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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:
2018
Reliability:
1 (reliable without restriction)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report date:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Reference substance name:
Zanthoxylum, ext.
EC Number:
310-094-8
EC Name:
Zanthoxylum, ext.
Cas Number:
102242-62-6
Molecular formula:
NA
IUPAC Name:
Zanthoxylum ext
Test material form:
liquid: viscous

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Test System

Species: Activated sludge, microorganisms from a domestic waste water treatment plant.

Origin: The (controlled) activated sludge was supplied by the sewage plant for domestic sewage in Balatonfüred, Hungary, on 06 April 2018 (seven days before the main test). The prepared activated sludge was continuously aerated (2L/minute) at the test temperature of 22±2oC, for about 7 days.

Preparation of Activated Sludge Inoculum:
The activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in isotonic saline solution with shaking and again centrifuged. This procedure was repeated twice.
An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to dry weight determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 5 g dry material per litre was mixed with mineral medium (see Section 5.4) and then aerated under test conditions (for 7 days) until use. The pH of the activated sludge inoculum after preparation was: 7.42, just before use: 7.39. A pH adjustment of activated sludge inoculum was not performed.
NaCl (for isotonic saline solution): Manufacturer: lach: ner; Batch Number: PP/2017/00996,
Expiry date: 24 November 2019

Pre-conditioning of Activated Sludge Inoculum:
Pre-conditioning consisted of aerating (2L/minute) activated sludge (in mineral medium ) for 7 days at the test temperature. During the aeration the cell count of inoculum was checked as follows: the viability of the cultured sludge was determined by plating 0.1 mL of the different, usually 10-1, 10-2, 10-3 and 10-4 dilutions of cultures on nutrient agar plates.
The viable cell number of the cultures was determined by these plating experiments by manual colony counting. The approximately cell count of aerated inoculum fell in the range of ~108 cells/L; therefore on the day of the test this inoculum was diluted 50000 x with mineral medium to reach the necessary ~104 105cells/L cell concentration. After preparation the sludge was filtered through cotton wool. Pre-conditioning improves the precision of the method.
The inoculum was not pre-adapted to the test chemical.
Nutrient agar: Supplier: MERCK; Batch Number: VM784250, Expiry date:20 April 2022
Duration of test (contact time):
28 d
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
Key result
Parameter:
other:
Remarks:
% degradation on COD
Value:
71.1
Sampling time:
28 d
Remarks on result:
other: ready biodegradable (removal al 60% COD in a 10-day window)

BOD5 / COD results

BOD5 / COD
Key result
Parameter:
COD
Value:
2.43 other: mg O2/mg test item
Results with reference substance:
ThODNH3 of reference item = 1.67 mg O2/mg reference item

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item is considered to be ready biodegradable, since fulfilled the pass level for ready biodegradability that is the removal of 60 % COD in a 10-day window.
In this study total oxidised nitrogen (nitrate and nitrite) concentration determination was not performed after each oxygen measurement.
According to the test guidelines the test item can be assumed as not inhibitory on the activated sludge microorganisms because the degradation in the toxicity control group was higher than 25 % within 14 days. The percentage biodegradation of the reference item confirms the suitability of the used activated sludge inoculum.