Home About us Contact
|
Home About us Contact | ||
|
|
||
Removal Efficiency (removal + efficiency)
Kinds of Removal Efficiency Selected AbstractsPrediction of the Removal Efficiency of a Novel Two-Stage Hybrid Scrubber for Flue Gas DesulfurizationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2006A. Bandyopadhyaya Abstract Emission of SO2 from various industrial sources occurs in varying concentrations and quantities. The operation of scrubbers as SO2 control devices is getting more and more attention as pollution control regulations are tightened. Experimental investigations on the scrubbing of SO2 in a novel two-stage hybrid (spray-cum-bubble column) scrubber using water and dilute sodium alkali are reported. Empirical and semi-empirical correlations are developed for the prediction of the performances of the bubble and the spray sections in terms of various pertinent variables of the system for water and alkaline scrubbing, respectively. The contribution of the mass transfer enhancement factor towards the removal of SO2 has been exploited while developing the semi-empirical correlation for the prediction of performance in alkaline scrubbing. The predicted values are in excellent agreement with the experimental values. Finally, the operating features of the scrubber and design aspects are discussed in order to develop our understanding for practical applications. [source] Fate of air toxics and VOCs in the odor control scrubbers at the deer island treatment plantENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2000Thomas Myslinski Process off-gases at the Deer Island wastewater treatment plant in Boston are collected and treated and its stack emissions regulated for selected gases including volatile organic compounds (VOCs), which are monitored as nonmethane hydrocarbons (NMHC). The air treatment processes of countercurrent wet oxidation scrubbing and granulated activated carbon adsorption are available for emissions control at Deer Island. In addition, since the wastewater treatment process of biochemical oxidation is fully enclosed at the site, microbial destruction of VOCs is an intrinsic treatment process for organic gases. Surveyed results of wastewater research literature indicate that the use of scrubbers for the removal of VOCs is controversial, as the fate of volatile hydrocarbon molecules across odor control scrubbers is complex and not fully understood. Continuous emission monitoring tests across the Deer Island scrubbers have consistently shown a VOC removal efficiency in excess of 50%. The fate of the scrubber inlet VOCs at Deer Island was researched as part of a plant-wide, on-going VOC study. Removal efficiencies across the pure oxygen bioreactors were also investigated. Preliminary results of this study indicate chemical reactions involving VOCs in odor control scrubbers partially oxidize and chlorinate derivatives possibly destroying a fraction of the compounds by complete oxidation. In addition, VOC reduction across the enclosed aerobic bioreactors was found to be significant. This article represents the opinions and(legal) conclusions of the authors and not necessarily those of the MWRA. [source] Preparation and sorption studies of ,-cyclodextrin/epichlorohydrin copolymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Dawn Y. Pratt Abstract ,-Cyclodextrin (,-CD) copolymer materials were synthesized by reacting different mole ratios (1 : 15, 1 : 25 and 1 : 35) of ,-CD with epichlorohydrin (EP). The products were characterized using N2 porosimetry, Fourier Transform Infrared spectroscopy, 13C CP-MAS NMR spectroscopy, thermogravimetry analysis, elemental (C and H) analysis, and scanning electron microscopy. The sorption properties in aqueous solution were studied using p-nitrophenol (PNP) with UV,Vis spectrophotometry. Sorption isotherms were obtained at pH 4.6 and three temperatures (22, 35, and 45°C) and at pH 10.3 at 22°C. The isotherms were analyzed using the BET isotherm model and the sorption parameters provided estimates of the surface area, sorption capacity, and isosteric heats of sorption for each polymeric material. The estimated surface areas are as follows: 58.2, 52.1, and 90.1 m2/g at pH 4.6. At pH 10.3, the estimated surface areas are 44.2, 40.5, and 58.5 m2/g, respectively. The removal efficiency of PNP by the polymeric materials ranged between 4.5 and 58% for the conditions investigated whereas the isosteric heats ranged between ,24.5 and ,13.6 kJ/mol. Removal efficiencies were concluded to strongly depend on the sorption conditions such as pH, temperature, and the relative amounts of sorbent and dye in aqueous solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Efficiency of permeable pavement systems for the removal of urban runoff pollutants under varying environmental conditionsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2010Kiran Tota-Maharaj Abstract Urban surface water runoff typically contains a high but variable number of pathogens, nutrients, and sediments that require removal before reuse. Permeable pavements can improve the water quality through interception, filtration, sedimentation, nutrient transformation, and microbial removal. There is currently insufficient scientific information available on the treatment efficiencies of permeable pavements combined with earth energy systems with regards to the removal of storm water pollutants such as nutrients, sediments, and microbial pollutants. This study evaluates the efficiency of 12 tanked combined systems during a medium-term study. The research assessed weekly