Chemicals Rapid Biodegradation Carbon dioxide production test
oecd tg 301b gb/t21856-2008
16775126210dy
Rapid biodegradability: The biodegradability of the test substance when it comes into contact with the inoculum for a limited time.
Total Carbon: The total amount of organic and inorganic carbon in the test medium.
Total organic carbon: The total amount of organic carbon in the test medium, including solutions and suspensions.
Dissolved organic carbon: the amount of organic carbon in the solution, often referred to as 0The organic carbon content of the liquid after filtration by 45 pm membrane, or the organic carbon content in the supernatant after centrifugation for 15 min at 4000 min.
Theoretical carbon dioxide: The amount of carbon dioxide that should be produced by the calculated total inorganic inorganic carbon contained in the test substance. It is usually expressed in milligrams of carbon dioxide per milligram of test substance produced (mg mg).
Stallion period: The period from the start of the trial to the degradation rate of 10%.
10-day observation period: 10-day test time after the biodegradability rate reaches 10%.
Degradation period: The period from the end of the stagnant phase to the degradation rate reaching 90% of the maximum degradation rate.
Stable phase: The period during which the biodegradability rate tends to stabilize (at least three assays).
Principles of chemical degradation:
In a certain volume of inoculated inorganic medium containing a known concentration of the test substance (10 mg L 20 mg L as DOC or TOC) as the only source of organic carbon, the test medium was aerated with decarbonized air at a controlled rate in the dark or diffuse light. The degradation rate was determined by measuring the amount of carbon dioxide produced on 28 days. The amount of carbon dioxide produced by the test substance is expressed as a percentage of THCO2 (corrected for a blank test containing inoculum only). The biodegradation rate can also be determined using supplemental DOC measurements performed at the beginning and end of inoculation.
Test preparation. Equipment.
a) flasks, 2 L 5 L, each flask is fitted with a vent tube with an outlet close to the bottom of the vessel (the vent tube must not interfere with the use of the magnetic stirrer);
b) magnetic stirrer, which is used in the determination of insoluble test substances;
c) Gas absorption bottles;
Selection of inoculum.
Activated sludge inoculum.
Other**inoculum.
Preparation of inoculum.
Preparation of culture medium.
Test operation: The air with CO2 removal is aerated to the suspension at a flow rate of 30ml min to 100ml min to start the test. It is recommended to measure CO2 every 1 d 2 days before the test, and at least every 5 days thereafter until day 28 to determine the ten-day observation period and degradation rate. For CO2 determination, remove the barium hydroxide absorber directly connected to the test flask, move the rest of the flasks forward sequentially, and connect a new absorber flask at the end. Remove the absorption bottle and use phenolphthalein as an indicator with 005mol LHCl titration to determine the amount of CO2 produced according to the change in Ba(OH)2 concentration. Observe the time it takes for the first vial to precipitate significantly, but the second flask to determine the sampling frequency. When NaOH is used as an absorbent, a syringe is used to draw a sample from an absorbent flask directly connected to the test flask, and the volume of the sample required depends on the carbon analyzer used, but the volume of the absorbent should not change significantly due to sampling during the test cycle. At the end of the test, the CO2 content in the second absorbent flask is determined to correct the amount of CO2 produced by the test. On the 28th day, 1ml of concentrated hydrochloric acid was added to each test bottle for overnight aeration to drive out the CO2 in the test suspension, and the CO2 production was finally measured on the 29th day.
Quality control. a) During the stabilization period, at the end of the test or at the end of the 10-day observation period, the maximum difference in degradation rate between parallel tests was less than 20%;
b) On the 14th day of the test, the degradation rate of the reference program control (in terms of THC2 production) was not less than 60%;
c) The inorganic carbon content in the test medium should be less than 5% of the total carbon at the beginning of the test;
d) The total amount of CO2 produced in the inoculum blank control at the end of the test is usually not higher than 40 mg L, if it is higher than 70 mg L, the data and test method should be tested.
Test results: The test report should include the following:
a) Test substance.
physical state and basic physical and chemical properties;
Identification data of test subjects.
b) Test conditions.
inoculum: status and sampling location, concentration and pretreatment method;
the proportion and condition of industrial wastewater in the effluent, if known;
test period and temperature;
Preparation method of suspension of insoluble test solution in water;
Reasons for the change in procedure and explanations.
c) Results: Fill in the data in the "Data Sheet" (see Appendix D);
any observed inhibition;
any observed non-biodegradation;
chemical substance analysis data (if applicable);
Analytical data of the degradation products of the test substance (if applicable);
Degradation curves of test objects and references, including stagnation period, degradation period and 10-day observation period;