Chapter 1: Introduction - Memorial University of …baiyu/ENGI 9605 files/lecture-1-1_updated.pdfOptimum temperature for biological activity 25 ºC ... Chromium Dermatitis ... •θ=

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


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


10

important in

assessing the

effectiveness of

treatment processes

(e.g., secondary

sedimentation,

effluent filtration,

effluent disinfection)

Particle size distribution


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


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


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)


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


BOD test on wastewater sample30


BOD test on polluted surface water sample31


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


if assuming a k of 0.15


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


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


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


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


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


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


US EPA

55

Guidelines for Drinking Water Quality from US EPA


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

Documents

Chapter 1: Introduction - Memorial University of …baiyu/ENGI 9605 files/lecture-1-1_updated.pdfOptimum temperature for biological activity 25 ºC ... Chromium Dermatitis ... •θ=