WATERSHEDS - Water Quality Engineering in Natural Systems - page 238

such as the use of erosion blankets, tie-downs, gabions,
mulches, hydromulching, increased seeding rate, and
hand planting, are often needed.

6.3.3.6 Sediment Basins and Detention-Retention
Ponds. Basins and ponds generally consist of earthen
embankments designed to trap and store sediment and
other pollutants. Tailwater detention ponds are used to
collect runoff from agricultural fields for storage and
pollution control. Such detention ponds are sometimes
called tailwater recovery ponds . Sediment basins can
remove 40-90% of the incoming sediment, up to 30%
of the adsorbed nitrogen, and 40% of the adsorbed
phosphorus. The effectiveness of detention-retention
ponds, especially those with aquatic vegetation, is gener-
ally higher. Sedimentation basins may not be effective
for removal of toxicity or dissolved toxic compounds
(Novotny, 2003).

6.3.3.7 Animal Waste Storage and Treatment. Prac-
tices for management of animal wastes include storage
and land disposal of treated waste. Lined manure
storage bins and liquid waste storage ponds hold waste
until it can be land applied without causing a water pol-
lution problem. Waste treatment processes include
lagoons that treat liquid waste biologically to reduce the
nutrient and BOD content, anaerobic treatment in
digesters, aerobic treatment by trickling filters and
suspended-growth processes, such as activated sludge,
and composting. A state-of-the-art lagoon waste man-
agement system for a 900-head hog farm is shown in
Figure 6.27, where this facility is completely automated
and temperature controlled.
Animal wastes are frequently classified as point
sources and require a discharge permit in many states.
however, pollution is generated by runoff from the con-
taminated premises and typically requires runoff control
BMPs in addition to treatment and/or safe disposal. The
basic principles of runoff control are that “clean” runoff
originating outside the feedlot or storage area should
be diverted so that it does not come in contact with the
contaminated soil, and runoff originating inside the
feedlot should be disposed of in a way that minimizes
its pollution potential.

Figure 6.27. Animal waste treatment lagoon. Source : Natural
Resources Conservation Service (2005b).

vegetation such as sod or bunch grasses or small-grain
crops with the primary purpose of water-quality protec-
tion. Filter strips are generally placed between agricul-
tural land being used and a water body being protected.
They are designed to remove sediment and other pol-
lutants from sheet runoff by slowing the water velocity
and allowing the suspended material and any adsorbed
pollutants to be removed by sedimentation.
Field borders normally consist of perennial vegeta-
tion planted at the edge of fields to control erosion
regardless of their proximity to water. Field borders are
effective in preventing detachment of soil particles on
the areas covered by the borders but have little effect
on controlling erosion or pollutant detachment or trans-
port from the fields they surround. Filter strips are very
effective in removing sediment and sediment-bound
nitrogen (35-90%) but less effective in removing phos-
phorus, fine sediment, and soluble nutrients, such as
nitrate (14%) or orthophosphate (5-50%). 6.3.3.8 Livestock Exclusion Fences. Keeping animals

out of a stream by installing fences and crossings will
reduce deposition of fecal material (a nutrient and bac-
terial source), eliminate turbidity from instream tram-
pling, and eliminate detachment of sediment from
streambanks.

6.3.3.10 Wetland Rehabilitation. Rehabilitation and
development of wetlands involves restoring, rehabilitat-
ing, or enhancing existing wetlands to function as
self-sustaining ecosystems that process, remove, trans-
fer, and store pollutants. Wetlands are 80-90% effective
in sediment removal, 40-80% effective in nitrogen
removal, and 10-70% effective in phosphorus removal.

6.3.3.9 Filter Strips and Field Borders. Filter strips
and field borders utilize strips of closely growing