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INSTITUTIONSPONS AGENCY

PUB DATEGRANTNOTEAVAILABLE FROM

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IDENTIFIERS

DOCUMENT RESUEE

SE 045 353

Zickefoose, Charles S.Rotating Biological Contractors (RBC's). Instructor'sGuide. Biological Treatment Process Control.Linn-Benton Community Coll., Albany, Oreg.Environmental Protection Agency, Washington,Office of Drinking Water.84EPA-T90123845p.; For related documents, see SE 045 333-354.Linn-Benton Community College, 6500 S.W. PacificBlvd., Albany, OR 97321 (Instructor's guide andaccompanying slides).Guides Classroom Use Guides (For Teachers) (052)

MF01 Plus Postage. PC Not Available from EDRS.*Biology; Laboratory Procedures; Post SecondaryEducation; *Sludge; *Training Methods; *WasteDisposal; *Waste Water; *Water Treatment*Rotating Biological Contactors; Unit Processes

ABSTRACTThis two-lesson unit on rotating biological

contactors (RBC's) is designed to be used with students who have hadsome experience in wastewater treatment and a basic understanding ofbiological treatment. The first lesson provides information on theconcepts and components of RBC treatment systems. The second lessonfocuses on design operation and maintenance. The teaching guideincludes: (1) an overview of the unit; (2) lesson plans; (3) lectureoutlines; (4) overhead transparency masters for use with the secondlessor. (5) student worksheets (with answers); and (6) two copies ofa fi quiz (with and without answers). The lecture outline for thefirst .,esson includes reference to a set of slides developed for usewith the lesson. Instructors are encouraged to add their own slidesor to change the order of slides to fit their own teaching styles.(JN)

************************************************************************ Reproductions supplied by EDRS are the best that can be made ** from the original document. ************************************************************************

U.S. DEPARTMENT OF EDUCATION

NATIONAL INSTITUTE OF EDUCATION

DUCA I IONAL RESOURCES INFORMATION

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BIOLOGICAL TREATMENT PROCESS CONTROL

ROTATING BIOLOGICAL CONTACTORS(RBCs)

INSTRUCTOR'S GUIDE

Text Written By:Charles S. Zickefoose

STRAAM EngineersPortland, Oregon

Currently with Brown & CaldwellPortland, Oregon

Edited By:Ronald M. Sharman

Linn-Benton Community CollegeAlbany, Oregon

John W. Carnegie, Ph.D.Project Director

Linn-Benton Community CollegeAlbany, Oregon

Instructional Design:Priscilla Hardin, Ph.D.

Priscilla Hardin Instructional ServicesCorvallis, Oregon

Developed Under:EPA Grant #T901238

1984

ROTATING BIOLOGICAL CONTACTORS

(RBC's)

Instructor's Guide

Table of Contents Page

Overview of Lessons

Lesson Plans

Lecture Outlines

Lesson I - Concepts and Components

Lesson II - Design, Operation and Maintenance

Overhead Masters

Answers to Worksheets

Final Quiz

Answers to Final Quiz

i ,1

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I-RBC-1

I-RBC-3

I-RBC-3

I-RBC-5

I-RBC-,9

I-RBC-28

I-RBC-31

I-RBC-36

ROTATING BIOLOGICAL CONTACTORS

Overview of Lessons

This group of training material on RBC's is designed to be used with the

intermediate student. It is assumed that this student has some experience

in wastewater treatment and a basic understanding of biological treatment.The objective of this section is to supply the basics and the operationalparameters of the RBC treatment system. At the conclusion of this section

each student should have a good understanding of how an RBC treatmentsystem fits into waste treatment and the every day characteristics ofoperation.

Lesson Plans

The material provided is divided up into two lectures. All the materials

are to be used as instructor lecture support. This is not designed to be

used as self-study or stand alone material. Each instructor should reviewthe written material and possibly use the references given before giving

a presentation.

equipment needed:

1. training room large enough to hold the expected number of participants

comfortably.2. 35mm slide projector and screen.3. overhead projector.4. chalkboard and/or acetate and overhead pens.

Lesson I: Concepts and Components

There are 36 slides in this section which covers the basic components ofan RBC system and how this system might fit into a wastewater treatment

flow scheme. Also covered in this section are the basics of processcontrol via visual observation. These slides are arranged in a suggested

presentation order. Each instructor should consider adding slides to thepresentation or changing the order of these slides to fit his or her

style. Slide number 36 is a lead-in slide for lecture II. Estimated time

of presentation: 30 min.

note: you may want to give the group a short break at this point.

