Journal of Environmental Engineering

The chemical-mass-balance (CMB) receptor model is a method for determining specific-source contributions of volatile organic compounds (VOCs) to concentrations of nonmethane organic compounds (NMOCs) measured in the ambient air. Because the method is based on air measurements, it offers an independent check on emission inventories developed by more traditional permit, survey, emission factor, and source-test techniques. This paper reports on the application of the CMB model to speciated NMOC air-measurement data sets collected during the summers of 1984–88 in five U.S. cities: Detroit; Chicago; Beaumont, Tex.; Atlanta; and Washington, D.C. Sources modeled were vehicle tailpipe emissions, fugitive gasoline-vapor emissions, architectural coating solvents, emissions from graphic arts, petroleum refineries, coke ovens, and polyethylene production. Comparisons of the CMB allocation of NMOC to emission inventory allocation of VOC for each city is discussed. Agreement with Environmental Protection Agency inventories for the five cities was generally very good for vehicles. Refinery inventory estimates are lower than CMB estimates by more than a factor of 10 in Chicago and Detroit. Trajectory analysis was used to validate coefficients for coke ovens.

Combined sewage overflow (CSO) discharges due to a storm event create strongly stratified pollutant plumes on the surface of Mt. Hope Bay, of Rhode Island and Massachusetts. To examine the CSO-induced pollutant impact, a three-dimensional numerical model was used to simulate the transport processes in the bay resulting from a dye release at CSO discharges during a storm event on September 22, 1990. The model used a vertical γ-coordinate system, with higher grid resolution near surface, to describe the constituent transport. Model predictions reasonably showed that the CSO plume remained concentrated near the surface and was transported down bay along the eastern shore. Agreement of predictions of sea surface elevation, currents, salinity, and dye concentrations with available observations was good. Time series of predicted dye concentrations were used to estimate the flushing time, which was approximately 2 days at midbay. Sensitivity studies were performed for several vertical-grid resolutions. The use of the γ-coordinate system was shown to be more efficient for describing the CSO-induced transport processes, with relatively less computational cost.

Increased quantities of wastewater-treatment sludge coupled with more stringent regulations make it important to develop alternatives for residuals management. The use of a mixture of anaerobically digested, lime-stabilized wastewater sludge (LSS) and soil as a cover material was evaluated for its effect on refuse decomposition and leachate quality. Tests were conducted in 4-L reactors filled with shredded refuse and operated to accelerate refuse stabilization. Cover mixtures evaluated in quadruplicate included pure soil, pure lime, and mixtures containing 40% and 70% LSS in soil. Methane production and leachate stabilization were enhanced in reactors containing added lime or LSS. The presence of LSS in the cover did not increase the concentrations of NH ₃ -N, PO ₄ -P, Cd, Cr, Fe, Ni, Pb, or Zn in the leachate. There was a slight increase in Cu attributable to LSS. The use of LSS, or other lime-containing wastes in landfill cover material has the potential to be beneficial as a source of inexpensive cover material, as an outlet for lime waste, and as a method to enhance refuse decomposition and leachate stabilization.

Tire pyrolysis kinetics was investigated to explore an economically viable design for the pyrolysis process. Derivative thermogravimetry (DTG) and thermogravimetric analysis (TGA) were found to provide valuable information on pyrolysis kinetics and mechanisms of a heterogeneous compound like scrap tire rubbers. Kinetic parameters of each compositional compound were obtained by analyzing DTG and TGA results with a series of mathematical methods proposed in this study. The pyrolysis kinetics of the scrap tire rubbers tested was well accounted for by the first-order irreversible independent reactions of three compositional compounds. The sidewall and tread rubber exhibited different thermal degradation patterns, suggesting a compositional difference between them. Isothermal pyrolysis results showed that the sidewall rubber would hardly be degraded at low temperature regions ( <600 K), whereas it would be more rapidly degraded than the tread rubber at higher temperatures (≥746 K). Because of the shorter pyrolysis time, the higher isothermal pyrolysis temperature appeared to be more economically favorable.

In recent years, the carbonaceous biochemical oxygen demand ( CBOD₅ ) test has been employed to determine the carbonaceous fraction of the biochemical oxygen demand ( BOD₅ ) of final effluents in nitrifying systems. More recently, several states have required plants to analyze influents using the CBOD₅ test to determine whether the 85% removal rule is being attained. The 1989 Standard for the Examination of Water and Wastewater Methods does not suggest—nor does the Environmental Protection Agency (EPA) CBOD₅ procedure studies justify—the use of the CBOD₅ test for raw and settled wastewaters. Analysis of operational data from several plants demonstrates that the CBOD₅ test seriously understates the true strength of influent and primary effluent wastewaters as defined by BOD₅ and chemical oxygen demand ( COD ) tests. The result of using CBOD₅ data could result in a 20–40% underdesign as well as cause nonexistent effluent violations of the EPA 85% removal criteria rule. The conclusion was that CBOD₅ is an improper test for influent and settled raw wastewater.

An innovative field sampling system for screening contaminated soils has been developed using laser ablation coupled with inductively coupled plasma–atomic emission spectrometry (LA-ICP-AES) technology. This sampling approach provides in-situ real-time analysis of trace inorganic elements and is conducted through a mobile testing facility that consists of an instrumentation vehicle called the Mobile Demonstration Laboratory for Environmental Screening Technologies (MDLEST) and an attached trailer called the Robotic Sampling Accessory (RSA). The RSA provides automated sampling capabilities through an attached three-degree-of-freedom robot that is equipped with a surface-sampling probe. The MDLEST-RSA was successfully tested at a Department of Energy (DOE) site in Fernald, Ohio, during the fall of 1992. This paper provides a description of the analysis technique, the MDLEST and RSA, and results of the field demonstration. In addition, benefits, limitations, and future plans are also discussed.

An advanced operational strategy was developed in this study for a batch microbial leaching process, employing sulfur oxidation for heavy metal removal from sewage sludge, to terminate the batch operation at its best moment. Due to the practical difficulties associated with on-line measurement of soluble metal concentrations during the leaching operation, the present methodology is based on pH measurements in the reacting system. To monitor the metal solubilization, the bioleaching process model was developed, corresponding with the activity of the less-acidophilic bacteria and the acidophilic bacteria. An advanced on-line predicting system was then implemented; it employed the techniques of extended Kalman filtering and the neural net-based model that was based on a large amount of experimental observations in our laboratory to predict concentrations of six heavy metals in the bioleaching system's liquid phase. Finally, a case study illustrating the application is presented.

This paper describes the use of system-specific and literature values for the distribution coefficient ( K _d ) in a screening-level ground-water contaminant-transport model. A comparison of observed contaminant transport (Cd ²⁺ ) in a laboratory soil column with predicted contaminant transport using a computer model is described and discussed. The results indicate that measured K _d values and K _d values taken from the literature can provide useful approximations of the sorption of inorganic ions in screening-level ground-water contaminant-transport models if experimental conditions (especially pH and electrolyte composition) and soil type are similar to those being modeled.