Comparative Study of Two Bioassays for Applications in Influent Wastewater Toxicity Monitoring

Bioluminescent bacteria-based assays can be used for influent wastewater toxicity monitoring for biological wastewater treatment systems. The most thoroughly studied bioluminescent bacteria-based test is the Microtox? assay. However, the response to toxicants of Photobacterium phosphoreum, the marine bacterial strain used in this assay, is different from that of the activated sludge microorganisms. We developed a continuous influent wastewater monitoring system based on the bioluminescent bacterium Shk1, a genetically modified Pseudomonad isolated from the activated sludge in an industrial wastewater treatment plant. The Shk1 toxicity data were correlated with the Microtox? toxicity data for 79 organic compounds and the two toxicity assays were compared. The Shk1 assay is less sensitive than the Microtox? assay and could therefore be more suitable for influent wastewater toxicity monitoring.     

低浓度有机废水活性污泥处理实验技巧的研究

文章针对活性污泥法处理工业废水实验中废水的保质、性能预判等关键的步骤,在实验数据分散条件下,采用平均值为基础来进行定性数据分析。     

Computer Program Development for the Design of Integrated Fixed Film Activated Sludge Wastewater Treatment Processes

The Integrated Fixed Film Activated Sludge (IFAS) wastewater treatment systems are activated sludge biological nutrient removal processes that have been enhanced by the addition of biofilm support media into the aerobic zone of the system to obtain year round nitrification in activated sludge systems that otherwise could not support it. The objective of this study was to develop a computer package called “IFAS” that allows steady-state simulation of IFAS wastewater treatment processes based on the International Association Water Quality general model for activated sludge and empirical equations for chemical oxygen demand (COD) uptake and nitrification on integrated fixed film developed at Virginia Tech. The current version of the IFAS program supports only sponge-type media; however, the model could be modified for other media if the appropriate equations and required parameters values are known. Data obtained from IFAS sponge media pilot scale plants treating a weak municipal wastewater supplemented by sodium acetate, urea, sodium bicarbonate, and potassium phosphates and operated at different aerobic mean cells residence times were used to evaluate the model with parameter values for nitrification and COD uptake rates developed in batch studies. The model-generated ammonia and soluble COD profiles were insignificantly different statistically from the experimental data. The IFAS model satisfactorily predicts carbonaceous removal and nitrification, and has the potential to be a useful tool for scientists and engineers seeking to design and optimize either IFAS or conventional biological nutrient removal activated sludge systems.     

Comparison of Bacterial Bioluminescence with Activated Sludge Oxygen Uptake Rates during Zinc Toxic Shock Loads in a Wastewater Treatment System

The use of a bioengineered bioluminescent bacterium (Shk1) for monitoring zinc toxicity was evaluated with samples from a municipal activated sludge wastewater treatment plant and in a bench-scale activated sludge system. Bioluminescent measurements were compared with oxygen uptake rates of activated sludge samples. In batch experiments with activated sludge, the Zn EC50 for Shk1 bioluminescence was 16 mg/L, while the Zn EC50 for activated sludge OURs was approximately 58 mg/L. In the bench-scale system, the influent Zn concentrations tested were 50 and 200 mg/L in toxic shock loads of about 4 h duration. Soluble Zn transport through the influent, aeration basin, and clarifier was able to be monitored by the decrease in Shk1 bioluminescence. However, bioluminescence in samples from the aeration basin decreased faster than activated sludge specific oxygen uptake rates. Differences in responses of Shk1 and the activated sludge community may be due to differences in the assay conditions, the growth forms, physiology of the organisms, or previous cultivation conditions.     

Application of Two-Directional Time Series Models to Replace Missing Data

Missing data commonly exist in operational records of wastewater treatment plants, such as influent and effluent water quality data. To deal with missing data, time series models that characterize trend, lag, and seasonality may be applied. In this paper, two-time series model-based methods, i.e., the two-directional exponential smoothing (TES) and TES with white noise (TESWN) added methods, are developed to replace missing data. Comparisons with traditional missing-data-replacement methods are also evaluated in the context of predicting missing values from influent data and the subsequent effect when the resulting influent time series are used as an input to process simulation models. The TES method is shown to be most appropriate when the goal is to minimize the average error associated with the missing value. The TESWN method is shown to be better suited for characterizing the amount of uncertainty that may be associated with the missing values.     

