KARACHI WATER SUPPLY AND THE ROLE OF ... WATER SUPPLY AND THE ROLE OF NUCLEAR DESALINATION IN MEETING FUTURE REQUIREMENTS ISMAT KAMAL Pakistan Atomic Energy Commission, Karachi, Pakistan

KARACHI WATER SUPPLY AND THE ROLEOF NUCLEAR DESALINATION IN MEETINGFUTURE REQUIREMENTSISMAT KAMALPakistan Atomic Energy Commission,Karachi, Pakistan

AbstractKARACHI WATER SUPPLY AND THE ROLE OF NUCLEAR

DESALINATION IN MEETING FUTURE REQUIREMENTS. Thepeculiar situation arising out of the extraordinarygrowth of population in Karachi is discussed withreference to the provision of basic amenities suchas water supply. The historical growth of populationand water supply is traced upto the present time.Alternative natural sources of fresh water in theKarachi area are assessed and shown to be inadequateto keep up with the growing water demand. Forecastsof population and water demand upto the year 1985 aremade and the water availability is shown to fallshort of the demand by 100 to 200 Eillion gallonsper day (mgd) during the 1980's. Reference is nadeto the studies being made by the Pakistan AtomicEnergy Commission (PAEC) on the feasibility of adual-purpose nuclear plant to come into operationround about 1980, in order to meet the power andwater requirements of the Karachi Area. The costeconomics of 4-00 MWe/100 Mgd dual-purpose plantsbased on imported oil, gas and nuclear fuel areworked out and show that nuclear desalination willbe the most economical means of converting sea waterfor large scale use in the Greater Karachi Area.

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1. INTRODUCTION

The phenomenon of rapid urbanization, aprominent feature of all developing economies,creates a number of problems in its wake. Carefulplanning and forethought are essential in orderto prevent baffling situations arising with thegrowth of cities. Provision of an adequate, regularsupply of hygienic water and efficient sewerage anddrainage systems are of basic importance, and aregiven top-priority by all metropolitan developmentauthorities and town planners.

Large-scale nuclear desalination, which maysoon become a reality, appears to be a promisingmeans of removing man's dependence on natural waterresources for choosing the locations of, andexpanding, his urban settlements. In West Pakistan,the bulk of- the population has remained confined tothe Indus River basin owing to the overwhelmingdependence on irrigation through dams on the Indusand its tributaries. Except for the port ofKarachi, West Pakistan's long coast-line hasremained undeveloped owing to the lack of freshwater supplies. Karachi itself, which is thelargest metropolitan area in Pakistan with apopulation of over three million, has been facinga growing water problem, with the result thatsupplies to industrial and domestic consumers havehad to be restricted. It is in this context thab

50

the Pakistan Atomic Energy Commission (PAiiC) hasbeen examining the feasibility of nuclear desali-nation as an alternative means of water supply tothe Makran Coast in general and to the Karachi areain particular. In this Paper, the Karachi daterSupply System is reviewed and the prospects ofnuclear desalination as a means of meeting futurerequirements are discussed.

2. KARACHI AND ITS GROWTH

The district of Karachi is situated at theextreme western end of the Indus delta at longitude67° east and latitude 25° north on the Arabian Seacoast ,and comprises the city of Karachi, 95 villagesand 5 islands. The city of Karachi is surrounded b;>the Arabian Sea and the desert of Sind. The nearestperennial river, the Indus, is 100 miles from KarachiThe average annual rainfall at Karachi is a meagre 7"to 8", and periods of drought may sometimes last for3 or 4- years at a stretch.

