Requirements for settling tank (clarifier equipment) for water treatment plant

IS 10313: Introduction and Scope — Key Specifications

1. Scope

• Covers materials and construction of settling tanks (clarifier equipment) for water treatment plants.
• Ensures durability, corrosion resistance, and compliance with Indian Standards (IS).

2. Materials for Components (Table 1 Summary)

3. Painting Specification (Clause 7.1)

• All steel surfaces: Red oxide primer + 3 coats finish paint
• Refer IS 1477 (Part I & II) for painting practice.

Summary Diagram: Material Flow in Settling Tank Components

graph TD
    A[Influent Pipe] -->|Cast Iron/Steel| B[Pipe Fittings]
    B --> C[Sludge Draw Off Pipe]
    C --> D[Sluice Valve]
    D --> E[Scraper Blades & Frame]
    E --> F[Rotating Bridge & Walkway]
    F --> G[Driving Equipment & Gears]
    G --> H[Bearings & Couplings]

Note: Refer to IS 10313 for detailed design, dimensions, and installation requirements.

IS 10313: General Requirements for Settling Tank (Clarifier Equipment)

Key Specifications & Materials (Clause 2.1, Table 1)

Notes:

• Materials are selected for durability, corrosion resistance, and mechanical strength.
• Protective coatings like epoxy or galvanization are recommended for mild steel components exposed to corrosion.
• Refer to respective IS codes for detailed material and dimensional specifications.

Typical Material Selection Flow

flowchart TD
    A[Component] --> B{Material Type}
    B -->|Pipe| C[Cast Iron / Steel]
    B -->|Valve|

IS 10313: Materials for Construction of Settling Tank Components

Painting (Clause 7.1)

• All steel surfaces: clean, dry, rust and grease free.
• Apply red oxide primer + 3 coats of finish paint.
• Refer IS 1477 (Part I & II) for painting specifications.

Notes:

• IS 1536: Centrifugally cast iron pipes.
• +IS 1537*: Vertically cast iron pipes.
• §IS 780*: Sluice valves.
• ||IS 226*: Structural steel.
• IS 1030: Carbon

IS 10313: Design & Structural Details for Settling Tank (Clarifier Equipment)

Key Material Specifications (Table 1 Highlights)

Structural Details & Design Notes

• Anchor bolts: Must be galvanized steel (Clause 4.1.1).
• For long rectangular tanks (>20 m length), provide series of collecting launders with interconnections for uniform weir loading.
• Launders may have weir plates or submerged orifice holes for flow distribution.
• Walkways and handrails must be anti-corrosive painted or galvanized mild steel.

Typical Construction Components

flowchart TD
    A[Influent Pipe] --> B[Settling Tank Body]
    B --> C[Sludge Draw Off Pipe]
    B --> D[Sludge Scraper Blades]
    D --> E[Rotating Bridge & Frame]
    E --> F[Driving Equipment (Gears, Wheels)]
    B --> G[Effluent Launders]
    G --> H[Weir Plates / Orifice Holes]

Summary

• Use materials as per IS codes for durability and corrosion resistance.
• Structural steel components should be galvanized or epoxy coated.
• Design provisions for sludge removal and uniform effluent flow

Mechanical Equipment and Drives (IS 10313 Key Points)

1. Centre Drive Mechanism (Clause 5.3.1):

• Consists of:
  • Drive unit with overload alarm
  • Tipping device
  • Structural steel scraper arms & bridge
  • Handrail and walkway (up to center)
• Drive train:
  • Motor → series of reduction gearboxes → internal/external spur gear & pinion → scraper arms
  • Chain drive allowed if necessary
• Gearbox:
  • Preferably oil-immersed type
• Motor standards:
  • IS 325-1970 (3-phase induction motors)
  • IS 996-1964 (single-phase/universal motors)

2. End Drive (Clause 5.3.2):

• Mounted on end carriage with rotating bridge
• Drive: motor + reduction gearbox → traction wheel via spur/bevel gear or chain
• Tip speed for circular tanks: ~0.3 m/min or below

3. Materials for Mechanical Components (Clause 2.1, Table 1):

4. Painting Specification (Clause 7.1):

• All fabricated steel surfaces:
  • Clean, dry, rust and grease free
  • One coat red oxide primer
  • Three coats finish paint
• Refer IS 1477 (Part I & II) for painting practice

Summary Diagram: Drive System Layout

graph LR
    Motor --> Gearbox[Reduction Gearbox (Oil-immersed)]
    Gearbox --> SpurGear[

Sludge Scrapping & Removal per IS 10313

1. Scraper Blades:

• Made of mild steel (IS: 226-1975).
• Inclined to rake arm axis, pushing sludge towards tank center.
• Blades are straight or curved inward with overlapping horizontal projections.
• Length: Typically cover ¾ or full tank diameter depending on size and peripheral speed.

