Phosphorus

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study performed according to GLP and international guidelines, well documented

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

adopted 22 July 2010

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

ferro phosphorus

IUPAC Name:

ferro phosphorus

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

- Name of test material (as cited in study report): ferro phosphorus
- BET (surface area): 0.193 m2/g
- Composition of test material, percentage of components: 63,9 % Fe, 24,66 % P
- Supplier: Luxalloy SA, 10B rueJean Steichen, L-5868 Alzingen, Luxembourg
- Lot: Brixham 12-0157
- Batch nr: 55380-B2
- V_Certificate of analysis: 9 oct 2012

Test solutions

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: due to the low aqueous solubility of ferro phosphorus, a stock solution was not prepare. Test solutions were prepared by the direct addition of a known weight of Ferro phosphorus to a total volume of 100 mL reverse osmosis (RO) water, synthetic sewage and activated sludge.

REFERENCE SUBSTANCE
- A nominal 100 mg/L stock solution of the reference substance 3,5-dichlorophenol was prepared in RO water. This stock solution was observed to be clear and colourless and its pH was 5.8 and subsequently adjusted to 7.7 with 2M NaOH before use.

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: Totnes Sewage Works, Totnes, Devon, UK
- Method of cultivation: inoculum received 1 day prior to the exposure of test and reference substances.
- Pretreatment: the activated sludge was settled and the supernatant decanted. The settled sludge was fed with 50 mL of OECD synthetic sewage feed per litre of sludge per day and aerated at room temperature, until it was used in the test. The total filterable solids concentration was determined on the day of the test and was found to be 7141 mg/L. The pH was measured as 7.1

Study design

Total exposure duration:

3 h

Test conditions

Test temperature:

20 +/- 2°C

Nominal and measured concentrations:

Nominal: 10, 100 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Aeration: yes. aeration at 20 +/- 2°C for 3 hours.
- Concentrations in triplicate
- No. of vessels per control (replicates): 2 control culture flasks
- No of batches: flasks were set up in batches of six. Each batch included a control flask and five test or reference substance flasks.
- 5 flasks containing the reference substance at nominal concentrations 2, 5, 10 and 32 mg/L
- 1 abiotic flask at 32 mg/L
- Each flask contained an excess of the synthetic sewage, sufficient activated sludge to five final solids concentrations of 1500 mg/L (with exception of the abiotic flask), an appropriate quantity of ferro phosphorus and 3,5-dichlorophenol stock solution and RO water to give a final flask contents volume of 100 mL.
- The pH in the flasks was measured at the start and end of the test. Temperature was measured at the end of the 3h aeration.


EXPERIMENTAL DESIGN
- the respiration rate was measured after 3h and compared with the mean respiration rate of the two control cultures. The rate of oxygen uptake was measured in glass sample tubes into which microcathode oxygen electrodes were inserted. The rates of oxygen uptake was expressed as mg/L/h.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol as recommended in the OECD guideline (ref 1)

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

ferro phosphorus

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 2

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

ferro phosphorus

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 3

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

ferro phosphorus

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 4

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

ferro phosphorus

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

all test concentrations (flasks with ferro phosphorus) showed inhibition less than 10 %

Results with reference substance (positive control):

The reference substance caused substantial inhibition of the respiration rate of the activated sludge. The 3h EC50 value was estimated to be 11 mg/L, within the expected normal range of 2 to 25 mg/L, indicating the sludge was responding normally and confirming the viability of the sludge organisms.

Reported statistics and error estimates:

- the EC50 value was estimated by computer software

Applicant's summary and conclusion

Conclusions:

The 3h NOEC is 1000 mg/L ferro phosphorus