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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1974
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
according to guideline
Guideline:
other: Standard Methods for the Examination of Water and Wastewater (1971). American Public Health Association, Washington DC
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Principles of method if other than guideline:
Method is similar to current OECD Guideline 301D: Closed Bottle test.
GLP compliance:
no
Specific details on test material used for the study:
- Name of test material: Diisobutyl ketone
- Molecular formula: (CH3)2CHCH2COCH2CH(CH3)2
- Analytical purity: not stated

Details on properties of test surrogate or analogue material (migrated information):
Glucose used as reference substance to demonstrate viability of the inoculum
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
Microbial seed was obatined in the form of settled raw domestic waste from the North Charleston Waste Treatment Works, Charleston, West Virginia, USA. Each test mixture (bottle) was inoculated with 3 mL of settled seed (passed through glass wool plug).
Duration of test (contact time):
20 d
Initial conc.:
10 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Stock solution of the reference substance (glucose) was prepared by gravimetrically weighing (in a syringe) the test substance, and quantitative transfer to volumetric flask and filled to volume with distilled water. Solutions (~1,000 mg/L) were prepared one day in advance of testing, and stored at 25 °C in tightly-capped bottles until used. The test substance, which was soluble to only 500 mg/L, was added directly to the BOD bottles using a micro-hypodermic syringe, in 3 uL portions giving approximately 10 mg/L as test substance.
Clean 300 mL glass BOD bottles were filled approx. 2/3 full with dilution water, which consisted of distilled water (carbon-filtered) amended with nutrient/buffers (equivlalent to that used in OECD 301D). The microbial seed (3 mL) and test substance (3 uL) or glucose stock solution (1, 2, and 3 mL) were added, and the bottles were filled to volume with additional dilution water. Bottles were sealed with ground-glass stoppers, and held in place with a polyethylene sheet over-wrap which was secured with rubber bands placed on the bottle neck.
Seeded blanks, with no added test substance, and glucose controls , were prepared in a similar manner.
Ten percent of the filled/sealed bottles were checked for initial dissolved oxygen concentration. All samples were incubated in darkness at 20 °C. Measured dissolved oxygen concentrations, corrected for concentration in inoculum blanks, was compared to the theoretical oxygen demand (ThOD), which was determined from the molecular formula of the test substance and its stoichiometric conversion to CO2 and water.
Reference substance:
other: glucose
Preliminary study:
not applicable
Test performance:
see below
Parameter:
% degradation (O2 consumption)
Value:
4
Sampling time:
5 d
Remarks on result:
other: BOD
Parameter:
% degradation (O2 consumption)
Value:
39
Sampling time:
10 d
Remarks on result:
other: BOD
Parameter:
% degradation (O2 consumption)
Value:
57
Sampling time:
15 d
Remarks on result:
other: BOD
Parameter:
% degradation (O2 consumption)
Value:
88
Sampling time:
20 d
Remarks on result:
other: BOD
Details on results:
Test substance exhibitied a short lag period before rapid biodegradation, meeting criteria for ready biodegradability in the closed bottle test.
Results with reference substance:
Biodegradation of glucose resulted in oxygen consumption values which were within required range of the APHA method.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance was shown to be readiliy biodegradable in a closed-bottle test, which is equivalent to OECD Guideline 301D.
Executive summary:

Each of the sixty materials shipped in bulk form by Union Carbide in deep-water tankers has been subjected to a series of tests designed both to evaluate the rate and extent of biodegradation in the marine environment and to determine the acute toxicity to marine organisms. The information developed in these test was combined with other physical and chemical properties of each material to make judgements with resspect to the advisability of releasing each material to the marine environment in the form of tanker washings.

This study included testing of biodegradability in the APHA closed-bottle BOD test, which is essentially equivalent to the current OECD 301D test. The materials, methods, and results are fully documented in the referenced report; and are sufficient for a fully valid study.

Description of key information

 Readily biodegradable, exhibiting 88% BOD in a 20-day closed bottle test equivalent to OECD 301D 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

This study included testing of biodegradability in the APHA closed-bottle BOD test, which is essentially equivalent to the current OECD 301D test. The materials, methods, and results are fully documented in the referenced report; and are sufficient for a fully valid study.