r-^r-N ,-, •"-••«w/i_ wt.|\l | Ite, FOR COMMUNITY WATER SUPPLY AND SANIiATION (IRC) . 37-43pp , I ,. 193No , 6 20 . 0043-1354/86 $3.0 0.00+ 0 - :at Britain. All rights reserved Copyright © 1986 Pergamon Press Ltd mij;!t 35 si 253 Pi 86 LO II LOW TECHNOLOGY WATER PURIFICATION BY BENTONITE CLAY FLOCCULATION AS PERFORMED IN SUDANESE VILLAGES VIROLOGICAL EXAMINATIONS*
EBBA LUND and BIRTH NISSEN The Department of Vet. Virology and Immunology, The Royal Veterinary and Agricultural University mv f Copenhageno Bulowsvej3 ,1 , DK-1870 Copenhagen, Denmark
(Received October 1984) n jij!ii«!1?5: Abstract—Viruses were removed from various type f wateso flocculntioy b r n with natural bentonite clays i:!!/+ from the banks of the Nile as well as with pure bentonite. The flocculation technique employed corresponds to that used to clarify Nile water in Sudanese villages. If proper flocculation occurred 3 to 4 log,0 units of virus could be removed. Some of the conditions for floe formation were examined.
Key words—water purification, bentonite clay, bentonite, flocculation, Sudanese villages
INTRODUCTION riological examinations [preliminary reported by Madse Schlundd nan t (1983)], parasitological exam- Jahn l Fadi(1976E d Jahd lan )an n(1984 } have ination virologicad san l examination continuation si n described liow the river Nile during the flooa season preliminara f o y wor Luny kJahb d an dn have been in Sudan, beginnin n Juni gd lastin an e g through carried e outpresenTh . t report deals wit viroe hth - September, is highly turbid. Suspended solids may be logical examinations. Preliminary viroresulte th -n so ! • '1" V as high as 8000 mgl~'. In the villages, water logical work were presente Luny e dJahb d th dt an n a purification by flocculation has been employed for Internationad 2n l Conferenc Impace th f n Virao o et l over 100 hundred years (Jahn, 1977). One of the Diseases on the Development of African and Middle methods employed in the villages is the addition of a East countries, Nairobi, 1980. suspension of "rauwaq", clarifier, which is a clay found in varying quality at the river banks. The main MATERIAL AND METHODS flocculating component is montmorillonite (ben- The rauwaq's (bentonite clays) benloniteand employed tonite) (Jahn, 1977). Jahn (1981) describew ho s Sample f rauwao s f gooo q d quality collecte n Norti d h Sudan and brought to Copenhagen by special messenger in pounded rauwaq is prepared as a suspension in a 1979 were: rauwaq Uqda and rauwaq Gir al. During a visit , deep plat r calabaseo stirred an h r 10-2dfo 0 min with in 1980 the senior author picked up rauwaq samples as a stick or spoon. The suspension is then added to the indicate y villagersb d . These samples werl E e d fromWa I turbid n earthenwarwatea n i r r otheo r rja e water Said, Alti and Eseba. The rauwaq samples were estimated for turbidity by appearance in 500 ml bottles after addition container. If the woman, who carries out the to Copenhagen tap water to which had been added I/I0 of purification choses ha , propee nth r concentratior fo n cell culture maintenance medium. The pH was around 1.3 the particular water and rauwaq, floes will form and and room temperature 20-23°C. The samples were left to settle. Concentrations above and below the proper stand for 3 h at room temperature and observed for tur- e wilon l leave wateth e r turbid. Satisfactory bidity Tabln I . observatione th e1 indicatede sar optiman A . l concentration is seen for the Uqda type, but for the others clarification will tak t leasa e t . Jah1 h s madha n a e only minimal doses were foun r flocculationfo d . preliminary investigation in 1974 on the removal of Pure bentonite (Sigma B-3378 a goo s dwa ) flocculant, I1' -" fi1 coliform e rauwath y b sq (clarifier) clareportd yan s when adde waterdo t s of different composition under similar Ijj fri that it is general knowledge in the villages that condition s employea s e rauwaqth r e watefo d Th . r bottles were inspected with the results indicated in Table 2. As may familie o treawh st their water have lower incidence be seen from Table 2, bentonite could also flocculate in rates of gastroentestinal disturbances than other water, if the ionic strength was sufficient. families. waterThe types employed Jahn inspire looo t s ku d inthygienie oth c aspects In all 7 different types of water were employed in the purificatioe oth f provided nan clae dth y materials.A experiments purpose Th . e was, and als ihn oi e experiments wherp u t estudse s fielywa d wor dons Sudankwa n ei , carrie Copenhagenn i t dou simulato t , closels ea s possiblya e and more complicated studies including the viro- watee th r condition Sudan si n during river flooding periods. logical studies were carrieDenmarkn i t ou d . Bacte- Therefore artificiae th , l Nile wate probabls wa r y e closth o et optimal for the flocculation experiments. This water was prepared by Madsen and Schlundt in the following way: to •Supporte granty b d s from DAN1DA (the Danish Inter- 1.01. of Copenhagen tap water was added 6.64 g of mud national Development Agency). fro Nile mth e banf Bact0.d o 1g kan o Pepton.
