Abundant supplies of fresh water are essential to the development of industry.Enormous quantities are required for the cooling of products and equipment, forprocess needs, for boiler feed, and for sanitary and potable water supply.THE PLANETARY WATER CYCLEIndustry is a small participant in the global water cycle .The finite amount of water onthe planet participates in a very complicated recycling scheme that provides for itsreuse. This recycling of water is termed the "Hydrologic Cycle" (see Figure 11).Evaporation under the influence of sunlight takes water from a liquid to a gaseousphase. The water may condense in clouds as the temperature drops in the upperatmosphere. Wind transports the water over great distances before releasing it insome form of precipitation. As the water condenses and falls to the ground, itabsorbs gases from the environment. This is the principal cause of acid rain andacid snow.WATER AS A SOLVENTPure water (H20) is colorless, tasteless, and odorless. It is composed of hydrogenand oxygen. Because water becomes contaminated by the substances with which itcomes into contact, it is not available for use in its pure state. To some degree,water can dissolve every naturally occurring substance on the earth. Because of thisproperty, water has been termed a "universal solvent." Although beneficial tomankind, the solvency power of water can pose a major threat to industrialequipment. Corrosion reactions cause the slow dissolution of metals by water.Deposition reactions, which produce scale on heat transfer surfaces, represent achange in the solvency power of water as its temperature is varied. The control ofcorrosion and scale is a major focus of water treatment technology.WATER IMPURITIESWater impurities include dissolved and suspended solids. Calcium bicarbonate is asoluble salt. A solution of calcium bicarbonate is clear, because the calcium andbicarbonate are present as atomic sized ions which are not large enough to reflectlight. Some soluble minerals impart a color to the solution. Soluble iron salts producepale yellow or green solutions; some copper salts form intensely blue solutions.Although colored, these solutions are clear. Suspended solids are substances thatare not completely soluble in water and are present as particles. These particlesusually impart a visible turbidity to the water. Dissolved and suspended solids arepresent in most surface waters. Seawater is very high in soluble sodium chloride;suspended sand and silt make it slightly cloudy. An extensive list of soluble andsuspended impurities found in water is given in Table 11.Table 11. Common impurities found in fresh water.

Constituent Chemical Formula Difficulties Caused Means of Treatment

Turbidity nonexpressed inanalysis as units

imparts unsightlyappearance to water;deposits in water lines,process equipment, etc.;interferes with mostprocess uses

coagulation, settling,and filtration

Hardness

calcium andmagnesium salts,expressed asCaCO3

chief source of scale inheat exchangeequipment, boilers, pipelines, etc.; forms curdswith soap, interferes with

softening;demineralization;internal boiler watertreatment; surface

CaCO3 with soap, interferes withdyeing, etc.

treatment; surfaceactive agents

Alkalinity

bicarbonate(HCO3),

carbonate (CO32),

and hydroxide(OH),expressed asCaCO3

foam and carryover ofsolids with steam;embrittlement of boilersteel; bicarbonate andcarbonate produce CO2in steam, a source ofcorrosion in condensatelines

lime and limesodasoftening; acidtreatment; hydrogenzeolite softening;demineralizationdealkalization by anionexchange

FreeMineral Acid

H2SO4 , HCI. etc.,expressed asCaCO3

corrosion neutralization withalkalies

CarbonDioxide

CO2corrosion in water lines,particularly steam andcondensate lines

aeration, deaeration,neutralization withalkalies

PH

hydrogen ionconcentrationdefined as:

pH = log1

[H+]

pH varies according toacidic or alkaline solids inwater; most naturalwaters have a pH of 6.08.0

pH can be increased byalkalies and decreasedby acids

Sulfate SO42

adds to solids content ofwater, but in itself is notusually significant,combines with calcium toform calcium sulfatescale

demineralization,reverse osmosis,electrodialysis,evaporation

Chloride Cl adds to solids contentand increases corrosivecharacter of water

demineralization,reverse osmosis,electrodialysis,evaporation

Nitrate NO3

adds to solids content,but is not usuallysignificant industrially:high concentrationscausemethemoglobinemia ininfants; useful for controlof boiler metalembrittlement

demineralization,reverse osmosis,electrodialysis,evaporation

Fluoride F

cause of mottled enamelin teeth; also used forcontrol of dental decay:not usually significantindustrially

adsorption withmagnesium hydroxide,calcium phosphate, orbone black; alumcoagulation

