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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. - PowerPoint PPT Presentation


E8 - Waste Disposal

E8 - WasteVivien Tsang & Melody MakWaste 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:LandfillOpen dumpingOcean dumpingIncinerationRecycling 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 materialFilled land can be utilised for building Filled land can be used for community purposesLand is not wasted

Landfill Disadvantages Local residents may objectOnce the land is filled, it may need a period of time to settleFilled 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 ConvenientInexpensive

Open Dumping Disadvantages Air and ground water pollution as waste easily comes into contact with theseSolid waste may get into drinking waterVisual pollutionBad smellHealth hazard may become a breeding ground for rodents and insectsCauses 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 ConvenientInexpensiveWaste may be a source of nutrients for marine plants and animals

Ocean Dumping - DisadvantagesDanger to marine animals as they may get tangled up in plastic bagsNon-biodegradable waste (e.g. plastic bags) pollute the oceanKilling of planktonDestruction 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 - AdvantagesReduces the volume of waste materialRequires minimal spaceProduces stable and odourless residueHeat generated may be used as a source of energyTreatment can be carried out in any weather conditions

Incineration - DisadvantagesExpensive to build and operateCan produce air pollutants if waste is not burned efficientlyRequires a great amount of energyRequires skilled labourRequires maintenanceMay 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 environmentLess wastage of fresh raw materialReduces energy usageReduces air and water pollution

Recycling Disadvantages ExpensiveNot all waste can be recycledDifficulty in separating the useful material from the waste

Recycling : MetalsThe metals recycled are mainly aluminium and steelThey are sorted and melted and either: - reused directly - added to the purification stage of metals formed from their oresRecycling of aluminium is especially important because it requires a great amount of energy to produce directly from its ore

Recycling : PaperWhen paper is recycled it is:Sorted into gradesWashed to remove any ink presentMade into a slurry to form new types of paper e.g. newspaper and toilet rolls

Recycling : GlassWhen glass is recycled, it is:Sorted by its colourWashed Crushed and meltedMoulded into new productsGlass does not degrade when recycled therefore it can be recycled many times

Recycling : PlasticsWhen plastics are recycled, they are broken down by: - Pyrolysis - Hydrogenation - Gasification - Thermal cracking - and finally, repolymerisedFewer pollutants are formedUses less energy than producing new plastics from crude oilHoweverSorting 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 handledHigh-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.