37 3& EBBA LUND and BIRTE NISSEN
Table 1. Eslimalion of fl peculation ability of ruuwaq added lo Copenhagen tup water with 10% cell culture maintenance medium, pH 7.4 Turbidity* Typ f rauwao e q lOgl ' 20g|- 30gl ' Uqda Turbid Slightly turbid Clear Clear Slightly turbid Turbid Gir al Clear Wad El Said Turbid at l-30gl-' Alti Turbid Turbid Somewhat turbid Clear
Eseba Turbid Somewhat turbid Clear Clear *Turbidit s observewa y y visuab d l inspectio e variouth r fo ns concentrations added.
Table 2. Flocculation when bentonite was added to water of various compositions Turbidity* watep Ita n r In demineralized water With 10% culture medium With no With 10% With no With And no Bentonite further culture further ' m6 g1 26 further With 133 mg|-' With 266 mg|-.' (gl ') addition medium addition of CaCI, addition of CaCI; of CaClj 0.5 Turbid Turbid Turbid Turbid Turbid Turbid Turbid 1.0 Turbid Slightly turbid Turbid Turbid Turbid Slightly turbid Slightly turbid 2.0 Clear Clear Very turbid Slightly turbid Turbid Clear Clear 3.0 Clear Clear Very turbid Clear Turbid Clear Clear 5.0 Clear Clear — — — — — *For characteristic watep ta demineralized f an ro s d wate e Tablse r . e3 fTurbidil s observewa y visuay db l inspection. {The same results were obtained with no addition of CaClj or employing 133 or 266 mg I"
e resultTh s obtained wite Nilth he waters e artificiath , l a surfac s d sizha it an ee quite different fro e enteromth - Nil Copenhagee e th wate d an r watep nta r wer t esseneno - viruses commonls i t I . y e intestinafounth n i d l tract, bus i t tially different in the present experiments. Flocculation was somewhat less resistant to environmental factors than the obtaine l cases al e characteristic n i Th d. e waterth f o s enteroviruses. It was grown and employed in the same way employe givee dar Tabln ni wher, e3 pone eth d wate fros ri m as the coxsackievirus. The liters varied somewhat, but was 60 5 a highly turbid duck Universite ponth f do y park. between 10 -10' TCIDiomt-' during the exptrienls. The bovine parvovirus (HADEN virus) employed was Viruses celland cultures employed received from the Danish Slale Veterinary Virus Research The human enterovirus Coxsackie B3 employed was Inslilule, Lindholm s titratewa t I .secondar n di y calf kidney originally isolated from biologically treated Copenhagen cells receive s primara d y cultures from Lindholme Th . waste a viruwater s i t sI .typ e whic s repeatedlha h y been media employed were like the ones for the Hela cells except found in waste water all over the world and must be for the use of horse serum instead of calf serum. The liter considered a good indicator for faecal virus pollution. The obtaine arouns dwa d lO'^TCID^ ml" '. This virus typs ewa tilers obtained were around lO'^TCID^ml" ' when titrated included, although specifically bovine, because parvoviruses in tube culture f Ilelo s a cells a huma, n cell line which are extremely resistant toward environmental factors (Sri- originated fro mcervia x carcinoma celle Th .s were growt na vastav d Lundan a , a goo1980 d dan ) humant typno s i e 37°C in a medium consisting of Eagle's solution with 10% available for routine work. borw ne n f calo f serum with antibiotics e maintenancTh . e medium consisted of the same medium with only 2% calf Experimental procedure serum. The tttra'.ions were carried out by CPE (cytopathic The slurries as they were made up from bentonite clays effect) determinations employing 3 tube cultures for each in Sudan involved stirrin r shakingo handy gb . Preliminary 10-fold dilution step with 0.1 ml inocula and the tiler experiments showed that floccualtions could be obtained calculated in TCID^ per 0.1 ml. employing a Griffin flask shaker with the same resulls as A strain of human adenovirus type 1 was also isolated wilh manual procedures, mechanically shaken slurries were from waste water and included in the present work, because employed in the experiments. The desired amount of rau-