I-RBC-1

Lesson II: Design Operation and Maintenance

This second lecture covers the design parameters of the RBC system.Overhead transparencies are supplied to help show the examples ofcalculating both the organic and hydraulic loadings. There are two

examples given for each loading parameter. It is suggested that moreexamples be given especially if the target group is weak in math skills.This second lecture reviews the method of process control via visualobservation. It is important to stress the value of observation of thebiomass characteristics under normal operating conditions ana abnormalconditions. This section finishes up with normal equipment maintenance

procedures. Estimated time of presentation: 30 min.

Self-Test

At the conclusion of the instructional material, a short self test isprovided to evaluate the student's progress. This test can be used

immediately following the lectures or possibly as a take-home exerciseto be handed in or mailed in later. If the test is given following thelectures give the students 15 min. to work on it. Go over the questions

and answers after all have finished,

Additional Comments

If possible you should bring in operators that have direct experiencewith the process control of a RBC treatment system. The material in

this section should only supply the basis for operational control andwhE-e possible real applications should be used. At the conclusion ofthe training session try and schedule a field trip to a treatment plant

with RBC's in use.

I-RBC-26

ROTATING BIOLOGICAL CONTACTORS(RBC's)

LECTURE OUTLINE

LESSON I - CONCEPTS AND COMPONENTS

I. Introdu.:tion

A. RBC uses in treatment flow schemes1. Secondary treatment2. Tertiary treatment3. Expanded secondary treatment4. RBC multi-uses

B. Review of secondary treatment1. General comparison to A/S and TF2. Biological treatment: fixed or dispersed3. RBC fixed growth: Biomass4. Aerobic conversion of organics to energy, CO2,

water, and new cell material5. Excess biomass sloughs and settles in clarifier

slide 4slide 5slide 6slide 7

slide 8slide 9slide 10slide 11

slide 12

II. RBC Components and Equipment

A. RBC shaft or drum components1. Plastic preformed discs stacked up to form a slide 13

shaft. 12 ft in diameter & 25 ft long2. RBC shaft covers for protection slide 14

B. RBC process flows1. No sludge recycle to RBC's slide 15

Note: at this time no original design callsfor any recycle. Sometimes sludge is recycledback to the primary clarifier for thickening.

2. Series and parallel flow patterns slide 163. RBC stage is distinct process unit, a series slide 17

of stages is called a train of stages.

Shaft drive mechanisms - introduction slide 18.#1. Mechanical drive slide 19

a. Motorb. Gear reducer or chainC. Shaft bearing

2. Mechanical drive advantages/disadvantages slide 203. Air drive sWe 21

a. Air control valveb. Air header and diffuserc. Air cups

4. Air drive advantages/disadvantages slide 22

I-RBC-3

III. RBC Process Monitoring

A. General monitoring - visual observation1. First stage - uniform color and thickness2. Middle stages - lighter color, patchiness3. Later stages - sparse growth, possible reddish

growth if nitrification is occurring4. Multi-stage comparison

Note: the photos used in this comparison arenot from the same unit. These extremes wereused to make the point.

B. Abnormal conditions - visual observation1. Filamentous bacteria or anaerobic conditicns2. System startup or toxic loadings

C. Monitoring for process control1. General monitoring - influent and effluent

a. BOD

b. Suspended solidsc. Tempd. pH

2. Monitoring for nitrificationa. Ammonia-nitrogenb. Nitrate-nitrogen

IV. Review

A. Uses of RBC in waste treatmentB. Biomass sloughing/settles in clarifierC. Flow patternsD. Visual observation for process controlE. Lead in to Lesson II

slide 23slide 24slide 25slide 26

slide 27

slide 28slide 29

slide 30

slide 31

slide 32slide 33slide 34slide 35slide 36

ROTATING BIOLOGICAL CONTACTORS(RBC's)

LECTURE OUTLINE

LESSON II - DESIGN OPERATION AND MAINTENANCE

I. RBC Design Parameters

A. Design characteristics for RBC application1. Flow rates2. Organic and solids loading3. Industrial waste influence4. Weather (temperature)

B. Example performance ranges1. Plans have been designed to treat flows ranging between

18,000 gpd to 50 MGD2. Hydraulic loading

a. BOD removal 1.5 to 6 gpd/sq ftb. Nitrogen removal 1.5 to 1.8 ypd/sq ft

3. Organic loading (soluble BOD) 3 to 5 lbs BOD/day/1,000 sq fta. BOD removal 80 to 95 percentb. Effluent total BOD 15 to 30 mg/1c. Effluent soluble BOD 7 to 15 mg/1d. Effluent ammonia-N 1 to 10 mg/1e. Effluent nitrate-N 2 to 7 mg/1