Karachi has a natural sea harbour and formedthe natural outlet for the agricultural products ofWest Pakistan between the two World Wars. Before194-7» "the city used to be a small provincial head-quarter with a population of about 500,000 people.On the emergence of Pakistan, Karachi was chosen asthe national capital and soon grew to be the largestand busiest metropolitan area of the country. Anumber of housing plans were initiated and the city

51

started bulging out eastward and northward. Thepopulation grew rapidly owing to natural increaseand migration from across the borders with Indiacoupled with migration of people from rural areasof Pakistan in search of employment and betterliving conditions. According to the 1961 Census, tliodistrict of Karachi had an area of 1,357 squaremiles with a population of 2.044- million/ 1 /. By1970 the population had increased to more thanthree million.

The city of Karachi has been experiencing amuch faster growth of population than any urbancentre of West Pakistan inspite of the shifting ofthe national capital to Islamabad. The reason forthe growth of Karachi is the fact that it is the onljsea port in West Pakistan and possesses the basicinfra-strucuture for the establishment of newindustries and commercial organisations.

The growth of industrial and commercialactivity in Karachi has been phenomenal, as seenfrom the fact that fro.m a meagre 46 number ofindustrial/commercial units in 1946, it increased.to 6,500 units by 1969 in addition to numerous smc~IIindustrial and commercial establishments. 200additional units already sanctioned are yet to beestablished in Karachi, besides the proposed ma¿orindustrial projects, namely, the steel mill andpetro-chemical complex. For the future, the total

52

industrial acreage planned so far i.e. 15»500 acresand available for development has been projectedfor the years 1970, 1975 and 1985 as 7,300 acres,10,000 acros and 15,500 acres respectively/TT.

The boundaries of Karachi have been extendingtowards Pipri and Gharo in the east and towards theHub River in the west. However, according to thepresent thinking of the Master Plan Department ofthe Karachi Development Authority (KDA), the citycannot develop continuously because of physicallimitations due to the hills on the northern sideand planned agricultural development under Hub DSJIIProject and the proposed Dhabeji lift irrigationscheme. A number of industrial township schemesare being planned by the Master Plan Department toabsorb the overflow of population from Karachi andWest Pakistan. However, these satellite townshipswould form part of the integrated Greater KarachiMetropolitan area in as far as the supply of waterand power are concerned.

Owing to the high rate of urbanization indeveloping countries and the fact that at presentmore than 90% of the 120 million people in Pakistanlive in the rural areas, it is expected that theGreater Karachi Metropolitan area would continue toper annumgrow at the rate of 6% vhich has prevailed since1953. At this growth rate the population of Karachiwill reach 6 million by 1980, exceed 10 million by1990 and approach 20 million by the year 20QO/ 3 A

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3. HISTORICAL GROWTH OF WATER SUPPLY

3.1 Old SchemesEarly settlers of Karachi obtained their

water supply from wells along the course of LyariRiver and in relation to this ground water named theareas as Kharadar or Mithadar meaning "BrackishWater Wells" and "Sweet Water Wells" respectively/47,.During the 1880's ground water was discovered inthe Malir River alluvium at Dumlotee and since thenwater has been obtained from shallow wells upto 30'deep and supplied to the city through a 20 mileslong conduit. This source ivas taxed very heavilyresulting in a gradual drop in the water table. Asthe old wells dried up and their yield declinedmore and more new wells were dug. By 1935» theDumlotee wells wore supplying about 8 milliongallons per day», >,•) for a population of about300,000/ 4- /. It was soon apparent, however, thatthis source was not very reliable, as it depended onrainfall. Therefore, the Haleji scheme was launchedon an emergency basis in 194-2 to bring an additional10 million gallons per day (mgd) indirectly from th¿River Indus. Through this scheme, which startedsupplying water in 1944, water from the River Induswas stored in an aritificial lake situated at Haleji,at a distance of 56 miles from Karachi, during theflood season via Kalri inundation canal. The waterwas drawn off under the effect of gravity through amasonry conduit of 20 mgd capacity over a distance of

54

about 14- miles to a diesel pumping station from whoreit was pumped through a cast iron rising mains,three miles in length, to a rapid sand filtrationplant located at an elevation of about 150 ft.abovesea level. The flow from this plant was maintainedby gravity through a 20 mgd non-pressure hume pipoconduit to Karachi where water was again pumped toa 150 ft. high service reservoir before itsdistribution/"4 /.

