Precise Chemical Dosing Guide for Wastewater Operation & Maintenance
1. Acidic Wastewater pH Correction | Sodium Hydroxide (NaOH)
Application: Low pH wastewater affecting biological treatment, coagulation efficiency, and microbial survival.
Dosing Method:
Prepare a diluted alkaline solution before dosing. Never add solid NaOH directly into water. Dose slowly in a mixing tank while continuously monitoring pH. Maintain pH within 6.5–8.5 for optimal biological performance.
Key Advantage: Fast pH adjustment, cost-effective, suitable for automated continuous dosing systems.
2. Alkaline Wastewater Neutralization | Citric Acid
Application: Excessively high pH wastewater; strong acid dosing may shock biological systems.
Dosing Method:
Dissolve citric acid in water and dose gradually in multiple small increments. Avoid sudden pH drops to protect activated sludge.
Key Advantage: Mild and safe acid adjustment, low corrosion risk, ideal for small and packaged wastewater treatment systems.
3. Pipeline & Equipment Descaling | Oxalic Acid
Application: Scaling in pipelines, tanks, sedimentation basins, and heat exchange systems caused by calcium and magnesium deposits.
Dosing Method:
Use circulation or soaking cleaning. After cleaning, neutralize wastewater with NaOH before discharge. Acidic cleaning waste must not enter biological treatment directly.
Key Advantage: Strong removal of hard inorganic scale, restores hydraulic capacity and equipment efficiency.
4. Effluent Decolorization | Specialized Color Removal Agent
Application: Textile, chemical, and coating wastewater with visible color exceeding discharge limits.
Dosing Method:
Conduct jar testing to determine optimal dosage. Apply in coagulation tanks together with flocculants for enhanced color removal and sludge formation.
Key Advantage: Rapid decolorization without process modification, widely applicable across industrial wastewater types.
5. Antiscalant & Chelation Control | Sodium Gluconate
Application: High-hardness water systems prone to scaling, membrane fouling, and corrosion.
Dosing Method:
Continuous dosing in pre-treatment stages. Chelates calcium, magnesium, and iron ions to prevent scale formation and protect pumps, pipelines, and membranes.
Key Advantage: Dual function of scale inhibition and corrosion protection; environmentally friendly and suitable for long-term operation.
6. Dechlorination & Oxidant Removal | Sodium Bisulfite (NaHSO₃)
Application: Residual chlorine, excess oxidants (e.g., H₂O₂), and high ORP conditions that may damage biological systems.
Dosing Method:
Dose after oxidation units and before biological treatment. Ensure full mixing to neutralize oxidants and reduce ORP levels.
Key Advantage: Protects microbial activity and stabilizes biological treatment performance.
7. Carbon Source Supplement & Bioactivation | Compound Carbon Source
Application: Insufficient organic carbon, poor sludge activity, high TN levels, slow system startup, or sludge disintegration.
Dosing Method:
Directly dose into anoxic or aerobic tanks to balance C/N ratio and enhance microbial growth and denitrification efficiency.
Key Advantage: Safer and more cost-effective than traditional methanol or sodium acetate, with better microbial adaptability.
General Operational Guidelines：
Store acid, alkali, oxidants, and reductants separately; never mix chemicals.
Perform jar tests before large-scale dosing to optimize dosage and reduce cost.
Use proper PPE when handling corrosive chemicals.
Follow a logical sequence:
Water quality adjustment → scaling removal → decolorization → biological stabilization
Conclusion：
Effective wastewater treatment is not about excessive chemical use, but precise and targeted dosing based on real operating conditions.
These seven core chemicals cover the full cycle of wastewater O&M—from pH control and equipment protection to biological stability and effluent compliance—helping operators reduce costs while ensuring stable discharge performance.