Waste Management OBJECTIVES OF THE COURSE • Identify the industrial and domestic sources of waste and their characteristics; • Develop knowledge of waste treatment disposal and remediation processes; • Understand the concepts of risk assessment and remediation standards; • Describe and share practical knowledge and technology of chemical ,physical and biological treatment of hazardous waste.
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Waste Management
OBJECTIVES OF THE COURSE• Identify the industrial and domestic sources
of waste and their characteristics;• Develop knowledge of waste treatment
disposal and remediation processes;• Understand the concepts of risk assessment
and remediation standards;• Describe and share practical knowledge and
technology of chemical ,physical and biological treatment of hazardous waste.
Waste Management
OBJECTIVES OF THE COURSE• Describe and be able to apply the current
remediation processes and technologies;• Understand the criteria behind selection of
treatment technologies and site remediation; and
• Educate communities and stakeholders on best practices in waste management.
Waste Management
Waste Types and Sources
Definition of Wastes“substances or objects which are disposed of or are intended to be disposed of or are required to be disposed of by the provisions of the law”
Disposal means“any operation which may lead to resource recovery, recycling, reclamation, direct re-use or alternative uses.
Waste Management
Solid wastes: domestic, commercial, mining and industrial wastes especially common as co-disposal of wastes
Examples: domestic washings, chemicals, oils, waste water from ponds, manufacturing industries and other sources
Waste Management
Classification of Wastes according to their Properties.
Bio-degradable can be degraded (paper, wood, fruits and others)
Non-biodegradablecannot be degraded (plastics, bottles, old machines,
cans, styrofoam containers and others)
Waste Management
Classification of Wastes according to their Effects on Human Health and the Environment
Hazardous wastesSubstances unsafe to use commercially, industrially, agriculturally, or economically.
Non-hazardous Substances safe to use commercially, industrially, agriculturally, or economically.
TYPES OF WASTES
residential industrialcommercial
agricultural
mining
construction
Municipal solid waste Hazardous waste
Waste Management
PROBLEMS CAUSED BY IMPROPER DISPOSAL OF WASTEThreat to public health
rodents, insects = vectors of diseases (transmit pathogens, typhoid, plague
poisonous materials
flammable materials
Irreversible environmental damage in ecosystemsterrestrial and aquatic
air pollution (incineration)
water pollution (land burial)
Technical and environmental difficulties +administrative, economic and social problems
Waste Management
PROBLEMS WITH LAND DISPOSAL OF WASTE• too little space for disposal• costs• harm to the environment and public health• landfills are unreliable in long run
Waste Management
Refuse (municipal solid waste)All non-hazardous solid waste from a communityRequires collection and transport to a processing or disposal site
RubbishGlass, rubber, tin cansSlowly decomposable or combustible material – paper, textile, wood
TrashBulky waste material that requires special handlingMattress, TV, refrigeratorCollected separately
COMPOSITION OF URBAN SOLID WASTE
paper
hard waste
plastics
metals
food waste
glass
wood
other
• 0,6 – 1,2 m3 waste / day / person
• 120 – 250 kg / m3 without compaction
• 40-50% is paper
Waste ManagementResponsibility of the local municipalityrefuse collection vehicles
enclosed, compacting type with a capacity of 15 m3
compaction: 50% reductionFrequency of collection and the point of pickup depends:
type of communitypopulation density
land use in the collection areacombined collection of garbage and rubbish is cheaper for recycling it is essential to separateseparated collection!!! (paper, metal, plastic, glass, organics, chemicals, batteries)
Waste ManagementWASTE TREATMENT AND RESOURCE
RECOVERY
1. Reduce the total volume and weight of material that requires disposal
Help to conserve land resources
2. Change the form or characteristic of wasteComposting, neutralizing, shredding, incineration
3. Recover natural resources and energy in the waste material
Recycling and reuse!!! (it takes 17 trees to make 1 ton of paper)
Waste Disposal Methods
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Predominant method of waste disposal in
developing countries Illegal dumping problems Groundwater contamination, air pollution, pest and health hazards
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Open Dumps
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Ocean Dumping
Source: The Independent
Sanitary Landfills
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Waste Disposal Methods (cont’d)
SOLID WASTE
What is a solid waste
• Any material that we discard, that is not liquid or gas, is solid waste– Municipal Solid Waste (MSW):
• Solid waste from home or office
– Industrial Solid Waste:• Solid waste produced from Mines, Agriculture or
Industry
Municipal Solid Waste (MSW)
Waste Management
Benefits of Recycling
The ultimate benefits from recycling are• cleaner land, air, and water, • overall better health, and • a more sustainable economy.
• Unsanitary, draws pests and vermin, harmful runoff and leachates, toxic gases
• Still accounts for half of solid waste
Sanitary Landfill
• Sanitary Landfill– Layer of compacted trash covered with a layer of earth
once a day and a thicker layer when the site is full– Require impermeable barriers to stop escape of leachates:
can cause problem by overflow– Gases produced by decomposing garbage needs venting
Sanitary LandfillLeachates
• is any liquid that in passing through matter, extracts solutes, suspended solids or any other component of the material through which it has passed.
• In the narrow environmental context leachate is therefore any liquid material that drains from land or stockpiled material and contains significantly elevated concentrations of undesirable material derived from the material that it has passed through
Sanitary Landfill
• Avoid:– Swampy area/ Flood plains /coastal areas– Fractures or porous rocks– High water table
• Prefer:– Clay layers– Heads of gullies
Monitoring of Sanitary Landfills
• Gases: Methane, Ammonia, Hydrogen sulphide• Heavy Metals: Lead, Chromium in soil• Soluble substances: chloride, nitrate, sulfate• Surface Run-offs• Vegetation: may pick up toxic substances• Plant residue in soil• Paper/plastics etc – blown by the wind
Incineration
Solves space problem but:– produces toxic gases like Cl, HCl, HCN, SO2
– High temp furnaces break down hazardous compounds but are expensive ($75 - $2000/ton)
– Heat generated can be recovered: % of waste burnt
Ocean Dumping
• Out of sight, free of emission control norms• Contributes to ocean pollution• Can wash back on beaches, and can cause death of
marine mammals • Preferred method: incineration in open sea• Ocean Dumping Ban Act, 1988: bans dumping of
sewage sludge and industrial waste• Dredge spoils still dumped in oceans, can cause habitat
destruction and export of fluvial pollutants
Ways of Reducing Solid Waste• Incineration, compacting• Hog feed: requires heat treatment• Composting: requires separation of organics from glass
and metals• Recycling and Reusing
Recycling: facts and figures• In 1999, recycling and composting activities prevented
about 64 million tons of material from ending up in landfills and incinerators. Today, this country recycles 32 percent of its waste, a rate that has almost doubled during the past 15 years.
