chapter 1: introduction - memorial university of …baiyu/engi 9605...
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ENGI 9605 – Advanced Wastewater Treatment
Winter 2011Faculty of Engineering & Applied Science
Chapter 1:
Introduction
1
(1) Source of wastewater flows
Domestic discharges from residential,
commercial, and institutional facilities
Industrial discharges from different
industries
Infiltration groundwater seepage that enters
sanitary sewer through cracks in pipe joints and
manholes
Inflow water that enters through drains
which is relatively unpolluted source of water
Storm water runoff from rain
Municipal wastewater 2
1.1 Wastewater flows
3
(Viessman et al., Water supply and pollution control, 2009)
4
Pollutants in domestic wastewater
(Tchobanoglous et al., Wastewater Engineering, 2003)
5
(2) Wastewater sewer system
receive liquid wastes
from the city buildings,
houses, institutions, and
other entities) and
transport them to the
treatment plant
consists of the
collection pipes and
appurtenances, such as
manholes, pumping
stations, and others
6
Types of sewer systems
Sanitary Sewer carries domestic, industrial, and
infiltration/inflow
Storm Sewer carries storm water
Combined Sewer carries both
Sources of municipal wastewater in relation to
collector sewers and treatment (Hammer, Water and Wastewater Technology, 2004 )7
Protect surface-water quality
Protect public health
Meet legal requirements
(1) Why treat wastewater?
How to evaluate water quality?
Obtain wastewater characteristics
Compare them with water quality standards
8
1.2 Wastewater characteristics
(2) Physical characteristics
Total solids (TS) residue left in a drying dish after
evaporation of a sample of water or wastewater and
subsequent drying in an oven
Solids
(Viessman et al., Water supply and pollution control, 2009)
9
Total suspended solids (TSS) nonfilterable residue
that is retained on a glass-fiber disk after filtration of a
sample of water or wastewater
Total dissolved solids (TDS) = TS - TSS
(Viessman et al., Water supply and pollution control, 2009)
10
important in
assessing the
effectiveness of
treatment processes
(e.g., secondary
sedimentation,
effluent filtration,
effluent disinfection)
Particle size distribution
(Tchobanoglous et al., Wastewater Engineering, 2003)
Analytical techniques
applicable to particle
size analysis of
wastewater
contaminants 11
Turbidity determination
Nephelometer scattering of light from particles
Turbidimeter interference to light passage in a
straight line
NTU is commonly used
Samples with turbidities > 40 NTU must be diluted
Turbidity Result of interference of passage of
light through the water containing suspended materials
normally used for process control
12
Schematic diagram of a turbidimeter and a nephelometer
(Zhang, Chemistry for Environmental Engineering, 2005 )
13
Apparent color caused by suspended matter
determined on the sample “as is”
True color caused by colloidal vegetable or
organic extracts remove suspended matter by
centrifugation then determine color of clarified liquid
1 standard unit of color
= 1 mg/L of Pt (as K2PtCl6)
Nessler tubes 0 ~ 70 color units
Color-comparison tubes
(Nessler tubes)
Color used along with composition and concentration
in describe wastewater refers to the age of wastewater
(Zhang, Chemistry for Environmental Engineering, 2005 )14
Temperature has important effects on chemical
reactions and reaction rates, aquatic life and the suitability
of the water for beneficial uses
Temperature of wastewater normally higher than
that of the local water supply
Without treatment river and lake water that has
been artificially warmed can be considered to have
undergone Thermal Pollution
Gas solubility decreases with increasing temperature
warm water contains less oxygen than cold water
Optimum temperature for biological activity 25 ºC
to 35 ºC15
Estimation of temperature effects on reaction rates
Thus, if we know θ and K1 at temperature T1 we
can get K2 at temperature T2 16
K = A RTEa
e/
K1 = A 1/ RTEae
K2 = A 2/ RTEae
Ea Activation energy; A preexponential factor
R gas constant = 8.31 J/mol/K
(2) Inorganic chemical characteristics
When placed in water, most inorganic
compounds dissociate into electrically charged
atoms referred to as ions atoms linked in
ionic bond
Can be classified into two
Metal (e.g., Pb2+, Hg2+, Cu2+)
Non-metal (e.g., H+,OH-, HCO3-, CO3
2-, Cl-, NO3-)
17
pH and acidity/alkalinity
pH condition of a solution related to [H+]
pH = - log[H+] determined by a pH meter
Acidity/Alkalinity the ability of natural water to
neutralize base/acid determined from a titration
Acidity = (Volume need to reach end point) ×(concentration of the strong base)
Mineral acidity = [H+] + [H2CO3] [OH-] titration
to pH = 3.7 (methyl orange end point)
Total acidity = [H+] + 2[H2CO3] + [HCO3-] [OH-]
titration to pH = 8.3 (phenolphthalein end point)
18
Alkalinity = (Volume need to reach end point) ×(concentration of the strong acid) => titrated with 0.02
N H2SO4
Phenolphthalein alkalinity (mg/L) = [OH-] + [CO32-] [H+]
titration to pH = 8.3
Total Alkalinity = Bromcresol-Green alkalinity (mg/L) =
[HCO3-] + [OH-] + 2 [CO3
2-] [H+] titration to pH = 4.5
End points for Acidity/Alkalinity titration
(Zhang, Chemistry for Environmental Engineering, 2005 )
19
Nitrogen and phosphorus
Known as nutrients or biostimulants essential to the
growth of microorganisms, plants and animals
Data required to evaluate the treatability of wastewater
by biological processes
Form of nitrogen
Form of phosphorus PO43-, HPO4
2-, H2PO4-, H3PO4
(Tchobanoglous et al., Wastewater Engineering, 2003)
20
Dissolved oxygen
The concentration of DO in water is small
precarious from ecological point of view
The dissolution process
The equilibrium constant the Henry’s Law
constant KH
)(dissolvedO(gas)O 22
2O
2H
PressurePartial
)(dissolvedOK
21
The amount of a gas that will dissolve in a solution is
directly proportional to the partial pressure of that gas in
contact with the solvent.
