This document provides an overview of subsurface sewage treatment systems (SSTS), also known as septic systems. It discusses the key components of septic systems including septic tanks, drainfields, and the soil beneath. It describes the physical, chemical, and biological treatment processes involved. Requirements for SSTS include proper site and soil conditions. Design considerations include sizing of tanks and drainfields. Proper operation and maintenance, such as periodic pumping, is also outlined. Advantages include low cost and returning nutrients to soil, while disadvantages can include odor and potential pollution.

1. GUIDED BY:
Asst. Prof. Mrs. AMRUTHA.S PRESENTED BY:
CIVIL DEPARTMENT ANU MARY BIJU
S7 CE
ROLL NO.:12
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2. CONTENTS
 INTRODUCTION
 SEPTIC SYSTEMS
 TREATMENTS IN SSTS
 REQUIREMENTS OF SSTS
 DESIGN OF THE SYSTEM
 OPERATION AND MAINTENANCE
 CAPACITY , AGE , PERFORMANCE, COST
 ADVANTAGES & DISADVANTAGES
 CONCLUSION
 REFERENCE
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3. INTRODUCTION
 Soil based water treatment
- to improve or upgrade the quality of waste water .
 Subsurface Sewage Treatment Systems (SSTS)
SEPTIC SYSTEMS Or INDIVIDUAL
SEWAGE TREATMENT SYSTEMS (ISTS)
 Used mainly in homes and business, not connected to
municipal sewer.
 With these systems, wastewater is re-introduced to the
environment for human needs.
 Common method to solve scarcity.
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4. SEPTIC SYSTEMS
 A permanent solution to waste water treatment , produced
in bedroom, kitchen, laundry.
 Used when treatment plants are not accessible.
 Main parts are: Septic tank , Drainfield , Soil beneath the
drain field.
1.SEPTIC TANK:
o Watertight concrete box, 9feet long and 5feet height
o Buried in ground just outside
o Retain waste water for 24-36 hours.
o Treat wastewater by bacteria. 4

5. 2.DRAINFIELD:
o Connected by a buried pipe.
o Consists of 2 to 5 trenches excavated into the subsoil.
o Also called nitrification field / soil absorption field.
o Sole purpose - deliver wastewater to soil.
CONTD…
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6. CONTD….
3.SOIL BENEATH DRAINFIELD:
o Wastewater trickle down through gravel to the soil.
o Used only on soils that will absorb and purify the effluents
o Soil will be in uniform brown, yellow/ bright red.
o Neither too sand or too clay, good structure, avoid rock.
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7. (Pic courtesy: www.septictreatmentsystemsimages.com )
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Fig 1 : Septic system method.

8. TREATMENT
 SSTS treatment is a combination of: physical , chemical
and biological .
 PHYSICAL TREATMENT:
Physical process include
Sedimentation , Screening , Aeration , Filtration ,
Floatation &Skimming , Equalization.
•Sedimentation process is by the use of septic tank.
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9. • In septic tank solid waste in waste water settle down due to
gravity(sludge).
• Scum will float on top of water, helps anaerobic bacteria to
degrade organic components.
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CONTD…..

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( Pic courtesy: www.septictreatmentsystemsimages.com )
Fig 2: Septic tank for SSTS

11. CONTD…..
• Pollutants like phosphorous can then be easily removed.
• Chemical industry uses polymer (later stage)
physical separation & excess microbial activity.
CHEMICAL TREATMENT:
• Chemicals used to create changes in pollutants.
• Increase the removal by physical process by adding chemicals
like alum, lime, iron salt.
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12. • Pathogens die-change in temperature, food, moisture or
absorbed by soil fungi.
• Negatively charged soil -chemicals, nutrients.
CONTD…...
BIOLOGICAL TREATMENT:
• Bacteria &small organisms treat wastewater by
biochemical decomposition.
• Viruses are removed by negatively charged soil particle.
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13. ( Pic courtesy: www.septictreatmentsystems images.com )
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Fig 3: Soil beneath the drainfield.

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Fig 4: Septic systems method
( Pic courtesy: www.septictreatmentsystemsimages.com)

15. REQUREMENTS OF SSTS
Installation should be approved by health department before
construction.
 Should conduct site & soil investigation to have best soil.
 Use only on soils which will adequately absorb and purify
the effluents.
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 Solid waste that accumulate on septic tank should be pumped
out and disposed off at appropriate locations.
 Do not pour paint, paint thinners, pesticides, poisons, fat,
cooking grease, oils, solvents, disinfectants etc.
 Septic tank & drain field should be properly maintained.
CONTD…..

