Sulphuric acid, compound with graphite

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in GLP conformity and according to internationally accepted guidelines.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Expanded Graphite Powder

IUPAC Name:

Expanded Graphite Powder

Details on test material:

Batch Number: 2205/09Purity (main component): 96.45 % (CoA)

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Vehicle:

no

Details on test solutions:

The concentration in the test vessels with test item was 12.5, 37.5, 112.5, 337.5 and 1012.5 mg Expanded Graphite Powder per liter nominal loading, respectively.

Test organisms

Test organisms (species):

activated sludge

Details on inoculum:

Fresh samples of activated sludge are withdrawn on March 17th, 2010 from the sewage treatment plant Ruhrverband Kläranlage, Sunthelle 6, 57392 Schmallenberg, Germany, which is mainly fed with municipal wastewater. On return to the laboratory the mixed liquor suspended solids level of the sludge was adjusted on about 4.1 g/L by adding tap water. The solution was kept aerated at 20 ± 2 °C until test start. The concentration used in the test was 1.64 g dry mass/litre.

Study design

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test conditions

Hardness:

No data

Test temperature:

20 ± 2 °C

pH:

pH 6.8

Nominal and measured concentrations:

The concentration in the test vessels with test item was 12.5, 37.5, 112.5, 337.5 and 1012.5 mg Expanded Graphite Powder per liter nominal loading, respectively.

Details on test conditions:

Test vessels were 1 L conical glass flasks. The volume of the test solution in each vessel was 500 mL.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

> 1 012.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 2

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 012.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 3

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

> 1 012.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

The results show, that up to and including a concentration of 1012.5 mg Expanded Graphite Powder per liter nominal loading, no loading depending effect on respiration rate occurred. With -9.6% to -14.9% inhibition, respiration rate of the inoculum was never inhibited more than +20 % at concentrations up to and including 1012.5 mg Expanded Graphite Powder per liter nominal loading when compared with the control. Probit analysis did not obtain a meaningful concentration/response dependence.The EC-values were assumed to be EC20 >1012.5 mg/L, EC50 >1012.5 mg/L, and EC80 >1012.5 mg/L, respectively, nominal loading.The test item showed no significant abiotic oxygen demand over the 3 h test period. The EC50 for the reference item was found to be 8 mg/L and therefore within the accepted range of 5 to 30 mg/L.

Results with reference substance (positive control):

The EC50 of the reference item 3,5-dichlorophenol for respiration inhibition was between 5.0 and 30.0 mg/l.

Any other information on results incl. tables

Table 1: Inhibition (%) of the respiration rate by the test item

Test concentration
12.5 mg/L	37.5 mg/L	112.5 mg/L	337.5 mg/L	1012.5 mg/L
-12.2 %	-9.6 %	-14.9 %	-13.4 %	-14.3 %

Table 2: Respiration rate (mg O2/(L*h)) after 3 h of incubation C1 and C2 = control; T1 – T5 = test assays with increasing concentrations (12.5 – 1012.5 mg/L nominal loading); AC = abiotic control; RI1, RI2 and RI3 = reference assays with 4, 12 and 36 mg 3,5-DCP per liter, respectively.

Vessel
C1	T1	T2	T3	T4	T5	AC	RI1	RI2	RI3	C2
20.1	22.6	22.0	23.1	22.8	23.8	0.1	14.9	7.0	3.5	21.6

Table 3: Respiration inhibition (%) when compared to the mean respiration rate of the control assays T1 – T5 = test assays with increasing concentrations (12.5 – 1012.5 mg/L nominal loading); AC = abiotic control; RI1, RI2 and RI3 = reference assays with 4, 12 and 36 mg 3,5-DCP per liter, respectively.

Vessel
T1	T2	T3	T4	T5	AC	RI1	RI2	RI3
-12.2	-9.6	-14.9	-13.4	-14.3	99.4	28.4	66.4	83.1

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

The test is considered valid, as - the pH of the test medium at test start was within the demanded range of 6.0 – 8.0 - the incubation temperature was within the demanded range of 20 ± 2 °C - the EC50 (3 hours) of 3,5-dichlorophenol is in the accepted ran

Conclusions:

There is no significant inhibition of bacterial respiration due to Expanded Graphite Powder up to and including a concentration of 1012.5 mg/L nominal loading. For the respiration rate the EC50 is > 1012.5 mg/L nominal loading.

Executive summary:

At the Fraunhofer-Institute for Molecular Biology and Applied Ecology the effect of Expanded Graphite Powder on the respiration rate of an activated sludge according to the OECD guideline 209 and EC method C.11 was investigated. As inoculum microorganisms from a sewage treatment plant mainly fed with municipal wastewater were used. The test item was given to the synthetic sewage with a loading of 12.5, 37.5, 112.5, 337.5 and 1012.5 mg Expanded Graphite Powder per liter. The content of the vessels was stirred and aerated for 3 h at 20 ± 2 °C. Two replicates were prepared for controls (synthetic sewage and inoculum only), solitaire vessels were used for the treated assays. The respiration rate of the activated sludge in the controls and incubated with concentrations of 12.5 to 1012.5 mg Expanded Graphite Powder per liter was found to be within 20.1 and 23.8 mg O2/(L*h) after three hours. The respiration rate was not affected by the test item. The results show, that up to a concentration of 1012.5 mg Expanded Graphite Powder, no respiration inhibition greater than 20 % occurred.

The calculated EC-values are:

Parameter	EC20	EC50	EC80
Value [mg/L]	> 1012.5	> 1012.5	> 1012.5
lower 95%-cl	n.d.	n.d.	n.d.
upper 95%-cl	n.d.	n.d.	n.d.

The EC₅₀ of the reference item 3,5-dichlorophenol for respiration inhibition was between 5.0 and 30.0 mg/L. No important physical-chemical oxygen consumption by Expanded Graphite Powder was detected after three hours. The validity criterions concerning the reference item and the comparability of the controls were fulfilled. The statistical analyses confirmed that there were no statistically significant effects on respiration rate.

The EC50 Expanded Graphite Powder is > 1012.5 mg/L nominal loading.