Sodium acrylate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

(Documentation of the older study falls short of today´s requirements, but corresponds to the standards at the time the study was conducted; the quality of the study performance is nevertheless not influenced. Sufficient data suitable for assessment.)

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Laboratory culture: Municipal activated sludge from laboratory wastewater treatment plant fed with municipal sewage and synthetic wastewater.
- Initial biomass concentration: Concentration of dry substance = 1 g/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Nominal and measured concentrations:

Nominal: control, 100, 500, 1000 mg/L

Details on test conditions:

- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

30 min

Dose descriptor:

other: EC20

Effect conc.:

900 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

30 min

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

EC20 = 3 mg/L
EC50 = 10 mg/L
EC80 = ca. 150 mg/L

Description of key information

Based on results of the structural analogue acrylic acid (CAS# 79-10-7) the inhibition of degradation activity of activated sludge is not anticipated when sodium acrylate is introduced into biological treatment plants in appropriately low concentrations.

 

Additional information

No experimental data on the test substance is available. Sodium acrylate (NaA) is dissociating fast in aqueous media (Henderson – Hasselbach calculation). Therefore, the evaluation of the endpoint toxicity to microoranism is based on a weight of evidence approach using the data of the structural analogue acrylic acid (AA) (CAS 79-10-7) (for WoE information, see chapter 13.2).

In a test with domestic activated sludge the inhibition of oxygen consumption in the presence of AA was examined similar to guideline ISO 8192 (BASF, 1992). Since the study was performed before strict documentation processes were required, the documentation does not meet todays standards. Nevertheless, the quality of the study performance was not influenced. Therefore, the study was rated with the Klimisch score 2. After 30 minutes oxygen uptake was inhibited by 16 % at 500 mg/L and by 21 % at 1000 mg/L, the highest concentration tested. Thus, the EC20 was determined to be 900 mg/L.

A publication from Bringmann et al. give hints for a specific sensitivity of the protozoan Chilomonas paramaecium. In a 48-h cell multiplication inhibition test a Toxicity Threshold of 0.9 mg/L was determined. Although this species does not influence the degradation processes in a wastewater treatment plant itself, it is necessary for a proper function of a WWTP; therefore, the result of this study was used for derivation of the PNEC STP in the EU Risk Assessment. 

In conclusion, based on the results of the structural analogue AA, inhibition of the degradation activity of activated sludge is not anticipated when NaA is introduced in appropriately low concentrations in WWTPs.