Tabl . Characterizatio3 e n e variouoth f s water types employe experimentse th n di * COD Total Total hardness Turbidity (permanganate) solids Conductivity 1 (FTU) (mgl-'j (mgl- ) °dHf CaCOj (mS m ') PH Tap water 7.0 425 13.5 270 56.2 82 Pond water 23 166.0 660 20.2 404 — 7.5 Artificial Nile water 1400 167.0 5385 13.5 270 57.2 7.9 Blue Nile Sept. MOO 167.0 2397 8.6 172 203 8.0 82 (flooding season) Blue Nile Apnl 7.8 12.6 340 5.7 114 16.5 7.8 (dr3 8 y season) White Nile Apri3 8 l 48 20.0 525 3.5 70 19.5 8.0 Irrigation 170 51 1570 9.5 190 37.0 7.9 Canal. Soba. Apri3 8 l Demineralized water 25-10 "The analyses were kindly performed by the Copenhagen Water Works Laboratory. We gratefully acknowledge this assistance. tOne degree of hardness (1 dH) corresponds lo lOmgl"1 of CaO Virus remova clay b l y flocculation
waq or bentonite svas suspended in 100ml of the water to experiments e tilerth sr obtaineFo . r viru- fo d ad s be teste mechanicalld dan y shake min 0 e viru3 s r Th . snwa fo sorbe floe e amoune th th s o dt t w t t adsorbewe g r dpe added after removin gsampla r titratioefo mako nt efinaa l is indicated e weighfloee Th th . sf o tvarie d somewhat dilution of 1:100 or up to 1:10,000, and the total water sampl s mado 1000mlt ewa p eu . Apparentl differenco yn e between the experiments but was within the interval was found in the removal capacity, whether a high tiler of 15-22g concentratioe Th . f floeo d f virug di sn o r pe s virus or a more diluted material was employed, but at least not give information that could tell much about the lO^TCIDjo/O. s desiree flocculatiowa th l n i dm l n experi- adsorbing capacit floe e t serv controa th bu sf s eya o l ments in order to get a good estimation of the removal of the experimental procedure, because the difference capacity. The sample stayed overnight at room temperature after careful mixin y handb g . Flocculations wer n prei e - in liter between the added virus and the one of the liminary experiments carried out at 20 and at 37=C. No treated water could have been the result of virus differenc n flocculatioi e n efficienc s founwa y d betweee nth inactivation rather than removal in the flocculation. two temperatures r eacFo .h flasko testw t . sIn werup t ese In addition the fact that the liter of the eluates was floee th se weron e allowe sedimeno dt t spontaneouslyd an , th ecentrifuges conten othewa e e th f ron o tt 5000-7000 da £ several logs higher than the one of the corresponding for 20-30 min. Both supernatants were titrated for virus. No supernatant serve to stress the fact that virus did significant difference literin s s were observed betweenthe adsor floee could th san elutede o bdt b . Therefore eth two supernatants, and the removal efficiency of the sediments could give potential hygienic problems. flocculatio tablee th n i s s indicatei n average e th th s d a f eo two values, thus improving the accuracy of the titrations. Experiments employing various bentonite clays (rau- e floeTh s fro e centrifugatiomth n were eluted employing II elutioe 10th %r nfo bee wit0 f 9. dilutioextraca h H p t a tn waqs)from Sudan on Copenhagen tap water to remove ;* factor of 1:5. After centrifugation at 1000^ for 30 min and coxsackievirus i!