Environmental Engineering Reference
In-Depth Information
and O
2
transfer from the atmosphere as well as O
2
release by emergent macro-
phyte roots probably created niches of high redox potential where this adsorbtion
occurred.
Surrency [63] reported on constructed wetland research from four locations in
the southeast and concluded that giant cutgrass (
Scirpus californicus
and
S. validus
),
maidencane, pickerelweed (
Pontedieria cordata
), arrowhead (
Sagittaria lancifolia
),
and cattail (
Typha latifolia
) are the best aquatic plants to use in constructed wet-
lands for treating wastewater from dairy and swine operations and for municipal
constructed wetland systems. In an in-situ containerized field study, Hubbard et al.
[69] evaluated growth and nutrient uptake response of the species Dahoon holly
(
Ilex cassine
), buttonbush (
Cephalanthus occidentalis
), Virginia sweetspire (
Itea
virginica
), saltmeadow cordgrass (S
partina patens
), soft rush (
Juncus effuses
), and
maidencane when swine lagoon wastewater was applied. They found that button-
bush and saltmeadow cordgrass were best at removing nutrients as compared to the
other species.
9.2.3 Hydroponics
A number of researchers have investigated using hydroponics to purify wastewater
from agriculture [70-74]. Snow and Ghaly [71] used barley (
Hordeum vulgare
)for
the purification of aquaculture wastewater in a hydroponics system. They found that
total solids (TS), COD, NH
4
-N, NO
2
-N, NO
3
-N, and PO
4
-P reductions ranged from
52.7 to 60.5%, from 72.9 to 83.1%, from 66.0 to 76.0%, from 97.6 to 99.2%, from
76.9 to 81.6% and from 87.1 to 95.1%, respectively. The effluent produced from
the hydroponics system had slightly higher levels of TS (420-485 mg L
-1
) than the
480 mg L
-1
recommended for aquatic animals. Snow and Ghaly [72] also tested
water hyacinth, water lettuce (
Pistia stratiotes
), and parrot's feather (
Myriophyllum
aquaticum
) for the hydroponic purification of aquaculture wastewater. With these
species they found that the TS, COD, NH
4
-N, NO
2
-N, NO
3
-N, and PO
4
-P reduc-
tions ranged from 21.4 to 48.0%, from 71.1 to 89.5%, from 55.9 to 76.0%, from
49.6 to 90.6%, from 34.5 to 54.4% and from 64.5 to 76.8%, respectively. In this
study they found that in terms of COD, NO
3
-N and PO
4
-P, the effluent leaving
the hydroponics system was suitable for reuse in aquaculture. However, the efflu-
ent had slightly higher levels of TS, NH
4
-N, NO
2
-N and pH after treatment. Snow
and Ghaley [70] found that at hydraulic retention times of 6 and 12 days, the aver-
age biomass of water hyacinth, water lettuce and parrot's feather were 83, 51 and
51 g m
-2
and 49, 29 and 22 g m
-2
, respectively. Wen and Recknagel [74] examined
the use of parrot's feather for treatment of agricultural drainage waters and reported
an average growth rate for parrot's feather of 7.12 g m
-2
day
-1
.
Jo et al. [73] evaluated the growth of water hyacinth and water lettuce plants for
30 days on effluent from an intensive recirculating aquaculture system and reported
biomass yields of 6402 and 10188 g m
-2
, respectively. At water temperatures of
30-38.5
◦
C the water lettuce and water hyacinth plants in this system reduced the
concentrations of NH
4
-N in the wastewater from 2.3 to 0.4 mg L
-1
and 0.6 mg L
-1
