The objective of this research was to characterize the anaerobic biodegradability of municipal refuse components by measuring methane yields, the extent of cellulose and hemicellulose decomposition, and leachate toxicity. Tests were conducted in quadruplicate in 2-L reactors operated to obtain maximum yields. Measured methane yields for grass, leaves, branches, food waste, coated paper, old newsprint, old corrugated containers, and office paper were 144.4, 30.6, 62.6, 300.7, 84.4, 74.3, 152.3, and 217.3 mL of CH4/dry g, respectively. Although, as a general trend, the methane yield increased as the cellulose plus hemicellulose content increased, confounding factors precluded establishing a quantitative relationship. Similarly, the degree of lignification of a particular component was not a good predictor of the extent of biodegradation. With the exception of food waste, leachate from the decomposition of refuse components was not toxic as measured by using an anaerobic toxicity assay.

The objective of this study was to characterize the anaerobic biodegradation of food waste, including its methane potential and the anaerobic toxicity of leachate associated with food waste decomposition. Biodegradation experiments were conducted in 2.2litre reactors and were seeded with well-decomposed refuse. Despite pH neutralization, reactors seeded with 30% old refuse failed to undergo methanogenesis. Food waste in a second set of reactors, containing 70% seed, produced 300.7 ml CH 4 dry g -1 . Leachate toxicity was evaluated by a modified anaerobic toxicity assay (ATA). The results of ATAs were typically consistent with the methane production behavior of the reactors. However, the toxicity observed in the ATA test could not be simulated with synthetic leachate containing high concentrations of carboxylic acids and sodium. Tests with 20, 5, 15 and 12 g 1 ' of acetate, propionate, butyrate and sodium, respectively, suggested that high concentrations of butyric acid and sodium inhibited the onset of methane production but that refuse micro-organisms could acchmatize to these concentrations within 5-10 days. The refuse ecosystem was shown to tolerate higher concentrations of undissociated carboxylic acids than previously reported for anaerobic digesters. © 1997 ISWA

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The objective of this paper is to evaluate the recycling potential of waste tires as an energy source and for use in road pavement. North Carolina, U.S.A., is used as a case study. Scrap tires may be burned for supplemental fuel in pulp and paper mill boilers and cement kilns. Five pulp and paper mill boilers in North Carolina could consume over 90% of the 6 million tires generated annually in the state. Cement kilns located within 400 km of North Carolina population centers could consume about 6.6 million tires annually. Based on the quantity of pavement laid in North Carolina, non-proprietary and proprietary versions of asphalt rubber concrete have the potential to consume 1.8 and 7.2 million tires, respectively. Rubber modified asphalt concrete has the potential to consume up to 16.5 million tires. However, technological and economic limitations suggest that large scale implementation is unlikely for the short term. Environmental considerations pertaining to each alternative are discussed. Estimates of this nature are critical as planning regions formulate solid waste management plans which include recycling.

A comprehensive nutrient removal evaluation to meet extremely low nutrient limits was performed for the South District Water Reclamation Plant (SDWRP) in Miami, Florida. Several alternatives were originally identified by the project team as possible candidates to complement SDWRP's proposed membrane filtration / reverse osmosis (RO) / ultraviolet disinfection and advanced oxidation processes to meet the required limits. A preliminary screening of these alternatives resulted in the selection of chemical phosphorus removal coupled with biologically active filters, movable bed biofilm reactors, second pass RO, ion exchange (IX), and breakpoint chlorination as the most viable nutrient removal processes for complementing SDWRP's originally anticipated three-stage RO system to meet the low nutrient limits required for the project. A comprehensive evaluation of the final alternatives resulted in the selection of chemical phosphorus removal and IX as the best processes for SDWRP. Decision factors included significant sustainable advantages compared to the other alternatives.