1
Q
What are Reaction Kinetics?
A
The rate at which a reaction or a conversion happens in a reactor.
2
Q
The CWA requires that secondary treatment removes at least ___% of plant influent BOD.
A
85%
3
Q
When is sludge considered properly digested?
A
When 50% of the organic matter has been destroyed and converted to gas.
4
Q
What is a common range for both BOD and TSS in primary clarifier influent?
A
150 - 400 mg/L
5
Q
Where is the first flow-measuring device in a plant?
A
After preliminary treatment
6
Q
Primary goal of WRRF?
A
Anything related to preventing disease or public health
7
Q
What is the threshold for something to be a dissolved solid?
A
1.5 - 2 microns. .000001 meters.
8
Q
What’s the flow rate of a primary sedimentation tank?
A
0.03 fps (0.009 m/s)
9
Q
What are the 3 methods for testing for organic content?
A
BOD, COD, and TOC
10
Q
Most U.S. plants are regulated to what limit for BOD and TSS?
A
30/30 (mg/L) for permit. Generally 85% according to EPA
11
Q
How do you calculate the F/M ratio?
A
(Q) Flow, in lbs per day of BOD into the AB / (V) lbs of MLVSS in the AB
12
Q
How much soil should you cover grit with?
A
6 inches
13
Q
What temperature do digesters run?
A
95 F or 35 C
14
Q
What is the recommended weir loading rate?
A
10,000 - 20,000 gpd per foot of weir
15
Q
How fast does water flow through a wastewater primary clarifier?
A
1-2 fpm
16
Q
Where does second-stage BOD removal happen and what is it called?
A
Tertiary process and nitrification
17
Q
TKN
A
Total Kjeldahl Nitrogen
18
Q
What’s the most common microcrustacen in a lagoon?
A
Daphnia, or water fleas.
19
Q
What do you call a lagoon that’s used after Primary Treatment?
A
An Oxidation Lagoon
20
Q
How many times heavier than air is H2S?
A
1.19
21
Q
POTW
A
Publicly Owned Treatment Works
22
Q
What can you to a collection system to reduce odors?
A
Caustic, hydrogen peroxide, and Ferric and ferrous salts.
23
Q
What measures settleable solids in ml/L?
A
A settleometer.
24
Q
Where in a pipeline is a flowmeter most accurate?
A
5 diameters downstream and 2 diameters upstream of bends or valves
25
What does COD measure?
The oxygen-consuming capacity of organic matter. The amount of oxygen consumed by a chemical oxidant in mg/L.
26
What is the typical removal percentage of BOD/COD in a wastewater primary clarifier?
25 - 45%
27
What's used to control the level of a lagoon and flow from one lagoon to the next?
Stop Log
28
What is a 1 Dalton equivalent to?
1/16 the mass of oxygen
29
0.1% is how many mg/L?
1000 mg/L
30
Activated Sludge plants are capable or removing __ to __ percent of BOD and SS.
90% - 99%
31
A high F/M ratio correlates with what kind of MCRT?
A low one
32
Which value will be higher in a COD and BOD test?
COD, because the oxidant in COD will react with things that bacteria do not.
33
What is the composition of the gas collection area of a digester?
70% Methane and 30% CO2
34
Secondary effluent must have a BOD and SS of less than __ mg/L.
30 mg/L
35
What % of methane in a digester?
65 - 70
36
What is the typical TSS removal efficiency for wastewater primary clarifiers?
30 - 65%
37
What is a typical organic loading rate for a lagoon?
10 - 50 lbs of BOD per day per acre
38
How do you calculate flow velocity for grit channels?
Channel Length divided by settling time
39
What 2 types of bacteria metabolize waste in anaerobic lagoons?
Acid Formers and Methane Fermenters
40
What's the best way to prevent emergent weed growth?
Maintain a water level above 3ft
41
How far apart are manholes?
300 - 500' apart
42
What's used to neutralize chlorine in WW?
SO2
43
How do you calculate sludge age?
Mass of solids in aeration tank (V x MLSS) / mass rate of solids entering the aeration tank (Q x TSS)
44
WRRF
Waste Resource Recovery Facilities
45
What is the decimal equivalent of 1 mg/L in grams?
0.001grams (per liter)
46
What does a high SVI mean?
The sludge settles slowly
47
What do you call the water that goes down homes' drains?
Domestic Contribution
48
Good settling sludge has an SVI below _____.
150
49
Wastewater Primary clarifiers are designed for ______ of detention time
2 - 3 hours
50
How big are the pores in a nanofilter?
0.1 - 2 microns
51
Why is ammonia bad for effluent?
It is toxic to aquatic wildlife and has a high chlorine and oxygen demand.
52
Typical mixed liquor solids concentration?
1000 - 4500 mg/L, maybe 3000
53
At what percentage is H2S lethal?
0.2% or 2000 ppm
54
Typical SS concentration of domestic wastewater?
150 - 400 mg/L
55
What are large, broken stone linings around a lagoon called?
riprap
56
How do you calculate SVI?
settled sludge volume after 30 minutes of settling in ml / the mixed liquor suspended solids concentration, times 1000.
57
What is a typical hydraulic loading rate for a lagoon in inches per day?
0.5 - 3 inches per day
58
How do you calculate grit-channel settling time?
Depth divided by settling rate
59
What is the common pH range for primary clarifiers?
6.5 - 8
60
Where does first-stage BOD treatment happen and what is it called?
Secondary process and carbonaceous
61
The 30-day average value in secondary effluent should not exceed ______?
30 mg/L
62
How long does it take for algae to grow in a new lagoon?
7 to 12 days
63
What does BOD measure?
The organic strength of wastewater. The amount of DO consumed in mg/L after 5 days at 68 F or 20 C .
