Solid Waste Management

1
Solid Waste Management
On completion of this module you should be able
to

• Have an overview of solid waste management,
  including some legislation
• Be aware of the responsible solid waste
  management authorities and some management costs
• Define the composition and quantity of solid
  waste generated
• Discuss the collection, transport, treatment and
  disposal strategies
• Have some understanding of hazardous wastes and
  their disposal methods

2
Objectives of solid waste management

• Safeguarding of public health
• Protection of the environment
• Transfer and treatment of waste, energy from
  waste and the conservation of basic materials
• Financial limitation of any scheme

3
Functional elements of waste management structure
4
Solid waste legislation

• Environmental Protection Act 1994
• Subordinate legislation referring particularly to
  solid waste Environmental Protection Policy -
  Waste Management
• Contaminated Land Act 1991

5
Waste management hierarchy

• Source reduction and reuse are allocated the
  highest priority
• Install recycling programs
• Design a suitable treatment system
• Residual waste to controlled landfill

6
Waste management hierarchy

• Waste avoidance
• Waste reduction
• Reuse
• Recycling
• Energy recovery
• Waste treatment
• Waste disposal

7
Reduce, reuse and recycle

• Public education and perception on the
  environment
• Household to separate recyclable
• Collection agencies to set target for waste
  reduction
• Disposal agencies to reclaim rather than dispose
• Industry to favour recycled feedstock
• Minimise packaging

8
Positive aspects of waste reduction, reuse and
recycle

• Reduces pollution and environmental degradation
• Reduces amount of waste to landfill
• Saves natural resources
• Reduces industry's impact on the environment
• Preserves open space used by landfill
• Reduces consumer costs
• Contributes to a cleaner environment by reducing
  energy use

9
Who is responsible for solid waste management?

• Local government in collection, treatment and
  disposal
• State agencies involved in quality guidelines
• Overriding powers of commonwealth in
  international issues

10
Municipal solid waste (MSW) composition

• Household or domestic waste
• Commercial waste
• Builders or demolition waste
• Industrial waste

11
Solid waste generation and cost

• Statistical data is paramount in solid waste
  management
• Problem of uniformity in reporting waste
  generation
• Household waste make up about half of total waste
  stream
• National average of MSW is about 776
  kg/person.year
• Solid waste management average cost is 28/person

12
Waste composition
13
Transfer and transport

• Siting of transfer station will impact on
  disposal costs. Facility for efficient collection
  service by reducing the turn-round times,
  improves payload, reduces the number of vehicles
  to the main disposal site
• Offers opportunity to implement treatment prior
  to disposal. Activities may include compaction
  and baling, shredding and pulverising
• Transportation may comprise road, rail and water

14
Management strategies

• Planning essential at outset
• Fewer but larger facilities at favourable
  operating cost
• Allow for changing nature of waste generation
• Duty of care on waste holders and producers

15
Management strategies (cont)

• Increased powers for waste disposal authorities
• Registration of waste carriers
• Introduction of polluter-pays principle

16
Waste disposal options
No single method is appropriate to every type of
wastes
17
Factors to be considered

• Analysis of waste stream
• Reduce, recovery and recycling viability
• Quantity and rate of disposal
• Environmental assessment and long-term impact
• Collection authority issues

18
Factors to be considered (cont)

• Availability of suitable void space or land
• Distance from collection centre
• Transfer and treatment facilities
• Transportation methods and routes
• Overall cost

19
MSW disposal routes
20
Controlled landfill

• Still the major disposal method but largely
  dependent on suitable void space
• Concepts of attenuate and disperse or containment
• Major concerns of landfill
• Leachate contaminating groundwater
• Landfill gas (methane)
• Infestation
• Litter, dust
• Noise and odour

21
Steps for implementing controlled landfill

• Site selection
• EIS, geology/hydrogeology of site
• Landfill design (attenuate and disperse or
  containment)
• Leachate collection treatment, gas utilisation
• Site operations
• Compaction, stability, leachate and gas
  monitoring
• Site restoration and aftercare
• Capping, soil erosion, settlement

