Registration Dossier

Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
biodegradation in water: sewage treatment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2006-09-25
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study was not conducted in conformance to GLP and OECD guidelines.
Qualifier:
according to
Guideline:
other: EPA method for assessing the biodegradability of compounds in biological treatment units (40 CFR 63, 2001)
Principles of method if other than guideline:
Study design was based on the EPA method for assessing the biodegradability of compounds in biological treatment units (40 CFR 63, 2001).
40 CFR 63 Subparts F, G, H, I – Hazardous Organic NESHAP (HON). 2001. Procedures & Test Methods: Appendix C to Part 63- Determination of Fraction Biodegraded (Fbio) in a Biological Treatment Unit. Section D Batch Tests Epi(Procedure 4).
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, industrial, adapted
Details on source and properties of surface water:
see below.
Details on source and properties of sediment:
Primary biodegradation of epichlorohydrin was evaluated using activated sludge from either the Specialties or Chlorohydrin wastewater treatment plants (WWTPs) in Freeport, Texas. Activated sludge samples were collected from each plant and shipped to the TERC (Toxicology & Environmental Research and Consulting) laboratory in Midland, Michigan. Sludge samples were diluted 1/5 (volume basis) with high salts (NaCl) mineral medium alone or mixed in sealed test vessels with authentic influent wastewaters from the Specialties and Chlorohydrin treatment plants. Sodium chloride was added to the mineral media to approximate the ionic strength of the wastewater streams to the WWTPs. Epichlorohydrin was added to the test systems at a nominal concentration of 60 mg/L and the reaction mixtures were continuously stirred for 24 hours at ambient temperature (22 ± 3ºC). Samples of
the reaction mixtures were periodically analyzed for residual epichlorohydrin using gas chromatography with mass spectrometry detection.
Details on inoculum:
see above.
Duration of test (contact time):
24 h
Test performance:
Rapid degradation of epichlorohydrin was observed in reaction mixtures prepared with activated sludge samples from both the Specialties and Chlorohydrin wastewater treatment plants in Texas Operations. Within two hours in Specialties sludge, epichlorohydrin concentrations decreased from 49 mg/L to non-detected levels in sludge diluted in mineral medium alone, and from 48 mg/L to 0.7 mg/L in sludge diluted in wastewater and mineral medium. In contrast, the concentration of epichlorohydrin remaining in the biologically inhibited controls diluted in mineral medium alone showed no change over the same time period (2 h), while the concentration decreased from 61 to 48 mg/L in the biologically inhibited controls diluted in wastewater and mineral medium.
Compartment:
other: water / sediment, material (mass) balance
Remarks on result:
other: not applicable
% Degr.:
56.3
Parameter:
test mat. analysis
Sampling time:
1 h
Remarks on result:
other: Mineral medium
% Degr.:
> 98
Parameter:
test mat. analysis
Sampling time:
2 h
Remarks on result:
other: Below detection limit of 1 mg/L. Mineral medium
% Degr.:
ca. 0
Parameter:
test mat. analysis
Sampling time:
1 h
Remarks on result:
other: biologically inhibited control of mineral medium
% Degr.:
ca. 0
Parameter:
test mat. analysis
Sampling time:
2 h
Remarks on result:
other: biologically inhibited control of mineral medium
% Degr.:
15.6
Parameter:
test mat. analysis
Sampling time:
4 h
Remarks on result:
other: biologically inhibited control of mineral medium
% Degr.:
62.8
Parameter:
test mat. analysis
Sampling time:
1 h
Remarks on result:
other: Wastewater + Mineral Medium
% Degr.:
98.5
Parameter:
test mat. analysis
Sampling time:
2 h
Remarks on result:
other: Wastewater + Mineral Medium
% Degr.:
6.9
Parameter:
test mat. analysis
Sampling time:
1 h
Remarks on result:
other: biologically inhibited control of Wastewater + Mineral Medium
% Degr.:
22.1
Parameter:
test mat. analysis
Sampling time:
2 h
Remarks on result:
other: biologically inhibited control of Wastewater + Mineral Medium
% Degr.:
27.7
Parameter:
test mat. analysis
Sampling time:
4 h
Remarks on result:
other: biologically inhibited control of Wastewater + Mineral Medium
Transformation products:
not measured
Details on transformation products:
Degradation products were not identified.
Details on results:
The biodegradation rate constant kb, corrected for abiotic losses, was 0.001 L/(mg h) in sludge diluted in mineral medium alone, and 0.0012 L/(mg h) in sludge diluted in wastewater and mineral medium. These results indicate that including authentic wastewater in the reaction mixtures with the mineral medium had little effect on the biodegradation rate of epichlorohydrin.

