Religion, psychopathology, and substance use and abuse; a multimeasure, genetic-epidemiologic study

Agency for Toxic Substances and Disease Registry (ATSDR) utilizes chemical-specific minimal risk levels (MRLs) to assist in evaluating public health risks associated with exposure to hazardous substances. The MRLs are derived based on the data compiled from current worldwide literature searches and presented in ATSDR's toxicological profiles. These documents profile not only individual chemicals, but also groups of chemically related compounds and chemical mixtures. ATSDR took several approaches when developing MRLs for chemical mixtures. In some instances, toxicity equivalency factors were used to estimate the toxicity of the whole mixture; in other instances, the most toxic chemical was assumed to drive the health assessment for the whole mixture. Another approach was to treat the mixture as one entity and develop a health guidance value for the whole mixture. In yet another approach, each chemical of the mixture was evaluated separately and several health guidance values were developed. In the future, ATSDR will evaluate priority chemical mixtures found at hazardous waste sites. A weight-of-evidence approach, physiologically based pharmacokinetic modeling and bench-mark dose modeling, and quantitative structure-activity relationships will have an impact on the development of MRLs and the assessment of chemical mixtures.     

Modeling Risk of Failure in Nitrification: Simple Model Incorporating Abundance and Diversity

A risk based approach to engineering provides a rational way to balance cost against the need to avoid failure. Such an approach has not been systematically incorporated into the design and operation of wastewater treatment plants. This is perhaps because engineers do not have the means to make risk based predictions of performance. We have adapted a classical technique for incorporating risk in engineering predictions to the oxidation of ammonia, the first step in nitrification. The approach incorporated random changes in load, aeration, and kinetic parameters. Two and three species models were used to evaluate the effect of increasing aeration on the risk of failure. Surprisingly, increased aeration did not lead to a monotonically decreasing risk of failure. Intermediate aeration rates typically increased the standard deviation of the effluent ammonia and thus the risk of failure. Reliable performance was predicted when there was a high abundance of one species or a similar abundance of both. These preliminary but encouraging results suggest risk based approaches offer new and important insights into the operation of biological treatment systems.     

Using Continuum Approach to Quantify the Remediation of Nonaqueous Phase Liquid Contaminated Fractured Permeable Formations

This study addresses the feasibility of using a continuum modeling approach to simulate pump-and-treat remediation of nonaqueous phase liquid (NAPL) contaminated fractured permeable formations. A simplified discrete fracture model, which incorporates permeable blocks with embedded parallel equidistant constant aperture fractures, was used to simulate the NAPL dissolution in an idealized fractured permeable formation. The applicability of this model is defined by the ranges of a dimensionless mobility number and interphase mass transfer coefficient. A continuum based model able to simulate phenomena predicted by the discrete fracture model has also been used. Three dimensionless parameters referring to organic solute advection and dispersion, and the continuum interphase mass transfer coefficient govern the performance of the continuum model. The nonlinear relationships between the discrete fracture and continuum model have been identified and formulated. However, the simplified conceptual models of this study may be inapplicable to many types of fractured formations. Ranges of possible use of the continuum modeling were determined in terms of dimensionless parameters. The discrete fracture and continuum approaches of this study can be useful for the preliminary evaluation of ideas concerning optimization of the remediation of NAPL contaminated fractured permeable formations.     

Simplified Databased Total Maximum Daily Loads, or the World is Log-Normal

The total maximum daily load (TMDL) approaches that have relied mostly on deterministic modeling have inherent problems with considerations of a margin of safety and estimating probabilities of excursions of water quality standards expressed in terms of magnitude, duration, and frequency. A tiered probabilistic TMDL approach is proposed in this paper. A simple databased Tier I TMDL that uses statistical principles has been proposed for watersheds that have adequate water quality databases enabling statistical evaluations. Studies have shown that for many pollutants, event mean concentrations in runoff, wastewater loads, and concentrations in the receiving waters follow the log-normal probability distribution. Other probability distributions are also applicable. Tier II Monte Carlo simulation, using a simpler deterministic or black box water quality model as a transfer function, can then be used to generate time series of data, which fills the data gaps and allows estimation of probabilities of excursions of chronic standards that are averaged over periods of 4 or 30 days. Statistical approaches, including Monte Carlo, allow replacement of an arbitrary margin of safety by a quantitative estimation of uncertainty and enable linking the model results to the standards defined in terms of magnitude, frequency, and duration.     