(l;! eluate readjustmen titrateds th virue 4 th ewa 7. sd H an , p o t t liters expressed as amount of virus per g wet wt of centri- Five different rauwaqs were tested as flocculants. fuged floes. Throughout the paper the log units employed concentratione Th s employed.were gauge face th t y db e logar lo units. f theo o m tw (frotha e th mtNortr an i l UqdGi d h aan Persistence of infectious virus in the sediments Sudan) were known locally to be of good quality, and In connection with corresponding bacteriological exam- the indications from the experiments shown in Tables inations suspension f coxsackieviruo s s were diluted 1:10 1-3 were employed. The results from the experiments wit whico ht Nild he mu rauwa beed qha n adde simulato dt e to remove coxsackievirus are shown in Table 4. It a floe. The mixture was then distributed in Petri dishes with a layer of around 10m thicknessmn i . They were left open e seeb ny thama t rauwaq efficiently removes virus to dry exposed to Sudan sunlight. Samples were exposed in from the water. Reliable removal was obtained when the open in such number that three could be taken out each the good flocculants were employed. With too high a day7 d ther an sfo n y lesda s frequentl day0 3 alln r i s .fo y concentration of the clay no proper flocculation and The Petri dishes were then closed with tape and kept in the cold until examined in Copenhagen (air transportation by litlle remova f viru o obtaineds l swa . Eve pooree nth r personal messenger). In the laboratory a I g sample from rauwaq qualities could remov log,e2 0 unit f virusso . each dish was eluated with beef extract, pH 9, to which was A strong adsorption to the fides was indicated with added penicillif 100o U 0 1 100d streptomycinf no an 0g d an , no virus inactivalion, but reversible binding. the eluates were centrifuge t 700a d r 030minH p #fo e Th . was adjusted to 7.0 and then titrated in Hel.a cell tube cultures employing O.l inoculam I e eluateTh . s froe th m Experiments employing a high turbidity duck .pond unexpose d samplemu dd tilerha s s between 10d San O waterattemptan in flocculate to coxsackievirus. l060TCIDso/0. e undiluteth , 1ml d original virus suspension contained lO^TCID^/O e sampleTh . ml s.I whic d beehha n e ponTh d water employe turbis witd wa dan ha exposed 2 4h (13-14 April) containe e samplon n i ed high loa f organido c material Tabl n resultI e . th e5 s ? 10" otheo n TCID n i r sampled Wan /0., 1ml s virus coule db compilede seee b ar ny thama t tI . compared wite th h demonstrated. The April temperature was around 32°C, and result watep ta resultTablf e so n th ro e4 s show less ther sunshins ewa edayse mosth supporo f T . o t t this result laboratora y experimen carries wa t d out, wher ef soi o 1 0lg efficient or erratic removal of virus. Thus if the water s mixewa f virudo l witsm 3 hsuspensio g d 1 kep an n i t is too heavily loaded the removal efficiency can be amounts ope t n incubator32a na an Ci a n eacy O . da h Apparently very much reduced. sampl s removewa e d eluatean d d like Sudath e n weather exposed samples. The zero sample eluate contained Experiments employing pure hentonite on various lO^TCIDjo/O.! litee ml s 10d lateth .0wa ran , 9 Afte h r 4 2 r no virus was demonstrated. Thus the drying alone at 32"C waters removeto