v-/EPA
United States
Environmental Protection
Agency
Office of Emergency and
Remedial Response
Washington, DC 20460
Office of
Research and Development
Cincinnati, OH 45268
Superfund
EPA/540/S-92/007
Octoberl 992
Engineering Bulletin
Rotating Biological Contactors
Purpose
Section 121(b) of the Comprehensive Environmental Re-
sponse, Compensation, and Liability Act (CERCLA) mandates the
Environmental Protection Agency (EPA) to select remedies that
"utilize permanent solutions and alternative treatment technolo-
gies or resource recovery technologies to the maximum extent
practicable" and to prefer remedial actions in which treatment
"permanently and significantly reduces the volume, toxicity, or
mobility of hazardous substances, pollutants, and contaminants
as a principal element." The Engineering Elulletins are a series of
documents that summarize the latest information available on
selected treatment and site remediation technologies and related
issues. They provide summaries of and references for the latest
information to help remedial project managers, on-scene coor-
dinators, contractors, and other site cleanup managers under-
stand the type of data and site characteristics needed to evalu-
ate a technology for potential applicability to their Superfund or
other hazardous waste site. Those documents that describe in-
dividual treatment technologies focus on remedial investigation
scoping needs. Addenda will be issued periodically to update
the original bulletins.
Abstract
Rotating biological contactors (RBCs) employ aerobic fixed-
film treatment to degrade either organic and/or nitro-
genous (ammonia-nitrogen) constituents present in aqueous
waste streams. Treatment is achieved as the waste passes by the
media, enabling fixed-film systems to acclimate biomass c apable
of degrading organic waste [1, p. 91]*. Fixed-film RBC reactors
provide a surface to which soil organisms can adhere; many in-
digenous soil organisms are effective degraders of hazardous
wastes.
An RBC consists of a series of corrugated plastic discs
mounted on a horizontal shaft. As the discs rotate through the
aqueous waste stream, a microbial slime layer forms on the sur-
face of the discs. The microorganisms in this slime layer degrade
the waste's organic and nitrogenous constituents. Approximately
40 percent of the RBC's surface area is immersed in the waste
stream as the RBC rotates through the liquid. The remainder of
the surface area is exposed to the atmosphere, which provides
oxygen to the attached microorganisms and facilitates oxidation
of the organic and nitrogenous contaminants [2, p. 6]. In gen-
eral, the large microbial population growing on the discs pro-
vides a high degree of waste treatment in a relatively short time.
Although RBC systems are capable of performing organic re-
moval and nitrification concurrently, they may be designed to
primarly provide either organic removal or nitrification singly [3,
p. 1-2].
RBCs were first developed in Europe in the 1950s [1, p. 6].
Commercial applications in the United States did not occur un-
til the late 1960s. Since then, RBCs have been used in the United
States to treat municipal and industrial wastewaters. Because bio-
logical treatment converts organics to innocuous products such
as CO2, investigators have begun to evaluate whether biologi-
cal treatment systems like RBCs can effectively treat liquid waste
streams from Superfund sites. Treatability studies have been per-
formed at at least three Superfund sites to evaluate the effective-
ness of this technology at removing organic and nitrogenous
constituents from hazardous waste leachate. A full-scale RBC
treatment system is presently operating in at least one Super-
fund site in the United States.
Technology Applicability
Research demonstrates that RBCs can potentially treat aque-
ous organic waste streams from some Superfund sites. During
the treatability studies for the Stringfellow, New Lyme, and Moyer
Superfund sites, RBC systems efficiently removed the major or-
ganic and nitrogenous constituents in the leachates. Because
waste stream composition varies from site to site, treatability test-
ing to determine the degree of contaminant removal is an es-
sential element of the remedial action plan. Although recent
Superfund applications have been limited to the treatment of
landfill leachates, this technology may be applied to groundwa-
ter treatment [4].