• 50 percent of all paper, 34 percent of all plastic soft drink bottles, 45 percent of all aluminum beer and soft drink cans, 63 percent of all steel packaging, and 67 percent of all major appliances are now recycled.
• Twenty years ago, only one curbside recycling program existed in the United States, which collected several materials at the curb. By 2005, almost 9,000 curbside programs had sprouted up across the nation. As of 2005, about 500 materials recovery facilities had been established to process the collected materials.
Waste Exchange
• One persons waste can be another persons raw material
• Isopropyl alcohol = cleaning solvent• Nitric Acid from Electronic Industry = high
grade fertilizer• Spent acid of steel industry = control for H2S
LANDFILL DESIGN• Modern landfills are designed to
minimise these problems:– Location– Landfill Liner– Compaction of waste– Daily Cover – Landfill Cap– Leachate Management System– Landfill Gas management System
LANDFILL LOCATION
• In order to obtain a permit a landfill operator must first carry out a detailed investigation and prove to the satisfaction of the planning authority and the EA that the site: – is located in a geologically stable area– is not located on a major aquifer;– Is not located in a vulnerable area;– is designed to reduce the risk of damage to
the environment and human health;– will be monitored regularly for the duration of
operations and aftercare period.
Installation of monitoring/site investigation borehole
LANDFILL LINERS• Landfill Liners are constructed on the base
and sides of a landfill site to prevent leachate from leaking into the surrounding soils.
• Landfill Liners may be constructed from:– Compacted Clay– Bentonite Enhanced Sand– Geomembrane– Geotextile Protector– Dense Asphaltic Concrete (DAC)– Combination of the above
LANDFILL LINERS
Construction of compacted clay liner
LANDFILL LINERS
LANDFILL LINERS
Installation of Geomembrane Basal Liner
LANDFILL LINERS
Construction of Dense Asphaltic Concrete Liner
This is a new method of lining landfills.
The first landfill to be constructed with this type of lining system in the UK is North of London and was completed this summer.
LANDFILL LINERS
CONSTRUCTION QUALITY ASSURANCE
• All construction carried out on landfill sites is supervised and recorded by an independent consultant.
• Following construction, certification reports are produced by the consultant and issued to the Environment Agency for approval.
LANDFILL OPERATIONS
• Waste is placed in layers approximately 3 m thick and compacted.
• At the end of each working day approximately 0.3 m of clay or sand material is placed on top of the waste to:– minimise the infiltration of rainwater– isolate the waste from birds and vermin– reduce odours
LANDFILL OPERATIONS• To prevent wastage and the formation of
layers of weakness within the waste mass the daily cover is scraped off and re-used each day.
• Leachate that collects at the base of the waste mass is collected and re-circulated into the waste. This:– increases the rate of decomposition of the waste
and therefore, rate of settlement;– decreases disposal costs.
LANDFILL CAP• Landfill caps placed above the waste
after completion of infilling prevent the infiltration of rainwater, minimising the production of leachate.
• Landfill Caps are usually constructed from:– Recompacted clay– Geomembrane
LANDFILL CAP
Construction of geomembrane cap
LANDFILL CAP
LEACHATE MANAGEMENT SYSTEM• Leachate management systems are installed to:
– prevent the accumulation of leachate in the base of the landfill
– collect, re-circulate and dispose of leachate during operations and after closure
• They comprise of:– leachate drainage blanket at base of landfill– pipes along base and sidewalls of landfill– wells to monitor and extract the leachate
LANDFILL GAS MANAGEMENT SYSTEM
• Landfill gas management systems are installed to prevent the build up of gases within the landfill and to prevent migration of landfill gas through the underlying strata.
• There are 2 ways landfill gas can be managed:– passive– active
LANDFILL GAS MANAGEMENT SYSTEM
• Passive management systems comprise of wells with perforated tops to allow the gas to vent into the atmosphere
• Active management systems involve the active extraction of the gas.
• The extracted gas can be used to generate electricity.
LANDFILL GAS MANAGEMENT SYSTEM
Electricity generating system
MONITORING
• Monitoring is carried out before, during, and after the placement of waste.
• Numerous monitoring wells are constructed around a landfill site (both upstream and downstream) to check for contamination.
• Chemical testing is carried out regularly on: – Groundwater – Leachate– Landfill Gas
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4- Landfills Public/private ownership and operation
In most developing countries landfills are owned and operated by local governments. Where expertise is available in the private sector, municipal planners should explore the option of privatizing landfill operations on a contractual basis. This option should be weighed carefully in bases of cost recovery and the payment of fees.
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Monitoring and control of leachate:
Leachate management is a key factor in safe landfill design and operation. The natural decomposition of MSW and rain infiltration into the site causes potentially toxic contaminants. The wetter the climate is the greater potential risks of ground- and surface water contamination. The geology of a site can exacerbate or reduce amount of leachate.
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Continue Monitoring and control of leachate:
Household hazardous waste (e.g., paint products, garden pesticides, automotive products, batteries) and hazardous wastes from commercial and industrial generators can release organic chemical and heavy metals contaminants in leachate.