co.tsackievirus was able to inactivate the virus in <48h. The flocculaling, removing factor in a clay definitely depend bentonite th n so e present t evebu , n EXPERIMENTS AND RESULTS with chemical and mineralogical analysis of the ben- tonite clays employe t i would e impossiblb d o t e The experiments were carried out during a period predic e removath t l capacit r s virusesfo ywa t I . thin years5 i f sd o perioan , sensitivite dth cele th l f yo therefore considere f intereso d o wort t k with pure cultures and the tilers of the viruses employed varied bentonite also. One single batch of bentonite was somewhat e actuaTh . l difference virue liten th i sf so r used throughou e experimentsth t , because ever fo n employed were however little more than experimental pure bentonite Ihe aclivity is not given by the mineral error. Therefore, it seems justified to compile the alone. As may be seen in Table 6, excellent removal individual results obtained fro varioue mth s serief so was obtained with I g I" ' of bentonite e.xcept for the t'*'. iI EIIBA LUN d BIRTDan E NISSEN
Table 4. Experiments employing various bentonite clays (rauwaqs) from Sudan on Copenhagen tap water to remove coxsackievirus B3 Log virus liter Virus adsorbe o floet d s In untreated In treated Virus removal (log10 TCIL^Mj g" l wet Bentonite clay water water (%) wt of floes) Rauwaq. Uqda Igl-' 67 6.7 0 69 5.1 3.4 98 4.7 2.7 0.1 99.7 4.8 2.4 0.7 98 4.8 6.1 4.1 99 5.3 2.8 O.I 99.8 5.1 5.0 2.2 99.8 5.4 3.8 0.8 99.9 4.8 4.4 0.8 99.97 4.0 30gl-' 4.4 3.4 90 4.8 Rauwaql a r Gi , 4.0 0.7 99.95 4.0 3.9 0.2 99.98 3.8 Rauwaq. AJti 30g|-' 2.6 0.0 99.8 3.3 Rauwaq, Eseba 20 g I " ' 2.6 0.3 99.5 4.0 Rauwaq. Wad El Saul 56 2.4 99.4 5.8
Tabl . Experimente5 s employing bentonite clay ducn o s k pond water with coxsackievirus added Log virus tiler g viruLo s tiler Virus adsorbed to floes r nilpe untreated per ml treaied Virus removal (log.oTCIDy, g-' wel Flocculam water waler f wHoeso t ) Rauwaq, Uqda Igl-" 6.7 6.7 0 6.8 2.4 2.4 0 5.3 6.1 5.1 90 50 2.8 0.5 99.5 4.8 3.8 2.9 87.4 4.8 lOgl-' 4.4 2.3 99.2 3.8 30g|-" 4.4 4.2 36.9 4.0 Rauwaq, Gil a r 4.0 2.3 98.0 3.8 3.9 2.6 95.0 4.5 •Waler sample lurbid after ireatment.
White Nile and the Irrigation Canal water, but even water some experiments4 wer7. H ep carriet a t ou d in these cases aroun remova% 99 ds obtained wa l . using demineralize seee b Tabldn ni y waterma e s A . bentonit7 e coul t efficientldno y flocculate under such conditions viruo n d s removaan , demonstrateds wa l . Experiments with low conductivity water and CaCl2 to In accordance with the preliminary observations of remove coxsackievirus Tabl 2 turbidite y coul e removeb d f CaCli d s wa 2 o examinT e importancth e e ionith cf o estrengt h added. Even when flocculatio obtaines nwa virue dth s for flocculation and removal capacity of virus in removal was less than optimal.
Table 6. Experiments employing pure benlonile to remove coxsackievirus from various waters ; Virus adsorbed Log virus tiler Log virus tiler to ftocs (loglo
Concentration l treatel untreatem m r r pe dpe d Virus removal TCIDg~ wet J0
of bentonite Water type water water f floeso t w ) (%) 1 Tap water 3.8 0.7 99.92 5.0 3.8 0.8 99.90 4.7 UP Artificial 3.9 0.2 99.98 5.7 Nile water Blue Nile 3.8 0.5 99.95 5.0 water* White Nile 3.8 2.1 98.0 4.4 w.alert Irrigation 3.8 1.7 99.2 3.4 Canal. Soba'J •Brough o Copenhaget t n after collectio y 198?Ma .n i n tSome turbidity left in treated water. ^Visible particular matter still present in treated water.
