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Waste Management > Solid Waste Test > Flashcards

Solid Waste Test Flashcards

1
Q

MSW

A

Municipal solid waste

Amounts generated in a region depends on:

  • rates of urbanisation
  • types and patterns of consumption
  • household revenue and lifestyles.

-Often more than 30% of public sector budget to prevent/mitigate pollution (main concerns are impact on human and enviro health).. We’re bad at it as Canadians.

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2
Q

Global MSW Outputs

A

1 - US, #2 - China, #3 - Canada

OECD - Organization for economic cooperation and development - wealthier 34 nations - have global lead on MSW output at 1.6 million tonnes/day

Global output - 1.2 billion tonnes/year, expected to double by 2025

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3
Q

Composition of MSW

A
  • Organics - biodegradable waste…
  • Recyclables - paper, glass etc.. & Electronic waste (e-waste, WEEE waste electrical and electronic equipment)
  • Inert Waste - construction & demolition waste, dirt etc (no toxicity concerns)
  • Composite Waste - hetergeneous mixtures of waste clothing, paper, glass etc (not easily separated)
  • Hazardous Waste - paints, chemicals, light bulbs etc
  • Toxic Waste - pesticides, herbicides, fungicides etc
  • Medical Waste

*CROMITH*

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4
Q

Solid waste legislation (national)

A

Part 3 of EMA - Municipal waste mgmt

Ministry of Environment required all regions and districts hand in solid waste mgmt plan - goal was 50% reduction by 2000, and 75% by 2015.

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5
Q

Solid waste legislation (reg/municip) - bylaws

A
  • CRD solid waste bylaws
    • solid waste disposal
    • recycling
  • Metro Vancouver bylaws
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6
Q

Five Rs

A
  • Reduce
  • Reuse
  • Recycle
  • Recovery
  • Residuals
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7
Q

Reduction Methods

A
  • Reduce amount of waste transported and deposited into landfill

Reduction methods:

  • Mechanical reduction processes - compaction, shredding
  • Source separation programs - blue bins, collections/drop off
  • Organics recycling - composting
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8
Q

Compaction

A
  • mechanical compaction occurs under your sink, in the collection vehicle, at transfer stations or during baling.. Can reduce volumes by 80%

Transfer stations: facilities used to consolidate wastes into larger transport vehicles (semi-trailers) when the disposal site is not in the vicinity of where the waste was collected. Allows for fewer waste vehicles on road.

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9
Q

Shredding/Pulverizing

A
  • Reduces MSW volumes by up to 40%
  • Homogeneously sized material facilitates mechanical separation machinery (metals, plastics..)
  • Vector (organism) reduction due to difficulty finding food scraps and habitat voids
  • Enhances biodegradation in organic wastes
  • Homogeneous reduced sizes required for incineration and waste to fuel processes
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10
Q

Baling

A
  • compacting solid waste into rectangular blocks or bales. Typically 1.5m3/1ton
  • volume reductions up to 80%
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11
Q

Sanitary Landfill Operation (once reduced MSW is dumped)

A
  • spread out and compacted with special heavy equipment.
  • Waste is covered typically each day with a layer of compacted soil, rock, biosolids…. Plastic sheeting cover prevents rain infiltration contributing to leachate.
  • Modern sites include the presence a both a bottom liner coupled to leachate control system.
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12
Q

Organic waste: Composting

A

The biological decomposition of the organic portion of MSW, typically under carefully controlled conditions. Occurs naturally, but we can speed it up.

  • Diverts 20-60% of MSW from landfills.(Co-composting of biosolid/organics mixtures)
  • Composting can result in organics volume reductions of 30-60%
  • Produces rich soil amendment/fertilizer: improved moisture retention, decreased erosion
  • Stabilizes organics-reduces leaching of nutrients
  • Kills pathogens
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13
Q

Composting: Biology

A

Primary Consumers:

  • Composters - eat organics- bacteria, (actinomycetes), fungi, nematodes, mites…
  • earthworms ,millipedes, sow bugs, snails, slugs….shred plant materials to increase surface area for microbes.

Secondary consumers:

  • eat primary consumers - beetles, nematodes, mites

Tertiarty consumers:

  • eat secondary consumers - larger beetles, ants
  • Resulting compost is composed of organic matter including plant, microbial*
  • and invertebrate residues*
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14
Q

Compost: Chemistry

A
  • C/N Carbon to Nitrogen ratios
  • Moisture
  • O2
  • Temperature
  • pH

•Nutrient balance:
-Adequate P, K and trace minerals

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15
Q

Carbon:Nitrogen Ratio

A
  • C/N is a serious limiting factor in composting efficiency.
  • “IDEAL” C/N = 30:1 (finished compost @10:1)
  • range of 25:1 to 40:1 supports rapid microbial decomposition.

