Self-Assessment Questions (SAQs) for Study Session 10
Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.
SAQ 10.1 (tests Learning Outcomes 10.1 and 10.2)
Which of the following waste disposal methods would you consider to be the safest to public and environmental health? Explain the reasons for your choice and why the other two options are less desirable.
- a.Disposal into open field away from residential areas.
- b.Disposal into a river.
- c.Disposal in a sanitary landfill.
Answer
Option (c), sanitary landfill, is the safest option.
- a.The open field is away from residential areas so odour may not be a problem but it would attract flies, rats and other scavengers. The waste is not covered so it could be blown around by wind or burn uncontrollably. Leachate from the waste could pollute water sources and there would be no control of landfill gas.
- b.Discarding waste into a river could cause all the above problems and would certainly pollute the river water which could affect people using the river as a water source for themselves, their animals or for irrigation. Pollution would also affect wildlife both in and around the river.
- c.A well-managed sanitary landfill is the safest option because this would ensure leachate was collected and treated and would contain and control landfill gas. The waste would be covered every day with soil to stop it blowing around, prevent fly breeding, discourage scavenging animals and prevent the waste from catching fire.
SAQ 10.2 (tests Learning Outcomes 10.1 and 10.2)
If a community wanted to transform its open dump site into a controlled landfill, what measures would it have to take?
Answer
Measures to transform an open dump site into a controlled landfill should include:
- surrounding the site with a child-proof and animal-proof fence
- employing a person to staff the site
- providing a tractor to spread and compact the waste
- covering the freshly deposited waste with a layer of soil each day.
SAQ 10.3 (tests Learning Outcomes 10.1 and 10.2)
Explain how incineration differs from open burning.
Answer
Incineration is burning that is enclosed and controlled. Open burning is uncontrolled. Incineration produces less smoke; the ash is contained and can be removed for burial; it is safer because the burning waste cannot be blown around and spread fire. A higher temperature can be maintained in an incinerator which ensures more of the waste is consumed, leaving little residue.
SAQ 10.4 (tests Learning Outcomes 10.3)
What are the key factors to be considered when planning a new landfill in small and medium-sized towns? List at least four factors.
Answer
Key factors to consider when planning a landfill in small and medium-sized towns include:
- available land
- required land area based on population size, both current and future, and estimated waste production rate
- distance from the site to the town to be served
- location of rivers that could be polluted
- presence of groundwater below the site
- soil type and geology
- local opinions and beliefs about the site.
SAQ 10.5 (tests Learning Outcomes 10.1 and 10.4)
- a.Identify the type of hazardous waste of each of the following:
- old batteries from wrecked cars and lorries
- firecrackers that were thrown away because they got damp
- empty pesticide can
- bloody bandages from a health centre
- liquid waste from a factory with pH 13
- used solvent from cleaning paint brushes.
- b.State four ways in which hazardous waste can be disposed of safely.
Answer
- a.The types of waste and their corresponding hazards are:
| Type of waste | Type of hazard |
| Old batteries from wrecked cars and lorries | Corrosive |
| Firecrackers that were thrown away because they got damp | Explosive or flammable |
| Empty pesticide can | Toxic |
| Bloody bandages from a health centre | Infectious |
| Liquid waste from a factory with pH 13 | Corrosive |
| Used solvent from cleaning paint brushes | Ignitable and flammable |
- b.Depending on the type of hazard, safe disposal methods of hazardous waste include:
- disposing of the waste in a secure landfill where the waste is kept completely isolated from the general environment
- subjecting it to various chemical treatment methods
- controlled incineration at a high temperature
- biological treatment using specific micro-organisms.
Summary of Study Session 10