Model Development for Biotrickling Filter Treatment of Graywater Simulant and Waste Gas. I

A mathematical model was developed to simulate a biotrickling filter capable of simultaneous treatment of graywater simulant and waste gas contaminated with ammonia and hydrogen sulfide. The model accounts for mass transfer of gas phase contaminants into the liquid phase and subsequent transfer into a biofilm where microbial conversions of contaminants are modeled by Monod kinetics. A set of laboratory experiments was conducted to estimate parameters for each of the two components of the model. Separation of parameter estimation both decreased the total number of parameters estimated simultaneously and ensured that each component of the system was adequately represented. Process performance, as predicted by the calibrated model, was compared to results from the operation of bench-scale reactors. The model was capable of accurately predicting contaminant removal and thus was used to make a preliminary assessment on the feasibility of a proposed dual treatment biotrickling filter system. This model is a valuable tool not only to describe and predict process performance, but also to identify relevant design parameters.     

Hydrodynamic Characteristics in Biotrickling Filters as Affected by Packing Material and Hydraulic Loading Rate

Hydrodynamics in biotrickling filters can be strongly influenced by packing material geometry and hydraulic loading rate. While it is generally accepted that increasing wetted area in a biotrickling filter can improve process performance, additional research on synthetic packing materials and parameters that improve hydrodynamics, resulting in increased wetted area, is desirable. For this research, a series of tracer tests was conducted to compare hydrodynamics in bench scale biotrickling filters with three different packing materials under three different flow rates. Results suggest that of the three packing materials, the material with the highest specific surface area resulted in channeling and excessive formation of stagnant zones within the biotrickling filters. Liquid distribution through the biotrickling filters substantially improved at a hydraulic loading rate of 1.9?m/hr for all packing materials, but based on these experiments, improvements were minimal when the hydraulic loading rate was increased further. The presence of a biofilm increased mean residence time in biotrickling filters and the factor by which the increase was observed decreased with increasing hydraulic loading rate.     

Effect of Biotrickling Filter Operating Parameters on Chlorobenzenes Degradation

In this paper the effect of operating parameters on biotrickling filter performance degrading chlorobenzene and o-dichlorobenzene mixture were studied. The large laboratory scale biofilter, total volume 40 L, filled with inert packing material was used. The biomass adaptation and cultivation were performed in a batch fermentor and were used to inoculate the biotrickling filter. After a starting period, the influence of the substrate load increase, liquid recirculation flow rate, and empty bed retention time on elimination capacity and removal efficiency were found. The most important recirculation liquid parameters were analyzed every day, that is: concentration of metabolites, dissolved organic carbon, nitrate, chloride, and biomass. A good correlation was found between intermediate concentration and the removal efficiency of the biotrickling filter. The measurements of the absorbance, very easy and rapid, can be used as a control parameter of the biofiltration efficiency.     

Behavior of Field-Scale Biotrickling Filter under Nonsteady State Conditions

The performance of a field-scale biotrickling filter was investigated for the treatment of styrene vapors released from a bathtub manufacturing process. The two-stage biotrickling filter was operated in series with an average gas flow rate of 350 m3?h?1 corresponding to an overall empty bed gas contact time of 84 s. Daily average values of styrene removal efficiency varied from 40 to 90% with inlet concentrations ranging between 0.4 and 1.7 g?m?3. System performance was not significantly affected by changes in temperature and was moderately susceptible to 3-day starvation or complete system shutdown. After 7 months of styrene treatment, toluene contaminated air was fed to the system and experiments were performed in which styrene and toluene were fed alternately at 3-h intervals. While styrene elimination remained unchanged over the cycles, the elimination capacity of toluene increased with the number of cycles, indicating some adaptation of the process culture to the new contaminant. Overall, the results suggest that biotrickling filters for air pollution control can be successful even under greatly varying operating conditions.     

Treatment of Styrene-Contaminated Airstream in Biotrickling Filter Packed with Slags

This paper reports the result of studies using a biotrickling filter with blast-furnace slag packings (sizes = 2–4 cm and specific surface area = 120 m2∕m3) for treatment of styrene in an airstream. The effects of volumetric styrene loading L, superficial gas velocity U0 and liquid recirculation rate VL on the styrene elimination capacity K, and the removal efficiency K∕L were tested. Variations of styrene concentration with packing height as well as rates of nutrient utilization were also tested. The results show that for L< 30 g∕m3?h, K∕L was nearly independent of U0 in the range of 29–67 m∕h and was independent of VL in the range of 3.84–9.60 m∕h. In this range, the rate of styrene removal was both reaction and diffusion limited and the reaction was of zero-order kinetics. For higher loadings, K∕L decreased with increasing U0 and increased with increasing VL and the system approached the condition of reaction limitation.     