C. Computing hydraulic loading1. Gallons per day per square foot of media surface2. Required information:

a. Flowb. Surface area of media in square feet

3. Equation:

Flow, gal/day

Surface area, sq ft

4. Example 1:

Flow, MGD = J.5 MGDSurface area, sq ft = 1,000,000 sq ft

3,500,000 gpd

1,000,000 so ft

= 3.5 gpd/sq ft

5. Example 2:

Flow, gpd = 66,000 gpdSurface area, sq ft = 40,000 sq ft

66,00 gpd

40,000 sq ft

= 1.65 gpd/sq ft

I-RBC-5

D. Computing organic (BOD) loading1. Pounds of BOD per day per 1,000 square feet of surface area2. Required information

a. Primary effluent BOD or soluble BODb. Surface area of media in 1,000 sq ft

3. Equation:

BOD applied, lbs BOD/day

Surface area in 1,000 sq ft

4. Example 1:

Soluble BOD = 2,000 lbs BOD/daySurface area = 1,000,000 sq ft(1,000,000 sq Ft is the same as 1,000 1,000 ssq ft units)

2,000 lbs BOD/day

1,000 X 1,000 sq ft

= 2.0 lbs BOD/day/1,000 sq ft

5. Example 2:Soluble BODSurface area

= 7,500 lbs BOD/day= 1,400,000 sq ft

= 7,500 lbs BOD/day

1,400 X 1,000 sq ft

= 5.4 lbs BOD/day/1,000 sq ft

Note: you may want to run through these calculations as metricexamples.

II. Characteristics of the Biomass-Process Control

A. Daily inspection of the biomass growth on the shafts by a trainedoperator is the single most important element of process controlmonitoring.

B. RBC first stage observations1. Most critical, reflects condition of waste stream2. Normal:

a. Uniform brown-to-gray colorb. Uniform biomass thickness, thin layer, no patches

3. Abnormal:a. Heavy, shaggy biomass represents organically overloaded

first stage. May be indication of high organic load toplant or in-plant side stream problem.

b. Heavy, shiny growth with white slime appearance is anindication of a filamentous bacteria, Be iatoa, growingon the 'media. Cause may be the presence of su fides anda low DO environment.

c. Black in color with odors, anaerobic conditions have developed.Possible organic overload or "dead" spots in RBC tanks.

I-RBC-6

C. RBC middle stage observations1. Same general observations as the first stage with:

a. Gradually lighter shades of brown

b. Progressively more patchy as you move away from the

first stage.

2. Abnormal - same as first stage observations

D. RBC final stage observations1. Very light in color and sparse growth as BOD is used up.

2. Light tan and golden shades are predominately nitrifyingbacterial populations.

3. Reddish colored biomass sometimes occurs, indication ofadvanced nitrifying stage. Reddish tint caused by the growth

of higher worm forms.

E. Severe sloughing1. Toxic or inhibitory materials2. Extremes in hydraulic or organic loadings3. Air flushing from air header (too much air)

III. Process Control Testing

A. Influent/effluent BOD1. Comparison for process efficiency

B. Influent/effluent SS1. Comparison for process efficiency

C. Dissolved oxygen1. Measure DO at each stage2. Look for anaerobic dead spots

D. Temperature1. Look for extreme changes

E. Nitrification process testing1. Ammonia-N2. Nitrate-N3. Alkalinity

IV. Making Process Control Changes

A. Flexibility available1. Multiple stages that can be taken on and off line2. Multiple RBC trains3. Series or parallel flow change4. Movable baffles to divide shafts

B. Set up for maximum BOD removal and/or high organic loadings1. Maximum number of shafts operable in first stage2. Monitor appearance and DO

C. Set up to encourage nitrification1. Maximize the number of stages ih series in a train2. Monitor pH and alkalinity

I-RBC-7

11

V. RBC Maintenance

A. Mechanical drive systems1. Observe for odd noises and heat from motor and bearings

2. Look for oil leaks or spills, check oil levels

3. Inspect chains or belts for alignment and tightness

4. Be sure all guards over moving parts and equipment are

in place and secure.

B. Air drive system1. Inspect blower condition:

a. Pressureb. Tempc. Vibrationd. Lubrication

2. Check shaft bearing for wear and vibra.ion

a. Lubrication schedule

3. Purge air lines ane header, exercise control valve

4. Check for damaged cr lust air cups

5. Time shafts for revolution speed (shaft speeds)

I-RBC-8

iGrit &ScreeningRemoval

Pri. Clar.

RBC' s

FIGURE 1

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ROTATING BIOLOGICAL CONTACTORS

Answers to Worksheet 1 - Concepts and Components

1. The wastewater treatment process in which a shaft containing synthetic

media is rotated in a tank filled with process water is called

rotating biological contactor .

2. The rotating drum of the RBC unit that is made up of the media from

end bearing to end bearing is called the shaft

3. A series of drums lined up in a row is called a train

4. The two basic arrangements for liquid to flow through an RBC plant is

series and parallel .

5. The tank or basin which is said to be the hydraulic point of no return

is called the stage .

6. Healthy biomass is brown colored on the first stage and tends toward

lighter brown, gold or reddish in later stages.

7. The two types of drum drive systems are:

mechanical drive

air drive

8. When excess growth on an RBC drum falls off the media the process is

called sloughing

9. If the surface of the RBC media has a black color and there are strong

odors then anaerobic conditions have developed.

ROTATING BIOLOGICAL CONTACTORS

Answers to Worksheet 2 - Process Control

1. Design flow rates for an RBC should fall in the2.25 to 2.50

gpd/square foot range.

2. The normal range of SOD removal for a well operated RBC system is

80 to 95 percent.

3. Heavy, shiny, white patches of growth on the first stage biomass is a

growth of Beggiatoa bacteria developing when sulfides are present.

4. The recommended set up for maximizing BOD removal and/or dealing with

high organic loads would be to maximize the number of shafts in

the first stage.

5. To set up to encourage nitrification maximize the number of stages

in a train.

6. Give two advantages of the mechanical shaft drive system:

low capital cost

positive speed control

low power usage

7. Give two disadvantages of the air drive system:

high capital costs

high Rower costs

requires speed adiustment

8. Calculate the hydraulic loading on an RBC system that has a total surface

area of 600,000 ft and has a flow of 2 MGD.

Hydraulic loading, gpd/ft2 2,000,000 gpd

=

600,000 ft2

= 3.33-0-dtft2

I-RBC-29

3 ,1

9. Calculate the organic loading for an RBC system that is 750,000 sq ft

and the BOD applied per day is 1800 lbs BOO/day.

Organic Loading,lbs BOD

1000 sq ft

1800 lbs

750 thousand ft'

= 2.4 lbs

1000 sq ft

10. Calculate the organic loading for an RBC system that has an influent BOD

of 100 mg/1, a flow of 1.75 MGD, and a surface area of 400,000 sq ft.

BOD, lbs/day - BOD, mg/1 X Flow, MGD X 8.34

= 100 mg/1 X 1.75 MGD X 8.34

= 1460 lbs/day

Organic Loading, lbs BOD , 1460 lbs

1000 sq ft 400 thousand ft2

= 3.65 lbs

1000 sq ft

I-RBC-30

3,)

RBC's

Final Quiz

Directions: for each question select the best answer and mark that

answer with either an X or a check. There is only one correct answer

per question.

1. The RBC treatment process is a:

a. chemical treatment processb. biological treatment processc. tertiary treatment processd. treatment additione. none o' the above

2. fhe m;:-nbial growth in an RBC secondary treatment process moreclosely resembles the:

a. MLSS in an activated sludge processb. feathery floc from an alum reactionc. heavy solids from a primary clarifierd. bacterial growth in the anaerobic digestere. zoogleal slime from a trickling filter

3. The rotating "drum" of the RBC unit that is defined as being themedia from end bearing to end bearing is called:

a. a trainb. the shaftc. a bio-unitd. a secondary unite. a stage

4. A series of RBC treatment units or "drums", lined up in a row,which take the flow from the influent to the effluent is called:

a. parallel flowb. stage groupsc. a series shaftd. a traine. a secondary series

I-RBC-31

3

5. The excess growth on an RBC disc eventually falls off the media

into the flow stream and settles in the secondary clarifier.

