18-Env-A6 Solid Waste Engineering and Management · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Reference texts: Tchobanoglous, Theisen & Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues; Vesilind, Worrell & Reinhart, Solid Waste Engineering; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); CCME, Guidance Document on Landfill Gas Management; Canadian Environmental Protection Act, 1999.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
1.1 Integrated solid waste management (ISWM) — the selection and coordinated application of applicable techniques, technologies and management programs to achieve specific waste-management objectives and goals, combining source reduction, recycling/materials recovery, composting, waste-to-energy and landfilling in a planned hierarchy rather than relying on any single disposal method.
1.2 The 3 T's in incineration — Time, Temperature and Turbulence: the three combustion-chamber parameters that must simultaneously be adequate (sufficient residence Time at a high enough Temperature, with enough Turbulence/mixing of fuel and combustion air) to achieve complete destruction of the waste and minimize products of incomplete combustion such as CO, dioxins/furans and unburned hydrocarbons.
1.3 The Perfect (ideal) Gas Law — $PV = nRT$, relating the absolute pressure $P$, volume $V$ and absolute temperature $T$ of an ideal gas to the number of moles $n$ present through the universal gas constant $R$; in solid waste engineering it is used to convert measured or estimated landfill-gas generation rates between standard and field conditions and to size collection piping, blowers and flares.
1.4 Darcy's Law — $q = -K\dfrac{dh}{dl}$, the linear relationship between the specific discharge (Darcy flux) $q$ of a fluid through a porous medium and the hydraulic gradient $dh/dl$ driving it, with hydraulic conductivity $K$ as the proportionality constant; it governs leachate seepage through a compacted clay liner and groundwater flow beneath and around a landfill.
1.5 Pyrolysis — the thermal decomposition of organic waste in the substantial absence of oxygen (an endothermic process, in contrast to combustion), producing a combustible off-gas, a liquid pyrolysis oil/tar, and a solid char residue, whose relative proportions depend on the process temperature and heating rate.
