Environmental Engineering Reference
In-Depth Information
NH
4
-N, and P as they decompose, decreasing the quality of receiving waters or
the water in a recirculating aquaculture system [41, 42]. Liao and Mayo [43] esti-
mated that 70% of the NH
4
-N in aquaculture wastewater is associated with organic
solids. Bergheim et al. [44] estimated that 47-84% of the total phosphorus (TP) in
aquaculture wastewater is particle-bound. Furthermore, high concentrations of sus-
pended solids (SS) may directly cause gill damage in fish by fouling. Gill damage
increases stress and susceptibility to diseases in fish [45].
Algal growth typically occurs in outdoor fishponds as a result of photosynthetic
productions [41, 42]. Large amounts of algae can increase pH levels, which can
harm the fish in a fishpond. Also, fishpond discharges contain algae as organic
SS, thus increasing O
2
demand in the receiving waters by bacterial degradation
[46]. Therefore, algae removal is also essential for aquaculture wastewater treatment
[41, 42].
9.2 Methods of Addressing Water and Wastewater Concerns
Generally the quality of surface water bodies is addressed through limiting point or
non-point pollution entering the water. Point source contamination of water bodies
may be from sources such as improper discharge from CAFOs. Point source pollu-
tant discharges tend to be continuous, with little variability over time, and often can
be monitored by measuring concentrations and discharge periodically at a single
point [9]. Nonpoint inputs can also be continuous, but are more often intermittent
and linked to seasonal agricultural activity or irregular events, such as heavy precipi-
tation or major construction. Nonpoint inputs are the major source of water pollution
in the United States [2]. Control of nonpoint pollution centers on land management
practices.
9.2.1 Land Application
Wastewater from lagoons generally is land applied. Land treatment systems may
include application of wastewater to crops or pasture [47-49], forest, or vegeta-
tive buffer systems [50, 51]. A number of investigators have used dairy wastewater
on forage systems [52-55]. At Tifton, GA, research investigated the utilization of
dairy lagoon wastewater on a frequent, around-the-year basis in an attempt to reduce
manure storage and its associated cost and potential for nutrient loss, odor and over-
flow; maximize recycling of nutrients in crops; and reduce labor demands associated
with seasonal manure application [49]. Two systems were investigated: a mixture of
Abruzzi rye and crimson clover overseeded in the autumn into a Tifton 44 bermuda-
grass (
Cynodon dactylon
)
sod
(for spring haylage), minimum tillage silage corn (
Zea
mays
) seeded after rye/clover harvest, and bermudagrass hay harvest in summer; and
conventional minimum tillage (no living cover crop) rye and clover established in
the autumn (for haylage), a first crop of temperate corn in spring and a second crop