Chemical Oxygen Demand

Chemical Oxygen Demand (COD)

Chemical Oxygen Demand or COD is one of  the most important water quality parameters. COD is defined as the amount of dissolved oxygen required in water to oxidize the chemical organic materials present. It is expressed in milligrams per liter (mg/L) or in parts per million (PPM).

COD can be measured using a reagent based test and a spectrophotometer or indirectly using UV254 and treating it as a surrogate. The latter does not require consumables and less time consuming than the former.

High chemical oxygen demand (COD) levels will lower dissolved oxygen in water. Over extended periods this can lead to an extreme negative environmental effect and potential legal judgments, heavy fines as well as wildlife culls.  COD is one of the most heavily regulated parameters when discharged into receiving water.

In addition to COD (Chemical Oxygen Demand) we can measure other organic parameter in water can easily with one of our field or process instruments using UV254 .

See our COD products

COD reagent 

The  COD (Chemical oxygen demand) lab method requires the use of expensive and carcinogenesis reagents and only gives a spot result at a particular time which may be hours or days after the sample was taken as the sample is taken to the lab to be processed, it is queued until the required equipment or operator is a available and only then the result is available to act on.

At best this only gives part of the picture and any changes between the sampling events are not captured. Not only can chemical oxygen demand spikes be missed, but that  over processing can occur as you may not know exactly when a process has completed.

How much do your COD Reagents Cost?

Reagents cost are not only in purchase, but also disposal, safe storage.  Addition compliance requirements costs in managing carcinogens and mercury loaded products on all your site.

There is a simple ready reckoner to allow you to calculate your basic annual reagents costs.

The introduction of a UV254 analyser can save 70%-90% of your reagents cost along with giving you continuous and trend data to optimise your processes, saving on chemicals, electricity and equipment maintenance.

Calculate how much you spend on COD Reagents 
Ready reckoner allowing operators to work out the annual cost of COD reagents
Inline UV254 Chemical oxygen demand system

What is UV254 and how does it replace my COD reagents costs?

What is UVT? Ultraviolet transmittance refers to the amount of light that passes through a sample at the wavelength of 254 nm.

UV254 absorption can be used as a surrogate  measurement of COD (Chemical oxygen demand) and uses only UV  light to measure, with none of the hassle of byproducts disposal.

UV254 is absorbed and scattered by the organics, colloids, and suspended solids. UV Absorbance often expressed as A254 or ABS is the light absorbed by a sample. 

UV254 a proven modern alternative to COD  reagents

Learn more about what we do

• Reagent free

• Results in seconds not minutes

• All data stored in excel compatible format

• 10 hours use without recharging

• Modern icon-driven touch screen

• All results come with time and date stamps

•Devices will store calibration for 16 different locations 

• Stores over 10 years of results

Portable  COD Devices
A modern UV254 Chemical Oxygen demand analyser


Lisburn, BT28 2GN, GB

About us

Photonic Measurements is:
Incorporated in N.Ireland (NI622996) 
VAT registered in UK (GB192
VAT registered in N.Ireland (XI192976846000)

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