Sodium Na+

adds to solids content ofwater: when combinedwith OH, causescorrosion in boilers undercertain conditions

demineralization,reverse osmosis,electrodialysis,evaporation

Silica SiO2

scale in boilers andcooling water systems;insoluble turbine bladedeposits due to silicavaporization

hot and warm processremoval by magnesiumsalts; adsorption byhighly basic anionexchange resins, inconjunction withdemineralization,reverse osmosis,evaporation

discolors water on aeration; coagulation

Iron Fe2+ (ferrous)Fe3+ (ferric)

discolors water onprecipitation; source ofdeposits in water lines,boilers. etc.; interfereswith dyeing, tanning,papermaking, etc.

aeration; coagulationand filtration; limesoftening; cationexchange; contactfiltration; surface activeagents for iron retention

Manganese Mn2+ same as iron same as iron

Aluminum AI3+

usually present as aresult of floc carryoverfrom clarifier; can causedeposits in coolingsystems and contributeto complex boiler scales

improved clarifier andfilter operation

Oxygen O2

corrosion of water lines,heat exchangeequipment, boilers, returnlines, etc.

deaeration; sodiumsulfite; corrosioninhibitors

HydrogenSulfide

H2S cause of "rotten egg"odor; corrosion

aeration; chlorination;highly basic anionexchange

Ammonia NH3corrosion of copper andzinc alloys by formationof complex soluble ion

cation exchange withhydrogen zeolite;chlorination; deaeration

DissolvedSolids none

refers to total amount ofdissolved matter,determined byevaporation; highconcentrations areobjectionable because ofprocess interference and

as a cause of foaming inboilers

lime softening andcation exchange byhydrogen zeolite;demineralization,reverse osmosis,electrodialysis,

evaporation

SuspendedSolids none

refers to the measure ofundissolved matter,determinedgravimetrically; depositsin heat exchangeequipment, boilers, waterlines, etc.

subsidence; filtration,usually preceded bycoagulation and settling

Total Solids nonerefers to the sum ofdissolved and suspendedsolids, determinedgravimetrically

see "Dissolved Solids"and "Suspended Solids"

Surface WaterThe ultimate course of rain or melting snow depends on the nature of the terrainover which it flows. In areas consisting of hard packed clay, very little waterpenetrates the ground. In these cases, the water generates "runoff". The runoffcollects in streams and rivers. The rivers empty into bays and estuaries, and thewater ultimately returns to the sea, completing one major phase of the hydrologiccycle shown in Figure 11.As water runs off along the surface, it stirs up and suspends particles of sand andsoil, creating silt in the surface water. In addition, the streaming action erodes rockysurfaces, producing more sand. As the surface water cascades over rocks, it isaerated. The combination of oxygen, inorganic nutrients leached from the terrain,and sunlight supports a wide variety of life forms in the water, including algae, fungi,bacteria, small crustaceans, and fish.Often, river beds are lined with trees, and drainage areas feeding the rivers areforested. Leaves and pine needles constitute a large percentage of the biologicalcontent of the water. After it dissolves in the water, this material becomes a major

content of the water. After it dissolves in the water, this material becomes a majorcause of fouling of ion exchange resin used in water treatment.The physical and chemical characteristics of surface water contamination varyconsiderably over time. A sudden storm can cause a dramatic short term change inthe composition of a water supply. Over a longer time period, surface waterchemistry varies with the seasons. During periods of high rainfall, high runoff occurs.This can have a favorable or unfavorable impact on the characteristics of the water,depending on the geochemistry and biology of the terrain.Surface water chemistry also varies over multi year or multidecade cycles of droughtand rainfall. Extended periods of drought severely affect the availability of water forindustrial use. Where rivers discharge into the ocean, the incursion of salt water upthe river during periods of drought presents additional problems. Industrial usersmust take surface water variability into account when designing water treatmentplants and programs.Groundwater

