PHNG PHP N GIN V R TIN LOI TR HOC GIM BT ARSENIC (THCH TN) TRONG NC NGM VIT NAM Nguyn Minh Quang, P.E. Thng 9 nm 2010

Ging ng do UNICEF ti tr [nh: AEWAG]

PHN M U

Arsenic (As), trong nc gi l thch tn hay arsen, l mt nguyn t ha hc t nhin c mt khp ni trn tri t. L mt nguyn t, arsenic lun tn ti, khng b phn hy, v khng c hi. Trong mi trng, n kt hp vi oxygen, chloride, hoc sulfur to thnh nhng hp cht arsenic hu c, l hp cht rt c v c C quan Bo v Mi sinh Hoa K (U.S. Environmental Protection Agency (USEPA)) cng nhn l mt tc nhn gy ung th cho con ngi (human carcinogen) [1]. Arsenic trong nc mt hay nc ngm c th pht xut t t hay sn phm hoc ph phm thng mi

v k ngh c cha arsenic; nhng nc ngm c cha arsenic ha tan t t c c bit quan tm t thp nin 1990 khi n c pht hin vi nng cao trong hu ht cc ging ng (tubewell) v nh hng n hng chc triu ngi Bangladesh [2]. Ngoi Bangladesh, nc ngm b nhim arsenic cng c tm thy Argentina, Bolivia, Canada, Chile, China, Germany, Ghana, Greece, Hungary, India, Japan, Mexico, Mongolia, Romania, Spain, Taiwan, United States, v Vit Nam [3].

nhim arsenic trong nc ngm Vit Nam c bit n t nm 1998, sau khi nc ngm t hn 150.000 ging ng, do

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Qu Nhi ng Lin Hip Quc (United Nations Childrens Fund (UNICEF)) ti tr, thay th ngun nc mt thiu v sinh trong chng trnh cung cp nc sch ca UNICEF chng li bnh tiu chy ca tr em. T nm 2001, UNICEF i tin phong trong vic khi xng cc hot ng nhm gim bt nh hng ca tnh trng nhim arsenic trong nc ngm Vit Nam. Trong nm 2005, UNICEF ti tr cho chnh ph Vit Nam th nghim 77.000 ging ng nhng vng tnh nghi c mc arsenic cao. Sau , chnh ph Vit Nam tip tc ti tr th nghim cho 110.000 ging na trong cc tnh thnh cn li. Kt qu cho thy c khong 12% s mu nc (tc khong 22.450 mu) c nng arsenic cao hn 50 microgram/lt (g/l), l tiu chun arsenic cho nc gia dng nng thn Vit Nam [4]. Mt nghin cu trong nm 2006 cho thy nc ngm c nng arsenic rt cao c tm thy nhiu ni trong ng bng sng Hng (BSH) v sng Cu Long (BSCL). BSH, cc mu nc ngm c nng arsenic thay i t 1 n 3.050 g/l vi tr s trung bnh l 159 g/l, trong khi cc mu nc ngm thu thp BSCL c nng thay i t 1 n 845 g/l vi tr s trung bnh l 39 g/l [5]. Tnh n nm 2008, s ngi c nguy c mc cc bnh do s dng ngun nc c hm lng thch tn (tc Arsenic) cao hn mc cho php ln ti hn 17 triu ngi, chim khong 21,5% dn s nc ta. [6] Nhiu nghin cu c thc hin khp ni trn th gii tm cch loi tr hoc gim bt nng ca arsenic trong nc cho cc nh my lc nc tn tin th hoc cho cc n v gia c nng thn, nht l nhng vng c ging ng qua chng trnh cung cp nc sch ca UNICEF [7-23]. Cc phng php p dng Vit Nam gm c b lc ct, bnh lc ArsenFree, v b lc nc WATTS USA [24-27]. Mc d nhng phng php ny t ra c hiu qu loi tr hoc lm gim nng arsenic trong nc xung di 10 g/l, l tiu chun ca T chc Y t Th gii (World Health Organization (WHO)), chng vn cha c ph bin v s dng mt cch rng ri v rt tn km, cn nhiu vt liu, tn nhiu cng, v bt tin trong vic vn hnh v bo tr.

nng thn, chng hn nh BSH v BSCL, vic p dng cc phng php ny li cng kh khn hn khin cho ngi dn nn lng ri ph mc cho s phn!

