DESALINATION OF SEAWATER BY USING ELECTROCOAGULATION TECHNIQUE

DESALINATION OF SEAWATER BY USING ELECTROCOAGULATION TECHNIQUE

Ahmed H. Al-Saad¹;Hanan A. Fouad² ;Rehab M. El-Hefny³

andMohamedAbdelmoniem Heikal⁴

Sanitary Engineering Department, Faculty of Engineering, benhaUniversity¹.

Professor of Sanitary & Environmental Engineering, Faculty of Engineering at Shoubra, BenhaUniversity²

Associate Professor of Sanitary & Environmental Engineering, Faculty of Engineering at Shoubra, BenhaUniversity³.

Consultant , International office for water & Environmental Studies⁴

ABSTRACT:

The aim of this study on the electro coagulation process, is to obtain the optimum values, for retention time, space between the electrodes and the electric current intensity, that can be used to yield the best result when treating sea water by this method. this was done by constructing a pilot -scale EC reactor and applying a set of electric currents (under a temperature of 20 degrees) through the electrodes and changing the retention time and the distance between them.

The removal percentages of the parameters that the study aimed to reduce were as the following: total hardness= 17.73%, Calcium hardness= 30.94%, total alkalinity= 90.78%, bicarbonate = 90.78%, calcium= 30.77%, sulfates = 49.75%; these results show that the treated seawater with the optimum electrocoagulation setup obtained from this study will cause less calcification when passing through the R.O filters making it easier to obtain potable water from the seawater.

1. INTRODUCTION

A portion of the components present in the water speaks to a perilous factor both for the general wellbeing of people and creatures or in any event, for the remainder of the procedures to evacuate salts through desalination procedures(Bintuan Zhu, (2005).For example, switch assimilation,among these components, are calcium and magnesium found in water as carbonate or bicarbonate calcium sulfate(Hu, 2003), which makes their expansion in surface of the membrane on the outside of the membrane This makes the membrane obstruct and crush them together; so we ought to consistently diminish the calcium content in the water to guarantee that these deposits are not present on the outside of the membrane. The expense of removing these components from water is high to such an extent that we have turned to unconventional techniques(Ennio Cardona, 2003).For example, EC to evacuate these components(Hakizimana et al., 2015), which may make harm human wellbeing or for separation forms whether by membranes or others(Graeme and Millar, 2014). Desalination, through the most recent 20 years, there is the introduction of another seawater handling process; EC So as to takes note of certain realities its context, relate it is a unique circumstance, and comprehend its conditions, this survey concerns a short depiction of the utilization of EC as another seawater pretreatment process all through crafted by (Sanfan, 1987) until crafted by Liet al. (2009) by means of work by Sanfan (1991), every one of them is distributed in Desalination. The principal paper talks about the system of removing a few particles from the salty water utilizing the EC technique (Sanfan, 1987). Test results present some significant parameters for the EC procedure. The most significant one inactivity is the electric current density (CD). Besides, the primary paper proposes the technique for choosing ideal density and a few different ways could raise the financial property of EC and could diminish taking care of expenses. In the paper of Sanfan (1991) the further research aftereffects of improving the monetary property of EC technique are examined. So as to decreases the expense and raise the taking care of proficiency, five distinctive innovative procedures are set up and considered (Sanfan, 1991). The best one was the utilizing Fe anode and aerating through for crude water consolidate with reusing flocs. It can lessen 60% of handling costs in withal cathode and expel 75% of hardness. At long last, Li et al. (2009) utilize a basic and new viable electrochemical strategy (EM) before the turn around assimilation for seawater desalination (Sozhan, 2009). The impacts of three primary factors in Ems-CD, working time and sedimentation time on the effectiveness of pretreatment-have been researched. It is demonstrated that EM is successful for expulsion of turbidity. The characteristics of the crude and the treated seawater have been estimated utilizing UV-Vis spectrometry. The morphologies and the molecule size are a dispersion of the came about slop has been portrayed by scanning electron microscopy (SEM) and a molecule size analyzer, and the component of the EM has been broke down hypothetically.  Raw seawater with a turbidity of 54.1 NTU, 94.48 mg L−1 SS.After EM pretreatment at 26.30 mA cm−2 CD for 40 min reduces the turbidity to 1.00 NTU. The time was taken for the same depletion of turbidity in case of 39.45 mA cm² CD is 35 min, and the absorbance of the curve decreases when EM treatment is applied. The experimental results reveal that particular size in seawater agglomerate and get bigger after EM treatment, and the turbidity removal is enhanced by charge clear coagulation.The sludge generated from the process is found to have larger specific surface areas at higher CD from SEM observation, leading to better treatment efficiency. EC was also used to remove silica from seawater(Xin Zhang, 2019). The objective was to investigate the performance of a pilot-scale EC reactor.The experiment works under a constant temperature of (20 c ± 2 c).

1. MATERIALS AND METHODS

The main objective of this study was evaluating the effect of EC. On seawater as a pretreatment to obtain the optimum setup that yields water with a value closer to the portable water. Therefore reducing the skimming that happens in the R.O. membrane. The seawater uses in the study comes from the waters of the Mediterranean Seain Egypt. The seawater uses in the study comes from the water of the Mediterranean Seain Egypt. The characteristics of seawater uses in the EC process shown in table (1).

