River water turbidity removal using new natural coagulant aids: case study of Euphrates River, Iraq

For turbidity removal, most of drinking water treatment plants are using coagulants due to the presence of suspended and colloidal materials at the coagulation and flocculation units. Aluminium and sulphates salts are the widely used coagulants, such as Aluminium sulphate (Alum) and ferric chloride. However, several researches have linked Alzheimer’s disease to the use of Aluminium sulphate. Hence, scholars have conducted several researches on the possibility to reduce the amount of Aluminium sulphate by using natural material/plants base as coagulant aids. In this study, Mallow’s Leaves Extracts (MLE) and Carob’s Pods Extracts (CPE) were used as an alternative coagulant aid. Couples of coagulation tests were implemented to find the optimal dosage of Aluminium Sulphates were used as coagulants. The results displayed that the maximum turbidity removal efficiency by adding 100% of each coagulant (i.e., Alum, MLE and CPE) were (61.16%, 51.175% and 37.12%), respectively. In addition, the minimum residual turbidity and maximum turbidity removal efficiency were 4.56 NTU and 97.72% by adding 22.5 Alum and 7.5 MLE presenting 30 mg/l dosing. Further, the minimum residual turbidity and maximum turbidity removal efficiency were 15.4 NTU and 92.3% by adding 22.5 Alum and 7.5 CPE presenting 30 mg/l dosing.


INTRODUCTION
In rural areas or underdeveloped countries, inadequate water treatment systems and limited availability of chemicals products are existed. Hence, the best possible alternative is to use as easy and comparatively cost-effective point-of-use (POU) technology such as coagulation (Sobsey et al. 2008). In the treatment process of drinking water and wastewater, coagulation is an important operation (Ansari et al. 2018a;Yaseen et al. 2019). It is applied to remove dissolved chemical and turbidity by the addition of synthetic chemical-based coagulants and the most common coagulants are including ferric chloride (FeCl 3 ), Alum (AlCl 3 ), and polyaluminium chloride (PAC) (Vijayaraghavan et al. 2011).
Since high quality of drinking water is required, coagulation and flocculation process are significantly applied for both fresh water and wastewater treatment plants (Al doury & Al samerrai 2019; Bhagat et al. 2020). In addition, it is widely used in fresh water and wastewater treatment due to its simplicity and cost-effectiveness (Tzoupanos & Zouboulis 2008;Ibrahim 2019). Figure 1 shows the advantages of natural plant-based coagulants (NPBCs) over chemical coagulants (Choy et al. 2014). The importance of using NPBCs reported recently due to their advantages as they are represented environmental-friendly materials, healthier and safer than Alum, decrease the sludge treatment and management cost, etc. (Jayalakshmi et al. 2017). In addition, NPBCs work as adsorbent of many chemical compounds when applied as coagulant aids and thus they are applied in wastewater treatment research (Iqbal et al. 2019).
As a matter of fact, using extra Alum dose in drinking water treatment plant could have a negative impact on human health in addition to the high processing cost of Alum coagulant dose (Muthuraman & Sasikala 2014). The scarcity of water resources has become the main problem in many countries of the world (Wan Mohtar et al. 2019). Therefore, other sources of surface water including, streams, lakes and ponds have been supplied to residential areas and used as drinking water after treatment (Kakoi et al. 2016). Application of chemical coagulants (e.g., Alum) materials are significantly used in fresh water and wastewater treatment to get high quality of water, which is considered a significant factor for the stability of the ecosystem. However, increasing pollutants in fresh water and wastewater more than the standard levels led to the use of natural coagulants (Chhipi-Shrestha et al. 2020). Since natural coagulants are considered as environment-friendly, an abundant source with low price, and rapid biodegradable compared to inorganic based coagulants, they became more desirable and are widely used in water treatment (Kumar 2020;Mehr & Akdegirmen 2021). The composition of fresh water and wastewater could highly contain turbidity, total suspended solid (TSS), and Chemical oxygen demand (COD), coming from both domestic and surface runoff sources (Alavi et al. 2021). Turbidity is represented by suspended and colloidal material that can be preliminarily removed through conventional fresh water and wastewater treatment methods using coagulation/flocculation processes (Gippel 1995). There are different types of coagulants and flocculants including inorganic and organic materials, which were commonly used in conventional wastewater treatment processes (Al-Doury & Alwan 2019; Shihab & Ahmad 2020). Globally, organic coagulants consist of aluminum that is commercially available and is the most substantially used as major coagulants in treatment processes for fresh water and wastewater. However, excessive using this traditional coagulant material has increased processing cost and resulting different diseases for human (Lee et al. 2014).
Many water treatments plants (WTPs) in various countries around the world began relying on natural coagulants rather than industrial coagulants to remove or reduce contaminants such as turbidity, color, suspended solids, etc. The main reason behind using these natural coagulants instead of chemical coagulants, they are widely available at a low cost and can be considered more healthy and efficient materials in comparison with others in water treatment. Therefore, many researchers started to investigate the use of these natural materials in water treatment and study their impact on turbidity removal. In this study, the motivation and focus is to use different types of plants which widely available in the west and middle part of Iraq region as a natural coagulant for turbidity removal from raw water.

