✓Waste water is a term that is used to describe waste material that includes.... Food scraps Oil and soaps. Human wastes. Industrial wastes. Sewage waste that is collected from urban areas. WASTE WATER AND THEIR TREATMENT (PRIMARY, SECONDARY AND TERTIARY)

1. SEMINAR TOPIC:
WASTE WATER AND THEIR TREATMENT (PRIMARY, SECONDARY
AND TERTIARY)

2. INTRODUCTION
■ Wastewater is a term that is used to describe waste material that includes industrial liquid
waste and sewage waste that is collected in towns and urban areas and treated at urban
wastewater treatment plants.
■ Water treatment is the process of removing contaminants from wastewater using physical,
chemical, and biological processes.
■ Its objective is to produce an environmentally safe fluid waste stream and a solid waste
suitable for disposal or reuse.

3. WHAT IS WASTE WATER?
■ Waste water is a term that is used to describe waste material that includes….
• Food scraps
• Oil and soaps.
• Human wastes.
• Industrial wastes.
• Sewage waste that is collected from urban areas.

4. WASTEWATER TREATMENT
■ A process to convert wastewater - which is water no longer needed or suitable for its most recent
use - into an effluent that can be either returned to the water cycle with minimal environmental
issues or reused.
■ Aquaculture production systems have progressively intensified. Despite their high output, the
intensive culture practices have adverse and negative impact on the environment. They are
associated with both uncontrolled use of feed and massive production of waste which if released
into the environment untreated and –
• Deteriorates the water quality
• Leads to eutrophication
• Spreads parasite diseases and causes metals and antibiotics pollution.

5. WHY TREAT WASTEWATER?
■ To remove pollutants from waste water for its recycling.
■ To promote health concern and public hygiene.
■ To preserve aquatic life and wildlife habitat.
■ To promote recreation and quality of life.
WASTE WATER CONTAMINANTS
 Suspended solids.
 Biodegradable organics.
 Pathogenic bacteria.
 Nutrients (N & P).

6. STAGES OF TREATMENT
1. Primary treatment
2. Secondary treatment.
3. Tertiary treatment.
OBJECTIVES OF WASTEWATER
TREATMENT
 Reduce organic content i.e., BOD
 Removal/reduction of nutrients i.e., N,P
 Removal/inactivation of pathogenic microbes

7. PRIMARY TREATMENT
 Removal of large objects from influent sewage. Ex. by physical separation
 About 25-50% of incoming biological demand(BOD), 50 to 70% of total suspended solids(TSS)
and 65% of oil & grease are removed during primary treatment
 Removal of solid particles by-
1. Screening(for larger coarse particles)
2. Skimming(Floating Solids)
3. Sedimentation

8. SCREENING
■ Screening is an essential step in sewage treatment from removal of large coarse particles. This is
the first treatment or operation which is carried out at the treatment plants.
■ Following are the main purposes of the screening:
I. To remove the floating solids which may clog the pumps at the treatment plants and outfall.
II. To remove the solids from the sewage which will form ugly sludge banks at the site of sewage
disposal, when the sewage is given only primary treatment.
III. To remove the solids which will clog the trickling filters and will also interfere with the aeration
in the activated sludge treatment units.

9. SKIMMING
■ In this process skimming tanks are used for removing oil,
grease and fats of the sewage. This tank is in the form of long,
trough-shaped structure. Tank surface is made as large as
possible, and the sides narrow down at a steep angle.
Detention period of 3 min is provided in these tanks..
■ Compressed air is circulated through out the container’s bed,
so that the oily matters can rise upwards and could be
collected in the side trough(beside the baffle), from where
they are removed.
■ After this process remaining water is takenout from outlet.

10. ■ Sedimentation is a physical water treatment process
using gravity to remove suspended solids from water.
■ Clarifiers are tanks built with mechanical means for
continuous removal of solids being deposited by
sedimentation.
■ In sedimentation process removal of suspended
partical depends upon the size and specific gravity of
those particles. Suspended solids retained on a filter
may remain in suspension if their specific gravity is
similar to water while very dense particles passing
through the filter may settle.
SEDIMENTATION
Fig. Clarifier used for treating sewage
water

11. SECONDARY TREATMENT
■ Removal of organic & inorganic soluble matter namely carbohydrates, fats, hydrocarbons and
other material which are degraded into smaller forms like CO2, H2O ,N2O etc.
■ Methods of Secondary Treatment
a. Activated Sludge
I. In this process, sewage is aerated by air or by mechanical means.
II. The residence time of water in this system is 1-20 hours
III. Vigorous aeration is needed to prevent water from dropping down to 2-3mg/li that slows down
the respiratory activity of the organisms in water.

12. b. Filtration
• Mechanical filtration - Untreated water passes through a mesh filter that traps suspended particles on the
surface or within the filter.
• Biological filtration (trickling filter) - It consists of a fixed bed of rocks, coke, gravel, polyurethane foam,
sphagnum peat moss, ceramic, or plastic media over which sewage or other wastewater flows downward and
causes a layer of microbial slime (biofilm) to grow, covering the bed of media.
c. Oxidation pond
• A conventional oxidation pond contains the algal bacterial culture , which oxidizes a organic matter into
CO2 ,H2O, H2S,NH3 and other decomposition products that are used as nutrients like nitrate , phosphate,
sulphate.
• About 85% of the suspended solids and BOD can be removed by well running plant with secondary
treatment.

13. TERTIARY TREATMENT
(DISINFECTION)
■ PURPOSE: Destruction of harmful (pathogenic) microorganisms i.e. disease causing
germs. Done through:
I. Chlorination
II. Ozone: more powerful but unstable to store.
III. Ultraviolet light
IV. Hydrogen peroxide: similar to ozone but activators such as formic acid is required to
improve its working.

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