the removal of the microbial indicators total coliforms, Escherichia coli, and fecal Streptococci, as well as the key nutrients ammonia-nitrogen, nitrate-nitrogen, and ortho-phosphate-phosphorus, and physical variables such as suspended solids and turbidity. Total coliforms, E. coli, and fecal Streptococci were removed by 98,99%. The ammonia-nitrogen and ortho-phosphate-phosphorus removal efficiencies were 84.6% and 77.5%, respectively. An analysis of variance indicated that the presence or absence of a geotextile did result in a very highly statistically significant difference (P < 0.001) with respect to the removal of both ammonia-nitrogen and ortho-phosphate-phosphorus. Suspended solids, turbidity, and biochemical oxygen demand were reduced by 91%, 82%, and 88%, respectively. These results indicate the potential of the proposed novel system in urban runoff pollutant removal and subsequent reuse of the treated water. © 2010 American Institute of Chemical Engineers Environ Prog, 2010 [source] A hollow fiber membrane photo-bioreactor for CO2 sequestration from combustion gas coupled with wastewater treatment: a process engineering approachJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2010Amit Kumar Abstract BACKGROUND: In the presence of light, micro-algae convert CO2 and nutrients to biomass that can be used as a biofuel. In closed photo-bioreactors, however, light and CO2 availability often limit algae production and can be difficult to control using traditional diffuser systems. In this research, a hollow fiber membrane photo-bioreactor (HFMPB) was investigated to: (1) increase the interfacial contact area available for gas transfer, (2) treat high nutrient strength (412 mg NO3, -N L,1) wastewater, and (3) produce algal biomass that can be used as a biofuel. RESULTS: A bench scale HFMPB was inoculated with Spirulina platensis and operated with a 2-15% CO2 supply. A mass transfer model was developed and found to be a good tool to estimate CO2 mass transfer coefficients at varying liquid velocities. Overall mass transfer coefficients were 1.8 × 10,6, 2.8 × 10,6, 5.6 × 10,6m s,1 at Reynolds numbers of 38, 63, and 138, respectively. A maximum CO2 removal efficiency of 85% was observed at an inlet CO2 concentration of 2% and a gas residence time (membrane-lumen) of 8.6 s. The corresponding algal biomass concentrations and NO3 removal efficiencies were 2131 mg L,1 and 68%, respectively. CONCLUSION: The results show that the combination of CO2 sequestration, wastewater treatment and biofuel production in an HFMPB is a promising alternative for greenhouse gas mitigation. Copyright © 2010 Society of Chemical Industry [source] Effect of thermochemical sludge pretreatment on sludge reduction and on performances of anoxic-aerobic membrane bioreactor treating low strength domestic wastewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2009Khac-Uan Do Abstract BACKGROUND: Reduction of excess sludge production has become an urgent issue. An investigation into the influence of thermochemical sludge pretreatment on sludge reduction in a bench-scale anoxic-aerobic membrane bioreactor was performed. Two systems were operated. In one system, part of the mixed liquid (1.5% of the influent flow rate) was pretreated thermochemically (at 80 °C, pH 11 and 3 h) and returned to the bioreactor. This study examined and evaluated the effect of thermochemical sludge pretreatment on the reduction of excess sludge and on the performance of the system. RESULTS: The average solubilization efficiency of the pretreated sludge was found to be about 0.2. The sludge production rate of the experimental system (E-MBR) was less than that of the control (C-MBR) by about 33%. The total phosphorus was removed mainly by normal cell synthesis, with removal efficiencies of 38,40% and 40,42% for the E-MBR and C-MBR, respectively. The total nitrogen removal in the E-MBR was slightly higher than in the C-MBR due to supply of soluble chemical oxygen demand (SCOD) from the digested sludge solution as an external carbon source. The mixed liquor volatile suspended solids (MLVSS) and mixed liquor suspended solids (MLSS) ratios for the two systems were almost identical, in the range 74,77%, indicating that the inorganics from the disintegrated cells do not accumulate as particulates in the reactor. The TMP was maintained at less than 6 cmHg for 180 days without membrane cleaning. CONCLUSION: Thermochemical sludge pretreatment can play an important role in reducing sludge production. The qualities of the effluent water were not significantly affected during 6 months of operation. Copyright © 2009 Society of Chemical Industry [source] The beneficial role of intermediate clarification in a novel MBR based process for biological nitrogen and phosphorus removalJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2009MinGu Kim Abstract BACKGROUND: A novel membrane bioreactor (MBR) is described, employing an intermediate clarifier. Unlike the established function of a final clarifier in a conventional biological nutrient removal system, the role of an intermediate clarifier has rarely been studied. Thus, this work focused on explaining the fate of nutrients in the intermediate clarifier, as influenced by the hydraulic retention time (HRT) of the preceding anaerobic bioreactor. RESULTS: The system was tested with two different anaerobic/anoxic/aerobic biomass fractions of 0.25/0.25/0.5 (run 1) and 0.15/0.35/0.45 (run 2) using synthetic wastewater. The major findings of the study were that phosphorus (P) removal was affected by the