Simulation of gas dispersion in a metallurgical bubble reactor

A better understanding of complex process phenomena and engineering of gas dispersion techniques in metallurgical processes can be obtained with the method of computer aided process simulation. Main target of this investigation is to analyze the influence of operational and design parameters such as gas flow rate, reactor diameter, liquid height, or injector size, number and location on the system quantities like mixing power, hold up or degassing rates. The bath aspect ratio should be between 0.8 and 1.2 if the desorption at the bath surface is playing an important role. An optimization of the injected gas quantitiy can be achieved with increased injector cross-section area (bigger bubbles ascending faster and increasing the mixing power) or higher aspect ratios (longer bubble residence times in the reactor). Dead zones can be avoided by distribution of gas through several injectors positioned symmetrically, increasing total mixing power and specific interface area in the system.     

Modeling Urban Storm-Water Quality Treatment: Model Development and Application to a Surface Sand Filter

A mathematical and statistical model for simulating contaminant removal from a surface sand filter is reported. The model was based on a mass balance equation and an advection-dispersion transport model. The unknown parameters of the model were the deposition rate and the hydrodynamic dispersion. Changes in space were allowed within the filter media depth and time variability of flow and influent contaminant concentration were taken into account. System field monitoring was performed between 2004 and 2006. A total of 17 storms were selected for the study. Runoff constituent analyses included: total suspended solids, total petroleum hydrocarbons-diesel range hydrocarbons, and zinc. The objective was to explore the capabilities of a two parameter model for predicting effluent contaminant concentrations. Optimized model parameter values were calculated on a storm by storm basis. Thereafter, a gamma distribution was fitted to the optimized values. A Monte Carlo simulation was performed to explore the predicting capabilities of the model by using two storms left for validation. Results of the validation phase show an acceptable performance of the model since, in general, estimated effluent concentrations fell within the uncertainty limits.     

Conversion of Full-Scale Wet Scrubbers to Biotrickling Filters for H2S Control at Publicly Owned Treatment Works

Until recently, biological treatment of odors in biofilters or biotrickling filters was thought to require a longer gas contact time than chemical scrubbing, hence bioreactors for air treatment required a larger footprint. This paper discusses the conversion of chemical scrubbers to biological trickling filters. Initially, research was conducted with a laboratory-scale biotrickling filter. An effective open-pore polyurethane packing material was identified and H2S biotreatment performance was quantified. Key technical issues in determining the general suitability of converting wet scrubbers to biotrickling filters were identified, and a generic ten-step conversion procedure was developed. Following the laboratory research, five full-scale chemical scrubbers treating odorous air at the Sanitation District of Orange County, Calif., were converted to biotrickling filters. The original airflow rate was maintained, resulting in a gas contact time as low as 1.6–3.1?s. The converted biotrickling filters demonstrated an excellent capability for treating high H2S concentrations to concentrations below regulatory limits. This study shows outstanding potential for converting chemical scrubbers to biotrickling filters at publicly owned treatment works.     

Interaction of Soil Air Permeability and Soil Vapor Extraction

A new theoretical model to analyze the measurements obtained from a typical soil column venting experiment is proposed. The principles of mass transfer, Darcy's law, and air compressibility in the form of pressure-volume relationships were coupled to calculate the contaminant concentration in the gas phase (air), and the rate of contaminant removal. The proposed model relates soil air permeability with the contaminant removal and is capable of calculating the variation of soil air permeability with time during the venting process. The contaminated sand sample was idealized as a system of straight capillary tubes in the direction of flow, lined by the liquid contaminant. A closed-form solution for radial diffusion of the contaminants in a cylinder, coupled with axial advection of air, was used to model contaminant removal. The results from the mass transfer model were then used to trace the change of soil air permeability with time. The model also uses, as an alternative approach, a modified form of Darcy's law for compressible flow.     

