O-ethylhydroxylamine

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge nitrification inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Three different GLP tests to investigate effects of the test subtance on sewage sludge (respiration inhibition, nitrifying ability, inhibition of anaerobic digestion) following different procedures of guidelines. The procedures of the respiration inhibition and the nitrifying test are only discribed fragmentary.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: ETAD Ecolgical Method No. 103

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: The Assessment of the Nitrífying Ability of Activated Sludge; Department of the Environment, UK (1980)

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: Modified amenability of sewage sludge to anaerobic digestion, Department of the Environment, UK (1977); Modification described by Owen et al (1979)

Principles of method if other than guideline:

Three different tests were reported in this study report:
- Effect on respiration rate of activated sludge followed ETAD Ecological Method No 103 - A Screening Test for the Assessment of the Possible Inhibitory Effect of a Chemícal Substance on Aerobic Waste-Water Bacteria
- Effect on the nitrifying ability of activated sludge were investigated following the procedures of the method "The assessment of the nitrifying ability of activated sludge" (Department of the Enviornment, UK (1980))
- Effect on sludge digestion were investigated following the procedures of the method "Amenability of sewage sludge to anaerobic digestion", Department of the Environment, UK (1977)) modified by Owen et al. (1979), Bioassay for monitoring biochemical methane potential and anaerobic toxicity . Water Research 13, 485-492.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

O-ethylhydroxylamine

EC Number:

402-030-3

EC Name:

O-ethylhydroxylamine

Cas Number:

624-86-2

Molecular formula:

C2 H7 N O

IUPAC Name:

O-ethylhydroxylamine

Details on test material:

- Name of test material (as cited in study report): Substance H109360 & Q125
- Physical state: colourless liquid
- Analytical purity: 50%
- Lot No.: EFI-100

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

not specified

Test organisms

Test organisms (species):

activated sludge

Details on inoculum:

- Respiration test: activated sludge
- Nitrifiying test: nitrifying sludge
- Anaerobic test: raw fed sludge and sludge from a heated digester collected from a local sewage treatment works, sieved to remove gross particles

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Remarks on exposure duration:

Respiration test: 3 h; nitrifying test: 4 h; anaerobic test: 15 days

Test conditions

Nominal and measured concentrations:

- Respiration inhibition test: control, 64, 200 mg/L
- Nitrifying ability test: control, 6.4, 20, 64, 200 mg/L
- Sludge degistion test (anaerobic): control; 0.5% Q12;, 1.0% Q125; 5.0% Q125

Details on test conditions:

- Respiration inhibition test: A sample of activated sludge was aerated for 3 h in the presence of the test substance and a synthetic sewage, and comparing its respiration rate after this period with that of the same activated sludge aerated for 3 h in the presence of the synthetic sewage alone
- Nitrifying ability test: Nitrifying sludge was incubated under aerobic conditions for a period of 4 h in an ínorganic medium containing ammonium ion . After this period the concentration of oxidised nitrogen formed in the presence of the test substance at a range of concentrations was compared with controls.
- Sludge digestion test: raw feed sludge and sludge from a heated digester were mixed in the ratio of 2 parts raw sludge.
The VSS of this mixture was calculated as 2.1% from the results obtained on the two component sludges . This 2 .1% VSS sludge was then placed in the incubation bottles of batch digestion units.The incubation bottles were swirled to mix the contents and then allowed to stand for approx. 30 min at 35°C before connection to the gas measuring Mariotte bottle devices. After a further 5 min to allow pressure equalisation, beakers were placed under the Mariotte bottles to collect the displaced liquid. Each day for the 15 days tthe volume of liquid collected in the beakers was recorded.
- Temperature: 35 ± 1.0°C (water bath)

Results and discussion

Effect concentrations

Duration:

4 h

Dose descriptor:

EC50

Effect conc.:

12 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of nitrification rate

Details on results:

- Aerobic sewage treatment:
Substance H109360 at a test level of 100 mg/L caused an inhibition of the respiration rate of an activated sludge as determined by the ETAD Method 103 of 36% and at 32 mg/L of 20% . It is considered that this level of inhibition is probably due to inhibition of nitrification.

Substance H109360 is an inhíbitor of the nitrifying ability of activated sludge whea measured by the ataadard Department of the Environment (UK) Method (Ref 2) . The EC50 value found was 12 mg/L and at 3 .2 mg/L the inhibition found was 10% which is
a level considered to be insignificant in terms of this test.

Anaerobíc sewage treatment
Inhibitíon of gas productíon was observed at the 2.5% test level but no significant inhibition of digestion was observed at the 0.5 and 0.25% levels.

- Based on the results it is suggested that the maximum level of Substance H109360 in sewage should be not greater than 2 mg/L to safeguard against possible inhibitory effects to nitrification or ludge digestion.