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Enhanced Coagulation for Algae Removal in a Typical Algeria Water Treatment
Plant
Article in Environmental engineering and management journal · October 2017
DOI: 10.30638/eemj.2017.238
CITATIONS
31
READS
199
7 authors, including:
Some of the authors of this publication are also working on these related projects:
University of Blida, Chemical Engineering Department View project
COST Action ES1403: New and emerging challenges and opportunities in wastewater reuse (NEREUS) View project
Djamel Ghernaout
University of Hail
114 PUBLICATIONS 2,536 CITATIONS
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Abdelmalek Badis
Saad Dahlab University, of Blida 1, Algeria
64 PUBLICATIONS 1,069 CITATIONS
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Ahmed Boucherit
Saad Dahlab University
30 PUBLICATIONS 523 CITATIONS
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All content following this page was uploaded by Djamel Ghernaout on 01 November 2018.
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Enhanced Coagulation for Algae Removal in a Typical Algeria Water Treatment
Plant
Article in Environmental engineering and management journal · October 2017
DOI: 10.30638/eemj.2017.238
CITATIONS
31
READS
199
7 authors, including:
Some of the authors of this publication are also working on these related projects:
University of Blida, Chemical Engineering Department View project
COST Action ES1403: New and emerging challenges and opportunities in wastewater reuse (NEREUS) View project
Djamel Ghernaout
University of Hail
114 PUBLICATIONS 2,536 CITATIONS
SEE PROFILE
Abdelmalek Badis
Saad Dahlab University, of Blida 1, Algeria
64 PUBLICATIONS 1,069 CITATIONS
SEE PROFILE
Ahmed Boucherit
Saad Dahlab University
30 PUBLICATIONS 523 CITATIONS
SEE PROFILE
All content following this page was uploaded by Djamel Ghernaout on 01 November 2018.
The user has requested enhancement of the downloaded file.
Environmental Engineering and Management Journal October 2017, Vol. 16, No. 10, 2303-2315
http://omicron.ch.tuiasi.ro/EEMJ/
“Gheorghe Asachi” Technical University of Iasi, Romania
ENHANCED COAGULATION FOR ALGAE REMOVAL
IN A TYPICAL ALGERIA WATER TREATMENT PLANT
Djamel Ghernaout1,2,3∗ , Abdelmalek Badis 3 , Ghania Braikia3 , Nadjet Matâam3 ,
Moussa Fekhar4 , Badiaa Ghernaout5 , Ahmed Boucherit3
1Binladin Research Chair on Quality and Productivity Improvement in the Construction Industry, College of Engineering,
University of Ha’il, PO Box 2440, Ha’il 81441, Saudi Arabia
2Department of Chemical Engineering, College of Engineering, University of Ha’il, PO Box 2440, Ha’il 81441, Saudi Arabia
3Saad Dahlab University of Blida, Chemical Engineering Department, Blida 09000, Algeria
4Algerian Waters, Tipaza Area, Tipaza 42000, Algeria
5Laboratory of Mechanics (LME), Department of Mechanical Engineering, University of Laghouat, PO Box 37G,
Laghouat 03000, Algeria
Abstract
This work aims to study the physicochemical and biological parameters of Boukerdene Dam’s water and treated water at
different steps of the treatment processes in Sidi-Amar’s Station (Tipaza, Algeria) with a particular interest to the phytoplankton.
This work is also related to the demonstration of the enhanced coagulation (EC) process as an efficient method in algae and
organic matter (OM) removal from surface water by its application in jar tests. The diversity of the phytoplankton shows the
presence of 21 genera comprising 30 algae species out of 8 samples taken from the Boukerdene Dam. Among the identified
genera, seven of them are responsible for the unpleasant tastes and odours of water; six others are responsible for filter fouling.
Generally, the conventional drinking water treatment processes employed at this water treatment plant shows a limited efficiency
of OM and algae removal. The novelty of this work is that the jar tests of EC (pH 6 and alum dose 15 mg L-1) as only one stage
of water treatment, without chlorination and filtration, improve the removal of OM and algae at 97 to 99%, respectively.
