September 2019 - 34

RESEARCH
filters can be back-flushed, and
pressure gauges should be placed
before and after the filter to indicate
when a backflush is necessary.
Although this was not an issue
at the case study operation, GAC
filters can also become clogged
with bacteria and algae, and if
the source has a lot of microbial
growth (such as pond water) it
may be necessary to sanitize (for
example, with chlorine) before
passing water through the GAC.
Remember that GAC will remove
most of the sanitizing agent, so
if a residual sanitizer is required
post-GAC then a sanitizer will need
to be re-injected.
The system cost $27,400 to set
up (Table 1), with annual costs of
$13,020 to treat ≈1.4M gallons
= $8.97/1,000 gallons. This is a
significant cost, and the benefit
would only occur if you have either
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a proven issue of pesticide residue
(based on crop symptoms and
water tests) or a serious risk such
as a surface water supply that is
vulnerable to herbicide contamination
by surrounding land users.
Each GAC filter contained 8×30
U.S. mesh (595-2380 micron)
bituminous coal-based GAC. We
have tested both coal and coconut
shell-based GAC, and both were
equally effective at removing
paclobutrazol. A particle size around
8x30 is important to ensure adequate
surface contact to allow adsorption
of the target chemical onto the
carbon, but still allowing sufficient
water flow rate through the filter.
A common question is how often
the carbon needs to be replaced.
Chemicals adsorb to the carbon
particles, eventually filling the
exchange sites, and the GAC will
no longer function effectively. In
the case study operation, GAC was
replaced once annually by the GAC
supplier at an annual cost of $3,909
(Table 1).
Item
GAC filter
purchase &
installation
Pump & prefilter
purchase
& installation
Pump
(electricity)
and pre-filter
(bags)
GAC (one
change/year)
LIA™ SERIES | Petunia
* Blooms early enough for any
market
* Controlled habit with large blooms
* Tested for pH sensitivity
CASCADIAS™ SERIES | Petunia
* Flowers early enough for any market
* Includes many different colors and
bloom patterns
* Semi trailing to trailing habit is a
great option for large premium
baskets and combinations
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For the full Danziger line as URC and Rooted Liners please contact:
Mike Fernandez: mike@danziger.co.il, Tel. +1-315-396-6684
Lisa Heredia: lisa.heredia@danziger.co.il, Tel. +1-239-248-0665
Randy Uhl: randy.uhl@danziger.co.il, Tel. +1-770-845-7350
VANESSA™ SERIES | Verbena
* Tested for flushing of color
* Trialed and selected for mildew
resistance
* Available in a wide range of colors
including bicolor
Labor for
maintenance
(3 hours/week
@ $25)
Monthly test
paclobutrazol
before & after
filter @ $70/
sample
Total
$791
Capital Per Year
$20,800 $2,080
$6,600 $660
$3,909
$3,900
$1,680
$27,400 $13,020
Table 1. Partial budget for GAC
filtration at the 20-acre case study
greenhouse.
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September 2019

Table of Contents for the Digital Edition of September 2019