Before Independence in 194-7, the average dailywater supply to Karachi was 13.3 mgd for a populationof about 500,000 - 3 to 8 mgd from the Dumloteewells and 10 mgd from Haleji reservoir. The rapidgrowth of population following Independence placeda great strain on the water supply and in 1951 ascheme was launched to utilise the Haleji sourceto its designed capacity of 20 mgd by the duplicationof the pumping and purification facilities. Thescheme was completed in 1953 and assured a firmsupply of 20 mgd from the Haleji source.

3.2 Greater Karachi BulkWater Supply SchemeOwing to its dependence on rainfall, water

supply from the Dumlotee wells was highly fluctuatingand the Haleji source was running into trouble owingto infestation of the lake with weeds. At the sametime, the population of Karachi was fast inoraaqingat a compund rate of 6% per annum. Realizing theacute water shortage and visualising the future

55

development of Karachi, the then Karachi Joint WaterBoard and the Central Government of Pakistan, inconsultation with foreign experts, drew up anambitious scheme in 1953 known as "The GreaterKarachi Bulk Mater Supply Scheme" (GKBWSS) and itsancillary projects, the Greater Karachi Water TrunkMains Scheme and Sewage Disposal Scheme/ 5 /. Thescheme was designed for an ultimate capacity of280 mgd from the Hiver Indus via Kalri Lake, in fourphases of 70 mgd each, for an expected population of3 million in the year 2000. It is interesting tonote that the population figure of 3 million hadalready been reached by 1968!

The scheme was launched in 195 and the FirstPhase completed in early 1962/~2r /* Water from theKalri Lake is carried over a distance of 60 miles invarious types of strucutures. It flows by gravityin an open canal and conduit for about 20 miles uptoa Pumping Station, Here it is pumped to a level of120 ft through a rising main and is carried throughconduits and tunnel to a filtration plant on theoutskirts of the city.

While executing Phase I, certain works whichcould not be economically duplicated at a later date,were designed and constructed for the ultimatecapacity of 280 mgd. It was decided that the watersupply to Karachi would be increased, as and whenthe need arose, by adding syphons, pumping stations.

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rising mains, water purification plants, etc., instages of 70 mgd each, until the four phases arecompleted.

With the completion of the First Phase inApril, 1962, the supply from Haleji Lake- was stopped(except as reserve supply). Since 1964, 20 mgd have-been diverted to the Halej'i conduit from the BulkWater Supply Canal.

By the time 70 mgd of water from the tfirstPhase had been added to the existing supply of about30 mgd, water demand had already been created forthe entire additional 70 mgd quantity, due to theaccelerated growth of industrial and commercialenterprises and increase in population. By the year1968 the overall demand of water had increased to120 mgd owing to further extension of townshipschemes and industries while the supply was only85 mgd, as only 1 or 2 mgd was available from theDumlotee wells, and KDA had accordingly decided notto bank upon these wells any more to supplement thewater supply to Karachi/ 2 A

In view of this situation, Phase II of theGKBWSS was launched by the KDA in 1968 to bring inan additional 70 mgd of water to Karachi. Thescheme is now in final stages of completion.According to the KDA estimates, a total of 14-8 mgdwill now be available for water supply to Karachiafter allowing for losses etc.

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KDA is now drawing up a proposal for the ThirdPhase of the GKBWSS which would bring the totalsupply to 213 mgd by 1976. The proposal for theThird Phase also includes certain balancing andimprovement works in order to improve the overallsupply and distribution system.

