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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
26 July 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Reference Identification: Sodium 2,4,5-trichlorobenzenesulphonate CAS#: 53423-65-7; EC# 258-548-3 Common Name: STB-FR
Product Sample: Sodium Trichlorobenzene Sulfonate; (STB-FR) Lot: 1804-11 Approx. 300g
Date and Quantity Received: 05 Jun 18; 314.3 g (GW)
Physical Description: Solid, white powder
Storage Conditions: Room temperature
Purity: 100% active ingredients per Sponsor information
Analytical monitoring:
not required
Details on sampling:
The control, test, and reference sample solutions were measured for its dissolved oxygen content independently in series such that each bottle is measured immediately after the expiration of the three hour contact time and after less than 10 minutes post contact time.
Vehicle:
no
Details on test solutions:
The test item was added to 234 mL of deionized water in a quantity appropriate for the desired concentration. Synthetic sewage (16 mL) and 250 mL of microbial inoculum (activated sludge) were added to each test bottle. The test item was prepared in the following concentrations: 10 mg/L, 100 mg/L, and 1000 mg/L
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The activated sludge sample was determined to have a salinity of 0.49 ppt, total residual chlorine of 0.78 mg/L, a temperature of 30C at collection, a pH of 7.3, dissolved oxygen of 4.76, and a conductivity of 1013 mhos prior to the wash/settling procedures. The sludge was washed three times and allowed to settle for approximately 20 hours. A sample of the sludge was weighed and dried to determine the level of suspended solids and the sludge was treated with 50 mL/L of synthetic sewage feed for storage.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
Respiration rates were measured for up to 10 minutes immediately following the exposure period.
Nominal and measured concentrations:
Nominal: 10 mg/L, 100 mg/L, and 1000 mg/L
Reference substance (positive control):
yes
Remarks:
3,5 dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
Based on O2 consumption
Key result
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
Based on O2 consumption
Results with reference substance (positive control):
EC20 = 6.77 mg/L based on O2 consumption
EC50 = 9.43 mg/L based on O2 consumption

Oxygen Dissolution and Consumption Rate of Blanks:

Sample

Contact Time

Dissolved oxygen

(mg/L)

Oxygen uptake rate

(mg/L)/hr

O2 Uptake rate

(mg/g)/hr

Blank 1

3 hours

8.67

240.1

196.0

10 minutes

2.00

Blank 2

3 hours

8.74

329.0

268.6

10 minutes

2.00

Average

284.6

Standard Deviation

62.9

Oxygen Dissolution and Consumption Rate of Test Item:

Sample

Contact Time

Dissolved oxygen

(mg/L)

Oxygen uptake rate

(mg/L)/hr

%

Inhibition *

Test Item

(10 mg/L)

3 hours

8.48

352.8

-24.0

10 minutes

2.00

Test Item

(100 mg/L)

3 hours

8.95

2465

-766.3

10 minutes

2.00

Test Item

(1000 mg/L)

3 hours

8.64

2033

-614.5

10 minutes

2.00

Test Item

(1000 mg/L)

3 hours

8.43

2409

-746.6

10 minutes

2.00

Test Item

(1000 mg/L)

3 hours

8.46

23365

-720.9

10 minutes

2.11

Mean of 1000 mg/L Replicates

2259.3

-694.0

* Negative values for % inhibition are considered 0% inhibition.

Oxygen Dissolution and Consumption Rate of Reference Item:

Sample

Contact Time

Dissolved oxygen

(mg/L)

Oxygen uptake rate

(mg/L)/hr

%

Inhibition

Reference Item

(5 mg/L)

3 hours

8.85

1727

-506.9

10 minutes

2.00

Reference Item

(10 mg/L)

3 hours

8.67

438.0

-53.9

10 minutes

2.01

Reference Item

(20 mg/L)

3 hours

9.37

281.8

1.0

10 minutes

2.13

Reference Item

(40 mg/L)

3 hours

8.99

43.4

84.7

10 minutes

4.44

Oxygen Dissolution and Consumption Rate of Abiotic Controls:

Sample

Contact Time

Dissolved oxygen

(mg/L)

Oxygen uptake rate

(mg/L)/hr

Abiotic A - Test Item

(1000 mg/L)

3 hours

8.77

57.6

10 minutes

8.26

Abiotic B - Test Item

(1000 mg/L)

3 hours

8.81

43.9

10 minutes

8.57

Abiotic C - Test Item

(1000 mg/L)

3 hours

8.80

56.4

10 minutes

8.35

Average

50.8

Validity criteria fulfilled:
yes
Conclusions:
The test substance did not inhibit the respiration rate of activated sludge at concentrations up to and including 1000 mg/L.
Executive summary:

In a GLP OECD 209 guideline study designed to measure the respiration rate of an predominately domestic activated sludge fed with a standard amount of synthetic sewage feed, the EC20 and EC50 of the test item was determined to be >1000 mg/L and can therefore be considered to not inhibit activated sludge if discharged to sewage treatment plants.

Description of key information

In a GLP OECD 209 guideline study designed to measure the respiration rate of an predominately domestic activated sludge fed with a standard amount of synthetic sewage feed, the EC20 and EC50 of the test item was determined to be >1000 mg/L and can therefore be considered to not inhibit activated sludge if discharged to sewage treatment plants.

Key value for chemical safety assessment

Additional information

EC20 >1000 mg/L

EC50 >1000 mg/L