role of the intermediate clarifier. In run 1, P was removed at a rate 0.16 g d,1 in the intermediate clarifier while in run 2, additional P was released at 0.49 g d,1. The nitrogen (N) removal efficiencies were 74 and 75% for runs 1 and 2 respectively, while P removal was 91 and 96%. P uptake by denitrifying phosphate accumulating organisms (DPAOs) accounted for 41,52% of the total uptake in the MBR. CONCLUSIONS: This study found that the intermediate clarifier assisted chemical oxygen demand (COD), N, and P removal. With respect to the fate of P, the intermediate clarifier functioned as an extended anaerobic zone when the HRT of the preceding anaerobic zone was insufficient for P release, and as a pre-anoxic zone when the anaerobic HRT was adequate for P release. Copyright © 2008 Society of Chemical Industry [source] Development of a correlation to study parameters affecting nitrification in a domestic wastewater treatment plantJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2008Gulnur Coskuner Abstract BACKGROUND: Nitrification performance of an activated sludge reactor treating weak domestic wastewater was investigated for 11 months. Ammonia nitrogen removals were investigated as a function of wastewater composition and operational conditions. Backward elimination experimental design was used to determine the influence of the most important independent variables on NH3 -N removal efficiencies. Influent ammonia and biological oxygen demand (BOD5) concentrations, hydraulic retention time (HRT), mixed liquid suspended solids (MLSS), temperature, pH and dissolved oxygen (DO) concentration were considered as independent variables. This study aimed to find the most important parameters to describe nitrification performance. RESULTS: The presence of nitrification was confirmed by ammonia and nitrate variations throughout the reactor; ammonia oxidizing bacteria (AOB) populations were determined using a fluorescence in situ hybridization (FISH) method. MLSS concentration, influent BOD5 concentration and temperature were found to be the most influential factors on nitrification performance. The empirical correlation using multiple linear regressions was statistically significant and produced an adjusted coefficient of multiple determinations (R2adj) of 92.5%. CONCLUSION: Correlation provides a good understanding of the various parameters that affect the nitrification process, and could be extended to other case studies. Using these results, operators can apply proper operational strategies to maintain nitrification in wastewater treatment plants. Copyright © 2007 Society of Chemical Industry [source] Reductive decolourization and total organic carbon reduction of the diazo dye CI Acid Black 24 by zero-valent iron powderJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2006Ming-Chin Chang Abstract In this study, wastewater contaminated by colour and total organic carbon from the diazo dye CI Acid Black 24 was successfully removed by reductive decolourization with zero-valent iron powder. The effects on decolourization of experimental variables such as iron dosage, initial dye concentration, pH and dissolved oxygen level were evaluated. The best removal efficiencies for decolourization of 99.7% and total organic carbon of 57.4% were obtained with an initial dye concentration of 25.0 mg L,1 and iron dosage of 200.0 g L,1. Moreover, the decolourization rates followed pseudo-first-order kinetic equations with respect to dye concentration. The colour removal efficiency was simultaneously dependent on iron dosage and various initial dye concentrations, although the colour and total organic carbon removal efficiencies linearly increased with increased iron dosage, reaching a maximum at 100.0 g L,1. A contour plot was developed to illustrate the 3D relation of removal efficiencies with initial dye concentration and iron dosage. For wastewater with a concentration range from 25 to 100 mg L,1 CI Acid Black 24 the suggested ideal operation conditions are 100.0 g L,1 iron dosage, pH 2-4, normal oxygen concentration of 5-7 mg L,1 and reaction time of 30-60 min. Copyright © 2006 Society of Chemical Industry [source] Comparison of chemical wet scrubbers and biofiltration for control of volatile organic compounds using GC/MS techniques and kinetic analysisJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2005James R Kastner Abstract Increasing public concerns and EPA air regulations in non-attainment zones necessitate the remediation of volatile organic compounds (VOCs) generated in the poultry-rendering industry. Wet scrubbers using chlorine dioxide (ClO2) have low overall removal efficiencies due to lack of reactivity with aldehydes. Contrary to wet scrubbers, a biofilter system successfully treated the aldehyde fraction, based on GC/MS analysis of inlet and outlet streams. Total VOC removal efficiencies ranged from 40 to 100% for the biofilter, kinetic analysis indicated that the overall removal capacity approached 25 g m,3 h,1, and aldehyde removal efficiency was significantly higher compared with chemical wet scrubbers. Process temperatures monitored in critical unit operations upstream from the biofilter varied significantly during operation, rising as much as 30 °C within a few minutes. However, the outlet air temperature of a high intensity scrubber remained relatively constant at 40 °C, although the inlet air temperature fluctuated from 50 to 65 °C during monitoring. These data suggest a hybrid process combining a wet scrubber and biofilter in series could be used to improve overall VOC