environmental chemistry ib option e. e1 air pollution e 1.1 describe the main sources of carbon...

Environmental Environmental ChemistryChemistry

IB Option EIB Option E

E1 Air PollutionE1 Air Pollution

E 1.1 Describe the main sources of carbon E 1.1 Describe the main sources of carbon monoxide (CO), oxides of nitrogen (NOmonoxide (CO), oxides of nitrogen (NOxx), ), oxides of sulfur (SOoxides of sulfur (SOxx), particulates and ), particulates and volatile organic compounds (VOCs) in the volatile organic compounds (VOCs) in the atmosphere.atmosphere.

E 1.2 Evaluate current methods for the reduction E 1.2 Evaluate current methods for the reduction of air pollution.of air pollution.

Too Much of a Good ThingToo Much of a Good Thing

E.1. Air Pollution

Composition of unpolluted air: 78% Nitrogen 21% Oxygen 1% Argon 0.03% Carbon dioxide Trace amounts of other gases +4%water vapour

Primary air pollutants: Carbon monoxide(CO) Oxides of nitrogen(NOx):N2O, NO, NO2

Oxides of sulfur(SO2) and SO3(oxidation of SO2) Particulates Hydrocarbons and volatile organic compounds

E.1.1E.1.1 Describe the main sources of carbon monoxide (CO), Describe the main sources of carbon monoxide (CO), oxides of nitrogen (NOx), oxides of sulfur (SOx), particulates oxides of nitrogen (NOx), oxides of sulfur (SOx), particulates and volatile organic compounds (VOCs) in the atmosphere.and volatile organic compounds (VOCs) in the atmosphere.

Air pollutant = any chemical in such concentration (greater than its natural levels) in the air that it produces an harmful effect on the environment i.e. humans, animals, vegetation or materials.

Primary air pollutant = an air pollutant which is a waste product from a human activity and which is added directly into the air (as opposed to a secondary air pollutant which is formed in the air as a product of a chemical reaction of a primary pollutant in the air).

E.1.1. Sources:Check out Table 25.2 for a great summary of sources

Carbon Monoxide:

Natural: Incomplete oxidation of methane, produced by anaerobic bacteria from decaying organic material:

CH4 + 1 ½ O2 => CO + 2 H2O

Man-made( Anthropogenic sources): Incomplete combustion of fossil fuels used in internal combustion engines and coal fired electrical generating facilities.

C8H18 + 8 ½ O2 => 8CO + 9 H2O

Oxides of Nitrogen:

Natural: Electrical storms and biological processes.

Man-made: High T inside combustion engines cause a direct reaction between atmospheric oxygen and nitrogen.

Oxides of sulfur:

Natural: Oxidation of hydrogen sulfides produced by decaying organic material and volcanos.

Man –made: Combustion of sulfur containing coal by smelters (furnace) and power plants.

Particulates:

Natural: Soot, ash, dust,asbestos,sand,smoke,pollen,bacterial and fungal spores.

Man-made: Burning fossil fuels, particularly coal and diesel.

Volatile Organic Compounds (VOC’s) aka Hydrocarbons:

Natural: Trees and plants(rice) emit hydrocarbons known as terpines.

Man-made: Unburned or partially burned gasoline, fuels, solvents escaping or evaporating.

E.1.1. Sources:

E.1.1. Effect on HealthCarbon Monoxide: Prevents hemoglobin from carrying oxygen to the cells. Oxides of Nitrogen: Respiratory irritant leading to respiratory tract infections Oxides of Sulfur: Respiratory irritant leading to respiratory tract infections

Particulates: Affects the lungs and the respiratory system causing emphysema, bronchitis, and

lung cancer

Volatile Organic Compounds (VOC’s) aka Hydrocarbons: Some (e.g.benzene) are carcinogenic. Some may form toxic secondary air

pollutants such as PAN’s.(peroxyacetyl nitrate)

Crash Course Nitrogen and Phosphorus Cycles: http://www.youtube.com/watch?v=leHy-Y_8nRs&index=10&list=PL8dPuuaLjXtNdTKZkV_GiIYXpV9w4WxbX

Respiratory Diseases

E.1.2E.1.2 Evaluate current methods for the reduction of air pollution.Evaluate current methods for the reduction of air pollution.