B lc ct [24]

Bnh lc arsenFREE [26]

gip ngi dn sng trong nhng vng b nhim arsenic nng thn c th t tc theo ui vic loi tr hoc gim thiu nng arsenic trong nc gia dng, nht l nc nu n v ung, bo v sc khe cho chnh mnh v gia nh, mt vi phng php tht n gin v r tin c gii thiu trong bi vit ny. Ty theo iu kin a phng, cc phng php n gin v r tin ny c th khng t c hiu qu nh mun, nhng t ra, chng cng c th gim bt nh hng c hi ca arsenic trong nc ngm i vi sc khe ca ngi dn cc tnh An Giang, ng Thp v Long An BSCL v cc tnh Vnh Phc, H Nam, Hng Yn, H

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Ty, Nam nh, Ninh Bnh, Thanh Ha, v H Ni BSH; c bit l An Giang ni c rt nhiu h dn vn v t s dng ngun nc b nhim arsen v khng c ngnh y t ca tnh thng bo rng ri. [28] NH HNG I VI SC KHE Arsenic trong nc ngm c xem l mt k st nhn v hnh v n khng c mi v hay mu sc. N git ngi mt cch thm lng v chm ri v nhng triu chng ca n thng phi mt t 5 n 10 nm mi c th pht hin r rt, v lc th qu tr, v cho n nay nhn loi vn cha tm c mt phng php iu tr hu hiu i ph vi nhng cn bnh do vic nhim c arsenic gy ra (arsenicosis).

Da i mu [29]

Vt nm v mn en lng bn tay [29]

Arsenic nh hng n hu ht cc b phn trong c th, nhng da l b phn nhy cm nht [29]. S dng nc ngm cha arsenic nng cao trong mt thi gian di c th lm da b i mu (trng hoc sm); lm nm da, ni mn hoc chai mu en lng

bn tay v bn chn, c th dn n ung th da; lm cho bun nn v ma; gy tiu chy; gy thit hi hoc lm gim mc sn xut huyt cu; lm ri lon nhp tim; gy cm gic nh b kim chch tay v chn; lm tay chn b t; gy t lit bn phn; v lm m mt. Ngoi da, arsenic cng c th gy ung th gan, phi, thn, ng h hp, v bng i [30].

Ung th lng bn tay [29]

C TNH CA NC NGM NG BNG SNG HNG V CU LONG V trong iu kin ym kh (anaerobic), hu ht arsenic trong nc ngm Vit Nam di dng arsenite [As(III)], mt hp cht arsenic hu c c c tnh cao nht. Khi tip xc vi khng kh hay tia t ngoi (ultra violet), arsenite b oxy ha thnh arsenate [As(V)] t c hn. BSH v BSCL c cu to bi ph sa mi trong thi k Holocene v Pleistocene nn nc ngm hai vng ny c c tnh gn ging nhau, l cha nhiu st (iron), manganese, v ammonium [5]. Kt qu phn cht cho thy nng ca st c th ln n 56 milligram/lt (mg/l) (trung bnh 2,26 mg/l) trong cc mu nc ngm An Giang v ng Thp vo nm 2004 [5] v 48 mg/l (trung bnh 13 mg/l) trong cc mu nc ngm gn H Ni vo nm 2002 [24]. S hin din ca st rt quan trng trong vic loi tr hoc lm gim nng arsenic trong nc ngm, v arsenate kt hp vi Fe(III) thnh FeAsO4 ri b loi ra khi

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nc ngm khi kt ta vi Fe(OH)3. Kt qu nghin cu cho thy nng arsenic c th gim t 20 n 90% trong nc ngm c nng st thay i t 1 n 12 mg/l, nhng chc chn gim trn 80% nu nng st cao hn 12 mg/l [24]. XC NH NNG ARSENIC TRONG NC NGM Nng arsenic trong nc ngm c th c xc nh bng phng php phn tch trong phng th nghim hoc bng b th ti ch (field test kits). Kt qu phn tch trong phng th nghim bng phng php USEPA 200.5 rt tin cy v chnh xc n 3 g/l [31], nhng tn km v mt nhiu thi gian. B th ti ch th r tin, n gin, v nhanh chng. Tuy khng chnh xc bng kt qu phn tch trong phng th nghim, nhng cng c th dng xc nh nng arsenic trong nc ngm nng thn.