removal efficiencies and process stability. Copyright © 2005 Society of Chemical Industry [source] Biological treatment of saline wastewaters from marine-products processing factories by a fixed-bed reactorJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2002Neji Gharsallah Abstract Wastewaters generated by a factory processing marine products are characterized by high concentrations of organic compounds and salt constituents (>30,g,dm,3). Biological treatment of these saline wastewaters in conventional systems usually results in low chemical oxygen demand (COD) removal efficiency, because of the plasmolysis of the organisms. In order to overcome this problem a specific flora was adapted to the wastewater from the fish-processing industry by a gradual increase in salt concentrations. Biological treatment of this effluent was then studied in a continuous fixed biofilm reactor. Experiments were conducted at different organic loading rates (OLR), varying from 250 to 1000,mg,COD,dm,3 day,1. Under low OLR (250,mg,COD,dm,3 day,1), COD and total organic carbon (TOC) removal efficiencies were 92.5 and 95.4%, respectively. Thereafter, fluctuations in COD and TOC were observed during the experiment, provoked by the progressive increase of OLR and the nature of the wastewater introduced. High COD (87%) and TOC (99%) removal efficiencies were obtained at 1000,mg,COD,dm,3 day,1. © 2002 Society of Chemical Industry [source] Operating and scale-up factors for the electrolytic removal of algae from eutrophied lakewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2002Catalino G Alfafara Abstract Electrolytic removal of algae was conducted in batch and continuous reactors to investigate operating factors affecting removal efficiency and to explore engineering relationships which could be useful for operation and scale-up. The system integrated both electro-flocculation and electro-flotation mechanisms by using polyvalent metal anodes and inert metal cathodes. Batch reactor studies confirmed that high electrical input power or higher electrical current achieved higher and faster removal efficiencies. Natural liquid circulation was observed during electrolytic operation and increased with higher electrical power. However, a small degree of external mixing may be useful at lower electrical power input. Electro-flotation alone could not achieve complete algae removal (maximum efficiency 40,50%), and showed the importance of algal floc formation for the complete removal of algae. In continuous electrolysis experiments, the ratio of the volumetric current intensity (amperes,dm,3) and the chlorophyll a loading (mg,dm,3,h,1) was found to be a useful operating and scale-up factor to balance high algal removal efficiency with minimum release of excess aluminum. This ratio was eventually found to be just the charge dose or the amount of coulombs required to remove a unit mass of chlorophyll a. The optimum charge dose was determined and used to relate the operating current and electrolysis time of a continuous process. © 2002 Society of Chemical Industry [source] The removal of iron and cobalt from aqueous solutions by ion exchange with Na-Y zeolite: batch, semi-batch and continuous operationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2002Jong Sung Kim Abstract The removal of single component and binary mixtures of divalent cobalt and iron from water by ion exchange with synthetic Y zeolite has been studied in batch, semi-batch and continuous modes of operation; the initial metal solution concentration did not exceed 2,mmol,dm,3. Binary Co/Na and Fe/Na ion exchange equilibrium isotherms (294,K) are presented wherein exchange site heterogeneity is evident in the case of the iron treatment. Under conditions of stoichiometric ion exchange, removal efficiencies for both cobalt and iron decrease with increasing metal concentration (0.2,2,mmol,dm,3) and the values were similar for both metals. Removal of cobalt under transient conditions was found to be temperature dependent. In the fixed bed operation, break-through behavior was sensitive to changes in both flow rate and inlet concentration. The break-through profiles for both metals under competitive and non-competitive conditions are presented; iron removal is lower in the presence of cobalt and vice versa. An in situ regeneration of the fully loaded zeolite by back exchange with sodium is considered and the exchange capacity of the regenerated zeolite is reported. The feasibility of employing cycles of heavy metal uptake/zeolite regeneration is addressed. © 2002 Society of Chemical Industry [source] Simultaneous organic carbon and nitrogen removal in an SBR controlled at low dissolved oxygen concentrationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2001Peng Dangcong Abstract Simultaneous organic carbon and nitrogen removal was studied in a sequencing batch reactor (SBR) fed with synthetic municipal wastewater and controlled at a low dissolved oxygen (DO) level (0.8,mg,dm,3). Experimental results over a long time (120 days) showed that the reactor achieved high treatment capacities (organic and nitrogen loading rates reached as high as 2.4,kg COD m,3 d,1 and 0.24,kg NH3 -N m3 d,1) and efficiencies (COD, NH3 -N and total nitrogen removal efficiencies were 95%, 99% and 75%). No filamentous bacteria were found in the sludge even though the reactor had been seeded with filamentous bulking sludge. Instead, granular sludge, which possessed high activity and good settleability, was formed. Furthermore, the sludge production rate under low DO was less