J. Jeffrey Peirce

Curbside recycling in the U.S.A. : convenience and mandatory participation

This research examines the relationship between the success of a residential curbside recycling program (RCRP), measured as material recovery rate (MRR), and two program factors: (1) whether or not participation is mandated; and (2) convenience, measured by container provision, collection frequency and collection day relative to municipal solid waste collection day. Residential curbside recycling programs, with correct strategies and program design, can be an important part of solid waste management plans world-wide. While residential curbside recycling programs are growing in popularity, many basic design questions lie unanswered and successful program strategies are not always obvious. Data from 357 residential curbside recycling programs in the United States are used to test the hypotheses. Mandatory participation residential curbside recycling programs are seen to collect more material than voluntary participation residential curbside recycling programs. Container provision appears effective for voluntary, but not mandatory, residential curbside recycling programs. Increasing collection frequency appears to have a small positive effect on residential curbside recycling program success, while collection day has little effect on material recovery rate.

Identification of hydraulic conductivity structure in sand and gravel aquifers: Cape Cod data set

This study evaluates commonly used geostatistical methods to assess reproduction of hydraulic conductivity (K) structure and sensitivity under limiting amounts of data. Extensive conductivity measurements from the Cape Cod sand and gravel aquifer are used to evaluate two geostatistical estimation methods, conditional mean as an estimate and ordinary kriging, and two stochastic simulation methods, simulated annealing and sequential Gaussian simulation. Our results indicate that for relatively homogeneous sand and gravel aquifers such as the Cape Cod aquifer, neither estimation methods nor stochastic simulation methods give highly accurate point predictions of hydraulic conductivity despite the high density of collected data. Although the stochastic simulation methods yielded higher errors than the estimation methods, the stochastic simulation methods yielded better reproduction of the measured In (K) distribution and better reproduction of local contrasts in In (K). The inability of kriging to reproduce high In (K) values, as reaffirmed by this study, provides a strong instigation for choosing stochastic simulation methods to generate conductivity fields when performing fine-scale contaminant transport modeling. Results also indicate that estimation error is relatively insensitive to the number of hydraulic conductivity measurements so long as more than a threshold number of data are used to condition the realizations. This threshold occurs for the Cape Cod site when there are approximately three conductivity measurements per integral volume. The lack of improvement with additional data suggests that although fine-scale hydraulic conductivity structure is evident in the variogram, it is not accurately reproduced by geostatistical estimation methods. If the Cape Cod aquifer spatial conductivity characteristics are indicative of other sand and gravel deposits, then the results on predictive error versus data collection obtained here have significant practical consequences for site characterization. Heavily sampled sand and gravel aquifers, such as Cape Cod and Borden, may have large amounts of redundant data, while in more common real world settings, our results suggest that denser data collection will likely improve understanding of permeability structure.

Laboratory study of NO flux from agricultural soil: Effects of soil moisture, pH, and temperature

Unique laboratory test chambers with attendant procedures are described, and the results of a comprehensive test protocol are discussed in terms of the mechanical, chemical and biological factors contributing to NO flux from agricultural soil to the lower levels of the troposphere. Soil moisture content, pH, and temperature are investigated to determine the effects of these important variables on NO flux. The flux is seen to increase with temperature and is greatest at pH 8 for the ranges studied. Further, NO flux is seen to decrease as soil moisture content is 45% water filled pore space. Mechanical, chemical, and biological factors in the soil which contribute to these observed fluxes are addressed.

The development of pulsed flow air classification theory and design for municipal solid waste processing

The development of pulsed flow air classification theory and design for municipal solid waste (MSW) processing is described. The results of previous theoretical and empirical work is summarized and the results of recent experimental studies are presented in greater detail. Pulse flow air classification using smaller scale (air flow regimes of approximately 161 cm2) air classifiers is found to process MSW into combustible and noncombustible fractions more efficiently than zig-zag and straight air classifiers. In recent studies with larger air classifiers (air flow regimes of 929 cm2 and greater), this result has been confirmed. Furthermore, with active pulsed air classifiers, the pulse frequency was found to have little effect on the efficiency in the 1 to 2.5 Hz range, while symmetric and quick-rise pulse shapes appeared to outperform slow-rise pulse shapes. Active pulsed air classifier performance improved as the percentage of the air flow pulsed increased. In direct comparisons using simulated and actual MSW feeds the passive pulsed stacked-triangle outperformed the active pulsed which in turn outperformed the zig-zag non-pulsing air classifier.