B th Merckoquant [nh: Merck]

B th ti ch c s dng rng ri Vit Nam hin nay l b th Merckoquant 1179270001 do Cng ty Merck ca c sn xut [4], c UNICEF gii thiu v c th t mua qua b phn cung cp ca t chc ny Copenhagen [32]. Nhng b th ny ch c th xc nh nng ca arsenic trong nc ngm di 500 g/l m thi. c th xc nh arsenic trong nc ngm c nng cao hn 500 g/l, cc tnh An Giang, ng Thp v Long An BSCL v cc tnh Vnh Phc, H Nam, Hng Yn, H Ty, Ninh Bnh, Nam nh, Thanh Ha, v H Ni BSH c th dng b th Merckoquant 117917001 hoc b th EZ Arsenic Kit

2822800 do Cng ty Hach ca Hoa K sn xut. B th Merckoquant 117917001 c th xc nh nng arsenic ln n 3.000 g/l, trong khi b th EZ Arsenic Kit c th xc nh nng arsenic ln n 4.000 g/l [33].

B th EZ Arsenic Kit [33]

PHNG PHP N GIN V R TIN LOI TR HOC GIM BT ARSENIC Khng s dng nc ngm va bm ln y l phng php n gin v t tn km nht lm gim c tnh ca arsenic trong nc ngm; v nu tip xc vi khng kh lu, arsenite [As(III)] s b oxy ha thnh arsenate [As(V)], mt hp cht arsenic hu c c c tnh ch bng c tnh ca arsenite. Ch cn vi thng phuy, lu, hoc h sn c cha nc ngm trong mt vi ngy trc khi ung hoc nu n. Hiu qu ca phng php ny cha c nghin cu su rng, nhng c th t c 25% [34]. Phi nng (SORAS)

Phng php phi nng [35]

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Bnh PET 20 lt dng cho SORAS [nh: Internet]

Phng php ny, c gi tt l SORAS (solar oxidation and removal of arsenic), dng tia t ngoi trong nh sng mt tri oxy ha v loi tr arsenic trong nc ngm ng trong bnh nha PET (polyethylene terephthalate) trong sut. SORAS do Vin Khoa hc v K thut Mi trng Lin bang Thy S (Swiss Federal Institute of Environmental Science and Technology) v C quan Hp tc v Pht trin Thy S Bangladesh (Swiss Agency for Development and Cooperation, Bangladesh) sng ch. Kt qu thc nghim Bangladesh cho thy SORAS c th gim t 45 n 78% (trung bnh 67%) nng arsenic trong nc ngm [35]. Phng php SORAS gm c cc giai on sau y: 1. Cho 16 lt nc ngm mi bm vo bnh

nha PET dung tch 20 lt. 2. Cho vo bnh PET 1 mung c ph nc

chanh ti. 3. Lc bnh PET khong 30 giy. 4. t bnh nm ngang v phi nng trong

mt ngy. 5. Lt bnh ng ln lng cn trong mt

m. 6. Khi cn lng, rt nc trong ra khi

bnh PET. Lng phn Phng php lng phn c ngi dn BSCL s dng hng th k nay lc ph sa trong nc sng Cu Long v n n gin, r tin, v tin li. Phn chua c dng thc y cc ht ph sa l lng kt ta ri lng ng tht nhanh xung y h hoc lu. Phn nc trong vt pha trn c s

dng cho n khi lp cn di y b khuy ng; lc , phn cn s c b, h hoc lu s c sc sch lng m mi. Phn chua (potassium aluminum sulfate), c cng thc ha hc l KAl(SO4)2, dng tinh th trong sut v c v chua, nn c gi nm na l phn chua.

