Journal of Environmental Engineering

Water-related cancers may be classified in four groups, which correspond closely and naturally with those used by Bradley for the classification of water-related communicable disease: (1) waterborne cancers induced by ingestion or inhalation of carcinogens present in drinking water (for example, arsenic-induced skin and radon-induced lung cancer); (2) water-washed cancers due to the use of inadequate volumes of water for personal and domestic hygiene (penile carcinoma; gastric cancer associated with Helicobacter pylori infection); (3) water-based cancers associated with helminthiases (bladder cancer due to Schistosoma haematobium infection; colorectal cancer associated with S. japonicum (possibly also S. mansoni) infection; bile duct cancer associated with Opisthorchis viverrini and Clonorchis sinensis infection); and (4) water-related insect vector cancers associated with a water-related insect vector communicable disease (Burkitt's lymphoma when associated with malaria infection). Caution should be exercised, however, when using such a classification: definition of a particular cancer as water related does not mean that all cases of such cancer are water related, but only that some cases may be water related.

Highly treated waters often contain viruses at concentration levels too low to detect. This paper describes a method for drawing inferences about the concentration of viruses in treated water when very few or none are detected in collected samples. The approach uses a volume-varying version of the negative binomial distribution to construct one-sided confidence intervals about the mean virus concentration. Information on the presence of viruses prior to treatment (i.e., when densities are high enough to measure) is used to estimate parameters for the model. Samples are provided based on measurements from three southern California wastewater-treatment plants. Based on 93,679 L of tertiary treated sewage effluent, confidence intervals for virus concentrations for Pomona, Calif., ranged from 0 to 2.68$\dot{s}$10⁻⁵ plaque forming units (PFU) per liter at the 50% confidence level to 0 to 5.83$\dot{s}$10⁻⁴ PFU/L at the 95% confidence level. These values are considerably above the risk-based public health goal that is being used to regulate viruses in drinking water (2.22$\dot{s}$10⁻⁷ PFU/L). Direct measurements to demonstrate treatment to drinking water quality are therefore impracticable.

A theoretical analysis of the selective catalytic reduction (SCR) process is presented to assist in the selection of a catalyst for efficient control of NO_x from flue gases. It is a two-dimensional (2D) numerical model accounting for the simultaneous effects of external diffusion and catalytic chemical kinetics. Experimental data of SCR performance employing different types of catalysts are taken from the literature and analyzed for their NH₃ adsorption constant and effective-rate constant. The catalysts' characteristics are then used to predict their SCR performance. Good agreement is obtained between model results and experimental observations on the NO removals. The activites of the catalysts are compared and strategies affecting SCR performance are discussed. It is shown that the effective reaction rate of a catalyst is the key parameter influencing its activity. The catalyst preparation procedure as well as the V₂O₅ content are important for determining its NO removal rate.

Activated carbon has long been used for removal or recovery of volatile organic compounds (VOCs) from exhaust gas streams. Moisture content in the gas streams has been shown to be unfavorable for adsorption of VOCs; however, limited quantitative models were found in the literature. This paper reports experimental data and proposes a model concerning the effect of moisture on the adsorption capacities of a granular activated carbon (GAC) for cyclohexane and normal hexane in air streams with relative humidities (RHs), equilibrium temperatures, and VOC concentrations in the ranges of 0–0.9, 33.6–76.4°C, and 500–3,000 ppmv, respectively. Results show that within the experimental conditions the adsorption capacities of the GAC for the VOCs both in humid and dry air streams can be related to vapor pressures of the VOCs by the Langmuir model. Effect of RH on the VOC adsorption capacities are related to RHs of the air streams by the Freundlich-like model: q_VOC/q_VOC, RH=0= 1 −kRH^1/n. Some literature-cited data are also shown to be fit to the proposed model.

The nature of hydrodynamically induced particle collisions in orthokinetic coagulation is examined. For a discrete region of fluid that is exposed to linear velocity-gradients the frequency of collisions between particles is shown to be a function of the strain rates acting on the volume element of fluid containing the particles. Through transformation of the strain-rate tensor by diagonalization into principal components, a new scalar value is obtained that accurately estimates the total collision rate. This value, the absolute maximum principal strain-rate, is used in conjunction with a new collision-frequency function derived for the normal strain rates to yield an accurate relation for orthokinetic coagulation. The new method is contrasted with estimates of a global average velocity-gradient based on energy dissipation and power input to the fluid system. It is also shown that the square root of the dissipation function is not directly proportional to the velocity-gradient and that a global average of the energy dissipation function does not represent a mean-square velocity-gradient.