Keywords: algae, bacteria, enhanced coagulation (EC), natural organic matter (NOM), surface water
Received: February, 2013; Revised final: February, 2014; Accepted: February, 2014
∗ Author to whom all correspondence should be addressed: e-mail: djamel_andalus@yahoo.fr; Phone/Fax: +213 25433631
1. Introduction
Since trihalomethanes (THMs) were found in
disinfected water using chlorine in the 1970s by
Rook (1974), disinfection by-products (DBPs) have
become a center of awareness in water treatment. In
fact, more than 700 species of DBPs have been
affirmed. Among DBPs, THMs and haloacetic acids
(HAAs) were the two DBP groups detected at the
greatest levels and most frequently found in
disinfected water using chlorine through the world
(Hong et al., 2013). In addition, the important DBP
precursor was usually suggested to be natural organic
matter (NOM). NOM is known as the complicated
matrix of naturally existing organic materials
detected in natural waters (Boucherit et al., 2015;
Ghernaout et al., 2011; Ghernaout and Boucherit,
2015). Indeed, the NOM may notably influence
several features of water treatment, comprising the
coagulation efficiency and disinfectants use
(Ghernaout et al., 2010a). Consequently, NOM
impacts drinking water quality by participating in
DBPs formation, biological re-growth in the
distribution system, colour, taste, and odour
generation (Chen et al., 2008; Wang et al., 2013).
In Algeria (North of Africa), it is well known
that water resources are basically surface waters
(Ghernaout et al., 2010b). In Tipaza City (North of
http://omicron.ch.tuiasi.ro/EEMJ/
“Gheorghe Asachi” Technical University of Iasi, Romania
ENHANCED COAGULATION FOR ALGAE REMOVAL
IN A TYPICAL ALGERIA WATER TREATMENT PLANT
Djamel Ghernaout1,2,3∗ , Abdelmalek Badis 3 , Ghania Braikia3 , Nadjet Matâam3 ,
Moussa Fekhar4 , Badiaa Ghernaout5 , Ahmed Boucherit3
1Binladin Research Chair on Quality and Productivity Improvement in the Construction Industry, College of Engineering,
University of Ha’il, PO Box 2440, Ha’il 81441, Saudi Arabia
2Department of Chemical Engineering, College of Engineering, University of Ha’il, PO Box 2440, Ha’il 81441, Saudi Arabia
3Saad Dahlab University of Blida, Chemical Engineering Department, Blida 09000, Algeria
4Algerian Waters, Tipaza Area, Tipaza 42000, Algeria
5Laboratory of Mechanics (LME), Department of Mechanical Engineering, University of Laghouat, PO Box 37G,
Laghouat 03000, Algeria
Abstract
This work aims to study the physicochemical and biological parameters of Boukerdene Dam’s water and treated water at
different steps of the treatment processes in Sidi-Amar’s Station (Tipaza, Algeria) with a particular interest to the phytoplankton.
This work is also related to the demonstration of the enhanced coagulation (EC) process as an efficient method in algae and
organic matter (OM) removal from surface water by its application in jar tests. The diversity of the phytoplankton shows the
presence of 21 genera comprising 30 algae species out of 8 samples taken from the Boukerdene Dam. Among the identified
genera, seven of them are responsible for the unpleasant tastes and odours of water; six others are responsible for filter fouling.
Generally, the conventional drinking water treatment processes employed at this water treatment plant shows a limited efficiency
of OM and algae removal. The novelty of this work is that the jar tests of EC (pH 6 and alum dose 15 mg L-1) as only one stage
of water treatment, without chlorination and filtration, improve the removal of OM and algae at 97 to 99%, respectively.