Density and Activity Characterization of Activated Sludge Flocs

Activated sludge flocs are made up of a conglomerate of materials including microorganisms, exocellular polymers, inert particulates, slow and nonbiodegradable organic particles, and water. The goal of this study was to determine if inert/unbiodegradable aggregates had higher densities than active biomass. It was also desired to determine whether mixed liquor could be gravimetrically settled to differentially stratify flocs based on density and biological activity. In this manner, if activity stratification is possible, then less active biomass could be wasted preferentially during wastewater treatment operations (e.g., during daily wastage), thereby increasing the effective solids retention time and improving process performance. This paper reports the initial set of results, which focused on establishing density values of inert/unbiodegradable fractions of activated sludge floc, and the heterotrophic activity measurements of faster settling flocs compared to slower settling flocs. The results indicate that activated sludge from a local wastewater treatment plant had aggregate densities as low as 1.038?g/mL for slower settling floc particles and as high as 1.065?g/mL for faster settling floc particles. Primary effluent “inert+unbiodegradable particulate organic” fractions, which ultimately accumulate in mixed liquor and contribute to the inactive activated sludge floc fraction, had densities of approximately 1.24?g/mL. Mixed liquor that was digested in excess of 90 days to reduce any degradable organics revealed aggregate densities between 1.11 and 1.12?g/mL. Settling column experiments indicated that floc particles settled at rates ranging from less than 5?m/h to greater than 30?m/h. Specific oxygen uptake rates signified that the heterotrophic activity was homogeneous across all settling velocities except those flocs with a settling velocity of less than 5?m/h. These flocs exhibited a specific oxygen uptake rate of between 31 and 110% higher than the remaining floc. Determination of the mass fraction of these flocs indicates that they account for approximately 2% of the overall biomass. This low fraction limits the usefulness of differentially settling unaltered waste activated sludge to recover portions with higher activity.     

Comparison of Three Bacterial Toxicity Assays for Imidazolium-Derived Ionic Liquids

Ionic liquids have become leading candidates for replacing many common organic solvents used in the chemical process industry. There is, however, a general lack of toxicology data relevant to wastewater treatment facility microbes for these compounds. In this study, we performed three bacterial-based toxicity assays on several imidazolium-derived compounds as well as the precursor compound 1-methylimidazole. Two of the assays, the Shk1 and Microtox assays, are used as surrogate assays for toxicity to bacterial respiration in activated sludge wastewater treatment plants. The third assay was a direct measure of the effect of toxicity on mixed bacterial culture respiration, using a commercially available consortium of naturally occurring bacteria to obtain IC50 values for direct comparison to the EC50 values from the surrogate assays. The Shk1 assay is based on a genetically engineered bioluminescent Pseudomonas bacterium and is more highly correlated with the respiration inhibition than the Microtox assay. The Shk1 assay gave EC50 values more similar to IC50 values from the bacterial respiration inhibition assay for the compounds tested in this work. The Shk1 EC50 values were similar to that of 1-butanol, an alcohol with an alkyl chain length similar to that of the cation of the tested compounds, which were 1-butyl-3-methylimidazolium bromide ([bmim][Br]), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, ([bmim][Tf2N]), and the precursor compound 1-methylimidazole, and were generally smaller than those typical of aromatic organic solvents.     

Excess Sludge Production in Membrane Bioreactors: A Theoretical Investigation

This paper presents a theoretical investigation on excess sludge production in membrane bioreactors for municipal wastewater treatment. Based on mass balances of sludge and substrate, a formula to predict the excess sludge production in membrane bioreactors is introduced and verified by experimental data. The effects of kinetic parameters and operating conditions on excess sludge production are discussed for strong-, medium-, and low-strength municipal wastewaters, respectively. The strategy for reducing excess sludge production is recommended in order of priority, as sludge retention time→kd→Y→hydraulic retention time. Furthermore, the differences between membrane bioreactors and activated sludge processes are analyzed from the viewpoint of excess sludge production.     

