-------
FIGURE 9-2
CONFIGURATION OF STATIC MIXER
Air
Flow
Source: USEPA, 1985
9-18
-------
This concentration is sufficient only for degradation of about 5 mg/1
hydrocarbons, and would therefore provide an inadequate oxygen supply. A
pressurized line can increase oxygen concentrations as can the use of pure
oxygen.
The equilibrium oxygen concentration in water increases with increased
air pressure according to Henry's Law (Sawyer and McCarty, 1967):
where: CL = PIL
CT = concentration of oxygen in liquid (mg/1)
Lt
= volume fraction (0.21 for 0 in air)
P = air pressure (atm)
H, = Henry's Law Constant for oxygen.
The value of Henry's Law Constant is 43.8 mg/1-atmosphere at 68°F (20°C).
Pressure increases with groundwater depth at the rate of 0.0294 atmospheres
per foot.
The use of in-situ aeration wells (Figure 9-3) is a more suitable method
for injecting air into contaminated leachate plumes. A bank of aeration wells
can be installed to provide a zone of continuous aeration through which the
contaminated groundwater would flow. Oxygen saturation conditions can be
maintained for degrading organics during the residence time of groundwater
flow through the aerated zone. The required time for aeration can be derived
from bench-scale studies. Residence time (t ) through the aerated zone can be
calculated from Darcy's equation (Freeze and Cherry, 1979) using groundwater
elevations (i.e., head) and hydraulic conductivity as follows:
t = (L )2/K(h1-h2)
L cl •*- *•*
where:
t = residence time (sec)
K = hydraulic conductivity (ft/sec)
L = length of aerated zone (ft)
3
h = groundwater elevation at beginning of aerated zone (ft)
ho = groundwater elevation at end of aerated zone (ft).
In the design of an in-situ aeration well zone system, the zone must be
wide enough to allow the total plume to pass through. The flow of air must be
sufficient to give a substantial radius of aeration while small enough to not
cause an air barrier to the flow of groundwater-
9-19
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Figure 9-3
POSSIBLE CONFIGURATION OF IN SITU AERATION WELL BANK
Plane View
Zone of Aeration
Surface Contours.
Direction of Groundwater Flow
Cross-sectional
View
A
c
1
^m<7
Y^M>
, ••••••
• 0 0
••*:
oO%
000
\
C
v: :
e o
* ft 0 0
• V . .
0 0 0
r o-o/.
0 '"'••.'
« ° o o
0 0 °
.x'.'t
» 9 • ° •
« • • « ,'
• o •»!
0 • .
[/ x^
• o » o
XX
• 0 « ^*
^•':i
^^^ Air Injection Wells
x^c^cg/y/^Cvj^'
^Aerated Zone
/^^ V
• 0
'•'. :
0 *
•
b
Source: USEPA, 1986
9-20
-------
Various methods can be used to inject air or pure oxygen. Air has been
sparged into wells using diffusers. For example, Raymond et al. (1975),
sparged air into wells using diffusers attached to paint sprayer type
compressors which could deliver approximately 2.5 cubic feet per minute. They
were fitted with steel end plates and fittings to accommodate a polyethylene
air line and a nylon rope and were suspended into the wells.
A blower can also be used to provide the flow rate and pressure for
aeration. At the groundwater bioreclamation project in Waldwick, NJ,
5 pounds per square inch pressure is maintained in nine 10-foot aeration
wells, each with an air flow of 5 cubic feet per minute (Groundwater
Decontamination Systems, Inc., 1983).
Microdispersion of air in water using colloidal gas aprons (CGA) creates
bubbles 25 to 50 micrometers in diameter. This is a newly developed method
which holds great promise as a means of introducing oxygen to the subsurface
(Michelsen, Wallis, and Sebba, 1984). With selected surfactants, dispersions
of CGA's can be generated containing 65 percent air by volume.
Oxygenation systems, either in-line or in-situ can also be installed in
order to supply oxygen to the bioreclamation process. Their advantage over
conventional aeration is that higher oxygen solubilities and hence, more
efficient oxygen transfer to the microorganisms can be attained. Solubilities
of oxygen in various liquids are four to five times higher under pure oxygen
systems than with conventional aeration. Therefore, in-line injection of pure
oxygen will provide sufficient dissolved oxygen to degrade 20 to 30 mg/1 of
organic material, assuming 50 percent cell conversion. The higher oxygen
solubilities may provide some flexibility in the design of cell banks,
especially at greater pressures, since the oxygen may not be used up
immediately, as with aeration.
Hydrogen peroxide (^02) as an oxygen source has been used successfully
at the cleanup of several spill sites (Brubaker, G.R. FMC Aquifer Remediation
Systems, Princeton, NJ, personal communication, 1985). Advantages of hydrogen
peroxide include:
• Greater oxygen concentrations can be delivered to the subsurface.
100 mg/1 HO provides 50 mg/1 0 .
• Less equipment is required to oxygenate the subsurface. Hydrogen
peroxide can be added in-line along with the nutrient solution.
Aeration wells are not necessary.
• Hydrogen peroxide keeps the well free of heavy biogrowth. Microbial
growth and subsequent clogging is sometimes a problem in air injection
systems (Yaniga, Smith, and Raymond, 1984).
Hydrogen peroxide is cytotoxic, but research has demonstrated that it can be
added to acclimated cultures at up to 1,000 ppm without toxic effects (Texas
Research Institute, 1982). The remediation at Granger, Indiana, involved
adding an initial concentration of 100 ppm, and increasing it to 500 ppm over
9-21
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the course of the treatment (API, Washington, DC, personal communication,
1985).
Hydrogen peroxide decomposes to oxygen and water (H-0 0 + HO). In
the subsurface, hydrogen peroxide decomposition is catalyzed by chemical and
biological factors. There has been some concern that decomposition could
occur so rapidly that oxygen would bubble out near the site of injection and
no oxygen would be made available to the distal portions of the treatment
zone. Research has shown that high concentrations of phosphates (10 mg/1) can
stabilize peroxide for prolonged periods of time in the presence of ferric
chloride, an aggressive catalyst (Texas Research Institute, 1982). However,
there are problems associated with adding such high phosphate concentrations
to the subsurface, such as precipitation. One company claims to have
developed specially stabilized hydrogen peroxide products for aquifer
remediation- However, process performance information on these products is
not available.
Ozone is used for disinfection and chemical oxidation of organics in
water and wastewater treatment. In commercially available ozone-from-air
generators, ozone is produced at a concentration of one to two percent in air
(Nezgod, W. PCI Ozone Corporation, West Caldwell, NJ, personal communication,
1983). In bioreclamation, this ozone-in-air mixture could be contacted with
pumped leachate using in-line injection and static mixing or using a bubble
contact tank. A dosage of 1 to 3 mg/1 of ozone can be used to attain chemical
oxidation (Nezgod, W. PCI Ozone Corporation, West Caldwell, NJ, personal
communication, 1983). However, German research on ozone pretreatment of
contaminated drinking waters indicates that the maximum ozone dosage should
not be greater than 1 mg/1 of ozone per mg/1 total organic carbon; higher
concentrations may cause deleterious effects to microorganisms (Rice, R.G.
Rip G. Rice, Inc., Ashton, MD, personal communication, 1983). At many sites,
this may limit the use of ozone as a pretreatment method to oxidize refractory
organics, making them more amenable to biological oxidation.
A petroleum products spill in Karlsruhle, Germany, was cleaned up in-situ
using ozone as an oxygen source for biological degradation (Nagel et al«, 1982
in Lee and Ward, 1984). The groundwater was pumped out, treated with ozone,
and recirculated. Approximately one gram of ozone per gram of dissolved
organic carbon was added to the groundwater and was allowed a contact time of
four minutes in the aboveground reactor. This increased the oxygen content to
9 mg/1 with a residual of 0.1 to 0.2 gram of ozone per cubic meter in the
treated water.
b. Nutrients
Nitrogen and phosphate are the nutrients most frequently present in
limiting concentrations in soils. Other nutrients required for microbial
metabolism include potassium, magnesium, calcium, sulfur, sodium, manganese,
iron, and trace metals. Many of these nutrients may already be present in the
aquifer in sufficient quantities and need not be supplemented.
9-22
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The optimum nutrient mix can be determined by laboratory growth studies
and from geochemical evaluations of the site. Caution must be exercised in
evaluating microbial needs based on soil and groundwater chemical analysis.
Chemical analysis does not necessarily indicate what is available to the
microorganisms. In some cases generalizations can be made, e.g., if calcium
is present at 200 mg/1 (a very high concentration), it is likely that calcium
supplementation is unnecessary.
The form of nutrients may or may not be critical in terms of microbial
requirements, depending on the site. Studies have shown that forms of
nitrogen and phosphate were not critical for microorganisms (Jamison, Raymond,
and Hudson, 1976). However, it has been recommended than an ammonia-nitrogen
source is preferable to a nitrate-nitrogen source because ammonia-nitrogen is
more easily assimilated by microorganisms (FMC, 1985). Nitrate is also a
pollutant limited to 10 mg/1 in drinking water.
The site geochemistry may be a critical factor in determining the form of
nutrients, as well as the added concentrations. For example, use of
diammonium phosphate could result in excessive precipitation (Jamison,
Raymond, and Hudson, 1976) and nutrient solution containing sodium could cause
dispersion of the clays, thereby reducing permeability (Anderson, D., K.W.
Brown, and Associates, Inc., College Station, TX, personal communication,
1985). Where calcium is high, it is likely to lead to the precipitation of
added phosphate, rendering it unavailable to microbial metabolism. If a site
is likely to encounter problems with precipitation, iron and manganese
addition may not be desirable. If the total dissolved solids content in the
water is extremely high, it may be desirable to add as little extra salts as
possible.
The compositions of some basal salts media are given in Tables 9-7 and
9-8. Only phosphate and nitrogen had to be added to a site in Ambler, PA.
Bulk quantities of ammonium sulfate [ (NH^^SO, )], disodium phosphate
(Na-HPO,), and monosodium phosphate (NaH.PO.) were mixed in a 2,200 gallon
tanE truck and added to the groundwater In the form of a 30 percent concen-
trate in water which was metered into the injection wells (Raymond, Jamison,
and Hudson, 1976). Phosphate concentrations in injection wells varied from
200 to 5,800 mg/1 throughout the site cleanup. Phosphate concentrations
in all wells were determined weekly and injection rates were adjusted
accordingly.
CDS, Inc. used the basal salt medium listed in Table 9-8 in the combined
surface/in-situ treatment system at the Biocraft site (Jhaveri and Mazzacca,
1984). The nutrient solution used at the Granger, Indiana, site was composed
of ammonium nitrate and disodium phosphate (FMC, 1985).
An organic carbon source, such as citrate or glucose, could be added if
the compound of interest is only degraded cometabolically and a primary carbon
source is required. Such additions could also be made when low levels of
contaminants are present and are not sufficient to sustain an active microbial
population. Citrate, or another chelate such as EDTA, could be added to hold
metals in solution if water is alkaline, a condition under which metals may
9-23
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TABLE 9-7
COMPOSITION OF BASAL SALTS MEDIUM
Salt Type
KH2P04
Na2HP04
(NH4)N03
MgS04.7H20
Na,CO,
£• J
CaCl2.2H20
MnS04.H20
FeS04.7H20
Concentration (mg/1)
400
600
10
200
100
10
20
5
Source: Jamison, Raymond, and Hudson, 1976
TABLE 9-8
BASAL SALT MEDIUM USED BY CDS INC.
Salt
NH,C1
4
KH2P04
K2HP04
MgS04
Na2C03
CaCl2
MnSO,
4
FeSOA
4
Concentration (mg/1)
500
270
410
1.4
9
0.9
1.8
0.45
Groundwater Decontamination Systems, Inc., 1983
9-24
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precipitate. Citrate, however, will be preferentially degraded relative to
other organics, and could slow the degradation of contaminants. Addition
of low concentrations of a source of araino acids, such as peptone or yeast
extract, could promote biodegradation. However, high concentrations of these
compounds could inhibit degradation of contaminants because of preferential
degradation.
c. Design of Delivery and Recovery Systems
One of the major factors determining success of an in-situ treatment
system is to ensure that the injection and recovery systems are designed to
accomplish the following:
• Provide adequate contact between treatment agents and contaminated
soil or groundwater
• Provide hydrologic control of treatment agents and contaminants to
prevent their migration beyond the treatment area
• Provide for complete recovery of spent treatment solutions and/or
contaminants where necessary.
A number of design alternatives are available for delivering nutrients
and oxygen to the subsurface and for collecting and containing the ground-
water. These methods can generally be categorized as gravity flow or forced
methods. Most of the systems that have been used for bioreclamation have
involved the use of subsurface drains (gravity system), injection wells and
extraction wells. Subsurface drains and extraction wells are described in
detail in Sections 5.2 and 5.1, respectively. Some examples of delivery and
recovery systems are described below.
Figure 9-4 illustrates a hypothetical configuration in which groundwater
is extracted downgradient of the zone of contamination and reinjected
upgradient. In-situ aeration supplies oxygen directly to the contaminated
plume while nutrients and oxygen are added in-line by way of mixing tanks.
Treated water is infiltrated through contaminated soil in order to flush
contaminants from the soil. Extraction and injection wells can be used to
treat contaminants to almost any depth in both the saturated and unsaturated
zone. However their use becomes cost-prohibitive in very low permeability
soils because of the need to space the wells very close together to ensure
complete delivery or recovery. Subsurface drains can be used under conditions
of moderately low permeability although delivery and recovery of chemicals
will be slow. They are generally limited to depths of 40 feet or less because
of the cost associated with excavation (shoring, dewatering, hard rock
excavation) of the trench. Surface gravity delivery systems (e.g., spray
irrigation, flooding, ditches) which involve application of treatment
solutions directly to the surface, as illustrated by "surface flushing" in
Figure 9-4, are most effective for treating shallow contaminated zones located
9-25
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FIGURE 9-4
SIMPLIFIED VIEW OF GROUNDWATER BIORECLAMATION
Subsurface Aeration Wells
Inaction Well
Extraction Well
Direction of Flow
Simplified View of
Bioreclamation of
Soil and Groundwater
Aeration Zone
Direction of Groundwater Flow
Extraction Well
9-26
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in the unsaturated zone. They can also be used to treat contaminants in the
saturated zone, provided the following conditions are met:
• The soil above the saturated zone (through which treatment solutions
percolate) is sufficiently permeable to allow percolation of treatment
solutions to the groundwater within a reasonable length of time
• Groundwater flow rates must be sufficient to ensure complete mixing of
the treatment solutions with the groundwater.
The feasibility and effectiveness of these methods is affected by
topography and climate.
Figure 9-5 shows the design of a groundwater injection/recovery system
which is currently being used for bioreclamation at an Air Force site.
(SAIC/JRB, 1985). The system, which is designed to operate in moderately low
permeability soils, consists of nine pumping wells and four injection wells.
Groundwater is pumped at an even rate from the pumping wells to a central flow
equalization (surge tank). Flow is metered from this tank into a length of
pipe into which measured amounts of nutrients and hydrogen peroxide are added.
The treated water then flows to a distribution box to be distributed at an
even rate to each of the four injection wells. Overflow from the equalization
tank will flow into an on-site storage tank.
The injection/recovery system was designed using a two-dimensional,
geohydrologic non-steady flow model which simulated the flow of groundwater at
the site in response to an injection/recovery pumping system.
Important criteria used for the design of the injection/recovery system
include the following:
• The groundwater injection rate will be the same as the rate determined
during the field testing program
• All injected groundwater and associated elements are to be kept within
the site boundary to prevent the transport of contaminants to adjacent
areas (this implies that there may be some net groundwater pumpage at
the site)
• The distance between the injection-pumping wells should be such that
approximately six injection-pumping cycles can be completed within a
6-month period.
Figure 9-6 illustrates an injection trench used in the treatment of the
Biocraft site (Jhaveri and Mazzacca, 1983). The trench was 10 feet deep by
4 feet wide by 100 feet long. The trench had a 15 mil plastic liner installed
on the bottom, back, ends, and top such that reinjected water only flowed out
of the front (downgradient) face of the trench. About 40 feet of slotted
steel pipe was installed horizontally in the trench to carry reinjected water
into the trench system. As water flowed into the injection trench, the water
was forced to exit only from the front face. Backflow is minimized by this
9-27
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FIGURE 9-5. PLAN VIEW OF EXTRACTION/INJECTION SYSTEM
USED AT AIM AIR FORCE SITE
KEY:
Pumping Wells
j) Injection Wells
' Untreated Groundwater Lines
— ~ Treated Groundwater Lines
9-28
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(0
UJ
o
UJ
cc
UJ
cc
u.
O
2
O
§
DC
3
O
EZ
2
O
U
ui
OC
3
O
1
(0
I
o
C/3
1
9-29
-------
design feature. Barriers can also be used behind the trench and extended to a
point where backflow is further minimized. In extreme cases, total control
over backflow and plume containment can be obtained by installing a
circumferential wall barrier.
Optimum extraction and injection flow rates will many times be pre-
determined by aquifer yield limits or hydraulic design for plume containment.
The factors affecting aquifer flow rates are described in Section 5.1.
Aquifer flow rates should be sufficiently high so that the aquifer is
flushed several times over the period of operation. Thus, if the cleanup
occurs over a three year period, flow rates between injection and extraction
wells should be such that a residence time of one-half year dr less occurs
between the well pairs. This corresponds to six or more flushes. Several
recycles would cause flushing of soils containing organics, preventing the
clogging caused by microorganism buildup because of increased flow rate; more
even distribution of nutrients and organic concentration within the plume; and
better and more controlled degradation. Flow rates and recycle should not be
high enough to cause excessive pumping costs, loss of hydraulic containment
efficiency because of turbulent conditions, corrosion, excessive manganese
deposition, flooding, or well blow out. The operating period will depend on
the biodegradation rate of the contaminants in the plume and the amount of
recycle. If the period of operation is excessively long, for example more
than five years, the operating costs of bioreclamation may outweigh the
capital costs of another remedial alternative.
9.1.3.2 Anaerobic Bioreclamation
Anaerobic treatment is generally not as promising for site remediation as
aerobic treatment. Anaerobic processes are slower, fewer compounds can be
degraded, and the logistics of rendering a site anaerobic have not been
developed to date.
Anaerobic metabolism includes: (1) anaerobic respiration, in which
nitrate or sulfate may be used by nitrate or sulfate reducers as a terminal
electron acceptor, and (2) interactive fermentative/methanogenic processes,
which are carried out by what is referred to as a methanogenic consortium.
If it were possible to provide proper reducing conditions, degradation by
methanogenic processes would be promising. A considerable body of research
indicates that methanogenic consortiums are active in the subsurface and are
capable of degrading certain organics (Ehrlich et al., 1982; Parsons et al.,
1982; and Suflita and Gibson, 1984). Most notably, methanogenic consortiums
are able to degrade TCE, PCE, and other lower molecular weight halogenated
organics which generally cannot be degraded by aerobic or other respiratory
processes. Reductive dehalogenation appears to be the primary mechanism
involved in degradation. Methanogenic consortiums are also able to degrade
various aromatics, halogenated aromatics, and some pesticides. Degradation of
9-30
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petroleum hydrocarbons, straight-chain and branched alkanes and alkenes, is
not possible under methanogenic conditions.
Methanogenic_activity requires a very low redox potential, -250 mv or
less. No 0«, NO. , or SO, can be present or the redox potential will not be
low enough. Currently, there are no demonstrated methods for rendering a site
anaerobic. When the contamination is shallow, there is an aquitard below the
zone of contamination, and the flow of groundwater can be contained, it might
be possible to induce reducing conditions by flooding the site, as one would a
rice paddy. Another possible method or rendering the site anaerobic would be
to add excessive amounts of easily biodegradable organics so that the oxygen
would be depleted. One other promising possibility might be to circulate
groundwater to the surface through anaerobic digesters or anaerobic lagoons.
These methods may require long retention times because of slow degradation
rates under anaerobic conditions. There have been no reports of pilot or
field studies using anaerobic degradation under methanogenic conditions.
Nitrate respiration may be a feasible approach to decontaminating an
aquifer. Denitrification (the reduction of NO to NH or N ) has been
demonstrated to occur in contaminated aquifers. Nitrate respiration was used
successfully in the treatment of an aquifer contaminated with aromatic and
aliphatic hydrocarbons (see Table 9-4) (Stief, 1984). Nitrate can be added
in-line along with other nutrients and intimate mixing with groundwater can
occur. The cost is moderate; all that is required is the nutrient feed system
and an in-line mixer.
Nitrate, however, is a pollutant, limited to 10 ppm in drinking water.
Consequently, it may be more difficult to obtain permits for use of nitrate at
a site than for oxygen or hydrogen peroxide. Additionally, degradation rates
under aerobic conditions are more rapid and a broader range of compounds can
be degraded. There is no reason why nitrate respiration would be a better
treatment approach given the amount of success that has been demonstrated with
aerobic treatment approaches to date.
9.1.4 Operation and Maintenance
Operation and maintenance of a bioreclamation process involve aspects of
the hydraulic system as well as the biological system. The hydraulic aspects
relate to pumps, extraction and injection wells, and injection trenches; these
are discussed in Sections 5.1 and 5.2.
Monitoring a number of parameters is necessary to determine process
performance. Monitoring of groundwater can be performed at the injection and
extraction wells, as well as at monitoring wells. Monitoring wells should be
placed on-site to monitor process performance and off-site to monitor for
pollutant migration as well as to provide background information on changes in
subsurface conditions due to seasonal fluctuation. Table 9-9 lists parameters
which should be monitored, and suggests methods which can be used to monitor
these parameters.
9-31
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TABLE 9-9.
RECOMMENDED PARAMETERS TO MONITOR
Parameter
Location Media
of Analysis
Analytical Method
Total Organic
Carbon (TOC)
Priority pollutant
analysis or analysis
of specific organics
Microbiology-
cell enumerations
laboratory groundwater
laboratory
laboratory
field
Temperature
conductivity
dissolved oxygen (DO)
PH
Alkalinity
Acidity, M&P
Chloride
Hardness (total
NH--N
NO^-N
PO,, all forms
SOT
TDS (total dissolved
solids)
Heavy metals
(if present)
field
soil and
groundwater
soil and
groundwater
groundwater
groundwater
field
groundwater
field
laboratory
groundwater
soil and
groundwater
TOC analyzer
Direct counts. Plate
counts on groundwater
media or enriched
media.
Plate counts with
portable water test
kits (e.g. Soil Test
Inc., Evanston, IL).
In-situ water quality
monitoring instrument
or prepackaged
chemicals, field test
kits.
Prepackaged chemicals/
field test kits; water
analyzer photometer
(Soil Test. Inc.,
Evanston, IL; Lamotte
Chemical, Chestertown,
MD).
Prepackaged chemicals/
test kits;
GC/MS; AAS.
(2)
(continued)
9-32
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TABLE 9-9. (continued)
Parameter Location Media Analytical Method
of Analysis
Hydrogen peroxide field groundwater Prepackaged chemicals
2) for ^2°2' test striPs
available. Titanium
sulfate titration and
spectrophotometer
analysis for H^C^ for
greater accuracy.
GC/MS = gas chromatography/mess spectrometry
(2)
v 'AAS = Atomic absorption spectrometry
In a biological system, pH should be maintained in a range between 6 and
8 and concentrations of both nutrients and organics should be kept as uniform
as possible to protect against shock loading. Dissolved oxygen should be
maintained above the critical concentration for the promotion of aerobic
activity, which ranges from 0.2 to 2.0 mg/1, with the most common being
0.5 mg/1 (Hammer, 1975).
Clogging of the aquifer, injection wells or trenches, or extraction wells
by microbiological sludge is a possibility. CDS Inc. installed two wells in
each of their injection trenches in case flushing was ever required to remove
sludge. After 1-1/2 years of operation, clogging had not occurred (Ground-
water Decontamination Systems Inc., 1983). However, problems with biofouling
and plugging of sparging points was encountered during a spill cleanup con-
ducted by Groundwater Technology (Yaniga, Smith, and Raymond, 1984). This
interfered with oxygen transfer and necessitated frequent mechanical cleaning.
When hydrogen peroxide was substituted for air sparging in order to deliver
increased quantities of oxygen to the aquifer, one added benefit was that the
hydrogen peroxide kept the wells free of heavy biogrowth.
The permeability of the aquifer could be reduced due to precipitation, as
discussed in Section 9.2.2. Other factors, such as dispersion of clays, could
reduce aquifer permeability. When calcium concentrations are high in the
soil, phosphates can be rapidly attenuated due to precipitation with calcium,
becoming unavailable for microbial metabolism. Nutrient formulations should
be devised with the help of experienced geochemists which will minimize
problems with precipitation and dispersion of clays. One company claims to
9-33
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have developed special soil preconditioners and nutrient formulations which
reduce these problems and maximize nutrient mobility and solubility; however,
no process performance data are available on these products.
Maintenance of the bacterial population at their optimal levels is also
important, especially for selective mutant organisms which tend to be more
sensitive than naturally occurring species. A continuous incubation facility
operating at higher temperatures and under more controlled conditions could be
used to maintain the microbial population. The high biomass-containing stream
formed from such a facility could then be reinjected via wells or trenches so
as to reinoculate the subsurface continuously with microorganisms.
Aeration wells may be particularly susceptible to operational problems.
If injected gas fluidizes the material around it, soil substrata shifts can
occur which may cause a well blowout (free passage of air to the surface).
The cone of influence in a blown out well will be greatly reduced, therefore
requiring the installation of a new well. The best method to prevent blowouts
is to keep gas velocities below those necessary to cause fluidization, or to
place wells deep enough so that overburden pressure prevents excessive fluidi-
zation, or both (Sullivan, Chemineer Kinecs, Dayton, OH, personal communica-
tion, 1983). Suntech stated that a number of aeration wells became inopera-
tive because of blowout during their groundwater cleanup in 1972 and had to be
replaced (Raymond, Jamison, and Hudson, 1976). This suggests that aeration
well blowout could become a commonly encountered problem if attention is not
paid to the design criteria.
9.1.5 Technology Selection/Evaluation
Aerobic bioreclamation has been demonstrated to be effective in degrading
organics at more than 30 spill sites. Although it has not yet been demon-
strated at hazardous waste sites, it can be expected to be effective and
reliable provided the organics are amenable to aerobic degradation and the
hydraulic conductivity of the aquifer is sufficiently high. There are sub-
stantial research data to suggest that microorganisms found at uncontrolled
hazardous waste sites are well-acclimated to the wastes. Effectiveness and
reliability could be adversely affected by factors, such as precipitation,
which could reduce the permeability of an aquifer.
Relative to conventional pump and treat methods, bioreclamation may be
more effective since it is capable of degrading organics sorbed to soils.
Sorbed organics are not removed using conventional pump and treat methods.
The nature of the delivery systems can effect the reliability of the
bioreclamation approach. Pumping systems are prone to mechanical and
electrical failure. However, repairs can be made relatively quickly.
Subsurface drains are less prone to failure since there are no electrical
components. Where mechanical failures do occur, repairs can be both costly
and time consuming.
9-34
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Implementation of a remedial action involving bioreclamation will take
longer than excavation and removal of contaminated soils. Depending upon the
site, it could also take longer than a conventional pump and treat approach.
The advantage of in-situ bioreclamation over a pump and treat approach is that
in-situ biodegradation treats contaminated subsurface soils, thereby removing
the source of groundwater contamination.
The increased time required for in-situ bioreclamation is dependent
primarily upon the degradation rates, which are in turn dependent upon oxygen
availability. The form in which oxygen is delivered to the subsurface and the
aquifer permeability are the critical factors in this respect. As discussed
previously, far more oxygen can be delivered to the subsurface in the form of
hydrogen peroxide•
Other aspects of implementation are similar to implementation of conven-
tional pumping or subsurface drain systems with a few exceptions. Depending
upon the hydraulic conductivity, drains or wells must generally be spaced
closer together to ensure nutrient and oxygen availability at all portions of
the zone being treated. The lower the flow rate of the nutrient/oxygen-
enriched water and the more rapidly nutrients and oxygen are attenuated, the
closer the injection wells or drains must be spaced. Well/drain spacing will
also be dictated by the need, if any, to contain the contaminated plume or
treatment solution.
There are few additional safety hazards associated with in-situ
bioreclamation aside from those hazards normally associated with being on a
hazardous waste site or a drill site. Since wastes are treated in the ground,
the danger of exposure to contaminants is minimal during a bioreclamation
operation relative to excavation and removal.
A nutrient/oxygen or nutrient/hydrogen peroxide solution does not
represent an environmental threat. Most of the nutrients will be utilized and
attenuated by microbial activity. If the form of the nutrient is carefully
selected (e.g. ammonia-nitrogen rather than nitrate-nitrogen), the remaining
nutrients will not present an environmental threat. The hydrogen peroxide
will rapidly decompose in the subsurface to oxygen and water.
The only treatment reagent which could pose a hazard, if used, is the
concentrated hydrogen peroxide solution prior to mixing with groundwater.
Worker protection for operations involving hydrogen peroxide outside of a
closed container or pipe should include the use of chemically resistant
gloves, an apron, and a face shield. Safety training in the use of hydrogen
peroxide should be provided by qualified personnel.
9.1.6 Costs
Costs for biological in-situ treatment are determined by the nature of
the site geology and geohydrology, the extent of contamination, the kinds
and concentrations of contaminants, and the amount of groundwater and soil
9-35
-------
requiring treatment. There is no easy formula for predicting costs. Costs
provided for actual site cleanups indicate that biological treatment can be
far more economical as an alternative to, or in conjunction with, excavation
and removal or conventional pump and treat methods.
In-situ treatment costs include costs for well construction and pumping.
These are provided in Sections 5.1 and 5.2. Unit costs for chemicals,
nutrients, and hydrogen peroxide are provided in Table 9-10. Cost data for an
actual and hypothetical site cleanups involving in-situ treatment are
presented below.
Total capital and research and development costs for cleanup of the
Biocraft site (Table 9-11) were $926,158 including $446,280 which were spent
on process development (R&D). Project costs also included the hydrogeological
study, and design and operation of the groundwater injection and collection
system, and biostimulation plant. Total operating costs, based on treating
13,680 gallons/ day, were approximately $226/day, or $0.0165/gal. The total
cost including amortization based on projected costs is $0.0358/gal over a
three year period. Prior to the biological treatment program, contaminated
water had been removed at a rate of 10,000 gal/month. The average disposal
cost had been $0.35/gal (Jhaveri and Mazzacca, 1984). The cost of biological
treatment of an equal number of gallons is an order of magnitude less than
that for disposal. The Biocraft site employed surface biological reactors as
well as enhancing in-situ treatment by reinfiltrating oxygen and nutrient
treated groundwater. Costs for in-situ treatment alone would have been less
because process plant design and equipment would not be included in an in-situ
approach. (See Table 9-11).
Table 9-12 presents the estimated site cleanup costs for hypothetical
sites involving the use of hydrogen peroxide as an oxygen source for the
enhancement of in-situ biodegradation (FMC, 1985). The cleanup of 300 gallons
of gasoline from a sand gravel aquifer over a period of 6 to 9 months is
between $70,000 and $120,000 (Site A). Cleanup of 3,000 gallons of diesel
fuel from a fractured bedrock formation is estimated to require 9 to 12 months
and $160,000 to $250,000. The cost estimate for degrading 10,000 gallons of
jet fuel from a fine gravel formation is estimated to cost $400,000 to
$600,000 and take 14 to 18 months.
9.2 Chemical Treatment
9.2.1 General Description
Generally, organic and inorganic contaminants can be immobilized,
mobilized for extraction, or detoxified. Technologies placed in the category
"immobilization" include precipitation, chelation, and polymerization. The
category encompassing methods for mobilizing contaminants for extraction is
termed "soil flushing." Flushing agents include surfactants, dilute acids and
9-36
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TABLE 9-10.
CHEMICAL COSTS
Category
Chemical
Cost/Unit
Acids
Hydrochloric acid, 20° Baume tanks
Nitric acid 36°to 42° Baume tanks
Sulfuric acid
virgin, 100%
smelter, 100%
$55-105/ton
$195/ton
$61-95.9/ton
$48-65/ton
Bases
Chelating agents
Fertilizers
(Microbial nutrients)
Caustic soda, liquid 50%, low iron $255-285/ton
Liming material
Oxidizing agents
Reducing agents
Precipitating agents
Ammonium chloride
Citric acid
Ammonia, anhydrous, fertilizer
Ammonium chloride
Ammonium sulfate
Sodium monophosphate
Sodium diphosphate
Phosphoric acid
75%, commercial grade
52-54% a.p.a., agricultural
grade
Potassium muriate, 60 to 62%,
minimum
Potassium chloride
Potassium-magnesium sulfate
Agricultural limestone (dolomite)
Lime
Hydrated lime
Hydrogen peroxide, 35%
Potassium permanganate
$18/100lbs
$0.81-$1.19/lb
$140-$215/ton
$18/100 Ibs
$73-79/ton
$55.75/100 Ibs
$54.50/100 Ibs
$27.5/100 Ibs
$3.10/unit-tona
$0.82-0.92/unit-ton
$105/ton
$59/ton
3.50-34/tonb
$30.75-45/ton
$32.5-34.5/ton
$0.24/lb
$1.03-1.06/lb
Caustic soda, liquid 50%, low iron $255-285/ton
Ferrous sulfate
heptahydrate
monohydrate
130/ton
160/ton
(continued)
9-37
-------
TABLE 9-10. (continued)
Category Chemical Cost/Unit
Surfactant c
Anionic Witconate 605A 0.65-0.85/lbc
Witconate P-1020BV 0.70-0.88/lb
(calcium sulfonates) c
Nonionic Adsee 799 0.75-0.87/b
Source: Schnell, 1985, unless otherwise noted.
a. unit-ton: 1 percent of 2,000 pounds of the basic constituent or other
standard of the material. The percentage figure of the basic constituent
multiplied by the unit-ton price gives the price of 2,000 pounds of the
material.
b. Source: USEPA, 1984a.
c. Source: Witco Chemical Corp., Houston, TX, personal communication, 1985:
cost varies depending on quantity purchased (drum, truckload, or bulk).
bases, and water. Detoxification techniques include oxidation, reduction,
neutralization, and hydrolysis.
These categories do not define the limits of each technology. For
example, a treatment method that immobilizes a contaminant may also serve to
detoxify it; a flushing solution that mobilizes one contaminant may
precipitate, detoxify, or increase the toxicity of another.
Tables 9-13 and 9-14 provide a summary of those in-situ chemical
treatment methods for organics and inorganics, respectively, that are most
promising or have been most widely discussed in the literature. The compounds
amenable to treatment, the treatment reagents, and the process are summarized.
9.2.2 Applications/Limitations
The feasibility of an in-situ treatment approach is dictated by site
geology and hydrology, soil characteristics, and waste characteristics. Since
the application of many chemical in-situ treatment techniques to hazardous
waste disposal site reclamation is conceptual or in the developmental stage,
there is little hard data available on the specific site characteristics
that may limit the applicability of each method. A list of site and soil
9-38
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9-39
-------
TABLE 9-12.
ESTIMATED COSTS FOR HYPOTHETICAL BIORECLAMATIONS
USING HYDROGEN PEROXIDE AS AN OXYGEN SOURCE
Site A
Site B
Site C
Contaminant
Formation
Flow Rate
Project Time
Estimated Costs
300 gallons
gasoline
Sand/gravel
50 gpm
6-9 months
$70-120M(1)
2,000 gallons
diesel fuel
Fractured bed rock
10 gpm
18-24 months
$200-300M(1)
10,000 gallons
jet fuel
Coarse gravel
100 gpm
18-24 months
$500-700M(1^
(1)M=1000
Source: FMC, 1985
characteristics considered important in evaluating the treatment applicability
is provided in Table 9-15 (Sims and Wagner, 1983).
Most of the treatment approaches discussed in this section involve the
delivery of a fluid to the subsurface. Therefore, the same factors that limit
the use of injection/extraction wells, drains, or surface gravity application
systems such as flooding and spray irrigation for bioreclamation will limit
the applicability of most in-situ chemical treatment approaches. Minimal
permeability requirements must be met if the treatment solution is to be
delivered successfully to the contaminated zone. Sandy soils are far more
amenable to in-situ treatment than clayey soils. Further, the contaminated
groundwater must be contained within the treatment zone. Measures must be
taken to ensure that treatment reagents do not migrate and, of themselves,
become contaminants. Care must be taken during the extraction process not to
increase the burden of contaminated water by drawing uncontaminated water into
the treatment zone from the aquifer or from hydraulically connected surface
waters.
Potential chemical reactions of the treatment reagents with the soils and
wastes must be considered. Most hazardous waste disposal sites contain a mix
of contaminants. A treatment approach that may neutralize one contaminant may
render another more toxic or mobile; for example, chemical oxidation will
9-40
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TABLE 9-15.
SITE AND SOIL CHARACTERISTICS IDENTIFIED AS IMPORTANT IN IN-SITU TREATMENT
Characteristics
Site location/topography
Slope of site-degree and aspect
Soil, type and extent
Soil profile properties
depth
boundary characteristics
texture*
amount and type of coarse fragments
structure*
color
degree of mottling
presence of carbonates
bulk density*
cation exchange capacity*
clay content
type of clay
pH*
Eh*
surface area*
organic matter content*
nutrient status*
microbial activity*
Hydraulic properties and conditions
depth to impermeable layer or bedrock
depth to groundwater*, including seasonal variations
infiltration rates*
permeability* (under saturated and a range of unsaturated conditions)
water holding capacity*
soil water characteristic curve
field capacity/permanent wilting point
flooding frequency
run-off potential*
aeration status*
(continued)
9-44
-------
TABLE 9-15. (continued)
Characteristics
Clitnatological factors
temperature*
wind velocity and direction
* Factors that may be managed to enhance soil treatment
Source: Sims and Wagner, 1983
(Manuscripts originally printed in the Proceedings of the National Conference
on Management of Uncontrolled Hazardous Waste Sites. 1983. Available from
Hazardous Materials Control Research Institute, 9300 Columbia Blvd., Silver
Spring, MD 20910).
destroy or reduce the toxicity of many toxic organics, but chromium III, if
present, will oxidize to the more toxic and mobile chromium VI state. The
permeability of soils may be reduced by the treatment approach. In soils high
in iron and manganese, for example, oxidizing the subsurface could result in
the precipitation of iron and manganese oxides and hydroxides, which could
clog the delivery system and the aquifer.
9.2.3 Soil Flushing
Organic and inorganic contaminants can be washed from contaminated soils
by means of an extraction process termed "soil flushing," "solvent flushing,"
"ground leaching," or "solution mining." Water or an aqueous solution is
injected into the area of contamination, and the contaminated elutriate is
pumped to the surface for removal, recirculation, or on-site treatment and
reinjection. During elutriation, sorbed contaminants are mobilized into
solution by reason of solubility, formation of an emulsion, or by chemical
reaction with the flushing solution.
Solutions with the greatest potential for use in soil flushing fall into
the following classes:
• Water
• Acids-bases
• Complexing and chelating agents
9-45
-------
• Surfactants
• Certain reducing agents.
Water can be used to flush water-soluble or water-mobile organics and
inorganics. Hydrophilic organics are readily solubilized in water. Organics
amenable to water flushing can be identified according to their soil/water
partition coefficient, or estimated using the octanol/water coefficient.
Octanol-water partition coefficients are available for a large number of
compounds in: Substituent Constants for Correlation Analysis in Chemistry and
Biology (Hansch and Leo, 1979).Chemical Property Estimation Methods (Lyinan,
Reehl and Rosenblatt, 1982) provides various methods for estimating the
octanol-water partition coefficient using readily available physical and
chemical data. Organics considered soluble in the environmental sense are
ones with a partition coefficient (K) of approximately less than 1000 (log K =
3). High solubility organics, such as lower molecular weight alcohols,
phenols, and carboxylic acids, and other organics with a coefficient less than
10 (log K _
-------
Another possibility for mobilizing metals which are strongly adsorbed to
manganese and iron oxides in soils is to reduce the metal oxides which results
in release of the heavy metal into solution. Chelating agents or acids can
then be used to keep the metals in solution. Treatment agents which may be
suitable for this purpose include hydroxylamine together with an acid, or
sodium dithionite/citrate.
Surfactants can be used to improve the solvent property of the recharge
water, emulsify nonsoluble organics, and enhance the removal of hydrophobic
organics sorbed onto soil particles. Surfactants improve the effectiveness of
contaminant removal by improving both the detergency of aqueous solutions and
the efficiency by which organics may be transported by aqueous solutions
(USEPA, 1985). Surfactant washing is among the most promising of the in-situ
chemical treatment methods.
Numerous environmentally safe and relatively inexpensive surfactants are
commercially available. Use of surfactants to date has been restricted to
laboratory research. Most of the research has been performed by the petroleum
industry for tertiary oil recovery (Barakat et al., 1983; Cash et al., 1977;
Doe, Wade, and Schechter, 1977; and Wilson and Brandner, 1977). Aqueous
surfactants have also been proposed for gasoline cleanup. In a study
performed by the Texas Research Institute (1979) for the American Petroleum
Institute, a mixture of an anionic and nonionic surfactants result in con-
taminant recovery of up to 40 percent. In a laboratory study conducted by
Ellis and Payne (1983), crude oil recovery was increased from less than
1 percent to 86 percent, and PCB recovery was increased from less than
1 percent to 68 percent when soil columns were flushed with an aqueous
surfactant solution.
Characteristics of surfactants and their environmental and chemical
properties are listed in Table 9-16 (USEPA, 1985). This table can be used to
aid in the preliminary selection of a surfactant. However, laboratory testing
of the surfactant should be performed to verify surfactant properties.
An economically feasible soil flushing method may involve the recycling
of elutriate through the contaminated material, with make-up solvent being
added to the system while a fraction of the elutriate stream is routed to a
portable wastewater treatment system. The appropriate types of wastewater
treatment operations will depend on waste stream characteristics, and a
discussion of their applications can be found in Section 10.1.
The advantages of the soil flushing process are that, if the waste is
amenable to this technique and distribution, collection, and treatment costs
are relatively low, solution mining can present an economical alternative to
the excavation and treatment of the wastes.
9-47
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-------
9.2.4 Immobilization
Immobilization methods are designed to render contaminants insoluble and
prevent leaching of the contaminants from the soil matrix and their movement
from the area of contamination. Little is currently known about the
effectiveness and reliability of immobilization techniques (Truett, Holberger,
and Banning, 1982).
Immobilization methods which are currently being investigated include:
precipitation, chelation, and polymerization.
Precipitation is the most promising method for immobilizing dissolved
metals such as lead, cadmium, zinc, and iron. Some forms of arsenic,
chromium, mercury, and some organic fatty acids can also be treated by
precipitation (Huibregtse and Kastman, 1979). All of the divalent metal
cations can be precipitated using sulfide, phosphate, hydroxide, or carbonate.
However, the solubility product and the stability of the metal complexes vary.
Because of the low solubility product of sulfides and the stability of the
metal sulfide over a broad pH range, sulfide precipitation looks most promis-
ing. The remaining anions decrease in effectiveness in the following order:
phosphate > hydroxide > carbonate. Metal carbonates and hydroxides are stable
only over a narrow pH range and the optimum pH range varies for different
metals. Precipitation of the metal as the metal phosphate may require very
high concentration of orthophosphate since calcium and other naturally
occurring soil cations present in high concentrations will precipitate first.
Sodium sulfate used in conjunction with sodium hydroxide has shown wide-
spread applicability for precipitatiion of metals. Precipitation takes place
at a neutral or slightly alkaline pH. Resolubilization of sulfides is low.
Addition of sodium hydroxide minimizes the formation of hydrogen sulfide gas
by assuring an alkaline pH. Experiments with sulfide precipitation of zinc
indicate that a high residual of unreacted sulfide may remain in solution.
As with other in-situ 'techniques, precipitation is most applicable to
sites with sand or coarse silt strata. Disadvantages include the injection of
a potential groundwater pollutant; the potential for formation of toxic gases
(in the case of sulfide treatment); the potential for clogging soil pore
space; and the possibility of precipitate resolubilization.
The use of chelating agents may also be a very effective means of
immobilizing metals although considerable research is needed in this area.
Depending upon the specific chelating agent, stable metal chelates may be
highly mobile (as described in Section 9.2.3) or may be strongly sorbed to the
soil. Tetran is an example of a chelating agent which is strongly sorbed to
clay in soils (USEPA, 1984a).
A third method for immobilizing metals applies specifically to chromium
and selenium. These metals can be present in the highly mobile, hexavalent
state but can be reduced to less mobile Cr (III) and Se (IV) by addition of
ferrous sulfate. Arsenic exists in soils as either arsenate, As (V), or as
9-50
-------
arsenite, As (ill), the more toxic and soluble form. Arsenic can be effec-
tively immobilized by oxidizing As (ill) to As (IV) and treating the As (IV)
with ferrous sulfate to form highly insoluble Fe-AsO,.
Polymerization involves injection of a catalyst into a groundwater plume
to cause polymerization of an organic monomer (e.g., styrene, vinyl chloride,
isoprene, methyl methacrylate, and acrylonitrile). The polymerization
reaction transforms the once fluid substance into a gel-like, non-mobile mass.
In-situ polymerization is a technique most suited for groundwater cleanup
following land spills or underground leaks of pure monomer. Applications for
uncontrolled hazardous waste sites are very limited. Major disadvantages
include very limited application and difficulty of initiating sufficient
contact of the catalyst with the dispersed monomer (Huibregtse and Kastman,
1979). In-situ polymerization was successfully performed to remedy an
acrylate monomer leak, in which 4,200 gallons of acrylate monomer leaked from
a corroded underground pipeline into a glacial sand and gravel layer. Soil
borings indicated that as much as 90 percent of the monomer had been
polymerized by injection of a catalyst, activator, and wetting agent
(Williams, 1982).
In-situ treatment of a leachate plume using precipitation or polymer-
ization techniques probably has limited application. Problems associated with
these techniques include:
• Need for numerous, closely-spaced injection wells even in coarse-
grained deposits because the action of precipitation or polymerization
will lower hydraulic conductivities near injection wells reducing
treatment effectiveness
• Contaminants are not removed from the aquifer or some chemical
reactions can be reversed allowing contaminants to again migrate with
groundwater flow
• Injection of a potential groundwater pollutant or the formation of
toxic byproducts.
Therefore, prior to the application of an in-situ precipitation or polymeriza-
tion technique at a hazardous waste site, thorough laboratory- and pilot-scale
testing should be conducted to determine deleterious effects and assure
complete precipitation or polymerization of the chemical compounds.
Solidification methods used for chemical soil consolidation can also
immobilize contaminants. Solidification and stabilization techniques are
assessed in terms of their applicability for in-situ treatment of landfilled
wastes in Guide to the Disposal of Chemically Stabilized and Solidified Wastes
(USEPA, 1982). The assessment concluded that most work with these techniques
has not involved in-situ treatment; most are not applicable to hazardous waste
sites, and most of the techniques involve a thorough mixing of the solidifying
agent and the waste (Truett, Holberger, and Banning, 1982). Injection of
silicate gel may be feasible to immobilize subsurface contaminants, but may
negatively impact groundwater quality (Truett, Holberger, and Sanning, 1982).
9-51
-------
9.2.5 Detoxification
In-situ treatment techniques discussed in this section are those which
serve to destroy, degrade, or otherwise reduce the toxicity of contaminants
and include neutralization, hydrolysis, oxidation/reduction, enzymatic
degradation, and permeable treatment beds. These methods are applicable to
specific chemical contaminants, therefore, use of these in-situ techniques at
waste sites will be limited.
Neutralization involves injecting dilute acids or bases into the ground-
water to adjust the pH. This pH adjustment can serve as pretreatment prior to
in-situ biodegradation, oxidation, or reduction to optimize the pH range. It
can be used to neutralize acidic or basic plumes that need no other treatment,
or to neutralize groundwater following another treatment. It can also be used
during oxidation, reduction, or precipitation to prevent the formation of
toxic gases including hydrogen sulfide and hydrogen cyanide.
The pH adjustment can also be used to increase the hydrolysis rate of
certain organics. Hydrolysis involves the displacement of a group on an
organic moiety with a hydroxyl group from water, according to the displacement
reaction:
RX + H20 -» ROH + HX
in which R is the organic moiety and X is the leaving group. Of the param-
eters which affect the rate of hydrolysis (temperature, solvent composition,
catalysis, and pH), pH adjustment has the greatest potential. The rate of
hydrolysis can be increased up to one order of magnitude for a change of one
standard unit in pH (USEPA, 1985). Classes of compounds with potential for
in-situ degradation by hydrolysis include:
• Esters
• Amides
• Carbamates
• Phosphoric and phosphonic acid esters
• Pesticides.
Because a hydrolysis product may be more toxic than the present compound, the
pathways for reactions must be determined to ensure toxic products are not
produced. USEPA (1985) has a more thorough discussion of this technology.
Many of the environmental, health, and safety considerations that apply
to solution mining also apply here. In contrast to solution mining, in-situ
neutralization/detoxification techniques do not inherently incorporate
collection systems. However, a collection system should be incorporated as a
fail safe measure, to prevent migration of the treatment reagents and any
contaminants which are not successfully treated.
9-52
-------
Oxidation and reduction reactions serve to alter the oxidation state of a
compound through loss or gain of electrons, respectively. Such reactions can
detoxify, precipitate, or solubilize metals, and decompose, detoxify, or
solubilize organics. Oxidation may render organics more amenable to bio-
logical degradation. As with many of these chemical treatment technologies,
oxidation/reduction techniques are standard wastewater treatment approaches,
but their application as in-situ treatment technologies is largely conceptual.
Oxidation of inorganics in soils, is for all practical purposes limited
to oxidation of arsenic and possibly some lead compounds. The in-situ
oxidation of arsenic compounds with potassium permanganate (KMnO,) has been
used to successfully reduce the arsenic concentrations in groundwater in the
vicinity of a zinc ore smelter near Cologne, Germany (Stief, 1984). 64,000
lb- of KMnO, were injected into 17 wells and piezometer wells resulting in an
average decrease in arsenic groundwater concentrations from 13.6 mg/1 to 0.06
mg/1 from 1975 to 1977. In 1979, however, an increase indicated that the
mixing of groundwater and KMnO, had not been thorough.