Henry’s law constant Linkage of solubility and
vapor pressure
Henry's Law
Pi = partial pressure of a contaminant i in the gas (atm)
Cw = concentration of the contaminant i in the solution (mol/m3)
KH = Henry's law constant (atm m3/mol)
KH =w
i
C
P
22
Chlorine (Cl2) used for disinfection of water
supplies and wastewater effluent to prevent water-borne
diseases
Free chlorine residuals Cl2 + HOCl + OCl−
Combined chlorine residuals NH2Cl + NHCl2 +
NCl3
Total chlorine residuals = free chlorine residuals +
combined chlorine residuals
Measurement of total chlorine residuals
Cl2 + 2 I− ==> I2 +2 Cl−
I2 + starch ==> blue color
I2 + 2Na2S2O3 ==> 2Na2S4O6 + 2NaI
Residual chlorine
23
Metals
Chemical Adverse effect
Antimony Blood disorders
Arsenic Skin damage, cancer
Barium Increased blood pressure
Beryllium Intestinal lesions
Cadmium Kidney damage
Chromium Dermatitis
Copper Gastrointestinal, liver or kidney damage
Cyanide Nervous system impairment
Lead Impaired mental development
Mercury Kidney damage, birth defects
Selenium Hair loss, circulatory problems
Sodium High blood pressure
Silver Thallium Blood, kidney, liver, intestinal effects
Iron/ Manganese Stains laundry and fixtures 24
• Light source (usually
Hollow Cathode Lamp)
• Atomizing cell (Flame
or Furnace)
• Monochromator
• Detector and read out
device
AAS
Hardness caused mainly by divalent metallic
cations (e.g. Ca2+ , Mg2+ , Sr2+ , Fe2+ , Mn2+)
determined by EDTA titrimetric method
EDTA = ethylenediaminetetraacetic acid (H4Y)
M2+ + EDTA [M-EDTA]complex
Total hardness = Ca hardness + Mg hardness (in
most cases)
(Zhang, Chemistry for Environmental Engineering, 2005 )
Hardness
26
(3) Organic chemical characteristics
Organic compounds composed of a combination
of carbon, hydrogen, and oxygen, together with
nitrogen in some cases
Organic matter in wastewater a very large
number of different synthetic organic molecules,
with structures ranging from simple to extremely
complex
proteins 46-60%
carbohydrates 25-50%
oils and fats 8-12%
urea 27
Organic matter divided into biodegradable
organics and non-biodegradable organics
biodegradable organics food to microorganism
fast and easily oxidized by microorganism (e.g.,
starch, fat protein, alcohol)
Non-biodegradable organics difficult to be
biodegraded or toxic to microorganisms (e.g.,
pesticide, cellulose, phenol)
Organic matter characterization in wastewater
Aggregate organic constituents (e.g., BOD, COD
and TOC)
Individual organic compounds (e.g., VOCs,
pesticides, emerging organic compounds) 28
BOD (Biochemical oxygen demand)
BOD amount of O2 required by bacteria in the
biochemical oxidation of organic matter
High BOD value = high organic-matter concentration
= poor water quality
– Decomposition of organic matter is a slow process
20 daysdecompose 95 to 99%
of organic matter
5 days decompose 60 to 70%
of organic matter
BOD5 the most widely used parameter to measure
organic matter in both wastewater and surface water29
Organic Matter – Classification