I. Catalytic Converters on vehicles: CO , Oxides of Nitrogen and VOCs Science Channel Deconstructed: http://www.youtube.com/watch?v=rmtFp-SV0tY

The hot exhaust gases are passed over a catalyst of Pt, Rh, or Pd.These fully oxidize CO and unburned volatile organic compounds, VOCs, and catalyse the reaction:

2CO(g) + 2NO(g) => 2CO2(g) + N2(g)


I. Catalytic Converters on vehicles: CO , Oxides of Nitrogen and VOCs

Burning fuel releases nitrogen oxides, CO and VOCs (HCs)

1. Stage 1:1. Platinum & rhodium plates are used to…

2. Withhold one atom…

3. Creating N2 and O2

2. Stage 2: 1. Platinum and palladium plates are used to…

2. Help the oxygen (created from stage 1) and hydrocarbons (VOCs) combust…

3. Creating CO2 and H2O


Electrostatic Precipitation( Particulates) Particulates are solid or liquid particles suspended in the air. Larger particles can be allowed to settle under the influence of gravity in

sedimentation chambers. Smaller particles can be charged and be attracted to oppositely charged

electrodes, which are shaken periodically so that the aggregated particles fall to the bottom of the precipitator where they can be removed.

E2 Acid DepositionE2 Acid Deposition

E 2.1 State what is meant by the term acid E 2.1 State what is meant by the term acid deposition and outline its origins.deposition and outline its origins.

E 2.2 Discuss the environmental effects of acid E 2.2 Discuss the environmental effects of acid deposition and possible methods to counteract deposition and possible methods to counteract them.them.

Acid deposition refers to how acidic particulars leave the atmosphere. A well known example is acid rain.

The term “acid rain” was coined in 1872 by Robert Angus Smith, an English scientist who observed that acidic precipitation could damage plants and materials.

However it wasn’t around the 1960’s or 70’s that acid deposition become a serious environmental issue, when scientist discover low ph level in lakes and streams.

Acid Rain

Natural rain is acidic with a pH level around 5.6.

H2O+CO2 H2CO3

Only a very small percentage is in rain. Typical acid rain has a pH level of 4.0 and pH level of 4.2 in lakes wouldn’t be able to support life.

DRY DEPOSITION Dry Deposition refers how

the acidic particulars leave the atmosphere without the presence of precipitation.

These particulars leave the atmosphere due to gravity, and these acidic gases such as sulfur dioxide have a direct harmful effect on the environment because the gases haven’t dissolved in the rain water.

WET DEPOSITION Wet deposition refers how

the acidic particulars leave the atmosphere through precipitation. Either by rain, snow, or fog.

The main source of acidity in the atmosphere is sulfur oxides produced from power plants. These sulfur acidity react with react in rain water.

Two types of acids are formed from there sulfur oxide.

SO2 + H2O H2SO3 Sulfurous acid

orSO3 + H2O H2SO4 Sulfuric Acid

Nitrogen oxides also contribute to acid rain. These nitrogen oxides are formed from vehicle engines. This gas combines with hydroxyl radical then forms with nitrous acid. HNO2

Acid deposition effects the environment in 5 ways:

1. pH level of lakes and streams, and organism in them

2. The availability of metal ions in the soil, and therefore affects nearby plant life and water

3. Directly affects plant life

4. Affects buildings & other structures

5. Affects human health

A pH level below 5.5 would kill some species of fish like Salmon, also kill algae and zooplankton which depletes the food for larger organisms. At low pH levels eggs are unable to hatch.

The pH of soil is a key factor whether or not if plants will grow.

Not only does it damage the soil, it lowers the amount of nutrients that plants need. Acid deposition directly affects of plants by turning leaves brown and reduces photosynthetic ability of the plant

Majority of historical buildings are made of limestone and marble which are forms of calcium carbonate which acid rain erodes.

CaCO3+H2SO4 CaSO4+H2O+ CO2 As for metallic building those made of iron or

steel are readily attack by acid deposition by both dry and wet deposition.

Dry depositionFe+ SO2+ O2 FeSO4

Wet depositionFe + H2SO4 FeSO4 + H2

To counteract acid deposition is by reducing the amount of sulfur and nitrogen oxides released in the atmosphere.

Nitrogen oxides have been reduce from vehicle emissions using catalytic converters.

EPA’s acid rain program focuses on power plants, the largest single source of SO2 emissions, and a major source of NOx emissions by issuing permits to power plants of the amount of emissions being released.