Of the numerous oxidizing agents available, three have been considered
potentially useful in the in-situ detoxification of organics groundwater and
soils contaminated with organics: hydrogen peroxide, ozone, and hypochlorites
(USEPA, 1985). Each can react with a broad range of organics and could
potentially oxidize a number of different organic contaminants in a hazardous
waste site- Selection of the appropriate oxidizing agent is dependent in part
upon the substance or substances to be detoxified, but also upon the feasi-
bility of delivery and environmental safety. Although there are some
compounds that will not react with hydrogen peroxide but will react with ozone
or hypochlorite, hydrogen peroxide appears to be the most feasible for in-situ
treatment.
Ozone gas is a very strong oxdizing agent that is very unstable and
extremely reactive. It cannot be shipped or stored; therefore it must be
generated on-site prior to application. Ozone rapidly decomposes and its
half-life in groundwater is only 18 minutes (USEPA, 1985). Ozone is used in
the treatment of drinking water, municipal wastewater, and industrial waste,
but has never been used in the treatment of contaminated soils or groundwater.
Ozone oxidation with ultraviolet irradiation successfully reduced concentra-
tions of benzene, phenols, and trichloroethylene in lake water (Glaze et al.,
1980).
Hypochlorite, generally available as potassium, calcium, or sodium hypo-
chlorite (bleach) is also used in the treatment of drinking water, municipal
wastewater, and industrial waste. Hypochlorites have never been used in the
treatment of contaminated groundwater or soils. Tolman et al. (1978) has
described the conceptual design and in-situ detoxification of cyanide with
sodium hypochlorite. The reaction of many organics with hypochlorite results
in the formation of chlorinated organics which can be as or more toxic than
the original contaminant. The formation of lower molecular weight chlorinated
organics (e.g., trihalomethanes) in drinking water from hypochlorite treatment
for disinfection purposes has become a major concern of the drinking water
industry.
9-53
-------
Hydrogen peroxide (H,^)-), a moderate strength chemical oxidant, is used
routinely in municipal wastewater treatment to control various factors of
biological treatment, and is also used in industrial waste treatment to
detoxify cyanide and various organic pollutants. Table 9-17, developed by
USEPA (1985), indicates chemical compound classes that may be degraded using
hydrogen peroxide.
Hydrogen peroxide is commercially available in aqueous solutions of
several concentrations and is miscible in water at all concentrations. It has
been delivered successfully in dilute solutions to the subsurface as an oxygen
source in a bioreclamation project (Raymond, Jamison, and Hudson, 1984) (see
Section 9.1). One supplier has developed a line of hydrogen peroxide
solutions specifically designed for reclamation purposes (FMC, 1985).
Chemical reduction is the process by which the oxidation state of a
compound is reduced. Reducing agents are election donors, with reduction
accomplished by the addition of elections to the atom.
Chemical reduction does not appears as promising as oxidation for the
treatment or organics. Although reseaches have demonstrated reductive
dehalogenation of a variety of chlorinated organics and reduction of
unsaturate aromatics and aliphatics in laboratory studies using catalyzed
metal powders the treatment reagents are costly and the effectiveness of
chemical reduction in soils has not been demonstrated.
Chemical reduction does, however, appear promising for treatment of
chromium and selenium in soils. The in-situ reduction of hexavalent to
divalent chromium has been accomplished in Arizona well water using minute
quantities of reducing agent. (Srivastava and Haji-Djafari, 1983).
There are a number of disadvantages with the use of oxidizing and
reducing agents which limit their use at hazardous waste sites. The treatment
compounds are non-specific and this may result in degradation of non-targeted
compounds. There is the potential, particularly with oxidation, for the
formation of more toxic or more mobile degradation products. Also, the
introduction of these chemicals into the groundwater system may create a
pollution problem in itself. As with soil flushing, uncertainty exists with
respect to obtaining adequate contact with the contaminants in the plume.
Enzymatic degradation of organics with cell-free enzymes holds potential
as a possible in-situ treatment technique. Purified enzyme extracts,
harvested from microbial cells, are commonly used in industry to catalyze a
variety of reactions, including the degradation of carbohydrates and proteins.
A bacterial enzyme preparation has been used to detoxify organophosphate waste
from containers (Munnecke, 1980). Parathion hydrolase has been tested under
field conditions in the degradation of the pesticide diazinon (Paulson et al.,
1984). The studies indicate that parathion hydrolase can be used to effec-
tively reduce rapidly large concentrations of diazinon in soil. The enzyme is
readily soluble in water, is reasonably stable at summer temperatures, and can
be easily handled in the field. The pH or organic content of the soil does
not appear to affect the enzyme's effectiveness. It appears from the study
9-54
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9-55
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that parathion hydrolase could be used effectively to clean up diazinon
spills, but more research is required to determine how to obtain optimal field
efficacy of the enzyme.
Permeable treatment beds are essentially excavated trenches placed
perpendicular to groundwater flow and filled with an appropriate material to
treat the plume as it flows through the material (see Figure 9-7). Some of
the materials that may be used in the treatment bed are limestone, crushed
shell, activated carbon, glauconitic green sands, and synthetic ion exchange
resins. Permeable treatment beds have the potential to reduce the quantities
of contaminants present in leachate plumes. The system is applicable to
relatively shallow groundwater tables containing a plume. To date, the
application of permeable treatment beds at hazardous waste sites has not been
performed. However, bench- and pilot-scale testing has provided preliminary
quantification of treatment bed effectiveness. Potentially numerous problems
exist in using a permeable treatment bed. These include saturation of bed
material, plugging of bed with precipitates, and short life of treatment
materials. Therefore, permeable treatment should probably be considered as a
temporary remedial action rather than a permanent one.
A limestone or crushed shell bed can be used to neutralize acidic ground-
water and retain certain metals such as cadmium, iron, and chromium. The
effectiveness of limestone as a barrier depends primarily on the pH and volume
of the solution passing through the limestone (Artiola and Fuller, 1979). The
nature of the heavy metal is also an important factor. A laboratory study
demonstrated that limestone was more effective at retaining chromium III than
for chromium VI and other metals (Artiola and Fuller, 1979).
Fuller and other researchers (USEPA, 1978) have discussed the use of
crushed limestone as an effective, low cost landfill liner to aid in attenu-
ating the migration of certain heavy metals from solid waste leachates.
According to the authors, dolomitic limestone (containing significant amounts
of magnesium carbonate) is less effective in removing ions than purer
limestone containing little magnesium carbonate. Therefore, in the design of
a limestone treatment bed, limestone with high calcium content is recommended
to remove heavy metals and to neutralize contaminated groundwater.
In regard to designing vertical permeable treatment beds, the particle
size of the limestone used should be selected dependent on the type of soil in
which groundwater flows (i.e., which controls flow rates) and the level of
contamination. In general, a mixture of gravel-size and sand-size limestone
should be used to minimize settling through dissolution. Where excessive
channelling through the bed by rapid groundwater movement is expected or where
improved contact time between the contaminated groundwater and the treatment
bed is required, a higher percentage of sand-size particles is more
appropriate.
A variation on the use of limestone permeable treatment beds to neutral-
ize plumes is the use of limestone or crushed shell layered over a waste site
to indefinitely stabilize the disposed waste. This approach will be used to
9-56
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FIGURE 9-7
INSTALLATION OF A PERMEABLE TREATMENT BED
Permeable Treatment Bed
9-57
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reduce solubility of metal hydroxides by maintaining highly alkaline
conditions in the waste (Francis, 1984).
Activated carbon as a possible treatment bed material has the capability
of removing nonpolar organic compounds from contaminated plumes, but is not
practical for the removal of heavy metals. Activated carbon will not remove
polar organics. However, the high cost of activated carbon, the potential for
desorption of adsorbed compounds, and the likelihood of a short bed-life in
the presence of high waste concentrations make the use of activated carbon
beds cost-prohibitive under most circumstances.
Glauconitic greensands have potential for the removal of heavy metals.
Bench-scale studies with leachate indicate that the highest removal effi-
ciencies are for copper, mercury, nickel, arsenic, and cadmium and that effi-
ciencies increase with contact time (Spoljaric, N. Delaware Geological Survey,
Newark, DE, personal communication, 1980). With contact time in the field
being on the order of days, metal removal efficiencies may be extremely high.
Experiments indicate that the greensands may also have a high capacity for
heavy metal cation retention, even when flushed with solutions of highly
alkaline or acidic pH (Spoljaric, N. Delaware Geological Survey, Newark, DE,
personal communication, 1980). An in-situ experiment in England (Ross, 1980)
demonstrated promising retention capabilities. Glauconitic greensands appear
promising; however, more research is required to determine their sorptive
capacity and capability for treating higher concentrations of heavy metals.
Advantages of glauconitic treatment beds, based on studies to date,
include good permeability, abundance in the Atlantic Coastal Plain (i.e., New
Jersey, Delaware, and Maryland), effectiveness in removal and retention of
many heavy metals, and good retention time characteristics for efficient
treatment. Among the disadvantages of using glauconitic treatment beds are
unknown saturation characteristics and potential for plugging over time,
potential reduction in pH, limited to areas of natural occurrence such as the
mid-Atlantic region, and possibility of land purchase requirements as
glauconite is not commercially mined•
9.2.6 Technology Selection/Evaluation
This section described a wide range of chemical and in-situ treatment
methods, therefore, generalizations regarding the feasibility and effective-
ness of these methods are not possible. However, all of these methods are
developmental or conceptual and none have been fully demonstrated for
hazardous waste site remediation.
Of all the methods described, soil flushing methods involving the use of
water surfactants appear to be most feasible and cost-effective for organics.
They .can use relatively cheap, innocuous treatment reagents, can be used to
treat a broad range of waste constituents, and do not result in toxic degrada-
tion products.
9-58
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The most feasible methods for treating inorganics in-situ include soil
flushing with dilute acids, chelating agents or other treatment agents which
will mibolize the metals. Precipitation of the metals as sulfides or
phosphates, and the use of permeable treatment beds have potential application
although there are potentially serious drawbacks with each of these methods.
For example, permeable treatment beds are prone to clogging, and sulfide
precipitation can clog soils and reduce permeability.
Mention of these potential drawbacks should not preclude consideration of
in-situ methods. However, laboratory- and possibly pilot-scale testing is
likely to be required in each case, resulting in delays in implementing the
remedial action.
As with biological treatment methods, chemical treatment methods used to
deliver and recover treatment reagents also affect the reliability of these
methods. Reliability of pumping and subsurface drainage systems have been
described previously.
Again, worker safety considerations are the same as those related to
in-situ biological treatment methods involving a potentially hazardous
chemical reagent. The same precautions required when working with hydrogen
peroxide (Section 9.1.6) are required when working with acids, bases,
surfactants, and other potentially hazardous reagents.
9.2.7 Costs
Costs for the chemical in-situ treatment approaches discussed in this
section are difficult to estimate since these methods have largely not been
demonstrated at hazardous waste sites and no actual cost data are available.
In-situ treatment costs are variable, but could be less than excavation and
removal methods and/or pump and treat methods. As with removal, in-situ
approaches are conducted on a one-time basis, so there are generally no
long-term operation and maintenance costs.
Costs for the chemical treatment approaches involving the delivery of a
reagent to the subsurface (soil flushing, various immobilization techniques,
neutralization, hydrolysis, oxidation, reduction, and enzymatic degradation)
will depend on the amount of material to be treated, the amount of chemical
reagent required, the costs for the delivery system (injection wells or
infiltration galleries), the chemical and feed system, and fees for probing,
excavation, and drilling. Costs for laboratory- and pilot-scale studies
should also be considered when performing such a treatment approach. Soil
flushing, which involves bringing contaminated water to the surface for
treatment, would require a wastewater treatment system. Costs for the drains
and pumping are presented in Sections 5.1 and 5.2, respectively. Table 9-10
provides unit costs for chemicals.
1985 unit costs for the installation of a permeable treatment bed are
shown in Table 9-18. Total closure costs for stabilizing approximately 8,000
9-59
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TABLE 9-18.
UNIT COSTS FOR INSTALLATION OF A PERMEABLE TREATMENT BED
Item
Assumptions
Costs
Trench excavation
Spreading
Well-point dewatering
Sheet piling
Walers, connections,
struts
Liner
Limestone
20 ft deep, 4 ft wide,
by backhoe
Spread by dozer to grade
trench and cover
500 ft header 8" diameter,
for one month
20 feet deep; pull
and salvage
2/3 salvage
30 mil PVC
30 mil CPE
Mixed "gravel size" and
"sand size"
Installation
(Backfill trench,
100 foot haul)
$1.40 cubic yard
$l/cubic yard
$115/linear foot
$7.70/square foot
$165/ton
$0.25-0.35/square foot
$0.35-0.45/square foot
$30-45/ton3
$3.70/cubic yard
-Godfrey, 1984; Costs are total, including contractor overhead and profit.
-Godfrey, 1984; Materials only.
fSchnell, 1985.
Cope, Karpinski, and Steiner, 1984.
9-60
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cubic yards of sludge contaminated with nickel hydroxide by covering the site
with a I inch layer of calcium carbonate are estimated at $100,000 to
$200,000, compared with $900,000 to $1 million estimated for excavation and
removal (Francis, 1984).
9.3 Physical In-Situ Methods
9.3.1 General Description
A number of methods are currently being developed which involve physical
manipulation of the subsurface in order to immobilize or detoxify waste
constituents. These technologies, which include in-situ heating, vitrifica-
tion and ground-freezing, are in the early stages of development and detailed
information is not available.
In-situ heating has been proposed as a method to destroy or remove
organic contaminants in the subsurface through thermal decomposition, vapori-
zation, and distillation. Methods recommended for in-situ heating are steam
injection (Hoogendorn, 1984) and radio frequency heating (Dev, Bridges, and
Sresty, 1984).
The radio frequency heating process has been under development since the
1970s. Field experiments have been conducted for the recovery of hydro-
carbons. The method involves laying a row of horizontal conductors on the
surface of a landfill and exciting them with an RF generator through a
matching network. The decontamination is accomplished in a temperature range
of 300° to 400°C, assisted with steam, and requires a residence time of about
two weeks. A gas or vapor recovery system is required on the surface. Exca-
vation, mining, drilling, or boring is not required. Field tests found that
leakage radiation levels did not exceed the recommended ANSI Standard C-95.
Preliminary design and cost estimates for a mobile RF in-situ decontamination
process (see Section 9.2.5) indicate that the method is 2 to 4 times cheaper
than excavation and incineration (Dev, Bridges, and Sresty, 1984). This
method appears very promising for certain situations involving contamination
with organics, although more research is necessary to verify the effectiveness
in-situ.
Artificial ground freezing involves the installation of freezing loops in
the ground and a self-contained refrigeration system that pumps coolant around
the freezing loop (Sullivan, Lynch and Iskandar, 1984). Although never used
in an actual waste containment operation, the technology is being used
increasingly as a construction method in civil engineering projects.
Artificial ground freezing is done not on the waste itself, which may have a
freezing point much lower than that of the soil systems, but on the soil
surrounding the hazardous waste. It renders the soil practically impermeable,
but is useful only as a temporary treatment approach because of the thermal
maintenance expense (Sullivan, Lynch, and Iskandar, 1984).
9-61
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In-situ vitrification is a technology being developed for the stabiliza-
tion of transuranic contaminated wastes, and is conceivably applicable to
other hazardous wastes (Fitzpatrick et al., 1984). Several laboratory-scale
and pilot-scale tests have been conducted, and a large-scale testing system is
currently being fabricated. The technology is based upon electric melter
technology, and the principle of operation is joule heating, which occurs when
an electrical current is passed through a molten mass. Contaminated soil is
converted into durable glass, and wastes are pyrolyzed or crystallized. Off-
gases released during the melting process are trapped in an off-gas hood. The
depth of the waste is a significant limiting factor in the application of this
technology: 1 to 1.5 meters of uncontaminated overburden lowers release
fractions considerably (Fitzpatrick et al., 1984).
Cost estimates for five in-situ vitrification large-scale configurations
are provided in Table 9-19 (Fitzpatrick et al., 1984, citing Oma et al.).
These cost comparisons are based on vitrifying to a depth of 15 feet. Of
these costs, approximately 30 to 46 percent is for power, 10 to 13 percent is
for equipment, 36 to 45 percent is for labor, and 5 to 10 percent is for
electrodes (Banning, 1984). Soil moisture can increase operating costs by
increasing requirements because the water in the soil must be evaporated.
Estimates for treating a humid site in the eastern United States is near
$85/cubic foot (1982 dollars) (Sanning, 1984).
The cost of a hypothetical hazardous waste site decontaminated by radio
frequency heating was estimated for a 1 acre landfill area with contamination
extending to 20 feet (Dev, Bridges, and Sresty, 1984). Volatile matter in the
landfill was assumed to range from 5 to 20 percent by weight, with 10 percent
of the total volatile matter being organic. Total capital costs for a
purchase power option was estimated at approximately $17 million. The capital
costs increase to $27.5 million if the power is generated on-site. Capital
costs for equipment for excavation and incineration were estimated at
$832,000. The total costs of decontamination (including operating costs but
not capital costs) was estimated to be between $4.6 and $5.7 million for radio
frequency heating (purchased power plant). Total treatment costs for
incineration (excluding capital costs) were estimated at between $9 and $25.2
million (Dev, Bridges, and Sresty, 1984).
Figure 9-8 provides estimated costs for ground freezing plotted as a
function of freezing rod space for a hypothetical site. The site requires a
1,000 foot frozen wall which is 3 feet thick and is placed down to depth of
bedrock (40 feet). The site is assumed to be located in coarse quartz sand,
150 miles from the drilling and refrigeration contractors. From Figure 9-5,
one can see that as the drill space becomes tighter, the fuel costs, equipment
rentals, and time for wall completion are reduced. A tight drill space yields
small frozen soil column radii and permits use of less expensive refrigeration
equipment. The drawback of close drill spacing is the expense associated with
the drilling operation. The linear footage of piping, a drive shoe for each
well drilled, and the labor charge per vertical foot drilled overwhelm all
other economic parameters. Analysis of costs for this hypothetical site
illustrated that ground/freezing is only applicable as a short-term remedial
measure (Sullivan, Lynch, and Iskandar, 1984).
9-62
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TABLE 9-19.
1982 COST ESTIMATES FOR FIVE IN-SITU VITRIFICATION LARGE-SCALE CONFIGURATIONS
Number
1
2
3
4
5
Site
Hanford
Hanford
Hanford
Generic
Generic
Power
Local
Local
Local
Local
Portable
Heat Loss
High
Average
Average
Average
Average
Manpower
Level
Average
Average
Above
Average
Average
Average
Total Cost
of Soil
Vitrified
$187/m3
$161/m3
3
$183/m
$180/m3
$224/m3
Total Cost
of Soil
Vitrified
$5.30/ft2
$4.60/ft2
2
$5.20/ft
$5.10/ft2
$6.30/ft2
Source: Fitzpatrick et al., 1984
9-63
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FIGURE 9-8
ECONOMIC OVERVIEW OF GROUND FREEZING FOR
A HYPOTHETICAL SITE
500 _.
400 -
8 sooj
5
I 200 J
100 L
FROZEN WALL 1000 X 3 X 40 FT
SOLID - OVERALL COST
_._._ - DRILL EXPENSE
- FUEL COSTS
- EQUIPMENT RENTAL
- DAYS
-50
30D
A
Y
S
4 6 8
DRILL SPACING (FT)
10
Source: Sullivan, Lynch, and Iskandar, 1984
9-64
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Antonio, Texas, March 6-8. EPA-600/9-78-016. Washington, DC. pp. 282-298.
Ventullo, R.M. and R.J. Larson. 1983. Neterotrophic Activity and
Biodegradation Potential of Microbial Communities in Groundwater. Presented
at the Fourth Annual Meeting of the Society of Environmental Toxicology and
Chemistry, Arlington, VA.
Wetzel, R.S., S.M. Henry, and P.A. Spooner. 1985. In Situ Treatment of
Contaminated Groundwater and Soils. Kelly Air Force Base, Texas. In:
Eleventh Annual Research Symposium on Land Disposal, Remedial Action,
Incineration, and Treatment of Hazardous Waste. USEPA, Cincinnati, OH.
White, D.C., G.A. Smith, M.J. Gehron, J.H. Parker, R.H. Findlay, R.F. Martz,
and H.L. Fredrickson. 1983. In: Developments in Industrial Microbiology
Vol. 24. John D. Lucas Printing Co., Baltimore, MD.
Williams, E.G. 1982. Contaminant Containment by In Situ Polymerization. In:
Proceedings of the Second National Symposium on Aquifer Restoration and Ground
Water Monitoring. National Water Well Association, Worthington, OH. pp.
38-44.
Wilson, P.M. and C.F. Braudner. 1977. Aqueous Surfactant Solutions Which
Exhibit Ultra-Low Tensions at the Oil-Water Interface. J. Colloid Interface
Science. Vol. 60, No. 3. pp. 473-479.
9-70
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REFERENCES (continued)
Wilson, J.T., J.F. McNabb, B.H. Wilson, and M.J. Noonan. 1983.
Biotransformaton of Selected Organic Pollutants in Groundwater. In:
Developments in Industrial Microbiology. Vol. 24. John D. Lucas Printing Co.,
Baltimore, MD.
Wilson, J.T. 1984. Presented at the Fifth Annual Meeting of the Society of
Environmental Toxicology and Chemistry, November 4-7, 1984, Arlington, VA.
Yaniga, P.M., W. Smith and R.L. Raymond. 1984. Biodegradation of Organic
Compounds. Enhanced Techniques for Diffusion of Oxygen in the Groundwater
System. In: Groundwater Treatment and Leachate Control Seminar Proceedings,
Atlanta, GA. Chemical Manufacturer's Association, Washington, DC.
9-71
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SECTION 10
DIRECT WASTE TREATMENT
This section describes direct waste treatment methods applicable for
treating aqueous, gaseous, and solid waste streams produced at hazardous waste
sites. Many of the treatment methods described in this section are widely
used in industrial waste treatment applications and information on their
design and construction is well described in the literature cited throughout
the section. As a result detailed information pertaining to design and
construction has not been included. Instead, this section emphasizes
applications and limitations of these methods for hazardous waste treatment.
Section 10.1 describes aqueous waste treatment methods. Section 10.2
describes methods for solid waste treatment including solids separation and
dewatering methods. Section 10.3 addresses solidification and stabilization
technologies applicable for liquid and solid wastes. Commonly used methods
for treating gaseous emissions (with the exception of incineration) are
addressed in Section 10.4 Incineration and other thermal treatment methods
are addressed separately in Section 10.5 since these methods apply to liquid,
solid, and gaseous wastes.
10.1 Aqueous Waste Treatment
Aqueous waste streams resulting from the clean up of hazardous waste
sites vary widely with respect to volume, level, and type of contaminants and
level of solids. The major sources of aqueous wastes include:
• Leachate plumes which have been pumped to the surface or collected via
subsurface drains
• Contaminated water generated during dredging operations
• Contaminated run-off collected in impoundments or basins
• Contaminated water generated from equipment cleanup
• Aqueous waste generated from sediment or sludge dewatering
• Highly concentrated wastewater streams generated from certain aqueous
waste treatment processes (e.g., backwash from filtration, concentrate
from reverse osmosis).
10-1
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Because these waste streams are so diverse in volume, type, and concen-
tration of contaminants, a wide variety of treatment processes will have
application to hazardous waste site cleanup. This section addresses those
processes which are considered most applicable for hazardous waste site
remediation. Rarely will any one unit treatment process be sufficient for
aqueous waste treatment. Therefore, the discussions which follow include
information on unit treatment processes which are frequently used in combina-
tion and any pretreatment requirements which are a prerequisite to effective
use of each treatment process. The unit treatment processes considered in
this section include:
• Activated carbon
• Activated sludge
• Filtration
• Precipitation/flocculation
• Sedimentation
• Ion exchange
• Reverse osmosis
• Neutralization
• Gravity separation
• Air stripping
• Chemical oxidation
• Chemical reduction.
Aqueous waste treatment at hazardous waste sites can be accomplished
using one of four general approaches:
• On-site treatment using mobile treatment system
• On-site construction and operation of treatment systems
• Pretreatment followed by discharge to a POTW
• Hauling of waste to an off-site treatment facility.
Mobile treatment systems and systems constructed on-site have broadest
applicability. Wastewaters discharged to POTWs often require extensive
pretreatment in order for the facility to meet its NPDES permit conditions.
Other factors which determine the feasibility of POTW discharge include
whether the facility has the hydraulic capacity to handle the waste, whether
accepting the waste will result in additional monitoring requirements or
process changes, and the potential for opposition in the community.
Hauling wastes off-site for treatment is limited to all but very small
wastewater volumes.
10-2
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10.1.1 Activated Carbon Treatment
10.1.1.1 General Description
The process of adsorption onto activated carbon involves contacting a
waste stream with the carbon, usually by flow through a series of packed bed
reactors. The activated carbon selectively adsorbs hazardous constituents by
a surface attraction phenomenon in which organic molecules are attracted to
the internal pores of the carbon granules.
Adsorption depends on the strength of the molecular attraction between
adsorbent and adsorbate, molecular weight, type and characteristic of
adsorbent, electrokinetic charge, pH, and surface area.
Once the micropore surfaces are saturated with organics, the carbon is
"spent" and must either be replaced with virgin carbon or removed, thermally
regenerated, and replaced. The time to reach "breakthrough" or exhaustion is
the single most critical operating parameter. Carbon longevity balanced
against influent concentration governs operating economics.
Most hazardous waste treatment applications involve the use of adsorption
units which contain granular activated carbon (GAG) and operate in a downflow
series mode such as that shown in Figure 10-1 (Brunotts et al., 1983).
The downflow fixed bed series mode has been found to be generally most
cost-effective and produces the lowest effluent concentrations relative to
other carbon adsorber configurations (e.g., downflow in parallel, moving bed,
upflow-expanded). The units may be connected in parallel to provide increased
hydraulic capacity.
10.1.1.2 Applications/Limitations
Activated carbon is a well developed technology which is widely used in
the treatment of hazardous waste streams. It is especially well suited for
removal of mixed organics from aqueous wastes. Table 10-1 provides an
indication of the treatability of organics commonly found in groundwater.
Table 10-2 delineates various factors which influence the applicability
of activated carbon treatment for any given waste (Nalco Chemical Co., 1979).
As carbon adsorption is essentially an electrical interaction phenomenon, the
polarity of the waste compounds will largely determine the effectiveness of
the adsorption process. Highly polar molecules cannot be effectively removed
by carbon adsorption. Another factor to consider in determining the likely
effectiveness of carbon adsorption is aqueous solubility. The more hydro-
phobic (insoluble) a molecule is, the more readily the compound is adsorbed.
Low solubility humic and fulvic acids which may be present in the groundwater
can sorb to the activated carbon more readily than most waste contaminants and
result in rapid carbon exhaustion.
10-3
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FIGURE 10-1.
TWO-VESSEL GRANULAR CARBON ADSORPTION SYSTEM
FEED WATER
REGENERATED/MAKEUP
ACTIVATED CARBON
BACKWASH EFFLUENT
BACK WASH FEED
ADSORBER I
ADSORBER 2
REGENERATED/MAKEUP
ACTIVATED CARBON
BACK WASH EFFLUENT
BACK WASH FEED
TREATED EFFLUENT
SPENT CAHBON
VALVE CLOSED
VALVE OPEN
Source: USEPA, 1973a
In addition, some metals and inorganic species have shown excellent to
good adsorption potential, including antimony, arsenic, bismuth, chromium,
tin, silver, mercury, cobalt, zirconium, chlorine, bromine, and iodine.
Carbon adsorption is frequently used following biological treatment
and/or granular media filtration in order to reduce the organic and suspended
solids load on the carbon columns, or to remove refractory organics which
cannot be biodegraded. Air stripping may also be applied prior to carbon
adsorption in order to remove a portion of the volatile contaminants, thereby
reducing the organic load to the column. These pretreatment steps all
minimize carbon regeneration costs.
The highest concentration of solute in the influent stream that has been
treated on a continuous basis is 10,000 ppm total organic carbon (TOC), and a
1 percent solution is currently considered as the upper limit (De Renzo,
10-4
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TABLE 10-1.
FACTORS AFFECTING EQUILIBRIUM ABSORBABILITY
Compound Adsorbability Favored by:
Increasing carbon chain length
Increasing aromaticity
Decreasing polarity
Decreasing branching
Decreasing solubility
Decreasing degree of dissociation
Functionality
Relative adsorbability: acids > aldehydes > esters > ketones >
alcohols > glycols when number of carbon atoms is <4
pH Effects
Undissociated species are mo're easily adsorbed ,
- low pH favors adsorption of acids (e.g., volatile acids, phenol)
- high pH favors adsorption of bases (e.g., amines)
Other compounds: adsorption can be favored by higher pH
- Postulated general effect:
Partial neutralization of surface acidity reduces
hydrogen-bonding of surface groups eliminating steric
blockage of micropores
Temperature
Increased temperatures can increase rate of adsorption due to
viscosity and diffusivity effects
Exothermic adsorption reactions are favored by decreasing
temperatures, usually a minor effect on equilibrium level
When the rate is controlled by intraparticle transport, decreasing molecular
size would result in faster rate, all else being equal.
This often is the most significant pH effect, so adsorption generally is
increased with decreasing pH;
Source: Conway and Ross, 1980.
10-5
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TABLE 10-2.
CARBON INFLUENT AND EFFLUENT
Organic Compounds
in Groundwater
Number of
Occurrences
Influent*
Concentration
Range
Carbon
Effluent*
Concentration
Achieved
Carbon tetrachloride 4
Chloroform 5
DDD 1
DDE 1
DDT 1
CIS-l,2-dichloroethylene 8
Dichloropentadiene 1
Disopropyl ether 2
Tertiary methyl-butylether 1
Diisopropyl methyl phosphonate 1
1,3-dichloropropene 1
Dichlorethyl ether 1
Dichloroisopropylether 1
Benzene 2
Acetone 1
Ethyl acrylate 1
Trichlorotrifloroethane 1
Methylene chloride 2
Phenol 2
Orthochlorophenol 1
Tetrachloroethylene 10
Trichloroethylene 15
1,1,1-trichloroethane 6
Vinylidiene chloride 2
Toluene 1
Xylene 3
130 ug/1-10 mg/1
20 ug/1-3.4 mg/1
1 ug/1
1 ug/1
4 ug/11
5 ug/1-4 mg/1
450 ug/1
20-34 ug/1
33 ug/1
1,250 ug/1
10 ug/1
1.1 mg/1
0.8 mg/1
0.4-11 mg/1
10-100 ug/1
200 mg/1
6 mg/1
1-21 mg/1
63 mg/1
100 mg/1
5 ug/1-70 mg/1
5 ug-16 mg/1
60 ug/1-25 mg/1
5 ug/1-4 mg/1
5-7 mg/1
0.2-10 mg/1
<0
<0
.05
.05
.05
ug/1
ug/1
g/1
ug/1
ug/1
<1 ug/1
<10 ug/1
<1 ug/1
<5.0 ug/1
<50 ug/1
<1 ug/1
<1 ug/1
<1 ug/1
<1 ug/1
<10 mg/1
<1 mg/1
<10 ug/1
<100 ug/1
<1 ug/1
<1 mg/1
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
*Analyses conducted by Calgon Carbon Corporation conformed to published U.S.
EPA protocol methods. Tests in the field were conducted using available
analytical methods.
Source: O'Brien and Fisher, 1983
10-6
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1978). Pretreatment is required for oil and grease and suspended solids.
Concentrations of oil and grease in the influent should be limited to 10 ppm.
Suspended solids should be less than 50 ppm for upflow systems, while downflow
systems can handle much higher solids loadings.
10.1.1.3 Design Considerations
The phenomenon of adsorption is extremely complex and not mathematically
predictable. To accurately predict performance, longevity and operating
economics, field pilot plant studies are necessary.
In order to conduct an initial estimate of carbon column sizing, the
following data need to be established during pilot plant testing:
• Hydraulic retention time (hours)
• Flow (gallons/minute)
• Hyraulic capacity of the carbon (gallons waste/pound carbon)
• Collected volume of treated waste at breakthrough (gallons)
• Carbon density (pounds carbon/cubic foot).
In the above data list, the term "breakthrough" refers to the moment when
the concentration of solute being treated first starts to rise in the carbon
unit effluent. The term "exhaustion" refers to the moment when the
concentration of solute being treated is the same in both effluent and
influent.
10.1.1.4 Technology Selection/Evaluation
Activated carbon is an effective and reliable means of removing low
solubility organics. It is suitable for treating a wide range of organics
over a broad concentration range. It is not particularly sensitive to changes
in concentrations or flow rate and, unlike biological treatment, is not
adversely affected by toxics. However, it is quite sensitive to suspended
solids and oil and grease concentrations.
Activated carbon is easily implemented into more complex treatment sys-
tems. The process is well suited to mobile treatment systems as well as to
on-site construction. Space requirements are small, start-up and shut-down
are rapid, and there are numerous contractors who are experienced in operating
mobile units.
The EPA's Mobile Physical/Chemical Treatment System includes three carbon
columns that can be operated either in series or in parallel and are designed
for a hydraulic loading of 200 gpm with a 27 minute contact time. This
contact time has been found to be adequate for many hazardous waste streams.
10-7
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However, longer contact times can be provided by reducing the hydraulic flow
rate (Ghassemi, Yu, and Quinlivan, 1981).
Use of several carbon adsorption columns at a site can provide con-
siderable flexibility. Various columns can be arranged in series to increase
service life between regeneration of the lead bed or in parallel for maximum
hydraulic capacity. The piping arrangement would allow for one or more beds
to be regenerated while the other columns remain in service.
The most obvious maintenance consideration associated with activated
carbon treatment is the regeneration of spent carbon for reuse. Regeneration
must be performed for each column at the conclusion of its bed-life so the
spent carbon may be restored as close as possible to its original condition
for reuse; otherwise, the carbon must be disposed of. Other operation and
maintenance requirements of activated carbon technology are minimal if
appropriate automatic controls have been installed.
It is recommended that the thermal destruction properties of waste
chemicals be determined prior to selection of activated carbon treatment
technology, since any chemicals sorbed to activated carbon must eventually be
destroyed in a carbon regeneration furnace. Therefore, of crucial importance
to the selection of activated carbon treatment is whether the sorbed waste
material can be effectively destroyed in the regeneration furnace; otherwise,
upon introduction to the furnace, they will become air pollutants.
The biggest limitation of the activated carbon process is the high
capital and operating cost. As described previously, the operating costs can
be substantially reduced by pretreatment of the waste using biological
treatment or air stripping.
10.1.1.5 Costs
The cost of activated carbon units depends on the size of the contact
unit which is influenced by the concentrations of the target and non-target
organic compounds in the waste stream and the desired level of target
compounds in the effluent. Table 10-3 presents construction, operation and
maintenance costs for cylindrical pressurized, downflow steel contactors
based on a nominal detention time of 17.5 minutes and a carbon loading rate of
5gpm/ft . The construction costs include housing, concrete foundation, and
all the necessary pipes, valves, and nozzles for operating the unit plus the
initial change of carbon. The operation and maintenance cost include the
electricity and assume carbon replacement once a year. However, systems for
unloading spent carbon and loading fresh carbon are not included.
There are a number of manufacturers such as Calgon Carbon Corporation who
market mobile activated carbon treatement systems. For example, Calgon Carbon
Corporation has a trailer-mounted carbon adsorption treatment unit that can be
shipped to a treatment location within 24 to 48 hours. The system can be
configured wih either single or multiple pre-piped adsorber vessels. It can
handle flow of up to 200 gpm. The following describes costs associated with a
10-8
-------
Table 10-3
GENERAL COST DATA FOR VARIOUS SIZES OF ACTIVATED CARBON CONTACT UNITS
Capacity (gpra) Column Column Housing Construction O&M
Diameter (ft) Length (ft) Area (ft ) Costs* Costs ($/yr)*
1.7
17
70
175
350
0.67
2
4
6.5
9
5
5
5
5
5
60
150
300
375
450
12,320
23,776
42,425
64,000
93,822
1,690
2,315
4,800
8,110
12,540
*Updated from 1979 to 1984 dollars using third quarter Marshall and Swift
Equipment Index.
Source: Adapted from Hansen, Gumerman, and Gulp, 1979.
10-9
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mobile system consisting of two 10-foot diameter, 10-foot high, skid mounted
vessels capable of handling up to 200 gpm (Calgon Corp, undated):
Delivery, supervision of installation $25,000
and startup, tests to conduct re-
activation of carbon, dismantling and
removal of system (including freight to
and from the site)
Delivery and removal of one truck- $15,200
load of carbon (2,000 Ibs)
(Two truckloads required for a
two-vessel system) - Rental fee (per month) $5,000/month
Calgon Carbon Corporation will take spent carbon back for reactivation.
Otherwise, disposal costs for spent carbon must be added.
10.1.2 Biological Treatment
10.1.2.1 General Description
The function of biological treatment is to remove organic matter from the
waste stream through microbial degradation. The most prevalent form of
biological treatment is aerobic, i.e., in the presence of oxygen. A number of
biological treatment processes exist which may be applicable to treatment of
aqueous wastes from hazardous waste sites, including conventional activated
sludge, various modifications of the activated sludge process including pure
oxygen activated sludge, extended aeration, and contact stabilization, and
fixed film systems which include rotating biologial discs, and trickling
filters.
In the conventional activated sludge process, aqueous waste flows into an
aeration basin where it is aerated for several hours. During this time, a
suspended active microbial population (maintained by recycling sludge)
aerobically degrades organic matter in the stream along with producing new
cells. A simplified equation for this process is shown below:
Organics + 02 > CO- + H~0 + new cells
The new cells produced during aeration form a sludge which is settled out in a
clarifier. A portion of the settled sludge is recycled to the aeration basin
to maintain the microbial population while the remaining sludge is wasted,
i.e., it undergoes volume reduction and disposal. Clarified water flows to
disposal or further processing.
10-10
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In the pure oxygen activated sludge process, oxygen or oxygen-enriched
air is used instead of air to increase the transfer of oxygen. Extended
aeration involves longer detention times than conventional activated sludge
and relies on a higher population of microorganisms to degrade wastes.
Contact stabilization involves only short contact of the aqueous wastes and
suspended microbial solids, with subsequent settling of sludge and treatment
of the sludge to remove sorbed organics. Fixed film systems involve contact
of the aqueous waste stream with microorganisms attached to some inert medium
such as rock or specially designed plastic material. The original trickling
filter consisted of a bed of rocks over which the contaminated water was
sprayed. The microbes forming a slime layer on the rocks, would metabolize
the organics, while oxygen was provided as air moved countercurrent from the
water flow (Canter and Knox, 1985).
Biological towers are a modification of the trickling filter. The medium
(e.g., of polyvinyl chloride (PVC), polyethylene, polystyrene, or redwood) is
stacked into towers which typically reach 16 to 20 ft. The contaminated water
is sprayed across the top and, as it moves downward, air is pulled upward
through the tower. A slime layer of microorganisms forms on the media and
removes the organic contaminants as the water flows over the slime layer.
A rotating biological contactor (RBC) consists of a series of rotating
discs, connected by a shaft, set in a basin or trough. The contaminated water
passes through the basin where the microorganisms, attached to the discs,
metabolize the organics present in the water. Approximately 40% of the disc's
surface area is submerged. This allows the slime layer to alternately come in
contact with the contaminated water and the air where oxygen is provided to
the microorganisms (Canter and Knox, 1985).
10.1.2.2 Applications/Limitations
There is considerable flexibility in biological treatment because of the
variety of available processes and adaptability of the microorganisms them-
selves. Many organic chemicals are considered biodegradable, although the
relative ease of biodegradation varies widely. Several generalizations can be
made with regard to the ease of treatability of organics by aerobic biological
treatment:
• Unsubstituted nonaromatics or cyclic hydrocarbons are preferred over
unsubstituted aromatics
• Materials with unsaturated bonds such as alkenes are preferred over
materials with saturated bonds
• Soluble organics are usually more readily degraded than insoluble
materials. Biological treatment is more efficient in removing
dissolved or colloidal materials, which are more readily attacked by
enzymes. This is not the case, however, for fixed film treatment
systems which preferentially treat suspended matter
10-11
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• The presence of functional groups affects biodegradability. Alcohols,
aldehydes, acids, esters, amides, and amino acids are more degradable
than corresponding alkanes, olefins, ketones, dicarboxylic acids,
nitriles, and chloroalkanes
• Halogen-substituted compounds are the most refractory to
biodegradation; chlorinated alphatics are generally more refractory
than the corresponding aromatics, although the number of halogens and
their position is also significant in determining degradation.
• Nitro-substituted compounds are also difficult to degrade although
they are generally less refractory than the halogen-substituted
compounds.
Although there are a number of compounds which are considered to be
relatively resistant to biological treatment, it is recommended in practice
that the treatability of waste be determined through laboratory Biological
Oxygen Demand (BOD ) tests on a case-by-case basis. Section 9.1 provides
further discussion of the degradability of organics.
Despite the fact that industrial type wastes may be refractory to bio-
logical treatment, microorganisms can be acclimated to degrade many compounds
that are initially refractory. Similarly, while heavy metals are inhibitory
to biological treatment, the biomass can also be acclimated, within limits, to
tolerate elevated concentrations of metals.
In terms of the variety of biological treatment processes available,
Table 10-4 presents the applications and limitations of each. The completely
mixed activated sludge process is the most widely used for treatment of
aqueous wastes with relatively high organic loads. However, the high purity
oxygen system has advantages for hazardous waste site remediation.
In addition, a number of other parameters may influence the performance
of the biological treatment system, such as concentration of suspended solids,
oil and grease, organic load variations, and temperature. Table 10-5 lists
parameters that may limit system performance, limiting concentrations, and the
type of pretreatment steps required prior to biological treatment.
10.1.2.3 Design Considerations
Design of the activated sludge or fixed-film systems for a particular
application can be achieved best by first representing the system as a
mathematical model, and then determining the necessary coefficients by running
laboratory or pilot tests.
10-12
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TABLE 10-4.
SUMMARY OF APPLICATIONS/LIMITATIONS FOR BIOLOGICAL TREATMENT PROCESS
PROCESS
APPLICATIONS/LIMITATIONS
Conventional
Completely-mixed
Conventional
Extended Aeration
Contact Stabilization
Pure Oxygen
Trickling Filters
Rotating Biological Disc
Applicable to low strength wastes; subject to
shock loads
Resistant to shock loads
Requires low organic load and long detention
times; low volume of sludge; available as package
plant
Not suitable for soluble BOD
Suitable for high strength wastes;
low sludge volume;
reduced aeration tank volume
More effective for removal of colloidal and
suspended BOD; used primarily as a roughing
filter
Can handle large flow variations and high organic
shock loads; modular construction provides
flexibility to meet increases or decreased
treatment needs.
10-13
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TABLE 10-5
CONCENTRATION OF POLLUTANTS THAT MAKE PREBIOLOGICAL
OR PRIMARY TREATMENTS DESIRABLE
Pollutant or
System Condition
Limiting
Concentration
Kind of Pretreatment
Suspended solids
Oil or grease
Toxic ions
Pb
Cr
pH
Alkalinity
Acidity
Organic load variation
Sulfides
Phenols
Ammonia
Dissolved salts
Temperature
>50-125 mg/1
flotation, lagooning
>35-50 mg/1
£0.1 mg/1
<1 mg/1
P mg/1
<_ 10 mg/1
<6, >9
0.5 Ib alkalinity
as CaCO /Ib BOD
removed
Free mineral acidity
MOO mg/1
>70-300 mg/1
>1.6 g/1
>10-16 g/1
13-38'C in reactor
Sedimentation,
Skimming tank or
separator
precipitation or ion
exchange
Neutralization
Neutralization for
excessive alkalinity
Neutralization
Equalization
Precipitation or
stripping with recovery
Extraction, adsorption,
internal dilution
Dilution, ion exchange,
pH adjustment and
stripping
Dilution, ion exchange
Cooling, steam addition
Source: Conway and Ross, 1980
10-14
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The following models have been found to be reliable for designing
biological treatment systems for waste streams containing priority pollutants
(Cantor and Knox, 1985).
Activated Sludge:
FS./X
V =
U S. - 1C
max i B
S. - S
i e
Biological Tower and Rotating Biological Contactor:
FS.
i
U S.
max i - K,,
B
S. - S
i e
•j
where V = volume of aeration tank ( f t )
F = flow rate (ft /day)
X = mixed liquor volatile solids (mg/1)
S. = influent BOD, COD, TOC, or specific organics (mg/1)
S1 = effluent BOD, COD, TOC, or specific organics (mg/1)
U and K = biokinetic constants (day )
A = surface area of biological tower or rotating biological
contactor ( f t )
The biokinetic constants are determined by conducting laboratory or pilot
plant studies. After the biokinetic constants are determined, the required
volume of aeration tank or the required surface area for a biological tower or
rotating biological contactor can be determined for any flow rate, influent
concentration of BOD, COD, TOC, or specific organic, and a required effluent
concentration of BOD, COD, TOC, or specific organic.
10.1.2.4 Technology Selection/Evaluation
Biological treatment has not been as widely used in hazardous waste site
remediation as activated carbon, filtration and precipitation/flocculation.
However, the process is well established for treating a wide variety of
organic contaminants. Kincannon and Stove as reported by Canter and Knox
(1985) have demonstrated the effectiveness of activated sludge for treating
priority pollutants. The results shown in Table 10-6 indicate that activated
sludge was effective for all groups of contaminants tested except for
halogenated hydrocarbons.
10-15
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TABLE 10-6.
REMOVAL MECHANISMS OF TOXIC ORGANICS
Compound
Percept Treatment Achieved
Stripping
Sorption
Biological
Nitrogen Compounds
Acrylonitrile
Phenols
Phenol
2,4-DNP
2,4-DCP
PGP
Aromatics
1,2-DCB
1,3-DCB
Nitrobenzene
Benzene
Toluene
Ethylbenzene
Halogenated Hydrocarbons
Methylene Chloride
1,2-DCE
1,1,1-TCE
1,1,2,2,-TCE
1,2DCP
TCE
Chloroform
Carbon Tetrachloride
Oxygenated Compounds
Acroleiln
Polynuclear Aromatics
Phenanthrene
Napthalene
Phthalates
Bis(2-Ethylhexyl)
Other
Ehtyl Acetate
21.7
2.0
5.1
5.2
8.0
99.5
100.0
93.5
99.9
65.1
19.0
33.0
1.0
0.58
0.02
0.19
91.7
0.50
0.83
1.19
1.38
99.9
99.9
99.
95,
97.3
78.2
97.8
97.9
94.9
94.6
33.8
78.8
64.9
99.9
98.2
98.6
76.9
98.8
Source: Canter and Knox, 1985 as cited by Kincannon and Stover, undated,
10-16
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Although biological treatment can effectively treat a wide range of
organics, it has several drawbacks for hazardous waste site applications. The
reliability of the process can be adversely affected by "shock" loads of
toxics. Start-up time can be slow if the organisms need to be acclimated to
the wastes and the detention time can be long for complex wastes. However,
the existence of cultures which have been previously adapted to hazardous
wastes can dramatically decrease start-up and detention time.
There are a number of cleanup contractors who have used biological treat-
ment as part of a mobile treatment system. The high purity oxygen treatment
process is well suited for mobile treatment applications because the high
oxygen efficiency enables use of smaller reactors, shorter detention time, and
reduced power consumptions relative to other activated sludge processes. A
hazard associated with the high purity oxygen process is that the presence of
low flash-point compounds can present a potential fire hazard. However, the
system is equipped with hydrocarbon analyzers and control systems that
deactivate the system when dangerously high concentrations of volatiles are
detected (Ghassemi, Yu, and Quinlivan, 1981). Loss of volatile organics from
other biological treatment processes can also pose some localized air
pollution and a health hazard to field personnel.
Rotating biological contactors also have advantages for hazardous waste
site treatment. The units are compact, and they can handle large flow
variations and high organic shock loads, and they do not require use of
aeration equipment.
Sludge produced in biological waste treatment may be a hazardous waste
itself due to the sorption and concentration of toxic and hazardous compounds
contained in the wastewater. If the sludge is hazardous, it must be disposed
in a RCRA-approved manner. If the sludge is not hazardous, disposal should
conform with State sludge disposal guidelines.
10.1.2.5 Costs
Costs for various sizes of activated sludge units are presented in Table
10-7. The costs for these units assume a detention time of 3 hours, and use
of aeration basins, air supply equipment, piping, and a blower building.
Clarifier and recycle pumps are not included. The basins are sized to the 50
percent recycle flow. The influent biological oxygen demand (BOD) is assumed
to be no greater than 130 ppm and the effluent BOD is assumed to .be 40 ppm.
The operation and maintenance costs assume that the hydraulic head loss
through the aeration tank is negligible. Sludge wasting and pumping energy
are not included.
Union Carbide manufactures a high purity oxygen activated sludge system
(UNOX) suitable for mobile system applications. The mobile UNOX systems have
a hydraulic capacity of 5 to 40 gpm, are contained within 40 foot van
trailers, and include an external clarifier. The oxygen required is also
10-17
-------
TABLE 10-7.
GENERAL COST DATA FOR VARIOUS SIZES OF ACTIVATED SLUDGE TREATMENT UNITS
Capacity (gpm)
70
140
350
694
Construction
Costs ($)*
78,500
85,600
107,000
160,000
O&M Costs ($/year)*
4,300
6,400
10,000
15,700
*Updated from 1978 to 1984 dollars using third quarter Marshall and Swift
Equipment Index.
Source: Adapted from USEPA, 1980.
supplied by Union Carbide. The customer is expected to provide installation
labor, operating manpower, analytical support, and utilities. A typical
installation requires three to four days (Ghassemi, Yu, and Quinlivan, 1981).
The mobile UNOX system can be either rented or purchased from the Union
Carbide Corporation. The estimated rental costs are as follows:
$6,540 for the checkout and refurbishment of equipment to make it
operational
$550/day for on-site service including engineering consultation on
program planning and execution
$9/day rental of equipment
Transportation charges to get the equipment from the manufacturer to
the site of operation and back again.