(Viessman et al., Water supply and pollution control, 2009)
BOD test on wastewater sample30
(Viessman et al., Water supply and pollution control, 2009)
BOD test on polluted surface water sample31
(Viessman et al., Water supply and pollution control, 2009)
BOD reaction curve showing the carbonaceous oxygen demand
(CBOD) and nitrogenous oxygen demand (NBOD) 32
Typical values of K for various water The equation for calculating BOD from a seeded
laboratory test is expressed as:
P
fBBDDBOD
)()( 2121
Where
D1 = DO of diluted seeded wastewater immediately after
preparation, mg/L
D2= DO of wastewater after incubation, mg/L
B1 = DO of diluted seed sample wastewater immediately
after preparation, mg/L
B2 = DO of seed sample after incubation, mg/L
f = ratio of seed volume in seeded wastewater test to
seed volume in BOD test on seed
P = volume of wastewater/volume of dilution water plus
wastewater33
Ultimate BOD (L0)
BODt = L (1 – e-kt)
Where
BODt = biochemical oxygen demand at time t, mg/L
L = ultimate BOD, mg/L
k = deoxygenation rate constants, day-1
The carbonaceous oxygen demand curve can be
expressed mathematically as:
If the sample is unneeded, the relationship is:
P
DDBOD 21
34
Where
• K2 = reaction rate constant at temperature T2, per day
• K1 = reaction rate constant at temperature T1, per day
• θ = temperature coefficient = 1.047
35
Water type K, per day
Tap water 0.04
Surface water 0.04 – 0.1
Raw sewage 0.15 – 0.30
Well-treated sewage 0.05 – 0.10
The reaction rate are temperature dependent:
)12(
12
TTKK
Example 1-1: A seeded BOD analysis was conducted on
a food-processing wastewater sample. Ten ml portions
were used in preparing the 300-ml bottles to determine
the DO of the aged, settled wastewater seed at 20ºC. The
seeded sample BOD bottles contained 2.7 ml of food-
processing wastewater and 1.0 ml of seed wastewater.
The results of this series of test bottles are listed below.
Seed Tests Sample Tests
Time B1 B2 D1 D2
(days) (mg/l) (mg/l) (mg/l) (mg/l)
0 7.8 - 8.1 -
1.0 7.8 6.9 8.1 5.6
2.0 7.8 6.6 8.1 4.3
3.0 7.8 6.3 8.1 3.6
4.0 7.8 5.8 8.1 3.0
5.0 7.8 5.7 8.1 2.5
6.0 7.8 5.3 8.1 2.0
7.0 7.8 5.4 8.1 1.8
(1) Calculate BOD5 at 20ºC
(2) Calculate BOD10 at 20ºC
if assuming a k of 0.15
(3) Calculate BOD5 at 30ºC
36
COD (Chemical oxygen demand)
COD to measure the oxygen equivalent of the organicmaterial in wastewater that can be fully oxidized chemically
The basis for the COD test nearly all organic compounds canbe fully oxidized to carbon dioxide with a strong oxidizing agentunder acidic conditions.
COD determination potassium permanganate (KMnO4) wasused for years potassium dichromate (K2Cr2O7) becomes themost effective oxidant now (it is relatively cheap, easy to purify,and is able to nearly completely oxidize almost all organiccompounds) need about 2.5 h to complete a COD test
CnHaObNc + d Cr2O72 + (8d+c) H+
n CO2 + [(a + 8d 3c)/2] H2O + c NH4+ + 2d Cr3+
where d = 2n/3 + a/6 c/2
37
Relationships between BOD and COD
COD > BOD? or COD = BODultimate ?
