Wednesday, December 7, 2011

Field Test Results

Formaldehyde Content of Untreated Waste. Pre-treatment formaldehyde concentrations ranged
from 41000 to 47000 mg/L for the pathology waste, from 44000 to 48000 mg/L for the tissue
processor waste, and 47000 and 48000 mg/L for the unused 10% NBF. Although these
concentrations are higher than the concentration of approximately 37000 mg/L cited as typical for
unused 10% NBF, they represent actual wastes generated in California.
Formalex-Treated Wastes. After treatment with Formalex, the residualformaldehyde concentration
ranged from 2300 to 6400 mg/L in the pathology waste, from 3300 to 5800 mg/L in the tissue
processor waste, and was 4700 and 5800 mg/L in the treated samples of unused 10% NBF. There
did not appear to be differences in the treatment results for the three waste types. The formaldehyde
content was reduced by about 85 – 95% compared with the initial concentrations in the wastes.
Acute aquatic 96-Hour LC50
bioassay determinations were performed on the untreated and treated
wastes. The data were intended for a comparison of relative toxicity. Although the data can be
compared to the hazardous waste threshold of <500 mg/L, they are not intended for waste
classification of 10% NBF wastestreams.
screening level LC50
determination of the wastes before treatment showed that all ten samples had
concentrations between 500 and 549 mg/L. These values are all above the hazardous waste
threshold of 500 mg/L. As a check on the ability of the screening test to provide the necessary
information on the waste toxicity, the treatment and LC50
determinations were repeated using the
definitive test. The results were very similar to the screening level tests, with LC concentrations
between 505 and 574 mg/L. Although the specific wastes tested were less toxic than the hazardous
waste threshold, it was recognized that the toxicity of 10% NBF wastes vary. DTSC has received
data from other facilities which indicate that 10% NBF can be more toxic than the hazardous
waste threshold. Therefore, the project was continued to determine the effects of treatment on waste
toxicity and reduction of formaldehyde concentrations.
A screening level LC50
determination of the Formalex treated wastes, using the standard procedure
showed that four of the ten wastes were more toxic after than before treatment. For these wastes thepost-treatment LC50
concentrations were between 354 and 477 m/L, more toxic than the <500 mg/L
threshold. Two of these wastes were pathology wastes, one was a tissue processor waste, and one
was unused 10% NBF. Five of the other wastes were less toxic after treatment, with LC50
concentrations >750 mg/L, and one waste was about the same toxicity before and after treatment, with
a post-treatment LC concentration of 528 mg/L.
The finding that some wastes were more toxic after treatment than before was unexpected. Therefore,
a replicate screening level experiment was performed as an additional QA/QC check. In the replicate
experiment, five of the wastes were more toxic after than before treatment. These five treated wastes
were all more toxic than the hazardous waste threshold of <500 mg/L. Interestingly, only two of the
five samples that were toxic after treatment in the replicate experiment were the same wastes as were
found to be toxic in the previous experiment, while three were from different wastes.
When the Formalex treated wastes were subjected to a modified aquatic LC analysis, without a
shaking period to homogenize the waste before adding it to the fish tank, all ten samples had LC50
concentrations >750 mg/L.

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