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Module 4: Fundamentals of Wastewater Treatment
Wastewater Treatment Plant Operator Training
Learning Objectives• Explain the general purpose of preliminary treatment.• Explain the purpose of screening, grit removal, and
pre-aeration.• Differentiate between manually and mechanically
cleaned racks and screens.• Define differences between screening and
comminution.• Describe safe disposal of screenings and grit.
Unit 1–Preliminary Treatment Unit 1–Preliminary Treatment
2
Manually Cleaned Bar ScreenManually Cleaned Bar Screen
3Diagram excerpted from Chapter 4: Racks, Screens, Comminutors and Grit Removal. In Operation of Wastewater Treatment Plants Volume I.
AERATION TANK
Mechanically Cleaned Bar Screen
4
AERATION TANK
Diagram excerpted from Chapter 4: Racks, Screens, Comminutors and Grit Removal. In Operation of Wastewater Treatment Plants Volume I.
5
Aerated Grit ChamberAerated Grit Chamber
AERATION TANK
Diagram excerpted from Chapter 4: Racks, Screens, Comminutors and Grit Removal. In Operation of Wastewater Treatment Plants Volume I.
Cyclone SeparatorCyclone Separator
6
AERATION TANK
Diagram excerpted from Chapter 4: Racks, Screens, Comminutors and Grit Removal. In Operation of Wastewater Treatment Plants Volume I.
Grit WasherGrit Washer
7
AERATION TANK
Diagram excerpted from Chapter 4: Racks, Screens, Comminutors and Grit Removal. In Operation of Wastewater Treatment Plants Volume I.
ComminutorComminutor
8
AERATION TANK
Diagram excerpted from Chapter 4: Racks, Screens, Comminutors and Grit Removal. In Operation of Wastewater Treatment Plants Volume I.
Comminutor with By-Pass ScreenComminutor with By-Pass Screen
9
AERATION TANK
Diagram excerpted from Chapter 4: Racks, Screens, Comminutors and Grit Removal. In Operation of Wastewater Treatment Plants Volume I.
BarminutorBarminutor
10
AERATION TANK
Diagram excerpted from Chapter 4: Racks, Screens, Comminutors and Grit Removal. In Operation of Wastewater Treatment Plants Volume I.
Learning Objectives• Explain sedimentation and flotation
principles.• List factors that indicate a clarifier is not
performing properly.• Use mathematical formulas to solve for
detention time, weir overflow, surface loading, and solids loading.
Unit 2–Primary Treatment: Sedimentation & Flotation Unit 2–Primary Treatment: Sedimentation & Flotation
11
Detention Time FormulasDetention Time Formulas
12
Formulas
Detention Time, hr. = Tank Volume, cu ft x 7.5 gal/cu ft x 24 hr/day Flow, gal/day
Rectangular Tank Volume, cu ft = Length, ft x Width, ft x Height (Depth), ft
Area of Circle, ft2 = (0.785)(Diameter2) or ()(Radius2)Note: = 3.14
Circular Tank Volume, cu ft = Area x Height (Depth), ft
Circular Tank Volume, cu ft = (0.785)(Diameter, ft)2 x Height (Depth), ft or (3.14)(Radius, ft)2 x Height (Depth), ft
What is the detention time when…
• The flow is 3.0 million gallons per day (MGD) or 3,000,000 gal/day, and
• Tank dimensions are 60 feet long by 30 feet wide by 10 feet deep?
Detention Time: Sample 2.1Detention Time: Sample 2.1
13
Given:
Volume = 60 feet by 30 feet by 10 feet
= 18,000 cu ft
Step #1 - VolumeStep #1 - Volume
14
Given:
Flow = 3.0 million gallons per day (MGD) or 3,000,000 gal/day
Step #2 - FlowStep #2 - Flow
15
Detention = Tank Volume, cu ft x 7.5 gal/cu ft x 24 hr/dayTime, hr Flow, gal/day
= 18,000 cu ft X 7.5 gal/cu ft x 24 hr/day3,000,000 gal/day
= 3,240,000 gal/hr/day3.0 MGD
= 1.08 hours
Step #3 - CalculationStep #3 - Calculation
16
What is the detention time when…
• The flow is 2.5 million gallons per day (MGD), and
• Circular clarifier is 60 ft in diameter with a depth of 12 ft?
