Journal of Environmental Engineering

To ascertain whether bottom ash, or mixtures of fly ash and bottom ash from power generation could serve as acceptable final covers for landfills, field revegetation studies and indoor plant elemental bioavailability studies were conducted. It was found that bottom ash alone, or mixed with as much as 10% fly ash performs as well as topsoil in serving as a final cover, in terms of revegetation potential. Based on bioavailability studies, the inhibitory effects of higher proportions of fly ash may be due to boron toxicity.

Using time series data of water quality, streamflow records, and mathematical modeling sensitivity results, an analysis of elasticity factors influencing algal water quality is presented. A case study evaluates total regional and local water quality impacts associated with waste treatment; the site is the tidewater Potomac River. Estimates of the partial derivatives of chlorophyll concentrations, with respect to influencing factors, are combined using the total differential to find output elasticities. The elasticities allow a ranking of important factors influencing advanced waste treatment decisions. The method can be transferred to other sites; herein, a local provider's viewpoint is presented. Results of the analysis indicate that the benefits of phosphorus control are small relative to the effort required to achieve such benefits measured in terms of reducing chlorophyll‐a levels. Recognizing the dominant effect of summer streamflow, the significant uncontrollable sources of phosphorus and the unaccounted for factors influencing water quality, reevaluation of highly restrictive phosphorus control is suggested.

Identifying the need for intermediate and/or end pumping in real life wastewater collection systems, an optimization algorithm is developed for the design of gravity‐cum‐pumped systems with recourse to dynamic programming. The problem of dimensionality is minimized through cost effective feasible groupings at junction manholes and with division of algorithm in two parts. The first part identifies optimal control variables associated with each link and stores the same while the second part uses these stored values along with input data to prepare detailed hydraulic and cost statements. The effectiveness of the algorithm is tested through two case studies.

The design, construction and performance data for hazardous waste surface impoundments (SIs) at nine facilities were reviewed, and actual and projected performances were compared. Discussions were also held with four design engineering firms, one waste management company, one liner installer/fabricator, and regulatory agencies in three states. The following were identified as being essential in achieving good site performance: (1) Siting in suitable geological formation; (2) continuity of the geotechnical support throughout the project planning, site investigation, design, and construction; (3) construction supervision to ensure adherence to specifications; (4) compaction of clay wet of optimum to eliminate air space; (5) consideration of compatibility with waste in selecting liner material; (6) rigorous QA/QC to ensure adequate design and proper liner installation; and (7) providing and maintaining protective cover for liners.

A predictive model for moving media reactor performance is presented adopting a dimensional analysis of parameters involved. It is demonstrated that the reduced equilibrium concentration is a function of sorbent‐solute mass input rate ratio. A value of about 20,000 (for $C_0=1\mathrm{mg}/L$), 2,000 (for $C_0=10\mathrm{mg}/L$) and 200 (for $C_0=100\mathrm{mg}/L$), for sorbent‐solute mass input rate ratio is observed to be optimum for the reactor operation. A correlation between the predicted and the observed values for the reduced equilibrium concentrations of sorbate exhibited a standard error ranging between 0.0004 and 0.017 and a coefficient of correlation between 0.86 to 0.99.

A simplified algebraic expression for biofilm kinetics is developed. This mathematical model assumes Monod‐type biological kinetics and diffusive mass transport. The algebraic expression relates the concentration of substrate at the biofilm surface, and the thickness of the biofilm to the substrate utilization rate. The algebraic relationship is particularly suited for use in the design of biofilm processes such as trickling filters, rotating biological contactors, anaerobic filters, and fluidized or expanded‐bed reactors.

A time‐variable one‐dimensional mathematical model has been applied to Round Valley Reservoir, New Jersey, to test its credibility for simulating oxygen resources in the hypolimnia of dynamic reservoirs. In particular, the model was used to simulate the documented accelerated depletion of hypolimnetic dissolved oxygen (DO) that accompanied the use of the reservoir to augment flow in a nearby river. The model successfully simulated the reduction in hypolimnetic dissolved oxygen that occurred, and displayed potential as a valuable research and management tool for the reservoir. For example, the model results suggested that the observed acceleration in DO depletion was mostly due to a decrease in the volume of the hypolimnion. Both a sensitivity analysis and a comparison of individual sources and sinks conducted with the model indicated that sediment oxygen demand (calibration $\mathrm{value}=0.43g\cdot m^{-2}\cdot {\mathrm{day}}^{-1}$) was the most important component of the oxygen budget in the hypolimnion of the reservoir.

