Journal of Environmental Engineering

Hydrophobic organic compounds (HOCs) are modeled as being distributed between aqueous, micellar, and sorbent compartments in a soil/aqueous system containing nonionic surfactant micelles. The partitioning of HOC between the hydrophobic interiors of the nonionic surfactant micelles and the surrounding solution can be characterized with a mole fraction partition coefficient. Nonionic surfactant sorption onto soil may be described by a maximum sorption parameter. Sorbed surfactant molecules tend to increase HOC sorption, and free surfactant monomers in solution tend to decrease HOC sorption by increasing the HOC apparent aqueous solubility; these effects can be represented by a modified HOC soil/water partition coefficient. The distribution of HOC between the three compartments can be estimated using a physicochemical model, for which model parameter values conceptually may be obtained from independent experiments.

Experimental data are compared with results from a model developed for nonionic surfactant solubilization of hydrophobic organic compounds (HOCs) in soil/aqueous systems. The model parameters that describe each of the major physicochemical processes affecting sorption and micellar uptake of both nonionic surfactant and hydrophobic organic compounds can be characterized with values obtained independently from separate experiments involving aqueous, soil, or soil/ aqueous systems. The experimental data presented in this paper demonstrate that the modeling approach is reasonably valid for several nonionic surfactants. It is also shown that treating a soil with successive surfactant washings results in greater removal of HOC than a single washing with the same total mass of surfactant. An inverse method is evaluated with experimental data. This method permits the determination of a ratio of the values of two of the model parameters from gross experimental data such that if one parameter is measured the other can be calculated.

Solvent flushing is a potential technique for remediating a waste disposal/spill site contaminated with organic chemicals. This technique involves the injection of a solvent mixture (e.g., water plus alcohols) that enhances contaminant solubility, reduces the retardation factor, and increases the release rates of the contaminants. A simulation model is developed to predict contaminant elution curves during solvent flushing for the case of one‐dimensional, steady flow through a contaminated medium. Column experiments are conducted with a Eustis fine sand that is initially equilibrated with an aqueous naphthalene solution, and then eluted with different methanol‐water mixtures to remove the naphthalene. The model simulations, based on parameter values estimated from literature data, agree well with the measured elution profiles. Solvent flushing experiments, where the soil was initially equilibrated with a solution of naphthalene and anthracene, show that compounds with different retardation factors are separated at low cosolvent contents, while coelution of the compounds occurs at higher contents. In general, the smaller the retardation factor in water and the higher the cosolvent fraction, the faster the contaminant is recovered. The presence of nonequilibrium conditions, soil heterogeneity, and type of cosolvent will influence the time required to recover the contaminant.

A laboratory‐scale continuously fed anaerobic attached film expanded bed (AAFEB) reactor is utilized to examine the feasibility of tetrachloroethylene/ trichloroethylene (PCE/TCE) dechlorination under methanogenic conditions at 35°C. Sucrose is used as the electron donor. After a short acclimation period (two weeks), the system shows excellent dechlorination capability for treating PCE and TCE. Influent PCE concentrations of 8.2–26 mg/L are reduced to less than 0.2 mg/L (greater than 98% removal) in most cases, even though efforts are made to achieve intermediate removal efficiencies to support kinetic analysis. TCE and cis‐1,2‐dichloroethylene (cis‐1,2‐DCE) remain at low concentrations, which indicates that they were not the rate‐limiting intermediates throughout much of the test program. Preliminary estimates of the half‐velocity coefficient $\left(K_s\right)$ and maximum PCE uptake rate $\left(q_{\max }\right)$ are 0.25‐mg PCE per liter and 22.9‐mg PCE per gram VS‐per day, respectively. Most of the PCE and TCE appear to be converted to vinyl chloride. The cometabolism‐like reactions require a minimum of about eight mass units of COD reduction for each mass of PCE dechlorinated with a range of less than five to greater than 10. The results of the study suggest that the AAFEB system with sucrose as carbon and energy source is efficient and rapid enough to appear to be a feasible bioremediation process for PCE and TCE treatment, but further treatment of vinyl chloride is necessary.