The purchase price for the UNOX mobile unit is between $260,000 and $330,000
(Ghassemi, Yu, and Quinlivan, 1981, updated using 1984 third quarter Marshall
Swift Index).
10-18
-------
10.1.3 Filtration
10.1.3.1 General Description
Filtration is a physical process whereby suspended solids are removed
from solution by forcing the fluid through a porous medium. Granular media
filtration is typically used for treating aqueous waste streams. The filter
media consists of a bed of granular particles (typically sand or sand with
anthracite or coal) (Figure 10-2). The bed is contained within a basin and is
supported by an underdrain system which allows the filtered liquid to be drawn
off while retaining the filter media in place. As water laden with suspended
solids passes through the bed of filter medium, the particles become trapped
on top of and within the bed. This either reduces the filtration rate at a
constant pressure or increases the amount of pressure needed to force the
water through the filter. In order to prevent plugging, the filter is
FIGURE 10-2.
TYPICAL FILTRATION BED
BACKWASH
DRAIN
HIGH HEAD
RAW FEED
BACKWASH
TROUGH r—
SINGLE OR
MULTIPLE LAYER
FILTER MEDIUM
BACKWASH
UNDER DRAIN
EFFLUENT
Source: Ghassemi, Yu, and Quinlivan, 1981
10-19
-------
backflushed at high velocity to dislodge the particles. The backwash water
contains high concentrations of solids and requires further treatment
(De Renzo, 1978).
10.1.3.2 Applications/Limitations
Filters find economic application in handling streams containing less
than 100 to 200 mg/liter suspended solids, depending on the required effluent
level. Increased suspended solids loading will reduce run lengths, and
require excessively frequent backwash (De Renzo, 1978). The suspended solids
concentration of the filtered liquid depends a great deal on particle size
distribution, but typically, granular media filters are capable of producing a
filtered liquid with a suspended solids concentration as low as 1 to 10 mg/1.
Large flow variations will deleteriously affect effluent quality.
Often, granular media filters are preceded by sedimentation to reduce the
suspended solids load on the filter (De Renzo, 1978). Granular media
filtration is also frequently installed ahead of biological or activated
carbon treatment units to reduce the suspended solids load and in the case of
activated carbon to minimize plugging of the carbon columns (De Renzo, 1978).
The granular media filtration process is only marginally effective in
treating colloidal size particles. In many cases, these particles can be made
larger by flocculation although this will generally reduce run lengths. In
cases where it is not possible to flocculate such particles (as in the case of
many oil/water emulsions), more advanced techniques such as ultrafiltration
may be appropriate (De Renzo, 1978).
10.1.3.3 Design Considerations
The composition and sizing of the filtration bed is an important design
consideration. Beds of 4 feet or less composed of 0.5 mm sand and 0.9 mm
anthracite are frequently used. However deep-bed filters are also available.
It is recommended that pilot plant studies be conducted to determine optimum
size and combination of filter material.
A filter bed can function properly only if the backwashing system
effectively cleans the material from the filter. Methods which can be used
for backwashing include water backwash only, water backwash with auxiliary
surface water wash, water wash proceeded by air scour, and simultaneous air
and water wash.
The duration of the backwash is about 20 min per cycle. Backwash water,
which amounts to 1 to 5 percent of the total flow, can be routed to a primary
clarifier often via a storage vessel to allow flow equalization. Several
filters are used in parallel to allow continuous processing during
backwashing; the backwash cycle usually is automated. Other processes must be
sized to handle this recycle flow.
10-20
-------
10.1.3.4 Technology/Selection Evaluation
Filtration is a reliable and effective means of removing low levels of
solids from wastes provided the solids content does not vary greatly and the
filter is backwashed at appropriate intervals.
Filtration equipment is relatively simple, readily available in a wide
range of sizes, and easy to operate and control. Filtration is also easily
integrated with other treatment steps.
Because of its small space requirements and relatively simple operation,
filtration is well suited to mobile treatment systems as well as on-site
construction. There is extensive experience with the operation of
granular-media filters at hazardous waste sites.
The EPA physical/chemical treatment system which has been in operation
for more than 9 years incorporates 3 "dual" media (sand-anthracite) filters
connected in parallel in its treatment train. The filters are designed for a
maximum hydraulic loading of 7 gpm/ft or 67 gpm (Ghassemi, Yu, and Quinlivan,
1981). There are also a number of manufacturers of package plant systems
suitable for being trailer mounted and a number of cleanup contractors who
operate mobile treatment systems which include granular media filters as a
part of the treatment process.
The most obvious maintenance consideration with granular media filtration
is handling of the backwash. The backwash will generally contain high
concentrations of contaminants and require subsequent treatment.
10.1.3.5 Costs
Figure 10-3 shows construction and operating costs for filtration
assuming a filtration rate of 5 gpm/ft . A minimimum of 4 filters are assumed
to provide flexibility of operation. Capital costs include filter structures,
backwash and surface wash systems, media and polymer feeding. Costs of
effluent filtering and pumping are not included. Power costs are based on
each filter backwashing once per 12 hours (Gulp, Wesner and Gulp, 1978).
The construction costs assume a filtration rate of 2 gpm/square foot and
76 in filter media (silica sand and anthracite coal mixture) depths inside two
open-topped cylindrical steel tanks. The construction costs also include
chemical feed systems (alum, soda ash, polymer, and chlorine), pumps,
pre-filter contact basin, a backwash storage basin, building, and all
necessary piping. The operation and maintenance costs include all building
utilities, process utilities, routine maintenance costs, and replacement of
filter media lost through normal backwash operations (Hansen, Gumerman, and
Gulp, 1979). The operation and maintenance costs do not include treatment
chemicals because usage rates of these chemicals would vary considerably
10-21
-------
FIGURE 10-3. COST OF EFFLUENT FILTRATION*
0
o
5,000
4,000
3,000
2,000
1,000
500
400
300
200
100
— "
• -~
^x
^
, "
^f
^^
-
,
^
<
/
s
^s
*^
X
,x
^
/
.
s
-
/
-
'
'
>
**
o
01
T3
I
,00 |
X
50 9.
40
20
in
Capital Costs
O&M Costs
5 6 7 8 9 10
30 40 50
Plant Capacity, MOD
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.908)
Source: Gulp, Wesner & Gulp, 1978
depending on the wastestream characteristics. Unit costs for treatment
chemicals are presented in Section 9.2. Costs for various sizes of package
neutralization, precipitation, and filtration plants are presented in Table
10-8.
10.1.4 Precipitation/Flocculation
10.1.4.1 General Description
Precipitation is a physiochemical process whereby some or all of a
substance in solution is transformed into a solid phase. It is based on
alteration of the chemical equilibrium relationships affecting the solubility
of inorganic species. Removal of metals as hydroxides or sulfides is the most
common precipitation application in wastewater treatment. Generally, lime or
sodium sulfide is added to the wastewater in a rapid mixing tank along with
flocculating agents (described below). The wastewater flows to a flocculation
chamber in which adequate mixing and retention time is provided for
agglomeration of precipitate particles. Agglomerated particles are separated
from the liquid phase by settling in a sedimentation chamber, and/or by other
10-22
-------
TABLE 10-8.
GENERAL COST DATA FOR VARIOUS SIZES OF NEUTRALIZATION,
PRECIPITATION, AND FILTRATION UNITS
Plant Capacity (gpm) Construction Operation and
Cost ($)* Maintenance ($/year)*
4
8
40
80
140
225
280
560
78,770
89,610
126,520
179,300
253,610
293,670
396,960
619,940
20,730
21,390
26,550
47,960
56,700
57,560
61,860
92,000
*Updated from 1979 to 1984 dollars using third quarter Marshall and Swift
Index.
Source: Adapted from Hansen, Gumerman, and Gulp, 1979.
physical processes such as filtration. Figure 10-4 illustrates a typical
configuration for precipitation flocculation and sedimentation.
Although precipitation of metals is governed by the solubility product of
ionic species, in actual practice, effluent concentrations equal to the
solubility product are rarely achieved. Usually, the amount of lime added is
about three times the stoichiometric amount that would be added to reduce
solubility due to the common ion effect. Figure 10-5 gives solubilities of
various metal hydroxides and sulfides at various pH levels. The metal
sulfides have significantly lower solubility than their hydroxide counterparts
and more complete precipitation is achieved. Metal sulfides are also stable
over a broad pH range. Many metal hydroxides, on the other hand, are stable
only over a narrow pH range; metals reach a minimum solubility at a specific
pH, but further addition of lime causes the metal to become soluble again.
Therefore, dosages of lime need to be accurately controlled. This may be
particularly challenging when working with aqueous wastes from waste disposal
sites where wide variations in flow rates and quantities of metals are to be
expected. The stabilities of metal carbonates are also quite dependent on pH.
10-23
-------
FIGURE 10-4.
REPRESENTATIVE CONFIGURATION EMPLOYING PRECIPITATION, FLOCCULATION,
AND SEDIMENTATION
PRECIPITATION
FLOCCULATtON
PRECIPITATING CHEMICALS—,
FLOCCULATING AGENTS
INLET LIQUID STREAM-
AFTER THE ADDITION OF PRECIPITATING BY SLOW AND GENTLE MIXING THE
CHEMICALS THE PRECIPITATION REACTION PRECIPITATED PARTICLES. AIDED BY
COMMENCES TO FORM VERY SMALL PAR- THE FLOCCULATING AGENTS, COLLIDE,
TICLES CALLED PRECIPITATION NUCLEI. AGGLOMERATE. AND GROW INTO LARGER
THE FLOCCULATING AGENTS ALLOW THESE SETTLEABLE PARTICLES
PARTICLES TO AGGLOMERATE
-»•
RA
1
•~.irx_n
(
/
c
c
IP
J
^
ki
c
c
LP
j
^
HQ
P i
r>ID MIX TANK FLOCCULATION CHAMBER
SEDIMENTATION
OUTLET LIQUID
STREAM
SEDIMENTATION BASIN
THE SETTLEABLE PARTICLES PRODUCED
BY THE FLOCCULATION STEP ARE SETTLED,
COLLECTED AND PERIODICALLY REMOVED
Source: De Renzo, 1978
Flocculation is used to describe the process by which small, unsettleable
particles suspended in a liquid medium are made to agglomerate into larger,
more settleable particles. The mechanisms by which flocculation occurs
involve surface chemistry and particle change phenomena. In simple terms,
these various phenomena can be grouped into two sequential mechanisms (Kiang
and Metry, 1982):
• chemically induced destabilization of the requisite surface-related
forces, thus allowing particles to stick together when they touch and
• chemical bridging and physical enmeshment between the now nonrepelling
particles, allowing for the formation of large particles.
Flocculation involves three basic steps:
• addition of flocculating agent to the waste stream
• rapid mixing to disperse the flocculating agent
• slow and gently mixing to allow for contact between small particles.
Typically, chemicals used to cause flocculation include alum, lime,
various iron salts (ferric chloride, ferrous sulfate) and organic flocculating
agents, often referred to as "polyelectrolytes." These materials generally
consist of long-chain, water-soluble polymers such as polyacrylamides. They
are used either in conjunction with the inorganic flocculants, such as alum,
or as the primary flocculating agent. A polyelectrole may be termed cationic,
anionic or ampholytic depending upon the type of ionizable groups; or nonionic
10-24
-------
FIGURE 10-5.
SOLUBILITY OF METAL HYDROXIDES AND SULFIDES
o>
S
•o
Q
"6
•I
10°
10-2
10'
,-6
10"8 '
10'10 '
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
pH
Source: Ghassemi, Yu, and Quinlivan, 1981
10-25
-------
if it contains no ionizable groups. The range of physical/chemical
characteristics (e.g., density, viscosity, toxicity and molecular weight) of
the several thousand available polymers is extremely broad.
The inorganic flocculants, such as alum, lime or iron salts, make use of
precipitation reactions. Alum (hydrated aluminum sulfate) is typically added
to aqueous waste streams as a solution. Upon mixing, the slightly higher pH
of the water causes the alum to hydrolyze and form fluffy, gelatinous
precipitates of aluminum hydroxide. These precipitates, partially due to
their large surface area, enmesh small particles and thereby create larger
particles. Lime and iron salts also have a tendency to form large fluffy
precipitates or "floe" particles. Many precipitation reactions, such as the
precipitation of metals from solution by the addition of sulfide ions, do not
readily form floe particles, but rather precipitate as very fine and
relatively stable colloidal particles. In such cases, flocculating agents
such as alum and/or polyelectrolytes must be added to cause flocculation of
the metal sulfide precipitates (Canter and Knox, 1985).
Once suspended particles have been flocculated into larger particles,
they usually can be removed from the liquid by sedimentation, provided that a
sufficient density difference exists between the suspended matter and the
liquid.
10.1.4.2 Applications/Limitat ions
Precipitation is applicable to the removal of most metals from wastewater
including zinc, cadmium, chromium, copper, fluoride, lead, manganese, and
mercury. Also, certain anionic species can be removed by precipitation, such
as phosphate, sulfate, and fluoride.
Precipitation is useful for most aqueous hazardous waste aqueous streams.
However, limitations may be imposed by certain physical or chemical character-
istics. In some cases, organic compounds may form organometallic complexes
with metals, which could inhibit precipitation. Cyanide and other ions in the
wastewater may also complex with metals, making treatment by precipitation
less efficient.
Flocculation is applicable to any aqueous waste stream where particles
must be agglomerated into larger more settleable particles prior to
sedimentation or other types of treatment. There is no concentration limit
for precipitation or flocculation. Highly viscous waste streams will inhibit
settling of solids.
In addition to being used to treat waste streams, precipitation can also
be used as an in-situ process to treat aqueous wastes in surface impoundments.
In an in-situ application, lime and flocculants are added directly to the
lagoon, and mixing, flocculation, and sedimentation are allowed to occur
within the lagoon. In some cases, wind and pumping action can provide the
energy for mixing.
10-26
-------
10.1.4.3 Design Considerations
Selection of the most suitable precipitate or flocculant and their
optimum dosages is determined through laboratory jar test studies. In
addition to determining the appropriate chemicals and optimum chemical
dosages, other important parameters which need to be determined as part of the
overall design include (Canter and Knox, 1985):
• most suitable chemical addition system
• optimum pH requirement
• rapid mix requirements
• sludge production
• sludge flocculation, settling and dewatering characteristics.
10.1,4.4 Technology Selection/Evaluation
Precipitation and flocculation are well established technologies and the
operating parameters are well defined. The processes requires only chemical
pumps, metering devices, and mixing and settling tanks. The equipment is
readily available and easy to operate. Precipitation and flocculation can be
easily integrated into more complex treatment systems.
The performance and reliability of precipitation and flocculation depends
greatly on the variability of the composition of the waste being treated.
Chemical addition must be determined using laboratory tests and must be
adjusted with compositional changes of the waste being treated or poor
performance will result.
Precipitation is nonselective in that compounds other than those targeted
may be removed. Both precipitation and flocculation are nondestructive and
generates a large volume of sludge which must be disposed.
Precipitation and flocculation poses minimal safety and health hazards to
field workers. The entire system is operated at near ambient conditions,
eliminating the danger of high pressure/high temperature operation with other
systems. While the chemicals employed are often skin irritants, they can
easily be handled in a safe manner.
10.1.4.5 Costs
Table 10-9 shows a breakdown of costs for the 40 gpm sulfex heavy metal
removal system illustrated in Figure 10-6.
10-27
-------
•o
c
(D
o
*
N
o
u.
O
UJ
cc
o
ui
z
m
o
o
oc
o
X
LU
U.
M
0.
O
I
UJ
oc
3
C9
c
g
1
3
O
cn
10-28
-------
TABLE 10-9. 1985 CAPITAL COSTS* FOR SULFEX
HEAVY METAL PRECIPITATION SYSTEM
Selling Price
Equipment Price
1. Precipitator with clear well, centrifuge
for dewatering,chemical feeds and
agitators, and engineering drawings $68,768
2. Filter with transfer pump and engineering
drawings 7,623
3. Neutralization systsem including agitators,
chemical feeds, pH controls, sump pump, and
engineering drawings 86,126
Total selling price $162,517
Installation Cost (estimated by
outside contractor) $66,657
TOTAL $229,174
*Costs were updated to $1985 using the 1983 and 1985 ENR Construction Cost
Index.
Source: Metal Finisher's Foundation, 1977
2
The precipitator is sized to operate at a surface rate of 1.6 gpm/ft and
the filter at a surface rate of 3.2 gpm/ft . Chemical costs for the Sulfex
process and a hydroxide precipitation process are shown in Table 10-10. These
costs were estimated for treament of an influent containing 4 mg/1 Cu, Cd,
Cr , Ni, and Zn at pH 6.0.
Figure 10-7 shows capital and operating costs for a flocculation system
including chemical storage, chemical feeding and rapid mix. A polymer dosage
of 1 mg/1 at 0.25 percent solution is assumed. Construction costs also
include piping and building to house the feeding equipment and bag storage.
Construction costs include: Piping and building to house the feeding
equipment and bag storage. 1 Mgal/d plant size and smaller use manual feed
procedures. 2 systems of tanks and feeders are included. 10 Mgal/d plant
size includes cost of feeders and mixing tanks, one day tank and 2 solution
feeders. 100 Mgal/d plant size includes costs for 4 feeders and mixing tanks,
2 holding tanks and 10 solution feeders. The rapid mix tank is concrete,
10-29
-------
TABLE 10-10. COMPARISON OF CHEMICAL COSTS* OF
HYDROXIDE AND SULFIDE PRECIPITATION PROCESSES
(1) Hydroxide Process
Eff. Qyal.
Chemical
Dosage
Cost
Cu
Cd
Cr
Ni
Zn
Cu
Cd
Cr
Ni
Zn
(mg/1)
pH 7.5 pH
0.1 <0.
3.8 <0.
<0.5 <0.
2.3 <0.
1.3 <0.
(2)
Eff. Qual.
(mg/1)
pH 8.5
0.01
0.1
<0.05
0.05
0.01
10
1 CA(OH)2
1 Polymer
1 2 4
1
Sulfex Process
Chemical
71% NaHS
FeSO. . 7H_0
Polymer
Ca(OH)2
lb/1000 gal.
pH 7.5 pH 10
0.33 0.92
0.03 0.03
0.61
Dosage
lb/1000 gal.
pH 8.5
0.09
0.77
0.03
1.13
(if/1000 gal.
i/lb pH 7.5 pH 10
3.16 1.05 2.99
105.4 3.16 4.22
8.8 - 5.45
Total 4.21 12.66
Cost
/1000 gal.
.lb pH 8,5
19.77 1.76
3.95 2.99
105.4 3.16
3.16 3.51
Total 11.42
*Costs were updated to $1985 using the 1977 and 1985 ENR Construction Cost
Index.
Source: Metal Finisher's Foundation, 1977
10-30
-------
FIGURE 10-7. POLYMER ADDITION COSTS*
IO
s ot
Millions of Dot
o
o
OJOOI
f.
:• CONSTRUCTION COST:
1
'' -r*'
mH
J-f
L^it
II
h , i1"
_^ J
±:=j
nH
**
II . ._
T ' '
n| : !
(
1
^ '
-4-
0.1
- 3
10 10
WMMwlt* Flow. Mg«l/d
100
OOOI
01
10 10
Wastew*Mr Flow. Mgal/d
OOOl
Jooooi
•Costs can be updated to $1966 using ENR Construction Cost Indices for 1902 and 1986
(multiply value shown on this figure by 1.303)
Source: USEPA, 1982a
10-31
-------
equipped with stainless steel mixer and handrails. 0.1 Mgal/d plant size: no
separate building is required. Manual operation of feeder, mix tank solution
feeder and holding tank.
10.1.5 Sedimentation Technology
10.1.5.1 General Description
Sedimentation is a process that relies upon gravity to remove suspended
solids in an aqueous waste stream. The fundamentals of a sedimentation
process includes (Kiang and Metry, 1982):
• A basin or container of sufficient size to maintain the liquid to be
treated in a relatively quiescent state for a specified period of time
• A means of directing the liquid to be treated into the above basin in
a manner conducive to settling
• A means of physically removing the settled particles from the liquid
(or liquid from the settled particles).
Sedimentation can be carried out as either a batch or continuous process
in lined impoundments, conventional settling basins, clarifiers, and high rate
gravity settlers. Modified aboveground swimming pools have been used many
times for sedimentation in temporary, short-term treatment systems at
hazardous waste sites. Figure 10-8 illustrates three different design
configurations for sedimentation. In sedimentation ponds the liquid is merely
decanted as the particles accumulate on the bottom of the pond. Backhoes,
draglines, or siphons are used periodically to remove settled solids.
Sedimentation basins and clarifiers usually employ a built-in solids
collection and removal devices such as a sludge scrapper and draw-off
mechanism. Sedimentation basins are general rectaggular, usually employ a
belt-like collection mechanism, and are mainly used for removal of truly
settleable particles from liquid.
Clarifiers are usually circular and are used in applications involving
precipitation and flocculation as well as sedimentation. Many clarifiers are
equipped with separate zones for chemical mixing and precipitation,
floculation, and sedimentation (Kiang and Metry, 1982).
10.1.5.2 Applications/Limitations
Sedimentation is commonly applied to aqueous wastes with high suspended
solid loadings. This may include surface run-off, collected leachate or
landfill toe seepage, dredge slurries, and effluents from biological treatment
and precipitation/flocculation. Sedimentation is also required as a
10-32
-------
FIGURE 10-8.
REPRESENTATIVE TYPES OF SEDIMENTATION
Setting Pond
Inlet Liquid
Overflow Discharge Weir
Accumulated Settled Particles
Periodically Removed by Machinical Shovel
Sedimentation Basin
Inlet Zone
Inlet Liquid
Settled Particles Collected
and Periodically Removed
Baffles to Maintain
"Quiescent Conditions
Outlet Zone
Outlet Liquid
Belt-Type Solids Collection Mechanism
Circular Clarifier
Circular Baffle
Inlet Zone "
— \
TTTTX;
^<^>-,.
—^
'
\ .
«•
/ !
/ — L_
s
/ Liquid
/ Flow
-'TTTT-
, ,. , -^-*^***
Annular Overflow V
Outlet Liquid
— Settling Partic
Settling Zone,
Revolving Collection
Mechanism
Settled Particles T Collected and Periodically Removed
i Sludge Drawoff
Source: De Renzo, 1978
10-33
-------
pretreatment step for many chemical processes, including carbon adsorption,
ion exchange, stripping, reverse osmosis and filtration.
This technology is applicable to the removal of suspended solids heavier
than water. Suspended oil droplets or oil-soaked particles may not settle out
and may have to be removed by some other means. Some sedimentation units are
fitted with skimmers to remove oil and grease that float to the water surface.
However, these would not be effective in removing emulsified oils.
10.1.5.3 Design Consideration
Sedimentation is frequently considered in terms of ideal setting. The
ideal setting theory results in the following equation for surface loading or
overflow rate .
V -2
where: V = setting velocity
Q = flow through the basin
A = surface area of the basin
Sedimentation basin loadings (Q/A) are often expressed in terms of gallons per
day per square foot. Thus under ideal settling conditions, sedimentation is
independent of basin depth and detention time, and depends only on the flow
rate, basin surface area and properties of the particle.
However sedimentation does not perform according to ideal settling
conditions since settling is affected by such conditions as turbulence, and
bottom scour. Therefore removal of particles is dependent on basin depth, and
detention time as well as flow rate surface area and particle size. The
performance of a sedimentation basin on a suspension of discrete particles can
be calculated, but it is not possible to calculate sedimentation basin
performance for a suspension of flocculating particles, such as a wastewater,
because settling velocities change continually. Laboratory settling tests,
however, may be performed to predict sedimentation basin performance.
10.1.5.4 Technology Selection/Evaluation
Sedimentation provides a reliable means to remove suspended matter from a
waste stream, provided the suspended matter is settleable and the treatment
process including the use of flocclants/coagulants has been appropriately
designed from laboratory settling tests. Most clarifiers are capable of
removing 90 to 99 percent of the suspended solids.
10-34
-------
Sedimentation employs readily available equipment and is relatively easy
to operate. The process is versatile in that it can be applied to almost any
liquid waste stream containing suspended solids. It can also be easily inte-
grated into a more complex treatment system as a pre- or post-treatment
method. Sedimentation is nonselective and nondestructive, resulting in a
large volume of potentially contaminated sludge that may require further
treatment and disposal.
10.1.5.5 Costs
The cost of a system which includes chemical clarification, rapid mixing,
flocculation with alum and polymer and sedimentation is shown in Figure 10-9.
The cost estimate assumed alum and polymer dosages of 200 mg/1 and 1 mg/1
respectively, and a flow rate to the clarifier of 800 gpd/ft . The costs of
chemical sludge proceessing and disposal are not included in the capital
costs. O&M costs include cost of chemical purchase (Gulp, Wesner and Gulp,
1978).
FIGURE 10-9. COST OF CHEMICAL CLARIFICATION WITH ALUM*
O
o
.1
Q.
(3
5,000
4,000
3,000
2,000
1,000
500
400
300
200
100
100
O
50
40
30
20
°<*
3 4 5 6789 10
20 30 40 50
100
10
Capital Costs
0&M Costs
Plant Capacity, MGD
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.908)
Source: Gulp, Wesner Ct Gulp, 1978
10-35
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10.1.6 Ion Exchange and Sorptive Resins
10.1.6.1 General Description
Ion exchange is a process whereby the toxic ions are removed from the
aqueous phase by being exchanged with relatively harmless ions held by the ion
exchange material. Modern ion exchange resins are primarily synthetic organic
materials containing ionic functional groups to which exchangeable ions are
attached. These synthetic resins are structurally stable (that is, can
tolerate a range of temperature and pH conditions), exhibit a high exchange
capacity, and can be tailored to show selectivity towards specific ions.
Exchangers with negatively-charged sites are cation exchangers because they
take up positively charged ions. Anion exchangers have positively charged
sites and, consequently, take up negative ions. The exchange reaction is
reversible and concentration dependent, and it is possible to regenerate the
exchange resins for reuse. Sorptive (macroporous) resins are also available
for removal of organics and the removal mechanism is one of sorption rather
than ion exchange (Ghassemi, Yu, and Quinlivan, 1981).
10.1.6.2 Applications/Limitat ions
Ion exchange is used to remove a broad range of ionic species from water
including:
• All metallic elements when present as soluble species, either anionic
or cationic
• Inorganic anions such as halides, sulfates, nitrates, cyanides, etc.
• Organic acids such as carboxylics, sulfonics, and some phenols, at a
pH sufficiently alkaline to give the ions
• Organic amines when the solution acidity is sufficiently acid to form
the corresponding acid salt (De Renzo, 1978).
Sorptive resins can remove a wide range of polar and non-polar organics.
A practical upper concentration limit for ion exchange is about 2,500 to
4,000 mg/1. A higher concentration results in rapid exhaustion of the resin
and inordinately high regeneration costs. Suspended solids in the feed stream
should be less than 50 mg/1 to prevent plugging the resins, and waste streams
must be free of oxidants (De Renzo, 1978).
10-36
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10.1.6.3 Design Considerations
Specific ion exchange and sorptive resins systems must be designed on a
case-by-case basis. It is useful to note that although there are three major
operating models (fixed bed cocurrent, fixed bed countercurrent, and
continuous countercurrent), fixed bed countercurrent systems are most widely
used. Figure 10-10 illustrates the fixed bed countercurrent and continuous
countercurrent systems. The continuous countercurrent system is suitable for
high flows. Complete removal of cations and anions ("demineralization") can
be accomplished by using the hydrogen form of a cation exchange resin and the
hydroxide form of an anion exchange resin. For removal of organics as well as
inorganics, a combination adsorptive/demineralization system, can be used. In
this system, lead beds would carry sorptive resins which would act as organic
scavengers, and the end beds would contain anion and cation exchange resins.
By carrying different types of adsorptive resins (e.g., polar and non-polar),
a broad spectrum of organics could be removed (Ghassemi, Yu, and Quinlivan,
1981).
10.1.6.4 Technology Selection/Evaluation
Ion exchange is a well established technology for removal of heavy metals
and hazardous anions from dilute solutions. Ion exchange can be expected to
perform well for these applications when fed wastes of variable composition,
provided the system's effluent is continually monitored to determine when
resin bed exhaustion has occurred. However, as mentioned previously, the
reliability of ion exchange is markedly affected by the presence of suspended
solids. Use of sorptive resins is relatively new and reliability under
various conditions is not as well known.
Ion exchange systems are commercially available from a number of vendors.
The units are relatively compact and are not energy intensive. Start-up or
shut-down can be accomplished easily and quickly (Ghassemi, Yu, and Quinlivan,
1981). These features allow for convenient use of ion exchange and sorptive
resin systems in mobile treatment systems.
Although exchange columns can be operated manually or automatically,
manual operation is better suited for hazardous waste site applications
because of the diversity of wastes encountered; with manual operation, the
operator can decide when to stop the service cycle and begin the backwash
cycle. However, this requires use of a skilled operator familiar with the
process (Ghassemi, Yu, and Quinlivan, 1981).
Use of several exchange columns at a site can provide considerable
flexibility. As described previously, various resin types can be used to
remove anions, cations, and organics. Various columns can be arranged in
series to increase service-life between regeneratation of the lead bed or in
parallel for maximum hydraulic capacity. The piping arrangement would allow
for one or more beds to be taken out for regeneration while the remaining
columns would remain in service. (Ghassemi, Yu, Quinlivan, 1981).
10-37
-------
FIGURE 10-10.
PERTINENT FEATURES OF ION EXCHANGE SYSTEMS
Types
Counlercurrenl Fixed Bed
HtOtNtHAllON
Continuous Counlercuirenl
HtGfNEFUTIOI
Description
of Process
Indications
(or Use
Advantages
Disadvantages
Regeneralion Hows opposite in direction
to Influent Backwash (in regeneration)
does not occur on ovary cycle to pre-
serve resin stage heights Resin bed is
locked in place during regeneration
Handles high loads at moderate Ihrupul
or low loads at high thruput (GPM x TDS
or GPM x PPM removal = 40,000 or
more) Where effluent quality must be
relatively constant, regeneration cost Is
relatively critical, disposal of single
batch waste volume no problem
Moderate capital cost Can be operated
with periodic attention Moderate
regeneration cost Lesser volume of
waste due to less frequent backwash
Consistent effluent quality
Increased conlrols and instrumentation,
higher cost Requires mechanism lo lock
resin bed Large single batches of waste
disposal Moderate water consmption
thru dilution and waste Requires sub-
stantial llooi space
Multi-stage counlercurrent movement of
resin in closed loop providing simul-
taneous treatment, regeneration, back-
wash and rinse Operation is onty Inter-
rupted for momentary resin pulse
Highloads with high thrupuls (GPM x
TDS 01 GPM x PPM removal = 40,000 or
more) Where constant effluent quality Is
essential, regeneration costs critical,
total waste volume requires small, con-
centrated stream lo be controllable
Where loss of product thru dilution and
waste must be mimmi/ed Where avail-
able floor space is limited
Lowest regeneration cost Lowest resin
Inventory Consistent effluent quality
Highest Ihrupul to floor space Large
capacity units factory preassernblud
Concentrated low volume waste stream
Can handle strong chemical solutions
and slurry Fully automatic opeiation
Requires automatic conlrols and inslru
mentation, highei capital cost Moie
headroom required
Source: Chemical Seperations Corporation
10-38
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Consideration must be given to disposal of contaminated ion exchange
regeneration solution. In addition to proper disposal, another important
operational consideration is the selection of regeneration chemicals. Caution
must be exercised in making this selection to ensure the compatibility of the
regenerating chemical with the waste being treated. For example, the use of
nitric acid to regenerate an ion exchange column containing ammonium ions
results in the formation of ammonium nitrate, a potentially explosive
compound.
10.1.6.5 Costs
Costs for various sizes of ion exchange units are presented in Table
10-11. The construction costs assume fabricated steel contact vessels with
baked phenolic linings, a resin depth of 6 feet, housing for the columns, and
all piping and backwash facilities.
Operation and maintenance costs include electricity for backwashing
(after 150 bed volumes have been treated) and periodic repair and replacement
costs. Costs for regenerant chemicals are not included because they vary
depending on the types and concentrations of target chemicals to be removed
from the wastewater.
TABLE 10-11.
GENERAL COST DATA FOR VARIOUS SIZES OF EXCHANGE UNITS
Plant Ccpacity (gpm) Construction Operation and
Cost ($)* Maintenance Costs
($/year)*
50
195
305
438
597
84,105
116,200
134,770
154,000
180,270
14,530
21,260
24,280
27,590
31,531
*Updated from 1979 to 1984 dollars using third quarter Marshall and Swift
Index.
Source: Adapted from Hansen, Gumerman, and Gulp, 1979.
10-39
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10.1.7 Reverse Osmosis
10.1.7.1 General Description
Osmosis is the spontaneous flow of solvent (e.g., water) from a dilute
solution through a semipermeable membrane (impurities or solute permeates at a
much slower rate) to a more concentrated solution. Reverse osmosis is the
application of sufficient pressure to the concentrated solution to overcome
the osmotic pressure and force the net flow of water through the membrane
toward the dilute phase. This allows the concentration of solute (impurities)
to be built up in a circulating system on one side of the membrane while
relatively pure water is transported through the membrane. Ions and small
molecules in true solution can be separated from water by this technique.
The basic components of a reverse osmosis unit are the membrane, a
membrane support structure, a containing vessel, and a high pressure pump.
The membrane and membrane support structure are the most critical elements.
10.1.7.2 Applications/Limitations
Reverse osmosis (RO) is used to reduce the concentrations of dissolved
solids, both organic and inorganic. In treatment of hazardous waste
contaminated streams, use of reverse osmosis would be primarily limited to
polishing low flow streams containing highly toxic contaminants. In general,
good removal can be expected for high molecular weight organics and charged
anions and cations. Multivalent ions are treated more effectively than are
univalent ions. Recent advances in membrane technology have made it possible
to remove such low moelcular weight organics as alcohols, ketones, amines, and
aldehydes (Gooding, 1985). Table 10-12 shows removal results obtained during
testing of a mobile RO unit using two favorable membrane materials (Whittaker,
1984).
RO Units are subject to chemical attack, fouling, and plugging.
Pretreatment requirements can be extensive. Wastewater must be pretreated to
remove oxidizing materials such as iron and maganese salts, to filter out
particulates, adjust pH to a range of 4.0 to 7.5, and to remove oil, grease,
and other film forms (De Renzo, 1978). The growth of slimy biomass on the
membrane surface or the presence of organic macromolecules may also foul the
membrane. This organic fouling can be minimized by prechlorination, addition
of biocides and/or pretreatment with activated carbon (Ghassemi, Yu, and
Quinlivan, 1981).
10.1.7.3 Design Considerations
The most critical design consideration applicable to reverse osmosis
technology is the design of the semipermeable membrane. In addition to
10-40
-------
TABLE 10-12.
RESULTS OF PILOT SCALE TESTING OF A REVERSE OSMOSIS UNIT
Percent removed in permeate
Chemical
Dichloromethane
Acetone
1 , 1-Dichloroethene
Tetrahydro f uran
Diethyl ether
Chloroform
1 , 2-Dichlorethane
1,1,1-Trichloro-
ethane
Trichloroethene
Benzene
Bromoform
Hexane
Feed
Concentration
(ppb)
406
110
34
17,890
210
270X
99
659
241
539
121
^
Percent
Concentrated
in Concentrate
203
355
795
467
439
567
415
651
346
491
633
704
Polyether-
polysul phone
membrane
58
84
99
98
97
98
92
99.8
99
99
99.1
99.8
Polyester/
amide poly-
sul phone
membrane
52
76
95
89
89
92
85
97
92
99
98
97
1. no standard available; concentration estimated.
Source: Whittaker, 1984
10-41
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allowing the achievement of the required degree of separation at an economic
flux level under ideal conditions, the membrane must be incorporated in an
operating system which satisfies- these practical requirements (Conway and
Ross, 1980):
o Minimum concentration polarization, ie., ratio of impurity
concentration at the membrane surface to that in the bulk stream
o High packing density, i.e., membrane surface area per unit volume of
the pressure module
o Ability to handle any particulate impurities (by proliferation if
necessary)
o Adequate support for the membrane and other physical features such as
effectiveness of seals, ease of membrane replacement, and ease of
cleanning.
Membranes are usually fabricated in flat sheets or tubular forms and are
assembled into modules. The most common materials used are cellulose acetate
and other polymers such as polyamides and polyether-polysulphone. There are
three basic module designs: tubular, hollow fiber, and spiral wound. These
are illustrated in Figure 10-11. Each type of membrane module has its own
advantages and limitations. The tubular module provides the largest flow
channel and allows for turbulent fluid flow regime; thus, it is least
susceptible to plugging caused by suspended solids and has the highest flux.
However, because of its small area/volume ratio the total product recovered
per module is small. The cost of a tubular module is approximately five times
that for the other modules for an equivalent rate of water recovery, and the
total space requirement is about three to five times that for the spiral wound
system (Ghassemi, Yu and Quinlivan, 1981).
A hollow fiber membrane is constructed of polyamide polymers and
cellulose triacetate by Dupont and Dow, respectively. The polyamide membrane
permits a wider operating pH range than cellulose acetate, which is commonly
used for the construction of spiral wound and tubular membranes. The flow
channel and the flux are about an order of magnitude lower than thee other
configurations. This small flux, however, is compensated for by the large
surface area/volume ratio, with the total product water per module being close
to that obtainable with spiral wound modules. However, because of the small
size of the channels (about 0.004 in.) and the laminar fluid flow regime
within the channels, this module is susceptible to plugging and may require
extensive pretreatment to protect the membrane (Ghassemi, Yu and Quinlivan,
1981).
The spiral wound module consists of an envelope of flat sheet membranes
rolled around a permeate collector tube. This configuration provides for a
higher flux and greater resistance to fouling than the hollow fiber modules;
it is also less expensive and occupies less space than a tubular module
(Ghassemi, Yu and Quinlivan, 1981).
10-42
-------
FIGURE 10-11. MEMBRANE MODULE CONFIGURATIONS
A. TUBULAR MEMBRANE
CASING
MEMBRANE
WATER
FLOW
b. SPIRAL-WOUND MODULE
ROLL TO
ASSEMBLE
FEED FLOW
V
PERMEATE FLOW
(AFTER PASSAGE
THROUGH MEMBRANE
FEED SIDE
SPACER
X
PERMEATE OUT
PERMEATE SIDE BACKING
MATERIAL WITH MEMBRANE ON
EACH SIDE AND GLUED AROUND \
EDGES AND TO CENTER TUBE
c. HOLLOW-FIBER MODULE
CONCENTRATE
OUTLET
FLOW
SCREEN
OPEN END
OF FIBERS
EPOXY
TUBE SHEET
POROUS
BACK-UP DISC
SNAP RING
"O" RING
SEAL
END PLATE
PERMEATE
FIBER
SHELL
POROUS FEED
DISTRIBUTOR
TUBE
"O" RING END PLATE
SEAL
Source: Ghassemi, Yu ft Quinlivan, 1981
10-43
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10.1.7.4 Technology Selection/Evaluation
Reverse osmosis is an effective treatment technology for removal of
dissolved solids presuming appropriate pretreatment has been performed for
suspended solids removal, pH adjustments, and removal of oxidizers, oil, and
grease. Because the process is so susceptible to fouling and plugging,
on-line monitors may be required to monitor pH, suspended solids, etc. on a
continuous basis. Reverse osmosis has not been widely used for treatment of
hazardous wastes.
Reverse osmosis will not reliably treat wastes with a high organic
content, as the membrane may dissolve in the waste. Lower levels of organic
compounds may also be detrimental to the unit's reliability, as biological
growth may form on a membrane fed an influent containing biodegradable
organics.
The fact that RO units can be operated in series or in parallel provides
some flexibility in dealing with increased flow rates or concentration of
dissolved species.
Memtek Corporation of Ontario, Canada has developed a mobile reverse
osmosis unit for Environment Canada. The unit, which is capable of handling
low flows of about 10 gpm is currently being tested for various types of
spills (Whittaker, 1984).
The volume of the reject generated by reverse osmosis is about 10 to
25 percent of the feed volume. Provisions must be made to treat this
potentially hazardous waste.
10.1.7.5 Costs
Costs for various sizes of reverse osmosis units are presented in Table
10-13. The construction costs include housing, tanks, piping, membranes, flow
meters, cartridge filters, acid and polyphosphate feed equipment, and cleanup
equipment. These costs are based on influent total dissolved solids concen-
trations of less than 10,000 ppm.
The operation and maintenance costs include electricity for the high
pressure feed pumps (450 psi operating pressure), building utilities, routine
periodic repair, routine cleaning, and membrane replacement every 3 years.
Operation and maintenance costs do not include costs for pretreatment
chemicals due to extreme usage rate variability between plants.
10-44
-------
TABLE 10-13.
GENERAL COST DATA FOR VARIOUS SIZES OF REVERSE OSMOSIS UNITS
Plant Capacity (gpra)
1.74
7
70
700
Construction
Costs ($)*
17,070
33,280
171,820
1,014,600
O&M Costs
($/year)
7,580
12,070
40,829
249,930
*Updated from 1979 to 1984 dollars using third quarter Marshall and Swift
Index.
Source: Adapted from dansen, Gumertnan, and Gulp, 1979.
The RO unit being tested by Environment Canada can handle flow up to
11,000 gpd and costs approximately $60,000. Membranes vary considerably in
cost. The Toray and DSI membranes discussed in Table 10-12, for example, cost
$360 and $915, respectively (Whittaker et al., 1985).
10.1.8 Neutralization
10.1.8.1 General Description
Neutralization consists of adding acid or base to a waste in order to
adjust its pH. The most common system for neutralizing acidic or basic waste
streams utilizes a multiple compartmental basin usually constructed of
concrete. This basin is lined with acid brick or coated with a material
resistant to the expected environment.
In order to reduce the required volume of the neutralization basin,
mixers are installed in each compartment to provide more intimate contact
between the waste and neutralizing reagents, thus speeding up reaction time.
Stainless steel plates mounted on the floor of the pit and directly below the
mixers will reduce corrosion damage to the structure. Basin inlets are
baffled to provide for flow distribution, while effluent baffles can help to
prevent foam from being carried over into the receiving stream (Conway and
Ross, 1980).
10-45
-------
In some cases, neutralization may be accomplished in a discharge sewer.
10.1.8.2 Application/Limitation
Neutralization can be applied to any wastestream or wastewater requiring
pH control. It is commonly used prior to biological treatment, since bacteria
are sensitive to rapid pH changes and values outside a pH range of 6 to 9.
Similarly, aquatic ecosystems are pH sensitive, therefore neutralization of
wastewater is required prior to discharge to a receiving water body. In the
case where hazardous wastes are hazardous because of corrosivity, neutraliza-
tion may be required prior to acceptance for disposal. It is also used as a
pretreatment for several chemical treatment technologies, including carbon
adsorption, ion exchange, air stripping, wet air oxidation, and chemical
oxidation/reduction processes. A pH adjustment is also dictated in several
other situations, including protection of construction materials, breaking of
emulsions, insolubilization of certain organic materials, and control of
chemical reaction rates (e.g., chlorination) (Conway and Ross, 1980).
10.1.8.3 Design Considerations
The choice of an acidic reagent for neutralization of an alkaline
wastewater is generally between sulfuric acid and hydrochloric acid. Sulfuric
acid is usually used due to its lower cost. Hydrochloric acid has the
advantage of soluble reaction end products.
The selection of a caustic reagent is usually between sodium hydroxide
and various limes; ammonium hydroxide is occasionally used. The factors to be
considered in choosing the most suitable reagent include: purchase cost,
neutralization capacity, reaction rate, storage and feeding requirement, and
neutralization products.
Although sodium hydroxide costs much more than the other materials, it is
frequently used due to uniformity, ease of storage and feeding, rapid reaction
rate, and soluble end products. The lime materials have the advantage of
relatively low cost. This low material cost is at least partially offset by
increased capital and operating costs for the rather complex feeding and
reaction system required (Conway and Ross, 1980).
While the rate of reaction between the completely ionized sodium
hydroxide and a strong acid waste is virtually instantaneous, the reactions of
lime bases require considerable time for completion. Reaction time can be
minimized by several approaches: a relatively high end point pH level,
efficient mixing, and slurry feeding as opposed to dry feeding (Conway and
Ross, 1980).
10-46
-------
10.1.8.4 Technology Selection/Evaluation
Neutralization is a relatively simple unit treatment process which can be
performed using readily available equipment. Only storage and reaction tanks
with accessory agitators and delivery systems are required. Because of the
corrosivity of the wastes and treatment reagents, appropriate materials of
construction are needed to provide a reasonable service-life for equipment.
The process is reliable provided pH monitoring units are used. The feed of
the neutralization agent may be regulated automatically by the pH monitoring
unit thereby ensuring effective neutralization and minizing worker contact
with corrosive neutralizing agents.
Neutralization of hazardous wastes has the potential of producing air
emissions. Acidification of streams containing certain salts, such as
sulfide, will produce toxic gases. Feed tanks should be totally enclosed to
prevent escape of acid fumes. Adequate mixing should be provided to disperse
the heat of reaction if wastes being treated are concentrated. The process
should be controlled from a remote location if possible.
10.1.8.5 Costs
Capital costs for a neutralization system include costs for chemical
storage, chemical feeding and mixing. These costs can be approximated using
Figure 10-7.
10.1.9 Gravity Separation
10.1.9.1 General Description
Gravity separation is a purely physical phenomenon in which the oil is
permitted to separate from water in a conical tank.
10.1.9.2 Applications/Limitations
Gravity separators are primarily used to treat two-phased aqueous wastes.
A typical application would be separation of free gasoline or fuel oil from a
fuel contaminated aquifer. Gravity separation has also been used to separate
PCS oils from contaminated groundwater. For efficient separation, the
nonaqueous phase should have a significantly different specific gravity than
water and should be present as a nonemulsified substance. Emulsion between
water and oil is common, and an emulsion breaking chemical must frequently be
added to the waste for efficient treatment.
10-47
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10.1.9.3 Design Considerations
Gravity separators can take many shapes and arrangements, depending in
part on the characteristics of the waste. The modern trend is to keep
separator design small and simple to reduce costs. Typical design configura-
tions include: horizontal cylindrical decanters, vertical cylindrical
decanters, and cone-bottomed settlers.
Baffles are frequently installed to provide additional surface area,
which promotes oil droplet coalescence. The cone-bottomed design is
particularly useful if heavy solids are to be settled out of the waste while
oil separation is proceeding.
10.1.9.4 Technology Selection/Evaluation
Gravity separation offers a straightforward, effective means of phase
separation provided the oil and water phases separate adequately within the
residence time of the tank. Simple, readily available equipment can be used
and operational requirements are minimal. If emulsion-breaking chemicals must
be added to promote oil-water separation, laboratory tests should be period-
ically conducted to ensure adequate dosing.
Consideration must also be given to the disposal of the extracted waste
constituents collected. For gravity separation processes, this material
consists of immiscible oil siphoned from the separator.
10.1.10 Air Stripping
10.1.10.1 General Description
Air stripping is a mass transfer process in which volatile contaminants
in water or soil are transferred to gas.
As shown in Figure 10-12, there are four basic equipment configurations
used to air strip liquids.
Air stripping is frequently accomplished in a packed tower equipped with
an air blower. The packed tower works on the principle of countercurrent
flow. The water stream flows down through the packing while the air flows
upward, and is exhausted through the top. Volatile, soluble components have
an affinity for the gas phase and tend to leave the aqueous stream for the gas
phase. In the cross-flow tower, water flows down through the packing as in
the countercurrent packed column, however, the air is pulled across the water
flow path by a fan. The coke tray aerator is a simple, low-maintenance
process requiring no blower. The water being treated is allowed to trickle
10-48
-------
FIGURE 10-12. AIR STRIPPING EQUIPMENT CONFIGURATIONS
PACKED COLUMN
INFLUENT-
DISTRIBUTOR
INFLUENT
DIFFUSED AIR BASIN
AIR SUPPLY
:r£F
SUPPORT
PLATE
br— INCOMING
,,. ^ *'"
EFFLUENT!
COKE TRAY AERATOR
RAW WATER
INUTT-0
DDDD
noon
•SPLASH
APRONS
•OUTLBT
•EFFLUENT
CROSS-FLOW TOWER
AIR,OUTLET
INLET
COLLECTION
BASIN
Source: Canter and Knox, 1985
through several layers of trays. This produces a large surface area for gas
transfer. Diffused aeration stripping and induced draft stripping use
aeration basins similar to standard wastewater treatment aeration basins.
Water flows through the basin from top to bottom or from one side to another
with the air dispersed through diffusers at the bottom of the basin. The
air-to-water ratio is significantly lower than in either the packed column or
the cross-flow tower (Canter and Knox, 1985).
10.1.10.2 Applications/Limitations
Air stripping is used to remove volatile organics from aqueous waste-
streams. Generally components with Henry's Law constants of greater than
0.003 can be effectively removed by air stripping (Conway and Ross, 1980).
This includes such components as 1,1,1-trichloroethane, trichloroethylene,
chlorobenzene, vinyl chloride, and dichloroethylene. The feed stream must be
low in suspended solids and may require pH adjustment of hydrogen sulfide,
phenol, ammonia, and other organic acids or bases to reduce solubility and
improve transfer to the gas phase. Stripping is often only partially
effective and must be followed by another process such as biological treatment
or carbon adsorption. Combined use of air stripping and activated carbon can
be an effective way of removing contaminants from groundwater. The air
stripper removes the more volatile compounds not removed by activated carbon
10-49
-------
and reduces the organic load on the carbon, thus reducing the frequency (and
expense) of carbon regeneration.
The countercurrent packed tower has been the most widely used equipment
configuration for air stripping at hazardous waste sites. The reason for this
are (Canter and Knox, 1985):
(1) It provides the most liquid interfacial area.
(2) High air-to-water volume ratios are possible due to low air pressure
drop through the tower.
(3) Emission of stripped organics to the atmosphere may be environ-
mentally unacceptable; however, a countercurrent tower is relatively
small and can be readily connected to vapor recovery equipment.
The major disadvantage of the packed column is the high energy cost.
10.1.10.3 Design Considerations
The design of a packed tower air stripper generally involves a deter-
mination of the cross-sectional area of the column and the height of the
column packing. The cross-sectional area of the column is determined from
physical properties of the air flowing through the column, the characteristics
of the packing and the air-to-water flow ratio.