RELATED RESEARCH
Since there is a serious concern about the relation between aluminum residuals in the treated water and human health, most of the natural coagulants and especially those made of plant were developed to be used as an alternative for Alum material (Bina et al. 2009;Li et al. 2020). Drinking water sources such as river, lakes, groundwater, etc. usually require the use of coagulation and flocculation stage to eliminate turbidity in the form of suspended and colloidal material (Asadollah et al. 2020). One of the major benefits of the treatment process is the capability to reduce or remove different pollutants such as color, organic compounds, bacteria, algae, and clay particles. For instance, suspended particles could clog filters or harm the disinfection process, significantly minimizing the risk of waterborne diseases (Fatoki & Ogunfowokan 2002;Ansari et al. 2018b). Also, adding aluminum salts could cause Alzheimer and there is a concern about its residuals in the treated water because of using an inadequate amount of Alum (Bina et al. 2009). Therefore, Iron salts are considered as one of the best choices. However, the cost of any imported chemicals can be considered as a serious problem especially for developing countries. Consequently, recently natural coagulants from plant-based coagulant sources have been developed and widely used for treatment of fresh water and wastewater compared to chemical coagulants. This is to reduce the cost of fresh water and wastewater treatment process and might be performed as well as chemical materials used for treatment (ELsayed et al. 2020;Lanan et al. 2020).
Many researchers have studied the efficiency of different natural coagulants. For example, Chitosan and Moringa Oleifera have been used as a coagulant in water treatment (Ravikumar & Sheeja 2012). These natural coagulants are equivalent to their chemical counterparts in terms of removal efficiency when they are used for water treatment at low-to-medium turbidity ranged from 50 to 500 NTU (Yin 2010). Jatropha was used to remove the turbidity ranging between (100-8,000 NTU) which was noticed to be agglomerated faster and bigger comparing to using Alum and the turbidity removal efficiency was (98%) (Abidin et al. 2013). Plant leaves of Cassia Alata (LCA) was applied as a coagulant and the experiments were showed that LCA can eliminate turbidity to 93.33% (Rak & Ismail 2012). Peanut seeds extract (PSE) was applied as coagulant with early turbidity of 200 NTU using only 20 mg/l of the extract. Turbidity removal efficiency of 93.2% was achieved. Patale & Pandya (2012) studied the Coccinia indica fruit extract (CIE) as coagulant to treat raw water with initial turbidity (100 NTU). The authors reported that CIE has high turbidity removal efficiency of (94%) was achieved. Opuntia dillenii (ODE) is a based-plant coagulant extracted from the Cactaceae family, Jar tests obtained that (ODE) can remove (89% to 93%) of the initial turbidity (Nougbodé et al. 2013). One study has used natural plants of Moringa Oleifera seed and leaves, which are widely available in the south part of Iraq (Ghawi 2017). The natural coagulants were used in the compact unit of drinking water treatment located in Al-Diwaniyah city in Iraq to remove turbidity as well as heavy metals from raw water. The results of the previous study proved that there is no health impact by using these natural coagulants (natural plants) in water treatment. In addition, this study confirmed that removal percentages of turbidity and heavy metals from raw water were up to 99 and 98%, respectively which met WHO's guidelines for drinking water (Kim et al. 2020). Also, it was concluded that Moringa Oleifera seed and leaves can be significantly used as a natural coagulant rather than other chemical coagulants used in removing turbidity and suspended solids from raw water.
Many factors led to the use of natural coagulants instead of Alum-based coagulants in water treatment. For example, human health problems are highly associated with using Alum-based coagulants in the drinking water treatment process because of aluminum residuals supplied to consumers (Xue et al. 2021). Moreover, an Alum-based coagulant is expensive. Consequently, safe, cost-effective, and environmentally friendly natural coagulants are required in the turbidity removal process. Another study showed that different diseases such as Alzheimer's, Carcinogenic and neurotoxic health effects are considerably linked to chemical coagulants using in water treatment (Kurniawan et al. 2020). A study has used Vigna mungo, Zea plants as natural coagulants to eliminate the turbidity from wastewater and recommended using these natural materials (Sasikala & Muthuraman 2017). It was