• W3111 COD Online Analyzer
W3111 COD Online Analyzer
W3111 COD Online Analyzer
Wet-Chemical Determination of Chemical Oxygen Demand (COD, Dichromate Method) Concentraion in Waste Water
• Based on a 24-bit high-resolution A/D converter
• Automatic sampling analysis and auto-calibration
• Measuring cycle time adjustable
• Wet chemistry analysis with Potassium Dichromate Reflux method
• Quantitative syringe system for precise dosing
• Sampling valve can resist high temperature, corrosion, acid, and alkaline
• Self-diagnosis & friendly calibration setting
• User-friendly graphical interface
• Highly stable and accurate with a wide measuring range
• 7” LCD color touch panel display
• Reagents free and cost-saving
• Simultaneously display parameters of Ammonia and analysis cycle time
• Language support in English and Chinese
• Automatic data storage with capacity up to 5000 historical records. (User could expend memory by using 32GB/64GB flash disk.)
• The automatic alarm of a shortage of liquid chemical replenishment dosing

Oxygen is important essential in environment. If water contains a great amount of organic matter which consumes excessive oxygen, it can lead to anaerobic conditions, which is deleterious to higher aquatic life forms. Because the environmental conscious is rising, in various industries raised the standards as well as governmental regulations. Chemical Oxygen Demand is an important water quality parameter and it provides an index to monitor the contamination in the water. W3111 COD on-line analyzer can measure water quality accurately to ensure the water quality safety. In water emission monitoring, discharge points could be located in suburban or places where can’t conduct continuous sample analysis. On-line analyzer can provide a solution and REAL-TIME monitor water quality. There are several methods to monitor the consuming oxygen in water, such as biochemical oxygen demand (BOD), Chemical Oxygen Demand (COD) and Total Oxygen Demand (TOD). COD contrasts with biochemical oxygen demand (BOD), which BOD test takes five days to complete, COD test take within 2hours or less to complete. COD with Potassium Dichromate Reflux method is more time-efficient and popular as a standard recognized by most governments in the world. W3111 COD on-line analyzer is automatic and reliable analyzer which can save time and staffs as well as dosing accurately to save cost.

Operational Principle
The principle of Chemmit W3111 COD analyzer is following US’ EPA 410.4 method and APHA Standard Method 5220D. It adopts Potassium Dichromate Reflux method to proceed continuous monitoring. When the sample transported into overflow cup, a certain volume sample is mixed with a dichromate reagent solution and sulfuric acid. The solution is refluxed at 150℃for a fixed period of time and then determines the consumption of dichromate by colorimeter. Reagents also contain silver sulfate as an oxidation catalyst and mercuric sulfate for the purpose to complex chloride ions in sample. Two simplified chemical equations to illustrate the reactions are:
CaHbOc + Cr2O72- + H+ →→→  Cr3+ + CO2 + H2O
Organics Cr6+ Acid →→→ Cr3+ + CO2 + H2O
The COD value is determined by innovated LED emitter colorimetric detection.
General Specifications
Function Wet Chemistry Analyzer for Measurement of Concentration of Chemical Oxygen Demand (COD) in Water, following Dichromated Method , according to NIEA W516.56A, US EPA 410.1 and APHA5220D
Model W3111
Installation Freestanding Type
Protection Class IP65
Dimensions H1250* W550* D430mm
Range 0-200 mg/L, to 0-2,000 mg /L , (higher range is available by dilution)
Accuracy F.S ±3 %
Repeatability F.S ±3 %
Optical Module Special LED, dual beams, auto gaining design, 24-bit high-resolution A/D converter, long life span, auto compensation of light intensity, and with system automatic light source abnormal judgment
Response Time Standard concentration range: 120 minutes per measurement
Digestion Time User selectable 90 to 120 minutes per measuring cycle. 
Digestion temperature 170ºC.
Auto Cleaning User selectable 1 to 3 times. Every time lasts for 15 minutes
Auto Calibration Automatic calibration. Can switch to manual calibration, high- and low- point
Shutdown Alarm • Concentration abnormal alarm (adjustable of high-point)
• System error alarm
Display 7” LCD color touch panel display
Self-Diagnosis The system is continuously self-diagnosis. The error management helps to identify problems. (Display errors and save historical data)
Electrical Conditions Power supply ranges:115 / 230 VAC, 50 / 60 Hz,<500 Watt
Certification CE Mark (Certificate No. 3X180605.KSIUN08)
Language Support Chinese, English
Sample Conditions • Sample temperature: 0 to 45 °C
• Sample flow: Continuous, 50 to 1,000 ml/min
• Sample consumption: 10ml/ analysis nominal
• Sample connection: use external pump connect with 4.75mm Teflon tube
• Suspended solids: 200 microns or less
• Ambient operating temperature: 0 – 60 °C 
• Ambient operating humidity: Up to 95 % RH non-condensing
Analog Outputs 1x isolated current output, 4-20mA range. With option of RS485 Modbus
Relay Outputs 1x alarm reply. With the option of extending up to 4 fully user-assignable relays