Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
From 14th to 28th November 1991.
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1991
Report Date:
1991

Materials and methods

Test guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Details on test material:
Test material: CYDI ((1,4,5,6-Tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide)
Description: Off-white powder
Storage: In original container at room temperature
Molecular formula: C5H4N4O2
Specific details on test material used for the study:
Test material: CYDI ((1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide).
Description: Off-white powder.
Storage: In original container at room temperature.
Molecular formula: C5H4N4O2.

Sampling and analysis

Analytical monitoring:
not specified

Test solutions

Vehicle:
no
Details on test solutions:
Direct dispersion in water.

Test organisms

Test organisms (species):
activated sludge
Details on inoculum:
A mixed population of activated sewage sludge microorganisms.
Souce: The aeration Stage of Severn Trent PLC Sewage Treatment Plant, Belper, Derbyshire.

Study design

Test type:
not specified
Water media type:
not specified
Limit test:
no
Total exposure duration:
3 h

Test conditions

Hardness:
Not specified.
Test temperature:
21°C.
pH:
6.5
Dissolved oxygen:
Not specified.
Salinity:
Not specified.
Conductivity:
Not specified.
Nominal and measured concentrations:
Nominal concentrations: 1, 10, 100 and 1000 mg/L in a range-finding study.
3 replicates of 100 mg/L in the final study.
Details on test conditions:
The sample was maintained at 21 " C wi th continuous aeration and used on the day of collection. The pH was buffered to pH 6.5 with sodium hydroxide solution and the suspended solids level adiusted to 3.6 g/l prior to use.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol

Results and discussion

Effect concentrations
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (total fraction)
Basis for effect:
inhibition of total respiration
Results with reference substance (positive control):
EC50 (3-hour contact time) = 8.8 mg/L.

Any other information on results incl. tables

Table 1: Range-finding study

Concentration

(mg/l)

O2 consumption rates mgO2/l/min

3-hour contact time

% Inhibition

Control 1

0.52

-

Control 2

0.50

-

1.0

0.52

<2>

10

0.51

0

100

0.50

2

1000

0.01

98

Reference 3.2 mg/L

0.43

16

Reference 32 mg/L

0.10

80

Table 2: 100 mg/L test substance replicates

Concentration

(mg/1)

O2 consumption rates mgO2/l/min

3-hour contact time

% Inhibition

Control 1

0.44

-

Control 2

0.45

-

100, Replicate 1

0.43

3

100, Replicate 2

0.44

1

100, Replicate 3

0.41

8

Reference 3.2 mg/L

0.35

21

Reference 32 mg/L

0.06

87

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
Conclusions:
The oxygen consumption rate of activated sludge decreases by an average of 4% in the presence of 100 mg/L of (1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide.

The EC50 after 3 hours of exposure was therefore determined to be > 100 mg/L.
Executive summary:

Respiration inhibition of (1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide on activated sludge has been studied. The activated sludge was subjected to various concentrations of test substance for 3 consecutive hours.

A preliminary study has been carried out with test substance concentrations of 1, 10, 100 and 1000 mg/L.

Based on the results obtained in this preliminary test, it was decided to make new measurements on 100 mg/L replicates.

The average respiration inhibition based on the 100 mg/L replicates was found to be 4%.

The EC50 for respiration inhibition of activated sludge by (1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide after 3 hours of exposure was therefore determined to be > 100 mg/L.