Role of Bioflocculation on Chemical Oxygen Demand Removal in Solids Contact Chamber of Trickling Filter/Solids Contact Process

The trickling filter/solids contact (TF/SC) process was developed in the late 1970s to improve the quality of the final effluent from existing trickling filter plants, to be able to meet stricter Environmental Protection Agency effluent requirements. Although this process has successfully achieved this objective, it is still not completely understood, there is limited information regarding the flocculation phenomena occurring in the solids contact chamber (SCC), and no information could be found on the relationship between flocculation and organic matter removal kinetics. To better understand the kinetics of biological flocculation in a continuous flow SCC, a long-term experimental program was conducted using a TF/SC pilot plant constructed at the Marrero, La., wastewater treatment plant. This program started in January 1998 and has continued through date. The present article will focus on two major areas: (1) the kinetics of bioflocculation in the SCC; and (2) effect of bioflocculation on chemical oxygen demand (COD) removal. Analysis of the wastewater composition revealed that, on the average, only 18.7% of the total COD in the SCC influent is truly dissolved. Therefore, most of the total COD removal observed in the SCC must be due to a physical process, such as flocculation. The experimental data confirmed that flocculation of the particulate COD contained in the trickling filter effluent explains the high total COD removal observed at the SCC. Both total and colloidal COD removals are well explained by the first-order flocculation model.     

New Process Design Procedure for Dealing with Variable Trickling Filter Effluent Suspended Solids

Based on a survey which showed that seven of eight conventional trickling filter (CTF) plants exceeded the U.S. Environmental Protection Agency secondary treatment regulatory requirements, a new design procedure is proposed. It recognizes that bioflocculation within CTFs is poor and that most of the effluent violations seen in the survey could be related directly or indirectly to the level of effluent suspended solids. In past practice, process design focus has been on soluble or settled effluent biochemical oxygen demand (BOD5) rather than the effluent suspended solids. The principal focus in CTF process design should be on predicting effluent suspended solids (SS) after secondary clarification, rather than effluent carbonaceous BOD5. If the total organic loading (TOL) is set in the proper range, the effluent carbonaceous BOD5 is primarily determined by the effluent SS. A new design procedure has been developed that identifies the highest TOL that can be sustained without posing a constraint on effluent SS due to effluent CBOD5 limitations. This is coupled with the incorporation of additional design features that can control effluent SS.     

Biodegradation of 1,4-Dioxane Using Trickling Filter

The ability of a laboratory-scale trickling filter to biodegrade cyclic ethers was investigated and a simple kinetic model was developed to predict ether biodegradation. The trickling filter received a feed solution designed to mimic ether concentrations typically encountered in contaminated groundwater. The reactor was operated for approximately 1 year and was capable of biodegrading 93–97% of 1,4-dioxane at various loading rates in the obligate presence of tetrahydrofuran (THF) as the growth substrate. A simple tanks-in-series hydraulic model combined with a kinetic model that incorporated cometabolism was utilized to simulate removal of THF and 1,4-dioxane. Model simulations of THF removal were satisfactory for all loading rates analyzed. However, the model somewhat over predicted 1,4-dioxane removal. This research demonstrates the ability to treat groundwater contaminated with low concentrations of ethers in attached growth reactors.     

Trickling Filter Nitrification Performance Characteristics and Potential of a Full-Scale Municipal Wastewater Treatment Facility

The trickling filter solids contact water pollution control facility for the city of Ames, Iowa has successfully nitrified wastewater with trickling filters for the past decade. Both first stage, carbonaceous biochemical oxygen demand removing trickling filters (TFs) and second stage, nitrifying TFs (NTFs) remove significant quantities of ammonia from the wastewater. Based on operating data from January 1999 through December 2001, the average specific ammonia removal rate for the TFs was 1.5×10?4?kg?N/(d?m2). Most probable number testing confirmed the presence of nitrifiers in the top media layer of both stages of trickling filters. An experiment was performed whereby flows to the TFs and NTFs were varied to test ammonia removal capabilities of the facility. During the experiment, the TFs removed an average of 2.4×10?4?kg?N/(d?m2) and the NTFs removed an average of 1.5×10?5?kg?N/(d?m2) due to low loading. Data collected during the study varied with operating conditions. It was compared to and used to calibrate NTF models. An empirical design model poorly fit the data, and a theoretically based model could not be calibrated well with apparent ammonia removal rates. A best-fit equation, dependent on hydraulic loading and influent ammonia concentration (adjusted for recirculation), was regressed directly to the data and is useful for describing nitrification in the Ames WPCF TFs.     