Limestone or calcium hydroxide is being use to increase the ph level in soil and lakes.

E3 Greenhouse EffectE3 Greenhouse Effect

E 3.1 Describe the greenhouse effect.E 3.1 Describe the greenhouse effect.

E 3.2 List the main greenhouse gases and their E 3.2 List the main greenhouse gases and their sources, and discuss their relative effects.sources, and discuss their relative effects.

E 3.3 Discuss the influence of increasing E 3.3 Discuss the influence of increasing amounts of greenhouse gases on the amounts of greenhouse gases on the atmosphere.atmosphere.

The greenhouse effect is supposedly the cause of global warming by trapping in high concentration of greenhouse gases, and by doing so it raises earth’s average temperature which could cause natural disasters.

Greenhouse effect is necessary to keep earth hospitable because it able to maintain heat.

However some argue that man has disturbed the natural equilibrium of atmosphere causing the earth to become warmer.

E.4.3. Greenhouse Effect The incoming radiation from the Sun is short wave UV and visible radiation.Some reflects back but some is

absorbed by the atmosphere before it reaches the surface. The energy reflected from the Earth is a longer wavelength infra red radiation. Greenhouse gases allow the passage of incoming short wave but absorb some of the reflected IR and re-radiate

it back to the Earth’s surface See Table on the next slide

http://youtu.be/Hi3ERes0h84

The contribution of a greenhouse gas to the warming of the atmosphere depends on three factors.

1. The amount of gas in the atmosphere

2. The ability of the gas to absorb infrared radiation.

3. The lifetime of the gas molecules in the atmosphere, before they have been chemically removed.

GWP or Global Warming Potential is a measurement of how much heat a green house gas can trap in the atmosphere.

Water Vapor, H2O - The most important greenhouse gas and about 1 to 4% is contains Water Vapor. Its GWP is 0.1 and estimates that it contributes 36 to 75% of global warming.

Carbon Dioxide, CO2- only .035% is in the atmosphere and has the GWP of 1, but more effective at absorbing infrared radiation than water. More importantly CO2 absorbs infrared in a window of wavelengths which water cant absorbed. However an increase of concentration of Carbon Dioxide disrupts the equilibrium absorption and transmission in the atmosphere.

Some human activities have increase the concentration.1. The amount of fossil fuels be burn in the atmosphere2. Manufacture of cement and concrete involves the thermal

decomposition of calcium carbonate to calcium oxide, releasing CaO2 (CaCO3 CaO + CO2)

3. Deforestation in the tropics lowers the rate of photosynthesis. Estimates that CO2 contributes 9% to 26% of Global Warming

Methane, CH4 - The concentration in the atmosphere is around 1.7 X 10-4 though its GWA is 72 but is remove from the atmosphere quickly. Methane is form when cellulose decomposes anaerobically from bacteria.

This reaction can occur from several human activities. 1. Rice cultivation2. Cows3. Leaking gas pipes 4. Fermentation of organic material in covered landfills Though its contribution ranges 4 to 9%

Nitrous oxide, N2O - has a GWP of 296 that can last over 100 years. Its less efficient at absorbing inferred radiation. Its concentration is at .031% however it is increasing. However only contributes 5% of global warming effects. Humans accounts of 10% of the Nitrous oxide being released.

1. Nitrogen-based fertilizers2. Decomposition of organic matter3. Naturally produced by bacteria from the ocean and

the soil

Chlorofluorocarbons, CFC’s- CFC is an important greenhouse gas. This gas is less damaging to the Ozone but has a higher GWP than CO2

1. Human: coolants (in refrigerators and air-conditioners), aerosols, foaming agens

2. Natural: none Ozone, O3-The production of ground level ozone

has dramatically increased since the industrial age. This ozone is formed by the action of sunlight on hydrocarbons and nitrous oxide from the burning of fossil fuels. This helps increase the greenhouse effects.

Gas Main source Heat trapping

Effectiveness compared with CO2

Overall contribution to increased GW

H2O (main)

Evaporation ocean and lakes 0.1 -

CO2

(main)Combustion fossil fuels and biomass 1 50%

CH4 Anaerobic decay of organic matter caused by intensive farming

30 18%

N2O Artificial fertilizers and combustion of biomass

150 6%

O3 Secondary pollutant in photochemical smogs

2000 12%

CFCs Refrigerants, propellants, solvents, foaming agents

10,000-25,000 14%

The increase of green house gases results in the temperature increases and then the sea level increases for two reasons.

