Environmental Engineering presentation 2.pdf

Engineering

1. Philadelphia University
Faculty of Engineering
Department of Civil Engineering
First Semester, 2013/2014

ENVIRONMENTAL
ENGINEERING
441

Lecture 3:
Water Treatment

2. OBJECTIVES OF WATER TREATMENT

“ To remove harmful microorganisms or chemicals,
thereby preventing the spread of disease in order to
supply clean and safe water for public demand”

3. WATER SOURCE

Water source could be
» River
+» Lakes

+ Groundwater; most likely better quality than surface
water

+ Rainwater ++/ Dam

o Raw water quality varies with the source, and if
the source is surface water, the quality vary
seasonally, particularly with flooding, upland and
lowland, etc

4. Table 11.5 Typical raw water analysis

Deep well Moorland River Arid zone Brackish
Parameter water water water water well Seawater
Colour Clear Slightly yellow Turbid Turbid
Conductivity, uS/em 580 150 915 1000-7000 2250 51.000
pH 73-79 65-72 7-8 7.5-8.5 7.45 79
TDS, ppm 410 105 640 700-5000 1500 36200
Cations mg/L as CaCO;
Gre 250 30 200 250-1500 60 350
Met 75 15 75 150-500 73 1330
Nat 25 35 200 150-2000 257 10300
x 15.4 350
Mn* 0.002
Fe+ 0.06
Anions mg/L as CaCO;
cr 40 30 125 <2000 502 20500
so,” $00 15 175 <1500 162 2850
ÓN 2.05
Sin 6 10 10-20 24.5 20
HCO;~ 250 30 125 170
NO;~ 10 5 50

Adapted from LORCH, 1987

5. Table 11.7 Comparison of surface water and groundwater quality

Parameter Surface water Groundwater

‘Temperature Varies with season Relatively constant

Turbidity and suspended solids Varies and is sometimes high Usually low or nil

Mineral content Varies with soil, rainfal, effluents, etc. Relatively constant at high value

Divalent iron and manganese in solution Some Always high

Aggressive carbon dioxide None Always some

Dissolved oxygen Often near saturation, except when Usually low, requires aeration

polluted

‘Ammonia ‘Only in polluted water Levels found to be increasing

‘Hydrogen sulphide None Usually some

Silica Moderate levels

Nitrate Generally none Levels found to be increasing due to
agricultural pollution

Living organisms May have high levels Usually none

6. ‘Table 11.4 Excerpts from US primary drinking water standards

‘Contaminants Health effects MCL (mg/L)
|
Inorganic chemicals |
Cadmium Kidney 0.005
Chromium Liver/kidney, skin and digestive system o1
Copper Stomach and intestinal distress; Wilson's disease Tre
Fluoride Skeletal damage 4
Lead Central and peripheral nervous system damage; kidney; highly toxic to TT
infants and pregnant women
Mercury Kidney, nervous system 0.002
Nitrate Methanoglobinaemia, “blue-baby syndrome” 10
Nitrite Methanoglobinaemia, “blue-baby syndrome” 1
Total (nitrate and nitrate) Not applicable 10
Microbiological
Giardia lamblia Stomach cramps, intestinal distress (Giardiasis) TT
Legionella Legionnaires’ disease (pneumonia), Pontiac fever TT
Total coliforms Not necessarily disease-causing themselves, coliforms can be indicators of |
‘organisms that can cause gastroenteric infections, dysentery, hepatitis,
typhoid fever, cholera and other diseases, Coliforms also interfere with
disinfection |
Turbidity Interferes with disinfection 05-10 NTU
(nephelomeme
turbidity unit)
Viruses Gastroenteritis (intestinal distress) TT
Other substances
Sodium Possible increase in blood pressure in susceptible individuals None (20mgiL

FTT = treatment technology required.

reporting level) oO
|

7. 442 ENVIRONMENTAL ENGINEERING TECHNOLOGIES
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8. WATER TREATMENT PROCESSES

Table 11.8 Classes of water treatment

Class
A

Denies
No treatment
Disinfection only

Standard water treatment
Special water treatment

Source

Some borehole water
Occasional upland water
Some borehole water
Occasional upland water
Lowland rivers and reservoirs
Some rural supplies (Fe and Mn)
Colour removal

Trace element removal
Industrial water

Electronics industry requirement
Algae removal

Organics removal

9. ‘Treatment
categorization

Pre-treatment

it

Disinfection

Advaned
treatment

Fluoridation

Distribution
network

[

Groundwater Standard Special
supply water treatment water treatment
Class B Class € Class D
Intake Intake Intake

Screening
Fine sereening Pumping
Pumping ‘Storage
‘Storage Equalization
Equalization Neutralization
fans
‘Aeration Aeration Soviening
Chemical pre-treatment Algae removal
‘Coagulation and mixing | [ Coagulation and mixing
Flocculation Focculation
Sedimentation Sedimentation
Filtration Filtration
Disinfection Disinfection Disinfection
Adsorption
Activated carbon
Membrane processes.
Fe and Mn removal
Halogenated compounds
removal
Fiuoridation Fluoridation Fluoridation
Yes Yes Industry

Figure 11.2 Flow chart outline of unit process in different raw water classes.

10. SELECTION OF TREATMENT PROCESSES

Selection of the set of Treatment Processes will be based on :
» Sources of water intake
+ Characteristic of water
Detailed raw water quality analysis for a minimum of one
year, or longer, at periods of high, low and medium

flows. The parameters to be looked at all those listed in
the legislative standards

+ Cost

+ Suitability of the processes for removing particulate
impurities. Example:
o Turbidity; suitable process might be coagulation,
sedimentation or filtration

o For pathogen, pre or post chlorination, UV, ozone, or
chloramines

11. Table 11.9 Recommended treatment for specific impurities

Parameter Treatment process
Floating matter Coarse screens, fine screens
Suspended matter Microscreens
Algae Microscreens, pre-chlorination, carbon adsorption, rapid filtration
Turbidity Coagulation, sedimentation, post-chlorination
Colour Flocculation, coagulation, filtration
‘Taste and odour Activated carbon
Hardness Coagulation, filtration, lime softening
Iron and manganese
> 1 mg/L Pre-chlorination
<Img/L Aeration, coagulation, filtration
Pathogens, MPN/100 ml
<20 Post-chlorination
20-100 Coagulation/filtration/post-chlorination
> 100 Pre-chlorination
Coagulation/filtration/post-chlorination
Free ammonia Post-chlorination

Adsorption

12. WATER TREATMENT PROCESSES

o Pretreatment of water

+ Screening
+ Storage, Equalization & Neutralization
+ Aeration

+ Chemical pretreatment
o Sedimentation, coagulation and flocculation
o Filtration
+ Slow Sand filtration
+ Rapid Gravity filters
o Disinfestations
+ Chloramines
+ Ozone
+ UVradiation
+ Chlorination
o Fluoridation
o Advance Water Treatment
Tron & Manganese Removal
Water Softening by Chemical Precipitation
Ion Exchange
Adsorption
Chemical oxidation
Membrane Processes

13. SURFACE WATER TREATMENT

Typical treatment plant for surface water

1. Screening and grit removal

Primary sedimentation (settling/clarification)
3. Coagulation (Rapid mixing)

4. Flocculation

5. Secondary sedimentation

6. Filtration

7. Sludge processing

s. Disinfection

n

14. GROUNDWATER TREATMENT

Typical treatment plant for groundwater
1. Aeration

2. Flocculation/precipitation

3. Sedimentation

4. Recarbonation

5. Filtration

6. Disinfection

7. Solids processing