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Continue Monitoring and control of leachate:
Natural or synthetic materials are used to line the bottom and sides of landfills to protect ground and surface water. Two feet or more of compacted clay, thin sheets of plastic made from a variety of synthetic materials and others used in lining landfills. Natural and synthetic liners can crack, if improperly installed, or can lose strength over time.
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4- Landfills
Continue Monitoring and control of leachate:
More than one liner or a mix of natural and synthetic liners, called a composite liner, is a recommended alternative. To minimize production of leachate, covering material should be applied after each day of MSW is spread.
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Leachate collection and treatment:
Leachate collection systems are installed above the liner and consist of a perforated piping system which collects and carries the leachate to a storage tank. Periodically, leachate removed from the storage tank and treated or disposed of.
Most common leachate management methods are: discharge to wastewater treatment plant, on-site treatment and recirculation back into the landfill.
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Leachate recirculation
over waste in landfills showed an increase the quantity (by factor of 10) and quality of methane gas for recovery as well as possibly reduces the concentration of contaminants in leachate and enhances the settling of the waste.
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Leachate reinjection may be appropriate for areas with low rainfall. This technology could be more cost-effective than other treatment systems.
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Possible drawbacks of leachate recirculation include clogging of leachate collection systems, increasing release of leachate to the environment and increasing odor problems.
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At controlled dumps monitoring operations may involve the scheduled withdrawal of samples to test for indicator contaminants such as bacteria, heavy metal ions, and toxic organic acids.
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Monitoring operations at sanitary landfills may involve computerized statistical sampling and automatic reporting of results at the regulatory agency. Such systems are costly and require skilled personnel.
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4- Landfills Monitoring and control of landfill gas
Gas management is required at sanitary landfills. At controlled dumps, it should be monitoring to determine if dangerous amounts of gas are being released. A low-cost design (passive collection system) to handle landfill gas consists of covered vertical perforated pipes, using natural pressure of gas to collect and vent or flare it at surface. More costly active collection systems utilize covered network of pipes and pumping to trap it. Gas is processed and used for process heat or electricity. This collection system is risky and expensive.
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4- Landfills Continue Monitoring and control of landfill gas
Gas management is required at sanitary landfills. At controlled dumps, it should be monitoring to determine if dangerous amounts of gas are being released. A low-cost design (passive collection system) to handle landfill gas consists of covered vertical perforated pipes, using natural pressure of gas to collect and vent or flare it at surface. More costly active collection systems utilize covered network of pipes and pumping to trap it. Gas is processed and used for process heat or electricity. This collection system is risky and expensive.
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Access and tipping area
Fencing should be designed to restrict unauthorized access to the landfill and to keep out animals. A staffed gate should be the point of entry to the facility for vehicles and any waste pickers. Gate should be equipped with scales for the weighing of vehicles as they enter and exit the facility. They provide critical information for planning purposes and for operational management of collection vehicles.
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Pre-processing and waste picker policy
Landfill is the least efficient alternative for materials recovery operations. Where composting is attractive at the landfill and/or waste picking activity is permitted, sorting of the waste should occur close to the gate or tipping area rather than at the working cell. Such activities reduce the volume of material to be landfilled and extend the life of the facility.
Waste picking policy should be established during the design phase of the facility
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Operations and safety manuals
Manuals should be prepared during the design phase of the landfill. This permits their content to be specifically adapted to the processes for which the facility is designed. Clear operating procedures and well-trained workers are vital to safe and effective landfill operations.
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Closure/post-closure plans
Essential closure and post-closure elements are:
• Plans for the sealing and application of final cover (including vegetation)
• Plans for long-term leachate and gas management system monitoring;
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Continue Closure/post-closure plans
• Plans for long-term ground and surface water monitoring;
• Financial assurance guarantees to the local or state government; and
• Land use restrictions for the site
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In the case of controlled dumps in most developing countries, closure and post-closure plans are not prepared. However, ongoing monitoring and control of the facility after its useful life is an unavoidable for periods that may exceed 30 years after their closure.
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Community relations
The designer should establish a program for ongoing dialog with community. This should be based on transparency in landfill operations and procedures to addressing community concerns. Some facilities offer give-backs to their host community.
Wastewater Treatment
Liquid Waste• Sewage• Highly toxic Industrial Waste & Used Oil
– Dilute and Disperse– Concentrate and Contain– Secure Landfill
• Sealed drums to be put in impermeable holds with monitoring wells to check for leakage: does not work
– Deep well Disposal• Pumping in deep porous layer bounded by impermeable
formations, well below water table• $1 million to drill, $15-20/ton afterwards• Restricted by geological considerations, can trigger earthquakes
Wastewater TreatmentPurpose:
To manage water discharged from homes, businesses, and industries
- Occurs in business or industry prior to discharge
- Prevention of toxic chemicals or excess nutrients being discharged
in wastewater
Wastewater TreatmentWater discharged from homes, businesses,
and industry enters sanitary sewersWater from rainwater on streets enters
storm water sewersCombined sewers carry both sanitary
wastes and storm water
Wastewater TreatmentWater moves toward the
wastewater plant primarily by gravity flow
Lift stations pump water from low lying areas over hills
Wastewater Treatment
Wastewater TreatmentPreliminary Treatment
- removes large objects and non-degradable materials - protects pumps and equipment from damage - bar screen and grit chamber
Wastewater TreatmentBar Screen
- catches large objects that have gotten into sewer system such as bricks, bottles, pieces of wood, etc.
Wastewater TreatmentGrit Chamber
- removes rocks, gravel, broken glass, etc.
Mesh Screen- removes diapers, combs, towels, plastic bags, syringes, etc.
Wastewater Treatment
Preliminary Treatment
Wastewater TreatmentMeasurement and sampling at the inlet
structure- a flow meter continuously records the volume of water entering the treatment plant- water samples are taken for determination of suspended solids and B.O.D.