4. WATER RESOURCES IN THE REGION

A preliminary assessment of the conventionalwater resources in the Karachi area has been madeby the PAEC/ 6 /and is summarised below:-

4.1 Ground V/aterIn the Karachi region the possibility of

obtaining an appreciable quantity of ground waterand its re-charge is remote because of low annualrainfall, location at the edge of a desert, absenceof perennial streams or rivers, excessive surfaceevaporation (about 66" per year) and unfavourablegeological formations which are mostly clayey, siltyand calcareous. Some ground water is found in low-lying areas around Karachi but it is highly brackish,The possibilities of finding sweet water in deepformations under artesian conditions have beenexplored upto a depth of 1500' but only brackishwater was struck. The only large deposits of sweet-ground water are in the Malir alluvium stretchingto a width of 2 miles and depth of 100 ft. There-charge of ground water acquifier depends verymuch on the monsoon rains. The ground water is

58

restricted to geological recent alluvial depositresting on an impervious stratum. A maximum of10 to 12 rngd has been drawn in the past from wellsat Dumlotee on the Llalir bank in addition to otherdiesel-operated wells which pump water for localirrigation.

4.2 Surface WaterTwo rivers, the Lyari and Malir pass

through Karachi but these are non-perennial andremain dry for the greater part of the year. TheRiver Hub situated about 1J miles to the west ofthe city is not strictly perennial, and often becomesdry in June in the lower reaches/ 7 /• The nearestperennial river is the Indus which is about 100miles from Karachi.

The water needs of Karachi so far have been•mostly met by taking Indus water indirectly fromthe Haleji and Kalri lakes in the Thatta district.Haleji is situated nearly 56 miles from Karachi. Ithas a surface area of 6.25 square miles and acapacity of about 13,000 million gallons. The lakeis now fed by water from the Indus River through asub-branch of the Jam Canal. In recent years thelake has been seriously affected by weeds and isnot being used for water supply except as areserve.

Kalri Lake is a large storage reservoir witha service area of about 51 square miles and is

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situated about 70 miles from Karachi. The lake wasconceived as an integral part of the Ghulam MohamiaadBarrage system and is filled during the summer bymeans of a main canal from the Barrage.

The River Hub is a shallow stream of the aridcoastal basin mainly fed by monsoon water. A danis being constructed on the Hub River about $5 milesnorth of Karachi under the Karachi IrrigationProject. Basically, t h i . s p r o j e c tis néant to supply about 250 mgd water to abou^85>000 crop acres per year to produce vegetables,fruits and fodder to support cattle and poultryfarming in the Karachi area. However, there is aproposal to use the scheme to augment the city watersupply by about 20 ngd. It is now expected that thescheme may be completed by 1974- at a cost ofRs. 190 million.

5. FUTURE WATER REQUIREMENTS & AVAILABILITY5 . 1 Forecast of Population

Ov/ing to the factors mentioned inSection 2, the population of Karachi has risensharply during the past few decades as shown by thefollowing census figures :- Annual Growth

Year Population Rate (%)4-35,887

1951 1,14-7,222 121961 2,048,668 6

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The phenomenal growth recorded in the 1951Census was largely due to the influx of refugeesfrom India. Although increase by migration fromacross the borders has been reduced to negligibleproportions, the population growth is expected tocontinue at a rate of 6 per cent per annum for thenext several years (3.2 per cent by internal migra-tion and 2.8 per cent by natural increase)/ 8 /»Thus the Master Plan Department of the KDA estimateda population of 3 million in 1968/2 /. A growthrate of 6 per cent is also indicated by the trendsand projections of urban population increase indeveloping countries/ 3 /. On this basis, the popu-lation of Karachi upto the year 1985 has beenprojected in Table I.

5-2 Forecast of Water DemandWith the completion of the Second Phase

of the Bulk Water Supply Scheme, Karachi will receivean average of 148 mgd for its estimated population of3.6 million. This would reflect a per capita usageof 41 gallons per day (gpd), including industrialuse, KDA have predicted the per capita water denandas 50 gpd in 1975 rising to 60 gpd in 1985. Thefuture water requirements of Karachi have beenworked out on these bases and are shown in Table I.

