COD or Chemical Oxygen Demand definition

A number of customers have asked us for a definition of COD or Chemical Oxygen Demand which is detailed below:

Chemical oxygen demand (COD) is a measure of the capacity of water to consume oxygen during the decomposition of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite. COD measurements are commonly made on samples of waste waters or of natural waters contaminated by domestic or industrial wastes. Chemical oxygen demand is measured as a standardized laboratory assay in which a closed water sample is incubated with a strong chemical oxidant under specific conditions of temperature and for a particular period of time. A commonly used oxidant in COD assays is potassium dichromate (K₂Cr₂O₇) which is used in combination with boiling sulfuric acid (H₂SO₄). Because this chemical oxidant is not specific to oxygen-consuming chemicals that are organic or inorganic, both of these sources of oxygen demand are measured in a COD assay.

Chemical oxygen demand is related to biochemical oxygen demand (BOD), another standard test for assaying the oxygen-demanding strength of waste waters. However, biochemicaloxygen demand only measures the amount of oxygen consumed by microbial oxidation and is most relevant to waters rich in organic matter. It is important to understand that COD and BOD do not necessarily measure the same types of oxygen consumption. For example, COD does not measure the oxygen-consuming potential associated with certain dissolved organic compounds such as acetate. However, acetate can be metabolized by microorganisms and would therefore be detected in an assay of BOD. In contrast, the oxygen-consuming potential of cellulose is not measured during a short-term BOD assay, but it is measured during a COD test.

You can find more about Camlab, Hach and Hanna COD – Chemical Oxygen Demand test vials and colrimters here. They maks measurement simple and do the calculations for you.

You can read more about the definition of COD here–> COD

Service, Maintenance and Repair for all your Hach Lange instruments

Service Plan

Getting the best performance from your Hach product and prolonging its life is important to us at Camlab. With 40 years experience we also know how valuable it is to offer our customers a first class service.

Our engineers are located locally throughout the UK; they will visit your premises to service and calibrate your Hach using traceable standards working to ISO9001. All spare parts are carried and not just for the latest models.

Supported Models: DR850, DR890, DR2100P, DR2010, DR2400, DR2500 DR2800, DR2000, DR3000, DR4000

Returning your Hach to us could not be any easier or quicker. By returning it you can be safe in the knowledge that it’s fully tracked through our system and serviced and calibrated in our fully equipped workshop in Cambridge to the highest standards.  

Combining this level of service and a service contract will give you complete peace of mind. Having a contract not only assures that your equipment will continue to operate at its best, you will find it cost effective, all spares and further call outs all receive a discount and if you cannot be without your equipment while we service or repair yours we will loan you a replacement at no extra charge, subject to availability.

For a service/maintenance contract quotation then click here. 

For technical help, spare parts and repairs please contact our service department on e-mail: service@camlab.co.uk or Tel: 01954 233130

COD in 10 minutes!

Aqua Diagnostic PeCOD from Camlab

Camlab has launched a revolutionary instrument from Aqua Diagnostic, which is capable of accurate, sensitive, real-time analysis of Chemical Oxygen Demand. The new green technology requires no hazardous chemicals, produces fast results and eliminates the time consuming digestion step.

The core of the technology is the PeCOD™ sensor which has a number of practical advantages compared with the traditional methods of COD analysis (Chemical oxygen demand). PeCOD’s ability to analyse samples containing chloride is significantly better than the dichromate method, and does not require the addition of toxic reagents like mercury and silver salts. The increased sensitivity of the method enables the measurement of clean water samples with low ppm levels of COD. Typical analysis times of less than 10 minutes are easily achieved.

The sensor consists of a UV-activated titanium dioxide film coupled to an external circuit. The high oxidising power of the sensor gives the analyser a significant advantage compared with the traditional dichromate method. The PeCOD™ COD analyser exhaustively oxidises all organics, and counts the electrons that are liberated to provide a direct measure of equivalent COD.

The PeCOD™ analyser is available as a true on-line monitor or can be supplied as a benchtop laboratory instrument, which has an optional battery pack for field use. The PeCOD™ technology allows the user to rapidly measure COD online in real time and enables a reading to be generated every 15 minutes to give unrivalled data on a waste or discharge stream. The online real time capability means that processes can be adjusted to reduce energy use or to make treatment more cost effective.

For more information on the PeCOD™ technology and for technical articles please contact the UK agent for PeCOD™, Camlab Ltd, on 01954 233100 or sales@camlab.co.uk

Rent Your Site Monitoring Equipment

Camlab are now able to offer an extensive rental program on the range of In-Situ water monitoring equipment. Whether it’s boreholes, tidal flows or storage tanks there’s an In-Situ product to suit your water testing needs.  And now with telemetry options you can even automatically collect your sample data for your project from wherever you are stationed. This service is ideal for short term projects or consultancy. Email water@camlab.co.uk for a pricelist or quote!