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.     

Model Sensitivity Analysis for Biotrickling Filter Treatment of Graywater Simulant and Waste Gas. II

A detailed sensitivity analysis was conducted to identify key parameters for a biotrickling filter simultaneously treating graywater and waste gas containing ammonia and hydrogen sulfide contaminants. Sampling-based approaches were applied to quantitatively assess the sensitivity of both design and intrinsic model parameters. Specifically, the sensitivity of contaminant removal rates under system conditions was investigated. Results suggested that contaminant removal rates can be substantially improved by increasing the fraction of wetted area in a biotrickling filter. Although recirculation flow rate is insensitive when considering liquid contaminant removal, increasing this parameter improves gas removal efficiency and also increases wetted area within the biotrickling filter. Reactor performance can also be improved by increasing gas and liquid residence times. Contaminant diffusivity through the biofilm is an important parameter and should be accurately assessed. This study differentiated key from insignificant biotrickling filter reactor design parameters for the biotrickling filter and provides guidance for similar research applications.     

Kinetics of Phosphorus Release and Uptake in a Membrane-Assisted Biological Phosphorus Removal Process

A long-term comparative study on the kinetics of enhanced biological phosphorus removal (EBPR) was carried out in pilot scale membrane-assisted and conventional biological phosphorus removal processes, by monitoring system performance, phosphorus mass balances, and maximum specific rates in off-line batch tests. The two systems exhibited similar performance in the removal of soluble phosphorus (P) from the influent wastewater, in the specific P release observed in the anaerobic zone, and in the maximum specific P release and volatile fatty acid (VFA) uptake rates. However, when the VFA in the influent was limiting, the conventional EBPR (CEBPR) process performed significantly better than the membrane (MEBPR) counterpart, and this behavior was also reflected in the kinetics of P release. Denitrifying dephosphatation was observed to be significant in both processes during periods of satisfactory P removal. When the aerobic recycle ratio was reduced to a minimum level, the anoxic P uptake activity in the CEBPR sludge was lower than that of the MEBPR sludge. Finally, the biomass decay rates of the two sludge types were estimated to be comparable, with significant reduction of the decay under unaerated conditions.     

Use of Total Suspended Solids in Characterizing the Impact of Spent Filter Backwash Recycling

Recycling of spent filter backwash water is a widely practiced residual management approach throughout the United States for drinking water utilities. The United States Environmental Protection Agency (USEPA), under the 1996 Safe Drinking Water Act Amendments, has recently proposed regulations governing the recycle of this waste stream. Considering this new regulation, a comprehensive study was conducted by researchers at Colorado State University, and a suspended solids mass balance model was developed to characterize the impact of backwash water recycling on the overall treatment process. Online particle count data indicated that certain recycle practices could impact the overall treatment process. Data from pilot-scale experiments showed that total suspended solids (TSS) is a useful tool for characterizing the impacts of the backwash recycle processes. TSS can be used to assess whether solids loading or suboptimal coagulation conditions are the cause of recycle related issues. For the study described here, filter breakthrough occurred at about the same total influent solids load, regardless of the manner in which backwash recycling was performed, indicating that recycle of backwash solids did not impact the overall treatment process.     

