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EC number: 201-070-7
CAS number: 77-93-0
Aerobic biodegradation of triethyl citrate in standard laboratory
soil mix was determined using laboratory bioreactors. The time required
to achieve 50% mineralisation (t50) increased as the TEC
concentration in the soil increased. At all test concentrations, the net
mineralization of the TEC was greater than that of the positive control
(cellulose). The TEC half-lives were calculated as 6.6 d at 40 mg
TEC-C/50 g soil which corresponds to 1,530 mg TEC/kg soil based on
52.17% carbon; 7.1 d at 80 mg TEC-C/50 g soil which corresponds to 3,070
mg TEC/kg soil; 9.4 d at 160 mg TEC-C/50 g soil which corresponds to
6,130 mg TEC/kg soil; 19.8 d at 300 mg TEC-C/50 g soil which corresponds
to 11,500 mg TEC/kg soil; 43.0 d at 600 mg TEC-C/50 g soil which
corresponds to 23,000 mg TEC/kg soil.
Aerobic soil biodegradation of TEC met or exceeded pass levels
defined by ASTM, FDA, EPA guidelines and OECD guidelines. The conversion
of TEC-C into CO2 exceeded 50% ThCO2within
the 64 -day time limit set by the equivalent FDA soil biodegradation
test (U.S. FDA, 1987) and 60% ThCO2 within the time
limits set by the equivalent ASTM methods (ASTM, 1999) (≤180 days) and
U.S. EPA methods (U.S. EPA, 1998) (≤64 days).
At the substrate loading concentrations in the range recommended
by the FDA and U.S. EPA tests (OPPTS 835.3110 Ready Biodegradability
test - U.S. EPA, 1998) of ≤ 5 mg substrate–C/g (i.e., includes test
concentrations up to and including 160 mg C/50 g soil , the conversion
of substrate-C into CO2 exceeded 60% ThCO2 within a 10 -14
day window following the lag period. At this concentration of 160 mg
C/50 g soil, the half-life was reported as 9.4 days and the T60 as
12.7 days. These results indicate that TEC can be considered readily
biodegradable (U.S. EPA, 1998). Therefore, the substrate loading
concentration of 160 mg C/50 g soil may be considered the NOEC(soil).
The NOEC(soil) is the basis for calculating the NOEC(water) and
NOEC(soilds) in sewage sludge.
Calculation of the NOEC(water) and NOEC(soilds):
160 mg C/50 g soil = 3.2 mg C/g soil = 3200 mg C/kg soil.
Based on a substance molecular weight of 276.29, and a chemical formula
of C12H20O7, carbon constitutes 52.17%
of the substance molecular weight. Therefore, 3200 mg C/kg soil = 6130
mg TEC/kg soil.
The soil-water partition coefficient (Kd) of the substance
was determined from the adsorption coefficient (Koc) of 5.959
L/kg and the default fraction organic carbon content in soil (foc
= 0.02), based on the relationship Kd = Koc* foc,
so that Kd = 5.959 * 0.02 = 0.1192 L/kg.
Assuming that the soil NOEC of 6130 mg/kg in soil (6130 ppm) indicates a
non-inhibitory concentration for both the soild and aqueous compartments
in sewage sludge,
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