64
What is the incubation temperature for the BOD5 test?
68F or 20C
65
What year was the Clean Water Act enacted?
1972
66
Primary sludge should have what percentage range of dry solids?
4% - 8%
67
What’s the BOD and TSS removal percentage requirement for secondary treatment?
85%
68
What are 2 reasons you don't want air in a digester?
Digesters are an anaerobic environment and air can mix with the methane and blow up.
69
What speed should a grit channel be at?
1 - 1.5 fps (.3 - .45 m/s)
70
How many times heavier than air is Sulfur Dioxide?
2.3X
71
How big are the pores in an ultrafilter?
0.005 - 1 microns
72
Keep the lagoon above pH ___ to avoid odors.
7.5
73
How is COD different than BOD.
The oxidant in COD will react with things that bacteria do not.
74
How fast are sanitary sewers designed to flow?
1 FPS or 0.6 m/s
75
What does a low SVI mean?
The sludge settles quickly
76
How are ultrafilters rated?
MWCO. Molecular Weight Cutoff. 1,000 - 5,000,000.
77
How slow should water move through a grit channel?
0.7 - 1.4 fps or 0.2 - 0.4 m/s
78
How do you calculate SRT?
Mass of solids in a system / mass of solids wasted per day
79
How much DO can aquatic life live on?
5 - 10 mg/L
80
What is OUR?
Oxygen uptake Rate: The rate at which micro organisms use oxygen while consuming substrate from wastewater.
81
What percentage of suspended solids will 2 hours of detention time settle?
60%
82
What is the typical removal efficiency of total suspended solids in a primary clarifier?
40% - 60%
83
Trickling filters are designed to remove __ to __ of BOD-causing wastes.
70% - 85%
84
An ultrafilter rated at 100 MWCO will retain most molecules at what size (or larger), in daltons?
100 daltons
85
What does it mean if your grit has a lot organic material?
Your grit-channel flow rate is too low
86
What does it mean if your grit chamber has mostly sand?
Your grit-channel flow rate is too high
87
How long does it take to properly digest sludge?
Approximately 30 days
88
What are 3 offensive gases other than H2S created by collections systems?
Mercaptans, Indole, and Skatole
89
What can cause brown or black scum to appear on the surface of a pond?
BOD overloading
90
What is the surface loading rate range for cold and warm weather?
300 - 1200 gpd/sq ft
91
How many times heavier than air is Carbon Dioxide?
1.5x
92
How many gallons of screenings can you expect to get per MGD?
0.2 - 12 gallons
93
What are the 3 ways to define the life of organisms or solids in a system?
SRT, MCRT, Sludge Age
94
What's the minimum DO for an aeration tank?
1 -2 mg/L
95
The NPDES permit program began as a result of which legislation?
The Clean Water Act of 1972
96
How much oxygen is in air?
20.93 %
97
How do you calculate the weight of nonsettleable solids?
Weight = TSS - (dissolved solids + settleable solids)
98
What is a common range for both BOD and TSS in primary clarifier efffluent?
50 - 150 mg/L
99
Expected BOD removal for a facultative pond?
70 - 80%
100
Expected BOD removal of a primary clarifier?
20 - 50%
101
Expected DO in aeration?
2 - 4 mg/L
102
Expected MLSS in ASP?
1,000 to 3,000/4,500 mg/L
103
Ideal pH for microorganism growth?
Between 6.5 and 7.5
104
What’s a good BOD:Nitrogen:Phosphorus ratio?
100:5:1
105
What’s the ratio of RAS solids concentration to MLSS in the aeration basin?
RAS concentration is twice the aeration tank MLSS concentration
106
A good RAS sludge pumping rate will leave how thick of a sludge blanket in the secondary clarifier?
6 inches to 3 ft
107
What percentage of wastewater flow is the RAS flow?
50% - 80%
108
What is a good SVI?
Less than 150 mL/G
109
Define sludge bulking
Usually caused by bound or filamentous bacteria like Nocardia, this is when sludge not settle properly and is billowy.
110
What color should mixed liquor be?
Light brown
111
What color is young mixed liquor?
Whitish
112
What does whitish mixed liquor indicate?
Young sludge age or high F/M ratio
113
What does light brown mixed liquor indicate?
Good mixed liquor
114
What does dark brown/black mixed liquor indicate?
Old sludge, too long an SRT, low F/M
115
What 4 things does excessive foam indicate in the aeration basin?
The presence of filamentous bacteria, excess surfactants, higher WAS flow than required, or low SRT
116
The secondary treatment standards require that BOD and TSS removal in the treatment process will not be less than ____ with a 30-day average value not exceeding ____ mg/L
85%, 30 mg/L
117
What are the 3 sources of waste water?
Domestic, commercial, and industrial.
118
COD
A measure of the oxygen-consuming capacity of organic matter present in the wastewater.
119
Optimum pH of ASP influent water for optimum ASP growth?
6.5 - 7.5
120
The RAS concentration should be _____ times MLSS for good settling sludge?
2
121
What is the most critical controlling variable in ASP?
WAS
122
Typical sludge age SRT?
1 - 5 days
123
What is the common % range for RAS flow rate as it relates to total flow rate?
50% - 80%. CAN BE 30 - 150
124
What is a common filamentous bacteria that causes white foam?
Nocardia
125
Thickening sludge goes from what percent?
1 to 3, 5 maybe 8
126
CBOD doesn’t include what element?
Nitrogen
127
Nitrification eats up what 2 things
Oxygen and alkalinity
128
2 nitrifying bacteria
Nitrobacter and nitrosomonnas
129
Denitrfication requires what 3 things?
BOD, no DO, and Nitrate
Water Study 2025
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