LA SANTE

UUf #t

iO;CtD HEALTI-I ORGANIS ATION MONDIALE

I K G A N I Z A T I O N

A

^DE

^{LA SANTE}

EGIONAL OFFlCE FOR

THE

&STERN MEDITERRANEAN

iGIOiWL

COP~?I'~PEE FOB TKE STERN

M E D I T r n N E I I N

BUREAU W&GIONAL

DE

L A M ~ D I T E R R A N ~ E ORIENTALE

E ~ i / R C 8 / ~ e c h . D i s c ,/6 27 August 2358

OR

IGIXAL

: ENGLISH

:ends

item 16

rC'tiNfCAf_l DISCUSSIONS

A

%ALL

PUNT FOX

SUPPLYING

RURAL COMdJUiSITIES WITH WATER FROiVI fEllZIGATION. C w

Joaquitl de kraoz, C.E.,

M.S.S.E.

T&O Public Health Engineer

Bilharziasis

Control Project Iraq 15

Generally, in countries in course of developnent rural environment i s characterised by i s o l a t e d communities s c a t t e r e d among open spaces used 'for agriculture and c a t t l e raising. The houses, b u i l t with

l o c a l materials,

are iradequato

i n

poor hygienic condition. Sanitation, with respect t o water supply, excreta and waste disposal, i s a faniily problem of

d i f f i c u l t soliltion t h a t i s usually disregarded o r neglected,

The

inhabitants l i v e ir, d i r e c t contact with domestic animals that move f r e e l y in yards and living quarters, manure i s an important a s s e t as f e r t i l i s e r and fuel. Isolation a d deficient

means

of communication make the people self-dependent as t o food and other e s s e n t i a l s .

The-

economic

level

of the peasant i s very low. Ill-health and i l l i t e r a c y are prevalent among the population, These c h a r a c t e r i s t i c s

illustrate

c l e a r l y the d i f f i c u l t i e g l iiivolved in "the impravement of s a n i t a r y conditions in rural areas.

Xith regard t~ the provision of a safe water supply f o r rural commu- n i t i e s there are r a y problems

to

overcome. I r r i g a t i o n water has

always

been the m a h source or' s u p p l y for the domestic needs of the people l i v i n g on the banks o f canals, i n many instances this i s the only source available.

-% For design, see Armex.

3Ilr/R~8/~ech .Disc ,/6 Page 2

The peasant i g n o r e s t h e iriherent dangers from polluting water used f o r drinking; ^%he c a n a l water serves for all purposes, including t h e d i s p o s a l or' a 4 wastes,

and

%he most mdimentwy precautions are disregarded. The construction of sati'sfaetory i n s t a i l a t i o n s i s o f t e n t o o g r e a t a burden on the people, an& funds have to be provided from government budgets.

Operational expenses are not a l w a y s accepted as a l i a b i l i t y by the users.

Voimtary p a r t i c i p a t i o n

i n

t h ~ construction i s limited t o t h e

execution

o f rough work by m s k i l l e d labourers. E l e c t r i c i t y or o t h e r mechanical power and r e l i a b l e tecbnicians are seldom fourtd i n rural areas. Trained personnel

I

- --

. .

f o r the adequate care of +&d-'instaUations a r e n o t available and maintenance is usually neglected. The construction, supervision and a d m i n i s t r a t i o n of c o l l e c t i v e systems i s more 'ekpemive and d i f f i c u l t

i n

a r e a s o f s c a t t e r e d houses than iE urban c o d t i e $ .

In

v i e w of these problems, t h e design of an i n s t a l l a t i o n f o r the supply of potable water f o r r u r a l communities i s l i m i t e d by t h e following require- ments :

a): ^The basic design should be flexible so as to cover communities varying -&defy

i n

population by i n c r e a s i n g o r reducing the g e n e r a l dimensions.

b) The const?%ction should be simple and standardized as f a r as p o s s i b l e t o reduce t h e i n i t i a l . c o s t . Full use should be made of t h e voluntary help o f the u s e r s by simplifying methods of construction and planning work that can be c a r r i e d o u t by u n s k i l l e d workers.

c ) OperaCviorr andmaintenance ~ v r k should be minimiged. No

mechanical equipnent can be c o ~ s i d e r e d where the possibiLity of i t s proper operation and. maintenance i s u n c e r t a i n ,

The c a r e and r o u t i n e a t t a n t i o n af t h e i n s t a l l a t i o n should be s i m p l i f i e d so a s t o enable one of tkic users, with a minimum t r a i n i n g , t o undertake t h i s task without r e g u l a r supervision, which cannot always 3e a v a i l a b l e due to t h e i s a l a t i o n and bad roads i n -al arsas.