Phn chua

Phn st chloride FeCl3 [nh: Internet]

Phn st sulfate Fe2(SO4)3 [nh: Internet]

Ngoi phn chua, mt vi loi phn khc, chng hn nh phn nhm [aluminum alum, Al2(SO4)3] v phn st [ferric chloride, FeCl3 hoc ferric sulfate, Fe2(SO4)3], cng c th loi tr arsenic trong nc ngm vi hiu qu cao [17]. Phn st tt hn phn chua v

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phn nhm nhng c l kh mua v mc tin hn v khng thng dng. Lng nc ngm lc arsenic cng tng t nh lng nc sng lc ph sa, nhng mun t hiu qu cao, phng php lng nc cn c iu chnh i cht do s khc bit v c tnh ca nc ngm v nc sng. Th nht, thay v bm trc tip vo h hoc lu, nc ngm nn c bm qua mt mng st (cng rng cng tt) hay li st (cng mn cng tt) arsenite [As(III)] c iu kin thun li oxy ha thnh arsenate [As(V)] v st c iu kin thun li oxy ha thnh Fe(OH)3; nh vy, cng nhiu arsenate kt ta vi Fe(OH)3 v b loi ra khi nc. Nu nc khng cht st, cn thm nc r st bng cch ngm cc chi nhm (steel wool) trong chai ring. Th hai, sau khi h v lu y, nn cho mt t t st sch ri quy u nc c mu c nh nc sng. Cc ht t st, ging nh cc ht ph sa, gip cho vic kt ta v lng ng c hiu qu hn v n lm tng trng lng v kh nng bm dnh (adsorption) ca cc ht kt ta.

Lu ng nc BSCL [nh: Internet]

Sau khi quy nc vi t st, nc c lng phn nh thng l. cc nh my lc nc, s lng phn chua c dng thay i t 5 n 50 mg/l, tc t 5 n 50 g phn chua cho 1 m3 nc [36]. BSCL, s lng phn chua s dng thay i ty theo kinh nghim v a phng. Thng thng, ngi dn ch cn cm mt cc phn chua trong tay nhn su vo lu nc ri khuy u cho n khi nhn thy ph sa bt u ng cc (kt ta).

Th nghim nh tnh (qualitative) s khi cho thy phn chua c th lng Fe(OH)3 rt nhanh. Ch cn mt nng khong 10 ug/l, phn chua c th lng nc c nng Fe(OH)3 khong 25 mg/l trong vng 3 ting ng h. Nu c t st, cc ht kt ta lng nhanh hn, nhng cn nhiu thi gian hn loi ht c.

Th nghim nh tnh - Bt u

Th nghim nh tnh Sau 3 gi

Th nghim nh tnh Sau 18 gi

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Nc trong vt sau 3 gi lng phn

Bnh lc t ch (KAF)

Bnh lc arsenic Kanchan (KAF) [37]

nhng vng m nc ngm cha t cht st, ngi dn c th t ch to bnh lc rt n gin v r tin vi nguyn vt liu c sn ti a phng. Bnh lc ny da theo nguyn tc ca KAF (Kanchan Arsenic Filter), mt bnh lc nc gia nh lc arsenic, st, cn, mi hi, vi sinh vt truyn bnh, v mt s cht nhim trong nc [37]. Bnh lc Kanchan do cc nh nghin cu Vin K

thut Massachusetts (Massachusetts Institute of Technology (MIT)), C quan Y t v Mi trng Nepal (Environment and Public Health Organization of Nepal (ENPHO)), v Chng trnh H tr Cung cp Nc v V sinh Nng thn Nepal (Rural Water Supply and Sanitation Support Program of Nepal (RWSSSP)) sng ch qua D n Nc cho Nepal ca MIT vo nm 2002. Bnh lc gm c hai ngn. Phn trn l mt ci thau c l ng mt lp inh st di v mt lp gch vn pha trn. Ngn di l thng ng mt lp sn di y, k l mt lp ct th, ri n mt lp ct mn lc cn v vi sinh vt. Khi tip xc vi nc v khng kh, inh st b oxy ha rt nhanh to nn cc ht r st Fe(OH)3. Khi nc ngm c cha arsenic chy qua lp inh st, arsenic s b bm dnh vo cc ht r st kt ta trong nc v b gi li trn mt ca lp ct mn trong thng cha. Kt qu nghin cu Nepal ca MIT cho thy bnh lc Kanchan c th gim 85 n 95% nng arsenic trong nc ngm.

