Reaction mass of Disodium decyl(sulphonatophenoxy)benzenesulphonate and Disodium oxybis[decylbenzenesulphonate]

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: screening test, other

Remarks:

OECD 303A

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was not conducted according to GLPs but was conducted according to guidelines and the report contains sufficient data for interpretation of study results.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

other: OECD Guidelines Number 303 A

Deviations:

yes

Remarks:

The test was modified in relation to sludge load and mean residence time (Sludge load 25 % of the original load due to an increase of the mean residence time and a decrease of the synthetic sewage concentration by a factor of 2). See M&M below.

Principles of method if other than guideline:

Not applicable

GLP compliance:

no

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
No data

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Inoculum Secondary effluent from the settling tank of a biological municipal waste water treatment plant, not adapted, not pre-conditioned
Concentration 3 ml/test unit
Source (Date; Time) ARA Werdholzli, CH-8048 Ziirich (02.12.93; 8.00 a.m.)

Duration of test (contact time):

50 d

Initial conc.:

10 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

Equilibration period:
The objective of this study was to determine the aerobic biodegradability of DOWFAX 3B2 under aerobic continuous exposure conditions using the OECD Coupled Units Test.

In this method, two OECD Confirmatory Test units, i.e.. model activated sludge plants, were operated in parallel whereby the parallelism was enhanced and assured by transinoculation of the activated sludge. The test material was mixed with synthetic sewage and added to one unit while the other was fed only with synthetic sewage. The degradation of the test material wasmonitored by the determination of the dissolved organic carbon (DOC) in both effluents at frequent time intervals. Any DOC difference of these effluent values was due to non- or only partially degraded test material.

Equilibration Period
Both test units were filled with the same synthetic sewage and inoculated with 3 ml of the secondary effluent from the settling tank of a biological municipal waste water treatment plant. The synthetic sewage was passed through the aeration vessel without further dilution at a rate corresponding to a mean residence time of 3 hours. By blowing sufficient air into the aeration chamber the activated sludge was kept constantly in suspension. The dissolved oxygen content of the aeration vessel was at least 2 mgll. With the air lift pump the activated sludge from thc settling vessel was continuously recycled to the aeration vessel. Sludge which has accumulated around the top of the aeration vessel was brought back into the system by brushing at least once a day.

Effluents from both units were collected and aliquots used for DOC determination. Effluent and influent DOC measurements were performed at least twice per week during the equilibration period. As soon as a sufficient amount of activated sludge had developed (dry matter content between 1.5 and 2.5 g/l) and a constant DOC removal was attained the test was started.

Test:
Two days before adding the test material to the influent of the test unit the sludge load of both units was reduced to 25 % of the original load by means of an increase of the mean residence time to 6 h and a decrease of the synthetic sewage concentration by a factor of 2. This sludge load was maintained during the whole test period.

The units were operated as described for the equilibration period. The concentration of the test material (as DOC) in the influent of the test unit was between 10 and 20 mg/l. The coupling of both units was achieved by interchanging half of the volume of the aeration vessels, including sludge. between the two units once a day. When no change of the DOC concentration in subsequent determinations was observed, determinations were performed less frequently but at a minimum of two a week. During the evaluation period DOC determinations were performed daily with the exception of the weekends.

Reference substance:

not specified

Preliminary study:

None

Test performance:

No data

Parameter:

% degradation (DOC removal)

Value:

7.4

Sampling time:

50 d

Remarks on result:

other: Ultimate biodegradability

Parameter:

% degradation (test mat. analysis)

Value:

100

Sampling time:

15 d

Remarks on result:

other: Primary degradation

Details on results:

This study was performed as a pilot study that means that the standard procedure was slightly modified as follows: (a) The transinoculation was not performed strictly during the whole test procedure and (b) the residence time was increased from 6 h to 10.4 h after the 33rd day of operation.

Based on the data of the individual DOC determinations, the degradation in the Coupled Units Test of DOWFAX 3B2 was calculated to be 7.4 % (95% confidence limits: +/-10.1 %). The calculation was based on 30 determinations (day 13 - 50). The corresponding standard deviation was 26.9 % DOC removal.
Significant degradation of the test substance as determined with DOC measurements could not be observed during the whole test procedure indicating no or only a poor mineralization. The relatively high scattering of the individual degradation values is characteristic for a test substance with poor ultimate biodegradability.

However, complete primary degradation of the parent compound as determined by HLPC was observed from the 20th day of operation. An increasing adaptation of the activated sludge to the test substance was obseved as shown by an increasing disappearance of the HPLC peaks with retention times between 10 and 25 minutes after 4, 15 and 20 days of operation. This complete degradation of the parent compound was observed until termination of the test after 50 days of incubation. It was assumed that the UV spectrum of the HLPC chromatogram represented all individual degradation products of the test substance since no additional peaks were detected during an extended HLPC run.

The mean residence time of 6 h was increased to 10.4 h on day 33 and maintained at this higher level during the remaining test time. Due to an operation failure the mean DOC concentration of the test substance of 10 mg/l in the influent of the test unit was increased to 16 mgll on days 33- 35.