Wastewater TreatmentSuspended Solids – the quantity of solid
materials floating in the water column
B.O.D. = Biochemical Oxygen Demand- a measure of the amount of oxygen required to aerobically decompose organic matter in the water
Wastewater TreatmentMeasurements of Suspended Solids and
B.O.D. indicate the effectiveness of treatment processes
Both Suspended Solids and B.O.D. decrease as water moves through the wastewater treatment processes
Wastewater TreatmentPrimary Treatment
-- a physical process-- wastewater flow is slowed down and suspended solids settle to the bottom by gravity-- the material that settles is called sludge or biosolids
Wastewater TreatmentPrimary Treatment
Wastewater TreatmentPrimary Treatment
Wastewater TreatmentPrimary Treatment
Sludge from the primary sedimentation tanks is pumped to the sludge thickener.- more settling occurs to concentrate the sludge prior to disposal
Wastewater Treatment
Wastewater TreatmentPrimary treatment reduces the suspended solids
and the B.O.D. of the wastewater.From the primary treatment tanks water is
pumped to the trickling filter for secondary treatment.
Secondary treatment will further reduce the suspended solids and B.O.D. of the wastewater.
Wastewater TreatmentSecondary Treatment
Wastewater TreatmentSecondary Treatment
Secondary treatment is a biological processUtilizes bacteria and algae to metabolize organic matter in the wastewaterIn Cape Girardeau secondary treatment occurs on the trickling filter
Wastewater TreatmentSecondary Treatment
the trickling filter does not “filter” the water water runs over a plastic media and organisms clinging to the media remove organic matter from the water
Wastewater TreatmentFrom secondary treatment on the trickling filter
water flows to the final clarifiers for further removal of sludge.
The final clarifiers are another set of primary sedimentation tanks.
From the final clarifiers the water is discharged back to the Mississippi River.
Wastewater TreatmentThe final clarifiers
remove additional sludge and further reduce suspended solids and B.O.D.
Wastewater TreatmentDisposal of Sludge or Biosolids
-- the sludge undergoes lime stabilization (pH is raised by addition of lime) to kill potential pathogens
-- the stabilized sludge is land applied by injection into agricultural fields
Wastewater TreatmentDisposal of Sludge or Biosolids
-- in the past, the sludge was disposed by landfill or incineration
-- landfill disposal discontinued to the threat of leachate
-- incineration discontinued because of the ineffectiveness and cost
Wastewater TreatmentThe final part of the field trip tour
will be in the treatment plant lab.
Wastewater TreatmentThe wastewater plant lab conducts a
Wastes other than radioactive wastes which, by reason of their chemical activity or toxic, explosive, corrosive or other characteristics cause danger or are likely to cause danger to health or the environment
TRP Chapter 2.1 116
Examples of hazardous waste definitions
UNDER United Nations REGULATIONS:
1 The waste is listed in UNEP regulations
2 The waste is tested and meets one of the four characteristics established by UNEP:
• Ignitable• Corrosive• Reactive• Toxic
3 The waste is declared hazardous by the generator
TRP Chapter 2.1 117
The objective of definitions
Why define wastes?
To decide whether or not that waste should be controlled - this is important for the generator as well as the regulator
Why create a list?
• Clear and simple
• No need for testing
TRP Chapter 2.1 118
Different methods of classification
Lists eg Basel Convention Annex I, Basel List A, EU European Waste Catalogue, US EPA list
Origin eg processes, Basel Convention Annex II
Hazardous characteristics eg toxicity, reactivity, Basel Convention Annex III
Chemical and physical properties eg inorganic, organic, oily, sludges
• Need to match classification to objectives
• No method will suit all cases
TRP Chapter 2.1 119
Methods of waste classification: by origin
•Waste streams eg Basel Convention
•Miscellaneous or ubiquitous wastes eg • contaminated soils• dusts• redundant pesticides from agriculture• hospital wastes
TRP Chapter 2.1 120
Example of waste classification by origin: Basel
The Basel Convention’s List of
Hazardous Waste Categories (Y1-Y18) identifies wastes from specific processes
eg Y1 Clinical wastes
Y6 Wastes from the production and use of organic solvents
Y18 Residues from industrial waste disposal operations
TRP Chapter 2.1 121
Methods of waste classification: by hazardous characteristics
Main characteristics:• Toxic• Corrosive
UN Committee on the Transport of Dangerous Goods by Road or Rail (ADR) lists waste characteristics. These have been adopted by Basel Convention - Annex III gives 13 characteristics, based on ADR rules, including:
• Explosive• Flammable• Toxic and eco-toxic
Represented as codes H1-H13
• Ignitable• Reactive
TRP Chapter 2.1 122
Hazardous characteristics: Toxicity
Toxic wastes are harmful or fatal when ingested, inhaled or absorbed through the skin
• Sludges eg from metal working, painting, wastewater treatment
TRP Chapter 2.1 128
•Hazardous waste from households - outside the controls in many countries
•Small quantity generators - often placed outside the system, at least initially
•Aqueous effluents discharged to sewer or treated on-site - controlled separately from hazardous wastes in most countries
•Sewage sludge - excluded in some countries•Mining wastes - often excluded•Agricultural waste - often excluded•Nuclear waste - always excluded
Exclusions from control systemsSome wastes may be excluded from the legal definition of hazardous wastes, and thus not subject to controls. These vary, but may include:
TRP Chapter 6.5 129
Thermal treatment
TRP Chapter 6.5 130
Definitions
Thermal treatment = destruction of hazardous waste by thermal decomposition
oxygen• gasification - incomplete combustion in the partial
absence of oxygen• pyrolysis - thermal decomposition in the total
absence of oxygen
TRP Chapter 6.5 131
Application of thermal treatment
Suitable for organic wastes Thermal treatment processes:
• require high capital investment • are highly regulated• need skilled personnel• require high operating and safety
standards• have medium to high operating costs
TRP Chapter 6.5 132
Good practice in hazardous waste combustion
3 Ts:
• Time
• Temperature
• Turbulence
Flue gas cleaning systems
TRP Chapter 6.5 133
Waste characteristicsDifferent waste types have different heat values ie
the amount of heat released during complete combustion - Calorific Value (CV)
• Gross Calorific Value (CV) includes heat released
by steam condensation• Net Calorific Value does not include the heat from
condensation
Also important: • Flash point• Viscosity• Chlorine, fluorine, sulphur & heavy metals
TRP Chapter 6.5 134
Examples of Calorific Value
Mixed waste from plant
cleaning operations 10,000 - 30,000 kj/kg
Wastewater 5,000 kj/kg
(0 - 10,000kj/kg depending on organic content)
Industrial sludge 1,000 - 10,000 kj/kg
Paints and varnishes >20,000 kj/kg
Chlorinated hydrocarbons 5,000 - 20,000 kj/kg
For comparison, MSW = ~10,000kj/kg
Source: Indaver
TRP Chapter 6.5 135
Combustion
Requires: • addition of excess air • mechanical mixing of waste • even distribution and aeration of waste