In general, biological systems can degrade only the soluble
fraction of the organic contamination. Thus the applicability of
RBC treatment is ultimately dependent upon the solubility of the
contaminant. RBCs are generally applicable to influents contain-
ing organic concentrations of up to 1 percent organics, or be-
tween 40 and 10,000 mg/l of SBOD. (Note: Soluble biochemi-
cal oxygen demand, or SBOD, measures the soluble fraction of
the biodegradable organic content in terms of oxygen demand.)
RBCs can be designed to reduce influent biochemical oxygen de-
mand (BOD) concentrations below 5 mg/l SBOD and ammo-
preference number, page number]
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Table 1
Effectiveness of RBCs on General Contaminant
Groups for Liquid Waste Streams
Contaminant Croups
Effectiveness
Halogenated volatiles
Halogenated semivolatiles
Nonhalogenated volatiles
Nonhalogenated semivolatiles
PCBs
Pesticides
Dioxins/Furans
Organic cyanides
Organic corrosives
Volatile metals
Nonvolatile metals
Asbestos
Radioactive materials
Inorganic corrosives
Inorganic cyanides
Oxidizers
Reducers
• Demonstrated Effectiveness: Successful treatability test at some scale com-
pleted.
V Potential Effectiveness: Expert opinion that technology will work.
L) No Expected Effectiveness: Expert opinion that technology will not work.
nia-nitrogen (NH3-N) levels below 1.0 mg/l [5, p. 2] [6, p. 60].
RBCs are effective for treating solvents, halogenated organics,
acetone, akohols, phenols, phthalates, cyanides, ammonia, and
petroleum products [7, p. 6] [8, p. 69]. RBCs have fully nitrified
leachates containing ammonia-nitrogen concentrations up to
700 mg/l [6, p. 61].
The effectiveness of RBC treatment systems on general con-
taminant groups is shown in Table 1. Examples of constituents
within contaminant groups are provided in "Technology Screen-
ing Guide for Treatment of CERCLA Soils and Sludges" [9]. Table
1 is based on the current available information or professional
judgment where no information was available. The proven ef-
fectiveness of the technology for a particular site or waste does
not ensure that it will be effective at all sites or that the treat-
ment efficiencies achieved will be acceptable at other sites. For
the ratings used for this table, demonstrated effectiveness means
that, at some scale, treatability was tested to show the technol-
ogy was effective for that particular contaminant group. The rat-
ings of potential effectiveness or no expected effectiveness are
based upon expert judgment. Where potential effectiveness is
indicated, the technology is believed capable of successfully treat-
ing the contaminant group in a particular medium. When the
technology is not applicable or will probably not work for a par-
ticular combination of contaminant group and medium, a no
expected effectiveness rating is given.
Limitations
Although RBCs have proven effective in treating waste
streams containing ammonia-nitrogen and organics, they are not
effective at removing most inorganics or non-biodegradable or-
ganics. Wastes containing high concentrations of heavy metals
and certain pesticides, herbicides, or highly chlorinated organ-
ics can resist RBC treatment by inhibiting microbial activity. Waste
streams containing toxic concentrations of these compounds
may require pretreatment to remove these materials prior to RBC
treatment [10, p. 3].
RBCs are susceptible to excessive biomass growth, particu-
larly when organic loadings are elevated. If the biomass fails to
slough off and a blanket of biomass forms which is thicker than
90 to 125 mils, the resulting weight may damage the shaft and
discs. When necessary, excess biofilm may be reduced by either
adjusting the operational characteristics of the RBC unit (e.g., the
rotational speed or direction) or by employing air or water to
shear off the excess biomass [11, p. 2].
In general, care must be taken to ensure that organic pr I-
lutants do not volatilize into the atmosphere. To control their
release, gaseous emissions may require offgas treatment [12, p.
31].
All biological systems, including RBCs, are sensitive to tem-
perature changes and experience drops in biological activity at
temperatures lower than 55°F. Covers should be employed to
protect the units from colder climates and extraordinary weather
conditions. Covers should also be used to protect the plastic discs
from degradation by ultraviolet light, to inhibit algal growth, and
to control the release of volatiles [13]. In general, organic deg-
radation is optimum at a pH between 6 and 8.5. Nitrification
requires the pH be greater than 6 [6, p. 61 ].
