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Analysis and Selection of Wastewater Flow
rates and Constituent Loading
Regional Training “Decentralized Wastewater Management”
By:Dr.Ghaida Abu-Rumman
Nov-3rd-2013
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Overview
Determining ww Flowrates and mass loadings is a
fundamental step in the conceptual process design of
wastewater treatment facilities.
Flowrates sizing of different treatment system
components
Loading to determine capacity and operational
characteristics of treatment facilities and ancillary
equipment.
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Components of Wastewater Flows
Components:
• Domestic discharge from residential, commercial, and
institutional facilities.
• Industrial
• Infiltration/inflow (I/I)
Types of sewer systems
• Sanitary Sewer carries domestic, industrial, and
infiltration/inflow
• Storm Sewer carries storm water
• Combined Sewer both
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Wastewater sources and flow rates Data that can be used to estimate average wastewater flowrates from various
domestic, industrial, and I/I are presented here.
Domestic Wastewater Sources and Flow rates:
• Residential Areas : Table 3-1
• Commercial Districts: Generally expressed in gal/acre.d
(m3/ha.d) range form 800 – 1500 gal/acre.d (Table 3-2)
• Institutional facilities Table 3-3
• Recreational (highly seasonal) facilities Table 3-4
Industrial Wastewater Sources and Flow rates:
Range:
• 1000 –1500 gal/acre.d light industrial development
• 1500–3000 gal/acre.d medium industrial development
• 85-95% of water use industries without internal water reuse
• For large industries separate estimates must be made.
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Wastewater sources and flow rates
Infiltration/Inflow (I/I)
• Infiltration defective pipes ----etc.
• Steady inflow from cellar and foundation drains, etc.
• Direct inflow from direct storm water runoff connections to
sanitary sewer possible source are roof leaders, yard drains,
manhole covers.
• Total inflow direct + upstream flow (overflows/pumping
stations bypasses)
• Delayed inflow storm water that requires several days to
drain through manholes, etc…..
Infiltration flowrate:
• The amount of water that can enter a sewer from groundwater
(or infiltration) ranges from 100 - 10,000 gal/d. in-mi .
• Or 20 – 3000 gal/acre.d. (Example 3-2)
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Statistical Analysis of flowrates, constituent concentrations, and mass loadings
Statistical analysis involves the determination of statistical
parameters used to quantify a series of measurements.
Important in developing wastewater management systems
Common statistical parameters:
• In normal distribution, data is described using: mean, median,
mode, standard deviation, and coefficient of variation. Table 3-10
• In skewed distribution, data is described using log of
the value of the normal distribution (geometric). Table 3-10
Graphical analysis of data:
• Used to determine the nature of distribution: plotting
data on both arithmetic and log-probability papers.
Examples 3-4 and 3-5
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Analysis of flowrate data
Because the hydraulic design of both collection and treatment facilities is
affected by variation in wastewater flowrates, it is important that the
flowrate characteristics be carefully analyzed.
Definition of terms: (Table 3-11)
Variations in wastewater flowrates.
• Short term variations: (Figure 3-4).
• Seasonal variations.
• Industrial variations.
Wastewater flowrate factors:
• Maximum flows are determined by peaking factor (PF).
•
flowrate term-long average
daily)hourly, (e.g., flowrate peakPF
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Analysis of constituent mass loading
• BOD and TSS mass loadings can vary up to two or
three times the average conditions.
• Design of wastewater treatment processes should
consider peak conditions.
Quantities of waste discharged: (Table 3-12)
• Typical BOD5 (not including kitchen waste) is .18
Ib/cap.d.
• Example:
Given: a town of 125,000 population. Estimate the BOD5 loading of
the raw wastewater
BOD5 = .18 x 125,000 cap= 22,500 lb/day
cap.d
Ib
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Analysis of constituent mass loading
Composition of Wastewater in Collection Systems.
• T3-15, p. 186. The values are based on 120 ,which is the
suggested EPA flow.
• Example: The average flow is 120 and the average BOD5 is
190 mg/l. What is the BOD5 loading in
• = Conc. (mg/l) x 8.34 x Q(MGD)
• = 190 x 8.34 x 120 x
• = .19 which aggress with value stated in T3-12, p.182.
cap.d
gal
cap.d
Ib
cap.d
gal
cap.d
Ib
mg/l
Ib/MG
cap.d
Ib
L
mg
mg/l
Ib/MG
cap.d
gal
gal10
MG6
cap.d
Ib
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Analysis of constituent mass loading
Short term variation in constituent values.
• Figure 3-6: Typical hourly variations in flow and strength of
wastewater.
Variations in industrial wastewater.
• Composition is highly variable depending on industry type.
• Concentrations (BOD, TSS) vary significantly throughout the day.
• Pre-treatment may be required before discharge to municipal
sewer.
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Design flowrates and mass loadings
Average daily flow
• It is the average flow occurring over a 24-hour period under dry
weather conditions.
