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Ref. No. [UMCES] CBL 11-037
6
4.3. Particle Size Distribution (PSD)
Water samples analyzed for particle size were drawn from ambient water, post-35-micron
water and after each Hydac filter tested at each time point. Analysis was conducted at the
Occoquan Watershed Monitoring Laboratory in Manassas, Virginia.
The EPA ASTM D4464 laser method was used in analysis. Due to low particle
concentrations or counts, particles were only detected in the ambient samples. No detectable
particles were found in the post-filter samples (below detection limits). Thus, the data below list
only the challenge conditions for the Hydac filtration system.
Trial Number Trial Date
Sample ID
PSD Mean (µm)
Hydac-1
25 Jan 2011 T0-Ambient
4.204
Hydac-2
31 Jan 2011 T0-Ambient
1.902
Hydac-3
2 Feb 2011
T0-Ambient
1.387
The 1-micron Laboratory Control Standard (LCS) samples ranged from 0.996 µm to 1.001 µm.
4.4. Zooplankton >50
The data below describes the numbers of zooplankton in both the ambient challenge
water and the post Hydac filter water during all test trials. Size-class distinctions or measures are
determined by considering the greatest available measure among the x, y, and z body axis,
exclusive of appendages such as legs, swimming appendages, sensory apparatus, or other fine
appendages.
Hydac Trials 1, 2, and 3
The zooplankton community was primarily composed of size class one organisms
(>75µm to <120µm), such as rotifers, which typically passed the filter. The calanoid copepods,
Eurytemora affinis
and
Acartia sp.,
were also found in various life stages. Size-class one also
contained copepod eggs and nauplii. While eggs were usually encountered singly, egg clusters,
when present, were also counted as single objects. The size class two (around 1mm) was
composed mainly of copepod adults. In addition, bivalve larvae and barnacle nauplii were
present in lessor abundance.
Hydac Trials 4, 5, and 6
The zooplankton community was primarily composed of size class one organisms
(>75µm to <120µm) such as rotifers. They were found in both ambient and post filter samples in
near comparable numbers. The dominant species were identified as
Brachionus calyciflorus
and
Trichocercas rousseleti
. Although rotifers were still abundant after the filter, many experienced
visible damage and may not have survived. Small nauplii of copepods were also found to be
fairly abundant pre and post filter. Bivalve larvae were present in moderate numbers both pre
and post filter. The filter generally stopped adult copepods (size class two), which were sparse in
abundance.