A key factor is the establishment of an acceptable air velocity. A
general rule of thumb used for establishing the air velocity is that an
acceptable air velocity is 60% of the air velocity at flooding. Flooding is
the condition in which the air velocity is so high that it holds up the water
in the column to the point where the water becomes the continuous phase rather
than the air. If the air-to-water ratio is held constant, the air velocity
determines the flooding condition. For a selected air-to-water ratio, the
cross-sectional area is determined by dividing the air flow rate by the air
velocity. The selection of the design air-to-water ratio must be based upon
experience or pilot-scale treatability studies. Treatability studies are
particularly important for developing design information for contaminated
ground water (Canter and Knox, 1985).
10-50
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The height of column packing may be determined by the following equation
(Canter and Knox, 1985):
In
-(1-A) + A
where
KLaC(l-A)(l-X)M
Z = height of packing, ft.
L = water velocity, Ib-mole/hr/ft
X~ = influent concentration of pollutant in ground water, mole
fraction
.
effluent concentration of pollution in ground water, mole
fraction
K a = mass transfer coefficient, gal./hr.
C = molar density of water = 3.47 Ib-mole/ft
H = Henry's law constant, mole fraction in air per mole fraction in
water
G = air velocity, Ib-mole/hr/f t
A = L/HG
(l-X)M = the average of one minus the equilibrium water concentration
through the column
Y, = influent concentration of pollutant in air, mole fraction
In most cases, the following assumption can be made :
(1) Y. = 0, there should be no pollutants in the influent air.
(2) (l-X)M = 1, the influent concentrations should be too small when converted
to mole fraction to shift this term significantly from 1.0.
The packing column height can then be determined by the simplified equation:
^2_ (1-A) + A | L
In I X
Z = ——
TO, a C(l-A)
"]
The mass transfer coefficient, Ka, is determined from pilot-scale
treatability studies, and is a function of type of compound being removed,
air-to-water ratio, groundwater temperature, type of packing and tower
geometry (Canter and Knox, 1985).
Calgon Carbon Corporation maintains a computer modelling system which
determines the appropriate tower diameters, parking heights, air/water ratios
and tower packing for a particular aplication (Calgon Carbon Corp. 1983).
This system facilitates rapid mobilization of the packed tower equipment to a
site.
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10.1.10.4 Technology Selection/Evaluation
In recent years, air stripping has gained increasing use for the
effective removal of volatile organics from aqueous wastestreams. It has been
used most cost-effectively for treatment of low concentrations of volatiles or
as a pretreatment step prior to activated carbon. Calgon manufacturers a
treatment system which combines air stripping and activated carbon.
The equipment for air stripping is relatively simple, start-up and
shut-down can be accomplished quickly, and the modular design of packed towers
makes air stripping well suited for hazardous waste site applications.
An important factor in the consideration of whether to utilize air
stripping technology for the removal of volatile contaminants is the air
pollution implications of air stripping. The gas stream generated during
treatment may require collection and subsequent treatment or incineration.
10.1.10.5 Costs
Packed tower air strippers have higher removal efficiencies than induced-
draft systems, which are similar to diffused aeration systems. However, the
induced-draft system is lower in capital cost and requires less energy to
operate than a packed-tower system. Table 10-14 describes the installed cost
of an induced-draft stripper manufactured and marketed by the Calgon Carbon
Corporation. As shown in Table 10-14, the installed cost of an induced-draft
stripper, capable of treating 700 gpm and removing 75 percent of the TCE
contamination, is about 31 percent ($19,000 vs. $61,300) of the cost of a
packed-tower capable of removing 95 percent of the TCE. Assuming that a well
pump with a minimum discharge head of 25 pisig is required to feed both units,
the packed-tower also uses an additional $5,100 per year in electrical energy
for operation of the blower.
In a typical treatment system, re-pumping of the treated water would be
required. Adding the cost of a sump, flow control, and a pump, the overall
project cost for the induced-draft system would be about one-half the cost of
the packed tower system (Calgon Carbon Corp., undated).
10.1.11 Oxidation
10.1.11.1 General Description
Reduction-oxidation (redox) reactions are those in which the oxidation-
state of at least one reactant is raised while that of another is lowered. In
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TABLE 10-14. AIR STRIPPING COST ESTIMATES
(Basis: 700 gpm; 1000 micrograms/liter TCE)
Induced-Draft
Stripper
(75% Removal)
Air Stripping Equipment
Stripper Assembly & Installation
Equipment Sub-total
Recharge Pump; Assembly and Controls
Found at ion/ Sump
Equipment Freight
Project Management
Project Contingency
Total
$15,000
4,000
$19,000
$16,000
18,000
2,000
10,000
7,000
$72,000
9
Packed-Tower
5-ft Diameter
(95% Removal)
$42,300
19,000
$61,300
$16,000
23,700
5,000
20,000
20,000
$146,000
Saigon Model No. 909B (8'0" x 9'1" x 9' 0").
2
Tower is made of fiberglass reinforced plastic and contains 15 ft. of 2-in.
diameter polypropylene pall ring packing.
3
Cost includes tower, packing, packing support, detnister, 4,000 cfm fan with
10 hp motor, damper, piping valves, and ductwork.
4
Sump 5" x 5" x 8' below grade concrete.
Source: O'Brien and Stenzel, undated.
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chemical oxidation, the oxidation state of the treated compound(s) is raised.
For example in the conversion of cyanide to cyanate under alkaline conditions
using permanganate, the oxidation state of the cyanide ion is raised as it
combines with an atom of oxygen to form cyanate. This reaction can be
expressed as follows:
2 NaCN + 2KMnO, + KOH 2 K MNO, + NaCNO + H_0
Common commercially available oxidants include potassium permanganate,
hydrogen peroxide, calcium or sodium hypochlorite and chlorine gas.
10.1.11.2 Applications/Limitations
Chemical oxidation is used primarily for detoxification of cyanide and
for treatment of dilute waste streams containing oxidizable organics. Among
the organics for which oxidative treatment has been reported are: aldehyde,
mercaptans, phenols, benzidine, unsaturated acids and certain pesticides
(Kiang and Metry, 1982).
Chemical oxidation can be an effective way of pretreating wastes prior to
biological treatment; compounds which are refractory to biological treatment
can be partially oxidized making them more amenable to biological oxidation.
One of the major limitations with chemical oxidation is that the
oxidation reactions frequently are not complete (reactions do not precede to
C0_ and HLO) . Incomplete oxidation may be due to oxidant concentration, pH,
oxidation potential of the oxidant, or formation of a stable intermediate
(Kiang and Metry, 1982). The danger of incomplete oxidation is that more
toxic oxidation products could be formed. Chemical oxidation is not well
suited to high-strength, complex waste streams. The most powerful oxidants
are relatively non-selective and any oxidizable organics in the waste stream
will be treated. For highly concentrated waste streams this will result in the
need to add large concentrations of oxidizing agents in order to treat target
compounds. Some oxidant such as potassium permanganate can be decomposed in
the presence of high concentrations of alcohols and organic solvents (Kiang
and Metry, 1982).
10.1.11.3 Design Considerations
Equipment requirements for chemical oxidation are simple and include
contact vessels with agitators to provide suitable contact of the oxidant with
the waste, storage vessels and chemical metering equipment. Some
instrumentation is required to determine pH and the degree of completion of
the oxidation reaction. Some oxidizing reagents react violently in the
presence of significant quantities of readily oxidizable materials. Therefore
reagents must be added in small quantities to avoid momentary excesses.
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10.1.11.4 Technology Selection/Evaluation
Oxidation reactions can be carried out using simple, readily available
equipment; only storage vessels, metering equipment, and contact vessels with
agitators are required. However, implementation is complicated because every
oxidation/reduction reaction system must be designed for the specific
application. Laboratory- and/or pilot-scale testing are essential to
determine the appropriate chemical feed rates and reactor retention times in
accordance with reaction kinetics. Oxidation and reduction has not been
widely used in treating hazardous wastestreams.
A major consideration in electing to utilize oxidation technology is that
the treatment chemicals are invariably hazardous, and great care must be taken
in their handling. In particular, the handling of many oxidizing agents is
potentially hazardous and suppliers' instructions should be carefully
followed.
In some cases, undesirable byproducts may be formed as a result of
oxidation. For example, addition of chlorine can result in formation of
bio-resistant end products which can be odorous and more toxic than the
original compound. The possibility of this undesirable side reaction needs to
be considered when using chlorine for oxidation of wastewaters (Conway and
Ross, 1980).
10.1.11.5 Costs
Capital costs for chemical oxidation include costs for chemical storage,
chemical feeding and chemical mixing. These costs can be approximated using
Figure 10-7. Chemical costs are listed in Table 9-10.
10.1.12 Chemical Reduction
10.1.12.1 General Description
Chemical reduction involves addition of a reducing agent which lowers the
oxidation of a substance in order to reduce toxicity or solubility or to
transform it to a form which can be more easily handled. For example, in the
reduction of hexavalent chromium (Cr(Vl)) to trivalent chromium (Cr(lll))
using sulfur dioxide the oxidation state of Cr changes from 6+ to 3+ (Cr is
reduced) and the oxidization state of S increases from 2+ to 3+ (S is
oxidized). The decrease in the positive valence or increase in the negative
valence with reduction takes place simultaneously with oxidation in chemically
equivalent ratios (Kiang and Metry, 1982).
10-55
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+ 3S02 + 3H20 Cr
Commonly used reducing agents include sulfite salts (e.g. sodium
bisulfite, sodium metabisulfite, sodium hydrosulfite) sulfur dioxide and the
base metals (iron, aluminum and zinc).
10.1.12.2 Applications/Limitations
Chemical reduction is used primarily for reduction of hexavalent
chromium, mercury and lead. There are currently no practical applications
involving reduction of organic compounds.
10.1.12.3 Design Considerations
Very simple equipment is required for chemical reduction. This includes
storage vessels for the reducing agents and perhaps for the wastes, meterring
equipment for both streams, and contact vessels with agitators to provide
suitable contact of reducing agent and waste. Some instrumentation is
required to determine the concentration and pH of the waste and the degree of
completion of the reduction reaction. The reduction process may be monitored
by an oxidation-reduction potential (ORP) electrode (Kiang and Metry, 1982).
10.1.12.4 Technology Selection/Evaluation
Chemical reduction is well demonstrated for the treatment of lead,
mercury and chromium. However, for complex waste streams containing other
potentially reducible compounds, laboratory and pilot scale tests will be
required to determine appropriate chemical feed rates and reactor retention
times.
Chemical reduction can be carried out using simple, readily available
equipment and reagents. Capital and operating costs are low and the process
is easy to implement.
10.1.12.4 Costs
Capital costs for chemical reduction include costs for chemical storage,
chemical feeding, and chemical mixing. These costs can be approximately using
Figure 10-7.
10-56
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10.2 Solids Treatment
10.2.1 Solids Separation
This section describes equipment and methods used to separate solids from
slurries, and/or to classify contaminated soils or slurries according to grain
size. The objective of separating solids from slurries is to attain two
distinct waste streams: a liquid waste stream that can be subsequently
treated for removal of dissolved and fine suspended contaminants; and a
concentrated slurry of solids and minimal liquid that can be dewatered and
treated.
Classification of particles according to grain size may be undertaken for
one of two reasons. The first reason is that more efficient use can be made
of equipment and land area by taking advantage of the differences in settling
velocity of different sized particles. For example, where only limited land
space is available, settling basins may be used to remove sand and gravel with
a high settling velocity and then high rate gravity settlers could be used to
remove fine-grained particles.
There is recent evidence to suggest that classification by grain size is
important in managing hazardous waste contaminated soils and sediments because
of the apparent tendency of contaminants to adsorb preferentially onto
fine-grained materials such as clay and organic matter. The separation of
solids by grain size and level of contamination could prove to be extremely
beneficial to the overall management (treatment, transport, and disposal) of
contaminated soil material. Whereas relatively non-contaminated soils and
sediments may be disposed of in ordinary sanitary landfills or discharged back
into the stream, the highly contaminated solids must be disposed in a hazard-
ous waste landfill, incinerated or treated to render them non-hazardous.
The most appropriate solids separation method for a given site depends
upon several factors, including the following:
• Volume of contaminanted solids
• Composition of soils or sediments, including gradation, percent clays,
and percent total solids
• Types of dredging or excavation equipment used, which determines the
feed rate to solids separation and, in the case of slurries, the
percent solids
• Site location and surroundings. The available land area and ultimate
or present land use may limit the type of system that can be utilized.
Solids separation methods addressed in this section include: sieves and
screens, hydraulic and spiral classifiers, cyclones, settling basins and
clarifiers.
10-57
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Many of the methods presented in this section are discussed in terms of
their ability to treat soils slurries or sediments containing particle within
a specific size range. Table 10-15 summarizes the particle sizes which
correspond to various soil types.
10.2.1.1 Screens and Sieves
Sieves or screens consist of bars, woven wire or perforated plate
surfaces which retain particles of a desired size range while allowing smaller
particles and the carrying liquid to pass through the openings in the
screening surface. Several types of screens and sieves have application for
solids separation at hazardous waste sites.
a. Grizzlies
General Description—Grizzlies consist of parallel bars which are
frame-mounted on an angle to promote materials flow and separation. Hoppers
are provided beneath the grizzly to collect removed material. Bar spacing is
generally 1 to 5 inches apart depending upon the desired separation. Both
TABLE 10-15. APPROPRIATE PARTICLE SIZES FOR VARIOUS SOIL CATEGORIES
USCS Classification U.S. Standard Sieve Size
Gravel
Coarse >3/4 in.
Fine No. 4 - 3/4 in.
Sand
Coarse No. 10 - No. 4
Medium No. 40 - No. 10
Fine No. 200 -No. 40
USCS Classification Particle Size (u)
Silt 10 - 74
Coarse Clay 1.0 - 10
Fine Clay <1.0
10-58
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fixed and vibrating grizzlies are available. Grizzlies generally have a
maximum width of 6 to 9 feet and a length of 12 to 18 feet (Mallory and
Nawrocki, 1974).
Applications/Limitations—Grizzlies are used primarily for scalping,
i.e., removing a small amount of oversized material from a stream which is
predominantly fines. They are generally limited to separating materials which
are 2 inches in diameter or coarser. Another major function of the grizzly is
to reduce velocity of a slurry for subsequent processing operations (Mallory
and Nawrocki, 1974).
Technology Selection/Evaluation—Grizzlies offer a reliable method for
removing coarse-grained material from slurries. By doing so, they
significantly improve the reliability and performance of subsequent solids
separation methods and also reduce maintenance costs by minimizing the amount
of abrasive material which reaches the screen, cyclone, etc. Grizzlies
contain no moving parts and are tough and abrasion resistant. Therefore
maintenance requirements are minimal. Space requirements are also minimal and
they can be installed in almost any area. They can easily be arranged in
series or parallel to accommodate very high flows or achieve classification of
coarse materials.
a. Moving Screens
General Description—Screening of fine particles from dry materials is
frequently accomplished using moving screens. Types of moving screens
include:
• vibrating screens
• revolving screens
• gyratory screens
Vibrating screens are more widely used than other screen types,
particularly for fine particle separation, because of their larger capacity
per unit of screen area and their higher efficiency (Perry and Chilton, 1973).
Only the vibrating screen will be described in this section.
Vibrating screens consist of a plane screening surface, usually stretched
tautly and set into a rectangular frame having sufficient sidewalls to confine
the material flow. Figure 10-13 illustrates a typical vibrating screen. They
may be composed of one, two or three screening decks. This allows for
progressively finer separation and lower space requirements. Screens are
usually inclined at a slope of approximately 20° from horizontal, although
horizontal screens are also available. Vibration is produced by circular
motion in a vertical plane. By vibration, the bed of material tends to
develop a fluid state. Larger particles remain on top of the bed while
smaller particles sift through the voids and find their way to the bottom.
Once the fine particles have sifted through the bed of material, the vibrating
action increases the probability that the small particles will pass through
10-59
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FIGURE 10-13. TYPICAL VIBRATING SCREEN
Screening Surface
Discharge End
Feed End
Source: Allis-Chalmers Corp., undated.
10-60
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the screen. An inclined screen allows the material to cascade down the screen
surface, increasing the probability that small particles will pass through
(Allis Chalmers, undated).
Vibrating screens typically range in size from about 3 to 10 feet wide
and 6 to 30 feet long. Solids handling capacity ranges from 300 to 950 tph.
Applications/Limitat ions—The function of vibrating screens is to
separate particles by grain size. The oversized particles are substantially
dewatered during the separation. Typically, vibrating screens are used to
separate materials in the size range of 1/8 inch up to 6 inches. However,
high speed vibrating screens are also available for separating finer particles
in the size range of 4 to 325 mesh (Chilton and Perry, 1973; Mallory and
Nawrocki, 1974). Although separation efficiencies are high with the vibrating
screen, some fine particles are invariably carried over with the coarse
particles. Conventional vibrating screens are best suited for handling dry
materials. Wet or sticky materials tend to blind the screen. Larger openings
can be used where blinding is a problem, but this reduces the efficiency of
the size separation. Vibrating screens with heated decks are also available
to reduce moisture content, although they are not cost-effective for waste
streams with a high moisture content. Because of these limitations, the
conventional vibrating screens are not well suited for handling dredge
slurries. Where the moisture content of the material is high resulting in
blinding wet screening with sprays can be used. Water is generally sprayed at
3 to 6 gpm per ton at a minimum of 20 psi to discourge blinding (Allis
Chalmers, undated).
The presence of abrasive material in the feed may result in the need for
frequent screen replacement. Therefore, wastes should be carefully
prescreened using a grizzly or wedge-bar screen.
Relative to other types of moving screens, vibrating screens generally
are the most efficient, have lowest space requirements and lowest maintenance
costs. Vibrating screens are the most efficient of the moving screens for
separating solids according to grain size. However, their reliability is
adversely affected by the fact that wet or sticky materials tend to blind the
screen. A water spray applied to a vibrating screen can significantly reduce
blinding. The effectiveness of vibrating screens should be determined on a
case-by-case basis.
The presence of abrasive material can result in the need for frequent
screen replacement thereby increasing maintenance costs.
Vibrating screens are relatively compact. They can be installed in areas
where space is limited and are well suited for use in mobile treatment
systems.
Cost—Costs for vibrating screens vary with the size and capacity of the
screens, The capital cost for a 10-ft. long, 5-ft. wide, 5-ft. high screen
with a capacity of 200 TPH is about $25,000. Operation and maintenance costs
10-61
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for vibrating screens are relatively low compared to other types of moving
screens (Allis Chalmers, undated; Derrick Manufacturing Corp., undated).
c. Stationary or fixed screens
Stationary or fixed screens differ from moving screens in that they
posess no moving parts. A continuous curved surface and the velocity of the
slurry across the surface provide a centrifugal force which holds the slurry
against the screens and allows for separation. One type of fixed screen which
has potential application for solids separation at hazardous waste sites is
the wedge-bar screen or bend-sieve. A typical wedge-bar screen is illustrated
in Figure 10-14. The hydrosieve, a modified wedge-bar screen which uses water
pressure to encourage solids separation is also used.
General Description—The wedge-bar screen is similar in design to a
grizzly insofar as it consists of parallel bars which are frame-mounted on a
curved deck. However, in the case of the wedged bar screen, bar spacing is
very close to effect fine particle separation. As the material enters the
feed inlet, a series of baffles in the feed box spread the material so that
the slurry is evenly fed over the width of the curved screen deck. The slurry
FIGURE 10-14. WEDGE BAR SCREEN
Self-Adjusting Feed Baffle
Screen Retainer
Screen
Surface
_. ^. , Undersize Discharge
Oversize Discharge
Source: Dorr-Oliver, 1983
10-62
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flows through the feed inlet at the top of the feed box and flows tangentially
down the surface of the screen. The continuous curved surface together with
the velocity across the surface provides a centrifugal force which holds the
slurry against the screen surface. As the slurry strikes the sharp edge of
the wedge bar, small particles are sliced off and directed downward through
the slots along with most of the liquid. Dewatered, oversized material slides
on top of the screen surface and is discharged. The slicing action of the
wedge bars sizes the undersize particles at a smaller dimension than the slots
themselves and helps to minimize blinding. For example, for a slot width of 1
mm, the thickness of the slurry layer being shaved off is about 1/4 mm. This
1/4 mm thick cut can transport particles of up to 1/2 mm in size; plus 1/2 mm
solids pass over the screen (Hoffman-Muntner Corporation., 1978; Dorr-Oliver,
1980; Dorr-Oliver, 1983).
Wedge-bar screens normally come in sizes of 2 to 6 feet wide, with
capacities of 30 to 200 gpm/ft .
The hydrosieve or pressure screen is a modification of the conventional
wedge-bar screen in which the pressure of a water spray encourages more
efficient separation. The water pressure helps to remove fines that are
adhering to coarse grain sized materials and breaks up clumps of material
which tend to clog the screen. Hydrosieves with capacities of up to 1500 gpm
are available.
Application/Limitation—Wedge-bar screens and hydrosieves are used to
separate particles in slurry by grain size. The wedge-bar screen is generally
less efficient in separating solids than the vibrating screen; the oversized
material typically carries a considerable amount of fines. The hydrosieve
minimizes this problem by employing a pressure spray which washes the fines
from the coarser material. Wedge bar screens may be used ahead of vibrating
screens. This provides a higher solids separation efficiency than the
vibrating screen alone (Allis Chalmers, undated).
Technology Selection/Evaluation—The wedge-bar screen offers a very low
cost method for separating solids according to grain size. However, the
effectiveness of the separation methods is not as good as that achieved using
vibrating screens or cyclones. Nevertheless, use of a water spray with a
wedge-bar screen (hydrosieve) can significantly improve separation efficiency
by removing fines which are sorbed to sands and gravel. The wedge-bar screen
contains no moving parts and is extremely easy to operate and maintain. It is
also more resistant to abrasion than the vibrating screen. It is compact and
requires a minimal amount of space.
10.2.1.2 Hydraulic Classifiers
a. General Description
Hydraulic classifiers are commonly used to separate sand and gravel from
slurries and classify them according to grain size. A typical hydraulic
classifier is shown in Figure 10-15. These units consist of elevated
10-63
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DC
Ul
CO
CO
o
u
DC
Q
>
in
6
m
DC
D
O
I
c
o
I
3
O
to
10-64
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rectangular tanks with v-shaped bottoms to collect the material. Discharge
valves which are located along the bottom of the tank are activated by motor-
driven vanes that sense the level of solids as they accumulate. The principal
of operation is simple. The slurry is introduced into the feed end of the
tank. As the slurry flows to the opposite end, solids settle out according to
particle size as a result of differences in settling velocity. Coarse
materials settle out first near the feed end and materials are progressively
finer along the length of the tank. Manually adjusted splitter gates below
the discharge valves can be used to selectively direct materials of specific
grain sizes to subsequent handling and treatment (Eagle, 1981; Mallory and
Nawrocki, 1974). Classifying tanks are generally available in sizes ranging
from 8 to 12 feet wide and 20 to 48 feet long (Mallory and Nawrocki, 1974).
Solids handling capabilities are generally limited to 250 to 350 tph (Mallory
and Nawrocki, 1974; Eagle Iron Works, 1981).
b. Applications/Limitations
Hydraulic classifiers are used to remove sand and gravel size particles
from slurries and to classify the removed materials according to grain size.
Materials are recovered from the classifier at about 30 percent moisture
content (Written communication, 1984 Eagle Iron Works, Des Moines, Iowa).
They are capable of removing and classifying materials within the size range
of 3/8 inch down to about 150 to 200 mesh (105 to 74 microns) (Mallory and
Nawrocki, 1974; Eagle Iron Works, 1981). The upper limitation of 3/8 inch is
handled by prescreen- ing the wastes to remove all large materials. Other
solids separation techniques are required to classify the fine-grained
materials «200 mesh). Another limitation is that some fines will be removed
with the sand and gravel fraction. This limitation is frequently overcome by
directing the solids to a spiral classifier where they are washed to remove
the fine-grained materials (see Section 10.2.1.3). Hydraulic classifers have
a relatively low solids handling capacity and are not well suited for handling
large volumes of flow or high-solids concentrations. A single average sized
tank with dimensions of 36 feet by 10 feet, for example, can handle 5300 gpm
when separating material down to 100 mesh and only 1400 gpm when separating
material down to 200 mesh (Eagle Iron Works, 1981).
Because of the inability of hydraulic classifiers to handle large volumes
of flow, a combination of solids separation methods may be advisable to reduce
the number of hydraulic classifiers needed for a large solids handling
operation. One possibility for reducing the number of classifers needed would
be to use these units to separate only those particles larger than 105
microns. Cyclones, hydrocyclones, or hydrosieves (see Sections 10.2.1.4 and
10.2.1.1) could then be used to remove the fine sand fraction (Mallory and
Nawrocki, 1974).
c. Technology Selection/Evaluation
Hydraulic classifers offer an effective method for operating and
classifying particles ranging in size from fine gravel to fine sands. Some
10-65
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fines are inadvertently removed with the sand and gravel, and the effective-
ness of the separation can be improved by washing the collected solids in a
spiral classifier to remove the fines.
Hydraulic classifier tanks are generally designed and sized to be truck
mounted for mobile system applications. Start-up and shut-down can be
accomplished quickly. Maintenance requirements are fairly simple.
Use of hydraulic classifiers can be easily integrated with other solids
separation methods and this is advisable where large flows are involved or
where classification of fine-grained materials (clays, silts) is required.
d . Co s t s
Costs for hydraulic classifiers vary with size and capacity of the
classifier. For a size range of 24 to 49 feet long, 8 to 12 feet wide, and 8
feet deep; and a feed rate of 200 to 350 TPH, the initial cost ranges from
$30,000 to $76,000 (Eagle Iron Works, 1981; Mallory and Nawroki, 1974).
10.2.1.3 Spiral Classifier
a. General Description
The spiral classifier consists of one or two long, rotating screws,
mounted on an incline within a rectangularly shaped tub. It is used primarily
to wash adhering clay and silt from sand and gravel fractions. Figure 10-16
shows a typical configuration of a spiral classifier.
The screw conveys settled solids from a hydraulic classifier (Section
10.2.1.2) up an incline to be discharged through an opening at the top of the
tub. Fines and materials of low specific gravity are separated from sand and
gravel through agitation and the abrading and washing action of the screw, and
are removed along with the wastewater overflow at the bottom of the tub. The
tumbling and rolling action caused by the continuous screw grinds particles
against each other and removes the deleterious material coating the sand
particles. This tumbling action also aids in dewatering materials by breaking
the moisture film on the sand particles. As the moisture is relieved of
surface tension, it is free to drain from the material (Eagle Iron Works,
1982). The sands which are finally discharged are substantially dewatered.
In general, the greater the length of the tub the higher the degree of
dewatering and the greater the screw diameter the larger the capacity of the
spiral classifier (Eagle Iron Works, 1982). Classifiers are available which
are capable of handling up to 950 tph.
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DC
UI
V)
W
u
(B
6
10-67
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b. Applications/Limitations
Spiral classifiers are used primarily to wash, dewater, and classify
sands and gravels up to 3/8 inch in diameter. They are not a singularly
viable solids separation technology, but they are effective when used together
with the hydraulic classifier. Spiral classifiers have a large capacity and
are completely portable.
c. Technology Selection/Evaluation
Spiral classifiers improve the efficiency of solids separation achieved
with the hydraulic classifier by removing fine grained materials attached to
coarser particles.
Spiral classifers are generally designed to be trailer mounted for use in
mobile treatment systems. Start-up and shut-down can be accomplished quickly
and maintenance requirements are simple.
d. Costs
Costs for spiral classifiers vary with size and configuration. For a
size range of 22 to 34 feet long, 8 to 19 feet wide, and 8 to 12 feet high the
initial cost of a spiral classifier ranges from $14,000 to $77,000 for a
single-screw-type; and from $37,000 to $150,000 for a double-screw-type.
Operational and maintenance costs vary with the type of power utilized; it can
be electricity, gas, or diesel fuel (Eagle Iron Works, 1982; Mallory and
Nawroki, 1974).
10.2.1.4 Cyclones and Hydrocyclone
a. General Description
Cyclones and hydrocyclones are separators in which solids that are
heavier than water are separated by centrifugal force. The major components
of a hydrocyclone are shown in Figure 10-17. A hydrocyclone consists of a
cylindrical/conical shell with a tangential inlet for feed, an outlet for the
overflow of slurry, and an outlet for the underflow of concentrated solids.
Cyclones and hydrocyclones contain no moving parts. The slurry is fed to the
unit with sufficient velocity to create a "vortex" action that forces the
slurry into a spiral and, as the rapidly rotating liquid spins about the axis
of the cone, it is forced to spiral inward and then out through a centrally
located overflow outlet. Smaller-sized particles remain suspended in the
liquid and are discharged through the overflow. Larger and heavier particles
of solids are forced outward against the wall of the cone by centrifugal force
10-68
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FIGURE 10-17. TYPICAL CYCLONE
Feed
Overflow
Air Core
Vortex Finder
Underflow
Source: Krebs Engineers, undated
10-69
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within the vortex. The solids spiral around the wall of the cyclone and exit
through the apex at the bottom of the cone (Dorr-Oliver, 1984).
Cyclones are available in an extremely wide range of sizes. The smallest
units handle flows of only a few gallons per minute, while the largest units
can handle between 2000 and 7000 gpm, depending upon slurry composition
(Dorr-Oliver, 1984; Krebs Engineers, undated). However, cyclones do not
scale-up as many other equipment types do. In general, the larger the cyclone
diameter and inlet, the coarser the separation and the greater the cyclone
capacity. The smaller the diameter and inlet, the finer the separation and
the lower the hydraulic capacity. In order to remove small particles from
large volume slurries, it is necessary to use multiple, small-diameter
cyclones connected in parallel. Banks of multiple cyclones, manufactured as a
single unit with a single feed pipe, are commercially available.
Cyclones can also be connected in series or in various staging arrange-
ments to accomplish different objectives. For example, a high degree of
particle size separation can be achieved by employing a bank of cyclones in
series with decreasing cyclone size and particle size removal in the direction
of flow. It is also possible to achieve a higher underflow concentration and
a more clarified overflow by staging the cyclones. The first stage of
cyclones could be used to classify the solids according to the desiged grain
size. The second stage overflow cyclone could serve as a clarifier and the
underflow cyclone could serve as the concentrator. However, the maximum
underflow concentration achievable with cyclones is about 60 percent, since
some liquid is necessary for solids discharge (Dorr-Oliver, undated).
It should be noted that cyclones are available which can handle some
variation in flow rate and particle size by interchanging certain parts of the
cyclone. For example, it is possible to add or delete sections to the cone,
or to change the size of the vortex finder.
b. Applications/Limitations
Cyclones are available for separating or classifying solids over a broad
particle size range, from 2000 microns down to 10 microns. However, in
hazardous waste site applications they would be used primarily to remove
smaller size particles from slurries and in situations where a sharp
separation by particle size is needed. They are particularly applicable to
situations where space is limited.
Cyclones are generally not effective for slurries with a solids
concentration greater than 30 percent, for highly viscous slurries, or for
separation of particle sizes with a specific gravity of less than about 2.5 to
3.2 (Krebs Engineers, undated). Slurries with a high clay content exhibit
high pseudoplasticity or high viscosity and cannot be effectively removed
using cyclones or hydrocyclones (Oklahoma State University, 1973).
10-70
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Cyclones are highly vulnerable to clogging by oversized particles, and a
high degree of prescreening (or use of progressively smaller cyclones in
series) may be needed to avert clogging.
c. Technology Selection/Evaluation
Cyclones offer an effective means of separating and classifying solids
over a broad range of particle size, provided the solids concentration is not
too high and the slurry is not too viscous. Cyclones are flexible insofar as
they can easily be arranged in parallel to accomplish fine size separation, or
in various series or staging arrangements to improve classification of the
overflow or concentration of the underflow. They can also be easily
integrated with other solids separation methods. However, each individual
cyclone is capable of handling only very limited variations in flow rate and
particle size.
The capital and operating costs of cyclones are relatively low. They are
simple to operate and easy to maintain since they contain no moving parts.
Liners require periodic replacement but this can be done easily.
Cyclone assemblies take up less space than most solids separation
equipment and are well-suited for tight locations. Because of their
compactness and simplicity of operation, cyclones are also well-suited for
inclusion in mobile treatment systems.
d . Co s t s
The cost of cyclones varies widely according to the size and the number
of cyclones placed in series. The feed rate can vary from a few gallons per
minutes up to several thousand gallons per minute, and the size of each
cyclone can vary from 1/2 inch to 30 inches in diameter. Initial costs for
cyclones can be as low as $5,000 and indefinately high, depending on the
configuration (Hoffman Muntnor Corp., 1978; Krebs Engineers, undated).
10.2.1.5 Settling Basin
A settling basin, as described in this section, is an impoundment, basin,
clarifier, or other container that provides conditions conducive to allowing
suspended particles to settle from a liquid by gravity or sedimentation. The
slurry is introduced into the basin and settling of solids occurs as the
slurry slowly flows across the length of the basin. Flow out of the opposite
end of the basin is reduced in its solids content.
The size of an impoundment basin or clarifier is ideally determined by
dividing the critical settling velocity by the overflow rate. The critical
settling velocity is a function of the diameter, and specific gravity of the
smallest particle size requiring removal and the viscosity of the water.
10-71
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However, ideal settling conditions are never achieved and the actual design of
the required surface area must make allowance for turbulence, short
circuiting, and scour velocity. Detailed procedures for sizing sedimentation
basins can be found in most wastewater engineering handbooks.
Settled solids accumulate on the bottom of settling basins where they are
temporarily stored. As the volume of accumulated solids increases, the
effective size of the basin decreases, reducing the basin's effectiveness or
efficiency. Accumulated solids must be periodically or continuously removed
in order for the basin to perform as intended.
Commonly used types of settling basins are described below:
a. Impoundment Basin
General Description — An impoundment basin is an earthen impoundment or
diked area that is lined in a manner that is appropriate for protecting
underlying groundwater. An adjustable weir is provided to control overflow
rate. A typical impoundment basin is illustrated in Figure 10-18.
Multiple basins, or bulkheads that separate a single basin into
compartments can be used in parallel to allow continuous sediment/water
separation while accumulated solids are being removed from individual basins.
Multiple basins can also be connected in series in order to separate solids
according to grain size. Each basin would be designed to retain sediments of
increasingly smaller grain size.
Applications/Limitat ions — Impoundment basins are used to remove
particles in the size range of gravel down to fine silt (10 to 20 microns with
flocculants) (Mallory and Nawrocki, 1974). They are also used to provide
temporary storage of dredged material and to classify sediment particles
according to grain size.
Impoundment basins are particularly well-suited for large-scale dredging
operations, provided there is adequate land space available for their
construction. They are not suitable for congested areas, or for areas where
adequate measures cannot be taken to protect groundwater supplies (e.g., high
groundwater table).
A major limitation with the use of impoundment basins is that unlike
clarifiers, they have no mechanism for solids collection. Therefore,
mechanical dredges (e.g., clamshells, backhoes) are typically used to remove
the settled solids. This greatly increases the operational costs associated
with use of impoundment.
b. Conventional Clarifers
General Description — Conventional clarifers are rectangular or circular
settling basins which are typically equipped with built-in solids collection
and removal mechanisms.
10-72
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FIGURE 10-18.
CONCEPTUAL DIAGRAM OF A DREDGED MATERIAL CONTAINMENT AREA
MOUNDED COARSE-GRAINED
DREDGED MATERIAL
DEAD ZONE
AREA FOR SEDIMENTATION
.DEAD ZONE
PLAN
PONDING DEPTH.
FOR^DlMEf'jfAfioN"
FREEBOARD
FOR HNE-GRANED
DREDGED MATERIAL STORAGE
COARSE-GRAINED
DREDGED MATERIAL
CLAY LINER SYSTEM
EFFLUENT
TO TREATMENT
CROSS SECTION
Source: Adapted from Palermo et al., 1978
10-73
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Typically, in a rectangular clarifier a flow with relatively high
suspended solids is introduced at one end of the clarifier, solids settle
along the length of flow, and a flow with relatively low suspended solids
leaves the clarifiers through trough-type overflow weirs. In most rectangular
clarifiers flights extending the width of the tank move the settled sludge
toward the inlet end of the tank. Some designs move the sludge toward the
effluent end of the tank, corresponding to the direction of flow of the
density current.
Circular clarifiers are of two general types. With the center feed type,
the waste is fed into a center well and the effluent is pulled off at the weir
along the outside. With a peripheral feed tank, the effluent is pulled off at
the tank center.
Figure 10-19 illustrates a center feed type clarifier. The circular
clarifer can be designed for center sludge withdrawal or vacuum withdrawal
over the entire tank bottom.
FIGURE 10-19. CIRCULAR CLARIFIER
Walkway truss
Skimmer
, \
Influent pipe
Side water
depth
Source: Dorr-Oliver, 1976
Many clarifiers are equipped with separate zones for chemical mixing and
precipitation, flocculation and settling.
Applications/Limitations — Clarifiers are able to remove particles down
to 10 to 20 microns (Mallory and Nawrocki, 1974) in diameter,with the use of
flocculants. They can also be used to produce a thickened sludge with a
solids concentration of about 4 to 12 percent (Metcalf and Eddy, 1979) and to
separate solids by grain size. This would be accomplished by connecting
clarifiers in series and providing a retention time sufficient to removal
materials of a certain grain size.
Clarifiers are best suited to small- to moderate-scale cleanup operations
or to large-scale operations where impoundment basins will not adequately
10-74
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protect groundwater supplies. Clarifiers can be barge mounted for solids
separation during dredging operations.
Circular clarifiers are generally more efficient in solids removal.
However, rectangular tanks are more suitable for barge-mounting and where
construction space is limited. In addition a series of rectangular tanks is
cheaper to construct due to the shared wall concept.
c. High Rate Clarifier
General Description — High rate clarifiers use multiple "stacked"
plates, tubes, or trays to increase the effective settling surface area of the
clarifier and decrease the actual surface area needed to effect settling.
Figure 10-20 illustrates a high rate clarifier. High rate clarifiers allow a
higher flow rate per unit of actual surface area (loading rate) than do
conventional clarifiers, thus the name "high rate" clarifiers. The trays,
plates, or tubes also induce optimum hydraulic characteristics for sedimen-
tation by guiding the flow, reducing short circuiting and promoting better
velocity distribution.
High rate clarifiers are able to handle between 2 to 10 times the loading
rate of conventional clarifiers and therefore require limited land use (Jones,
Williams and Moore, 1978). Package units capable of handling 1,000 to
2,000 gpm are available and are easily transportable by truck or barge.
Applications/Limitations — High rate clarifiers are best suited to
small- to moderate-scale cleanup operations, or to large-scale operations
where construction of earthen impoundments will not adequately protect
groundwater. High rate clarifiers are particularly applicable to cleanup
operations where land space is limited and where barge mounting of clarifiers
is required.
High rate clarifiers are not suitable for removal of particles larger
than 0.1 inch or less than 10 microns. Use of high rate gravity settlers has
not been demonstrated for applications in solid/water separation and they are
generally used in applications with lower solids concentrations (Mallory and
Nawrocki, 1974). There is the possibility that cohesive sediments or soils
may clog the channels, tubes, or plates (Jones, Williams and Moore, 1978).
d. Technology Selection/Evaluation
Sedimentation employing impoundment basins and conventional clarifiers is
a well established technology for removing particles ranging in size from
gravel down to fine silt. However, proper flocculation is essential to ensure
removal of silt-sized paticles. Sedimentation methods have not been widely
employed for classifying solids according to particle-size. They can be
expected to be less effective in classifying solids than other methods
described in this section (e.g., classifier, cyclones, and screens).
Impoundment basins have a high capital and operating cost. For this
reason their use is generally limited to large-scale cleanup operations.
10-75
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FIGURE 10-20. HIGH RATE GRAVITY SETTLER
FLOW DISTRIBUTION ORIFICES
OVERFLOW BOX
DISCHARGE FLUMES
/FEED BOX
FLOCCULATION TANK
SLUDGE HOPPER
(REMOVABLE)
Source: Parkson Corp., 1984
10-76
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Impoundment basins also pose the greatest potential for secondary impacts of
all solids separation methods; contaminants may leach into groundwater if the
liner system is not properly designed and the large surface area of the
impoundment can result in volatilization of contaminants and localized air
pollution problems.
Impoundment basins require a long set-up time and the need to obtain
construction permits can further delay the start-up of the cleanup operation.
Conventional clarifiers and high-rate clarifiers eliminate some of the
problems associated with impoundment basins. Operating costs are
substantially less because clarifiers have a build-in solids collection
system. Clarifiers also pose no threat to groundwater contamination.
However, capital costs associated with the use of clarifiers can also be quite
high for a large-scale cleanup operation.
Both types of clarifiers can be barge mounted in areas of limited space.
High-rate clarifiers with their relatively small space requirements, may be
the only suitable sedimentation method in congested areas. Clarifiers and
impoundment basins are easy to operate and maintain.
10.2.2 Dewatering
Dewatering is a physical unit operation used to reduce the moisture
content of slurries or sludges in order to facilitate handling and prepare the
materials for final treatment or disposal. Devices which can be used to
dewater slurries or sludges include gravity thickeners, centrifuges, filters,
and dewatering lagoons. Selection of the most appropriate method depends on
such factors as the volume of the slurry, solids content of the waste stream,
land space availability and the degree of dewatering required prior to
treatment or disposal.
Although several of the dewatering methods are extremely effective in
removing water, the solids are often not sufficiently dry to meet requirements
for final disposal, and require further treatment to fixate or solidify the
wastes (Section 10.3). The contaminated water generated during dewatering
generally contains hazardous constituents as well as several hundred to
several thousand mg/1 suspended solids, and will require additional treatment
(Section 10.1).
10.2.2.1 Gravity Thickening
a. General Description
Gravity thickening is generally accomplished in a circular tank, similar
in design to a conventional clarifier. The slurry enters the thickener
through a center feedwell designed to dissipate the velocity and stabilize the
density currents of the incoming stream (Figure 10-21). The feed sludge is
10-77
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allowed to thicken and compact by gravity settling. A sludge blanket is
maintained on the bottom to help concentrate the sludge. The clarified liquid
overflows the tank and the underflow solids are raked to the center of the
tank and withdrawn by gravity discharge or pumping. Flocculants are often
added to the feed stream to enhance agglomeration of the solids and promote
quicker or more effective settling (Metcalf and Eddy, 1979; Dorr-Oliver,
1981). Tanks are usually constructed of concrete or steel.
Gravity thickener size and specifications depend on the following
factors: maximum flow, type of wastes, pH, volume of solids/day, percent
solids, specific gravity, maximum particle size, and percent solids required
in the underflow.
b. Applications/Limitations
Gravity thickeners are used to concentrate slurries and are capable of
achieving a solids concentration of approximately 2 to 15 percent (USEPA,
1979). They generally produce the thinnest and least concentrated sludge of
all the dewatering methods described in this section. The intent in using a
gravity thickener is usually to reduce the hydraulic load of a slurry that is
to be fed to a more efficient dewatering method, such as filtration or centri-
fugation. They also provide a high sludge storage capacity. Conventional
gravity thickeners require large land areas for operation and therefore are
FIGURE 10-21. GRAVITY THICKENER
Coitrteiy Link Btll
SCRAPER BLADES
2 UNDERFLOW
ELEVATION
Source: Gulp, Wesner, and Gulp, 1978
10-78
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not applicable where space is restricted. However, high-rate gravity
thickeners designed to provide up to 15 times the throughput of a conventional
thickener are available and can reduce land requirements considerably
(Dorr-Oliver, 1981).
c. Technology Selection/Evaluation
Gravity thickening provides a simple, low maintenance method for
concentrating slurries, thereby reducing the hydraulic load to subsequent
dewatering processes. They are suitable for operations where a high degree of
operator supervision cannot be provided. Because of the requirements for a
large surface area, localized air pollution and odors may be significant.
d. Costs
Equipment costs for gravity thickeners are illustrated in Figure 10-22.
Costs are based on the use of a circular reinforced concrete basin and related
drive and motor.
FIGURE 10-22. GRAVITY THICKENING CONSTRUCTION COSTS, 1975*
i
o
s
2 S 4 S6789 ^ 34 S 6 T t« I it »«T«t
100 1,000
Area, ft2
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.908)
Source: Gulp, Wesner, and Culp, 1978
10-79
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10.2.2.2 Dewatering Lagoons
a. General Description
Dewatering lagoons use a gravity or vacuum assisted underdrainage system
to remove water. The base of the lagoon is lined with clay plus a synthetic
liner or other appropriate liner material to prevent migration of contaminants
into the underlying soils and groundwater. At a minimum, the liner consists
of a low permeability clay layer which is several feet thick. When the lagoon
is no longer in use, the clay liner is excavated and properly disposed of. In
some instances this design may not be adequate to protect groundwater
supplies. A combination clay/synthetic liner and a secondary leachate
collection system are required in some instances.
The underdrainage system can be designed and operated using one of the
following approaches:
• Gravity underdrainage - This system consists of a filler material
(well-graded sand or filter fabric) underlain by a porous free-
draining gravel layer. Perforated drainage pipe is embedded in the
gravel. The drainage pipe network is designed with flow gradients
leading towards a central collection point or sump. Information on
the hydraulic design of a gravity drainage system can be found in
Section 5.2.
• Vacuum pumping - Vacuum pumping systems can use either pumped wells or
wellpoints. Pumped wells with large vacuum pumps may be installed
directly in the waste material. Wellpoints may be used, provided they
are installed to the depth of an underlying sand filter. Installation
of wellpoints directly in the sludge, contaminated sediments^ or soils
is not cost-effective, because it is necessary to space the wellpoints
very close together in order to dewater low permeability material
(Haliburton, 1978). Information on the design of wells and wellpoints
can be found in Section 5.1.
• Vacuum assisted drying beds - Vacuum assisted drying beds use a porous
media filter plate set above an aggregate filled support plenum which
drains to a sump. A relatively small vacuum pump is connected to
drain a vacuum from the sump. The vacuum is activated when the volume
of the slurry has been reduced by half due to gravity drainage. The
vacuum holds until the solids crack, allowing air through the bed
(USEPA, 1982).
• Electroosmosis - This technique involves a process in which a direct
current electrical potential is set-up in the soil by means of
electrodes. This electric potential induces the flow of water in the
pores of the fine-grained sediment or sludge towards the negative
pole, or cathode. A line of wells or wellpoints can be installed to
intercept and remove the water (Mallory and Nawrocki, 1974).
10-80
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b. Applications/Limitations
Dewatering lagoons are best suited to large-scale dewatering operations
where the volume of sludge or sediment would require an inordinately large
number of mechanical dewatering units (e.g., filters or centrifuges). Lagoons
are one of the more effective dewatering methods. A gravity dewatering system
is capable of achieving 99 percent solids removal and a dewatered cake of 35
to 40 percent solids after 10 to 15 days (based on municipal sludges)
(DeRenzo, 1978; USEPA, 1982). Vacuum assisted systems may be capable of
achieving a dry cake in a shorter retention time.
The major limitations on the use of dewatering lagoons is that they
require large land areas and long set-up times. Because of their large
surface area they may not be well suited to areas with heavy rainfall or to
areas where long periods of freezing would prevent dewatering.
Each of the types of dewatering lagoons described in this section has its
own specific applications and limitations.
Gravity drainage systems have the lowest operating costs. However,
dewatering is achieved at a relatively slow rate and this may result in the
need for more land area than required with the other methods. Gravity
drainage systems are also more prone to clogging, particularly if the system
is not carefully designed.
Vacuum pumping or vacuum assisted dewatering beds are capable of
dewatering at a much more rapid rate than gravity systems. Vacuum assisted
dewatering beds reportedly increase the rate of dewatering by about 50 percent
(with a negative pressure of 8 psi or less) (Haliburton, 1978). However, they
require a higher degree of maintenance and are considerably more costly to
operate than gravity systems.
Electroosmosis is a very costly technique which would be limited to
dewatering of very fine grained (2 to 10 microns), very hazardous and
difficult to dewater solids.
c. Technology Selection/Evaluation
Dewatering lagoons provide an effective means of dewatering solids. They
are also versatile in that they can provide storage capacity for solids prior
to disposal. Of all the dewatering technologies they require the largest time
to implement and have the greatest potential for secondary impacts due to
localized air pollution and groundwater contamination. Operating costs are
higher than other dewatering technologies because of the need to remove the
solids with mechanical dredging equipment.
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10.2.2.3 Centrifuges
a. General Description
Centrifugal dewatering is a process which uses the force developed by
fast rotation of a cylindrical drum or bowl to separate solids and liquids by
density differences under the influence of centrifugal force. Dewatering is
usually accomplished using solid bowl or basket centrifuges. Disc centrifuges
are also available and are mainly used for clarification and thickening.
Figures 10-23 through 10-25 illustrate the three types of centrifuges.
The operation of the solid-bowl centrifuge is a continuous process. The
unit consists of a long bowl, normally mounted horizontally and tapered at one
end. Sludge is introduced into the unit continously and the solids concen-
trate on the periphery. A helical scroll within the bowl, spinning at a
slightly different speed, moves the accumulated sludge towards the tapered end
where additional solids concentration occurs prior to discharging the solids
(USEPA, 1982a and USEPA, 1979).
In the basket centrifuge, flow enters the machine at the bottom and is
directed toward the outer wall of the basket. Cake continually builds up
within the basket until the centrate, which overflows a weir at the top of
this unit, begins to increase in solids. At that point, feed to the unit is
shut off, the machine decelerates, and a skimmer enters the bowl to remove the
liquid layer remaining in the unit. A knife is then moved into the bowl to
cut out the cake which falls out the open bottom of the machine. The unit is
a batch device with alternate charging of feed sludge and discharging of
dewatered cake (USEPA, 1982a and USEPA, 1978).
In the disc centrifuge, the incoming stream is distributed between a
multitude of narrow channels formed by stacked conical discs. Suspended
particles have only a short distance to settle, so that small and low density
particles are readily collected and discharged continuously through fairly
small orifices in the bowl wall. The clarification capability and throughput
range are high, but sludge concentration is limited by the necessity of
discharging through orifices of 0.05 inches to 0.1 inches in diameter.
