Philadelphia University
Faculty of Engineering
Department of Civil Engineering
First Semester, 2013/2014
ENVIRONMENTAL
ENGINEERING
343
Lecture 5:
Water Quality
WATER QUALITY REQUIREMENTS
Water quality parameters - qualitatively reflect
the effect of various impurities on the intended
use of water
 Standard Methods for the Examination of Water
and Wastewater- Standard analytical test
procedures which provide quantitative
measurements of these parameters

WATER QUALITY REQUIREMENTS
Water quality parameters - qualitatively reflect
the effect of various impurities on the intended
use of water
 Standard Methods for the Examination of Water
and Wastewater- Standard analytical test
procedures which provide quantitative
measurements of these parameters

WATER QUALITY REQUIREMENTS
Water quality requirements vary according to
proposed use of the water. Water unsuitable for
one use may be satisfactory for another. These
are set by the user. It represents a known or
assume need and are based on prior experience of
the user.
Water Quality Standards are set by a
governmental agency and represent a statutory
requirement
WATER QUALITY REQUIREMENTS



In-Stream standards – Streams have minimum
quality standards based on its use. Wastewater
discharged from human activities together with the
geology and natural characteristics of the watershed.
Potable-water Standards – EPA ; WHO addresses
turbidity, SS taste, odor, moderate dissolved inorganic;
absence of organics, toxic substances and pathogens
Wastewater effluent standards- e.g. EPA standards
for the discharge of wastewater. – require secondary
treatment. Industrial wastewater must be pretreated
to become compatible with receiving domestic WW.
TOPICS

Physical water-quality parameters

Chemical water-quality parameters

Biological water-quality parameters

Water quality requirements
PHYSICAL WATER-QUALITY PARAMETERS
Parameters:
• Suspended Solids
• Turbidity
• Colour
• Taste
• Odor
• Temperature
SOLIDS(IMPURITIES) TYPES OF SOLIDS
1.
2.
3.
Dissolved Solids (in Liquid) cannot be removed from
liquid without accomplishing a phase change such
as distillation, precipitation, adsorption, extraction
or high pressure membrane
Suspended solids (filterable solids) those solids that
can be filtered by a glass fiber filter disc can be
removed from water by physical methods such as
sedimentation, filtration and centrifugation.
Colloidal particles
1.
2.
3.
Size in range between dissolved substances and
suspended particles
Can be removed by high-force centrifugation or
filtration – very small pore size
Measured by turbidity
1.0 SUSPENDED SOLIDS
Sources of Suspended Solids
Suspended Solids
Inorganic
-Clay
-Silt
Source – Surface
Waters; Domestic
WW; Industrial
WW
Organic
-Plant Fiber
-Biological Solids (Agal
Cells; Bacteria;)
Source – Surface Waters;
Domestic WW; Industrial
WW
Immiscible liquids
-Oils
-Grease
Source- Surface
waters; Domestic WW
and Industrial WW
Seldom found in groundwaters due to the
natural filtering capacity of soils
SUSPENDED- LARGER THAN MOLECULAR SIZE SUPPORTED BY BUOYANT AND
VISCOUS FORCES
DISSOLVED-MOLECULES OR IONS HELD BY MOLECULAR STRUCTURE OF WATER
COLLOIDS- TECHNICALLY SUSPENDED BUT EXHIBITS CHARACTERISTICS OF
DISSOLVED
Difference Between Dissolved, Suspensions and
Colloidal Solutions
Property
Particle size
Dissolved
Less than 10
Suspensions
-6
Greater than 10
mm
3
mm
Invisible to naked eye not
Colloidal Solutions
-
Between 10
-6
and 10
-3
mm
Invisible to naked eye.
Visibility of
visible under powerful
Easily visible
Visible under powerful
particles
microscope
microscope.
Sedimentation of
Settle down due
Settle down under high
to gravity
centrifugation
Do not settle down
particles
Filtration through
Residue is
No residue is formed
filter power
No residue is formed
formed
Water Pollution – The presence in water of
impurities in such quantity and of such nature as to
impair the use of the water for a stated purpose
Water quality is predicted on the intended use
SOLID
Measured in mg/L
 Sources (s):

