CEE 421, Lecture #1
Municipal WW Management Systems
Sources of
Wastewater
Transmission
and Pumping
Processing at
the Source
Treatment
Wastewater
Collection
Reuse/Disposal
Elements of a WW Mgmt. System
Element
Description
Sources
Sources of WW in a community, such as
residences, commercial est., and industries
Facilities for pretreatment or flow
equalization of WW before it is discharged
to a collection system
Facilities for collection of WW from
individual sources in a community
Facilities to pump and transport collected
WW to processing and treatment sites
Facilities for treatment of wastewater
Processing at the
source
Collection
Transmission
Treatment
Reuse/Disposal
Facilities for reuse and disposal of treated
effluent and residual solids resulting from
treatment
1972: Federal Water Pollution Control Act
 PL 92-500
subsequently amended and now
called the Clean Water Act
– established water quality goals “fishable &
swimmable” and timetable
– established National Pollution Discharge
Elimination System (NPDES)
– construction grants for WW treatment
 required
secondary treatment (30/30)
– 30 mg/L BOD5
– 30 mg/L TSS
Conventional WW Treatment
Preliminary
Treatment
Secondary
Sedimentation
Primary
Sedimentation
Biological Process
Sludge
Disinfection
Sludge
TYPICAL AERIAL VIEW
OF A WASTEWATER
TREATMENT
PLANT
Wastewater Treatment
 Primary

– Removes Solids
Physical Operations – Screening , Sedimentation
 Secondary

Biological and Chemical Operations
 Tertiary

– Removes Organics
– Removes Nutrients
Biological and Chemical Operations
Wastewater Characteristics (Table 3-1)
 Physical
– Temperature, Odor, Taste, Solids
 Chemical
– Organics, Inorganics
 Biological
– Animals, Plants, Microorganisms
Typical WW Characteristics
Parameter
Conc.
BOD
TSS
COD
Ammonia
TOC
Chloride
250 mg/L
250 mg/L
500 mg/L
30 mg/L
100 mg/L
+ 50 mg/L
Solids: significance
 TDS:
used as a measure of inorganic salt
content in drinking waters and natural
waters
 TSS: used to assess clarifier performance
 VSS: used to estimate bacterial populations
in wastewater treatment systems
Solids Analysis
Total Solids
TS
Filtration
filtrate
TDS
TSS
retained matter
Total Dissolved Solids
Total Suspended Solids
ignition
FSS
VSS
Fixed S.S.
Volatile S.S.
ODORS
 Gases
produced by decomposition of
organic matter (Hydrogen Sulfide)
 Effect of odors: psychological stress,
nausea, vomiting, headaches, poor appetite,
deterioration of community, lower socioeconomic status etc.
 Classification of odors: See Table 3-5
Table 3-5 Odorous Compounds
Compound
Ammonia
Diamines
Hydrogen Sulfide
Mercaptans
Organic Sulfides
Skatole
Amines
Odor Quality
Decayed Flesh
Rotten Eggs
Decayed Cabbage, Skunk
Rotten Cabbage
Fecal Matter
Fishy
Odor Characterization and Measurement
 Factors:
Intensity, Character, Hedonics,
Detectability
 Methods: Sensory Method –Olfactometer
(Human Errors), Electronic Nose
 TON- Threshold Odor Number
 MDTOC – Minimum Detectable Threshold
Odor Concentration
Temperature

Higher in wastewater than waster supply
 Mean
annual temperature 10-21.1oC
 Effects
reaction rates, chemical reactions,
suitability of the water for beneficial reuse,
solubility
Chemical Characteristics
 Organics
and Inorganics
Organic Matter 75% of Suspended Solids and
40% of the filterable solids are organic in nature
 Principal groups – proteins, carbohydrates, fats
and oils, surfactants, VOCs, Pesticides
 Priority Pollutants – 129 Compounds controlled
by USEPA

Oxygen Demand
 It
is a measure of the amount of “reduced”
organic matter in a water
 Relates to oxygen consumption in a river or
lake as a result of a pollution discharge
 Measured in several ways
– BOD - Biochemical Oxygen Demand
– COD - Chemical Oxygen Demand
– ThOD - Theoretical Oxygen Demand
ThOD
This is the total amount of oxygen required to completely oxidize a
known compound to CO2 and H2O. It is a theoretical calculation
that depends on simple stoichiometric principles. It can only be
calculated on compounds of known composition.
C6H12O6 + 6O2 = 6CO2 + 6H2O
If you have 100 mg/L of Glucose what is the ThOD in mg/L ?
BOD: A Bioassay
Briefly, the BOD test employs a
bacterial seed to catalyze the
oxidation of 300 mL of full-strength or
diluted wastewater. The strength of
the un-diluted wastewater is then
determined from the dilution factor
and the difference between the initial
D.O. and the final D.O.
BODt  DOi  DO f
BOD
Bottle
BOD with dilution
When BOD>8mg/L
- DOf
DO
i
BOD t =
 Vs 