Therefore, it is generally considered a thickener rather than a dewatering
device (USEPA, 1978) .
b. Applications/Limitations
Centrifuges can be used to concentrate or dewater soils and sediments
ranging in size from fine gravel down to silt. Effectiveness of
centrifugation depends upon the particle sizes and shapes, and the solids
concentration among other factors. Data from the dewatering of municipal
sludges (where extensive information is available), indicate that solids
concentrations ranging from about 15 to 40 percent are achievable with the
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FIGURE 10-23.
SCHEMATIC OF TYPICAL SOLID BOWL DECANTER CENTRIFUGE
FEED
COVER
."•'•." OEWATERE0
.' '•'.'. SOLIDS
Source: USEPA, 1979
10-83
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FIGURE 10-24.
GENERAL SCHEMATIC OF IMPERFORATE BASKET CENTRIFUGE
FEED
POLYMER
SKIMMINGS
KNIFE
CAKE
CAKE
10-84
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FIGURE 10-25.
SCHEMATIC OF A DISC NOZZLE CENTRIFUGE
FEED
EFFLUENT
DISCHARGE
FEED
EFFLUENT
DISCHARGE
CONCENTRATING
CHAMBER
SLUDGE
DISCHARGE
ROTOR
BOWL
ROTOR
NOZZLES
SLUDGE
DISCHARGE
RECYCLE FLOW
Source: USEPA, 1979
10-85
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solid bowl centrifuge. For the basket centrifuges the cake solids
concentration typically ranges from about 9 to 25 percent. Solids capture
typically ranges from about 85 to 97 percent with chemical conditioning, both
for the solid bowl centrifuge and the basket centrifuge. Disc centrifuges can
concentrate a 1 percent sludge to a 6 percent solids (USEPA, 1978; USEPA
1982a).
Centrifuges are capable of removing particles as small as 1 micron in
diameter. However, removal efficiencies are reduced dramatically for
particles smaller than 10 microns (Krizek, Fitzpatrick and Atmatzidis, 1976).
Although the basket centrifuge does not acheive as dry a cake as does the
solid bowl centrifuge, it has the advantage of being able to handle hard to
dewater sludges and is not significantly affected by grit. It has the highest
capital cost but lowest operation and maintenance cost of the three centrifuge
types (USEPA, 1979 and USEPA, 1982b) . A major limitation is that it must be
operated on a batch basis.
The solid bowl centrifuge is very flexible in that it can handle higher
than design loadings, such as temporary increases in hydraulic loading or
solids concentrations; however, the cake solids content may be reduced.
Higher feed rates make the solid bowl centrifuge better suited for large-scale
dewatering operations. Maintenance and pretreatment requirements are more
extensive than for the basket centrifuge. The scroll of the solid bowl
centrifuge is very susceptable to abrasion. This results in the need to
degrit the effluent (USEPA, 1979 and USEPA, 1982a).
The disc centrifuge has more limited application at hazardous waste sites
than the other types of centrifuges. Although it can yield a highly clarified
centrate even without the use of chemicals, the percent solids concentration
is low, maintenance requirements are relatively high, and pretreatment
requirements (grit and fibrous material removal) are extensive.
c. Technology Selection/Evaluation
Centrifugation offers a simple, clean and reliable method for dewatering
sludges and other solids. They are less effective than filtration methods and
dewatering lagoons, but more effective than gravity thickeners. Centrifuges
are compact and are well suited to use in mobile treatment systems.
Although reliable for their intended function, centrifuges generated a
centrate and a sludge which require further treatment prior to disposal.
Suspended solids levels from centrifugation may be as high as several thousand
parts per million.
Since centrifugation relies on the settling of particles according to
density, the process tends to classify the solids, settling the heavier
particles first. Dewatering processes which rely on filtration achieve a more
even distribution of solid capture. It is possible for a buildup of fines to
10-86
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occur in the effluent from centrifugation, particularly if the centrifuge is
operating improperly due to inadequate solids conditioning or due to a mal-
function (USEPA, 1982a). Since most organic and inorganic waste constituents
tend to sorb to fine clay and silt particles, this may result in unacceptable
levels of contaminants in the overflow.
Advantages of centrifuges for thickening and dewatering methods include
relatively limited space requirements and fast start-up and shut-down. They
also generate little or no air emissions since the process is essentially
enclosed.
d. Costs
This section presents construction and O&M costs for basket and solid
bowl centrifuges. It should be recognized that the curve for construction
cost is not capital cost. The curve does not include costs for special site
work, general contractor overhead and profit, engineering, land, legal,
fiscal, and administrative work and interest during construction. These cost
items are all more directly related to the total cost of a project rather than
the cost of any one of the individual unit processes. These costs are
therefore most appropriately added following cost summation of the individual
unit processes, if more than one unit process is required. Typically, these
costs add 35 to 45 percent, depending on project size and complexity, to the
actual construction costs which are shown in the curves (USEDA, 1982a).
Construction costs include housing for the centrifuges. Housing costs may
not be applicable for hazardous waste sites because of the short time period
the unit will be on-site.
No costs were available for mobile treatment units involving use of
centrifuges.
Basket Centrifuge — Figure 10-26 shows construction costs for single and
multiple basket centrifuges with capacities ranging from 4,000 to 700,000 gpd.
Centrifuge costs are for automatic machines operating on a preprogrammed
cycle, an approach which requires only minimal operator attention.
In addition to the basic machines, the costs include equipment for
polymer preparation, storage, and application. If other conditioning
chemicals are used, the costs would have to be adjusted accordingly. The
costs do not include sludge and centrate pumping, sludge conveying, and sludge
storage. It was assumed that centrifuges are located in two story concrete
block buildings with bottom discharge to trucks or storage bins. Housing
requirements were developed from equipment manufacturers' recommended layouts
(USEPA, 1982a).
Figures 10-27 and 10-28 present O&M costs for basket centrifuges.
Electrical energy requirements were computed from connected and operating
10-87
-------
FIGURE 10-26. CONSTRUCTION COST FOR BASKET CENTRIFUGES *
i
9
2
1 0.000.
1
•
4
« *
i *
i
« 1 .000.
1 J
3 1
X 4
<* 3
Z
too.
s
7
•
5
4
3
I
000
000
ooo
M • «
illSLE
INIT
I-!!- "
L— *
>
£
/
WLTIPL
(UNITS
. , .^r_.--.
s~
'
S
x
9 « '
• •
10.000
TOTAL tUCHINC CAMCtTY -»<
1 00.000
TOTAL HACHINC CArAC
1 .000,000
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.193)
Source: USEPA 1982a
horsepower information provided by equipment manufacturers. Basket centrifuge
operating horsepower, computed on the basis of a complete cycle involving
machine acceleration, sludge feeding, skimming, decelerating, and sludge
plowing, averages 40 to 60 percent of the connected horsepower. Electrical
power for polymer preparation and feeding is included, but energy for sludge
pumps, centrate pumping and sludge conveying equipment is not included.
Maintenance costs were obtained from equipment manufacturers and from
operating installations and represent an industrywide average of annual
expenditures for maintenance, replacement parts, lubrication, and other
consumable items associated with basket centrifuge operation. Maintenance
material costs do not include the cost of polymers.
Labor requirements for O&M assume 24 hours per day of operation, with
occasional downtime for maintenance as required. The major portion of the
operating labor is devoted to machine start-up and adjustment, polymer
preparation, and required maintenance (USEPA, 1982a) .
10-88
-------
FIGURE 10-27. BASKET CENTRIFUGES-BUILDING ENERGY, PROCESS ENERGY
AND MAINTENANCE MATERIAL REQUIREMENTS*
1 •
1000
:
BUILDING
ENERCY,
0.000
s •ritiocoo 2 S 4 9 t re
FCCD sujooe FLOW RATE -utt
I.OOO.C
100.000 I .OOO.OOO
FEED SLUOflE FLOW HATE -Hurt/Mr
FIGURE 10-28. BASKET CENTRIFUGES-LABOR AND TOTAL ANNUAL OPERATION
AND MAINTENANCE COST*
00
K
«
- 5
)
J
:»
f
?
B
5
4
0 IOJ
.*
t
3
4
S
i
)OC
s
Si
¥ *
'!'
- J Z
- 100
00
3
„. - -*
_ p* •
•
:: i
,— •
^eL
'
s
£
7
NTT
TO
C(
7
/
s
,'
LABOB
/
000 i 4 MftlOOOO 214 »«7i OOOOOt
TAl
ST
-7
/
/
/
f?
.
/T
£ '
-------
It should be recognized that operation and maintenance costs will vary
widely depending on sludge dewatering characteristics and specific operating
conditions related to the installation, and appropriate adjustment should be
made if conditions vary significantly from those stated above (USEPA, 1982a).
Solid Bowl Centrifuge (High G)—Construction costs for solid bowl
centrifuges are shown in Figure 10-29. Machine throughput is significantly
affected by the polymer dosage, and therefore the construction cost for a
given feed rate varies with the polymer dose. In this figure, single machines
were assumed to be used for feed rates up to 500 gpm, with multiple units
being usedfor higher feed rates. All machines are equipped with automatically
controlled eddy current backdrive and have sintered tungsten carbide conveyor
tips. Polymer storage preparation, and feed equipment is included in the
costs, but costs for sludge feed pumping and centrate pumping are not included
(USEPA, 1982a).
FIGURE 10-29. CONSTRUCTION COST FOR A HIGH G SOLID BOWL CENTRIFUGES*
1
9
4
3
2
10.000
t
9
4
3
2
I.OOO
2
9
4
3
2
100
1
9
4
9
2
,000
000
^<
000
.-"
•*
r;<
0 1 3 4 91
4
j^
»'' "^^
• •
j
Ib/ton polymer^yr
>
r
\^
[—
^
/
• 100 2 S 4 9 * f
-Y
/I
™—
n P
!
1
'
lolY"1*
I
*"*"
1 IOOO 2 3*9 «Ttt IO.OOO
10 100
MUMHC CAHCITr - MOT/W
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.193)
Source: USEPA, 1982a
10-90
-------
Operation and Maintenance Cost for solid bowl centrifuges are shown in
Figure 10-30 and 10-31. Process energy was calculated from information
supplied by a manufacturer of high G centrifuges and assumes use of an eddy
current backdrive. Energy requirements could be reduced between 5 to 20
percent if the backdrive is not utilized. Included in the process energy
requirements are the main drive motor, the eddy current backdrive, and equip-
ment required for polymer preparation and feed. Energy required for feed
sludge pumping and handling of the dewatered sludge is not included.
Maintenance material requirements include replacement of the conveyor
tips every 30,000 hours of operation, as well as replacement of other
necessary components of the centrifuge and the electrical controls.
Operation and maintenance labor requirements are based on 24 hours per
day of continuous operation. Most operational labor is devoted to polymer
preparation and machine start-up and adjustment. Occasional maintenance is
required for lubrication, with more extensive maintenance required
approximately every 30,000 hours for replacement of the sintered tungsten
carbide conveyor tips.
The cost curves presented do not include the cost of polymer. The
polymer dosage is highly dependent on the characteristics of the sludge being
dewatered, and polymer dosage will also have a great influence on the
throughput of the centrifuge.
10.2.2.4 Filtration
a. General Description
Filtration is a physical process whereby particles suspended in a fluid
are separated from it by forcing the fluid through a porous medium. Three
types of filtration are commonly used for dewatering: belt press filtration,
vacuum filtration, and pressure filtration.
Belt filter presses employ single or double moving belts to continuously
dewater sludges. As Figure 10-32 illustrates, the belt press filtration
process includes three stages: chemical conditioning of the feed, gravity
drainage to a nonfluid consistency and dewatering. A flocculant is added
prior to feeding the slurry to the belt press. In the next step, free water
drains from the conditioned sludge. The sludge then enters a two-belt contact
zone, where a second upper belt is gently set on the forming sludge cake. The
belts with the captured cake between them pass through rollers of generally
decreasing diameter. This stage subjects the sludge to continuously
increasing pressures and shear forces. Progressively more and more water is
expelled throughout the roller section to the end where the cake is dis-
charged. A scraper blade is often employed for each belt at the discharge
point to remove the cake from the belts (USEPA, 1982).
10-91
-------
FIGURE 10-30. HIGH G SOLID BOWL CENTRIFUGES-BUILDING ENERGY, PROCESS ENERGY AND
MAINTENANCE MATERIAL REQUIREMENTS*
10
I
•
3
4
3
Z
\
\
t
5
4
3
Z
!
&
4
3
Z
•
i!
» •
2 3
§ *
\
.000.0
: 1
•
3
4
I
000,00
?
•
*
«
- jl t
OQ.OQfi
: M
a *
- J 4
' i'
10.000
• !
1- •
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4
3
Z
1000
00
0
y
X
'
^
0
r~
x^
/
/
^"'"
*
,
...- —
L-rl*
., ^^
/
X
/
/
• -7* PROCESS -
• !»*• ENEROT -
t '
X^BUILOH
M.
FIGURE 10-31. HIGH G SOLID BOWL CENTRIFUGES-LABOR AND TOTAL
ANNUAL OPERATION AND MAINTENANCE COST*
.ooc
!
9
:
•
100
1
4
:
10.
i
•
s
4
3
2
l,(
1
•
ft
4
3
Z
1
.OOO
»
S
- 4
S
Z
000
: <
9
4
t
OOO
\
•
4
3
I
oo
>'V
r * *
Fr.
a
0
SB!
0
=
^
ae =
34 C
I
.-•^
— *
^
^
s
" *
» t 00 > » « •
S
,/T
•'
•"
OT»
L
cos-
LABOR
• •1000 1 > «
1
T««
HID U.UOM FLOW KATI - H>
PEEP SLUOQE FLOW RATE - Htm/m.
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.193)
Source: USEPA 1982a
10-92
-------
FIGURE 10-32. THE THREE BASIC STAGES OF A BELT PRESS
CHEMICAL
CONDITIONAL
STAGE
POLYELECTROLITE
SOLUTION
GRAVITY
DRAINAGE
STAGE
COMPRESSION
DEWATERING
STAGE
SLUDGE•
CONDITIONED
SLUDGE
WASH WATER
Source: USEPA, 1979
A vacuum filter consists of a horizontal cylindrical drum which rotates
partially submerged in a vat of sludge (Figure 10-33). The drum is covered
with a continuous belt of fabric or wire mesh. A vacuum is applied to the
inside of the drum by means of a connection within a central trunion. The
vacuum causes liquid in the vat to be forced through the filter medium leaving
wet solids adhering to the outer surface. As the drum continues to rotate, it
passes from the cake forming zone to a drying zone, and finally to a cake
discharge zone where the sludge cake is removed from the media (Metealf and
Eddy, 1979; USEPA, 1982).
Pressure filtration is used to describe a category of filters in which
rigid individual filtration chambers are operated in parallel under relatively
high pressure. The filter press (Figure 10-34), the most common represen-
tative of the group consists of vertical plates that are held rigidly in a
frame and are pressed together by a large screw jack or hydraulic cylinder as
shown in Figure 10-34. The liquid to be filtered enters the cavity formed by
the frame. Pressed against this hollow frame are perforated metal plates
covered with fabric filter medium. The plate operates on a cycle which
includes filling, pressing, cake removal, media washing, and press closing
(USEPA, 1982a and USEPA, 1979). As the liquid flows through the filter
10-93
-------
FIGURE 10-33.
ROTARY VACUUM FILTER
CLOTH CAULKING
STRIPS -
AUTOMATIC VALVE
DRUM
FILTRATE PIPING
CAKE SCRAPER
SLURRY AGITATOR
VAT
AIR BLOW-BACK LINE
SLURRY FEED
Source: USEPA, 1979
10-94
-------
FIGURE 10-34.
FILTER PRESS (ILLUSTRATIVE CROSS-SECTIONAL VIEW OF ONE RECTANGULAR CHAMBER)
Perforated Backing Plate
Fabric Filter Medium
Inlet Liquid to be
Filtered
Fabric Filter Medium
Solid Rectangular
End Plate
Entrapped Solids
\
Plates and Frames are Pressed
Together During Filtration Cycle
Rectangular Metal Plate
Filtered Liquid Outlet
Rectangular Frame
When the cavity formed between plates A and C is filled with solids, the plates are separated.
The solids are than removed and the medium is washed clean.
The plates are than pressed together and filtration resumed.
Source: De Renzo, 1978
10-95
-------
medium, solids are entrapped and buildup within the cavity until the cavity is
full. The slurry is dewatered until no filtrate is produced. The press is
then opened, the dewatered slurry is removed, the plates are cleaned, and the
cycle is repeated (De Renzo, 1978). In certain applications, the filter media
is precoated with diatotnaceous earth, fly ash, or other filter aids to improve
performance.
Diaphragm filters are specially designed filter presses. Instead of the
conventional plate and frame unit in which constant pumping pressure is used
to force the filtrate through the cloth, diaphragm filters combine an initial
pumping followed by a squeezing cycle that can reduce the cost and process
time.
b. Applications/Limitations
Filtration can be used to dewater solids over a wide range of solids
concentrations and particle sizes. Effectiveness for a particular application
depends on the type of filter, the particle size distribution, and the solids
concentrations. For dewatering of municipal sludges where considerable
performance data is available, typical ranges for solids content and solids
removal or capture are as follows (USEPA, 1979; USEPA, 1982; Metcalf and Eddy,
1979):
SolidsContent (%) Solids Capture(%)
Belt Press Filtration 15 to 45 85 to 95
Vacuum Rotary Filtration 15 to 35 or 40 88 to 95
Pressure Filter 30 to 50 98
Manufacturers' data is also available on the performance of filtration
methods in dewatering coal slurries. This data indicates that belt press and
filter press filtration are capable of producing a filter cake of up to 70 to
80 percent solids. Also, tests conducted by Rexnord, Inc. demonstrated that
high density dredged materials can be dewatered to a cake solids concentration
of 70 percent using belt press filtration (Erickson and Hurst, 1983).
Although the filter press achieves a dry filter cake and has the greatest
capacity for solids capture, there are a number of other factors which enter
into the decision to use a particular method of filtration.
Filter presses generally require larger quantities of conditioning
chemicals than the other filtration methods. They also have the highest
capital and operating cost and require the largest amount of space.
Replacement of filter media on a filter press is both expensive and time
consuming (USEPA, 1982a).
10-96
-------
Vacuum filtration is the most energy intensive of the three methods and
the least effective in dewatering. Another limitation on the use of vacuum
filtration is that the incoming feed must have a solids content of at least
3 percent in order to achieve adequate cake formation (USEPA, 1982a). A big
advantage to vacuum filtration is that because dewatering is accomplished by a
vacuum rather than by mechanical means, the hydraulic throughput is higher
than for the other filter types. Vacuum filtration has an advantage over belt
press filtration in that it is easier to maintain and can operate effectively
even without optimum chemical conditioning.
Recent advances in belt press filtration has made this method nearly as
effective as pressure filtration. The belt press filter also has the
advantage of being the least energy intensive of the filtration methods. The
major limitation on the use of this method is that the process is very
sensitive to incoming feed characteristics and chemical conditioning. How-
ever, these limitations can be overcome to a certain extent; most belt presses
can be equipped with sensing devices which can be set to automatically shut
off feed flow in the case of underconditioning. The feed characteristics can
be optimized by carefully prescreening the slurry to remove large objects and
fibrous material which can deteriorate the belt quickly (USEPA, 1982a).
c. Technology Selection/Evaluation
Filtration appears to offer the most effective method for dewatering
slurries. The processes are generally reliable, provided the slurries have
been properly prescreened and conditioned. Filtration equipment, particularly
belt press and vacuum filtration, is well suited for inclusion in mobile
treatment systems. Mobile systems are available from several manufacturers.
However, the maintenance requirements associated with filtration are
significant. The filter cloth or belts must be periodically replaced and the
filter media periodically washed to remove contaminated solids.
Despite their effectiveness in dewatering sludges, both the filtrate and
the dewatered sludge are likely to require further treatment prior to
disposal. The water generated from washing of the filter media will also
require treatment.
d. Costs
This section presents construction and O&M costs for diaphragm,
belt-press and vacuum filters. It should be recognized that the curve for
construction cost is not capital cost. The curve does not include costs for
special site work, general contractor overhead and profit, engineering, land,
legal, fiscal, and administrative work and interest during construction.
These cost items are all more directly related to the total cost of a project
rather than the cost of any one of the individual unit processes. These costs
are therefore most appropriately added following cost summation of the
10-97
-------
individual unit processes, if more than one unit process is required.
Typically, these costs add 35 to 45 percent, depending on project size and
complexity, to the actual construction costs which are shown in the curves
(USEPA 1982a).
Diaphragm filter press—Construction costs for diaphragm filter presses
ranging in size from 1,200 to 15,505 ft are shown in Figure 10-35. The
largest machine manufactured is about 6,000 ft , and multiple presses are
required for larger press areas. Construction costs include the diaphragm
press, feed pump, pumps for the diaphragm and cloth washing, vacuum pumps an
air compressor and receiver, lime and ferric chloride storage and feed
facilities and all electrical and controls necessary for complete automatic
operations. Housing costs are also included (USEPA, 1982a),
Operation and maintenance costs shown in Figures 10-36 and 10-37 were
developed for a 4 percent feed of anaerobically digested sludge, chemically
conditioned with 5 percent ferric chloride and a 20 percent lime. Press
loading was 1.0 Ib/sq ft/hr, without chemicals, and cake discharge was taken
at 35 percent. Press operation time was 19 hours per day, with the remaining
time dedicated to press cleanup and maintenance.
FIGURE 10-35. CONSTRUCTION COST FOR DIAPHRAGM FILTER PRESS*
«
5
4
3
2
oo.ooo
<
ft
s
4
3
2
I 0.000
1
J
c
5
4
3
2
..000
I
e
5
4
3
2
too.
000
000
000
— t—
i
1
300
< 00
i
1
1
^
i
i i
U-i--
V
V
'
r 1 — r-
|
! ' ' i
1
i ,
y
>\
.f
<; _]
1
i i !'
i f
i
1
!
1
i
j
j
t
i
i
i
t»
TOt»L FILTER PRESS AREA-ft2
I 00 I 000
TOTAL flLTER PRESS AREA-m*
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1986
(multiply value shown on this figure by 1.193)
Source: USEPA, 1982a
10-98
-------
FIGURE 10-36. DIAPHRAGM FILTER PRESS-LABOR AND TOTAL ANNUAL
OPERATION AND MAINTENANCE COST*
1
•
s
J
.0010
1
5
I
IQOJM
9
•
*
3
9
2
10X0
1
5
4
S
1
f »
r 6
1
00
E f
k- «
t :
• s
i ,
o 1001
?
«
K 9
o itxo
^ !
>- e
"*'
-I5
• 5 *
1000
300
00
I :
^
—
X
**
/
-\- -
. *
'
TOTAL
.X
y'
/
<
LAB
CO
OR
>T
ta
bOOD
100
TOTAL I
FIGURE 10-37. DIAPHRAGM FILTER PRESS-BUILDING ENERGY, PROCESS ENERGY
AND MAINTENANCE MATERIAL REQUIREMENTS*
«
4
5
J
.
6
S
2
.OOO.OOI
T
5
3
2
100,00
3
4
3
Z
10,000
1
6
s
2
10.00
1
5
3
2
1,00
r?
* 4
z z
0 100
I
10,
— :
0,000
0,000
000
000
00 Z 3 4 9 0 7
X
_/
/
'
s
1
T
1
X
y ^
2
,.'006 1 1 — 1
PR
EN
/
IIJ/IMJ
«
x
'MAI
r M
'Ct
pit
4TE
»TE
— ; ~'tn
1
— t-*-t-h
i , ' 1
ss
e
-q
Trt
i
1
MA
Rl
' "10.000' '
NCE
,u
i
*10
0 1 00 ' 000
n]
It
1
p
L
o.ooo
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.193)
Source: USEPA, 1982a
10-99
-------
Process energy requirements are for the sludge feed pump, the air pump
for inflating the diaphragm, and a vacuum pump for removal of liquid sludge
remaining in the internal piping prior to opening the press. Energy is also
required to open and close the press, for cloth washing, and for conditioning
chemical preparation and feed. Building energy requirements are based on 84
kwh/sq ft/yr.
Maintenance material costs consist principally (over 90 percent) of
replacement of diaphragms and filter cloths. Other costs are for
miscellaneous equipment parts and for miscellaneous electrical components.
Labor required is for both operation and maintenance, with the majority
of the labor devoted to operational requirements. Labor requirements are
based on operational experience of the manufacturer (USEPA, 1982a).
Belt Press Filters—Construction costs are for belt filter press
dewatering systems that include the belt press unit, wash water pump,
conditioning tank, feed pump, polymer storage tank and pump, belt conveyor,
and electrical control panel. Machines are generally sized using metric
dimensions and are rated on the basis of sludge flow in gpm/m of belt width.
For mixtures of digested primary and secondary sludges, a value of 50 gpm/m
belt width is a typical loading recommendation, and was used in the cost
development. Higher loadings are possible in some cases if the sludge can be
easily dewatered (USEPA, 1982a) .
Estimated construction costs are presented in Figure 10-38 as a function
of total installed machine capacity.
FIGURE 10-38. CONSTRUCTION COST OF A BELT FILTER PRESS
<§ '
-J-
Total Installed Machine Capacity-gpm
KO^0too
Total Installed Machine Capacity-liters/sec
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.193)
Source: USEPA, 1982a
10-100
-------
Figures 10-39 and 10-40 present operation and maintenance costs for the
belt filter press. Process energy requirements were developed from the total
connected horsepower for the belt drive unit, belt wash water pump,
conditioning tank, feed pump, polymer pump and tanks, belt conveyor, and
electrical control panel. A belt filter loading of 50 gpm/m of machine width
was used in selecting unit sizes and determining power requirements.
Twenty-two hours of continuous operation with 2 hour of downtime for routine
maintenance was assumed in calculating process energy requirements (USEPA,
1982a).
Labor and maintenance requirements were estimated from information
provided by equipment manufacturers, as well as information from plants
operating belt filter presses. The maintenance material requirments assume
the replacement of a set of belts every 6 months in continuous service.
As operation and maintenance costs vary widely depending on the nature
and solids concentration of the sludge being processed, and adjustments to
these O&M requirements may have to be made on a case-by-case basis.
Conditioning chemical costs are not included in the total annual O&M cost
curve (USEPA, 1982a).
Vacuum Filters—Costs for vacuum filter installations are presented
in Figure 10-41. The costs include the vacuum filter, conditioning tank,
vacuum and filtrate pump assemblies, vacuum receiver, a short belt conveyor
for the dewatered sludge, feed sludge piping, lime and ferric chloride storage
and feed facilities, electrical controls, and necessary housing for the entire
assembly (USEPA, 1982a).
Operation and Maintenance cost are shown in Figures 10-42 and 10-43.
Electrical energy curves are presented for bothprocess and building energy.
Process energy is for vacuum filer drumdrive, cake discharge roller, vacuum
and filtrate pumps, tank agitators, and the dewatered sludge belt conveyor.
Process energy requirements were calculated for a sludge solids loading of
17 Ib dry 1.7 Ib/sq ft/hr. Building sizes are based on conceptual layouts for
various total filter areas, and energy requirements are based on 34 kwh/sq
ft/yr of building/year (USEPA 1982a).
Labor and maintenance material requirements are based on opeating
experience at operating dewatering facilities. Labor requirements are based
on 24 hour per day operation, and will have to be adjusted if filters are
operated for only one or two shifts per day. Maintenance material costs are
for periodic repair and replacement of equipment. Costs are not inlcuded for
purchase of the lime or ferric chloride utilized for conditioning, since
chemcial requirements are highly variable from sludgeto sludge, and are not
generally a function of vacuum filter surface area (USEPA, 1982a).
Table 10-16 shows capital and operating costs for a portable filter press
used for dewartering 20,000 gal/yr of 2 percent solids sludge.
10-101
-------
FIGURE 10-39. BELT FILTER PRESS-LABOR AND TOTAL ANNUAL
OPERATION AND MAINTENANCE COST*
I
«
s
4
3
2
1.000,
i
<
s
4
5
1
IOCUX
t
•
T
t
9
3
I
tOyCC
!
3
I
3
6
S
9
Z
000
I
t
t
4
3
!
0 IOOI
$
t
9
4
1
2
D IOC
tS:
fi;
IQOO
000
00
0
• '*
-."
.^
,'
,.^
^_
X
,/
1 —
/
/
/TOT
LAB
/
KL
3R
0!
T
ft SLUDOt FLOW BATE ~W«
FEED SLUOOt FLOW R*Tt -iltiri/»c.
FIGURE 10-40. BELT FILTER PRESS-BUILDING ENERGY, PROCESS ENERGY AND MAINTENANCE
MATERIAL REQUIREMENTS*
1
*
3
4
1
"
OOJX
t
5
4
i
r
•
i
4
s
too
J
ft
4
t
t
9
2
S \tV»
3
3
I
» I£C
.$
• N •
' * *
• 5 4
r
D lOOy
*
%
4
3
w
xbooo
WXO
000
OOD
--.
/
."/
/
f
~*
£
7
,''
1
/
/
,*
**^
8UILD
EMCB
MAI
1
PR
E>
MU
GT
Hilt,
*1EB
1CSSE
1 c
- t
FCCO tLUOQC FLOW MATE -
o aLtwec FLOW MTC
•Costs can be updated to $19% using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.193)
Source: USEPA,1982a
10-102
-------
FIGURE 10-41. CONSTRUCTION COST FOR VACUUM FILTERS*
I
t
3
4
1
I
IO.OOC
i
•
s
4
1
I
l.OOO,
T {
s s
i ;
i .
« tOO.
»
9
4
1
2
!
.000
1
OOO
000
o
INQ
UN
-H-t
LE
r
[ '
Tl
~ T
-'J
-~n • — • — *—
L MU
LTI
(Nil
^
..-^-[ J -H i . — , — J— — J
PL
S
-X*
'•
-
1
1
1
i
'
'
/
; i
'••
< lOOOO
TOTAL. FILTER *MCA -f«
ror*;. FILTM AREA -» 2
1000
FIGURE 10-42. VACUUM FILTERS-LABOR AND TOTAL ANNUAL OPERATION
AND MAINTENANCE COST*
7 -
K 3- S
i 3- J
S I- 2
* ICCUKB IQQyC
; f ?
i *r *
1 * '
tf- t
loon iw
Jt ;;
•t- < •
•r • •
5rj'
.i-i.
a • »
4 4
> 3
t • *
i 100
00
—•—
300
.
***
*'*
j {
_^
,
; ^
f..:f .._ ,-
Ix1
x^
^
^
^
j
-_J
_^ ;
^ TOT4L C
. — J
LABOfl
OST ' ! "
. i . ,i . 4
i i 1
1 f
1
t
'
j
TOTAL Ft-Ttll *«* -ft *
Tic-
Tioo
TOTAL nLTCM AftCA -
"Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.193)
Source: USEPA,1982a
10-103
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FIGURE 10-43. VACUUM FILTERS-BUILDING ENERGY, PROCESS ENERGY
AND MAINTENANCE MATERIAL REQUIREMENTS
I
s
4
5
S
t
:«i
ft
-
IOO
F— =
100 '
10
x'
X""
^
y
/
,.'
,,. '
H^
**
^r
r"e''
TOTAL *Xn* A«A -1
" :^iis
P UA1
x
'
' ENE«
/
• ' AuiLN
ENEN
«
FN
tH
8T
M(J
QV
Jt E
...
— '
7*5 ft" i4o '*°°
TOtAL riLTflt A«* -•*
•Costs can be updated to $1985 using ENR Construction Cost Indices for 1982 and 1985
(multiply value shown on this figure by 1.193)
Source: USEPA, 1982a
10.3 Solidification/Stabilization
Solidification and stabilization are terms which are used to describe
treatment systems which accomplish one or more of the following objectives
(USEPA, 1982b):
• Improve waste handling or other physical characteristics of the waste
• Decrease the surface area across which transfer or loss of contained
pollutants can occur
• Limit the solubility or toxicity of hazardous waste constituents.
Solidification is used to describe processes where these results are
obtained primarily, but not exclusively, by production of a monolithic block
of waste with high structural integrity. The contaminants do not necessarily
interact chemically with the solidification reagents, but are mechanically
10-104
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TABLE 10-16. 1985 CAPITAL AND OPERATING COSTS FOR PORTABLE FILTER PRESS*
The recurring annual costs for dewatering are as follows:
Total labor time to transport, hook-up, operate and
wash the press = 40 hrs/month.
Filter cloth cost
Disposal cost
TOTAL
- $ 5,990/yr
= $ 1,040/yr
= $ 6.032/yr
$13,062/yr
The capital cost required is as follows:
24" SPERRY HHC (or equal filter press (delivered)
* polypropylene construction
* 40" W x 102" L x 62" H
* 4,000 Ibs. (dry)
$15,600
Trailer and mounting (including a sludge collection
pan) = $ 2,080
Trailer mounted filtrate return pump = $ 2,080
Miscellaneous hoses and filterings = $ 1 ,040
TOTAL $20,800
*Costs updated to $1985 using 1983 and 1985 ENR construction cost indices.
Source: Moore, Gardner and Assoc., Inc. 1983
10-105
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locked within the solidified matrix. Contaminant loss is minimized by
reducing the surface area. Stabilization methods usually involve the addition
of materials which limit the solubility or mobility of waste constituents even
though the physical handling characteristics of the waste may not be improved
(USEPA, 1982b; Cullinane and Jones, 1985). Methods involving combinations of
solidification and stabilization techniques are often used.
Solidification/stabilization methods can be categorized as follows:
• Cement solidification
• Silicate-based processes
• Sorbent materials
• Thermoplastic techniques
• Surface encapsulation
• Organic polymer processes
• Vitrification.
Detailed discussions of solidification/stabilization methods can be found
in Guide to the Disposal of Chemically Stabilized and Solidified Waste and
Technical Handbook for Solidification/Stabilization of Hazardous Waste
(Cullinane and Jones, 1985).
These documents should be consulted for detailed information on these
processes. However, it should be noted that the state-of-the-art of
solidification/stabilization methods is advancing rapidly. Many manufacturers
are marketing processes which involve the use of various combinations of
alkaline earth materials (e.g., lime, cement kiln dust, silicaceous materials,
cement) often together with organic polymers and proprietary chemicals.
10.3.1 Cement-Based Solidification
10.3.1.1 General Description
This method involves mixing the wastes directly with Portland cement, a
very common construction material. The waste is incorporated into the rigid
matrix of the hardened concrete. Most solidification is done with Type I
Portland cement, but Types II and V can be used for sulfate or sulfite wastes.
This method physically or chemically solidifies the wastes, depending upon
waste characteristics (USEPA, 1982b). The end product may be a standing
monolithic solid or may have a crumbly, soil-like consistency, depending upon
the amount of cement added.
10-106
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10.3.1.2 Applications/Limitations
Most hazardous wastes slurried in water can be mixed directly with cement
and the suspended solids will be incorporated into the rigid matrix. Although
cement can physically incorporate a broad range of waste types, most wastes
will not be chemially bound and are subject to leaching.
Cement solidification is most suitable for immobilizing metals because at
the pH of the cement mixture, most multivalent cations are converted into
insoluble hydroxides or carbonates. However, metal hydroxides and carbonates
are insoluble only over a narrow pH range and are subject to solubilization
and leaching in the presence of even midly acidic leaching solutions (e.g.,
rain). Portland cement alone is also not effective in immobilizing organics.
The end product of cement solidification will not be acceptable for
disposal without secondary containment regardless of whether the wastes are
organic or inorganic in nature. Another major disadvantage is that cement-
based solidification results in wastes that are twice the weight and volume of
the original material thereby increasing transportation and disposal costs
(USEPA, 1982b). Because of these limitations, Portland cement is generally
used only as setting agent in other solidification processes particularly
silicate-based processes described in Section 10.3.2.
Another problem with cement solidification is that certain wastes can
cause problems with the set, cure, and permanence of the cement waste solid
unless the wastes are pretreated. Some of these incompatible wastes are
(USEPA, 1982b):
• Sodium salts of arsenate, borate, phosphate, iodate, and sulfide
• Salts of magnesium, tin, zinc, copper, and lead
• Organic matter
• Some silts and clays
• Coal or lignite.
Major advantages to the use of cement include its low cost, and the use
of readily available mixing equipment.
10.3.1.3 Implementation Considerations
Since cement is primarily used as a setting agent in other solidification
processes, Sections (10.3.2 and 10.3.5) should be consulted for information
related to implementation.
10-107
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10.3.1.4 Costs
Cement costs range from $60 to $90 per ton at the mill. However, capital
expenditure and transportation will vary widely depending on the site and the
waste (see Section 10.3.2). Cost information for specific wastes should be
obtained from vendors. Vendors include: Atcor Washington, Inc., Park Mall,
Peeksville, New York; and Chemfix, Inc., Kenner, Louisiana.
10.3.2 Silicate-Based Processes
10.3.2.1 General Description
Silicate based processes refer to a very broad range of solidification/
stabilization methods which use a siliceous material together with lime,
cement, gypsum, and other suitable setting agents. Extensive research is
currently underway on the use of siliceous compounds in solidification. Many
of the available processes use proprietary additivies and claim to stabilize a
broad range of compounds from divalent metals to organic solvents. The basic
reaction is between the silicate material and polyvalent metal ions. The
silicate material which is added in the waste may be fly-ash, blast furnace
slag or other readily available pozzolanic materials. Soluble silicates such
as sodium silicate or potassium silicate are also used. The polyvalent metal
ions which act as initiators of silicate precipitation and/or gelation come
either from the waste solution, an added setting agent, or both. The setting
agent should have low solubility, and a large reserve capacity of metallic
ions so that it controls the reaction rate. Portland cement and lime are most
commonly used because of their good availability. However, gypsum, calcium
carbonate, and other compounds containing aluminum, iron, magnesium, etc. are
also suitable setting agents. The solid which is formed in these processes
varies from a moist, clay-like material to a hard-dry solid similar in
appearance to concrete (Granlund and Hayes, undated).
Some of the additives used in silicate based processes include (Cullinane
and Jones, 1985):
• Selected clays to absorb liquid and bind specific anions or cations
• Emulsifiers and surfactants which allow the incorporation of
immiscible organic liquids
• Proprietary absorbents that selectively bind specific wastes. These
materials may include carbon, zeolite materials and cellulosic
sorbents.
10-108
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There are a number of silicate-based processes which are currently
available or in the research stages. Manufacturers' claim differ signif-
icantly in terms of the capabilities of these processes for stabilizing
different waste constituents.
The Chemfix process uses soluble silicates with cement as the setting
agent. Research data shows that the process can stabilize sludges containing
high concentrations of heavy metals even under very acidic conditions
(Spencer, Reifsnyder, and Falcone, 1982).
The Envirosafe I process uses fly ash as the source of silicates and lime
as the alkaline earth material. This method has been shown to stabilize oil
bearing sludge (49% oil and grease) and neutralize inorganic metal sludge.
Success was demonstrated by use of compressive strength tests (using ASTM
methods) and leaching tests (Smith and Zenobia, 1982).
The DCM cement shale silicate process is a proprietary process formulated
by Delaware Custom Material, Inc., State College, PA. It involves use of
cement, an emulsifier for oily wastes, and sodium silicate. Testing by
Brookhaven National Laboratories showed that the process could stabilize oily
wastes with up to a 30 percent volumetric loading (Clark, Colombo, and
Neilson, 1982). Manufacturers claim that the process can be used to solidify
wastes containing acids, organic solvents and oils (Hayes and Granlund,
undated).
PQ Corporation of Lafayette Hill, Pennsylvania, has done extensive
research on the use of silicates. Their research describes successful
stabilization of a mixed heavy metal/organic sludge; a waste containing high
levels of organics and petroleum by-products; and a waste containing organic
solvents using modifications of the process which involves the use of sodium
silicates (Spencer, Reifsnyder, and Falcone, 1982).
10.3.2.2 Applications/Limitations
There is considerable research data to suggest that silicates used
together with lime, cement or other setting agents can stabilize a wide range
of materials including metals, waste oil and solvents. However, the
feasibility of using silicates for any application must be determined on a
site-specific basis particularly in view of the large number of additives and
different sources of silicates which may be used. Soluble silicates such as
sodium and potassium silicate are generally more effective than fly ash, blast
furnace slag, etc.
There is some data to suggest that lime-fly ash materials are less
durable and stable to leaching that cement fly ash materials (Cullinane and
Jones, 1985).
Common problems with lime-fly ash and cement-fly ash materials relate to
interference in cementitious reactions that prevent bonding of materials.
10-109
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Materials such as sodium borate, calcium sulfate, potassium dichromate and
carbohydrates can interfere with the formation of bonds between calcium
silicate and aluminum hydrates. Oil and grease can also interfere with
bonding by coating waste particles (Cullinane and Jones, 1985). However
several types of oily sludges have been stabilized with silicate based
processes.
One of the major limitations with silicate based processes is that a
large amount of water which is not chemically bound will remain in the solid
after solidification. In open air, the liquid will leach until it comes to
some equilibrium moisture content with the surrounding soil. Because of this
water loss, the solidified product is likely to require secondary containment.
Silicate-based processes can employ a wide range of materials, from those
which are cheap and readily available to highly specialized and costly
additives.
The services of a qualified firm are generally needed to determine the
most appropriate formulation for a specific waste type.
10.3.2.3 Implementation Considerations
Commercial cement mixing and handling equipment can generally be used for
silicate-based processes. Equipment requirements include chemical storage
hoppers, weight or volume-based chemical feed equipment, mixing equipment and
waste handling equipment. Ribbon blenders and single and double shaft mixers
can be used for mixing. A number of mobile, trailer mounted systems are
available.
Silicate-based solidification can also be accomplished on a batch basis
in drums. Equipment requirements include on-site chemical storage system,
chemical batching system, mixing system, and drum handling system. One
company has developed a solidification kit for processing wastes in a drum.
The kit consists of a drum containing a disposable mixer blade with the shaft
held by bearings welded to the inside of the lid and the bottom of the drum.
The upper end of the shaft is accessible through a bung in the lid for turning
with an external motor. The cement can be added to the drum before it is
capped. The liquid waste and silicate are added through bungs in the lid. An
air driven motor is clamped to the drum lid to turn the mixer (Granlund and
Hayes, undated).
Solidification can also be accomplished in-situ using a lagoon or mixing
pit. This would involve the use of common construction machinery such as a
backhor or pull shovel to mix the waste and reagents. However, the ability of
in-situ solidification to prevent leaching of contaminants would need to be
demonstrated on a case-by-case basis.
10-110
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10.3.2.4 Costs
Table 10-17 provides estimated costs for silicate cement solidification
using three different mixing methods: in-drum mixing, in-situ mixing and a
mobile cement mixing system. In all cases it was assumed that 500,000 gallons
(2,850 tons) of wastes were solidified with 30 percent portland cement and 2
percent sodium silicate. On-site disposal was assumed. These costs are
intended mainly to show the relative cost of various mixing methods and the
proportion of total cost for reagents, equipment and labor. It should be
emphasized that actual costs are highly waste-and site-specific and that
specific site and/or waste characteristics could change these cost estimates
by several fold.
In-drum mixing is by far the most expensive alternative and requires the
greatest amount of labor and production time. Because of the high cost,
in-drum mixing is limited to sites have highly toxic or incompatible wastes in
drums (Cullinane and Jones, 1985).
The cost of in~situ mixing and mobile treatment are much more comparable.
All are quite sensitive to reagent cost since it typically makes up from 40 to
65% of the total cost. The in-situ technique is the fastest and most
economical of the bulk methods because the wastes typically only have to be
handled once, or not at all if they are to be left in-place. Labor and
equipment each make up less than 5% of the total treatment cost. However,
in-situ mixing is the least reliable because of difficulties in accurate
reagent measurement and in getting uniform and/or complete mixing of wastes
and treatment reagents. Mobile mixing plants, although giving excellent
mixing results and reasonably good production rates, require that both the
treated and untreated product be handled, thereby increasing the costs above
those for in-situ treatment (Cullinane and Jones, 1985).
10.3.3 Sorbents
10.3.3.1 General Description
Sorbents include a variety of natural and synthetic solid materials which
are used to eliminate free liquid and improve the handling characteristics of
wastes. Commonly used natural sorbent materials include flyash, kiln dust,
vermiculite, and bentonite. Synthetic sorbent materials include activated
carbon which sorbs dissolved organics, Hazorb (product of Dow Chemical) which
sorbs water and organics and Locksorb (product of Radecca Corp.) which is
reportedly effective for all emulsions (Cullinane and Jones, 1985).
10-111
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TABLE 10-17. SUMMARY COMPARISON OF RELATIVE 1985 COST
OF STABILIZATION/SOLIDIFICATION ALTERNATIVES1
Parameter
In-drum
In-situ"
Plant Mixing
Pumpable
Unpumpable
Metering and
mixing efficiency
Processing days
required
Good
374
Fair
4
Excellent
10
Excellent
14
Cost/ton
Reagent
Labor and per diem
Equipment rental
Used drums
@ $11 /drum
Mobilization-
demobilization
Cost of treatment
process
Profit and
overhead (30%)
TOTAL COST/ TON
$ 24.46
(9%)*
61.09
(23%)
44.43
(17%)
57.69
(21%)
18.76
(7%)
$206.38
61.91
(23%)
$248.29
$21.27
(63%)
1.41
(4%)
1.43
(4%)
-
1.64
(5%)
$25.75
6.73
(23%)
$33.48
$21.27
(53%)
3.97
(10%)
4.07
(10%)
-
1.48
(4%)
$30,79
9.29
(23%)
$40.03
$21.27
(42%)
7.19
(14%)
7.82
(16%)
-
2.34
(5%)
$38.62
11.59
(23%)
$50.21
*% of total cost/ton for that alternative.
Costs updated from 1983 costs using 1985 ENR Index.
2
Assumed 49 gallons of untreated waste per drum and an average processing rate
of 4.5 drums per hour.
Assumed wastes would be mixed by backhoe with a lagoon and left there.
Remedial Action is located 200 miles from its nearest equipment.
4 . 3
Assumed pumpable sludge had a~daily throughput of 250 yd and the unputnpable
sludge a throughput of 180 yd /day. Remedial Action is assumed to be located
200 miles from the nearest equipment.
Source: Cullinane and Jones, 1985
10-112
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10.3.3.2 Applications/Lira itations
Sorbents are widely used to remove free liquid and improve waste
handling. Some sorbents have been used to limit the escape of volatile
organic compounds. They may also be useful in waste containment when they
modify the chemical environment and maintain the pH and redox potential to
limit the solubility of wastes (Cullinane and Jones, 1985). Although sorbents
prevent drainage of free water, they do not necessarily prevent leaching of
waste constituents and secondary containment is generally required.
10.3.3.3 Implementation Considerations
The quantity of sorbent material necessary for removing free liquid
varies widely depending on the nature of the liquid phase, the solids content
of the wate, the moisture level in the sorbent, and the availability of any
chemical reactions that take up liquids during reaction. It is generally
necessary to determine the quantity of sorbent needed on a case-specific
basis .
Equipment requirements for addition and mixing of sorbents are simple.
Any of the mixing methods described in Section 10.3.2.3 can be used.
10.3.4 Thermoplastic Solidification
10.3.4.1 General Description
Thermoplastic solidification involves sealing wastes in a matrix such as
asphalt bitumen, paraffin, or polyethylene. The waste is dried, heated, and
dispensed through a heated plastic matrix. The mixture is then cooled to
form a rigid but deformable solid. Bitumen solidification is the most widely
used of the thermoplastic techniques.
10.3.4.2 Applications/Limitation
Thermoplastic solidification involving the use of an asphalt binder is
most suitable for heavy metal or electroplating wastes. Relative to the
cement solidification, the increase in volume is significantly less and the
rate of leaching significantly lower. Also, thermoplastics are little
affected by either water or microbial attack.
10-113
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There are a number of waste types which are incompatible with thermo-
plastic solidification. Oxidizers such as perchlorates or nitrates can react
with many of the solidification materials to cause an explosion. Some
solvents and greases can cause asphalt materials to soften and never become
rigid. Xylene and toluene diffuse quite rapidly through asphalt. Salts that
partially dehydrate at elevated temperatures can be a problem. Sodium sulfate
hydrate, for example, will loose some water during asphalt incorpoation and if
the waste asphalt mix containing the partially dehydrated salt is soaked in
water, the mass will swell and crack due to rehydration. This can be avoided
by eliminating easily dehydrated salts or coating the outside of the waste/
asphalt mass with pure asphalt. Chelating and complelxing agents (cyanides
and ammonium) can cause problems with containment of heavy metals (Cullinane
and Jones, 1985) .
High equipment and energy costs are principal disadvantages of therm-
oplastic solidification. Another problem is that the plasticity of the
matrix-waste mixture generally require that containers be provided for
transportation and disposal of materials which greatly increases the cost.
Certain wastes, such as tetraborates, and iron and aluminum salts can
cause premature solidification and plug up the mixing machinery (USEPA,
1982b).
10.3.4.3 Implementation Considerations
Thermoplastic solidification requires specialty equipment and highly
trained operators to heat and mix the wastes and solidifier. The common range
of operating temperatures is 130° to 230°C. The energy intensity of the
operation is increased by the requirement that the wastes be thoroughly dried
before solidification.
10.3.4.4 Costs
Cost data for thermoplastic solidification outside of the nuclear indus-
try is not readily available. Wernen and Pfleudern Corporation has developed
an asphalt binder based process called the Volume Reduction and Solidification
System; solidification costs for non-radioactive materials are estimated at
$20 to $70 per ton. This cost includes secondary containment but not final
transport and disposal (Doyle, 1980).
10-114
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10.3.5 Surface Microencapsulation
10.3.5.1 General Description
Surface encapsulation describes those methods which physically micro-
encapsulate wastes by sealing them in an organic binder or resin.
Surface encapsulation can be accomplished using a variety of approaches.
Three methods which have been the subject of considerable research are
described briefly below:
One process developed by Environmental Protection Polymers involves the
use of 1,2-polybutadiene and polyethylene (PE) to produce a microencapsulated
waste block onto which a high density polyethylene (HOPE) jacked is fused.
