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Ref. No. [UMCES] CBL 2017-050
ACT VS17-05
7
were conducted to evaluate performance under controlled challenge conditions including:
concentration range, temperature, salinity, turbidity, and dissolved organic carbon (details below).
All Laboratory tests were conducted in polypropylene tank using RO water as the initial matrix,
within a temperature controlled room. All instruments sampled from a common, well-mixed, test
tank of approximately 250L volume, maintained at a documented level of known challenge
condition. Instruments were set-up by the manufacturer daily prior to start of each individual
laboratory tests. Instruments were exposed to each test condition for a period of three hours and
programmed to sample at a minimum frequency of 30 minutes. Reference samples were collected
every 30 minutes for five timepoints during instrument sampling times for each test. Laboratory
tests included the following ‘controlled’ challenge conditions:
Test 1: Accuracy and Precision over a broad concentration range
–
Tested response across a broad range of concentrations representative of natural waters.
o
Concentration levels for NO
3
(mgN/L): 0.005, 0.1, 1.0, 5, 10, and 50
o
Concentration levels for PO
4
(mgP/L): 0.002, 0.01, 0.05, 0.1, 0.5, and 2.0
–
The range test was split into two separate tests with concentrations for levels 1-4 conducted
on day 1 and the last two concentrations tested on day 6 due to time constraints. Note that
the starting level on day 6 was mistakenly set to 5 mgN/L and the 10 mgN/L level was not
actually tested.
–
Three hour sampling windows were provided at each of the six concentrations during
which instruments measured concentrations at a minimum frequency of every 30 minutes.
–
Discrete reference samples were collected every 30 minutes, corresponding to instrument
sampling times, to generate five comparative measurements to assess accuracy and
precision against reference values.
–
RO water was used as the test matrix to which known amounts of nutrient salts (KNO
3
and
K
2
HPO
4
) were added. Analysis of ambient blanks indicated a small amount of inorganic
nutrients in the RO water.
–
Tests were conducted at 20
o
C in a temperature controlled room with samples drawn from a
common well-mixed 250L test tank.
Test 2: Temperature Response
–
Instrument response was tested for three concentrations, corresponding to levels C2, C3,
and C4 from the range test, at temperatures of 5
o
C versus the temperature of 20
o
C on the
first day.
–
Temperature was regulated and maintained within a temperature controlled room and
independently verified in the test tank with an YSI EXO2 reading at 15 min intervals.
–
Instruments were equilibrated to the new 5
o
C test temperature overnight.
–
Instruments were exposed for three hours at each of the 3 concentrations with reference
samples collected every 30 minutes following an initial 30 minute equilibration period to
each condition.
Test 3: Salinity Response
–
Accuracy and precision was tested over three additional salinities (10-20-30) at the C3
concentration level of the range test at 20
o
C.