NaOH Dosing Guide for Wastewater Treatment -- pH Control & Coagulation

In wastewater treatment, NaOH (caustic soda) is a sin alkaline chemical that plays an important role in pH adjustment, heavy metal removal, and supporting precipitation of pollutants. This process helps increase wastewater treatment efficiency and reduce negative impacts on the environment. Below is a detailed guide on the correct way to dose NaOH for optimal results.

Identifying NaOH Chemical

NaOH, also known as caustic soda, is a sinly alkaline chemical widely used in many industries, including wastewater treatment, paper production, soap manufacturing, and many others—particularly NaOH in wastewater treatment, where it is used to adjust pH, remove heavy metals, and support the settling process. NaOH (caustic soda, caustic flakes, liquid caustic) is an important industrial chemical with sin alkalinity, commonly applied in wastewater treatment, paper production, soap manufacturing, textile dyeing, and many other industries.

In wastewater treatment, NaOH helps neutralize acids, adjust pH, and precipitate heavy metals so they can be easily removed from the water. To identify NaOH in a laboratory or in industrial applications, here are a few basic and effective methods:

• Litmus paper test: Litmus paper turns a deep blue when it comes into contact with NaOH solution, confirming the sin basicity of NaOH.






• Phenolphthalein indicator: Phenolphthalein pH indicator turns deep pink in an alkaline environment when NaOH is present.






• Visual inspection: NaOH exists as a white solid (caustic flakes, caustic pearls) or a clear solution (liquid NaOH). When dissolved in water, it produces a sinly exothermic reaction that can heat up the container.

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How to Dose NaOH for Wastewater Treatment

Correctly dosing NaOH ensures effective wastewater treatment and reduces the risk of chemical accidents. Follow these steps:

• Step 1: Safety Preparation
  
  
  
  • Work in a well-ventilated space or one equipped with an extraction system to minimize inhalation of chemical vapors.
  
  

  
  

  • Wear safety goggles, rubber gloves, and an air-filtering mask, and avoid direct contact with solid NaOH or liquid NaOH vapor.
  
  

  
  

  • Work in a well-ventilated area with an extraction system or fans.
  
  

  
  

  • Do not touch NaOH with bare hands, as it can cause severe skin burns.
  
  
  
  






• Step 2: Calculating the Required Amount of NaOH
  
  
  
  • Determine the volume of wastewater to be treated and the desired pH level.
  
  

  
  

  • Calculate the amount of NaOH to add to the wastewater based on its current pH and the target pH.
    
    
    
    • General formula for calculating the required amount of NaOH
      
      
      
      • Mass of NaOH (g) = (C×V×M/100
      
      

      
      

      • Where:
        
        
        
        • C: Desired NaOH solution concentration (%)
        
        

        
        

        • V: Volume of solution to be prepared (ml)
        
        

        
        

        • M: Molar mass of NaOH = 40 g/mol
        
        

        
        

        • 100: Conversion factor from percentage (%) to the appropriate unit
        
        
        
        
      
      
      
      
    
    

    
    

    • Formula for calculating the volume of solution to prepare from a given mass of NaOH
      
      
      
      • If you already have the mass of NaOH and want to calculate the volume of solution needed:
        
        
        
        • Volume of solution (ml) = (Mass of NaOH (g) × 100) / (C × M)​​​
        
        
        
        
      
      
      
      
    
    
    
    
  
  

  
  

  • Example: To prepare 500L of 10% NaOH solution, you need: (10×500×10)/40 = 50kg of NaOH
  
  
  
  






• Step 3: Preparing the NaOH Solution
  
  
  
  • Use NaOH solution at an appropriate concentration, typically ranging from 10% to 50%, depending on the level of alkalinity needed to adjust the wastewater's pH.
    
    
    
    • Important rule: Always pour NaOH into water, NEVER the other way around!
    
    

    
    

    • Dilute step by step: Use distilled or deionized water, adding NaOH slowly to avoid a sinly exothermic reaction.
    
    

    
    

    • Stir continuously with a glass rod or mechanical stirrer until the NaOH is fully dissolved.
    
    
    
    
  
  
  
  






• Step 4: Adding NaOH to the Wastewater
  
  
  
  • Slowly and gently add the prepared NaOH solution to the wastewater. Stir continuously to ensure even distribution of NaOH throughout the wastewater.
  
  

  
  

  • Monitor the pH of the wastewater after adding NaOH and continue adjusting until the desired pH is reached.
  
  
  
  






• Step 5: Checking and Adjusting
  
  
  
  • After adding NaOH and stirring thoroughly, re-check the pH of the wastewater. If needed, adjust the amount of NaOH or water added to achieve the desired result.
  
  
  
  

Applications of NaOH in Wastewater Treatment

• pH adjustment: Industrial wastewater often contains large amounts of acid, and NaOH is used to neutralize these acids, helping bring the pH back to neutral or slightly alkaline, creating favorable conditions for subsequent treatment steps.






• Heavy metal removal: Heavy metal precipitation—NaOH can react with heavy metals in wastewater to form insoluble or poorly soluble hydroxides. These hydroxides can then be removed through precipitation, settling, or filtration.






• Supporting precipitation and settling: Creating an alkaline environment—some precipitation or settling processes only occur effectively in an alkaline environment. NaOH helps create these conditions, enhancing the removal of solids and other pollutants from water.

Where to Buy Affordable 10% - 50% NaOH?

If you're wondering where to buy NaOH in Ho Chi Minh City, or where to buy NaOH in Binh Duong or Dong Nai, please contact Loc Thien Chemicals. We supply genuine chemical products in Vietnam that meet factory quality standards. With the advantage of a network of 6 warehouses in Ba Ria – Vung Tau, Dong Nai, Binh Duong, Da Nang, Can Tho and Bac Ninh, combined with a young, dedicated technical team, we always bring customers quality products and the most satisfying consultation.

• Reasonable prices. Abundant, high-quality supply.






• Nationwide supply — fast delivery straight to your location.

When you choose Loc Thien's products, we guarantee to bring your business and production the highest efficiency, while saving you money and the time spent sourcing chemicals. Feel free to call us anytime you need our products or would like consultation. Our hotline 0979 89 19 29 is always ready to listen to your needs.