This is about the Hazardous Waste Management.

1. HAZARDOUS WASTE MANAGEMENT
The generation of waste and the collection, processing, transport and disposal of
waste—the process of ‘waste management’—is important for both the health of the
public and aesthetic and environmental reasons. Waste is anything discarded by an
individual, household or organization. As a result waste is a complex mixture of different
substances, only some of which are intrinsically hazardous to health. The potential health
effects of both waste itself and the consequences of managing it have been the subject of
a vast body of research.
Methods of Waste Management
Waste management is now tightly regulated in most developed countries and
includes the generation, collection, processing, transport and disposal of waste. In
addition the remediation of waste sites is an important issue, both to reduce hazards
whilst operational and to prepare the site for a change of use (e.g. for building).
The major methods of waste management are:
1. Recycling—the recovery of materials from products after they have been used by
consumers.
2. Composting—an aerobic, biological process of degradation of biodegradable organic
matter.
3. Sewage treatment—a process of treating raw sewage to produce a non-toxic liquid
effluent which is discharged to rivers or sea and a semi-solid sludge, which is used as
a soil amendment on land, incinerated or disposed of in land fill.
4. Incineration—a process of combustion designed to recover energy and reduce the
volume of waste going to disposal.
5. Landfill—the deposition of waste in a specially designated area, which in modern
sites consists of a pre-constructed ‘cell’ lined with an impermeable layer (man-made
or natural) and with controls to minimize emissions.
Hazardous Waste
Hazardous waste is any unwanted material the disposal of which poses a threat to the
environment, i.e. it is explosive, flammable, oxidizing, poisonous/infectious, radioactive,
corrosive and/or toxic/eco-toxic.
Source of Hazardous Waste
Sources of hazardous waste include hospitals, timber treatment, petrol storage, metal
finishing, paint manufacture, vehicle servicing, tanneries, agriculture/horticulture,
electricity distribution and dry cleaning.

2. Examples of Hazardous Waste
Managing Hazardous Waste
The Waste Management Hierarchy
In deciding on the best method for managing any waste there is a hierarchy for decision
making which addresses issues such as sustainability, cleaner production, health, safety,

3. and environmental protection. It is applied to existing or proposed practices, examining
and testing these at each level, starting at the top of the hierarchy.
For hazardous waste the hierarchy is as follows:
 -Eliminate the production of hazardous waste
 -Where elimination is not possible apply methods to reduce the quantity or hazard
involved
 -Minimize amount of waste for disposal by recycling, reuse and/or recovery. This
includes the recovery of energy which may be available from the waste.
 -Treat waste to stabilize, immobilize, contain or destroy hazardous properties.
 -Dispose of residues with a minimum of environmental impact.
 -Appropriately contain, isolate and store hazardous waste for which no acceptable
treatment or disposal option is currently available.
Waste Minimization
Examples of ways in which waste minimization can be achieved include:
- substituting a hazardous material used in a process with a non-hazardous material
- process changes
- reducing the amount of hazardous materials used
- recovering and reusing materials
Examplesof Waste MinimizationsPractices

4. Treatment of Hazardous Wastes
Chemical Methods
Neutralization
Waste acid with an alkali e.g. sulfuric acid with sodium carbonate:
Oxidation
Using common oxidizing substances such as hydrogen peroxide or calcium hypochlorite
e.g. cyanide waste with calcium hypochlorite:
Reduction
Used to convert inorganic substances to a less mobile and toxic form e.g. reducing
Cr(VI) to Cr(III) by the use of ferrous sulphate:
Hydrolysis
Decomposition of hazardous organic substances e.g. decomposing certain organo-
phosphorus pesticides with sodium hydroxide.
Precipitation
Particularly useful for converting hazardous heavy metals to a less mobile, insoluble form
prior to disposal to a landfill e.g. precipitation of cadmium as its hydroxide by the use of
sodium hydroxide:
Physical Methods
Encapsulation
Immobilizing hazardous materials by stabilization and incorporation within a solid matrix
such as cement concrete or proprietary organic polymers prior to and filling. e.g.
encapsulating beryllium in concrete

5. Filtration/Centrifuging/Separation
Physically separating phases containing hazardous substances from other nonhazardous
constituents e.g. separation of oils from ship bilges waters.
Biological Methods
These involve the use of microorganisms under optimized conditions to mineralize
hazardous organic substances e.g. the use of pseudomonas under aerobic conditions
break down phenols.
Thermal Methods
These are the treatment processes which involve the application of heat to convert the
waste into less hazardous forms. It also reduces the volume and allows opportunities for
the recovery of energy from the waste.
High Temperature Incineration
In North America and Europe the treatment method most commonly used to destroy
hazardous organic wastes, including organochlorines such as polychlorinated biphenyls
(PCBs), is high temperature incineration. Figure 5 schematically illustrates the processes
involved. There is a high temperature incinerator for the destruction chemical wastes in
New Plymouth but its use is dedicated solely to those generated on site.
Incineration is the controlled combustion process which can be used to degrade organic
substances. For a simple hydrocarbon, involving complete combustion, for example the
chemical reaction can be illustrated as follows:

6. In practice, complete combustion is difficult if not impossible to achieve but for
hazardous waste 99.99% or greater destruction or removal is required for the process to
be generally acceptable.