2-Civil - IJCSEIERD - OPERATING - Neha-p

International Journal of Civil, Structural, Environmental and Infrastructure Engineering Research and Development (IJCSEIERD) ISSN 2249-6866 Vol.2, Issue 3, Sep 2012 12-29 Š TJPRC Pvt. Ltd.,

OPERATING COST ANALYSIS OF CONTINUOUS MODE ELECTROLYTIC DEFLUORIDATION PROCESS 1

NEHA MUMTAZ, 2GOVIND PANDEY, 3PAWAN KUMAR LABHSETWAR& 4 SUBHASH ANDEY 1

Student of M.Tech (Civil) Environmental Engineering, M. M. M. Engineering College, Gorakhpur, U. P., India

2

Associate Professor, Department of Civil Engineering, M. M. M. Engineering College, Gorakhpur, U. P., India

3

4

Principal Scientist and Head, Water Technology and Management Division, National Environmental Engineering Research Institute (NEERI), Nagpur, India

Principal Scientist, Water Technology and Management Division, National Environmental Engineering Research Institute (NEERI), Nagpur, India

ABSTRACT One of the major challenges faced by mankind today is to provide clean water to a vast majority of the population around the world. The need for clean water is particularly critical in increased resource demand scenario. In the present work, the design of electrolytic defluoridation unit based on continuous mode has been given taking into account the design criteria well suited for the school located in Seoni district of Madhya Pradesh, India. It appears to be a promising alternative for the treatment and will go long way towards providing safe drinking water in the fluoride affected areas of the developing countries. The recurring cost for the treatment worked out for electrolytic defluoridation demonstration plant is Rs. 7.75 per 1000 L of treated water which is much cheaper than the treatment cost by any other defluoridation system available in the market. What is needed is a simple scalable system using the locally available material for the treatment of raw water to render the same fit for human consumption. The present system provides a technically simple, cost-effective and reliable community drinking water purification system for supplying drinking water.

KEYWORDS: Aluminium electrodes, Coagulant, Continuous process, Electrolytic defluoridation, Water treatment.

INTRODUCTION In developing countries like India where access to safe drinking water is not guaranteed for a majority of the population, it is of great importance to maintain the quality of surface water sources. One of the major challenges faced by mankind today is to provide safe drinking water to a vast population around

13

Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process

the world. It is learnt that fluoride concentrations in groundwater in the world ranges from 0.01 to 48 mg/L (Emamjomeh et al., 2009). According to the guidelines of World Health Organization (WHO) issued in 2011, the guideline value is 1.5 mg/l for drinking water quality. People in more than 35 nations across the globe face issues of excess fluoride in drinking water, the intensity and severity of which varies with the environmental settings in terms of their geographical and economical status. Fluorides are released into the environment naturally through weathering and dissolution of rock minerals, in emissions of volcanoes, and in marine aerosols. The two most populated countries of the world, China and India, stand at the top in the list of worst hit nations in groundwater contamination with fluoride. In both these countries, the major source of fluoride pollution is the natural weathering process. Drinking water containing high fluoride content for longer time can result in mottling of teeth, softening of bones and ossification of tendons and ligaments.

(Ayoob et al, 2008).

Almost 25 nations and 200 million people globally are affected by the fluorosis. It has been estimated that fluorosis is prevalent in 20 states of India affecting approximately a population of 65 million (State of Environment Report India, 2009). Desirable concentration of fluoride to be maintained in drinking water is 1 mg/L and permissible limit in the absence of alternate sources is 1.5 mg/L as per Indian drinking quality standards (IS 10500-1991).

Although fluoride is regarded as an essential chemical element, there is no evidence that overt clinical signs of fluoride deficiency exist. In contrast, however, scientific evidence suggests that excess fluoride has adverse health effects (Dasarthy et al., 1996).

Yousuf et al. (2001) have reported that the need for clean water is particularly critical in increased resource demand scenario. One of the major challenges faced by mankind today is to provide clean water to a vast majority of the population around the world.

