OECC 303A: Activated Sludge Simulation

Summary

OECD 303A is an aqueous aerobic biodegradation test that determines the biodegradability of a material by measuring the dissolved organic carbon or chemical oxygen demand under environmentally realistic conditions. This method is typically used for materials that did not reach non-persistent thresholds in either OECD 301 or OECD 302.

OECD 303A Testing Method

The OECD 303A method measures the DOC/COD removal during biodegradation. Two parallel units are generally used, one containing an organic medium as a blank control and another containing both the organic medium and the test substance. 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.

Here are some additional details on the OECD 303A test:

• Measurement: DOC (or COD) and/or substance itself
• Carbon source: Easily biodegradable organic medium (synthetic sewage) and test compound
• Two systems: One test system and one blank control
  • Blank control is not required if the substance itself can be measured
• Reference control: 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 hours
• Test substance dosage: 10-20 mg/L of DOC
• Initial activated sludge dosage: 2.5g/L suspended solids
• Bioadsorption distinction: Done by examining the elimination-time curve and confirming with ready biodegradability test using an acclimatized inoculum from the unit
• Sampling: Filtration with membrane filters (0.45 μm) or centrifugation (40,000 m/s^2)
• Test substance requirement: Normally non-volatile and soluble, able to calculate DOC or COD
• Reproducibility: Errors within 10-15% for substances degraded more than 80%. 
  • Larger error could be acceptable with lower degradation.

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