How to Test COD In-House

Chemical oxygen demand (COD) testing is an important parameter to measure, and is a required step before water can be legally discharged into local sewerage systems. We cover why COD is important, how to test in-house and the method for testing with a Hanna COD spectrophotometer below:

Why measure chemical oxygen demand?

The Water Industry Act 1991 requires the measurement of COD for trade effluent discharge before it can be discharged. Monitoring and maintaining records allows local water utilities to provide a consent to discharge within specific, defined limits. COD measurement also provides insight into the efficiency of water processing, and the impact of discharged water on the environment.

What are the benefits of testing COD in-house?

Minimal training requirements: Using a spectrophotometer to test COD in-house does not require extensive training or laboratory experience. Our team at Hanna offers personalised training with purchase of the Iris to make the transition easy.
Fast results: Using the ISO-compliant COD method allows you to have the results of testing within two hours, providing same-day information about water quality.
Improved response time: IIn-house testing provides complete control over the process, allowing you to respond swiftly or retest for COD parameters as required.
Internal routine: In-house testing allows you to consistently test on your own schedule. reducing the risk of penalties from local water utilities deadlines.
Cost effectiveness: Testing COD in-house reduces the cost of sending tests to external services or laboratories.
Administrative control: Outsourcing COD testing has a larger administrative burden than in-house testing, where samples need to be booked in, sent and potentially followed up with the laboratory.

To test COD in-house you will need:

A spectrophotometer

Spectrophotometers provide reliable results for COD testing, while also having the capability to perform measurements across a wide range of other parameters and methods for water testing. Hanna’s Iris Spectrophotometer is a highly accurate solution for in-house water testing, ideal for smaller benchtops, with a built-in battery for use in the field.

A thermoreactor

A thermoreactor, or heater block, is a required part of the process for measuring chemical oxygen demand in water. The sample and reagent needs to be heated to 150°C to comply with ISO requirements for testing. The HI-839800 Heater Block includes an in-built timer and has capacity for up to 25 simultaneous digestions at once, making it an ideal solution for COD.

Reagents

Reagents are combined with water samples to provide a COD measurement that can be identified by a spectrophotometer. Hanna’s range of reagents include ISO-compliant solutions that start from 0 to meet industry requirements.

An image of the Hanna Iris spectrophotometer in a laboratory setting

How to prepare your sample for testing COD in-house

Only three steps are required to prepare your sample and blank for COD testing:

Add 2 ml of your sample water to the pre-dosed reagent and a secondary 2 ml sample of distilled water to another reagent within the same lot to create your blank
Replace the cap on your reagents and mix them by tilting
Place the sample and blank in the preheated thermoreactor and set digestion to 150°C for two hours