Self-Assessment Questions (SAQs) for Study Session 4
Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.
SAQ 4.1 (tests Learning Outcome 4.1)
Match the following words to their correct definitions.
Using the following two lists, match each numbered item with the correct letter.
eutrophication
aerobic
organic matter
septic tank
point-source of pollution
soil erosion
inorganic material
sewerage
algal bloom
non-point source of pollution
suspended solids
pollution
pollutants
sewage
diffuse pollution
catchment
sediments
leachate
anaerobic
photosynthesis
a.a polluting liquid that is produced when water passes through materials and takes with it components from them
b.the introduction into the environment of substances likely to cause harm to humans, animals, plants and the environment in general
c.substances that can cause harm to human health, plants, animals and the environment in general
d.material that comes from living organisms
e.a process by which a high concentration of nutrients, especially phosphates and nitrates from agricultural or other activities, enters a water body and lead to excessive plant growth and eventual decay, resulting in depletion of oxygen in the water
f.the process by which plants generate chemical energy
g.the area of surrounding land that slopes towards a river
h.an identifiable source of pollution
i.solids that have settled at the bottom of a river
j.a network of sewers
k.without oxygen
l.pollution from non-point sources
m.particles carried in flowing water
n.material which does not originate from living organisms
o.mixed wastewater that contains human waste from flush toilets
p.an underground tank into which sewage is piped
q.containing oxygen
r.a sudden increase in the algal population
s.a source of pollution that encompasses a wide area, the exact point of origin being difficult to ascertain
t.the washing away of soil by rainwater run-off
- 1 = e
- 2 = q
- 3 = d
- 4 = p
- 5 = h
- 6 = t
- 7 = n
- 8 = j
- 9 = r
- 10 = s
- 11 = m
- 12 = b
- 13 = c
- 14 = o
- 15 = l
- 16 = g
- 17 = i
- 18 = a
- 19 = k
- 20 = f
SAQ 4.2a (tests Learning Outcome 4.2)
Classify the following examples of water pollutants using the categories shown in the table below:
- copper
- insecticides
- sand
- protozoa
- nitrates
- bacteria
- lead
- silt
- phosphates
- faecal matter
- intestinal worms
| Category of water pollutant | Examples |
| Sediments and suspended solids | |
| Organic matter | |
| Biological pollutants | |
| Plant nutrients | |
| Other chemical pollutants |
Answer
The answer is as follows:
| Category of water pollutant | Examples |
| Sediments and suspended solids | sand, silt |
| Organic matter | faecal matter |
| Biological pollutants | bacteria, protozoa, intestinal worms |
| Plant nutrients | nitrates, phosphates |
| Other chemical pollutants | copper, lead, insecticides |
SAQ 4.2b (tests Learning Outcome 4.2)
The following are pollution sources. Give two specific pollutants for each source.
A residential area: ………………………………………………
A metal plating plant: ………………………………………………
Agricultural activities: ………………………………………………
An uncontrolled landfill site: ………………………………………………
Urban surface water run-off: ………………………………………………
Answer
There are several possibilities, listed below.
| A residential area: | human excreta, wastewater containing dissolved and suspended organic matter, suspended inorganic matter, pathogenic micro-organisms |
| A metal plating plant: | cyanides, heavy metals |
| Agricultural activities: | nitrates, phosphates, pesticides |
| An uncontrolled landfill site: | leachate containing dissolved organic matter, inorganic components and heavy metals |
| Urban surface water run-off: | sediment, metals, hydrocarbons, rubber, detergents, litter |
SAQ 4.3 (tests Learning Outcomes 4.2 and 4.3)
Read Case Study 4.1 and then answer the questions that follow.
Case Study 4.1
Mekanisa is a place in the southern part of Addis Ababa where urban agriculture is practised. A group of farmers grow different varieties of vegetables and sell them to people in the city. The farmers use water from the nearest river (the River Kera) for irrigation. They mostly grow leafy vegetables, with two harvests a year.
The Kera River originates a few kilometres from Mekanisa and passes through residential, commercial and industrial areas before reaching Mekanisa. Along its way, human excreta and industrial wastes are indiscriminately discharged into the river. One of the prominent polluters of the river is the city’s biggest slaughterhouse, located at the side of the river. Untreated wastewater from the slaughterhouse is discharged into the river giving a blue-black colour to the water. Farmers like this type of water for irrigation as it helps their crops grow.
One of the authors of this Module undertook research assessing the level of pollution of the river water. The results are shown in Table 4.2.
| Parameters | FAO* Guideline Concentrations for components in irrigation water (Pescod, 1992) | River water |
| Faecal coliforms | >2500 per 100 ml | |
| Copper | 0.2 mg l-1 | 25.5 mg l–1 |
| Zinc | 2.0 mg l-1 | 56.3 mg l–1 |
| Iron | 5.0 mg l-1 | 71.0 mg l–1 |
| Lead | 5.0 mg l-1 | 19.0 mg l–1 |
| Manganese | 0.2 mg l-1 | 37.0 mg l–1 |
| *FAO is the Food and Agriculture Organization of the United Nations. | ||
- a.What nutrients in the river water do you think benefited the crops grown by the farmers?
- b.State which components in the river water might be harmful to people and give your reasons.
- c.Suggest what should be done regarding the pollution of the River Kera.
Answer
- a.There are likely to be nitrates and phosphates in the river water which are vital to plant growth.
- b.The presence of a high number of faecal coliformsindicates that the water is unsafe, and also that other micro-organisms, which may be pathogenic, may be present. The concentrations of copper, zinc, iron, lead and manganese in the river water are all greater than the guideline values recommended by the FAO. This implies that they are harmful.
- c.Pollution control at source is required. This would entail treating the sewage, industrial effluents and slaughterhouse wastewaters before they are discharged into the river.
SAQ 4.4 (tests Learning Outcome 4.3)
Which of the following statements is false? In each case, explain why it is incorrect.
- A.Latrines should be sited up-slope of a water source so that they don’t get flooded.
- B.For the protection of springs, a fence, a diversion ditch, a watertight concrete box, and a tight-fitting cover are enough.
- C.Farmers should use the minimum amount of fertiliser that is necessary for their crops, and apply it after rain.
- D.Catchment management involves several different activities to ensure that the integrity of a water source is maintained.
- E.To save time water pollution control legislation is best drawn up by one ministry.
Answer
A is false. Latrines should be below a water source on sloping ground otherwise seepage from the pit could flow down into the water source.
B is false. The protection measures are correct but the cover should have a lock.
E is false. Water use is relevant to several different ministries, all of which should be consulted when legislation is being prepared.
Summary of Study Session 4