Aerobic Sewage Treatment Simulation Test: OECD 303A
This test is used to generate data concerning the fate of a test substance during biological treatment, using a laboratory-scale aerobic sewage treatment plant (STP) based on OECD guideline 303A. The study has been designed to determine the elimination of the test substance by aerobic microorganisms in a continuously operated test system simulating the activated sludge process, using a modified Husmann Unit.
Naturally occurring carbon in the sewage feed and the test substance are the sources of carbon and energy for the microorganisms.
For non-biocidal substances, the test substance is normally added at between 10 and 20 mg dissolved organic carbon (DOC) l-1.
Biocidal substances may also be tested using radiolabelled test material, at concentrations of about 100 µ C l-1.
The study can investigate the distribution of the radioactivity between the aqueous phase, the biomass (activated sludge) and any volatile products in the gaseous phase including 14CO2. Specific analysis will generally be carried out on the treated effluent. If sufficient radioactivity is detected in the biomass, attempts can also be made to extract and characterise this radioactivity.
