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The OECD 303A Activated Sludge Unit measures the DOC/COD removal during biodegradation. Two parallel units are generally used, one containing organic medium only as a blank control, while the other containing both organic medium and the test compound. The difference of the DOC removal between the two units is believed to be the contribution of the test compound. This method cannot be used for testing insoluble or volatile materials.
▶ Measurement: DOC (or COD) and/or substance itself;
▶ Carbon source: easily biodegradable organic medium (synthetic sewage) and test compound;
▶ Duration: normally 9 weeks, no more than 12 weeks;
▶ Two systems: one test, one blank control (to determine the degradation of organic medium);
▶ Blank control is not required if the substance itself can be measured;
▶ Reference control is not required but the reference (e.g., adipic acid, 2-phenyl phenol, 1-naphthol, diphenic acid, and 1-naphthoic acid) may be added occasionally together with the test substance;
▶ Mean hydraulic retention time: 6 h;
▶ Mean sludge age (retention time): 6-10 day;
▶ Test substance dosage: 10-20 mg/L of DOC;
▶ Initial activated sludge dosage: 2.5 g/L suspended solids;
▶ Distinguish from bioadsorption: by examining the elimination-time curve, and confirming with ready biodegradation test using an acclimatized inoculum from the unit;
▶ Sampling: filtration with membrane filters (0.45 μm) or centrifugation (40,000 m/s2);
▶ Test substance requirement: normally involatile and soluble, able to calculate DOC or COD;
▶ Reproducibility: errors usually within 10-15% for substances degraded more than 80%. Lower degradation, larger error;
▶ Little difference for the two apparatus (303A vs 303B), but the real sewage water may be better than the synthetic one.
Different testing methods are applicable for materials with different properties. Below is a summary of the applicability of OECD 303A. Find the applicability for all other methods on Aropha Resource Center
|Test||Analytical method||Sample info required||Poorly soluble||Volatile||Adsorbing|
|303A (Activated sludge unit)
||DOC and/or COD
||Carbon content and/or COD
To learn more about different types of biodegradation tests, their applicability, biodegradation mechanisms, and many other information such as case studies, publications, and blogs, please check our Aropha Resource Center