Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters

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:

2017 - 01 - 31 - 2017 - 03 - 30

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

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters

Molecular formula:

unspecified

IUPAC Name:

Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters

Test material form:

liquid

Specific details on test material used for the study:

Name: Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters
Batch No.: RP GW 915 MU

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany.
The aerobic activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight. This suspension was used for the experiment.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

ca. 100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The purpose of this study was to determine the ready biodegradability of the test item Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters. The test item was exposed to aerobic activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.
This type of study is recognized by the international test guidelines and should provide a rational basis to assess the ready biodegradation properties of the test item when incubated with aerobic activated sludge.

The test flasks prepared according paragraph 6.6 were incubated at 22°C * 1°C. The pressure decrease in the reaction vessels was measured over complete experimental phase of 28 days using the BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany. The test flasks were closed gas-tight by a measuring head. Potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide. The amount of O2 consumed by the activated sludge was calculated from the decrease of pressure in the reaction vessel.

Course of the Test
Preparation of Test Flasks: The amounts of test item and reference item were directly weighed into the test flasks. No emulsifiers or solvents were used.
Incubation: The closed test flasks were incubated in a climatised chamber under continuous stirring. The consumption of oxygen was determined by measuring the change of pressure in the flasks. Evolved carbon dioxide was absorbed in an aqueous solution (45%) of potassium hydroxide.
Test Duration: 28d
Measurement of Oxygen: The change of pressure in the test flasks was measured by means of a manometric method (BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany) each day.
Temperature: The temperature was recorded by means of the automated software AMR Wincontrol©.
pH-Value: pH-values were measured in procedure control, a separately prepared test flask with test item (to prevent loss of test item in the test flasks) and a separately prepared test flask without test item (control) at test start and in all flasks at the end of the test, except in the abiotic and toxicity control, using a pH-electrode WTW pH 340i.

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

% Degradation

Key result

Parameter:

% degradation (O2 consumption)

Value:

22

Sampling time:

28 d

Remarks on result:

not readily biodegradable based on QSAR/QSPR prediction

Details on results:

Biodegradation of Test Item
Percentage Biodegradation:
The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10% degradation.

The mean biodegradation of 10% of Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters was reached at day 9 (ThODNH4). At the end of the 10-day window at day 19, the degradation of Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters was 16% (ThODNH4) and therefore the 10 day window criterion was not passed. The mean biodegradation at test end after 28 days was 22% (ThODNH4).

Incubation time [d] Degradation[%]

9 (start of 10-day window) 12 (mean)
19 (end of 10-day window) 16 (mean)
28 (end of test) 22 (mean)

Conclusion:
The degradation rate of Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters did not reach 60% within the 10-day window and after 28 days. Therefore, Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters is considered to be not readily biodegradable.

BOD5 / COD results

BOD5 / COD

Parameter:

ThOD

Value:

22 other: %

Remarks on result:

other:

Remarks:

ThOD NH4 after 28 days

Results with reference substance:

Biodegradation of Reference Item Sodium Benzoate
Percentage Biodegradation:
The reference item sodium benzoate was sufficiently degraded by 76% after 14 days and by 85% after 28 days of incubation.

Conclusion
The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

Any other information on results incl. tables

Percentage Biodegradation of Test Item, of Sodium Benzoate and of the Toxicity Control based on ThOD_NH4

Time	Percentage Biodegradation^1
(Days)	Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters^1		Sodium Benzoate^2	Toxicity control^1, 2
	Flask 1 [%]	Flask 2 [%]	Flask 5 [%]	Flask 7 [%]
1	0	0	23	13
2	2	2	38	18
3	2	2	44	22
4	4	4	50	27
5	5	5	57	28
6	7	7	60	30
7	8	8	64	30
8	8	11	70	30
9	10	13	73	33
10	11	14	74	32
11	10	13	73	31
12	12	13	76	33
13	12	15	76	34
14	12	15	76	33
15	12	15	76	33
16	15	17	79	33
17	15	17	79	33
18	15	17	79	35
19	15	17	79	35
20	15	17	79	35
21	17	17	82	35
22	17	19	82	35
23	17	19	82	38
24	19	19	82	38
25	19	21	82	38
26	21	23	85	39
27	21	23	85	39
28	21	23	85	39

¹ThOD_NH4of Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters: 2.320 mg O₂/mg test item  

²ThOD_NH4of sodium benzoate: 1.666 mg O₂/mg reference item

pH-Values at the End of the Test

Flask No.	Treatment	pH-value
1	Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters	7.2
2	Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters	7.4
3	Inoculum control	7.5
4	Inoculum control	7.6
5	Reference item (procedure control)	7.6

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Biodegradation of Test Item

The degradation rate of Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters did not reach 60% within the 10-day window and after 28 days.
Therefore, Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters is considered to be not readily biodegradable.

Biodegradation of Reference Item Sodium Benzoate

The reference item sodium benzoate was sufficiently degraded by 76% after 14 days and by 85% after 28 days of incubation.
The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

Biodegradation in the Toxicity Control
In the toxicity control containing both, the test item and the reference item sodium benzoate, 33% bio-degradation was noted within 14 days and 39% bio-degradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.

According to the test guidelines the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.

Abiotic Control
Oxygen demand: The oxygen demand in the abiotic control was 0 mg/L during the test duration. There was no need to correct the degradation of the test item and toxicity control.

Executive summary:

Title:	Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters: Ready Biodegradability in a Manometric Respirometry Test
Guidelines:	This study was designed to comply with the following methods: -     Commission Regulation 440/2008/EC, Method C.4-D of: Manometric Respirometry Test (EEC Publication No. L 142/496, May 2008) -     OECD Guideline for Testing of Chemicals No. 301 F: "Ready Biodegradability: Manometric Respirometry Test", adopted
Material and Methods:
Test Item:	Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters; Batch No.:RP GW 915 MU
Test Species:	Aerobic activated sludge (microorganisms from a domestic waste­water treatment plant) was supplied by the sewage treatment plant of Rossdorf,.
Test Design:	The test item Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters was investigated for its ready biodegradability in a manometric respirometry test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.
Endpoints:	Degradation rate of test item calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.
Test Item Loading Rate (initial concentration in medium C0):	102.9 mg/L corresponding to an oxygen demand of about 238.7 mg/L (ThODNH4)
Reference Item:	Sodium Benzoate
Reference Item Loading Rate:	102.9 mg/L corresponding to an oxygen demand of about 171.4 mg/L (ThODNH4)
Test Conditions:	22°C ± 1°C, darkness
Results:
Biodegradation of Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters:	The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10% degradation. The mean biodegradation of 10% of Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters was reached at day 9 (ThODNH4). At the end of the 10-day window at day 19, the degradation of Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters was 16% (ThODNH4) and therefore the 10 day window criterion was not passed. The mean biodegradation at test end after 28 days was 22% (ThODNH4).   Incubation time [d] Degradation[%] 9 (start of 10-day window) 12 (mean) 19 (end of 10-day window) 16 (mean) 28 (end of test) 22 (mean)   Therefore, Phosphoric acid, mono C16-20 (branched, even numbered) alkyl esters is considered to be not readily biodegradable based on ThODNH4.
Biodegradation of Sodium Benzoate:	The reference item sodium benzoate was sufficiently degraded by 76% after 14 days and by 85% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.
Biodegradation of the Toxicity Control:	In the toxicity control containing both, the test item and the reference item sodium benzoate, 33% biodegradation was noted within 14 days and 39% biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.