Download - Drinking Water Treatment and Disinfection
Water Quality of Drinking Water Resources
and Formation of Disinfection by-products
Prof Dr. Mohamed I. Badawy
1
Egyptian-German Workshop on Sustainable
Water Technologies
(SusWaTec Workshop) 18.-20th February 2013 - Cairo, Egypt
National Research Centre, Water Pollution Research Department
Dokki, Cairo, Egypt
e-mail: [email protected]
SusWaTec Workshop 19 February 2013
Contents
2
Challenges in water Quality.
Disinfection By-Products (DBPs) in Four Drinking Water
Treatment Plant in Greater Cairo.
Minimization of the formation of DBPs.
SusWaTec Workshop 19 February 2013
Objectives
Evaluation of River Nile water
quality.
Impacts of the water quality.
The formation of Disinfection by-
products. Emphasis on chlorine
DBPs.
Minimization of the formation of
disinfection by-products
Water Supply
19 February 2013 SusWaTec Workshop 4
The River Nile forms the main water resource of Egypt. According to Sudan agreement a stable 55.5 billion m3/yr. was allocated to Egypt, which represents 95 % of all renewable water resources.
Ground Water: Four different groundwater aquifers: the Nile Aquifer, the Nubian Sandstone Aquifer, the Moghra Aquifer and the Coastal Aquifer. Each resource has its limitations on use. These limitations relate to quantity, quality, location, time, and cost of development. The maximum renewable amount of ground water is around 7.5 BCM.
Average rainfall in Egypt is estimated at 18 mm or 1.8 billion m³ per year. Furthermore.
Non-conventional water resources include agricultural drainage water, desalinization of brackish groundwater and/or seawater, and treated municipal wastewater. The total amount of such indirect reuse is estimated to be about 12,6 BCM/year.
Water Demand
19 February 2013 SusWaTec Workshop 5
Various demands for freshwater are exerting excessive pressure on the available water supply.
The agricultural sector (including fisheries) is the highest freshwater consumer, utilizing about 86% of the available supplies.
The domestic and industrial sectors consume 7% and 8% of the total natural supplies.
It is now evident that non-conventional water sources of freshwater are necessary to meet the current and future freshwater demand.
Population growth and per capita water
share in Egypt (m3/year)
19 February 2013 SusWaTec Workshop 6
It is worth mentioning that the availability of renewable water resources in Egypt has dropped from 1500 m3/capita/year in 1966 to 700 m3/capita/year in 2010.
Today, the per capita water availability of less than 700 m3 per year in Egypt is already below the water poverty line of 1,000 m3 per capita a year, accepted by the World Bank
Furthermore, it is forecasted that in 2025 the population will reach 95 million, which would mean a per capita share of only 600 m³ per year
2- Source of Water Pollution
7 SusWaTec Workshop 19 February 2013
2.1. Wastewater
discharges
Nile River from Aswan to
Delta Barrage receives
wastewater discharge from
124 point sources, of which
67 are agricultural drains
and the remainder is
industrial and domestic
sources.
8 SusWaTec Workshop 19 February 2013
2.2 -Industrial Waste Water
9
Egyptian industry uses 7.6 Bm3/yr of water.
The River Nile supplies 65% of the industrial water needs and
receives more than 57% of its effluents.
12 % treat their wastes a complete scientific treatment, 14 %
partially treat their wastes and the 74 % don't treat them at all.
Food industries contribute to 45% of total effluent discharge
and to 67% of the total BOD load introduced. However, the
chemical industry is responsible for more than 60% of the
heavy metal discharges
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2.3-Agricultural drainage water
10
The agricultural drainage of the southern part of Egypt returns directly to the Nile River where it is mixed with the Nile fresh water. The total amount of such indirect reuse is estimated to be about 4.07 BCM/year.
In the Delta region the amount of agricultural drainage water reuse officially was estimated to be around 4.27 BCM/year, in addition to about 0.3 BCM/year lifted to surface water (Rossetta branch) from west delta drains. Additional unofficial reuse done by farmers themselves has been estimated to be around 2.8 BCM/year.
The remaining drainage water is discharged to the sea and the northern lakes via drainage pump stations. The total amount of drainage water that was pumped to the sea has been estimated to be 12.41 BCM/year.
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2.4-Domestic Wastewater
11
The amount of collected wastewater is about 6.5 BCM /Yr
3.65 BCM /Yr
(Treated)
20 % Primary
(0.73BCM)
80% Secondry
(2.92 BCM)
2.85 BCM /Yr
(not Treated)
(5 % of Nile Share)
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Activated Sludge Treatment Plant
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Other biological treatment techniques
Oxidation Pond Aerated Lagoons
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3- Impact of Wastewater Discharge
14
The constituents of concern in domestic and municipal wastewater are pathogens, parasites, nutrients, oxygen demanding compounds and suspended solids.
High levels of toxic substances in industrial wastewater have been reported such as heavy metals & organic micro-pollutants.
Trace micro-pollutants are mainly attached to suspended material, most of it accumulates in the sludge. Improper sludge disposal and/or reuse may lead to contamination of surface and ground water.
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3- Impact of Wastewater Discharge (Cont.)
15
Increased salinity due to agricultural drainage reuse.
Drainage return flow to the Nile result into an increase in
salinity of the water from 130 mg/l at Aswan (far
upstream) to 250 mg/l near the delta barrage.
Organic and inorganic pollution associated with disposal
of untreated or partially treated industrial effluents into
water ways (mainly drains) at specific locations and hot
spots.
Pollution resulting from agrochemicals and pesticides.
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3- Impact of Wastewater Discharge (Cont.)
16
Formation of chlorine DBPs in treated water
Chlorination is one of the most widely used disinfection processes in water treatment plants in Egypt to ensure a safe drinking water.
The Nile River supplies about 97 % of the annual renewable drinking water resources in Egypt. One of the major quality problems facing the use of surface water for drinking purposes is the formation of carcinogenic compounds such as DBPs due to the reaction of NOM with chlorine during drinking water treatment processes.
Numerous treated water samples collected from various locations in Egypt have shown high THM and HAA levels.
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4- DBPs Precursors and DBPs
Levels in DWTPs in Greater Cairo
A Case Study
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Introduction
18
This study is a joint research project between NRC, Egypt and
University of South Carolina, USA, aims to:
Develop an efficient treatment scheme for drinking water containing
NOM and reduction of formation of DBPs (THMs and HAAs).
To achieve this task different treatment schemes were investigated
consisting of enhanced coagulation, sedimentation, disinfection by
using chlorine dioxide, ozone, filtration by sand filter, and/or GAC.
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Introduction (Cont.)
19 February 2013 SusWaTec Workshop 19
Intake Screening Pre-
chlortination
Coagulation Flocculation Sedimentation
Sand filtration
Post-chlorinatin
Distribution
Disinfection of water
during treatment
process
Disinfection of
water during
distribution
•Raw water should have low concentrations of all contaminants.
•Exhibit minimal variability from day to day.
•By avoiding the contamination of water resource, water treatment becomes easier, less expensive and more quality.
Introduction (Cont.)
19 February 2013 SusWaTec Workshop 20
NOM
Cl2
DBPs
THMs
• CHCl3
• CHCl2Br
• CHClBr2
• CHBr3
HAAs
• MCAA
• DCAA
• TCAA
• MBAA
• DBAA
Several studies reported that these
compounds have been related to:
• occurrence of cancer,
• growth retardation, spontaneous
abortion,
• and congenital cardiac defects
Factors affecting DBPs formation:
pH,
temperature,
dissolved organic carbon (DOC),
bromide concentrations,
and operational factors (chlorine dose,
contact time).
Experimental
19 February 2013 SusWaTec Workshop 21
Monitoring program was conducted in 4 drinking water treatment plants which are located in Giza and Cairo Governorates.
El-Dahab Island and Embaba DWTPs were selected in Giza Governorate.
In Cairo Governorate, Mostorod and Fostat DWTPs were chosen.
Several samples were collected from each treatment step including inlet, after clarifier, after sedimentation, and finally from plant outlet
Parameters related to DBPs formations
Physico chemical parameters related
to DBPS formation such as Turbidity,
pH, residual CL2, conductivity,
Alkalinity and Color(at ּ455ג ).
TOC& DOC which give an
indication on the natural organic
matter (NOM).
UV254 and specific Ultraviolet
absorption at 254 nm (SUVA254), an
indicator of carbon aromaticity in
water and hydophlocity of NOM.
Parameter TOC
DOC
UV254
SUVA
254
THMs
HAAs
Algae
Sample
Intake
Clarifier
Filter
Outlet
Locations Cairo
Mostorod DWTP
Fostat DWTP
Giza
El-Dahab Island DWTP
Embaba DWTP.
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Results
23
• Average NOM contents in raw waters were 5.14, 4.43, 4.24 and 3.28 mgC/L with an average UVA254 of 0.1, 0.0947, 0.0948, 0.069 and 0.066 L/mg-M at Embaba, El-Dahab Island, Fostat and Mostorod DWTPs, respectively.
• In parallel, SUVA254 values in all DWTPs were also in the low to medium range (1.62 - 2.54 L/mg-M)
• This indicates that NOM in raw waters is of low molecular weight with hydrophobic and aromatic characteristics.
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Parameters Unit Range Average
PH - 7.55 - 7.35 7.45
Turbidity NTU 6.5 - 52.5 28.77
Color mg/l Pt- Co 13 - 41 20.56
Conductivity µS/cm 406 - 1003 569.25
Alkalinity mg/l CaCO3 128.4 - 193.6 149.77
DOC Mg /L 2.73 - 3.66 3.22
TOC mg/L 3.20 - 5.11 4.30
UV254 1/cm 0.05 - 0.14 0.08
SUVA254 1/mg*m 1.75 - 3.72 2.36
Seasonal variation of raw water quality
Seasonal Variations of surrogate Parameters
25
pH did not display seasonal variation and remains constant around 7.5.
Both turbidity and UV absorbance showed strong seasonal variation since The turbidity values increased in summer52 NTU
and 6.5NTU in spring season respectively.
While in winter and autumn there were no significant change in its value.
TOC increased moderately in spring season to reach 5.11mgC/l.
Maximum true color (455 nm) was observed in winter season (41 Pt/Co).
0
1
2
3
4
5
6
Jan
Feb
Marc
h
April
May
June
July
Augst
Sept
Oct
Nov
Dec
DOC TOC
SUV UV × 10
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DWTP Performance efficiency
26
The obtained results indicated that the DWTS are not very effective in removal of total organic carbon (TOC), especially DOC removal was about 9 %.
The conductivity of the water samples slightly increased through the treatment stages .
PH of the collected samples was nearly constant within the treatment steps.
Alkalinity of the collected
samples was decreased through the treatment steps by 20.47%.
95,9 89,7
20,5 22
9
84
40
0
20
40
60
80
100
120
Rem
oval P
erc
ent
%
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Results
27
• To assess the Efficiency of DWTPs, samples were collected
from the treatment stages. The parameters related to DBPs formations were analyzed in each sample.
• Current treatment processes were found to be effective in the removal of suspended solids as turbidity values reduced by 90.06%, 87.25%, 90.73% and 87.86% in Embaba, El-Dahab Island, Fostat and Mostorod DWTPs, respectively.
• The conductivity removals were 25.91, 15.90, 1.79 and 8.25% for Embaba, El-Dahab Island, Fostat and Mostorod DWTPs, respectively.
• In general, the studied DWTPs were relatively not very effective in removal of total organic carbon (TOC) since the removal percentages of DOC in Embaba, El-Dahab Island, Fostat and Mostorod DWTPs were 32.41, 22.35, 22.64, 14.63%, respectively.
• The DOC removal might be due to reaction between chlorine used in disinfection and DOC and/or adsorption on sand filter. The low DOC percent removal indicates that water after passing through settling basins and filters was still loaded with organic matter.
• Consequently, the latter compounds would contribute to increase the levels of THMs as the retention time is extended during the water treatment processes.
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% Removal of algae in the studied DWTPs
28
Percentage of algal removal ranged between 77.7 to 84.8% of the total algae count of raw water samples as an average value between 4 different water treatment plants.
After sand filtration composition of algae was further changed. and diatoms represent the highest ratio in the outlet water.
It is indicated the abilities of diatoms algae to pass through the sand filter due to their spindle structure and their small size.
After ClarifierAfter Filtration
Final Outlet0
1020304050
60
70
80
90
100
After Clarifier After Filtration Final Outlet
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Efficiency of DWTPs in Bacteria Removal
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The studied DWTPs showed high efficiency for the removal of bacteria from raw water.
The reduction in total bacterial count mostly occurs after prechlorination process (70-88%). The remaining counts removed after post-chlorination at the DWTPs outlets.
Total Coliform, Fecal Coliform and Fecal Streptococci were absent in all samples after clarification.
Determination of Optimal Treatment Processes for
Natural Organic Matter Removal and Disinfection By-
Product Formation Reduction
Mohamed I. Badawya, Tarek A. Gad-Allaha,⇑, Mohamed E.M. Alia , Yeoman Yoon
a Water Pollution Research Department, National Research Centre, P.O. Box 12311, Dokki, Cairo, Egypt b Department of Civil/Environmental Engineering, University of South Carolina, Columbia, SC 29201, USA
30 SusWaTec Workshop 19 February 2013
Factors Affecting DBP Formation
Water quality - TOC - Temperature - pH - Bromide
Point of disinfection Time
- Alkalinity - Turbidity - Other components
Disinfectant used - Chlorine - Chloramine - Chlorine dioxide
- Ozone
Effect of TOC and UV254
NOM + Cl2 → THMs + HAAs + other DBPs.
TOC is one of the most widely used measures for quantifying the amount of NOM in water.
DOC represented the relative amount of precursor material
UV254 has been widely used to predict (DOC) in water or its reactivity in forming disinfection by-products.
The results show that a higher available TOC or UV254 will provide more DBPs.
SUVAs and DBPS formation
The SUVA reflects the hydrophobic fraction of organic matter.
Waters with a low humic acid fraction have SUVAs less than 3
L/mg m, while waters with a high humic acid fraction have SUVAs
between 3 and 5 L/mg m.
The obtained results showed the SUVA is less than 3 L/mgm,
therefore the effect of the coagulant dosage may be negligible
and relatively low removal percentages and high levels of DBPs
formation were obtained.
Effect of Contact Time
34 SusWaTec Workshop 19 February 2013
• Cl2 reacts very fast to produce reasonable amounts of THMs and HAAs within short time (30 min); the subsequent increase is slightly slow.
• The increase in THMs and HAAs concentration with time is due to more contact between Cl2 and NOM present in water.
• It is interesting to note that the extent of formation varies from one compound to another.
• THMs • CHCl3: (i.e., 76%) within 100 min . • CHBr2Cl: 14% within 100 min • CHBr3 : 20% within 100 min • CHBrCl2 : the most affected, 55% increase in 100
min. • HAAs
• MCAA: 79.64 µg/L 98.87 i.e. 16.5 % within 90 min
• DCAA and TCAA: 26, and 25 %, respectively in the same time intervals.
• Brominated acetic acid compounds were not detected.