• used in evaluating plant capacity, estimating pumping and
chemical cost, sludge production, organic loading rates
Maximum daily flow
• It is the maximum flow on a typical dry weather diurnal flow curve.
• used for the design of facilities involving retention time, such as:
– Equalization basins and Chlorine Contact Tanks
Minimum daily flow
• It is the minimum flow on a typical dry weather diurnal flow curve.
• used in sizing of conduits for minimum deposition
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Design flowrates and mass loadings
Peak hourly flow
• The peak hourly flow occurs during or after precipitation and
includes a substantial amount of I/I.
• used for the design of
– Collection and interceptor sewers
– Pumping stations
– Flow meters, grit chambers, conduits, channels in plant
• Peak Flowrate Factors may be projected using Figure 3-13,
p.202.
Minimum hourly flow
• It is the lowest flow on a typical dry weather diurnal flow curve.
• used in sizing wastewater flowmeters, wastewater pumping
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Design flowrates and mass loadings
Mass loading:
• Table 3-20
• Important in the design of treatment facilities such as:
– Sizing aeration tanks.
– Biosolids processing facilities (Biosolids produced are directly related to BOD mass loading)
– Oxygen requirements are affected by mass loading
Origin of waste
Biochemical oxygen
demand
“BOD” (kg/ton
product)
Total Suspended
solids
“TSS” (kg/ton
product)
Domestic sewage 0.025
(kg/day/person)
0.022
(kg/day/person)
Dairy industry 5.3 2.2 Yeast industry 125 18.7 Starch & glucose industry 13.4 9.7 Fruits & vegetable canning
industry 12.5 4.3
Textile industry 30 - 314 55 - 196 Pulp & paper industry 4 - 130 11.5 - 26 Beverage industry 2.5 - 220 1.3 - 257
* Rapid assessment for
industrial pollution
Tannery industry
48 - 86 85 - 155
Mass Loading Calculations
Mass = Conc x Flow Rate
= mg/L x MGD x 8.34 x 1/24
= lbs/hr
Mass = Conc x Flow Rate
= mg/L x ft3/sec x 0.22
= lb/hr
Mass Balance Calculations
Fundamental Law: Massin = Massout
Massin = Q1 x Conc1 + Q2 x Conc2 (knowns)
Massout = QT x ConcT
(unit constants cancel out)
QT = Q1 + Q2
ConcT = unknown
Determination of the pollution load in waste water expresed as
population equivalent (PE)
Population equivalent (in waste-water monitoring and treatment) refers to the amount of oxygen—demanding substances whose oxygen consumption during biodegradation equals the average oxygen demand of the waste water produced by one person. For practical calculations, it is assumed that one unit equals 54 grams of BOD per 24 hours.
population equivalent (p.e.) is a measure of
pollution representing the average organic
biodegradable load per person per day: it is
defined in Directive 91/271/EEC as the organic
biodegradable load having a five-day
biochemical oxygen demand (BOD5) of 60g of
oxygen per day.
Determination of the pollution load in waste
water expresed as population equivalent (PE)
Site works – 48 h:
Meauserment of flow every 15 minutes
Sampling every 15 minutes to prepare 2 h composite samples
Meauserment of temperature every 2 h
Population Equivalents
1. Wastewater discharge: 100 -120 gpcd
- 70 gpcd domestic
- 10 gpcd industrial/commercial
- 20 to 40 gpcd infiltration
2. Suspended Solids and BOD
SS = 0.2 lb pcd (without kitchen grinder)
SS = 0.22 lb pcd (with kitchen grinder)
BOD = 0.17 lb BOD pcd
BOD = 0.26 lb BOD pcd (with kitchen grinder)
Population Equivalents cont.
For 100 gpcd and consider for one person:
BOD0.17 lb
100 gal
1
8.34 lb
106
galmg
L
BOD 204mg
L
SS0.2 lb
100 gal
1
8.34 lb
106
galmg
L
SS 240
mg
L
Population Equivalents cont.
Used to
• Establish population equivalency of an industrial waste.
• Establish charge for treating industrial waste based on BOD or SS rather than flow.
Find the BOD and flow equivalent for an industrial waste
with the following characteristics:
Q 0.1MGDMGDMGD BOD 450mg
L
Flow:0.1MGD
100 gal
person day
1000peoplepeoplepeople
BOD: 0.1MGD 450 mg
L
8.34 lb
MGDmg
L
0.17 lb BOD
person day
2208peoplepeoplepeople
BOD equivalent is 2.2 times greater than flow equivalent.
Summary
Domestic wastewater is a well balanced, nutrient rich medium for bacterial decomposition.
After primary treatment, biodegradation is the most cost effective secondary treatment.
- Effective biodegradation requires
BOD:N:P = 100:5:1
- Domestic wastewater contains 100:20:5.
- Organics (BOD) limits N and P reduction.
Advanced treatment is required to
remove excessive N and P.