Statistical Comparison of Bioassays for Assessment of Toxicity of Organic Components of Wastewater to Activated Sludge

In aquatic toxicity testing, no single test species responds appropriately to all toxicants. Therefore test batteries consisting of several individual assays are becoming more common. The species comprising a test battery should be representative of the entire system of interest. Each assay should be complementary to other components in the test battery and the test battery should not include redundant tests. We studied the selection of test battery components for the assessment of the toxicity of organic chemicals to activated sludge. The assays considered were the continuous Shk1, Microtox, Polytox, activated sludge respiration inhibition, Nitrosomonas, and Tetrahymena assays. The correlations between the toxicity data obtained from these assays were analyzed by examining the correlation matrix and by principal component analysis. These statistical methods showed that the Nitrosomonas assay should be included in test batteries plus one of the remaining five assays for assessing toxicity of organic compounds to activated sludge.     

Toxicity Estimation of Phenolic Compounds by Bioluminescent Bacterium

Phenolic compounds are environmentally important due to their extensive use in various industries, presence in wastewaters, and potential toxicity. When phenolic compounds reach the activated sludge processes of publicly owned treatment works, they can cause upsets in the operations of the treatment plants. A continuous toxicity testing system was developed based on the bioluminescent bacterium Shk1. The toxicities of 23 phenolic compounds to Shk1 were studied and the 5 min EC50 values were obtained. Quantitative structure-activity relationship models based on the logarithm of the octanol-water partitioning coefficient [log(Kow)] were established for estimating the toxicity of phenolic compounds and the model validity was verified.     

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.     

Treatment of Chlorophenols by UV-Based Processes: Correlation of Oxidation By-Products, Wastewater Parameters, and Toxicity

The aim of the study was to evaluate the toxicity and biodegradability of para-chlorophenol (p-CP) model wastewater when treated by UV and UV/H2O2 processes. We investigated the correlations between the toxicity and the concentration of p-CP and its oxidation by-products, as well as other parameters—summarizing characteristics which potentially indicate hazardous water components, e.g., AOX (adsorbable organic halides), TOC (total organic carbon), and COD and BOD5 (chemical and biochemical oxygen demand). Biodegradability is estimated by the BOD5/COD ratio. The toxic effects were investigated on luminescent bacteria Vibrio fischeri, determining the EC50 value. The correlation between each data pair was estimated using a statistical approach calculating the Spearman rank coefficients. The biodegradability of the p-CP model wastewater was improved by the UV/H2O2 process; the BOD5/COD ratio increased from 0.37 to 0.73 after a 1-h treatment (F = 1243??mJ?cm-2). According to the calculated Spearman rank coefficient, the highest correlation with toxicity data among all monitored parameters was obtained for hydroquinone and benzoquinone, as by-products of p-CP degradation, as well as for the BOD5/COD ratio.     

Seasonal Variation Pattern of Monthly Wastewater Influent

This study investigates the seasonal variation pattern of monthly wastewater influent data collected from the active treatment plants in Kuwait from 1999 to 2009. An attempt to examine the relationship with the population connected to the sanitary network is achieved indirectly by correlating monthly totaled influent data with climatological parameters of monthly averaged temperature and totaled rainfall. The periodograms of the influent, temperature, and rainfall data are also determined. The results reveal two significant periods in influent data of 12 and 6?months. The 12-month period is found in the two climatological data but the 6-month period exists only in rainfall data. The source of the 6-month period in the influent data has been related here to the illegal connection of storm sewers into the sanitary networks in many residential houses and to the typical variation of four seasons of the year during which the mode of people for watering activities or travel plans may change on average. The existing connection between residential stormwater and the sanitary networks may constitute a possible rainfall-harvesting system for arid countries as long as the wastewater plants have the capacity to handle the treatment process. The study concludes with the possibility of employing readily available climatological data to analyze the relationship between the seasonal wastewater influent and the population. The study also considers the detected periodicities to develop a time-series model that can be used to set a management plan for securing a nonconventional water supply for the country.     