Nguyn tc ca bnh lc Kanchan [37]

Da theo kiu Bnh lc KAF Gem 505 mi nht, nguyn vt liu cho bnh lc gm c 1 thng nha khong 50 lt c np y, mt thau nha c cng ng knh, 5 kg inh st (cng nh cng tt) (c th dng cc chi nhm thay th cho inh st), gch vn (ng knh 5-10 cm) ph kn lp inh st, ng nha, 20 lt ct mn (nh hn 1 mm), 4 lt ct th (3 n 6 mm), v 6 lt sn (6 n 15 mm). Cch lp rp, iu hnh, v bo tr bnh lc KAF Gem 505 c m t chi tit trong cm nang do MIT, ENPHO, v

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Trung tm K thut Nc v V sinh i chng (Center for Affordable Water and Sanitation Technology) n hnh [38]. Kiu bnh lc ny ch dng cho nc c nng arsenic thp hn 500 g/l. Nu nc ngm c nng cao hn, cn phi tng thm inh st hoc lc 2 ln. in gii (ECAR) in gii l mt phng php mi m nhng tng i n gin gim bt nng arsenic trong nc ngm khng c hoc c t cht st. Phng php, c gi l ElectroChemical Arsenic Remediation (ECAR), do Phng Th nghim Quc gia Lawrence (Lawrence Berkeley National Laboratory (LBL)) thuc trng i hc California/Berkeley nghin cu t nm 2005 v th nghim thnh cng Bangladesh v Cambodia vo nm 2008 [39].

Nguyn tc ca phng php in gii ECAR [39]

Cc giai on trong phng php ECAR [nh: LBL]

Phng php ECAR dng dng in c in th thp hn 12 Volt; t ngun in nh, in mt tri, hoc bnh in xe hi; lm cho hai in cc bng st b r st nhanh chng. R st s ha tan vo nc ngm, bm dnh v loi arsenic ra khi nc khi kt ta. Cht kt ta c gn ra khi nc bng cch lng t nhin. Kt qu th nghim cho thy ECAR c th gim nng arsenic trong 20 lt nc ngm t trn 600 g/l xung di 10 g/l m ch tn c 0.6 Wh/l. Ty theo c tnh ca nc ngm, thi gian cn thit lc mt m c th thay i t 40 pht cho n trn 3 ngy [40]. Phng php lng phn c th c dng rt ngn thi gian lng cn sau giai on khuy u (mixing stage) nh trnh by trong hnh. PHN KT LUN Vn nhim arsenic (thch tn) trong nc ung Vit Nam c bit n t nm 1998, sau khi hn 150.000 ging ng c khoan thay th ngun nc mt thiu v sinh trong chng trnh cung cp nc sch ca UNICEF nhm chng li bnh tiu chy ca tr em. Mt nghin cu nm 2006 cho thy nc ngm c nng arsenic cao gp nhiu ln hn 50 g/l, l tiu chun arsenic trong nc ung nng thn Vit Nam, c tm thy nhiu ni trong BSH v BSCL. Nng arsenic c th ln n 3.050 g/l BSH v 845 g/l BSCL. Tnh n nm 2008, s ngi c nguy c mc cc bnh do s dng ngun nc c nng arsenic cao hn tiu chun cho php ln ti hn 17 triu ngi, tc khong 21,5% dn s. Nhiu nghin cu c thc hin khp ni trn th gii tm cch loi tr hoc gim bt nng ca arsenic trong nc cho cc nh my lc nc tn tin th hoc cho cc n v gia c nng thn. Mc d nhng phng php ny t ra c hiu qu gim nng arsenic trong nc xung di 10 g/l, l tiu chun ca T chc Y t Th gii, chng vn cha c ph bin v s dng mt cch rng ri v rt tn km, cn nhiu vt liu, tn nhiu cng, v bt tin trong vic vn hnh v bo tr. nng thn BSH v BSCL, vic p dng cc phng php ny li cng kh khn hn