reported that natural coagulants including Allium cepa peel ash, waste tea powder, Phyllanthus niruri, Vigna mungo and Zea were effectively used in turbidity removal between 70 and 97% for synthetic and surface water samples at neutral pH (Choy et al. 2016). The chemical coagulants are widely used in drinking water treatment. However, the excessive using of these materials has increased the costs and environmental disadvantages. On the other hand, the synthetic organic polymer and polyacrylamide-based coagulant materials including acrylamide have neurotoxic and carcinogenic effects. Thus, these materials are usually harmful since they have ability to pass in the food chain resulting in human health problems. Several researchers suggested alternatives to the use of natural coagulants in pretreatment of drinking water (Leiknes et al. 2004).
It was indicated that the Alum (organic materials) used in wastewater treatment plant has negative human health impacts and water drainage system (Ge et al. 2020). In addition, using more amount of Alum in fresh water and wastewater treatment plant requires more cost of processing. Cassava peels starch (CPS), therefore, was used in form of natural coagulants in another study instead of Alum materials in the wastewater treatment process to remove turbidity from fresh water and wastewater (Kumar 2020). Using sing natural coagulant CPS instead of Alum does for turbidity removal from raw water (turbidities ranging from 20 to 400 NTU) proved that there were not any harmful effects on human health with efficient removal of turbidity up to 81% at pH of 8. Moreover, results obtained from the previous study met the WHO and water quality standards (A & B) for drinking water supplies (Kumar 2020). It was also concluded that the application of CPS in the fresh water and wastewater treatment showed high removal efficiency as a natural coagulant instead of chemical coagulant for turbid particles in the water and wastewater, and it is safe for keeping the health of water according to the recommended standards to discharge wastewater back to the environment after treatment processes (Kumar 2020).
Based on the survey in the Scopus database for 'river water turbidity removal using natural coagulant', 65 research articles were appeared. The major keywords of two keyword occurrence in which 186 keywords presented in Figure 2, using the VOSviewer algorithm. The exhibited keywords connection revealed the significant of this topic within domain of environmental engineering and freshwater science management. Drinking water, potable water, chemical treatment, chemical removal are the major links with the water turbidity and natural coagulants. Based on the timeline of years, limited researches have been adopted only 5 articles in 2021. However, it is worth to mention about 27 countries have displayed major interest in this research domain due to the necessity for providing easy and newly advanced technology for water treatment (Table 1). It is worth to have an idea for the regions that have focused on this kind of research. Based on Table 1 abstracted from the Scopus database, 27 countries were observed to study the development of natural coagulant for river water turbidity. China and Malaysia were on the top of those countries followed by Australia and Brazil. However, limited research was observed for Iraq region and thus more investigations are needed. Recently, several studies confirmed the viability of the natural coagulants for water treatment. For instance, natural polymers abstracted from Sago and Tapioca were used for river water turbidity and chemical oxygen demand (Zainol et al. 2020). The ability of Scallop shells were used as natural coagulant for water turbidity removal (Siswoyo et al. 2021). In another research, the authors tested the effectiveness of the Moringa oleifera seeds as bio-coagulant for surface water turbidity treatment (Nhut et al. 2021). Hexane, Saline and Crude were extracted from Kenaf plant seed for determining a reliable coagulation to remove organic matter (Okoro et al. 2021).
The inspiration of the current research was adopted from the reported literature on the proposition of new natural coagulants aid and particularly for a country like Iraq. Hence, the research objectives are: i) to find out the effect of using locally plants-based bio-flocculants (natural coagulants) as coagulant aids on turbidity removal efficiency of raw water that has initial turbidity 200 NTU, pH of 7.5, and Total Dissolved Solids (TDS) about 450 mg/l, ii) to find the optimum dosage (at the best turbidity removal efficiency) of natural coagulants that can be added for turbidity removal from raw water compared with other types of coagulants materials.

