ISO 14851 pdf download.Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous medium
1 Scope
This International Standard specifies a method, by measuring the oxygen demand in a closed respirometer, for the determination of the degree of aerobic biodegradability of plastic materials, including those containing formulation additives. The test material is exposed in an aqueous medium under laboratory conditions to an inoculum from activated sludge, compost or soil. If an unadapted activated sludge is used as the inoculum, the test simulates the biodegradation processes which occur in a natural aqueous environment; if a mixed or pre-exposed inoculum is used, the method can be used to investigate the potential biodegradability of a test material. The conditions used in this International Standard do not necessarily correspond to the optimum conditions allowing maximum biodegradation to occur, but the standard is designed to determine the potential biodegradability of plastic materials or give an indication of their biodegradability in natural environments. The method enables the assessment of the biodegradability to be improved by calculating a carbon balance (optional, see annex E). The method applies to the following materials: – Natural and/or synthetic polymers, copolymers or mixtures thereof. – Plastic materials which contain additives such as plasticizers, colorants or other compounds. – Water-soluble polymers. – Materials which, under the test conditions, do not inhibit the microorganisms present in the inoculum. Inhibitory effects can be determined using an inhibition control or by another appropriate method (see e.g. ISO 81 92 [3] ). If the test material is inhibitory to the inoculum, a lower test concentration, another inoculum or a pre-exposed inoculum can be used.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
3 Definitions
For the purposes of this International Standard, the following definitions apply: 3.1 ultimate aerobic biodegradation the breakdown of an organic compound by microorganisms in the presence of oxygen into carbon dioxide, water and mineral salts of any other elements present (mineralization) plus new biomass 3.2 activated sludge biomass produced in the aerobic treatment of waste water by the growth of bacteria and other microorganisms in the presence of dissolved oxygen 3.3 concentration of suspended solids in an activated sludge the amount of solids obtained by filtration or centrifugation of a known volume of activated sludge and drying at about 1 05 o C to constant mass 3.4 biochemical oxygen demand BOD the mass concentration of the dissolved oxygen consumed under specified conditions by the aerobic biological oxidation of a chemical compound or organic matter in water, expressed as milligrams of oxygen uptake per milligram or gram of test compound 3.5 theoretical oxygen demand ThOD the theoretical maximum amount of oxygen required to oxidize a chemical compound completely, calculated from the molecular formula, expressed as milligrams of oxygen uptake per milligram or gram of test compound 3.6 total organic carbon TOC all the carbon present in organic matter which is dissolved or suspended in water 3.7 dissolved organic carbon DOC that part of the organic carbon in water which cannot be removed by specified phase separation, for example by centrifugation at 40 000 m⋅s -2 for 1 5 min or by membrane filtration using membranes with pores of 0,2 µm to 0,45 µm diameter