Modeling of Class I Settling Tanks

Sedimentation is one of the earliest and most important unit operations in water and wastewater treatment. Conventional approaches for studying sedimentation of Class I settling tanks did not present enough information on suspended particle size distribution in the effluent. This information is very important for further treatment units such as filtration. In this research, a relatively simple and practical mathematical model is introduced to study sedimentation of non-uniform particle size in Class I settling tanks. The model is capable of providing such information as removal efficiency, size distributions in sludge and in effluent suspension, and thickness of bottom sludge. If desired removal efficiency is provided, the length of the tank can also be determined. Through numerical experiments, a sensitivity analysis was performed to examine the effects of tank dimensions, overflow rate, and detention time on the removal efficiency. Comparison with other models and a set of experimental data indicates a good agreement.     

Attenuation of Roadway-Derived Heavy Metals by Wood Chips

Wood chips were evaluated for their ability to attenuate heavy metals in roadway runoff. Column experiments with controlled synthetic runoff composition and flow rate were used to assess effects of flow rate (intercepted sheetflow from a 3-m wide roadway section), runoff salt concentration, wood exposure to alternating wetting and drying cycles, wood aging, competition among dissolved heavy metals, and removal of particle-associated heavy metals. Overall, wood chips damped the “pulse” of copper in the synthetic runoff such that the effluent was characterized by lower concentrations (3–25% of input) over longer periods of time, but with little retention of the total copper mass. The most effective treatment was wood chips aged up to 9 months. Increased aging and chip water content reduced effluent concentrations, relative to no treatment. Flow rate had no effect on effluent concentrations. The presence of salt (>2?mS/cm) or dissolved lead (500?μg/L) in the runoff caused greater copper effluent concentrations than the no treatment case. Removal of suspended particles (and associated contaminants) was greater than 85% with an estimated capacity of 0.16?g/gwood. Field evaluation with concentrated flow to a gutter containing a wood chip treatment showed little effect on total or dissolved copper and zinc runoff concentrations and indicated that wood chips may be a source of contaminants in subsequent storm events. Applications of wood chips to treat roadway runoff would not provide a significant decrease in total maximum daily load contributions (e.g., kg/d); however, there may be some scenarios for which wood chip treatments to decrease peak storm water concentrations of dissolved heavy metals in sheetflow runoff is desirable.     

Quantitative structure-based modeling applied to characterization and prediction of chemical toxicity

Quantitative modeling methods, relating aspects of chemical structure to biological activity, have long been applied to the prediction and characterization of chemical toxicity. The early linear free-energy approaches of Hansch and Free Wilson provided a fundamental scientific framework for the quantitative correlation of chemical structure with biological activity and spurred many developments in the field of quantitative structure-activity relationships (QSARs). In addition to modeling of chemical toxicity, these methods have been extensively applied to modeling of medicinal properties of chemicals. However, there are important differences in the nature and objectives of these two applications, which have led to the evolution of different modeling approaches (namely, the need for treating sets of noncongeneric toxic compounds). In this paper are discussed those approaches to chemical toxicity that have taken a more "personalized" configuration and have undergone implementation into software programs able to perform the various steps of the assessment of the hazard posed by the chemicals. These models focus both on a variety of toxicological endpoints and on key elements of toxicity mechanisms, such as metabolism.     

Fate and Transport Model of CRYPTOSPORIDIUM

The waterborne pathogen Cryptosporidium has been identified in surface drinking water supplies. Suspected sources of this pathogen include sewage and the feces of animals, particularly dairy calves. There are many dairy cattle and significant sewage effluent discharges in the Catskill-Delaware watershed that is part of the New York City water supply system. This water supply serves 8,000,000 customers with 5.8 × 109 L (1.5 billion gal. of water daily). This paper is concerned with the movement and fate of pathogens from wastewater and dairy sources and the resulting raw water quality for New York City. Manure and Cryptosporidium oocysts are modeled as surface pollutants and assumed to move in response to runoff events in the six watershed-reservoir systems within the Catskill-Delaware watershed. Oocyst degradation in manure and in water is modeled with first-order kinetics. Rudimentary stream routing and reservoir modeling with a first-order decay function complete the fate and transport modeling of oocysts in the watercourse. Reported effluent discharge rates and oocyst concentrations in secondary treated sewage allow estimation of wastewater-derived oocyst contributions. This research highlights the importance of wastewater-derived oocysts, the need for expanded research into oocyst fate in streams and reservoirs, and the concentration of oocysts in sewage effluent.     