 Vb 
Where
BODt =
DOi =
[mg/L]
DOf =
Vb
=
Vs
=
biochemical oxygen demand at t days, [mg/L]
initial dissolved oxygen in the sample bottle,
final dissolved oxygen in the sample bottle, [mg/L]
sample bottle volume, usually 300 or 250 mL, [mL]
sample volume, [mL]
BOD - Oxygen Consumption
y
NBOD
or
BOD
(mg/L)
CBOD
Time
L=oxidizable carbonaceous material remaining to be oxidized
BODt  yt  Lo  Lt
L or BOD remaining
BOD - loss of biodegradable
organic matter (oxygen demand)
BOD
Bottle
Lo
Lt
Lo-Lt = BODt
Time
BOD
Bottle
BOD
Bottle
BOD
Bottle
BOD
Bottle
BOD Modeling
"L" is modelled as a simple 1st order decay:
Which leads to:
L  Lo e
And combining with:
We get:
dL
  k1 L
dt
 k1t
BODt  yt  Lo  Lt
BODt  yt  Lo (1  e  k1t )
Temperature Effects
Temperature Dependence

Chemist's Approach: Arrhenius Equation
d (ln k )
Ea

dTa
RTa2
kTa  k293o K e

Ea ( Ta 293)/ RTa 293
Engineer's Approach:
k T  k 20o C
T  20o C
NBOD
Nitrogeneous BOD (NBOD)

2
NH3  15
. O2 
 NO  H2 O  H
Nitrosomonas

1
Nitrobacter
NO  O2  NO3
2

2
2 moles oxygen/1 mole of ammonia
4.57 grams oxygen/gram ammonia-nitrogen
Like CBOD, the NBOD can be modeled as a simple 1st
order decay:
N
dL
N
 k N L
dt
COD: A chemical test
The chemical oxygen demand
(COD) of a waste is measured in
terms of the amount of potassium
dichromate (K2Cr2O7) reduced by the
sample during 2 hr of reflux in a
medium of boiling, 50% H2SO4 and in
the presence of a Ag2SO4 catalyst.
COD (cont.)
The stoichiometry of the reaction between
dichromate and organic matter is:
2
7

Cn Ha Ob  Cr2 O  8H  nCO2  2 Cr
3
a

  4    H2 O

2
2n a b

 
3 6 3
• COD test is faster than BOD analysis: used for quick
assessment of wastewater strength and treatment
performance
• Like the BOD, it does not measure oxidant demand due to
nitrogeneous species
• It does not distinguish between biodegradable and nonbiodegradable organic matter. As a result COD's are
Where:
Organic Content
 TOC:
total organic carbon
– measured with a TOC analyzer
– related to oxygen demand, but does not reflect
the oxidation state of the organic matter
 other
group parameters
– oil & grease
 specific
organic compounds
Organic Carbon Fractions
Total Carbon (TC)
|
.
|
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Inorganic Carbon (IC)
Total Organic Carbon (TOC)
|
|
.
|
|
|
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Purgeable Non-Purgeable
Purgeable Organic Non-purgeable Organic
(Dissolved) (Particulate)
Carbon (POC)
Carbon (NPOC)
|
.
|
|
Particulate
Dissolved
(PtOC)
(DOC)
TOC
Total organic carbon analysis is a determination of
organic carbon in a sample regardless of its oxidation state or
biodegradability. Other measures of total organic matter (e.g.,
COD, BOD) may respond differently to solutions of equal
carbon concentration depending on the oxygen content or the
bidegradation kinetics. For the measurement of total organic
carbon, the sample is exposed to an oxidizing environment
often at very high temperatures. With complete oxidation all
carbon is converted to carbon dioxide and swept into a detector
by the carrier gas. The oxidation process is based on the
following stoichiometry:
b d
b
c
Ca Hb N c Od  (a   )O2  aCO2  H2 O  N 2
4 2
2
2
TOC - Pyrolysis Instrument
Syringe
Sample Inlet
Furnace
CO2 Detector
Condensor
O2
Recorder
TOC - UV/persulfate Instrument
Syringe
Sample
Inlet
CO2 Detector
Recorder
Condensor
UV Reactor
O2
Persulfate
Solution
TOC - The CO2 Detector
Sensing
Cell
Chopper
Reference
IR
Source
Sample
In
Out
A non-dispersive infra-red analyzer (NDIR)
Demodulator
Amplifier