The 1,2-polybutadiene is mixed with particulated waste which yields, after
solvent evaporation, free flowing dry resin-coated particulates. The
resulting polymers are resistent to oxidative and hydrolytic degradation and
to permeation by water. The next step involves formation of a block of the
polybutadiene/waste mixture. Powdered, high density PE is grafted chemically
onto the polymer backbone to provide a final matrix with ductile qualities.
Various combinations of the two resins (polybutadiene and PE) permit tailoring
of the matrix's mechanical properties without reduction of system stability
when exposed to severe chemical stress. In the final step, a 1/4 inch thick
HDPE jacket is mechanically and chemically locked to the surface of the micro-
encapsulated waste (Lubowitz and Wiles, 1981).
Another encapsulation method developed by Environmental Protection
Polymers involves a much simpler approach. Contaminated soils or sludges are
loaded into a high density polyethylene overpack. A portable welding
apparatus developed by Environmental Protection Polymers is then used to spin
weld a lid onto the container thereby forming a seam free encapsulate.
A third surface encapsulation method involves use of an organic binder to
seal a cement-solidified mass. United States Gypsum Company manufacturers a
product called Envirostone Cement which is a special blend of high-grade
polymer modified-gypsum cement. Emulsifiers and ion exchange resins may be
added along with the gypsum cement which hydrates to form a freestanding mass.
A proprietary organic binder is used to seal the solified mass (United States
Gypsum Co., 1982). The process can be used to stabilize both organic and
inorganc wastes. It has been shown to effectively immobilize waste oil
present at concentration as high as 36 volume percent (Clark, Colombo, and
Neilson, 1982). The volume of waste is smaller than that obtained with cement
solidification alone.
10.3.5.2 Applications/Limitations
The major advantage of encapsulation processes so far as research shows
is that the waste material is completely isolated from leaching solutions.
10-115
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These methods can be used for both organic and inorganic waste constituents.
However, each of the available encapsulation processes are quite unique and
the feasibility must be determined on a case-specific basis.
Other advantages associated with hazardous waste encapsulation include
(USEPA, 1982b):
• The cubic and cylindrical encapsulates allow for efficient space
utilization during transport, storage, and disposal
• The hazard of accidental spills during transport is eliminated
• Materials used for encapsulation are commercially available, very
stable chemically, nonbiodegradable, mechanically tough, and flexible
• Encapsulated waste materials can withstand the mechanical and chemical
stresses of a wide range of disposal schemes (landfill, disposal in
salt formations, ocean disposal).
The major disadvantages associated with encapsulation techniques include:
• Binding resins required for agglomeration/encapsulation (high density
polyethylene; polybutadiene) are relatively expensive
• The processes are energy intensive and relatively costly
• Skilled labor is required to operate molding and fusing equipment.
10.3.5.3 Costs
Environmental Protection Polymers has estimated that the cost of the
polybutadiene/HDPE microencapsulation method will be approximately $90/ton.
Encapsulation in the seam-free HDPE overpack is approximately $50 to $70 for a
80 gallon drum load (Lubowitz, H., Environmental Protection Polymers, personal
communication October 13 and 14, 1983).
10.3.6 Vitrification
10.3.6.1 General Description
Vitrification of wastes involves combining the wastes with molten glass
at a temperature of 1,350°C or greater. However, the encapsulation might be
done at temperatures significantly below 1,350°C (a simple glass polymer such
as boric acid can be poured at 850°C). This melt is then cooled into a
stable, noncrystalline solid (USEPA., 1982b) .
10-116
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10.3.6.2 Applications/Lira itations
This process is quite costly and so has been restricted to radioactive or
very highly toxic wastes. To be considered for vitrification, the wastes
should be either stable or totally destroyed at the process temperature.
Of all the common solidification methods, vitrification offers the
greatest degree of containment. Most resultant solids have an extremely low
leach rate. Some glasses, such as borate-based glasses, have high leach rates
and exhibit some water solubility. The high energy demand and requirements
for specialized equipment and trained personnel greatly limit the use of this
method.
10.3.6.3 Implementation Considerations
Classification of wastes is an extremely energy intensive operation and
requires sophisticated machinery and high trained personnel.
10.3.6.4 Cost
No cost information was available for glassification.
10.3.7 Technology Selection/Evaluation
Evaluation of the technical feasibility and effectiveness of
stabilization/solidification methods must be determined on a case-by-case
basis. Commercial firms specializing in these processes should be consulted
whenever solidification/stabilization is being considered. Samples of the
solidified product will need to be subjected to extensive leaching tests
unless a reliable, effective means of secondary containment is to be used. It
should be noted that secondary containment is recommended with most of the
previously described methods (except microencapsulation and glassification for
some waste types). Similarly, where the end product is intended to be a
monolithic block, samples must be subjected to compressive strength tests.
Solidification/stabilization methods run the gamut from those which use
simple, safe, readily available equipment (cement and most silicate-based
processes) to those which require highly sophisticated, costly, and
specialized equipment (e.g., glassification and thermoplastic techniques).
Use of these high technology processes should be limited to wastes which
cannot be treated cost-effectively using any other methods. Regardless of the
simplicity of some of the equipment, professionals trained in these processes
should be consulted since formulations including proprietary additives are
very waste specific.
10-117
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10.4 Gaseous Waste Treatment
Gaseous wastes may be present at hazardous waste sites as a result of
bulk gas disposal in containers, volatilization of organic liquids, byproducts
of waste decomposition, or byproducts of treatment or other on-site processes.
Once captured and collected, gaseous wastes can be treated thermally to render
contaminants less hazardous or treated physically or chemically to remove and
concentrate contaminants. The following three categories of gaseous waste
treatment are described in this section:
• Incineration
• Flaring
• Adsorption.
10.4.1 Flaring
10.4.1.1 General Description
Combustion is a chemical reaction that thermally oxidizes a substance
into products that generally include ash, gases, water vapor, and heat.
Flaring is a special category of combustion where wastes are exposed to an
open flame and no special features are employed to control temperatures or
time of combustion. Supplementary fuels may be needed to sustain continuous
combustion.
10.4.1.2 Applications/Limitations
Flares are commonly used in the oil and gas industry to dispose of waste
gases and fumes at refineries; at sewage treatment plants to dispose of
digestor gas; and at sanitary landfills to dispose of landfill gas. Although
flares provide sufficient destruction of contaminants for conventional
applications, destruction removal efficiencies (DREs) required by current
environmental regulations for thermal destruction of hazardous wastes are
generally too stringent to be met by flaring. Exceptions may be gaseous waste
streams consisting of relatively simple hydrocarbons (emissions from fuel
tanks, landfill methane gas, etc.).
Supplemental fuel is required to sustain a flame with gases of low
heating value. Gases with heating values as low as the low hundreds of Btu's
per cubic foot can sustain a flame (natural gas has a heating value of approx-
imatley 1,000 Btu's per cubic foot).
Flame sensors, pilot flames, automatic sparkers, and alarms are often
used to sense loss of flame, attempt reignition, and alert operators to system
10-118
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performance problems. Shields can be placed around floors to serve as
windbreaks for containing and preventing "blowing out" of the flame.
The flow rate dictates the diameter and height of the flare and the
number of flares to be employed. The flare must be designed such that the
flame is largely contained within the body of the flare for safety reasons and
to allow adequate mixing of gas and air. The oxygen content of the gas
influences the air/gas ratio that is sought in the combustion area of the
flare.
10.4.1.3 Costs
Purchase costs of flares depend primarily on the waste-gas flowrate, and
secondarily on design and elevation. Costs in dollars for flowrates between
1,000 and 100,000 Ib/h are given in Figure 10-44. Costs include ladders,
platforms, knockout drums with seals, and stacks high enough to ensure
grade-level radiation no greater than 1,500 Btu/(h)(ft ). Costs described in
Figure 10-44 refers to self-supporting type elevated flares (approximately 40
feet high). Costs for elevated flares supported by guyed wires (nominally 100
feet tall) range from 30 percent higher (than the self-supporting type) at
250,000-lb/h flowrates, to 80 percent higher at 2,500-lb/h flowrates.
Operating costs for flares are high because of the substantial quantity
of natural gas and steam (in the smokeless type) consumed. If the waste-gas
must be driven, fan power costs for overcoming pressure drops may also be
FIGURE 10-44. PURCHASE COSTS OF ELEVATED FLARES
10*
103
103 104 105
Waste-gas flowrate, Ib/h
(high Btu-ethylene)
(low Btu-60 Btu/ft3)
Source: Vatavuk and Neveril, 1983
10-119
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high. This pressure drop depends on the size of the flare, knockout drum,
puiping and stack height, with the maximum allowable pressure drop being
approximately 60 in. HO.
Elevated flares require supplemental fuel, (in addition to gas for pilots
and purging) when a low-Btu gas is being burned. The supplemental fuel
(natural gas) required is plotted against waste-gas flowrate in Figure 10-45.
This graph is based on an 880-h/yr operating factor, for gas flowrates in the
range of 1,000 to 250,000 Ib/h.
Steam consumption for smokeless flares (or others requiring steam
injection) can be estimated at 0.6 Ib/lb of waste-gas.
10.4.1.4 Technology Selection/Evaluation
Flaring systems, by virtue of their relative lack of controllability, are
generally considered to perform inconsistently. They are relatively simple
to both fabricate and install. Conventional steel plate, pipe, and welding
are employed in fabrication.
When properly designed and operated, flares pose no unusual safety
impacts to operators or others. The presence of a visible flame is sometimes
considered by the public to be a nuisance.
FIGURE 10-45. NATURAL GAS REQUIREMENTS FOR ELEVATED FLARES
S
10*
1Q3
'Elevated
1Q2 103 10* 106
Natural gas, million Btu/yr
Source: Vatavuk and Neveril, 1983
10-120
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Properly designed flaring systems operate automatically. The most basic
design of flaring requires tnonical ignition. Pilot flames, sensors, and
igniters may require regular maintenance. Monitoring of air quality local to
the flame is advisable to ensure that adequate treatment is being afforded.
10.4.2 Adsorption
10.4.2.1 General Description
Adsorption is the adherence of one substance to the surface of another by
physical and chemical processes. Treatment of wastestreams by adsorption is
essentially a process of transferring and concentrating contaminants (the
adsorbate) from one medium (liquid or gas) to another (the adsorbent). The
most commonly used adsorbent is activated carbon; generally, the granular form
(GAG) is used to treat gaseous wastes. Other adsorbents are specially
manufactured resins.
Activated carbon is a highly porous material. Adsorption takes place on
the walls of the pores because of an imbalance of forces on the atoms of the
walls. The adsorption of molecules onto the wall surfaces serves to balance
the forces (Calgon Corp., undated). Adsorption onto resins occurs in a
similar fashion.
Adsorption gas treatment systems consist of containerized beds of
adsorbent. Large and highly permeable void spaces between relatively large
GAG particles or pellets (nominal size of several millimeters) allow the
contaminated medium to flow through the bed, contacting the particles and
allowing adsorption to take place. The treated medium leaves the bed with
reduced concentrations of adsorbate until the adsorbent has reached capacity.
Once adsorbents have reached capacity, little or no further adsorption occurs
and some contaminants can be released back into the medium (desorption) and
actually increase contaminant concentrations.
Adsorbents at capacity can be disposed of in appropriate landfills,
incinerated, or can be regenerated, driving off the adsorbate and allowing
reuse of the adsorbent for treatment. GAG is regenerated by heating in a
reduced-pressure atmosphere (Calgon Corp, undated). Resins are regenerated by
washing with appropriate solvents (Kiang and Metry, 1982). The adsorbate can
be recovered and reused (solvents, for example) from the regeneration process.
Multiple bed vessels are often required to allow adequate contact time
and/or to optimize the frequency of adsorbent changeover or regeneration.
Partial or total redundant capacity is often provided by extra bed vessels to
allow continuous operation during changeover or regeneration.
10-121
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10.4.2.3 Applications/Limitations
Carbon adsorption is generally accepted for use in controlling volatile
hydrocarbons; organic-related emissions; certain sulfur-related emissions such
as hydrogen-sulfide; mercury; vinyl chloride; most halogenatd organics; and
radioactive materials such as iodine, krypton, and xenon. Carbon adsorption
can also control oxides of sulfur and nitrogen and carbon monoxide (Calgon
Corp., undated).
Resins are capable of removing most organic contaminants from water and
are also applicable to removal of organics from gaseous streams. However,
resins are not widely used for gaseous waste treatment.
Adsorption is widely used in industry for air pollution and odor control,
often in association with solvent recovery and reuse systems. Generally, GAG
acts as an accumulator of organic contaminants until the bed is saturated.
Hot gases are passed through the bed to desorb the organics which are
condensed and recovered or are incinerated (Calgon Corp., undated).
Monitoring of gas flowrate and influent and discharge adsorbate concen-
trations are needed to determine changeover/regeneration schedules. Automatic
monitors and microprocessors may be warranted for highly complex and variable
systems. Alarms and/or shut-down controls may also be warranted for complex
systems or in sensitive or populated areas.
10.4.3 Technology Selection/Evaluation
Adsorption techniques are well-established for removal of organic
compounds and some inorganic compounds from gaseous streams. Adsorption is
highly reliable provided that adsorbate and adsorbent are properly matched,
sufficient contact time is allowed, and the adsorbent is regenerated or
replaced before saturation (and desorption) is reached. Many adsorption
systems are prepackaged and can be quickly installed and placed into operation
by contractors, suppliers, or manufacturers. Specially designed systems
employ off-the-shelf towers, blowers, and other equipment, and require
additional installation time.
Operation of properly designed adsorption gas treatment systems is
essentially as automatic as the gas delivery system although manual or special
automatic adjustments may be warranted for highly variable flows or adsorbate
concentrations. Changeover or regeneration of the adsorbent bed must be
conductd on a predetermined basis to ensure continuous effective treatment.
10-122
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10.5 Thermal Destruction of Hazardous Wastes
Thermal destruction is a treatment method which uses high temperature
oxidation under controlled conditions to degrade a substance into products
that generally include C0~, H-0 vapor, SO-, NO , HCl gases and ash. The
hazardous products of the thermal destruction/incineration such as partic-
ulates, SO,,, NO , HCl, and products of incomplete combustion require air
pollution control equipment to prevent release of undesirable species into the
atmosphere. Thermal destruction methods can be used to destroy organic
contaminants in liquid, gaseous and solid waste streams.
The most common incineration technologies applicable to hazardous wastes
include:
• Liquid injection
• Rotary kiln
• Fluidized bed
• Multiple hearth
The operating principles and general applications of these methods are
summarized in Table 10-18. Mobile incinerators, at sea incinerators and
coincineration commonly employ these technologies.
Emerging technologies for the thermal destruction of wastes include
(Monsanto Research Corp.; 1981, Keitz and Lee, 1983; Lee, 1983; State of
California, 1981):
• Molten salt
• Wet air oxidation
• Plasma arch torch
• Circulating bed
• High temperature fluid wall
• Pyrolysis
• Supercritical water
• Advanced electric reactor
• Vertical tube reactor.
10-123
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10.5.1 Liquid Injection
10.5.1.1 General Description
A liquid incineration system consists of a single or double refractory-
lined combustion chamber and a series of atomizing nozzles. Two chamber
systems are more common. The primary chamber is usually a burner where
combustible liquid and gaseous wastes are introduced. Noncombustible liquid
and gaseous wastes are introduced downstream of the burner in the secondary
chamber. A schematic diagram of a two-stage system is shown in Figure 10-46.
Single chamber incinerators are used for systems handling only combustible
wases (Kiang and Metry, 1982).
FIGURE 10-46.
LIQUID INJECTION INCINERATION SYSTEM
FLUE GAS
FEED
STEAM WATER
WATER
LIQUID WASTE
FUEL
AIR
SALT
SOLUTION
Source: Kiang and Metry, 1982
The most popular liquid injection incinerators are horizontally and
vertically fired units. A liquid waste has to be converted into a gas before
combustion. The liquid is atomized passing through the burner nozzles while
entering the combustor. This is necessary to ensure complete evaporation and
oxidation. If viscosity precludes atomization, mixing and heating or other
means should be applied prior to atomization to reduce waste viscosity.
The operating temperatures vary from 1300 to 3,000°F, with the most
common temperature being about 1600°F. Residence times vary from less than
0.5 seconds to 2 seconds (Lee, Keitz, and Vogel, 1982; State of California,
10-125
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1981). The process usually requires 20 to 60% excess air to ensure complete
combustion.
10.5.1.2 Application Limitations
Liquid injection can be used to destroy virtually any pumpable waste or
gas. These units have been used in the destruction of PCBs, solvents, still
and reactor bottoms, polymer wastes, and pesticides (State of California,
1981). Unlikely candidates for destruction include heavy metal wastes and
other wastes high in inorganics. It does not have a need for a continuous ash
removal system other than for pollution control (Monsanto Research Corp.,
1981).
Liquid incinerators have no moving parts and require the least
maintenance of all types of incinerators. The major limitations of liquid
injection are its ability to incinerate only wastes which can be atomized in
the burner nozzle and the burner's susceptibility to clogging. It also needs
a supplemental fuel.
Liquid injection incinerators are highly sensitive to waste composition
and flow changes. Therefore, storage and mixing tanks are necessary to ensure
a reasonably steady and homogenous waste flow (Kiang and Metry, 1982).
10.5.2 Rotary Kiln
10.5.2.1 General Description
Rotary kilns are capable of handling a wide variety of solid and liquid
wastes.
Rotary kiln incinerators are cylindrical, refractory-lined shells. They
are fueled by natural gas, oil, or pulverized coal. Most of the heating of
the waste is due to heat transfer with the combustion product gases and the
walls of the kiln. The basic type of rotary kiln incinerator, illustrated in
Figure 10-47, consists of the kiln and an afterburner (Kiang and Metry, 1982).
Wastes are injected into the kiln at the higher end and are passed
through the combusion zone as the kiln rotates. The rotation creates
turbulence and improves combustion. Rotary kilns often employ afterburners to
ensure complete combustion. Most rotary kilns are equipped with wet scrubber
emission controls.
The residence time and temperature depend upon combustion characteristics
of the waste. Residence times can range from a few seconds to an hour or more
for bulk solids. Combustion temperature range from 1500 to 3000°F.
10-126
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10.5.2.2 Application/Limitations
Rotary kilns are capable of burning waste in any physical form. They can
incinerate solids and liquids independently or in combination and can accept
waste feed without any preparation (Monsanto, 1981). Hazardous wastes which
have been treated in rotary kilns include PCBs, tars, obsolete munitions,
polyvinyl chloride wastes, and bottoms from solvent reclamation operations
(State of California, 1981).
FIGURE 10-47. ROTARY KILN INCINERATOR SCHEMATIC
OXIDATION
CHAMBER
FLUE GAS
SCRUBBER
WASTE
STORAGE
HOPPER
©
STACK
L VA/ yy i
ASH /
REMOVAL
MECHANISM
J»
©
1 1
T ©
LIQUID
HOLDING
TANK
LEGEND:
1. INFLUENT WASTE
2. COMBUSTION AIR
3. FLUE GAS
4. RESIDUALS
5. SCRUBBER WATER
6. FUEL
Source: Ghassami, Yu, and Quinlivan, 1981
Because of their ability to handle waste in any physical forms, and their
high incineration efficiency, rotary kilns are the preferred method for
treating mixed hazardous solid residues (Lee, Keitz, and Vogel, 1982).
The limitations of rotary kilns include susceptibility to thermal shock,
the necessity for very careful maintenance, need for additional air due to
leakage, high particulate loadings, relatively low thermal efficiency, and a
high capital cost for installation (Monsanto Research Corp., 1981).
10-127
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10.5.3 Multiple Hearth
10.5.3.1 General Description
A multiple hearth incinerator consists of a refractory lined steel shell,
a rotating central shaft, a series of solid flat hearths, a series of rabble
arms with teeth for each hearth, an air blower, waste feeding and ash removal
systems, and fuel burners mounted on the walls (Monsanto Research Corp.,
1981). Figure 10-48 illustrates the components of the.multiple hearth. It
can also be equipped with an afterburner, liquid waste burners and side ports
for tar injection. Temperature in the burning zone ranges from 1400 to 18008F
and residence time may be very long.
10.5.3.2 Applications/Limitations
The multiple hearth incinerator can be used for the disposal of all forms
of combustible industrial waste materials, including sludges, tars, solids,
liquid and gases. The incinerator is best suited for hazardous sludge
destruction. Solid waste often requires pretreatment such as shredding and
FIGURE 10-48. MULTIPLE HEARTH INCINCERATOR
AIR
FLUE GAS
WASH
WATER
All
I IHCIHIRATOR
| ASH
ASB
SLURJtt
BLOW*
Source: Kiang and Metry, 1982
10-128
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sorting. It can treat the same wastes as the rotary kiln provided that
pretreatment of solid waste is applied. The principal advantages of multiple
hearth incineration include high residence time for sludge and low volatile
materials; ability to handle a variety of sludges; ability to evaporate large
amounts of water; high fuel efficiency and the utilization of a variety of
fuels. The greatest disadvantages of the technology include susceptibility to
thermal shock; inability to handle wastes containing ash, which fuses into
large rock-like structures, and wastes requiring very high temperatures. Also
control of the firing of supplemental fuels is difficult. The multiple hearth
incinerator has high maintenance and operating costs (Monsanto Research Corp.,
1981; State of California, 1981). The operating cost may be reduced by
utilizing liquid or gaseous combustible wastes as secondary fuel (Monsanto
Research Corp., 1981).
10.5.4 Fluidized Bed
10.5.4.1 General Description
The fluidized bed incinerator illustrated in Figure 10-49 consists of a
cylindircal vertical refractory lined vessel containing a bed of inert
granular material, usually sand on a perforated metal plate. Combustion air
is introduced through a plenum at the bottom of the incinerator and rises
vertically fluidizing the bed and maintaining turbulent mixing of bed
particles. Waste material is injected into the bed and combustion occurs
within the bubbling bed. Heat is transferred from the bed into the injected
wastes. Auxiliary fuel is usually injected into the bed. Bed temperatures
vary from 1400 to 1600°F. Since the mass of the heated, turbulent bed is much
greater than the mass of the waste, heat is rapidly transferred to the waste
materials; a residence time of a few seconds for gases and a few minutes for
liquids is sufficient for combustion (State of California, 1981).
The residence time is long enough to allow the solid materials to become
small and light enough to be carried off as particulates. Suspended fine
particulates are usually separated in a cyclone when exhaust gases pass
through air pollution control devices before being released into the
atmosphere.
10.5.4.2 Applications/Limitations
Fluidized bed incinerators are a relatively new design, presently being
applied for liquid, solid and gaseous combustible wastes. The most typical
wastes treated in fluidized beds include slurries and sludges. Some wastes
require pretreatment prior to entering the reactor. The pretreatment may
involve drying, shredding and sorting. The fluidized bed handles the same
waste that can be treated in the rotary kiln (Monsanto Research Corp., 1981).
10-129
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FIGURE 10-49. FLUIDIZED BED INCINERATOR
FLUE
GAS
ASH
J • y/»< X'^f :•" v," ^."?~£st) f.
s^^nH'HrfiiiftfiimHiMi
FUEL
BURNER
MAKE-UP SAND
WASTE
. AIR
Source: Kiang and Metry, 1982
Fluidized beds are typically used for the disposal of municipal waste-
water treatment plant sludges, oil refinery waste, and pulp and paper mill
waste. There is only limited data on the use of fluidized bed for hazardous
waste incineration. The technology has been used for pharmaceutical wastes,
phenolic wastes, and methyl methacrylate (State of California, 1981).
It is particularly well suited for incineration of high-moisture wastes,
sludges and wastes containing large quantities of ash. Because of the low bed
temperature, the exhaust gases usually contain low nitrogen oxides (Kiang and
Metry, 1982).
The advantages of the fluidized bed incinerator include simple design,
minimal NO formation, long life of the incinerator, high efficiency,
sitnplicityxof operation, and relatively low capital and maintenance costs. It
also has the ability to trap some gases in the bed, reducing the need for and
the cost of an emission control system. The disadvantages include difficulty
in removing residual materials from the bed, a relatively low throughput
capacity, the difficulty in handling residues and ash from the bed and the
10-130
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relatively high operating costs (State of California, 1981; Monsanto Research
Corp., 1981).
10.5.5 At-Sea Incineration, Mobile Incineration, and Coincineration
At-sea incineration usually utilizes a liquid injection unit mounted on a
ship, to destroy hazardous waste far away from populated areas and shipping
lanes. No acid gas pollutant removal system is applied. The wastes treated
include toxic organochloride compounds, herbicides, and Agent Orange. The
basic advantage of at-sea incinertaion is the distance from populated areas
and the high efficiency of combustion. The disadvantages are problems with
monitoring an at-sea process, the danger of spills and the need to operate
on-shore auxiliary facilities.
Mobile incineration has not been widely used yet but the demand for the
application of this technique grows with future bans on the landfill disposal
of certain wastes. Existing mobile systems include liquid injection and
rotary kiln incinerators equipped with secondary combustion chambers and
environmental controls. These mobile incinerators are capable of handling a
variety of wastes including PCBs, carbon tetrachloride, other hazardous wastes
and soils. The primary advantage of the mobile incinerator is its ability to
treat on-site and thus eliminate the need for off-site transport of waste.
There is currently only limited experience with mobile incinerators. Mobile
incinerators must meet all applicable state requirements which typically
include air emission permits.
Coincineration is a process of using combustible wastes as supplemental
fuels in fossil fuel boilers or any type of incinerator (State of California,
1981; Monsanto Research Corp., 1981). As a result of Coincineration, the
energy value of the waste is used to produce steam and the original form of
the waste is destroyed through combustion. This incineration technique can be
implemented in any boiler where the parameters of combustion and feed make it
feasible. The principal advantages of Coincineration include low capital
cost, and no need for the transport of on-site generated wastes. Dis-
advantages include the possibility of damaging the boiler by some harmful
waste and the difficulty in obtaining high efficiency of combustion.
10.5.6 Advanced Incineration Technologies
10.5.6.1 Molten Salt
The molten salt incinerator can be used for destruction of hazardous
liquids and solids. In this method (illustrated in Figure 10-50) wastes
undergo catalytic destruction when they contact hot molten salt maintained at
a temperature between 1382 and 1832°F (Ross, 1984; Solsberg, Parent, and Ross,
1985). Hot gases rise through the molten salt bath, pass through a secondary
10-131
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FIGURE 10-50. MOLTEN SALT INCINERATOR
MOLTEN SALT COMBUSTOR SCHEMATIC
LIQUID OR SOLID WASTE x ATOMIZING
AIR
OFF
DOWNCOMER
METAL
CONTAINMENT
VESSEL
SUPPORT
STRUCTURE
INSULATED
ENCLOSURE
SIMPLIFIED FLOW SCHEMATIC
MOLTEN SALT DESTRUCTION
SALT DISPOSAL
Source: Rockwell International, 1980
10-132
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reaction zone, and through an off-gas clean-up system before discharging to
the atmosphere (Kiang and Metry, 1982). Supplemental fuel may be required
when wastes are not sufficiently combustible to maintain temperatures.
Liquid, free-flowing powders, sludges, and shredded solid wastes can be
fed directly into the incinerator. The technology has been demonstrated to be
highly effective for chlorinated hydrocarbons including PCB, chlorinated
solvents, and malathion (Kiang and Metry, 1982). However, the process appears
to be sensitive to materials containing high ash content or high chlorine
content which must ultimately be removed in the purge system (Ross, 1984).
10.5.6.2 Wet Air Oxidation
Wet air oxidation involves aqueous phase oxidation of dissolved or
suspended organic substances at elevated temperatures and pressures. The
temperature of the process is relatively low, 350-650°F, and the pressure
varies between 300-3000 PSI. Figure 10-51 shows a simplified scheme of the
wet air oxidation process.
The waste is pumped into the system by the high pressure pump and mixed
with air from the air compressor. The mixture passes through a heat
exchanger, and then into the reactor where oxygen in the air reacts with
organic matter in the waste. The oxidation is accompanied by a temperature
rise. The gas and liquid phases are separated after the reactor, and the
liquid passes through the heat exchanger, heating the incoming material. The
gas and liquid streams are discharged from the system through control valves.
The degree of oxidation is primarily a function of reaction temperature and
residence time.
WAO is used primarily to treat concentrated waste streams containing
organic and oxidizable inorganic wastes. It is generally selected for
treating or pretreating a waste stream which has a high COD/BOD,, ratio and is
not readily amenable to biological treatment. It is also selected where it is
determined to be more cost-effective than incineration. Waste streams for
which WAO is particularly applicable include concentrated streams containing
pesticides, herbicides or other complex organics which are not readily
biodegradable.
10.5.6.3 Plasma Arc Torch
Plasma arc torch may be used to destory either liquid or solid wastes by
pyrolyzing them into combustible gases in contact with a gas which has been
energized to its plasma state by an electrical discharge (see Figure 10-52).
The plasma gas temperature is about 90,000°F. Wastes are atomized, ionized
10-133
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FIGURE 10-51.
FLOWSHEET OF WET AIR OXIDATION
WASTK.
STORAGE
TANK
l*^
\
/
****
GAS
SEPARATOR |
*"— T
^_
S-
?
" /S
*'• OXIDIZED
i^i x^ UT° ?
AIR r~\ £?\ 4 T
COMPRESSOR!^ 1 V HF 1
•t
o~
PUMP
^^T ^"^ *— IV-J
1 r
REACTOR
h-J
HEAT EXCHANGER
Source: Pradt, 1976
FIGURE 10-52.
PLASMA REACTION VESSEL SCHEMATIC
r-
Source: Lee, Keitz and Vogel, 1982
10-134
-------
and destroyed in contact with the plasma. The advantages of this method are
possibilities of using the exiting gas as a fuel (after removal of halogens
and other contaminants in a scrubber), the lack of hazardous interim
combustion products, high efficiency and the ability to be portable. Costs
are not presently available (State of California, 1981).
10.5.6.4 Circulating Bed Combustion (CBC)
Circulating bed combustion is an outgrowth of conventional fluidized bed
incineration. However, the fluid bed operates with higher velocities than
conventional fluid beds and it recirculates the fluidized material within the
system returning it back to the feed section (Ross, 1984). Figure 10-53
illustrates a CBC.
The CBC is suitable for burning solid, liquid, sludge or gaseous waste
streams. The advantages of this incinerator are similar to those of a
conventional fluidized bed system with lower susceptibility to corrosion of
the boiler, a less complicated scrubbing system, close temperature control and
dry solid waste recovery.
10.5.6.5 High Temperature Fluid Wall (HTFW)
The high temperature fluid wall process quickly reduces organic wastes to
their elemental state in a very high temperature process (about 4000°F) (Keitz
and Vogel, 1982). The process is carried out in a patented reactor which
consists of a tubular core of refractor material capable of emitting radiant
energy supplied by large electrodes in the jacket of the vessel. During the
process, an inert gas is injected to coat the wall of the reactor and prevent
destruction from high temperatures. A cross-section of a typical high-
temperature fluid wall reactor is shown in Figure 10-54. HTFW has been used
to treat PCB contaminated earth and other wastes. It ensures high destruction
efficiency, eliminates the formation of intermediate pyrolysis products but
requires some preparation of the feed material and it also incurs high energy
costs.
10.5.6.6. Pyrolysis
Pyrolysis is the thermal conversion of organic material into solid,
liquid and gaseous components. Pyrolysis takes place in an oxygen-deficient
atmosphere at temperatures from 900° to 1600°F. The volatile organics
generated in the process are burned in a second stage fume incinerator at
temperatures of 1800 to 3000°F. The two-stage process minimizes the volatil-
ization of inorganic components and ensures that inorganic.s, including heavy
metals, form an insoluble solid char residue. The technology may be used for
the destruction of materials containing carbon, hydrogen and oxygen.
Pyrolysis can not handle wastes with nitrogen, sulfur, sodium contents.
10-135
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FIGURE 10-53. CIRCULATING BED COMBUSTOR
PROCESS STEAM
FOR HEATING
SUPERHEATED
STEAM
COMBUSTOR
WASTES, FUEL
AND
ADDITIVES
FEED
QEN
t— ELEC-
TRICITY
feri
J/%T I
HOT
CY-
LONEJ
••'•'/
...7
»
^^
1
X
EVAPORATIVE &
-"SECTION
*H2O
1 — |
DUST
COLLECTOR
EXHAUST
GAS
AIR-KPO)))))))))))!
Source: Ross, 1984
INERT
DUST^
TURNS LOW GRADE FUEL INTO POWER
FIGURE 10-54. CROSS-SECTION OF A TYPICAL HIGH-TEMPERATURE
FLUID-WALL REACTOR [E]
Source: Lee, Keitz and Vogel, 1982
10-136
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10.5.6.7 Supercritical Water, Advanced Electric and Vertical Tube
Reactors
These incineration methods are basically in the developmental stage and
even though they seem to be very promising further testing is required before
these processes can be commercialized. The supercritical water process
involves thermal destruction of organics in waste water based on the ability
of many organic compounds to dissolve in super critical water. The process
can probably be applied to dilute organic wastewaters (5 to 10 percent by
weight) (Ross, 1984).
The vertical tube reactor is a very unique system for the destruction of
organic wastes in a deep well with the appropriate temperature and pressure.
The advanced electric reactor is also a unique design to treat organic sub-
stances such as PCBs and others. The process is based on a high temperature
fluidized bed reactor (Ross, 1984).
10.5.7 Environmental Controls
10.5.7.1 Air Pollution Controls
Sources of air pollutants in hazardous waste incinerators include
products of incomplete combustion of organic constituents and conversion of
certain inorganic constituents resulting in gaseous or particulate
contaminants.
Wet scrubbers are air pollution control devices that use a scrubbing
fluid to wash contaminants from a gas. Both gaseous pollutants and
particulates may be removed, although particulates may be more
cost-effectively removed using other equipment in some cases (Peacy, 1984).
Electrostatic precipitation is a process by which particles suspended in
a gas are electrically charged and separated from the gas stream on collecting
plates. Both dry and wet electrostatic precipitators are available. Dry
electrostatic precipitators have high efficiency for removal of particulates.
The wet electrostatic precipitator can theoretically remove organic fumes as
well as fine particulates (Peacy, 1984; Kiang and Metry, 1982).
After burners are basically simple combustion chambers used to burn gases
being emitted from the incinerators.
Fabric filters or baghouses are air pollution control devices, consisting
of a series of larger tubular bags which remove particulates from gases.
Baghouse filters can be 99 percent effective in the removal of particulates,
provided they are kept clean.
Gaseous pollutants can be removed from flue gases using one of three
devices: spray towers, packed-bed towers or plate towers. All are mass
10-137
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transfer devices for gas absorption. Spray towers have lower removal
efficiencies than that of packed and plate towers and are seldom used for gas
removal (Kiang and Metry, 1982).
10.5.7.2 Heat Recovery
There are a variety of methods for recovering waste heat through various
types of heat exchangers. The most commonly used device is the waste heat
boiler. Each type of boiler has its own operating characteristics and can be
used to develop steam or hot water.
Another device for energy recovery is the turbine generator. It is more
costly than the heat exchangers but has more versatility in terms of product
usage (Peacey, 1984).
10.5.7.3 Water Pollution Control
When water scrubbers are used in an incineration system, the acid
scrubber water must be neutralized prior to discharge.
10.5.8 Overall Operation and Design Considerations
The overall design of a hazardous waste incinerator requires the
evaluation of many factors including:
• Transportation and unloading
• Waste segregation
• Toxicity, flammability and explosiveness of wastes
• Storage
• Monitoring
• Emissions control
• Residue handling and disposal
• Other environmental factors.
10.5.9 Costs
It is very difficult to calculate the cost of incineration because of the
high degree of complexity of the problem. The basic factors involved are:
• The limited industrial experience with incineration of bulk quantities
of wastes
10-138
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• The differences in type of waste, operation and design of an
incinerator
• The difficulty in estimating all capital, operating and maintenance
costs.
The capital cost is comprised basically of the cost of purchased equipment and
installation. The first is a firm cost and the second can vary depending on
the geographic location, the assembly of control devices, topography and the
availability of utilities. It consists of the costs of labor and material for
foundations, structural supports, handling and erection, electrical insula-
tion, construction, permitting and test burn protocol, etc. The purchased
equipment costs are comprised of the costs of auxiliary equipment, instru-
mentation and control devices (Monsanto Research Corp., 1981). Annual
operating and maintenance costs consist of the cost of labor; material,
including fuel oil and chemicals; residual ash and waste water disposal;
taxes; insurance; overhead; etc. These costs also include depreciation over
the life of the facility and depend on the depreciation method and interest
rate of the loan. Estimated annual operation and maintenance costs vary
depending on size and characteristics of the waste stream, size and mechanical
complexity of the incinerator and how it is used. Maintenance costs usually
run about 5% of the depreciable capital cost.
10.5.9.1 Examples of Cost Estimates
Figure 10-55 depicts approximate capital costs for three basic types of
incinerators as a function of thermal input. To obtain the real cost of the
installed facility the numbers from the figure should be multiplied by 1.5.
The costs of multiple hearth and liquid injection incinerators are similar for
the heat input ranging from 5 to 10 MBtu. The rotary kiln is three times as
FIGURE 10-55. GENERAL ESTIMATES OF COSTS FOR THREE
PREVALENT TYPES OF INCINERATORS
3.0
2.1
I-
0.6
0.2
Rotary-kiln -a
He»rtn-
?
Liquid-injection
4 6 8 10 20 40 60 S0100
HIM Input, million Btu/h
Source: Vogel and Martin, 1983
10-139
-------
expensive for the same heat input (Vogel and Martin, 1983). The operating and
maintenance costs add several hundred thousand dollars to the capital costs
(Vogel and Martin, 1984).
The estimation of capital costs of an exemplary rotary kiln incinerator
is given in Table 10-19. The annual operation and maintenance cost for the
same incinerator are listed in Table 10-20.
Estimated capital and O&M costs for a liquid injection incinerator are
shown in Table 10-21 and 10-22, respectively. Table 10-23 shows another
estimate of O&M costs for a liquid injection incinerator based on the raw
material requirements shown in Table 10-24. These costs were derived using a
cost estimation model (McCormick, 1983) and are considerably higher than costs
shown in Table 10-22.
10-140
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TABLE 10-19. ESTIMATED CAPITAL COST FOR A ROTARY KILN
Item 1985 Cost $*
Combustion chambers:
Refractory $ 214,840
Shell 207,575
Burners 83,030
Water-storage system (two 10,000-gal tanks) 122,470
Waste-feed system (screw feeder) 10,379
Ash-handling system 62,272
Energy-recovery boiler 200,984
Air-pollution control system (quench chamber,
scrubber and absorber) 425,530
Blower, 304 stainless steel 126.620
Stack (carbon steel, 90 ft at $90/ft) 8,406
Breeching (refractory-lined, 30 ft. at $300/ft) 9,341
Total equipment cost Si,571,447
Installation (50% of total equipment cost) 786,254
Startup (10% of total equipment cost) 157,238
Spare parts (8% of total equipment cost) 125,790
Engineering (7% of total equipment cost) 110,118
Instrumentation (20% of total equipment cost) 314,580
Total capital cost $3,065,467
Adapted from Vogel and Martin, 1984.
*Costs updated from 1983 to 1985 dollars using ENR Construction Index.
10-141
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TABLE 10-20. ESTIMATION OF ANNUAL OPERATION AND MAINTENANCE COST
FOR A ROTARY KILN
Item 1985 Cost $/yr*
Personnel (1 supervisor, 2 operators,
4 yard-crew workers, 1 secretary) $ 151,322
Electricity (473 hp) (7,200 h/yr) 130,772
Water (3.1 x 108 gal/yr) 257,393
Auxiliary fuel
Startup (10) (8 h) (10 x 10 Btu/h) 4,670
Operating (4.8 x 10 Btu/h)
(7,200 h/yr) 430,407
Chemicals (2.25 x 106 Ib lime/yr) 39,128
Effluent disposal:
Scrubber liquid (3.1 x 10 gal/yr) 386,089
Ash (2.88 x 10 Ib/yr) 14,945
Laboratory 62,272
Maintenance (10% of total equipment cost) 157,238
Refractory replacement (8-yr life) 26,984
Direct operating cost 1,661,220
Value of recovered steam 1,245,450
Net operating cost 415,770
Adapted from Vogel and Martin, 1984.
*Costs updated from 1983 to 1985 dollars using ENR Construction Index.
10-142
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TABLE 10-21. CONCEPTUAL LEVEL CAPITAL COST ESTIMATES
FOR A LIQUID INJECTION SYSTEM
Components Cost
Site Acquisition and Development $ 500,000
Tanks 150,000
Pumps, Piping, and Compressors 35,000
REceiving Station and Compressor Enclosure 70,000
Control Room, Auxiliaries, and Laboratory 150,000
Liquid Injection Incinerator 175,000
Scrubbing System 175,000
Total Installed Cost: 1,255,000
Construction, Overhead, and Fee 125,000
Contingency 125,000
Permitting 100,000
Start-up and Spare Parts Inventory 25,000
Total Project Cost: $1,630,000
TABLE 10-22. CONCEPTUAL LEVEL OPERATIONS AND MAINTENANCE COST
ESTIMATES FOR A LIQUID INJECTION SYSTEM
Components Cost
Labor and Supervision (2 shifts/day) $100,000
Fuel, Electric Power, Water and
Chemicals and Caustic Soda) 75,000
Ash and Wastewater Disposal (assuming use of
existing wastewater treatment plant) 5,000
Waste Analysis 30,000
Insurance, Taxes, and Overhead 50,000
Maintenance 40,000
Depreciation 75,000
Total Annual O&M Cost: $375,000
Maintenance costs are difficult to predict due to numerous and complex
factors. Conceptual level estimates for a liquid injection system are
typically five percent of depreciable capital costs, or, as in this case,
approximately $40,000/yr.
2
Annualized capital costs depend on how the system is depreciated and the
interest rate if a loan is taken out instead of taking from cash flow.
Assuming a 10 year straight-line depreciation, annualized capital cost
estimates are approximately $75,000/yr. Given the current tax codes, such
costs must take into account investment tax and energy recovery credits, as
well as other corporate income tax adjustments.
Source: Star, 1985
10-143
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TABLE 10-23. ESTIMATED ANNUAL O&M COSTS AND CREDITS
FOR A LIQUID INJECTION INCINERATOR
1985
Item Annual Cost
Natural gas $ 36,326
No. 2 fuel oil 1,245
Power 72,665
Water 12,450
Caustic soda solution (50 wt %) 118,490
Liquid nitrogen 5,397
Sewer 60,197
Labor 166,060
Maintenance 77,841
Depreciation 155,681
Insurance/taxes 62,272
Total $768,624
Source: McCormick, 1983.
Costs updated to $1985 using 1983 and 1985 ENR Construction Cost Indices,
10-144
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TABLE 10-24. ESTIMATED RAW MATERIAL/UTILITY REQUIREMENTS
Item
Normal Rate
Total Annual Quantity
Fuel
Natural gas for flame
stabilization
No. 2 fuel oil for startup
1000 scfh
100 gal/startup
7 M ff
1400 gal
Power
Id fan
Compressor
Blower
Pumps
Agitators
Total
Water
Caustic soda solution
(50 wt %)
Liquid nitrogen
Sewer use
95 hp
70 hp
35 hp
20 hp
nil
220 hp
110 gpm
230 Ib/hr
38 ft3/hr
110 gpm
-
-
-
-
-
1.15 Gwh
48 M gal
1.6 M Ib
270 M ft3
45 M gal
Source: McCormick, 1983
10-145
-------
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Clark, D.E., P. Colombo, and R.M. Neilson, Jr. 1982. Solidification of Oils
and Organic Liquids. BNL-5162. Prepared for: Brookhaven National
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Conway, R.A. and R.D. Ross. 1980. Handbook of Industrial Waste Disposal.
Van Nostrand Reinhold Co., NY.
Cullinane, M.J. and L.W. Jones. 1985. Technical Handbook for
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Hazardous Waste Engineering Research Laboratory, Cincinnati, OH.
Gulp, R.L., Wesnar and G.L. Gulp. 1978. Handbook of Advanced Wastewater
Pretreatment. Van Nostrand Reinhold Environmental Engineering Series, New
York, N.Y.
De Renzo, D. (ed.) 1978. Unit Operation for Treatment of Hazardous Wastes.
Noyes Data Corporation, Park Ridge, NJ.
Derrick Manufacturing Corporation. Undated. Principles of High Speed
Screening and Screen Machine Design. Buffalo, N.Y. 3 pp.
Dorr-Oliver, Incorporated. 1984. The Dorrclone Hydrocyclone. Bulletin DC-2.
Stamford. CT.
Dorr-Oliver, Incorporated. 1983. DSM Screens for the Process Industries.
Bulletin No. DSM-1. Stamford. CT.
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REFERENCES (continued)
Dorr-Oliver. 1980. Fine screening for mineral processing - Rappafine DSM
Screen. Bulletin DSM6. Stanford. CT.
Dorr-Oliver, Incorporated. 1976. Dorr-Oliver Clarifiers for Municipal and
Industrial Wastewater Treatment. Bulletin No. 6192-1. Stamford, CT.
Doyle, R.D. 1980. Volume Reduction and Detoxification of Hazardous Wastes by
Encapsulation in an Asphalt Binder. 35th Industrial Waste Conference. Purdue
University. Anne Arbor Science Inc., Lafayette, IN. pp. 761-767.
Eagle Iron Works. 1982. Eagle Fine and Coarse Material Washers. General
Catalog, Section C. Des Moines. IOWA.
Eagle Iron Works. 1981. Eagle Water Scalping and Coarse Material Washers.
General Catalog, Section B. Des Moines. IOWA.
Erickson, P.R. and J. Hurst. 1983. Mechanical Dewatering of Dredged
Slurries. Ninth Meeting, U.S.-Japan Conference on Management of Bottom
Sediments Containing Toxic Substances. Jacksonville, FL, October 17-18.
Ghassemi, M., K. Yu, and S. Quinlivan. 1981. Feasibility of Commercialized
Water Treatment Techniques for Concentrated Waste Spills. Prepared for:
USEPA, Municipal Research Laboratory, Cincinnati, OH.
Gooding, C.H. 1985. Reverse Osmosis and Ultrafiltration. Chemical
Engineering, January 5, 1985. pp. 56-62.
Granlund, R.W. and J.F. Hayes. Undated. Solidification of Low-Level
Radioactive Liquid Waste Using a Cement-Silicate Process. Delaware Custom
Material Inc., State College, PA.
Haliburton, T.A. 1978. Guidelines for Dewatering/Densifying Confined Dredged
Material. Technical Report DS-78-11. Prepared for: Office, Chief of
Engineers, U.S. Army, Washington, DC.
Hansen, S.P., R. Gumerman, and R. Gulp. 1979. Estimating Water Treatment
Costs. Volume 3: Cost Curves Applicable to 2500 gpd to 1 mgd Treatment
Plants. EPA-600/2-79-162c. USEPA, Municipal Environmental Research
Laboratory, Cincinnati, OH.
Hoffman Muntner Corporation. 1978. An Engineering/Economic Analysis of Coal
Preparation Plant Operation and Costs. Preparation for US Department of
Energy and US Environmenatl Protection Agency. Washington, D.C. PB-285-251.
Jones, R.H., R.R. Williams and T.K. Moore. 1978. Development and Application
of Design and Operation Procedures for Coagulation of Dredged Material Slurry
and Containment Area Effluent. Prepared for: Office, Chief of Engineers,
U.S. Army. Technical Reprot D-78-54.
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REFERENCES (continued)
Keitz, E.L. and C.C. Lee. 1983. A profile of Existing Hazardous Waste
Incineration Facilities. In Proceedings of the Ninth Annual Research
Symposium Incineration and Treatment of Hazardous Wastes, EPA 600/9-83-003.
US Environmental Protection Agency, Industrial Environmental Research
Laboratory, Cincinnati, OH.
Kiang, Y. and A.R. Metry. 1982. Hazardous Waste Processing Technology. Ann
Arbor Science Publishers, Inc., Ann Arbor, MI.
Krebs Engineers. Undated. Krebs Cyclones for the Mining Industry. Krebs
Bulletin No. 21-130. Menlo Park, CA.
Krebs Engineers. Undated. Krebs Water Only Cyclones. Menlo Park, CA.
Krizek, R.J., J.A. Fitzpatrick and O.K. Atmatzidis. 1976. Investigation of
Effluent Filtering Systems for Dredged Material Containment Facilities.
Prepared for: Office, Chief of Engineers, U.S. Army, Washington, DC. Report
D-76-8.
Lee, C.C. 1983. A comparison of innovative technology for thermal
destruction of hazardous waste. In: Proceedings of 1st Annual Hazardous
Materials Management Conference, Philadelphia, PA. July 12-14.
Lee, C.C., E.L. Keitz and G.A. Vogel. 1982. Hazardous Waste Incineration:
Current/Future Profile. In: Proceedings of the National Conference on
Management of Uncontrolled Hazardous Waste Sites. Nov. 29-Dec. 1, Washington,
D.C.
Lee, M.D. and C.H. Ward. 1984. Reclamation of Contaminated Aquifers:
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Lubowitz, H.R. and C.C. Wiles. 1981. Management of Hazardous Waste by
Clinque Encapsulation Process. In: Land Disposal of Hazardous Waste.
Proceedings of the Seventh Annual Research Symposium. EPA-600/9-81-002b.
USEPA, Municipal Environmental Research Laboratory, Cincinnati, OH.
pp. 91-102.
Mallory, C. and M. Nawrocki. 1974. Containment Area Facility Concepts for
Dredged Material Separation, Drying, and Rehandling. Contract report D-74-6.
Hittraan Associates, Inc. Prepared for: U.S. Army Engineer Waterways
Experiment Station. Vicksburg, MS.
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REFERENCES (continued)
Monsanto Research Corporation. 1981. Engineering Handbook In Hazardous Waste
Incineration. NTIS-PB81-248163.
Moore, Gardner and Associates. 1983. Final Activity Report Shipyards
Investigation Pearl Harbor Navy Shipyard, Pearl Harbor, Hawaii. Prepared for
Department of the Navy, Naval Facilities Engineering Command.
Nalco Chemical Co. 1979. Nalco Water Handbook. McGraw-Hill, Company,
New York, NY. p. 12-1.