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khin cho ngi dn nn lng ri ph mc cho s phn! gip ngi dn sng trong nhng vng b nhim arsenic nng thn c th t tc theo ui vic loi tr hoc gim thiu nng arsenic trong nc gia dng, nht l nc nu n v ung, mt vi phng php tht n gin, r tin, v tin li; chng hn nh khng dng nc ngm va mi bm ln, phi nng nc, lng phn, dng bnh lc t ch, hay in gii nc; cn phi c ph bin rng ri. Trong cc phng php ny, lng phn c l l phng php thch hp nht. Cc phng php n gin v r tin ny c th khng loi tr ht arsenic, nhng t ra, chng c th gim bt nh hng c hi ca arsenic i vi sc khe ca ngi dn nng thn. Gn y, Ngn hng Th gii (World Bank) d nh ti tr cho mt d n nhm duyt xt, th nghim, v son tho ti liu v nhng h thng v phng php i chng v hiu qu loi tr arsenic trong nc ngm Lo, Cambodia, v Vit Nam [41]. Mt trong nhng mc tiu ca d n l duyt xt v ngh nhng m hnh v phng php th nghim v p dng cc quc gia va nu. Phng php lng phn, nht l lng phn vi t st, cn c quan tm v nghin cu nh lng (quantitative) xc nh hiu qu ca n trong vic loi tr arsenic trong nc ngm, chng nhng BSCL m cn nhiu ni khc trn th gii. TI LIU THAM KHO [1] USEPA. Accessed September 8, 2010.

Arsenic Coumpounds. http://www.epa.gov/ttn/atw/hlthef/arsenic.html

[2] World Health Organization (WHO). 2001. Arsenic and Arsenic Compounds. Environmental Health Criteria 224. Second Edition. Geneva, Switzerland. http://www.inchem.org/documents/ehc/ehc/ehc224.htm#3.1

[3] National Research Council (NRC). 2000. Arsenic in Drinking Water. National Academy Press. Washington, D.C.

[4] Mhd Rakariya and Simon Deeble. December 2008. Evaluation of Arsenic Mitigation in Four Countries of the Greater Mekong Region Final Report. UNICEF AusAID. http://www.unicef.org/evaldatabase/files/2008_EAPRO_Arsenic_Evaluationl.pdf

[5] Michael Berg, et al. November 2006. Magnitude of arsenic pollution in the Mekong and Red River Deltas Cambodia and Vietnam. Science of the Total Environment 372 (2007) 413-425. http://www.sciencedirect.com/

[6] Phng Anh TTX. 13 thng 3 nm 2008. 21,5% dn s mc bnh v ngun nc nhim thch tn. Nht bo Tin Phong. H Ni, Vit Nam.

[7] USEPA. December 2000. Technologies and Costs for Removal of Arsenic from Drinking Water. Office of Water. Washington, D.C.

[8] USEPA. July 2003. Arsenic Treatment Technology Evaluation Handbook for Small Systems. Office of Water. Washington, D.C.

[9] USEPA. November 2005. Treatment Technologies for Arsenic Removal. National Risk Management Research Laboratory. Cincinnati, Ohio.

[10] National Environmental Services Center. Fall 2006. Development of Low-Cost Treatment Options for Arsenic Removal in Water Treatment Facilities. Tech Brief. West Virginia University. Morgantown, West Virginia.

[11] Dan Krotz. January 21, 2005. Water Filter Could Help Millions of Bangladeshis Innovative technology could also help California comply with tighter U.S. EPA standards for arsenic in drinking water. Lawrence Berkeley National Laboratory. Berkeley, California. http://www.lbl.gov/Science-Articles/EETD-Gadgil-water-filter.html

[12] Susan Amrose and Johanna Mathieu. April 12, 2007. Trip Report: LBNL/UC Berkeley ARUBA Project, Bangladesh 2/23/2007-4/7/2007. Lawrence Berkeley National Laboratory. Berkeley, California. http://www.lbl.gov/tt/publications/1742B'deshTripReport.pdf

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[13] USFilter. 2003. GFH Media for Arsenic Removal. USFilter. Ames, Iowa. http://www.usfilter.com

[14] Sudipta Sarkar, et al. March 20, 2005. Well-head arsenic removal units in remote villages of Indian subcontinent: Field results and performance evaluation. Water Research 39 (2005) 2196-2206.