Behaviour of waste during combustion varies according to its heat value and its formSome low CV wastes burn easily = strawSome low CV wastes are difficult to burn = wet sludgesSome high CV wastes burn easily = tank bottoms Some high CV wastes are difficult to burn = contaminated soils, certain plastics
Certain wastes change their physical characteristics during combustion
TRP Chapter 6.5 136
Combustion techniques
Bed plate furnaces: use gravity to mix waste - used for homogeneous and wet wastes such as sludge cake
Fluidised bed furnaces: waste is introduced into a bed of sand which is kept in suspension - used for wastes of similar size and density
Incineration grates: wastes fed onto the grate are turned or moved to ensure aeration of the waste mass via holes in the grate - used for solid wastes eg municipal wastes, not liquids or sludges
Rotary kilns: wastes are placed in slowly rotating furnace - suitable for solids, sludges and liquids
TRP Chapter 6.5 137
Operation of the furnace
• good understanding of waste characteristics
• technical skills• control of waste feed • mixing of wastes • temperature to be kept at required
level despite variations in waste• excess air• flue gas control• regular maintenance
Must be consistentNeeds:
Source: David C Wilson
TRP Chapter 6.5 138
Energy recoveryWaste combustion produces heat but combustion of low CV wastes may not be self-supporting
Energy recovery is via production of steam to generate electricity
• Only steam production: 80% efficiency is typical• Steam can be used for in-house demands• Steam can be delivered to adjacent users eg other industrial
plants• Electricity can be generated: 25% efficiency typical
Opportunities to sell heat are improved where facilities are in industrial areas
Sale of surplus energy improves plant economics
TRP Chapter 6.5 139
By-products of incinerationMay be:
• solid • liquid• gaseous
Comprise:• recovered materials such as metals, HCl• flue gases• slag and ash• products of the flue gas treatment, also called air pollution control (APC) residues
• wastewater
TRP Chapter 6.5 140
Solid residues
• bottom ash or slag
• fly ash
• air pollution control (APC) residues
Terms and regulations on treatment and disposal of solid residues differ between countries
Bottom ash may be landfilled or used as an aggregate substitute eg for road building
TRP Chapter 6.5 141
Flue gases
Quantity and type of pollutants in emissions depend on:
• pollutants in waste• technology • efficiency of operation
Average 6 - 7 Nm3 of flue gas per kg waste
Specific collection/treatment for:
Dust - staged filters
Chlorine - neutralised by scrubbing with lime
Sulphur - washing stage
Dioxins - combustion control, activated carbon
Source: David C Wilson
TRP Chapter 6.5 142
Dioxins
• Family of around 200 chlorinated organic compounds, a few of which are highly toxic
• Widespread in the environment
• Present in waste going to incineration
• Can be re-formed in cooling stages post-combustion
• 3Ts help destroy dioxins in waste, reduce reformation
• Use of activated carbon to filter from flue gases
• Emissions limits extremely low
TRP Chapter 6.5 143
Example of flue gas cleaning technology
Source: Indaver
TRP Chapter 6.5 144
Wastewater from incineration
•Controls vary from country to country•Quantity:
• influenced by gas scrubbing technology chosen ie wet, semi-dry, dry
•Treatment:• in aerated lagoons• widely used• low cost • may not meet required standard
• physico-chemical treatment may also be needed
TRP Chapter 6.5 145
Measurement
Of what:• controlled parameters eg carbon monoxide
How: • regular • continuous
Set out in:• national regulations
• permitted operating conditions
Problems:·Measuring equipment may be imprecise
·Errors in correlation
·Errors in sampling
TRP Chapter 6.5 146
Measurement: an example
Emissions from rotary kiln incinerator
Continuous monitoring for:
HCl, CO, dust, SO2, HF, TOC, Nox, O2
Monthly measurement for:
9 heavy metals
Twice a year (soon to be continuous):
PCDD/PCDF
ALSO monitored: wastewater and solid residues Source: Indaver, Belgium
TRP Chapter 6.5 147
Costs
• Related to site-specific and country-specific factors
• High level of sophistication & control = high construction costs
• Air pollution control costs = 30-40% of total
• Treatment costs per tonne similar to other technologies
• Cost savings because volume, weight and hazard of waste remaining for disposal greatly reduced
• Recovery and sale of energy/heat from the process improves economics
TRP Chapter 6.5 148
Cement kiln incinerationWidely used for range of hazardous wastes eg oily wastes, wastewaters, sludges, solvents, organic compounds
Provides:• good combustion conditions
• alkaline environment
• vacuum operation
• high thermal inertia
• no impact on quality of cement product
• opportunity to recover energy content of waste
• no by products
TRP Chapter 6.5 149
Requirements for co-combustion in cement kilns
• suitable for pumpable organic wastes
• not suitable for wastes with high water, sulphur, chlorine, heavy metals content
• waste needs pre-treatment/blending for use as fuel
• adaptations may be needed eg fuel feed, dust controls
• must meet Health and Safety concerns re handling of hazardous wastes
• dependent on demand for product
TRP Chapter 6.5 150
Examples of technology 1Rotary kiln incinerator
Source: Guyer, Howard H Industrial processes and waste stream management, Wiley
TRP Chapter 6.5 151
Examples of technology 2 Fluidised bed combustion
Circulating fluidised bed Bubbling fluidised bed
Source: Guyer, Howard H Industrial processes and waste stream management, Wiley
TRP Chapter 6.5 152
Pyrolysis
Pyrolysis = thermal decomposition process which takes place in the total absence of oxygen
Products of pyrolysis: • combustible gases• mixed liquid residue
Advantages: • low operating temperature • no need for excess air so less flue gas• by-products are combustible
TRP Chapter 6.5 153
Application of pyrolysis
For single waste streams such as:
• scrap tyres • waste plastics
For treatment of contaminated soils
TRP Chapter 6.5 154
Gasification
Gasification = incomplete combustion in the partial absence of oxygen
Enables efficient destruction of hazardous waste at lower temperatures than incineration
Thermal destruction is ensured by a combination of high-temperature oxidation followed by high temperature reduction
Key considerations• Waste reduction and avoidance by generators
should always be a priority
• Need to consider residues from treatment processes and their disposal
• Thermal treatment is the best available technology for some organic hazardous wastes - providing that it is designed, managed and operated properly
• There is often opposition from the public and from environmental groups, largely based on dioxin concerns
TRP Chapter 6.5 156
Summary
Thermal treatment:
• is suitable for organic wastes• includes different technologies, all require high
capital investment • is highly regulated, requires high operating and
safety standards• needs skilled personnel• has medium to high operating costs• generates useful energy• has by-products which need careful handling• often attracts opposition
TRP Chapter 4.2 157
Waste minimisation
TRP Chapter 4.2 158
Why minimise waste?