Dosage Control of the Fenton Process for Color Removal of Textile Wastewater Applying ORP Monitoring and Artificial Neural Networks

Textile wastewater containing a high level of color and refractory chemical oxidation demand (COD) is difficult to treat using traditional wastewater treatment processes. Typically, a chemical process was suggested as a pretreatment to remove color and increase biodegradability of refractory organic materials. A biological process was then used to remove organic materials and reduce chemical costs for textile wastewater treatment. Fenton oxidation is one of the most effective chemical processes for removing color and COD for textile wastewater. In Fenton processes, oxidations by generated hydroxyl radical are the key factor for color removal in textile wastewaters; thus, monitoring oxidation reduction potential (ORP) should have high potential in Fenton dosage control for color removal in textile wastewater treatment. The main object of this study is to build a Fenton dosage control strategy that uses ORP monitoring and artificial neural network (ANN) models for removing color from textile wastewaters. Two wastewaters, synthetic and real textile, were used in this study. Experimental results have shown that the ANN models precisely represent the correlation between monitoring ORP, Fenton doses, color removal efficiency, and effluent color value, and therefore can be used to control Fenton doses for removing color from textile wastewater. Finally, another series of Fenton dose-control experiments for different color removal control targets were conducted to evaluate this proposed Fenton dose control strategy. Experimental results indicate that the proposed control strategy precisely controls the required Fenton doses for different control targets for both synthetic and real textile wastewaters, and result in reduced chemical costs.     

Biosensor for Toxic Detection and Process Control in Nitrification Plants

This paper presents the design and possible applications of a nitrification biosensor suitable for continuous monitoring of the potential toxicity of incoming wastewater at a treatment plant. The measurement principle of the biosensor is based on the on-line determination of the alkaline (Na2CO3) consumption required for the neutralization of protons produced during nitrification. Toxicity is detected by a rapid decrease in the consumption of Na2CO3. Based on early diagnosis of incoming toxicity, a process control concept for flow pattern manipulation is proposed and tested in a pilot plant, where programmed toxic substances were added. The pilot plant behavior with and without flow pattern control was compared. The control system was capable of diverting most of a toxic load to a buffer tank at the head of the plant, from which it can be released it later in a safer way. A significant process improvement is demonstrated in the case of flow pattern control. The experimental results show that the biosensor is a useful diagnostic tool for continuous monitoring of the nitrification activity and potential toxicity of incoming wastewater to the treatment plant.     

Use of Recombinant Bioluminescent Bacteria for On-Site Monitoring of Toluene Analogs at Petroleum Contaminated Sites

This paper describes the application of a genetically engineered microorganism, Pseudomonas putida mt-2 KG1206, to monitor toluene analogs in groundwater collected from petroleum hydrocarbon contaminated sites. KG1206 contains the intact TOL plasmid and a second plasmid with the Pm-lux gene allowing it to produce bioluminescence in the presence of toluene analogs and their derivatives such as toluene, xylenes, and m-toluate. The simple bioluminescence assay consisted of mixing one volume of groundwater sample with four volumes of broth culture followed by bioluminescence measurement after 30?min. The maximum bioluminescent response with pure chemicals followed the order: m-methyl benzyl alchohol>m-toluate>toluene>m-xylene>benzoate>p-xylene>o-xylene. The bioluminescence production was well correlated to the m-toluate concentrations (R2>0.97) in field samples, with concentrations predicted from the bioassay falling within 75–158% of true concentration. However, no strong correlation was observed between the bioluminescence intensity and the total inducer concentration in the groundwater. Results from this study demonstrate the potential of using recombinant bioluminescent bacteria as a rapid and simple tool for monitoring specific pollutants at contaminated sites.     

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.     

Anaerobic Treatment of High Sulfate Wastewater with Oxygenation to Control Sulfide Toxicity

In this study, oxidation-reduction potential (ORP) was employed to regulate oxygen dosing for online sulfide toxicity control during anaerobic treatment of high sulfate wastewater. The experiment was conducted in an upflow anaerobic filter, which was operated at a constant influent total organic carbon of 6,740 mg/L [equivalent to a chemical oxygen demand (COD) of 18,000 mg/L], but with different influent sulfates of 1,000, 3,000, and 6,000 mg/L. The reactor was initially run at natural ORP (the system’s ORP without oxygenation) of about ?290 to ?300?mV and then was followed by oxygenation to raise ORP by +25?mV above the natural level for each influent sulfate level. At 6,000 mg/L sulfate under the natural ORP, methanogenesis was severely inhibited due to sulfide toxicity, and the anaerobic process was almost totally upset. Upon oxygenation by raising ORP to ?265?mV, the dissolved sulfide was quickly reduced to 12.2 mg S/L with a concomitant improvement in methane yield by 45.9%. If oxygen was not totally used up by sulfide oxidation, the excess oxygen was consumed by facultative bacteria which had been found to stabilize about 13.5% of the influent COD. Both sulfide oxidation and facultative activity acted as a shield to protect the anaerobes from an excessive oxygen exposure. This study showed that direct oxygenation of the recirculated biogas was effective to oxidize sulfide, and the use of ORP to regulate the oxygen dosing was practical and reliable during anaerobic treatment of high sulfate wastewater.     

