Phosphocreatine, sodium salt

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 June - 29 July 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

2006

Deviations:

yes

Remarks:

see 'Principles of method if other than guideline'

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Version / remarks:

Regulation (EC) No 440/2008

Deviations:

yes

Remarks:

see 'Principles of method if other than guideline'

Principles of method if other than guideline:

Deviation from the study plan and/or the guideline: The temperature deviated from the recommended range (in °C: Maximum: 24.8; Minimum: 22.7; Mean: 23.6; Delta Mean - Max.: 1.2; Delta Mean - Min.: 0.9).
While the slight deviation on the temperature regulation (± 1.2°C instead of ± 1°C) is potentially relevant since it directly influences the measured BOD values, it does not have a significant influence on the calculated degradation, since all test flasks were exposed to the same conditions (i.e. also the blanks, whose BOD values are subtracted from the test suspensions vessels for the calculation of the biodegradation rates).
The influence of the deviation from the required maximum temperature could have, if any, a positive influence on the biodegradation, since biological processes would have been enhanced.
However, since the calculated biodegradation is significantly below the 60% pass level at the end of the 10-day window (46%), and significantly above it after 28 days (79%), this deviation also does not have any significant influence on the outcome of the test.

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Phosphocreatine, sodium salt

EC Number:

213-074-6

EC Name:

Phosphocreatine, sodium salt

Cas Number:

922-32-7

Molecular formula:

C4H8N3O5P.2Na

IUPAC Name:

sodium [carbamimidoyl(methyl)amino](phosphono)acetate

impurity 1

Reference substance name:

Water

EC Number:

231-791-2

EC Name:

Water

Cas Number:

7732-18-5

Molecular formula:

H2O

IUPAC Name:

Oxidane

Test material form:

solid: crystalline

Details on test material:

Batch No: 1413900

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: Sludge from the aeration tank of the ARA Werdhölzli (CH-8048 Zürich), a municipal biological waste water treatment plant.
- Preparation of inoculum for exposure: The sludge was pre-conditioned for 7 days (aerated but not fed) to reduce the amount of O2 consumed by the blank controls. Therefore, the sludge was washed twice with tap water and once with test medium.
- Pretreatment: The activated sludge was used after sampling from the treatment plant without adaptation.
- Concentration of sludge: 30 mg/L dry matter in the final mixture.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

91.8 mg/L

Based on:

other: nominal test item concentration based on 105 mg ThOD/L

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of test medium: Aerobic mineral salts medium prepared with ultrapure water (conductivity: <1.5 µS/cm; DOC: <0.5 mg/L)
* mineral stock solution A (10mL/L): 8.5 g/L KH2PO4, 28.49 g/L K2HPO4.3H2O, 33.4 g/L Na2HPO4.2H2O, 0.5 g/L NH4Cl, pH 7.4
* mineral stock solution B (1 mL/L): 36.4 g/L CaCl2.2H2O
* mineral stock solution C (1 mL/L): 22.5 g/L MgSO4.7H2O
* mineral stock solution D (1 mL/L): 0.25 g/L FeCl3.6H2O
* Final test medium: 10 mL of solution A and 1 mL of solutions B, C and D per L of test medium

- Test temperature: 22±2°C, controlled at ± 1°C, in a thermostat cabinet
- pH: 7.4±0.2°C (measured prior to testing and if necessary adjusted with NaOH or HCl (except in flask C).
- Continuous darkness: yes, test bottles were in a thermostat cabinet.

TEST SYSTEM
- Test flasks: 510 mL glass bottles (tightly closed with manometric BOD measuring devices) containing a total volume of test solution of 200 mL. The bottles were equipped with stirring rods and butylrubber quivers which contain 2 pellets of sodium hydroxide each to absorb the produced CO2 from the head space.
- Test performed in duplicate (two test flasks)

After centrifugation, the sludge was suspended in test medium, at about 2 g/L dry matter. Before the test, this suspension was diluted down to 60 mg/L dry matter, i.e. twice the final concentration, since this suspension was diluted 1:1 (v:v) afterwards. The test item was applied by direct addition into the test vessels to give a final test concentration as ThOD of about 100 mg O2/l.

CONTROL AND BLANK SYSTEM
B: Inoculum blank (two replicates)
R: Procedure control (two replicates): 60.2 mg/L Sodium benzoate (99.9 mg ThOD/L)
C: Abiotic sterile control (one replicate): 92.5 mg/L test item (104.4 mg ThOD/L)
X: Toxicity control (one replicate): 98.5 mg/L test item and 60.0 mg/L reference item (total 211.1 mg oxygen demand/L)

SAMPLING
The test vessels were stirred by an inductive stirring system for a maximum test period of 28 days. During the test the O2 uptake was continuously measured with a manometric BOD measuring device. Temperature was recorded with a data logger.
At the end of the test, the pH was measured in all flasks except the abiotic sterile control (C).
Total elimination was determined in each test vessel (test suspension, blank and procedure control) based on the theoretical carbon content and the analysis of the dissolved organic carbon (DOC) concentrations at the end of the test.

