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en tng tbuilar dn ofhiced to purify it. The solar distillation unit when installed as a decentralised system

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Desalination 278 (2011) 333336

Contents lists available at ScienceDirect

Desalin

.e lrelative to other halides. The range of uorine-containing compoundsis vast because uorine is capable of forming compounds with all theelements except helium and neon [4]. Common uoride mineralsinclude uorspar, cryolite, micas and uorapatite [2,5,6]. Fluoride inwater derives mainly from dissolution of natural minerals in the rocksand soils with which water interacts. Groundwater from crystallinerocks, especially granites are particularly susceptible to uoride build-up because they often contain abundant uoride-bearingminerals [5].Fluoride is found naturally in low concentrations in drinking waterand foods. Fluoride levels in vegetables and fruits are relatively low

1.1. Drinking water standards regarding uoride intake

Drinking water serves as a major source of uoride to the humanbody. Though there are no imposed limits with regards to theconcentration of drinking water, the WHO recommends a minimumof 0.5 mg/l and a maximum of 1.5 mg/l [9]. The WHO, however,recommends concentrations between 0.5 and 1.0 mg/l for articialuoridation of water supplies [2]. Unfortunately, over 70 millionpeople are exposed to uoride above theWHO limit [10]. In Ghana, theEnvironmental Protection Agency (EPA) recommends maximumand range from 0.1 to 0.4 mg/kg [2]; howevand rice may contain up to 2 mg/kg of uWHO [7], sh and canned sh may contain uuoride, respectively.

Corresponding author. Tel.: +233 547483320.E-mail address: edwardantwi@hotmail.com (E. Antw

0011-9164/$ see front matter 2011 Elsevier B.V. Aldoi:10.1016/j.desal.2011.05.044ncentrations as low as

rties that are distinct

between 1000 and 1500 mg/kg, it has been proven that amaximum of3.5 mg may be swallowed accidentally in a day [1].0.1 mg/l or less [3].

Fluorine compounds often have prope1. Introduction

Due to its high reactivity and electin nature in the form of uorides. It cthe earth crust [1]. The concentrationsare approximately 0.5 ng/m3 [2] anFluoride is present in groundwater aabout 67 mg/l, and in surface watertivity, uorine (F) existstes about 0.060.09% ofride in air and sea waterpm [1,3], respectively.entrations from zero to

In industry, uorine compounds are extensively used in theproduction of aluminium, steel, and glass bre [2,8], and are releasedinto the environment through anthropogenic activities such as theproduction of phosphate fertilisers, bricks, tiles, and ceramics [2].Other uorine compounds such as sodium hexauorosilicate andsodium uoride are used in municipal water uoridation schemes [7].Even though toothpaste contains high levels of uoride, usuallyer, foods such as barleyoride [1]. According top to 5 and 370 mg/kg of

uoride concentmanufacturer oftration of zero (0

High concentin terrains thatuorides. South-are among the awater, ranging bi).

l rights reserved. 2011 Elsevier B.V. All rights reserved.

is an effective means of reducing the high uoride contamination making the water safe for drinking.Flouride average of about 0.7 mg/l wsolar distillation unit was usUse of solar water distiller for treatment oBongo district of Ghana

Edward Antwi a,, Edem Cudjoe Bensah b, Julius Cuda Mechanical Engineering Department, Kumasi Polytechnic, P. O. Box 854, Kumasi Ghanab Chemical Engineering Department, Kumasi Polytechnic, Kumasi Ghana

a b s t r a c ta r t i c l e i n f o

Article history:Received 7 April 2011Received in revised form 17 May 2011Accepted 18 May 2011Available online 6 June 2011