jiZIWi?!^ •fr^-f^~j^7^-l^/ fttJ'T"*Tii'- 1 TI • r r - iir<" T" t_r—Vfr- mi - i._i.-V""- •- —r" " ~ """ "-^ m-"-' ---•••• — • ——— —• — -— - - •s
1&s & Virus removay b l clay flocculation 41 fer 1I *- II Tabl . Experimente7 s employing bentonit demineralizen eo d wate2 ( r 5 mS m"') to which virus suspensions were added in dilution 1/1000 Turbiditg viruLo s titey r g viruLo s titer Virus cone sedimenn i , t I ifi\A.; m Bentonite after per ml untreate l treatedm r pe d Virus remova! l (log,0 unit f TCIDyo s , concentration CaCl added treatment water water (%) g~' ) we-wt t f 1 ; fl «?•1 1 None 4 4 Turbid - • 1 o removaN l 7 4. 4.2 & IP' 3 None Very turbid 4.4 4.4 0 4.2 m I 1 133mg|-4 4. ' Clear 2.7 • 98.0 6.4 IH&' 4 4. Clear 2 3.6. 4 90.0 il* W; mg|-6 26 4 4. ' Clea 3 r 23 99.2 6.3 P
Experiments to remove adenovirus by flocculation 20-29DC and the water temperature 20-25°C. In 1 watere Somth d flocculantf eo an s s employer fo d .40-44°e y wateb th n d r ca Can r summeai e th r temperature 29-3 1°C. It was found that the 1 the remova f coxsackieviruo l s were examinee th r dfo P remova f adenoviruso l e resultTh . s see Tabln ni e8 flocculation apparentl t chang regioe no th d n ei yndi if indicate that the removal of adenovirus functions 20-37° arounH p thad e Cslightlr an th dt o y abov0 e8. | e closelsamy witth wa en hi y aroun e samth d e after addition of bentonite clay was optimal for i efficienc r coxsackievirusfo s a y . flocculation importans i t removae I . th r fo t l capacity i that the floes be formed slowly, i.e. during one to m Experiments removeto bovine parvovirus several hours and be allowed to settle spontaneously. 11 Corresponding to the experiments on adenovirus It seem s possibls wa tha t i o t simulatte e th e the abilit f rauwao y r puro q e bentonit o removt e e flocculation in the laboratory and study some of the jiH factors of importance. : parvoviru flocculatioy sb examineds nwa e resultTh . s iji i are shown in Table 9. It seems possible that the Flocculation in water treatment m remova f parvoviruo l s is somewhat less efficient than ! the removal of coxsackievirus, but the difference Flocculation is routinely a part of the conventional i demonstrate s smal i dd probablan l t significantyno . waterworks treatmen removo t t e turbidity e floeTh . s are often obtained by the addition of alum, and it is i|I recognized that the efficiency of flocculation depends i t& ib'-' •j* DISCUSSION very much on the water quality. Langelier et al. !«•• 1 (1952) found that a preadjustment of buffer capacity Flocculation bentoniteby Wi .- X; y improvma e flocculationH th p e d an . Optimum c>2 88 e purpos presene Th th looo t f t eo k t no wors wa k flocculation requires that an equilibrium be obtained, ;!» m i!r into kineti r otheo c r studies relate o flocculatiot d n in which many parameters are involved, such as Sji: !?>pV.' theories studo t t ybu , virus removal under conditions turbidity, particle size distribution, exchange capac- iiv' simulating what could take place in Sudanese vil- ity, pH and alkalinity. The exchange capacity of a fsI lages. It seems that during winter (Jan. -March) the water can be increased by the addition of negatively jj; vS air temperature in Northern Sudan is around charged colloids, such as activated silica, bentonite ill 1 8> m Table 8. Experiments employing bentonite clay and bentonite o removt e adenovirus fro watep mta d artificia an r l Nile water ij 1 Log virus titer Log virus titer Virus cone, in floes i l untreatem r pe d l treatem r dpe Virus removal (log,0 unit f TCIDo s M §£ Flocculam Water water wate rt wt we ) ' ~' .g (%) u.5 jjiS y Rauwaq. Gir al Copenhagen 6.0 5.27 6. 84.2 i Igl"' tap water \\ watep Ta r 10 gl~63' 3.1 0 7. 99.94 $ i Rauwaq l a r Ci 5 , 5. Artificial 2.7 99.8 6.1 ' m $ 10 gT' Nile water |.i Bentonite 3U" 1P* 0.2 gl~' Tap water 5.8 7 6. 5 3. 99.5 M7< 0 5. p wateTa r 1 gl~ ' 1.0 9999 4.7 g <& a: fr: Table 9. Experiments to remove bovine parvovirus 9";1 Log virus liter Log virus titer Virus adsorbed to floes K'K-3i per ml untreated l treatem r pe d Virus removal (log,u unit f TC1Do s M in p Flocculant Water water water (%) g~' wet wt) \:- j' 1f4 Rauwaq. Uqda Copenhagen I}' tap water Igl-1 3.7 3.0 80.1 3.2 r!~ i: I0g|-' 2.8 0.0 99.8 4.4 If Bcn'.onite ii '•' •• 1.02 5. 99.6 f '"' Igl-' 3.4 ; i v 2g|-' 2.9 0.0 99.9 4.8 I'-, Ftcmoniie Artificial B.'l' : Nile water