钢中夹杂物去除技术的进展

钢中夹杂物去除的主要环节为夹杂物的长大、上浮和分离。钢中夹杂物去除技术的主要进展有:气体搅拌-钢包吹氩、中间包气幕挡墙和RH-NK-RERM法;电磁净化-钢包电磁搅拌、中间包离心分离和结晶器电磁制动;渣洗技术;过滤器技术。文中分析了各种夹杂物去除技术的冶金功能,将不同夹杂物去除技术进行合理组合,实现多功能精炼,可取得最佳冶金效果。     

Factors Affecting Effectiveness and Efficiency of DNAPL Destruction Using Potassium Permanganate and Catalyzed Hydrogen Peroxide

This paper describes laboratory studies conducted to evaluate the impact of varying environmental conditions (dense nonaqueous phase liquid (DNAPL) type and mass, and properties of the subsurface porous media) and design features (oxidant type and load) on the effectiveness and efficiency of in situ chemical oxidation (ISCO) for destruction of DNAPL contaminants. Porous media in 160?mL zero-headspace reactors were employed to examine the destruction of trichloroethylene and perchloroethylene by the oxidants potassium permanganate and catalyzed hydrogen peroxide. Measures of oxidation effectiveness and efficiency include (1) media demand (mg-oxidant/kg-porous media), (2) oxidant demand (mol-oxidant/mol-DNAPL), (3) reaction rate constants for oxidant and DNAPL depletion (min?1), (4) the percent (%) DNAPL destroyed, and (5) the relative treatment efficiency, i.e., the rate of oxidant depletion versus rate of DNAPL destruction. While an obvious goal of ISCO for DNAPL treatment is high effectiveness (i.e., extensive contaminant destruction), it is also important to focus on oxidation efficiency, or to what extent the oxidant is utilized for contaminant destruction instead of competing side reactions, for improved cost effectiveness and/or treatment times. Results indicate that DNAPL contaminants can be treated both effectively and efficiently under many environmental and design conditions. In some cases, DNAPL treatment was more effective and efficient than dissolved/sorbed phase treatment. In these experiments, permanganate was a more effective oxidant, however catalyzed hydrogen peroxide treated contaminants more efficiently (e.g., less oxidant required per mass contaminant treated). Results also indicate that oxidation treatment goals can be dictated by environmental conditions, and that specific treatment goals can dictate remediation design parameters (e.g., faster contaminant destruction was realized in catalyzed hydrogen peroxide systems, whereas greater contaminant destruction occurred in permanganate systems).     

YT膜分离技术在密闭矿热炉高温荒煤气除尘的应用

密闭矿热炉在铁合金冶炼过程中产生的高温荒煤气必须经过净化除尘后才能作后续利用,现有净化除尘方式不能满足高温荒煤气净化和高效利用的要求。介绍了YT分离技术在密闭矿热炉荒煤气除尘的应用,并与传统布袋除尘进行了对比。实践证明,采用YT高温荒煤气除尘工艺可实现经济高温、高精度连续稳定地除尘,净化后的粉尘含量完全满足国家标准要求,系统同时具有工艺流程短、占地面积小的优点。     

Practical Modeling of SVE Performance at a Jet-Fuel Spill Site

A coupled flow and transport model (VENT3D) was used to simulate the performance of soil vapor extraction at a jet-fuel (JP-4) contaminated site. The contaminant mixture was approximated with 10 surrogate components categorized by carbon number class. The contaminant was distributed heterogeneously throughout the soil. The initial total contaminant mass was the only parameter that was adjusted, and it was fit to the observed removal during the pilot tests. The predicted total mass removal using the most general approach matched the observed hydrocarbon mass removal within ±4%. The effects of the following selected simplifying assumptions were examined with the model: (1) uniform contaminant distribution; (2) 2D horizontal flow; and (3) single equivalent contaminant. The uniform soil contamination distribution and the horizontal flow assumptions yielded similar results—both estimated removal rates that were initially higher by 30% and eventually overpredicted the total removal by 10%. The equivalent single-component approximation underpredicted the removal by as much as 50% during the first half of the operation and then overpredicted the removal, ultimately overpredicting the total removal by <10%.     

两相雾化除尘参数对热轧机组除尘效率的影响

为了提高热轧机组除尘效率,降低热轧现场粉尘污染,研究了两相雾化除尘技术的气压、液压对雾场参数的影响.首先,在理论分析的基础上进行雾场的数值模拟;其次,搭建试验平台进行喷雾试验,验证了所建模型的准确性.分析了不同气、液两相的压力组合对雾场参数的影响,着重分析了对雾滴粒径的影响.结果 表明,随着气相压力和液相压力的增大,喷...     

