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This paper presents the results of development and optimization of an industrial combined-cycle gas turbine system for plasma disposal of sewage sludge. The enhanced system flow diagram, critical elements selection, and heat and mass balance optimization provide a solid basis for prototyping a plant for the disposal of sewage sludge with up to 75% water content. [ABSTRACT FROM AUTHOR]

Alum salts are commonly used in the water industry to promote coagulation in the production of clean drinking water, which results in the generation and accumulation of ‘waste’ by-product ‘alum sludge’ in large volumes. Effective and efficient management of alum sludge in an economically and environmentally sustainable manner remains a significant social and environmental concern with ever increasing demand for potable water as a result of rapidly escalating world population and urban expansion. Various intensive practices have been employed to reuse the alum sludge in an attempt to figure out how to fill the gap between successful drinking water treatment process and environmentally friendly alum sludge management for over the years. This paper primarily aimed at comprehensive review of the existing literature on alum sludge characteristics, its environmental concerns and their potential utilization, especially in agricultural and horticultural sectors leading to update our recent state of knowledge and formulate a compendium of present and past developments. Different types of alum sludge utilizations in various fields were recognized and examined. The strengths, weaknesses, opportunities and potential risks of alum sludge reuse options with particular reference to agriculture were highlighted and knowledge gaps were identified. Research priorities and future challenges that will support in the development of effective alum sludge management practices in agriculture with multi-prong strategies were discussed. [ABSTRACT FROM AUTHOR]

While anaerobic digestion is commonly practiced in the municipal sector, it has not gained popularity in the pulp and paper industry mainly because of its long sludge residence time requirement of 20–30 days. The construction of large digesters to provide such extended residence times is capital-intensive and thus the implementation of anaerobic digestion has remained economically prohibitive. A review of the literature suggests that recent developments in sludge preconditioning technologies have substantially reduced the sludge residence time requirement to the order of 7 days. Also, the preconditioned sludges have been reported to hold potential for higher methane recovery with reduced excess sludge production requiring disposal. Such advantages, coupled with escalating fuel prices and the introduction of carbon credits under the Kyoto Accord, have significantly improved the economics of anaerobic digestion. As the cost of sludge management varies from one mill to another, mill-specific economic assessment of anaerobic digestion could identify cost-saving opportunities. [Copyright &y& Elsevier]

Abstract: We studied the growth of perennial ryegrass in soils amended with 5–100% composted sewage sludge (CSS), and the impacts of CSS amendment on soil physical and chemical properties. Soils amended with ≤20% CSS did not significantly affect the seedling emergence, while the contents of chlorophyll, nitrogen, phosphorous, and potassium of perennial ryegrass grown in such soils were greatly improved. Bulk density, water retention, and nutrient contents of the soil were also improved with the amendment of CSS, but high CSS contents introduced excessive amounts of heavy metals and soluble salts. Results show that Cu, Zn, and Pb accumulated slightly (up to ∼2.3 times) in clippings of perennial ryegrass grown in CSS-amended soils compared to those grown in the base and reference soils, while no significant Cd absorption in shoots of perennial ryegrass occurred. The detrimental effects on seedling emergence and turfgrass growth observed on substrates with high (≥40%) CSS contents were mainly attributed to the presence of high soluble salt concentrations. The findings suggest that addition of CSS at 10–20% levels can greatly improve the soil nutrient supply for turfgrass growth without significantly affecting heavy metal and soluble salt contents of the soil. [Copyright &y& Elsevier]

The shear strength of an arsenic bearing sludge derived from gold mining was evaluated as a function of lime content. Lime was used as a physico-chemical stabilization agent of this waste to enhance slope stability and increase site storage capacity. Shear strength characteristics of the sludge before and after lime stabilization were obtained through unconsolidated undrained triaxial tests performed at lime content weight percentages of 0, 5, 10, and 20%. The shear strength testing results show an increase in cohesion from 5 kPa at 0% lime content, to 27 kPa at 20% lime content. Slope stability analysis indicates that stabilization of the sludges improves storage capacity by 43%. This represents an increase from 3,487.5 m3/m (0% lime content) to 4,987.50 m3/m (20% lime content). Thus the addition of lime is effective in improving the shear strength and storage capacity of arsenic bearing sludge. [ABSTRACT FROM AUTHOR]

Many communities face a waste management crisis. An increase in waste generation and decline in available landfill capacity have led to rapid increases in waste management costs. Using sewage sludge management in coastal New York and New Jersey as an example, this paper examines optimal multimedia waste disposal under cost uncertainty. Using expected value-variance analysis, the study looks at the effects on the optimal disposal strategy of uncertainty associated with waste-management cost and the community's risk preferences. The results indicate that, based on available cost data, the optimal strategy of a moderately risk-averse decision maker is to manage sludge through land-based facilities. These results hold over a wide range of risk-aversion parameters and even at low levels of cost uncertainty. Thus, the Ocean Dumping Ban Act of 1988 is consistent with such results. [ABSTRACT FROM AUTHOR]