Oxidation-Reduction Potential as a Monitoring Tool in a Low Dissolved Oxygen Wastewater Treatment Process

Research was undertaken to investigate the relationship between two biochemical events and the oxidation-reduction potential (ORP) measurement in a low dissolved oxygen (D.O.) wastewater treatment process. The biological events considered were the depletion of organic waste and the depletion of ammonia nitrogen. Two lab-scale sequencing batch reactors fed with a synthetic waste were operated under controlled conditions using seed material from a local wastewater treatment plant. The on-line monitoring of ORP, D.O., and pH was complemented by intensive track studies in which physical measurements of biochemical parameters such as chemical oxygen demand and TN were taken. The results indicated that low D.O. processes (e.g., the simultaneous nitrification/denitrification process) may have their own distinctive on-line profiles, with certain biochemical events such as the depletion of organic carbon and the depletion of ammonia nitrogen being readily detectable on the ORP profile. The fact that these specific events are displayed on the on-line ORP profile means that the profile could possibly be used as a process control parameter.     

Contribution of the Estrogen-Degrading Bacterium Novosphingobium sp. Strain JEM-1 to Estrogen Removal in Wastewater Treatment

This study aimed to investigate the contribution to estrogen removal from the activated sludge of an estrogen-degrading bacterium, Novosphingobium sp. Strain JEM-1, isolated by the writers from the activated sludge. The cell numbers of the Strain JEM-1 were investigated in two full-scale wastewater-treatment plants using real-time PCR. Strain JEM-1 appears to be commonly distributed in the activated sludge. The cell numbers of Strain JEM-1 in the oxidation ditch process were higher than those in the conventional activated sludge (CAS) process, and the effluent concentrations of E1 in the CAS process tended to decrease with increased cell numbers of Strain JEM-1. In a bench-scale experiment to investigate bioaugmentation with Strain JEM-1, there was a significant difference in the effluent concentrations of estrogens between the experimental series and the control series. Linear relationships were observed between cell numbers of Strain JEM-1 and the efficiency of removal of estrogens. These results suggest that Strain JEM-1 contributes to the estrogen removal in the activated sludge.     

Visual Pattern Recognition Supporting Defect Reporting and Condition Assessment of Wastewater Collection Systems

Computational approaches to visual data and information processing can assist asset management procedures. In this paper, we present a computerized visual pattern recognition approach to facilitate inspection and condition assessment of wastewater collection systems in realistic settings. This research aims to provide a basis for condition assessment and defect reporting in wastewater infrastructure, enabling automatic detection and recognition of defects and patterns from inspection images or videos. An approach for sensing and automatically detecting critical areas or regions of interest, and further discovering and recognizing objects of interest in large image data sets, is described. The major steps of the approach are illustrated by examples using actual inspection images acquired from wastewater pipelines.     

Evaluation of Influent Medium Composition and Concentration in a Batch Reactor for Effective Startup of UASB Reactors

This study demonstrated the use of batch bioreactor experiments as an evaluation tool to determine appropriate influent medium composition and concentration for effective startup of an upflow anaerobic sludge blanket (UASB) reactor. Using seed sludge from a domestic treatment plant, the weight ratio of glucose and volatile fatty acids (VFA) present in the influent synthetic medium was varied and the batch performance was assessed in terms of pH variation during the course of the experiment, chemical oxygen demand (COD) reduction, specific substrate uptake rates, methanogenic activity, and methane yield. The performance was also evaluated by increasing the concentration of influent COD. Medium composition with glucose to VFA weight ratio at or below 2:8 and COD concentration at 11?g/L was determined to be optimum for effective startup of the UASB reactors. Utilization of the optimized influent medium provided a pH variation from 6.5 to 7.8 over the length of the UASB reactor and resulted in granule formation, high methanogenic activity, and methane yield. The evaluation method provided a practical approach to determine the applicability of seed sludge from a particular source and the desired influent characteristics for reduced startup duration in UASB processes.     

On-line Monitoring of Wastewater True Color Using Digital Image Analysis and Artificial Neural Network

The American Dye Manufactures’ Institute (ADMI) 3 and 31 wavelength (WL) methods are the most well-known analytical methods for measuring wastewater true color. However, these two methods use a spectrophotometer as the measurement device. The measurements thus must be conducted in the laboratory and cannot provide on-line monitoring data for process control. This study applies the digital image analysis (DIA) method to develop an effective and economical method for on-line monitoring of the wastewater true color. The DIA method was used to measure three types of colored samples including the platinum-cobalt color standard solutions, synthetic colored samples and real colored samples. Experimental results show that the DIA method performed not only with good accuracy and precision but also high sensitivity in the measurement of true color. However, the DIA values present different linear relationship with the ADMI 3 and 31 WL values for different sample hues. Direct substitutions of DIA, ADMI 3 and 31 WL values may be inappropriate. Finally, a back-propagation neural network (BPNN) was proposed to calibrate the DIA, ADMI 31 and 3 WL values. The BPNN models were proven to be highly effective for the calibrations among the ADMI 3, 31 WL, and DIA values.     

