Wastewater pH-adjusting calcium carbonate is mainly ground calcium carbonate (GCC). It features low production cost, moderate alkalinity release, mild neutralization effect and stable pH regulation. It is widely used to neutralize acidic industrial wastewater, mine drainage, printing & dyeing wastewater and electroplating wastewater. Its purity standard is lower than drinking water grade, focusing on reaction speed and practical treatment effect.
1. Raw Material Selection
- Preferred raw material: Ordinary calcite, limestone with CaCO₃ ≥ 92%
- Impurity control: Low clay, low mud content; properly limit iron and manganese content to avoid water discoloration
- Reject ore with excessive silicon, sulfur and heavy metals that exceed wastewater discharge limits
- No need for high-purity premium ore to cut raw material cost
2. Standard Production Process Flow
Step 1 Primary Crushing
Crush raw limestone into 10–30 mm small stones by jaw crusher to facilitate secondary breaking.
Step 2 Secondary Crushing
Use hammer crusher or cone crusher to crush materials into 2–8 mm particles.
Step 3 Target Fine Grinding
Produce two mainstream specifications according to wastewater dosing ways:
- Granular type (1–3 mm)
Used for filter tank contact neutralization, slow alkali release, long-term steady pH adjustment
- Fine powder type (D50: 15–35 μm)
Easy to prepare water slurry, fast neutralization reaction, suitable for rapid on-site pH correction
Common equipment: Raymond mill, vertical roller mill
Step 4 Simple Impurity Removal
Adopt magnetic separation to remove iron impurities; simple water washing to remove surface dust, no deep purification required.
Step 5 Low-cost Drying
Dry materials to moisture content ≤1.0% via natural airing or low-temperature hot air drying.
Step 6 Grading and Screening
Classify finished products by particle size, pack separately for different wastewater treatment usage.
3. Optional PCC Production (Rarely Used)
Precipitated calcium carbonate has finer particle size and faster neutralization speed, but high production cost. It is only used for special wastewater requiring rapid pH rise.
Process: Limestone calcination → quicklime digestion → carbonation precipitation → filter pressing → drying → grinding into finished powder.
4. Core Quality Index for Wastewater pH Adjustment
- Calcium carbonate content: ≥92%
- Moisture: ≤1.0%
- Acid insoluble substance: ≤3.0%
- Particle size: adjustable per treatment demand
- Low soluble salt content, avoid increasing wastewater salinity sharply
- Harmful substances meet industrial wastewater treatment auxiliary standards
5. Key Production Control Points
- Adjust grinding fineness freely: finer powder = faster pH rising; coarse grain = slow and lasting neutralization
- Simplify production procedures, cancel high-precision classification and deep purification to reduce overall cost
- Prevent fine powder caking to ensure smooth slurry mixing and pipeline conveying
- Strictly control raw ore mud content to avoid pipeline blockage and excessive sludge output
6. Neutralization Reaction Principle
CaCO₃ + 2H⁺ = Ca²⁺ + CO₂↑ + H₂O
It steadily consumes hydrogen ions in acidic wastewater, gently raises pH value, effectively avoids over-adjustment caused by strong alkali, and produces less sludge than lime.
7. Production Advantages
- Abundant raw materials and low manufacturing cost
- Mild neutralization, easy pH value control
- Less sludge generation, lower subsequent sludge treatment cost
- Stable chemical property, convenient storage and transportation
- Compatible with most types of acidic wastewater treatment systems