Inorganic compounds such as clay, sand
 Organic compounds such plant fibre, human wast


Effects (s):
Aesthetics
 Adsorption point/centre for chemical and microorganism
 Health aspect

2- TURBIDITY
Turbidity: The presence of suspended material such
as clay, silt, finely divided organic mater, and other
particulate material in water
The unit of measure is a Turbidity Unit (TU) or
Nephlometric Turbidity Unit (NTU)
It’s a measure of the cloudiness
River values range from 2 to 200mg/L of SiO2
The EU drinking water upper limit is 10mg/L with a
guideline value of 1mg/L
3-COLOR

Color in water is caused by dissolved minerals,
dyes or humic acids (decomposition of lignin)
from plants.
Apparent Color: Color that is partly due to
suspended solids (SS)
 True Color (water treatment): Color that is
contributed by dissolved solids (DS) after removal of
SS


Color itself is not usually undesirable from the
stand point of health- it indicates that water
needs appropriate treatment
4- ODOR
Many organic and inorganic chemicals are
odorous including algae and other organisms
 H2S – hydrogen sulfide sometimes present in
ground water and wastewater.
 Threshold odor is determined by diluting a
sample with odor –free water until the last
perceptible odor is detectable (dilution factor)

5-TASTE

Like odor, may be due to decaying microorganisms or algae or due to high conc. of salts
such as Ca & Mg
6- TEMPERATURE


One of the most important parameters in natural
surface waters.
It influences the number and type of microorganism
species present and their rate of activities;
affect most chemical reactions;
 affect solubility of gases e.g oxygen decrease with increase
temp. Conc of O2 around 8mg/L @ 25 degree Celsius



In WWTP, T above 36oC, the aerobic MO population
tends to be less effective as WW purifiers
In rivers, as increased water temp reduces the
amount of oxygen in water, thereby making river less
desirable for fish, particularly salmonoids.
CHEMICAL WATER QUALITY PARAMETERS
Parameters






TDS
Alkalinity
Hardness
Metals
Nutrients
pH
1- ALKALINITY
Alkalinity measures the buffering capacity of the
water against changes in pH; measuring the
amount of acid needed to lower the pH in a water
sample to a specific endpoint (4.5).
 Water that has a high alkalinity can accept large
doses of acids or bases without altering the pH
significantly.
 Waters with low alkalinity, such as rainwater or
distilled water, can experience a drop in the pH
with only a minor addition of an acid or base.
 Alkalinity is expressed as mg (CaCO3)/L

ALKALINITY
In water the only significant contribution to
alkalinity are carbonate species and free H+ and
OH_
 Acid base reaction
H2CO3
H+ +HCO3

HCO3-
H+ + CO32-
2- HARDNESS
Measure of “multivalent” cations in water such as
Ca2+,Mg2+, Fe2+, Mn3+
 Ca2+ and Mn2+are very important


Source (s):


natural mineral on earth
effect (s):
excessive soap usage (a waste !)
 precipitate form on hardware
 precipitate in pipe – temperature and pH increases

HARDNESS
Total Hardness
 The sum of the divalent metallic cations (Ca & Mg).
These cations reacts with soap to form precipitate and
with other ions present in water to form scale in
boilers.
 Measured as mg CaCO3/L
 Two kinds of hardness:
carbonate hardness; temporary in characteristics,
precipitated through boiling
 non-carbonate hardness- chloride and sulfate; permanent
in characteristic, eliminated through chemical softness /
ion exchange


WT goal is to provide water with a hardness of less in
the range of 75 to 120mg/L as CaCO3 by using
softener
3-NUTRIENTS:
Two nutrients are essential for the growth of organisms:
 Nitrogen
 Phosphorus
 Both are indictors of water pollution
I-Nitrogen (N)
Source (s)
 Elements for protein, chlorophyll and biological compounds
 Decomposition of compounds
 animals and human wastes, chemicals (fertilizers)
Effect (s)
 NO3- poisoning to human specially babies below than
6month old and animals
 NO3-> NO2-(in acidic condition) – will substitute O2 in blood
vessel
NUTRIENTS
Nitrogen; Exist in a form of “inorganic”, and “organic
nitrogen
Measured by TKN “total Kjeldahl Nitrogen; is a
measure of the total organic and ammonia nitrogen.
NUTRIENTS
II-Phosphorus (P)
Exist in a form of “inorganic”, and “organic
phosphate”.
Source (s):
readily present in soil
 fertilizers
 human wastes (“organic phosphate”
 domestic wastes (element in detergent)

effects (s)
Cellular activity and aquatic plants
 > 0.2 mg/L – disturb coagulation processes in water
treatment plants

