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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental test result performed using standard test guidelines
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
not specified
Specific details on test material used for the study:
- Name of test material: 2,2,2-Trichloroethane-1,1-diol (Chloral hydrate)
- Molecular formula: C2-H3-Cl3-O2
- Molecular weight: 165.4026g/mol
- Smiles notation: C(C(O)O)(Cl)(Cl)Cl
- InChl: RNFNDJAIBTYOQL-UHFFFAOYSA-N
- Substance type: Organic
- Physical state: Solid
Oxygen conditions:
aerobic
Inoculum or test system:
other: Mixed Inoculum
Details on inoculum:
Mixed Inoculum Preparation (In-House):Domestic waste water, surface soil and soil samples from polluted sites receiving predominantly domestic waste was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions. This gave the bacterial count as107to 108CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitalityand CFU count of microorganism.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
BOD
Details on study design:
1. Respirometer flasks were allowed to reach the desired temperature at 20 deg C.The test item, i.e., 2,2,2-trichloroethane-1,1-diolwas taken at a concentration of 100 mg/L in mineral medium. The reference item chosen was Sodium benzoatewith a concentration of 100 mg/L in the mineral medium was directly added to the Respirometer Flask according the volume of mineral media taken.
2. The Respirometer Flasks of test item& reference itemwere filled with 400ml and 250mlof mineral media,respectively. Test suspension volume was decided by considering the available information on biodegradability of that test item.
3. All the Respirometer Flaskswereinoculated with prepared mixed inoculum at the concentration of 10ml/L. This concentration gave the bacterial CFU/ml as 107to 108.
4. The initial pH of the test medium was 7.3. The pH of all test vessels was measured at 28th day.
5. 2-4 pellets of KOH was addedin the alkali holder, which acts as CO2 absorber.
6. The respirometric sensors containing the KOH pelletswere tightly and carefully screwed on eachof the Respirometer Flasks. The sensors were reset by deleting old recorded data and choosing the appropriate scale (The sensor gives the oxygen consumption values in mgO2/l).
7. Respirometer Flaskwere kept in the respirometer incubator at constant temperature of 20 ± 1°C for 28 days.
8. Every day oxygen consumption (mg O2/l)into the each bottle wasrecorded.Temperature and stirring condition were checked regularly.

Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
BOD
Value:
44.04
Sampling time:
28 d
Details on results:
The oxygen consumed by the test systems wascorrected for oxygen consumption occurring in the blank test systems.TheBOD Values (mgO2/mg) and percent biodegradation results for each test system arereported in Tables 2 and 3, respectively.

The BOD28 value of 2, 2, 2trichloroethane-1, 1-diol (CAS No. 302-17-0) was observed to be 0.085 mgO2/mg. ThoD was determined by calculation as 0.193 mgO2/mg. % Degradation was calculated using the values of BOD and ThODfor test item andwas found to be 44.04%. The % degradation of procedure control (reference item) was also calculated using BOD &ThOD and was found to be77.24%.

The mean BOD values(mg O2/l) in control on 28th day was 28.4 mg O2/l thereby fulfilling the control validity criteria (i.e., The oxygen consumption of the inoculum blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days).

The percentage degradation of reference substance (Sodium benzoate)has reached the pass levels (60% of its ThOD) by Day 14. Thus, fulfilling the validity criteria of the study.
Results with reference substance:
Sodium benzoate: 73.24% after 28 days

BOD28, ThOD AND % BIODEGRADATION VALUES

Method details

BOD28(mgO2/mg)

ThOD (mgO2/mg)

% Biodegradation

Test Item

0.085mgO2/mg

0.193mgO2/mg

44.04 %

Reference Item

1.286mgO2/mg

1.665mgO2/mg

77.24 %

pH OF RESPIROMETER FLASK

Respirometer Flask

pH on 0thDay

pH on 28thDay

Inoculum Blank(Control)         B1

7.1

7.8

B2

7.1

7.8

Test Suspension

B1

7.3

8.6

B2

7.3

8.8

Procedure Control

B1                 

7.4

7.6

B2

7.4

7.5

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The test item 2, 2, 2 trichloroethane-1, 1-diol (CAS No. 302-17-0) undergoes 44.04%biodegradation after 28 days in the test condition. Thus, the test item can be considered as inherently biodegradable.
Executive summary:

28-days Manometric respirometry test following the OECD guideline 301F to determine the ready biodegradability of the test item 2, 2, 2 -trichloroethane-1, 1 -diol (CAS No. 302 -17 -0) was conducted. The test system included control, test item and reference item. The concentration of test and reference item (Sodium Benzoate) chosen for the study was 100 mg/L, while that of inoculum was 10ml/l. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % Degradation was calculated using the values of BOD and ThOD for test item and reference item.

The BOD28value of 2,2,2 -trichloroethane-1, 1 -diol(CAS No. 302 -17 -0) was observed to be 0.085 mgO2/mg. ThOD was calculated as 0.193 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was found to be 44.04%. Based on the results, the test item, under the test conditions, was found to be inherently biodegradable at 20 ± 1°C over a period of 28 days.

Description of key information

The test item 2, 2, 2 trichloroethane-1, 1-diol (CAS No. 302-17-0) undergoes 44.04%biodegradation after 28 days in the test condition. Thus, the test item can be considered as inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

Experimental key and predicted supporting data for the test substance chloral hydarte is reviewed for biodegradation in water which is summarised as follows:

IN experimental key study, 28-days Manometric respirometry test following the OECD guideline 301F to determine the ready biodegradability of the test item2, 2, 2 -trichloroethane-1, 1 -diol(CAS No. 302 -17 -0) was conducted. The test system included control, test item and reference item. The concentration of test and reference item (Sodium Benzoate) chosen for the study was 100 mg/L, while that of inoculum was 10ml/l. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % Degradation was calculated using the values of BOD and ThOD for test item and reference item.

The BOD28value of 2,2,2 -trichloroethane-1, 1 -diol(CAS No. 302 -17 -0) was observed to be 0.085 mgO2/mg. ThOD was calculatedas 0.193 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was found to be 44.04%.Based on the results, the test item, under the test conditions, was found to be inherently biodegradable at 20 ± 1°C over a period of 28 days.

Supporting above data, Estimation Programs Interface Suite (EPI suite, 2018) was run to predict the biodegradation potential of the test compound  2,2,2-trichloroethane-1,1-diol (Chloral hydrate)(CAS no. 302 -17 -0) in the presence of mixed populations of environmental microorganisms. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical 2,2,2-trichloroethane-1,1-diol (Chloral hydrate) is expected to be not readily biodegradable.

Thus based on the above data it can be observed that substance is likely to be inherently biodegradable or not readily biodegradable. However considering the experimental key value the substance chloral hydrate is concluded to be inherently biodegradable in water.