E8 - WasteVivien 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 DisposalThere 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 wasteRadioactive 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 concrete-lined 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/green-science/landfill3.htm

http://www.deq.state.ok.us/factsheets/local/opendump.pdf

http://health.co.st-clair.il.us/NR/rdonlyres/26E2433A-896E-44BA-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