17. DESIGN CRITERIA
SEPTIC TANK
Water tight , stable structure for performance, durable,
resistant to corrosion.
 Tank size: bedrooms, no. of inhabitants , water using
appliances.
Should hold at least one week of waste flow.
Key factor: quantity of sewage it can store, rate of waste
discharged, liquid surface area.
Inlet, outlet, inspection holes, risers-lid.
Location: away from wells, surface waters, building
foundations. 17

18. (Pic courtesy : www.septictankimages.com) 18
Fig 4 : Cross section of a septic tank

19. DRAINFEILD
 Soil absorption system – “biomat” or “clogging mat”.
 Absorption beds and trenches are used .
 Trench-3 feet wide, provide more surface area.
 Bottom(15.24cm)-gravel or crushed rock, 10.16cm-
perforated pipe , additional rock-over and above.
 Location- at least 100ft away from well.
SOIL BENEATH THE DRAINFEILD
 Depend on site condition.
 Soil should be good in absorption and purification.
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20. OPERATION AND MAINTENACE
• Requires limited operator attention.
• Management needs.
• Regular pumping is needed every 3 to 5 years.
1. Size of the tank.
2. Amount of waste water generated by your household.
3. Amount of solids carried in waste water.
4. Age of the system.
 Sludge depth is one-third of liquid depth , regular
pumping is necessary.
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21. CONTD….
• MAINTANACE TIPS:
 Annual checking and cleaning.
 Mark the location of the septic tank.
 System should not be installed when soil is wet.
 Septic tank additives is not recommended.
 Minimize the use of harmful substances.
 Restrict the use of garbage materials
 Do not allow the trees to grow, not to dig.
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22. CAPACITY
 Size of the house.
 Load requirements.
 Water-using appliances.
AGE
 Depends -Site, Pumping, Maintenance.
 Last for 15 to 40 years .
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23. PERFORMANCE
 Depend on –depth of unsaturated soil beneath the
absorption field.
 On-site treatment methods for long-term domestic use.
 Offer the highest level of performance among all.
COST
 Depends on –location, access, subsurface site condition,
type of tank installed
 Offer lowest cost than any other method.
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24. ADVANTAGES
o Simplicity, reliability, and low cost.
o Most popular on-site water treatment.
o Nutrients are returned to soil.
o Act as a permanent source of water treatment.
DISADVANTAGES
o Pose an odor problem.
o Pollution of nearby ditches or streams.
o Toilet overflowing.
o Pump failure or blockage in pumping.
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25. CONCLUSION
 Very common on-site waste water treatment .
 Septic systems –septic tank, distribution box or
drainfield, and soil beneath the drainfield-percolates
down to ground water.
 Alternative to wastewater treatment plants.
 Widely used in rural areas to save money.
 Efficient, inexpensive, convenient method for treating
household waste.
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26. REFERENCE
1. “International Journal of Advanced Research Trends in Engineering
and Technology”(IJARTET), Vol.2, March 2015, Page 118-183,
‘Performance Evaluation of Improved Septic Tank for Domestic Waste
Water Treatment’.
2.“International Journal for Engineering and Technology”,Vol.4, May
2014, Page 1-7, ‘The effect of septic tank location on borehole water
quality in Port Harcourt, Nigeria’ .
3. “Journal of Environmental and Public Health”, March 2015, Page 1-12,
‘A Review of On-site Waste Water Treatment Systems in Western
Australia from 1997-2011’.
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4. “51st ASC Annual International Conference Proceedings”,
2015, page 1-10, ‘Home Owner’s Knowledge and
Responsibilities Of Residential Waste Water Treatment Systems
in Rural Texas’.
5. “EPA, United State Environmental Protection Agency”, July 2015,
Page 1-5, ‘Preventing Septic System Failure”.
6. “Neb Guide-University Of Nebraska-Lincoln Extension, Institute Of
Agriculture & Natural Resources”, May 2015, Page 1-4,
‘Residential On-Site Waste Water Treatment : The Role Of Soil’.
7. “Oklahoma Department of Environmental Quality” , Page 1-7,
‘Subsurface sewage treatment systems ,it’s your on-site system’.
CONTD…
8. www.googlesearch.com

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