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MERC ER01-10
4
RNA colony blot and
ctxA
DNA colony blot hybridization. Viable toxigenic
V. cholerae
was
assayed with a commercial DFA kit specific for serogroup O1 using monoclonal antibodies
tagged with fluorescein isothiocyanate.
To evaluate the toxicity of treated water at the completion of each trial, samples from
each mesocosm were collected and tested for acute and chronic toxicity, and for total residual
chlorine. Filter “backflush” (retenate/filtrate during initial treatment of water) was also tested for
total residual chlorine. The toxicity protocols and species used were consistent with the USEPA
methods for Whole Effluent Toxicity (WET). The algal species tested was
Isochrysis galbana,
the fish species was the Sheepshead minnow
(Cyprinodon variegatus)
while the invertebrate
species was the Mysid shrimp
(Americamysis bahia).
A chlorine concentration in samples was
analyzed immediately upon collection to avoid potential loss of oxidant with time.
The
Standard
Methods for the Examination of Water and Wastewater Low-Level Amperometric Titration
method 4500-Cl D and DPD Colorimetric method 4500-Cl G were used to measure
Total
Residual Oxidants (TRO) and Total Residual Chlorine (TRC)
. A Fischer and Porter amperometric
titrator was also used for amperometric measurements.
5. Summary of Results
Biological Performance
- The
Severn Trent De Nora
BALPURE
Ballast Water
Management System dramatically reduced the numbers of live organisms in ballast water during
MERC land-based testing in the Port of Baltimore. For all biological categories, the treatment
system consistently met IMO D2 discharge standards.
Discharge Toxicity -
Treated ballast water upon discharge
was not chronically toxic to
either mysid shrimp or sheepshead minnows for any of the trials conducted. All five of these
samples, however, were chronically
toxic to the marine algal species
Isochrysis galbana
.
Additional testing of several dilutions of the treated ballast water was conducted on the last three
samples (STDN-03 through -05). EC
50
’s, measured as a reduction in growth, were found at
22%, 42% and 53% for STDN 03, STDN-04 and STDN-05 respectively.
Additional toxicity testing has revealed that under certain circumstances dechlorinated
estuarine water remains toxic to some types of algae. The continued toxicity of dechlorinated
water is species specific with several golden brown algal species (
Isochrysis galbana
and
Pavlova lutheri
) exhibiting decreased growth after TRO is at or below detection (DPD method).
In contrast, similarly treated water was non toxic to the diatom
Phaeodactylum tricornutum
.
Toxicity was found in samples that were chlorinated by either electrochlorination or sodium
hypochlorite addition; and aged for five days.
Toxicity in high initial TRO samples was found after dechlorination with one of two
sulfur-based reducing compounds, sodium thiosulfate or sodium bisulfite. Neither of these
reducing compounds alone was found to be toxic at relevant concentrations with NOECs of 100
and 200 mg/l for sodium thiosulfate and sodium bisulfite, respectively. Additional algal toxicity
tests are being conducted to investigate the cause, as well as the extent, of toxicity caused by
dechlorinated water. Results of this investigation are being submitted to a peer-reviewed journal
for publication.
Chemical Analysis of Discharge
– Detailed chemical analyses of various consitients (e.g.,
chloroform, bromoform, trichloroacetic acid, etc.) of treated water upon discharge were
conducted by Analytical Laboratory Services, Inc. (www.analyticallab.com). Summary of
reuslts can be found in Appendix B.