Keywords:SolarDistillation

Bongo district in the Uppeunderground water bodies othis, majority of the peopleaffects their condence wheffective solution to reduciwater distillation unit waspuried water from the solFrom an initial concentratio

j ourna l homepage: wwwuoride-contaminated water: The case of

Ahiekpor b

ast Region of Ghana is noted for the high concentration of uoride in itshich the people depend somuch on tomeet their drinking needs. As a result ofthe most endemic areas suffer from dental uorosis, a problem that greatlyhey move out of the district to other places. In nding a sustainable and costhe uoride content of their underground waters before being used, a solart using local materials from Anaafobiisi. Results from test conducted on theistiller showed a signicant reduction in the levels of uoride in the water.20.6 mg/l of uoride in the water from a local borehole, this was reduced to anh is below the WHO acceptable limit for uoride in drinking water when the

ation

sev ie r.com/ locate /desa lration of 1.5 mg/l. Voltic Ghana Limited, the leadingbottled water, produces water with uoride concen-).rations of uorides are usually found in groundwaterhave rock formations containing high levels ofEast Asia and the Rift Valley Region in East Africareas with extremely high concentrations in ground-etween 1640 and 2800 mg/l [7].

In Ghana, high uoride levels (N1.5 mg/l) in underground waterhave been recorded in Bongo and surrounding communities [11,12].The Bongo water crisis has been a thorny developmental issue inGhana over the years, and major attempts to nd sustainable solutionto the problem have proved futile.

1.2. Bongo district

Bongo district is one of the nine districts in the Upper East Regionof Ghana, with Bongo as its district capital. It lies on latitude 10 54

Assistance from national institutions such as Community Waterand Sanitation Agency (CWSA) and international agencies such asWaterAid, ActionAid, Rural Aid, and World Vision have mainlyfocussed on the construction of boreholes and wells in areas withlow levels of uoride. The government, with support from someinternational organisations, is developing a Small TownWater System

Water inlet

Collection pointof distilled water

Plain silicate glass

334 E. Antwi et al. / Desalination 278 (2011) 33333628 North and longitude 0 48 29 West, and covers an area of459.5 km2 [13]. The district is mostly rural; apart from Bongo, allcommunities are made up of scattered settlements. The area isgenerally at with outcrops of granite and Birimian rocks at analtitude of 90300 m. About 40% of the land surface is covered withrocks which make farming and other activities very difcult. Thedistrict's vegetation falls within the Guinea savannah. About 90% ofthe working population in the district are engaged in the agriculturalsector [14]. The coarse-textured sandy-loam soils are moderately welldrained and are rich in potash and phosphate; moreover, the sub-soilsgrade below into reddish brown, mottled pink and yellow coarsesandy clay loam of partially decomposed granite [13].

The district population was 77,885 in 2000 [15] with a populationdensity of 169 persons per square kilometre and was estimated at91,949 in 2006 by the planning section of the district assembly, withfemales representing 53.3% of the population [13]. About 48% of thepopulation lies within the age group 1564 years, and children below5 years represent about 12.5%. The average household size is 9.2persons which is quite large compared to the national average of 4[16]. This can be attributed to the low acceptance rate (18.9%) offamily planning programmes [13] and the practise of the extendedsystem of living.

1.3. Water availability at Bongo

Themain sources of potablewater are boreholes andhanddugwells,even though water is also obtained from a large dam, nine small dams,ve dug-outs, a few ferro-cement banks, and a number of streams. In2005, the percentage of the populationwith access to potablewaterwas65%, even though the percentage with access to potable water within aradius of 500 m was 11% [12,13]. Thus, a large percentage depends onwater sources outside a 500 m radius, and school children have towakeup very early and walk long distances to fetch water, a situation thatleads to absenteeism and lateness at school.

1.4. Incidence of uorosis at Bongo

Fluorosis is a health condition caused by intake of excessiveuoride (N1.5 mg/l), and usually affects children below the age of8 years [5]. Health impacts of drinking uoride-containing watercome in several forms with respect to the concentration of uoride inthe water, as seen in Table 1.

Dental uorosis is characterised by staining and pitting of the teethand may lead to damage of the enamel in severe cases [18]. In skeletaluorosis, uoride accumulates in the bone progressively over many

Table 1Health impacts of drinking uoride-bearing water.