On-site recycling
Off-site recycling
disposal
disposalsource
sourcewaste
No waste minimisation
With waste minimisation, recycling and treatment
to treatment
waste
TRP Chapter 4.2 159
Preferred hierarchy of waste management options
Source reduction
On-site/off-site recycling
Treatment
Final disposal
Waste diversion
TRP Chapter 4.2 160
Source reduction opportunities
Source reduction
Housekeeping improvement
Product reformulation
Input material alteration
Technology alteration
TRP Chapter 4.2 161
Factors influencing waste minimisation
•Government policy and regulations
•Technological feasibility
•Economic viability
•Management commitment and support
TRP Chapter 4.2 162
Waste minimisation - incentives
•Reduced costs:
• raw materials, energy, water
• storage and handling
• waste disposal
• health and safety
•Regulatory compliance
•Improved efficiency
•Improved corporate image
TRP Chapter 4.2 163
Waste minimisation - barriers
•Economic barriers
•Technical barriers
•Regulatory barriers
TRP Chapter 4.2 164
Waste minimisation opportunities applicable to all operations 1
•Use higher purity materials•Use less toxic raw materials•Use non-corrosive materials•Convert from batch to continuous process•Improve equipment inspection & maintenance•Improve operator training•Improve supervision•Improve housekeeping
Waste minimisation opportunities applicable to all operations 2
Improve material tracking and inventory control:
•avoid over-purchasing• inspect deliveries before acceptance•make frequent inventory checks• label all containers accurately•ensure materials with limited shelf-life are
used by expiry date•where possible, install computer-assisted
inventory control
Case studies
Delivering textile dyeing wastewater, Thailand
TRP Chapter 4.2 167
Implementing a company waste minimisation programme
• A systematic and ongoing effort to reduce waste generation
• Must be tailored to specific company needs and practices
• 3 main phases:
• planning and organisation
• conducting a waste audit
• implementing, monitoring and reviewing
TRP Chapter 4.2 168
Phase 1: Planning and organisation
•Obtain management commitment
•Establish programme task force
•Set goals and priorities
•Establish an audit team
TRP Chapter 4.2 169
Phase 2: Waste audit
6 main steps:
identify plant operations
define process inputs
define process outputs
assess material balance
identify opportunities
conduct feasibility study
TRP Chapter 4.2 170
Step 1: Identify plant operations
• Inspect the site
• Identify different processes undertaken on site
• List processes and obtain as much information as possible on them
TRP Chapter 4.2 171
Step 2: Define process inputs
Account for all the material flows into each individual process
• materials• energy• water
Make sure all inputs are accounted for in detail eg kg of raw materials, kilowatts of electricity, litres of water
Make sure figures are on same basis eg annual, monthly, weekly inputs
TRP Chapter 4.2 172
Step 3: Define process outputs
Identify and quantify all process outputs• primary products• co-products• waste for re-use or recycling• waste for disposal
TRP Chapter 4.2 173
Step 4: Assess material balance
To ensure that all resources are accounted for, conduct a materials balance assessment
=Total material in
Total material
out+ Product
TRP Chapter 4.2 174
Typical components of a material balance
Inputs Outputs
Production process or unit
operation
Raw material 1
Raw material 2
Raw material 3
Water/air
Product
By-product
Wastewater
Wastes for storage or off-site disposal
Gaseous emissions
TRP Chapter 4.2 175
Step 5: Identify opportunities for waste minimisation
Using data acquired during the waste audit, make preliminary evaluation of the potential for waste minimisation
Prioritise options for implementation
TRP Chapter 4.2 176
Step 6: Conduct feasibility study
Conduct feasibility analysis of selected options
Technical considerations: •Availability of technology•Facility constraints including compatibility with existing operation
•Product requirements•Operator safety and training•Potential for health and environmental impacts
Economic considerations:•Capital and operating costs•Pay-back period
TRP Chapter 4.2 177
Phase 3: Implementing, monitoring and reviewing
•Prepare Action Plan
•Identify resources
•Implement the measures
•Evaluate performance
TRP Chapter 4.2 178
Summary
•There are a number of good reasons for minimising waste - source reduction comes at the top of the waste hierarchy
•Factors which influence waste minimisation include regulations, technological feasibility, economic viability and management support
•There are both incentives and barriers; some opportunities widely applicable - and valuable experience from demonstration projects
•Guide to implementing a company waste minimisation programme and conducting an audit
Recycling turns materials that would otherwise become waste into valuable resources and generates a host of environmental, financial, and social benefits. After collection, materials (e.g., glass, metal, plastics, and paper) are separated and sent to facilities that can process them into new products and materials
Step 1. – Key People - Select a Recycling Coordinator The recycling coordinator will need to have good communication and organizational skills. Creativity, patience, persistence, a sense of humor, and good rapport with other people in your business are important character qualities If you are the owner or manager of a small business, you will probably be the coordinator, at least in the beginning
A coordinator’s role typically includes: Conduct a waste audit and determine what to recycle Selecting the contractor Designing the collection system Educating employees Tracking the program’s progress Designate area monitors to assist the coordinator in: - Keeping the collection containers free of non-recyclable material - Notifying the coordinator if containers overflow - Encouraging employee participation
Step 1. – Key People - Cleaners Always involve janitors in the planning process for any recycling program Additional training may be necessary to familiarize them with new or alternative waste collection procedures Realistically assess their safety concerns and how changes will affect their workload The cleaners' commitment and cooperation in executing your recycling program are crucial to success You may need to modify the janitorial contract to specify recycling services.