2. Scraper Arm & Bridge:

• Scraper arm attached to:
  • Rotating bridge (driven at periphery or both ends for large tanks ≥ 55 m diameter).
  • Centre drive cage (driven at tank center).
• For square tanks, fixed bridge up to center with pivoted pentograph extensions and corner blades.
• Bridge and rake arm materials: Mild steel (IS: 226-1975).

3. Driving Equipment:

• Main driving wheel: Cast iron or cast steel (IS: 210-1978, IS: 1030-1974).
• Worm, bevel, spur gears: Cast iron, alloy steel (various IS codes).
• Traction wheels: Rubber/chrome-nickel or carbon steel case hardened.

4. Materials Summary Table:

Key Design Notes:

• Scraper blades must maintain continuous contact with sludge.
• Peripheral speed and blade overlap are critical for effective sludge removal.
• For tanks > 55 m diameter, dual-end driven bridges are preferred.
• For rectangular tanks, scrapers may be mounted on travelling bridges or endless chains.

flowchart LR
    A[Sludge Tank] --> B[Scraper Blades]
    B --> C[Inclined &

IS 10313: Operational Checks and Testing - Key Points

1. Operational Checks for Bridge (Clause 5.5)

• If bridge height < 90 cm, provide hand railing on top beam.
• Total height with railing = 1.0 m minimum.

2. Testing of Scrapping Mechanism (Clause 6)

• No detailed formulas provided; ensure functional testing of mechanical scrapers.
• Check smooth operation, clearance, and removal efficiency.

3. Material Specifications (Clause 2.1)

• Refer to Table 1 for materials used in components (steel grades, coatings).
• Use red oxide primer + 3 coats of finish paint per IS 1477 (Part I & II).

4. Detention Time & Weir Loading (Clause 2.5)

5. Bottom Slopes

• Circular tanks with mechanical scraper: slope ≥ 1:12
• Manual cleaning: slope ≈ 1:10
• Rectangular tanks: floor slope 10% to center + longitudinal slope ≥ 5%
• Sludge hopper slope: ≥ 60° (gravity withdrawal ≥ 55°)

Summary Diagram: Settling Tank Slopes and Detention Time

flowchart TD
    A[Inlet] --> B[Rectangular Tank Floor]
    B --> C[Slopes: 10% sides to center]
    C --> D[Longitudinal slope ≥ 5%]
    D --> E[Outlet]
    F[Detention Time]
    F --> |Plain settling| G[3-4 hrs]
    F --> |Coagulated water| H[2-2.5 hrs]
    F --> |Solid contact| I[1-1.5 hrs]

Note: For detailed testing procedures, refer to manufacturer guidelines and

IS 10313 - Painting and Corrosion Protection (Clause 7.1)

• Surface Preparation: All fabricated steel surfaces must be thoroughly dried and free from rust and grease before painting.
• Painting System:
  • 1 coat of Red Oxide Primer
  • 3 coats of Finish Paint
• References for Paints:
  • IS 1477 (Part I) - 1971 (Primer specifications)
  • IS 1477 (Part II) - 1971 (Finish paint specifications)
• Purpose: To ensure corrosion protection of steel components, especially in water treatment equipment.

Summary Table for Painting Coats

Additional Notes:

• Follow IS Code of Practice for Painting of Ferrous Metals in Buildings:
  • Part I: Pretreatment
  • Part II: Painting
• Proper surface cleaning (removal of rust, grease) is critical for paint adherence and longevity.
• Use epoxy or anti-corrosive paints for enhanced protection in aggressive environments.

flowchart TD
    A[Fabricated Steel Surface] --> B[Dry & Clean (Remove Rust & Grease)]
    B --> C[Apply 1 Coat Red Oxide Primer]
    C --> D[Apply 3 Coats Finish Paint]
    D --> E[Protected Steel Surface]

This ensures durability and corrosion resistance of steel components in water treatment plants.

IS 10313: Electrical and Motor Protection Key Points

1. Motor Overload Protection (Clause 5.4)

• Mandatory: Protective devices must be provided to stop motors against overload.
• Typically includes:
  • Thermal overload relays
  • Magnetic circuit breakers
  • Electronic motor protection relays

2. Painting Specifications (Clause 7.1)

• All fabricated steel surfaces must be:
  • Thoroughly dried, free from rust and grease
  • Coated with one coat of red oxide primer
  • Followed by three coats of finish paint
• Refer IS:1477 (Part I & II) for painting standards on ferrous metals.

