Part 1 SEWAGE

Untreated raw sewage contains organic material ( faeces ,food fragments, soap etc)

Bacteria feed on this organic waste, breaking it down to release energy.

They use this extra energy to multiply.

The larger numbers of bacteria use up more oxygen

Oxygen supply is depleted (reduced)

The effect of untreated sewage on rivers

Animals like fish die due to oxygen starvation

Rivers contain bacteria.

These bacteria use oxygen during aerobic respiration.

The breakdown of sewage by bacteria releases Nitrates and Phosphates

Nitrates and phosphates are used by green algae to grow fast and cover the surface of the river/lake (algal bloom)

The algae stop light getting to lower aquatic plants, which then die -- the oxygen they provide during photosynthesis is no longer available

Organic waste on river bed broken down by bacteria to release foul smelling gases and rotting materials.

Water has little oxygen

Fish die due to lack of oxygen

Smelly gas

Anaerobic bacteria digest sewage to form methane gas

Algal bloom

Nitrates and phosphates

Bacteria feed on raw sewage2

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Raw sewage1

Water borne diseases

Untreated sewage can contain micro- organisms causing ;-

Dysentery, typhoid and cholera.

In Britain sewage is treated in a Sewage treatment works to make it safe.

Natural disasters ;- earthquakes can fracture

underground pipes and cause raw sewage to mix with drinking water.

Treatment of Raw Sewage

This is done at a Sewage Treatment works

Material entering the sewage works is firstly screened to remove large objects eg. Rags and grit.

Primary Settlement

Once screened, the sewage is passed to a primary settlement tank where it stays for 6 hours to separate solid from liquid waste.

Primary settlement tank

Aerobic breakdown of sewage

Breakdown of sewage by anaerobic bacteria will always leave some sewage material untreated (unsafe).

Aerobic bacteria, however will give complete breakdown, leaving only carbon dioxide and water (safe).

Sewage + oxygen carbon dioxide + water

aerobic bacteria

Sewage contains a range of materials requiring particular micro-organisms for their breakdown, therefore a range of micro-

organisms are needed to break it down fully.

Secondary treatment

Oxygen can be provided in two ways;

A. Biological filtrationThe sewage is trickled through filter beds and is broken down by bacteria coating the stones. Air spaces between the stones provide the oxygen.

B. Activated sludge processThe sewage is mixed with activated sludge (sewage with sewage – eating bacteria added to it). Oxygen is then supplied by bubbling compressed air through the mixture.

Primary settlement sludge

Biological filtration

Activated sludge tank

The sludge collected is reused in the activated sludge process.

The purified effluent is released into the river.

The treated sewage is then passed to final settlement tanks.

Here, activated sludge present in the mixture from either process is allowed to settle out.

Anaerobic breakdown of sewage

Sludge from primary settlement and activated sludge from the final settlement tank are combined and kept under anaerobic conditions, where bacteria break them down to produce methane gas (fuel).

Waste from this process is either dumped at sea or treated to kill pathogens, and then offered to farmers for spraying on fields as fertiliser.

Anaerobic digester

Sewage Treatment -- Summary

Treatment NotesScreening / grit removal Grit, stones + rags are removed by a filter

Primary Settlement Solids are separated from liquid waste

Secondary treatment Aerobic breakdown of sewage by a range of micro organisms

1. Biological filtration – oxygen provided by air spaces between stones

2. Activated sludge process – oxygen provided by compressed air

Final Settlement Activated sludge remaining from secondary treatment settles out before clean water released

Sludge Treatment Anaerobic breakdown of sludge by micro organisms to produce methane gas

Sludge Disposal Pathogens killed then sludge dumped at sea or sprayed on fields as fertiliser

A range of micro-organisms are needed to break down sewage because

Sewage + oxygen carbon dioxide + water

It contains a range of materials which cannot be broken down by only one type of micro organism

Fungal spores and bacteria can travel in the air and land on surfaces.

Floors in hospitals ,schools etc are washed regularly to minimise the spread of any harmful microbes

We can grow colonies of microbes using a nutrient gel or Agar in a petri-dish.

Airborne microbes

Culturing Microbes

Working with Microbes

• We already know how microbes can help in the manufacture of food and drink.

• Also that some microbes cause disease if they enter the bodies of living things.

• It is obviously important when working with microbes in the lab to adopt “safe practice”.

• This avoids unwanted growth of microbes and disease.

Unwanted Microbes• Contamination is the presence of

unwanted, possible harmful microbes.

• To prevent contamination all equipment must be clean and sterilised.

• This is done in an autoclave, where equipment is heated to very high temperatures by steam (boiling is not enough).

Safe Practice

• The bench is thoroughly cleaned with disinfectant and hands are washed.

• Sterile (very clean) equipment is collected:– Petri dishes with agar food jelly– Plating loop– Culture of bacteria– Bunsen burner

•Working close to the hot bunsen flame the loop is heated till red hot then allowed to cool.•This kills organisms on the loop

•A sample of bacteria is collected from the culture bottle. The culture bottle is carefully opened and closed next to the flame.

•Working close to the flame the loop is now gently rubbed over the surface of the agar jelly in the dish.

•The loop is again heated till red hot and allowed to cool. •The dish is sealed, then labelled and placed in an incubator.

