Physical Properties
The following table outlines the key physical characteristics of walnut shell filter media, based on standard industry data.
| Property | Value/Description |
|---|---|
| Specific Gravity | 1.2 – 1.4 |
| Bulk Density | 0.85 g/cm³ (approximate) |
| Hardness (Mohs Scale) | 2.5 – 3.0 |
| Grain Shape | Angular, multi-faceted |
| Color | Light brown |
| Moisture Content | ≤ 11% by weight |
| pH Value | 7.5 (neutral) |
| Charring Temperature | 243°C (470°F) |
| Attrition Rate | < 5% per year |
Chemical Composition
Walnut shell filter media is composed of natural organic compounds, ensuring it is non-toxic, biodegradable, and chemically inert. The typical chemical makeup is as follows:
| Component | Percentage (%) |
|---|---|
| Nitrogen | 0.10 |
| Cellulose | 40 – 60 |
| Lignin | 20 – 30 |
| Toluene Solubility | 0.5 – 1.0 |
| Methoxyl | 6.5 |
| Chlorine | 0.10 |
| Ash | ≤ 1.5 |
Available Particle Sizes
Walnut shell filter media is available in various granular sizes to suit specific filtration requirements. Sizes are typically specified in U.S. Mesh or metric equivalents. Common sizes include:
- 6/10 Mesh (3.36 – 2.00 mm)
- 8/12 Mesh (2.38 – 1.68 mm)
- 12/20 Mesh (1.68 – 0.84 mm)
- 20/30 Mesh (0.84 – 0.59 mm)
- 30/60 Mesh (0.59 – 0.25 mm)
Custom sizes can be provided upon request. For water filtration applications, 12/20 or 12/16 Mesh is commonly recommended for optimal performance in removing hydrocarbons and solids.
Performance Data
Walnut shell filter media demonstrates high efficiency in deep-bed filtration systems. Key performance metrics include:
- Suspended Solids Removal: 95% – 99% (effective down to 5 microns)
- Insoluble Hydrocarbons Removal: 90% – 99%
- Oil Discharge Levels: Typically ≤ 5 ppm
- Filtration Flux Rate: 10 – 12 gpm/ft² (higher than sand or anthracite filters)
- Backwash Efficiency: Requires 0.5% – 1% of throughput volume; media regenerates fully without chemicals or air sparging
- Service Life: Media lasts the lifetime of the filter with minimal replacement (5% – 10% annually if needed)
- Filtering Speed: 25 – 30 m/h
- Backwashing Strength: 6 – 7 L/s·m²
These parameters ensure reliable operation with >99% uptime in demanding environments.
Applications
Walnut shell filter media is versatile and suitable for a range of water treatment scenarios, including:
- Produced water treatment in oil and gas industries
- Industrial wastewater filtration for removing oil, grease, and suspended solids
- Groundwater remediation and surface water polishing
- Cooling water recycling in manufacturing and power generation
- Municipal and petrochemical liquid treatment for suspended solids, oily residues, ash, and metallic hydroxides
It is compatible with multimedia filters, sand filters, and activated carbon systems, enhancing overall filtration efficiency.
Key Advantages
- High Oil Absorption: 2-3 times greater than traditional sand media, preventing clogging and mudball formation.
- Durability and Low Maintenance: Angular shape and high strength result in low breakdown; media can be reclaimed and reused multiple times.
- Environmental Benefits: Natural, biodegradable, and non-toxic; reduces chemical usage and waste.
- Cost Efficiency: Higher throughput reduces equipment size and operational costs; efficient backwashing minimizes water consumption.
Certifications and Standards
Walnut shell filter media complies with relevant industry standards to ensure quality and safety:
- AWWA B100 for granular filter material quality
- GSA Specification AA-1722 Type 2
- MIL-G-5634 Type 3 MIL-G-5634 3
- NSF/ANSI certified for drinking water applications