3. Materials for Motor Components (from related tables)

• Use mild steel or cast iron for motor frames and structural parts.
• Bearings: High carbon steel (IS:2898)
• Couplings: Cast iron (IS:2693)
• Gear components: Cast iron, cast steel, alloy steel per IS standards.

Typical Motor Overload Protection Formula

[ I_{set} = k \times I_{FL} ]

• (I_{set}): Overload relay setting current
• (I_{FL}): Full load current of motor
• (k): Setting factor (usually 1.15 to 1.25)

Summary Diagram: Motor Protection System

graph LR
A[Motor] --> B[Overload Relay]
B --> C[Circuit Breaker]
C --> D[Power Supply]
B -.-> E[Trip Signal]

• Overload Relay detects excess current → trips circuit breaker → stops motor to prevent damage.

References:

• IS 10313 Clause 5.4 & 7.1
• IS 1477 (Painting)
• IS 2898 (Bearings), IS 2693 (Couplings)

Hydraulic Testing of Pipes (IS 10313)

• Test Pressure: Pipes after laying and jointing must be tested at 2 × maximum working hydrostatic head (Clause 3.2.1).
• Scope: Includes internal and external pressure tests before embedding pipes in concrete or laying the floor (Clause 3.1.1).
• Purpose: Ensures pipe integrity against leakage and withstand subsoil water pressure or settlement stresses.
• Materials: Pipes and fittings must conform to relevant IS standards (e.g., Cast Iron pipes IS 1536/1537, fittings IS 1538, sluice valves IS 780).

Key Specification Summary:

Hydraulic Test Procedure:

1. Lay and joint pipe as per Clause 3.1.1.
2. Fill pipe with water, remove air.
3. Apply test pressure = 2 × max working pressure.
4. Maintain pressure for specified duration (typically 2 hours).
5. Check for leaks and pressure drop.

Formula:

[ P_{test} = 2 \times P_{working} ]

Where:

• (P_{test}) = Test pressure (hydrostatic head)
• (P_{working}) = Maximum working hydrostatic head

flowchart TD
    A[Pipe Laying & Jointing] --> B[Hydraulic Testing]
    B --> C{Apply 2 × Max Working Pressure}
    C --> D[Check for Leakage]
    D --> E{Pass?}
    E -- Yes --> F[Embed Pipe in Concrete]
    E -- No --> G[Repair & Retest]

Note: Refer IS 10313 Clause 3.1 and 3.2 for detailed methodology and IS 1536/1537/1538 for material specifications.

IS 10313: Key Specifications for Weir and Launder Arrangements

1. Launder Type & Placement (Clause 4.1 & 4.2)

• Circular/Square Tanks: Peripheral collecting launder provided around the tank.
• Rectangular Tanks (>20 m length): Series of collecting launders with cross connections at the tank's opposite end.
• Launders may have:
  • Mild steel weir plates with 90° 'V' notches
  • Orifices at predetermined points for uniform flow.

2. Weir Plate Specifications (Clause 4.1)

• Material: Mild steel (see IS: 226-1975)
• Thickness: Not less than 6 mm (per IS: 9108-1979)
• Weir clamps to secure plates.

3. Overflow Rate & Weir Loading (Clause 3.1)

4. Material References for Launder & Weir Components (Clause 2.1 Table)

Summary Diagram: Launder & Weir Arrangement in Circular Tank

flowchart TB
    A[Settling Tank] --> B[Peripheral Launder]
    B --> C[Weir Plates with 90° V Notches]
    B --> D[Orifices at Predetermined Points]
    C --> E[Uniform Overflow Collection]
    D --> E

Note: Ensure launder design maintains uniform flow distribution and structural integrity per IS standards for long-term durability.

IS 10313 Key Formulas & Specifications for Detention Time and Hydraulic Parameters

1. Detention Time (t)

• For plain settling tanks:
  [ t = 3 \text{ to } 4 \text{ hours} ]
• For coagulated water:
  [ t = 2 \text{ to } 2.5 \text{ hours} ]
• For solid contact (vertical flow) units:
  [ t = 1 \text{ to } 1.5 \text{ hours} ]

2. Overflow Rate (Surface Loading Rate)

• Horizontal flow circular tanks:
  [ Q_o = 30 \text{ to } 40 , m^3/d/m^2 ]
• Vertical flow tanks:
  [ Q_o = 40 \text{ to } 50 , m^3/d/m^2 ]

Note: Overflow rate should not exceed particle settling velocity.

