Triammonium citrate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is inorganic

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

test conducted prior to implementation of OECD guidelines

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Version / remarks:

test conducted prior to implementation of OECD guidelines

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

test conducted prior to implementation of OECD guidelines

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

test conducted prior to implementation of OECD guidelines

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

test conducted prior to implementation of OECD guidelines

Principles of method if other than guideline:

- Principle of test: Several biodegradability test systems were conducted to determined the biodegradability of fourty-four compounds which were either considered to exhibit a good biodegradaility, a bad biodegradability or showed no effect in this test systems
- Short description of test conditions: The conditions used were similar to that desscribed in the respective OECD guideline
- Parameters analysed / observed: see respective OECD guideline

GLP compliance:

no

Remarks:

tests conducted prior to implementation of GLP in the EU

Oxygen conditions:

not specified

Inoculum or test system:

activated sludge (adaptation not specified)

Remarks:

industrial and domestic origin

Details on inoculum:

Details of the inoculum were not reported

Duration of test (contact time):

>= 14 d

Based on:

not specified

Remarks:

initial concentrations were not specified

Details on study design:

The coupled units test:
- is the adaptation of the OECD Confirmatory Test (OECD, 1976) for the application of summary parameters. The conventional form of the test has a legal status in the EEC (Council Directive, 1973) and various national detergent legislations, e.g., in Germany (Verordnung, 1977). Of all the tests discussed here, it is doubtlessly the best model for a communal sewage treatment plant, and it is the only one to work under steady-state conditions, i.e., as a continuous flow system, and to employ an organic base medium, i.e., to maintain nutrient competition at all times. Since it has furthermore a proved record in identifying sufficiently degradable surfactants, an important class of environmental chemicals, it was accorded something of a referee role in the present study unless results from more sophisticated investigations were available. Unfortunately it is too involved to serve as a general screening test. In the present program the test was started with a full load (2.5 g/liter of dry matter) of sludge from a communal sewage treatment plant. Its results are reported in the following manner in the tables: the working-in time, since this constitutes often some very pertinent information; and the mean DOC removal with its tolerance limits at a 95% probability level. Only the DOC removal is reported here since the COD removal is considered too undependable for reasons discussed elsewhere.
The Zahn-Weffens test (Zahn and Wellens, 1974; Umweltbundesamt, 1978) is meant to represent an industrial sewage treatment plant, i.e., it was designed to evaluate the removability of industrial chemicals released by point discharge through industrial sewage treatment plants into the aqueous environment. It is, incidentally, very similar to a test proposed by Pitter (1976). Its results are reported
as the percentage DOC removal achieved. The time period within which this DOC removal was attained was added in order to differentiate further the results obtained in this vigorous test. Here also only the DOC rather than both DOC and COD removals are reported for the reasons mentioned above.
The Swiss EMPA test (1977)
- is in principle very similar to the Zahn- Wellens test but is conducted at a different test material to sludge ratio. It was usually used instead of the latter when surfactants were tested. The removal results always represent 14day values.
The Japanese MITI test
- has already acquired a legal status in the Japanese environmental chemicals legislation. It is not specified in every detail therein. We used the Sapromat, basically a BOD determination apparatus with an electrolytic oxygen supply for its conduction. Other obvious possibilities within the realm of the description given in the law would be the Warburg apparatus or a closed
bottle test with an overhead gas phase. The inoculum was prepared in accordance with the procedure with the single exception that the partial inoculum samples were not collected from all over Germany but in the closer surroundings of the investigating laboratory. These encompass, however, so many different industries that the final inoculation mixture may safely be assumed to be representative for all of Germany. Since the test concentration is rigidly defined in the law, only the DOC removals after 14 days and the corresponding biochemical oxygen demands (BODT14 (%)) are reported. These oxygen depletions were calculated as percentages with respect to the theoretical biochemical oxygen demand, whereby the final oxidation state of nitrogen, if contained in the test compounds, was assumed to be that of ammonia unless the starting material was a nitro compound.
The French norm procedure AFNOR (1977)
- will probably obtain a legal status in the French environmental chemicals legislation. Here also the test concentration is rigidly fixed. The results are stated as percentage DOC removal. The inhibition test which is part of this procedure was also conducted in every case.
The carbon dioxide evolution test
- according to Sturm (1973); besides the conventional carbon dioxide production the DOC removal was followed as a further biodegradation measure. Of the tests included in this program it is the only one to employ a preacclimation procedure (therefore in table 1 two test durations are given, 28 days without and 42 days including the acclimation). The preacclimation was modified in such a way that 20 mg/liter of material, 20 mg/liter of yeast extract, and 10% of sewage treatment plant effluent rather than raw sewage were added to BOD water in order to avoid anaerobic conditions.
The OECD Screening Test (Umweltbundesamt, 1978; OECD, 1976)
- was adapted to the application of the DOC analysis. It was usually run with a test concentration corresponding to 20 mg C/liter, later on with 10 mg C/liter, except in the case of surfactants where 5 mg AS/liter were employed. In order to maintain
an optimal C:N:P ratio the ammonium concentration specified in the OECD procedure was tripled. Furthermore, a trace metal and an essential vitamin solution were added in order to optimize test conditions. This test has in its conventional form, i.e., with specific analyses, a legal status in the EEC and various national detergent legislations where it is a companion of the OECD Confirmatory Test. The first attempt to adapt it to the DOC analysis was published by Wuhrmann and Mechsner (1974). The results elaborated in this test are reported as percentage DOC removal after 19 days.
The closed bottle test according to Fischer et al. (1974);
- the results are reported as the biochemical oxygen demand as a percentage of the theoretically possible amount (theoretical biochemical oxygen demand, BODT) after 30 days at the standard test concentration of 2 mg/liter unless otherwise stated. The BODT of nitrogen-containing compounds was calculated with the assumption that the final oxidation state of nitrogen would be -3 unless the starting material was a nitro compound, in which case it was assumed to be +5. The first four tests described in the above series may involve elimination mechanisms other than or in addition to biodegradation and are usually claimed to
represent sewage treatment plant models. The last four are, with only few and simple precautions, true biodegradability tests and may be viewed as surface water models.