STATISTICAL METHODS:
Values of % degradation were calculated for each test flask and day. The arithmetic mean of % degradation in each test flask on each day was calculated.

Reference substance

Reference substance:

other: Sodium benzoate

Remarks:

CAS 532-32-1

Results and discussion

% Degradation

Key result

Parameter:

% degradation (O2 consumption)

Value:

79

Sampling time:

28 d

Remarks on result:

other: test flask 1 after 28 d: 82.1% test flask 2 after 28 d: 76.6%

Details on results:

The biodegradability Phosphocreatine, sodium salt based on O2 consumption was calculated to be 79% after 28 days as compared to the theoretical oxygen demand (ThOD).
The biodegradation reached 46% at the end of the 10-d window (i.e. within 10 days after attainment of 10% degradation).
Biodegradation of the test item started without any significant lag-phase.

The respective concentrations of organic carbon at the beginning (theoretical value based on the test item’s carbon content and the test concentration, as mg TOC/L) and at the end of the test (mean measured value of the two replicates, as mg DOC/L) were, respectively:
- 17.2 (theoretical value calculated based on the carbon content and the test concentration) and 3.87 for the test units (mean of two replicates)
- <0.5 and 0.82 for the blank control (mean of two replicates)
- 35.0 (theoretical value calculated based on the carbon content and the test concentration) and 0.88 for the procedure control (mean of two replicates)

The total elimination calculated based on dissolved organic carbon (DOC) measurements reached 82% for Phosphocreatine, sodium salt and 100% for sodium benzoate, respectively. The data is in line with the degradation calculated based on O2 consumption.
Phosphocreatine, sodium salt (CAS no. 922-32-7) did not reach the pass level of 60% for ready biodegradability in the Manometric Respirometry Test within the 10-d window and, therefore, cannot be termed as readily biodegradable. However, the pass level was reached within 28 days of incubation.

Any other information on results incl. tables

Procedure control:

The procedure control sodium benzoate reached 90% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

Toxicity control:

At the applied initial test concentration of 98.5 mg/L the test item was not judged to have any inhibitory effect on the microbial population, since the biodegradation of the mixture (test item + reference item sodium benzoate) exceeded 25% within 14 days.

Abiotic steril control:

Phosphocreatine, sodium salt was not abiotically degraded (by processes using O2) during the whole test period of 28 days in the absence of microorganisms as confirmed by the lack of significant oxygen consumption (the sudden increase at day 1 is most likely an experimental artefact, since the BOD values are varying between 12.4 and 14.4 mg O2/L for all the next 27 days).

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

A 28-d ready biodegradability test (OECD 301F, Manometric Respirometry Test) using activated sludge of a municipal sewage treatment plant indicated that Phosphocreatine, sodium salt (CAS no. 922-32-7) reached a biodegradation of 79% based on O2 consumption. The substance did not reach the pass level of 60% for ready biodegradability in the Manometric Respirometry Test within the 10-d window and, therefore, cannot be termed as readily biodegradable. However, the pass level was reached within 28 days of incubation.

Executive summary:

The biodegradability of Phosphocreatine, sodium salt (CAS no. 922-32-7) exposed to microorganisms derived from activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions, following the test guideline OECD 301 F.

The reference value for the calculation of the biodegradability of the test item was the theoretical oxygen demand (ThOD).

The biodegradability of Phosphocreatine, sodium salt based on O2 consumption was calculated to be 79% after 28 days as compared to the theoretical oxygen demand (ThOD).

The biodegradation reached 46% at the end of the 10-d window (i.e. within 10 days after attainment of 10% degradation).

Biodegradation of the test item started without any significant lag-phase.

The procedure control sodium benzoate reached 90% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

The total elimination calculated based on dissolved organic carbon (DOC) measurements reached 82% for Phosphocreatine, sodium salt and 100% for sodium benzoate, respectively. This data is in line with the degradation calculated based on O2 consumption. Phosphocreatine, sodium salt (CAS no. 922-32-7) did not reach the pass level of 60% for ready biodegradability in the Manometric Respirometry Test within the 10-d window and, therefore, cannot be termed as readily biodegradable. However, the pass level was reached within 28 days of incubation.

All validity criteria were fulfilled.