1. It causes the acceleration of the polar ice caps melting and deposit in the ocean.

2. As the ocean warms up, the water in them will occupy more volume.

Glaciers undergo a seasonal melting and

refreezing cycle as temp vary throughout the year. Increased melting increases erosion and risks of flooding downriver. A particular problem in low-lying countries.

Because of the increase of greenhouse gases the humidity and rainfall also increases.

This causes a greater chance of fungal crop diseases and migration of tropical insects to higher latitudes.

In addition an increase of weed growth leading to a greater use of herbicide. There is a greater chance of extreme weather like flooding, and storms that can lead to soil erosion that would ruined harvest.

In tropical regions temperature increases may lead fertile land becoming a desert

These are some effects of global warming however there could be more consequences.

http://youtu.be/VuH-ThmNUjM

Gas Main source Heat trapping

Effectiveness compared with CO2

Overall contribution to increased GW

H2O Evaporation ocean and lakes 0.1 -

CO2 Combustion fossil fuels and biomass 1 50%

CH4 Anaerobic decay of organic matter caused by intensive farming

30 18%

N2O Artificial fertilizers and combustion of biomass

150 6%

O3 Secondary pollutant in photochemical smogs

2000 12%

CFCs Refrigerants,propellants,solvents,foaming agents

10000-25000 14%

E4 Ozone DepletionE4 Ozone Depletion

E 4.1 Describe the formation and depletion of E 4.1 Describe the formation and depletion of ozone in the stratosphere by natural processes.ozone in the stratosphere by natural processes.

E 4.2 List the ozone-depleting pollutants and E 4.2 List the ozone-depleting pollutants and their sources.their sources.

E 4.3 Discuss the alternatives to CFCs in terms E 4.3 Discuss the alternatives to CFCs in terms of their properties.of their properties.

E.4. Ozone Depletion D.4.1. Formation and depletion of ozone in the stratosphere:

(CFC’s and oxides of NOx from combustion engines, power stations and jet airplanes)

The ozone layer occurs in the stratosphere between about 12km and 50km above the surface of the Earth. Stratospheric ozone is in dynamic equilibrium with oxygen and is continually being formed and decomposed.

Formation: UV(high energy)

O=O(g) ---------------> 2 O ● (g)

O ●(g) + O2(g) --------> O3(g)

The oxygen free radicals are very reactive. The bonds in ozone are weaker so UV light of less energy breaks them. When they are broken, a reverse process happens forming back oxygen and the radical.

Depletion:

Ozone is depleted in two ways: UV(low energy)

O3(g) ---------------> O2(g) + O●(g)

O3(g) + O●(g) -----------> 2O2(g)

Overall the rate of production of ozone is equal to the rate of ozone destruction

The formation and depletion of ozone absorbs a wide range of UV so the ozone layer protects the surface from damaging radiation.

E.4.2. Ozone Depleting Pollutants

Pollutants :

Chlorofluorocarbons (CFCs)

Nitrogen oxides (NOx)

Sources:

Propellants for aerosol sprays Refrigerants They are volatile and chemically

inert in the troposphere

Nitrogen-based fertilizers Decomposition of organic matter Naturally produced by bacteria

from the ocean and the soil

E.4.3. Alternatives to CFC’s

Montreal Protocol (1987) CFCs banned.CFC’s , low reactivity-remain atmosphere for 80 years.Destroy ozone layer( UV breaks C-Cl bond)

The alternatives should have low reactivity, similar properties but no bonds that can break with UV, low toxicity and no C-Cl bonds, should not absorb infrared so they will not become a global warming gas.

Some alternatives:

Hydrochlorofluorocarbons (HClFCs): chlorodifluoromethane Hydrofluorocarbons (HFCs): 1,1,1,2-tetrafluoromethaneHydrocarbons (HCs): mixtures of propane and butane

E.4.3. Alternatives to CFC’s

Hydrochlorofluorocarbons (HCFCs): chlorodifluoromethane Have stronger C-F bonds so less likely to break and pose a threat to ozone Problems:

Contain C-Cl bonds that reduce ozone layer (thus, a temporary solution)

Hydrofluorocarbons (HFCs): 1,1,1,2-tetrafluoromethane Have stronger C-F & C-H bonds so less likely to break and pose a threat to

ozone No C-Cl bonds, low reactivity, low toxicity, low flammability Problems:

Greenhouse gas that contribute to global warming

Hydrocarbons (HCs): mixtures of propane and butane Have stronger C-H bonds (413 kJ/mol) than C-Cl bonds (346 kJ/mol) Problems:

Volatile Greenhouse gases that contribute to global warming

substance flammable toxicity

HydrocarbonCH3CH(CH3)CH3

yes high

FluorocarbonsCF4

no not known

HydrofluorocarbonsCF3CH2F

no low

E5 Dissolved Oxygen in E5 Dissolved Oxygen in WaterWater

E 5.1 Outline biochemical oxygen demand (BOD) as a measure of oxygen- demanding wastes in water.

E 5.2 Distinguish between aerobic and anaerobic decomposition of organic material in water.

E 5.3 Describe the process of eutrophication and its effects.

E 5.4 Describe the source and effects of thermal pollution in water.

E.5.1. Outline biochemical oxygen demand (BOD) as a measure of oxygen-demanding wastes in water

Dissolved oxygen in water

BOD: the amount of oxygen (in ppm) needed / used by bacteria

to decompose the organic matter aerobically in a fixed volume

of water over a set period of time.

The greater the quantity of degradable organic waste, the higher

the BOD.

BOD versus DO (dissolved oxygen) content of the water.

Rivers: oxygen level is regenerated, lakes: limited.

Measurement: BOD is often measured over a set time period of 5

days. Water with a BOD above 5ppm is regarded as polluted.

E.5.1. Outline biochemical oxygen demand (BOD) as a measure of oxygen-demanding wastes in water

Importance of oxygen in water… At a pressure of 1 atm and 20C the solubility of oxygen in

water is 0.009 gdm-3. Oxygen (DO) is crucial for aquatic plants and animals that

require it for aerobic respiration (fish require at least 3ppm)

BOD- cont.

E.5.2. Distinguish between aerobic and anaerobic decomposition of organic material in water

Aerobic: If there’s sufficient oxygen present in the water, organic matter is broken down by microbes aerobically. This oxidizes the C, N, P, S, and H to produce CO2, NO3

-, PO43-,

SO42-, and H2O.

Anaerobic: If there’s an insufficient amount of oxygen present in the water, organic matter is decomposed by microbes that don’t require oxygen. They break down C, N, S, and P to form CH4, NH3, H2S, and PH3.

See chart on next page

elementaerobic decay

productanaerobic decay

product

Carbon CO2 CH4

Hydrogen H2O CH4, NH3, H2S, H2O

NitrogenNO3

- (oxidation number: +5)

NH3, amines(oxidation number: -3)

SulfurSO4

2-

(oxidation number: +6)H2S

(oxidation number: -2)

PhosphorusPO4

3-

(oxidation number: +5)PH3

(oxidation number: -3)

E.5.3. Describe the process of eutrophication and its effects

Eutrophication: the natural process by which a lake or river becomes

excessively rich in nutrients…

This is not a good thing!

This process is usually very slow, but can be greatly accelerated by

human activity.

Man-made eutrophication usually begins with algal blooms and can be

caused by: Large amounts of nitrates (from fertilizers) and phosphates (from

detergents) accumulating in lakes and streams, or

Large amounts of organic waste from sewage, meat processing, food

packing

E.5.3. Describe the process of eutrophication and its effects

Nutrients can increase the growth of plants and algae

Impacts the BOD because if plant growth increases too fast

DO will not be sufficient to decompose organic material

and waste by aerobic decomposition

Anaerobic decomposition will occur

Producing ammonia & hydrogen sulfide

More species will die

The lake will be stagnant

Little / no life

E.5.4. Describe the source and effects of thermal pollution in water.

Sources of thermal pollution: Many industries use water as a coolant and release the heated

water into rivers

Effects of thermal pollution: Higher temperature = lower solubility of gases

So, warm water holds less DO than cold water Higher temperature = increased metabolism (CR) in aquatic

animals (fish & amphibians) greater consumption rate of food requires more oxygen, which is less available

E.5.4. Describe the source and effects of thermal pollution in water.

As a result one has the problem of compromising food chains of

the old and new environments. Biodiversity (the degree of

variation of life forms within a given ecosystem, biome, or an

entire planet) can be decreased as a result.

Temperature changes of even one to two degrees Celsius can

cause significant changes in organism metabolism.

