Diethyl bis(2-hydroxyethyl)aminomethylphosphonate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Version / remarks:

(1986)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

(1984)

Deviations:

not applicable

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Direct weighings were used to prepare the different test item concentrations.
For the reference compound a stock solution at a concentration of 500 mg/L was prepared by dissolving 500 mg 3.5-Dichlorophenol in 10 mL of 1 M NaOH and diluting to 1 litre with deionised water. The pH was adjusted to pH 7±0.5 with H2SO4

Test organisms (species):

activated sludge

Details on inoculum:

- mixed population of aquatic microorganisms, origin of a laboratory scale sewage treatment unit (31), treating predominantly industrial sewage.
(Location: Bürrig / Germany))
- pretreatment: aeration of the activated sludge at 20°C ± 2°C, daily fed with synthetic medium
- test concentration of the activated sludge: 6 g/L dry weight
- Preparation of inoculum for exposure:
- first, the sludge was settled and the supernatant was decanted
- after centrifuging (20 min at 4000 rpm and 20°C) the supernatant was decanted
- approx. 1 g of the wet sludge was dried in order to calculate the amount of sludge to achieve a concentration of activated sludge of 6 g/i (dry
weight) suspended solids
- the calculated amount of sludge was first dissolved in synthetic medium and than filled up to a defined end vofume with deionised water
- Before use the pH of the activated sludge was measured and adjusted to pH 6-8.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

no data

Test temperature:

20.4 °C (concerning the highest concentration of 10000 mg/L)

pH:

7.8 (concerning the highest concentration of 10000 mg/L)

Dissolved oxygen:

oxygen (mg/L): O2-start 5.3; O2-end 2.9 (concerning the highest concentration of 10000 mg/L)

Salinity:

no data

Nominal and measured concentrations:

test item: 100, 1000 and 10000 mg/L (nominal)
reference compound: 1 and 20 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 300 mL glass Erlenmeyer flasks
- type of application: direct weighing
- temperature: 20 +/- 2 °C
- test concentration: 3 (100, 1000, 10000 mg/L)
- test parameter: respiration rate
- incubationtime: 3 hours with permanent aeration

- Two controls without test item were included in the test design, one at the start and the other at the end of the test series.
- The exposure medium to determine the physico-chemical oxygen consumption was prepared as the medium with the test item, but without activated sludge.

Reference substance (positive control):

yes

Remarks:

3.5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

See tables in "Any other information on results incl. tables".

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: See table 3 in "Any other information on results incl. tables". 0% and 68.6% inhibition were measured at 1 and 20 mg/L of 3,5-dichlorophenol, respectively. The EC50 of the reference compound is well in the range 5-30 mg/L.

Table 1: Oxygen content, temperature and pH-values during exposure phase

	Test item concentration (mg/L)	O2 start (mg O2/L)	O2 end (mg O2/L)	Time (start-end) (min.)	Temperature (°C)	pH
Test item	100	5.20	2.40	5.0	20.4	8.0
	1000	5.90	2.70	6.0	20.4	8.0
	10000	5.30	2.90	5.0	20.4	7.8
Control 1 Control 2		5.00 5.80	2.50 4.80	5.0 2.0	20.0 20.4	7.9 8.0
Physico-chemical oxygen consumption control	10000	9.00	9.00	10.0	20.4	8.0
3,5-dichlorophenol	1	4.10	2.00	4.0	20.0	7.9
	20	7.60	6.50	7.0	20.2	7.9

 

Table 2: Results of test item

Nominal test item concentration (mg/L)	Respiratory rate (mg/L.h)	% inhibition
Control mean	30.0	--
100	33.6	0
1000	32.0	0
10000*	28.0	4

Comments: Test concentrations are given as nominal concentrations and were not confirmed by analytical methods.

* The physico-chemical oxygen consumption has been determined at 10000 mg/L test item concentration. As no physico-chemical oxygen consumption was observed at that test item concentration this observation also holds true for the lower test item concentrations.

 

Table 3: Results of the reference compound 3,5-dichlorophenol

Nominal reference compound concentration (mg/L)	Respiratory rate (mg/L.h)	% inhibition
Control mean	30.0	--
1	31.5	0
20	9.4	68.6

Validity criteria fulfilled:

yes

Remarks:

(respiratory rates of the 2 controls differ less than 15 % from each other)

Conclusions:

Diethyl bis(2-hydroxyethyl)-aminomethylphosphonate showed 4% respiration inhibition of activated sludge at the highest test item concentration of 10000 mg/L. The EC5O is > 10000 mg/L.

Executive summary:

According to ISO 8192 the test substance showed 4% respiration inhibition of activated sludge at the highest test item concentration of 10000 mg/L. The EC5O is > 10000 mg/L. Activated sludge from predominantly domestic sewage plant was exposed to the test solution of three nominal concentrations of the substance (100, 1000, and 10000 mg/L), blank control solution and solution with positive reference substance for a period of 3 hours. Dissolved oxygen was recorded and respiration rates were claculated. No physico-chemical oxygen consumption was observed at the highest test concentration. No respiration inhibition was observed at 100 and 1000 mg/L; and only 4 % inhibition at 10000 mg/L. This toxicity study is classified as acceptable and satisfies the guideline requirements for the toxicity study to microoragnisms.

Description of key information

 Diethyl bis(2-hydroxyethyl)-aminomethylphosphonate showed 4% respiration inhibition of activated sludge at the highest test item concentration of 10000 mg/L (Müller, 1990). The EC5O was > 10000 mg/L.

Additional information

A reliable, guideline, non GLP study is available, and therefore considered as key.