Brown - C/N too high, too little N= limited cell growth - slow decay

Green - : C/N too low, too much N

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16
Q

Composting Chemistry: Moisture

A

Optimum moisture content 40-60% (“squeeze test”)

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17
Q

Composting Chemistry: O2

A 
C6H12O6 + **6O2** -\> 6CO2 +6H2O
Rapid aerobic (low odor) decomposition requires sufficient oxygen.

Concentrations > 15% optimal *

Concentrations < 5% : composting slows

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18
Q

Composting Chemistry: Temp requirements

A
  • Psychrophilic (<5o C)
  • Mesophilic (10 - 45o C)
  • Thermophilic (>50oC)

Decomposition occurs most rapidly in thermophilic stage (40 – 60oC)

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19
Q

Composting Chemistry: Temperature Regulations

A

O.M.R.R. (under the Waste Management Act)

Organic Matter Recycling Regulations

Pathogen reduction requirements:

a.) Windrows: *(controlled compost rows. Piles are mechanically mixed/aerated.) *

** ≥ 55o C** for at least 15 days with no fewer than 5 turnings during high temp period….

b.) Static aerated piles: (mixed piles remain stationary; aerated through pipes/floor vents ( +/-). )

                    insulated piles **≥ 55o C** for at least 3 days

c.) In Vessel ‘bioreactors’: (compost medium enclosed, carefully controlled aeration/odor control.)

** ≥ 55o C** for at least 3 days

**All methods involve regular monitoring of O2/Temp/moisture within the piles

20
Q

Composting Chemistry: pH

A
  • efficient between pH 5.5 and 8.5, with absolute optimums of pH 6.5 to 7.5
  • Bacteria and fungi release organic acids during early stages of composting.
          -drop in pH encourages fungi and the breakdown of lignin and cellulose.
21
Q

Biofilters

A

Odor control is primary concern for compost facilities, especially those near residential areas. Use biofilters because…

least expensive, most effective and most widely used. Composed of moist organic materials and microbes to adsorb, then biologically degrade odorous compounds.

22
Q

Composting: Physics

A
  • Microbial activity generally occurs on the surface of the organic particles.
  • Particle size can increase surface areas, increasing rates of decomposition.
           - if particle size is *too small*, the *porosity* and the amounts of *O2 **available decreases*. Bulking agents used (wood chips)

•Shape and Size of compost pile: must be sufficient to retain heat and moisture, yet small enough to maintain aeration. Ambient temperatures a factor (arctic vs tropics)

23
Q

Windrows

A
  • Commercial, large scale operations
  • Rows typically sized for optimum SA/volume balance for O2/heat control.
  • Outside or covered
  • Rows are mechanically turned for aeration and mixing as required
24
Q

Aerated Static Piles

A

Variety of commercial systems that biodegrade organics without physical manipulation during 1o composting phase.

  • Can be in windrows, open/covered or closed systems.
  • Good for high moisture feed stocks
  • Reduced handling time/costs..
  • Some disposable residuals….
25
Q

In Vessel

A
  • Primary composting process fully enclosed and controlled; often insulated to retain heat
  • Improved site hygiene and vector control
  • Typically vessel acts as a mixer to ensure homogeneous aeration; continuous input/output
  • Odorous gases are trapped -> biofilter
  • High infrastructure costs/lower handling costs
  • Monitoring moisture can be difficult
26
Q

Solid Waste: Recycling

A
  • Paper
  • Plastics
  • Metals
  • Waste to Energy
27
Q

Solid Waste Recycling: Paper

A
  • About 35-40% of MSW (before recycling) by weight consists of paper or paper products.
  • Pulping, de-inking and screening often more costly than making paper from virgin wood.
28
Q

Recycled Paper

A

•Collection/Sorting/ Baling/Transport

  • •Pulping*
  • •Screening*
  • •Centrifugal cleaning*
  • •Deinking*

•Fragmenting/Washing/ Bleaching

•Papermaking

•71% of the fibre used in making Canadian pulp and paper now comes from recycled fibres that used to go into landfills….same fibers can be recycled about 7 times as they get shorter every cycle.

29
Q

Pulping

A

using a mechanical chopper, water and heat and to separate paper fibers into pulp.

30
Q

Screening

A

pulp is then filtered through screens to remove impurities such as staples, plastics, glues, fillers and loose ink particles.

31
Q

Centrifugal Cleaning

A

spinning pulp in a cleaning fluid separates particles denser than pulp fibers.

