Journal of Environmental Engineering

I Although admittedly effective for removing organic compounds, concerns have been raised about the cost of using GAC for treating drinking water. This paper is devoted to the discussion of the cost of granular activated carbon for removing organic compounds from drinking water. Activated carbon has been shown to be effective for removing a broad spectrum of organics from drinking water (VOC's, SOC's, TOC, etc.) but is most effective for removing high molecular weight compounds. The costs developed in this paper coupled with the proper performance relationships should be useful for all of these applications. Extensive cost sensitivity analysis is performed. Several variables are identified as being important. These include choice of system configuration, loading rate and size of system, reactivation frequency, interest rate and design life of system, local construction and operating costs and carbon use rate.

Steady state models based on the stream tube concept are presented to predict far‐field concentration distributions of pollutants in mixing zones of rivers. Analytical solutions for pipe and diffuser outfall sources, presented by Yotsukura and Cobb (30), are modified to account for the reach‐dependency of pollutant decay rate, transverse diffusion factor and channel hydraulic parameters. The models are validated using field data for a conservative tracer (chloride ion) and a nonconservative pollutant (total residual chlorine) collected in shallow rivers located in Southern Ontario, Canada. In general, the models presented in this paper are applicable to conservative and exponentially decaying pollutants.

Introduction of environmental regulations can affect the cost and completion time of civil engineering projects. Discussion focuses on public policy issues associated with environmental regulations. The basis for promulgating environmental regulations, economics of regulations, and the public view of environmental regulations are the issues presented. A number of substantive concerns about formulation and administration of environmental regulations are also examined. Quantitative information regarding the effects of environmental regulations on productivity are presented. Procedural and substantive regulatory reforms, including an innovative approach for establishing a regulatory budget, are presented. Finally, it is postulated that problems associated with environmental regulations arise largely from two types of inefficiencies (allocative inefficiencies and X‐inefficiencies). These inefficiencies are discussed and specific recommendations for minimizing them are presented.

The physical processes governing moisture transport in solid waste landfills are analyzed by the theory of unsaturated flow through homogeneous porous media and experimental work. A laboratory column was constructed and monitored to determine the behavior of unsaturated flow through solid wastes. The hydraulic properties of the refuse were determined from small scale experiments. A mathematical model was formulated and the experimental results were used to calibrate and verify it. Comparisons of measured and computed leachate discharges showed reasonable agreement. The theory of unsaturated flow through homogeneous porous media was successfully used to model moisture transport through the refuse material of a laboratory column.

This paper analyzes and evaluates the EPA's hazard ranking system for uncontrolled hazardous waste sites. Two hypothetical sites were developed from several actual case studies for use in the analysis. Sensitivity analyses were performed to determine the system response to route characteristics, containment conditions, waste characteristics and quantity, and location of the facility, under conditions with and without the release of chemical constituents. It was found that use of the ranking system requires considerable information about the facility, its surroundings, waste characteristics, and the geological character of the area. The system provides an expedient format for site evaluation, although it may sacrifice some accuracy in failing to account for the varying meteorological, hydrological, and environmental conditions across geographical regions. When an observed release is evidenced in the air route, the system responds poorly to extremely varied site conditions. The system appears to heavily weight the protection of population with less emphasis toward the protection of natural resources such as critical habitat or national parks.

A simple, accurate, Lagrangian numerical scheme is developed for modeling the advection and dispersion of a nonconservative pollutant in one‐dimensional, nonuniform river flow. The scheme is free from the common propensity to produce false oscillations and smearing in steep front regions. Testing of the scheme demonstrates its high accuracy, which is maintained on very coarse grids. A successful application is demonstrated in which it has been used to model the passage of patches of anoxic water down the Waipa River, New Zealand. Longitudinal dispersion coefficients were inferred by matching model predictions to observed steep fronts of DO and ${\mathrm{BOD}}^5\text{.}$ These were confirmed by subsequent dye studies. River reaeration and deoxygenation coefficients were also inferred, these being useful for management oriented simulation in this river and elsewhere.

Iron in titanium‐dioxide plant industrial wastewater is removed by limestone in the dune sand into which the waste is disposed. A pilot scale laboratory column experiment to investigate the interactions between the waste and the sand showed that the iron was removed from solution as iron carbonate just beyond the acid neutralization zone. As the acid front progresses the iron is redissolved and redeposited ahead of the slow moving acid neutralization zone. The net effect is that the iron is deposited in a narrow band which is moved along by the advancing acid front. Management conclusions for disposal of the waste into the dune sand are derived, based on the results of the investigation.

A cost sensitivity analysis for granular activated carbon using nine design parameters is presented. The cost analysis calculates the change in total annual plant cost for an equivalent percent change in each parameter value. This method is useful for preliminary cost estimates to predict how sensitive plant costs are to changes in design parameters, and to determine which parameters should be more closely evaluated in pilot plant work and final cost estimates.