than that under high DO. Significant benefits, such as low investment and less operating cost, will be obtained from the new process. © 2001 Society of Chemical Industry [source] Grass-Shrub Riparian Buffer Removal of Sediment, Phosphorus, and Nitrogen From Simulated Runoff,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2007Kyle R. Mankin Abstract:, Riparian buffer forests and vegetative filter strips are widely recommended for improving surface water quality, but grass-shrub riparian buffer system (RBSs) are less well studied. The objective of this study was to assess the influence of buffer width and vegetation type on the key processes and overall reductions of total suspended solids (TSS), phosphorus (P), and nitrogen (N) from simulated runoff passed through established (7-year old) RBSs. Nine 1-m RBS plots, with three replicates of three vegetation types (all natural selection grasses, two-segment buffer with native grasses and plum shrub, and two-segment buffer with natural selection grasses and plum shrub) and widths ranging from 8.3 to 16.1 m, received simulated runoff having 4,433 mg/l TSS from on-site soil, 1.6 mg/l total P, and 20 mg/l total N. Flow-weighted samples were collected by using Runoff Sampling System (ROSS) units. The buffers were very efficient in removal of sediments, N, and P, with removal efficiencies strongly linked to infiltration. Mass and concentration reductions averaged 99.7% and 97.9% for TSS, 91.8% and 42.9% for total P, and 92.1% and 44.4% for total N. Infiltration alone could account for >75% of TSS removal, >90% of total P removal, and >90% of total N removal. Vegetation type induced significant differences in removal of TSS, total P, and total N. These results demonstrate that adequately designed and implemented grass-shrub buffers with widths of only 8 m provide for water quality improvement, particularly if adequate infiltration is achieved. [source] REEXAMINING BEST MANAGEMENT PRACTICES FOR IMPROVING WATER QUALITY IN URBAN WATERSHEDS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2003Stephen R. Pennington ABSTRACT: Municipalities will be implementing structural best management practices at increasing rates in their effort to comply with Phase II of the National Pollutant Discharge Elimination System (NPDES). However, there is evidence that structural best management practices (BMPs) by themselves may be insufficient to attain desired water quality standards. This paper reports on an analysis of the median removal efficiencies of structural BMPs and compares them to removal efficiencies estimated as being necessary to attain water quality standards in the Rouge River in Detroit, Michigan. Eight water quality parameters are reviewed using data collected from 1994 to 1999 in the Rouge River. Currently, five of the eight parameters in the Rouge River including bacteria, biochemical oxygen demand, and total suspended solids (TSS) exceed the required water quality standards. The reported analysis of structural BMP efficiencies reveals that structural BMPs appear capable of reducing only some of the pollutants of concern to acceptable levels. [source] RECIRCULATING WELLS: GROUND WATER REMEDIATION AND PROTECTION OF SURFACE WATER RESOURCES,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2000Keith W. Ryan ABSTRACT: Several chlorinated solvent plumes threaten the sole-source aquifer underlying the Massachusetts Military Reservation at the western end of Cape Cod. Sensitive surface water features including ponds, cranberry bogs, and coastal wetlands are hydraulically connected to the aquifer. For one of the plumes (CS-10 the original remedy of 120 extraction and reinjection wells has the potential for significant disruption of surface water hydrology, through the localized drawdown and mounding of the water table. Recirculating wells with in-well air stripping offer a cost-effective alternative to conventional pump-and-treat technology that does not adversely affect the configuration of the water table. Pilot testing of a two well system, pumping 300 gpm, showed a capture radius of > 200 feet per well, in-well trichloroethylene (TCE) removal efficiencies of 92 to 98 percent per recirculation cycle, an average of three recirculation cycles within the capture zone, and no measurable effect on water table elevations at any point within the recirculation/treatment zone. During 120 days of operation, the mean concentration of TCE in the treatment zone was reduced by 83 percent, from 1,111 ,g/l to 184 ,g/l. Full-scale design projections indicate that 60 wells at an average spacing of 160 feet, having an aggregate recirculation 11 MGD, can contain the CS-b plume without ground water extraction or adverse hydraulic effects on surface water resources. The estimated capital costs for such a system are about $7 million, and annual operations-and-maintenance costs should be about $1.4 million, 40 percent of those associated with a pump and treat system over a 20-year period. [source] Treatment of Carbon Tetrafluoride with Gas DischargesPLASMA PROCESSES AND POLYMERS, Issue 7-8 2007Gerhard J. Pietsch Abstract Waste gases from semiconductor industry contain perfluorocarbons, which cause global warming and therefore should be removed. There are several possibilities to do this, for example the treatment of the gas by thermal and non-thermal plasmas, as well as by heating. In model gases containing up to 10,000 ppm CF4, destruction removal efficiencies of nearly 100% have been reached at atmospheric pressure using dielectric barrier and arc discharges. In