minerals, i.e. removal of up to I-21og|0 units of virus. in the real life situation that viruses do not multiply It was also found that resuspension of virus could in the environment, i.e. outside the proper living cells. take placionie th f cei strengt s loweredhwa ; than i t In additio e enterith n c viruses employe e verar d y fact the process was completely reversible. It was stabl wida t rangH ea p e e als t temperatureoa s like indicated that there would be competition for ad- here between 20-37°C, so that the time factor is of no sorptio nclae th sitey n betweeo s n viruse d othesan r importance in the flocculation experiments. proteinaceous materials. The coxsackievirus employed in the study can s beeAha sn pointe t repeatedldou y (e.g. Lunt de almos e considereb t a dvira l indicato r faecafo r l al., 1969; Lund, 1971; Schaub and Sagik, 1975; pollution s veri t yi s frequentla , y reported frol mal Welling s beeha t nal.,e s w generall no 1976 d an ) y over the world. Addy and Otatume (1976) have one accepte o wory alwh b dlk with environmental Africaw fe e nth f reportsa o viru s i st I .whic s i h samples, the enteric viruses, as far as they have been relatively stablenvironmente th n ei t typican bu ,a r fo l examined, have affinity for solids, be it clays or enterovirus it does not withstand drying very well, as particulate matter from faeces. The adsorptio presenne th seee i sb n ni ay t reportma e adenoviruTh . s physical-chemical reversible reactione solith dd an , was included, because it is chemically and structurally associated viruse e probablar s y more resistano t t a very different enteric virus, and so is the parvovirus. spontaneous inactivation than free viruses. In a sew- All three types were removed with about equal e treatmenag t e viruplanth f st o loa abou% d 50 t efficiency t woulI . d have been interestin includo gt ea follow primare th s y sludge (Lund, 1971). Clay miner- rotaviru studye th n si , both becaus probabls i t ei e yth s pla al importann ya t rol soin ei l microbiology (e.g. most important agent for infantile diarrhea, and Filip, 1979). Among the normally applied chemical becauss beeha nt i e reported (Smit d Gerbaan h , flocculants in \s-ater and waste water treatments are 1982), that rotaviru s lesi s s efficiently removen i d alum, limferroud ean ferrid an s c chloride. These ear waste water treatments than cnteroviruscs. "•?&}'• '
Virus removal by clay flocculation 43
Persistence of virus in the floes , WoodarJr Carlso , Wentwort. d F E. an . . . nF G d F . hD Sproul O. J. (1%S) Virus inactivation on clay particles in As can be seen from the results of the present work natural waters . J Wat.. Pollut. Control , Fed.40 high liters of infectious virus are contained in the R89-RI06. floese nativTh . e habi f disposino t g wite sedith h - Engelbrecht R. S. (1971) Removal of viruses by coagulation ments fro watee mth throwiny b r t oveg i wale f th r o l and fioccuialion . Wat.. /Ass.s .Am , 298-300Wk 63 . village th n i e t streeou yare d tth dan coul d thea e nb Feachem R., Garelic Sladd an . . (1981eJ kH ) Enterovjmses in the environment. Trap. Dis. But/. 78, 185-230. hazardous impressioproceduren a t e ge th o f T o n. Filip Z. (1979) Wechselwirkungen von Milcroorganismen potential public health problem of the floe disposal und Tonmineralen—eine (JBersicht. Z. Pfltrniihr. the experiments of the present report where virus Bodenk. 142, 375-386. containing mud was exposed to the Sudan weather Grabow W. O. K., Burger J. S. and Nupen E. M. (1980) Evaluation of acid-fast bacteria, Candida albicans. enteric were carried outvirue Th . s contents were withih 4 n2 viruses and conventional indicators for monitoring waste- t demonstrablreduceno a o dt e level fro addee mth d water reclamation systems. Prog. Wat. Tcchnol. 12, 50 lSO 10 -10 TCIDs0 /0.. Laborator1ml y experiment- sin 803-817. dicated that the drying alone would destroy the virus IAWPRC Study Group on Water Virology (1983) The health significanc f viruseo e n wateri s , . 