Adjoint Sensitivity Analysis of Contaminant Concentrations in Water Distribution Systems

Sensitivity analysis is used to determine how a system state or a model output changes due to a change in the value of a system parameter or a model input. We present the adjoint approach for determining the sensitivity of the concentration of a contaminant in a water distribution system to a change in a system parameter such as the location of the source of contamination, the reaction rate of the contaminant, and others. With the adjoint method, the sensitivity of the model output to any number of parameters can be obtained with one simulation of the adjoint model. If the number of parameters of interest exceeds the number of model outputs for which the sensitivity is desired, the adjoint method is more efficient than traditional direct methods of calculating sensitivities. We develop the adjoint equations for water quality in a water distribution system, verify the adjoint-based sensitivity equation using an analytical example, and demonstrate the numerical calculation of adjoint sensitivities using EPANET.     

Modeling an Airlift Bioscrubber for Removal of Airphase BTEX

Biological treatment of airstreams has been shown to be useful when the airstreams are contaminated with low concentrations of volatile organic chemicals. One type of airphase biological reactor, the bioscrubber, has operational advantages over the two other types of airphase bioreactors, biofilters, and biotrickling filters. The airlift bioscrubber is a new bioscrubber configuration that offers some advantages over the conventional two-stage bioscrubber. In this work, a practical mathematical model was developed for the airlift bioscrubber for the removal of aromatic hydrocarbons, benzene, toluene, and ethylbenzene. The model input parameters were defined, and typical values were determined from the published literature. A sensitivity analysis was conducted on the mathematical model to define the operating range of the airlift bioscrubber for the removal of the benzene, toluene, and ethylene compounds. In addition, the sensitivity analysis results were used to define the range of testing that is appropriate for laboratory validation and calibration of the proposed mathematical model.     

Modelling zinc heap bioleaching

A comprehensive modelling study of the HydroZinc™ heap bioleach process, using the HeapSim modelling tool, is described. The model was calibrated on the basis of a small number of column leach experiments and compared against pilot heap test results. The model calibration thus confirmed, a detailed sensitivity study was conducted in order to establish the key parameters that determine the overall rate of Zn extraction. In the present case these were found to be oxygen gas–liquid mass transfer, various factors affecting the delivery of acid into the heap, and factors affecting the temperature distribution within the heap. A set of improved design parameters are proposed that would almost double the zinc conversion rate measured in the pilot plant – from 83% in 740 days to 78% in 383 days – and increase zinc production rate from 1.77 to 4.35 kg/m²/day. However, this improvement must be evaluated in the context of various implications for the downstream process.     

质子交换膜燃料电池用膜增湿器仿真分析

膜增湿器为质子交换膜燃料电池水热管理系统的关键部件,本研究考虑与燃料电池工作条件的强耦合,系统地进行了膜增湿器运行参数和几何参数的敏感性仿真分析。基于Matlab/Simulink建立了膜增湿器稳态数学模型,分析了湿侧和干侧的入口质量流量、温度和压力以及膜厚度和面积对膜增湿器传热量、水分传递量、干侧出口相对湿度和水分传递率的影响。研究表明:提高入口质量流量会提高传热量,并且能有效提高水分传递量,但会使水分传递率和出口相对湿度降低;干湿两侧温度的增加可以使膜中水的扩散系数和水传递量增加,但过高的温度会显著提高水蒸气饱和压力,降低水的活度,进而降低膜含水量,不利于水的传递;压力的变化对传热的影响很小,但总压的提高会使湿侧入口含湿量下降,水分传递量下降,但水分传递率升高;较大的膜面积以及较低的膜厚度能够提高膜水分传递量和水分传递率,可以有效地提高膜增湿器和燃料电池系统水热管理性能。      

正压高效气液分离器设计与应用

工业生产中,需要采用气液分离器对气液混合介质进行分离,以实现气液混合介质净化回收或无害化处理的目的。详细介绍了气液分离的工作原理及不同类型气液分离器的优缺点和正压高效气液分离器的结构设计方案、工作方式、参数选型,以及其分离特性。工程应用表明:正压高效气液分离器分离效率较高,处理能力大,设备占地面积小,安装维护方便,可进行推广应用。