Journal of Environmental Engineering

The environmental and health risks posed by unregulated landfills are concerns that must be addressed. These concerns have been highlighted with the recent reauthorization of the Resource Conservation and Recovery Act (RCRA) Subtitle D, which requires the closure of all unregulated landfills by October 1993. Most communities with unregulated landfills do not have the financial resources to conduct full-scale risk assessments. This paper proposes the use of a multicriteria assessment system as a tool for screening and prioritizing unregulated disposal sites according to their level of environmental and health hazard. This multicriteria assessment system uses a technique termed composite programming and allows for the use of imprecise information through fuzzy set theory. Using this methodology in landfill hazard assessment allows for the consideration of uncertainty associated with parameters that impact the hazard assessment. Additionally, the user can specify hazards that are most detrimental. The complexity of input parameters (first level indicators) were selected to minimize the time required to collect and/or analyze site-specific data. The result obtained in the assessment is a fuzzy number that indicates the most likely range of hazard and the largest likely range of hazard relative to the best and worst case scenarios. A case study, in which this method is applied to a small rural landfill, is presented to illustrate the methodology.

GIGO, a spreadsheet-based model of municipal solid waste (MSW) management systems is described. The model is intended for general system-level simulation consisting of linked detailed facility, process and cost models that can also be used independently to simulate components of a solid-waste-management system. The model requires no special programming skills beyond knowledge of the use of a common spreadsheet. The model is flexible, easy to use and modify, and is in the public domain. Model formulation and implementation are described.

A leachate recycle system was constructed and operated at an existing lined landfill in North-Central Florida to observe the effects of leachate recycle on landfill stabilization. Samples of leachate, landfill gas, and landfilled solid waste were collected and analyzed throughout a four-year period, before and after the start of leachate recycle. The settlement of landfilled waste was also measured in wetted and dry areas of the landfill. Leachate quality was not dramatically impacted by leachate recycle. Moisture content was significantly greater in the area of the landfill subjected to leachate recycle. Waste temperature and pH measurements indicated that conditions suitable for anaerobic decomposition were present in both the treated and untreated areas. Measurements of solid waste biochemical methane potential and subsidence showed that a greater degree of landfill stabilization had occurred in the leachate recycle area relative to the untreated area.

Onondaga Lake, N.Y., experiences a marked annual dissolved oxygen depletion over the entire water column at fall turnover. Depletion occurs as a result of the entrainment of reduced substances that have accumulated in the lake's hypolimnion over the summer. Recovery (return to near-saturated conditions) occurs over a period of 3–4 weeks. Observations of dissolved oxygen (DO) levels during the recovery period of two years are used to calculate the reaeration coefficient ( K _a,20= 0.22 d ⁻¹ in 1989, and 0.13 d ⁻¹ in 1990) and the liquid film transfer coefficient for oxygen ( K _L,20= 2.64 m⋅d ⁻¹ in 1989, and 1.50 m⋅d ⁻¹ in 1990). Local wind measurements are used to develop an empirical relationship between wind speed ( U₁₀, m⋅s ⁻¹) and K _L,20: K _L,20=$\alpha \cdot {\mathit{U}}_{10}^{\beta }$, with α= 0.2; β= 1.0 for U₁₀≤ 3.5 m⋅s ⁻¹ and α= 0.057; and β= 2.0 for U₁₀> 3.5 m⋅s ⁻¹. Model output and field observations are compared with estimates generated using other published relationships.

Copper has been used in the marine environment for decades as cladding on ships and pipes to prevent biofouling by marine mussels ( Mytilus edulis L.). This motivated the present investigation into the possibility of using copper to prevent biofouling in freshwater by both zebra mussels and quagga mussels ( Dreissena polymorpha and D. bugensis collectively referred to as “zebra mussels”). Copper and copper alloy sheet proved to be highly effective in preventing biofouling by zebra mussels over a three-year period. Further studies were conducted with copper and copper-nickel mesh (lattice of expanded metal) and screen (woven wire with a smaller hole size), which reduced the amount of copper used. Copper screen was also found to be strongly biofouling-resistant with respect to zebra mussels, while copper mesh reduced zebra mussel biofouling in comparison to controls, but did not prevent it entirely. Preliminary investigations into the mechanism of copper antifouling, using galvanic couples, indicated that the release of copper ions from the surface of the exposed metal into the surrounding water is directly or indirectly responsible for the biofouling resistance of copper.

An aerobic fluidized bed reactor process with internal media cleaning to control attached biomass thickness was developed. Biomass control was achieved by the periodic creation of a turbulent zone within a specially designed cylindrical screened region surrounding the effluent port. A screen washer aided in keeping the cylindrical screen clean. A bed lifter produced turbulence throughout the bed to allow individual media particles to enter the cleaning zone for the removal of excess biofilm. The reactor system operated continuously without excessive biomass buildup on the support media and without the need for external media cleaning or recovery. Four analytical methods—systematic scanning electron microscope (SEM) analyses, granular activated carbon drained density, phospholipid analyses, and fluorescein diacetate activity (FDA) measurements—were modified/developed for use in characterizing the microbial population attached to the media of the fluidized bed. The SEM analyses was valuable for monitoring changes the cleaning cycle caused to the biofilm. Phospholipid and FDA analyses were found to have potential for use as design and monitoring tools of the process.