Treatment of High-Strength Pharmaceutical Wastewater and Removal of Antibiotics in Anaerobic and Aerobic Biological Treatment Processes

Anaerobic and aerobic treatment of high-strength pharmaceutical wastewater was evaluated in this study. A batch test was performed to study the biodegradability of the wastewater, and the result indicated that a combination anaerobic-aerobic treatment system was effective in removing organic matter from the high-strength pharmaceutical wastewater. Based on the batch test, a pilot-scale system composed of an anaerobic baffled reactor followed by a biofilm airlift suspension reactor was designed. At a stable operational period, effluent chemical oxygen demand (COD) from the anaerobic baffled reactor ranged from 1,432 to 2,397?mg/L at a hydraulic retention time (HRT) of 1.25 day, and 979 to 1,749?mg/L at an HRT of 2.5 day, respectively, when influent COD ranged from 9,736 to 19,862?mg/L. As a result, effluent COD of the biofilm airlift suspension reactor varied between 256 and 355?mg/L at HRTs of from 5.0 to 12.5 h. The antibiotics ampicillin and aureomycin, with influent concentrations of 3.2 and 1.0?mg/L, respectively, could be partially degraded in the anaerobic baffled reactor: ampicillin and aureomycin removal efficiencies were 16.4 and 25.9% with an HRT of 1.25 day, and 42.1 and 31.3% with HRT of 2.5 day, respectively. Although effective in COD removal, the biofilm airlift suspension reactor did not display significant antibiotic removal, and the removal efficiencies of the two antibiotics were less than 10%.     

The Influence of Surface Chemistry on the Rheology and Flow of Flocculated Particulate Suspensions

Abstract

The role of the surface chemistry of particles in controlling the rheology of flocculated particulate suspensions is discussed. The case is developed for the measurement of the shear yield stress of a suspension of alumina particles and a theoretical interpretation of the yield stress is presented which is able to describe the effect of particle size distribution, solid loading, pH and hence, electrokinetics of the suspension. Scaling of the data to the maximum yield stress at a given volume fraction provides a means of removing particle size and volume fraction related effects and gives information as to the mode of failure in yielding of suspensions and the mode of action of molecular additives.     

Influence of COD:N:P Ratio on Nitrogen and Phosphorus Removal in Fixed-Bed Filter

This study examined the effects of COD:N:P ratio on nitrogen and phosphorus removal in a single upflow fixed-bed filter provided with anaerobic, anoxic, and aerobic conditions through effluent and sludge recirculation and diffused air aeration. A high-strength wastewater mainly made of peptone, ammonium chloride, monopotassium phosphate, and sodium bicarbonate with varying COD, N, and P concentrations (COD: 2,500–6,000, N: 25–100, and P: 20–50 mg/L) was used as a substrate feed. Sodium acetate provided about 1,500 mg/L of the wastewater COD while the remainder was provided by glucose and peptone. A series of orthogonal tests using three factors, namely, COD, N, and P concentrations, at three different concentration levels were carried out. The experimental results obtained revealed that phosphorus removal efficiency was affected more by its own concentration than that of COD and N concentrations; while nitrogen removal efficiency was unaffected by different phosphorus concentrations. At a COD:N:P ratio of 300:5:1, both nitrogen and phosphorus were effectively removed using the filter, with removal efficiencies at 87 and 76%, respectively, under volumetric loadings of 0.1?kg?N/m3?d and 0.02?kg?P/m3?d.     

Influence of COD/N Ratios on Simultaneous Removal of C and N Compounds in Biological Wastewater Treatment in Sequencing Fed-Batch Reactor and Kinetic Analysis

The impact of chemical oxygen demand/nitrogen (COD/N) values of feed wastewater on COD and nitrogen removal and biomass growth in a sequencing fed-batch reactor (SFBR) operation was investigated. The multiple microbial reactions involved in the simultaneous removal process of carbonaceous and nitrogenous components in the SFBR system were analyzed using a set of kinetics mathematical model. The results indicate that COD/N ratios strongly influence COD and total nitrogen removal efficiency. The COD removal efficiency per gram microorganism changed from 64.3 to 78.1% at COD/N = 11.9–2.5. The total nitrogen removal efficiency changed from 10.3 to 34.2% at COD/N = 2.5–11.9. However, variable COD/N ratios of feed wastewater are not marked for biomass growth rate.     

