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Biodegradation in water and sediment: simulation tests

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Reference
Endpoint:
biodegradation in water: sewage treatment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1983
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Detailed information given. Test protocol and raw data are included in the report. Quality assurance was applied.
Qualifier:
equivalent or similar to guideline
Guideline:
EPA OPPTS 835.3240 (Simulation Test - Aerobic Sewage Treatment: A. Activated Sludge Units)
Deviations:
yes
Remarks:
Full protocol reference is in the report: ABC Protocol: Semi-continuous Activated Sludge (SCAS)Biodegradation " dated March 18, 1983
GLP compliance:
not specified
Remarks:
Quality assurance was applied and signed for, similar to current GLP practises
Specific details on test material used for the study:
The Santicizer 8, test material, a viscous lightly yellow colored liquid at >95% purity, Lot No. QH-18 was provided by Monsanto Polymer Products Company, 800 North Lindbergh Boulevard, St. Louis, Missouri.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
The activated sludge used in this study was obtained from·Scott Boulevard waste water treatment plant, City of Columbia, Columbia, Missouri, within four hours of the initiation of the study. Prior to initiation of the study, the sludge was kept refrigerated. Also, the solids concentration of the sludge was determined and subsequently adjusted to approximately 3000 mg/l. The initial microbial population of the sludge was found to have an average value of 2.1 x 10^6 organisms per milliliter of mixed liquor. The sludge was found to contain 18.2 % organic carbon by analysis of a portion of the sludge taken from the control system following termination of the study.

14d acclimation period was applied before a 21d biodegradation phase was started.
Duration of test (contact time):
35 d
Initial conc.:
50 mg/L
Based on:
test mat.
Initial conc.:
69.9 mg/L
Based on:
test mat.
Initial conc.:
157 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
A stock solution was prepared at a concentration of 10 mg/ml by disolving 10.00 g in one liter of deionized water
Reference substance:
ethylene glycol
Remarks:
The triethylene glycol, positive control, a viscous colorless liquid at 99+% purity was obtained from Sigma Chemical Company, St Louis, Missouri.
Test performance:
Analytical methodology was developed and suitable. The positive control substance performed as expected.

One goal of running the study was to maintain a mixed liquor suspended solids (MLSS )level level at 2000-3000 mg/l (protocol section 5.2.1). It is seen that MLSS levels remained consistently within this range throughout the sutdy. The MLSS values exceed the limits only on two occasions with values of 3080 and 3010.

A second goal of running the study was to maintain a dissolved oxygen level in each vessel of at least 2.0 mg/l (protocol section · maintained at 500 ml/minute throughout the entire study. No dissolved oxygen levels were observed below 2.0 mg/l over the acclimation phase of the study.

Examination of the microbial population data shows no evidence of adverse effects of the test compounds upon the microflora present in the sludge
Key result
% Degr.:
>= 99
Parameter:
test mat. analysis
Sampling time:
21 d
Remarks on result:
other: biodegradation phase: HPLC analysis based on 69.9 ppm initial concentration
Key result
% Degr.:
50.6
Parameter:
DOC removal
Sampling time:
21 d
Remarks on result:
other: biodeg phase initial conc 157 ppm test material
% Degr.:
45.9
Parameter:
DOC removal
Sampling time:
14 d
Remarks on result:
other: biodeg phase initial conc 157 ppm test material
% Degr.:
56.4
Parameter:
DOC removal
Sampling time:
7 d
Remarks on result:
other: biodeg phase initial conc 157 ppm test material
% Degr.:
48.4
Parameter:
DOC removal
Sampling time:
3 d
Remarks on result:
other: biodeg phase initial conc 157 ppm test material
Transformation products:
not measured
Details on results:
% removal = 100 - [(DOCt=0h or influent) - (DOCt=3,7,14,21 or effluent)] / (DOCt=0h or influent) x 100
Mixed liquor suspended solids during the acclimation phase were within specified range 2000-3000 mg/L except on two occassions, pH ranging 6.9 - 7.2 and dissolved oxygen >= 2.2 ppm.

Examination of percent of DOC removal values obtained during the acclimation phase of the study shows a possibility of inhibition by both test compounds. This possible inhibition appears to be insignificant by the end of the acclimation period.