[15] Khan, A.H., et al. No date. On Two Simple Arsenic Removal Methods for Groundwater of Bangladesh. Accessed September 10, 2010. http://www.bing.com/search?q=Om+two+simple+arsenic+removal+methods&go=&form=QBRE&qs=n&sk=

[16] M. Ashraf Ali, et al. No date. Development of Low-Cost Technologies for Removal of Arsenic from Groundwater. Accessed September 10, 2010. http://www.unu.edu/env/Arsenic/Ali.pdf

[17] M. Feroze Ahmed. No date. An Overview of Arsenic Removal technologies in Bangladesh and India. Accessed September 10, 2010. http://www.unu.edu/env/Arsenic/Ahmed.pdf

[18] SenGupta, Arup K. 2005. Arsenic Crisis in India Subcontinent: An Indigenous Solution. Accessed September 10, 2010. http://www.lehigh.edu/%7Eaks0/arsenic.html

[19] Vu, Kiem B., Michael D. Kaminski, and Luis Nunez. April 2003. Review of Arsenic Removal Technologies for Contaminated Groundwaters. Argone National Laboratory, University of Chicago. Argone, Illinois.

[20] Kathryn VanderWeele. 2005. Removal of Arsenic from Drinking Water by Water Hyacinths. U.S. Stockhom Junior Water Prize Winner 2005. Water Environmental Federation. Alexandria, Virginia.

[21] Jorge Porras. March 10, 2006. A case study of arsenic removal on Sorghum Biomas A new biomaterial. Accessed September 10, 2010. http://wscsd.org/a-case-study-of-

arsenic-removal-on-sorghum-biomass-a-new-biomaterial/

[22] Zafar Adeel and M. Ashraf Ali. No date. A Comparative Evaluation and Field Implementation ofTreatment Technologies for Arsenic Removal from Groundwater. Accessed September 10, 2010. http://www.unu.edu/env/Arsenic/Adeel%20KJIST%20Paper.doc

[23] Nadim R. Khandaker, Patrick V. Brady, and James L. Krumhansl. March 31, 2009. Aresenic Removal from Drinking Water: a Handbook for Communities. Sandia National Laboratories. Albuquerque, New Mexico. http://www.sandia.gov/water/docs/NRK_PVB_JLK_As_Book.pdf

[24] Samuel Luzi, et al. May 2004. Household Sand Filters for Arsenic Removal Technical Report. An Option to mitigate arsenic from iron-rich groundwater. Swiss Federal Institute for Environmental Science and Technology. Duebendorf, Switzerland. http://www.arsenic.eawag.ch/pdf/luziberg04_sandfilter_e.pdf

[25] Pham Hung Viet, et al. No date. Arsenic Removal Technologies for Drinking Water in Vietnam. Accessed September 10, 2010. http://www.unescap.org/esd/water/publications/CD/escap-iwmi/arsenic/Arsenic%20removal%20technologies%20for%20drinking%20water%20in%20Vietnam..pdf

[26] HOANGGIATTS. Khng ngy thng. Bnh lc nc ArsenFREE, Gii php cho nc n ung an ton. c ngy 10 thng 9 nm 2010. http://HOANGGIATTS.com

[27] Cng ty lc nc Long Thnh. Khng ngy thng. B lc arsen nhn hiu Watts. c ngy 13 thng 9 nm 2010. http://thietbiloc.com/nuoc-sinh-hoat/66-bo-loc-arsen-nhan-hieu-watts

[28] Song Tun. 31 thng 7 nm 2006. Ngi dn vn dng nc nhim arsen. Nht bo Ngi Lao ng. c ngy 15 thng 9 nm 2010. http://nld.com.vn/159184P0C1002/nguoi-dan-van-dung-nuoc-nhiem-asen.htm