MATERIALS AND METHODS
The main purpose of the study is to apply natural Iraqi locally plants such Carob's Pods Extract (CPE) and Mallow's leaves Extract (MLE) as coagulant Aids for surface water turbidity removal.

Water sampling
In this research, stream water was investigated, and water samples were collected during wet season (January-April of 2020) after storm events, Figure 3 shows the sampling station map and Figure 4 presents the tests processes stages and measurements (data collection). All tests were carried out in dams and water resources engineering, university of Anbar. Table 2 reports the characteristics of the raw water samples taken from Euphrates River near the large Ramadi drinking water treatment plant intake, Anbar province, Iraq. Euphrates River is considered as one of the essential surface fresh-water for Iraq region and its water quality is highly important (Al-Sulttani et al. 2021; Khaleefa & Kamel 2021). Turbidity and pH measurements were recorded in field. Samples were left 24 hours (settling period) and measurements recorded in laboratory again. The turbidity of settled raw water were fixed about (200 NTU) by adding distilled water to raw samples, which was very high turbidity. 30 Liters containers of such samples were collected. All experiments were carried out within (ASTM) in the Environmental Lab of Dams and Water Resources Engineering Department in the University of Anbar at (January-April of 2020).

Apparatus
All tests were carried out in dams and water resources engineering, university of Anbar. The main apparatus used in this research were included:

Coagulants
Coagulation could be carried out using either chemical-based coagulants like Alum or natural coagulants like natural plantbased coagulants (NPBCs) (Choy et al. 2014).

Alum
The common coagulant Alum was applied in this research (i.e., Al 2 (SO 4 ) 3 .18H 2 O) chemical formula was adopted from the literature (Choy et al. 2014).

Natural plant-based coagulants preparation
Firstly, (ML and CP) were collected, washed with distilled water, drying for (1 hour at 40°C). then, grinding manually to powder form. The extraction of active coagulants was carried out by mixing 0.5 g of the (ML and CP) powder with 100 mL of the Sodium chloride (NaCl) for 1 hour at 40°C. NaCl with (0.3 Molarity) concentrations were used. The obtained mixture was centrifuged and filtrated. The clear solution was used as a coagulant aid in the subsequent experiments. This process was followed the reported literature (Šcíban et al. 2009). Fresh coagulants were extracted and diluted by double distilled water to get a stock of (10 mg/L) and used directly to avoid the aging effects, as pH and coagulation efficiency due to the microbial decomposition of the organic matters during storage.
Residual turbidity (T s ) was determined by applying the following equation: where, T r , T ο and T f are the residual, initial and final turbidity's (NTU) of the waters respectively. The turbidity removal efficiency (η%) calculated by using the following equation: where, η% is turbidity removal efficiency (Salvato et al. 2003).

Flocculation experiments
Experiments were carried out using the standard conventional Jar test (6-jar apparatus) to figure out the optimal coagulant dose. For experimental work, samples of water with average turbidity of 200 NTU were obtained. The samples were poured into the jar test unit. The set-up used was as follows: the turbid water was initially easily stirred at 250 rpm for 1 minute, then Alum salt and coagulant aids (MLE or CPE) were added and the mixture was stirred for another minute at the same speed, then, the mixture was mixed gently for (fifteen minutes) with (fifty rpm) rotating speed, after that, the flocs were left to precipitate for (10-30 minutes), then, the supernatant liquid were analyzed. Finally the optimum dose of coagulant could be determined (Salvato et al. 2003).

Uncorrected Proof
All tests were carried out at temperature of (22 + 1°C). Although, the pH did not alter much throughout flocculation, the pH value has been controlled (pH:8) . The integral design of a flocculation processes taking into account both particle destabilization and particle transport (Bhatia et al. 2007). The research was studied the capability of using MLE and CPE as NPBCs coagulant aids and with Alum as a main coagulant. Different dosages of (15,20,25,30,35, 40 mg/l) were applied.
Based upon the coagulant dosages, settling times have differed. At the end of the settling period, A 100 ml samples of were taken from 1 cm below the water surface using suction apparatus. The magnitude of residual turbidity was recorded, and the   Uncorrected Proof turbidity removal efficiency of the Alum used with each coagulant aid (MLE and SPE) materials with the different percentages were determined. These percentages were applied for all dosages added in the study. This method was repeated for each coagulant aid and for each coagulant aid percentage.

RESULTS AND DISCUSSION
The results of the laboratory work were presented in Figure 6(a)-6(l). These findings were graphed against various parameters such as coagulant aids percentage dosages verse different parameters such as residual turbidity, turbidity removal efficiency. Whereas, the pH-value were exhibited in Figure 7(a)-7(g), were obtained using the Jar-Test. The original values of the parameters were as follows: (200 NTU turbidity, pH of 7.5, and TDS about 460 mg/l).

