Transcript Waste - chemoptione

E8 - Waste
Vivien Tsang & Melody Mak
Waste Disposal
Waste disposal is the transportation, management, recycling
and disposal of waste materials usually produced by human
activity.
However, due to the continuously growing human population
and industrialisation, more waste material is generated than
ever before. This is growing concern as we now have to deal
with the problem of where to place our waste without causing
detrimental harm to our health and our environment.
Methods of Waste Disposal
There are various different methods of waste disposal:
 Landfill
 Open dumping
 Ocean dumping
 Incineration
 Recycling
However, each of these have their pros and cons and is
worth evaluating.
Landfill
In landfills, waste is buried in a structure built under the
ground so that it is not in contact with the surrounding
environment (e.g. air, groundwater). This gap in the
ground is then covered with a layering of soil.
The waste material buried in landfills is kept relatively dry
therefore it will not decompose much.
Landfill – Advantages
 Efficient in dealing with large volumes of waste material
 Filled land can be utilised for building
 Filled land can be used for community purposes
 Land is not wasted
Landfill – Disadvantages
 Local residents may object
 Once the land is filled, it may need a period of time to
settle
 Filled land requires maintenance as methane gas may
be released
Open Dumping
Open dumping is the disposal of large quantities of waste
in open areas of land which are not designed for the
purposes of holding waste material.
It is a prohibited act and against the law.
Examples where it may occur: road sides, ditches, river
beds, secluded areas.
Open Dumping – Advantages
 Convenient
 Inexpensive
Open Dumping – Disadvantages
 Air and ground water pollution as waste easily comes into
contact with these
 Solid waste may get into drinking water
 Visual pollution
 Bad smell
 Health hazard – may become a breeding ground for
rodents and insects
 Causes flooding due to the clogging of drainage systems
Ocean Dumping
Ocean dumping is the disposal of waste materials in
designated areas of the ocean.
It is generally banned in many countries.
Ocean Dumping – Advantages
 Convenient
 Inexpensive
 Waste may be a source of nutrients for marine plants and
animals
Ocean Dumping - Disadvantages
 Danger to marine animals as they may get tangled up in
plastic bags
 Non-biodegradable waste (e.g. plastic bags) pollute the
ocean
 Killing of plankton
 Destruction of food sources for marine organisms
Incineration
Incineration is the destruction of waste material using
heat energy. Organic substances within the waste is
combusted and turned into ash and heat.
Incineration - Advantages
 Reduces the volume of waste material
 Requires minimal space
 Produces stable and odourless residue
 Heat generated may be used as a source of energy
 Treatment can be carried out in any weather conditions
Incineration - Disadvantages
 Expensive to build and operate
 Can produce air pollutants if waste is not burned
efficiently
 Requires a great amount of energy
 Requires skilled labour
 Requires maintenance
 May be a visual pollution
Recycling
Recycling involves processing waste into new products to
avoid wastage of any material that may be useful.
It also aims to avoid using fresh raw material.
Recycling – Advantages
 Provides a sustainable environment
 Less wastage of fresh raw material
 Reduces energy usage
 Reduces air and water pollution
Recycling – Disadvantages
 Expensive
 Not all waste can be recycled
 Difficulty in separating the useful material from the waste
Recycling : Metals
 The metals recycled are mainly aluminium and steel
 They are sorted and melted and either:
- reused directly
- added to the purification stage of metals formed
from their ores
 Recycling of aluminium is especially important because it
requires a great amount of energy to produce directly
from its ore
Recycling : Paper
 When paper is recycled it is:
1. Sorted into grades
2. Washed to remove any ink present
3. Made into a slurry to form new types of paper e.g.
newspaper and toilet rolls
Recycling : Glass
 When glass is recycled, it is:
1. Sorted by its colour
2. Washed
3. Crushed and melted
4. Moulded into new products
 Glass does not degrade when recycled therefore it can
be recycled many times
Recycling : Plastics
 When plastics are recycled, they are broken down by:
- Pyrolysis
- Hydrogenation
- Gasification
- Thermal cracking
- and finally, repolymerised
 Fewer pollutants are formed
 Uses less energy than producing new plastics from crude oil
However
 Sorting plastics can be difficult
Radioactive waste
Radioactive waste can be categorised into two types:

Low-level waste:
- Level of activity is low
- Short half-life
- E.g. rubber gloves, paper towels, protective clothing, anything used where radioactive
materials are handled

High-level waste:
- High level of activity
- Long half-life, waste remains active for long periods of time
- E.g. spent fuel rods
Storage & Disposal: Low-level Waste
The decay of low-level waste produces heat therefore
they are stored in tanks of cooled water. Here it loses
much of its activity.
The waste is then filtered through an ion exchange resin
where strontium and caesium, the main radioactive
wastes, are removed before being discharged out to the
sea.
Or it could be kept in steel containers inside concretelined vaults.
Storage & Disposal: High-level Waste
High-level waste is treated by a method called
vitrification. The liquid waste is dried in a furnace and
then mixed with glass-making material.
This molten material is then poured into steel tubes with
air flowing around it to cool it down. Eventually it
solidifies.
However
The waste still remains radioactive for possibly thousands
of years. Thus there is a problem of storing it and the risk
of leaking radioactive substances into water supply.
References
 http://science.howstuffworks.com/environmental/greenscience/landfill3.htm
 http://www.deq.state.ok.us/factsheets/local/opendump.pd
f
 http://health.co.st-clair.il.us/NR/rdonlyres/26E2433A-896E44BA-BF26-D37831B7F595/0/ODBrochure.pdf
 http://www.hamiltoncountyhealth.org/en/permits_licensing_
inspections/waste_management/open_dumping.html
 http://www.gdrc.org/uem/waste/disposal.html