Journal of Environmental Engineering

CE‐QUAL‐ICM is a three‐dimensional, time‐variable, eutrophication model. CE‐QUAL‐ICM incorporates 22 state variables that include physical properties; multiple forms of algae, carbon, nitrogen, phosphorus, and silica; and dissolved oxygen. The model is part of a larger package that includes a three‐dimensional hydrodynamic model and a benthic‐sediment diagenesis model. Application to Chesapeake Bay over a three‐year period, 1984–86, indicates the model successfully simulates water‐column and sediment processes that affect water quality. Phenomena simulated include formation of the spring algal bloom subsequent to the annual peak in nutrient runoff, onset and breakup of summer anoxia, and coupling of organic particle deposition with sediment‐water nutrient and oxygen fluxes. The study demonstrates that complex eutrophication problems can be addressed with coupled three‐dimensional hydrodynamic and water‐quality models.

The impact of the presence of molecular oxygen on multicomponent adsorption is evaluated in this study. Adsorption equilibria for binary mixtures of phenol/o‐cresol and ternary mixtures of phenol/o‐cresol/3‐ethylphenol on granular activated carbon (GAC) are determined at 23°C using three different initial‐concentration combinations. Experiments were conducted under conditions where molecular oxygen is present (oxic adsorption) and under conditions where oxygen was excluded from the adsorbate solution and the GAC particles (anoxic adsorption). The ideal adsorbed solution theory, using the Myers equation for correlating the single‐solute anoxic isotherms, is found to accurately describe the competitive adsorption behavior of these phenolic mixtures under anoxic conditions. When the Freundlich equation was used to describe the single solute behavior, increased deviations were observed. Poor model predictions for the oxic isotherms are attributed to the presence of molecular oxygen, which promotes the polymerization of the adsorbates on the surface of GAC.

The impact of the presence of molecular oxygen in the test environment is further evaluated for adsorption behavior of a mixture of phenolic compounds on fixed‐bed GAC adsorbers. Adsorption breakthrough curves are obtained for the single‐solute system phenol, o‐cresol, and 3‐ethylphenol; the binary solute system of phenol and o‐cresol; and the ternary solute system of phenol, o‐cresol, and 3‐ethylphenol. The plug‐flow homogeneous surface diffusion model is evaluated as a predictor of adsorber performance for these systems. The binary and ternary solute calculations of the model are performed using kinetic parameters determined for the single‐solute system. The ideal adsorbed solution theory is used to describe the equilibrium on the surface of the adsorbent particle. The model predictions for the single‐solute system agree very well with the experimental breakthrough curves conducted under anoxic conditions, with exceptions to the later portion of the o‐cresol breakthrough, where tailing of the experimental breakthrough has been noticed due to the presence of limited concentrations of dissolved oxygen in the feed. The model predictions for the binary and ternary solute systems agree well with the experimental data collected under anoxic conditions.

Insufficient oxygen transfer can result in anaerobic biofilms and odor generation during biochemical oxygen demand (BOD) removal in trickling filters, and can limit ammonia oxidation in nitrifying trickling filters. Since oxygen transfer to biofilms in plastic media trickling filters occurs by diffusion of oxygen through thin fluid films, previous models used solutions based on penetration theory to calculate BOD removal. However, it is shown in this paper that penetration theory is not valid for typical hydraulic conditions in trickling filters since oxygen can diffuse through the fluid film and reach the biofilm surface. As a result, numerical solutions are required to solve the equations describing oxygen mass transport to the biofilm. Computer models are therefore used to calculate the maximum oxygen transfer during BOD and ammonia oxidation in plastic media trickling filters. These models can be used by design engineers to minimize conditions that may cause odor generation in trickling filters, and to provide an upper limit to the efficiency of nitrifying trickling filters.

The emission rates of semivolatile organic compounds during surface aeration can be estimated from the oxygen mass‐transfer coefficient $K_L{a}_{O_2}$ and a modified coefficient ${\Psi }_M$, which incorporates the fraction of liquid‐phase mass‐transfer resistance to total resistance. In order to verify this method, the mass‐transfer coefficients for oxygen and 20 volatile organic compounds (VOCs) were simultaneously measured in a laboratory‐scale surface‐aerated reactor. Using these measurements, the ratios of gas‐phase and liquid‐phase mass‐transfer coefficients were determined by nonlinear regression. These ratios then were used to estimate the fraction of liquid‐phase resistance to total resistance. The method was validated by excellent agreement between observation and theory. The correlation between the ratios of gas‐ and liquid‐phase transfer coefficients and specific power input was also studied.

A relationship developed in a companion paper to estimate emissions from surface‐aerated reactors that accounts for both gas‐ and liquid‐phase mass‐transfer resistances is extended to reactors with diffused‐aeration systems. The method accurately predicts the observed stripping rate of 20 volatile organic compounds (VOCs) with a wide range of Henry's coefficients over a wide range of hydrodynamic conditions. The degree of gas saturation and the liquid‐ and gas‐phase mass‐transfer coefficients are estimated.

Diffuser fouling is classified as one of three types, A, B, and C, based on the nature of the foulant. The accumulation of inorganic foulants, such as fine particles and precipitates, characterize type A fouling, and the formation of biomass‐characterize type B fouling. Type C fouling is characterized by the formation of biofilm, fortified by the entrapment of inorganic particles within the biomass. Hypotheses were developed to describe the mechanisms of dynamic change in diffuser operating performance as a result of the three different types of diffuser fouling. The hypotheses specific to each type were evaluated by testing the appropriate hypothetical equations using the data produced in this study. Results indicate that the physical properties of the biofilm are important factors in fouling, causing a significant change in diffuser characteristics. Entrapment of inorganic particles, such as sands, within the biofilm, significantly increase the dynamic wet pressure (DWP) and alter the bubble size. The association between DWP and bubble size could be quantitatively described by a hypothetical fouling equation for the three different types of fouling in these laboratory studies.

