Potassium hexadecyl hydrogen phosphate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2005-05-24 until 2005-06-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

A robust, OECD guideline study and GLP-like study.

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EN ISO 14593 (1999)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: activated sludge from the sewage plant at Hildesheim 13 well suited as it comprises mostly municipal sewage
- Pre-treatment: The activated sludge was washed twice and re-suspended in autoclaved tap water. Afterwards the activated sludge was maintained in an aerobic condition by aeration for at least 24 hours and then homogenized with a mixer. The homogenized activated sludge was filtrated through a folded filter 50 mL inoculum/L stock solution was used to initiate inoculation
- Initial cell/biomass concentration: 10² - 10³ CFU/mL

Duration of test (contact time):

28 d

Initial conc.:

35 mg/L

Based on:

test mat.

Initial conc.:

18.4 other: mg C/L

Based on:

other: TOC (carbon content in test vessel)

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral solution according to OECD TG 310
- Test temperature: 20 - 25 °C
- Suspended solids concentration: 50 mL inoculum/L
- Continuous darkness: yes
- Aeration: yes

TEST SYSTEM
- Culturing apparatus: 120 mL headspace flask
- Measuring equipment: Three controls, three flasks containing reference item, three flasks containing test item, one flask containing test item and HgCl2 (testing for abiotic degradation) and one flask containing test item and aniline (testing for toxic effects) were tested.
• Toc analyser : Multi N/C 3000 Analytik Jena
• Thermo-hygrograph, Luft
• Gas tight syring, 1 mL SGE
• Shaker, Bühler
• Shaker, Heidolph

SAMPLING
- Sampling frequency: on days 0, 1 ,3 ,7, 14, 21 and 28
Determination of CO2 was carried out by IC analysis with a carbon analyser according to DIN EN 1484.
The TIC of the sodium hydroxide solution (blank value) was determined at each sampling time

CONTROL AND BLANK SYSTEM
- Inoculum blank: three test vessel was used for inoculum control

STATISTICAL METHODS:
The 95 % confidence interval for the mean percentage biodegradation after 28 days was calculated for the test item and functional control using software SIGMAPLOT (windows) rel 600.2000, SPSS Corporation

Reference substance:

benzoic acid, sodium salt

Test performance:

The test fulfilled the validation criteria.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

37

Sampling time:

28 d

Results with reference substance:

The percentage degradation of the functional control reached the pass level of 60 % after 3 days and came to 87 % after 28 days. The 95 % confidence interval on day 28 was 83 - 91 %.

	Biodegradation (%)						Confidence interval on day 28
Day (d)	1	3	7	14	21	28	P 95 %
Test item 35 mg/L	0	0	3	13	13	37	32 - 42
Functional control 30 mg/L	0	62	75	82	93	87	83 - 91

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Based on the results of the study, the test item should be regarded as not ready biodegradable in the 10 days-window and after 28 days.

Executive summary:

The ready biodegradability was determined with a non adapted activated sludge for potassium hexadecyl hydrogen phosphate over a test period of 28 days in the Headspace Test. The study was conducted according to OECD 310. Potassium hexadecyl hydrogen phosphate was tested with a concentration of 35 mg/L in triplicates, corresponding to a carbon content (TOC) of 18.4 mg C/L in the test vessels. The biodegradation of the test item was followed by TIC analyses of the quantity of CO2 produced by the respiration of bacteria. The amount of TIC produced was calculated by correcting the results of the test and reference item for endogenous TIC production of the control groups.

The 10 % level (beginning of biodegradation) was reached after 12 days. The pass level of 60 % was not reached during the test period. The biodegradation of the test item came to a maximum of 37 % after 28 days. The 95 % confidence interval on day 28 was 32 - 42 %.

The percentage degradation of the functional control (activity of the test system sodium benzoate) reached the pass level of 60 % after 3 days and came to 87 % after 28 days. The 95 % confidence interval on day 28 was 83 - 91 %. The validity criteria according to the guideline were fulfilled.

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1992-09-16 until 1992-10-14

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Not performed in accordance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))

Deviations:

no

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aire) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and re-suspending in mineral medium) and kept aerobic until being used on the same day.

Duration of test (contact time):

28 d

Initial conc.:

30 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: according to OECD guideline 302 C
- Test temperature: 25 °C
- pH: 7.4 (initial)
- pH adjusted: no
- Suspended solids concentration: 100 mg/L (dry weight)
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: test vessels containing 250 mL
- Number of culture flasks/concentration: Two controls, two flasks containing aniline as reference item, two flasks containing test item
- Measuring equipment: SAPROMAT D12, made by J.M.VOITH GmbH, D-7920 Heidenheim, Germany

SAMPLING
- Sampling frequency: every day
- Sampling method: using the SPAROMAT apparatus

CONTROL AND BLANK SYSTEM
- Reference control: Aniline

Reference substance:

aniline

Test performance:

The validation driteria were fulfilled.

Key result

Parameter:

% degradation (O2 consumption)

Value:

86

Sampling time:

28 d

Results with reference substance:

Degradation of aniline (reference substance) was 84 % after 7 days, and 82 % after 14 days, widely in excess of the validity criterion: the activity of the inoculum is thus verified and the test is considered as valid.