17 Water x Re within 48 h. Consequently, the risk of spreading viral 121-132. infections with unsanitary disposal of rlocs is consid- Jahn S. al A. (1976) Sudanese native methods for the erably reduced under dry and sunny conditions as in purification of Nile water during the flood season. In Sudan removae Th . l fro t connectewatee mth no s ri d Biological Control of Water Pollution (Edited by Tourbier witviruy han s inactivation t witbu , concentratioha n . d PiersoJr) . 95-106W an ,pp . . J R n . Universitf o y Pennsylvania Press. Pa , in the (Iocs. Therefore the improved water quality Jahn S. al A. (1977) Traditional methods of water depends entirely on a proper separation of the floes purification in the riverain Sudan in relation to geo- from the water. It could even be imagined, that an graphic and socio-economic conditions. Erdkunde 31, amount of water with residual floes would be of 120-130. poorer hygienic quality than the untreated l waterFadiE d l (1984an . . A Jahl )a . WaterqualitnS y fluctuations e Bluith n e Nild Whitan e e green-beleth Nild an e t What would be a sufficient removal of virus to make a irrigation canal South of Khartoum. Wat. Qua/. Bull. 9, 149-155. potable water? Kirch M. F. (1974) We cut dcwatering costs. Wat. Wastes The question of acceptable virus standards for Engng , 1-511 . ill Langelie Luciwid . , (1952an LudwiF G . . . F R g W r. ) gH V*-.T drinkin t gbee no wate ns solveha r t mucbu d h dis- Flocculation phenomen n turbii a d water clarification. rii cussed (e.g. WHO, 1979; IAWPRC Study Group, Proc. Am. Soc. civ. Engrs 78, Separate No. 118, 1-17. IH 1983; Feachem et a/., I9S1). It is not easy to solve the Libor D., Barkaes K. and J0rgensen S. E. (1973) In- problem r pipeFo . d supplie might si reasonable b t o et vestigation of phosphorus removal from water. Water demand a "virus-free" water, but we do not have the Res. 7, 1885-1897. Lund E. (1971) Observations on the virus binding capacity method guaranteo st e that facn have I . w gooo t en d f sludgeo . Proceedingsh International5t e th f o Water definition for "virus-free". Among other things be- Pollution Conference, pp. 1-24/1-1-24/5. cause we do not even have proper cultivation meth- Lund E., Hedstrom C. E. and Jantzen N. (1969) Occurrence ods for a number of the relevant human pathogenic of enteric viruses in waste water after activated sludge treatment. J. Wat. Pollul. Control Fed. 41. viruses. A number of piped supplies have contained Madsen M. and Schlundt J. (1983) Hygiejniske aspekter af demonstrable amounts of virus. traditionelle vandrensningsmetoder i Sudan (Hygienic Would a 3-4 log,0 unit removal of virus be ade- aspect f traditionao s l method r watefo s r purification i n quate? As quoted by Feachem et ul. (1981) polluted Sudan). Dansk. Vet. Tidsskr. 66, 785-792. surface wate bees rha n reporte0 contaio 30 dt o t p nu Olphe . vanM n , Kapsenberd an e . G.d gJ n , Baava . E n Kroon W. A. (1984) Removal of enteric viruses from infectious units 1~' f thiI . s numbe realistis i r c thena surface wate t eigha r t water e NetherlandsworkTh n i s . 3~4log|0 unit removal would- probablim n a e b y Appl. envir. Microbiol. , 927-93247 . portant improvement of water. There is strong epi- Sagi. (1975d P Schau an . . kB )A . AssociatiobS n ofenlero- demiological evidence thamose th t t important spread virus with natura d artificiallan l y introduced colloidal solids in water and infeclivily of solids associated virions. f enterio c viru s froi s m perso o persont n . Con- Appl. Microbiol. , 212-22230 . sequently a further improvement of drinking wate Gerbd ran . aSmit . M (1982C P . E h ) Developmena f o t may fro a mvirologica o ls poine b f vie o t t wno method for detection of human rotavirus in water and important to prevent spread of infections and disease sewage. Appl. envir. Microbiol. , 1440-145043 . as improvement of sanitary conditions in general. Srivastava R. N. and Lund E. (1980) The stability of bovine parvoviru n indicato a s possible it s th a d r e an sfo reus This question is going to be further discussed in a persistence of enteric viruses. Water Res. 14, 1017-1021. late rwhol e papeth y eb r group. Welling . M.d F Mountais an , . (1976. LewiL W . . 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