Fusidic acid

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1995-04-30 to 1995-05-30

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

other: Nyholm, N. and Berg, U.T.: Activated sludge simulation test modified for low substance concentrations (draft)

Version / remarks:

Draft version January 30, 1995

Principles of method if other than guideline:

Modified SCAS test:
Laboratory simulation of the aeration tank of a sewage treatment plant. The test consists of two part
1) A semi-continuous long-term test of biodegradation and adaptation (1 month)
2) A short-term test (batch test) with determinations of rate constants for degradation (24h)

The modifications are (compared to SCAS): Addition of a much lower concentration of the test substance (corresponding to the concentration observed in sewage treatment plants (STP)) + the retention time has been prolonged- corresponding to the retention time in a STP. Prolonging the retention time allows for the evaluation of adaption of microorganisms in the activated sludge.

The short-term test is conducted with a concentration of activated sludge and test substance similar to the long term test. Both adapted and not adapted sludge is applied in order to evaluate the degree of adaption (quantitatively).

During the long-term study, the supernatant is removed on a daily basis and test substance and primary substrate (inlet water) is added. Furthermore, part of the activated sludge is removed in order to achieve a constant retention time.

GLP compliance:

no

Specific details on test material used for the study:

The test was performed on Na-fusidin. Sodium fusidate, Chemical formular C31H47NaO6 was delivered by LEO Pharma A/S. No information on purity.

The degree of dissociation of fusidic acid can be calculated as a function of pH (α = Ka/(Ka+[H+]) with the pKa for fusidic acid determined to be 4.9:
pH α
6.00 0.93
6.50 0.98
7.00 0.99
7.50 1.00
8.00 1.00
For environmental realistic conditions at pH 7-8, fusidic acid will be almost completely (99-100%) dissociated and will be present in the fusidate form. Due to the dissociation of the substance, it is therefore justified to use environmental data on the fusidate form to describe fusidic acid under these conditions.

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Remarks:

I/S avedøre Kloakværk

Details on source and properties of surface water:

NA

Details on source and properties of sediment:

NA

Details on inoculum:

Wastewater (inlet) and activated sludge was derived from I/S Avedøre Kloakværk, Denmark
Final concentration of 3.5 g SS (suspended solids).

Duration of test (contact time):

30 d

Initial conc.:

ca. 10 mg/L

Based on:

test mat.

Remarks:

per L of reactor volume

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

An 1-liter aerated reactor with a dispenser enabling 4/5 of the volume to be tapped. A flow meter is controlling the aeration and ensures an oxygen concentration of 4-5 mg/L (and never below 2 mg/L). Aeration (500ml/min) furthermore ensures that the sludge is dispersed evenly in the suspension. After passage through the reactor, air is led through a water bottle containing clean water in order to trap possible aerosols before air is released to the laboratory.

Test performance:

Rate constants for removal of test substance did not indicate an adaptation of the microorganisms. Rate constants were more or less similar during the study.

Key result

% Degr.:

> 94

Parameter:

other:

Sampling time:

24 h

Remarks on result:

other: The turnver of Fusidic acid is stable over the entire operating period (> 94%) after a 23-hour daily cycle

Key result

Compartment:

activated sludge

DT50:

< 24 h

Remarks on result:

other: The turnover of Fusidic acid is stable over the entire operating period (>94%) after a 23-hour daily cycle

Transformation products:

not measured

Details on transformation products:

NA

Rate constants for removal of test substance did not indicate an adaptation of the microorganisms. Rate constants were more or less similar during the study.

Semi-continuous addition of wastewater from Avedøre Kloakværk A/S and Na-fusidin for 28 days revealed a removal of approximately 94% of fusidic acid during a daily operating cycle. One operating cycle consist of  23 hours of aeration and 0,5-1 h of sedimentation under anoxic conditions.

During 3 hours aeration 39-46 % of fusidcic acid was removed.

Rate constants were estimated during a short-term study. Rate constants at the beginning of the study and after 28 days were 1,5 and 1,8 d-1*l*g*SS-1 respectively. Indicating no adaption of microorganisms. Rate constants (3h) estimated during the long-term study also indicate no adaption. Values were between 2,27 and 2,67 d-1*l*SS-1

Validity criteria fulfilled:

not applicable

Conclusions:

Semi-continuous addition of wastewater from Avedøre Kloakværk A/S and Na-fusidin for 28 days revealed a removal of approximately 94% of fusidic acid during a daily operating cycle.

Rate constants were estimated during a short-term study. Rate constants at the beginning of the study and after 28 days were 1.5 and 1.8 d-1*l*g*SS-1, respectively. Indicating no adaption of microorganisms. Rate constants (3h) estimated during the long-term study also indicated no adaption. Values were between 2.27 and 2.67 d-1*l*SS-1.

Executive summary:

A long-term study (SCAS) was conducted in order to evaluate the degradation of fusidic acid in activated sludge. The test was performed with Na-fusidin.

For environmental realistic conditions at pH 7-8, fusidic acid will be almost completely (99-100%) dissociated and will be present in the fusidate form. Due to the dissociation of the substance, it is therefore justified to use environmental data on the fusidate form to describe fusidic acid under these conditions.

Semi-continuous addition of wastewater from Avedøre Kloakværk A/S and Na-fusidin for 28 days, revealed a removal of approximately 94% of fusidic acid during a daily operating cycle. One operating cycle consisted of  23 hours of aeration and 0.5-1 h of sedimentation under anoxic conditions. During 3 hours aeration, 39-46 % of fusidic acid was removed.

Rate constants were estimated during a short-term study. Rate constants at the beginning of the study and after 28 days were 1.5 and 1.8 d-1*l*g*SS-1, respectively. Indicating no adaption of microorganisms. Rate constants (3h) estimated during the long-term study also indicated no adaption. Values were between 2.27 and 2.67 d-1*l*SS-1

Description of key information

A long-term study (SCAS) was conducted in order to evaluate the degradation of fusidic acid in activated sludge. The test was performed with Na-fusidin.

For environmental realistic conditions at pH 7-8, fusidic acid will be almost completely (99-100%) dissociated and will be present in the fusidate form. Due to the dissociation of the substance, it is therefore justified to use environmental data on the fusidate form to describe fusidic acid under these conditions.

Semi-continuous addition of wastewater from Avedøre Kloakværk A/S and Na-fusidin for 28 days, revealed a removal of approximately 94% of fusidic acid during a daily operating cycle. One operating cycle consisted of  23 hours of aeration and 0.5-1 h of sedimentation under anoxic conditions. During 3 hours aeration, 39-46 % of fusidic acid was removed.

Rate constants were estimated during a short-term study. Rate constants at the beginning of the study and after 28 days were 1.5 and 1.8 d-1*l*g*SS-1, respectively. Indicating no adaption of microorganisms. Rate constants (3h) estimated during the long-term study also indicated no adaption. Values were between 2.27 and 2.67 d-1*l*SS-1

Key value for chemical safety assessment

at the temperature of:

15 °C