32
Q

Deinking

A

air floatation and surfactants are used to collect ink particles from a surface foam phase

33
Q

Washing

A

Waste particles and shorter pulp fibers are removed by passing water through the pulp.

34
Q

Bleaching

A

Bleaching uses peroxides or hydrosulfites to remove colour from the pulp, if white paper is desired.

35
Q

Papermaking

A
  1. cleaned/bleached fiber is made into a “new” paper.
  2. certain amount of new pulp is added.
  3. pulp is finally mixed with water and chemicals then placed on a screen which drains the pulp of water.
  4. strained sheet of pulp is then passed through heated metal rollers that dry the paper.
36
Q

Residual waste disposal: Recycled paper

A

The unusable material left over from recycled papermaking, mainly ink, plastics, filler and short fibers, is called sludge.

The sludge is buried in a landfill, burned to create energy at the paper mill…or under certain conditions, used as an agricultural soil conditioner.

37
Q

Solid Waste recycling: Plastic degradation

A

•When plastics enter the oceans and other waterways, they erode into small fragments known as micro-plastics which are often ingested by animals.

38
Q

(MRF) & Macro levels: Plastics

A

At the Materials Recovery Facility(MRF ) level, a container’s recyclability is determined by two factors:

  1. what resin it is made from (indicated by the ASTM code and triangle symbol on the bottom), and
  2. the shape of the container.

At the macro-level, a container’s recyclability is determined by the market demand for that specific type of reclaimed product. *Buy products made of recycled materials*

39
Q

Plastic grading

A
40
Q

Plastics - popular

A

•PETE (#1) easiest and most commonly recycled:

  • New beverage containers
  • Polyethylene Fibers - for outerwear clothing; fleece vests, sails, car bumpers, rope, etc.

•HDPE (#2)- often recycled into toys, piping, plastic lumber and rope. Like #1, it is widely accepted at recycling centers.

41
Q

Microbeads

A

•Microbeads (polyethylene) in facial cleansers (and eroded plastics) accumulate up the food chain, concentrating in tissues , disrupting function…UK researchers attribute 50% of sea life beachings to plastics ingestion.

•“North Pacific Garbage Patches”. Microplastic soups. Current estimates put the plastic-to-plankton ratio in certain areas of the Pacific at 6 to 1.

42
Q

Solid Waste Recycling: Metals

A

•Metals are the most recyclable materials in our economy. They can be recycled repeatedly without any change in the properties of the metal.

research conducted by the US EPA, recycling scrap metals in place of virgin iron ore can yield:

  • 75% savings in energy (18M homes/year).
  • 86% reduction in air pollution
  • 76% reduction in water pollution
43
Q

Recycling Metals: Iron/non iron

A

Classified as either Ferrous and Nonferrous

  • Ferrous- contains iron (Fe) and is magnetic eg. steel, cast iron.
  • Nonferrous- any metals, including alloys, that do not contain Fe in appreciable amounts: aluminium, copper, lead, nickel, tin, titanium and zinc, and alloys such as brass
44
Q

Recycling Metals: Aluminum

A

requires only 5% of the energy used to make new aluminium. Al is simply re-melted rather than having to mine bauxite and extract metal through the electrolysis of aluminium oxide (Al2O3).

 - still more cost efficient even when collection, sorting and transport are factored in.
  - can be **recycled indefinitely** into many things including beverage cans (60 day cycle)

•Together, Canadian provinces collect approximately 73%–75% of their aluminum cans …

45
Q

WTE

A

*Waste to Energy *

  • The process of generating energy in the form of electricity and/or heat from the incineration of residual MSW, commercial or industrial wastes.
  • Most common method through incineration.
  • Modern incinerators reduce waste volumes by 95% depending upon composition and degree of recovery of materials such as metals for recycling.
  • Efficiencies for electricity (14-28%) and heat cogeneration can reach 80%.
46
Q

Pros and Cons of WTE

A

Pros:

  • Reduce landfill volumes/costs and extend working life cycles.
  • Cogeneration of energy and heat (depending on process, potential for fuel production, i.e. gasification.. a process that converts organic or fossil based materials into CO, H and CO2)
  • New technologies mitigate air pollution lime scrubbers and electro-static precipitators, fabric (bag) filters on stacks and flue gas emissions.

Cons:

  • Destroys valuable resources and may discourage recycling initiatives.
  • Hazardous waste residuals management: bottom ash/heavy metals/dioxins
  • Potential Air Quality concerns: NOx, SOx, CO2,dioxins, PM

Waste Management (3 decks)

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