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There are plenty of methods used for the assessment of organic compounds biodegradability, but lack of comprehensive literatures in systematically introducing the assessment methods and guiding the choice of the methods. This paper briefly introduced the indicative parameters in assessing organic compounds biodegradability and the assessment methods of aerobic and anaerobic biodegradation, with the focus on the principles and criteria in the choice of the assessment methods, and analyzed in detail the reasons for the differences in the biodegradation rates of organic compounds when different test methods were adopted. Taking the standards established by the Organization for Economic Co-operation and Development (OECD) as an example, the process of choosing and applying the assessment methods was introduced, the systematic method-choosing route was integrated, and the advantages of the OECD standard methods were pointed out.

Polydimethylsiloxane (PDMS) is widely used in industrial products, medical and health care products, and personal care products. In the treatment process of sewage, PDMS can be hardly biodegraded but enter the environment mainly through the discharge of excess sludge, and only a small amount of PDMS adsorbed on the suspended solids or sludge particle surface is discharged into water body and sediment with treated sewage. There is no enough evidence to verify that PDMS can vertically migrate in sediment. The degradation of PDMS in sediment is very slow, but PDMS can be degraded in different types of soils. PDMS has less risk to aquatic ecosystem, and no apparent acute toxicity to benthos. In soil environment, PDMS and its degradation products have no significant effects on the soil microorganisms, soil animals, and crops. Though a few studies indicated that PDMS and its degradation products have relatively low ecological toxicity in various environments, it is still very important to clarify the potential threat of PDMS to the environment because of the increasingly large number of PDMS being produced and used.