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EC number: 266-582-5
CAS number: 67124-09-8
Activated sludge toxicity test, OECD 209, EC50 (3h) > 10000 mg/L
The acute toxicity to microorganisms of the
test substance was investigated in accordance with OECD guideline 209
and GLP compliance (Goodrich, 1994). Activated sludge was used in the
static freshwater experiment with an exposure time to the test substance
of 3 hours. The testing system consisted of two units: 1) a system used
to expose the sludge inoculum to the test material and 2) a system to
measure the rate of oxygen consumption of the sludge in a closed bottle.
Initial test concentrations were 1, 10, 100, 1000 and 10000 mg/L. A
control test system and 3,5 -dichlorophenol were run in parallel. The
inoculum was exposed to the test material in 1-L flint glass bottles.
Low-pressure oil-free air was delivered to each test vessel using a
glass pipet. All of the test vessels were held in a Forma Scientific
Model 3956 water-jacketed incubator in the dark during the three-hour
exposure period. To measure the oxygen consumption after the exposure
period, a Model 51 Yellow Springs Instruments (YSI) dissolved oxygen
meter was used. The oxygen meter was fitted with a BOD bottle probe,
with a standard sensitivity membrane and an external output to a Fisher
Recordal (Model 5000) strip chart recorder. For this purpose, 300 mL of
the sludge mixture were transferred into a BOD bottle containing a
teflon-coated magnetic stir bar. The bottle was capped with the BOD
bottle oxygen probe to eliminate air space and placed on a magnetic
stirring plate. The sludge mixture was stirred at a constant rate and
the consumption of oxygen over time was recorded on a strip chard
recorder. The resultant respiration rates were respectively: 21.2, 30.7,
20.4, 19.9 and 23.8 mg O2/L * hr. These data are translated into percent
inhibitions of 18.6 %, -17.9 %, 21.7 %, 23.6 % and 8.6 %, respectively.
Because none of the test concentrations produced an inhibition greater
than 50 %, an EC50 could not be calculated. Hence the EC50 is > 10,000
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