Waste Engineering Introduction
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Questions and Answers

What is the first step in the design of a composting plant?

  • Refining, screening
  • Market product
  • Weighting/storage
  • Source (correct)

    • Which of the following is an air emission from composting?

  • Dust (correct)
  • Leachate
  • Condensate
  • Run-off

    • What is the purpose of mechanical treatment at Material Recovery Facilities (MRFs)?

  • To sort recyclables and enhance handling and transport (correct)
  • To recycle all types of waste without sorting
  • To completely reduce waste to ash
  • To incinerate waste for energy generation

    • What process is directly involved in the formation of biogas?

    <p>Methanogenesis</p> Signup and view all the answers

    Which of the following is NOT a factor in the technological process of composting?

    <p>Thermal expansion rate</p> Signup and view all the answers

    What does the typical methane yield range from in anaerobic digestion?

    <p>60-120 v/m3</p> Signup and view all the answers

    What characterizes a unit generation rate for residential waste?

    <p>The quantity of waste per defined time frame and per generating unit</p> Signup and view all the answers

    Which step in the anaerobic digestion system involves managing the residual material?

    <p>Digestate management</p> Signup and view all the answers

    Which type of waste does NOT fall under the category of residential waste?

    <p>Food processing waste</p> Signup and view all the answers

    What is the primary objective of air pollution control (APC) systems?

    <p>Dioxin removal</p> Signup and view all the answers

    What flow should glass and paper fine fibers go through in a Material Recovery Facility?

    <p>Flow through a debris screen followed by various screens</p> Signup and view all the answers

    What defines the difference between LHV and HHV?

    <p>LHV indicates energy potential after vaporizing water, HHV indicates total energy potential.</p> Signup and view all the answers

    What percentage of energy is contributed from incineration?

    <p>6% energy, 24% heating</p> Signup and view all the answers

    What are material fractions within waste?

    <p>Visually identifiable fractions with common features</p> Signup and view all the answers

    Which of the following is an example of a unit generation rate for commercial waste?

    <p>kg/year/m2 of store</p> Signup and view all the answers

    Which of the following technologies is used during mechanical treatment for size reduction?

    <p>Vibrating screens</p> Signup and view all the answers

    What is bottom ash composed of and from where does it originate?

    <p>A mix of metals and solid residues formed in a combustion chamber through a grate.</p> Signup and view all the answers

    Which method is specifically effective for both dioxin and heavy metal removal?

    <p>Activated carbon</p> Signup and view all the answers

    What is the range of methane contribution from landfills?

    <p>6-13%</p> Signup and view all the answers

    What are the two methods used for acid neutralization?

    <p>Wet and dry</p> Signup and view all the answers

    What does the term 'L/S' refer to in the context of waste treatment?

    <p>Liquid to Solid ratio indicating the amount of liquid in contact with solids.</p> Signup and view all the answers

    What characterizes fly ashes or air-pollution-control residues from waste incineration?

    <p>A fine grey powder that is hazardous waste and needs special treatment</p> Signup and view all the answers

    Which statement about waste incineration is accurate?

    <p>Wet flue gas cleaning systems often involve removal of fly ash after the wet scrubbers</p> Signup and view all the answers

    Which chemical element is likely to be the most problematic in typical fly ashes?

    <p>Hg</p> Signup and view all the answers

    Based on the C/N ratio, which type of waste is best for separate composting?

    <p>Source-segregated organic waste with a C/N ratio of 20-40</p> Signup and view all the answers

    During composting, nitrogen is primarily lost in what form?

    <p>NH3</p> Signup and view all the answers

    What is the main reason for managed water inputs in landfills?

    <p>To enhance degradation and gas generation</p> Signup and view all the answers

    What is the expected lifetime gas production from landfills per ton of waste?

    <p>120-150 m3 gas</p> Signup and view all the answers

    Which temperature range facilitates more methane (CH4) release from landfilled waste?

    <p>A temperature lower than 72</p> Signup and view all the answers

    What is a primary component of leachate generated in landfills?

    <p>Organic components</p> Signup and view all the answers

    What is the expected gas collection efficiency in Denmark?

    <p>50%</p> Signup and view all the answers

    What are liners in landfills primarily used for?

    <p>Controlling gas and leachate</p> Signup and view all the answers

    What environmental factor is NOT mentioned as affecting leaching?

