Requirements for biological treatment equipment, Part 1: Trickling filters

IS 8413 Part 1: Introduction and Scope - Key Points

• Scope: Specifies materials, construction, and components for trickling filters used in wastewater treatment.
• Rounding Off: Final test or analysis values must be rounded as per IS 2-1960, maintaining the same significant figures as the specified values.

Materials for Trickling Filter Components (Table 1 Highlights)

Notes:

• Materials are chosen for durability and compatibility with wastewater environments.
• Standards referenced ensure quality and consistency (e.g., IS 456 for concrete, IS 226 for steel).

Summary Diagram: Material-Component Relation

graph TD
    A[Trickling Filter Components] --> B[Rotary Distributor]
    A --> C[Filter Media]
    A --> D[Filter Blocks]
    A --> E[Civil Structures]

    B --> B1[Mild Steel (IS 226)]
    B --> B2[Cast Iron (IS 210)]
    B --> B3[High Carbon Steel (IS 226)]
    B --> B4[Fiberglass, PVC]

    C --> C1[Granite, Basalt, Gravel]
    C --> C2[Blast Furnace Slag, Ceramics]

    D --> D1[Vitrified Clay (IS 456)]
    D --> D2[Cement Concrete (IS 456)]

    E

IS 8413 (Part 1) - Definitions and Parameters Summary

Key Definitions (Clause 2.0)

• Defines terms related to trickling filter equipment for uniform interpretation.

Materials for Components (Clause 3.1 & Table 1)

Rounding Off (Clause 0.5)

• Use IS: 2-1960 for rounding test or calculated values with the same significant figures as specified.

Notes:

• Materials are selected per component function and durability.
• Referenced IS codes provide detailed specs for materials.
• No explicit formulas in Clause 2 or 3; focus is on standard materials and definitions.

flowchart TD
    A[Trickling Filter Equipment] --> B[Rotary Distributor]
    A --> C[Filter Media]
    A --> D[Filter Blocks]
    A --> E[Support Piers]
    A --> F[Drainage Channel]
    A --> G[Civil Structure]

    B --> B1[Mild Steel (IS:226)]
    B --> B2[Cast Iron (IS:210)]
    B --> B3[High Carbon Steel (IS:226)]
    C --> C1[Granite, Basalt, etc.]
    D --> D1[Vitrified Clay (IS:456)]
    E --> E1[Cement Concrete (IS:456)]

Essential Parts of Trickling Filters (IS 8413 Part 1)

Clause 4.1 specifies the essential components:

• a) Tank: Rectangular or circular, constructed of concrete/masonry with impervious floor.
• b) Underdrainage: For collection and removal of treated effluent.
• c) Ventilators: To allow air circulation.
• d) Filter Media: Materials such as granite, basalt, blast furnace slag, broken bricks, ceramic cylinders, plastic, etc.
• e) Distributors: Rotary distributors with components made from mild steel, cast iron, and other materials.

Key Materials (Table 1 Highlights)

Notes:

• Filter media must be inert and durable.
• Distributors often have rotary arms with mild steel or cast iron arms, supported on cast steel or high-grade cast iron parts.
• Underdrainage system should ensure uniform flow and avoid clogging.
• Ventilation is critical for aerobic biological action.

Simplified schematic of trickling filter components:

flowchart TB
    Tank[Concrete/Masonry Tank]
    Underdrain[Underdrainage System]
    Ventilators[Ventilators]
    FilterMedia[Filter Media]
    Distributor[Rotary Distributor]

    Tank --> FilterMedia
    FilterMedia --> Underdrain
    Distributor --> FilterMedia
    Tank --> Ventilators

For detailed design, refer to IS 8413 Part 1 (1977) and associated IS codes for materials.

Underdrainage System (IS 8413 Part 1 - Clause 4.3 & 4.3.1)

• Purpose: Collect effluent & provide ventilation in trickling filters.
• Components:
  • Filter blocks: Act as lateral drains (vitrified clay or cement concrete).
  • Supporting piers: Support filter blocks (cement concrete).
  • Main drainage channel: Collects effluent (vitrified clay or cement concrete).

Materials (Refer Table 1)

Painting Specification (Clause 6.1)

• Clean steel surfaces thoroughly.
• Apply 1 coat anticorrosive primer.
• Apply at least 3 coats bitumastic or equivalent anticorrosive paint.
• Alternative: Epoxy or similar coating (see IS:1477 Part I & II).