Key result

Parameter:

% degradation (DOC removal)

Value:

93

St. dev.:

5

Sampling time:

0 d

Remarks on result:

other: readily biodegradable in the coupled units test within the first day of incubation

Key result

Parameter:

% degradation (DOC removal)

Value:

85

Sampling time:

1 d

Remarks on result:

other: readily biodegradable in the Zahn-Wellens-test within the first 6 days of incubation

Key result

Parameter:

% degradation (DOC removal)

Value:

100

Remarks on result:

other: readily biodegradable in the AFNOR test, sampling time not reported

Key result

Parameter:

% degradation (CO2 evolution)

Value:

97

Remarks on result:

other: readily biodegradable in the Sturm test, sampling time not reported

Key result

Parameter:

% degradation (DOC removal)

Value:

100

Remarks on result:

other: readily biodegradable in the Sturm test, sampling time not reported

Key result

Parameter:

% degradation (DOC removal)

Value:

100

Remarks on result:

other: readily biodegradable in the OECD Screening test, sampling time not reported

Key result

Parameter:

other: BODT30

Value:

90

Remarks on result:

other: readily biodegradable in the Closed bottle test, sampling time not reported

Validity criteria fulfilled:

not applicable

Interpretation of results:

readily biodegradable

Conclusions:

In the present publication of Gerike et al (1979) the biodegradability of citric acid was determined using different, accepted test methods. Regardless of the method used citric acid exhibited a biodegradability of at least 85% up to 100% within the frist days of incubation, thus citric acid is considered to be readily biodegradable.

Executive summary:

In the present publication of Gerike et al (1979) the biodegradability of citric acid was determined using different, accepted test methods. Regardless of the method used citric acid exhibited a biodegradability of at least 85% up to 100% within the frist days of incubation, thus citric acid is considered to be readily biodegradable.

Description of key information

No data available for Triammonium citrate. Based on the ionic structure of the substance aqueous solutions will only contain the free ions, namely citrate and ammonium. Data are available for citric acid.

Published data for biodegradation of citric acid using several reliable test methods similar to OECD 301 B,C, D, E, tests were conducted prior to implementation of OECD guidelines, RL2, citric acid was readily biodegradable in all tests.

For azanium-ions the biodegradation cannot be determined due to its inorganic nature. According to Regulation (EC) No 1907/2006 (REACH) Annex VII, section 9.2.1.1., a test does not need to be conducted if the substance is inorganic.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

There are no data for the salt Triammonium citrate. However, due to the ionic nature of the substance Triammonium citrate is expected to dissociate in aqueous solutions, thus biodegradation will be investigated only with the free ions, namely citrate and ammonium.

Triammonium citrate is the ammonia salt of citric acid in which all carboxy groups are deprotonated and associated with ammonium ions as counter-cations. Its physical appearance are white crystals at 1013 Pa and ambient temperature. Furthermore, Triammonium citrate is very water soluble. It is used as food additive mainly due to its buffer capacity. Once, dissolved in water the ionic structure will split thereby generating free citric acid and ammonium ions. Both molecules are ubiquitously present and also integral part of the intermediary metabolism.

Citric acid was evaluated for biodegradation with accepted test methods and it was shown that cirtic acid is readily biodegradable.

Based on the ionic structure of ammonium it is not expected to bioaccumulate, however, due to ion-ion interactions the mobility of ammonium in soil is considered to be reduced. Ammonium remaining in soil is largely adsorbed onto positively charged clay particles, and will undergo nitrification and denitrification as part of the nitrogen cycle and be taken up by plants via nitrogen fixation (WHO, 1986). Ammonium is known to be metabolised by many organisms also frequently present in sewage treatment plants.

Based on these information ammonium ions are not considered to have an impact on the biodegradability of citric acid and thus, triammonium citrate is expected to be readily biodegradable.