BS ISO 18830:2016 download free.Plastics — Determination of aerobic biodegradation of nonfloating plastic materials in a seawater/sandy sediment interface — Method by measuring the oxygen demand in closed respirometer.
Introduction
Products made with biodegradable plastics are designed to be recovered by means of organic recycling in composting plants or in anaerobic digesters. The uncontrolled dispersion of biodegradable plastics in natural environments is not desirable. The biodegradability of products cannot be considered as an excuse to spread wastes that should be recovered and recycled. However, test methods to measure rate and level of biodegradation in natural environments (such as soil or the marine environment) are of interest in order to better characterize the behaviour olpiastics in these very particular environments. As a matter of fact, some plastics are used in products that are applied in the sea (e.g. fishing gear) and sometimes they can get lost or put willingly in marine environment. The characterization of biodegradable plastic materials can be enlarged by applying specific test methods that enable the quantitative assessment of biodegradation of plastics exposed to marine sediment and seawater.
Plastic products are directly littered or arrive with fresh waters in the pelagic zone (free water). From there, and depending on density, tides, currents, and marine foiling may sink to the sublittoral, and reach the seafloor surface. Many biodegradable plastics have a density higher than I and therefore tend to sink. The sediment passes from aerobic to anoxic and finally anaerobic conditions going from the surface (the interface with seawater) into deeper layers, displaying a very steep oxygen gradient.
1 Scope
BS ISO 18830 specifies a test method to determine the degree and rate of aerobic biodegradation of plastic materials when settled on marine sandy sediment at the Interface between seawater and the seafloor, by measuring the oxygen demand in a dosed respirometer,
Measurement of aerobic biodegradation can also be obtained by monitoring the carbon dioxide evolution. This is not In the scope of BS ISO 18830 but of ISO 19679.
This test method is a simulation under laboratory conditions of the habitat found in different seawater/sediment-areas in the sea. e.g. in a benthic zone where sunlight reaches the ocean floor (photic zone) that, in marine science, is called sublittoral zone
The determination of biodegradation of plastic materials buried In marine sediment is outside the scope of this International Standard.
The conditions described in BS ISO 18830 may not always correspond to the optimum conditions for the maximum degree of biodegradation to occur.
2 Normative references
The following documents, in whole or in part, are normatively referenced In this document and are Indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 14851:1999, DetermInation of the ultimate aerobic biodegradability of plastic materials man aqueous medium — Method by measuring the oxygen demand in a closed respfrometer
ISO 8245, Water quality — Guidelines for the determination total organic carbon (TOC) and dissolved organic carbon (DOC)
3 Terms and definitions
For the purposes of BS ISO 18830, the following terms and definitions apply.
biochemical oxygen demand
BOD
mass concentration of the dissolved oxygen consumed under specified conditions by the aerobic biological oxidation of a chemical compound or organic matter in water
Note ito entry: It is expressed as milligrams of oxygen uptake per milligram or gram of test compouncL
7.4 pH meter (usual laboratory equipment)
8 Procedure
8.1 Test material
The test material should be In Aim or sheet form, Cut samples of the test material In the shape ola dIsk. Disks shall have a smaller diameter than the glass flasks, so that the disks can be easily laid on the bottom of the glass flask
The sample shall be of known mass and contain sufficient carbon to yield a 80) that can be adequately measured by the respirometer used
Use a test material concentration of at least 100 mg/I of seawater plus sediment. The mass of the samples should correspond to a ThOD of about 170 mg/I or a TOC of about 60 mg/i The maximum mass of sample per flask is limited by the oxygen supply to the respiromeler.
Calculate the ThOD (see ISO 14851:1999. Annex A) and the TOC (using ISO 8245 or from the chemical formula or determine by elemental analysis).
The form and shape of the test material may influence its biodegradability. Similar shapes and thicknesses should preferably be used ii different kinds of plastic materials are to be compared.
NOTE 1 The test material may also he Introduced as powder. However. this can be critical, as practical expenence has shown that it is difficult to keep a powder settled at the sediment/seawater Interlace without special measures. Refer to iSO 10210 for preparation of powder from pLastic materials..
NOTE 2 The test material In form of film laid down on the surface of the sediment could limit the gas exchange between the water body and the sediment, promoting the formation olanaeroblc zone under the test material. in order to reduce this effect, It Is possible to perfurate the Aim sample homogeneously over the entire surface.
8.2 Reference material
Use ashless cellulose filters as a reference materiaL’).
if possible, the TOC, form and size should be comparable to that of the test material. As a negative control, a non-biodegradable polymer (e.g. polyethylene) In the same form as the test material can optionally be used.
8.3 PreparatIon of the sediment
Filter the sediment in a funnel with a coarse filter paper to eliminate excess seawater. Sediment is ready for testing when dripping of sea water is ended. Sediment after filtering is named wet sediment’ hereafter.
8.4 Test setup
Provide several flasks, so that the test Includes at least the following:
a) three flasks for the test material (symbol FT);
b) three flasks for the blank (symbol FB);
c) three flasks for reference material (symbol Fc).
Information on the toxicEty of the test material may be useful In the Interpretation of test results showing a low biodegradability.
10 Validity of results
The test is considered valid, if
a) the degree of biodegradation of the reference material (Ec) is >60% after 180 days.
b) the HOD of the blank Fnat the end of the test does not exceed an upper limfting value,
NOTE This value depends on the amount of Inoculum; In a typical case, reported In L. the value is 300 mg/I after 6 months, as shown In the intc’rlaboratory test Hi.
c) the HOD values of the three blanks Fit are within 20 % of the mean at the plateau phase or at the end of the test.
d) the difference between the percentage biodegradation of the reference material in the different vessels Is less than 20 % of the mean at the end of the test.
If flask FN (negative control) was included, no significant amount of HOD shall be observed,
If these criteria are not fulfilled, repeat the test using another sediment.
11 Test report
The test report shall contain the following information;
a) a reference to BS ISO 18830. i.e. ISO 18830:2016;
b) all information necessary to identify the test and reference materials, including their TOC. ThOD. chemical composition and formula (if known), shape, form and amount in the samples tested;
c) the main test parameters, Including test volume, test medium used, incubation temperature and final pH;
d) the source and amount of the marine sediment used:
e) the analytical techniques used, Including the principle of the respirometer and the TOC and nitrate/nitrite determinations;
f) all the test results obtained for the test and reference materials (in tabular and graphical form). including the measured BOO, the percentage biodegradation values, the respective curves of these parameters against time and the nitrate/nitrite concentrations;
g) the duration of the lag phase, hiodegradation phase and maximum level of degradation, as well as the total test duration, and, optionally, ii run or determined, the negative control FN;
h) any other relevant data (e.g result of the visual final inspection and analysis of final samples, If still retrievable; photos of the final samples):
i) details of the methods used during the test period in order to support microbial diversity or to avoid nutrient deficiency (II used);
j) any deviations from the test conditions described in BS ISO 18830.