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TABLE IYear

1970197519801985

Population(Millions;

3.44.56.08.0

Per Capita Total 'waterWater Demand DemandCgpd; (mgdj

40 13650 22555 33060 480

5•3 Water AvailabilityAccording to the KDA, the total net water

.supply (ex-Purification Works) to Karachi aftercompletion of the Third Phase would be 213 mgd.This phase is scheduled for completion in 1976»Assuming that Indus River water would be availablefor the Fourth Phase, it may be completed by 1980,raising the supply to 280 mgd. It is highlyunlikely that any further quantity of Indus waterwould be available for supply to Karachi, owing tocommitments for irrigational use. Diversior ofwater from the Karachi Irrigation Project (Hub Dam)may ease the situation for a short period, but acutewater shortages can be anticipated for the yearsfollowing 1980, unless alternative sources arefound.

6. COST ECONOMICS OF DUAL-PURPOSE POWER-GUM-DESALINATION PLANTS AT KARACHI

It is expected that by 1980 there would be ajustification for a 400 Mwe power plant in theKarachi area/ 6 /. The electricity can be suppliedthrough a dual-purpose plant producing, in addition,

62

100 ingd of desalted water. The cost economics ofsuch a plant baseâ en nuclear fuel, inported oiland natural gas (the alternatives worth consideringin the Karachi area)/T9 /, are worked out in thepresent Section.

6.1 Description of the PlantsIn the dual-purpose station steam supply

from a nuclear reactor or a conventional boiler isexpanded through a back pressure turbine for gener-ating electricity and the exhaust is supplied to amulti-stage flash desalination plant. The steamsupply system and the turbo-generator plant arereferred to as the Power Plant while the brine heaterand multi-stage flash units are referred to asWater Desalinator (MSF Plant).

6.1.1 Steam Supply SystemOnly two reactor concepts, the pressurized

light water reactor (PwR) and the Picker ing-Brucetype heavy water reactor (H R") have been considered.The conventional (oil- and gas-fired) plants usedfor comparison are based on high efficiency, hightemperature cycles with vapour re-heat. The charac-teristics of the plants were selected from publisheddata/9,10/*

6.1.2 Turbine GeneratorThe steam from the reactor/boiler is

expanded in a back-pressure turbine to a pressureconsistent with the maximum desired brine temperature,

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For all the cases considered, the steam temperaturein the heat input section (brine heater) is assumedto be 5°F above the top brine temperature and thepressure drop in the steam line (between the turbineexhaust and the heat input section) is assumedequivalent to 15°F/3L7. Therefore, the pressureat the turbine exhaust has been taken as being equalto the pressure corresponding to a saturation tem-perature 20 F higher than the selected top brinetemperature. In view of the higher efficiency ofthe conventional cycle, the saturation temperatureof the steam exhausted from the back-pressure turbinehas been taken as 2?0 F in the case of the conven-tional plant and 210°F in the case of the nuclear(F«i/R and Ew7R) plants. The higher temperature in thecase of the. conventional plant permits a lower per-formance ratio* (and hence lower capital cost) ofthe MSP evaporator than would be possible with anexhaust temperature of 210°F. The two exhausttemperatures correspond to top brine temperatures of250°F and 190°F respectively. In general, an optimumtop brine temperature and performance ratio can beprecisely determined for a given water output. This,however, has not been attempted in the presentstudy.

^Defined as the quantity of water produced, in Ib,per 1000 Btu of heat input to the brine heater,64

6.1.3 Brine Heater and MultistageFlash Distillation Plant

The steam exhausted from the turbine iscondensed in the brine heater and the temperatureof the brine is thus raised to the required tempér-ature before distillation. The Ï.ÏSF distillationprocess has "been selected for the present study.In this process, the heated sea water is passedthrough a series of closed chambers which aremaintained at a progressively lower pressure thanthe vapour pressure of the heated sea water. As aresult, a portion of the sea water flashes intovapour, v/hich in turn is condensed on tubes contain-ing the inconing brine. Re-circulation of the brineis employed to reduce blow-down, make-up flows andsea water pre-treatment costs.