Because utilities with hard waters tend to have higher concentrations of arsenic, removal of arsenic via precipitative softening processes was investigated in the context of the more stringent proposed arsenic regulation. Arsenic removal can be facilitated by a variety of solids formed during softening including CaCO₃, Mg(OH)₂, Mn(OH)₂, and Fe(OH)₃. The extent of As(V) removal is decreased in the presence of orthophosphate and carbonate. As(III) removal is much lower than As(V) removal. At typical solids concentrations, arsenic removal followed a linear isotherm for CaCO₃, Mg(OH)₂, and Fe(OH)₃, with constant percentage arsenic removal regardless of initial arsenic concentrations. However, for Mn(OH)₂ solids arsenic removal was sensitive to arsenic concentrations. A framework for predicting arsenate removal when multiple solids form during softening is presented.

The blast-furnace waste generated in steel plants has been converted into a low-cost adsorbent. The resulting activated slag has been characterized and used for the removal of lead and chromium. The effect of pH, sorbent dosage, adsorbate concentrations, presence of other metal ions, temperature, and contact time on the sorption of lead and chromium were studied in batch experiments. Kinetic studies were undertaken to have an idea of the mechanistic aspects of the process. The uptake of lead is found to be greater than that of chromium. Adsorption on activated slag follows both Freundlich and Langmuir models. In addition, a series of fixed-bed experiments were performed in an attempt to simulate industrial conditions. The bed-depth-service-time (BDST) model proposed by Hutchins was successfully applied to the sorptive removal of lead. Some experiments were also performed with a view to recover Pb²⁺ and chemically regenerate the spent slag columns in situ.

An equilibrium model for simultaneous biodegradation and adsorption was developed and verified with existing data. For simplicity the model was restricted to only two components: one biodegradable and one not. The results from modeling over 300 hypothetical situations identified conditions where biodegradation significantly extends the service life of granular activated carbon (GAC) columns. When the nonbiodegradable chemical controls the service life, the only significant gains in service life occurred when the biodegradable and nonbiodegradable chemical had similar adsorbabilities. When the biodegradable chemical controls the service life, the service life was 1.2–7 times that with adsorption alone, depending on the relative adsorbability of the two chemicals. The increase in service life can be maximized by ensuring that biodegradation begins as soon as possible after start-up. The model provides a good screening tool for initial assessments of process feasibility, preliminary economic analyses, and planning of detailed experimental and computer modeling studies.

The relationship between exocellular biopolymer concentration and cation concentration was examined using laboratory scale activated sludge reactors with bactopeptone as a feed. An increase in the divalent cation concentration in the feed to the reactors was associated with an increase in the bound exocellular protein concentration, and high sodium concentrations resulted in a decrease in the bound protein concentration. The changes in bound biopolymer were explained according to the cation bridging model. Incubation of a laboratory activated sludge with a proteolytic enzyme resulted in deflocculation of the suspension as measured by an increase in the number of particles in the 5–40 μm range, which suggested that the exocellular protein was strongly involved in the aggregation of bacteria into flocs. SDS PAGE results revealed the presence of a single protein in the exocellular biopolymer extract from municipal, industrial, and laboratory activated sludge samples. The molecular weight of the protein was approximately 15 daltons. Amino acid analysis and amino acid sequencing results suggested the protein was a lectinlike protein, and binding site inhibition studies demonstrated that the protein had lectinlike activity.