Optimization models have been used in the preliminary design of wastewater treatment systems to obtain a least cost design. However, this may not produce the best design if other unmodeled issues and incomplete information of the cost and performance data of the treatment processes are considered. Optimization models may be more useful in the design of wastewater treatment systems, if they can be used to generate “good” but “different” design alternatives for evaluation. A study was conducted to examine two modeling‐to‐generate‐alternatives (MGA) methods (the generating and screening, G&S, method and the efficient random generation, ERG, method) for the purpose of generating good and different preliminary designs for a typical wastewater treatment system design problem. The results showed that various attractive designs, which are good with respect to the objectives specified but widely different with respect to the treatment processes, could be generated by the two MGA methods. In comparing the alternatives produced by the two methods with those derived from the original optimization model and a constraint method, it was found that the MGA methods were more effective for the development of various preliminary wastewater treatment system designs, which not only met minimal requirements but were also widely different from each other.

The removal of $F^{-}\text{,}$ ${\mathrm{PO}}_4^{-3}\text{,}$ and ${\mathrm{SO}}_4^{-2}$ from phosphogypsum leachate (pH 1.7) by soil minerals was investigated using a serial batch procedure. PH was the controlling factor in removal of orthophosphate and fluoride, but had less effect on sulfate. Calcium carbonate precipitated major fractions of fluoride and orthophosphate, and smaller amounts of sulfate, during the early stages of leaching; with continued leaching, redissolution of fluoride and orthophosphate occurred, resulting in release of these anions at concentrations exceeding those in the original phosphogypsum leachate. Removal of fluoride and orthophosphate by kaolinite and montmorillonite was strongly affected by pH, due to complex formation, degree of ionization, and charge on the clays. Iron (III) hydroxide had little effect on fluoride or orthophosphate removal due to formation of Ca‐, Al‐, and Fe‐complexes which possibly interfered with adsorption. The iron hydroxide was important to sulfate removal at all pH values; the removal was markedly enhanced by the presence of calcium, presumably due to formation of calcium phosphate complexes that prevented orthophosphate competition with sulfate for adsorption sites.

Factors affecting the nitrification rate in post‐secondary water hyacinth treatment systems are investigated. Parameters studied include ammonia concentration, dissolved oxygen concentration, and system mixing. The nitrification rate was found to be influenced by all of the foregoing parameters, and was most sensitive to dissolved oxygen concentration. Based on the results of this study, nitrification in full‐scale water hyacinth treatment systems is ratelimited by dissolved oxygen concentration.

Shallow depth to groundwater, surface drainage, and subsurface flow during storm events can cause major environmental problems in low‐level radioactive waste management operations in humid regions. These three problems were encountered at two waste disposal sites on the Oak Ridge Reservation. In September 1983, two similarly designed, engineered drainage projects were initiated at the disposal sites. The SWSA 4 (solid waste storage area four) project was designed to divert surface runoff and shallow subsurface flow originating upslope of the site away from the disposal area. The second project, a passive French drain constructed in SWSA 6, was directed strictly toward suppressing the site water table, thus preventing its intersection with the bottoms of disposal trenches. Postconstruction monitoring for performance evaluation showed that the water table in the SWSA‐6 area is suppressed to a depth $>4.9m$ below the ground surface over 50% of the site, as compared to a depth of only 2.1m for certain parts of the same area observed during seasonally wet months. The SWSA 4 project evaluation indicates that 56% of the winter‐spring 1984 runoff was diverted around SWSA 4 via the drainage system. As a result of the reduced flow in the SWSA 4 tributary to White Oak Creek, a 44% reduction in ${}^{90}\mathrm{Sr}$ flux from SWSA 4 was calculated.