Measuring the success of recycling programs

Abstract Drawing from resource recovery unit operations research, a single-value-parameter reflecting both material recovery and purity considerations is suggested for calculating recycling program efficiency. Other measures of success are presented and data from a 1989 survey of over 1200 residential curbside recycling programs are used to assess the degree to which these measures are used. The ability of block leaders to estimate block participation rates is also explored. Two important measures of recycling program success which do not take into account purity considerations are presented, annualized per capita material recovery rate (MRR), and annualized per capita recycler material recovery rate (RMRR) as is the participation rate (PR). It is suggested that, in conjunction with the annualized per capita material availability rate (MAR), knowledge of PR and RMRR can be used to determine program recruitment strategy. If PR is low, program recruitment strategy should target non-recyclers. If RMRR is low compared to MAR, strategies should encourage participants to recycle a greater percentage of the available recyclable material. Survey results indicate that success measures MRR and PR are under-utilized and unstandardized. Block leaders appear to be able to estimate general levels of block participation, but not specific participation rates.

Predicting particle behavior in air classifiers

Abstract A test to predict the behavior of irregularly shaped particles in a vertical air flow is developed and evaluated. The fundamental aspects of particle behavior are discussed, while irregularly shaped particles are highlighted. Dropping such particles in calm air at a height to establish a defined terminal settling velocity is the basis for the test. Meaningful comparisons are made as the same particles are injected in a vertical air flow. Conclusions point to the usefulness of the drop test for predicting particle behavior in a vertical air flow in general and organic/inorganic solid waste particles in air classifiers in particular.

Boundary Layer Model for Air Pollutant Concentrations Due to Highway Traffic

A numerical solution of the three-dimensional, steady-state diffusion equation for a finite width lihe source is presented. The wind speed and eddy diffusivjty are a function of height above the roadway and are obtained from the surface roughness, the net heat flux, and the upper wind speed. Normalized ground level and elevated concentrations near a highway are obtained for winds perpendicular to the roadway, parallel, and at 45° to the roadway.

Statistical determination of steady state condition in bioremediation tests

Linear regression and two newly developed statistical techniques were used to determine steady states in the dependent y-variables (effluent concentration or removal rate of pollutants) using correlation coefficients (r) for the relationship between the independent x-variables (reactor operating or treatment time) and the dependent y-variables. The statistical technique applied to chlorophenol bioremediation using a varying number of data points for linear regression analysis was more useful in determining a steady state for six general data patterns from bioremediation tests than the statistical technique using a fixed number of data points for linear regression analysis.

DIFFERENTIAL FLOW PATTERNS THROUGH COMPACTED CLAYS

The determination of the hydraulic conductivity of compacted clays is vital when the clay is to be used as a liner for contaminant of hazardous waste. Therefore different types of permeameters were used and modified to investigate the homogeneity of a compacted specimens. Flexible wall and fixed wall permeameters were modified using multiple ring bases to determine the magnitude of differential flow patterns during hydraulic conductivity testing. The hydraulic conductivity was calculated for different portions of the specimen. The outer ring of the specimen was found to have a permeability two to five times larger than that of the core of the specimen, resulting in an overall permeability, which was 50 to 100% higher than that of the core of the specimen. Thorough determination of the variation of the density within a specimen does not explain the variation of the hydraulic conductivity. The clay near the periphery is apparently exposed to a somewhat different type of compaction resulting in a different structure of the clay and thus a higher permeability. Tests with a 19 port base indicated that isolated areas could contain channels where major flow takes place.

Methodology for Identifying Optimal Locations of Water Quality Sensors in River Systems

A method to optimally site river water quality sensors is expanded and applied to a case study river to explore the application of mathematical siting methods to the design of river sampling networks. Fecal coliform contamination due to flooded swine waste lagoons was modeled as it moves downstream, and optimal sensor locations are located by minimizing the objective function of the optimization problem. The results of the simulations are analyzed by varying the number of allowed sampling locations and the simulated contamination event. For the case study application, the model suggests three sampling locations along the modeled river section. These three suggested sensing points did not greatly vary in location for different river flows and contamination events, indicating the robustness of the model results for this specific case study. Generally, the application of mathematical contaminant modeling is a useful and systematic approach to aid the design of river water quality monitoring networks.