Trisodium 2-(carboxylatomethyl(2-hydroxyethyl)amino)ethyliminodi(acetate)

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Not reported

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 A (Inherent Biodegradability: Modified SCAS Test)

Deviations:

not specified

GLP compliance:

not specified

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Oxygen conditions:

not specified

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: activated sludge suspended solids, non-adapted and adapted under different mean biomass retention time (sludge age) in days
- Preparation of inoculum for exposure: adaptation procedure described in Pitter and Sykora 1996
- Concentration: 200 mg/L
- All other template details: not reported

Duration of test (contact time):

<= 30 d

Initial conc.:

50 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

Not reported

Preliminary study:

Not reported

Test performance:

Not reported

Parameter:

% degradation (DOC removal)

Value:

> 0 - <= 15

Sampling time:

30 d

Details on results:

The chelating reagents ECTA, DTPA, HEDTA, PDTA were stable under experimental conditions. DOC removal varied within 0% and 15%. The influence of sludge age up to 30 d was not observed.

Results with reference substance:

Not reported

Not reported.

Interpretation of results:

not inherently biodegradable

Conclusions:

HEDTA was stable under environmental conditions.

Executive summary:

The biological degradability (Zahn-Wellens test) of ethylenediame derivatives with carboxymethyl and 2 -hydroxyethyl groups was investigated. Mixed bacterial culture (activated sludge) was used as inoculum (non-adapted sludge and sludge adapted at different mean biomass retention time, the so-called sludge age). Biodegradability of ethylene(propylene)di(tri)amine-based complexing agents depends on the character and number of substituents and nitrogen atoms in the molecule. Tetra(penta)substituted derivatives with two or more tertiary nitrogen atoms and carboxymethyl or 2 -hydroxyethyl groups in the molecule (EDTA, DTPA, PDTA, HEDTA) are very stable from an environmental point of view. On the contrary, disubstituted derivatives with two secondary nitrogen atoms in the molecule (e.g., EDDA) are potentially degradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Principles of method if other than guideline:

Method: The carbon dioxide evolution test was conducted according to Sturm (1973). Sturm RN (1973). J. Amer. Oil Chem. Soc. 50: 159-167

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: sewage treatment plant effluent, adapted

Duration of test (contact time):

42 d

Initial conc.:

10 mg/L

Based on:

DOC

Parameter:

% degradation (CO2 evolution)

Value:

10

Sampling time:

28 d

Details on results:

RS-Freetext:
CO2 evolution: 10 %
DOC removal: 22 %

Interpretation of results:

other: Under the conditions of the test, the test substance was poorly biodegradable.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Principles of method if other than guideline:

The closed bottle test was conducted according to Fischer et al. (1974). Fischer WK, Gerike P, Schmid R (1974). Z. Wasser Abwasser Forsch. 7: 99-118

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, domestic (adaptation not specified)

Details on inoculum:

Inoculum: 1 drop of effluent/L

Duration of test (contact time):

30 d

Initial conc.:

1 mg/L

Based on:

DOC

Parameter:

% degradation (O2 consumption)

Value:

0 - 10

Sampling time:

30 d

Interpretation of results:

under test conditions no biodegradation observed

Reference 4

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

Principles of method if other than guideline:

Method: The OECD Screening test was conducted according to a method described by the Umweltbundesamt (1978) and The OECD (1976).
Umweltbundesamt (1978). OECD Chemicals Testing Programme. Expert Group C  "Persistence", Draft Working Papers, 31 Mar 1978 OECD Environment Directorate (1976). Proposed Method for the  Determination of the Biodegradability of Surfactants used in Synthetic  Detergents,

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, domestic (adaptation not specified)

Duration of test (contact time):

19 d

Initial conc.:

3 - 20 mg/L

Based on:

DOC

Parameter:

% degradation (DOC removal)

Value:

10

Sampling time:

19 d

Interpretation of results:

other: Under the conditions of the test, the test substance was poorly biodegradable.

Reference 5

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Principles of method if other than guideline:

Method: Zahn-Wellens test conducted according to the method described by Zahn and Wellens (1974). Zahn R, Wellens H (1974). Chemiker Z. 98: 228-232

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, industrial (adaptation not specified)

Duration of test (contact time):

14 d

Initial conc.:

400 mg/L

Based on:

DOC

Parameter:

% degradation (DOC removal)

Value:

30 - 40

Sampling time:

14 d

Interpretation of results:

other: Under the conditions of the test, the test substance was partly eliminated from water.

Reference 6

Endpoint:

biodegradation in water: screening tests

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Principles of method if other than guideline:

Method: The study was conducted according to the French AFNOR T 90-302 test guideline (1977).

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: aerobic microorganisms

Duration of test (contact time):

42 d

Initial conc.:

40 mg/L

Based on:

DOC

Parameter:

not specified

Value:

0 - 10

Sampling time:

42 d

Interpretation of results:

under test conditions no biodegradation observed

Reference 7

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Deviations:

yes

Remarks:

Water from the river Rhine was used as inoculum

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: fresh water from the river Rhine

Details on inoculum:

Water from the river Rhine was used as inoculum which had been taken downstream from the spot where the effluent of waste water treatment plant was discharged into the river.