Detention Time: Sample 2.2Detention Time: Sample 2.2
17
Reminder:
• Circular Tank Volume, cu ft = 0.785 x (Diameter, ft)2 x Depth, ft
• Volume = (0.785) x (60 ft)2 x 12 ft deep
= 33,912 cu ft
Step #1 - VolumeStep #1 - Volume
18
Given:
Flow = 2.5 million gallons per day (MGD) or 2,500,000 gal/day
Step #2 - FlowStep #2 - Flow
19
DetentionTime, hr= 33,912 cu ft x 7.48 gal/cu ft x 24 hr/day
2.5 MGD
= 6,087,882 gal/hr/day 2,500,000 gal/day
= 2.44 hours
Step #3 - CalculationStep #3 - Calculation
20
Formulas
• Weir Overflow, gpd/ft = Flow Rate, GPD Length of Weir,
ft
• Length of Circular Weir = 3.14 x Weir Diameter, ft
Weir Overflow RateWeir Overflow Rate
21
What is the weir overflow rate when…
• The flow rate into the unit is 3.5 MGD, and
• The circular clarifier has a 75 foot diameter overflow weir
Weir Overflow Rate: Problem 2.1Weir Overflow Rate: Problem 2.1
22
Weir overflow rate,gpd/ft
= 3,500,000 gallons/day 3.14 x 75 feet
= 3,500,000 gal/day 235.5 feet
= 14,862 gpd/ft
Weir Overflow Rate: Problem 2.1Weir Overflow Rate: Problem 2.1
23
What is the surface loading rate when…
• The flow into a rectangular clarifier is 5.0 MGD
• The clarifier is 40 feet wide by 110 feet long by 12 feet deep
– Reminder:Surface loading rate , gpd/ft2 = Flow Rate, gpd Surface area, ft2
Surface Loading Rate: Problem 2.2Surface Loading Rate: Problem 2.2
24
Surface loading rate, gpd/ft2
= 5,000,000 gallons/day 40 ft x 110 feet
= 5,000,000 gal/day 4400 ft2
= 1,136 gpd/ft2
Surface Loading Rate: Problem 2.2Surface Loading Rate: Problem 2.2
25
Pa DEP - Domestic Wastewater Facilities
Manual
Operation of Wastewater Treatment Plants, Vol I
Primary Clarifiers Not considered Not generally considered
Conventional Activated SludgeSecondary Clarifiers
40 #/day/sq ft average, 50 peak
12 to 30 lbs/day/sq ft
Extended Aeration Secondary Clarifiers
30 #/day/sq ft average, 50 peak
N/A
Nitrification Secondary Clarifiers:Separate Nitrification Stage
30 average, 50 peak N/A
Carbonaceous Stage 45 average, 50 peak N/A
Dissolved-Air Flotation 40 #/day/sq ft (w/o polymer addition),20 #/day sq ft (w polymer addition)
5 to 40 lbs/day/sq ft
Sludge Thickening 5 to 12 #/day/sq ft 5 to 20 lbs/day/sq ft
Solids Loading GuidelinesSolids Loading Guidelines
26
Formulas
• Solids Loading, lbs/day/ft2 = Solids Applied, lbs/day Surface Area, ft2
– Solids Applied, lbs/day = Flow, MGD x Conc., mg/L x 8.34 lbs/gal
Solids LoadingSolids Loading
27
Calculate the solids loading at which a clarifier is operating given the following…
•The circular clarifier has a diameter of 125 feet
•Forward flow is 6.0 MGD and the return sludge flow is 2.0 MGD
•MLSS is 4.000 mg/L
Solids Loading: Problem 2.3Solids Loading: Problem 2.3
28
Reminder:
Solids Applied, lbs/day
= Flow, MGD x MLSS conc., mg/L x 8.34 lbs/gal
Solids Applied = 8 MGD x 4,000 mg/L x 8.34 lbs/gal
= 266,880 lbs/day
Step # 1 - Solids AppliedStep # 1 - Solids Applied
29
Given: The circular clarifier has a diameter of 125 feet
Area of Circle, ft2 = (0.785)(Diameter)2
= (0.785)(125 ft)2
= (0.785)(15,625 ft2)
= 12,266 ft2
Step # 2 – Surface AreaStep # 2 – Surface Area
30
Solids Loading,lbs/day/ft2
= Solids Applied, lbs/day Surface Area, ft2
= 266,880 lbs/day 12,266 ft2
= 22 lbs/day/ft2
Step # 3 – Solids LoadingStep # 3 – Solids Loading
31
Learning Objectives• List four biological secondary treatment processes.
