TM 5-814-8
removal may be increased by aeration devices,
mixing level through the addition of mixing
increased aeration tank volumes, roughing units
equipment, draft tubes or hydraulic modifications.
or polishing filters. Ammonia standards may
(a) Reducing organic loading. As with hy-
require t h e addition of biological vitrification
draulic overloading, organic overloads may be
units, in-plant control, or the operation of existing
caused by either peak loads or excessive average
biological systems to provide vitrification.
loads. Peak loads may be dampened by equaliza-
tion at the source or at the treatment plant. If
5-6. Environmental impact
the average load still represents an organic over-
load, other correctional methods must be used. In
The environmental impact statement (E IS) and
activated sludge systems with low dissolved oxy-
the environmental assessment are documents
gen concentrations, increasing aeration capacity
which present the results of a study of all the
may provide the oxygen required by the bacteria
potential effects of a proposed or existing facility
to assimilate excessive quantities of organic mat-
or activity on its environment. A discussion of
ter. Additionally, enrichment with pure oxygen
the requirements and preparation of the EIS is
may also provide the necessary oxygen. If the
included in chapter 4 of this manual. Detailed
problem is not insufficient oxygen, increasing the
instructions on the preparation of environmental
aeration tank mixed liquor volatile suspended
impact statements are set forth in AR 200-2.
solids (MLVSS) level would provide a larger
Additional guidance is available in the DA Pam-
biological population which could subsequently
phlet 200-1.
oxidize more organic matter. This line of action is
5-7. Other considerations
contingent upon the capability of the secondary
clarifiers to accommodate higher solids loadings.
In many instances, establishing a pollution con-
A similar effect can be achieved by increasing the
trol program involves consideration of factors
volume of the aeration basin.
different from those experienced at similar instal-
(b) Temperature. One important factor in
lations and can be evaluated only at the prospec-
all biological treatment systems is operation at
tive site. Such factors may include the treatment
low temperatures. Since biological reactions slow
needs of a new type of process waste; integration
down as temperature drops, many plants experi-
with an existing waste system; the effect of
ence operational difficulties under winter condi-
system performance under different climatic con-
tions. Upgrading methods for winter operation
straints; and peculiar needs such as architecture,
and associated problems are directed toward bet-
landscaping, and materials of construction. A site
ter heat conservation within the treatment plant.
visit should be conducted to establish the mission
Among the possible winter upgrading methods
of the installation and to determine any unusual
are reduced mixing in equalization basins, com-
site conditions which may dictate certain pollu-
plete or partial bypass around equalization ba-
tion control plans.
sins, covering equalization basins, and shift from
a. Bench and pilot studies. A basic consider-
surf ace to diffused aeration.
ation during wastewater treatment investigations
(c) Capital expansion. Finally, the addition
is evaluation of the need for bench (laboratory)
of supplementary organic load reduction units
and pilot scale studies. There are usually two
such as roughing trickling filters before biological
objectives of such studies. The first is to deter-
systems or polishing filters following biological
mine whether the waste is amenable to treatment
systems, may be necessary to properly upgrade
by the proposed unit operations or processes. The
the treatment plant.
second is to obtain sufficient data to effectively
(5) Upgrading to meet more stringent stan-
design the full scale facility. Laboratory tests
dards. Many plants are facing the prospect of
should be conducted before proceeding to pilot
having to meet more stringent standards than
scale studies. For existing plants, full scale plant
those for which the plant was designed. Optimiza-
testing may be substituted for pilot studies under
tion of all operational and design aspects of the
some circumstances.
existing system may be insufficient to meet the
(1) Factors considered. Generally, consider-
new, more strict standards. Compliance may re-
ation of the need for bench (laboratory) and pilot
quire construction of additional units depending
scale studies is encountered with treatment of
on the parameters which must be met. Three
process or industrial wastes. Requirements may
parameter commonly subject to increasing strict
be to treat a waste stream or streams for which a
standards are TSS, BOD, and NH3. Suspended
suitable treatment method has not previously
been established. These studies can also be used
solids removal may be increased by addition of
to determine if a particular process waste can be
filters, clarifiers, or air flotation systems. BOD
5-18
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