Activated‐carbon, oxidation, conventional‐treatment, filtration, and membrane studies are conducted to determine which process is best suited to remove the herbicide glyphosate from potable water. Both bench‐scale and pilot‐scale studies are completed. Computer models are used to evaluate the results. The activated‐carbon results show that glyphosate adsorbs very strongly in distilled water, but has a much lower capacity in Ohio River water. The jar‐test studies with an alum coagulant show that as turbidity is removed, so is glyphosate. The majority of the glyphosate removal occurs as turbidity is reduced below 2 nephelometric turbidity units (NTUs). Powdered‐activated‐carbon treatment is ineffective. Ultrafiltration membranes and 0.45 μm filters do not remove glyphosate in Ohio River water even though the effluent turbidity is reduced below 0.2 NTU. The oxidation results indicate that glyphosate is easily destroyed by chlorine and ozone. Chlorine dioxide, permanganate, and hydrogen peroxide are less successful. These conventional‐treatment and adsorption results are confirmed by pilot‐scale studies.

A mathematical model incorporating the performance relationships and cost functions for the component units of a conventional water‐treatment system (viz rapid mix, clariflocculator, and rapid sand filters) was developed. An algorithm using dynamic programming is described for functional and minimal‐cost design of the system. An analysis of the stability of optimal design and its sensitivity with respect to some system parameters (viz input characteristics, interest rate and construction and power costs) is also incorporated specifically with respect to a case study.

The purpose of this research was to chemically characterize refuse and extract samples and to evaluate gas generation from the Fresh Kills Landfill on Staten Island, N.Y., and to use this information to draw conclusions about the overall rate and extent of decomposition within the landfill. The refuse samples were characterized in terms of moisture content, lignin, cellulose, and various selected chemical species. Analysis of the extract samples included measurements of total organic carbon, volatile acids, pH, and other specific materials. Gas‐production factors, such as temperature and moisture content, were also studied. Results indicate that refuse samples ranged from basically undecomposed to well decomposed, based on the wide range of cellulose concentrations and cellulose to lignin ratios. Organic parameters in the refuse were strongly correlated to refuse age. Interrelationships between the liquid parameters are generally consistent with published phases of decomposition. For gas‐producing refuse samples, moisture contents were significantly higher than for those samples not producing gas. Temperatures between 30°C and 40°C were preferable for gas production.

Energy recovery from municipal solid waste (MSW) is attractive to state and local governments due to the economic value of the recycled materials, the energy cost savings from recycling, and the cost savings derived from reduced landfill volumes. The energy cost savings included in the study are both avoided costs from the recycling and reuse of materials and recovered energy through waste‐to‐energy conversion of MSW. This study compiles information from several sources in order to define the avoided energy costs and recovered waste‐to‐energy. The scenarios outlined in this report illustrate the projected energy savings from different programs designed to: (1) Recycle 100% of certain MSW; (2) recycle 25% of certain MSW; (3) recycle MSW to achieve maximum energy recovery; (4) recycle MSW to minimize landfill disposal and; (5) minimize landfill volumes utilized and maximize energy recovery by incineration of plastic waste. It was concluded that waste‐to‐energy conversion is necessary if energy recovery and volume minimization are to be optimized simultaneously.

This paper provides a description of tire recycling conditions in the state of Wisconsin, a summary of the status of legislation affecting tire disposal in the United States, and a list of the major scrap‐tire applications. The paper also provides an evaluation of the economics of the scrap‐tire processing industry. The economics of the entire disposal cycle is examined in five steps, each addressed as a separate investment scenario. First, the economics of a licensed collection site is examined. Second, the economics of adding a shredding operation to the collection site (in order to free some of the escrow money held by the state) is considered. Third, the hauling of the shredded tires to a landfill (in order to recover the rest of the escrow and eliminate storage liability) is discussed. Fourth, the economics of hauling the shredded tires to an end user, eliminating landfill fees, is evaluated. Fifth, the ideal scenario of hauling of shredded tires to a buyer is examined. Under the assumptions used, the tire‐shredding industry can yield a rewarding return on investment. However, profitability of the investment is particularly sensitive to the amount of escrow required by the regulatory authorities. It is suggested that regulatory authorities reexamine the amount and distribution of escrow to encourage tire processors in completing the recycling process by finding an end user for the recycled materials.

Novel oxygen‐based modifications of the Claus process for sulfur recovery from gases containing hydrogen sulfide are analyzed and compared with the conventional air‐based technology. Oxygen‐based modifications include systems with air enrichment by oxygen, with oxygen‐air‐water oxidizers, with recycle of cooled products from boilers back into the Claus furnace, and systems with consecutive or parallel‐consecutive Claus furnaces. The analysis used in this work involves the process thermodynamics and kinetics, as well as modeling of the entire system. The thermodynamics was evaluated using the STANJAN chemical equilibrium solver program, which utilizes the principle of minimization of free Gibbs energy. The process kinetics was evaluated using published data on full‐scale Claus systems. The performance of various process modifications was evaluated by the use of numerical analyses. The major findings of the work are that oxygen‐based Claus systems can be used for: (1) Upgrading existing systems and for use in new systems; and (2) reducing the equipment size requirement in new systems. In addition the Claus process may be used for a variety of conditions met in various industries.