22
Controlled landfill
23
Controlled landfill
24
Combustion of MSW

• Not widely used in Australia
• Expensive disposal option involving high
  maintenance costs
• Products are energy, flue gas and solid residues
• Residues represent 10 by volume and 25 by
  weight of input

25
Types of combustion

• Incineration of 'as received' waste
• Refused derived fuel in grate combustion
• Pyrolysis

26
Mass combustion
27
Potential environmental concerns of stack gases

• Particulates
• Carbon dioxide, carbon monoxide
• Acid gases (HCl, HF, SO2, NOx)
• Heavy metals (Hg, Cd, Zn, Cu, Ni, As, Mn)
• Products of incomplete combustion (PICs)

28
Refused derived fuel (RDF)

• Coarse RDF
• Fluff RDF
• Pelletised RDF

29
Coarse RDF

• Feed subjected to pulverisation
• Removal of ferrous metal
• Result in smaller particle size
• More uniform fuel

30
Pulverising, shredding equipment
31
Air classification
32
Fluff RDF

• Lower moisture and metal contaminants
• Higher calorific value
• Lower ash residue after combustion
• Used usually in dedicated combustors
• High bulk density results in high transport cost
• Short storage period

33
Magnet separators
34
Pelletised RDF

• Fluff RDF after compression into discrete form
• Can be stored for extended periods
• Replace coal in boiler market place
• Smaller plants may lack suitable emission control

35
Pyrolysis

• Combustion in the absence of oxygen
• Produces gaseous, liquid and solid fuels
• Endothermic process requiring external heat
  source
• Limited to processing specialist waste

36
Composting
Composting is controlled bioxidative process
involving

• Heterogeneous organic substrate in the solid
  phase
• Passing through a thermophilic phase and
  temporary release of phytotoxin
• Production of CO2, water, minerals and stabilised
  organic matter

37
Managing composting at 3 levels

• At source through household education
• Organic material separated at source requiring a
  separate collection system
• Centrally separated by mechanical processing,
  requires a sophisticated processing
  infrastructure at transfer station

38
Important composting criteria

• Bulk density increases from 0.35 to 0.6 t/m3 as
  organic matter is reduced
• Maintain free air space of 30 - 35 for aerobic
  activity
• Size to maximise surface area and to permit air
  flow
• Initial moisture 65 to 40 towards the process
  end
• Temperature for exothermic process 50 - 70o C
• to reduce pathogens, pests, seeds
• controlled by air flow and material turning

39
Important composting criteria (cont)

• Carbonnutrient (CN) ratio of 301 - 151 for
  rapid aerobic growth
• High ratio is detrimental to plants and low ratio
  releases odour
• Tendency for ratio to fall from fresh to mature
  compost
• Final product pH should be about 7 - 8
• Contaminants of concern are heavy metals
• Pathogens - maintain and control high
  temperatures to maximise destruction of pathogens
  and minimise health risks

40
Hazardous waste
Defined as hazardous because of its quantity,
concentration or physical, chemical, infectious
properties that may

• increase or cause mortality, illness
• present a hazard to human, health or the
  environment when improperly treated, stored,
  transported or disposed

41
Hazardous waste (cont)
It may also be defined according to other
attributes of

• reactivity ie unstable substances
• ignitable substances
• corrosivity ie 2 lt pH gt 12.5
• toxicity when ingested or absorbed

42
Hazardous waste management

• Cradle-to-grave management technique
• Control at a national level
• Waste minimisation
• Recycle and recovery
• Treatment and incineration
• Land disposal

43
Transport and storage of hazardous waste

• Transport and tracking system with a manifest
  document to accompany any waste
• A permitting system to ensure safe operation to
  treat, store or dispose

44
Treatment and disposal of hazardous waste

• Solidification
• Chemical treatment
• Incineration
• Landfill