Many organic substances which are difficult to
oxidize biologically (e.g., lignin) can be oxidized
chemically
Inorganic substances that are oxidized by the
dichromate increase the apparent organic content of
the sample high COD values may occur because
of the presence of inorganic substances with which
the dichromate can react
Certain organic substances may be toxic to the
microorganisms used in the BOD test
38
TOC (Total organic carbon)
To determine the total organic carbon in an aqueous
sample an indicator of water quality or cleanliness
Measurement TOC = total carbon (TC) –
inorganic carbon (IC) done instrmentally
It takes only 5 to 10 min to complete
BOD/COD ≥ 0.5 easily treated by biological
means (biodegradable organic)
BOD/COD ≤ 0.3 have some toxic compounds
or acclimated microorganisms may required in its
stabilization (non-biodegradable organic)
39
Interrelationships between BOD, COD and TOC
Type of wastewater BOB/COD BOD/TOC
Untreated 0.3-0.8 1.2-2.0
After primary settling 0.4-0.6 0.8-1.2
Final effluent 0.1-0.3 0.2-0.5
(Tchobanoglous et al., Wastewater Engineering, 2003)
Comparison of ratios of various parameters used to
characterize wastewater
40
(4) Biological characteristics
Organisms in surface water and wastewater
bacteria, fungi, algae, protozoa, plants and animals,
and viruses
Pathogenic organisms in water and wastewater
pathogen = specific agent causing disease (special
concerns!) can be classified into four broad
categories
viruses obligate, intracellular parasites that replicate only
in living hosts’ cells
bacteria microscopic single-celled organisms that use
soluble food and are capable of self-reproduction without
sunlight
protozoa intestinal parasites that replicate in the host
helminths intestinal worms that do not multiply in the
human host41
(Shanahan, Water and Wastewater Treatment Engineering, 2005)
42
(Viessman et al., Water supply and pollution control, 2009)43
Rotaviruses Noroviruses Adenoviruses
Enteroviruses Poxviruses
Wastewater Microbial Life_Viruses
Smallest 0.01-
0.1 µm diameter
Simplest
nucleic acid +
protein coat (+
lipoprotein
envelope)
(Shanahan, Water and Wastewater Treatment Engineering, 2006 )
Escherichia Francisella Bacillus
Yersinia Vibrio Salmonella Shigella
Wastewater Microbial Life_Bacteria
0.1-10 µm diameter + prokaryotes + cellular(Shanahan, Water and Wastewater Treatment Engineering, 2006 )
46intestinal parasites that replicate in the host
(Shanahan, Water and Wastewater Treatment Engineering, 2006 )
Cryptosporidium Giardia and Cryptosporidium
Entamoeba Microsporidia Cyclospora
Wastewater Microbial Life_Protozoa
uni-cellular
flexible cell
membrane
no cell wall
most >10 µm
wide range of sizes
and shapes
(Shanahan, Water and Wastewater Treatment Engineering, 2006 )
48
a large group of
eukaryotic organisms
that includes
microorganisms such as
yeasts and molds
fungal cells have
cell walls that
contain chitin,
unlike the cell walls
of plants, which
contain cellulose
(Shanahan, Water and Wastewater Treatment Engineering, 2006 )
Three main steps
recovery and concentration
purification and separation
assay and characterization
Detection of pathogens in water and wastewater
It is often too difficult to directly monitor a specific
pathogen or virus/phage Instead, monitoring is
usually done for indicator organisms
Common indicator bacteria Coliforms
Coliform bacteria testing
Coliform group of bacteria aerobic and
facultative anaerobic, nonspore-forming,
Gram’s-stain negative rods that ferment lactose
with gas production within 48 hr of incubation at
35ºC
the more popular technique for total coliform
bacteria testing fermentation tube technique
based on gas production during the
fermentation of lauryl tryptose broth, which
contains beef extract, peptone (protein
derivatives), and lactose (milk sugar)
50
(Viessman et al., Water supply and pollution control, 2009)
Diagram of the coliform bacteria testing51
(5) Water quality standards
Federal standards
Guidelines for Canadian Drinking Water Quality
Canadian Water Quality Guidelines for the Protection of
Aquatic Life
Canadian Water Quality Guidelines for the Protection of
Agricultural Water Uses
Guidelines for Canadian Recreational Water
Standards in Newfoundland and Labrador
Guidelines for Canadian Drinking Water Quality
Standards for Bacteriological Quality of Drinking Water
Standards for Chemical and Physical Monitoring of
Drinking Water52
Guidelines for Canadian Drinking Water Quality (Health
Canada, 2008, http://www.hc-sc.gc.ca/ewh-semt/pubs/water-
eau/2010-sum_guide-res_recom/index-eng.php#a14)
(Health Canada, Guidelines for Canadian Drinking Water Quality, 2008) 53
(Health Canada, Guidelines for Canadian Drinking Water Quality, 2008)
MAC maximum
acceptable concentration
Substances in conc.
greater than the MAC
drinking water is either
capable of producing
deleterious health effects
or is aesthetically
objectionable
54
(Viessman et al., Water supply and pollution control, 2009)
US EPA
55
Guidelines for Drinking Water Quality from US EPA
(Viessman et al., Water supply and pollution control, 2009)
Continued
US EPA
56
Water-quality
Constituent
Units Canada U.S. EPA European
Union
World Health
Organization
E. coli Number/
100ml
0 Detected in <
5% of samples
0 0
Arsenic μg/l 10 10 10 10
Copper mg/l 1 1.3 2 2
Lead μg/l 10 15 10 10
TTHM μg/l 100 100 100 200/100/100/60a
Chloride μg/l 250 250 250 250
Iron μg/l 300 300 200 No guideline
Benzene μg/l 5 5 4 4
Carbon
tetrachloride
μg/l 5 5 4 4
a Chloroform/bromoform/dibromodichloromethane/bromodichlorodimethane
Comparison of standards
57