TM 5-814-8
A.
Removes 40 to 60% of
Capital costs are generally Very small power consump-
Simple to operate and main- Sludge-solids con-
Severe odor problems
-
tain. Most operational labor tent 3 to 6%.
if sludge is not
lower than secondary
tion for sludge collection
suspended solids and
associated with sludge
removed periodically.
mechanism.
treatment. O&M costs
30 to 40% of BOO.
removal.
are low.
Relatively simple and
Filter flies that
Overall BOD removal
O&M costs are quite low.
Sludge - humus that
Minimal power costs.
B.
breed in filter
(including primary
sloughs off filter
stable operation. Not as
sedimentation) about
medium is generally
medium. Potential
easily upset as activated
85%. Effluent sus-
returned to primary
odors if overloaded
sludge systems. Tends to
pended solids 30 to
sedimentation.
or improperly main-
pass rather than treat
50 mg/L. Unless
shock loads.
tained.
covered, removals
drop off consider-
ably In winter.
c.
Generally can remove
Sludge - considerably None if properly
High electrical power
Requires more skilled
O&M costs are consid-
90+% of carbonace -
operated. Potential
more than trickling
erably higher than
consumption to oper-
operation than trickling
odors if improperly
filter system. Low
ous BOD. Effluent
trickling filter system.
ate aeration equipment.
filter. Subject to upsets
operated.
solids content (0.5
suspended solids
with widely varying organ-
ic load, but can handle
to 1.0%).
usually are less
than 30 mg/L.
and treat shock loads.
None.
Odor problems during
Minimal operation. Close
Removes 99+% of ori-
D.
None except land.
Relatively low construc-
effluent lines during ice
spring thaw as pond is
tion cost and very low
ginal BOD, but algae
turning from anaerobic
cover and retain all waste-
in effluent may re-
O&M costs.
to aerobic conditions.
water until spring thaw.
sult in suspended
solids (100 mg/L)
and BOD (30 mg/L).
High vitrification
during warm weather.
Must provide winter
storage; no treat-
ment during ice
cover.
E.
Greatly dependent on
Costs similar to the
Generally requires super-
Almost negligible
None if properly
High power consumption
environmental factors
appropriate secondary
vision equivalent to the
operated.
in suspended growth
sludge production.
such as temperature
appropriate secondary
treatment system (acti -
system.
and pH. Can reach
vated sludge, trickling
treatment process.
effluent ammonia
filter, RBC).
Concentrations down
to 1 to 2 mg/L.
Also removes much
of the carbonaceous
BOD remaininq from
secondary treatment.
None apparent at
A relatively small
Requires skilled opera-
High construction costs.
Chemical use such as
Nitrates (as nitro-
F.
time.
amount of waste
tion, careful control of
O&M costs relatively high
gen) can be reduced
methanol; miminal power
sludges are generated
methanol feed, and sys-
due to carbon source
consumption.
to below 1 mg/L.
in suspended growth
tem monitoring.
such as methanol that
Columnar system with
system and coarse
usually is added to sys-
fine grain media
grain columnar system.
tem.
also can double as
Backwash water in
filter with appro-
fine grain columnar
priate suspended
system.
solids removal.
(1) Chlorination. Chlorine is the principal
converted to the use of hypochlorite solutions due
chemical utilized for disinfection in the U.S.
to the potential hazards involved in transporting
Chlorine dosages vary, but for secondary treat-
chlorine through populated areas. Where treat-
ment effluents the normal range is from 5 to 15
ment facilities are remotely located, such as many
mg/L with requirements for a chlorine residual of
military installations, gaseous chlorine will be
not less than 0.2 to 1.0 mg/L after a 15 minute
acceptable provided suitable safety precautions
detention time at maximum flow rate (108).
are taken with shipping and handling. Possible
Regulatory requirements may differ in various
disadvantages of chlorine disinfection are the
States and consultation with the appropriate
toxicity of the chlorine residual to aquatic life and
agency is recommended. Disinfection must meet
the potential of the chlorine combining with
the U.S. EPA fecal coliform level of 200/100 mL.
organic material in the effluent or the receiving
General practice is to provide the chlorine feed
stream to form cancer-causing compounds. Some
either as gaseous chlorine, normally vaporized
States and the U.S. EPA have proposed limita-
from liquid storage, or from a calcium
tions on the residual chlorine concentration in
hypochlorite solution feeder. Other than for ex-
both effluent and streams. Thus, for some chlori-
tremely small plants, the gaseous chlorines more
nation systems additional detention time, addi-
economical. However, many of the large metropol-
tion of a reducing agent (sodium bisulfite or
itan areas, such as New York and Chicago, have
sulfur dioxide), or passage through activated
6-16
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