Effect of coagulant type on turbidity removal
The removal efficiency of different coagulant aids NPBCs for the initial 200 NTU of raw river water was investigated in this study using Alum as main coagulant, MLE, and CPE with 100% ratio of Alum. It can be seen from Figure 6(a) the results of residual turbidity by adding 100% of Alum, (MLE) and (CPE) coagulants, the lowest concentrations of residual turbidities of 5.47, 97.65, and 125.76 NTU that were measured by adding coagulant dosages of 30, 30, and 25 mg/l for Alum, MLE, and CPE, respectively. The maximum removal efficiency of turbidity was found by adding 100% of Alum, MLE, and CPE coagulants ( Figure 6(b)). The turbidity removal efficiencies were 97.265, 51.175, and 37.12% for coagulant dosages of 30, 30, and 25 mg/l for alum, MLE and CPE, respectively. However, the residual turbidity and turbidity removal efficiency were measured by adding different MLE percentages ratio of Alum as a coagulant aid (i.e., 100, 50, 40, 25, and 0%) with Alum. According to Figure 6(c) and 6(d), it was observed that the minimum residuals turbidity were 97. 65,20.53,16.83,4.56,and 65.47 NTU by adding 100,50,40,25,and 0%,respectively. Figure 6(d) Figure 6(g) and 6(h), they improved the separation of suspended solids remarkably. However, Figure 6(g)-6(i) illustrated the residual turbidity by adding MLE and CPE at the same concentration or ratio. The forgoing Water Supply Vol 00 No 0, 10 Uncorrected Proof results described showed clearly that Alum of 22.5 mg/l in combination with (7.5 mg/l) of MLE had the favorable performance and can be represented as the optimum coagulants dosages because these coagulants had given minimum residual turbidity and maximum turbidity removal efficiency. Figure 6(j)-6(l) illustrated the turbidity removal efficiency by adding MLE and CPE at the same concentration or ratio. The results described above showed clearly that Alum of 22.5 mg/l in combination with (7.5 mg/l) of MLE had the favorable performance and can be represented as the optimum coagulants dosages because these coagulants had given minimum residual turbidity and maximum turbidity removal efficiency.

Effect of coagulant on pH
In precipitation, the pH of raw water takes a significant role (Misbahuddin & El-Rehaili 1995). The raw water has initial pH of around 7.6, based on the findings and Figure 7(a)-7(g) revealed that adding Alum alone with a percentage of 100%, there is  Uncorrected Proof a slight change in the pH value. In addition, there is no more change when adding MLE and CPE as coagulant aids in combination with Alum with all percentages of (50, 60 and 75%). Further, it was observed small change in the pH when adding MLE only (100%). The maximum magnitude of pH of (7.73) was recorded using 40 mg/l of MLE with the 100%. The values of TDS have not changed much and thus these values may not effect on water treatment efficiency. The major factors affecting turbid water treatment include coagulants type coagulants percentages and pH value. Finally, it is worth to report the summary percentages of the additives NPBCs aids (Table 3).

CONCLUSION AND RECOMMENDATIONS
The following research conclusions and recommendations were summarized from the current study: Uncorrected Proof 1. High turbid water can be treated with high removal efficiency by adding natural plant-based bio-flocculants as a coagulant aid with 75% of Alum, where the values that recorded when using MLE were: final turbidity 4.56NTU, removal turbidity efficiency of 97.72%. This value of turbidity is complying with Iraqi specification of drinking water. 2. Alum application is not strongly advised because it record more residual turbidity than if it is applied with other coagulant aids such as MLE and CPE with different concentrations, which will reduce the amount of alum added and thus reduce the cost. 3. Increasing the concentration of the coagulants has an efficient effect in increasing the turbidity removal efficiency and reducing the residual turbidity. 4. Increasing the MLE and CPE dosages does not result in a significant change in the pH and TDS values. 5. The research recommended to study the removal efficiency of the same coagulant aids with high turbid water (more than 200) NTU.

ACKNOWLEDGEMENT
The authors acknowledge the support obtained from the University of Anbar.

CONSENT TO PARTICIPATE
Not applicable.

CONSENT TO PUBLISH
The research is scientifically consent to be published.

COMPETING INTERESTS
The authors declare no conflict of interest.

DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information. The data is presented in the manuscript results.

ETHICAL APPROVAL
The manuscript is conducted within the ethical manner advised by the Environmental Science and Pollution Research.

FUNDING
The research received no funds.