Carbazamidine sulphate

Biodegradation in water: screening tests

Administrative data

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Test guideline 3

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Guanidinium phosphate (1:1)

EC Number:

226-551-9

EC Name:

Guanidinium phosphate (1:1)

Cas Number:

5423-22-3

Molecular formula:

CH5N3.H3O4P

IUPAC Name:

Guanidium phosphate (1:1)

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', Heeswijk-Dinther, The Netherlands, receiving predominantly domestic sewage.

- Treatment: The freshly obtained sludge was kept under continuous aeration until further treatment. The concentration of suspended solids was determined to be 4.8 g/L in the concentrated sludge. Before use, the sludge was allowed to settle (76 minutes) and the supernatant liquid was used as inoculum at the amount of 10 mL/L of mineral medium.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

14 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: According to OECD Guideline 301 B

- Test temperature: varied between 22 and 23°C
- pH:
At t=0 d: 7.5 - 7.6
At t=28 d: 7.4 – 7.8
- pH adjusted: yes. At the start of the test, the pH in the blank and positive control bottles was adjusted from 7.8 to 7.6 using 1N HCl
- Aeration of test medium: Overnight prior to the start of the test. During the test the medium was aerated and stirred continously.
- Suspended solids concentration: The concentration of suspended solids was 4.8 g/L in the concentrated sludge.

TEST SYSTEM
- Culturing apparatus: 2 litre all-glass brown coloured bottles
- Number of culture flasks/concentration:
Test suspension: containing test substance and inoculum (2 bottles).
Inoculum blank: containing only inoculum (2 bottles)
Positive control: containing reference substance and inoculum (1 bottle).
Toxicity control: containing test substance, reference substance and inoculum (1 bottle).
- Method used to create aerobic conditions:
A mixture of oxygen (ca. 20%) and nitrogen (ca. 80%) was passed through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. The synthetic air was sparged through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min).
- Details of trap for CO2:
The CO2 produced in each test bottle reacted with the barium hydroxide in the gas scrubbing bottle and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating the remaining Ba(OH)2 with 0.05 M standardized HCl (1:20 dilution from 1 M HCl (Titrisol® ampul). Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day, for the inoculum blank and test suspension. Titrations for the positive and toxicity control were made at least 14 days.

SAMPLING
- Sampling frequency: Titration were made on day: 2, 5, 7, 9, 14, 19, 23, 27 and 29
- Sampling method: Titration of the whole volume of CO2-absorber

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Positive control: yes
- Toxicity control: yes

Reference substance

Reference substance:

acetic acid, sodium salt

Results and discussion

% Degradation

Key result

Parameter:

% degradation (CO2 evolution)

Value:

7.5

St. dev.:

0.71

Sampling time:

29 d

Remarks on result:

other: Average of 2 test bottles

Details on results:

- Theoretical CO2 production: The TOC concentration of the 1 g/L Guanidine phosphate (1:1) solution was determined to be 77.95 mg/L. The ThCO2 of Guanidine phosphate (1:1) was calculated to be 0.29 mg CO2/mg.

- Biodegradation: The relative biodegradation values calculated from the measurements performed during the test period revealed no significant biodegradation of Guanidine phosphate (1:1). In the toxicity control more than 25% biodegradation occurred within 14 days (33%, based on ThCO2). Therefore, the test substance was assumed not to inhibit microbial activity.

- Acceptability of the test:
The positive control substance was biodegraded by at least 60% (81% was observed) within 14 days.
The difference of duplicate values for %-degradation of the test substance was always less than 20%.
The total CO2 release in the blank at the end of the test did not exceed 40 mg/L (51 mg CO2per 2 litres of medium, corresponding to 25 mg CO2/L).
The Inorganic Carbon content (IC) of the test substance (suspension) in the mineral medium at the beginning of the test was less than 5% of the Total Carbon content (TC). Since the test medium was prepared in tap-water purified by reverse osmosis (Milli-RO water, carbon levels < 500 ppb), IC was less than 5% of TC (mainly coming from the test substance, 14 mg TOC/L).

BOD5 / COD results

Results with reference substance:

- Functioning of the test system was checked by testing the reference substance sodium acetate, which showed a normal biodegradation curve. Biodegradation of sodium acetate at 14 days was 81%. The ThCO2 of sodium acetate was calculated to be 1.07 mg CO2/mg.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Guanidine phosphate (1:1) was not readily biodegradable under the conditions of the modified Sturm test.

Executive summary:

The readily biodegradation of Guanidine phosphate (1:1) under the conditions of the carbon dioxide (CO2) evolution test (modified Sturm test) was investigated according to OECD guideline 301 B and GLP principles. A single test concentration of 14 mg TOC/L was tested during 28 days. Based on the obtained results, Guanidine phosphate (1:1) was not readily biodegradable. The study is considered to be reliable without restrictions.