E M / R C ~ / T ~ C ~ . M S C ./6 Page 3

In

areas where underground water is unsuitable for cbmestic consumption, due either to contamination or to

excessive

salinity, the treatment ^of surface water

is

the only practical method

for

supplying %he people with

safe

water;

tK3.s being the case in most rural areas in Iraq.

T h i s r e p o r t deals with the design o f a small plant

for

treating water from irrigation canals or ot,her similar watercourses.

To

comply w i t h the above mentioned limitations,

it was

necessary

to restrict

the installation to its essential components and to mdi& t h e standard layout for t h i s

twe

of plants; the design, however,

is in

conformity ~ d t h established speci-

.c- - - A : - n r P n w - n n m nnn7mnf-i nn12 d e q i ~s l t ~ a d i n mnrp developed communities

,.A"'.. 4&"*.U A "-

.-- - ..

^{".- * ..}

-.

<...--.- ur~dt;s Z ~ t t G i - C ~LZlti;;'i;.

n ~ c t - w - . m v ~ , . \ i ? ;:3-~ p1;?~??

2. U - U V U . . * . - C - I

T .. ^,-- ...-

Thc paLy ^f c=t$~rc sf t h e d e s i p 19 t.np l ~ c ~ t , j nn of tile whole

installation

trithjn ithe wahr.cuur*st;, W U ~ - G ~ of srik;~lj; of Llc. r;la.t,.

Irr

this way raw pmierS is nu++ cj.iver.i,ed h i l t the strzan

arJ

o ~LI?z i

m.oxn+v

demanded by the

-

popuhtior, e n t e r s ^tke p l m t f o r treshefit, Ynus obviating the problens

created by ~ x c ~ ~ s water and its dispsssl. 39 space

is

occupied on t h e margins o f the c m a , md t h e filter szruct.m@

Is

isolated f r o m the direct approach of the public, The +rater flovs by gravity to the settling basin and i n t o the f i l t e r w i t h -

a

~in5m.m

loss

of l e v e l ,

Thc conventional tape af p l a n t installed at one s i d e of t h e H a t e r source r e q u i r e s an intake structure, z diversion close conduit, or open cl-tannel w i t h a cul?.rert for crossing the mad that generally runs along tkre b w k of the car,ai, to convey water to the p l a n t site, pumping equipment

is

required f o r f i l l k g t h e s e t t l i n g tank

and

filter, for cleaning purposes and for elimination of waste water; all these

works

and installations affect the i n i t i a l c o s t of tk cons-truction and demand experienced and

camful a t t a t i o n for

t h e i r proper

operation

a d maintenance.

The p h q t described in this r e p o r t c o n s i s t s of a diversion channel, a s e t t l i n g basin ^and a s b w sand f i l t e r , with the necessary piping, service tariks and :hand-pumps f a r serving t h e publlc.

~p@V28/~ech;Dikt~/6 Page 4

The diversion ci.lanne2 EUrd set- 'a&&& are formed by gradually videning the section of ths 6irrjZL-=&-%%& %&9 at the pl&t

site,

so

as to increase its final

water

carry-

^capacity

to

double.the normal.

amount

Bben

the

f i l t e r structure i s built in ed-stream, This gradual enlargement pre- vents the formation of eddies and cross-currents

i n the

canal near We filter

structure. The enbrged section of the canal at t h e plant ' s i t e is

krapezoidal, w i t h horizontaf bottom and

slop-

sides

a t an i n c l i n a t i o n

of 45 d e e e e s . A brick pavement 1&d on the b o t t ~ m and banks af the canal in the

widened section,

the

t r a n s i t i o n portions and

a t the

beginning of the

undisturbed par% of %he stream, prevents erdsion, assures the regularity of the cross-section and makes easier the removal of deposited

silt

and debris w i t h rakes and

wire

brushes. Periodic & caning, at

comreni6nt

intervals,

~ L l l

prevent

the growth

of

weeds and

aquatic'vegetat2on.