Bacteria Loads from Point and Nonpoint Sources in an Urban Watershed

A pathogen impaired watershed in Houston, Tex., was studied to assess the spatial and temporal nature of point and nonpoint bacterial load contributions. End-of-pipe sampling at wastewater treatment plant effluent and storm sewers discharging under dry weather conditions was undertaken. Relatively low concentrations of E. coli were found in wastewater treatment effluent, with a geometric mean of 5 MPN/dL, while dry weather storm sewer discharges exhibited a geometric mean concentration of 212 MPN/dL. Loads from both point and nonpoint sources of E. coli were calculated and compared to in-stream bacteria loads. Nonpoint loads were estimated using an event mean concentration approach on an annual basis. Nonpoint source (NPS) loads were the primary source of bacteria loading to the bayou. Wastewater treatment plant and dry weather storm sewer loads, however, dominated in dry weather conditions. While NPS loads remained relatively constant from headwaters to the mouth of the bayou, point source loads exhibited greater spatial variability depending on the distribution of the discharging pipes. The study points to the need for spatial and temporal considerations in managing bacterial pollution in streams.     

Electrochemical Oxidation and Ozonation for Textile Wastewater Reuse

Ozone and electrochemical oxidation treatment technologies were evaluated for wastewater recycling in the textile industry. Textile wastewater was collected from eight textile mills that use different dying processes. Both ozone and electrochemical oxidation removed the color from wastewater containing acid, reactive, and natural dyes, while mixed results were achieved with pigment and disperse dyes. The variability in color removal for the pigment and disperse dyes may be related to the concentration and type of auxiliary chemicals used. Color criteria for reusing wastewater for reactive dye was determined to be ΔE ? 2. This level of treatment provided an acceptable level of residual color for reuse in dark color dyeing operations and for rinse water. Some reformulation of the dye concentration and auxiliary chemicals is necessary for wastewater reuse in light color dyeing operations. Also, multiple reuse of the treated wastewater, as would occur in a completely closed system, would require changes in salt and other auxiliary chemicals to achieve the same fabric color as clean process water.     

铜矿矿山废水的物化净化处理研究

针对某铜矿矿山酸性废水与选矿废水的所形成的混合废水的pH值较低,COD及重金属离子浓度较高的特点,研究利用Fenton氧化-电石乳中和-絮凝联合工艺处理酸碱混合废水的效果,试验表明:联合工艺对废水中的COD和重金属有着较高的去除率,当双氧水、电石乳及PAM投加量分别为340mg/L、12g/L以及2mg/L时,废水经处理后,COD<100mg/L,重金属Zn2+、Cu2+无检出,总铁<0.1mg/L、总锰<0.1mg/L,出水达到国家《污水综合排放标准》(GB8978-1996)一级排放标准。     

User-Friendly Mathematical Model for the Design of Sulfate Reducing H2/CO2 Fed Bioreactors

This paper presents three steady-state mathematical models for the design of H2/CO2 fed gas-lift reactors aimed at biological sulfate reduction to remove sulfate from wastewater. Models 1A and 1B are based on heterotrophic sulfate reducing bacteria (HSRB), while Model 2 is based on autotrophic sulfate reducing bacteria (ASRB) as the dominant group of sulfate reducers in the gas-lift reactor. Once the influent wastewater characteristics are known and the desired sulfate removal efficiency is fixed, all models give explicit mathematical relationships to determine the bioreactor volume and the effluent concentrations of substrates and products. The derived explicit relationships make application of the models very easy, fast, and no iterative procedures are required. Model simulations show that the size of the H2/CO2 fed gas-lift reactors aimed at biological sulfate removal from wastewater highly depends on the number and type of trophic groups growing in the bioreactor. In particular, if the biological sulfate reduction is performed in a bioreactor where ASRB prevail, the required bioreactor volume is much smaller than that needed with HSRB. This is because ASRB can out-compete methanogenic archaea (MA) for H2 (assuming sulfate concentrations are not limiting), whereas HSRB do not necessarily out-compete MA due to their dependence on homoacetogenic bacteria (HB) for organic carbon. The reactor sizes to reach the same sulfate removal efficiency by HSRB and ASRB are only comparable when methanogenesis is inhibited. Moreover, model results indicate that acetate supply to the reactor influent does not affect the HSRB biomass required in the reactor, but favors the dominance of MA on HB as a consequence of a lower HB requirement for acetate supply.     