Health impact of uoride-bearing water Fluoride concentration, mg/l

Dental caries b0.5Good dental health 0.51.5Dental uorosis 1.54Dental, skeletal uorosis N4Crippling uorosis N10Source: Ref. [17].years. The early symptoms of skeletal uorosis include stiffness andpain in the joints, and in severe cases, the bone structure may changeand ligaments may calcify, resulting in impairment of muscles andpain [7,18]. An estimated one million people are leaving with seriousskeletal uorosis [19]. The dental effects of uorosis develop muchearlier than the skeletal effects in people exposed to large amounts ofuoride. It is also known that ingestion of uoride after 6 years of agewill not cause dental uorosis [18].

In a study of groundwater quality in Ghana, the most serious directhealth problems related to drinking water was considered to be fromuoride excess and iodine deciency in parts of the Upper Regions ofnorthern Ghana [1]. In 2005, out of a total of 335 boreholes and wellsconstructed in Bongo district, 35 were capped due to excessiveconcentration of uoride in the water [12]. Even though the people ofBongo are aware of the consequences of drinking water with excessiveconcentrations of uoride some communities are unable to stopdrinking from uoride contaminated wells due to non-existence ofalternative sources of safe drinkingwater. The prevalence rate of dentaluorosis among school children has been estimated at 33% inBongo andsurrounding communities [13]. It appears major research and mediaattention have focused on dental uorosis, and there is therefore theneed to study the incidence of the other forms of uorosis in Bongo.

Attempts have been made by the Bongo district assembly,government, local and international non-governmental organisationsto nd a lasting solution to the problem. The use of uoride removalmethods such as precipitation and ion exchange has been tried byseveral organisations to no avail due to the relatively high cost of suchsystems and problems with availability of chemicals and equipment.

Fig. 1. Some school children suffering from dental uorosis.Fig. 2. Schematic diagram of a solar still.

=the density of water (kg/m3)

hv=the latent heat of vaporisation of water (kJ/kg).

Civil Engineering of Kwame Nkrumah University of Science and

Fig. 4. Composition of borehole water at Bongo compared with WHO standard.

335E. Antwi et al. / Desalination 278 (2011) 333336(STWS) which is expected to provide some relief to water-scarcecommunities in the district.

Even though an STWS is being developed for the district there is theneed to nd a sustainable solution to the uoride problem. It is againstthis backdrop that the Centre for Energy, Environment and SustainableDevelopment (CEESD), a leading non-prot organisation in renewableenergy promotion in Ghana, surveyed Bongo in October, 2010 in orderto comeupwith a low cost technology for uoride removal. The Centrefor Energy, Environment and Sustainable Development (CEESD) hasidentied the solar water distiller as a technology that has the poten-tial to solving Bongo's water problems since it can effectively generateuoride-free water from uoride-contaminated water.

This paper assesses the effectiveness of two designs of solar waterdistillers that were installed by CEESD at Anaafobiisi primary school inBongo district, with nancial support from Vodafone Ghana Founda-tion, under the World of Difference programme. A survey conductedby CEESD on the incidence of dental uorosis at Anaafobiisi revealed ahigh prevalence rate of 80% among children. Fig. 1 shows two schoolchildren suffering from dental uorosis.

2. Experimental setup

Two solar distillation stills were designed and built at Anaafobiisikindergarten. Eq.1 was used to determine the quantity of water perunit area exposed to the sun.

V = A I = hv 1

where:

Fig. 3. Solar water distillation units built at Anaafobiisi.V=the quantity of water from the still (l/day),A=the area of the aperture, is the efciency of the still,I=the average solar insolation in the area (MJ/m2),

Table 2Characteristics of borehole water sample.

Parameter mg/l

TDS 138.0TSS 0.0Total hardness (CaCO3) 90.0Calcium 23.0Magnesium 7.8Iron 0.0Fluoride 20.65Chloride 11.0Sulphate 0.0pH: 6.73Turbidity: 0.1Technology. Samples were taken for ve consecutive days to evaluatethe performance of the stills with regards to the reduction in uorideconcentration.