3. Minimum Side Water Depth

• Rectangular or circular horizontal flow tanks:
  [ \geq 2.5 , m ]

4. Weir Loading

• Normal weir loading:
  [ \leq 300 , m^3/d/m ]
• Higher values possible with proper design.

5. Bottom Slopes

• Circular tanks (mechanical scraper):
  [ \text{slope} \geq \frac{1}{12} ]
• Circular tanks (manual cleaning):
  [ \text{slope} \approx \frac{1}{10} ]
• Rectangular tanks:
  [ \text{floor slope} \approx 10% \text{ from sides to center}, \quad \text{longitudinal slope} \geq 5% ]
• Sludge blanket vertical flow tanks hopper slope:
  [ \geq 60^\circ \quad (\text{or } 55^\circ \text{ for gravity sludge withdrawal}) ]

Summary Table

| Parameter | Value/Range | Unit | |----------------

IS 10313 Key Points on Floor Slopes & Hopper Design for Settling Tanks

1. Floor Slopes (Clause 3.1)

• Bottom slopes are provided to facilitate sludge removal.
• Typical slopes are designed to ensure sludge flows towards the hopper outlet.
• Slopes must balance effective settling without disturbing sedimentation.

2. Hopper Design (Clause 3.1.3 & 3.2.2)

• Inlet pipe laid across the tank center, brought vertically into the hopper.
• Sludge draw-off pipe follows hopper slope and exits vertically through tank wall.
• Hopper bottom tanks have inclined surfaces for sludge collection.

3. Typical Overflow Rates (Clause 3.1)

4. Materials for Components (Table 3.2, Clause 2.1)

Summary Diagram: Hopper Bottom Tank Sludge Flow

flowchart TD
    A[Inlet Pipe] -->|Across tank center| B(Hopper Bottom)
    B -->|Sludge follows slope| C[Sludge Draw-off Pipe]
    C -->|Exits vertically| D[Sludge Outlet]

Note: Design slopes typically range from 1:6 to 1:8 (vertical:horizontal) to ensure smooth sludge flow without resuspension.

For detailed dimensions and design, refer to Fig. 1 in IS 10313 and related hydraulic design parameters

IS 10313: Installation & Maintenance Guidelines for Settling Tank (Clarifier Equipment)

Key Specifications & Materials (Clause 2.1, Table 1)

Painting & Surface Treatment (Clause 7.1)

• All steel surfaces must be cleaned, dried, and free from rust/grease.
• Apply 1 coat red oxide primer + 3 coats finish paint as per:
  • IS 1477 (Part I & II) - 1971
• Use epoxy or galvanized coatings for corrosion protection on mild steel parts.

Maintenance Highlights

• Regular inspection of sludge draw-off pipes and sluice valves for blockages.
• Periodic lubrication of gears and bearings (high carbon steel balls per IS 2898-1976§§).
• Maintain protective paint layers to prevent corrosion.

Summary Diagram: Clarifier Components & Materials

graph LR
A[Influent Pipe] -->|Cast Iron| B[Pipe Fittings]
B --> C[Sludge Draw Off Pipe]
C --> D[Sluice Valve]
D --> E[Scraper Blades]
E --> F[Rotating Bridge]
F --> G[Driving Equipment]
style A fill:#f9f,stroke:#333,stroke-width:2px
style G fill:#bbf,stroke:#333,stroke-width:2px

**Note

IS 10313: References to Related Indian Standards

This standard references important IS codes related to painting and electrical motor specifications for water treatment equipment:

• Painting of Steel Surfaces

  • IS 1477 (Part I) - 1971: Code of Practice for Painting of Ferrous Metals in Buildings - Pretreatment
  • IS 1477 (Part II) - 1971: Code of Practice for Painting of Ferrous Metals in Buildings - Painting

• Electric Motors Specifications

  • IS 325 (Third Revision): Specification for Three-Phase Induction Motors
  • IS 996 (Revised): Specification for Single-Phase Small AC and Universal Electric Motors

Key Painting Specification (Clause 7.1)

• All steel surfaces must be:
  • Thoroughly dried
  • Free from rust and grease
  • Coated with one coat of red oxide primer
  • Followed by three coats of finish paint

Summary Table of Related IS Codes

Additional Notes:

• These standards ensure durability and performance of water treatment equipment components.
• Refer to IS 10313 for detailed settling tank (clarifier) requirements.

flowchart LR
    A[Steel Surface Preparation] --> B[Dry & Clean]
    B --> C[Red Oxide Primer Coat]
    C --> D[Three Finish Paint Coats]
    D --> E[Durable Coating]

For full details, consult the respective IS codes and IS 10313 document.