The structure that holds the fiAter i s -built

along

^the centre-line of t h e enlarged section of %he canal ahd &videti -the stream longitudinally -to two equal portions so that %he water mqy n o w

on

both sides of t h e structWe.

As t h e water carrying capadty of each of these two portions

is

equal

to that

of the canal, one of these can be shut oEf so as

to

allow t h e t o r n ' w a t e r disc-@ in the stran to flow through the

open p r t i o n on the

opposite side of the structure, Thus a settUng basin is formed

in

the closed s i d e , w h i l e the open one acts as diversion channel. The

filter structure forma

a parbitlon

wall

between the

diversion channel

and the s e t t l l n g basin.

Both portions on .the sides of the s t r u c t u r e can _operate alternatively as diversion channel and s e t t l i n g basin by changing the posiZion o f the flashboard at the datjnstmsramt and of t h e Til%ar

structure.

A baffle and screen in 2Yunt of the structure diverts the surface

water

in the c a n a l , t o t h e

diversion

^channel axid prevents t h e entrance of f l o a t i n g

m t h r

and debris

into

the settling basin. The .height of this baffle can be aausted by means of a pulley to the required water l e v e l in the canal, which may vary in accordance with the- r o t a t i o n service of

E&'RCB/~ech.Disc 4 6 Page 5

irrigation W B ~ E ~ ~ ' The

baffle

swings

round

a pivot fixed t o the f i l t e r struc-bwe so that

it

can be s e t

in

po~&t&u.n on either side a t the entrance o f the

portion of canal

functioning as

settling

basin,

The f i l t e r sttucture consists of

a hollow

concrete

box

shaped

as

a bridge p i e r

wifh

boat-like

ends.

The

lower part of t h i s

box is embedded in the so3.l o f the stream to a depth of 0.80 m, so

that

i t s foundation rests on compact and dry

naaterial

^that assures proper anchorage and s t a b i l i t y against uneven settlements.

The

tog part

of

the box extends above the maximum

water level in

t h e

canal,

^and it

i s

covered by t h i n

concrete

slabs t o prevent the entrance of dust, Insects, leaves, e t c , These slabs are removed

f o r

the periodic cleaning o f %he filter,

Two smstll valve chambers a r e built in the pointed ends of the structure by

partikion walls

.that separate

these chambers &am

the

filter, The

i n l e t valves control t h e amouat of

water

_passing from the s e t t l i n g basin into the

f i l t e r ; two valves are required

f o r

the alternate operation of either s i d e of the enlarged

section of canal.

as s e t t l i n g basin,

The

o u t l e t valves supply t h e service t a n k s with filtered water.

A t t h e end of the s e t t l i n g basin water i s

conveyed to the f a t e r

through

a

f l o a t i n g strainer connected with the intake pipe by a f l e x i b l e hose.

The

design of this device r e s u l t e d from the need of extracting a

d o r m

amount of

water

from t h e top of the s e t t l i n g

basin,

_where the water i s clearest, without being affected by the v a r i a t i o n

of water level in

t h e

canal.

The strainer is mounted on legs so that when the water depth

i n

the basin

is

0.20

rn.

the inflow t o the f i l t e r i s wtomatically stopped, thus heavily silted water f r o m t h e bottom cannot ^{enter the} sand filter.

The

water, after

passing through t h e intake device,

flows

along a metallic trough o f semicircular section on the centre-line of t h e f i l t e r a t the l e v e l of the top of the sand bed,

Water

overflowing

from this

trough i s uniforfnly d i s t r i b u t e d over the f i l t e r bed without disturbing the sand, it passes through the f i l t e r i n g material, and filtered water i s collected by an under-drain running lengthwise to t h e f i l t e r on the bottom of th.e con- crete s t r u c t u r e . From t h e under-drain, water flows t o the outlet pipes and

valves

and i s distributed t o the service tanks,

Small

concrete %arks provided wiWl adequate hand-pumps, conveniently located in'the village, serve Gfre popufa%ion with t r e a t e d water from t h e p l a n t . The nuniber and capacity of these tanks should be such t h a t

s u f f i c i e n t water within a reasonable distance i s provided f o r the domestic needs of t h e people, considering t h a t the j a t e r supply

i n

t h e canal may be temporarily interrupted, as i t happens during the closing periods of i r r i g a t i a n service,

Thc type of f i l t e r designed for this plant

-

is the slow sand f i l t e r which requires no mechanical equipment f o r

its

operation and cleaning.