Keywords: algae, bacteria, enhanced coagulation (EC), natural organic matter (NOM), surface water
Received: February, 2013; Revised final: February, 2014; Accepted: February, 2014
∗ Author to whom all correspondence should be addressed: e-mail: djamel_andalus@yahoo.fr; Phone/Fax: +213 25433631
1. Introduction
Since trihalomethanes (THMs) were found in
disinfected water using chlorine in the 1970s by
Rook (1974), disinfection by-products (DBPs) have
become a center of awareness in water treatment. In
fact, more than 700 species of DBPs have been
affirmed. Among DBPs, THMs and haloacetic acids
(HAAs) were the two DBP groups detected at the
greatest levels and most frequently found in
disinfected water using chlorine through the world
(Hong et al., 2013). In addition, the important DBP
precursor was usually suggested to be natural organic
matter (NOM). NOM is known as the complicated
matrix of naturally existing organic materials
detected in natural waters (Boucherit et al., 2015;
Ghernaout et al., 2011; Ghernaout and Boucherit,
2015). Indeed, the NOM may notably influence
several features of water treatment, comprising the
coagulation efficiency and disinfectants use
(Ghernaout et al., 2010a). Consequently, NOM
impacts drinking water quality by participating in
DBPs formation, biological re-growth in the
distribution system, colour, taste, and odour
generation (Chen et al., 2008; Wang et al., 2013).
In Algeria (North of Africa), it is well known
that water resources are basically surface waters
(Ghernaout et al., 2010b). In Tipaza City (North of
Ghernaout et al./Environmental Engineering and Management Journal 16 (2017), 10, 2303-2315
Algeria), potable water is provided mostly from one
big surface water source of Boukerdene Dam and the
raw water is transferred to the water treatment plant
(Sidi-Amar’s Station, SAS) for treatment operations.
Raw water is treated to satisfy the World Health
Organisation (WHO) and Algerian water quality
standards. Chlorine is employed for organic matter
(OM) pre-oxidation. Moreover, chlorine is as well
added as the final step of water treatment chain.
However, OM chlorination in fresh water results in
formation of DBPs (Ghernaout, 2017; Ghernaout et
al., 2014; Uyak and Toroz, 2007; Uyak et al., 2007).
On the other hand, the important portion of aquatic
NOM is constituted of humic substances (HS). These
macromolecular compounds have been illustrated to
be particularly responsive with a range of oxidants
and disinfectants that are employed during the
treatment of potable water, especially chlorine
(Ghernaout, 2014; Slavik et al., 2012). In fact, HS
interact with chlorine species (OCl - /HOCl) to
generate THMs, HAAs and other halogenated DBPs
(Bekbolet et al., 2005; Kristiana et al., 2013).
Algae are abundant and diverse in drinking
water supplies including lakes, reservoirs, rivers, and
streams (Ghernaout and Ghernaout, 2012b).
Occasional algal blooms, comprised of blue-green
(B-G) algae (cyanobacteria) and/or green algae,
cause significant challenges in drinking water
treatment due to the release of organic compounds
(algogenic organic matter, AOM) into water
extracellularly and, upon cell lysis, intracellularly
(Ghernaout et al., 2010b; Her et al., 2004). Besides,
algae are photosynthetic, aquatic plants that utilise
inorganic nutrients such as nitrogen and phosphorus.
Cyanobacteria are typically referred to as B-G algae
because they perform photosynthesis and are similar
in size and colour, even though they are bacteria.
Furthermore, algal cells and associated AOM are
THM precursors, which have resulted in the
restriction of chlorine usage. Similarly, the potential
for toxin release by cyanobacteria, in particular from
Microcystis, has resulted in the WHO setting a
guideline value of 1 μg L-1 for the associated toxin,
microcystin-LR (MCLR) (Henderson et al., 2008).
Another problem of the presence of offensive
taste and odour compounds, including 2-
methylisoborneol (2-MIB) and geosmin in the
resultant drinking water supply, has also been
attributed to high alga populations (Henderson et al.,
2008). Unfortunately, surface water drinking supplies
are also particularly vulnerable to the growth of these
organisms and current US drinking water treatment
practices, as an example, do not monitor or actively
treat for B-G algal toxins including the microcystins.
Besides, harmful algal blooms (HABs) represent a
significant threat to fisheries, public health, and
economies around the world and have increased in
frequency, duration, and distribution in recent
decades (Gobler et al., 2008). On the other hand,
algae are traditionally characterised according to
differences in pigmentation and cell complexity
arising as a result of evolution. Within a particular
phylum, the species can vary significantly in terms of
their morphology and other important functionalities
including the composition and quantity of excreted
extracellular organic matter (EOM). Algae are
typically removed using the following treatment
chain: coagulation/flocculation (C/F) and
clarification either by dissolved air flotation (DAF)
or sedimentation, followed by granular media
filtration. Direct filtration can also be used as a
clarification process. More recently, ozone and
granular activated carbon (GAC) filters have been
installed downstream of clarification, primarily for
pesticide removal (Henderson et al., 2008).
Ultrafiltration (UF) technology, as a promising
substitute technique to classical, may eliminate algae
totally. Nevertheless, transmembrane pressure sorely
augments or flux diminishes throughout algae bloom
for UF application. Moreover, the algal cells liberate
the extracellular polymeric substances (EPS), which
conduct to permeability decrease and more elevated
energy requirements for preserving a fixed permeate
flux. The excretion of EPS depends on algal types.
These EPS play an important role in UF fouling
(Liang et al., 2008).
Classical water treatment technology,
consisting of C/F, decantation and sand-filtration, has
been the greatest frequent one for NOM elimination
from the natural waters (Ghernaout et al., 2011). The
performance of NOM elimination during coagulation
process is highly influenced by several parameters,
such as: nature and properties of NOM particles, type
and dose of coagulant, pH, ionic strength and
temperature (Ghernaout et al., 2015a). In addition, a
fraction of the coagulant (metal salts) that has been
introduced to water is not eliminated troughout the
treatment and remains present in the potable water.
The amendment of the coagulation technique to
obtain higher NOM reductions is named “enhanced
coagulation” (EC) (Ghernaout et al., 2009). EC
correlates with the employment of coagulant
injections efficient for total organic carbon (TOC)
elimination (Uyak and Toroz, 2007). Nevertheless,
an additional alternative of EC has been suggested to
establish performant decrease in DBP generation by
employing an enlarged principle of EC. In fact, in
EC, both the coagulant injection and the coagulation
pH can be well conceived to importantly decrease the
coagulant requirement at the same time augmenting
NOM elimination (Xiao et al., 2013).
Therefore, the most efficient action plan to
decrease the generation of DBPs would be to
diminish the quantity of NOM which is the principal
generator of DBPs, prior to disinfection using
chlorine. EC has been observed to be very
performant in the elimination of NOM from surface
waters, by that means decreasing DBP generation
and reducing chlorine need. Nevertheless, the
shortages of EC comprise the augmented cost of
chemical products, elevated sludge formation, lower
pH conditions (influencing corrosion monitoring),
and augmented treatment chemical products like
aluminium or iron in potabilzed water (Zhang et al.,
2304
Algeria), potable water is provided mostly from one
big surface water source of Boukerdene Dam and the
raw water is transferred to the water treatment plant
(Sidi-Amar’s Station, SAS) for treatment operations.
Raw water is treated to satisfy the World Health
Organisation (WHO) and Algerian water quality
standards. Chlorine is employed for organic matter
(OM) pre-oxidation. Moreover, chlorine is as well
added as the final step of water treatment chain.
However, OM chlorination in fresh water results in
formation of DBPs (Ghernaout, 2017; Ghernaout et
al., 2014; Uyak and Toroz, 2007; Uyak et al., 2007).
On the other hand, the important portion of aquatic
NOM is constituted of humic substances (HS). These
macromolecular compounds have been illustrated to
be particularly responsive with a range of oxidants
and disinfectants that are employed during the
treatment of potable water, especially chlorine
(Ghernaout, 2014; Slavik et al., 2012). In fact, HS
interact with chlorine species (OCl - /HOCl) to
generate THMs, HAAs and other halogenated DBPs
(Bekbolet et al., 2005; Kristiana et al., 2013).
Algae are abundant and diverse in drinking
water supplies including lakes, reservoirs, rivers, and
streams (Ghernaout and Ghernaout, 2012b).
Occasional algal blooms, comprised of blue-green
(B-G) algae (cyanobacteria) and/or green algae,
cause significant challenges in drinking water
treatment due to the release of organic compounds
(algogenic organic matter, AOM) into water
extracellularly and, upon cell lysis, intracellularly
(Ghernaout et al., 2010b; Her et al., 2004). Besides,
algae are photosynthetic, aquatic plants that utilise
inorganic nutrients such as nitrogen and phosphorus.
Cyanobacteria are typically referred to as B-G algae
because they perform photosynthesis and are similar
in size and colour, even though they are bacteria.
Furthermore, algal cells and associated AOM are
THM precursors, which have resulted in the
restriction of chlorine usage. Similarly, the potential
for toxin release by cyanobacteria, in particular from
Microcystis, has resulted in the WHO setting a
guideline value of 1 μg L-1 for the associated toxin,
microcystin-LR (MCLR) (Henderson et al., 2008).
Another problem of the presence of offensive
taste and odour compounds, including 2-
methylisoborneol (2-MIB) and geosmin in the
resultant drinking water supply, has also been
attributed to high alga populations (Henderson et al.,
2008). Unfortunately, surface water drinking supplies
are also particularly vulnerable to the growth of these
organisms and current US drinking water treatment
practices, as an example, do not monitor or actively
treat for B-G algal toxins including the microcystins.
Besides, harmful algal blooms (HABs) represent a
significant threat to fisheries, public health, and
economies around the world and have increased in
frequency, duration, and distribution in recent
decades (Gobler et al., 2008). On the other hand,
algae are traditionally characterised according to
differences in pigmentation and cell complexity
arising as a result of evolution. Within a particular
phylum, the species can vary significantly in terms of
their morphology and other important functionalities
including the composition and quantity of excreted
extracellular organic matter (EOM). Algae are
typically removed using the following treatment
chain: coagulation/flocculation (C/F) and
clarification either by dissolved air flotation (DAF)
or sedimentation, followed by granular media
filtration. Direct filtration can also be used as a
clarification process. More recently, ozone and
granular activated carbon (GAC) filters have been
installed downstream of clarification, primarily for
pesticide removal (Henderson et al., 2008).
Ultrafiltration (UF) technology, as a promising
substitute technique to classical, may eliminate algae
totally. Nevertheless, transmembrane pressure sorely
augments or flux diminishes throughout algae bloom
for UF application. Moreover, the algal cells liberate
the extracellular polymeric substances (EPS), which
conduct to permeability decrease and more elevated
energy requirements for preserving a fixed permeate
flux. The excretion of EPS depends on algal types.
These EPS play an important role in UF fouling
(Liang et al., 2008).
Classical water treatment technology,
consisting of C/F, decantation and sand-filtration, has
been the greatest frequent one for NOM elimination
from the natural waters (Ghernaout et al., 2011). The
performance of NOM elimination during coagulation
process is highly influenced by several parameters,
such as: nature and properties of NOM particles, type
and dose of coagulant, pH, ionic strength and
temperature (Ghernaout et al., 2015a). In addition, a
fraction of the coagulant (metal salts) that has been
introduced to water is not eliminated troughout the
treatment and remains present in the potable water.
The amendment of the coagulation technique to
obtain higher NOM reductions is named “enhanced
coagulation” (EC) (Ghernaout et al., 2009). EC
correlates with the employment of coagulant
injections efficient for total organic carbon (TOC)
elimination (Uyak and Toroz, 2007). Nevertheless,
an additional alternative of EC has been suggested to
establish performant decrease in DBP generation by
employing an enlarged principle of EC. In fact, in
EC, both the coagulant injection and the coagulation
pH can be well conceived to importantly decrease the
coagulant requirement at the same time augmenting
NOM elimination (Xiao et al., 2013).
Therefore, the most efficient action plan to
decrease the generation of DBPs would be to
diminish the quantity of NOM which is the principal
generator of DBPs, prior to disinfection using
chlorine. EC has been observed to be very
performant in the elimination of NOM from surface
waters, by that means decreasing DBP generation
and reducing chlorine need. Nevertheless, the
shortages of EC comprise the augmented cost of
chemical products, elevated sludge formation, lower
pH conditions (influencing corrosion monitoring),
and augmented treatment chemical products like
aluminium or iron in potabilzed water (Zhang et al.,
2304
Enhanced coagulation for algae removal in a typical Algeria water treatment plant
2012). Regardless of these observed deficiencies, EC
remains contemplated to be the best available
technology (BAT) and the most economical manner
of eliminating generator (i.e., NOM) matter (Uyak
and Toroz, 2007; Xiao et al., 2013).
Further, it was summarised that the major
mechanisms by which NOM can be removed by
coagulation involve charge neutralisation (CN) of
colloidal NOM, precipitation as humates or fulvates,
and coprecipitation by adsorption on the metal
hydroxide (Uyak and Toroz, 2007). Precipitation of
NOM corresponds to the generation of Al- or Fe-
humate with a lower solubility product (Zhang et al.,
2012). The level of NOM elimination using
coagulation is influenced by the type and injection of
coagulants and the pH. The performance of a selected
coagulant to eliminate NOM can change with the
energetic charge density, the floc surface area free for
adsorption, and the type of the bonds among the
NOM and the metal hydroxide flocs (Uyak and
Toroz, 2007; Ghernaout et al., 2015b). Lower pH
reduces the charge density of NOM, making them
more hydrophobic (adsorbable) (Alexander et al.,
2012; Xiao et al., 2013).
Consequently, coagulation removes humic
and high molecular weight OM better than it removes
non humic and low molecular weight OM. Thus, non
humic fraction of NOM can be removed by using
adsorption process. Powdered activated carbon
(PAC) is used for removal of low molecular weight
organics and taste-odour causing materials in raw
water. There are several advantages to adding PAC
during EC which may have greater DBP precursors
removal capacities (Uyak et al., 2007).
In this research, the focus is accorded to SAS
since disagreeable taste-odour manifestation in the
tap water and not well optimized employment of the
PAC in the Station throughout 2006 summer. These
issues evoked consumer’s doubt and attracted the
attention on the treatment stages applied in SAS.
Consequently, a performant and economical solution
must be suggested. First, a physicochemical and
biological comparison between the Boukerdene
Dam’s water and the Station’s treated water is
performed. Secondly, the determination of
responsible agents of disagreable tastes in the
potabilized water is done. Finally, EC tests using jar
tests in the laboratory, where pH is slightly acidified
(pH 6) for the optimised coagulant dose using the
conventional coagulation (CC) procedure, are
realised proving that this process may be the efficient
solution for this Station.
2. Experimental
2.1. Source waters collection
The natural water sources used in this study
are Boukerdene Dam’s waters. Boukerdene Dam was
constructed in 1986 and is located at 1.3 km to SAS.
Quality parameters of these raw waters over 15
month period are summarised in Table 1. Daily
consumption of 2 × 16800 m3 (two chains) drinking
water is supplied from these surface waters in Tipaza.
Table 1. Evolution of turbidity τ, pH, and temperature T (°C) for raw water (a); optimal chemicals doses for performed CC jar
tests in the laboratory (b); and water characteristics after jar tests (c) (numbers between brackets present the corresponding
removal efficiency (%))
Date Raw water characteristics (a) Chemicals doses (mg L -1) (b) Water characteristics after settling (c)
τ (NTU) pH T (°C) Coagulant Polymer PAC τ (NTU) pH T (°C) Taste
01.04.07 7.19 8.13 14.2 20 0.075 24 2.07 (71.21) 7.73 15.2 Light
03.04.07 7.62 8.12 15.7 20 0.075 18 2.25 (70.47) 6.93 15.6 Very light
08.04.07 8.18 8.05 14.9 30 0 12.5 2.10 (74.33) 7.50 16.0 Light
09.04.07 9.79 8.08 15.4 20 0 20 2.05 (79.06) 7.63 17.5 Tasteless
11.04.07 6.81 8.08 15.0 25 0.050 20 2.80 (58.88) 7.56 17.3 Tasteless
16.04.07 5.90 7.94 15.1 20 0.050 20 1.72 (70.85) 7.78 16.2 Very light
18.04.07 5.37 7.98 15.8 40 0.050 15 2.29 (57.35) 7.13 18.1 Tasteful
21.04.07 9.66 7.96 15.7 30 0.100 12.5 1.07 (88.92) 7.29 18.9 Light
22.04.07 8.78 7.90 16.5 40 0.075 15 1.21 (86.22) 6.97 18.7 Tasteful
25.04.07 7.36 7.98 16.5 50 0.075 15 0.71 (90.35) 7.16 19.1 Tasteful
30.04.07 6.01 8.05 15.3 30 0.075 - 1.53 (74.54) 7.62 17.4 -
05.05.07 6.15 7.94 16.7 30 0.050 - 1.81 (70.57) 7.39 17.8 -
12.05.07 22.4 7.87 17.5 20 0.050 - 1.01 (95.49) 7.47 19.9 -
19.05.07 4.73 7.81 18.1 20 0.100 - 0.76 (83.93) 7.39 22.0 -
26.05.07 7.88 7.77 17.4 20 0.100 - 0.41 (94.79) 7.35 22.3 -
02.06.07 4.91 7.73 17.0 20 0.050 - 0.94 (80.85) 7.52 21.2 -
09.06.07 5.88 7.69 18.5 25 0.050 - 0.56 (90.47) 7.07 21.7 -
17.06.07 5.23 7.40 19.1 40 0.075 - 0.91 (82.60) 7.00 24.3 -
24.06.07 6.94 7.63 18.5 15 0.075 - 0.82 (88.18) 7.42 23.1 -
03.07.07 4.31 7.46 18.9 15 0.025 - 0.82 (80.97) 7.33 20.1 -
11.07.07 6.94 7.45 19.9 15 0.030 - 0.84 (87.89) 7.35 22.5 -
21.07.07 6.99 7.52 21.4 20 0.025 - 0.81 (88.41) 7.27 25.1 -
28.07.07 3.54 7.44 20.4 15 0.030 - 0.52 (85.31) 7.31 27.7 -
04.08.07 3.94 7.47 22.5 15 0.015 - 0.72 (81.72) 7.45 24.1 -
11.08.07 3.64 7.41 23.4 15 0.015 - 0.86 (76.37) 7.35 25.5 -
19.08.07 6.22 7.49 24.5 20 0.015 - 1.17 (81.19) 7.34 26.0 -
26.08.07 9.77 7.72 25.0 20 0.025 - 0.76 (92.22) 7.52 28.0 -
2305
2012). Regardless of these observed deficiencies, EC
remains contemplated to be the best available
technology (BAT) and the most economical manner
of eliminating generator (i.e., NOM) matter (Uyak
and Toroz, 2007; Xiao et al., 2013).
Further, it was summarised that the major
mechanisms by which NOM can be removed by
coagulation involve charge neutralisation (CN) of
colloidal NOM, precipitation as humates or fulvates,
and coprecipitation by adsorption on the metal
hydroxide (Uyak and Toroz, 2007). Precipitation of
NOM corresponds to the generation of Al- or Fe-
humate with a lower solubility product (Zhang et al.,
2012). The level of NOM elimination using
coagulation is influenced by the type and injection of
coagulants and the pH. The performance of a selected
coagulant to eliminate NOM can change with the
energetic charge density, the floc surface area free for
adsorption, and the type of the bonds among the
NOM and the metal hydroxide flocs (Uyak and
Toroz, 2007; Ghernaout et al., 2015b). Lower pH
reduces the charge density of NOM, making them
more hydrophobic (adsorbable) (Alexander et al.,
2012; Xiao et al., 2013).
Consequently, coagulation removes humic
and high molecular weight OM better than it removes
non humic and low molecular weight OM. Thus, non
humic fraction of NOM can be removed by using
adsorption process. Powdered activated carbon
(PAC) is used for removal of low molecular weight
organics and taste-odour causing materials in raw
water. There are several advantages to adding PAC
during EC which may have greater DBP precursors
removal capacities (Uyak et al., 2007).
In this research, the focus is accorded to SAS
since disagreeable taste-odour manifestation in the
tap water and not well optimized employment of the
PAC in the Station throughout 2006 summer. These
issues evoked consumer’s doubt and attracted the
attention on the treatment stages applied in SAS.
Consequently, a performant and economical solution
must be suggested. First, a physicochemical and
biological comparison between the Boukerdene
Dam’s water and the Station’s treated water is
performed. Secondly, the determination of
responsible agents of disagreable tastes in the
potabilized water is done. Finally, EC tests using jar
tests in the laboratory, where pH is slightly acidified
(pH 6) for the optimised coagulant dose using the
conventional coagulation (CC) procedure, are
realised proving that this process may be the efficient
solution for this Station.