• Explain the principles of the trickling filter process.
• Identify the different types of trickling filters.
• Explain the principles of the rotating biological contactor (RBC) process.
• Explain the principles of the activated sludge process.
• List the three waste treatment pond classifications and explain the principles of each.
Unit 3–Overview of Biological Secondary TreatmentUnit 3–Overview of Biological Secondary Treatment
32
Trickling Filter ProcessTrickling Filter Process
33
AERATION TANK
Prelim inaryTreatm ent
SolidsHandling
Wet PitTrickling
Filter
Distributor
FilterPum p
Station
SecondaryClarifier
ChlorineContact
Basin
WasteSolids
RawWastewater
PlantEffluent
TricklingFilter Process
Prim aryEffluent
Recirculation
FilterUnderflow
SecondaryClarifierInfluent
Prim aryClarifier
TRICKLING FILTER PROCESS FLOW SCHEMATIC
Trickling FilterTrickling Filter
34Diagram excerpted from Chapter 6: Trickling Filters. In Operation of Wastewater Treatment Plants Volume I.
AERATION TANK
Rotating Biological Contactor ProcessRotating Biological Contactor Process
35
AERATION TANK
No. 1 No. 2 No. 3 No. 4
ROTATING BIOLOGICAL CONTRACTOR PROCESS FLOW SCHEMATIC
RawWastewater
Prelim inaryTreatment
PrimaryClarifier
PrimaryEffluent
SolidsHandling
WasteSolids
SecondaryClarifier
SecondaryClarifierInfluent
RBC Process
RBC ReactorsChlorineContact
Basin
PlantEffluent
Shafts
Baffle (Typ)
Tank (Typ)
Media (Typ)
CONVENTIONAL ACTIVATED SLUDGE SCHEMATIC(COMPLETE MIX)
RawWastewater
Prelim inaryTreatment
PrimaryClarifier
PrimaryEffluent
SolidsHandling
WasteSolids
SecondaryClarifierAeration Tank
or Reactor
ChlorineContact
Basin
PlantEffluent
Return Activated Sludge
Waste Activated Sludge
Complete Mix Activated SludgeComplete Mix Activated Sludge
36
37
Contact Stabilization SchematicContact Stabilization Schematic
AERATION TANK
Aeration Contact Tankor Reactor
CONTACT STABILIZATION ACTIVATED SLUDGE SCHEMATIC
SolidsHandling
RawWastewater
Prelim inaryTreatment
ChlorineContact
Basin
WasteActivated
Sludge
WasteSolids
SecondaryClarifier
PlantEffluent
Reaeration Tankor Reactor Return
ActivatedSludge
38
AERATION TANK
Return Activated Sludge
Aeration Tankor Reactor
EXTENDED AERATION ACTIVATED SLUDGE SCHEMATIC
RawWastewater
Prelim inaryTreatm ent
ChlorineContact
Basin
Waste Activated Sludge
ClarifierPlant
Effluent
WasteSolids
SolidsHandling
Extended Aeration SchematicExtended Aeration Schematic
Two Unit SBR Time ChartTwo Unit SBR Time Chart
39
Time Period (hrs) Unit #1 Unit #20 - 1 Fill Aeration1 - 2 Fill Settle2 - 3 Fill / Aeration Settle3 - 4 Fill / Aeration Draw4 - 5 Aeration Fill5 - 6 Settle Fill6 - 7 Settle Fill / Aeration7 - 8 Draw Fill / Aeration
Oxidation Ditch Schematic
40
AERATION TANK
OXIDATION DITCH SCHEMATIC
RawWastewater
SolidsHandling
WasteSludge
Prelim inaryTreatm ent
WasteSolids
Return Sludge
FinalClarifier
ChlorineContact
Basin
PlantEffluent
Rotor (Typ)Level
ControlWeir
Oxidation Ditch
ReturnSludge
Pum ping