Membrane Fouling in Membrane Bioreactors for Wastewater Treatment

Membrane bioreactors (MBRs), in which membranes are applied to biological wastewater treatment for biomass separation, provide many advantages over conventional treatment. However, membrane fouling in MBRs restricts their widespread application because it reduces productivity and increases maintenance and operating costs. Recently much research and development has taken place to investigate, model, and control membrane fouling processes. However, unified and well-structured theories on membrane fouling are not currently available because of the complexity of the biomass matrix, which is highly heterogeneous and includes living microorganisms. Membrane fouling in MBR systems can be reversible (i.e., removable by physical washing) or irreversible (removable by chemical cleaning only), and can take place on the membrane surface or into the membrane pores. Although establishing a general model to describe membrane fouling in such a process is made extremely difficult by the inherent heterogeneity of the system, the nature and extent of fouling in MBRs is strongly influenced by three factors: biomass characteristics, operating conditions, and membrane characteristics. Fouling control techniques which have been investigated include low-flux operation, high-shear slug flow aeration in submerged configuration, periodical air or permeate backflushing, intermittent suction operation or addition of powdered activated carbon (PAC). Of these, only PAC addition is currently not used in existing large-scale installations.     

含锰废水处理研究

本文提出了用石灰-碱式氯化铝处理含锰废水的新方法，经实验确定了合理的技术条件，处理后的水质达到国家排放标准。     

离子交换法回收电解金属锰废水中锰的研究

为了验证离子交换树脂在电解金属锰废水行业中的应用效果,通过静态吸附实验、中试动态实验的方法,研究了不同类型离子交换树脂对锰离子的吸附性能及回收特性。结果表明,离子交换树脂对锰离子有一定的交换吸附能力,且同类树脂对各二价金属离子选择性无明显区别,其中各树脂对二价金属离子的吸附能力：D113〈732〈D851。经过一次再生后,离子交换树脂交换吸附能力下降,之后进行多次再生后,其交换吸附能力基本趋于稳定,钙离子对离子交换树脂的再生一吸附有较大负面影响。洗脱液中锰离子浓度最高可达20000mg／L以上。     

Determination of Temperature Dependence of Electrical Conductivity and Its Relationship with Ionic Strength of Anaerobic Digester Supernatant, for Struvite Formation

Electrical conductivity (EC) is used for monitoring different types of aqueous systems. The measured EC value at any temperature needs to be corrected for a standard temperature, for reporting or comparison, since EC is dependent on temperature. A temperature compensation factor has been derived for conductivity correction from anaerobic digester supernatant/centrate samples of five different wastewater treatment plants in western Canada. For a temperature compensation factor of 0.0198°C?1, corresponding to the standard temperature at 25°C, the estimated EC25 values were found to be reasonably accurate, with a maximum error of 2.01%. The estimated EC values, based on any standard temperature, were found to be statistically similar to each other. Considering the temperature dependence of EC, a relationship between EC and ionic strength was developed in this study for anaerobic digester supernatant/centrate samples. This relationship can be used to estimate the ionic strength of the solution in a system associated with struvite formation from anaerobic digester supernatant/centrate and effectively monitor the system performance.     

Evaluation of a System for Residential Treatment and Reuse of Wastewater

Approximately one-quarter of housing units in the United States are not connected to centralized, publicly owned wastewater treatment works and instead operate their own cesspools or septic tanks that provide only partial treatment. A study was conducted in which a commercially available, on-site, residential wastewater package unit was tested at its design capacity according to an established protocol to determine if it could produce a high-quality effluent. Additional pilot-scale sand filtration and ultraviolet disinfection units were fabricated and operated to determine the feasibility of producing recycled water suitable for residential reuse and which could meet strict water reuse regulations. The results indicate that the package unit can produce an effluent equivalent to secondary effluent when properly operated and maintained. In addition, using add-on sand filter and ultraviolet light disinfection units, it was possible to produce the highest quality of reclaimed water recognized by Hawaii regulations (oxidized, filtered, disinfected, unrestricted use). It was also possible and may be economically feasible to produce a slightly lower quality reclaimed water (oxidized, disinfected, R-2) suitable for residential subsurface irrigation.