4-IONS – ANIONS AND CATIONS
Major Ions (conc. In mg/L) such as Ca, Mg, Na,
K, SO2, Cl, NO3, HCO3
 Minor Ions: Conc in µg/L such as Al, Cu, Fe,
Mn
Source (s):
 Minerals readily available from nature
 Effect (s):
 Colour, odour, taste and turbidity
 Deteriorate health (at high concentration)

4-IONS – ANIONS AND CATIONS
Metals – non toxic and toxic
Heavy metals: such as As, Ba, Cd, Cr, Pb, Hg, Se, Ag
Source (s)
 human activities such as mining and industries
Effect (s):
 dangerous disease such as cancer, abortion and
deformation in newborn baby
5- PH
The negative log of the hydrogen ion concentration
 pH of most mineral waters is 6 to 9
 If pH is out side the range 6 – 9, it might kill off the
active microbiological population including the
aquatics organisms
 pH is important in ensuring proper chemical
treatment

ELECTRICAL CONDUCTIVITY/
CONDUCTIVITY
It is a measure of the ability of an aqueous
solution to carry an electric current by the
movement of ions.
 The higher the numbers of ions, the higher
magnitude of conductivity
 Pure water has 0.05µS/cm (microsiemens/cm)
 Sea water has about 40000 µS/cm
 Groundwater 200-1500

6-DISSOLVED OXYGEN
One of the most important measures of water quality
is dissolved oxygen. Oxygen, although poorly soluble in
water, is fundamental to aquatic life. Without free
dissolved oxygen, streams and lakes become
uninhabitable to aerobic organisms, including fish and
most invertebrates.
It is found that the concentration of DISSOLVED
OXYGEN in water is SMALL
Dissolved oxygen is inversely proportional to
temperature, and
the maximum amount of oxygen that can be dissolved
in water at 0°C is 14.6 mg/L to 7.6 at 30C.
DISSOLVED OXYGEN

Dissolved oxygen in water is consumed by the oxidation
of dissolved ammonia (NH3)and ammonium ion (NH4+)to
form the nitrate ion (NO3⎯).
NH3(aq) + 2O2(aq) + OH


NO3-(aq) + 2H2O(aq)
The most common substance oxidized by oxygen in water
is ORGANIC MATTER OF BIOLOGICAL ORIGIN
Such organic matter (such as dead plant material
like polymerized carbohydrate below), is oxidised
by dissolved oxygen.

e.g. CH2O+O2(aq)
CO2(g) + H2O(aq)
DISSOLVED OXYGEN

Under oxygen free (anaerobic) conditions
dissolved organic matter will decompose if
appropriate bacteria are present:

2CH2O
CH4+ CO2
Such anaerobic conditions are common in
SWAMPS and at the bottom of deep lakes
 The Methane (CH4) produced in this process
bubbles up towards the surface of the swamps
and is the reason that methane used to be known
as ‘marsh 'or ‘swamp 'gas

ORGANIC SUBSTANCES
The main element of organic compounds is Carbon.
 Organic substances may be

Natural occurring organic substances includes protein,
lipids, carbohydrates and plant pigments
 Synthetic organic chemicals
 Pesticides and agrochemicals
 Surface active agent including emulsifier, wetting agent,
foams, detergents
 Halogenated hydrocarbons ( CHCl3, CHBr3, CHCl2Br, etc


Over 120 toxic organic compounds listed on the
USEPA Priority Pollutant List including pesticides
and solvents
ANALYSIS OF ORGANIC SUBSTANCES
Various parameters are used as a measure of the
organic strength of wastewater:
BOD –Biochemical oxygen demand
 COD –Chemical oxygen demand
 TOC –Total organic carbon
 VSS –Volatile suspended solid