Exploratory physical-model studies were made of the hydraulics of stormwater dropshafts in the city of Edmonton. Under certain conditions, it is necessary to provide a curved inlet at the top of the dropshaft to increase its carrying capacity. Except for very small discharges, the falling water in the dropshaft does not form a coherent central jet but takes the form of a complex jet with a spreading flow around the periphery of the dropshaft. Such a flow also forms a pool at the bottom of the shaft. The energy loss in the dropshaft is significant. For the case studied, with the diameter of the shaft (D_s) equal to about twice the diameter (D) of the inflow sewer and a fall of 6.6D_s, and over a wide range of flow rates, the relative energy loss in the dropshaft was about 80–95%. Further, the air flow Q_a required by the falling water, relative to the water flow rate Q, decreased from about 1.4 to 0.5 as Q_* increased from 0.1 to about 1.0. Q_*=$\mathit{Q}/\left({\mathit{gD}}^5\right)\text{.}$Q= water discharge and g= acceleration due to gravity.

The pollution plume outside Milwaukee Harbor, Wis., is investigated based on data for ammonia, chloride, and turbidity collected by the Milwaukee Metropolitan Sewerage District (MMSD) through the period 1983–94. Results of stepwise multiple regression show that the turbidity at station OH-13,B close to the Howard intake crib is strongly correlated to the turbidity at station OH-02,M in the outfall area of the Jones Island Wastewater Treatment Plant. For chloride the correlation is also significant, and for ammonia it is insignificant at OH-13,B but measurable at station NS-07,B close to the Linnwood intake. Kriging interplation is used to obtain pollution estimates at unsampled locations during average spring conditions and during two episodic spring runoff events in 1985 and 1987 for which conditions may have been similar to those during the 1993 chryptosporidiosis outbreak. The results show that improved water quality can be obtained by extending the present Howard intake pipe up to 4.64 km and/or relocating the intake pipe about 2 km south of the present location at a larger bearing (N 71° E) relative to the north-south direction.

Studies were conducted to evaluate a novel approach of emplacing chemically reactive barriers composed of zero-valent iron (Fe⁰) by injecting suspensions of colloidal-size Fe⁰ particles into porous media. The specific objective of this study was to evaluate the effect of influent colloid concentration, rate, and volume of colloidal suspensions on Fe⁰ colloid emplacement in sand columns. Relatively even distributions of Fe⁰ throughout a sand column were obtained at low influent colloid concentrations and high injection rates. As the concentration of influent suspension was increased, a point was reached beyond which a significant increase in the filtration of Fe⁰ particles near the front of the column was observed. This point was also found to occur at lower influent colloid concentrations as the injection rate was decreased, i.e., there was an interactive effect of influent colloid concentration and injection rate on the extent of filtration that occurred near the front of the column. As the volume of the colloidal suspension injected into the column was increased, the distribution of Fe⁰ colloids within the column became increasingly even.

Experiments were conducted to quantify binding of phenol, 4-chlorophenol (4-CP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) to a sandy surface soil under aerobic and anoxic conditions, with and without autoclaving. Water and methylene chloride were used to extract the physisorbed contaminants. The chemically bound contaminant was characterized as biologically or abiotically coupled. A portion of the residual contamination on soil was attributed to the presence of a desorbable but mass transfer-rate limited component of the sorbate. Autoclaving the soil or eliminating O₂ from the system had no observable effect on the total sorption of chlorophenols. However, the amount of bound material that was resistant to extraction was at least twice as high in nonautoclaved soils under oxic conditions as compared to soil in systems from which O₂ or biochemical activity, or both had been eliminated. The initial aqueous concentration of the contaminant appeared to govern the amount of nonextractable material. A biodegradation study found that approximately 50% of the coupled contaminant was bioavailable.

The purpose of this study is to demonstrate the benefits of applying spatial decision support system (SDSS) methodologies for assessing soil contamination problems. A nonparametric geostatistical technique, indicator kriging (IK), was used to determine the probability distributions for characterizing the uncertainty in the unsampled area. Such distributions over a contaminated site allow mapping of block maps of the probability above some maximum allowable limit, estimate the risks of decisions, and provide information for remediation assessment. Geographical information systems offer spatial analysis and data management capabilities that can benefit IK analysis. A prototype system, PASCA (Probability Analysis for Soil Contamination Assessment), was developed for this study. It utilizes a menu-driven interface to combine the Taiwan geographical database and models for IK analysis. PASCA was designed to specially aid users in preliminary screening of remediation priorities and in designating contaminated soil blocks that need additional sampling. The application of PASCA is analyzed through a case study involving the heavy metal cadmium.