Determination of biodegradability via oxygen consumption in closed respirometers.
The manometric respirometry test determines the oxygen consumption in closed respirometers via semi-continuous pressure measurement. The test substance is the only carbon source in a mineralic medium. As standard, 30 mg/L of activated sludge from a municipal wastewater treatment plant are used. The under-pressure caused by the oxygen consumption is recorded over a period of 28 days. The released carbon dioxide is bound to NaOH. The biological degradation extent is calculated by the relation of the oxygen consumption (minus the oxygen consumption of the blank controls) and the theoretical or chemicals oxygen demand (ThOD or COD).
A degradation extent of > 60% ThOD (or COD) within 28 days and within a "10-days window" after the end of the lag-phase is defined as criterion for classifying a particular test substance as "readily” biodegradable.
Test substance properties
The Manometric Respirometry Test is applicable for soluble and insoluble substances, substances with a high volatility and waste water samples.