This process is referred to as:

a. sloughingb. purgingc. toxic shockd. bio-growth removal

e. none of the above

6. Biomass is the general term describing growth on the RBC media.The characteristics of a normal biomass used for the removal ofcarbonaceous: ',taste would be:

a. uniformly thinb. uniform brown colorc. no bare spots or patchesd. only a few hundredths of an inch in thickness

e. all of the above are correct

7. Visual observation of the middle stages of an RBC treatment system

would normally show:

a. thick, heavy growthb. very sparse growth, red in colorc. lighter shades of brown, some clear patchesd. shiny, greasy appearancee. looks the same as the first stages

8. Observation of the last stages of an RBC treatment system that isset up for nitrification would have the characteristics of:

a. heavy, dark brown growthb. sparse growth with possible reddish colorc. uniform covering, golden colord. shiny, greasy appearancee. all of thP above will occur

9. If the surface of the RBC media has a black color and there arestrong odors, then:

a. filamentous bacteria are growingb. there is a grease buildupc. the plant has received a toxic loadd. nitrification is occurringe. anaerobic conditions have developed

3 7I-RBC-32

10. A heavy, shiny growth with a white slime appearance that mayoccur on the RBC disc is an indication of:

a. the growth of Beggiatoa, a filamentous bacteriumb. a severe buildup of greasec. the failure of the pretreatment systemd. denitrification is occurringe. a white colored growth never shows up

11. Usually, a great deal of flexibility is built into an RBC systemso that adjustments can be made in accordance to the changes inthe characteristics of the influent waste stream. The set up formaximum BOD removal and/or high organic loads would be:

a. maximize the number of shafts in the first stageb. increase the flow rate to all trainsc. recycle 50% of effluent to head of plant.d. maximize the number of stages in a traine. bypass excess flow and go for coffee

12. To set up an RBC system to encourage nitrification to take placeyou would:

a. slow down the flow coming to the plantb. add ammonia nitrogen at head of plantc. decrease the RAS rated. maximize the number of stages in a traine. none of the above

13. The normal range of BOD removal for a well operated RBC system isusually given as:

a. between 75% and 80%b. between 80% and 95%c. between 85% and 99%d. around 50%e. with recycle about 85%

14. Total effluent BOD of a well operated RBC system should fall inthe range of:

a. 1 to 5 mg/1b. 5 to 10 mg/1c. 15 to 30 mg/1d. greater than 50 mg/1e. none of the above

3OI-RBC-33

15. The hydraulic loading of RBC's is given in terms of gallons per

day per square foot of media surface. Calculate the hydraulicloading of an RBC system that has a total surface area of 500,000sq ft and sees a flow of 1.75 MGD.

a. 0.286b. 3.0

c. 3.5

d. 40,875e. 558

16. To calculate the organic loading for an RBC system, you wouldneed to:

a. multiply the BOD by the flowb. divide BOD mg/1 by surface areac. multiply surface area by lbs BODd. divide by 1000 sq ft unitse. divide lbs BOD/day by surface area

17. Calculate the organic loading of an RBC system that has a solubleBOD of 95 mg/1, a flow of 1.8 MGD, and a surface area of 700,000sq ft.

a. 1,426

b. 0.002c. 0.244d. 2.0

e. 3.5

18. There are two types of drive systems that are used to rotate theRBC shafts the waste stream. Which of the answers given below isnot an advantage of a mechanical shaft drive system?

a. high torque on shaftb. low capital costc. positive speed controld. low power usagee. all are advantages

19. When considering the advantages and disadvantages of an air drivesystem, which of the answers given below is not a disadvantage ofan air drive system?

a. thinner biomassb. high capital costsc. high power costsd. rotational speed adjustments requirede. all are disadvantages

3!)I- RBC -34

20. If you were to make the required adjustments to the RBC systemthat force nitrification to occur, what additional laboratorytest would you perform to monitor this process?

a. influent and effluent BODb. ammonia-N, nitrate-N, and alkalinityc. influent and effluent ammonia-Nd. BOD, DO, and alkalinitye. DO, ammonia-N, and nitrogen gas

I-RBC-35

RBC's

Answers to Final Quiz

Directions: for each question select the best answer and mark that

answer with either an X or a check. There is only one correct answer

per question.

