Water: Water Pollution

What is eutrophication?

• The enrichment of water with nutrients, leading to excessive growth of algae and other plants.

• The process by which water bodies become depleted of essential nutrients, resulting in a decline in aquatic plant and animal populations.

• A phenomenon where water becomes too acidic due to the accumulation of industrial pollutants, leading to the death of aquatic organisms.

• A natural process where water bodies become increasingly saline, causing the proliferation of salt-loving microorganisms and reducing biodiversity.

What causes eutrophication?

• It is caused by excess nitrates [NO₃^-] and phosphates [PO₄^3-].

• It is caused by the presence of excess oxygen in water, which stimulates the growth of algae and aquatic plants.

• It occurs due to the depletion of nutrients in water bodies, leading to a lack of resources for aquatic life.

• It is primarily caused by the accumulation of heavy metals such as mercury and lead in water, which disrupt the balance of aquatic ecosystems.

Sources of nitrates [NO₃^-] and phosphates [PO₄^3-]

• Fertilisers

• Silage effluent

• Pig slurry

• Sewage

• All of the above.

What is B.O.D.?

• Bad Odour Detected

• Biochemical Oxygen Demand

• Best Oxygen Detector

• Bacteria Organic Decay

B.O.D is defined as ...

• amount of dissolved oxygen consumed by biological action.

• the amount of dissolved oxygen consumed by pollutants in the water.

• the amount of dissolved O₂ consumed by biological action by a sample of H₂O kept for 5 days in the dark.

• the amount of dissolved O₂ consumed by biological action by a sample of H₂O kept for 5 days in the dark at 20^oC.

For polluted water to cause fish deaths the B.O.D must be greater than ...

• 100 ppm

• 20 ppm

• 300 ppm

• 30,000 ppm

In measuring B.O.D the second sample is kept in the dark. Why?

• To prevent more oxygen in the water due to respiration.

• To prevent photosynthesis adding oxygen to the water.

• To keeping it in the dark helps keep the temperature constant.

• To make the bacteria do not use up the oxygen.

Why is it necessary to dilute polluted water and aerate it before measuring the B.O.D?

• because of the high solubility of oxygen in water ansure there is enough oxygen for the 5 day period.

• because of the low solubility of oxygen in water and there is not too much oxygen for the 5 day period.

• because of the low solubility of oxygen in water ensure there is enough oxygen for the 5 day period.

• none of the above are correct.

Why must the sample bottle of water be filled to the top completely filled when measuring the B.O.D.?

• To prevent photosynthesis.

• To ensure no air is present in the sample bottle.

• To prevent respiration.

• To allow photosynthesis to take place.

Water pollution can be caused by heavy metal ions such as ...

• Lead (Pb²⁺)

• Mercury (Hg²⁺)

• Cadmium (Cd²⁺)

• All of the above