testing method of WWTP parameters using labs
- 1. COD Closed Reflux, Colorimetric method Two reagents need for COD • Digestion solution • Sulfuric acid reagent Digestion solution preparation ( High range) Required Chemicals and apparatus Pottasium Dichromate (K2Cr2O7) Mercuric Sulphate ( HgSO4) conc. Sulfuric acid Distilled water
- 2. Apparatus • 1000 ml Volumetric Flask • Glass rod • Funnel About 10.216g K2Cr2O7 ( Primary standard grade, previously dried at 150 °C for 2h) was added in to the 1000 ml volumetric flask. Then 500 ml distilled water was added in to it and mixed well. After that 167 ml conc. Sulfuric acid was added gently in to it. About 33.3 g HgSO4 was added and dissolved. Solution was cooled to room temperature and dilute to 1000 ml by using distilled water.
- 3. Sulfuric acid Reagent preparation Required Chemicals and apparatus • Silver Sulfate ( Ag2SO4) • Sulfuric acid Apparatus • 500 ml beaker • Glass rod
- 4. • Add Ag2SO4 powder, to Conc. Sulfuric acid at the rate of 5.5g Ag2SO4/Kg H2SO4. Let stand 1 to 2 d to dissolve. • Conversion of H2SO4 mass to volume Density= 𝑚𝑎𝑠𝑠 𝑉𝑜𝑙𝑢𝑚𝑒 1.83 gcm-3 = 1000 𝑔 𝑉𝑜𝑙𝑢𝑚𝑒 = 546.44 ml 5.5 g Ag2SO4 was added in to the 500 ml beaker and 546.44 ml H2SO4 was added in to it. Let stand 1 to 2 days to dissolve.
- 5. Vial Preparation • 2.5 ml waste water sample was added in to the COD vial. 1.5 ml digestion solution was added in to it. After that 3.5 ml sulfuric acid reagent was added in to the vial and mixed well. Blank preparation 2.5 ml distilled water was added in to the COD vial. 1.5 ml digestion solution was added in to it. After that 3.5 ml sulfuric acid reagent was added in to the vial and mixed well.
- 6. Digest the sample • COD digester machine was preheated at 150 °C. After that vials were placed in to the machine and maintained 150 °C for 2h. Finally vials were cooled to room temperature and read the value using colorimeter. • Reference: