Conclusión de la propuesta de mejora

Sha A.I la found naturally In many ^p1rt1 of the world. and may lhercf ore be in llpuftcan1 amount In areas In which 1nduslrial or other pollution is abcmely Umhed. concerted effort is desirable to ensure protection of the population fiom poisoning when planning water supply systems. The primary problems with arsenic 1n drinking waler have occum:d in groundwater wilh levels of 3000 micro-grams per litre and higher recorded (Snow ^1992). Deep \\·ells have been particularly implicated ^IS containing higher levels. It therefore becomes necessary to carry out surveys ^IS to

possible problems with rocks bearing Dl"SCnic. In the obscnce of helpful geological infonnation, or when n decision hos been token to ^use n groundwater ^source:, it \\'OUld be prudent to ^carry out test drilling tn order to obtain approprinte SlllTlplcs of waler for analysis prior to full-scale development. In linnll) selecting o source, it is essential to take a holistic vie,v ond balnnce the \'urious risk agn,nst the requirements of the

population to be SCf"cd. ft must be opprccintcd thot \\ hile microbiological contaminants poses ^{an acute} threat to health, chemtail contominants also poses o chronic threat to health. It is also usually difficult to deal ,vith chemicals tJuin it is ,vith micro organisms.

According to American Ground \Vater Trust (USGS. 2003), testing is the first

and most imponant step for Y,ell O\\-ners or for ^An) consumer concerned about Y.uter quality. The Trust recommended that 111 least once a year test for coli fonn bacteria.

nitrate and pH (i.e. acidity) be ^carried out and that if pl1 is less that 7.0, test for lelld should be carried out. For new facilities such ^ns nev,ly constructed \\'Clls nnd boreholes,

or for such faeilitie, where records of previous test ore not 11,•11il11ble, the follo,\ing tests have been recommended: colifonn bacteria, nitrate/nitrite, pH, chloride, uun, m•npocsc, sulphate, hllrdness, alkalinity, total dissolved solids ^(TDS).

for wells that arc close to an operational or abandoned gas stntton or buried fuel 11Dn&C, ^lCl1J should ^be conducted for arsenic, mdon and fluoride. It ^has also been augestcd that after the 1nst11ll111ton of new equipnu:nt or if there hos been a change of

colour or odour. it is ncccaary to test for bacteria. Tcs1in1 arc desirable to be carried

OUl in certified laboretoria and by experts (USOS, 2003). Tho pouibility of ¹¹ pmtloUlly 1181,lc poundWIICr 111pply to have lnc:rc:ucd or dccrcued concentration of

,.. over ^time hll been obtcrvcd (Chappel c:t al ^1994; Oorosova ct 11 ²⁰⁰¹⁾

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AFRICAN DIGITAL HEALTH REPOSITORY PROJECT

Since As is found naturally in many pans or the \Vorld, and may therefore be round in significant amount in areas in which industrial or other pollution is extremely limited, concerted effort is desirable to ensure protection of the population f ^ro m poisoning \Vhen planning \Voter supply systems. The primary p ^ro blems \vith arsenic in

drinking \Vater have occurred in ground,vater with levels of 3000 micro-grams per litre and higher recorded (Sno\v 1992). Deep ,veils have been particularly implictlled as containing higher levels. It therefore becomes necessary to carry out surveys as to possible problems with rocks bearing arsenic. In the absence of helpful geological

information, or \Vhen a decision hos been taken to use a ground\vater source. ^It ,vould be prudent to cony out lest drilling in order to obtain appropriate srunples of \\'Oter for

analysis prior to full-scale development In tinnily selecting a source, 1t is essential to take a holistic v,e,v and balance the vnnous risk against the n:quiren1en15 of the population to be served. It must be appreciated that ,,hile microb ¹ ologicol contaminants poses an acute threat to hcalU,, chemical contaminants also poses ^il chronic threat to

hc:alU1 It is also usually difficult to deal \\'ilh chcn11cnls than ^II is ,vith mic ^ro organisms.