Additionally, nutrient and oxygen deficiencies can reduce
microbial activity, causing significant decreases in biodegrada-
tion rates [14, p. 39], Extremes in pH can limit the diversity of
the microbial population and may suppress specific microbes
capable of degrading the contaminants of interest. Fortunately,
these variables can be controlled by modifying the system de-
sign.
Technology Description
A typical RBC unit consists of 12-foot-diameter plastic discs
mounted along a 25-foot horizontal shaft. The total disc surface
area is normally 100,000 square feet for a standard unit and
150,000 square feet for a high density unit. Figure 1 is a dia-
gram of a typical RBC system.
As the RBC slowly rotates through the groundwater or
leachate at 1.5 rpm, a microbial slime forms on the discs. These
microorganisms degrade the organic and nitrogenous contami-
nants present in the waste stream. During rotation, approxi-
mately 40 percent of the discs' surface area is in contact with the
aqueous waste while the remaining surface area is exposed to
the atmosphere. The rotation of the media through the atmo-
sphere causes the oxygenation of the attached organisms. When
Engineering Bulletin: Rotating Biological Contactors
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Figure 1
Typical RBC Plant Schematic (12)
Offgas
Treatment
Offgas
Treatment
t
Offgas
Treatment
Primary
Treatment
Secondary
Clarifier
operated properly, the shearing motion of the discs through the
aqueous waste causes excess biomass to shear off at a steady rate.
Suspended biological solids are carried through the successive
stages before entering the secondary clarifier [2, p. 13.101 ].
Primary treatment (e.g., clarifiers or screens), to remove ma-
terials that could settle in the RBC tank or plug the discs, is often
essential for good operation. Influents containing high concen-
trations of floatables (e.g., grease, etc.) will require treatment us-
ing either a primary clarifier or an alternate removal system [11,
p. 2].
The RBC treatment process may involve a variety of steps,
as indicated by the block diagram in Figure 2. Typically, aque-
ous waste is transferred from a storage or equalization tank (1)
to a mixing tank (2) where chemicals may be added for metals
precipitation, nutrient adjustment, and pH control. The waste
Sludge
Disposal
stream then enters a clarifier (3) where the solids are separated
from the liquid. The effluent from the clarifier enters the RBC
(4) where the organics and/or ammonia are converted to innocu-
ous products. The treated waste is then pumped into a second
clarifier (5) for removal of the biological solids. After secondary
clarification the effluent enters a storage tank (6) where, depend-
ing upon the contamination remaining in the effluent, the waste
may be stored pending additional treatment or discharged to a
sewer system or surface stream. Throughout this treatment pro-
cess the offgases from the various stages should be collected for
treatment (7). The actual treatment train will, of course, depend
upon the nature of the waste and will be selected after the
treatability study is conducted.
Staging, which employs a number of RBCs in series, en-
hances the biochemical kinetics and establishes selective biologi-
cal cultures acclimated to successively decreasing organic load-
Figure 2
Block Diagram of the RBC Treatment Process
Aqueous
Waste
Treated
Storage | Effkjents
Tank
(6)
Sludge Removal
Engineering Bulletin: Rotating Biological Contactors
-------
ings. As the waste stream passes from stage to stage, progres-
sively increasing levels of treatment occur [2, p. 13.105],
In addition to maximizing the system's efficiency, staging
can improve the system's ability to handle shock loads by ab-
sorbing the impact of a shock load in the initial stages, thereby
enabling subsequent stages to operate until the affected stages
recover [15, p. 10.200].
Factors effecting the removal efficiency of RBC systems in-
clude the type and concentration of organics present, hydraulic
residence time, rotational speed, media surface area exposed and
submerged, and pre- and post-treatment activities. Design pa-
rameters for RBC treatment systems include the organic and hy-
draulic load rates, design of the disc train(s), rotational velocity,
tank volume, media area submerged and exposed, retention
time, primary treatment and secondary clarifier capacity, ,ind
sludge production [8, p. 69].