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Contamination. Reprinted from: Water/Engineering and Management.
O'Brien, R.P. and M.H. Stenzel. 1984. Combining Granular Activated Carbon
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Oklahoma State University. 1973. Feasibility Study of Hydrocyclone Systems
For Dredge Operations. AD-766-212, Prepared for: Army Engineer Waterways
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10-151
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SECTION 11
CONTAMINATED WATER SUPPLIES AND WATER AND SEWER LINES
Hazardous substances can enter public water systems through a wide
variety of pathways, contaminating the components of the systems as well as
the water. Once contaminated, water systems can serve as secondary sources of
contamination, and the systems' users can be exposed to hazardous substances
over long periods of time.
Sanitary and storm sewers can become contaminated by infiltration of
leachate or contaminated groundwater through cracks, ruptures, or poorly
sealed joints in piping and by direct discharges into the lines. Potable
water supply mains can become contaminated by contact with contaminated water
that may inadvertantly flow through them, or by infiltration of leachate or
contaminated groundwater. However, water mains are less susceptible to the
infiltration of contaminants, since they are generally full-flowing, pres-
surized systems. The public health consequences of the contamination of
municipal mains carrying potable water supplies to commercial and residential
consumers are potentially much greater than the consequences of the contami-
nated sewage flowing to a treatment plant or of surface runoff draining to
surface waters.
This Section presents methods for providing water supplies of acceptable
quality with the minimum disruption of service; the methods are as follows:
• Water supply replacement:
- New central water supply
Point-of-use water supplies
• Water Treatment:
Central water treatment
Point-of-use water treatment
• Alteration of water and sewer pipelines:
Replacement
Inspection and leak detection
- Cleaning
Repairing and lining.
11-1
-------
11.1 Replacement of Contaminated Central Water Supplies
Replacement of central water supplies, or sources of water that serve
many users through central distribution systems, generally involves one or
more of the following approaches:
• Purchase of water from another supply
• Provision of a new surface water intake(s)
• Provision of a new groundwater well(s).
The contaminated water supply may be abandoned or may be blended with the
new supply to achieve acceptable water quality by dilution. Combinations of
the approaches may be employed either concurrently (multiple replacement
supplies) or consecutively (emergency water purchased from a neighboring
supply unit, followed by new wells or intakes.)
Purchase of treated water from another supply requires a cross-
connection^) between the systems. Many neighboring public water departments,
authorities, and companies maintain networks of interconnections that allow
ready flow and meeting between systems for emergencies such as droughts,
fires, line breakage, or malfunction of treatment facilities. Where cross-
connections do not exist, water transmission lines can be installed. The
information provided in Section 11.5 generally applies to new water pipelines.
Numerous references are available that guide the design and installation of
water transmission and distribution systems, including Fair (1971) and
American Society of Civil Engineers (ASCE, 1975).
Provision of new surface water intake may be feasible where a groundwater
source is to be replaced or where a replacement surface water intake would
hydraulically isolate the water supply system from contaminated surface water
(e.g., intake upstream of the source of contamination).
Surface water is drawn from rivers, lakes, and reservoirs through
relatively simple submerged intake pipes, or through fairly elaborate
towerlike structures that rise above the water surface. Important in the
design and operation of intakes is that the water they draw be as clean,
palatable, and safe as the source of supply can provide. River intakes are
constructed well upstream from points of discharge of sewage and industrial
wastes. Optional location should take advantage of deep water, a stable
bottom and favorable water quality, all with proper reference to protection
against floods, debris, ice, and river traffic. Small streams may be dammed
up by diversion or intake dams to keep intake pipes submerged and preclude
hydraulically wasteful air entrainment. Lake intakes are sited with due
reference to sources of pollution, prevailing winds, surface and subsurface
currents, and shipping lanes. Shifting the depth of draft makes it possible
to collect clean bottom water when the wind is offshore, and, conversely,
clean surface water when the wind is onshore. Reservoir intakes, resemble lake
intakes but generally lie closer to shore in the deepest part of the
reservoir. They are often incorporated into the impounding structure itself
(Fair, 1971).
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The feasibility of providing new surface water intakes is dependent on
numerous case-specific requirements and conditions, summarized as follows:
• Proximity of the point of intake to the water supply system
• Peak demand flow versus historic and predicted low flow in the water
body
• Downstream environmental, recreational, and commercial effects of
reduced flow
• Quality of the surface water and corresponding treatment requirements.
Provision of new groundwater wells is often feasible where the extent of
aquifer contamination is relatively confined and would not be expected to be
drawn to the area of influence of the new wells, or where other (usually
deeper) aquifers can be tapped as a replacement water supply. The information
provided in Section 5.1 generally applies to the design and construction of
new groundwater wells.
11.2 Point-of-Use Water Supplies
Central water supplies that are contaminated at the source or in trans-
mission through pipelines can be replaced permanently or temporarily with an
independent supply at each point of usage. Such supplies could include one or
a combination of the following:
• Bottled and bulk water
• Point-of-use wells
• Collection of rain water.
The use of bottled and bulk water is common for temporary or semi-
temporary water supplies on an emergency basis until more permanent water
supply arrangements can be made. Bottled water is widely available in small
quantities from common retail outlets (grocery and drug stores) and in large
quantities from commercial distributors. Larger bottles (e.g., five-gallon
"water cooler" bottles) require dispensers in order to be conveniently used.
Their full weight (approximately 50 pounds) may present handling and
change-over problems for some users.
Bulk water can be provided in portable tanks (trailers or tank trucks) by
commercial, clean water contractors and by public emergency service organiza-
tions (e.g., Army National Guard). Tanks normally used for other purposes,
such as milk tank trucks, have also been used. The tanks are typically made
available to homeowners at temporary, centrally located distribution points,
where small containers can be filled for home use. Whole tanks can be made
available to commercial and institutional establishments.
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Point-of-use wells, or individual wells for each user establishment, may
be feasible as a permanent alternative to a contaminated central supply,
provided that the available groundwater is and can be expected to remain
non-contaminated. The information provided in Section 5.1 generally applies
to development of new groundwater wells.
Rainwater is rarely the immediate source of municipal water supplies, but
could serve as a replacement to a contaminated water supply. The use of rain-
water is generally confined to farms and towns in semiarid regions devoid of
satisfactory groundwater or surface water supplies. For individual users,
rainwater running off the roof is led through gutters and downspouts to a
cistern situated on or below the ground. Cistern storage converts the
intermittent rainfall into a continuous supply. For municipal service, roof
water may be combined with water collected from sheds or catches on the
surface of ground that is naturally impervious or rendered so by grouting,
cementing, paving, or similar means (Fair, 1971).
The gross yield of rainwater supplies is proportional to the receiving or
drainage area and the amount of precipitation. Because of the relatively
small catchment area available, roof drainage cannot be expected to yield an
abundant supply of water, and a close analysis of storm rainfalls and seasonal
variations in precipitation must be made if catchment areas, standby tanks,
filters, and cisterns are to be proportioned and developed properly (Fair,
1971).
11.3 Treatment of Contaminated Central Water Supplies
Central water supplies that are contaminated at the source can be treated
to acceptable quality at central treatment systems. For some supplies, such
as in small communities that pump groundwater directly to distribution systems
without treatment, central treatment may require installation of new facili-
ties. For other supplies, such as in large communities that already treat
surface water before distribution, upgrading of existing treatment with the
installation of polishing units may be necessary (Morrison, 1981).
Available water treatment methods include physical, chemical, and
biological technologies, and combinations of these methods may be used for
removal of some contaminants.
Many of the technologies described in Section 10-1, for treatment of
aqueous wastes also apply to treatment of contaminated water supplies. In
general, however, those technologies that are normally associated with
"polishing" (i.e., removal of low concentrations of contaminants), such as
activated carbon, ion exchange, and reverse osmosis, are most applicable to
treatment for public water supplies.
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11.4 Point-of-Use Water Treatment
11.4.1 General Description
Central water supplies that are contaminated at the source or in
transmission can be treated to acceptable quality at the point of use (POU)
with a variety of commercially available systems. Most applications of POU
treatment units are for aesthetic purposes (taste, odor, and color), although
their use is increasing for removal of organic contaminants from drinking
water (Anderson, 1984a).
POU units are generally used in one of the following situations in
residential applications:
• Line-bypass, where separate faucets are provided for treated and
non-treated water; treated water is generally used for drinking,
cooking, etc.
• Faucet-mounted, where all water passing through the faucet is treated.
• Whole-house, where all water entering the house is treated.
Line-bypass systems afford a compromise, providing only for treatment of water
to be consumed, thereby minimizing treatment demands and costs.
POU treatment processes include the following (Anderson, 1984a; Perry,
1981):
• Activated carbon
• Activated alumina
• Reverse osmosis
• Ion exchange
• Distillation
• Ozonation
• Ultraviolet irradiation.
Of these processes, activated carbon is the most widely used and accepted
process. Reverse osmosis and ion exchange are also widely available for
applications where more stringent water quality requirements apply (hospitals,
laboratories, etc.). Section 10.1 should be consulted for the applications
and limitations of these methods.
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11.4.2 Applications/Limitations
POU units are designed to remove a wide variety of contaminants from
water. Manufacturers' claims vary, and numerous studies have been conducted
to test the effectiveness of various units (Anderson, 1984a and b; Perry,
1981; Taylor, 1978).
Table 11-1 summarizes the general applications and limitations of the
commonly used types of POU units. A major limitation common to all POU units
is their reliance on the user (or service contracted by the user). If the
units are not properly installed, operated, and maintained, the desired treat-
ment may not be affected, or the accumulated contaminants may be released from
the treatment unit after the treatment material is exhausted. (Taylor, 1978).
TABLE 11-1.
APPLICATIONS AND LIMITATIONS OF COMMONLY USED POINT-OF-USE TREATMENT UNITS
Process
Applications
Limitations
Activated carbon
Organics, hydro-
carbons, chlorine,
trihalomethanes (THM)
some pesticides
Reverse osmosis
Fluoride, total dis- <
solved solids, sodium,
sulfate, salts, metals
Ion exchange
Dissolved minerals,
metals, most inorganics
Potential for excess growth of
bacteria (Taylor, 1978)
Short-lived effectiveness for
some contaminants (chlorine,
THM, pesticides) (Taylor, 1978)
Potential desorption (release
of contaminants) following
exhaustion of carbon (Taylor,
1978)
High-pressure required to
affect filtration
Low flow rate capacity requires
storage tank and/or multiple
systems in parallel
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11.4.3 Design Considerations
The primary design considerations for POU units are 1) selection of the
appropriate units for the contaminant(s) of concern, 2) selection of the
appropriate hydraulic capacity for the application, and 3) provision of
appropriate criteria and schedules for maintaining the units. This informa-
tion is generally available from the manufacturer or supplier.
Manufacturers' and suppliers' performance information should be confirmed
by laboratory or trial tests under any of the following circumstances:
• Information has not been confirmed by a reputable organization or
laboratory (National Sanitation Foundation (NSF), 1981)
• Disparate contaminants are present
• Concentrations of contaminants vary widely over time
t Contaminants and concentrations pose a high risk to human health
• Large numbers of units are to be employed.
11.4.4 Construction/Implementation Considerations
Installation procedures are provided by the manufacturer of each POU
unit. Installation should be made by a licensed plumber and/or approval of
the installation should be given by a local plumbing inspector. This is
particularly important for whole-house units and by-pass units to ensure that
backflow and inappropriate cross-connections are averted.
11.4.5 Operation, Maintenance, and Monitoring
Once installed, POU units operate relatively passively and require little
or no attention. Proper maintenance and monitoring, however, are essential to
the effectiveness and safety of the units. Maintenance generally consists of
changing the cartridges on a regular schedule. However, few units give any
detectable indication of having reached capacity. Conservative change-over
schedules are recommended to help ensure that the units continuously serve
their intended purpose. Alternatively, frequent monitoring of the quality of
the treated water could be conducted by sampling and analysis to identify the
need for cartridge changes. Many full-service water treatment companies
provide installation and maintenance services.
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11.4.6 Technology Selection/Evaluation
The selection of the appropriate POU unit is based largely on the
contaminants to be removed. The applicability of the commonly used type of
POU units is provided in Table 11-1. Reliability of performance should be a
major consideration in evaluating POU units relative to other water supply or
treatment technologies, as their reliance on the user or user-contracted
services for installation and maintenance does not necessarily ensure a
continuously safe water supply.
11.4.7 Costs
Typical initial equipment, installation, and monthly maintenance costs
for POU treatment devices are shown in Table 11-2. Maintenance costs include
changing of treatment cartridges on schedules consistent with the units'
capacities and residential rates of water consumption.
1985
TABLE 11-2.
COSTS FOR POINT-OF-USE WATER TREATMENT SYSTEMS
Type of System
Initial Costs
Maintenance Cost
Activated carbon
Activated alumina
Reverse osmosis
Deionization
Combined activated carbon
$300-400/unit
$200-400/unit
$550/unit
$700/unit
$700-800/unit
$2-3/month
$1-4/month
$7-11/month
$4-6/month
$8-12/month
Source: Anderson, 1984b; Consumers Union 1984; Ingram, R., Culligan Water
Conditioning of Greater Washington, Vienna, VA, personal communication, March
1985.
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11.5 Replacement of Water and Sewer Lines
11.5.1 General Description
Replacement of water and sewer pipelines that are contaminated by contact
with hazardous substances is seldom more cost-effective than rehabilitation,
but may often be the only practical alternative. Replacement involves exca-
vation of trenches, laying of new lines with noncontaminated pipe materials,
laying new connections and/or tying in connections, and associated backfilling
and surface restoration. Contaminated pipelines may either be abandoned
in-place or removed in the course of trench excavation. Construction of water
and sewer lines is common in land development projects and the associated
methods, materials, and equipment are well-established.
11.5.2 Applications/Limitations
Pipeline replacement is applicable to virtually all cases of pipeline
contamination. Excavation and replacement of defective sewer pipe segments is
normally undertaken when the structural integrity of the pipe has deteriorated
severely; for example, when pieces of pipe are missing, pipe is crushed or
collapsed, or the pipe has large cracks—especially longitudinal cracks, and
alternative rehabilitative techniques are not feasible. In addition, pipeline
replacement is often required when the pipe is significantly misaligned (Water
Pollution Control Federation (WPCF), 1983). Factors that would limit the
feasibility of pipeline replacement are:
• Disruption of service and interim provisions
• Accessibility of pipeline and connections
• Interference of other utilities
• Disruption of vehicular traffic
• Depth of excavation
• Soil and groundwater
• Costs.
The primary disadvantage of pipeline replacement is the high cost.
Analyses to determine the cost-effectiveness of pipe replacement must include
all costs associated with the replacement. These costs typically include
pavement removal and replacement; excavation; possible substitution of select
backfill to replace poor quality existing material; dewatering and shoring,
pipe materials and couplings, and traffic control. Potential cost increases
resulting from interference with other underground utilities and narrow
casements or limited space for construction must also be considered. In
addition, consideration must be given to the need for temporary flow rerouting
11-9
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to maintain service. Depending on the service life assumed for other reha-
bilitation methods, the possible higher capital costs may be somewhat offset
by the longer service life a new line provides (WPCF, 1983).
11.5.3 Design Considerations
In general, new pipeline systems will mimic the systems that they replace
(size, material, grade, location, capacity, etc.). The considerations that
govern the design of new systems will apply, but not control. Logistics and
the presence of fixed constraints will dictate how the replacement system is
designed. However, the need for replacement may provide an "opportunity" to
upgrade the systems in terms of capacity, improved materials and methods,
location, and/or direction of flow, and some consideration would be given to
criteria for the design of new systems (WPCF, 1983).
The design of water distribution and sanitary sewer systems is addressed
in numerous manuals and guidebooks, including ASCE (1975 and 1976). Informa-
tion that is needed as input to the design includes:
• Population drawing from or contributing to the system
• Per capita water demand or sewage discharge
• Commercial, industrial, and institutional demand or discharge
• Minimum and peak daily demand or discharge
• Fire-fighting requirements
• Soil, groundwater, near-surface and geologic conditions
• Topography and grades
• Locations of potentially interfering features (utilities, buildings,
etc.) .
ASCE (1976) recommends that estimates of sewage flow be based on con-
sideration of the following:
• The design period during which the predicted maximum flow will not be
exceeded,, usually 25 to 50 years in the future.
• Domestic sewage contributions based on future population and future
per-capita water consumption. If a more satisfactory parameter than
water consumption is available, that parameter should be used.
• In some instances, maximum flow rates may be determined almost
entirely by extraneous flows, the source of which may be foundation,
basement, roof, or areaway drains, storm runoff entering through
manhole covers, or infiltration.
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• Commercial area contributions are sometimes assumed to be adequately
provided for in the peak allowance for per capita sewage flows in
small communities
• Industrial waste flows should include the estimated employee contri-
bution, estimated or gauged allowances per acre for industry as a
whole, and estimated or actual flow rates from plants with process
wastes that may be permitted to enter the sanitary sewer
• Institutional wastes are usually domestic in nature although some
industrial wastes may be generated by manufacturing at prisons,
schools, hospitals, etc.
• Air-conditioning and industrial cooling waters, if permitted to enter
sewers, may amount to 1.5 to 2.0 gpm per ton of nonwater-conserving
cooling units
• Infiltration may occur through defective pipe, pipe joints, and
structures. Design allowances should be larger (under some circum-
stances, very much larger) than those stipulated in construction
specifications for which acceptance tests are made very soon after
construction.
The relative emphasis given to each of the foregoing factors varies among
engineers. Some have set up single values of peak design flow rates for the
various contributory items listed above. It is recommended, however, that
maximum and minimum peak flows used for design purposes be developed step by
step, giving appropriate consideration to each factor which may influence
design. (ASCE, 1976).
If a sewer is to transport stormwater or wastewater from one location to
another, it must be constructed sufficiently deep (below the ground surface)
to receive these flows from basic or service connections. It should be
resistant to both corrosion and erosion and its structural strength must be
sufficient to carry backfill, impact, and live loads satisfactorily. The size
and slope, or gradient, of a sewer must be adequate for the flow to be carried
and be sufficient to avoid deposition of solids. The type of sewer joint
must be selected to meet the conditions of use as well as those of the ground.
Economy of maintenance, safety to personnel and the public, and public
convenience during its life and during construction also must be considered
(ASCE, 1976).
The pipe material used for sanitary and storm sewers can influence other
design decisions and should, therefore, be selected early in the design
process.
Factors that should be considered in the selection of materials for both
water and sewer construction are (ASCE, 1976):
• Flow characteristics-friction coefficient
• Life expectancy and use experience
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• Resistance to scour
• Resistance to acids, alkalis, gases, solvents, etc. (sewers only)
• Ease of handling and installation
• Physical strength
• Type of joint - watertightness and eas-e of assembly
• Availability and ease of installation of fittings and connections
• Availability in sizes required
• Cost of materials, handling, and installation.
No single material will meet all conditions that may be encountered in
sewer design. Selections should be made for the particular application and
different materials may be selected for parts of a single project (ASCE,
1976).
New materials are continuously being offered for use in sewer construc-
tion. Some of the more commonly used materials are (ASCE, 1976):
• Asbestos cement
• Brick masonry
• Vitrified clay
• Concrete
- Precast
Reinforced precast
Cast-in-place
• Iron
- Cast iron
Ductile iron
• Fabricated steel
Corrugated
Plain
• Organic synthetic materials
Solid-wall plastic (polyvinyl chloride (PVC), polyethylene,
acrylonitrile-butadiene-styrene (ABS), fiberglass reinforced
plastic)
Truss pipe
Corrugated polyethylene.
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Estimates of flow and system pressure in water distribution systems are
based on the following (Fair, 1971):
• Domestic, industrial, and other normal uses, determined in a manner
similar to estimating sewage flow
• Standby requirements for fire-fighting as required by local codes
and/or the American Insurance Association
• Estimates of system leaking
• Calculation of in-transit frictional pressure losses.
A variety of pipe materials are also available for water systems; among
the most common are (ASCE, 1975):
• Iron
Ductile iron
- Cast iron
• Concrete
• Asbestos - cement
• Steel
• Organic synthetic materials:
- Polyvinyl chloride (PVC)
- Polyethylene (PE)
Acrylonitrile - butadiene - styrene (ABS).
11.5.4 Construction/Implementation Considerations
A variety of conventional and nonconventional methods are available for
constructing water and sewer lines. The most common method is open-trench
excavation, which often requires lateral bracing of trench walls in deep cuts
and/or non-cohesive soils. This method of sewer construction is described in
ASCE, (1976). Other methods of construction include:
• Augering, or boring, where the pipe is pushed through the soil and the
soil ahead of the pipe is removed by an auger that is advanced with
the pipe
• Jacking, where the pipe is pushed through the soil and the soil ahead
of the pipe is removed by laborers working from inside the pipe
• Tunneling by various means.
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11.5.5 Operation, Maintenance, and Monitoring
Replacement water and sewer lines require no operations, maintenance, or
monitoring beyond that required for other newly constructed lines. For water
lines, this includes flushing, leak detection and repair, and hydrant testing
to ensure that fire-fighting requirements are met (Fair, 1971). For sewer
lines, this includes occasional flushing and cleaning (see Section 11.6),
removal of blockages, ensuring adequate ventilation, and leak detection and
repair.
11.5.6 Technology Selection/Evaluation
Factors that generally favor the selection of line replacement over other
technologies are the complete removal of contaminants from the system and the
provision of new systems with associated functional lines. Major drawbacks of
replacement are disruption of surface activities and costs. Performance and
reliability of replacement systems are the maximum obtainable; i.e., new
systems are the basis of comparison for evaluating other pipeline alteration
technologies.
11.5.7 Costs
Typical costs for replacement of water and sewer lines ae provided in
Table 11-3.
11.6 Inspection and Cleaning of Water and Sewer Lines
11.6.1 General Description
Available techniques for inspecting and cleaning sewer lines are
generally applicable to water lines. However, the water lines are normally
smaller in diameter than sewer lines, and size is often a limiting factor in
the applicability of inspection and cleaning technologies. Inspection
techniques include smoke testing, dye-water flooding, first-hand visual
observation, and closed-circuit television visual observation.
Inspection is generally conducted to identify one or more of the
following conditions:
• Points of groundwater leakage
• Structural defects in need of repair
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TABLE 11-3.
1985 COSTS FOR REPLACEMENT OF WATER AND SEWER LINES
Item
Unit
Cost Per Unit
Sewer pipe, material and
installation, in-place:
8-inch diameter
18-inch diameter
36-inch diameter
Water pipe, material and
installation, in-place:
2-inch diameter
4-inch diameter
12-inch diameter
Pipe bedding material
Trench excavation,
backfill, and
compaction:
Water lines
Sewer lines
Linear foot
Linear foot
Cubic yard
Linear foot
Cubic yard
$6-10
$13-31
$33-120
$3-7
$5-11
$16-27
$14-25
$1-3
$6-10
Source: Godfrey, 1984
• Points of connection
• Areas in need of cleaning.
Inspection of pipelines for leaks or infiltration points may be part of a
regular sewer or water line maintenance program. Methods to detect and locate
pipeline breaches include the use of dyes and other tracer chemicals, patented
audiophone leak detectors, smoke testing, and installation of pressure gages
along a given length of pipe to monitor changes in hydraulic gradient (Linsley
and Franzini, 1979). The interiors of small diameter sewers and large
diameter water lines are commonly inspected by pulling skid-mounted minia-
turized closed-circuit television cameras through the line. The entire
inspection can be recorded on videotape for future reference.
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Cleaning of water and sewer line removes deposits and debris from the
pipelines and is conducted for one or more of the following reasons:
• Improve flow conditions and capacity
• Allow visual inspections
• Provide clean surfaces for placement of repair materials.
Available sewer-cleaning techniques include mechanical scouring, hydrau-
lic scouring and flushing, bucket dredging, suction cleaning with pumps or
vacuum, chemical absorption, or a combination of these methods. Access to
sewer lines for interior cleaning and repair is most commonly afforded by
manholes. Basin inlets and service connections provide additional points of
access. Service and fire hydrant connections allow access to municipal water
lines.
11.6.2 Applications/Limitations
Pipeline inspection is applicable to all visually observable cases of
pipeline contamination or leakage of contaminated water. The methods are
well-developed and accepted. Small-diameter pipelines (less than 6 inches)
cannot be inspected by closed-circuit television, and pipelines less than 48
inches in diameter cannot readily be inspected first-hand by workmen.
Television inspection offers the advantages of worker safety and a permanent
videotape record of the inspection. It is common practice to clean pipelines
before inspection to ensure visibility of defects and free access of workmen
and/or equipment.
11.6.3 Design Considerations
Design of inspection and cleaning operations for water and sewer lines
consists primarily of planning for the logistics of implementation. Sections
of pipeline to be inspected and/or cleaned are selected based on evidence of
the presence of contamination or contaminated seepage; sections may be added
or deleted in process, depending on interim findings. Critical points of
operation such as access manholes, base of operation, and material storage are
selected. Methods of managing disruption of service (water or sewer) and
surface activities such as traffic are also planned. Affected parties are
notified in advance of the planned work.
11.6.4 Construction/Implementation Considerations
Smoke bombs or canisters are used to generate the smoke required for
smoke testing of pipelines. The smoke should be nontoxic, odorless, and non-
staining. Air blowers are used to force the smoke into the pipes. Smoke
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coming out of the ground, catch basins, pipes, and other sources during the
test is noted and recorded by observers and photographs are taken for perman-
ent documentation of the results. Sand bags and/or plugs can be used to block
the sewer sections to prevent the smoke from escaping through the manholes and
adjacent sewer pipes (WPCF, 1983).
Dye-water flooding is used to simulate rainfall and thus identify points
of runoff-related infiltration and sources. Equipment needed for dye-water
testing is limited to that required to carry the water to the testing site and
to block the sewer sections to be tested. A fire hose is all that is needed
to deliver the water to the testing site. When the water source is not close
by, water tankers are required to deliver the water. Sand bags or sewer pipe
plugs are normally used to block the sewer sections. Fluorescent dyes are
usually employed for high visibility (WPCF, 1983).
The following is a general procedure for dye testing for possible
infiltration from a storm sewer to a sanitary sewer; similar procedures are
used for evaluating other sources:
• Plug both ends of the storm drain section to be tested with sand bags
or other materials. Block all the overflow and bypass points in the
sewer section. Provide bypassing of flow, if necessary.
• Fill the storm drain section with water from fire hydrants or other
nearby water sources. Add dye to the water.
• Monitor the downstream manhole of the sanitary sewer system for
evidence of dyed water.
• Measure the flows in the manhole before and during the dye-water
testing. As an alternative, the flows can be simultaneously measured
at both the upstream and downstream manholes during the test.
• Record the location of storm drains and sanitary sewer lines being
tested; the time and duration of tests; the manholes and the flow
rates where the flows are monitored; the observed presence, concentra-
tions and travel time of the dyed water into the flow monitoring
manholes; and the soil characteristics (WPCF, 1983).
First-hand visual observation of conditions is possible in large diameter
sewers that permit workmen to enter. Physical proximity to the pipeline
interior enables workman to observe structural conditions, condition of
joints, location and nature of deposits and debris, and locations of points of
infiltration. Worker safety is an important consideration under such
conditions (WPCF, 1983).
Television inspection is accomplished by using closed circuit systems
specifically designed for sewer inspection. There are several configurations
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of closed-circuit systems for sewer inspections, each of which have in common
the following (WPCF, 1983):
• Power for operation generated on-site
• Power control
• Transport winches
• Video (color, if possible) and lighting control
• Recording and documentation
• Radio communication
Television inspection provides a video screen picture of pipeline being
inspected to an operator in a nearby van. The operator controls the speed of
movement along the pipeline and records details of conditions observed. Most
systems also provide for videotape recording of the inspection for future
reference.
Pipeline cleaning is necessary for efficient collection system operation
and for exposing pipe materials for television inspection. All collected
sediment and debris should be removed from the line and disposed of at an
approved site. Care should be taken during the cleaning to minimize transport
of deposits into downstream lines. As extensive outline of sewer cleaning
methods can be found in WPCF (1982). The procedures for the most common
methods are briefly described below.
Mechanical scouring techniques include the use of power rodding machines
("snakes"), which pull or push scrapers, augers, and brushes through the
obstructed line (Figure 11-1). "Pigs," bullet-shaped plastic balls lined with
scouring strips, are hydraulically propelled at high velocity through water
and sewer mains to scrape the interior pipe surface.
Hydraulic scouring is achieved by running high-pressure hoses into sewer
lines through manholes and flushing out sections of the sewer. This technique
is often used after mechanical scouring devices have cleared the line of solid
debris or loosened sediments and sludges that coat the inner surface of the
pipe.
A bucket machine can be used to dredge grit or contaminated soil from a
sewer line (Figure 11-2). Power winches are set up over adjacent manholes
with cable connections to both ends of a collection bucket. The bucket is
then pulled through the sewer until loaded with debris. The same technique
can be used to pull "sewer balls" or "porcupine scrapers" through obstructed
pipes (Hammer, 1975). Bucket dredging is also useful for collecting samples
of contaminated sediments, groundwater, or leachate that may have infiltrated
the lines.
Suction devices such as pumps or vacuum trucks also may be used to clean
sewer lines of liquids and debris. Again, manholes and fire hydrants provide
easy access for the setup and operation of such equipment.
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FIGURE 11-1.
POWER RODOING MACHINE
Clecninq tool
Source: Hammer, 1975
11-19
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FIGURE 11-2.
SCHEMATIC OF BUCKET MACHINE CLEANING
Power winch with
loading chute
Truck for hauling
•way debris
Roller
Bucket
Source: Hammer, 1975
Another method of sewer pipeline cleaning is the use of hydrophilic
polymer foams and gels that absorb and physically bind liquid pollutants in a
solid elastromeric matrix (Johnson, J., Chemical Research Division, 3m Com-
pany, personal communication, March 1980). These polymers are special
chemical grouts that can either be applied internally to pipelines or injected
through breaks in the line from the exterior. Once the absorbent grout has
set (solidified), the solid grout/pollutant matrix can be hydraulically
flushed from the line. The applications of any of these hydrophilic grouts,
whose formulations are often proprietary, are still in the developmental and
testing stages.
11.6.5 Operation, Maintenance, and Monitoring
Inspection and cleaning of water and sewer lines are essentially oper-
ating and maintenance activities. Montoring for effectiveness of cleaning may
be warranted upon completion and periodically thereafter to ensure ongoing
absence of contaminants from the pipeline.
11.6.6 Technology Selection/Evaluation
Inspection and cleaning of water and sewer lines is established and
accepted technology for conventional applications. Removal of hazardous
contaminants from pipelines may be afforded by conventional methods where
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contaminants are associated with deposits or debris such as sludge, slime, or
sediments. Contaminants that are sorbed onto the pipe material may not be as
readily removed. Information concerning the effectiveness of conventional
methods in such cases is not available.
11.6.7 Costs
Inspection and cleaning of water lines can be accomplished by a variety
of methods, and costs vary accordingly. Television inspection and light high-
pressure water cleaning (the minimum required in preparation for repairing or
lining pipelines) typically costs $100 to $150 per hour, or $0.40 to $0.60 per
linear foot for a rate of progress of 2,000 feet per eight-hour day and $0.80
to $1.20 per linear foot at a rate of 1,000 feet per day. (D'Angelo, T., Pipe
Maintenance Services, Inc., Exton, PA, personal communication, April 1985).
Costs for other inspection and cleaning methods are highly variable and
dependent on the type of pipeline and nature of the material being removed.
11.7 Rehabilitation of Water and Sewer Lines
11.7.1 General Description
Water and sewer lines that are in contact with contaminated substances or
allow infiltration of contaminated water can be lined or sealed in-place with
chemically inert material in order to isolate the water being transmitted from
the contaminants. Available methods include the following:
• Insertion of a new pipe inside of existing pipe (sliplining)
• In-place forming of new pipe inside of existing pipe
• Point repairs of leaks and other defects.
Sliplining involves sliding a flexible liner pipe of slightly smaller
diameter into an existing circular pipeline and then reconnecting the service
connections to the new liner. Polyethylene is the most common material used
for sliplining pipelines (WPCF, 1983).
A patented system called "inversion lining" uses a flexible lining
material that is thermally hardened. Access to the pipeline can be made
through manholes or excavations. After the lining system has been installed
and cured, a special cutting device is used with a closed-circuit TV camera to
reopen service connections. The system is available only through licensed
contractors (WPCF, 1983).
Because inversion lining can be accomplished relatively quickly and
without excavation, this method is particularly well-suited for repairing
pipelines located under existing structures or large trees. It also is
particularly useful for repairing pipelines located under busy streets or
11-21
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highways where traffic disruption must be minimized. Because the liner
expands to fit the existing pipe geometry, this method is applicable to all
pipeline shapes. The cured resin material is reportedly corrosion-resistant.
Inversion lining also affords minor structural reinforcement. Inversion
lining may be used for misaligned pipelines or in pipelines with bends where
realignment or additional access is not required (WPCF, 1983).
Inversion lining using water to cure the resins is generally used in
pipelines with diameters less than 57 inches and manhole-to-manhole segments
less than 1000 feet long. Larger diameter pipelines (to 108 inches) have been
lined by inversion techniques using air (WPCF, 1983).
Inversion lining is relatively new in the U.S. and its cost-competitive-
ness has not yet been fully established (WPCF, 1983). It is a patented system
available only through a limited number of licensed contractors.
Chemical grouting is commonly used for sealing leaking joints in
structurally sound sewer pipes. Small holes and radial cracks can also be
sealed by chemical grouting (WPCF, 1983).
Chemical grouts are synthetic materials that are applied as low-viscosity
liquids and cure as flexible, form-fitting solids. Commonly used chemical
grouts are acrylamide gel, acrylate polymer, and polyurethane gel (WPCF,
1983).
11.7.2 Applications/Limitations
Repairing and lining of water and sewer lines applies to lines that are
1) contaminated as a result of ongoing contact with contaminated substances,
or 2) allowing the infiltration of contaminated water. The application of
materials to the interior of the pipe should resolve either or both problems
if the materials are properly selected. The materials used have low suscepti-
bility to chemical degradation and have relatively low permeability to water,
and would be expected to effectively isolate sewage and water flows from
contaminated pipelines and seepage. However, the repair and lining materials
and techniques were not developed for control of hazardous contaminants and
there is no information available that addresses their effectiveness under
these special circumstances. Factors that could adversely affect the
performance and reliability of repairs and lining are: 1) incompatability of
repair materials and contaminants, and 2) permeability of repair materials
with respect to contaminants.
Sliplining is used to rehabilitate extensively cracked pipelines,
especially lines in unstable soil conditions. It is also used to rehabilitate
pipe installed in a corrosive environment and in areas where sewer pipes have
massive destructive root intrusion problems (WPCF, 1983). The flexible liner
pipes have the advantage of being able to accoraodate a normal amount of future
settlement or, moderate horizontal or vertical deflection.
11-22
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If the existing pipeline joints are offset, service lateral taps are
protruding, or if the diameter of the pipeline has been significantly reduced
in some other manner, the liner pipe diameter may need to be much smaller than
the diameter of the existing pipeline. Such conditions can limit the utility
of this method (WPCF, 1983).
Premanufacturered sliplining pipe cannot be used in pipe that is signifi-
cantly "out of round," since its cross section must pass through that of the
existing pipe. New pipe formed in-place cannot be used where the existing
pipe has low structural integrity, unless reinforcing is added in the forming
(generally limited to larger diameters where workmen can enter).
Point repairs can be used where problems are confined to joints or to
relatively few short sections of pipe.
Chemical grouting is generally used to seal open pipeline joints and
cracks. It does not improve the strength of a pipeline, and should not be
used when pipe is severely cracked, crushed, or badly broken. Chemical
grouts, once applied, may dehydrate and shrink if the surrounding moisture is
reduced significantly. Some joints and cracks may be difficult to seal
chemically using gel grouts when large voids exist outside the pipe joint and
extremely large quantites of grout may be required to seal the joint (WPCF,
1983).
Inspection and cleaning of pipelines is generally necessary in prepara-
tion for rehabilitation. These methods are addressed in Section 11.6.
11.7.3 Design Considerations
Design of water and sewer line rehabilitation consists primarily of
planning for the logistics of implementation. Sections of pipeline to be
rehabilitated are identified based on television or other inspections.
Critical points of operation such as access manholes, base of operation, and
material storage are selected. Methods of managing disruption of service
(water or sewer) and of surface activities such as traffic are also planned.
Affected parties are notified in advance of the planned work.
11.7.4 Construction/Implementation Considerations
Typical sliplining materials include high-density polyethylene (HOPE) and
fiberglass-reinforced pipe (FRP).
Before installing a liner pipe, the existing pipeline should be inspected
by closed circuit TV to identify all obstructions such as displaced joints,
crushed pipe, and protruding service laterals to locate service connections.
The existing pipe is thoroughly cleaned immediately before sliplining begins
(WPCF. 1983).
11-23
-------
HDPE sliplining is pulled through existing pipelines by a cable that is
fed through the section to be lined. The cable and pipe are advanced by a
winch and pully assembly (see Figure 11-3). An approach trench is excavated
at the insertion end of the existing pipe section to allow a gradual transi-
tion from the ground surface, where sections of HDPE pipe are heat fused to
form a continuous pipe to an opened section of pipe. Several thousand feet of
water or sewer line can be sliplined in a single set-up of such an operation
(Waste Engineering and Management, 1983). FRP can be sliplined in a manner
similar to that used for HDPE, although a combination of pushing and pulling
of the pipe can be employed (see Figure 11-3) (A.O. Smith-Inland, undated).
Wastewater flow in existing sewers may not need to be interrupted during
insertion of a sliplining as low flows may continue through the annular space
between the two pipes. Alternatively, it may be necessary to temporarily plug
the upstream lines and pump the flow around the section being lined using
above-ground piping (WPCF, 1983). The annulus between the old and new
pipelines is sometimes filled with grout where structural failure of the old
pipe could concentrate loads and cause problems with the HDPE pipelines.
In-place forming of new pipe inside of existing pipe is accomplished with
portland cement grout and mortar, chemical grouts, and synthetic resins.
FIGURE 11-3.
SEWER SLIPLINING METHODS
.WINCH ASSEMBLY
VREMOTE MANHOLE
OR ACCESS PIT
RAMP FOR TWO-WAY.
INSERTION
.CABLE ATTACHED
TO SUIOE CONE
MIN. OP
12 X LINER MIN. OP
DIAMETER 2.5 XD
LINER
PIPE
PIPE SUPPORT-
ROLLER
"PULL" METHOD
.WINCH AS3AMBLY
MINIMUM OP STANDARD PIPE LENGTH
JOINING MACHINE
PUSH PLATE-
' \CABLE PASSING THROUGH
' EXISTING PIPE ALINING PIPE ANCHORED
V REMOTE MANHOLE T0 PUSH PUATE
OR ACCESS PIT „ _
"PUSH" METHOD
^•LINER PIPE
•PIPE SUPPORTED ROLLER
Source: WPCF, 1983
11-24
-------
Chemical grouts can be used to seal fractures and leaking joints to
waterproof points of infiltration/exfiltration. Grout materials used for this
application include acrylamide, acrylate, urethane and polyurethane.
The chemicals necessary to form acrylamide or acrylate gels are usually
mixed in tanks and pumped through separate hoses to the pipeline joint to be
sealed. The water and catalyst solution initiates the chemical reaction when
mixed with the acrylamide solution. Additives can be included in either
solution to help control shrinkage, reaction or "gel" time, and other
variables (WPCF, 1983).
The two solutions are pumped through separate hoses to the point to be
sealed. The solutions are mixed as they are injected into the leaking
opening, initiating the chemical reaction. This reaction changes the two
solutions into a gel. The gel time can be controlled from just a few seconds
to several minutes. The grouts or gels stabilize soil around joints or cracks
by filling the voids (WPCF, 1983).
Urethane grout materials form either an elastomeric gel, much like the
acrylamide and acrylate gels, or a rubber-like foam. Water is the catalyst
for the urethane gel material. Urethane gel seals pipeline joints by forming
a collar within the pipe joint as well as by consolidating soils and filling
voids outside the joint (WPCF, 1983).
Urethane gel is applied in essentially the same manner as the acrylamide
and acrylate gels.
Polyurethane foam differs from the gel grouts in that the foam is used to
form an in-place pipeline gasket and does not fill voids or stabilize the soil
outside of the pipe joint (WPCF, 1983).
Small and medium diameter pipes can be grouted using a hollow metal
cylinder with inflatable rubber sleeves on each end of a center band, called a
"packer." An inflated packer can be used both to test and chemically seal a
pipeline joint. A van is used as the operation and control center for a TV
monitor, pumps, air compressors, and the feed system equipment. A closed-
circuit TV camera allows positioning of the packer at pipeline joints and
cracks for sealing. The packer and the TV camera are pulled along with a
cable from manhole to manhole, and the process is viewed on the TV monitoring
screen in the van (see Figure 11-4) (WPCF, 1983).
The amount of grout needed to seal a defect depends upon the size of the
leak. The gels usually are pumped until the grout solidifies; the back
pressure will then indicate to the operator that the leak has been sucessfully
sealed. The rubber sleeves are deflated and moved to the next joint for
sealing (WPCF, 1983).
For grouting large-diameter pipes, pressure grouting or manual placement
of oakum soaked with grout may be used. Pressure grouting is accomplished
using pipe grouting rings or predrilled injection holes (Figure 11-5).
11-25
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FIGURE 11-4.
TYPICAL ARRANGEMENT FOR APPLYING CHEMICAL GROUT TO SMALL DIAMETER PIPE
CHEMICAL, CATALYST, AND
•'AIR PRESSURE FEED LINES: ALSO
POWER SOURCE FOR TV CAMERA
WINCH
-MANHOLE ASSEMBLY
ROLLER
Source: WPCF, 1983
FIGURE 11-5.
TYPICAL ARRANGEMENT FOR SEALING LARGE DIAMETER PIPE WITH GROUTING RINGS
CHEMICAL, CATALYST
AND AIR PRESSURE
FEED LINES
CONTROL
PANEL -HAND-HELD PROBE
SEALING
RIN6
Source: WPCF, 1983
11-26
-------
Grouting using sealing rings requires the use of a small control panel,
chemical and water pumps, and various other accessories depending on the type
of sealing grout being used. A worker must enter the line, manually place the
ring over the joint, and inflate the ring to isolate the joint. Sealing grout
is pumped into the small void between the pipe wall and the face of the ring
through a hand-held probe. As the pressure in the void increases, the grout
solution is forced into the joint and surrounding soil. The catalyst solution
is injected and the grout cures, sealing the joint from infiltration (WPCF,
1983).
Linings and coatings can be used to protect pipelines from internal
corrosion. Most linings, however, are integrated into the pipe when it is
made (WPCF, 1983).
Reinforced shotcrete (gunite) is a mixture of fine aggegate, cement, and
water applied by air pressure using a cement ejector. Compared to cement
mortar linings, gunite is denser and has a higher ultimate compressive
strength. It also improves a pipeline's structural integrity. Gunite adheres
well to other concrete and brick sewers and is more corrosion-resistant than
normal concrete. It can be trowled to a finish to improve a pipeline's
hydraulic characteristics (WPCF, 1983).
Gunite is well-suited for extremely deteriorated large sewers where
persons and equipment can work without restriction. Long lengths of sewers
may be effectively renewed with little excavation and minimal traffic
disruption.
Gunite can be applied under low wastewater flows; however, totally
dewatering the pipeline is more effective. Welded wire mat or small diameter
rod reinforcing is used for structural gunite applications (WPCF, 1983).
In-place forming with synthetic resins (inversion lining) can be
accomplished without excavation in most cases. The reconstruction is done
through existing pipe access points, requiring only limited disruption of
surface conditions and activities. A four-step installation process, shown in
Figure 11-6, can normally be accomplished in a matter of days (Utz, 1983). A
fiberfelt tube impregnated with a liquid resin is fed into an inversion
standpipe which has been erected on site. The felt tube has an impermeable
coating on the outside which eases handling and provides a water barrier for
the inversion process (insituform, undated). The end of the tube is pulled
through the inversion standpipe, turned inside out and clamped to the stand-
pipe such that a leak-proof seal is established. As more water is added to
maintain the weight of the column, additional tubing is fed into the stand-
pipe, and the impregnated tube snakes its way forward through the pipe being
rehabilitated (WPCF, 1983).
The weight of the water presses the coated felt at the nose, inverts it,
and then presses the resin-impregnated side against the insides of the
existing pipe, leaving the smooth coated side as the new interior surface of
the rehabilitated pipe. After the inverted tube reaches the next manhole or
other access point, the water is heated to cure the resin, forming an
impermeable new pipe within the old pipe. The ends are cut off, the head of
11-27
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FIGURE 11-6.
INVERSION LINING INSTALLATION PROCEDURE
INVERSION ^
LINER ATTACHED \TUBE MATERIAL
TO HEADE- V
PIPE
2 VPIPE TO
^ BE LINED
STEP I
STEP 2
HOT WATER(OR AIR)
CIRCULATION HOSE
STEP S
LINED PIPELINE RETURNED TO SERVICE AFTER THE CURED
LINER HAS BEEN TRIMMED, THE INSTALLATION EQUIPMENT
HAS BEEN REMOVED, AND ANY SERVICE CONNECTIONS HAVE
BEEN REOPENED
STEP 4
Source: WPCF, 1983
11-28
-------
water is released, and the operation is complete. Service connections are
reinstated in non-man-entry pipes by means of remotely controlled cutting
device (insituform, undated).
11.7.5 Operation, Maintenance, and Monitoring
If properly implemented, lined, and repaired, water and sewer lines
should require no operation or maintenance beyond that required for other
lines. Periodic monitoring for contaminants of concerns in water or sewage
should be conducted to determine whether leaking or other failure of the
measures has occurred.
11.7.6 Technology Selection/Evaluation
Repairing and lining offer the advantage of eliminating contaminants
without the need for disruption of surface activities. However, the presence
of contaminants in close proximity to water or sewage may be cause for ongoing
concern. Because these technologies were not specifically developed for con-
trol of hazardous substances, their performance and reliability under such
special circumstances is neither certain nor can be fully evaluated with
available information. Coordination of material selection with manufacturers
may be useful in determining material compatability. Also, laboratory
bench-scale and/or field pilot-scale tests may be warranted to ensure that
effective, long-term isolation of contaminants can be affected.
11.7.7 Costs
Costs of sliplining water and sewer lines vary with the diameter and
depth of the pipeline. Costs for relatively small diameter (less than
15-inch) HDPE sliplining projects range from $20 to $30 per linear foot
(D'Angelo, T., Pipe Maintenance Services, Inc, Exton, PA, personal
communication, April 1985; Metcalf, K. Norfolk, VA, personal communication,
April 1985). Larger diameter sliplining projects are seldom undertaken and
must be costed on a project-specific basis.
Inversion lining costs are normally given on a per-linear-foot basis for
initial television inspection, cleaning, by-pass pumping, and post-construc-
tion television inspection combined. The following are representative unit
costs for typical inversion lining of sewer lines.
Diameter (inches) Cost (Linear Foot)
8 $45-50
10 $47-52
12 $49-54
11-29
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Reconnection of laterals typically costs $100 to $250 each, depending on
logistics and the number of laterals in a given project. (Tice, M.,
Insituform East, Inc. Landover, MD, Personal communication, April 1985.)
Grout repairs to sewer pipelines are generally accomplished by pumping
grout into a joint until soil voids are filled, as determined by back-
pressure. A wide range of grout volumes can be pumped into a joint, and sewer
grouting work is typically conducted on a per-hour basis for manpower and
equipment ($100 to $150 per hour) and on a per-gallon basis for grout ($5 to
$10 per gallon for chemical grout).
11-30
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REFERENCES
American Society of Civil Engineers (ASCE). Pipeline Design for Water and
Wastewater 1975. New York, NY. 127 pp.
American Society of Civil Engineers (ASCE). 1976. Design and Construction of
Sanitary and Storm Sewers. Manual of Practice no. 37. New York, NY. 331 pp.
Anderson, M., R.A. Cottier and G.E. Bellen. 1984a. Point-of-Use Treatment
Technology to Control Organic and Inorganic Contaminants, Part I.
Water Technology. September 1984. pp. 36-41.
Anderson, M., R.A. Cottier and G.E. Bellen. 1984b. Point-of-Use Treatment
Technology to Control Organic and Inorganic Contaminants,
Part II. Water Technology. October 1984. pp. 41-45.
A.O. Smith-Inland, Inc. undated. 1 1/3 Miles of Red Thread® Inserted as
Water main Under Portland Harbor, Pipefacts File 120, Little Rock, AR. 2 pp.
Association Francaise de Travaux en Souterrain (AFTES). 1975. Recommenda-
tions for the Use of Grouting in Underground Construction, trans, by G.W.
Clough.
Comsumers Union of United States, Inc. 1984. 1985 Buyers Guide Issue.
Mount Vernon, NY. pp. 82-85.
Fair, G.M. et al. 1971. Elements of Water Supply and Wastewater Disposal.
John Wiley and Sons, Inc., New York, NY. 752 pp.
Godfrey, R.S. 1984. 1985 Means Building Construction Cost Data, 43rd Annual
Edition. Robert Snow Means Co. Inc., Kingston, MA.
Insituform of North America, Inc. undated. Design Guide for Pipeline
Reconstruction. Memphis, TN. 6 pp.
Linsley, R. and J. Franzini. 1979. Water Resources Engineering. 3rd Ed.
McGraw-Hill Book Company, New York, NY.
Morrison, 1981. If Your City's Well Water has Chemical Pollutants, Then What?
Civil Engineering. Vol. 51, No. 9. pp. 65-67.
Perry, D. L. et al. 1981. Development of Basic Data and Knowledge Regarding
Organic Removal Capabilities of Commercially Available Home Water Treatment
Units Utilizing Activated Carbon, Phase 3/Final Report. EPA Contract No.
68-01-4766. Gulf South Research Institute. Prepared for: Criteria and
Standards Divison, Office of Drinking Water, U.S. Environmental Protection
Agency. October 23, 1981. 74 pp.
11-31
-------
REFERENCES (continued)
National Sanitation Foundation (NSF) Drinking Water Treatment Units, Health
Effects. Standard Number 53. Ann Arbor, MI. 11 pp. and appendices.
