1. Scope 1.1 This test method is designed to index plastic materials which are more or less biodegradable relative to a standard in aerobic activated-sludge-treatment systems. 1.2 This test method is designed to be applicable to all plastic materials that are not inhibitory to the bacteria present in the activated sludge. Compounds with toxic properties may delay or inhibit the degradation process. 1.3 This test method measures the degree and rate of aerobic biodegradation of plastic materials (including formulation additives which may be biodegradable) on exposure to activated-sludge biomass in the concentration range from 0.1 to 2.5 g/L mixed-liquor volatile suspended solids (MLVSS) under laboratory conditions. 1.4 The high MLVSS concentration relative to other biodegradation tests has the advantage of improved repeatability and increased likelihood of more rapid adaptation or acclimation of the biomass. 1.5 This test method allows for the determination of biological nitrification and the oxidation of other non-carbon components of the plastic. 1.6 This test method does not purport to determine whether or not a plastic material will pass through primary treatment to the aeration basin of an activated-sludge wastewater-treatment plant. The size or density of the plastic material may exclude it from the secondary-treatment stage of a treatment facility. 1.7 There is no similar or equivalent ISO standard. 1.8 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For a specific hazards statement, see Section 8.