Producers are affected by warm water because higher water

temperature increases plant growth rates, resulting in a shorter

lifespan and species overpopulation.

This can cause an algae bloom which reduces oxygen levels.

E6 Water TreatmentE6 Water Treatment

E 6.1 List the primary pollutants found in waste water and identify their sources.

E 6.2 Outline the primary, secondary and tertiary stages of waste water treatment, and state the substance that is removed during each stage.

E 6.3 Evaluate the process to obtain fresh water from sea water using multi-stage distillation and reverse osmosis.


Waste water contains floating, suspended, and colloidal organic matter,

dissolved ions with a wide range of microorganisms and bacteria as well as

chemicals.

Pesticides: agriculture (DDT, herbicides, fungicides)

Dioxins: large scale processes, such as waste combustion, manufacture of

herbicides, paper pulp bleaching with chlorine. Very toxic and can

accumulate in the liver.

Polychlorobiphenyls (PCBs): used in electrical insulators, circuit breakers,

transformers and capacitors, which can leak. Persists in the environment and

can accumulate in the liver, also carcinogenic. Overexposure can lead to

chloroacne, a skin condition that creates cysts


Nitrates: from fertilisers or acid rain. They are toxic at high

levels, especially to babies because they have less stomach acid

than adults, can cause blue baby syndrome

Heavy metals: Cadmium (Cd) (rechargeable batteries),

Mercury (Hg) (batteries, paints), Copper (Cu) (household

plumbing), Lead (Pb) (pipes, fuel)

Organic matter: household waste (sewage water),

Phosphates: from fertilisers.

Pollutants Sources Effects

PesticidesAgriculture (DDT, herbicides,

fungicides)

Dioxins

Large scale processes, such as waste combustion, manufacture

of herbicides, paper pulp bleaching with chlorine

Teratogens (deform unborn fetuses), highly poisonous /

toxic

PCBsPlasticisers (now banned),

electrical insulatorsHard to degrade in environment,

build up through food web

Heavy metals Cu, Cd, Hg, Pb

Pretty much anything with metal

Organic matter Sewage

Nitrates Fertilizer or acid rain Toxic at high levels

Phosphorus Fertilizer

E.6.2: Outline the primary , secondary, and tertiary stages of waste water treatment, and state the substance that is

removed during each stage.

Summary: Primary Treatment: Filtration (screening) to

remove solids followed by sedimentation of sand, grit, and sludge.

Secondary Treatment: Use of oxygen and bacteria to remove matter

Tertiary Treatment: Chemical precipitation of remaining organic compounds, heavy metals, nitrates, phosphates.


Primary treatment: the removal of large solids (filtration & sedimentation)

Primary treatment involves running water through the below mechanisms in

order:

1. Bar screens: these remove large objects and debris from the surface of the water

and remove floating solids.

2. Settling tanks: these are used to settle out sand and small objects from the water

(as they sink to the bottom); these particles are then sent to landfills.

3. Sedimentation tanks: Alum (Ca(OH)2 and Al2(SO4)3) precipitates out and carry

with them solid suspended particles (this process is called flocculation).

Al2(SO4)3 (aq) + 3Ca(OH)2 (aq) → 2Al(OH)3 (s) + 3CaSO4 (s)


Secondary treatment: the removal of organic materials

using microbes (oxygen and bacteria)

Activated sludge process:

1. Air is bubbled into sewage which has been mixed with

bacteria-filled sludge.

2. Aerobic bacteria oxidize organic material in the sewage.

3. Water-containing decomposed suspended particles are

passed through the sedimentation tanks where the activated

sludge is collected.


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

landfills.

5. This removes 90% of organic oxygen-demanding waste,

50% of nitrogen, and 30% of phosphates.

Effluent is then treated with chlorine or ozone to kill pathogenic

bacteria before releasing the water to lakes or rivers.


Tertiary treatment: the removal of remaining organics, nutrients and toxic

heavy metal ions

Heavy metal ions and phosphates are removed by precipitation, for

example, nickel:

Ni2+(aq) + 2OH−(aq) → Ni(OH)2 (s)

Aluminum sulfate or calcium oxide can be used to precipitate

phosphates:

Al3+ (aq) + PO43- (aq) → AlPO4 (s)

3CaO (aq) + 2PO43- (aq) + 3H2O → Ca3(PO4)2 (s) + 6OH−(aq)


Heavy metals will precipitate in the presence of hydroxide:

Cr3+(aq) + 3OH−(aq) → Cr(OH)3 (s)

Nitrates are more difficult to remove by precipitation because they’re

quite soluble, however, there are some ways to remove them:

1. Anaerobic denitrifying bacteria can reduce nitrates into nitrogen

2NO3− (aq) → N2 (g) + 3O2 (g)

2. Another method is to pass them into algae ponds where algae uses

nitrate as a nutrient.