In India, it was first detected in Nellore district of Andhra Pradesh in 1937 (Shortt et al., 1937). In India, it was first detected in Nellore district of Andhra Pradesh in 1937 (Shortt et al., 1937). According to the report of Ministry of Water Resources (2008), mentioned in Table 1, it is estimated that fluorosis is prevalent in 19 states of India (State of Environment Report India, 2009).

14

Neha Mumtaz, Govind Pandey, Pawan Kumar Labhsetwar & Subhash Andey

Table 1: State-wise Details of Distribution of Fluoride in Groundwater above Permissible Limit.

Number of S.No.

State

districts

Fluoride Districts (in parts)

affected Adilabad, Anantpur, Chitoor, Guntur, Hyderabad, Karimnagar, Andhra

Khammam, Krishna, Kurnool, Mehaboobnagar, Medak, Nalgonda, 19/23

1 Pradesh

Nellore, Prakasham, Rangareddy, Vishakhapatanam, Viziangaram, Warangal, West Godawari.

2

Assam

4/27

3

Bihar

9/38

Goalpara, Kamrup, Karbi, Anglong, Naugoan.

Aurangabad, Banka, Buxar, Jamui, Kaimur, Munger, Nawada, Rohtas, Supaul.

Bastar, Bilaspur, Dantewara, Janjgir-Champa, Jashpur, Kanker,

4

Chhattisgarh

12/21 Korba, Koriya, Mahasamund, Raipur, Rajnandgoan, Suguja.

East Delhi, New Delhi, Northwest Delhi, South Delhi, Southwest

5

Delhi

6/9 Delhi, West Delhi.

Ahmedabad, Amreli, Anand, Banaskantha, Bharuch, Bhavnagar,

6

Gujarat

18/26

Dahod, Junagarh, Kachchh, Mahesana, Narmada, Panchmahals, Patan, Rajkot, Sabarkantha, Surat, Surendranagar, Vadodara.

Bhiwani, Faridabad, Gurgaon, Hissar, Jhajjar, Jind, Kaithal,

7

Haryana

14/21 Kurkshetra, Mahendragarh, Panipat, Rewari, Rohtak, Sirsa, Sonepat.

Jammu 8

and 2/22

Rajauri, Udhampur.

6/9

Bokaro, Giridih, Godda, Gumla, Palamau, Ranchi.

Kashmir 9

Jharkhand

Bagalkot,

Bangalore,

Chamarajnagar, 10

Karnataka

Bellary,

Belgaum,

Bidar,

Bijapur,

Chikmagalur, Chitradurga, Devangere, Dharwar,

20/30 Gadag, Gulbarga, Haveri, Kolar, Koppala, Mandya, Mysore, Raichur, Tumkur.

11

Kerala

1/14

Palakkad.

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Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process

Bhind, Chhatarpur, Chhindwara, Datia, Dewas, Dhar, Guna, Gwalior, Madhya 19/50

12

Harda, Jabalpur, Jhabua, Khargone, Mandsaur, Rajgarh, Satna, Seoni,

Pradesh Shajapur, Sheopur, Sidhi.

Amrawati, Chandrapur, Dhule, Gadchiroli, Gondia, Jalna, Nagpur, 13

Maharashtra

8/35 Nanded.

Angul, Balasore, Bargarh, Bhadrak, Boudh, Cuttack, Deogarh,

14

Orissa

11/30 Dhenkanal, Jajpur, Keonjhar, Suvarnapur.

Amritsar, Bhatinda, Faridkot, Fatehgarh Saheb, Firozpur, Gurdaspur,

15

Punjab

11/20 Mansa, Moga, Muktsar, Patiala, Sangrur.