The performance ratio, defined in the previousSection, expresses the efficiency of the MSF plantand determines the capital cost of the plant. Inpractice, fche performance ratio generally varies inthe range of 4 to 18. Apart from economical consi-derations, the upper limit is set by the availableflash range and hence the maximum possible top brinetemperature, which is restricted to 2 0°F withcurrent methods of scale-control, vïith the brineconcentrations (two times the normal sea waterconcentration) presently employed in the re-circulation MSP process, calcium sulphate scalingwould set in at higher temperature.

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Although several MSF plants are in operationaround the world, unit sizes are generally restrictedto 1-2 ngd. The largest units, with outputs of5 mgd, are being installed in Kuwait bya French fina. For large-seele waterproduction, several MSF units can be installed inparallel. According to studies made by the UnitedKingdom Atomic Energy Authority (UKAEA), the costadvantage in going to unit sizes bigger than 10 mgdis negligible, and this is the maximum unit sizeconsidered in the present study.

6•2 Steam CyclesHeat balances for the conventional and

PwR cycles have been made on the basis of an IAEAreport/ 9V and for the HV/R cycles on the basis ofa paper by K.L. Williams/ 10^/« Auxiliary powerrequirements for the power and water plants havebeen evaluated from published data/9 , 11y. Pumpingpower requirements for the MSF plant have beencalculated from graphs given in Reference/ 9 7. Thedesign data obtained is summarised in Table II»

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TABLE IICHARACTERISTICS OF 400 ivUeCNS

DUAL-PÜRPOSE PLAN

Thermal Capacity, MvY(th)Gross ElectricalCapacity, MV7eMSP Plant PerformanceRatio (Ib water/1000 Btu)Top Brine TemperaturePower Plant Auxiliaries, MY/ eMSP Plant Auxiliaries, Ivlvj'e

Pw'R2100

4758

190°F3441

.T) ANDÏS

ffvffi2600

4876

190°F4740

100 I5GD

Conven-tional*

1620

466

11

3036

* Oil or Gas-Fired

6.3 Cost EvaluationA dual-purpose plant carries with it the

advantage of joint management. If the credit forelectric power is deducted from the- total annualcosts, only the remaining cost will be charged towater production. Therefore, the following costsmust be determined in making a cost evaluation ofa dual-purpose plant:-

a: capital investment,b: annual cost for the whole plant, andc: electricity credit and water cost.

6.3.1 Capital Investment(a) Power Plant; The assumed cost

for the PWR and conventional plants are based on datagiven by Lane/ 12 / on the basis of mid-1970 prices.Assumed cost for the HvVR are based on a paper byGrey and Moon/ 137 for the Bruce reactor updated

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by a aonp-crand escalation factor of 9% per annum asindicated in the case of the R7R plants/12,1V. Thetotal capital costs have been increased by 25% toallow for duties and taxes in Pakistan. Capitalcosts for the power production component of the dual-purpose plant have been evaluated by converting thothermal output to net Mw"e• equivalent size, and bymaking deductions to allow for the smaller turbinegenerator and the absence of a condenser and therelatively expensive low pressure section of theturbine. It has been assumed that the cost of thoturbine-generator varios as the 0.8 exponent of theMWe size/1^ /, and that a back-pressure turbinecosts 10 per cent less than a condensing turbineof the same electrical output/ 16 /.

(b) water Desalinator(I/'SF Plant) :Capital costs of the desalination plant are basedon information provided by the UEAZA/ 1?__/« Ithas been assumed that the unit cost of an LiSF plant-varies as the 0.7 exponent of the performanceratio / 10 / The capital costs have been increased by25% to allow for duties and taxes in Pakistan.

