CE 6001, Unit 4 Domestic sewage and System of Sewerages

 

🔷 4.1 Building Sanitation

✅ 4.1.1 Necessity of Sanitation

Sanitation ensures clean and healthy surroundings. It prevents the spread of diseases, keeps drinking water sources clean, and helps in maintaining hygiene in buildings and cities.

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✅ 4.1.2 Necessity to Treat Domestic Sewage

• Domestic sewage contains harmful bacteria, organic waste, and chemicals.

• If left untreated, it can pollute water bodies, harm human health, and damage the environment.

• Treatment makes it safe before disposal or reuse.

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✅ 4.1.3 Definitions

4.1.3.1 Sewage:

Wastewater from homes, bathrooms, kitchens, and toilets containing human waste and waste from activities.

4.1.3.2 Sullage:

Wastewater from non-toilet sources like kitchens, bathrooms, and washbasins. It does not contain human waste.

4.1.3.3 Types of Sewage:

1. Domestic Sewage – From houses.

2. Industrial Sewage – From factories.

3. Storm Water – Rainwater runoff from roads and roofs.

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✅ 4.1.4 Terms Related to Building Sanitation

• Water Pipe: Carries clean drinking water to bathrooms, kitchens.

• Rainwater Pipe: Carries water collected from rooftops.

• Soil Pipe: Carries discharge from toilets.

• Sullage Pipe: Carries wastewater from kitchens and bathrooms.

• Vent Pipe: Provides air flow to prevent foul gas buildup in drainage system.

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✅ 4.1.5 Building Sanitary Fittings

4.1.5.1 Water Closet (WC):

Toilet seats used to dispose of human waste.

• Indian Type: Squatting type toilet pan.

• European Type: Sitting type toilet seat (Western closet).

4.1.5.2 Flushing Cistern:

Tank used to flush water into toilet bowls after use.

4.1.5.3 Wash Basin:

Used for hand and face washing.

4.1.5.4 Sinks:

Used in kitchens for washing utensils and food.

4.1.5.5 Urinals:

Fixtures used for urination in male toilets.

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✅ 4.1.5.6 Traps

Traps are U- or S-shaped pipes that hold water to prevent sewer gases from entering the building.

4.1.5.6.1 Types of Traps:

• P Trap – Common in Indian closets.

• S Trap – For floor-mounted closets.

• Bottle Trap – Used below washbasins.

• Intercepting Trap – Prevents entry of sewer gas.

4.1.5.6.2 Qualities of a Good Trap:

• Water seal should not break.

• Should be self-cleaning.

• Made of corrosion-resistant material.

• Easily accessible for cleaning.

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✅ 4.1.5.7 Systems of Plumbing

4.1.5.7.1 One Pipe System

• Both soil and waste pipes connected to the same pipe.

• Has ventilation.

4.1.5.7.2 Two Pipe System

• Separate pipes for soil and waste water.

• Better hygiene and less smell.

4.1.5.7.3 Single Stack System

• One vertical pipe for all waste, but with proper venting.

4.1.5.7.4 Choice of System

• Based on budget, space, building size, and type of use.

4.1.5.7.5 Inspection and Junction Chambers

• Purpose: For cleaning and inspecting the sewer line.

• Location: At pipe junctions, bends, or changes in direction.

• Size/Shape: Generally square or rectangular, made of brick or concrete.

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🔷 4.2 Systems of Sewerage and Sewer Appurtenances

✅ 4.2.1 Types of Sewers

• Sanitary Sewer: Carries only domestic sewage.

• Storm Sewer: Carries only rainwater.

• Combined Sewer: Carries both sewage and storm water.

• Sub-surface Sewer: Used in low-lying areas, works with pumps.

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✅ 4.2.2 Systems of Sewerage

• Separate System: Two different sewers for sewage and stormwater.

• Combined System: One sewer for both sewage and stormwater.

• Partially Combined: One pipe for small stormwater flow and sewage.

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✅ 4.2.3 Self-Cleansing & Non-Scouring Velocity

• Self-Cleansing Velocity: Minimum velocity required to keep solids moving in sewer and prevent blockage (usually around 0.6 m/s).

• Non-Scouring Velocity: Maximum velocity to avoid damage to the sewer pipe (usually around 3 m/s).

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✅ 4.2.4 Laying, Testing, and Maintenance of Sewers

Laying:

• Done at proper slope to maintain flow.

• Pipes are laid in trenches.

Testing:

• Water test or air test is done to check for leaks.

Maintenance:

• Periodic cleaning using rodding machines or flushing.

• Remove blockages to avoid backflow or overflow.

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✅ 4.2.5 Manholes and Drop Manholes

• Manhole: Opening built over sewer line to inspect, clean, or remove blockages.

  • Types: Shallow (up to 0.9m), Medium (0.9–1.5m), Deep (more than 1.5m)

  • Material: Usually RCC, brick masonry.

• Drop Manhole: Used when there is a sudden vertical drop in sewer level.

  • Prevents erosion and damage to pipe at steep gradients.