Key Notes:

• Underdrain blocks act as lateral drains.
• Ventilators spaced @ 200 cm c/c along periphery.
• Use mosquito-proof dome vent shafts for ventilation.
• Materials must conform to relevant IS standards for durability and corrosion resistance.

flowchart TD
    A[Filter Media] --> B[Filter Blocks (Lateral Drains)]
    B --> C[Supporting Piers]
    C --> D[Main Drainage Channel]
    D --> E[Effluent Collection]
    B --> F[Ventilators @ 200 cm c/c]
    F --> G[Mosquito-proof dome vent shaft]

This system ensures efficient drainage and ventilation of trickling filters as per IS 8413 Part 1.

Key Specifications for Ventilators (IS 8413 Part 1 - Clause 4.4):

• Spacing: Ventilators shall be provided along the entire periphery of the filter at 200 cm centre-to-centre.
• Diameter: Each ventilator must have a diameter greater than 100 mm.
• Elevation: Ventilators should be raised 75 mm above the media top.
• Covering: Each ventilator must be covered with a cowl to prevent ingress of debris and pests.

Painting of Steel Surfaces (Clause 6.1):

• Surfaces must be dry, rust and grease-free.
• Apply one coat of anticorrosive primer.
• Follow with at least three coats of bitumastic or equivalent anticorrosive paint.
• Alternatively, epoxy or similar coatings can be used.
• Refer IS:1477 (Part I & II) for painting practice.

Summary Table: Ventilator Dimensions and Spacing

Materials Reference (for associated components):

• Ventilator pipes: Typically mild steel or structural steel (IS:226-1969).
• Covers/cowls: Should be corrosion resistant or painted as per Clause 6.1.

flowchart LR
    A[Filter Bed Periphery] -->|Ventilators @ 200cm c/c| B(Ventilator Pipes)
    B --> C{Diameter > 100mm}
    B --> D[Raised 75mm above media top]
    B --> E[Covered with Cowl]

This ensures proper aeration and prevents clogging or pest entry into the filter media.

Key Specifications for Filter Media (IS 8413 Part 1 - Clause 4.5)

• Ideal Filter Medium Characteristics:

  • High surface area per unit volume.
  • Should not clog easily.
  • Typically locally available crushed stone or gravel.
  • Other materials: slag, cinders, hard coal.

• Materials Used (Table 1, Clause 3.1):

  Component	Material	IS Code Reference
  Filter Media	Granite, gneiss, basalt, trap, gravel, blast furnace slag, broken hard bricks, ceramics, plastic, slate, inert blocks	-
  Filter Blocks	Vitrified clay or cement concrete	IS : 456-1964
  Support Piers	Cement concrete	IS : 456-1964
  Drainage Channel	Vitrified clay or cement concrete	IS : 456-1964

• Additional Notes:

  • Filter media must be inert and durable.
  • Particle size and gradation should ensure proper voids for air and water flow.
  • Sodium Sulphate Test is recommended to check durability.

Summary Table: Filter Media Properties

Conceptual Diagram: Filter Media Layer

flowchart TD
    A[Influent Wastewater] --> B[Filter Media Layer]
    B --> C[Microbial Growth on Media Surface]
    C --> D[Effluent Water]
    B -.-> E[Air Circulation Through Voids]

This shows wastewater passing through filter media with microbial action and air voids for aerobic treatment.

For detailed design, particle size gradation, and test procedures, refer to IS 8413 Part 1 and related IS codes (e.g., IS 456 for concrete).

IS 8413 Part 1: Key Specifications for Distributors

1. Types of Distributors (Clause 4.6.1)

• Rotary Distributors:
  • Hydraulic-reaction-driven (Fig. 2 reference)
  • Motor-driven rotary
• Other Types:
  • Fixed-spray nozzles
  • Longitudinal travelling distributors

2. Rotary Distributor Speed (Clause 4.6.1.3)

• Two-arm distributors: ~2 rev/min
• Four-arm distributors: ~1.4 rev/min
• Speed must stay within agreed max/min limits for max/min flow conditions.

3. Motor-Driven Rotary Distributor (Clause 4.6.1.2)

• Construction similar to reaction type but arms rotated by motor + reduction gear.
• Motor speed fixed; comply with IS 325-1970 or IS 996-1964.
• Motor located centrally requires walkway access for maintenance even during rotation.

