Report No FR0426

P H Jago

Dec 1993



The customer will benefit from a better understanding of all the current procedures that have been reported for the determination of the biodegradable organic matter in water, and how these procedures can be applied.


To produce a state of the art review of assimilable organic carbon (AOC) and biodegradable organic carbon (BDOC) measurement procedures and their application.


The water industry requires a better understanding of the impact of novel water treatment processes on biodegradable organic matter (BOM), and on the implications of BOM on water quality in distribution. Reliable methods of measurement are therefore req uired. A review of the literature is required to establish which method or methods are most reliable and usable in the operational situation.


  1. The two approaches to the measurement of BOM are fundamentally different.

  2. AOC is a measure of the growth potential of a water determined by measurement of the growth response of bacteria to the nutrients in water.

  3. BDOC is a measure of the potential mineralisation of organic carbon in water that can be achieved by heterotrophic micro-organisms.

  4. Most established procedures are complicated and take at least a week to produce a result. Much of the progress that has been reported has been in the simplification of procedures and reduction of response times.

  5. Both types of procedure have been reported to successfully monitor the effects of water treatment processes on BOM.

  6. Biostability of water has only been defined in terms of AOC at a concentration of less than 10 - 20 g l-1. BDOC is limited by the current sensitivity of TOC analysis of 100 g l-1, which is around the expected level for biostability.

  7. The growth of heterotrophic bacteria and coliforms are reported to be limited at AOC concentrations of less than 50 g l-1.

  8. BDOC is best applied to the optimisation of water treatment processes as it gives a measure of the ultimate DOC removal that can be achieved biologically.

  9. AOC is best applied to the measurement of potential growth response and biostability in distribution.


This report has been produced in connection with the Foundation for Water Research contract on Water Quality in Distribution (F-1702). The report is a review of current methods for determining the concentration of biodegradable organic matter in water.

Copies of the Report are available from FWR, price 15.00 less 20% to FWR Members