Table (1) seawater characteristics.

A bench-scale EC reactor was constructed 13 liters glass basin for the experimental works under a constant temperature of (20 C ± 2 C) The bars were fixed vertically and parallel to each other and connected to a variable power supply (MCH 0-30 V/10A) as shown in fig (1). 

Fig (1) EC process

The reactor was worked on 9 runs to determine the optimum ampere.The spacing between the bars and the duration of reaction for the process to achieve the best removal ratio. The experiments were operated at a temperature (22ºC ± 2ºC) throughout the reactor was worked on 9 runs, the purpose of the first three runs to determine the ideal current for the process. The distance between the electrodes was fixed by 2 cm and the samples were taken at 30 minutes. The test was carried out according to the standard methods for the examination of water and wastewater (American Public Health Association, 2017).

1. RESULT AND DISCUSSION

The result for total hardness, calcium hardness, for total alkalinity,Bicarbonate HCO_3, calcium (Ca⁺⁺) and for sulfate (SO4⁺⁺) shown in the fig(2,3,4,5,6,7) respectively.

 Fig2 current effects in the removal of total hardness.

Fig 3 Current effects in the removal of calcium hard.

Fig 4 current effects in the removal of total alkalinity. 

Fig 5 current effects in the removal ofBicarbonate HCO₃^-.

Fig 6 current effects in the removal of calcium (Ca⁺⁺). 

Fig 7 current effectsin the removalof sulfate (SO₄⁺⁺).

According to the equation, the greater the concentration, the greater the sedimentation at 3 A, the voltage on the plates is low and the release of ions is low and the reaction time is insufficient for sedimentation. At 8 amps the voltage is higher and the ions release is higher but the reaction time is insufficient to complete the deposition but at 10 amps, the release of the ions is large, thus increasing the concentration and increasing the sedimentation.

The second three runs their aim was selected the best space between bars the second case with variable distance and constant time (40 min) and constant current (6 ampere) the result was for total hardness, calcium hardness, for total alkalinity, Bicarbonate HCO_3, calcium (Ca⁺⁺) and for sulfate (SO4⁺⁺) as shown in the fig (8,9,10,11,12 and 13) respectively.

Fig8 spacing effects in the removal of total hardness

Fig 9 spacing effects in the removal of calcium hard.

Fig 10 spacing between the electrodes effects in the removal of total alkalinity.

 Fig11 spacing effects in the removal of Bicarbonate HCO₃^-

Fig 12 spacing effects in the removal of calcium (Ca⁺⁺). 

Figure 13 spacing effects in the removal of sulfate ( SO₄⁺⁺).

When increasing the distance between the electrodes from 1 cm to 2 cm. We find that separation rates increased because this increase allows free movement of iron ions between electrodes and gives a full opportunity to interact with existing calcium and carbonate to complete the complete deposition process when it increases to more than 2%. Cm) you find that the concentration of these ions has become diluted, so the reaction is very slow and the separation rate is lower.This phenomenon is called Hindrance, which explains the process of reducing the rate of separation of these elements in water, while excess iron ions reduce their interaction with calcium carbonate or with existing calcium It does not give a complete chance to ionize a portion of calcium to react with iron or carbonate present to complete the deposition process it is always preferable that the current applied to these panels with distances that allow the ionization process of the iron to react with carbonates and bicarbonates The deposition process also allows the reaction of iron ions released with other elements such as sulfate in the same way and when these elements are released and separated (carbonates and sulfates) and their interaction with iron to form deposits, thus eliminating the proportion of sulfates, bicarbonates, and bicarbonates Calcium automatically after being released from the carbonates and sulfates to the water content to precipitate as a result of increasing its concentration and not the result of Ec. that it is part of this calcium before deposition is attracted to the negative plates because it carries the positive charge and therefore visible on the negative plates deposition of calcium element This is the scientific explanation for the increase in the proportion of efficiency extraction It can be summarized that increasing the distance between the electrodes reduces the efficiency of the extraction process and increasing the current intensity on the electrodes reduces the separation process. The current intensity applied to the panels must be balanced with the distance between the electrodes that allow the freedom of cations and anions to interact together to complete the deposition process as well.

In the final runs, the best current and the best distance was taken with time changes to get the ideal time for reaction The third case with variable time and constant current (10 amperes) and constant distance between the electrodes (2cm) the result was as shown in fig (14,15,16,17,18 and 19).

Fig 14 time effects in the removal of total hardness

 Fig 15 time effects in the removal ofcalcium hard.

Fig 16 time effects in the removal of total alkalinity.

Fig 17 time effects in the removal of Bicarbonate HCO₃^-.

Fig 18 time effects in the removal of calcium ( Ca⁺⁺).

Fig 19 time effects in the removal of sulfate

The increase in reaction time may not be strong because the amount of ions emitted by the electrodes is not as dependent on time as it depends on the intensity of current and the distance between the electrodes if, in the case of carbonate, it may increase slightly as a result of electrolysis of water producing carbon dioxide. Not Results from the presence of EC.