Treatment StageSubstance(s)

RemovedMethod(s)

Primary

Secondary

Tertiary

Treatment StageSubstance(s)

RemovedMethod(s)

PrimaryLarge solids / solid waste

Filtration & sedimentation

SecondaryOrganic

substances

Activated sludge process:

oxygen & bacteria used

TertiaryIons (metals &

phosphates)Precipitation

reactions

E 6.2 Outline the primary, secondary and tertiary stages of waste water treatment, and

state the substance that is removed during each stage.

http://www.youtube.com/watch?v=9z14l51ISwg

E 6.3 Evaluate the process to obtain fresh water from sea-water using multi-stage

distillation and reverse osmosis.

DISTILLATION The sea water is heated in

series of coiled pipes and then introduced into a partially evacuated chamber.

Under reduced pressure some of the water boils instantly.

The water vapour is condensed by contact with cold water pipes carrying sea water.

The heat released by the water condensing is used to preheat more sea water.

Multi-stage distillation

E 6.3 Evaluate the process to obtain fresh water from sea-water using multi-stage

distillation and reverse osmosis.

REVERSE OSMOSIS A high pressure is applied to

the solution side of a partially (semi) permeable membrane made of cellulose ethanoate.

Water is forced out of the salt solution through the membrane leaving the salt behind.

Reverse osmosis moves water AWAY from the concentrated solute

Commercial plants: 70atm and 1m3 of membrane-250000L fresh water/day

Reverse osmosis

E7 SoilE7 Soil

E 7.1 Discuss salinization, nutrient depletion and soil pollution as causes of soil degradation.

E 7.2 Describe the relevance of the soil organic matter (SOM) in preventing soil degradation, and outline its physical and biological functions.

E 7.3 List common soil pollutants and their sources.

E 7.1 Discuss salinization, nutrient depletion and soil pollution as causes of soil degradation.

Salinization: this is the result of continually irrigating soils Irrigation waters contain dissolved salts, which are left behind after

water evaporates In poorly drained soils, the salts are not washed away and begin to

accumulate in the topsoil Plants (most) cannot grow in soil that is too salty Salt concentration reaches a toxic level or plants die of dehydration

(osmosis) Treatment for salinization is to flush the soil with large volumes of

water This, however, can result in salinization of the rivers and

groundwater

E 7.1 Discuss salinization, nutrient depletion and soil pollution as causes of soil

degradation. Nutrient depletion: agriculture disrupts the normal cycling of

nutrients through the soil food web when crops are harvested This removes all nutrients & minerals absorbed from soil while

growing Practices leading to amelioration of nutrient depletion may further

contribute to environmental pollution Solutions: rotation, using legumes (nitrogen), compost (organic waste),

ploughing (air, oxygen)

E 7.1 Discuss salinization, nutrient depletion and soil pollution as causes of soil

degradation. Soil pollution: this is the consequence of the use of chemicals such

as pesticides and fertilizers These chemicals can disrupt the soil food web (plants & animals),

reduce soil’s biodiversity and ultimately ruin the soil Chemicals also run off the soil into the surface waters and move

through the soil, polluting the groundwater Other sources of soil pollution: mining, improper disposal of toxic

waste … or Poo Poo Beach, Lagos Problems do not occur directly in the soil but in waterways where the

pollutants are leached out of the soil

E 7.2 Describe the relevance of the soil organic matter (SOM) in preventing soil degradation, and

outline its physical and biological functions. SOM: organic constituents in the soil,

such as undecayed plant and animal tissues, their partial decomposition products and the soil biomass.

SOM only constitutes about 5% of soil

SOM includes: Identifiable, high molecular mass

organic materials (polysaccharides & proteins)

Simpler substances (sugars, amino acids, other small molecules)

Humic substances

E 7.2 Describe the relevance of the soil organic matter (SOM) in preventing soil degradation, and

outline its physical and biological functions.

