is made to take water coming fromthe spout of a tube well. Waterentering the PVC pipe flows hori-zontally over the charcoal chips tillit drips through the perforated bot-

Design and performance of a community-level iron removal plantby Cecil ChibiA simple iron removal plant can make watertaste, smell and look better. This system willsatisfy local desires for clean and safe water.

Downpipe

2-3cmCharcoal chips

Granite chips

-Overflow

( I

Handpump spout~

lr--~8

A completed iron removal unit in ahomestead yard.

tom end of the pipe into anotherchannel, which is half-filled withgranite chips. The water is suffi-

'-"- '-- '-""-Clear water 1--

~ ~ ---..----...

Precipitationchamber

----------------• • ••.• • •. <I.. ., , •.• • ••. •. ••••

••~.::.:( o.8-2mm·gra~el . f:>-::. .~.:.- ': -:. .-..: -.:- •. ~:' .....••. :. (-------------0000 C>C>C>~C 00--- D

c::> c:::1 5-8mm gravel I Q

c> 0 c::. '-" <:::) 0 1..10<;;;) -=><:::.- - _ - C2.. __

OCo ~~O c:>0 00 00000COOl roo00 c: 2-4mm gravel C) C)

000 0 ClOO~ Q<JOO

200/drum

\

Figure 1. Section through the iron removal plant.

to strain the unsettled iron preCIpI-tates. Although the water qualityfrom the system was very good«lmgll), the system was consid-ered too bulky and therefore unsat-isfactory. After further investiga-tions, the compact system shown inFigure I was designed and con-structed, featuring a 200-litre drumand pieces of guttering as the maincomponents.

The aeration channel is made ofa IOOcm-long, IOcm-diameter poly-vinyl chloride (PVC) pipe, which iscapped at the two ends but has aninlet opening near the right end andan outlet opening near the left endof the pipe. About half the depthof the pipe is filled with 2 to 3cmcharcoal chips. The inlet of the pipe

IRON IS FOUND in groundwaterthroughout the Lowveld region andin the semi-arid areas of the north-ern Transvaal. Many of the ruralareas are served by handpumpswhich yield water with iron concen-trations well in excess of the WorldHealth Organisation (WHO) upperlimit of I.Omg/l. Concentrationsexceeding 20mg/1 are noted fre-quently, and result in taste, odour,and colour problems. Upon contactwith oxygen in the air, soluble ironcompounds in the ferrous forrn areoxidized into insoluble ferric com-pounds, which are responsible forthe colour problem. Unpleasanttaste and odours arise from thedecay of some organisms (iron bac-teria) present in iron-rich water.Because of these aesthetic consid-erations, rural people generally re-fuse to use tube-well water in ironproblem-areas, and they are moreinclined to use unprotected surfacewater sources.

In an inforrnal survey around theMajaneng area near Hammanskraalit was found that people would bewilling to pay a reasonable amountof money if a low-cost iron removalunit were to be developed. Thus aprimary consideration in the designand development of the plant wasto ensure the use of readily obtain-able materials so that with a littletechnical guidance any householdwould be able to construct their owntreatment unit.

Cecil Chibi is an Environmental Engineerand a Project Leader for the Division ofWater Technology, CSIR. PO Box 395.Preloria 0001, South Africa.

Plant designThe first system tested comprisedfour different chambers. The firstwas an aeration stage in which waterwas sprayed over charcoal, and thesecond was when the precipitatediron was allowed to settle. Stagesthree and four were merely wheretwo different-sized media were used

WATERLINES VOL. 10 NO.2 OCTOBER 199\ 9

Perforation

I-t!\,,

Table 2: Turbidity of raw andtreated water

somewhat unpopular. It wasstrongly suggested that a unitwhich would treat the waterdirect from the spout would beeven more welcome. The com-munity would be keen to contrib-ute towards such a system shouldthe need arise.Taking into account user's views,

a new prototype has been devel-oped. It works on the principles ofaeration and uses South Africantubewells, which usually have aspout height of only about half ametre, and therefore could not beconnected to the initial iron-re-moval unit. Tn the new unit the airis introduced into the water thoughthe sucking action of a venturivalve, which eliminated much of theloss in head experienced initially.The water then goes through asedimentation chamber, overflowsinto the filtration chambers, andfinally goes out through anotherspout and into a receiving con-tainer. The unit has not yet beenfieldtested.

Day Raw (mg/~ Treated (mg/~ Day Raw (mg/~ Treated (mg/~

1 9.50 2.25 1 95 382 10.30 2.50 2 63 303 10.50 2.25 3 73 704 10.00 5.25 4 64 475 11.50 2.30 5 105 246 0.46 0.12 6 65 237 14.25 0.76 7 84 148 8.75 0.41 8 56 79 10.25 0.40 9 73 7

10 13.00 0.18 10 79 511 36.25 0.39 11 117 912 14.75 0.20 12 78 813 19.75 0.24 13 87 7

000::> :":;"00 ( 0 ~

oo~ ( ') ,..:'.:,:,..000 .

l>ot~ •• • '.o 0 0 .'.:= '.. :OO()06 ') ':: .:::; Q00001 •••• ' ,'. IOODe .... :; ..•cf?00' .,,'.,..,e:pCOOj :':.::'.

j flY o#ltg~:':r~ BucketHandpump Sedimentation Gravel Sand B~wash

chamber valveFigure 2. The new prototype iron-removal plant.

Table 1: Iron content of raw andtreated water

to go on to build more for them-selves.

The unit was set up next to acommunity handpump. As a pre-caution against vandalism, the com-munity proposed that the unit beinstalled in the yard of a house-holder next to the tube-well.

Turbidity and total iron contentwas monitored fortnightly for abouttwo months, and thereaftermonthly. Over the six months theplant was monitored, and the ironand turbidity removal efficiencieswere in excess of 90 per cent.

The following views emergedwhen individuals were interviewedabout the iron removal unit:a Where previously the raw, rusty

water from the tube-well wouldstain their china and discolourtheir porridge and laundry, thetreated water from the iron re-moval unit was much better.

a The fact, however, that a userhad to carry a 251 container fromthe tube-well to the drum filter(a distance of about 10m) proved

ciently aerated because of the in-creased contact with air.

The aerated water then dripsthrough the downpipe into the sedi-mentation chamber, which has aminimum retention time of fiveminutes. At this stage a portion ofthe precipitated iron particles settleat the bottom of the chamber.Because of pressure differenceswithin the downpipe, the water thenflows upwards through three differ-

Using the iron removal plant: notetuhewell hehind to the right.

ent layers of successively smallergradings of gravel and sand.

The treated water is then col-lected through a tap. The filter iscleaned by opening a valve at thebottom of the drum, so that waterflows quickly down through thesand, flushing out the accumulateddeposits.

Tables I and 2 show the perform-ance of the plant in removing ironas well as turbidity. They showresults from start-up until the unitreached steady-state after about 13days of operation.

The maximum hydraulic loadingrate attained was about IOI/min,after which fluidization occurred.This implies a surface loading ofabout 3m3/m2fhr.

ImplementationAt a community meeting held inMay 1989 at Majeneng it wasresolved that a unit should beinstalled in one of the homes in thecommunity for evaluation. If itproved satisfactory, then a secondone would be installed at anotherwell-stand where interested peoplefrom the neighbourhood could helpbuild it and would thus learn enough

10 WATERLINES VOL. 10 NO.2 OCTOBER 1991