Step 1. – Key People - Landscape Contractors Plant waste from decorative landscaping for many downtown courtyards, atriums, and sidewalks often goes straight to landfill By working with your landscape contractor, you can potentially have plant waste hauled to a commercial composting facility
Step 1. – Key People – Food Handlers Food and other "wet wastes" contaminate dry recyclable waste unless you keep them in separate dumpsters It may be possible to reduce food waste through the suggestions of food handlers Donating food may be another alternative rather than disposal Food waste can also be recycled through composting
Step 1. – Key People - Construction Contractors The materials generated during the demolition phase of a renovation are mostly recyclable It is necessary to provide the contractor with a staging area and time in which to separate the materials If the contractor separates the materials, the value of the material can be rebated back to reduce hauling costs
Step 2. – Conduct a Waste Audit The reason to conduct a waste audit is to find out what’s in your trash The waste audit will help you identify which materials to collect for recycling, what size and type of containers you will need, and what waste could possibly be prevented in the first place Find out if your company or individual employees are already collecting any materials for recycling A waste sort or “dumpster diving” should be the first place to gather “bottom line” information and should be done just prior to refuse pickup
Step 2. – Conduct a Waste Audit Gather the following materials and resources: sorting tables a large scale for weighing the waste separate bins for each sorting category gloves surgical masks a calculator materials for recording data
Step 2. – Conduct a Waste Audit Safety First! Talk to your facility safety representative prior to doing a waste sort Wear protective clothing such as long-sleeved shirts, pants, gloves, and surgical masks If you discover any hazardous material, don’t touch it and contact your safety representative
Step 2. – Conduct a Waste Audit Once you have transferred all of the garbage to your sorting table, identify the materials you generate (for example, cardboard, office paper, and food waste) Weigh each type of material and record your findings Total the different amounts of waste found in each dumpster to find the “bottom line” Do similar waste sorts within the facility to determine what size recycling containers you’ll need and where they should be placed
Step 3. – Deciding What to RecycleCertain materials are either banned or restricted from from disposal facilities, such as: Tires Green Waste (yard trimmings) Appliances Used Oil Scrap Metal Auto Batteries •Contact your landfill to find a listing of restricted materials and how these materials can be disposed
Step 3. – Deciding What to RecycleIn some municipalities, businesses are required to recycle certain commodities such as: Bars and restaurants serving alcoholic beverages might be required to recycle glass Office buildings might be required to recycle office paper, newspaper and cardboard Hotels, restaurants, food courts, grocery stores, hospitals, and food manufacturers who generate large volumes of food waste might be required to recycle food waste•You should contact your local solid waste regulator to determine what materials you must recycle
Step 3. – Deciding What to RecycleTarget materials with reliable markets, such as: Aluminum Corrugated cardboard Used Oil Copper/Brass Office/Computer paper Tires Steel Newspaper Green Waste Glass
Step 3. – Deciding What to RecycleThe following liquids may be recycled and reused on your premises in most areas with special equipment: Solvents Antifreeze Frying oil
Step 4. – Selecting a Collection Contractor In selecting a collection contractor, you are looking for good, reliable service at the best price The prices paid for recyclable materials vary with the type of material and can fluctuate dramatically from month to month Moreover, your company’s economic benefit from recycling will probably come from reduced disposal costs, rather than money paid to you from the sale of recyclables
Step 4. – Selecting a Collection Contractor Option 1: Refuse hauler is also the recycling hauler If your refuse hauler provides both waste disposal and recycling collection, the hauler should be able to offer a combined cost/pay structure In other words, he would charge you for the hauling of both refuse and recyclables and credit you the current market value on the recyclables This can reduce your overall disposal costs or at least provide a break-even arrangement
Step 4. – Selecting a Collection Contractor Option 2: Recycling company picks-up A second option is to have a recycling company (or processor) collect and pay you for a material or collect it at no charge/no pay, depending on the current value of each material A small collector will most likely provide no charge/no pay service If you select a recycler, you should discuss lowering disposal costs with your refuse hauler, once your recycling program is underway
Step 4. – Selecting a Collection Contractor When you talk to the various companies to compare prices and services, ask the following questions to help you make your decision: What materials do you collect? What materials do you purchase, and how much is paid for each? Do you charge for collection of recyclables? If you’re picking up trash and recyclables, what will be the net savings in my disposal costs? Do you pick up on schedule or on call? If on schedule, how often? If on call, how much lead time is needed?