Process Residuals
During primary clarification, debris, grit, grease, metals, and
suspended solids (SS) are separated from the raw influent. The
;,olids and sludges resulting from primary clarification may con-
tain metallic and organic contaminants and may require addi-
tional treatment. Primary clarification residuals must be disposed
of in an appropriate manner (e.g., land disposal, incineration,
solidification, etc.).
Following RBC treatment, the effluent undergoes second-
ary clarification to separate the suspended biomass solids from
the treated effluent. Refractory organics may contaminate both
the clarified effluent and residuals. Additional treatment of the
solids, sludges, and clarified effluent may be required. Clarified
secondary effluents which meet the treatment standards are gen-
erally discharged to a surface stream, while residual solids and
sludges must be disposed of in an appropriate manner, as out-
lined above for primary clarification residuals [2, p. 1 3.120]
Volatile organic compound (VOC)-bearirig gases are often
liberated as a byproduct of RBC treatment. Care must be taken
to ensure that offgases do not contaminate the work space or
the atmosphere. Various techniques may be employed to con-
trol these emissions, including collecting the gases for treatment
[13].
Site Requirements
RBCs vary in size depending upon the surface area needed
to treat the hazardous waste stream. A single full size unit with
a walkway for access on either side of the unit takes up approxi-
mately 550 square feet [16]. The total area required for an RBC
system is site-specific and depends on the number, size, and con-
figuration of RBC units installed.
Contaminated groundwater, leachates, or waste materials
are often hazardous. Handling and treatment of these materials
requires that a site safety plan be developed to provide for per-
sonnel protection and special handling measures. Storage should
be provided to hold the process product streams until they have
been tested to determine their acceptability for disposal, reuse,
or release. Depending on the site, a method to store waste that
has been prepared for treatment may be necessary. Storage ca-
pacity will depend on waste volume.
Onsite analytical equipment capable of determining site-
specific organic compounds for performance assessment make
the operation more efficient and provide better information for
process control.
Performance Data
Limited information is available on the effectiveness of RBCs
in treating waste from Superfund sites. Most of the data came
from studies done on leachate from the New Lyme, Ohio;
Stringfellow, California; and Moyer, Pennsylvania Superfund sites.
The results of these studies are summarized below.
In order to compensate for the lack of Superfund perfor-
mance data, non-Superfund applications are also discussed. The
majority of the performance data for non-Superfund applications
were obtained from industrial RBC operations. Theoretically this
information has a high degree of application to Superfund
leachate and groundwater treatment.
The quality of the information present in this section has not
been determined. The data are included as a general guidance,
and may not be directly transferable to a specific Superfund site.
Good characterization and treatability studies are essential in
further refining and screening of RBC technology.
New Lyme Treotobility Study
The EPA performed a remedy selection study on the leachate
from the New Lyme Superfund site located in New Lyme Town-
ship, Ashtabula County, Ohio, to help determine the applicabil-
ity of an RBC to treat hazardous waste from a Superfund site.
Samples of leachate collected from various seeps surrounding the
landfill showed that the leachate was highly concentrated. Re-
sults indicated that the leachate contained up to 2,000 mg/l dis-
solved organic carbon (DOC), 2,700 mg/l SBOD, and 5,200 mg/
I soluble chemical oxygen demand (SCOD) [1 7, p. 12]. (Note:
SCOD measures the soluble fraction of the organics amenable
to chemical oxidation, as well as certain inorganics such as sul-
fides, sulfites, ferrous iron, chlorides, and nitrites.)