2. Experimental
2.1. Source waters collection
The natural water sources used in this study
are Boukerdene Dam’s waters. Boukerdene Dam was
constructed in 1986 and is located at 1.3 km to SAS.
Quality parameters of these raw waters over 15
month period are summarised in Table 1. Daily
consumption of 2 × 16800 m3 (two chains) drinking
water is supplied from these surface waters in Tipaza.
Table 1. Evolution of turbidity τ, pH, and temperature T (°C) for raw water (a); optimal chemicals doses for performed CC jar
tests in the laboratory (b); and water characteristics after jar tests (c) (numbers between brackets present the corresponding
removal efficiency (%))
Date Raw water characteristics (a) Chemicals doses (mg L -1) (b) Water characteristics after settling (c)
τ (NTU) pH T (°C) Coagulant Polymer PAC τ (NTU) pH T (°C) Taste
01.04.07 7.19 8.13 14.2 20 0.075 24 2.07 (71.21) 7.73 15.2 Light
03.04.07 7.62 8.12 15.7 20 0.075 18 2.25 (70.47) 6.93 15.6 Very light
08.04.07 8.18 8.05 14.9 30 0 12.5 2.10 (74.33) 7.50 16.0 Light
09.04.07 9.79 8.08 15.4 20 0 20 2.05 (79.06) 7.63 17.5 Tasteless
11.04.07 6.81 8.08 15.0 25 0.050 20 2.80 (58.88) 7.56 17.3 Tasteless
16.04.07 5.90 7.94 15.1 20 0.050 20 1.72 (70.85) 7.78 16.2 Very light
18.04.07 5.37 7.98 15.8 40 0.050 15 2.29 (57.35) 7.13 18.1 Tasteful
21.04.07 9.66 7.96 15.7 30 0.100 12.5 1.07 (88.92) 7.29 18.9 Light
22.04.07 8.78 7.90 16.5 40 0.075 15 1.21 (86.22) 6.97 18.7 Tasteful
25.04.07 7.36 7.98 16.5 50 0.075 15 0.71 (90.35) 7.16 19.1 Tasteful
30.04.07 6.01 8.05 15.3 30 0.075 - 1.53 (74.54) 7.62 17.4 -
05.05.07 6.15 7.94 16.7 30 0.050 - 1.81 (70.57) 7.39 17.8 -
12.05.07 22.4 7.87 17.5 20 0.050 - 1.01 (95.49) 7.47 19.9 -
19.05.07 4.73 7.81 18.1 20 0.100 - 0.76 (83.93) 7.39 22.0 -
26.05.07 7.88 7.77 17.4 20 0.100 - 0.41 (94.79) 7.35 22.3 -
02.06.07 4.91 7.73 17.0 20 0.050 - 0.94 (80.85) 7.52 21.2 -
09.06.07 5.88 7.69 18.5 25 0.050 - 0.56 (90.47) 7.07 21.7 -
17.06.07 5.23 7.40 19.1 40 0.075 - 0.91 (82.60) 7.00 24.3 -
24.06.07 6.94 7.63 18.5 15 0.075 - 0.82 (88.18) 7.42 23.1 -
03.07.07 4.31 7.46 18.9 15 0.025 - 0.82 (80.97) 7.33 20.1 -
11.07.07 6.94 7.45 19.9 15 0.030 - 0.84 (87.89) 7.35 22.5 -
21.07.07 6.99 7.52 21.4 20 0.025 - 0.81 (88.41) 7.27 25.1 -
28.07.07 3.54 7.44 20.4 15 0.030 - 0.52 (85.31) 7.31 27.7 -
04.08.07 3.94 7.47 22.5 15 0.015 - 0.72 (81.72) 7.45 24.1 -
11.08.07 3.64 7.41 23.4 15 0.015 - 0.86 (76.37) 7.35 25.5 -
19.08.07 6.22 7.49 24.5 20 0.015 - 1.17 (81.19) 7.34 26.0 -
26.08.07 9.77 7.72 25.0 20 0.025 - 0.76 (92.22) 7.52 28.0 -
2305
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