3. Results and discussion

As can be seen in Table 2, the borehole water sample containedalarmingly high concentration of uoride when compared with WHOstandard. However, the presence of other minerals was far below theWHO standards and Ghana Water Company for drinking purposes, asshown in Fig. 4. The uoride contamination of 20.65 mg/l puts users atrisk of dental, skeletal and crippling uorosis, making it a very seriousissue.

Analysis of the solar puried water collected on ve differentdays indicates that the uoride level in the raw borehole water hadreduced signicantly by an average of 96.3%, from 20.65 mg/l to anSince there is no weather monitoring station in Bongo, the averagesolar insolation for Tamale, which lies between latitude 9.16 and 9.34North and longitudes 00.36 and 00.57, was used to determine theoutput of the still. The average insolation for Tamale is about21 MJ/m2 [20]. Fig. 2 shows the schematic diagram of the solar stillwith the dimensions. The water holding basin was 1122 ft for themodel. The still has an inlet for the uoride contaminated water andtwo collection points for the distilled water. Apart from the glazing,which was a plane silicate glass, all the materials were obtainedlocally. The two solar stills were built with the full participation of theindigenes. Fig. 3 shows the picture of the two completed stills.

Samples of water from boreholes were taken and analysed at thelaboratories of GhanaWater Company Limited and the Department ofFig. 5. Fluoride concentration of the water sample before and after treatment with solarenergy.

which has bedevilled the people in that part of Ghana since timeimmemorial.

References

[1] K. Abuzeib, L. El Hatow, Impact of uoride content in drinking water, Waterresources management programme, Centre for Environment and Developmentfor the Arab Region and Europe (CEDARE), Cairo, Egypt.

[2] WHO: Fluoride in drinking-water, Background document for development ofWHO guidelines for drinking-water quality, WHO/SDE/WSH/03.04/96, 2004,Available at: http://www.who.int/water_sanitation_health/dwq/chemicals/uoride.pdf (accessed 02.01.11).

[3] WHO: Nutrients in drinking waterpotential health consequences of long-termconsumption of demineralized, remineralized and altered mineral contentdrinking water, Expert Consensus, Meeting Group Report, WHO, Geneva, p. 8,Available: http://www.who.int/water_sanitation_health/dwq/nutrientschap1.pdf (accessed 26.12.10).

[4] N.N. Greenwood, A. Earnshaw (Eds.), Chemistry of the Elements, 2nd edition,

Table 3Cost of solar still models.

Item Unit price ($) Quantity Cost ($)

Glaze, (23 ft) 5.33 6 31.98Cement blocks 0.8 55 44Cement 10 2 20Sand 43.33 1/10 4.33Wood, 2 2 2 4Pipe, 3 10.67 1 10.6790 elbow, 3 4 1 4Pipe cover 2 1 2Sealant 8 5 40Black polythene 6.67 1 6.67White polythene 6.67 1 6.67Valve 4 2 8Water tank 3.33 2 6.67

336 E. Antwi et al. / Desalination 278 (2011) 333336average of 0.76 mg/l which falls within the WHO accepted level of01.5 mg/l. This is shown in Fig. 5.

The cost of building one unit was about $250. The full costbreakdown is shown in Table 3. From Table 3, the cost of cementblocks, glazing, sealant and labour constitute about 70% of the totalcost. The average household income of the Upper East Region is about$500 per annum [21]. If a good nancing plan is put in place eachhousehold can build and own one still.

The nature of settlement in Bongo where households live widelyapart makes the solar water useful as a decentralised water purifyingsystem. A study conducted by WHO suggested that because desa-lination is expensive only water meant for cooking and drinkingshould be treated.While the overall water requirement may be higherthan a litre, household chores such as washing of bowls, washing ofclothes and bathing can be done safely with uoride contaminatedwater.

4. Conclusions

Clean drinking water remains one of the most challenging globalhealth issues of today, and solar distillation offers an important andeffective solution in meeting potable water needs in communitiesaffected by high uoride concentration and salinity. Decentralisedsolar stills offer an immediate and effective solution in reliably pro-viding safe drinking water.