Leachate from the New Lyme site was transported from New
Lyme to a demonstration-scale RBC located at the EPA's Testing
and Evaluation Facility in Cincinnati, Ohio. After an adequate
biomass was developed on the RBC discs using a primary efflu-
ent supplied by Mill Creek Treatment Facility (a local industrial
wastewater treatment facility), the units were gradually accli-
mated to an influent consisting of 100 percent leachate. Results
indicated that within 20 hours the RBC removed 97 percent of
the gross organics, as represented by DOC, from the leachate
(see Figure 3 and Table 2) [18, p. 7j. Priority pollutants were
either converted and/or stripped from the leachate during treat-
ment. After normal clarification, the effluent from the RBC was
Engineering Bulletin: Rotating Biological Contactors
-------
eligible for disposal into the sewer system leading to the Mill
Creek facility.
Stringfellow Treatability Study
A remedy selection study using an RBC was conducted on
leachate from the Stringfellow Superfund site located in Glen
Avon, California. After the leachate from this site received lime
treatment to remove metal contamination, the leachate was
transported to the EPA's Testing and Evaluation Facility in Cin-
cinnati for testing similar to the New Lyme study. The objective
of this study was to determine whether the leachate from
Stringfellow could be treated economically with an RBC system.
The leachate from this site was generated at a daily rate of
2,500 gallons. Compared to the New Lyme leachate, it con-
tained moderate concentrations of gross organics with DOC
values of 300 mg/l, SBOD values of 420 mg/l, and SCOD val-
ues of 800 mg/l [4, p. 44].
Results indicated that greater than 99 percent of SBOD was
removed, 65 percent of DOC was removed, and 54 percent
SCOD was removed within four days using the RBC laboratory-
scale treatment system [4, p. 44]. Table 3 presents pertinent
information on the treatment of 100 percent leachate. Since
the DOC and SCOD conversion rates were low, a significant frac-
tion of the refractory organics remained following treatment. Ac-
tivated carbon was used to reduce the DOC to limits acceptable
to the Mill Creek Treatment Facility.
Table 2
Removal of Pollutants from New Lyme Leachate (17, p. 17)
Experiment 5
Figure 3
Disappearance of DOC with Time (17, p. 14)
Experiment 5*
SBOD
BODT
DOC
TOC
SCOD
NO3'N
SS
VSS
Volatile PP
Benzene
Toluene
Additional Volatiles
Cis 1 ,2-Dichloroethene
Xylenes
Acetone
Methyl Ethyl Ketone
Total Organic Halides
Total Toxic Organics
Influent
(mg/l)
2700
3000
2000
2100
5200
<1
1400
240
0.28
4.9
0.94
2.8
140
470
<0.250
Effluent
(mg/l)
4
6.6
17
19
33
60
6600
2600
<0.002
<0.002
ND
ND
ND
ND
1.2
<0.010
10
20
Time (hours)
30
40
BODT = Total Biochemical Oxygen Demand
NO3-N = Nitrogen as Nitrate
VSS = Volatile Suspended Soilds
* The influent for Experiment 5 consisted of 100 percent leachate and the
biomass on the RBCs was acclimated. Nutrient addition was also employed
(at a ratio of 160/5/2 for C/N/P).
Moyer Treotability Study
During a recent remedy selection study, three treatability-
scale RBCs were used to degrade a low-BOD (26 mg/l), high
ammonia (154 mg/l) leachate from the Moyer Landfill Superfund
site in Lower Providence Township near Philadelphia, Pennsyl-
vania [19, p. 971 ]. The leachate has low organic strength (e.g.,
26 mg/l BOD, 358 mg/l COD, and 68 mg/l TOC) which is typi-
cal of an older landfill and it also contains mainly non-biodegrad-
able organic compounds [19, p. 972]. (Note: Total organic car-
bon, or TOC, is a measure of all organic carbon expressed as
carbon.) The abundance of ammonia found in the leachate
prompted investigators to attempt ammonia oxidation with an
RBC system. Relatively low substrate loading rates were em-
ployed during the study (0.2, 0.4, and 0.6 gpd/square foot of
disc surface area per stage). Ammonia oxidation was essentially
complete (98 percent) and a maximum of 80 percent of the BOD
and 38 percent of the COD in the leachate was oxidized [19, p.
