Isaure de Zélicourt

little organic molecules Highly poisonous Teratogens: deform unborn foetus Small quantities: wood burned Large quantities: waste incineration plants Chemically stable = remain for a long time

in the environment

Cl

Cl

Cl

Cl

O

O

2 benzene rings joined by two ether links

Hard to degrade in the environment Found in polluted water Find their way into the food chain Effect on nervous system Accumulate in the liver Used for transformers

Cl

ClCl

Cl

ClCl

Uncontrolled use of pesticides Infiltrates the ground water Herbicides and insecticides Enters the food chain DDT: on type of pesticides that attacks the

nervous system of insects and kills them right away

CCl3Cl H

C

Cl

Despite consequences on the environment, it saved

millions of lives as it is sprayed over areas suffering of malaria

Copper, Cadmium, Mercury, Zinc, Chromium.

Either compound or elemental form

toxic at high levels, especially to babies because they have less stomach acid than adults, can cause blue baby syndrome

Blue baby syndrome: decreased oxygen carrying capacity of hemoglobin in babies leading to death

Bar screens remove large objects and debris from the surface of the water and remove floating solids.

Grit chambers are used to settle out sand, grit, and small objects from the water; these particles are then sent to landfills.

Sedimentation tanks: Alum Ca(OH)2 and Al2(SO4)3precipitates out and carry with them solid suspended particles

Activated sludge process:

Air is bubbled into sewage which has been mixed with bacteria-laden sludge.

Aerobic bacteria oxidize organic material in the sewage.

Water-containing decomposed suspended particles are passed through the sedimentation tanks where the activated sludge is collected.

Some of the sludge is recycled, and some is sent to landfills.

Removes 90% of organic oxygen-demanding waste, 50% of nitrogen, and 30% of phosphates

Charcoal filtering: - removes organic pollutants through

absorption. - Filter can be regenerated by using heat to

drive off organics

Precipitation: - get rid of heavy metal ions or phosphate ions - ions are added - forms insoluble precipitates with phosphate

anions or metal cations - solids can then be filtered out

Desalination is not easy and is expensive Can be done by reverse osmosis Osmosis is found in biological systems Osmosis: if two solutions are separated by a

semi permeable membrane, then any solvent will move across that membrane towards the side of higher solute concentration

if two solutions are separated by a semi permeable membrane, then any solvent will

move across that membrane towards the side of higher solute concentration

Hence, water will move to dilute a salty solution

This is the last thing you want if your aim is fresh water!

Seawater Fresh water

Diluted Seawater

Seawater Fresh water

Concentrated sea water More fresh water

•Salty solution put under high pressure• pressure pushes the water molecules into the fresh water• initial solution is left more concentrated

Distillation: the process that allows the sepatation of a volatile liquid (ex. water) from a non-volatile material (ex. Salt)

Grit Chamber: Tank in which the flow of wastewater is slowed, allowing heavy solid materials such as pebbles, sand, coffee grounds and eggshells to sink to the bottom.

Sedimentation: a physical water treatment process used to settle out suspended solids in water under the influence of gravity.

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IB chemistry course companion IB chemistry Option E study guide