6.3*2 Annual Costs

The annual cost is the sum of the fixedcharges (proportional to the capital investment),operation and maintenance costs, insurance and fuelcosts.

(a) Capital Charges: Annual fixedcharges have been calculated on the basis of 30years plant life,--- an interest rate of 6 per cent

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and interim replacement costs of 0.35 per cent perannum. As in the case of the power productionplant, the plant life for the LISF plant has beentaken as 30 years. It has been assumed thatcondenser tube-bundles will have to be replacedafter 15 years of operation, and this has beenaccounted for in the operation and maintenancecosts for the evaporator plant.

(b) Operation & kaintenance Costs:Operation and maintenance costs for the power planthave been calculated on the basis of publisheddata/12,18/ and for the MSF plant on the basis ofinformation provided by the UKaEk/""17 /.

(°) Fuel Costs: Fuel costs for thePVVR and HWR plants have been calculated on the basisof published data/12.18'/. Costs from the nuclearplants are worked out on the basis of no taxes orduties on fuel, as well as under the assumption of50% taxes and duties on fuel. Costs from the oiland gas fired plants have been calculated with andwithout the prevailing taxes and duties on thesefuels in the Karachi area. In one additionalexcercise, the costs without duties, taxes or dis-tributor's margin on oil prices have been evaluatedfor the oil-fired plant. The conventional fuelprices are given in the following Table :-

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TABLE- IIICONVENTIONAL FUEL PRICES

Oil Gas(1) With duties Rs.213.22 per ton Rs.1.65 per 1000and taxes (108 cents per cft(35.6 cents

prevailing m Btu) . per m Btu) .in WestPakistan

(2) Without duties Rs.?5 90 per ton Rs.1.25 per 1000or taxes (3? -4- cents • eft (2? cents

& Btu) . per m Btu) .(3) Without duties Rs.58.S per ton

taxes or dis- (29.8 centstribut or1 s per ni Btu) .margin

A boiler efficiency (heat to steara/heat infuel) of 90 per cent has been assumed. The sa¡¿eheat rate for the gas- and oil-fired plants hasbeen assumed as a simplification.

6.3.3 Water Cost

The 'power credit1 method has beenused in arriving at the cost of via ter from thedual-purpose plant. Strictly speaking, theallowable credit for electricity sales shouldbe taken as the rate at which the energy wouldbe produced in the most economical power-onlyplant having the same net electrical output asthe dual-purpose installation. However, forpurposes of simplification, a flat credit rateof 7 mills per kWh has been assumed for allcases considered. A plant factor of 80 per centhas been assumed for the power plant as well as

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TABLE LVCOMPARATIVE COST ECONOMICS OF 400 MB'e (NET)——————& -100 MGD DUAL-PURPOSE PLANT Conven-tional

I - CAPITAL COST'(Million Dollars)(i) Power Plant(ii) Evaporator(MSP Plant)

K7R

171.187.3Total }258.6

II- ANNUAL COSTS (Million Dollars)(a) With Duties & Taxes onCapital Costs and Fuel

Fixed Charges —O&M. Costs — — . — —Fuel Costs -Total Annual Costs -Power Credit —- —Net Annual Water Cost —

UNIT WATER COST,Centa per1000 gallons(b) With Duties & Taxes on

Capital Cost but no

BTO

19.703.7111.1854.5919.6014.9951.4

mitl

HWR

212.371.0283.3

HWR

21.603.394.7729.7619.60

Toil- orGas-Fired)112.6109.0221.6

Oil

16.902.9946.8066.6919.60

10.16 47.0934.8 161.0

Duties or Taxes on FuelFixed Charges — —O&M Costs — — — —Fuel Costs — — — —Total Annual Costs » —Power CreditNet Annual Water Cost —