0
200
400
600
800
1000
1200
1400
1600
0 20 40 60 80 100 120 140H
AA
s (µ
g/L
)
Time (min)
MCAA DCAA TCAA(b)
0
200
400
600
800
1000
1200
1400
1600
0 20 40 60 80 100 120 140
Co
nce
ntr
tio
n (
µg/
L)
Time (min)
CHCl3 CHClBr2 CHCl2Br CHBr3(a)
Effect of pH
35
increasing pH from 5 to 8.5 has
significant effect on the formation of
DBPs
Maximum yields of THMs pH 7.
Maximum yields of HAAs pH 8.
At high pH values: decomposition of
many halogenated DBPs occurs and
the concentration of DBPs decreased.
0
200
400
600
800
1000
1200
4 6 8 10
Co
nce
ntr
tio
n (
µg/
L)
pH (-)
CHCl3 CHCl2Br CHClBr2 CHBr3(a)
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0
200
400
600
800
1000
1200
4 5 6 7 8 9 10
HA
As
(µg/L
)
pH (-)
MCAA DCAA TCAA(b)
Effect of initial Cl2 dose
36
• In general, as chlorine dose is increased, THMs and HAAs yield attains higher values. However, THMs formation was not directly proportional to the applied chlorine dose.
• The DOC in real surface waters is a contribution of different organic compounds and some substances are not THM precursors. and/or that chlorination yields several halogenated organics other than THMs.
• Among the four THMs, CHCl3 was the dominant species and occupied over 69 % of the total THMs concentration (TTHM).
0
200
400
600
800
1000
1200
1400
1600
0 5 10 15
Co
ncen
trti
on
(µ
g/L
)
Initial Cl2 dose (mg/L)
CHCl3 CHCl2Br CHClBr2 CHBr3(a)
0
200
400
600
800
1000
1200
0 2 4 6
Co
ncen
trti
on
(µ
g/L
)
Initial Cl2 dose (mg/L)
MCAA DCAA TCAA(b)
Effect of Chlorine dose on (a) THMs and (b) HAAs formation
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Effect of bromide ion
37
In the formation of THMs, with the Br− content increasing, the content of
DCBM, DBCM and TBM increase.
In general, TBM concentration increases slightly with increasing bromide ion
concentration. But, a slight decrease in TTHM with higher Br− dosage.
The results show that in the compositions of DBPs, with the increasing Br−
concentration, the component of chlorine decreased gradually, and the
component of bromine increased.
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Effect of initial TOC concentration
38
• THMs • Chloroform is the most affected compound • Other compounds were slightly affected by TOC value.
• HAAs
• MCAA concentration increased by 20 %. • DCAA and TCAA concentration increased by 49 and 40 %, respectively.
TOC : 10 mg/L 15 mg/L
0
200
400
600
800
1000
1200
1400
1600
0 4 8 12 16
Co
ncen
trti
on
(µ
g/L
)
TOC (mgC/L)
CHCl3 CHCl2Br CHClBr2 CHBr3(a)
0
200
400
600
800
1000
1200
1400
0 2 4 6 8 10 12 14 16
HA
As
(µg/
L)
TOC (mgC/L)
MCAA DCAA TCAA(b)
Effect of initial TOC concentration on (a) THMs and (b) HAAs formation
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DOC fractions and their contribution in
DBPs formation
39
For understanding of the correlation between DOC fractions and DBPs formation, a series of
bench scale experiments were conducted.
Raw water sample was collected from Nile River and then fractionated.
Finally, each fraction was chlorinated with 5 mg/L Cl2 for one hour.
the DBPs formation for the hydrophilic species was usually higher than that of hydrophobic
species.
This indicated that the hydrophilic fraction was a more reactive precursor for THMs than the
hydrophobic fraction.
0
100
200
300
400
500
600
700
Raw HPL HPO TPL
Co
ncen
trati
on
(u
g/L
)
CHCl3 CHCl2Br CHClBr2 CHBr3
0
50
100
150
200
250
300
350
400
Raw HPL HPO TPL
Co
ncen
trati
on
(u
g/L
)
MCAA DCAA TCAAMBAA BCAA DBAA
Contribution of DOC fractions in DBPs formations, (a) THMs and (b) HAAs
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Disinfection by-products (DBP)
levels
40 SusWaTec Workshop 19 February 2013
(DBP)formation
41
The concentration found to
increase through the processes
about 27% of THMs formed in
flash mix process (the point of
chlorine addition).