Semiconductors are electrical devices that perform functions such as processing and display, power handling, and conversion between light and electrical energy. Semiconductor production processes involve over 100 proprietary solutions and 200 generic materials to achieve the final product. This industry generates significant quantities of spent solvents and liquids containing metals. The economic and liability incentives caused by increasing disposal costs and more stringent regulations are resulting in efforts to minimize such wastes at the source. This paper provides information about: (1) The type and quantity of wastes produced by this industry, much of which are listed hazardous wastes; (2) the hazardous waste disposal problems facing this industry; and (3) waste minimization case studies.

Knowledge‐based system technology has recently been introduced in activated sludge plant operations. A knowledge‐based expert system (KBES) called ASPX (Activated Sludge Process Expert) is developed for nitrification process control of a specific petroleum refinery activated sludge plant. This knowledge‐based system has been created to diagnose and correct problems with the nitrification process using rule‐based knowledge (heuristics), statistics, and a predictive mathematical model. The knowledge base consists of rules for each of six process control parameters. For each parameter the process control strategy is executed by the knowledge compiled in logic trees. Database functions such as data entry, statistical evaluation, and the simulation model for effluent ammonia concentration are also included. A user‐friendly interface enables operators who are not familiar with computers to use all of the program functions with little or no difficulty. The goal of the program is to provide an inexperienced operator with the same problem solving capability as that of a senior operator with extensive practical experience.

The effect of Acid Orange 7 (AO7) (C.I.15510), an azo dye commonly used in textile, pharmaceutical, food, and cosmetic industries, on the nitrification process is studied using completely stirred tank reactors (CSTR) and batch treatment systems. Azo dyes are of concern because many of the dyes or their metabolic intermediates are carcinogenic. AO7 biodegradation is found to be essentially complete when solids retention times (SRT) are maintained above 7.5 days, but systems with lower SRTs are unstable. It is shown that AO7 inhibits all stages of the nitrification process. Nitrite oxidizers are found to be more sensitive to AO7 than ammonium oxidizers. The results of kinetic studies indicate that the inhibition of ammonium oxidation is typified by noncompetitive inhibition; the presence of AO7 decreases the maximum substrate utilization rate and very slightly increases $K_s$, the half‐saturation constant. AO7 is found to be less toxic to nitrification than some metal and phenolic compounds, but more toxic than some common organic compounds such as formalin, methanol, or acetone.

This study investigates the complexity of wastewater flow phenomena using state‐of‐the‐art chaos analysis. Techniques used are power spectrum, correlation exponent, and Lyapunov exponent analyses. These techniques are general and can be used for other dynamic systems. The analyses provide a qualitative description of the irregular behavior of wastewater flow. Flow time series of three Ohio wastewater treatment plants are investigated. Among other things, the results indicate the presence of underlying strange attractors, which qualify the investigated flows as chaotic. These findings indicate that the structure of wastewater flow data can be very complex and that accurate prediction using stochastic models may be invalid. The procedures employed in this study can be used to evaluate flow models normally used in process control studies.

Fecal coliform and fecal streptococcus concentrations were measured at five locations across the Ruston land farm for periods ranging from 69 to 92 consecutive days. The resulting data structure was found to be log‐normal for both types of organisms. Depending on the location, statistically significant $(\alpha =0.05)$ autocorrelation was either not present, present with a lag period of one day or, in some cases, one and two days. Even though the $\mathrm{fc}/\mathrm{fs}$ ratio in the sludge storage lagoon measured 5.08 and the fecal coliform concentration in the effluent from the land farm increased by a factor of 6.5 over that of the background, the $\mathrm{fc}/\mathrm{fs}$ ratio across the site increased only marginally, from 1.77 to 2.23, suggesting that the $\mathrm{fc}/\mathrm{fs}$ ratio is not a reliable indicator of the source of bacterial contamination in natural systems, even when samples are collected close to the source of contamination.