UNIT WATER COST, Cents per1000 gallons(c) With Duties & Taxes on Ca-

pital Cost but without Taxes,Duties or Distributor'sMargin~on Pil^EricesFixed charges — —O&M Costs — — — —Fuel. Cost •— — — —Total Annual Costs - —Power Credit — — — -Net Annual Water Cost —

UNIT WATER COST, Cents per ¿iOOO gallons

16-.-902.9912.903277919.60T37T345.1

Gas

16.902.9915.4535.3419.60

54.0

19.703.717.45

30.8619.6011.26

38.6

21.603.393.18

28.1719.608.57

29.4

16.902.99

16.7036.5919.6016.99

58.1

16.902.99

11.7031.5919.6011.99

41.0

Assumptions: (i)

(u)(iii)(iv)

Fixed Charges on Capital(a) Interest Rate : 6%(b) Amortization (30 years): 1.265%(c) Interim Replacement: 0,35%

Total: 7.615%Plant Factor : 80%Mid-1970 Price Level assumed forall Capital Costs. . n. . , . m i-i T-TConventional Fuel Prices as listed in Tablelxl,

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the desalting plant. The annual water &ost isthe difference between the total annual costand the electrical power credit and, on dividingby the quantity of water produced per annum,gives the unit water cost as shown inTablelV.

7. CONCLUSIONS

Unless additional water from the River Indusis allocated to Karachi, a serious water shortage inanticipated in the region from 1980 onwards, -^s t.icsupply of additional Indus water at the cost ofirrigation requirements is highly improbable, thePakistan .atomic Energy Commission (PAïCG) is studyij r,the feasibility of nuclear desalination as analternative source of water supply. A preliminary-cost estimate indicates that, at a power credit of7 mills/kT»Vh and conditions prevailing in V/estPakistan, the cheapest water cost (35 cents per1000 gallons) will be obtained from an HWR plantproducing 400 Mvi/e power and 100 wigd water. ThePÁEC proposes to undertake more de bailed studies onconventional alternatives (with reference to theiravailability and cost economics), integration ofdesalted water supply into the existing distributionsystem, storage problems, water and power ratio,flexibility and other technical and economicalaspects of the dual-purpose plant.

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R E F E R E N C E S

/I/ Government of Pakistan, Ministry of Hone &Kashmir Affairs, Karachi District CensusReport, 1961.

/ 2 / Karachi Development Authority, P.C.I Profornafor Third Phase of Bulk Water Supply Schene,1970:

737 IAEA, Report of a Mission to Pakistan,April-May 1970.

74-7 Rizvi, KiH, , Our Water Resources, KarachiDevelopment Authority, Karachi, 1960.

75 7 Nabi Baksh, ¿i.í1. , Problems of Urbanizationin Pakistan, The National Institute of PublicAdministration, Karachi, 1967.

767 Pakistan Atomic Energy Commission, PreliminaryStudy on a Dual-Purpose Nuclear Power-cum-Desalination Plant for Karachi-Sonmiani Area,To be published, 1971,

777 West Pakistan Water & Power DevelopmentAuthority, Sediment Appraisal of West PakistanRivers, 1969.

Z_8_y Ali, M.A., Jafri, A., and Moinuddin, K»,Karachi: Population Growth and Composition,Karachi Development Authority, March, 1964.

7 9 7 lAE±i, Guide to the Costing of Water fromNuclear Desalination Plants, TRS No. 80,Vienna, 1967.

/ 10 / Williams, N.L., Some Considerations on Uti-lizing a Canadian Heavy Water Reactor in aDual-Purpose Power-Desalination Plant,Nuclear Energy for Via ter Desalination, TRSNo. 51, IAEA, Vienna, 1966.

/ 11 / Hurst D., Outlook for OaNDU Reactors -Technical and Economic Aspects, InternationalSurvey Course on Technical and EconomicAspects of Nuclear Power, IAEA-114-, Vol.1,Vienna, 1969.

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