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• They are often found in the form of
solids, sludge or gases.
• Safe collection, handling and disposal of
these wastes are very important and
great care must be taken for these
• The threat to public health and the
environment is
dependent on the
quantity and characteristics of a waste
Identify and classify hazardous wastes
Explain the techniques of hazardous
waste management, treatment and
Describe the physical, chemical,
thermal and biological methods of
treating them
Adopt waste minimization ,pollution
prevention techniques
• By using either or both of the following
criteria we can find a substance is
hazardous or not;
• The list provided by the government
agencies declaring that substance as
• Characteristics as ignitability,
corrosivity, reactivity and toxicity of
the substance.
• This list reduces the need to test the
wastes and simplifies waste
• Wastes from different industries are
covered under four lists.
• They are F,K,P and U industrial waste
• The F-list contains wastes from
non-specific source, i.e., various industrial
processes that may generated this waste.
• Consists of solvents commonly used in
degreasing, metal treatment, sludge and
wastewater from metal plating operations and
dioxin containing chemicals.
• E.g.; benzene(F005),carbon tetrachloride
• Solvent mixtures or blends containing
• more than 10% of one or more of the solvents
listed as above are also considered F-listed
• Generated by specific industrial processes.
E.g., Wood preservation, pigment
production, chemical production, petroleum
refining, iron and steel production and
explosive manufacturing
• Discarded commercial chemical products,
off-specification chemicals, container
residues and residues from the spillage of
• These 2 lists include any technical grades
of the chemical that are produced or
E.g., Pesticide (for P & U)
• Primary difference between them is the
quantity at which the chemical is
• P- list consists of acutely toxic wastes
that are regulated when the quantity
generated per month, or accumulated at
any time, exceeds one kilogram.
• U- list are regulated when the quantity
generated per month exceeds 25
• E.g., pesticide applicators and chemical
• Ignitability (EPA identification Number
• Corrosivity (EPA identification Number
• Reactivity (EPA identification Number
• Toxicity (EPA identification Number
• If the waste has a flash point of less than 60 ºC; readily
catches fire and burns so vigorously as to create a hazard.
• Material safety data sheet provides the flash points of wastes.
Examples : Naphtha, adhesives, oil based paints, etc.,
• A liquid waste which has a pH of ≤ 2 or ≥ 12 is corrosive.
• NaOH, Caustic solution (with high pH) is used to clean or
degrease metal parts
• HCl (low pH) is used to metal parts prior to painting.
• Disposal of these form corrosive hazardous waste.
 Reactivity
o Unstable, reacts violently with water, generates toxic gases or
explosion when exposed to heat or a flame.
o Examples of reactive wastes would be waste gun powder, Na
metal or wastes containing cyanides or sulphides.
 Toxicity
o The toxic characteristic identifies wastes that are likely to
leach dangerous chemicals into ground water.
o To determine toxicity, a representative sample of the material
must be subjected to a test conducted in a certified laboratory.
• Even though many industries are producing
more amount of wastes, hospitals and
biological research centers are the
principal sources.
• Other sources are industries of
automobile, chemical, coal, electroplating,
leather, metallurgical, petroleum, textile,
paint and related industries.
• Hospitals and research laboratories.
Chemical wastes
Biological wastes
Flammable wastes
Radioactive wastes are some of the
types of hazardous wastes.
• Extensive use of chemicals for
industrial and agricultural purposes .
• Detergents, Fertilizers, Toxic metals in
industrial waste and Soil based
technology are the main source.
• Cadmium, Mercury, Chromium, lead,
Arsenic and Barium are some of the
toxic pollutants
• As a by-product of industrial biological
conversion processes
• They have the ability to produce toxins
and infect living organisms.
• Malignant tissues taken during surgery,
hypodermic needles, bandages and
expired medicines etc.,
• Often they are liquids.
• Organic solvents, oils, plasticizers and
organic sludge.
• Sources : Dry cleaners, petroleum
reclamation plants, petroleum refining
and processing facilities, service
• These wastes resulting from weapons
• They have a high potential for hazard in
storage, collection and disposal.
• They may exist in solid, liquid or gaseous form.
E.g. Construction companies, dry cleaners,
ammunition production facilities, etc.
• The radiations from radioactive substances –
prolonged exposure results in damage to the
living organisms and they contaminate air,
water and land.
• Natural sources;1.Cosmic rays from outer
space. 2.Naturally occurring isotopes.
• Man made sources;1.Nuclear weapons
2.Atomic reactors and nuclear fuel 3.Mining
and refining of radioactive wastes(U,Pu,&Th)
• Radioactive isotopes.
• Since the radioactive wastes are essentially
created in a nuclear power reactor, it is accepted
that it is the responsibility of the country which
uses uranium to generate power
• There are three kinds of radiation to consider:
alpha, beta and gamma. A fourth kind, neutron
radiation, generally only occurs inside a nuclear
Different types of radiation require different forms of protection:
Alpha radiation cannot penetrate the skin and can be blocked out by a
sheet of paper, but is dangerous in the lung.