980]. Runs performed using lower loading rates experienced the
largest removals. A limited denitrification study was also per-
formed using an anoxic RBC to treat an RBC effluent generated
during the aerobic segment of the treatability investigation. This
study demonstrated the feasibility of using denitrification to treat
Engineering Bulletin: Rotating Biological Contactors
-------
the nitrate produced by aerobic ammonia oxidation [19, p. 980].
Non-Superfund Applications
The Homestake Mine in Lead, South Dakota has operated
an RBC wastewater treatment plant since 1984. Forty-eight RBCs
treat up to 5.5 million gallons per day (MOD) (21,000 m3) of
discharge water per day. The system was designed to degrade
thiocyanate, free cyanide, and metal-complexed cyanides, to re-
duce heavy metal concentrations, and to remove ammonia,
which is a byproduct of cyanide degradation [20, p. 2]. Eight
parallel treatment trains, utilizing five RBCs in series, were em-
ployed to degrade and nitrify the metallurgical process waters
(see Table 4 for a characterization of the influent). The first two
RBCs in each train were used to degrade the cyanides and re-
move heavy toxic metals and particulate solids through biologi-
cal adsorption. The last three RBCs employed nitrification to
convert the ammonia to nitrate. Table 5 provides an average
performance breakdown for the system. During its operation,
overall performance improved significantly, as demonstrated by
an 86 percent increase in the systems ability to reduce total ef-
fluent cyanide concentrations (e.g., from 0.45 to 0.06
mg/l). Concurrently, the cost per kg to treat cyanide dropped
from $11.79 to $3.10, while the cost per m3 to treat effluent
decreased by 50 percent [21, p. 9]. In general, the system has
responded well to any upsets or disturbances. Diesel fuels, lu-
bricants, degreasers, biocides, dispersants, arid flocculants have
been periodically found in the influent wastewater but normally
only create minor upsets in the performance of the plant. Dur-
ing the life of the system, the number of upset* and the biomass's
ability to recuperate have both improved [21, p. 6].
A significant difference between the Homestake system and
the other RBC systems described within this report is that instead
of removing the metals contaminating the wastewater in the
pretreatment stage, metal reduction is accomplished through
bioadsorption during the treatment phase. Bioadsorption of
metals by biological cells is not unlike the use of activated car-
bon, however the number and complexity of binding sites on
the cell wall are enormous in comparison [20, p. 2].
In a study by Israel's Institute of Technology, a laboratory-
scale RBC was used to treat an oil refinery wastewater. The waste-
water had been pretreated using oil-water separation and dis-
solved air flotation. As summarized in Table 6, 91 percent of
the hydrocarbon and 97 percent of the phenol were removed,
as well as 96 percent of the ammonia-nitrogen [22, p. 4] By
gradually increasing the concentration of phenols present in the
influent (e.g., over a 5 day period) from 5 mg/l to 30 mg/l, the
system demonstrated that it was capable of quickly adapting to
influent changes and higher phenolic loads [22, p. 6]. During
this period, the RBC was able to maintain effluent COD concen-
trations at levels comparable to previous loadings. The system's
resiliency was further demonstrated by its ability to recover from
a major disturbance (e.g., such that effluent COD removal was
interrupted) within 4 days [22, p. 7].