The effect of feed water flow rate on the concentration-polarization of magnesium sulfate, sodium chloride, and sodium selenate in reverse osmosis (RO) spiral-wound elements was investigated and modeled. Experiments were performed with 40 in. long and 2.5 in. in diameter spiral-wound elements tested with feed solutions of the single electrolyte magnesium sulfate, and a mixture of sodium chloride and sodium selenate as major and trace components, respectively. The feed flow rates investigated ranged from 1.12 to 13.5 L/min, corresponding to Reynolds numbers from 25 to 300. The element was modeled by dividing it into n identical subelements, each separated into two compartments, feed channel and product water carrier, by the RO membrane. The feed channel compartment of each subelement was assumed to be an ideal continuous-flow stirred tank reactor (CSTR). Model predictions correlated generally well with experimental observations. Predicted product water flow rates and solute concentrations were within 12 and 24%, respectively, of corresponding experimental values.

The pyrolysis kinetics of cellulosic uncoated printing and writing paper, which is one of the principal materials contributing to the municipal solid waste (MSW) of Taiwan, was investigated with a thermal gravimetric analysis (TGA) reaction system. The experiments were carried out in a nitrogen environment in the 450–850 K temperature range at various constant heating rates of 1, 2, and 5 K/min. The results indicated that there were two principal reactions in TGA curves as distinguished by the two significant and distinct mass changes over the experimental conditions. The pyrolysis of uncoated printing and writing paper can be adequately described by a two-reaction model. The corresponding activation energies, preexponential factors, and reaction orders were determined. The experimental results were satisfactorily fitted by the proposed chemical reaction model.

To date, the hydrocyclone has played an important role in producing classified or concentrated materials and in removing harmful or hazardous substances. The material behavior is dominated not only by the centrifugal force and the mean fluid velocity but also by the structure of turbulence in the hydrocyclone. In this paper the structure of turbulence has been evaluated first by analyzing observed turbulent characteristics and then, the effect of turbulence on the separation performance has been numerically evaluated taking into account the propagation of turbulent energy by diffusive mixing. The results indicate that the separation performance is deteriorated as the intensity of turbulence is increased in the hydrocyclone. In order to improve the separation performance two types of turbulence-free cyclone-like separators, called Minoclone and Staticlone, have been developed, which have been successfully applied to classifying fine particles. Finally, the Staticlone has been applied to remove metallic pollutants from fine slimes. Consequently, it has been proved that the turbulence-free separator can play an excellent role in processing of fine slimes compared with a conventional hydrocyclone.

Soil column experiments were performed to differentiate between abiotic and biological mechanisms for removal of residual organics from chlorinated municipal effluent during soil aquifer treatment (SAT) and to relate SAT efficiency to degree of wastewater treatment. Three water-quality parameters were examined: dissolved organic carbon (DOC), ultraviolet (UV) absorbance at 254 nm (UVA ₂₅₄ ), and adsorbable organic halide (AOX). Secondary and tertiary-treated effluents were applied to 1-m unsaturated columns containing soils from the Sweetwater Underground Storage and Recovery Facility, Tucson, Ariz. DOC was removed primarily by biological activity during SAT. Through-column removal using chlorinated secondary effluent averaged 48%. UVA ₂₅₄ reductions were dependent on biological and abiotic removal mechanisms. Aerobic biological activity did not contribute significantly to AOX removal. Through-column reductions for UVA ₂₅₄ and AOX from secondary effluent averaged 30% and 17%, respectively. Forty-four percent of the through-column DOC removal and 57% of UVA ₂₅₄ attenuation occurred in the top 8 cm of soil. The post-SAT organic quality of secondary and tertiary (dual-media filtered) effluents was essentially equivalent.

This study was to evaluate the leaching characteristics of a solidification/stabilization system, using a static-renewal leaching test in which the leachant was renewed periodically after intervals of static leaching. Tricalcium aluminate was selected as a solidification agent and CuO as a contaminant to simplify the solidified waste. The model solidified waste matrix was vulnerable to the renewable acetic acid (1 N) solutions. The release of Ca was rapid; in about 10 extractions, the amount of Ca released had reached the maximum. Similarly, the leaching of Al was significant; about 90% of the total Al solidified was transferred to the acetic acid solution after 10 extractions. The proton promoted surface reaction is hypothesized to be the controlling process in dissolving the calcium compounds. The dissolution reactions would enlarge the capillary pores and produce new voids in the matrix that enhance solute leaching. Since both Ca and Al hydration compounds were rapidly leached out of the solid matrix, C₃A eventually played an insignificant role in immobilizing the CuO constituent.

Widespread use of s -triazine herbicides such as atrazine, simazine, and cyanazine has led to the contamination of many ground-water and surface-water supplies with the parent compounds as well as by primary metabolites (e.g., deethylatrazine, deisopropylatrazine, and deethylcyanazine). Ozonation has been shown to produce many of the same byproducts. Activated carbon adsorption has been designated by the U.S. Environmental Protection Agency as the best available technology (BAT) for the treatment of herbicides in drinking water. Little data is available, however, on the applicability of activated carbon treatment for the control of the primary degradation products of herbicides. In this study, the adsorption of deethylatrazine, deisopropylatrazine (deethylsimazine), and deethylcyanazine on powdered activated carbon (PAC) was examined including development of Langmuir and Freundlich isotherm coefficients. It was found that deethylatrazine, deisopropylatrazine and deethylcyanazine were readily treatable using powdered activated carbon (PAC). However, the PAC's adsorptive capacity for deethylatrazine, deisopropylatrazine, and deethylcyanazine was generally less than for atrazine resulting in higher estimated carbon costs.