High‐density polyethylene (HDPE) and polystyrene (PS) resins were used to encapsulate municipal solid waste (MSW) combustor ash. Ash:plastic cylinders containing up to 70% ash were produced using a mix, melt, and compaction technique. Compressive strength of the ash:plastic cylinders varied with resin type and generally decreased with increasing ash content. Toxicity characteristic leaching procedure (TCLP) regulatory leaching tests conducted on both whole and fragmented ash:plastic cylinders showed that the metal contents of the leachates did not exceed regulatory limits for toxicity. In addition, lead and cadmium were not detected in leachates from distilled‐deionized water tank leaching studies. Sodium leaching provided a valuable tool for determining the extent of ash encapsulation within the ash:plastic cylinders. Results of this study show that thermoplastic stabilization of refuse‐derived fuel (RDF) combustor ash can produce physically strong cylinders that effectively encapsulate the ash particles resulting in significant reductions in the potential for contaminant leaching.

A novel optical technique is used to investigate the dynamics of coagulation of particle suspensions with aluminum salt. The relative size of aggregates formed during coagulation, expressed as a “coagulation index,” can be continuously measured by this technique. Coagulation of clay particles with aluminum sulfate is examined at various aluminum concentrations, solution pH, and mixing intensities. Results indicate that the coagulation index provides valuable information about aggregate dynamics and coagulation mechanisms with aluminum salts.

The effect of oxidant type and flow rate were evaluated in a bench scale study using granular activated carbon (GAC) that had been loaded in a drinking water‐treatment plant and in the laboratory. The rate of regeneration of the GAC was found to be controlled by the rate of steam flow per unit GAC mass. The rate of regeneration increases with increasing steam flow in the range of steam flow rates used for commercial regeneration. At higher steam flow rates, the rate of reaction reaches a plateau value and is insensitive to changes in steam flow rate. Carbon dioxide has little, if any, effect on regeneration. Changing the inert gas flow rate used for fluidization of the GAC had no effect on the rate of regeneration at a fixed oxidant flow rate, even though it affected the oxidant partial pressure. Subbituminous GAC required higher temperatures than lignite GAC to regenerate to a specific apparent density in a fixed time period. Diffusion was not found to control the rate of regeneration. Different types of adsorbates used in a variety of studies were found to form chars of similar reactivity.

A procedure was developed to predict the removal of trace organic compounds from natural water by powdered activated carbon (PAC) adsorption systems, which function as a batch reactor or a continuous stirred tank reactor (CSTR). The procedure uses the equivalent background compound method coupled with the ideal adsorbed solution theory to quantify the competition between trace organics and background organic matter in water, and uses the pseudo single‐solute homogeneous surface diffusion model to describe the adsorption kinetics of the target compound under the influence of the background organic matter. The parameters required by the model as input data can be independently determined from adsorption isotherms and a set of batch kinetic test data. Good agreement between predicted and actual performance was found for adsorption of atrazine from Central Illinois ground water at different initial concentrations and different carbon doses using a batch reactor and two CSTRs, one of which was a PAC/ ultrafiltration system.

Because of its importance as a drinking water supply for 20,000,000 Californians, the Sacramento‐San Joaquin delta and its tributaries have received much attention with respect to drinking water quality in general and trihalomethane formation potential (THMFP) in particular. Although THMFP is a good measure of source water precursor levels, it gives only limited insight into typical finished water quality. Yet water supply decisions must ultimately consider how precursors at the source translate into THMs at the tap. This paper develops an effective tool for estimating simulated distribution system THM (SDS‐THM) species concentrations from source water precursor measurements such as THMFP. Empirical relationships for SDS‐THM formation are successfully calibrated and verified with data collected over a 14‐month period from six locations in California. The framework is shown to be a necessary link in evaluating source water management alternatives, even within a planning context where model results are reported as incremental changes between base and plan conditions.

A method of designing a stratified cooling channel for managing the excess heat of a thermal discharge is presented. The cooling channel is connected to a larger body of water such as a river, lake, or ocean. A continuous exchange flow with a larger body of water allows mixing to play an important role in reducing the temperature of a discharge in the cooling channel. The equations governing the flow and temperature in a deep cooling channel are derived from basic principles of momentum and heat balance. The numerical solutions show that most of the thermal impact of a heated discharge may be confined to within the boundaries of the cooling channel, minimizing the ecological impact on the natural environment. An example is used to demonstrate the method of designing a cooling channel. The example shows that cooling channels could operate under thermal loading conditions significantly higher than those required in cooling ponds.