Ajmer, Alwar, Banswara, Barmer, Bharatpur, Bhilwara, Bikaner, Bundi,

16

Rajasthan

30/33

Chhittorgarh,

Churu,

Dausa,

Dholpur,

Dungarpur,

Ganaganagar, Hanumangarh, Jaipur, Jaisalmer, Jalore, Jhunjhunu, Jodhpur, Karauli, Kota, Nagaur, Pali, Rajasamand, SawaiModhopur, Sikar, Sirohi, Tonk, Udaipur.

Coimbatore, Dharmapuri, Dindigul, Erode, Karur, Krishnagiri,

17

Tamil Nadu

16/32

Namakkal,

Perambalur,

Puddukotai,

Ramnathpuram,

Salem,

Shivaganga, Theni, Thiruvannamalai, Vellore, Virudunagar.

Agra, Aligarh, Etah, Firozabad, Jaunpur, Kannauj, Mahamayanagar, 18

Uttar Pradesh

10/71 Mainpuri, Mathura, Maunathbhanjan.

Bankura, Bardhhman, Birbhum, Dakhin, Dinajpur, Malda, Nadia,

19

West Bengal

8/19 Purulia, Uttar Dinajpur.

Source: Ministry of Water Resources 2008

ELECTROLYTIC DEFLUORIDATION Currently, there is a growing interest in Electrocoagulation (EC) process or electrolytic defluoridation. The technique is used to treat restaurant wastewater (Chen et al., 2000), textile wastewater (Bayramoglu et al., 2004), and fluoride-containing wastewater effectively. The EC process is reported to be efficient for drinking water defluoridation (Zuoa et al., 2008). Electrocoagulation process (EC) using sacrificial aluminum electrodes has been demonstrated to be an effective process since it does not require a substantial investment, presents similar advantages as chemical coagulation and reduces disadvantages, (Hu et al., 2005) and less waste slurry production (Mollah et al., 2001, Essadki et al., 2009). The technology lies at the intersection of three more fundamental technologies—electrochemistry, coagulation and flotation.

16

Neha Mumtaz, Govind Pandey, Pawan Kumar Labhsetwar & Subhash Andey

Defluoridation efficiency by EC process depends on applied current intensity, initial fluoride concentration, initial pH, the residence time and raw water quality.

Electrolytic defluoridation is a complex electrochemical process, which comprises chemical and physical processes involving many surface and interfacial phenomena. The technology lies at the intersection of three more fundamental technologies—electrochemistry, coagulation and flotation. Defluoridation efficiency by electrocoagulation process depends on applied current intensity, initial fluoride concentration, initial pH, raw water quality and flow rate. The main reactions involved in the EC are as following:

Al Al3+ +3H2O Al(OH)3 +xF− 2H2O + 2e-

→ → → →

Al3+ +3eAl(OH)3 +3H+ Al(OH)3−xFx +xOH− H2 +2OH−

at the anode

at the cathode

It is generally accepted that the EC process involves three successive stages: (a) formation of coagulants by electrolytic oxidation of the ‘sacrificial electrode’; (b) destabilization of the contaminants, particulate suspension, and breaking of emulsions; (c) aggregation of the destabilized phases to form flocs.

The destabilization mechanism of the contaminants, particulate suspension, and breaking of emulsions has been described in broad steps and may be summarized as follows: 

Compression of the diffuse double-layer around the charged species, which is achieved by the interactions of ions generated by dissolution of the sacrificial electrode, due to passage of current through the solution.



Charge neutralization of the ionic species present in wastewater, which is caused by the counter ions, produced by the electrochemical dissolution of the sacrificial electrode. These counter ions reduce the electrostatic inter-particle repulsion sufficiently so that the Van der Waals attraction predominates, causing coagulation. A zero net charge results in the process.



Floc formation, and the floc formed as a result of coagulation creates a sludge blanket that entraps and thus bridges colloidal particles that have not been complexed. Details of these steps are lacking and require further study.

METHODS The methodology applied in the present study is illustrated here.