Step 4. – Selecting a Collection Contractor Do you provide collection and/or storage containers? Will you help us organize and promote our recycling program? Are you willing to sign a long-term agreement? (A one-year minimum is recommended.) What is the allowable level of contamination? What are your reporting and accounting procedures? How long have you been in business? Once you have made the selection, include the information you have gathered in a written agreement
Step 5. – Designing a Recycling System KEY: MAKE IT AS SIMPLE AND EASY TO RECYCLE AS IT IS TO THROW AWAY! The goal is to design a collection system that is convenient for everyone and does not incur additional labor costs
Step 5. – Designing a Recycling System Recyclables should flow from individual employees to area collection containers or directly to central collection/storage Place area recycling containers in convenient locations normally frequented by employees Recycling containers should look distinctly different from trash containers Place regular trash cans nearby to avoid unwanted trash getting mixed in with the recyclables
Step 5. – Designing a Recycling System At Desks Each employee usually gets their own small recycling tray or upright box for convenience When full, the employee empties the paper into the larger paper bins Trays and upright bins may be available from your municipality for free.
Step 5. – Designing a Recycling System Office Suites Some space is required in offices for recycling bins Based on weekly service, the rule-of-thumb for a white or mixed paper program is one 12-gallon container in each copy or printer areaFor a beverage bottle and can program, you need one lined container per kitchen area
Step 5. – Designing a Recycling System Dumpsters Most buildings have dumpsters for garbage Dumpster sizes are measured in cubic yards; one cubic yard is equal to about three toters Dumpsters are good for larger loads or bulky materials, such as cardboard They have lids which are easy to lock (which will protect materials from theft and or contamination if the dumpsters are located outside). Special garbage trucks are equipped to pick up and empty dumpsters automatically.
Step 5. – Designing a Recycling System Compactors Where space is limited, many buildings prefer to invest in compacting equipment Compactors come in a wide range of styles and sizes They can be rented or purchased and are often customized for a specific site or use Some of the investment can be recovered by disposal savings because you need less frequent garbage or recycling pick ups
Step 5. – Designing a Recycling System To select the best containers for your needs, consider the following: durability, cost, capacity, ease of handling, and attractiveness Check with local vendors on the types and styles available While containers need to be convenient for everyone, you also need to consider the work involved in emptying them By keeping in mind the needs of both employees and custodial or maintenance people you will find an acceptable balance that works for everyone involved
Step 5. – Designing a Recycling System Transferring to Central Collection and/or Storage KEY: INTEGRATE RECYCLING COLLECTION WITH EXISTING SYSTEMS KEY: DISTRIBUTE THE RESPONSIBILITIES.
Step 5. – Designing a Recycling System Central Collection/Storage AreaDetermine the best location for you with your building or facility manager and your collection contractor, using these guidelines: Is the site large enough? Is there easy access to freight elevators and loading docks? Does the area meet with local fire and building codes? Are sprinklers required/in place?
Step 6. – Training and Promotion Phase 1: Program Announcement Announce the start of the program with a brief, upbeat memo from the head of the company The memo should highlight the benefits of the program to everyone, outline the collection procedure, and give the time for a meeting to formally introduce the recycling program and answer questions
Step 6. – Training and PromotionPhase 2: Meeting/Educational Session Encourage everyone to attend an information session about the new program The meeting should focus on the cooperative nature of recycling and the importance of each individual to its continued success Highlight the main points of the program, taking care to explain the separation and collection procedures Emphasize the benefits to the environment, the company and the employees
Step 6. – Training and PromotionPhase 3: Follow-Up Follow-up can be done as a part of a regular meeting agenda or with memos or newsletters Consistency is the key to any successful program, and recycling is no different Note how much is being taken out of the waste stream, how much was donated to charity, how big the party fund is, and so on
Problem 1: Low Participation Rate Here are some of the things you can do to stimulate participation: Solution, Part 1: Provide Information People may not know how to recycle Provide reminders to tenants in memos and other promotional pieces Check that signs explain the recycling program See the Training and Promotion Section of this training
Solution, Part 2: Put Containers in the Right Places Check the location of recycling bins Make sure there are enough of them and that they are conveniently located Make it easier to put recyclable materials in the recycling bins than to put them in the garbage Make sure everyone can easily reach a recycling bin
Solution, Part 3: Appoint Recycling Experts It helps everyone to have an expert available to ask questions Designate motivated employees to be recycling coordinators for specific areas and let everyone know how to reach them Include the names or phone numbers for the experts in all the promotional materials
Solution, Part 4: Motivate Some people simply don't care at all about recycling Some people are very busy and might consider recycling to be a waste of time that is better spent on their "real work" Some of these people can be convinced to participate by providing incentives, such as games, prizes, and recognition or by making recycling easier than not recycling You can also put recycling into contracts when doing business outside your company
Problem 2: Contamination This is when non-recyclables are mixed with recyclables Solution: If contamination of recyclables is a problem throughout your building, ask your recycling company to help find procedural flaws or collection deficiencies If contamination is isolated to certain individuals in the building, focus your educational efforts on making sure they know the policies Solicit management help to change behavior
Problem 3: Unauthorized Scavenging This is when people are stealing the recyclables.Solution: Provide a secure, central storage area for recyclable materials between pick ups It should be secured from public access, yet easily accessible to your custodial staff and the recycling company Inform cleaners when unauthorized scavenging takes place and ask them to report suspicious activities to management
Problem 4: Lack of Space This can either be a lack of space near the points of generation or at the central collection and storage.Solution Lack of storage space is one of the biggest problems in many downtown office buildings Request assistance from your recycling company The two most practical solutions are to: (1) have materials collected more frequently and (2) install compacting equipment Be sure to consider health and safety as well as fire hazards when you address space issues
Closing the Loop Business must also support the purchase of recycled products By purchasing recycled products made with recycled materials, you are helping to ensure that a market will continue to exist for the materials collected in your recycling programs Building managers, through purchasing recycled products, can make a difference
Identifying Recycled-Content Products “Recycled-content products” are made from materials that would otherwise have been discarded (i.e. aluminum soda cans or newspapers) “Postconsumer content” refers to material from products that were used by consumers or businesses and would otherwise be discarded as waste. If a product is labeled "recycled content," the rest of the product material might have come from excess or damaged items generated during normal manufacturing processes—not collected through a local recycling program
“Recyclable products” can be collected and remanufactured into new products after they've been used There are more than 4,500 recycled-content products available, and this number continues to grow Make the commitment to “Close the Loop” and to purchase these products