Effect of Carbon Source on Biological Nitrogen and Phosphorus Removal in an Anaerobic-Anoxic-Oxic (A2O) Process

The effects of acetate and propionate on biological nitrogen and phosphorus removal in a plug-flow A2O process were evaluated in this study. The wastewater quality indexes and operation parameters were the same when different carbon sources were used. However, we observed no obvious effect of carbon source on nitrogen removal. Denitrifying phosphorus removal was found to play an important role in simultaneous nitrogen and phosphorus removal in anoxic reactors because almost the entire carbon source was used for polyhydroxyalkanoate (PHA) synthesis in anaerobic reactors, and there was no external carbon source left for heterotrophic denitrification. Propionate was found to be a more effective and energy-saving carbon source for biological nitrogen and phosphorus removal. In addition, the variations in the metabolic chemicals, such as phosphorus, PHA, glycogen, and oxygen, were lower when propionate was used than when acetate was used.     

高铁酸盐对焦化废水中COD、NH_3-N的处理效果的研究

高铁酸盐加入量对COD和NH3-N去除效果的实验结果表明:在常温下,当高铁酸盐的加入量为14mg/L时,焦化废水中COD的质量浓度由320mg/L下降到88mg/L,去除率达72.5%;NH3-N质量浓度由68mg/L下降到14.9mg/L,去除率达78.1%。     

水力旋流分离技术在瓦斯泥脱锌工程中的应用与研究

利用水力旋流技术对瓦斯泥进行湿法脱锌,是现有瓦斯泥脱锌技术中设备最简单、占地面积最小、运行费用最低的技术.简要介绍了宝钢利用水力旋流技术进行1BF瓦斯泥脱锌的科研及工程实施的情况,在保证脱锌率为70%时,回收率可达60%以上.着重从工程设计角度介绍实施瓦斯泥脱锌工程需解决的一系列关键问题,并对采用水力旋流分离技术实施高炉瓦斯泥脱锌工程的投入与产出进行了初步分析.     

浅谈冷板厂废乳化液、酸性废水处理工艺的改进

介绍了废乳化液、酸性废水的产生过程及用NaOH破乳处理废乳化液，并用破乳产生的废碱水中的酸性废水中的新工艺，对原设计与现在在处理工艺进行了对比。     

卡尔多炉处理锌氧浸渣及中浸渣工艺的研究

介绍了卡尔多炉搭配处理锌氧浸渣及中浸渣生产工艺,利用氧浸渣中硫代煤或焦,可自热闪速熔炼,能耗低,熔炼烟气SO2浓度可直接制酸,由于只有氧化阶段,没有还原阶段,制酸烟气SO2浓度是稳定的,不需SO2部分冷凝,制酸是连续的,为锌浸出渣的处理提供了一种节能环保的清洁生产工艺。     

稀土在国内铜及铜合金加工中的作用

从热力学的角度阐述了稀土在铜中的反应,综述了国内对稀土在铜及铜合金加工中的应用.适量的稀土在铜和铜合金熔铸中主要起净化作用、变质作用和合金化作用,可以提高热处理温度,增强塑性加工的效果.     

The Role of Fairness in Mediating the Effects of Voice and Justification on Stress and Other Outcomes in a Climate of Organizational Change.

Organizational change can become a source of resistance and stress if it is implemented without attention to the needs of organizational members. The participants in the present study (604 government employees) work in a climate of ongoing change and, thus, are at particular risk for experiencing high levels of stress and other deleterious consequences. This study examines and finds support for the central role played by procedural and distributive fairness in mediating the effects of change justification and voice on the extent to which employees experience stress, which, in turn, predicts their levels of work effort, intention to leave, and a host of physiological and affective symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of eye movement desensitization and reprocessing (EMDR) therapy on posttraumatic stress disorder in survivors of the 1999 Marmara, Turkey, earthquake.

As part of a program of response to the 1999 Marmara, Turkey, earthquake, an estimated 1,500 trauma victims with posttraumatic stress disorder (PTSD) symptoms were treated in tent cities with eye movement desensitization and reprocessing (EMDR). A field study evaluating a representative group of 41 participants with diagnosed PTSD indicated that a mean of five 90-minute sessions was sufficient to eliminate symptoms in 92.7% of those treated, with reduction in symptoms in the remaining participants. Significant reductions occurred between the pre and posttreatment PTSD Symptom Scale Self-Report version (PSS-SR) total scores and all subscales. These gains were maintained at 6-month follow-up. The same pattern of recovery was observed regardless of the use or nonuse of psychotropic medication at the time of intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)