Summary Table: Rotary Distributor Speeds

flowchart LR
    A[Wastewater Distributors] --> B[Rotary Distributors]
    A --> C[Fixed-spray Nozzles]
    A --> D[Longitudinal Travelling Distributors]
    B --> E[Hydraulic-reaction Rotary]
    B --> F[Motor-driven Rotary]
    F --> G[Motor + Reduction Gear]
    G --> H[Fixed Speed Motor (IS 325/996)]

This concise overview aligns with IS 8413 Part 1 clauses for distributor design and operation.

Key Specifications & Formulas for Dozing Siphons (IS 8413 Part 1)

1. Purpose:

• Provide intermittent spray of waste water in standard rate filters with fixed nozzle distributors.
• Maintain minimum head for distributor operation during variable gravity flows.

2. Dozing Tank Size:

• Minimum detention time: 2 to 2.5 minutes at maximum flow rate.
• Drawdown depth: 250 to 300 mm.
• Tank depth: At least 150 mm below low water level.

3. Elevation Requirements:

• High water level in tank: 600 to 1350 mm above orifice level in distribution arm.
• Low water level: At least 300 mm above distribution orifices.
• For standard rate filters with fixed nozzles: high water level ~3 m, low water level ~1.5 m above orifices.

4. Construction Details:

• Siphon bell supported on legs anchored to tank floor.
• Cast iron feed and overflow pipes above tank floor.
• Mild steel control pipe with cast iron fittings between bell and overflow.
• Sniff pipe with mild steel guard for air entry.

5. Painting:

• Steel surfaces: one coat primer + three coats bitumastic or epoxy (per IS 1477 Part I & II).

Typical Dozing Siphon Tank Dimensions & Flow

Conceptual Diagram of Dozing Siphon Tank

flowchart TB
    A[High Water Level] -->|600-1350 mm| B(Orifice in Distribution Arm)
    B -->|≥300 mm| C[Low Water Level]
    C -->|≥150 mm| D[Bottom of Dozing Tank]
    E[Siphon Bell] -.-> B
    F[Sniff Pipe] -.-> E
    G[Overflow

IS 8413 Part 1 - Painting & Corrosion Protection Summary

Key Specifications (Clause 6.1):

• Surface Preparation: Steel surfaces must be thoroughly dried and free from rust and grease before painting.
• Primer: Use a suitable anticorrosive primer.
• Coating: Apply one coat of primer followed by at least three coats of bitumastic or other anticorrosive paints after erection.
• Alternative Coatings: Epoxy or similar coatings may be considered.
• Reference Codes:
  • IS 1477 (Part I) - Pretreatment
  • IS 1477 (Part II) - Painting

Painting Procedure Overview:

Typical Anticorrosive Paint System:

• Primer: Zinc chromate or red oxide primer (as per IS 1477)
• Finish: Bitumastic or epoxy coating for long-term protection

Additional Notes:

• Proper surface prep is critical for paint adhesion and corrosion resistance.
• Bitumastic paints provide good water resistance and durability.
• Epoxy coatings offer superior chemical and abrasion resistance.

flowchart TD
    A[Steel Surface] --> B[Surface Cleaning]
    B --> C[Apply Anticorrosive Primer]
    C --> D[Apply 3 Coats of Bitumastic/Epoxy Paint]
    D --> E[Protected Steel Surface]

For detailed paint specifications, refer to IS 1477 (Parts I & II).

Sodium Sulphate Test on Filter Media (IS 8413 Part 1)

Test Procedure (Clause A-1.1)

1. Sample Preparation:

   • Select minimum 10 pieces randomly.
   • Dry at 105 ± 5°C for 4 hours.
   • Weigh dry pieces.

2. Immersion:

   • Immerse pieces in concentrated sodium sulphate solution (400 g/L).
   • Maintain solution temperature between 20°C to 30°C.
   • Soak for 16 to 18 hours.

3. Drying Cycle:

   • Remove, air dry for 30 minutes.
   • Oven dry again at 105 ± 5°C for 4 hours.
   • Cool for 1 hour.

4. Repetition:

   • Repeat test 20 times for media from top 450 mm depth.
   • Repeat 10 times for media from deeper layers.

Acceptance Criteria (Clause 12.5)

• Media is unsuitable if:
  • More than 10% by mass of tested pieces fail.
  • Material passing a 12.5 mm sieve exceeds 10% by mass.
• High silica content media must be tested for soundness.

Summary Table

This test ensures filter media durability against chemical attack and freeze-thaw cycles, crucial for long-term filter performance.