While 43% of THMs occurs in
slow mix unit and reach to 72% of
their value through sedimentation
and 75% through filtration.
After the post chlorine is added
THMs increased with about 25%
0
10
20
30
40
50
60
70
80
90
100
% T
HM
s R
em
oval
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Disinfection by-products (DBP) levels after
the storage tank
42
THMs and HAAs are the most important groups of DBPs.
The average concentrations of TTHMs were 64.38, 43.94, 52.41 and 51.72 µg/L in water samples collected from the outlet of Embaba, El-Dahab Island, Fostat and Mostorod DWTPs, respectively, which still less than the Egyptian standards for Drinking Water Quality (100 µg/L).
While the corresponding average concentrations of HAAs were 57.64, 54.79, 36.38 and 61.52 µg/L for Embaba, El-Dahab Island, Fostat and Mostorod DWTPs, respectively.
The average concentration of studied HAAs was on the margin of the maximum contaminant level of 60 μg/L
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TTHMs for Summer Event in Nasr City Tap Water
Smith and El Deen (2009)
43 SusWaTec Workshop 19 February 2013
The monthly change of THMs
19 February 2013 SusWaTec Workshop 44
A relative decrease in
concentration of THMs was
noticed during January to
March.
The levels of THMs
increased started from March
until May.
TOC increased moderately in
the same period to reach
5.2mgC/l.
0
10
20
30
40
50
60
Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul.
Co
ncen
trati
on
(µ
g/L
)
CHCl3 CHCl2Br CHClBr2 CHBr3 TTHM
(a)
Minimization of the formation of
disinfection by-products
Mohamedy. Badawy a, Tarek A. Gad-Allah a, ,Mohamed.M. Alia, Yeoman Yoonb
a Water Pollution Research Department, National Research Centre, P.O. Box 12311, Dokki, Cairo, Egypt b Department of Civil/Environmental Engineering, University of South Carolina, Columbia, SC 29201, USA
45 SusWaTec Workshop 19 February 2013
OVERVIEW
46
Ozone Destruction
Gas Feed
System
Ozone
Generator
Influent
Effluent
Atmosphere
Ozone Gas
Ozone
Quench
(Option)
Off-Gas
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Technologies for the reduction of DBP
formation
47
Enhanced coagulation
Granular activated carbon
Membrane filtration
Alternate disinfectants
Chlorine dioxide
Ozone
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Additional Treatment for DBPs Control
48
Sorption
Powder activated carbon (PAC)
Granular activated carbon (GAC)
Synthetic resins
Oxidation/reduction
Ozone
Advanced oxidation processes (AOPs)
Ozone/hydrogen peroxide
Ozone/UV radiation
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Enhanced coagulation
49
The coagulation process was optimized by the selection of coagulants and
coagulant aid rather than by adjusting the pH value because it is expensive to
adjust the pH to acidic conditions where the source water has high alkalinity of
150 to 200 mg/L.
Sedimentation
Filtration
Raw water Flocculation
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Ozonation
Benefits Problems
50
Adequate disinfection
Reduction of chlorine or
chloramine dosage
Reduction of some DBPs:
THMs, HAAs, and HANs
Very small THM formation
when applied with
chloramine
Increase of some DBPs: chloropicrin, chlorinated hydrate and CNCl
Reduction with bromide ion resulting in brominated DBPs
Increase in biodegradable organic matter
Need for identification of DBPs
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Treatment trains used in bench scale
experiments
51
Cl2 gas coagulation Rapid Sand
Filter Cl2 gas
ClO2 gas Enhanced
coagulation Rapid Sand
Filter Cl2 gas
ClO2 gas Enhanced
coagulation GAC Filter Cl2 gas
O3 gas Enhanced
coagulation Rapid Sand
Filter Cl2 gas
O3 gas Enhanced
coagulation GAC Filter Cl2 gas
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Optimization of Coagulation-flocculation
process
52
AP: Anionic polymer. NP: Nonionic polymer. CP: Cationic polymer
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Effect of coagulant aid on the treatment of
drinking water
53 SusWaTec Workshop 19 February 2013
Comparison among different treatment
trains
54
Chlorine dioxide reduces the DBPs
formation of about 70 to 79.6% for THMs
and 70 to 76.4 for HAAS with respect to
the chlorine disinfection.
