2-isopropoxyethanol

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Full study report available. Study scientifically sound

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.10 (Biodegradation: Activated Sludge Simulation Test)

Deviations:

yes

Remarks:

. Relatively volatile substance tested by Henry's constant suggests this should not be problematic. Pure oxygen supplied to reactor to simulate site WWTP.

Principles of method if other than guideline:

Single reactor used with measurement of influent and effluent concentrations at different time points during different regimes of spiking influent with test substrates. (Other substrates apart from isopropyl glycol ether assessed in study.) Study designed to assess the effect of specific effluent streams on a plant WWTP.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-isopropoxyethanol

EC Number:

203-685-6

EC Name:

2-isopropoxyethanol

Cas Number:

109-59-1

Molecular formula:

C5H12O2

IUPAC Name:

Propan-2-ol

Radiolabelling:

no

Study design

Oxygen conditions:

aerobic

Remarks:

pure oxygen

Inoculum or test system:

activated sludge, industrial, adapted

Details on inoculum:

- Source of inoculum/activated sludge: INEOS Antwerp WWTP.

Duration of test (contact time):

75 d

Initial test substance concentration

Initial conc.:

75 - 150 other: ul/litre

Based on:

test mat.

Parameter followed for biodegradation estimation:

other: COD of influent and effluent

Details on study design:

TEST CONDITIONS
- reactor size: 10 litres
- aeration: pure oxygen
- Influent: mixture of actual influents supplied to full scale WWTP.
- Mixing :reactor mixed
- Separation of sludge by sedimentation.
- Influent of INEOS stream adjusted to pH11 to compensate for CO2 formation.
- Biomass concentration: ~4g/l, considered highly loaded.

TEST REGIMES:
- Day 1-24: Influent of INEOS at 5l/day (reference period)
- Days 25-42. As above plus 6.6ml Dow effluent added per litre of INEOS effluent - COD of influent 3945mg/l (test period 1)
- Days 43-57: As above plus 75ul isopropyl glycol ether/litre influent (Test period 2a)
- Days 58-68: As above plus 150ul isopropyl glycol ether/litre influent. (Test period 2b)
- Days 69-77: Further changes to influent composition but isopropyl glycol ether concentration maintained at 150ul/ml - COD of influent 4255mg/l

OTHER
- nutrient solution of urea and potassium dihydrogen phosphate along with a micronutrient solution dosed to reactor, as used on the full scale WWTP.

Results and discussion

% Degradation

% Degr.:

97

Parameter:

other: COD

Remarks on result:

other: degradation based on equilibrium obtained during 8-25 day continuous operation

Transformation products:

not measured

Evaporation of parent compound:

not measured

Volatile metabolites:

not measured

Residues:

not measured

Details on results:

Efficiency of removal at end of reference period (by COD of influent compared to effluent): 93%
Efficiency of removal at end of test period 1 (by COD of influent compared to effluent): 94%
Efficiency of removal at end of test period 2a (by COD of influent compared to effluent): 96%
Efficiency of removal at end of test period 2b (by COD of influent compared to effluent): 97%

Any other information on results incl. tables

The presence of isopropyl glycol ether in the influent stream did not adversely affect the following

- ability of the sludge to settle.

- Flock formation of the sediment

- impact on filament growth in sediment.

- microbial diversity

Applicant's summary and conclusion

Conclusions:

The authors concluded that isopropyl glycol ether does not have a negative effect on the COD removal of the WWTP of the manufacturing site where the substance is produced.

Executive summary:

In a study that followed the principles of a guideline activated sludge similation test, a reactor system set up to model the WWTP used on the site of a manufacturer was dosed with increasingly levels of isopropyl glycol ether. The sludge reactor influent composition used was the same as used for the full scale plant as was the activated sludge. When running with an influent stream containing up to 150ul/litre of isopropyl glycol ether, the reactor ran with a degradation efficiency of 97%. There was evidence of adaptation occurring and also complete removal of all biologically available oxygen from the influent stream.

On the basis of adaptation being proven, it is unlikely that exposure of sediment will occur and therefore such a study can be waived based on exposure grounds.