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Environmental fate & pathways

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:
November 5, 2001 till December 5, 2001
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study according to OECD guideline 301F (Ready Biodegradability: Manometric Respirometry Test) under GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report date:
2002

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

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Identity: ZP-TIX 1014
Batch No.: NW-01-028
Purity: >99%
Appearance: white solid
Storage: At room temperature at about 20°C (in the dark)

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Activated Sludge from a wastewater treatment plant (ARA Ergolz II, Füllinsdorf, Switzerland) treating predominantly domestic wastewater was used. The sludge was washed once with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliqout of the final sludge supsension was weighed, thereafter dried and the ration of wet to dry weight was calculated.
Based on this ratio calculated amounts of wet sludge were suspended in test water to obtain concentrations equivalent to 4 g dry material per liter. During holding the sludge was aerated at room temperature until use. Prior to use, the sludge was diluted with test water to a concentration of 1 g /L (dry weight basis). The diluted activated sludge was used to give a final concentration of 30 mg dry material per liter.
Duration of test (contact time):
ca. 28 d
Initial test substance concentration
Initial conc.:
ca. 101 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
Principle: The biogradation process consumes the dissolved oxygen in the liquid and generates CO2 (at 22°C, pH at start 7.4)). The CO2 is adsorbed by soda lime and the total pressure dcreases in the airtight test flasks. The pressure drop is detected and converted into an electrical signal by means of an electrode type manometer. The consumed oxygen is replaced by electrocally generated oxygen from a copper sulfat solution.

Light regimen: Darkness

Test tempertaure: 22°C (checked weekly)

The test flask were incubated unter continous stirring in a SAPROMAT D12 (Voith, Heidenheim), Oxygen consumption was recorded manually by a daily reading at least each working day.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
Parameter:
% degradation (CO2 evolution)
Value:
ca. 0
Sampling time:
28 d
Details on results:
The percent biodegradation of the test item was calculated based on the theoretical oxygen demand, which was in the range of 2.2 to 2.39 O2/mg test item without nitrification (ThOD (NH4)) and 2.60 to 2.72 O2/mg test item with nitrification (ThOD(NO3)).


The percentage of the reference item (sodium benzoate) was degraded by an average of 82% by exposure 14 days, thus confirming suitablity of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 91%.
The percent biodegradation in the toxicity control containing both test item and reference item was calculated based on the ThOD of the teste item and the reference item. The biodegradation rate in the toxicity control containing both test item and reference itemshowed a similar course of biodegradation over the 28-day exposure period as the two procedure controlls containing the reference item, only. Within 14 days of exporsu a biodegradation rate of 35% and 31% was observed based on the ThOD(NH4) and the ThOD(NO3) respectively (based on the lowest possible ThOD). Based on the hightst possible ThOD, the corresponding values were 33% and 31%.
Thus, according to the test guidelines the test item has no inhibitory effect on activated sludge microorganism because the biodegradation rate in the toxicity controll was >25% within 14 days.

BOD5 / COD results

Results with reference substance:
The biochemical oxygen demand (BOD) of the test item ZP-TIX 1014 in the test media was within the range of the inoculum controls. Consequently ZP-TIX 1014 was found to be not biodegradable under the test conditions within 28 days.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
not inherently biodegradable
Conclusions:
The test item ZP-TIX 1014 was found to be not biogradable under the test conditions. Any inhibitory effects on the biodegration could not be shown in the toxicity tests while the reference item (sodium benzoate) reached a biogradation of 91 % during the test period of 28 days.
Executive summary:

The test item ZP-TIX 1014 was investigated for its ready biogradebility in an manometric respriometry test over 28 days (according OEDC No. 301 F). The biochemical oxygen demand (BOD) of the test item ZP-TIX 1014 in the test media was within the range of inoculum controls. Consequently ZP-TIX 1014 was found to be not biogradeble under the test conditions.

In the toxicity control no inhibitory effect on the biodegradation was shown by the test item ZP-TIX 1014. In the procedure control, the reference item sodium benzoate was biodegraded by an average of 82 % on exposure 14 days and reached an average biodegradation rate of 91 % by the end of the test (28 days).