Loading s Calculations by Dr. Ghaida Abu Rumman en (1)

8/10/2019 Loading s Calculations by Dr. Ghaida Abu Rumman en (1)

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Analysis and Selection of Wastewater Flow

rates and Constituent Loading

Regional Training DecentralizedWastewater Management

By:Dr.Ghaida Abu-RummanNov-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.

Flowratessizing of different treatment system

components

Loadingto determine capacity and operational

characteristics of treatment facilities and ancillary

equipment.


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Components of Wastewater Flows

Components:

Domesticdischarge fromresidential, commercial, andinstitutional facilities.

Industrial

Infiltration/inflow (I/I)

Types of sewer systems

Sanitary Sewercarries domestic, industrial, andinfiltration/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 8001500 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:

10001500 gal/acre.dlight industrial development 15003000 gal/acre.dmedium industrial development 85-95% of water useindustries 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)

Infiltrationdefective 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 todrain 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 203000 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


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In skewed distribution, data is described using log ofthe value of the normal distribution (geometric).Table 3-10

Graphical analysis of data:

Used to determine the nature of distribution: plottingdata 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 theflowrate 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).

flowrateterm-longaverage

daily)hourly,(e.g.,flowratepeakPF
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Analysis of constituent mass loading

BOD and TSS mass loadings can vary up to two orthree times the average conditions.

Design of wastewater treatment processes shouldconsider peak conditions.

Quantities of waste discharged: (Table 3-12)

Typical BOD5 (not including kitchen waste) is .18Ib/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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Composition of Wastewater in Collection Systems.

T3-15, p. 186. The values are based on 120 ,which is thesuggested 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.dIb

cap.d

gal

cap.d

Ib

mg/l

Ib/MG

cap.d

Ib

L

mg

mg/l

Ib/MG

cap.d

gal

gal10

MG

6

cap.d

Ib


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Short term variation in constituent values.

Figure 3-6: Typical hourly variations in flow and strength ofwastewater.

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 municipalsewer.


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Design flowrates and mass loadings

Average daily flow

It is the average flow occurring over a 24-hour period under dryweather conditions.

used in evaluating plant capacity, estimating pumping andchemical 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 flowcurve.

used in sizing of conduits for minimum deposition


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Peak hourly flow

The peak hourly flow occurs during or after precipitation andincludes 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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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


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Origin of waste

Biochemical oxygen

demand

BOD kg/ton

product

Total Suspended

solids

TSS kg/ton

product

Domestic sewage0.025

(kg/day/person)

0.022

(kg/day/person)Dairy industry 5.3 2.2Yeast industry 125 18.7Starch & glucose industry 13.4 9.7

Fruits & vegetable canningindustry 12.5 4.3

Textile industry 30 - 314 55 - 196Pulp & paper industry 4 - 130 11.5 - 26Beverage industry 2.5 - 220 1.3 - 257

* Rapid assessment for48 - 86 85 - 155


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Mass Balance Calculations

Fundamental Law: Massin= Massout

Massin= Q1x Conc1+ Q2x Conc2 (knowns)

Massout= QTx ConcT(unit constants cancel out)

QT = Q1+ Q2

ConcT= unknown


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Determination of the pollution load in waste water expresed as

population equivalent (PE)

Population equivalent (in waste-watermonitoring and treatment) refers to theamount of oxygendemanding substanceswhose oxygen consumption duringbiodegradation equals the average oxygendemand of the waste water produced by oneperson. For practical calculations, it isassumed that one unit equals 54 grams of BODper 24 hours.


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population equivalent (p.e.) is a measure of

pollution representing the average organic

biodegradable load per person per day: it isdefined in Directive 91/271/EECas the organic

biodegradable load having a five-day

biochemical oxygen demand (BOD5) of 60g of

oxygen per day.
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Determination of the pollution load in waste

water expresed as population equivalent (PE)

Site works48 h:

Meauserment of flow every 15 minutes

Sampling every 15 minutes to prepare 2 hcomposite samples

Meauserment of temperature every 2 h


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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)


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Population Equivalents cont.

For 100 gpcd and consider for one person:

BOD 0.17lb

100 gal

1

8.34lb

106

gal m g

L

BOD 204 m g

L

SS 0 . 2 l b

100 gal

1

8.34lb

106

gal m g

L

SS 240 m g

L


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Population Equivalents cont.

Used to

Establish population equivalency of an industrial

waste.

Establish charge for treating industrial waste basedon BOD or SS rather than flow.


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Find the BOD and flow equivalent for an industria l w

with the fol lowing characteristics:

Q 0.1 MGDMGDMGD BOD 450mg

L

Flow: 0.1MGD

100 gal

person day

1000peoplepeoplepeople

BOD: 0.1 MGD 450 mg

L

8.34lb

MGDmg

L

0.17lb BOD

person day

2208peoplepeoplepeople

BOD equivalent is 2.2 time s greater than flow equiva


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Summary

Domestic wastewater is a well balanced, nutrient richmedium 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

i N d P

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Loading s Calculations by Dr. Ghaida Abu Rumman en (1)