Experimental Protocol At present, most of the work in India is done using batch process. In its simplest form, an electrocoagulating reactor is made up of an electrolytic cell with one anode and one cathode. When connected to an external power source, the anode material electrochemically corrodes due to oxidation, while

17

Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process

the cathode is subjected to passivation. A feed tank of 200 L (A nestable tank) capacity was filled with raw water of initial fluoride concentrations of 5, 8, 6 and 10 mg/L. The initial pH of raw water was adjusted around 6.5-6.9 by adding concentrated HCl. A peristaltic pump of maximum efficiency of 1L/min was used to maintain the flow rate accordingly for a continuous process. The flow rate was adjusted by setting the rpm (rotation per minute) on the digital display.

Experiments were performed in a reactor consisting of plastic bucket of 19 L capacity. A direct current (DC) by stabilized power supply (TESTRONIX 34C, Volt and Ampere Digital Display) was applied to the terminal electrodes in which electrical current was controlled by a variable transformer. Constant current was maintained during each run by appropriately adjusting the impressed cell voltage from a regulated DC power supply. A bucket of 52 cm height and diameter of 44 cm was used as a settling tank in the lab scale experiment for electrolytic defluoridation by continuous process.

Electrode Configurations Aluminum plates were cut from a commercial grade aluminum sheet (99% purity) of 2 mm thickness each with a dimension of 100 mm×180 mm and an effective area of 180 cm2 on each side.

Distance between the electrodes was 5 mm. Monopolar configurations with three aluminium plate electrodes were used. Central plate was connected to anode and two end plates were connected to cathode. The electrodes were designed with a surface area to volume ratio of 7.2 m2 / m3 which is within cited range of 6.9 - 43 m2 / m3 as reported by P.K. Holt, 2003.

Raw water of various fluoride concentrations was prepared by diluting the stock solution in tap water. The experimental procedure was divided into two major steps i.e. start up batch process and continuous treatment process.

Each run was conducted using 19 litre of raw water in the reactor for start-up batch process and rendering it upto the desired limit of 1 mg/L by providing proper detention time. Detention time (t) is calculated by using Eq. 3.1 based on Faraday’s law: m=K.i. t

(3.1)

Where, M K

= Weight of aluminium dissolved (g) = Electro-chemical constant

I

= Current (Ampere)

t

= Time of electrolysis

Value of m can be calculated by; m= (C0 – Cf) × volume × (Al / F) Where,

(3.2)

Neha Mumtaz, Govind Pandey, Pawan Kumar Labhsetwar & Subhash Andey

C0

=

Initial fluoride concentration = 5 mg/l

Cf

=

Fluoride conc. in treated water = 1 mg/L

Volume

= Volume of treated water

Al/F ratio

= 3 (At pH 6)

18

All experiments were conducted at room temperature in the range 26º – 28 ºC. Concentrated hydrochloric acid was used for pH adjustment to 6.0-6.5 which is the optimum range for efficient electrocoagulation process. Current was varied from 2.0A to 3.0A, however, it was held constant for each run by appropriately adjusting the impressed cell voltage from a regulated DC power supply. The Ion Selective Electrode method was used to determine concentration of fluoride and in the treated water, residual aluminium estimation was carried out by Eriochrome cyanine R method.

RESULTS Attempts have been made to develop systems capable of treating fluoride bearing water and supplying significantly large quantities of potable water. Many of the known water treatment plant involve considerable expenditure and require the use of measured amounts of chemicals e.g. Alum, PAC, aluminium chloride, different filtration materials such as, membranes, activated alumina and ion exchange resins, for the removal of excess fluoride in water. Each technique can remove fluoride under specific conditions.

The fluoride removal efficiency varies according to site-specific situation, chemical used, geographical and economic conditions. Most of the methods have been reported to be non-functional in the field for a long duration. This may be due to some of the severe disadvantages such as high cost skilled unpalatable taste of treated water and limited adsorbing capacity of the material. These disadvantages are needed to be minimized for successful implementation of defluoridation technology in the field on the field on sustainable basis. The technology should be tested using the actual water to be treated before implementation in the field.

