MICROBESF 2

SL and HL

Consequences of releasing nitrate fertilizer into water bodiesMost of nitrate ions can be washed into the

lake and river and cause pollution.

Sewage----------------Water PollutionFROM HOUSE- Human feces, Kitchen residue, Detergents.

INDUSTRY- waste----- – strongly acidic/alkaline chemicals Toxic metal ions- Cu, Zn and Cr.

ANIMAL FARMLeakage of animal slurries from animal waste. FARM FIELDSRun off water--- contain artificial fertilizers (nitrate)

If water is pollutedRapid changes in the physical factors of the

environment

The main components of sewage and their effects in a fast flowing river.

Water pollutionBOD-biochemical oxygen demand.Sample of water –at 20 o C for 5 days.

Presence of Polluting OM

Increased activity of Bacteria

Decomposition of OM Resulting

High demand of dissolved Oxygen The BOD measurement –indication of the level of organic

pollution

Changes in water quality after the introduction of raw sewage in fast flowing river

Intial stagesSewage enters the the river

Immediate decomposition of OM (aerobic bacteria)

Demand for dissolved O2 is high

Resulting

Rapid decrease in O2 concentration.

Oxygen Sagoccurs-when the rate of consumption is greater

than the rate at which O2 is produced

Decomposition of OM-Number of aerobic bacteria decreases

No. of the Protozoans increases

EutrophicationArtificial enrichment of nutrients in a river

or lake. Algal bloom-Excess nutrients in the water encourages rapid

growth of algae and blue-green bacteria resulting Algal bloom.

Algal bloom-Number of algae increases when- Suspended solids settles Water becomes clear Light penetrate Photosynthesis takes place Dissolved Oxygen level rises NO3 and PO4 ions absorbed

Algae die aerobic bacteria Oxygen level falls very low

Sudden death of masses of fish

If water is anaerobic H2S and CH4 is produced

Blue-green bacteria -------toxins------cause the death of fish and other animals. Recovery of riverOxygenation of water improvesDilution of the sewage and nutrients

Role of Saprotrophic bacteria in the treatment of sewage water

In sewage treatment plant- Uses natural decay processes conditions for micro organisms Decomposition of OM (aerobic ) Final product are CO2 released in

atmosphere NO3 and PO4 –dissolved in water

Sediment and sludge is decomposed anaerobically to produce CH4

Sewage purification

Sewage treatment1. Screening of water ------allowing water into a grit

settlement tank. Grit—small stones and sand2. Water is passed thru trickling filter - degraded stones, grit and clinker 3. Bacteria, fungi and protozoa degrade OM as the

waste water trickles thru the bed and 4. These are consumed by predatory protozoa and

insect larvae.

An alternative methodUse of Reed bedThe Common Reed ( Phragmites australis.) has

the ability to transfer oxygen from its leaves, down through its stem, and out via its root system.

As a result of this action, a very high population of micro-organisms occurs

Able to breakdown any soluble material.

Use of Biomass Production of methane and ethanol

What is Biomass? total mass of living material in an area. Dry mass in Kg per square metre. (Kg/m2)

FermentationSugar by Sacccharomyces --- YeastConvert biomass into ethanol ---used as fuelEg., GASOHOL Unleaded petrol mixed with ethanol(10-

20%) used in modified motor vehicles.

Sugar ----sugarcane—tropical countries sugarbeet--- temperate countries

Fermentation by bacteriaBiomass----biogas---CH4

Mixture of different gases produced as a result of action of anaerobic microorganisms on domestic and agricultural wastes.

Methane 50-68% CO2 25-35%

traces of H2S , NH3, H2 and N2

Methane from biomass

Intially Faeces ferment

Aerobic bacteria

hydrolyse Carbohydrates, Lipids, Protein

Sugars, glycerol and fatty acids and amino acids

Available oxygen is used up

acetogenic bacteria converts

sugars

short chains of Fatty acids especially Ethanoate ions (CH3COO-) and H2

and CO2

this stage is termed as acetogenesis

Final stage-methanogenesisby methanogenic bacteriaAre obligate anaerobes (only active in the

absence of oxygen)Members of Archaebacteria Ethanoate and other acids

methane CH3COOH CH4+ CO2

Biogas production30-40 degrees CelsiusClosed tank-digesterChina, India, NepalDeveloped countries-dispose large quantity of

animal waste from intensive farming.