The Nitrogen Cycle

IB Biology

What is nitrogen?

Periodic Table

•

Nitrogen is in the Nonmetals/BCNO Group

Where is nitrogen found in the environment?

The largest single source of nitrogen is in the atmosphere.

Nitrogen makes up 78% of our air!

It is one of nature’s great ironies…

Nitrogen is an essential component of DNA, RNA, and proteins—the building

blocks of life. Although the majority of the

air we breathe is nitrogen, most living organisms are unable to use nitrogen as it exists in the atmosphere!

How does atmospheric nitrogen get

changed into a form that can be

used by most living organisms?

NN

By traveling through one of the four processes in the Nitrogen Cycle!

(1) Nitrogen Fixation

(3) Nitrification (2) Ammonification

(4) Denitrification

Nitrogen Cycle

Nitrogen inthe air

animal protein

dead plants & animalsurine & faeces

ammonia

nitrites

nitrates

plant madeprotein

decomposition by bacteria & fungi

Azobacter

(nitrifying bacteria)

nitrates absorbed

denitrifyingPseudomonas denitrificans

root nodules(containing Rhizobium)

nitrogen fixing planteg pea, clover

Nitrobacter

Your task!

• Imagine you are a nitrogen atom!

• Send postcard to your nitrogen friends explainig the following:

-Where you were…

-Where you are now….

-Where you are going next….

• Don´t forget to explain any meetings with bacteria or how you have changed as a molecule!

Sewage

IB Biology

Flushed with success?

Seoul, South Korea

Built by Sim Jae-Duck, involved with World Toilet Association

Why?

2 billion

To draw attention to the

people who do not have toilets or proper sanitation

SewageWhat is it?

organic material

mineral salts

bacteria

What does it contain? examples

Untreated raw sewage is waste which has come from our toilets, sinks, baths etc.

Faeces, food fragments, enzymes, soap, gel, hair

Phosphates, nitrates

Food poisoning, disease-causing

Some from detergents & washing powders

Environmental damage In rivers can cause algal blooms (as sewage is a

good food source for them), killing animals and plants living in water.

May release methane and ammonia gases (foul smelling).

Eutrophication

14 July 07

14 Sept 07Sussex River Ouse

Sea trout nursery

Eutrophication

• High concentrations of inorganic substances can cause algal blooms

• Substances encourage rapid growth of algae and blue-green bacteria

Biological Oxygen Demand

1. Sample of water measured at 20˚C over 5 days

2. Increase in organic pollutants increases number of bacteria

3. BOD will increase

Copy the steps above and give a reason as to why each step is

occurring-use your handout to help!

Sewage treatment works

Examples of diseases which may be spread by untreated sewage.

dysentery, typhoid, cholera

Why treat it?

May cause disease if it contaminates drinking water, due to harmful bacteria present.

Sewage treatment process0 Untreated

raw sewage enters the sewage works

1a Screening (coarse filter)

Metal grids strain out large objects

Grit tank

Stones and heavy solids sink to the bottom

Lighter solids such as faeces sink to the bottom and form a sludge

1b

Sewage water to: 5

Aerobic conditions 3

Anaerobic conditions

4

2Sedimentation tank

Sludge digestion tank

Bacteria feed on sludge, producing methane. Can be used as a fuel.

3

Anaerobic conditions

Activated sludge tank

Sludge mixed withextra air (oxygen), stirred, bacteria produce harmless liquids.

4

Aerobic conditions

Biological filter tank

Fluid from tank sprinkled over stones* coated with microbes. Bacteria produce harmless liquids

5

Treated waste emptied into rivers

6*or biobeads

Now complete your Sewage Treatment cut and

paste sheet!

Increasing energy levelsThe main fuels which can be obtained from biomass:

Biofuels

Methane

Alcohol

Both are products of fermentation

Methane (biogas) production occurs naturally by fermentation (anaerobic respiration) when animal or plant material decays.

Generation of methane from biomass

1. Fermentation of faeces-aerobic bacteria hydrolyse carbs, proteins, fats

2. Oxygen used up -acetogenic bacteria convert sugars to short chain fatty acids (e.g. acetate), CO2 and H2

-acetogenesis stage

3. Methanogenesis-final stage is anaerobic and involves methanogenic bacteria-conversion of actetate to methane

Temp: 30-40˚C