The mai;ntenance work i s reduced to periodic scraping6 of the surface of the sand bed, where dirt accurmrlates and obstructs the passage of water through the f i l t e r , and the r e p l a c e w n t of the t o p layers of t h e bed w i t h clean sand,

The g r e a t e s t advantage of the slow sand f i l t e r i s its high efficiency in the removal of bacteria. Although t h e spaces between sand grains are W g e when compared ~ 5 t h t h e s i z e of bacteria, about 99% of bhese micro- organisms are held in t h e , w p e r f i c i a l layers o f the f i l t e r , This is due

t o

the formation of a gelatinous and adhesive film of k c t e r i a l origin t h a t coats each sand grain and develops into a carpet-like mass on the top of t h e f i l t e r which holds back b a c t e r i a and o t h e r micro-organisms present in the water.

The specified load f o r

slow

s a d f i l t e r s

varies

between 2 and 20 m i l l i o n g a l l o n s of water p e r day per acre of filter surface, according to the

t u r b i d i t y of the inflow water, Considering an average load f o r the filter of this p l a n t of 5.55 mgd per acre (5 r00 cu,m. per day per sq.m, of filter bed), ons square metre of sand

area

w i l l f i l t e r 5000 litres per day; if the f i l t e r bed i s 1.00 m wide, 50 persons

can

be supplied with a water datation of 100 litres per head per day f o r each metre length of the filter

area. Thus a v i l l a g e of 200 inhabitants w i l l require a filter 4.00 m.

long, and a v w e of double the populat3.on mqufres t w l c e this filter length,

@ ~ ~ ~ 8 / ~ e c h . ~ i s c ./6 Page 7-

The length of the s e t t l i n g basin increases sirmiltaneousl;y with the

. ..

-

enlargement o f the filter structwe, cunsequently the basin's capacity i s

increased

proportionately. The same basic design

of

the p l a n t can be adapted t o a wide variation

i n

population served by increasing tho length of the f i l t e r at the rate of 1.00

rn.

f o r each 50

inhabitants.

f * ,-,-

d l 6cs.cloped w a l areas -with a higher standard of living, where mechanical equipment

can

be properly operated and maintained, the treated water from the p h t m y be di-scharged i n t o

an

underground

reservoir,

pwrped

to an elevated tank

and

d i s t r i b u t e d

to

t h e population through pressure pipes that supply public fountains and s e r v i c e c omections t o the houses, A chlorination device f o r final d i s i n f e c t i o n of t h e treated water can be connected with tkre discharge pipe of t h e plant or the suction pipe ^of the

Pump*

General data of the performance of a p l a n t f o r 200 inhabitants (20,000 l i t r e s per day)

are

summarfsed as follows:

S e t t l i n g basin

Detention period, tfme taken ^by a drop

o f water to _{f l o w} through t h e basin 12 hours Load, work- capacity

of basin

per

nit surface area

--- -

1.30 ^{1.03 mgd per} cu.m,/day/sq.m, ^acre H o r i z ~ : i k l -.-cloci tg o f

water

flowing

through basin

---

60 em, per how

= 1.97 ft. per hour Vertical s e t t l i n g velocity of particles

--

^{4.6 cm. per hour}

0.15

ft.

per hour

At

this settling v e l o c i t y 75% of t h e

p a r t i c l e s 0.005 mm in

diametre w u i

settle on the bottom of the basin.

Slow sand f i l t e r

Filtering period, time taken by a 6,-op of water to pass through the

fLlter

bed

...

^{4.8 h o ~ s}

Load, working capacity of filter p e r

unit surface area

---

^5.00 cu.m./day/sq.m.

= 5.35 mgd per acre Vertical v e l o c i t y of water through

f i l t e r bed ----c--rr--r--r--- 22

m e

per hour

= 0.69

ft.

per hour

@ 4 ~ ~ ~ 8 / 2 l e c h . ~ f sc ,/6 Page 8

General Dinensions

S e t t l i n g basin,- Length

- ^- - - - - - - - -

^{a 6.00 n,}

Depth

-

r u l e d by

dimensions of canal = Depth of canal

Width

- ^"

^{f 1 fl = ;3f5 of width of canal}