>>Application
This method is suitable for wastewater with a chemical oxygen demand (COD) ranging from 10 to 5000 mg/L and chloride ion (Cl-) concentrations below 2 g/L. Based on actual user requirements, it can also be applied to wastewater with chloride ion (Cl-) concentrations below 20 g/L.
>>Technical parameters
1. Method Basis: National Standard HJ 828-2017 "Water Quality-Determination of Chemical Oxygen Demand-Potassium Dichromate Method".
2. Measurement Range: 10-5000 mg/L.
3. Indication Error: ≤±8% for concentrations <100 mg/L; ≤±5% for concentrations ≥100 mg/L.
4. Repeatability: ≤5%.
5. Measurement Cycle: Minimum digestion time of 30 minutes; adjustable between 10-30 minutes based on actual water samples.
6. Sampling Cycle: Interval measurement (adjustable from 20-9999 minutes) or fixed-point measurement modes.
7. Calibration/Verification Cycle: Adjustable at any interval (1-99 days) and time.
8. Maintenance Cycle: ≥168 hours; each maintenance takes ~1 hour.
9. Reagent Consumption: <0.5 yuan/sample.
10. Output: RS-232, 4-20 mA, RS-485.
11. Environmental Requirements: Temperature-controlled indoor environment (5-40°C recommended); humidity 45-85%.
12. Power Supply: AC220±10% V, 50±1% Hz, 5A.
13. Dimensions: H1500 × W500 × D450 (mm).
14. Additional Features:
- Data retention during alarm or power failure;
- Touchscreen display and command input;
- Automatic residual reactant discharge and state recovery after power restoration or abnormal reset.
>>Feature
Unique Design: This product features a distinctive design that ensures lower failure rates, reduced maintenance requirements, minimal reagent consumption, and higher cost-effectiveness compared to similar products.
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Selector Valve Assembly:
- Enables flexible reagent sampling timing and diverse channel configurations.
- Minimizes dead volume for easy maintenance and extended service life.
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Micro-Dosing Unit:
- Utilizes a visual photoelectric system for precise reagent measurement, eliminating quantitative errors caused by peristaltic pump tube wear.
- Achieves accurate micro-dosing with 0.7 mL per dose, significantly reducing reagent usage.
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Sample Introduction Unit:
- Employs a peristaltic pump with negative pressure suction, creating an air buffer zone between reagents and the pump tube to prevent corrosion.
- Simplifies and enhances flexibility in reagent mixing.
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Sealed Digestion Unit:
- Operates under high-temperature and high-pressure conditions to accelerate reactions.
- Eliminates corrosion risks from volatile gases in open systems.
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Reagent Tubing:
- Uses imported modified PTFE (polytetrafluoroethylene) transparent tubing with an inner diameter >1.5 mm to minimize clogging by particulate matter in water samples.
>>Analytical Principle
The mixture of the water sample, potassium dichromate digestion solution, silver sulfate solution (added as a catalyst to enhance oxidation of linear aliphatic compounds), and concentrated sulfuric acid undergoes high-temperature digestion. During this process, the dichromate ions oxidize organic matter in the solution, causing a visible color change. The analyzer detects this colorimetric shift and converts it into a corresponding COD (Chemical Oxygen Demand) value for output.