Beta radiation can penetrate into the body but can be blocked out by a
sheet of aluminium foil.
Gamma radiation can go right through the body and requires several
centimetres of lead or concrete, or a metre or so of water, to block it.
All of these kinds of radiation are, at low levels, naturally part of our
environment. Any or all of them may be present in any classification of
Radioactive wastes are normally classified as low-level,
medium-level or high-level wastes, according to the amount
and types of radioactivity in them.
Another factor in managing wastes is the time that they are
likely to remain hazardous. This depends on the kinds of
radioactive isotopes in them, and particularly the half-lives
characteristic of each of those isotopes.
half-lives ranging from fractions of a second to minutes, hours
or days, through to billions of years. Radioactivity decreases
with time as these isotopes decay into stable, non-radioactive
Depends on duration of exposure
Strength of radiation
Half-life period
Rate of diffusion
Environmental conditions
Radioactive substances
Various trucks & railroad equipment
wastes; special marking to show safety
Toxic chemicals
Flatbed trucks – wastes stored in
Tractor-trailer tank with truck – large
volumes of waste, railroad tank cars,
Special interior linings such as glass,
fiber glass or rubber
Biological wastes
Flatbed trucks – wastes stored in
drums; precautions to prevent contact
between wastes and the collector.
Flammable wastes
Same as those for toxic chemicals,
special colorings and safety warning
printed on vehicles.
Same as those for toxic chemicals,
Restriction on transport routes.
Storage and Handling
Light-Gauge Closed
Head Drum
Light-Gauge Open
Head Drum
Hazardous wastes are not compacted or delivered
by numerous community residents.
Instead , liquid hazardous wastes are generally
pumped from collection vehicles and sludge or
solids are reloaded without removal from the
collection containers for transport to processing
and disposal facilities.
It is unusual to find a hazardous waste
transfer facility, where wastes are simply
transferred to larger transport vehicles. Some
processing and storage facilities are often the
part of the material handling sequence at a
transfer station.
Example, Neutralization of corrosive wastes
might result in the use of lower-cost holding
tank on transport vehicles. As in the case of
storage, great care must be exercised to avoid
the danger of mixing incompatible wastes.
Processing of hazardous waste is done for purposes of
recovering useful materials and preparing wastes for
the disposal.
Processing can be accomplished on-site or off-site.
The variables affecting the selection of processing
site include the characteristics of wastes, the quantity
of wastes, the technical, economical and environmental
aspects of available on-site treatment processes and
the availability of nearest off-site treatment facility.
The treatment of hazardous waste can be
accomplished by physical, chemical, thermal or
biological means.
Physical &Chemical treatment
• They are the essential part of most
hazardous waste treatment.
• Filtration and separation: A method of
separating solid particles from a liquid
using a porous medium.
• Liquid and gas wastes like inorganic
chemical with and without heavy metal
and organic chemical with or without
heavy metal are treated by this process.
Chemical precipitation
• This is a process by which the soluble
substance is converted to an insoluble
• Settling or filtration can then remove the
precipitated solid.
• This includes waste containing arsenic
,barium, cadmium ,copper ,lead ,mercury ,
nickel, selenium , silver and zinc
• The sources of wastes containing metals
are metal plating and polishing ,
inorganic pigment and electronic
• Hazardous waste containing metal are
also generated from cleanup of
uncontrolled hazardous waste sites
• Example: leachate or contaminated
ground water
Chemical oxidation and
• Such reactions are used in treatment of
metal wearing waste , sulphides ,
cyanides and chromium and in the
treatment of organic waste such as
phenols, pesticides and sulphur
containing compounds.
• These treatment process involve
chemical reactions both reactants are
generally in solutions.
• Commonly used oxidising agents are sodium
hypochlorite , hydrogen peroxide ,
potassium permanganate and ozone.
• Reducing agents are sulphur dioxide, sodium
• This oxidation and reduction treatment
tends to be more suitable for more
• It is a process in which materials are
added to the waste to produce a solid.
• It may or may not involve a chemical
bonding between the toxic contaminant
and additive.
• It is a process by which a waste is
converted to a more chemically stable
• Stabilization represents the use of a
chemical reaction to transform the
toxic component to a new non-toxic
compound or substance.
Chemical fixation
• This implies the transformation of toxic
contaminants to a new non-toxic
• This term has been misused to describe
processes which do not involve chemical
bonding of the contaminant to the
• This process involves the complete coating or
enclosure of a toxic particle or waste agglomerate
with new substance.
• The encapsulation of the individual particles is known
as micro encapsulation.
• An agglomeration of waste particle or micro
• Its function is storage.
• Its waste types include inorganic chemical with and
without heavy metals, organic chemical with and
without heavy metals.
• Form of waste is- liquid and solid
• It is defined as the conversion of the liquid from
solution or slurry into vapour.
• The process equipment which is quite flexible and
can handle waste in various forms.
• It is also used in cases when no other treatment
method is used.
• Its function is volume reduction and separation.
• Types of waste - inorganic chemical with and
without heavy metals and radiological.
• Forms of waste - liquid.
• It is a relatively unstable gas
consisting of 3 oxygen atoms
per molecule.
• It is one of the strongest
oxidizing agent.
• It can be substituted for
oxidants such as chlorine,
potassium permanganate.
• It is used to detoxify
Thermal treatment
• Two types of thermal treatment
• It can be regarded as either a pre-treatment of
hazardous waste or as a means of vaporizing waste
by recovering agent.
• It includes both the burning of mixed solid waste
or burning of selected parts of the waste stream
as a fuel.
• Its function is volume reduction and detoxification
• Types of waste - organic chemical without heavy
metal ,radiological ,biological ,flammable ,explosive
• Forms of waste- solid ,liquid ,gas
• It is defined as the chemical decomposition
or change brought about by heating in the
absence of oxygen.
• It is used for transformation of solid and
liquid carbonaceous materials into gaseous
Pyrolysis includes two step process for disposal.
In the first step, wastes are heated separating the
volatile content from non-volatile char and ash.
In the second step, volatile components are burnt
under proper condition to assure incineration of all
hazardous components.
Its function is volume reduction and detoxification.
Types of waste is organic chemical with and
without heavy metals and biological.
Forms of waste - solid ,liquid ,gas
Biological treatment Composting
• The principles involved in composting organic
hazardous waste are same as those in composting
organic material with moderate modifications.
• The reaction is that certain types of hazardous
waste molecules can be degraded by one or few
microbial species.
• The waste governs biological reactions.
• The physical parameters are shape, dimension,
temperature , pH and moisture.
 In general disposal of hazardous wastes should be
separate from those of municipal wastes.
 As hazardous wastes can exist in the form of
liquids, sludges, solids and dusts, a correct approach
for co-disposal for each of the hazardous wastes
should be determined.
To avoid the co-disposal of incompatible wastes,
separate storage areas within the total landfill site
should be designated for various classes of
compatible wastes.
Liquid wastes are usually stored in a tank near the
site and can be introduced into landfill by means of
trenches or lagoons, injection or irrigation. Sludges
are also placed in trenches.
During disposal of light weight wastes, the disposal
area must be kept wet to prevent dust emissions.
Hazardous solid waste characterized by a high
degree of impermeability as such must not be
disposed off over large areas.
Three general principles are employed in the
management of radioactive wastes:
The first two are also used in the management of
non-radioactive wastes. The waste is either
concentrated and then isolated, or it is diluted to
acceptable levels and then discharged to the
Delay-and-decay however is unique to radioactive
waste management; it means that the waste is stored
and its radioactivity is allowed to decrease naturally
through decay of the radioisotopes in it.
• Low –level wastes is generated from hospitals,
laboratories and industries. It comprises
papers, rags,tools,filters etc.,
• They contain small amounts of short-lived
• Intermediate-level wastes contains higher
amounts of radioactivity and require special
• It comprises resins chemical sludges and
reactor components and contaminated materials
• It may be solidified in concrete or bitumen for
• High-level wastes may be the used fuel itself, or
• It holds 95% of the radioactivity with long life.
• It generates large amount a considerable
amount of heat and requires cooling as well as
special shielding during handling and transport.
• If the fuel is reprocessed the separated waste
is vitrified by incorporating it into borosilicate
glass which is sealed inside stainless steel
canisters for disposal deep underground.
Storage pond for spent fuel at UK reprocessing plant
Final disposal of high-level waste is delayed for 40-50 yrs to
allow its radioactivity to decay, after which <1000th of its initial
radioactivity remains, and it is much easier to handle. Hence
canisters of vitrified waste, or used fuel assemblies, are stored
under water in special ponds, or in dry concrete structures or
casks, for at least this length of time.
The ultimate disposal of vitrified wastes, or of used fuel
assemblies without reprocessing, requires their isolation from
the environment for a long time. The most favored method is
burial in stable geological formations some 500m deep. Several
countries are investigating sites that would be technically and
widely acceptable.
After being buried for about 1000 yrs most of the radioactivity
will have decayed. The amount of radioactivity then remaining
would be similar to that of the corresponding amount of
naturally-occurring uranium ore from which it originated, though
it would be more concentrated.
Status in India
• Based on Ministry of Environment and Forest,
at present around 7.2 million tonnes of
hazardous wastes is generated in India.
• Of which 1.4 million tonnes is recyclable,0.1
million tonnes is incinerable and 5.2 million
tonnes is destined for disposal on land.
• There are 323 recycling units, of which 303
use indigenous raw material and 20 depend on
imported recyclable wastes.
Chemistry can be a good and bad thing. Chemistry is good
when you make love with it. Chemistry is bad when you make
crack with it.
~Adam Sandler