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MERC ER02-10
4
standard USEPA method: membrane filtration on modified mTEC agar. Abundances of total
and toxigenic
V. cholerae
were calculated by filtration and selection on TCBS agar and
enumerated using a species-specific 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.
Toxicity -
To evaluate the toxicity of treated water at the completion of each trial, samples
from each mesocosm were collected and tested for 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).
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).
A Fischer and Porter
amperometric titrator was also used for amperometric measurements.
To assess disinfection by-products, a nine-liter carboy of water was drawn at the
following 4 time-points: T-0 Control inflow, T-0 Treated inflow, T-0 backflush discharge and T-
F Treated discharge. The carboy of water was immediately sampled for analyses of the
following compounds:
Trihalomethanes (TTHM), Haloacetic Acids (HAA5), Tribromoacetic
Acid (TBAA), Bromate (Br), Chlorate (ClO3), Sodium (Na, as a metal), and various Nitriles (-
CN group – triple bond). Samples were iced and delivered same-day via courier to the
Analytical Laboratory Services, Inc. (ALSI) for analysis.
5.0 Summary of Results
Live Organisms -
For essentially all biological categories, the Siemens SiCURE
TM
BWMS reduced the numbers of live organisms in ballast water to levels below IMO D2
discharge standards. The only anomaly was found in one trial where
Enterococci
abundances
increased slightly in both treated and control water during the 5-day hold time, with a TF value
just over (107.4 + 33.5) the IMO D2 discharge standard of less than 100 cfu/100 ml. However, it
is important to note the relatively large standard deviation, that the most probably number
(MPN) method used (Idexx Enterolert kit) to quantify
Enterococci
commonly over estimate
abundance when compared to the a traditional membrane filtration method (G. Ditcher, personal
communication), and in all other test trials (over two different years)
Enterococci
appeared to be
successfully treated by the SiCURE
TM
system.
Chronic Toxicity -
Toxicity testing was conducted on five treated discharge samples
between 4/27/10 and 6/15/10. Results indicate that treated ballast water discharge (TF) was not
chronically toxic to mysid shrimp or Sheepshead Minnows. However the treated water upon
discharge did significantly inhibit the growth of the algae species,
Isochrysis galbana
(T-Iso.) for
three of the test trials (
Trial 1 22-27 April
,
Trial 2 13-18 May, and Trial 5 3-8 June),
which is
reported as “toxic” for this algal assay. These samples had LOECs of 100% and NOECs of 56%.
All three algae tests with a toxicity response in the undiluted sample (100%) had similar EC50s
of 70%, 71% and 78% for SIE-03, -05 and -08, respectively.