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primary and secondary treatment

TITTLE OF ASSIGNMENT
Submitted to Dr. Saghir Ahmad
Submitted by Wasif Hussain
Roll Number 35 (018458)

• Municipal wastewater treatment plants carry out a series of
treatment process most of the fundamental process are listed
here
1. Primary treatment (settleable solids are removed)
2. Secondary treatment ( BOD is reduced and oxidized by organic
constituents)

 Primary treatment removes material that will either float or readily settle out by
gravity.
 It includes the physical process such as SCREENING, GRINDING, GRIT
CHAMBER and SEDIMENTATION.
1. SCREENING ( long closely spaced narrow metal bars. It block the floating
debris such as wood,rags and bulky objects.
2. GRINDING ( used to grind and shred the debris that passes through the
screens.
3. GRIT CHAMBER ( long narrow tanks designed to slow down the flows so that
solids such as sand, coffee ground and eggshells will settle out of water
4. SEDIMENTATION ( units , tanks ,basins or mechanical devices used for
concentrating and collecting the particulates materials referred as sludge.

 It is also a biological treatment
 It includes the oxidation of organic material in the liquid wastewater by microbial
activity.
 Oxidation methods employed are FILTRATION, AERATION, OXIDATION
PONDS.
 Filtration. By intermittent sand filters, contact filters and trickling filter
 Aeration. By the activated sludge process or by contact aerators.

 A pile of rocks over which sewage or organic wastes slowly trickle.
 Consist of basin with support media
 Wastewater is applied intermittently or sometime continuously over the media
 Microorganisms attached to media and form a zoological film hich consist of bacteria,
fungi,protozoa and algae.
 Organic matter in the wastewater diffused into the fi where it is metabolized.
 Oxygen normally supplies Ito film by natural flow of air.
 Thickness of biofilm increase the new organisms grow.
 Periodically portion of the film slough off the media.
 Sloughed media is separated from liquid in secondary clarifier and discharged to
sludge processing.
 Clarified liquid from secondary clarifier is secondary effluent and portion is often
recycled to the biofilter to improve hydraulic distribution of the wastewater over the
film.

The video
dipicted
about the
trickling
filter how it
works.

 Coined by English researcher EDWARD ARDREN and WILLIAM LOCKETT
 Activated sludge treatment plants mainly comprise
 An aeration tank where the water to be purified is brought into contact with purifying
bacteria mass.
 A clarifier where purified water is separated from bacterial culture.
 A recirculation arrangement used to return biological sludge collected from the
clarifier to the aeration tank.
 An excess sludge extraction and removal arrangement.
 Mechanism for supplying oxygen.
 A mixing arrangement for this tank in order to ensure that best possible contact
between that bacterial cell and their nutrients.
 Widespread diffusion of oxygen to those areas requiring oxygen and to prevent the
formation of deposit.

• This video
illustrated the
activated
sludge process
(secondary
treatment)
from the
primary
settling tank.

 It is also called as Lagoons or stabilization ponds.
 Shallow ponds ( 2-4 ft in depth).
 Designed to allow algal growth on the wastewater effluent.
 Oxygen for biochemical oxidation of nutrients supplied from the air.
 Chlorella pyrenoidosa provids an additional important source of oxygen during
photosynthesis.

1. Aerobic ponds
2. Anaerobic ponds
3. Facultative ponds
4. Maturation ponds ( tertiary Ponds )

Types of Ponds Application
Aerobic ponds Treatment of soluble organic
waste And effluent from the
wastewater treatment
Anaerobic ponds Treatment of domestic and
industrialWaste
Facultative ponds Treatment of Untreated
screening Wastewater
Maturation ponds Remove pathogenic
microorganisms from the
wastewater which mainly occur
due to sunlight

 Extract pollutants
 Remove toxicants
 Neutralise Coarse particles
 Kill pathogens
 Reduction of BOD , COD and eutrophication.
 Prevention of BIO-MAGNIFICATION Of toxic substance in food chain.

 Pelczar, M.J.Jr., Chan,E.C.S and Kreig,N.R.1986. Microbiology McGraw Hill 5th
edition
 Https://wwww.bing.com/search.
 http://www.slideshare.net/mobile

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primary and secondary treatment

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primary and secondary treatment