Duration of test (contact time):

60 d

Initial conc.:

20 mg/L

Based on:

DOC

Initial conc.:

62 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The pH of the test medium was adjusted to 6.5 at test start and during the course of the study controlled and if necessary readjusted.

Reference substance:

aniline

Key result

Parameter:

% degradation (DOC removal)

Value:

>= 0 - <= 10

Sampling time:

60 d

Interpretation of results:

under test conditions no biodegradation observed

Reference 8

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Deviations:

yes

Remarks:

Water from the river Rhine was used as inoculum

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: fresh water from the river Rhine

Details on inoculum:

Water from the river Rhine was used as inoculum which had been taken upstream from the spot where the effluent of waste water treatment plant was discharged into the river.

Duration of test (contact time):

60 d

Initial conc.:

20 mg/L

Based on:

DOC

Initial conc.:

62 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The pH of the test medium was adjusted to 6.5 at test start and during the course of the study controlled and if necessary readjusted.

Reference substance:

aniline

Key result

Parameter:

% degradation (DOC removal)

Value:

>= 0 - <= 10

Sampling time:

60 d

Interpretation of results:

under test conditions no biodegradation observed

Reference 9

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Deviations:

yes

Remarks:

Water from the river Rhine was used as inoculum

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: fresh water from the river Rhine

Details on inoculum:

Water from the river Rhine was used as inoculum which had been taken downstream from the spot where the effluent of waste water treatment plant was discharged into the river.

Duration of test (contact time):

60 d

Initial conc.:

20 mg/L

Based on:

DOC

Initial conc.:

62 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The pH of the test medium was adjusted to 8.5 at test start and during the course of the study controlled and if necessary readjusted.

Reference substance:

aniline

Key result

Parameter:

% degradation (DOC removal)

Value:

ca. 90

Sampling time:

60 d

Details on results:

Kinetic of test substance (in %):
= 0 after 28 day(s)
= 16 after 40 day(s)
= 57 after 49 day(s)
= 76 after 54 day(s)
= 89 after 60 day(s)

Interpretation of results:

other: biodegradable after adaptation

Reference 10

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Deviations:

yes

Remarks:

Water from the river Rhine was used as inoculum

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: fresh water from the river Rhine

Details on inoculum:

Water from the river Rhine was used as inoculum which had been taken upstream from the spot where the effluent of waste water treatment plant was discharged into the river.

Duration of test (contact time):

60 d

Initial conc.:

20 mg/L

Based on:

DOC

Initial conc.:

62 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The pH of the test medium was adjusted to 8.5 at test start and during the course of the study controlled and if necessary readjusted.

Reference substance:

aniline

Key result

Parameter:

% degradation (DOC removal)

Value:

>= 70 - <= 80

Sampling time:

60 d

Details on results:

Kinetic of test substance (in %):
= 0 after 28 day(s)
= 5 after 32 day(s)
= 22 after 35 day(s)
= 52 after 46 day(s)
= 73 after 60 day(s)

Interpretation of results:

other: biodegradable after adaptation

Reference 11

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on inoculum:

The inoculum was activated sludge adapted to the test substance taken from a previous biodegradation study (Project No. 99/0668/21/4).

Duration of test (contact time):

28 d

Initial conc.:

61.9 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Reference substance:

aniline

Key result

Parameter:

% degradation (CO2 evolution)

Value:

>= 0 - <= 10

Sampling time:

28 d

Interpretation of results:

other: poorly biodegradable

Reference 12

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on inoculum:

The inoculum was activated sludge, adapted to the test substance, taken from a previous biodegradation study (Project No. 99/0668/21/2).

Duration of test (contact time):

28 d

Initial conc.:

61.9 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Reference substance:

aniline

Key result

Parameter:

% degradation (CO2 evolution)

Value:

>= 0 - <= 10

Sampling time:

28 d

Interpretation of results:

other: poorly biodegradable

Reference 13

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, industrial (adaptation not specified)

Details on inoculum:

The activated sludge inoculum used in this study originated from an industrial wastewater treatment plant (BASF AG). The concentration of dry substance was 1 g/L.

Duration of test (contact time):

28 d

Initial conc.:

400 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Parameter:

% degradation (DOC removal)

Value:

0 - 10

Sampling time:

28 d

Details on results:

Kinetic of test substance (in %):
= 0 after 3 hour(s)
= 0 after 7 day(s)
= 5 after 11 day(s)
= 8 after 28 day(s)

Interpretation of results:

other: poorly eliminated from water

Reference 14

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: fresh water from the river Rhine

Duration of test (contact time):

72 d

Initial conc.:

40 mg/L

Based on:

DOC

Initial conc.:

140 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The test substance was added directly to the inoculum without addition of mineral test medium.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

0 - 10

Sampling time:

28 d

Parameter:

% degradation (DOC removal)

Value:

90 - 100

Sampling time:

72 d

Details on results:

Test duration (days) : 72

pH: 7 - 7.5
Degradation degree of the test substance at the end of the test (% DOC): < 10

pH: 8
Duration of adaptation phase (days): 28 (mean)
Duration of the biodegradation phase (days): 20
Degradation degree of the test substance at the end of the 10-day window (% DOC): 0
Degradation degree of the test substance at the end of the test (% DOC): 80 - 90

pH: 8.5
Duration of adaptation phase (days): 28 (mean)
Duration of the biodegradation phase (days): 30
Degradation degree of the test substance at the end of the 10-day window (% DOC): 0
Degradation degree of the test substance at the end of the test (% DOC): 90 - 100


Biodegradation degree (DOC removal) after 28 days: < l0%
Biodegradation degree (DOC removal) after 72 days: 90 -100%


Inhibition control (sodium benzoate):
Inhibition control (DOC removal) after 14 days (pH 7.0): 40 - 50%

Interpretation of results:

other: The test substance is in this test biodegradable after adaptation at pH 8.0-8.5.

Reference 15

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: fresh water from the river Rhine

Details on inoculum:

Mixture from fresh Rhinewater and adapted Rhinewater from Scas-Test.

Duration of test (contact time):

44 d

Initial conc.:

20 mg/L

Based on:

DOC

Initial conc.:

72 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Parameter followed for biodegradation estimation:

DOC removal

Parameter:

% degradation (CO2 evolution)

Value:

30 - 40

Sampling time:

28 d

Parameter:

% degradation (DOC removal)

Value:

90 - 100

Sampling time:

28 d

Details on results:

Test duration (days): 44
Duration of the adaptation phase (days): 16
Duration of the degradation phase (days): 28

Biodegradation degree (C02/ThCO2) after 28 days: 30-40 % (14 %, 27 %, 55 %)
Elimination degree (DOC) after 28 days: 90-100 % (76 %, 100 %, 101 %)

The deviation of the degradation degree of the test substance in the plateau phase (> 20 %) was justified in the high pH value from > 9.0 and the difference in the test-vessels. So CO2 was solved as (CO3)2- and not stripped and measured in the absorption-vessels.

The test substance is in this test moderately or partially biodegradable.
But the test substance is in this test well eliminable from water.

Interpretation of results:

other: moderately or partially biodegradable and well eliminable from water

Reference 16

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: fresh water from the river Rhine

Details on inoculum:

Rhine-water from the gauging station in Bad Honeff. Concentration of dry substance was not measured.

Duration of test (contact time):

70 d

Initial conc.:

20 mg/L

Based on:

DOC

Initial conc.:

104 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

0 - 10

Sampling time:

28 d

Parameter:

% degradation (DOC removal)

Value:

80 - 90

Sampling time:

59 d

Details on results:

Test duration (days): 70
Duration of the adaptation phase (days): 50
Duration of the degradation phase (days): 10

Degradation of the test substance at the end of the 10-day window (% DOC): 0

Degradation degree of the test substance after 59 days at the end of test 1 (% DOC): 80-90
Degradation degree of the test substance after 70 days at the end of test 2 (% DOC): 80-90

Biodegradation degree (DOC removal) after 28 days: 0-10 %
Biodegradation degree (DOC removal) after 59 days: 80-90 %

Kinetic of test substance (in %):
= 0 after 28 day(s)
= 4 after 49 day(s)
= 86 after 57 day(s)
Kinetic of control substance (in %):
= 90 ... 100 after 14 day(s)

Interpretation of results:

other: The test substance was biodegradable after adaptation, but not readily biodegradable according to OECD criteria

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, not fulfilling specific criteria

Type of water:

freshwater

Additional information

Information on the substance itself is limited to a single, poorly documented study of inherent biodegradation. A large number of degradation tests are available for EDTA and its salts, a structural analogue of the substance (for justification on read-across, see Section 13). Results from OECD guideline tests indicate that EDTA is not readily biodegradable and tests on inherent biodegradability result in low biodegradation rates.

Influence of pH

It could be shown that a change of the pH-value has a great impact on the biodegradability of EDTA. Results obtained in a DOC removal test according to the principles of OECD Guideline 301 using natural surface water from the river Rhine as inoculum showed that up to 100% EDTA was degraded after 60 days at pH 8.5 but less than 10% at pH 6.5. Such slightly alkaline conditions are realistic in environmental surface water compartments. 

Degradation pathway

The degradation pathway of EDTA has been summarised in the EU Risk Assessment (2004). The first degradation product described is ethylenediaminetriacetate (ED3A) which can react spontaneously to ketopiperazinediacetate (KPDA) by intramolecular cyclisation. KPDA itself is biodegradable.

Conclusion

EDTA, and by analogy HEDTA, is not readily biodegradable according to OECD criteria. It has been shown that, under slightly alkaline pH or adaptation, the biodegradability of EDTA is considerably improved. EDTA was >60% biodegradable in an enhanced test using pre-adapted activated sludge. Therefore, it can be concluded that the substance is ultimately biodegradable under such conditions.