4. CONCLUSION

Through the above experimental that have been done to study the effect of the process of electrocoagulation on the removal of different elements such as Total Hardness, Calcium Hardness, Total alkalinity, Bicarbonate HCO₃^-, Calcium Ca⁺⁺, TDS, Chloride Cl ^-, Sulfate SO₄⁺⁺, and pH in terms of the impact of different parameters such as Reaction time, space between electrodes, ampere with one of them and the change of the last parameter and through the previous forms it is clear that:-

1. It was observed that the effect of ampere was very clear and observed that the best effect was at 10 ampere although the different elements above was increased than the original value in the feed water and this due to the analysis of the carbonate and change from bicarbonate to carbonate except for Ca hardness, Ca⁺⁺ and sulfatethe best effective at 6 ampere.

1. Effect of the pace as observed and the best result for removal at 2 cm due to the strike elements above of charge on the plate of electrodes.
2. Time was very effective for removal at 120 min due to high retention time for complete analysis and reaction.

REFERENCES

American Public Health Association, A. W. (2017). Standard Methodes for th Examination of Water and Wastewater . American Public Health Association.

Bintuan Zhu, D. A. (2005). Comparison of electrocoagulation and chemical coagulation pretreatment for enhanced virus removal using microfiltration membranes. ScinceDirect, 3098-3108.

Ennio Cardona, S. C. (2003). Energy-saving with MSF-RO series desalination plants. ScienceDirect, 153, 167-171.

Graeme J. Millar, J. L. (2014). Evaluation of electrocoagulation for the pre-treatment of coal seam water. ScienceDirect, 166-178.

Hakizimana, Jean Nepo ; Gourich Bouchaib ; Ch. Vial ; P. Drogui ; A.  Oumani ; Jamal Naja and L. Hilali (2015):Assessment of hardness, microorganism and organic matter removal from seawater by electrocoagulation as a pretreatment of desalination by reverse osmosis. Desalination, 393: 1-10.

Hu, L. S. (2003). Effect of co-Exixtting anions on fluoride removal in electrocoagulation EC process using aluminum electrodes. Water Res., 4513-4523.

Li, Tao  ; ZhangYi  and SindhwaniVikas (2009): A Non-negative Matrix Tri-factorization Approach to Sentiment Classification with Lexical Prior Knowledge. Association for Computational Linguistics., 244–252

Sanfan, W. (1991). Studies on the economic property of the pretreatment process of brackish water using electrocoagulation (EC) method. Science Direct, 159-163.

Sozhan, S. V. (2009). Studies on a Mg‐Al‐Zn Alloy as an Anode for the Removal of Fluoride from Drinking Water in an Electrocoagulation Process. Wiley Online Library, 372-378.Sanfan, W. Q. (1987). Experimental studies on the pretreatment process of brackish water using electrocoagulation (EC) method. Desalination, 353–364.

Xin Zhang, M. L. (2019). Performance of precipitation and electrocoagulation as pretreatment of silica removal in brackish water and seawater. Sciencedirect, 18-24.

تحلیه میاه البحر باستخدام تقنیه التخثیر الکهربائی

احمدحمیدالسعد¹ ‘حنان احمدفؤاد²‘رحاب محمد الحفنی³  ‘محمدهیکل⁴

1. قسم الهندسة الصحیة ، کلیة الهندسة ، جامعة بنها
2. أستاذ الهندسة الصحیة والبیئیة ، کلیة الهندسة فی شبرا ، جامعة بنها
3. أستاذ مساعد فی الهندسة الصحیة والبیئیة ، کلیة الهندسة بشبرا ، جامعة بنها
4. مستشارالمکتب الدولی لدراسات المیاه والبیئة

الهدف من هذه الدراسة حول عملیة التخثر الکهربائی ، هو الحصول على القیم المثلى ، لوقت الاحتفاظ ، والمسافة بین الأقطاب وکثافة التیار الکهربائی ، والتی یمکن استخدامها لتحقیق أفضل نتیجة عند معالجة میاه البحر بهذه الطریقة. وقد تم ذلک عن طریق بناء مفاعل EC ذو مقیاس تجریبی وتطبیق مجموعة من التیارات الکهربائیة (تحت درجة حرارة 20 درجة) من خلال الأقطاب الکهربائیة وتغییر وقت الاحتفاظ والمسافة بین الاقطاب.

کانت نسب الازالة للعوامل التی تهدف الدراسة إلى خفضها على النحو التالی: العسرة الکلیة = 17.73 ٪ ، عسرة الکالسیوم = 30.94 ٪ ، القلویة الإجمالیة = 90.78 ٪ ، البیکربونات = 90.78 ٪ ، الکالسیوم = 30.77 ٪ ، الکبریتات = 49.75 ٪ ؛ توضح هذه النتائج أن میاه البحر المعالجة باستخدام خلیة تخثیر کهربائی ذات قیم مثلى مشابهة للتی وصلت الیها الدراسة تجعل ماء البحر المعالج بها یسبب تکلسا اقل عند المرور عبر مرشحات R.O مما یسهل معالجتها.