Biodegradation of epichlorohydrin was also rapid in Chlorohydrin sludge diluted in a mixture of wastewater and mineral medium. Within one hour, the concentration of epichlorohydrin decreased from 28 mg/L to non-detected levels, while little change occurred in the biologically inhibited controls (decreasing from 52 mg/L to 48 mg/L over one hour). Note the low concentration of epichlorohydrin measured at time 0, in a sample collected 15 minutes after test compound addition. This value (i.e., 28 mg/L), compared to the nominal 60 mg/L added, indicates that very rapid biodegradation began immediately upon addition of the test compound to the test system. The biodegradation rate constant kb, corrected for abiotic losses, was
0.007 L/(mg h).

Oxygen concentrations were monitored in the headspace of the individual reaction mixtures in order to ensure the degradation reactions were not oxygen limited. In the Specialties and Chlorohydrin sludge experiment, the O 2 concentration in the headspace of the viable reaction mixtures was at least 16% or higher within the first five to six hours of incubation indicating that the degradation reactions were not O 2 limited. Also, neither the test compound, epichlohydrin, nor the authentic wastewater proved toxic or inhibitory to the Specialties and Chlorohydrin activated sludge since little difference was noted in the decrease in oxygen concentrations between the blanks, test, viability, and toxicity control mixtures.

Although epichlorohydrin levels reached non detect levels in the viable reaction mixtures within 6 h, O 2 levels in the headspace were monitored for an additional 18 h in order to evaluate the robustness of the test system. In the Specialties sludge reaction mixture with mineral medium alone, O2 levels were maintained around 16-17% after 24 h. In contrast, after 24 h O2 levels in the viable reaction mixtures mixed with authentic wastewater decreased to ~11% even though these reactions were fortified with supplemental oxygen after 6 h. These results were not surprising as the authentic wastewater likely contained a significant oxygen demand. Texas Operations’ laboratory reported total organic carbon (TOC) values of 631 and 211 ppm for the Specialties and Chlorohydrin wastewater samples, respectively.

In both studies, the pH of the viable reaction mixtures decreased during incubation. The pH of viable mixtures in the Specialties sludge decreased from approximately pH 7.8 at the start of the study to the pH range of 7.0 to 7.5 after 24 hours. Similarly, the pH of the viable mixtures in the Chlorohydrin sludge decreased from approximately pH 7.4 at the start of the study to the pH range of 6.6 to 6.8 after 24 hours. These decreases in pH (less than 1 pH unit) were not likely to affect the viability of the activated sludge.
Results with reference substance:
Some biodegradation of the dipropylene glycol (DPG) reference compound was observed in the Specialties sludge. After one day of incubation, 34% of the DPG added to the viability control was degraded based on DOC removal. In addition, 22% of the DOC from DPG and epichlorohydrin was degraded in the toxicity control after 24 hours. This slow biodegradation of DPG observed in the Specialties sludge suggests that for studies of short duration (i.e. 24 hours), DPG may not be an optimum reference compound to assess the viability of the activated sludge and inhibitory potential of the test compound. As noted above, measurement of oxygen consumption may be a more sensitive indicator. Thus, for the Chlorohydrin sludge experiment, oxygen consumption was used to assess the viability of the activated sludge and inhibitory potential of epichlorohydrin.

Rapid primary biodegradation of epichlorohydrin was measured in activated sludge from both the Specialties and Chlorohydrin wastewater treatment plants (WWTPs) in Texas Operations.

Conclusions:
Approximately 99% of epichlorohydrin was degraded within two hours in the reaction mixtures.
Executive summary:

Epichlorohydrin is a common wastewater constituent found in the Specialties and Chlorohydrin wastewater treatment plants at The Dow Chemical Company’s Texas Operations in Freepor t, Texas. Primary biodegradation of epichlorohydrin was evaluated using activated sludge from either the Specialties or Chlorohydrin wastewater treatment plants (WWTPs). Activated sludge samples were collected from each plant and shipped to the TERC (Toxicology & Environmental Research and Consulting) laboratory in Midland, Michigan. Sludge samples were diluted 1/5 (volume basis) with high salts (NaCl) mineral medium alone or mixed in sealed test vessels with authentic influent wastewaters from the Specialties and Chlorohydrin treatment plants. Sodium chloride was added to the mineral media to approximate the ionic strength of the wastewater streams to the WWTPs. Epichlorohydrin was added to the test systems at a nominal concentration of 60 mg/L and the reaction mixtures were continuously stirred for 24 hours at ambient temperature (22 ± 3ºC). Samples of the reaction mixtures were periodically analyzed for residual epichlorohydrin using gas chromatography with mass spectrometry detection. Within two hours of initiation of the reactions, greater than 99% of the epichlorohydrin was degraded in the viable reaction mixtures prepared from the Specialties and Chlorohydrin sludge samples. In contrast, loss or degradation of epichlorohydrin in biologically inhibited controls (sodium azide added as chemical sterilant) was limited to 21% or less in two hours, confirming that the degradation observed in the viable mixtures was primarily biologically mediated. Biodegradation rate constants in Specialties sludge mixtures were determined to be 0.001 L/(mg h) in reaction mixtures prepared with mineral medium and 0.0012 L/(mg h) in reaction mixtures prepared with mineral medium mixed with authentic Specialties wastewater. In the Chlorohydrin sludge mixtures, a biodegradation rate constant of 0.007 L/(mg h) was calculated for a reaction mixture prepared with mineral medium mixed with authentic wastewater.

Endpoint:
biodegradation in water: sewage treatment simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No data on GLP, guideline type study, limited documentation
Qualifier:
equivalent or similar to
Guideline:
other: Method for the determination of the biodegradability of surfactants used in synthetic detergents, OECD 1976
Deviations:
yes
Remarks:
The process is run under anaerobic conditions with NO3 as terminal H acceptor. This allows one to investigate the degradation of volatile substances without incurring losses due to stripping
Principles of method if other than guideline:
Organization of Economic Cooperation and Development OECDI. Environment Directorate Proposed Method for the Determination of the Biodegradability of Surfactants used in Synthetic Detergents, Paris l976.
GLP compliance:
not specified
Radiolabelling:
no
Oxygen conditions:
other: under closed, denitrifying conditions to avoid loss from stripping
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
no data.
Duration of test (contact time):
3 h
Initial conc.:
20 mg/L
Based on:
test mat.
% Degr.:
< 10
Parameter:
other: Cl elimination
Sampling time:
3 h
% Degr.:
35
Parameter:
other: Cl elimination
Sampling time:
24 h
% Degr.:
75
Parameter:
other: Cl elimination
Sampling time:
48 h
% Degr.:
95
Parameter:
other: Cl eliminaiton
Sampling time:
96 h
Transformation products:
not measured

The incubations were done under denitrifying conditions to avoid loss by aeration, hence the results (35% in 24 hr and 75% in 48 hours) were given without a stripping effect. When the incubations were continued for 96 hours total, 91% biodegradation occurred. BOD30 was estimated as 97% of Theoretical Oxygen Demand (ThOD).

Conclusions:
Study documents elimination likely due to mineralisation as Chlorine is released under non-standard (denitrifying) condition.
Executive summary:

The incubations were done under denitrifying conditions to avoid loss by aeration, hence the results (35% in 24 hr and 75% in 48 hours) were given without a stripping effect. When the incubations were continued for 96 hours total, 91% biodegradation occurred. BOD30 was estimated as 97% of Theoretical Oxygen Demand (ThOD).

Description of key information

Key value for chemical safety assessment

Additional information

Elimination of Epichlorohydrin in the aqueous phase of a sewage treatment plant has been simulated in two studies. Volatilisation has been controlled by the use of closed vessels. One study followed the EPA method for assessing the biodegradability of compounds in biological treatment units (40 CFR 63, 2001) and used an inoculum from an industrial waste water treatment plant that is exposed to waste water containing Epichlorohydrin, the other used unadapted inoculum under denitrifying conditions. In the study with adapted inoculum, rapid elimination was observed (based on test material analysis) at an exposure time typical for a sewage water treatment plant (less than 1 mg/l after 2 hrs). Under denitrifying conditions, elimination after 3 hours (relevant residence time for a sewage treatment plant) was <10%, significant elimination (95%) was reached after 96 h. The results suggest a rapid elimination from STP with sludge that is accommodated to emission of Epichlorohydrin and delayed elimination for unadapted sludge.