Requirements for sludge dewatering equipment, Part I: Sludge drying beds-sand, gravel and underdrains
1981 Edition

Overview of IS 10037 Part 1 (1981) – Summary and Core Requirements

Scope:

• Defines requisites for sludge drying beds employing sand, gravel, and underdrain materials for dewatering treated sludge.
• Excludes alternative media types.

Objective:

• To guide selection of suitable sand, gravel, and underdrain components.
• Illustrates a typical sludge drying bed cross-section (Fig. 1) featuring pipes beneath gravel layers.

Key Highlights:

• Sand and gravel serve as filtration and drainage strata.
• Beds may be exposed to sunlight or enclosed.
• Aligns with international standards and Indian practical applications.
• Values rounded off according to IS 2-1960.

Typical Layer Arrangement (Fig. 1)

Important Notes:

• Proper selection of sand and gravel gradation is vital for optimal dewatering efficiency.
• Underdrain design must prevent clogging and allow free filtrate flow.
• Maintenance and operational practices significantly affect performance.

For specific grain size ranges or underdrain design data, detailed documents are available.

Scope Description for IS 10037 Part 1 (1981): Sludge Drying Beds

Coverage Summary:

• Addresses specifications for sludge drying beds utilizing sand, gravel, and underdrain systems as dewatering media.
• Applicable to both open-to-sunlight and covered beds.
• Excludes synthetic or alternative media types.
• Provides guidance on selecting sand, gravel, and underdrain materials.
• Includes typical cross-section details (refer to Fig. 1).

Core Specifications:

• Dewatering media: Sand and gravel meeting specified gradation and quality criteria.
• Underdrains: Proper design to effectively collect filtrate while avoiding blockages.
• Bed design: Layered structure with sand above gravel and underdrain piping beneath.
• Value rounding: Per IS 2-1960 standards.

Conceptual Cross-Section (Fig. 1)

graph TD
  A[Sludge Layer] --> B[Sand Layer]
  B --> C[Gravel Layer]
  C --> D[Underdrain Pipes]
  D --> E[Drain Outlet]

Additional Remarks:

• Part of a series on sludge dewatering equipment guidelines.
• Harmonizes with global standards and Indian field practices.
• Historical price noted as Rs 5.00.

Refer to the complete IS 10037 Part 1 for detailed gradation tables and design calculations.

Definitions and Key Concepts in IS 10037 Part 1 (1981) for Sludge Drying Beds

• Scope: Pertains to sludge drying beds employing sand, gravel, and underdrain elements for sludge dewatering.
• Dewatering Media: Limited to sand and gravel; other media excluded.
• Typical Cross-Section: Features sand and gravel layers with underdrain piping as depicted in Fig. 1.
• Rounding of Values: Testing and calculation results must follow IS 2-1960 rounding rules, consistent with significant figures.

Essential Terms (Clause 2.0):

• Sludge Drying Bed: Structure designed for the removal of water from sludge via natural filtration through sand and gravel layers.
• Underdrains: Drainage pipes or channels located beneath gravel to collect filtrate.
• Dewatering Media: The sand and gravel layers facilitating water extraction from sludge.

Typical Layer Thicknesses:

Important Notes:

• Sand must be clean, well-graded, and free of organic contaminants.
• Gravel requires well-graded particles without fines.
• Underdrain design ensures uniform and uninterrupted filtrate collection.

flowchart TB
  A[Sludge Layer] --> B[Sand Layer (300-450 mm)]
  B --> C[Gravel Layer (150-300 mm)]
  C --> D[Underdrain Pipes]
  D --> E[Filtrate Collection System]

See the full IS 10037 Part 1 document for comprehensive design parameters and material criteria.

Specifications for Sand Quality in IS 10037 Part 1

• Minimum Specific Gravity: 2.5 or higher (Clause 3.1.1).
• Silica Content: At least 90%, determined per IS 2000-1962 Method 7.
• Permissible Impurities: Maximum 10% by volume of clay, silt, or loam measured after one hour of settlement in water (per IS 8419 Part 1, Appendix A) (Clause 3.1.2).
• Acid Soluble Matter: Should not exceed 10%, as per solubility testing detailed in IS 8419 Part 1, Appendix B (Clause 3.1.3).