Tape

Lid

Joe Bloggs microbeX 25/02/10

Label placed on bottom of dish

Bacterial Culture showing growth after incubation

Precautions ReasonsHands washed before and after work Remove bacteria picked up from the

environment / remove any picked up during lab work

Benches swabbed with disinfectant Remove bacteria and spores from benches

Lab coat should be worn Prevent contamination of clothes by bacteria

Use only safe bacterial cultures Other sources, e.g. air, soil etc. may contain pathogenic bacteria

Autoclave all equipment Heating in an autoclave kills all foreign bacteria

Work beside bunsen, flaming loops and necks of culture bottles

Prevent entry of foreign bacteria and kill cultured bacteria on loops etc.

Incubate bacterial cultures below body temperature

This discourages the growth of pathogens which grow best at 37oC

Autoclave all equipment after use, and cultures before disposal

Kill all bacteria in case any pathogens have appeared

Summary

Summary

Precautions taken during

Manufacturing Processes

In most industrial processes involving microbes, the biggest danger is foreign bacteria or fungi getting into the process, rather than the cultured microbe escaping.

Some bacteria and fungi make resistant spores when faced with adverse conditions e.g. extreme drought, heat, pH etc.

The thick coat they produce only disintegrates when conditions become favourable again.

CREDIT

If these get into the manufacturing process

they may cause;

1. A health hazard – they may be pathogenic.

2. Financial loss if a whole batch of product is contaminated.

To prevent this, all equipment (fermenters, pipework etc. is frequently steam-cleaned.

The high temperature of the steam can kill the spores.

CREDIT

Decay and Recycling

Decomposition is a natural process.

The bacteria or fungus obtain energy from breaking down the organic material

Bacteria and fungi can breakdown organic matter

This process is called Decomposition.

DecayCREDIT

Decomposers breakdown dead bodies and waste materials to organic compounds.

The organic compounds contain Mineral salts that are released into the soil.

Plants use these Mineral salts to grow

Apart from Mineral salts the elements Carbon and Nitrogen also have to be recycled

Recycling CREDIT

Plant protein

Animal protein

eaten

Faeces + dead remains

death death

Lightning storms

Ammonium compounds

Nitrifying bacteria

Decomposers (bacteria+fungi)

Soil nitrates

Nitrites

absorbed through roots

Nitrifying bacteria

Denitrifying bacteria

Atmospheric nitrogen

Nitrogen-fixing bacteria (in root nodules)

Nitrogen Cycle

Nitrogen is used by animals and plants to make protein

Root nodulesPlants like clover, peas and

beans have root nodules containing nitrogen fixing bacteria on the roots.

These bacteria take nitrogen gas from the air and change it into nitrates in the roots.

the clover uses the nitrates to make proteins.

Farmers like clover to grow in a field to replace the supply of natural nitrates in the soil

CREDIT

Carbon Cycle

There are three main processes;

Photosynthesis - uses carbon dioxide

Respiration – releases carbon dioxide

Combustion – releases carbon dioxide

CREDIT

Carbon CycleAtmospheric carbon dioxide

Carbon compounds in animalsCarbon compounds

in plants

Carbon in fuels e.g. coal

Carbon compounds in dead organic matter (humus)

respirationrespirationrespiration by decomposers

combustion

photosynthesis

eaten

death death

CREDIT

Food and Fuel from Waste

Many manufacturing processes produce waste products.

These waste products can be upgraded -- fed to microbes which convert them to products which are useful to people and other animals.

Advantages of upgrading waste;

Unwanted waste products can be converted into products with a high energy content (fuels), or a high protein value (foods).

Savings on waste disposal and environmental pollution.

CREDIT

Examples;

Fuels from Microbes

• Fermentation is an energy releasing process.

• This is carried out by some microbes in the absence of oxygen.

• Alcohol and methane gas are products of fermentation, they are fermentation fuels.

Fossil fuels are NON RENEWABLE

Fermentation fuels are RENEWABLE

1. Fermentation of Manure by bacteria To produce methane gas

When microbes feed on fresh manure, they produce methane gas ( BIOGAS )

2. Fermentation of sugar into alcohol by Yeast.

Glucose YEAST Alcohol + Carbon dioxide + Energy

The Alcohol can be separated from the water by distillation.

Alcohol burns so it can be used as a fuel

Brazil has lots of sunshine and land for growing crops. It can therefore grow lots of sugar cane.

It does not have rich supplies of fossil fuels (COAL,GAS AND OIL ).

These are expensive to import.

Instead, sugar cane is fermented into alcohol which is then mixed with petrol to make GASOHOL .

This is used instead of petrol in many vehicles.

FERMENTATION FERMENTATION FUELSFUELS FOSSIL FUELSFOSSIL FUELS

Harmless to the Harmless to the environmentenvironment

Harmful to the Harmful to the environmentenvironment

Easy to obtainEasy to obtain Difficult to obtainDifficult to obtain

Cheap to obtainCheap to obtain Expensive to obtainExpensive to obtain

RenewableRenewable Non-renewableNon-renewable

There are advantages in using fermentation fuels rather than fossil fuels;

• Most micro-organisms reproduce themselves much faster than the cells of plants and animals.

• Given food, water and heat, one bacterium can reproduce asexually to produce many thousands of bacteria within a few hours.

Protein from Microbes

The table and graph show bacterial growth under ideal conditions

Industry is able to use fast growing bacteria to manufacture protein-rich foods.

The bacteria are grown, harvested and dried to form a protein-rich powder called single-celled protein which is used as animal feed.

Some fungi produce a protein called mycoprotein, which can be processed to produce meat substitutes for cooking.

Most of a bacterial cell is composed of protein.