The equilibration period for both units was 7 days. The working-in time after the first application of the test substance and the evaluation period was 12 and 38 days, respectively.

The dry matter content of the control and test unit ranged from 1.06 to 3.12 g/l and from 1.29 to 3.32 g/l, respectively. 20 % of the activated sludge were removed on day 35, since the dry matter content of both units was significantely higher than 2.5 g/l. The activated sludge of both test units showed good floculation during the whole test period as confirmed by the good settling behaviour. The settled sludge volume after 30 min ranged for the control and test unit from 125 to 350 ml/l and from 125 to 420 ml/l, respectively. The pH values and the oxygen concentration of both units were within an acceptable range.

Results with reference substance:

No data

None

Validity criteria fulfilled:

not specified

Interpretation of results:

other: Ultimate biodegradability was only 7.4% out to day 50. Primary degradability is complete after 15 days.

Conclusions:

The DOC based ultimate biodegradability measured between days 13 and 50 was low and reached only a mean value of 7.4 % (95 % confidence limits +/- 10 %; 30 determinations). However, the HPLC chromatograms of the analyzed effluent samples indicate that after 15 days of adaptation complete primary degradation occurs: already after 4 days of operation the HPLC peaks characteristic for the test material were significantly reduced before they completely disappeared as from day 15. This finding was confirmed with effluent samples taken at later stages up to day 50 of operation.

Executive summary:

DOWFAX* 3B2 consists of a 45 % solution of the disodium salt of mono- and didecylphenyloxide disulfonic acid in water. The aerobic biodegradability of the product was assessed in a continuous laboratory sludge treatment plant for primary and ultimate biodegradability according to the OECD Guidelines Number 303 A.

Two OECD Confirmatory Test units were run in parallel. The test material dissolved in OECD synthetic sewage at a concentration of approx. 10 mg/l Dissolved Organic Carbon (DOC) was continuously fed to the aeration vessel of the first unit. A second unit where only synthetic sewage was continuously added served as a control. The two units were coupled by interchanging half of the volume of each aeration vessel once a day. Both units contained activated sludge at a concentration of approximately 2.5 g/l (dry weight). Incubation took place at 18 - 25 "C with normal day-night cycles (diffuse day light). The hydraulic residence time (HRT) was kept at 6 h until the 33rd day of operation and was then raised to 10.4 h. Effluents of both units were collected and aliquots used for DOC determination as well as for analysis with high pressure liquid chromatography (HPLC). Ultimate biodegradation was calculated based on the percentage DOC removal by comparing influent and effluent DOC concentrations corrected by the effluent DOC concentration of the control unit. Primary biodegradation is based on the disappearance of the parent compound.

The DOC based ultimate biodegradability measured between days 13 and 50 was low and reached only a mean value of 7.4 % (95 % confidence limits +/- 10 %; 30 determinations). However, the HPLC chromatograms of the analyzed effluent samples indicate that after 15 days of adaptation complete primary degradation occurs: already after 4 days of operation the HPLC peaks characteristic for the test material were significantly reduced before they completely disappeared as from day 15. This finding was confirmed with effluent samples taken at later stages up to day 50 of operation. No further investigations were undertaken to identify the degradation products which seem to be recalictrant as shown by the lack of a significant DOC decrease over the whole period of operation.

Reference 2

Endpoint:

biodegradation in water: screening test, other

Remarks:

Soap & Detergent Association Confirming Test (Semi-Continuous Activated Sludge)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 OCT 1981 through 30 NOV 1981. The 7-day period of level operation began on 10 NOV 1981 and ended on 16 NOV 1981.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to a standard published method, under early GLP regulations. Though not specifically named in the report, the GLP regulations are assumed to be those of the U.S. Environmental Protection Agency.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

no guideline followed

Principles of method if other than guideline:

The Subcommittee on Biodegradation Test Methods of the Soap and Detergent Association. "A Procedure and Standards for the Determination of the Biodegradability of Alkylbenzene Sulfonate and Linear Alkylate Sulfonate," Journal of the American Oil Chemists Society, 42, 986-993 (1965).

GLP compliance:

yes

Specific details on test material used for the study:

Dowfax 3B2 Surfactant Lot No. MM01310

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on inoculum:

Return activated sludge was collected from the East Lansing, Michigan, Municipal Wastewater Treatment Plant was used as bacterial inoculum. Activated sludge from this plant was used because it received a minimal amount of industrial waste.

Duration of test (contact time):

7 d

Initial conc.:

20 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Remarks:

via methylene blue, chloroform extraction method

Details on study design:

Return activated sludge was collected from the East Lansing, Michigan, Municipal Wastewater Treatment plant was used as bacterial inoculum. Activated sludge from this plant was used because it receives a minimal industrial waste. Duplicate aeration units were run on a blank (no surfactant), LAS control and each sample tested. Sludge cylinders of the prescribed design, accommodating 1.5 liters, were used. The sludge was acclimated and equilibrated over an 8-day period, up to the operational level of 20 mg/L of test and control surfactant. Aeration, during the 23-hour daily test period, was maintained at 500 ml/min. Each day after the sludge had settled for one-half hour, one liter of the effluent liquid was removed from each unit. Each unit was then recharged with tap water, synthetic sewage concentrate, and surfactant test solution. The refill solution was sampled for MBAS as the influent. The blank influent and effluent provided a correction for the analytical procedure and the small amount of MBAS contributed by the activated sludge.