Solid phase microextraction as a tool to determine membrane/water partition coefficients and bioavailable concentrations in in vitro systems

Solid phase microextraction (SPME) is an extraction technique that uses a polymer-coated fiber as the extraction device. After extraction, the compound of interest can be desorbed from the fiber and subsequently analyzed by GC or HPLC. One of the properties of SPME is that only the freely dissolved fraction of a chemical is available for partitioning to the extraction device. The method can be applied in a way that small amounts are extracted from the sample, which allows negligible depletion extraction. These two properties make SPME devices particularly suitable for measurements of free concentrations. In toxicological studies the free concentration is considered to be a more relevant parameter, concerning toxic effects, than the nominal concentration that is used most frequently. In the current study, the usefulness of this method to measure phospholipid/water partition coefficients and free concentrations in three different in vitro test systems (rat hepatocytes in primary culture, 9000 g and 100,000 g homogenate fractions of rainbow trout liver) was demonstrated. Results show separate relationships between phospholipid/water and n-octanol/water partition coefficients for a set of polar and nonpolar organic chemicals, respectively. These observations suggest that phospholipid/water partition coefficients may be a more suitable parameter in modeling the kinetic behavior of organic chemicals. Additionally, differences between the nominal and the actual free concentration in in vitro systems are more pronounced for more hydrophobic compounds, as was expected based on theoretical considerations. To our knowledge, the approach presented here is the first analytical method to measure toxicologically relevant concentrations in in vitro test systems in a fast and efficient way.     

Salt Inhibition Effects in Biological Treatment of Saline Wastewater in RBC

Design and operation of saline wastewater treatment systems are difficult because of adverse effects of salt on microbial flora. Quantification and modeling of salt inhibition effects are essential in designing biological treatment processes for saline wastewater. Synthetic wastewater containing 0–10% salt (NaCl) was treated in a rotating biodisc contactor (RBC) unit operating in a continuous mode. Effects of important process variables such as the A∕Q ratio, COD loading rate, and salt concentration on COD removal rate and efficiency were investigated. The system's performance improved with an increasing A∕Q ratio; however, performance decreased with an increasing COD loading rate and salt content. The liquid phase was aerated to keep suspended cells active at high feed COD concentrations such as S0 = 5,000 mg∕L. A mathematical model was developed to describe the system's behavior. Model parameters were determined by using the experimental data. Salt inhibition was found to be significant for salt concentrations larger than 2% NaCl. The experimental results and mathematical model may be used in design of RBC units treating saline wastewater.     

Advanced Hybrid Fuzzy-Neural Controller for Industrial Wastewater Treatment

Many uncertain factors affect the operation of wastewater treatment plants. These include the physical and chemical properties of wastewater streams as well as the degradation mechanisms exhibited by biological processes. Because of the rising concerns about environmental and economic impacts, improved process control algorithms, using artificial intelligence technologies, have received wide attention. Recent advances in control engineering suggest that hybrid control strategies, integrating some ideas and paradigms existing in different soft computing techniques, such as fuzzy logic, genetic algorithms, and neural networks, may provide improved control of effluent quality. The methodology proposed in this study employs a three-stage analysis that integrates three soft computing approaches for generating a representative state function, searching a set of multiobjective control strategies, and autotuning the fuzzy control rule base used for controlling a treatment plant. The case study, using an industrial wastewater treatment plant in Taiwan as an example, demonstrates the applicability of the approach. The findings from this research suggest that a genetic-algorithm–based hybrid fuzzy-neural controller can produce better plant performance than does a simple fuzzy logic controller, in terms of both environmental and economic objectives. This methodology can be extended to control many other types of wastewater treatment processes, as well, by making only minor modifications.     

Age-dependent stimulation or inhibition of calcium release from bone cultures by interleukin-1 beta

Ecological risk assessments can be used to establish the likelihood that an adverse effect will result from exposure to one or more chemicals. When evaluating contaminated sites with many chemicals present, risk assessors must grapple with the problem of quickly identifying the chemicals that are most likely to be of concern, based on effect and exposure assessment information. Many times data gaps exist and the risk assessor is left with decisions on which models to use to estimate the parameter of concern. In the present paper, a procedure is presented for ranking agrichemicals, utilizing the ASTER (ASsessment Tools for the Evaluation of Risk) system. The procedure was employed to rank the relative ecological risk of forty-nine pesticides historically used in agricultural sites in the Walnut Creek watershed near Ames, lowa, USA. Empirical data from the ASTER system were used when available in the associated databases, and quantitative structure-activity relationships and expert systems were invoked when data were lacking. Separate rankings were conducted based on major species taxonomic groupings. Resulting toxic effects thresholds were compared to surface water concentrations.     