Results from the solar stills installed at Bongo indicate that solarwater distillation is a viable means of reducing ouride levels in waterto within levels accepted by WHO for consumption. The project areahas high solar radiation intensity which can be used to solve the

Labour 60TOTAL 248.99incidence of dental uorosis which is a major problem in the area. Thistechnology when deployed on decentralised basis at Bongo in theUpper East Region can help curb the incidence of dental uorosisOxford: Butterworth-Heinemann, ISBN: 0080379419, 1997, p. 804.[5] British Geological Survey (BGS): Water quality factsheet: uoride, Prepared for

WaterAid.[6] S. Battaleb-Looie, F. Moore, A study of uoride groundwater occurrence in Posht-

e-Kooh-e-Dashtestan, South of Iran,World Applied Sciences Journal 8 (11) (2010)13171321.

[7] WHO: Fluorides, Environmental Health Criteria 227, International Programme onChemical Safety (IPCS), World Health Organization, Geneva, 2002, Available athttp://www.who.int/ipcs/publications/ehc/en/ehc227.pdf (accessed 13.01.11).

[8] W.M. Apambire, D.R. Boyle, F.A. Michel, Geochemistry, genesis and healthimplications of uoriferous groundwaters in the upper regions of Ghana, Environ.Geol. 35 (1997) 1324.

[9] WHO: Guidelines for drinking-water quality, Guidelines for drinking-waterquality, 3rd edition, Incorporating the rst and second addenda, Volume 1recommendations, Geneva, p. 377, 2008, Available at http://www.who.int/water_sanitation_health/dwq/fulltext.pdf (accessed 14.01.11).

[10] WHO: Fluoride in drinking water, IWA Publishing, London, 2006, p. 33, Available athttp://www.who.int/water_sanitation_health/publications/uoride_drinking_water_full.pdf (accessed 11.11.10).

[11] British Geological Survey (BGS). Groundwater quality: Ghana. Prepared forWaterAid Ghana ofce, Accra, Ghana.

[12] F.A. Atipoka, Water supply challenges in rural Ghana, Desalination 251 (2010)212217.

[13] Bongo District Assembly: Bongo district, Ghana districtsa repository of all districtsof Ghana, Available at http://ghanadistricts.com/districts1on1/bongo/?arrow=dnf&_=103 (accessed 15.06.10).

[14] District Capacity Building Project (DISCAP): The decentralized poverty monitoringand evaluation exercise: Bongo District. Available at http://www.discap.org/Publications/The%20Decentralized%20Poverty%20Monitoring%20and%20Evaluation%20Exercise%20Bongo%20District.pdf (accessed 15.06.10).

[15] Ghana Statistical Service (GSS), 2000 Population and Housing CensusAnalysis ofDistrict Data and Implications for Planning, Accra, Ghana, 2005.

[16] GSS, 2000 Population and Housing Census, Summary of Final Results, Accra, Ghana,2002.

[17] C.B. Dissanayake, The uoride problem in the groundwater of Sri Lankaenvironmental management and health, international, Journal of EnvironmentalStudies 19 (1991) 195203.

[18] WHO: Fluorosis, Water-related diseases, Water, Sanitation and Health (WSH),Available at http://www.who.int/water_sanitation_health/diseases/uorosis/en/[Accessed on 14/01/11].

[19] UNICEF: Learning from experience: Evaluation of UNICEF's water and environmen-tal sanitation programme in India, 19661998, Evaluation Ofce Division ofEvaluation, Policy and Planning, UNICEF Headquarters, New York. p.36, Available:http://www.unicef.org/evaldatabase/les/IND_2000_800.pdf (accessed 08/01/11).

[20] Energy Commission, Solar and Wind Energy Resource Assessment (SWERA), Accra,Ghana, 2005.

[21] GSS, Ghana Living Standards Survey Report of the Fifth Round, Accra, Ghana, 2005.

Use of solar water distiller for treatment of fluoride-contaminated water: The case of Bongo district of Ghana1. Introduction1.1. Drinking water standards regarding fluoride intake1.2. Bongo district1.3. Water availability at Bongo1.4. Incidence of fluorosis at Bongo

2. Experimental setup3. Results and discussion4. ConclusionsReferences