🔷 METAL USED IN WATER & WASTEWATER TREATMENT PLANTS
🟦 1. Mild Steel (MS)
Most common industrial
🔧 Material
- Carbon steel / Mild steel
- Often rubber-lined, epoxy-coated, or FRP-lined
🏭 Typical Tank Types
- Raw water
- Equalization (ET)
- Neutralization
- Flash mixing
- Chemical solution (with lining)
- Sludge holding
✅ Advantages
- Low cost
- Easy fabrication
- Large sizes possible
❌ Limitation
- Corrosion if not lined
🟦 2. Stainless Steel (SS)
High-purity & corrosion-resistant
🔧 Grades Used
- SS 304 – potable water
- SS 316 / 316L – chemicals, high chloride
- SS 904L – aggressive wastewater (rare)
🏭 Typical Tank Types
- DM / RO permeate
- Treated water storage
- Chemical dosing
- CIP
- Ozone contact
- Food & pharma water
✅ Advantages
- Excellent corrosion resistance
- Hygienic
- Long life
❌ Limitation
- High cost
🟦 3. Galvanized Iron (GI)
Zinc-coated steel
🔧 Material
- Hot-dip galvanized steel
🏭 Typical Tank Types
- Potable water storage
- Overhead water
- Utility water
✅ Advantages
- Corrosion resistant (moderate)
- Cheaper than SS
❌ Limitation
- Not suitable for aggressive wastewater
🟦 4. Bolted Steel
Factory-coated modular
🔧 Materials & Coatings
- Glass-Fused-to-Steel (GFS / GLS)
- Epoxy-coated steel
- Fusion-bonded epoxy
🏭 Typical Tank Types
- Raw sewage
- Aeration
- Clarifiers
- Sludge digesters
- Equalization
✅ Advantages
- Fast installation
- Long service life
- Large capacity
❌ Limitation
- Higher initial cost than RCC
🟦 5. Aluminum
Lightweight & corrosion resistant
🏭 Typical Tank Types
- Portable water
- Temporary storage
- Small utility
✅ Advantages
- Lightweight
- Corrosion resistant
❌ Limitation
- Low strength
- Rare in wastewater plants
🟦 6. Duplex & Super Duplex Stainless Steel
Extreme corrosion environments
🔧 Grades
- Duplex 2205
- Super Duplex 2507
🏭 Typical Tank Types
- Seawater intake
- Desalination plants
- High chloride wastewater
✅ Advantages
- Very high corrosion resistance
- High strength
❌ Limitation
- Very expensive
🟦 7. Alloy Steel
Special industrial applications
🔧 Materials
- Nickel alloys
- Hastelloy
- Inconel (rare in water sector)
🏭 Typical Tank Types
- Highly corrosive chemical
- Special industrial effluent
🟦 8. Carbon Steel with Internal Lining
Hybrid solution (very common)
🔧 Linings Used
- Rubber lining
- HDPE lining
- FRP lining
- PU lining
🏭 Typical Tank Types
- Acid storage
- Alkali
- Chemical mixing
- Sludge
🟦 9. Steel Clarifiers & Thickeners
Structural steel
🏭 Applications
- Primary clarifiers
- Secondary clarifiers
- Lamella clarifiers
- Sludge thickeners
🔧 Material
- MS / GFS / Epoxy-coated steel
🟦 10. Pressure Vessels (Metal)
Closed under pressure
🔧 Materials
- MS
- SS 304 / 316
🏭 Applications
- Pressure sand filters (PSF)
- Activated carbon filters (ACF)
- Softener vessels
- RO feed (pressurized)
✅ QUICK SUMMARY TABLE
| Material | Typical Use | Cost | Corrosion Resistance |
| MS | ET, sludge | Low | Low (needs lining) |
| SS 304/316 | Treated water | High | High |
| GI | Potable storage | Medium | Medium |
| GFS | STP | Medium–High | Very High |
| Aluminum | Portable | Medium | Medium |
| Duplex SS | Seawater | Very High | Excellent |
🎯 INDUSTRY PRACTICE (Important)
- STP / ETP: RCC + GFS steel
- RO & DM: SS
- Chemical storage: MS + rubber lining
- ZLD: DTRO + GFS + SS combination