The functions of SOM can be classified into:

Biological: provides source of nutrients (PNS) and contributes to the resilience of the soil / plant system

Physical: improves structural stability (organic matter loosens the soil, increasing the amount of pore space → air, water), influences water-retention properties and alters the soil thermal properties


organic pollutant source

petroleum hydrocarbonstransport, solvents, industrial

processes

agrichemicals pesticides, herbicides, fungicides

volatile organic compounds (VOCs)

solvents, especially paints and protective coatings, dry cleaning

and industry

solvents industry

polyaromatic hydrocarbons (PAHs)

incomplete combustion of coal, oil, gas, wood, garbage

organic pollutant source

polychlorinated biphenyls

(PCBs)

coolant, insulator in electrical

equipment (transformers and

generators)

organotin compounds bactericides, fungicides used in

paper, wood, textile

semi-volatile organic

compounds (SVOCs)

solvents, industrial processes


E8 WasteE8 Waste E 8.1 Outline and compare the various methods

for waste disposal.

E 8.2 Describe the recycling of metal, glass, plastic and paper products, and outline its benefits.

E 8.3 Describe the characteristics and sources of different types of radioactive waste.

E 8.4 Compare the storage and disposal methods for different types of radioactive waste.

E 8.1 Outline and compare the various methods for waste disposal.

Method Advantages Disadvantages

Landfill

(the land must be

isolated from

groundwater)

Efficient method to deal

with large volumes. Filled

land can be used for

building

•Local residents may object•Land needs time to settle and

may require maintenance

(methane), non-biodegradable

plastics

Open dumping Convenient, inexpensive

•Causes air and ground water

pollution•Health hazard (rodents)

Incineration

•Reduces volume.•Requires minimum space.

Produces stable, odorless

residue•A source of energy

•Expensive to build and run

•Can cause pollutants (CO2,

CO, HCl, dioxin)•Requires energy

Method Advantages Disadvantages

Ocean dumping

•Source of nutrients

•Convenient

•Inexpensive

•Danger to marine

animals

•Sea pollution

RecyclingProvides a sustainable

environment

•Expensive

•Difficulty in

separating different

materials


Metal: Mainly aluminium, steel Sorted (steel by magnet), melted, used for

purification (saving energy aluminium) Saves reserves, reduces energy costs Aluminium is resistant to corrosion, high cost

of the initial extraction process


Glass: Sorted by colour, washed, crushed, melted,

and moulded into new products Non-degradable, can be recycled many times Reduces energy costs, the need for sandstone

and limestone quarries


Plastic: • Sorted, degraded into monomers (in the

absence of air, pyrolysis) then repolymerized• Less pollutants, less energy than producing

new plastics• Sorting can be problematic


Paper: sorted, washed (ink, additives are removed),

slurry (by adding water then repulping), formation of new types of paper (reduced strength, low-grade products, cellulose fibers are damaged)

Energy required to transport, compost more efficient

E 8.3 Describe the characteristics and sources of different types of radioactive waste.

Nature of waste Source Characteristics

Low Level:Lab equipment,

protective clothing

Power stations, hospitals & research

establishments

1. 0.001% of waste radioactivity2. Compressed into steel

containers & buried or incineration

3. High volume

Intermediate Level: Cladding around nuclear fuel elements, ‘sludge’

from treatment

Power stations 1. 1% of waste radioactivity2. Cemented inside steel drums

and stored in secure repository under layers of clay

High Level: Waste nuclear fuel

Able to generate heat

Power stations 1. 99% of waste radioactivity2. ‘Vitrified’, i.e. changed to a

dense glass block and stored in secure repository, underground

3. Low volume


Low level

Decay process produces heat, waste is stored in water till activity level is low. Water is passed through an ion exchange resin, diluted, released into the sea. Other method: keeping the waste in steel containers inside concrete-lined vaults.


High level

The spent rods removed from the reactor, transfered to deep pools cooled by water containing neutron absorber. Cased in ceramic, packed in metal containers, buried deep in the Earth (granite rock, unused mine). The site must prevent the material from entering the underground water supply. The waste is buried in remote places that are geologically stable (earthquake).

environmental chemistry ib option e. e1 air pollution e 1.1 describe the main sources of carbon...

Documents

reduction of air pollution

oxides of nitrogen nox

toxic secondary air

oxides of sulfur sox

combustion of sulfur

organic material

respiratory irritant

volatile organic compoundse