Lovibond ® Roewe State, Germany ® water quality analysis

Chemical Oxygen Demand (COD) Test

Measuring organic pollution in water quality

There are various types of organic compounds in water quality, and existing technologies are difficult to distinguish and quantify them. Based on the common characteristic that organic matter can be oxidized, the amount of oxygen consumed during the oxidation process can be used as a comprehensive indicator of the total amount of organic matter for quantification, usually expressed as biological oxygen demand (BOD) or chemical oxygen demand (COD). [1]

Due to the long detection time of BOD, usually 5 days, it is difficult to provide timely guidance for practical production. When the water contains high concentrations of difficult to biodegrade organic matter, the by-products have an inhibitory effect on the growth and reproduction of microorganisms, making it difficult to effectively biodegrade organic matter and resulting in significant testing errors. Chemical oxygen demand (COD) can indicate the organic matter content in water quality within a few hours. COD represents the amount of oxygen consumed by strong oxidants (such as potassium dichromate) to oxidize organic and reducing inorganic substances into CO2 and H2O under acidic conditions.

Key indicator COD for sewage treatment

COD and BOD are both key parameters for evaluating the environmental damage caused by wastewater. The higher the COD, the more organic matter that can be oxidized is present in the wastewater, and the dissolved oxygen (DO) in the water is often very low. Organic matter will be decomposed by heterotrophic bacteria, consuming dissolved oxygen. The decrease in dissolved oxygen in water quality is not conducive to the survival of advanced aquatic organisms (such as fish) and damages the ecosystem. COD testing has a short time and is usually used as an alternative method to BOD. [2]

Common industrial wastewaterCOD contentAnd emission standards

Lovibond COD Testing Plan

Testing principle - COD potassium dichromate oxidation method

A certain amount of water sample is added to the prefabricated tube reagent, and potassium dichromate is used to nourish all oxidizable organic compounds under acidic conditions of sulfuric acid. By testing the absorbance of+6 valent chromium in potassium dichromate or the absorbance of+3 valent chromium in the product using photometry, the consumption of oxides and the amount converted into oxygen can be obtained, which is the chemical oxygen demand of the water sample.

Instrument - photometer&spectrophotometer

• Single parameter photometer COD Vario - portable/desktop

MD100 CODIntegrated portable photometer that conforms to human mechanics, convenient for on-site testing.

MD200 CODHigh quality stable light source, LED light source+interference filter, accurate at any timeresult.

• Multi parameter photometer - portable/laboratory type

MD600More than 120 built-in testing parameters can be used to test various parameters of sewage and drinking water quality. Meet the needs of modern water quality laboratories.

MultiDirectA microprocessor controlled photometer with an ergonomically designed keyboard and comfortable display screen.

• spectrophotometer

XD7000 visible light spectrophotometer:

XD7500 UV Visible spectrophotometer:Time saving and labor-saving efficient testing assistant - built-in 154 pre programmed curves, saving time and reducing testing errors.

Instrument - Dissolver

RD125：Multi purpose thermal digester for sample preparation for photometric determination of COD, total chromium, total phosphate, total nitrogen, and TOC. Digestion can be carried out at three temperature ranges (100/120/150 ℃) and three pre programmed reaction times (30/60/120 minutes).

Reagent - Pre packaged tube reagent/standard solution

•Pre packaged tube reagentEasy to use.

The upper limit of chloride interference resistance for medium and low range prefabricated tube reagents is 1000 mg/l, and the upper limit of chloride interference resistance for high range prefabricated tube reagents is as high as 10000 mg/l.

If the sample does not contain chloride, mercury free prefabricated tube reagents can be used.

• Optional 4 ranges:

3 - 150 mg/l， Low range, compliant with ISO 15705:2002

15 - 300 mg/l， Medium to low range, compliant with ISO 15705:2002

20 - 1500 mg/l， Medium to high range, compliant with ISO 15705:2002

200 - 15000 mg/l， high range

COD standard solutionIt is a solution with a known COD concentration, mainly used to check the operation method of COD testing, the condition of optical systems and filters, and other possible conditions that may affect the test results of the instrument. Choose from 3 concentrations:

100 mg/l COD

500 mg/l COD

5000 mg/l COD

Please refer to the attachment for the testing steps

If you have any questions or suggestions, please contact Lovibond for water quality analysis