Comparison between Train #1 and Trains
#1*, #3 and #3* indicated that much
stronger DOC removal was achieved by
pre-ozonation prior to coagulation and
filtration by using sand filter or GAC
filter.
This Figure clearly indicate that the
effluent from trains #3 and #3* reduced
the DOC values by 64 and 70 %,
respectively.
In addition, ozonation induced increase
in DOC removal on coagulation
processes.
0
10
20
30
40
50
60
70
80
Train # 1 Train #1* Train #2 Train #2* Train #3 Train #3*
UVA254 DOC THMs HAAs
Train 1 [enhanced coagulation by CP and sand filtration];
Train 1* [enhanced coagulation by CP and GAC filtration];
Train 2 [disinfection by ClO2, enhanced coagulation by CP and
sand filtration];
Train 2* [disinfection by ClO2, enhanced coagulation by CP and
GAC filtration];
Train 3 [disinfection by O3, enhanced coagulation by CP and sand
filtration];
Train 3* [disinfection by O3, enhanced coagulation by CP and GAC
filtration].
SusWaTec Workshop 19 February 2013
Conclusion
55
The studied DWTPs were relatively not very effective in removal of dissolved organic carbon (DOC) since the removal percentages of DOC ranged between 15 and 32 mg/l.
The concentrations of THMs in the studied drinking water treatment plants were all below the Egyptian standards for Drinking Water Quality (100 µg/L).
The average concentrations of studied HAAs in water DWTPs exceeded the maximum contaminant level of 60 μg/L.
SusWaTec Workshop 19 February 2013
Conclusion (Cont.)
56
Chlorine dioxide is strong oxidizing agent and reduces the DBPs formation of about 70 to 79.6% for THMs and 70 to 76.4 for HAAS with respect to the chlorine disinfection.
However chlorine dioxide represents a potential source of risk for human health due to the introduction of inorganic by-products such as chlorite (ClO2
-) and chlorate (ClO3-) ions.
2ClO2 + 2OH- = H2O + ClO3- (Chlorate) + ClO2
-(Chlorite)
Using pre-ozonation/enhanced coagulation/activated carbon filtration treatment train appears to be the most effective method for reducing DBPs precursors and DBPS in drinking water treatment.
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Recommendations & Action
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58 SusWaTec Workshop 19 February 2013
What should be taken to achieve the water
situation?
59
Applying Integrated Water Resources Management approach
through developing governmental and non-governmental
Institutions as well as enforcement of laws and legislations .
Allocating different conventional and non-conventional water
resources (agricultural drainage and wastewater reuse, sea
water and brackish water desalination, rain harvesting, flash
flood harvesting).
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What should be taken to achieve the water
situation? (Cont.)
60
Irrigation improvement and changing crop patterns.
Cooperation with the Nile Basin countries
Supporting and enhancing the private sector role in water
management
Pollution abatement as well as preserving water resources
SusWaTec Workshop 19 February 2013
The Nile River supplies about 97 % of the annual Drinking water
resources in Egypt.
The domestic sectors consumes 7bcm3/year of the total fresh water
supplies.
Raw water should have low concentrations of all contaminants and exhibit minimal variability from day to day.
By avoiding the contamination of water resource, water treatment becomes easier, less expensive and more reliable.
Drinking Water Resource and Demand
61 SusWaTec Workshop 19 February 2013