    <p>Air pressure</p> Signup and view all the answers

    Which treatment process is used for advanced leachate treatment?

    <p>Reverse osmosis</p> Signup and view all the answers

    Which waste management process typically has the highest unit generation rate?

    <p>Demolition</p> Signup and view all the answers

    What best defines hydrolysis in waste management?

    <p>Breakdown of solid organic matter into water-soluble organic compounds</p> Signup and view all the answers

    Which of the following is a typical structure of a composite liner?

    <p>A clay layer with a thin plastic sheet on top</p> Signup and view all the answers

    What is the primary incentive for establishing a transfer station?

    <p>Savings in transportation costs</p> Signup and view all the answers

    Which function is NOT typically associated with a conventional Materials Recovery Facility (MRF)?

    <p>Chemical transformation</p> Signup and view all the answers

    Positive sorting in recycling typically refers to which process?

    <p>Separating valuable recyclables from a mixed stream</p> Signup and view all the answers

    How does the IPCC characterize biogenic carbon dioxide released into the atmosphere?

    <p>0 kg CO2-eq/kg biogenic CO2</p> Signup and view all the answers

    Which method is employed to ensure mercury is removed from flue gas at waste incinerators?

    <p>Using activated carbon injections</p> Signup and view all the answers

    Study Notes

    Waste Engineering Introduction

    • Waste management steps: Generation, collection, transport, and treatment
    • Generation/production refers to the source and quantification of waste before management.
    • Waste treatment can be done in transport stations with mechanical methods like compacting or shredding.
    • Desired waste treatment reductions are odor, volume, and impurities.
    • Thermal treatments for waste include incineration and gasification/pyrolysis.
    • Biological treatments include composting and biogasification (anaerobic digestion).
    • Waste utilization options include land application, construction materials, and fuel.
    • Materials Recovery Facility (MRF) sorts, processes, and recovers recyclable materials from mixed waste streams.

    Waste Management in Denmark

    • Denmark has 12 million tons of waste.
    • Construction and demolition (40%) and households (29%) are the largest waste contributors.
    • Residential waste categories include household, garden, bulky, and hazardous household waste.

    Solid Waste Issues

    • Solid waste main issues: Space, collection/separation, health issues, toxicity, different systems, cost, complex materials, and odor.

    Waste Characterization Methods

    • Waste characterization challenges include spatial, temporal, and uncertainty due to mixtures.
    • Waste sample analysis methods include physical, chemical, and performance tests.
    • Disc screens are used for organic waste characterization.

    Organic Household Waste Sub-sampling

    • Waste sub-sampling process steps are documented in figures.
    • Step-by-step procedure details from field to laboratory stages, including mass, screening and shredding, mixing in pile, barrel, dry/wet blending, high-speed blending, drying, hammer milling and final dry sample are documented.

    Waste Definitions

    • Waste categories are broad classes with common characteristics. Categories include residential, commercial/institutional, industrial and construction/demolition waste.
    • Waste types are subclasses within categories with common characteristics in source and composition, potentially resulting in separate collection and handling. Examples for residential waste are household, garden, bulky and hazardous waste. Industrial waste types vary according to the industry.

    Waste Quantification

    • Waste quantities are usually reported as wet weight.
    • Unit generation rate (kg/year/person, kg/week/household, etc.) is a key parameter for estimating waste quantities.

    Waste Minimization and Prevention

    • Waste minimization and recycling prevention is a key area.
    • A typical analysis considers factors such as material fractions, substances, wet weight, etc.

    Mechanical Treatment at MRFs

    • Purpose is to separate recyclables and residual streams, and to improve handling and transport.
    • Technologies used are separation, reduction in size, and compacting.

    Composting Technological Factors

    • Key parameters are oxygen content, particle size, aeration, pH, biodegradation, temperature, moisture content, and nutrients.

    Composting Plant Design

    • Critical components are source, weighting/storage, pre-processing, composting, refining/screening, and market production.
    • Emissions include liquid (leachate, etc.) and air emissions (NH3, N2O, CH4, dust, bioaerosols).

    Composting Process Steps

    • Degradation, stabilization, and curing.

    Nitrogen Transformation During Composting

    • Nitrogen transformation through microbial activity is an important process.

    Anaerobic Digestion

    • Hydrolysis is the first step, involving extracellular enzymes on carbohydrates, proteins, and lipids to break down organic waste. This results in dissolved organic matter, relevant in digestion and landfill processes.