Technology Status
RBCs have been used commercially in the United States since
Table 3
Treatment of 100% Stringfellow Leachate (4, p. 44)
RBC
Leachate Effluent
SBOD
BOD
DOC
TOC
SCOD
COD
SS
VSS
NH3-N
NO3-N
(mg/l) (mg/l)
420 <3.0
440
300 110
310
800 360
840
43
31
3.4
44
Use APC plus
Effluent
(mg/l)
0.9
22
20
22
79
95
23
14
6.3
34
APC = Activated Powered Carbon
COD = Chemical Oxygen Demand
Table 4
Homestake Mine Wastewater Matrix
Thiocyanate
Total Cyanide
WAD Cyanide
Copper
Ammonia-N
Phosphorus-P
Alkalinity
PH
Hardness
Temperature°C
Decant
Water
(mg/l)
110-350
5.5-65.0
3.10-38.75
0.5-3.1
5-10
0.10-0.20
50-200
7-9
400-500
1.0-27.2
Mine
Water
(mg/l)
1-33
0.30-2.50
0.50-1.10
0.10-2.65
5.00-19.00
0.10-0.15
1 50-250
7-9
650-1400
24-33
Influent
Blend
(mg/l)
35-110
0.50-11.50
0.50-7.15
0.15-2.95
6-12
0.10-0.15
125-225
7.5-8.5
500-850
5-25
WAD = Weak Acid Dissociable
•Adapted from reference [20, p. 8]
Table 5
Influent, Effluent and Permit Concentrations at the
Homestake Mines (20, p. 8)
Thiocyanate
Total Cyanides
WAD Cyanide
Total Copper
Total Suspended Soilds
Ammonia-Nitrogen
Influent
(mg/l)
62.0
4.1
2.3
0.56
-
5.60*
Effluent
(mg/l)
<0.5
0.06
<0.02
0.07
6.0
<0.50
Permit
(mg/l)
.
1.00
0.10
0.13
10.0
1.0-3.9
•Ammonia peaks at 25 mg/l within the plant as a cyanide
degradation byproduct
Engineering Bulletin: Rotating Biological Contactors
-------
Table 6
Refinery Wastewater Quality Before and After
RBC Treatment (22, p. 4)
Constituent
COD Total
Soluble
BOD Total
Soluble
Phenols
Suspended Solids
Total
Volatile
NH -N
Influent
(mg/l)
715
685
140
128
7.5
32
29
12.8
Effluent
(mg/l)
197
186
8
6
0.22
7
6
0.48
During the Stringfellow treatability study researchers determined
that by augmenting the existing carbon treatment system with
RBCs, reductions in carbon costs would pay for the RBC plant
within 3.3 years [4, p. 44]. The RBC plant model used to for-
mulate this estimate was a scaled-up version of the pilot unit used
during the treatability study.
EPA Contact
Technology-specific questions regarding rotating biological
contactors may be directed to:
Edward J. Opatken
U.S. EPA Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
Telephone: (51 3) 569-7855
the late 1960s to treat municipal and industrial wastes. In the
past decade, studies have been performed to evaluate the effec-
tiveness of RBCs in treating leachate from hazardous waste sites.
Treatability studies have been performed on leachate from
the Stringfellow, New Lyme, and Moyer Superfund sites. Results
of these studies indicate that RBCs are effective in removing or-
ganic and nitrogenous constituents from hazardous waste
leachate. Additional research is needed to define the effective-
ness of an RBC in treating leachates and contaminated ground-
water and to determine the degree of organic stripping that
occurs during the treatment process. RBCs are being u>ed to
treat leachate from the New Lyme Superfund she.
RBCs require a minimal amount of equipment, manpower,
and space to operate. Staging of RBCs will vary from site to site
depending on the waste stream. The cost to install a single RBC
unit with a protective cover and a surface area of 100,000 to
150,000 square feet ranges from $80,000 to $85,000 [16] [23].
Acknowledgments
This bulletin was prepared for the U.S. Environmental Pro-
tection Agency, Office of Research and Development (ORD), Risk
Reduction Engineering Laboratory (RREL), Cincinnati, Ohio, by
Science Applications International Corporation (SAIC) under
contract No. 68-C8-0062. Mr. Eugene Harris served as the EPA
Technical Project Monitor. Mr. Gary Baker was SAIC's Work
Assignment Manager. This bulletin was written by Ms. Denise
Scott and Ms. Evelyn Meagher-Hartzell of SAIC.