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[29] Agency for Toxic Substances & Disease Registry. October 1, 2009. Arsenic Toxicity What are the Physiologic Effects of Arsenic Exposure? U.S. Department of Health and Human Services. http://www.atsdr.cdc.gov/csem/arsenic/physiologic_effects.html

[30] USEPA. Accessed September 13, 2010. Arsenic in Drinking Water. http://water.epa.gov/lawsregs/rulesregs/sdwa/arsenic/index.cfm

[31] USEPA. Accessed September 13, 2010. Analytical Methods Approved for Drinking Water Compliance Monitoring of Inorganic Contaminants and Other Inorganic Constituents. http://www.epa.gov/ogwdw/methods/pdfs/methods/methods_inorganic.pdf

[32] UNICEF Supply Division. March 2004. Monitoring Arsenic in Water. Technical Bulletin No. 8. Accessed September 14, 2010. http://www.supply.unicef.dk/catalogue/bulletin8.htm

[33] Hach Company. Accessed September 14, 2010. EZ Arsenic Test Kit, 0-4000 ppb, 100 tests. Loveland, Colorado. http://www.hach.com/hc/search.product.details.invoker/PackagingCode=2800000/NewLinkLabel=Arsenic+Test+Kit%2C+0-500+ppb%2C+100+tests

[34] Trn Hiu Nhu, Nguyn Vit Anh, Nguyn Vn Tn, Hi. Khng ngy thng. Mt s cng ngh x l arsen trong nc ngm, phc v cho cp nc sinh hot th v nng thn. B mn Cp thot nc Mi trng nc, Trng i hc Xy dng. c ngy 10 thng 9 nm 2010. http://www.idm.gov.vn/Nguon_luc/Xuat_ban/Anpham/Arsen/a87.htm

[35] Wegelin, Martin, et al. No date. SORAS a simple arsenic removal process. Accessed September 2, 2010. http://phys4.harvard.edu/~wilson/arsenic/remediation/sodis/SORAS_Paper.html

[36] Clark, John W., Warren Viessman, and Mark J. Hammer. 1977. Water Supply and Pollution Control. Third Edition.

Harper & Row, Publishers. New York, New York.

[37] Ngai, T; Dangol B.; Murcott, S; Shrestha, R.R. January 2006. Kanchan Arsenic Filter. Second Edition. Massachusetts Institute of Technology (MIT) and Environment and Public Health Organization (ENPHO). Kathmandu, Nepal. http://web.mit.edu/watsan/Docs/Other%20Documents/KAF/KAF%20booklet%202nd%20edition%20final%20Jan06.pdf

[38] Tommy Ngai, Susan Murcott, and Bipin Dangol. No date. Construction, Installation, Operation and Troubleshooting of Kanchan Arsenic Filter (KAF) Gem505 Version. Presented at Kanchan Arsinic Filter Local Entrepreneurs Training Workshop. Janurary 16-20, 2006. Katmandu, Nepal. http://web.mit.edu/watsan/Docs/Other%20Documents/KAF/KAF%20construction%20manual%202006.pdf

[39] Prof. Ashok Gadgil and Dr. Susan Addy. 2009. Arsenic-Free Drinking Water, Electrochemical Arsenic Remediation (ECAR), Affordable Access to Clean Water. Berkeley Arsenic Alleviation Group, University of California/Berkeley, and Lawrence Berkeley National Laboratory. http://arsenic.lbl.gov/pdf/ECAR_Pamphlet_v8.pdf

[40] Prof. Ashok Gadgil and Dr. Susan Addy. August 17, 2010. ECAR-FAQ. Answers to Frequently Asked Questions (FAQs) about ElectroChemical Arsenic Remediation (ECAR). Dept of Civil and Env. Engineering. UC Berkeley. http://arsenic.lbl.gov/pdf/ECAR_FAQ_v10.pdf

[41] World Bank. July 12, 2010. Request for Expressions of Interest. Appropriate Arsenic Removal Technology for Drinking Water in Viet Nam, Cambodia and Lao PDR. http://www.devex.com/projects/appropriate-arsenic-removal-technology-for-drinking-water-in-vietnam-cambodia-and-lao-pdr