Taylor, R. H., M. J. Allen and E. E. Geldreich. 1978. Testing of Home Use
Carbon Filters. Presented at AWWA Water Quality Technology Conference.
Louisville, KY. December 4, 1978. 9 pp.
Utz, John H. 1983. Solving a Difficult Sewer Rehabilitation Problem. Public
Works. March 1983. pp. 59-60.
Water/Engineering and Management. 1983. Sliplining Water Mains Overcomes
Leakage. February, 1983. pp. 14-15.
Water Pollution Control Federation (WPCF). 1983. Existing Sewer Evaluation
and Rehabilitation. Manual of Practice FD-6. Washington, D.C. 106 pp.
Water Pollution Control Federation (WPCF) 1982. Operation and Maintenance of
Wastewater Collection Systems. Manual of Practice No. 7. Washington, D.C.
11-32
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APPENDIX A
INDEX
Accessibility
in Data Needs 2-5
Acids
in compatibility testing 7-26
and biodegradation 9-5
Acrylamides
as grout 5-98, 5-99, 5-100,
5-101
Activated carbon 10-3, 10-49, 11-5,
10-121
Activated sludge 10-10
Adsorption 10-121
Aeration 10-11
Aerobic 6-1, 9-2, 9-3, 9-5, 9-15,
9-34, 10-10
Air pollution controls 4-1 to 4-0,
10-137
Air quality
in climatology, data needs 2-5
in specific site problems 2-4
Air stripping 10-48
Alcohols
and biodegradation 9-5
and toxicity to microbes 9-11
Aldehydes
and biodegradation 9-5
and toxicity to microbes 9-11
Aliphatic alcohols
as floating immiscible liquids 4-2
Alkanes
and biodegradation 9-5
Alkyl halides
and biodegradation, 9-3, 9-5
Amides
and biodegradation 9-5
Amines
and biodegradation 9-5
and toxicity to microbes
Anaerobic 6-1, 9-2, 9-3, 9-5, 9-28
Anganochlorine
in waste analysis 7-28
Aquifer
artesian 5-14
confined 5-5, 5-8, 5-11, 5-19
data needs 2-5
heterogeneous 5-5, 5-7
homogeneous 5-5
unconfined (water table) 5-5,
5-8, 5-10, 5-15, 5-19
Aromatics
and biodegradation 9-3, 9-5
Asphalt
as a dust suppressant 4-5
as mulch for revegetation 3-29
Augers
hand 5-32, 5-33
rotary bucket 5-33, 5-35, 5-44
spiral 5-33, 5-35, 5-44
Backfilling
and subsurface drains 5-71
and slurry walls 5-89
Backhoes 7-2 to 7-6, 7-22, 8-2, 8-5,
8-32, 8-35
Barriers
and pumping 5-39
and subsurface drains 5-47 to
5-49, 5-51, 5-53
A-l
-------
APPENDIX A (Continued)
low permeability 5-1, 5-55 to
5-59
concrete 3-4
bituminous membranes 3-4
subsurface 5-83 to 5-113
Bases
in compatability testing 7-26
in pretreatment 7-27
Basket centrifuges 10-82
Bedrock
in site geology data needs 2-5
fractured or jointed 5-2
Belt filter presses 10-91
Benches 3-3, 3-52 to 3-56
Bentonite 3-7
and slurry walls 5-83, 5-93
5-96
for wells 5-25
Berms 3-3, 3-12, 3-36 to 3-40, 8-48
Biological towers 10-11
Biological treatment 10-10
Bioreclamation 9-1 to 9-39
Biphenyls
and biodegradation 9-3, 9-5
Bitumen 3-7
Block displacement 5-112
BOD/COD ratio 9-3, 9-4
Bottom ash
and soil treatment 3-7
Bottom sealing 5-112, 5-113
Bucket factor 7-6
Bucket ladder dredge 8-2, 8-6, 8-7
Butyl alcohol
as floating immiscible liquid 4-2
Butyl rubber
and synthetic membranes 3-7,
3-12, 3-16, 7-35
Capping
general 3-1, 3-2 to 3-12, 6-28
multi-layered 3-5 to 3-8, 3-9
single-layered 3-5, 3-9
Carbon dioxide 6-1
Carboxylated styrene-butadiene copol-
omer as dust suppressant 4-5
Casing
for wells 5-23, 5-31, 5-33, 5-37
Cercla 1-1, 2-1
Cement
Portland 3-7, 5-83, 5-92
Cement-based solidification 10-106
Centrifuges 10-82
Channels 3-1, 3-3, 3-40 to 3-52
Chelation
and chemical treatment 9-36,
9-43, 9-45, 9-46
Chemical Composition
in waste characteristics,
data needs 2-5
in technology selection 2-7
Chemical stabilizers 3-7
Chemical treatment 9-39 to 9-61
Chlorinated Polyethene
and synthetic membranes 3-7,
3-12, 3-16
Chromium
as alloy 7-14
A-2
-------
APPENDIX A (Continued)
Chutes 3-1, 3-3, 3-57 to 3-63
Circulating Bed Combustion 10-135
Clamshells 7-6, 7-22, 8-2 to 8-4,
8-32, 8-35
Clarifiers 10-72
Clean Water Act
in remedial action alternatives
2-10
Climatology
in data needs 2-5
Cofferdams 8-21 to 8-25
Coke tray aerator 10-49
Compatibility testing 7-25 to 7-27
Cone of depression 5-8, 5-9, 5-12,
5-18
Cone of impression 5-18
Contour furrowing 3-21
Costs
of activated carbon units 10-8
of activated sludge 10-17
of active gas control 6-25 to
6-27, 6-31
of airstripping 10-52
of benches and terraces 3-56,
3-82
of bioreclamation 9-35 to 9-39
of capping 3-11, 3-12
of cement-based solidification
10-108
of centrifuges 10-87
of channels and waterways 3-52,
3-82
of chemical clarification 10-35
of chutes and downpipes 3-57,
3-82
of cyclones 10-71
of dikes and berms 3-40, 3-82
of dredging 8-36 to 8-42, 8-46
of dust suppressants 4-5, 5-6
of excavation equipment 7-6,
7-8, 7-9, 7-10
of filtration 10-97
of floating covers 3-19
of grading 3-24 to 3-26
of ground freezing 9-64
of grouting 5-103, 5-104, 5-109
of heavy metal precipitation
10-29
of hydraulic classifiers 10-66
of hydroxide and sulfide
precipitation 10-30
of incineration 10-141
of in-situ treatment 9-35, 9-59
of in-situ vitrification 9-62
of ion exchange 10-39
of levees and floodwalls 3-79,
3-82
of liners 7-35
of microencapsulation 10-116
of neutralization 10-47
of off-site disposal 7-25
of on-site disposal 7-38
of oxidation 10-55
of passive gas control 6-12
to 6-14
of permeable treatment 9-60
of polymer addition 10-31
of polypropylene spheres 4-3
of pumping 7-15
of reduction 10-56
of remedial action
alternatives 2-11 to 2-13
of revegetation 3-31 to 3-35
of reverse osmosis 10-44
of sedimentation basins/ponds
3-74, 3-82
of sediment treatment 8-46
of seepage basins and ditches
3-67, 3-82
of sewer line cleaning and
inspection 11-21
of sewer line rehabilitation 11-29
of sewer line replacement 11-14
of sheet piling 5-112
of silicate cement solidification
10-111
A-3
-------
of slurry walls 5-92, 5-93, 5-97
of spiral classifiers 10-68
of subsurface drains 5-73 to 5-82
of surface water controls 3-80 to
3-85
of surfactant layers 4-3
of thermoplastic solidification
10-114
of vacuum loaders 7-16
of well systems 5-40 to 5-46
of wind screens 4—7
Covers
synthetic 4-8
and sediments 8-49 to 8-54
Cranes 7-2, 7-6 to 7-8, 7-22
Cross-flow tower 10-49
Cutterhead Dredge
and hydraulic dredging 8-9,
8-32, 8-35
Cyanides
in compatibility testing 7-26
in pretreatment 7-27
in waste analysis 7-28
Cyclones 10-68
Darcy's Law 5-8, 9-19
Data needs
in site-specific
characteristics 2-5
Dessication Caps 5-94
Detoxification 9-52
Dewatering
in subsurface drain
installation 5-69, 5-75
Dewatering lagoons 10-80
Diaphragm Walls 5-97
APPENDIX A (Continued)
Diaphragm filters 10-96
Diffused air basin 10-49
Dikes 3-1, 3-3, 3-36 to 3-40,
8-48
Disposal
of wastes 7-1 to 7-40
off-site 7-24 to 7-30
on-site 7-30 to 7-38
Distillation 11-5
Ditches 3-1, 3-2, 3-3, 3-63 to 3-67
Diversion channels 3-1
Diversion (channel) 3-42, 3-43
Diversion Dikes 3-38, 3-39, 3-40
DOT
and transportation of
wastes 7-29
Downpipes 3-1, 3-3, 3-57 to
3-63
Dozers 7-2, 7-8, 7-9, 7-22
Dragline 7-2, 7-6, 7-7, 7-8,
7-22, 8-2, 8-4, 8-5,
8-32, 8-35
Drains
interceptor 5-51 to
5-55, 5-82
relief (parrallel) 5-51,
5-55 to 5-59
subsurface 5-1, 5-46 to
5-82, 9-25
installation 5-70 to 5-72
Drawdown 5-8, 5-9, 5-12, 5-15,
5-17, 5-21, 5-22, 5-25,
5-30
in plots 5-19, 5-20, 5-21
A-4
-------
APPENDIX A (Continued)
Dredging
mechanical 8-2 to 8-6, 8-32,
80-35
hydraulic 8-7 to 8-17,
8-32, 8-35
pneumatic 8-17 to 8-20,
8-32, 8-35
Drilling
rotary 5-32, 5-3A, 5-36, 5-44
cable tool 5-34, 5-44
Drums
and transportation of
wastes 7-29
Dust suppressant 4-4 to 4-6
Dustpan dredge
and hydraulic dredging
8-10, 8-32, 8-35
Electroosmosis 10-80
Embankments 3-2
Encapsulation 10-115
Envelope
and subsurface drains
5-47, 5-62, 5-64, 5-71
and leachate collection 7-34
EP Toxicity
in waste analysis 7-28
Epichlorohydrin rubbers
and synthetic membranes 7-35
Epoxides
and biodegradation 9-5
Epoxy
as grout 5-100
Erosion
control of 3-1, 3-3, 3-7,
3-8, 3-19. 3-20, 3-24, 3-36,
3-52, 3-57
Esters
and biodegradation 9-5
Ethylene propylene rubber
and synthetic membranes
3-7, 3-12, 3-16
Evapotranspiration 3-5, 3-9
in climatology, data needs
2-5
Excavation
general 7-1 to 7-24
equipment 7-2 to 7-16
Feasibility study (FS) 1-1, 2-2,
2-3
Fermentation 9-3, 9-5
Filters
and subsurface drains
5-62, 5-71
Filter pack
for wells 5-24, 5-25, 5-30,
5-31, 5-37
Filtration 10-19, 10-91
Flaring 10-118
Flammability
in compatibility testing 7-27
Flash point
in waste analysis 7-28
Floating covers 3-13 to 3-19
Flocculation 10-22
Flooding
protection from 3-2, 3-3,
3-74 to 3-79
Floodplain
in surface water,
data needs 2-5
A-5
-------
APPENDIX A (Continued)
in disposal requirements
7-30
Floodwalls 3-1, 3-2, 3-3,
3-74 to 3-79
Flood control dikes 3-2
Flow
equilibrium (steady state)
5-8, 5-10
non-equilibrium 5-8
laminar 5-8
and velocity distribution
plots 5-19
Fluidized bed incinerator
10-129
Flumes 3-1, 3-57
Flyash
and soil treatment 3-7
and slurry walls 5-96
Fugitive dusts/emissions
4-1, 4-4 to 4-8, 7-20
Furnace slag
and soil treatment 3-7
and slurry walls 5-96
Gabions 3-64
Gas
collection system 3-5,
3-16, 3-17, 4-4, 6-14
to 6-25
migration 2-4, 3-30, 4-4,
3-30, 6-2
emissions 4-1 to 4-4, 6-28
controls 6-1 to 6-32
organic 6-1
detectors 6-9, 7-23
passive perimeter controls
6-21 to 6-14
active perimeter controls
6-14 to 6-24
extraction wells 6-14 to
6-25
collection headers 6-14
to 6-25
treatment or utilization
6-14 to 6-25
active interior controls
6-26 to 6-31
cylinders 7-24
Gaseous waste treatment 10-118
Geology
in data needs 2-5
Geotextiles
as capping 3-12
as dust suppressant 4-5
and subsurface drains
5-62, 5-72
Classification 10-116
Glycols
and biodegradation 9-5
Grade control
in subsurface drains 5-69
Grading 3-1, 3-3, 3-19 to 3-26
Grapples 7-6
Gravel pack (see filter pack)
Gravity collection systems 5-1
Gravity separation 10-47
Gravity thickening 10-77
Gravity underdrainage 10-80
Grizzlies 10-58
Ground freezing 9-61
Ground leaching
(see soil flushing 9-45)
A-6
-------
Groundwater
in data needs 2-5
Groundwater
monitoring 7-37
temperatures 9-9
Groundwater
extraction 3-4
containment 3-4
Groundwater
controls 5-1 to 5-118
diversion 5-1
pumping 5-1 to 5-46
Groundwater
barriers 5-5
Groundwater quality
in specific site
problems 2-4
APPENDIX A (Continued)
Heat recovery 10-138
Henry's law 9-19
Herbicides
and biodegradation
9-3, 9-5
Heterogeneous aquifers 5-5
High temperature fluid wall
10-135
Hoists 7-6
Homogeneous aquifiers 5-5
Hopper dredges
and hydraulic dredging
8-11, 8-32, 8-35
Grouting
and subsurface barriers
5-97 to 5-109
cement 5-97
clays 5-98, 5-99
bentonite 5-98, 5-99
silicates 5-98, 5-99
organic ploymers 5-98, 5-99
curtains 5-103 to 5-109
port method 5-105, 5-107
and bottom sealing 5-112
and sediments 8-55, 8-56
Grouting
for wells 5-24, 5-37, 5-38
Gyratory screens 10-59
Halogens
in compatibility testing
7-26
Haulers 7-9, 7-10, 7-22
Head 5-8, 5-9, 5-20, 5-26,
5-27, 5-28, 5-56
Hydraulic barriers (boundary
conditions) 5-8, 5-16,
5-17, 5-18, 5-19, 5-20
Hydraulic classifiers 10-63
Hydraulic conductivity 5-2,
5-8, 5-10, 5-51
in well selection 5-5, 5-7,
5-19, 5-38, 5-58, 5-73
Hydraulic gradient 5-2, 5-8,
5-59, 5-60
Hydrocarbons
and biodegradation 9-3, 9-5
Hydrocyclones 10-68
Hydrogen sulfide 6-1, 6-8, 9-50
Hydrogen peroxide
and bioreclamation
9-15, 9-17
Hydrolysis 9-40, 9-42, 9-52
Hydrosieve 10-63
A-7
-------
APPENDIX A (Continued)
Hydroxy compounds
and biodegradation 9-5
Hypalon
and synthetic membranes
3-7, 3-12, 3-16, 3-19, 6-8
Immobilization 9-47
Impoundment basin 10-72
Incineration 7-25
Infiltration
prevention of 3-1, 3-3, 3-8,
3-20, 3-26, 3-44, 5-2
through capping 3-4, 3-5
In-situ heating 9-61
Interceptor dike 3-36, 3-37, 3-38
Inversion lining 11-22
Ion exchange 10-36, 11-5
Jetting
and well installation 5-33,
5-35, 5-36, 5-44
Ke tones
and biodegradation 9-5
and toxicity to microbes 9-11
Lagoon
covers 3-2, 3-3
Landfills 7-25, 7-30 to 7-38
Latex
as dust suppressant 4-5
Leachate
in specific site
problems 2-4
Leachate
prevention 5-1
control 5-101
Leachate
collection 7-32, 7-33, 7-36
Levees 3-2, 3-3, 3-12,
3-74 to 3-79, 7-33
Lifters 7-6
Lignosulfonate
as dust suppressant 4-5
Lime
and soil treatment 3-7
Liners
natural 3-4 to 3-6, 3-12,
7-20, 7-30 to 7-32, 7-33, 7-36
synthetic 3-4, 3-5, 3-6, 3-7,
3-10, 3-11, 3-12, 3-13, 3-16,
4-1, 7-30 to 7-32, 7-33,
7-34, 7-35
admixed 3-4, 3-5, 3-6, 3-12,
7-32, 7-33
-Liquid injection 10-123
Liquid migration
requirements 3-2
Loaders 7-2, 7-8, 7-9,
7-15, 7-16, 7-22
Magnets 7-6
Manholes
and subsurface drains
5-62, 5-65, 5-81
Manning formula 3-44, 3-49, 3-50
Methane 6-1, 6-8
Methanogenic processes
and bioreclamation 9-2,
9-30, 9-37
Microencapsulation 10-115
Mobile incineration 10-131
A-8
-------
APPENDIX A (Continued)
Molten salt incineration 10-131
Monitoring wells 3-4, 3-11, 5-72
National contingency plan (NCP)
1-1, 2-1, 2-8
Native vegetation
in data needs 2-5
Neoprene
and synthetic membranes
3-7, 3-12, 7-35
Neutralization 9-52, 10-45
NIOSH 7-21
Nitrate
and anaerobic bioreclamation
9-30, 9-31
Nutrients
and bioreclamation 9-22
to 9-23
Nitrites
and biodegradation 9-5
Nitro compounds
and biodegradation 9-5,
9-32
Nitrogen 6-1, 9-22
Octanol-water partition
coefficients 9-46
Organophosphates
and biodegradation 9-3,
9-5
OSHA 7-21
Osmosis 10-40
Oxidation 9-3, 9-5, 9-38,
9-41, 9-42, 9-53, 9-54
Oxidizing agents
in compatibility testing
7-26
Oxygen 6-1, 6-8, 7-23, 9-15
and requirements for
bioreclamation 9-3, 9-15
to 9-22
Packed tower 10-48
Packer 5-28, 5-37
PCS
and incineration 7-25
in compatibility testing
7-26
in waste analysis 7-28
and sediment treatment
8-45
PCE
and biodegradation 9-2, 9-30
Permeability 5-8, 5-25
of slurry walls 5-87,
5-88, 5-94
of grouts 5-99
and gas control systems
6-4, 6-7
Permeable treatment bed
9-56
Peroxides
in compatibility testing
7-26
Pesticides
and biodegradation 9-2,
9-30
PH
in waste analysis 7-28
in bioreclamation
monitoring 9-9, 9-32
Phenolic grouts 5-99, 5-100
A-9
-------
APPENDIX A (ContinuedO
Phenols
and biodegradation 9-3,
9-5
Phosphates
and bioreclamation
9-8, 9-22, 9-32
Phytotoxic 3-26, 3-28
Piezometric surface 5-14
Piezometers 5-72
Pipes
and subsurface drains
5-47, 5-59 to 5-62, 5-70,
5-71, 5-79
and leachate collection
systems 7-34
Piping
and liners 3-8, 7-3
Plasma Arc Torch 10-133
Plume
containment 5-1, 5-2,
5-16, 5-19, 5-47, 5-54
prevention 3-4
removal 5-1, 5-2, 5-47
diversion 5-5, 5-6
non miscible 5-17
floating contaminants
5-12
delineation 5-46
Point dumping
and sediment covers
8-50, 8-51
Polydimethyl siloxane
as floating immiscible
liquid 4-2
Polyester
and silt curtains 8-28
and filters 5-62
as grout 5-100, 5-101
A-10
Polyethylene
and synthetic membranes
3-7, 6-8, 7-17, 7-35
and filters 5-62
Polyhydrldes
and biodegradation 9-5
Polymerization
and chemical treatment
9-36, 9-42, 9-51
Polyolefin
and synthetic membranes 3-7
Polypropylene
as filters 5-62
and synthetic membranes 7-35
spheres 4-2, 4-3
as pump coating 7-11
Polyvinyl chloride (see PVC)
Ponds 3-2, 3-3, 3-67 to 3-74
Potentiometric surface
map 5-17, 5-23, 5-51
Precipitation 9-47, 9-51, 10-22
in climatology,
data needs 2-5, 3-9
Precipitation
and chemical treatment
9-36, 9-43, 9-50
Pretreatment
of wastes 7-27
Proctor Density 3-21
Production rates
backhoes 7-4, 7-6, 8-6
cranes and attachments 7-6, 7-8
dozers and loaders 7-9
Production rates
clamshells 8-2
draglines 8-5
pneumatic dredges 8-17
-------
APPENDIX A (Continued)
Public health
in screening remedial
action alternatives
2-8, 2-11
Pumps
submersible 5-25, 5-42, 7-14
vertical lineshaft 5-26
performance curves 5-27
ejector (jet) 5-28, 5-42
suction (vacuum) 5-5,
5-30, 5-42
centrifugal 7-11
reciprocating 7-11 to 7-13
diaphram 7-11, 7-12
bellow 7-11, 7-12
piston 7-11, 7-12
positive displacement
7-13
gear 7-13
flexible impeller 7-13
flying vane 7-13
immersion 7-14
Pumpdown
and sedmiment covers
8-50, 8-51, 8-52
Pump Test 5-8, 5-19
Pumping
equilibrium vs non-
equilibrium 5-17, 5-20
Pumping
rates 5-22
and groundwater controls
5-1 to 5-46
PVC (Polyvinylchloride)
and synthetic membranes
3-7, 3-12, 6-8, 7-35
dand filters 5-62
and silt curtains 8-28
as pump coating 7-11
PVDF
as pump coating 7-11
Pyrolysis 10-135
Radioactivity
meters 7-23
in compatibility
testing 7-26
in waste analysis
7-28
Radius of influence
of a well 5-2, 5-8, 5-9,
5-10, 5-12, 5-17, 5-19, 5-20
Rainfall
in climatology,
data needs 2-5
events (storms) 3-44
RCRA
and disposal regulations 3-5
and capping design 3-5
and off-site disposal 7-24
and incineration 7-25
and transporatation 7-29
and on-site disposal 7-30, 7-37
and landfill liner systems 7-32
and leachate collection systems
7-32
and ground water monitoring 7-37
in remedial action alternatives
2-10
landfill closure requirements
3-2
Reactors 10-137
Reamers 5-35
Recharge
in groundwater characteristics,
data needs 2-5
Recharge
rates 5-8
Reduction
and chemical treatment
9-38, 9-43, 9-54, 10-55
A-ll
-------
Remedial Investigation
(RI) 1-1
Remedial technology
catagories 2-4
data needs 2-5, 2-6
Removal 7-1 to 7-24
Resins 10-36
as grout 5-98
as dust suppressant 4-5
as mulch for revegation 3-29
Revegetation 3-1, 3-3, 3-19, 3-26
to 3-32
Reverse osmosis 10-40, 11-5
Revolving screens 10-59
RI/FS 1-1, 2-1, 2-2
Rock grouting 5-101 to 5-103
Rotating biological contacter
10-11
Rotary kiln 10-126
Roughness coefficient 5-60
Runoff
prevention of 3-1, 3-3, 3-36
interception of 3-1, 3-3, 3-52
diversion of 3-36, 3-40, 3-42,
3-52, 3-57, 3-79
Safe Drinking Water Act
(SDWA)
in remedial action
alternatives 2-10
Safety
in remedial action
alernatives 2-10
field personnel 7-20
APPENDIX A (Continued)
Salts
Salts
and soil treatment 3-7
and bioreclamation
9-23, 9-24
Scarification 3-21
Scrapers 7-10, 7-22
Screens 4-6, 4-7, 5-37
Screen
for wells 5-23 to 5-25,
5-31, 5-33, 5-38, 5-43
Screens and sieves 10-58
grizzlies 10-58
vibrating 10-59
gyratory 10-59
revolving 10-59
fixed 10-62
Sediments
removal 8-1 to 8-42, 8-44
treatment 8-43 to 8-57
in-situ control 8-47 to 8-57
covers 8-49 to 8-54
surface sealing 8-54 to 8-56
in-situ grouting 8-56
Sediments, contaminated
in specific site
problems 2-4
removal and
containment of
8-1 to 8-60
Sediment trap 3-64, 3-65
Sedimentation 10-23, 10-32
Sedimentation basins 3-2,
3-3, 3-67 to 3-74, 10-32
Seepage basins 3-2, 3-3, 3-63
to 3-67
Seismic history
in site geology,
data needs 2-5
A-12
-------
APPENDIX A (Continued)
Settling basin 10-71
Sewer lines, contaminated
in specific site
problems 2-4
Sewer lines 11-1
replacement 11-9
inspection and
cleaning 11-14
rehabilitation 11-21
Sheet piling 5-109 to 5-112
Silicate based solidification 10-108
Silicon
as alloy 7-14
Silt curtains 8-28 to 8-31
Site-specific characteristics
in technology screening 2-3
in geology 2-5
in ground water 2-5
in surface water 2-5
in climatology 2-5
in in-situ treatment
9-44
Slings 7-6
Sliplining 11-22
Slurry Walls 5-2, 5-83 to
5-97
soil-bentonite 5-83 to
5-92
cement-bentonite 5-92
to 5-97
as gas migration
barriers 6-7
Soils
in data needs 2-5
treatment for liners 3-7
tests 3-9
characteristics for
revegetation 3-28
Soils, contaminated
in specific site
problems 2-4
Soil flushing
and chemical treatment
9-36, 9-41, 9-43, 9-45 to 9-46
Soil water partition
coefficient 9-46
Solid bowl solidifications 10-108
Solidification 9-51, 10-106
Solids separation 10-57
Solution mining (see soil
flushing)
Solvent flushing (see soil
flushing)
Sorbents 10-111
Sorptive resins 10-36, 10-122
Specific capacity 5-8
Specific gravity
in waste analysis 7-28
Specific yield 5-22
Spiral classifier 10-66
Stabilization 9-51, 10-106
Stage-down
and grout curtains
5-105, 5-107
Stage-up
and grout curtains 5-105,
5-107
Stagnation point 5-19, 5-22
A-13
-------
Storage coefficient(s)
5-8, 5-17, 5-19, 5-20
APPENDIX A (Continued)
Swales 3-42, 3-43, 3-44
TCE
Submerged diffuser system
and sediment covers 8-52,
8-54
Subsurface barriers (see
Barriers, subsurface)
Suction Dredge
in hydraulic dredging
8-8, 8-32, 8-35
Sulfates
and bioreclamation 9-31,
9-32
Sulfides
in combatibility testing
7-26
in pretreatment 7-27
Sulfur
in waste analysis 7-28
Sumps 5-64, 5-66, 7-34
Superfund 2-1
Surface encapsulation 10-115
Surface water
in data needs 2-5
controls 3-1 to 3-88
collection and transfer
3-1, 3-3
storage and discharge
3-2, 3-3
diversion and collection
3-32 to 3-85, 7-20, 8-21
Surface water quality
in specific site
problems 2-4
Surfactants 9-46 to 9-48,
9-49
and biodegradation 9-2,
9-3, 9-30
Technology limitations
in technology screening
2-7
Technology screening
in site characteristics
2-3, 2-5
in technology limitations 2-7
in waste characteristics
2-5, 2-7
in remedial action
alternatives 2-8
Terraces 3-1, 3-3, 3-21,
3-52 to 3-56
Thermal Destruction 10-123
Thermoplastic elastomers
and synthetic membranes 7-35
Thermoplastic solidification
10-113
Thiols
and biodegradation 9-5
TOG
and bioreclamation monitoring
9-32
Topography
in data needs 2-5
Toxic substance control act
in remedial action
alternatives 2-10
Tracing 3-21
Transmissivity (T) 5-8, 5-15,
5-17, 5-19, 5-20, 5-39, 5-45
A-14
-------
APPENDIX A (Continued)
Trenches
excavation 5-67 to 5-70
Trickling filter 10-11
TSCA 2-10
Turbitity control
and sediments removal
8-27 to 8-31
Universal soil loss equation
3-8
Ure a-f o rmaldehyde
as grout 5-100, 5-101
Ur ethanes
as grout 5-99, 5-100
Vacuum assisted drying
beds 10-80
Vacuum loaders 7-15, 7-16, 7-22
Vacuum pumping 10-80
Vapor detectors 7-23
Vegetable gum
as dust suppressant 4-5
Venturi
and ejector wells 5-28
Vibrating beam
and grout curtains
5-105, 5-107, 5-108
Vibrating screens 10-59
Viscosity
in waste analysis 7-28
Vitrification 10-116
Wall stabilization
and subsurface drains
5-70
Waste characteristics
in technology screening
2-5, 2-7
in specific site
problems 2-4
Waste migration 3-4
Waste treatment
in-situ 9-1 to 9-70
Water Spraying 4-7
Water supply 11-1
contamination 11-1
replacement 11-2
treatment 11-4
Water table 5-8, 5-15,
5-54, 7-33
Waterways 3-1, 3-3,
3-40 to 3-52
Wedge bar screen 10-62
Wellpoints 5-1, 5-5, 5-7,
5-30, 5-31, 5-43, 5-69
Wells
suction 5-1, 5-5, 5-7
ejector 5-1, 5-5, 5-7,
5-26 to 5-30
deep 5-1, 5-5, 5-7,
5-23 to 5-26, 5-69
extraction 5-2, 5-3,
5-4, 5-16, 5-22, 5-46,
5-47, 9-25 to 9-28
injection 5-2, 5-4,
5-16, 5-22, 9-25 to 9-28
Wells
partially penetrating
5-8, 5-12, 5-14
design 5-17 to 5-23
components 5-23 to 5-31
driven 5-32, 5-33
completion 5-37, 5-38
development 5-38
A-15
-------
APPENDIX A (Continued)
installation 5-32 to 5-38
maintenance 5-38, 5-39
Wet air oxidation 10-133
Wind fences/screens 4-6, 4-7
XR-5 3-16
A-16
-------
APPENDIX B
COPYRIGHT NOTICE
Figure 3-15
Figure 3-21
Figure 3-22
Figure 3-23
Figure 3-24
Figure 3-30
Figure 3-31
Table 5-1
Figure 5-5
Table 5-5
Figure 5-6
Figure 5-7
From Tourbier, J. and R. Westmacott. 1974. Water Resources
Protection Measures in Land Development—A Handbook. Used by
permission of Water Resource Center, University of Delaware.
From Tourbier, J. and R. Westmacott. 1974. Water Resources
Protection Measures in Land Development—A Handbook. Used by
permission of Water Resource Center, University of Delaware.
From Tourbier, J. and R. Westmacott. 1974. Water Resources
Protection Measures in Land Development—A Handbook. Used by
permission of Water Resource Center, University of Delaware.
From Tourbier, J. and R. Westmacott. 1974. Water Resources
Protection Measures in Land Development—A Handbook. Used by
permission of Water Resource Center, University of Delaware.
From Tourbier, J. and R. Westmacott. 1974. Water Resources
Protection Measures in Land Development—A Handbook. Used by
permission of Water Resource Center, University of Delaware.
From Linsley, R. and J. Franzini, 1979. Water Resources
Engineering, 3rd Edition. Used by permission of McGraw-Hill
Book Company. New York, N.Y.
From Tourbier, J. and R. Westmacott. 1974. Water Resources
Protection Measures in Land Development—A Handbook. Used by
permission of Water Resource Center, University of Delaware.
From Powers, J.P. 1981. Construction Dewatering: A Guide
to Theory and Practice. Used by permission of John Wiley and
Sons, Inc. New York, NY.
From Davis, S.N.and R.J.M. Deweist. 1966. Hydrogelogy.
Used by permission of John Wiley and Sons, Inc. New York,
NY.
From Johnson Division. UOP, Inc. 1975. Groundwater in
Wells: A Reference Book for the Water Well Industry. Used
by permission of Johnson Division, UOP, Inc. St. Paul, MN.
From Davis, S.N.and R.J.M. Deweist. 1966. Hydrogelogy.
Used by permission of John Wiley and Sons, Inc. New York,
NY.
From Powers, J.P. 1981. Construction Dewatering: A Guide
to Theory and Practice. Used by permission of John Wiley and
Sons, Inc. New York, NY.
B-l
-------
APPENDIX B (continued)
Table 5-7
Figure 5-9
Table 5-9
Figure 5-10
Figure 5-11
Figure 5-12
Figure 5-14
Figure 5-15
Table 5-16
Figure 5-16a&b
Figure 5-16c
Modified from Lundy, D.A. and J.S. Mahan. 1982. Manuscripts
originally printed in the proceedings of the National
Conference on Management of Uncontrolled Hazardous Wastes -
1982. Nov. 29 - Dec. 1. Used by permission of Hazardous
Materials Control Research Institute. Available from
Hazardous Materials Control Research Institute, 9300 Columbia
Blvd., Silver Spring, MD 20910.
From Freeze, R.A. and J.A. Cherry. 1981. Groundwater. Used
by permission of Prentice-Hall, Inc. Englewood Cliffs, NJ.
From Church, H.K. 1981. Excavation Handbook. Used by
permission of McGraw-Hill Book Company, New York, NY.
From Davis, S.N.and R.J.M. Deweist. 1966. Hydrogelogy.
Used by permission of John Wiley and Sons, Inc. New York,
NY.
From Ferris, et. al. 1982. As cited by Lohman, S.W. 1972.
Ground Hydraulics Geological Survey Professional Paper 708.
Used by permission of US Geological Survey, Reston, VA.
From Johnson Division. UOP, Inc. 1975. Groundwater in
Wells: A Reference Book for the Water Well Industry. Used
by permission of Johnson Division, UOP, Inc. St. Paul, MN.
From Flint and Wailing, Inc. 1980. Putting water to work
since 1866. Technical Information Brochure. Used by
permission of Flint and Walling, Inc. Kendallville, IN.
From Powers, J.P. 1981. Construction Dewatering: A Guide
to Theory and Practice. Used by permission of John Wiley and
Sons, Inc. New York, NY.
Adapted from Jefferis, S.A. 1981. Bentonite-Cement Sluries
for Hydraulic Cut-offs. In: Proceedings of the Tenth
International Conference on Soil Mechanics and Foundation
Engineering. Stockholm, Sweden. June 15-19, 1981. Used by
permission of S.A. Jefferis.
From Johnson Division. UOP, Inc. 1975. Groundwater in
Wells: A Reference Book for the Water Well Industry. Used
by permission of Johnson Division, UOP, Inc. St. Paul, MN.
From Powers, J.P. 1981. Construction Dewatering: A Guide
to Theory and Practice. Used by permission of John Wiley and
Sons, Inc. New York, NY.
B-2
-------
APPENDIX B (continued)
Figure 5-22 From Giddings, T. 1982. The Utilization of a Groundwater
Dam for Leachate Containment at a Llandfill Site. In:
Aquifer Restoration and Groundwater Rehabilitation. 2nd
National Symposium on Aquifer Restoration and Groundwater
Monitoring. May 26-28. Used by permission of National Water
Well Assoc., Worthington, OH.
Figure 5-25 Adapted from Van Schlifgaarde, J. 1974. Drainage for
Agriculture, Agronomy monograph number 17, pages 245-270.
Used by permission of American Society of Agronomy. Madison,
WI.
Figure 5-32 Adapted from Jefferis, S.A. 1981. Bentonite-Cement Slurries
for Hydraulic Cut-offs. In: Proceedings of the Tenth
International Conference on Soil Mechanics and Foundation
Engineering. Stockholm, Sweden. June 15-19, 1981. Used by
permission of S.A. Jefferis.
Figure 5-33 Adapted from Bowen, R. 1981. Grouting in Engineering
Practice. 2nd. Ed. Used by permission of John Wiley and
Sons, Inc. New York, NY.
Figure 5-35 From Soletanche, undated. Soils Grouting. Technical
Bulletin. Used by permission of Soletanche. Paris, France.
Figure 5-36 From Ueguhardt, L.C. et al. 1962. Civil Engineering
Handbook. Used by permission of McGraw-Hill Book Company.
New York, NY.
Figure 6-1 From Emcon Associates and Gas Recovery Systems, Inc. 1981.
Landfill Gas - An Analysis of Options. Published by
permission of Emcon Associates. San Jose, CA.
Figure 6-4 From Emcon Associates. 1980. Methane Generation and
Recovery From Landfills. Published by permission of Ann
Arbor Science Publishers, Inc. Ann Arbor, MI.
Figure 6-8 From Emcon Associates and Gas Recovery Systems, Inc. 1981.
Landfill Gas - An Analysis of Options. Published by
permission of Emcon Associates, San Jose, CA.
Figure 7-1 From Stubbs, E.W. 1959. Handbook of Heavy Construction.
1st Edition. Used by permission of McGraw-Hill Book Company.
New York, NY.
B-3
-------
APPENDIX B (continued)
Figure 7-4
Table 7-5
Table 7-6
Figure 8-3
Figure 8-10
Table 9-1
Figure 9-1
Figure 9-6
Table 9-7
Table 9-8
From Buecker, D.A. and M.L. Bradford. 1982. Page 299.
"Safety and Air Monitoring Considerations of the Cleanup of a
Hazardous Waste Site." Manuscripts originally printed in
Proceedings of the National Conference on Management of
Uncontrolled Hazardous Waste Sites - 1984. Used by
permission of Hazardous Materials Control Research Institute.
Available from Hazardous Materials Control Research
Institute, 9300 Columbia Blvd., Silver Spring, MD 20910.
From Cope, F., G. Karpinski, J. Pacey and L. Stein. Use of
Liners for Containment of Hazardous Waste Landfills.
Pollution Engineering. Vol. 16. No. 3. Used by permission
of Pudvan Publishing Co. Northbrook, IL.
From Cope, F., G. Karpinski, J. Pacey and L. Stein. Use of
Liners for Containment of Hazardous Waste Landfills.
Pollution Engineering. Vol. 16. No. 3. Used by permission
of Pudvan Publishing Co. Northbrook, IL.
From Merritt, F. 1976. Standard Handbook for Civil
Engineers. Used by permission of McGraw Hill Book Company.
New York, NY.
From Alluvial Mining and Shaft Sinking Co., Ltd. 1984,
Equipment and Services Brochure. Used by permission of
Alluvial Mining and Shaft Sinking Co., Ltd. Basildon,
5S14-1EA, England.
From Lyman, Reehl and Rosenblatt. 1982. Handbook of
Chemical Property Estimation Methods. Used by permission of
McGraw-Hill Book Company. New York, NY.
From Johnson Division. UOP, Inc. 1975. Groundwater in
Wells: A Reference Book for the Water Well Industry. Used
by permission of Johnson Division, UOP, Inc. St. Paul, MN.
From Jhaveri, V. and A.J. Mazzacca. 1983. Bio-reclamation
of Ground and Groundwater by CDS Process. Used by permission
of Groundwater Decontamination Systems. Waldwick, NJ.
From Jamison, V.W., R.L. Raymond and J.O. Hudson. 1976.
Biodegradation of High-Octane Gasoline. In: Proceedings of
the Third International Biodegradation Symposium. Used by
permission of Elsevier Applied Science Publishers. Barking,
Essex 1G11, 8JU, England.
From Groundwater Decontamination Systems, Inc. Report 1.
Experiments from Sept. 15 to Nov. 5. Used by permission of
Groundwater Decontamination Systems. Waldwick, NJ.
B-4
-------
APPENDIX B (continued)
Figure 9-8
Table 9-15
Table 9-19
Table 10-1
Table 10-2
Figure 10-3
Figure 10-4
Table 10-5
From Sullivan, J.M., D.R. Lynch, and I.K. Iskandar. 1984.
The Economics of Ground Freezing for Management of
Uncontrolled Hazardous Waste Sites. In: Proceedings of the
1984 Hazardous Material Spills Conference. Used by
permission of Government Institutes Inc. Rockville, MD.
From Sims, R.C. and K. Wagner. 1983. In-situ Treatment
Techniques Applicable to Large Quantities of Hazardous Waste
Contaminated Soils. In: Proceedings of National Conference
on Management of Uncontrolled Hazardous Waste Sites. October
31 - Nov. 2. Used by permission of Hazardous Materials
Control Research Institute. Available from Hazardous
Materials Control Research Institute, 9300 Columbia Blvd.,
Silver Spring, MD 20910.
From Fitzpatrick, V.F., J.L. Vcelt, K.H. Ource, and C.L.
Timmerman. 1984. In Situ Vitrification - A Potential
Remedial Action for Hazardous Wastes. In: Proceedings of
the 1984 Hazardous Material Spills Conference. Reproduced
with permission of Government Institutes Inc. The entire
publication 1984 Hazardous Material Spills Conference
Proceedings is available from Government Institutes, Inc.,
966 Hungerford Drive, #24, Rockville, MD 20850.
From Conway, R.A. and R.D. Ross. 1980. Handbook of
Industrial Waste Disposal. Used by permission of Van
Nostrand Reinhold Company. New York, NY.
From O'Brien, R.P. and J.L. Fisher, 1983. There is an Answer
to Groundwater Contamination. Reprinted from
Water/Engineering and Management. Used by permission of
Scranton Gillette Communications, Inc. Des Plaines, IL.
From Gulp, R.L., G.M. Wesnar and G.L. Gulp. 1978. Handbook
of Advanced Wastewater Treatment. 2nd Ed. Used by
permission of Van Nostrand Reinhold Co. New York, NY.
From DeRenzo, D. (ed). 1975. Unit Operations for Treatment
of Hazardous Wastes. Used by permission of Noyes Data
Corporation. Park Ridge, NJ.
From Conway, R.A. and R.D. Ross. 1980. Handbook of
Industrial Waste Disposal. Used by permission of Van
Nostrand, Reinhold Company, New York, NY.
Figure 10-6
From DeRenzo, D. (ed). 1975. Unit Operations for Treatment
of Hazardous Wastes. Used by permission of Noyes Data
Corporation. Park Ridge, NJ.
B-5
-------
APPENDIX B (continued)
Figure 10-9
Figure 10-10
Table 10-10
Table 10-12
Figure 10-12
Table 10-14
Figure 10-13
Figure 10-14
Figure 10-15
Figure 10-16
Figure 10-17
From Gulp, R.L., G.M. Wesnar and G.L. Gulp. 1978 Handbook
of Advanced Wastewater Treatment. 2nd Ed. Used by
permission of Van Nostrand Reinhold Co., New York, NY.
From Chemical Separations Corp.
Ridge, TN.
Ion Exchange Systems. Oak
Hale, F.D., C. Murphy, Jr., and R. Parrat. 1983. Page 195.
"Spent Acid and Plating Waste Surface Impoundment Closure."
Manuscripts originally printed in the Proceedings of the
National Conference on Management of Uncontrolled Hazardous
Waste Sites - 1984 and Hazardous Wastes and Environmental
Emergencies - 1984. Available from Hazardous Materials
Control Research Institute, 9300 Columbia Blvd., Silver
Spring, MD 20910.
From Whittaker, H. 1984. Development of a Mobile Reverse
Osmosis Unit for Spill Clean Up. In: Proceedings of the
1984 Hazardous Materials Spills Conference. Reproduced with
permission of Government Institutes, Inc. The entire
publication 1984 Hazardous Material Spills Conference
Proceedings is available from Government Institutes, Inc.,
966 Hungerford Drive, #24, Rockville, MD 20850.
From Canter, L.W. and R.C. Knox. 1985. Groundwater
Pollution Control. Used by permission of Lewis Publishers,
Inc. Chelsea, MI.
From O'Brien, R.P. and M.H. Stenzel.
Calgon Corp. Pittsburgh, PA.
Used by permission of
From Allis-Chalmers Corp. undated. Model SH-Rip-Flo-
Inclined vibrating screen. Bulletin 26B11211. Used by
permission of Allis-Chalmers Corp. Milwaukee, WI.
From Dorr-Oliver Inc. 1983. DSM Screens for the Process
Industries. Bulletin No. DSM-1. Used by permission of
Dorr-Oliver, Inc. Stamford, CT.
From Eagle Iron Works. 1982. Eagle Fine and Coarse Material
Washers. General Catalog, Section C. Used by permission of
Eagle Iron Work. Des Moines, IW
From Eagle Iron Works. 1982. Eagle Fine and Coarse Material
Washers. General Catalog, Section C. Used by permission of
Eagle Iron Work. Des Moines, IW
From Krebs Engineers, undated. Krels Water Only Cyclones.
Used by permission of Krebs Engineers. Menlo Park, CA.
B-6
-------
APPENDIX B (continued)
Figure 10-19
Figure 10-20
Figure 10-21
Figure 10-22
Figure 10-34
Figure 10-44
Figure 10-45
Figure 10-46
Figure 10-48
Figure 10-49
Figure 10-50
Figure 10-51
From Dorr-Oliver Inc. 1976. Dorr-Oliver Clarifiers for
Municipal and Industrial Wastewater Treatment. Bulletin No.
6192-1. Used by permission of Dorr-Oliver, Inc. Stamford,
CT.
From Parkson Corporation, 1984. Lamella Gravity
Settler/Thickener, Bulletin LT-103. Used by permission of
Parkson Corporation. Fort Lauderdale, FL.
From Gulp, R.L., G.M. Wesnar and G.L. Gulp. 1978 Handbook
of Advanced Wastewater Treatment. 2nd Ed. Used by
permission of Van Nostrand Reinhold Co., New York, NY.
From Gulp, R.L., G.M. Wesnar and G.L. Gulp. 1978 Handbook
of Advanced Wastewater Treatment. 2nd Ed. Used by
permission of Van Nostrand Reinhold Co., New York, NY.
From DeRenzo, D. (ed). 1975. Unit Operations for Treatment
of Hazardous Wastes. Used by permission of Noyes Data
Corporation. Park Ridge, NJ.
From Vatavuk, W.M. and R.B. Neveril. 1983. Cost of Flares
Chemical Engineering. Vol. 90, No. 4. Used by permission of
McGraw-Hill, New York, NY.
From Vatavuk, W.M. and R.B. Neveril. 1983. Cost of Flares
Chemical Engineering. Vol. 90, No. 4. Used by permission of
McGraw-Hill, New York, NY.
From Kiang, Y and A.R. Metry. 1982. Hazardous Waste
Processing Technology. Used by permission of Ann Arbor
Science Publishers, Inc. Ann Arbor, MI.
From Kiang, Y and A.R. Metry. 1982. Hazardous Waste
Processing Technology. Used by permission of Ann Arbor
Science Publishers, Inc. Ann Arbor, MI.
From Kiang, Y and A.R. Metry. 1982. Hazardous Waste
Processing Technology. Used by permission of Ann Arbor
Science Publishers, Inc. Ann Arbor, MI.
From Rockwell International. 1980. Molten Salt Destruction
of Hazardous Wastes. Pub. 523-K-18-1. Used by permission of
Rockwell International. Canoga Park, CA.
Pradt, L.A. 1972. (updated 1976). Developments in Wet Air
Oxidation. Chemical Engineering Progress. Used by
permission of American Institute of Chemical Engineers, New
York, NY.
B-7
-------
APPENDIX B (continued)
Figure 10-52
Figure 10-53
Figure 10-54
Figure 10-55
Table 10-19
Table 10-20
Table 10-21
Figure 11-1
From Lee, C.C., E.L. Keitz and G.A. Vogel. 1982. Hazardous
Waste Incineration: Current/Future Profile. Manuscripts
originally printed in Proceedings of the National Conference
on Management of Uncontrolled Hazardous Waste Sites - 1982.
Used by permission of Hazardous Materials Control Research
Institute. Available from Hazardous Materials Control
Research Institute, 9300 Columbia Blvd., Silver Spring, MD
20910.
From Ross, R.D. 1984. Hazardous Waste Incineration: More
Attractive Now than Ever Before. Hazardous Materials and
Waste Management Magazine. Vol. 2, No. 5. Used by
permission of the Hazardous Materials & Waste Management
Assoc., Kutztown, PA.
From Lee, C.C., E.L. Keitz and G.A. Vogel. 1982. Hazardous
Waste Incineration: Current/Future Profile. In:
Proceedings of the National Conference on Management of
Uncontrolled Hazardous Waste Sites. Nov. 29 - Dec. 1, 1982.
used by permission of Hazardous Materials Control Research
Institute. Silver Spring, MD.
From Vogel, G.A. and E.J. Martin. 1983. Equipment Sizes and
Integrated Facility Cost. Chemical Engineering. Vol. 90,
No. 18. Used by permission of McGraw-Hill, Inc. New York,
NY.
Adapted from Vogel, G.A. and E.J. Martin. Estimating
Operating Costs. Chemical Engineering. Vol. 91, No. 1.
Used by permission of McGraw-Hill, Inc. New York, NY.
Adapted from Vogel, G.A. and E.J. Martin. Estimating
Operating Costs. Chemical Engineering. Vol. 91, No. 1.
Used by permission of McGraw-Hill, Inc. New York, NY.
From Star, A. 1985. Cost Estimating for Hazardous Waste
Incineration. Pollution Engineering. Vol. 16, No. 7. Used
by permission of Pudvan Publishing Co., Northbrook, IL.
From Hammer, M.J. 1975. Water and Wastewater Technology.
Used by permission on John Wiley and Sons, Inc. New York,
NY.
Figure 11-2
From Hammer, M.J. 1975. Water and Wastewater Technology.
Used by permission on John Wiley and Sons, Inc. New York,
NY.
B-8
-------
APPENDIX B (continued)
Figure 11-3 From Water Pollution Control Federation. 1983. Existing
Sewer Evaluation and Rehabilitation. Manual of Practice
FD-6. Used by permission of Water Pollution Control
Federation. Washington, DC.
Figure 11-4 From Water Pollution Control Federation. 1983. Existing
Sewer Evaluation and Rehabilitation. Manual of Practice
FD-6. Used by permission of Water Pollution Control
Federation. Washington, DC.
Figure 11-5 From Water Pollution Control Federation. 1983. Existing
Sewer Evaluation and Rehabilitation. Manual of Practice
FD-6. Used by permission of Water Pollution Control
Federation. Washington, DC.
Figure 11-6 From Water Pollution Control Federation. 1983. Existing
Sewer Evaluation and Rehabilitation. Manual of Practice
FD-6. Used by permission of Water Pollution Control
Federation. Washington, DC.
B-9
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