Reference substance:

other: Linear alkylbenzene sulfonate (LAS) standard, prepared by U.S. EPA in cooperation with the Soap and Detergent Association.

Preliminary study:

No data

Test performance:

The test was valid in that the LAS control biodegraded more than the required 97.5%.

Key result

Parameter:

% degradation (test mat. analysis)

Value:

98.7

Sampling time:

7 d

Remarks on result:

other: Inherently biodegradable (primary)

Details on results:

The apparent biodegradability for an average of seven days operation for Dowfax 3B2 Surfactant was 98.7%. The LAS, control unit, had an apparent biodegradability of 99.1%.

Results with reference substance:

The test was valid in that the LAS control biodegraded more than the required 97.5%.

None

Validity criteria fulfilled:

yes

Interpretation of results:

other: The test confirms the inherent (primary) biodegradability of Dowfax 3B2 Surfactant

Conclusions:

DOWFAX 3B2 surfactant met the requirement of more than 90% reduction in methylene blue active substance to be considered biodegradable under the SDA Semi-Continuous Biodegradability Test.

The test was valid in that the LAS control biodegraded more than the required 97.5%.

Executive summary:

DOWFAX 3B2 surfactant (Lot No. MM01310) was tested for biodegradability using the Soap and Detergent Association Confirming (semi-continuous activated sludge) Test.

The procedure involves exposing the samples under study to acclimated activated sludge and measuring the loss of methylene blue activity after one day, for 7 consecutive days. The loss of methylene blue activity is interpreted as biodegradation sufficient to destroy the surfactant properties, which is taken convervatively as an indication of primary biodegradation.

The DOWFAX 3B2 surfactant passed the test of biodegradability with 98.7% reduction in methylene blue active substance. The LAS (linear alkylbenzene sulfonate) control passed the test with a biodegradation of 99.1%. The results of this test confirm the biodegradability of DOWFAX 3B2 Surfactant.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, not fulfilling specific criteria

Additional information

The biodegradability of Dowfax 3B2 has been evaluated in various biodegradability screening studies.

DOWFAX* 3B2 consists of a 45 % solution of the disodium salt of mono- and didecylphenyloxide disulfonic acid in water. The aerobic biodegradability of the product was assessed for primary and ultimate biodegradability in a continuous laboratory sludge treatment plant according to the OECD Testing Guideline Number 303 A. The ultimate biodegradability based on DOC removal measured between days 13 and 50 was low, and reached a mean value of 7.4 % only (95 % confidence limits +/- 10 %; 30 determinations). However, the HPLC chromatograms of the analyzed effluent samples indicate that after 15 days of adaptation, complete primary degradation occurred. Already after 4 days of operation, the HPLC peaks characteristic for the test material were significantly reduced before they disappeared completely as of day 15. This finding was confirmed with effluent samples taken at later stages up to day 50 of operation.

In two separate studies, the biodegradability of DOWFAX 3B2 surfactant samples was studied using the Soap & Detergent Association (SDA) Semi-Continuous Activated Sludge test. In both studies, DOWFAX 3B2 was degraded by 97 % or more based on reduction in methylene blue active substance, meeting the 90 % threshold for passing this test. The tests were considered valid in that the LAS control biodegraded more than the required 97.5%.

DOWFAX* 3B2 consists of a 45 % solution of disodium mono and didecylphenyloxide disulfonic acid in water. The ready biodegradability of the product was evaluated in an aerobic aqueous medium with the Modified OECD Screening test. The study conformed to OECD Guidelines for Testing of Chemicals Guideline Number 301E and Method C.3 in Commission Directive 84/449/EEC. DOWFAX 3B2 is not considered to be readily biodegradable since the percent biodegradation of DOWFAX 382 did not exceed 70% of the initial test concentration within 28 days.

DOWFAX* 3B2 consists of a 45 % solution of disodium mono and didecylphenyloxide disulfonic acid in water. The ready biodegradability of the test material was evaluated in an aerobic aqueous medium with the Modified OECD Screening test. The study conformed to OECD Guidelines for Testing of Chemicals Guideline Number 301E and Method C.4-B in Commission Directive 92/69/EEC. DOWFAX 3B2 attained 4 % decrease in DOC after 28 days. Prolongation of the incubation period up to 42 days didn't lead to a detectable increase in biodegradability. Based on these results the test material cannot be classified as being readily biodegradable.

Additional members of the ADPODS category have been tested for ready and inherent biodegradability in water using OECD guideline methods as well as the SDA Semi-Continuous Activated Sludge test. As with DOWFAX 3B2, these substances also demonstrate inherent primary biodegradability.