活性污泥数学模型研究进展

活性污泥数学模型作为污水生物处理系统工艺设计、污水处理厂优化运行和管理以及污水生物处理新工艺研发的一种有效工具,受到国内外的广泛关注。综述活性污泥数学模型的发展历程,介绍活性污泥静态模型和动态模型的建模机理及其研究现状,重点阐述国际水协发布的ASM系列模型3个方面的研究进展:ASM系列模型水质组分测定研究、ASM系列模型校正研究和ASM改进模型的应用研究。最后对活性污泥数学模型的研究发展方向进行了展望。      

Flotation as a remediation technique for heavily polluted dredged material. 1. A feasibility study

Wastewater sludges were analysed in the Allium cepa genotoxicity test. They were sampled during three winter periods from three Danish municipal wastewater treatment plants differing in size and industrial load. The toxicity of the sludge was tested in the Allium root inhibition assay, and the results expressed as EC30 and EC50 values showed that the toxicity could be positive correlated to the industrial load. However, when genotoxicity was tested at concentrations corresponding to the EC30 and EC50 values in the A. cepa anaphase-telophase assay, only two sludge samples from the smallest plant with the lowest industrial load induced significant chromosome aberrations. Concentrations of the heavy metal's Pb, Ni, Cr, Zn, Cu, and Cd were also determined and could partly be correlated with the toxicity of the sludge and the industrial load of the treatment plants.     

Experimental Determination of Energy Content of Unknown Organics in Municipal Wastewater Streams

A bomb calorimetry method has been used for the first time to measure the energy content of raw municipal wastewater. The method was first validated using standard compounds (arginine, glucose, and propionic acid) and then tested with municipal sludge samples, with the results compared to previously published values. By drying a large enough sample to yield approximately 0.5 g of solid residue and using benzoic acid in a 1:1 ratio as a combustion aid, an accurate and precise measurement of the energy content of raw municipal wastewater can be made. The energy content measurements indicate that for the full-scale treatment facility examined, the potential energy available in the raw waste-water exceeds the electricity requirements of the treatment process by a factor of 9.3.     

粘胶废水处理系统改扩建工程设计介绍

本文介绍粘胶废水处理系统改扩建工程的设计 改扩建设计将原工艺中生化处理部分的传统活性污泥法改为SBR法 ,只需新建一座均合池和四座SBR反应池中的二座 ,就使得污水处理能力由 2 5 0 0 0m3/d增加到 45 0 0 0m3/d .而且出水水质仍能达到辽宁省污水排放标准     

Full-Scale Demonstration of Improvement in Aeration Efficiency

This paper describes the results of side-by-side full-scale aeration testing of a plug-flow process and a modified contact stabilization process incorporating an anaerobic selector at the wastewater treatment facility in Fredonia, N.Y. Over 40 tests were completed utilizing the off-gas technique during the 2-month investigation period (summer of 1995). Compared to the plug-flow process, the modified contact stabilization process with internal sludge recycle was shown to have higher α values and to require less blower energy consumption when the selector operation was properly controlled. Dissolved oxygen concentration, selector COD concentration, and internal recycle sludge levels were found to be critical parameters in the successful operation of the modified process. Higher internal recycle sludge levels allowed the plant to run at more stable operating conditions in terms of the oxygen transfer efficiency, α, and sludge volume index.     

Determining the Volatile Fatty Acid Equivalent in Thermophilic Aerobically Digested Sludge Supernatant

Thermophilic aerobically digested (TAD) sludge supernatant has been found to be a potential carbon alternative for biological nutrient removal (BNR) enhancement in wastewater treatment plants. Carbonaceous substrates, other than the volatile fatty acids (VFAs) in TAD supernatant, were also found to be utilizable in BNR enhancement; however, these carbon compounds could not be detected by conventional chemical analyses (e.g., gas chromatography). A headspace carbon dioxide (CO2) monitoring method was tested in this study to estimate the overall available carbon source, or the VFAs accumulated in a microaerated TAD operation. This on-line method uses real activated sludge and TAD supernatant samples to determine the available carbon equivalent in real time. In comparison to the gas chromatography (GC) analyses of the TAD supernatant samples, the headspace CO2 monitoring method resulted in “overestimation” of VFA concentrations, in both the phosphorus release and denitrification reactions. Operating results suggested that the CO2 monitoring approach was capable of revealing the overall VFA equivalent that could be available for the main BNR reactions.     