Examination of the microbial population data shows no evidence of adverse effects of the test compounds upon the microflora present in the sludge.

Measurements of test material concentrations during the biodegradation phase of the study indicate that >99% of the 69.9 ppm of Santicizer 8 initially present in the test system is biodegraded and that 92.9% of the 56.9 ppm of Santicizer 9 initially present in the test system is biodegraded with 4.03 ppm Santicizer 9 remaining after twenty-one days.

Measuremen ts of dissolved organic carbon (DOC) in the test systems during biodegradation shown no differences in trends between the four test chambers. The percent DOC removal during biodegradation was calculated relative to measured DOC levels at the initiation of the biodegradation phase of the study.
Results with reference substance:
% DOC removal for the positive control substance ethylene glycol was 63.4% at day 3, 57.3% at day 7, 40 % at day 14 and 55.4% at day 21

 DOC levels in sludge mixed liqour during the biodeg phase of the study:

 

ppm

ppm

ppm

ppm

ppm

day

0

3

7

14

21

control

121

54.5

66.7

87.6

91

pos control

142

52

60.7

85.2

63.4

Santicizer 8

157

81

68.4

85

77.6

Santicizer 9

142

76.8

67.7

85.7

73.7

 

Validity criteria fulfilled:
not specified
Conclusions:
The substance showed:
- an insignificant effect on DOC removal at the end of the acclimation phase (at 50 ppm, 14d)
- no evidence of adverse effects upon microflora in sludge
- > 99% biodegradation at 21d of the biodegradation phase by HPLC analysis, showing at least rapid primary biodegradation
- Similar percentages of DOC removal as positive control during the biodegradation phase, indicating persistency is not anticipated
Executive summary:

A semi-continuous activated sludge (SCAS) biodegradation study was performed with Santicizer 8 and Santicizer 9 according to the ABC test lab protocol under quality control review. An analytical method for each of the two test compounds, Santicizer 8 and Santicizer 9, was developed. The method involved dichloromethane extraction with quantification by HPLC. It was judged that the concentration of each test material in the aqueous phase of a sludge mixed liquid sample accurately represents the total test material present in the mixed liquor. Recoveries of Santicizer 8 and Santicizer 9 from water were found to be 101 ± 2.3% and 97.7 ± 5.6% respectively. A thirty-five day activated sludge study was conducted composed of a fourteen day acclimation period and a twenty-one day biodegradation period. The effects of Santicizer 8 and Santicizer 9 on the waste water treatment process were found to be negligible when present at or below 70 ppm. Assessment of the effect of Santicizer 8 and Santicizer 9 on the sludge microbial population s showed no discernable effect. During the twenty-one day biodegradation phase of the study, Santicizer 8 was biodegraded >99% when initally present at 69.9 ppm; Santicizer 9 was 92.9% biodegraded when initially present at 56.9 ppm. The substances also showed similar percentages of DOC removal compared to the positive control substance, indicating similar fate, hence no persistency is anticipated.

Description of key information

A semi-continuous activated sludge (SCAS) biodegradation study was performed with Santicizer 8 and Santicizer 9 according to the ABC test lab protocol under quality control review. An analytical method for each of the two test compounds, Santicizer 8 and Santicizer 9, was developed. The method involved dichloromethane extraction with quantification by HPLC. It was judged that the concentration of each test material in the aqueous phase of a sludge mixed liquid sample accurately represents the total test material present in the mixed liquor. Recoveries of Santicizer 8 and Santicizer 9 from water were found to be 101 ± 2.3% and 97.7 ± 5.6% respectively. A thirty-five day activated sludge study was conducted composed of a fourteen day acclimation period and a twenty-one day biodegradation period. The effects of Santicizer 8 and Santicizer 9 on the waste water treatment process were found to be negligible when present at or below 70 ppm. Assessment of the effect of Santicizer 8 and Santicizer 9 on the sludge microbial population s showed no discernable effect. During the twenty-one day biodegradation phase of the study, Santicizer 8 was biodegraded >99% when initally present at 69.9 ppm; Santicizer 9 was 92.9% biodegraded when initially present at 56.9 ppm. The substances also showed similar percentages of DOC removal compared to the positive control substance, indicating similar fate, hence no persistency is anticipated.

Key value for chemical safety assessment

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