Grain Size Uniformity:

• Uniformity Coefficient (Cu):

[ Cu = \frac{D_{60}}{D_{10}} ]

Where:

• (D_{60}) is particle diameter at 60% finer by weight
• (D_{10}) is particle diameter at 10% finer by weight

This coefficient measures the consistency of grain size distribution (Clause 2.2).

Summary Table:

flowchart LR
  A[Sand Sample] --> B[Grain Size Analysis]
  B --> C{Determine D10 and D60}
  C --> D[Calculate Cu = D60/D10]
  A --> E[Chemical Analysis]
  E --> F[Verify Silica ≥ 90%]
  E --> G[Check Acid Soluble Matter ≤ 10%]
  A --> H[Impurity Testing]
  H --> I[Confirm Impurities ≤ 10%]

These parameters ensure sand suitability for filtration and sludge drying.

Gravel Quality Requirements as per IS 10037 Part 1

• Particle Shape and Size:

  • Gravel particles should ideally be spherical (Clause 4.2.1).
  • Flat, thin, or elongated particles must constitute no more than 2% by volume, where the longest dimension exceeds three times the shortest (Clause 4.1.2).

• Chemical Purity:

  • Acid solubility limits according to IS 8419 Part 1 - 1977, Appendix B:

    Gravel Size	Maximum Acid Solubility (%)
    Less than 10 mm	5%
    10 mm or greater	10%

  • Gravel should be free of excessive limestone or shell fragments (Clause 4.1.3).

• Layer Thickness:

  • Minimum gravel thickness above underdrains is 150 mm (Clause 4.3).
  • The uppermost 80 mm of gravel must be sized between 3 to 6 mm.

Summary Table:

These criteria guarantee effective filtration and structural soundness within drying beds.

Underdrain Requirements According to IS 10037 Part 1 (1981)

Key Design Features:

• Layout (Clause 5.1):

  • Open-jointed lateral and main drains installed on the drying bed floor.
  • Lateral pipes spaced between 3 and 6 meters.

• Material Options (Clause 5.2):

  • Asbestos cement pipes conforming to IS 6908-1975.
  • Concrete pipes per IS 4350-1967.
  • Vitrified clay pipes or tiles.
  • Burnt clay bricks placed on edge.

• Gravel Layer Above Underdrain (Clause 4.3):

  • Minimum depth of 150 mm.
  • Top 80 mm layer comprising 3 to 6 mm gravel.

Typical Underdrain Cross-Section:

graph TB
  A[Sludge Drying Bed Surface]
  B[Sand Layer]
  C[Gravel Layer (min 150 mm)]
  D[Underdrain Pipes (3-6 m spacing)]
  E[Bed Floor]

  A --> B --> C --> D --> E

Notes:

• Open joints are essential for unobstructed drainage.
• Gravel sizing and depth prevent clogging and support filtration.
• Pipe material selection depends on environmental durability and compatibility.

For detailed pipe specifications and mechanical properties, consult IS 6908 and IS 4350.

Construction Parameters for Sludge Drying Beds as per IS 10037 Part 1

Material Specifications:

• Gravel:

  • Hard, preferably rounded stones.
  • Specific gravity ≥ 2.5.
  • Free from clay, sand, loam, and organic impurities (Clause 4.1.1).

• Sand:

  • Hard, durable silica grains.
  • Specific gravity ≥ 2.5.
  • Silica content minimum 90% as per IS 2000-1962 (Clause 3.1.1).

Typical Layer Thicknesses and Functions:

Design Considerations:

• Underdrain system must be adequately installed for efficient drainage.
• Bed slope generally maintained at 1:100 to facilitate flow.
• Bed dimensions depend on sludge volume and drying duration.

flowchart TB
  A[Sludge Layer] --> B[Sand Layer (300-450 mm)]
  B --> C[Coarse Gravel Layer (150-300 mm)]
  C --> D[Fine Gravel Layer (150-300 mm)]
  D --> E[Underdrain System]

This setup ensures efficient sludge dewatering consistent with IS 10037 Part 1 standards.