Infiltration Considerations for Ground-Water Recharge with Waste Effluent

Water reuse and ground-water recharge can be used to meet the growing demands for water, particularly in arid regions. Ground-water recharge using fresh water or treated wastewater is most often accomplished by infiltration from surface basins. The water percolates through the unsaturated soil region to an underlying aquifer for storage and future use. In the case of wastewater, additional treatment occurs as the effluent flows through the soil. The system hydraulics of recharge basins have been examined through a combination of field and laboratory investigations. These studies indicate that infiltration rates and soil aquifer treatment of wastewater are influenced by soil type and soil profile characteristics, surface clogging material, pond depth, and wetting∕drying cycle times. The surface-clogging layer was found to be susceptible to consolidation and to associated reduction in hydraulic conductivity under seepage forces.     

Formation of Secondary Containment Systems Using Permeation of Colloidal Silica

U.S. Environmental Protection Agency (USEPA) regulations require the capture of spills from liquid tanks containing hazardous chemicals by using a secondary containment system. Compacted clay or geomembrane liners are commonly used in secondary containment systems, but they are cumbersome when used in conjunction with existing liquid tanks because of pipeline networks surrounding the tanks. This study evaluates the formation of hydraulic barriers for secondary containment through the permeation of colloidal silica grout. A simplified infiltration model is presented to predict the downward movement of the colloidal silica grout into a soil layer, considering the time-dependent increase in dynamic viscosity of the colloidal silica for different concentrations of an electrolyte accelerator. Because the simplified infiltration model cannot predict the soil-grout interaction or the permeation of the colloidal silica by fingering, its results were calibrated by using the observations from a large-scale column test involving the permeation of colloidal silica into sand. The predicted position of the wetting front was found to match that of the experiment when the parameter governing the change in viscosity of the colloidal silica was increased by a factor of 30. The infiltration model calibrated with observations from column infiltration experiments provides a simple approach to the design of the secondary containment systems using permeation of colloidal silica.     

A biophysically based dermatopharmacokinetic compartment model for quantifying percutaneous penetration and absorption of topically applied agents. I. Theory

We present a general comprehensive mathematical model to stimulate and predict percutaneous absorption and subsequent disposition of chemicals in vivo that is chiefly based on biophysical parameters estimated or measured with in vitro and ex vivo perfused skin preparations. Current physicochemical principles of drug diffusion and partitioning across the skin barrier, solute and solvent concentration dynamics, the influence of solute and solvent on the stratum corneum barrier, and dynamic vascular perfusion effects are integrated in this model. Such a comprehensive approach is necessary to achieve optimal biological relevance in a quantitative model of percutaneous absorption, particularly when a chemical is applied as a binary (solute and solvent) or more complex formulation or chemical mixture. The proposed model should have applications in (a) designing drugs and permeation enhancers for passive or active (e.g., electrically assisted) transdermal drug delivery, (b) assessing the systemic exposure of topical drugs used in dermatology, and (c) integration into other mathematical models being developed to assess the risk after topical exposure to mixtures of environmental pollutants. We also have included experimental data to provide a preliminary illustration of the performance of the model.     

Development of a Simple Phosphorus Model for a Large Urban Watershed: A Case Study

Often, the initiation of a total maximum daily load (TMDL) program is delayed until intensive monitoring data can be collected—even in watersheds where large historical data sets exist. This paper provides a case study of a modeling effort that utilizes available historical data to fulfill an intermediate goal of a TMDL program for the Passaic River Basin. The subject model is developed to simulate total phosphorus concentrations (and loads) within the basin’s effluent-dominated streams. The model is based on the assumption that the primary process controlling in-stream total phosphorus concentrations is the dilution of the cumulative upstream effluent load—which was computed on a continuous (daily) basis. Model comparisons indicate a generally good fit to long-term river-monitoring data at several key sites. Model results, and data analyses, suggest that secondary processes have a relatively minor impact on total phosphorus (TP) concentrations in this relatively large, urbanized system. This finding is consistent with a previous QUAL2E model study of the system, and consistent with the relatively conservative behavior of TP reported in many medium-to-large river systems throughout the United States. Model results are used to facilitate TMDL planning efforts for a major water supply reservoir in the basin.