生活污泥用于焦化废水处理的培养驯化

介绍了用生活污水厂的干污泥做菌种,进行焦化废水处理的培养驯化过程。采用连续曝气、间歇进水的方式对污泥进行驯化,通过调整温度、pH值、磷酸三钠和萄葡糖的投加量等工艺参数,32d内使污泥恢复了活性并完全适应了焦化废水环境,使废水中酚的去除率达到99.8%以上,CODcr去除率达到60%以上。     

Radiation-Assisted Process Enhancement in Wastewater Treatment

Laboratory and pilot tests were conducted to investigate the use of ionizing radiation at an activated sludge wastewater treatment facility with residuals processing. Operational enhancements were investigated with respect to bulking control, thickening enhancement, and anaerobic stabilization processes. Radiation caused permanent effects in measured sludge parameters including solids content, chemical oxygen demand, ammonia-nitrogen, zeta potential, specific surface area, resistance to filtration, sludge volume index, pH, organic acid production, and digester gas evolution. Analysis of beneficial effects from preliminary studies and pilot tests demonstrated that a dose of 2–3 kGy would be potentially successful for bulking control and to a lesser degree, enhanced thickening and radiation-assisted anaerobic digestion. A cost analysis based on preliminary tests determined that a centralized electron beam irradiator could be applied economically in an integrated approach at an estimated annual savings of $0.2–2.7 million depending upon the application. Considering that the annual cost of operating an accelerator unit was estimated at $2.4 million ($2.16/m3), this might translate into an important savings for a large-scale wastewater treatment facility.     

焦化废水改造期间好氧活性污泥养护

介绍了焦化改造期间污泥养护,通过对好氧池污泥在改造期间进行间歇进水、曝气、保持污泥活性,缩短了改造完成后污泥培养时间,实现了快速达标排放,取得了明显效果.     

Solids Loading Limitations of Rectangular Secondary Clarifiers

Basin configuration and equipment design govern whether rectangular secondary clarifiers will experience problems of inadequate sludge transport capacity. The operating factors to be considered, other than peak flows which may be severe, are the potential for sludge bulking and the higher mixed liquor suspended solids concentrations and solids retention times employed for biological nutrient removal processes. Rectangular clarifiers longer than 20?m and loaded at more than 3.5?kg/m2?day often have sludge transport/shortcircuiting problems. Shortcircuiting of mixed liquor into the return sludge is a common situation that can be avoided in new designs and easily corrected in existing facilities. A step-by-step design approach is presented as a series of process calculations with graphs. Results from the unmodified and the improved rectangular clarifiers at Phoenix 91st Avenue wastewater treatment plant, Ariz., are presented.     

污泥脱水技术在邯钢焦化厂的应用

介绍了邯钢焦化厂污水处理体系原工艺存在的问题,针对工艺中的问题提出了污泥脱水技术的解决方案、操作事项及问题对策,并列出了相关技术数据及费用指标、效益及效果。     

Low-Strength Wastewater Treatment with Combined Granular Anaerobic and Suspended Aerobic Cultures in Upflow Sludge Blanket Reactors

Combined cultures were developed from anaerobic granular and suspended aerobic cultures in three upflow sludge blanket reactors aerated at 10?mL air/min 4?h/day (R2), every other day (R3), and 24?h/day (R4). The use of combined cultures was found to be advantageous compared to the anaerobic granules for the treatment of low-strength wastewaters. During municipal wastewater treatment at influent 5-day biochemical oxygen demand (BOD5) concentration of 53–118?mg/L (hydraulic retention time: 0.75?day), combined cultures in R2, R3, and R4 exhibited average BOD5 removal efficiencies of 52, 75, and 76%, respectively. The use of these cultures might be proposed as an alternative for municipal wastewater treatment due to their advantages such as achievement of required discharge standards, prevention of biomass loss/settleability problems unlike activated sludge systems and possible methanogenic activity, as well as high settling characteristics comparable to those of anaerobic granules.