The electrolytic defluoridation process uses totally new concept for removal of fluoride drinking water supply in fluoride affected area where villages do not have alternate potable drinking water source. The electrolytic defluoridation produces potable water with palatable taste as against the other methods which use chemicals, for example; aluminium salts for the fluoride increases the concentration of sulphate and decrease alkalinity of treated water imparting unpalatable taste to water to water. The electrocoagulation technology could be an effective process for defluoridation of water.

19

Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process

Design of School-based Electrolytic Defluoridation Unit Seoni is a city and a municipality in Seoni district in the Indian state of Madhya Pradesh. In 2011 the city had a population of 101,953. It was founded in 1774, and contains large public gardens, a market place and a tank. It has 37% forest cover. The Seoni district is located in the southern part of Madhya Pradesh.

Geographically, it is located between latitudes 21035' and 22058' N and longitudes 79012' and 80018' E and extends over an area of 8758 km2. It is bordered by Jabalpur, Narsinghpur and Mandla districts to the north, Balaghat to the east and Chhindwara to the west and shares its southern boundary with Nagpur (Maharashtra).

The proposed design is given for a school located in Ghoghari Village of Seoni. The proposed location is shown in Fig. 1. The salient features are mentioned as follows:

State District Block Village Population Initial Fluoride Concentration Mode of operation Treated water concentration

Madhya Pradesh Seoni Dhanora Ghoghari 250 Students 5 mg/L

Continuous process ≤ 1 mg/L

Design Considerations The reactor design, aluminium electrodes, current supply and other components such as, pumps required for the installation are to be included. The design considerations for school based Electrolytic Defluoridation Unit can be illustrated as follows: 

No. of students

250



Drinking Water demand

5 lcpd [IS-1172-(1993)]



Cooking requirements (Mid-day Meal)

5 lcpd [IS-1172-(1993)]



Total water demand per day

2500 L

Neha Mumtaz, Govind Pandey, Pawan Kumar Labhsetwar & Subhash Andey

Reactor design (Figure 1) 

Number of reactor

1



Capacity of reactor

200 L



Height of the reactor

91.44 cm



Diameter of the reactor

55.88 cm

Figure 1: Reactor for installation

Aluminium Electrodes (Figure 2) 

Size of Aluminium plates (cm)

45.72 × 76.20 × 4 mm (thick)



Number of plates

3



Cathode

First and third plate



Anode

Central plate



Distance between two plates

1 cm



Effective area of anode

0.45 × 0.76 × 2 = 0.69 m2



Density of Aluminium

2700 kg/m3



Volume of each plate

0.457 × 0.762 × 0.004 = 0.00139 m2

20

21

Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process



Weight of plate

5.3 g

Figure 2: Aluminium Electrodes

DC Power Supply Calculation of current intensity can be done by applying Faraday’s Law: m=Kit

(5.1)

Where, m K i t

= Weight of aluminium dissolved (g) = Electro-chemical constant = Current (Ampere) = Time of electrolysis (s)

Value of electrochemical constant can be calculated by: K= M / ZF Where, M Z F

= Atomic weight of aluminium = 27 = Valency of aluminium = 3 = Faraday’s constant = 96500

So, value of ‘K’ will be:

K = 27/ (3×96500) K = 9.326 × 10-5 m = 9.326 × 10-5 × i × t

(5.2)

22

Neha Mumtaz, Govind Pandey, Pawan Kumar Labhsetwar & Subhash Andey

m

= (C0 – Cf) × volume × (Al / F)

(5.3)

Where,

C0

= Initial fluoride concentration = 5 mg/l

Cf

= fluoride conc. in treated water = 1 mg/L

Volume

= Volume of treated water

Al/F ratio

= 3 (At pH 6)

Therefore, m

= (5-1) × 200 × 3

m

= 2.4 g

So, value of ‘i × t’ i×t

= 2.4/ 9.326 × 10-5

i×t

25734.5

If i

= 10 Ampere;

t = 2574 sec = 43 min

If i

= 20 Ampere;

t = 1287 sec = 22 min

Thus, for the reactor, 10-20 Amp DC power is required for 22 to 43 min. For the treatment of 200 L of water in the reactor for reducing the fluoride concentration from 5 mg/L to 1 mg/L. If the solar photovoltaic system is to be installed the following components will be required: Solar panels

=

74 watts × 4 Nos.

