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Endpoint:
activated sludge nitrification inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1977
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication, which meets basic scientific principles
Qualifier:
no guideline followed
Principles of method if other than guideline:
Screening test on inhibition of ammonia-/nitrite-oxidation
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
other: Nitrosomonas sp. and Nitrobacter sp. (mixed nitrifying  culture)
Details on inoculum:
- Laboratory culture: autrophic nitrifying bacteria maintained in 12-L fiber-wall reactor with continuous feeding (solids retention time: 24 d); aeration (12.5 L/min) through submersed diffusers; buffered at pH 8 (Na carbonate/Na bicarbonate)
- Preparation of inoculum for exposure: mixed liquor removed from stock culture, centrifuged (18400 x g, 15 min), supernatant discarded, cells dispersed in feed solution; 90-mL aliquots added to each test flask
- Pretreatment: no
- Initial biomass concentration: no data
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
2 h
pH:
8.1 (buffered with Na carbonate/bicarbonate)
Nominal and measured concentrations:
nominal: 0 (control) and 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: reaction flasks, fill volume: 100 mL
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- agitation: shaker with 80 rpm

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: de-ionized water
- Nitrogen concentration: 200 mg/L NH3-N
- Culture medium different from test medium: no


OTHER TEST CONDITIONS
- Adjustment of pH: yes (pH 8.1)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- determination of NO3-N and NO2-N after 25 min, 1 h and 2 h
Duration:
2 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of nitrification rate
Validity criteria fulfilled:
yes
Conclusions:
Tributylamine does not inhibit nitirifcation (NOEC: 100 mg/L).
Executive summary:

The inhibiting effect of tributylamine was tested on a mixed autotrophic culture of nitrifying bacteria (Nitrosomonas sp. and Nitrobacter sp.; laboratory culture). The test was a limit test with a control and a test concentration of 100 mg/L tributylamine, both run in duplicate. The pH was buffered at pH 8.1. The NH3-N concentration was 200 mg/L. The nitrite and nitrate concentration were determined after 25 min, 1 h and 2 h. Tributylamine did not inhibit the nitrification. The NOEC was determined to be 100 mg/L.

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Basic data given: comparable to guideline study
Justification for type of information:
For details on endpoint specific justification please see read-across report in section 13 or find a link in cross-reference “assessment report”.
Reason / purpose:
assessment report
Qualifier:
no guideline followed
Principles of method if other than guideline:
Respiration inhibition test with activated sludge using glucose as substrate
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge, domestic
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): municipal sewage treatment plant treating domestic sewage from Tokyo
- Concentration of sludge: 30 mg/L
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
7 d
Test temperature:
25 °C
Duration:
7 d
Dose descriptor:
other: EC5
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate

Relative oxygen consumption after 7 d:

control (activated sludge and glucose): 1.0

tributylammonium chloride (act. sludge + glucose + test item): 0.95

Validity criteria fulfilled:
not specified
Conclusions:
The 7-d EC5 is 100 mg/L in the respiration inhibition test.
Executive summary:

The effect of tributylamine on the respiration rate of microorganisms was tested in a non-guideline study. The HCl salt of tributylamine was used as test item (100 mg/L). The test method was a respiration inhibition test with domestic activated sludge (30 mg/L) using glucose (40 mg/L) as substrate. The observation period was 7 d. The oxygen consumption was monitored continuously. Tributylammonium cloride inhibited the respiration slightly. The relative oxygen consumption was 0.95 compared to a control without the test item. Therefore the 7-d EC5 is 100 mg/L.

Description of key information

The 7-d EC5 for respiration inhibition of activated sludge is 100 mg/L (tributylammonium chloride; non-guideline study; Yoshimura et al., 1980).
The 2-h NOEC for inhibtion of nitrification is 100 mg/L (non-guideline study; Hockenbury & Grady, 1977).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

There is one relevant study available regarding the assessment of effects on the functioning of wastewater treatment processes (Yoshimura et al., 1980). There is another relevant study available dealing with the effect of tributylamine on the nitrification process (Hockenbury & Grady, 1977).

Endpoint

Organism group

Test system

Value [mg/L]

Reliability

Remarks

Source

7-d EC5

Microorganisms

Activated sludge, domestic

100

2

key study

HCl salt of tributylamine used as test item

Yoshimura et al. (1980)

2-h NOEC

Microorganisms

Nitrosomonas sp. and Nitrobacter sp.

100

2

key study

Hockenbury & Grady (1977)

The effect of tributylamine on the respiration rate of microorganisms was tested in a non-guideline study (Yoshimura et al., 1980). The HCl salt of tributylamine was used as test item (100 mg/L). The test method was a respiration inhibition test with domestic activated sludge (30 mg/L) using glucose (40 mg/L) as substrate. The observation period was 7 d. The oxygen consumption was monitored continuously. Tributylammonium cloride inhibited the respiration slightly. The relative oxygen consumption was 0.95 compared to a control without the test item. Therefore the 7-d EC5 is 100 mg/L.

The study from Hockenbury and Grady (1977) showed that tributylamine did not disturb the nitrifying abilities of a mixed culture of Nitrosomonas sp. and Nitrobacter sp. The 2-h NOEC was determined to be 100 mg/L.

Based on these results, it was concluded that disturbances of wastewater treatment processes are not to be expected when tributylamine is released in appropriate amounts.