Oxygen uptakes, as read on the SAPROMAT meters were corrected:

- by deducting the basal oxygen uptake of sludge

- proportionally to account for the differences between actual and nominal concentrations of test substances.

Biological Oxygen Demand (BOD, mg O2/L, adjusted to nominal concentrations):

		Days:	5	7	10	14	21	28
BOD Sludge	1st flask	B1	54.0	58.0	70.0	82.0	92.0	98.0
	2nd flask	B2	48.0	50.0	56.0	61.0	65.0	67.0
	Mean	B	51.0	54.0	53.0	71.5	78.5	82.5
BOD Test subs	1st flask	C1	64.5	74.2	95.7	114.3	129.9	141.6
	2nd flask	C2	59.0	67.0	85.0	101.0	114.0	127.0
	1st flask corr.	C1-B	13.5	20.2	32.7	42.8	51.4	59.1
	2nd flask corr.	C2-B	8.0	13.0	22.0	29.5	35.5	44.5
% degr.	1st flask	D1	22	33	54	71	85	98
	2nd flask	D2	13	21	36	49	59	73
	mean	D	18	27	45	60	72	86

B = (B1 + B2) / 2

D1 = 100 * (C1-B) / ThOD * [S]

D2 = 100 * (C2-B) / ThOD * [S]

D = (D1 + D2) / 2

[S] : Initial test substance concentration (mg/L)

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

Potassium hexadecyl hydrogen phosphate was considered as ultimately inherently biodegradable according to this test.

Executive summary:

The inherent biodegradability of potassium hexadecyl hydrogen phosphate was determined by the manometric respirometry test according to the OECD guideline 302C. A measured volume of inoculated mineral medium, containing 30 mg/L test substance as the nominal sole source of organic carbon, was stirred in a closed flask at a constant temperature (± 1 °C) for up to 28 days. The consumption of oxygen was determined by measuring the quantity of oxygen required to maintain constant the gas volume in the respirometer flask. The amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum, run in parallel) was expressed as a percentage of ThOD. Potassium hexadecyl hydrogen phosphate undergoes an average of 86 % biodegradation after 28 days under the test conditions. Biodegradation proceeds steadily from the first day to the last, suggesting that solubilisation or hydrolysis is the limiting rate factor. Thus, potassium hexadecyl hydrogen phosphate was regarded as ultimately inherently biodegradable according to this test.

Description of key information

The test item is not ready biodegradable (37 % after 28 days) according to OECD TG 310 but can be considered as primarily inherently biodegradable. According to OECD TG 302C the test item was shown to be ultimately inherently biodegradable (86 % after 28 days). Therefore, the test item is considered to be inherently biodegradable, based on a weight of evidance approach.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, fulfilling specific criteria

Type of water:

freshwater

Additional information

Biodegradation of potassium hexadecyl hydrogen phosphate in water was examined in two studies in a weight of evidance approach. The first study which was performed according to OECD guideline 310 showed that the test substance is not readily biodegradable (37 % after 28 days) and the second study that was performed according to OECD guideline 302C showed that the test item is inherently biodegradable (86 % after 28 days).

 

The ready biodegradability was determined with a non-adapted activated sludge for potassium hexadecyl hydrogen phosphate over a test period of 28 days in the Headspace Test. The study was conducted according to OECD 310. Potassium hexadecyl hydrogen phosphate was tested with a concentration of 35 mg/L in triplicates, corresponding to carbon content (TOC) of 18.4 mg C/L in the test vessels. The biodegradation of the test item was followed by TIC analyses of the quantity of CO2 produced by the respiration of bacteria. The amount of TIC produced was calculated by correcting the results of the test and reference item for endogenous TIC production of the control groups.

The 10 % level (beginning of biodegradation) was reached after 12 days. The pass level of 60 % was not reached during the test period. The biodegradation of the test item came to a maximum of 37 % after 28 days. The 95 % confidence interval on day 28 was 32 - 42 %.

The percentage degradation of the functional control (activity of the test system sodium benzoate) reached the pass level of 60 % after 3 days and came to 87 % after 28 days. The 95 % confidence interval on day 28 was 83 - 91 %. The validity criteria according to the guideline were fulfilled.

The test item is considered to be primarily inherently biodegradable under the test conditions.

 

The inherent biodegradability of potassium hexadecyl hydrogen phosphate was determined by the manometric respirometry test according to the OECD guideline 302C. A measured volume of inoculated mineral medium, containing 30 mg/L test substance as the nominal sole source of organic carbon, was stirred in a closed flask at a constant temperature (± 1 °C) for up to 28 days. The consumption of oxygen was determined by measuring the quantity of oxygen required to maintain constant the gas volume in the respirometer flask. The amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum, run in parallel) was expressed as a percentage of ThOD. Potassium hexadecyl hydrogen phosphate undergoes an average of 86 % biodegradation after 28 days under the test conditions. Biodegradation proceeds steadily from the first day to the last, suggesting that solubilisation or hydrolysis is the limiting rate factor. Thus, potassium hexadecyl hydrogen phosphate was regarded as ultimately inherently biodegradable according to this test.

In conclusion, based on the weigh of evidance approach the test item is classified as inherently biodegradable.