(II) were removed from synthetic aqueous solutions by using Z. ramigem, an activated sludge bacterium, and R. arrhizus, a filamentous fungus. The adsorption isotherms were developed and it was seen that the adsorption equilibrium data fit both Freundlich and Langmuir isotherms. Heavy metal adsorption on free and immobilized cells was also investigated in various reactor types such as stirred tank reactors (single and multi-stage) and packed bed reactors.     

低强度超声波强化ABR 处理低浓度污水

为提高ABR (厌氧折流板反应器)对低浓度污水的处理效果,通过设置超声组和对照组ABR 的对比试验,考察低强度超声波对ABR 处理低浓度污水的强化效果.结果表明,当采用声能密度为 0.1 W/mL 的超声波,每隔24 h 从ABR 中各隔室内取出10 %的污泥进行10 min 的辐照处理时,平均 COD 总去除率提高7.2 %左右. 通过该辐照处理,ABR 中各隔室内的胞外聚合物总量基本不变尧蛋 白质的含量有所提高尧多糖的含量有所降低尧DNA 的含量变化不大尧颗粒污泥的粒径减小. 研究还发 现,低温条件下,超声组ABR 的平均COD 去除率比对照组提高了8.6 豫,只低于常温条件下对照组 0.7 豫.低温条件下的超声强化效果比常温条件下更显著,而且超声组ABR 比对照组提前4 d 恢复稳 定运行.      

Microbial depyritisation of three different coals by Acidithiobacillus ferrooxidans in a batch stirred tank reactor

Abstract

The present study aimed to investigate the depyritisation potential of Acidithiobacillus ferrooxidans on two different types of coals, namely lignite and anthracite collected from three different countries (Korea, China and Indonesia). The experimental work was conducted on a batch mode in a stirred tank reactor. All the batch biooxidation of pyrite in the different coal samples were conducted in a pH controlled condition (pH?=?1·5). The growth medium employed for the batch biooxidation of pyritic coal was free from iron supplement. At. ferrooxidans oxidised mineral pyrite of Korean anthracite at a greater rate (98%) compared to 96 and 92% of pyrite oxidation for Indonesian and Chinese lignite respectively. The ratio of bioleach residue to the feed was reasonably good with range of 8·56–9·06 stating the net mass loss of 9–14. Coal depyritisation was carried out by the available Fe³⁺ ion in the inoculum producing Fe²⁺ ion as a product and this Fe²⁺ ion was further oxidised to Fe³⁺ ion by At. ferrooxidans. This Fe³⁺ ion produced by At. ferrooxidans continued the oxidation of the residual pyrite in the coal until all pyrite content was oxidised completely. The three different coals were found to be feasible for biological depyritisation of the coal could be scaled up for further studies in a continuous stirred tank bioreactor.

L’étude présente avait pour but d’examiner le potentiel d’enlèvement de la pyrite par Acidithiobacillus ferrooxidans dans deux types de charbons, soit le lignite et l’anthracite, récoltés dans trois pays, soit la Corée, la Chine et l’Indonésie. On a effectué le travail expérimental dans un mode en vrac, dans un réacteur agité. On a effectué toute la bio-oxydation en vrac de la pyrite des échantillons de charbon à un pH contrôlé de 1·5. Le médium de croissance utilisé pour la bio-oxydation en vrac du charbon pyritique ne contenait pas de supplément de fer. At. ferrooxydans oxydait le minerai de pyrite de l’anthracite coréen en plus grande proportion (98%) que l’oxydation de la pyrite du lignite indonésien (96%) ou chinois (92%), respectivement. Le rapport de résidu de biolixiviation à l’alimentation était raisonnablement bon, avec une gamme de 8·56 à 9·06, établissant la perte de masse nette de 9 à 14. L’enlèvement de la pyrite du charbon était effectué par l’ion Fe³⁺ disponible dans l’inoculum, donnant lieu à l’ion Fe²⁺ comme produit et cet ion Fe²⁺ était davantage oxydé en ion Fe³⁺ par At. ferrooxidans. Cet ion Fe³⁺ produit par At. ferrooxidans continuait l’oxydation de la pyrite résiduelle dans le charbon jusqu’à ce que toute la pyrite soit complètement oxydée. On a trouvé qu’il était possible d’effectuer l’enlèvement biologique de la pyrite des trois charbons et d’augmenter l’échelle pour des études futures dans un bioréacteur en continu agité.     

Studies on alloying process of a ferritic/martensitic oxide dispersion strengthened (ODS) steel prepared by mechanical alloying of elemental powders

Ferritic/martensitic oxide dispersion strengthened steel with a nominal composition of Fe–9Cr–2W–0.2Ti–0.12C–0.35Y₂O₃ was produced by mechanical alloying in a high energy horizontal Simoloyer attritor. Powder samples were collected at intervals of 0.5, 1, 2, 3, 5, 7 and 10?h and analysed by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and differential thermal analysis. The alloying elements (Cr and W) got dissolved in the matrix in 7?h milled powder. Crystallite size decreased rapidly with milling time up to 5?h milling and reached a stable size of ～12?nm after 7?h, whereas strain and lattice parameter were found to increase with milling time. The particle size increased up to 2?h milling and then decreased with milling time. A fine and uniform particle size of ～25?nm was obtained after 7?h milling. The alloying process and distribution of alloying elements/Y₂O₃ is studied in the present work.