PRESENTATION ON USE OF MICROORGANISMS

IN WASTE WATER TREATMENT

PRESENTED BY-VAISHALI JAINM.Sc. (Tech) Environmental sciences and technology

Fig: A typical sewage/waste water treatment plant

Waste water treatment comprises of three different procedures:

1- Primary Treatment 2- Secondary Treatment (Biological treatment)3- Tertiary Treatment

SECONDARY Treatment can be of different types such as :

WASTE WATER TREATMENT

A trickling filter consists basically of a layer or bed of crushed rocks on which primary effluent is sprayed over the surface and is trickled downwards to an under-drain system.

A rotary distributor arm with nozzles along its length is used to spray the sewage water.

A biological slime of microbes develops on the surface of the rocks .

The microbes absorbs the dissolved organics, thus removing oxygen-demanding substances from the wastewater.

Air circulating through the void spaces in the bed of stones provide the needed oxygen for stabilization of the organics by the microbes.

TRICKLING FILTER

In fig1 – round TRICKLING FILTER is shown at small scale

In fig 2- large rectangular trickling filters with layers of rocks ,on which primary effluent is spraying is shown

It basically consists of an aeration tank and a secondary settling basin or clarifier.

In aeration tank, microorganisms consume the dissolved organic pollutants as food.

The aerobic microorganisms in the tank grow and multiply forming a suspension of biological solids called activated sludge.

The combination of activated sludge and wastewater in aeration tank is called mixed liquor.

A tank detention time of about 6hrs is required for stabilization of most of organics in mixed liquor.

The mixed liquor flows to the secondary or final clarifier ,in which activated sludge solids settles out by gravity.

ACTIVATED SLUDGE TREATMENT

In fig 1- illustration of activated sludge treatment is shown

In fig 2- large aeration tanks in a working STP is shown

It consists of a series of large plastic discs (3m in diameter)

mounted on a horizontal shafts.A typical bio-disc unit is partially submerged in settled

sewage i.e. primary effluent and partially exposed to air.A layer of biological slime grows on each disc and the

attached microbes that forms the slime absorb the organic material in the waste.

The speed of rotation and the number of discs can be varied to achieve specific levels of pollutants removal.

A secondary clarifier is needed to settle the excess biological solids that slough off the discs as the slime layer thickness.

ROTATING BIOLOGICAL CONTACTORS (RBC)

In fig 1- working of rotating bio-disc (pollutants removal depends upon speed of rotation)

In fig 2- rotating bio-discs are arranged together in STP ( no. of bio-discs also matters)

MICROORGANISMSBiological treatment involves the use of different

microorganisms. These microorganisms are present throughout the process.

These could be : bacteria , viruses and protozoa These organisms are present in the treatment

vats ,grows and moves with sewage water.They metabolize the biodegradable organics , convert

them in the carbon dioxide, water and energy for their growth and reproduction.

The biological treatment systems must provide these microorganisms with enough oxygen, comfortable home, suitable temperatures and adequate contact with the organic materials.

Various and broad strains of bacteria can cause countless human , plants and animals diseases through ingestion of contaminated food and water.

Bacteria of such capabilities include : Escherichia coli 0157:H7, Vibrio cholera and Helicobacter pylori.

These bacteria are present right from the start of treatment vats due to their arrival with sewage water.

E. coli strains are removed after biological treatment by UV radiations, ozonation and chlorination while vibrio cholera is eradicated by high doses of UV rays.

HARMFUL BACTERIA

In fig 1- Escherichia coli serotype 0157:H7 is shown. It can cause food poisoning and diarrhea.it works at pH value of 7-7.5

In fig 2- Vibrio cholera 01 strain is shown and can cause cholera . It works at pH value 0f 6.3-6.7

BENEFICIAL BACTERIABiofilm forming bacteria are present in the systems of the

secondary treatment, considered to be beneficial in the removal of organic materials.

This include aerobic bacteria such as Pseudomonas zooglea, Chromobacter and Flavobacterium and anaerobic such as bdellovibrio bacteriovorus and brocadia anammoxidans .

Nitrogen removing bacteria are known as Nitrifiers and denitrifiers. nitrifiers include strains Nitrosomonas europaea and nitrobacter hamburgenesis while Denitrifiers include strains Thiobacillus denitrificans.

sulphate removing bacteria such as Desulfotomaculum and Desulfovibrio.

These bacteria are removed in the tertiary treatment of the process.

Bdellovibrio bacteriovorus (ANAEROBIC)

Brocadia anammoxidans (ANAEROBIC)

Nitrosomonas europaea ( NITRIFIER)

Nitrobacter hamburgenesis (NITRIFIER)

PROTOZOASeveral types of protozoans are present in sewage

water such as Amoeba, Ciliates and Flagellates through out the process.

The importance of protozoans in wastewater treatment is to maintain a slime layer within the systems.

They also play a predator role in removing bacteria, other protozoans and several small particles.

Protozoans can be detrimental to humans if ingested, and can contribute to human mortality and morbidity.

Protozoans are removed by the process of dual-media filtration.

Giardia lamblia (waterborne pathogen) causing Backpacker’s disease

Cryptosporidium (waterborne pathogen) causing Cryptosporidiosis

VIRUSEnterovirus and rotavirus are excellent indicators of

human fecal contamination in wastewater.These viruses are detrimental to humans, if

consumed.Life threatening diseases such as Polio and Hepatitis

A are caused by Enterovirus.Life threatening forms of Diarrhea are caused by

Rotavirus.Viruse are removed from water through Ozonation, a

process of disinfection.

In fig- Different strains of ENTEROVIRUS

In fig- ROTAVIRUS causing diarrhea is shown

THANK YOU