order to reach high values, the dissociation products of CF4 must be bonded by reaction partners such as SiO2, CaO or H2O. [source] Treatment of Highly Contaminated Groundwater: A SITE Demonstration ProjectREMEDIATION, Issue 3 2001Daniel Sullivan From September through November 1994, the U.S. Environmental Protection Agency (EPA) conducted a field demonstration of the remediation of highly contaminated groundwater at the Nascolite Superfund site located in Millville, New Jersey. Besides high concentrations of the major contaminant, methyl methacrylate (MMA), the groundwater also contained small amounts of volatile and semivolatile organic compounds. ZenoGem® technology, an integrated bioreactor and ultrafiltration membrane system, was employed for this demonstration project. Approximately 30,000 gallons of groundwater containing MMA in concentrations of 567 to 9,500 milligrams per liter (mg/L) and chemical oxygen demand (COD) values ranging from 1,490 to 19,600 mg/L was treated. The demonstration focused on the system's ability to remove MMA and reduce COD from the groundwater. Results of the three-month demonstration showed that average MMA and COD removal efficiencies were greater than 99.9 and 86.9, respectively. The total cost of treatment, depending on the duration of the project, is estimated to vary from $0.22 to $0.55 (in 1994 dollars) per gallon of groundwater treated. © 2001 John Wiley & Sons. [source] Biological treatment of milk processing wastewater in a sequencing batch flexible fibre biofilm reactorASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Mohamed Abdulgader Abstract Biological treatment of dairy wastewater was investigated using a laboratory scale aerobic sequencing batch flexible fibre biofilm reactor (SBFFBR). The SBFFBR system was modified from a typical sequencing batch reactor system by using eight flexible fibre bundles with a very high specific surface area, which served as support for microorganisms. The reactor was operated under different influent chemical oxygen demand (COD) concentrations (610, 2041 and 4382 mg l,1) and constant hydraulic retention times of 1.6 days. The results have shown successful applicability of the SBFFBR system to treat this dairy wastewater. High COD removal efficiencies between 89.7 and 97% were achieved at average organic loading rates of 0.4 and 2.74 kg COD m,3 d,1, respectively. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Novel application of oxygen-transferring membranes to improve anaerobic wastewater treatmentBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005Anthony S. Kappell Abstract Anaerobic biological wastewater treatment has numerous advantages over conventional aerobic processes; anaerobic biotechnologies, however, still have a reputation for low-quality effluents and operational instabilities. In this study, anaerobic bioreactors were augmented with an oxygen-transferring membrane to improve treatment performance. Two anaerobic bioreactors were fed a synthetic high-strength wastewater (chemical oxygen demand, or COD, of 11,000 mg l,1) and concurrently operated until biomass concentrations and effluent quality stabilized. Membrane aeration was then initiated in one of these bioreactors, leading to substantially improved COD removal efficiency (>95%) compared to the unaerated control bioreactor (,65%). The membrane-augmented anaerobic bioreactor required substantially less base addition to maintain circumneutral pH and exhibited 75% lower volatile fatty acid concentrations compared to the unaerated control bioreactor. The membrane-aerated bioreactor, however, failed to improve nitrogenous removal efficiency and produced 80% less biogas than the control bioreactor. A third membrane-augmented anaerobic bioreactor was operated to investigate the impact of start-up procedure on nitrogenous pollutant removal. In this bioreactor, excellent COD (>90%) and nitrogenous (>95%) pollutant removal efficiencies were observed at an intermediate COD concentration (5,500 mg l,1). Once the organic content of the influent wastewater was increased to full strength (COD = 11,000 mg l,1), however, nitrogenous pollutant removal stopped. This research demonstrates that partial aeration of anaerobic bioreactors using oxygen-transferring membranes is a novel approach to improve treatment performance. Additional research, however, is needed to optimize membrane surface area versus the organic loading rate to achieve the desired effluent quality. © 2005 Wiley Periodicals, Inc. [source] Optimization of catechol production by membrane-immobilized polyphenol oxidase: A modeling approachBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2003A. Boshoff Abstract Although previous research has focused on phenol removal efficiencies using polyphenol oxidase in nonimmobilized and immobilized forms, there has been little consideration of the use of polyphenol oxidase in a biotransformation system for the production of catechols. In this study, polyphenol oxidase was successfully immobilized on various synthetic membranes and used to convert phenolic substrates to catechol products. A neural network model was developed and used to model the rates of substrate utilization and catechol production for both nonimmobilized and immobilized polyphenol oxidase. The results indicate that the biotransformation of the phenols to their corresponding catechols was strongly influenced by the immobilization support, resulting in differing yields of catechols. Hydrophilic membranes were found to be the most suitable immobilization supports for catechol production. The successful biocatalytic production of 3-methylcatechol, 4-methylcatechol, catechol, and 4-chlorocatechol is demonstrated. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 1,7, 2003. [source] Aggregation Experiments on Fine Fly Ash Particles in a Gradient Magnetic FieldCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2007W. Li Abstract Aggregation experiments were conducted on two kinds of fly ash particles in the size range of 0.023,9.314,,m in a gradient magnetic field produced by permanent magnetic rings. The two types of fly ash particles were obtained from Dongsheng and Datong coal combustion. The effect of particle size, total particle mass concentration, particle residence time in the magnetic field and gas velocity were examined. Experimental results showed that the removal efficiencies in a gradient magnetic field are much higher than those in a uniform magnetic field. The total and single-sized particle removal efficiencies can be improved by increasing the total particle mass concentrations and the particle residence time in the magnetic field or reducing the gas velocity. Mid-sized particle removal efficiencies are higher than those of the larger and smaller ones. With the increase in total particle removal efficiencies, the particle size corresponding to the maximum values of single-sized particle removal efficiencies and the particle number median diameters both decrease. Both the single-sized and total removal efficiencies for the particles from the Dongsheng coal combustion are higher than those from the Datong coal combustion. [source] Post-treatment of anaerobically treated medium-age landfill leachateENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2010Ebru Akkaya Abstract This study focused on the removal of COD and NH4+ from medium-age leachate. Experiments were performed in a laboratory-scale upflow anaerobic sludge blanket (UASB), a membrane bioreactor (MBR), and using magnesium ammonium phosphate (MAP) precipitation. MBR and MAP were used for the post-treatment steps for anaerobically treated leachate to increase the removal of organics and ammonium. The UASB reactor removed nearly all biodegradable organics and supplied constant effluent COD for all concentration ranges of influent leachate. Ammonium removal efficiency in the UASB reactor was relatively low and the average value was ,7.9%. Integration of MBR to the effluent of UASB reactor increased the average COD removal efficiency from 51.8 to 65.6% and maximum removal efficiency increased to 74.3%. MAP precipitation was applied as a final step to decrease the ammonium concentration in the effluent of UASB+MBR reactors. The effect of pH and the molar ratio of MAP constituents on the removal of ammonium were evaluated. At optimal conditions (pH: 9.0 and Mg/NH4/PO4: 1/1.2/1.2), 96.6% of ammonium was removed and MAP provided additional COD and turbidity treatment. Consequently, the combined system of MBR and MAP precipitation could be used as an appropriate post treatment option for the anaerobically treated medium-age landfill leachate. © 2009 American Institute of Chemical Engineers Environ Prog, 2010 [source] Organic carbon and nitrogen removal in anoxic/oxic-membrane bioreactor treating high-strength wastewaterENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2009Zhimin Fu Abstract The performance of an anoxic/oxic membrane bioreactor system for the simultaneous removal of nitrogen and chemical oxygen demand (COD) was investigated. This process removed up to 87% of total nitrogen (TN) and 94% of COD, with the influent concentrations of 200 mg NH4+ -N/L and 4000 mg COD/L and a recycle ratio (R) of 200%. Biological assimilation and simultaneous nitrification and denitrification (SND) were considered on nitrogen removal process. The TN removal efficiency was above 87.5%, while the nitrogen being removed through SND was above 75.5% and nitrogen assimilated into the biomass was below 24.5%, with influent concentration below 200 mg NH4+ -N/L. Increasing the influent concentration to 400 mg NH4+ -N/L, TN removal efficiency decreased significantly to 37.5%, of which 49.5% was provided by microorganism growth. Batch experiments provided evidence for the phenomena of SND. Furthermore, the SND removal efficiency increased gradually from 26.8 to 90.0%. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source] Ni2+ removal from aqueous solutions using conditioned clinoptilolites: Kinetic and isotherm studiesENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2009Semra Çoruh Abstract The aim of this study is to investigate the effects of conditioning with NaCl and HCl solutions on removal of Ni2+ ions from aqueous solutions using natural clinoptilolite. Batch studies were performed to evaluate the effects of various parameters such as chemically conditioning, adsorbent amount, contact time, initial pH of the solution, mixing temperature, and initial metal ions. The results clearly showed that the conditioning improved both the exchange capacity and the removal efficiency. Langmuir, Freundlich, Temkin, and Dubinin-Kaganer-Radushkevich (DKR) isotherm models were adopted to describe the adsorption isotherms. Adsorption isotherms of Ni2+ ions could be best modeled by Langmuir equation. Three simplified models including pseudo-second-order, intraparticle diffusion and Elovich were used to test the adsorption kinetics. These results indicate a significant potential for the natural and conditioned clinoptilolites as an adsorbent/ion-exchange material for heavy metal removal. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source] Cushioning the pressure vibration of a zeolite concentrator system using a decoupled balancing duct systemENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2007Feng-Tang Chang Abstract A honeycomb Zeolite Rotor Concentrator (HZRC) is the main air pollution control device utilized by many semiconductor and optoelectronics manufacturers. Various plant exhaust streams are collected and then transferred to the HZRC for decontamination. In a conventional HZRC, the exhaust fan movement and the switching between different air ducts can cause significant duct pressure variations resulting in production interruption. The minimization of pressure fluctuations to ensure continuous operation of production lines while maintaining a high volatile organic compounds (VOCs) removal efficiency is essential for exhaust treatment in these high technology manufactures. The article introduces a decoupled balancing duct system (DBDS) for controlling the airflows to achieve a balanced pressure in the HZRC system by adding a flow rate control device to the VOCs loaded stream bypass duct of a conventional system. Performance comparisons of HZRC with DBDS and other air flow control systems used by the wafer manufacturers in Hsinchu Science Park, Taiwan are presented. DBDS system had been proved effectively to stabilize the pressure in the airflow ducts, and thus avoided pressure fluctuations; it helped to achieve a high VOCs removal efficiency while ensuring the stability of the HZRC. © 2007 American Institute of Chemical Engineers Environ Prog, 2007 [source] Photocatalytic degradation of organic dyes in the presence of titanium dioxide under UV and solar light: Effect of operational parametersENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2005Feryal Akbal The photocatalytic degradation of methylene blue and methyl orange have been studied in the presence of titanium dioxide powder illuminated with a 300-W UV lamp. The effect of hydrogen peroxide on the degradation process was also determined. It was found that the color removal efficiency was affected by the concentration of dye, amount of TiO2 added, and the pH of the solution. The degradation of dyes obeys first-order kinetics, with the apparent first-order rate constant increasing with decreasing dye concentration. The rate constants were evaluated as a function of the concentration of dye, amount of TiO2, and pH. © 2005 American Institute of Chemical Engineers Environ Prog, 2005 [source] Fate of air toxics and VOCs in the odor control scrubbers at the deer island treatment plantENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2000Thomas Myslinski Process off-gases at the Deer Island wastewater treatment plant in Boston are collected and treated and its stack emissions regulated for selected gases including volatile organic compounds (VOCs), which are monitored as nonmethane hydrocarbons (NMHC). The air treatment processes of countercurrent wet oxidation scrubbing and granulated activated carbon adsorption are available for emissions control at Deer Island. In addition, since the wastewater treatment process of biochemical oxidation is fully enclosed at the site, microbial destruction of VOCs is an intrinsic treatment process for organic gases. Surveyed results of wastewater research literature indicate that the use of scrubbers for the removal of VOCs is controversial, as the fate of volatile hydrocarbon molecules across odor control scrubbers is complex and not fully understood. Continuous emission monitoring tests across the Deer Island scrubbers have consistently shown a VOC removal efficiency in excess of 50%. The fate of the scrubber inlet VOCs at Deer Island was researched as part of a plant-wide, on-going VOC study. Removal efficiencies across the pure oxygen bioreactors were also investigated. Preliminary results of this study indicate chemical reactions involving VOCs in odor control scrubbers partially oxidize and chlorinate derivatives possibly destroying a fraction of the compounds by complete oxidation. In addition, VOC reduction across the enclosed aerobic bioreactors was found to be significant. This article represents the opinions and(legal) conclusions of the authors and not necessarily those of the MWRA. [source] Measurement of Henry's law constant for methyl tert -butyl ether using solid-phase microextractionENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2001Britta G. Bierwagen Abstract Increasing groundwater contamination with methyl tert -butyl ether (MTBE) requires more efficient remediation technologies. Accurate measurement of MTBE's air,water partitioning coefficient (Henry's law constant, H) is important for the design and optimization of removal efficiency for many treatment systems as well as for predicting its fate and transport. Previously published data for MTBE appear to have some unusual nonlinearity at lower temperatures (15,30°C), and a wide range of values exists for dimensionless H at 25°C, from 0.0216 to 0.1226 in the published literature. We measured H for MTBE using headspace solid-phase microextraction (SPME) and a static method that considers equilibrium partitioning in a closed system, for temperatures between 15 and 40°C. To validate our methods, we measured H for benzene, toluene, and trichloroethylene and compared our results to previously published values, with excellent agreement. The Arrhenius plot for MTBE indicates that ln(HMBTE) = 6.85,2,900 T,1, with T in K. At 25°C, HMBTE = 0.0555 ± 0.0122. [source] | ||||||||||||||||||||||