23

Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process

Charge controller for charging

=

150 AH battery

DC regulator

=

25 A – 39 A

Battery

=

150 AH

DC to AC convertor for recirculation pump

=

100 watts

Other Components 

Recirculation pump of 20-30 L/ min at 2-3 m head for recirculating the water in the reactor during electrolytic process to keep the flocs of aluminium hydroxide in suspension.



Submersible pump (1HP) for pumping the raw water from hose pipe to overhead tank for treatment.

Designing Of Sedimentation Tank The design of sedimentation tank is carried out to cater to the requirement of safe drinking water for drinking (5 lcpd) and cooking (5 lcpd) for 250 students in the school.

So, total flow rate to be adopted for the design of sedimentation tank = (5 + 5) × 250 lpd = 2500 lpd = 2.5 m3/m2/d Let us adopt Surface Overflow Rate (S.O.R) for Type-II settling in the tank with a detention period of 2.5 hours.

Surface area of the tank, A = 2.5/35 = 0.071 m2 Volume of the tank, V = 2.5 × (2.5/24) = 0.26 m3 Let us provide L/B ratio as 3:1 So,

3.B2 = 0.071 m2

Width of the tank, B = 0.15 m Length of the tank, L= 3B = 3 × 0.152 = 0.45 m Depth of the tank, H = V/A = 0.26/0.06 = 4.3 m Let us provide a free board of 0.3 m.

Thus a sedimentation tank of size 0.45 m × 0.15 m × 4.3 m will be provided. A flow chart depicting the design procedure for sedimentation tank of the defluoridation unit is shown in Fig. 3.

24

Neha Mumtaz, Govind Pandey, Pawan Kumar Labhsetwar & Subhash Andey

MAXIMUM RATE OF FLOW AND TANK TYPE

Decide

Decide Rate

Retention

Surface

Loading

Calculate Volume

Calculate Area

Decide on No. of Tanks

Decide on Critical Proportion Dimensions

Amend, or Change no. of Tanks

Calculate Dimensions of Tanks

Are Dimensions Reasonable

NO

YES Check Rate

Weir

Overflow

YES PROCEED WITH DETAILED DESIGN

Figure 3: Flow chart for the design of sedimentation tank of defluoridation unit

Cost Estimates The cost estimates includes the capital cost and the operating cost.

25

Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process

Estimated Cost

Figure 4: Flow chart for assessment of cost estimation Capital cost      

Cost of overhead tank, reactor, electrodes, pipes and fitting: Cost of Submersible pump (1HP) for pumping water from hose pipe to overhead tank: Cost of Recirculation pump: Option I : Regular power supply- AC to DC convertor with 20 Amp supply: Option II : Solar photovoltaic supply- Solar system with battery: Cost of Inverter for both the options(I and II)

Estimated Capital Cost

Option I

Option II Solar system with battery

Total cost incurred Rs 1,49,650

Figure 4: Flow chart for total capital cost incurred

Rs. 14,000 Rs. 20,000 Rs. 650 Rs. 30,000 Rs. 1 lakh Rs. 15,000

26

Neha Mumtaz, Govind Pandey, Pawan Kumar Labhsetwar & Subhash Andey

Operating cost (Per 1000 L of treated water)

1.

Cost of Aluminium required for treatment Ø Amount of Al required for 1000 L a)

C0 = 5 mg/L : Al = 12 gm. (by eq. 3)

Ø Cost of Al plates

= Rs. 170/kg

Ø Cost of Al per 1000 L a)

C0 = 5 mg/l

= Rs. 2.04

2.