Sludge Drying Bed Dimension Guidelines per IS 10037 Part 1

Important Specifications:

• Side Walls (Clause 6.1):

  • Constructed from durable brick or stone masonry.
  • Walls extend 40 to 45 cm above bed surface.
  • Extend at least 15 cm below bed surface.
  • Outer walls include kerbing to prevent sand loss.

• Gravel Size (Clause 4.2.2):

  • Gravel used should range between 25 mm and 50 mm.

• Underdrain Pipes (Clause 5.1):

  • Open-jointed laterals and mains laid on bed floor.
  • Lateral spacing from 3 to 6 meters.

Typical Dimensions:

Conceptual Layout Diagram:

graph TB
  A[Sludge Drying Bed] --> B[Side Walls (40-45 cm above surface)]
  A --> C[Sand Layer (30-50 cm)]
  A --> D[Gravel Layer (15-30 cm, size 25-50 mm)]
  A --> E[Underdrain Laterals (3-6 m spacing)]

Summary: Proper masonry ensures containment of sand and prevents erosion. Gravel size and underdrain spacing are critical for efficient drainage. Bed sizes must be tailored to sludge treatment requirements following these baseline parameters.

Procedure to Assess Impurities in Sand as per IS 10037 Part 1

Impurity Limits:

• Maximum 10% by volume of impurities (clay, loam, silt) after one hour settling in water (Clause 3.1.2).
• Acid soluble matter capped at 10% by weight (Clause 3.1.3).
• Specific gravity minimum 2.5 (Clause 3.1.1).
• Silica content must be at least 90% (per IS 2000-1962).

Testing Summary (following IS 8419 Part I - 1977):

1. Impurity Settlement Test:

   • Agitate a measured volume of sand sample in water.
   • Let settle for 60 minutes.
   • Measure the volume occupied by impurities.
   • Calculate impurity percentage by volume: [ %\text{Impurities} = \frac{\text{Volume of impurities}}{\text{Sample volume}} \times 100 ]

2. Acid Solubility Test:

   • Treat sample with dilute hydrochloric acid as per Appendix B.
   • Calculate acid soluble matter percentage based on weight loss: [ %\text{Acid Soluble Matter} = \frac{\text{Weight before} - \text{Weight after}}{\text{Weight before}} \times 100 ]

Additional Notes:

• Refer to IS 8419 (Part I) Appendices A and B for detailed methodology.
• Round values according to IS rounding standards.
• Sand must be durable silica grains (Clause 3.1.1).

flowchart TD
  A[Sand Sample] --> B[Shake in Water]
  B --> C[Settle for 1 Hour]
  C --> D[Measure Impurity Volume]
  D --> E[Calculate % Impurities]
  A --> F[Acid Treatment]
  F --> G[Measure Weight Loss]
  G --> H[Calculate % Acid Soluble Matter]

This process verifies that sand meets the quality criteria for use in sludge drying beds.

Guidelines for Acid Soluble Matter Testing in IS 10037 Part 1

Key Limits from IS 10037 & IS 8419 (Part I) Appendix B:

• Acid soluble matter limits are:
  • Sand: Maximum 10% by weight.
  • Gravel:
    • Less than 10 mm: Maximum 5%.
    • 10 mm or larger: Maximum 10%.

Test Procedure (Summarized from IS 8419 Appendix B):

1. Sample Preparation:

   • Obtain a representative dry sample.
   • Accurately weigh sample (W1).

2. Acid Treatment:

   • Treat with a specified volume of dilute hydrochloric acid.
   • Allow reaction under controlled conditions.

3. Filtration and Washing:

   • Filter out residue and wash to remove soluble components.

4. Drying and Reweighing:

   • Dry residue and weigh (W2).

5. Calculation:

[ %\text{Acid Soluble Matter} = \frac{W_1 - W_2}{W_1} \times 100 ]

Limits Summary:

Notes:

• Acid soluble matter includes carbonates, shells, and limestone impurities.
• Excessive acid solubility indicates risk of poor durability.
• Follow IS 8419 Part I for exact test conditions and acid concentrations.

flowchart TD
  A[Initial Weighing W1] --> B[Acid Treatment]
  B --> C[Filtration and Washing]
  C --> D[Residue Drying and Weighing W2]
  D --> E[Calculate % Acid Soluble Matter]

This test ensures chemical stability of sand and gravel for sludge drying bed applications.