    Biogas Formation

    • Biogas formation steps include hydrolysis, fermentation, acetogenesis, and methanogenesis.

    Oxidation and Methane Potential

    • Oxidation state and degradability are key factors in methane potential.
    • Anaerobic digestion process steps include receiving, pretreatment, digestion, and gas collection, utilization and digestate management.

    Incineration

    • Incineration energy contribution percentage to heating is 6% (energy), and 24% (heating).
    • LHV (lower heating value) and HHV (higher heating value) are used to determine energy content.
    • Pyrolysis is thermal degradation in the absence of oxidising agents.
    • Gasification is partial oxidation of carbon with oxidizing agents.
    • Combustion is full oxidation of carbon.
    • APC (air pollution control) systems are used for dust/fly ash removal.

    CCS (Carbon Capture and Storage)

    • CCS benefits: Energy, material and heat recovery, CO2 storage.
    • CCS burdens: Electricity, air emissions, residues, and extra materials
    • Difference in kg Co2-eq is -820; reduction of ~90%.

    Air Pollution Control

    • Dust control methods: Electrostatic precipitators, fabric filters, wet scrubbers, dry/semi-dry systems, and dust filters.
    • Acid gas control methods: Wet scrubbers, dry/semi-dry systems.
    • Heavy metal control methods: Activated carbon, SNCR, SCR.
    • Dioxin control methods: Activated carbon.
    • CO2 control methods: Carbon capture and amine.

    Incineration Residues

    • Bottom ash (mixture of metals and solids), fly ash (fine ash), and other residues (sludge, etc.).
    • Ash treatment methods: Extraction, separation, thermal treatment, chemical stabilization, and solidification.

    Landfill Emission

    • Landfill emissions include global warming, ozone depletion, toxic gases, odours, noise, litter/dust, fire risk, vegetation damage, soil, and surface water pollution, and ground water pollution.

    Landfill CH4 Contribution

    • Landfill methane (CH4) contribution is in the 6–13% range.

    Landfill Risks

    • Landfill risks: Odour, vectors, explosions, groundwater pollution, surface water, soil, vegetation damage, noise, litter, dust, global warming, and ozone depletion.

    Landfill Water Balance

    • Water balance in landfill involves leachate generation, change in moisture storage in top covers, precipitation, evapotranspiration, surface runoff, change in moisture content, surface water inflow, managed water input, water vapour, and water consumption.
    • Water input is often used in landfill procedures to control dust production and improve degradation processes.
    • Key factors for landfilling include total waste managed in Denmark (3–4%), combustible waste disposal, tax on landfilling, enhanced waste sorting, and post-sorting at landfills.
    • Temperature (T) below 72°C is beneficial for CH4 release in landfills.

    Landfill Gas Generation

    • Landfill gas generation (LFG) is influenced by anaerobic digestion of organic waste (CH4 and CO2).
    • Key factors are waste composition, waste age, temperature, and moisture content.
    • Peak CH4 emissions typically occur around 7 years into landfill lifespan.

    LFG Utilization Issues

    • LFG utilization issues include potential aeration, vertical/horizontal pipes, corrosion, blockage by water, and discontinuity.

    Landfill Collection Efficiency

    • Landfill gas collection efficiency in Denmark is about 50%.

    Leachate Generation and Factors

    • Factors influencing leachate generation in landfills include water (diffusion, advection, concentration), chemical factors (solubility, availability, pH – metals), and environmental factors.

    Landfill Liners

    • Liner functions include gas control, leachate drainage and collection, impermeability, and separation.

    Leachate Treatment

    • Leachate treatment options include biological treatment (tertiary/advanced/polishing), reverse osmosis, and physicochemical processes.
    • Sequencing batch reactor (SBR) is one system for leachate treatment, involving reactor monitoring along with it.

    General Questions (A1-A16)

    • Various questions are included, addressing waste hierarchy, waste generation rates, and waste characteristics.
    • These include factors like waste composition, different types of waste, waste management, treatment methods, and environmental effects.

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    Introduction to Waste Engineering

    Description

    This quiz covers the fundamentals of waste engineering, including the steps of waste management such as generation, collection, transport, and treatment. Delve into the various treatment methods, material recovery processes, and specific waste management practices in Denmark. Enhance your understanding of both the challenges and solutions in modern waste management.

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