BIOCHEMICAL OXYGEN DEMAND (BOD)
The quantity of oxygen utilized by a mixed
population of micro organisms to biologically
degrade the organic matter in the wastewater
under aerobic condition.
BOD is the most important parameter in water
pollution control.
it is used a measure of organic pollution as a basis
for estimating the oxygen
Needed for biological processes, as and indicator
of process performance
Expressed in milligrams of oxygen required per
liter of wastewater (mg/L).
BIOCHEMICAL OXYGEN DEMAND
BOD : BOD5: is the amount of dissolved oxygen
used up from the water by microorganisms as they
break down organic material at 20C over a 5-day
periods.
BOD5 for Rivers if > 5 mg/L, they considered polluted
 BOD For MWW range 150-1000mg/L

CHEMICAL OXYGEN DEMAND
(COD)
COD





Determine the amount of oxygen needed to oxidize
the organics in a water or wastewater using a strong
oxidizing chemical agent- Potassium dichromate
rather than using micro-organisms as in BOD
It measures the total organic carbon with the
exception of some aromatics such as benzene which
are not oxidized in the reaction.
Indirectly measure amount of organic matter in the
water sample
Faster determination of oxygen demand in a water
sample, than BOD
It takes shorter time ( 2hrs) compared to 5 days for
BOD5
The EU upper limit of 125mg/L for treated
wastewaters prior to discharge to rivers
RELATION BETWEEN COD AND BOD
COD > BOD
 COD ~ ultimate BOD
 COD/BOD ~ 2, biodegradable organic
 COD >> BOD, non-biodegradable organic

TOTAL
ORGANIC CARBON- TOC
TOC- : measures all carbon as CO2 in mg/L
 Inorganic carbon ( HCO3, CO2, CO3, etc) must be
removed prior test by acidifying and aerating the
sample.
 Theoretically the COD is 2.66 times greater than
TOC

BIOLOGICAL WATER-QUALITY PARAMETERS
the three most significant microbial groups are the
bacteria, fungi, and protozoa.
Bacteria have the primary role of decomposing
wastewater compounds, forming settleable solids,
and at times are the source of operational
problems.
Fungi are significant since many operational
problems are caused by members of this group.
Protozoa are microorganisms that play a key role
as predators and help control the bacterial
populations.
COMPOSITION OF WW
RECALL
solids
99.9 % Water
0.1% Solids
Organic
(70%)
Solids are divided into
Organic and inorganic
Suspended
Organics
(Colloidal –
protein)
Secondary
Treatment
Dissolved Organics
and Suspended
Inorganic
(30%)
Dissolved
Organics
(Carbohydrate
s)
Suspended
Inorganics
(Grit)
Primary
Treatment
60% SS; 30%
Dissolved
Inorganics
(metals,
salts,P,N)
Tertiary
Treatmen
t
Composition of WW
Suspended
Solids
Soluble organics
Body waste, food
waste rags, paper,
biological cells
Protein (4060%) – amino
acids
Pathogens
Biodegradable Organics
Carbohydrates 2550% - sugars
starch, cellulose
Bacteria, virus
etc.
Lipids (10%)fats, oils and
grease
Contain Carbon – exert an oxygen
demand
TYPICAL COMPOSITION OF UNTREATED DOMESTIC
WASTEWATER [METCALF AND EDDY, 1991].
Concentration (mg/lt.)
Contaminants
Weak
Medium
Strong
Total Solids (TS)
350
720
1200
Total Dissolved Solid (TDS)
250
500
850
Suspended Solid (SS)
100
220
350
Settleable Solid
5
10
20
Biological Oxygen Demand (BOD5)
110
220
400
Total Organic Carbon (TOC)
80
160
290
Chemical Oxygen Demand (COD)
250
500
1000
Nitrogen (total as N)
20
40
85
Organic
8
15
35
Free ammonia
12
25
50
Nitrites
0
0
0
Nitrates
0
0
0
Phosphorous (total as P)
4
8
15
Chlorides
30
50
100
Sulfate
20
30
50
Alkalinity (as CaCO3)
50
100
200
Grease
50
100
150
Total coliform (no/100 ml)
106-107
107-108
107-109