Cost of the electric energy consumption

Ø Pumping of water

= Rs. 2.00

Ø Electrolytic Process a) (P)

Power

C0 = 5 mg/L ; consumption

#NAME? = 12 volt × 10 ampere × 3.6 hours = 429 watts hour = 0.429× 4 (1KW=1 unit electricity = Rs. 4) = Rs. 1.71

3.

Cost of hydrochloric acid for pH adjustment Quantity of HCl required

= 200 ml

Cost of HCl (commercial grade)

= Rs. 10/L

Cost of HCl for pH adjustment

= Rs. 2.00

Operating cost for the treatment of 1000 L of water can be calculated as follows: = Rs. (2.04 + 2.00 + 1.71 + 2.00) = Rs.7.75

27

Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process

CONCLUSIONS In the present work, the study has focused on the design of electrolytic defluoridation for the installation in a school located in a remote area of Madhya Pradesh. It is a viable methodology of treatment and the following facts are revealed: 

The design is carried out to cater to the requirement of safe drinking water for drinking (5 lcpd) and cooking (5 lcpd required for Mid-day meal) for 250 students in the school.



The electrolytic defluoridation reactor was made up of high density polyethylene with a capacity of 200 L which is durable and chemical resistant.



Three Aluminium electrodes were placed into the reactor. Central plate was connected to anode and two end plates were connected to cathode.



A direct current (DC) by stabilized power supply could be applied to the terminal electrodes in which electrical current was controlled by a variable transformer. Constant current should be maintained during each run by appropriately adjusting the impressed cell voltage from a regulated DC power supply.



Places where there are frequent power cut offs and proper infrastructural facilities are not available, this process can be utilized for defluoridation with the help of solar panels.



A proposed dimension of sedimentation tank 0.45 m × 0.15 m × 4.3 m is also provided considering the Surface Overflow Rate (S.O.R) for Type-II settling in the tank with a detention period of 2.5 hours.



The recurring cost for the treatment worked out for electrolytic defluoridation demonstration plant is Rs. 7.75 per 1000 L of treated water which is much cheaper than the treatment cost by any other defluoridation system available in the market.



The capital cost of the electrolytic defluoridation unit is about Rs. 75,000 providing DC power supply.



If Solar photovoltaic supply would be installed the capital cost would be Rs. 2 lakhs.

The present design of school based electrolytic defluoridation unit provides a technically sound, costeffective and reliable community drinking water defluoridation system. It is well suited for the situations in which the electric supply is not available for longer duration, the operators and maintenance workers are not highly trained technicians, such as in rural or remote locations.

Neha Mumtaz, Govind Pandey, Pawan Kumar Labhsetwar & Subhash Andey

28

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2.

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3.

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4.

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5.

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6.

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7.

Essadki A.H., Gouricha B., Vial Ch., Delmasc H and Bennajaha M. (2009), ‘Defluoridation of drinking water by electrocoagulation/electroflotation in a stirred tank reactor with a comparative performance to an external-loop airlift reactor’. Journal of Hazardous Materials. Vol. 168, pp: 1325–1333.

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Hu C.Y., Lo S.L. and Kuan W.H. (2005), ‘Effects of the molar ratio of hydroxide and fluoride to Al (III) on fluoride removal by coagulation and electrocoagulation’. J. Colloid Interf. Sci. Vol. 283, pp: 472– 476.

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13. World Health Organization (2011), ‘Guidelines for Drinking-Water Quality’.

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Operating Cost Analysis of Continuous Mode Electrolytic Defluoridation Process

14. Zuoa, Xueming Chena, Wei Li a, Guohua Chenb (2008), ‘Combined electrocoagulation and electroflotation for removal of fluoride from drinking water’, Journal of Hazardous Materials, Vol. 159 pp: 452–457.