According to American Ground \\ ntcr Trust (USGS, 2003). testing 1s the first and most important step for v.ell O\!•ncrs or for any consumer concerned about \\Jter quality The Trust recommended that at least once ^il year test for coli form bactcna.

rutrote and pH (i.e. acidity) be earned out and that if pl I is less that 7.0, test ror l ^ea d should be cru-ried out. For nc,v fncihttc� �uch o, ncv.Jy constructed ,veils and bo ^n: holes, or for )UCh fncilitics "here records of previous test ,ire not o, nilablc, the follo\\·1ng tc�ts have.; been rccorn111cndcd: coliform b,tctcrin, nitratc/nttritc. pl I, chloride. iron,

manganese. sulphate:, hardness, nll.alintt)', total dissol\'ed solids ( fl)S)

For \\ells U1nt arc close ¹⁰ an optrationnl or abandoned gas �tulton or buried fuel t.torJgc, tests �hould be conducted for nrscnic, n1don nnd fluoride ^It h,b nlsa been suggested thJt ofter the installotion ol nc,v equipment or ii there has bccn a change ol' colour or odour, ¹¹ 1s necessary to test tor bactc:na ·1 cs11ng urc d ^e5 ir tbh: to be cnmed out 1n certified labonnoncs and ^b) c�pcns (USGS, 2003). n,c po�s1h1hl) of a pn:viously stable ground\\nter upph to hn,c increnscd or decreased conct.'lltmlton ol As o\'cr tirnc has been obsc:n cd (C.:h.1pptl ct al 199-1, Uorosovn ct nl 200 I)

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The need to develop a monitoring procedure for water has been advocated

(Hassan, 200S). This is with the understanding that water quality changes from time 10

time depending on many factors. In what may appear to be a stable ground"'&ler, pumping for example may pull in contaminants from more distant parts of the ^aquifer

and changes in pH or oxygenation can cause changes in the solubility of inorganics (Brewster, 1992; Edwards. 1994, Ali ct al, 2001; Ahmed ct al, 2002; WHO 2003 ).

There is need therefore to establish a surveillance regime that is appropriate to the circumstances of a particular source with a view to monitor quality or drinking ,w1er supplies thereby protecting Public Health. This "·ould specifically be required for woter sources that have once been screened and found 10 be As-free. l11c main purpose of this 5\11'\'cillance should be to monitor the ,vater resource qualil) trend so as to be able to identify fairly obvious increases from very low concentrations to higher concentrations.

In areas "·here concentrations of As is nil or ,,·ell bclo,v the guideline value, it may be appropriate to limit suf\eillnnce monitoring to a duplicate sample taken once every year and "hile at concentrations close to guideline values, more frequent sampling may be required, e.g. once e,ery month or two months. Should the coneentrution pro,·cd stable over a period of a ^)Car, san1pling may therefore be reduced to once a year. (Gebal, 1997: Boroso,a ct al. 2001). The primary purpose or monitoring trend should be to identify ob,·ious increases from very lo,v concentrations to higher concentrations (ruther than minor variations). Thus some analytical information "ould be of imminent use in demonstrating significant changes in concentrnt1on over time. In

designing a drinking \\'Dier :\Uf\eillance programme for public health protection, it 1s important ¹⁰ specif) the t)pe of samples to be tal,;cn and the ,,11y 1n ,vh1ch it should be tn:ated in order to ensure that ^II reaches the nnal)tical loboratol) ^II \\ould not ha,e clwlgcd (Guha ct al 1992).

In the absence of ancn1c or conccn11Ut1oru \\'CII below the guideline value, 11 has

been su&aested that surveillance could be hmitcd to duplicate: snmplcs taken once: e,c:I)

year (Hassan 2005) In do1ns this. 11 S)'Stc:m of aquifer mapping has been 1ugaes1cd