1. The RBC treatment process is a:

a. chemical treatment processx b. Liological treatment process

c. tertiary treatment processd. treatment additione. none of the above

2. The microbial growth in an RBC secondary treatment process moreclosely resembles the:

a. MLSS in an activated sludge processb. feathery floc from an alum reactionc. heavy solids from a primary clarifierd. bacterial growth in the anaerobic digester

x e. zoogleal slime from a trickling filter

3. The rotating "drum" of the RBC unit that is defined as being themedia from end bearing to end bearing is called:

X

a. a trainb. the shaftc. a bio-unitd. a secondary unite. a stage

4. A series of RBC treatment units or "drums", lined up in a row,which take the flow from the influent to the effluent is called:

a. parallel flow

b. stage groupsc. a series shaftd. a traine. a secondary series

4 1

I-RBC-36

5. The excess gro4Zh on an RBC disc eventually falls off the mediainto the flow stream and settles in the secondary clarifier.This process is referred tO as:

a. sloughingb. purgingc. toxic shock

d. bio-growth removale. none of the above

6. Biomass is the general term describing growth on the RBC media.The characteristics of a normal biomass used for the removal ofcarbonaceous waste would be:

X

a. uniformly thinb. uniform brown colorc. no bare spots or patchesd. only a few hundredths of an inch in thicknesse. all of the above are correct

7. Visual observation of the middle stages of an RBC treatment systemwould normally show:

a. thick, heavy growthb. very sparse growth, red in color

X c. lighter shades of brown, some clear patchesd. shiny, greasy appearancee. looks the same as the first stages

8. Observation of the last stages of an RBC treatment system that isset up for nitrification would have the characteristics of:

a. heavy, dark brown growth

X b. sparse growth with possible reddish colorc. uniform covering, golden colord. shiny, greasy appearancee. all of the above will occur

9. If the surface of the RBC media has a black color and there arestrong odors, then:

a. filamentous bacteria are growingb. there is a grease buildupc. the plant has received a toxic loadd. nitrification is occurring

X e. anaerobic conditions have developed

10. A heavy, shiny growth with a white slime appearance that mayoccur on the RBC disc is an indication of:

X a. the growth of Beggiatoa, a filamentous bacteriumb. a severe buildup of greasec. tLe failure of the pretreatment systemd. denitrification is occurringe. a white colored growth never shows up

11. Usually, a great deal of flexibility is built into an RBC systemso that adjustments can be made in accordance to the changes inthe characteristics of the influent waste stream. The set up formaximum BOO removal and/or high organic loads would be:

X a. maximize the number of shafts in the first stageb. increase the flow rate to all trainsc. recycle 50% of effluent to head of plantd. maximize the number of stages in a traine. bypass excess flow and go for coffee

12. To set up an RBC system to encourage nitrification to take placeyou would:

a. slow down the flow coming to the plantb. add ammonia nitrogen at head of plantc. decrease the RAS rate

x d. maximize the number of stages in a traine. none of the above

13. The normal range of BOD removal for a well operated RBC system isusually given as:

a. between 75% and 80%

X b. between 80% and 95%c. between 85% and 99%d. around 50%e. with recycle about 85%

14. Total effluent BOO of a well operated RBC system should fall inthe range of:

a. 1 to 5 mg/1b. 5 to 10 mg/1

-17 c. 15 to 30 mg/1d. greater than 50 mg/1e. none of Ihe above

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15. The hydraulic loading of RBC's is given in terms of gallons per

day per square foot of media surface. Calculate the hydraulic

loading of an RBC system that has a total surface area of 500,000sq ft and sees a flow of 1.75 MGD.

a. 0.286b. 3.0

X c. 3.5d. 40,875e. 558

16. To calculate the organic loading for an RBC system, you would

need to:

X

a. multiply the BOD by the flowb. divide BOD mg/1 by surface areac. multiply surface area by lbs BOO

d. divide by 1000 sq ft unitse. divide lbs 80D/day by surface area

17. Calculate the organic loading of an RBC system that has a solubleBOD of 95 mg/1, a flow of 1.8 MGD, and a surface area of 700,000

sq ft.

a. 1,426

b. 0.002c. 0.244

X d. 2.0e. 3.5

18. There are two types of drive systems that are used to rotate theRBC shafts the waste stream. Which of the answers given below isnot an advantage of a mechanical shaft drive system?

X a. high torque on shaftb. low capital costc. positive speed controld. low power usagee. all are advantages

19. When considering the advantages and disadvantages of an air drivesystem, which of the answers given below is not a disadvantage ofan air drive system?

X a. thinner biomassb. high capital costsc. high power costsd. rotational speed adjustments requirede. all are disadvantages

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20. If you were to make the required adjustmits to the RBC systemthat force nitrification to occur, %that additional laboratorytest would you perform to monitor this process?

a. influent and effluent BOD

x b. ammonia-N, nitrate-N, and alkalinity

c. influent and effluent ammonia-Nd. BOO, DO, and alkalinity

e. DO, ammonia-N, and nitrogen gas

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