The following other Agency and contractor personnel have
contributed their time and comments by participating in the
expert review meetings and/or peer reviewing the document:
Dr. Robert L. Irvine
Mr. Richard A. Sullivan
Ms. Mary Boyer
Mr. Cecil Cross
University of Notre Dame
Foth & Van Dyke
SAIC
SAIC
Engineering Bulletin: Rotating Biological Contactors
'U.S. Government Printing Office: 1992— 648-080/60066
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REFERENCES
1. Cheremisinoff, P.E. Biological Treatment of Hazardous
Wastes, Sludges, and Wastewater. Pollution Engineering,
May 1990.
2. Envirex, Inc. Rex Biological Contactors: For Proven, Cost-
Effective Options in Secondary Treatment. Bulletin 315-
13A-51/90-3M.
3. Design Information on Rotating Biological Contactors,
EPA/600/2-84/106, U.S. Environmental Protection
Agency, June 1984.
4. Opatken, E.J., H.K. Howard, and j.J. Bond. Stringfellow
Leachate Treatment with RBC. Environmental Progress,
Volume 7, No. 1, February 1988.
5. Walker Process Corporation. EnviroDisc™ Rotating
Biological Contactor. Bulletin 11-S-88.
6. Opatken, E.J., and J.J. Bond. RBC Nitrification of High
Ammonia Leachates. Environmental Progress, Volume
10, No. 4, February 1991.
7. Guide to Treatment Technologies for Hazardous
Wastes at Superfund Sites. EPA/540/2-89/052, U.S.
Environmental Protection Agency, March 1989.
8. Data Requirements for Selecting Remedial Action
Technology. EPA/600/2-87/001, U.S. Environmental
Protection Agency, January 1987.
9. Technology Screening Guide for Treatment of
CERCLA Soils and Sludges. EPA/540/2-88/004, U.S.
Environmental Protection Agency, 1988.
10. O'Shaughnessy et al. Treatment of Oil Shale Retort
Wastewater Using Rotating Biological Contactors.
Presented at the Water Pollution Control Federation,
55th Annual Conference, St. Louis, Missouri, October
1982.
11, Rotating Biological Contactors: U.S. Overview. EPA/
600/D-87/023, U.S. Environmental Protection
Agency. January 1987.
12. Nunno, T.J., and J.A. Hyman. Assessment of Interna-
tional Technologies for Superfund Applications. EPA/
540/2-88/003, U.S. Environmental Protection
Agency, September 1988.
13. Telephone conversation. Steve Oh, U.S. Army Corps
of Engineers, September 4, 1991.
14. Corrective Action: Technologies and Applications. EPA/
625/4-89/020, U.S. Environmental Protection Agency,
September 1984.
15. Lyco, Inc., Rotating Biological Surface (RBS) Waste-
water Equipment: RBS Design Manual. March 1986.
16. Telephone conversation. Gerald Ornstein, Lyco
Corporation, September 4, 1991.
17. Opatken, E.J., H.K. Howard, and J.J. Bond. Biologi-
cal Treatment of Leachate from a Superfund Site.
Environmental Progress, Volume 8, No. 1, February
1989.
18. Opatken, E.J., H.K. Howard, and J.J. Bond. Biological
Treatment of Hazardous Aqueous Wastes. EPA/600/
D-87/1 84, June 1987.
19. Spengel, D.B., and D.A. Dzombak. Treatment of Landfill
Leachate with Rotating Biological Contractors: Bench-
Scale Experiments. Research Journal WPCF, Vol. 63, No.
7, November/December 1991.
20. Whitlock, J.L. The Advantages of Biodegradation of
Cyanides. Journal of the Minerals, Metals and Materials
Society, December 1989.
21. Whitlock, J.L. Biological Detoxification of Precious Metal
Processing Wastewaters. Homestake Mining Co., Lead,
SD.
22. Galil, N., and M. Rebhun. A Comparative Study of RBC
and Activated Sludge in Biotreatment of Wastewater from
an Integrated Oil Refinery. Israel Institute of Technology,
Haifa, Israel.
23. Telephone conversation. Jeff Kazmarek, Envirex Inc.,
September 4,1991.
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
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