Water that falls on porous terrains, such as sand or sandy loam, drains or percolatesinto the ground. In these cases, the water encounters a wide variety of mineralspecies arranged in complex layers, or strata. The minerals may include granite,gneiss, basalt, and shale. In some cases, there may be a layer of very permeablesand beneath impermeable clay. Water often follows a complex three dimensionalpath in the ground. The science of groundwater hydrology involves the tracking ofthese water movements.Table 12. A comparison of surface water and groundwater characteristics.

Characteristic Surface Water Ground WaterTurbidity high lowDissolved minerals lowmoderate highBiological content high lowTemporal variability very high low

In contrast to surface supplies, groundwaters are relatively free from suspendedcontaminants, because they are filtered as they move through the strata. Thefiltration also removes most of the biological contamination. Some groundwaters witha high iron content contain sulfate reducing bacteria. These are a source of foulingand corrosion in industrial water systems.Groundwater chemistry tends to be very stable over time. A groundwater maycontain an undesirable level of scale forming solids, but due to its fairly consistentchemistry it may be treated effectively.Mineral Reactions: As groundwater encounters different minerals, it dissolves themaccording to their solubility characteristics. In some cases chemical reactions occur,enhancing mineral solubility.A good example is the reaction of groundwater with limestone. Water percolatingfrom the surface contains atmospheric gases. One of these gases is carbon dioxide,which forms carbonic acid when dissolved in water. The decomposition of organicmatter beneath the surface is another source of carbon dioxide. Limestone is amixture of calcium and magnesium carbonate. The mineral, which is basic, is onlyslightly soluble in neutral water. The slightly acidic groundwater reacts with basiclimestone in a neutralization reaction that forms a salt and a water of neutralization.The salt formed by the reaction is a mixture of calcium and magnesium bicarbonate.Both bicarbonates are quite soluble. This reaction is the source of the most commondeposition and corrosion problems faced by industrial users. The calcium andmagnesium (hardness) form scale on heat transfer surfaces if the groundwater is nottreated before use in industrial cooling and boiler systems. In boiler feedwaterapplications, the thermal breakdown of the bicarbonate in the boiler leads to highlevels of carbon dioxide in condensate return systems. This can cause severe

levels of carbon dioxide in condensate return systems. This can cause severesystem corrosion.Structurally, limestone is porous. That is, it contains small holes and channels called"interstices". A large formation of limestone can hold vast quantities of groundwaterin its structure. Limestone formations that contain these large quantities of water arecalled aquifers, a term derived from Latin roots meaning water bearing.If a well is drilled into a limestone aquifer, the water can he withdrawn continuouslyfor decades and used for domestic and industrial applications. Unfortunately, thewater is very hard, due to the neutralization/dissolution reactions described above.This necessitates extensive water treatment for most uses.

CHEMICAL REACTIONSNumerous chemical tests must be conducted to ensure effective control of a watertreatment program. Most of these tests are addressed in detail in Chapters 3971.Because of their significance in many systems, three tests, pH, alkalinity, and silica,are discussed here as well.pH ControlGood pH control is essential for effective control of deposition and corrosion in manywater systems. Therefore, it is important to have a good understanding of themeaning of pH and the factors that affect it.Pure H2O exists as an equilibrium between the acid species, H+ (more correctlyexpressed as a protonated water molecule, the hydronium ion, H30+) and thehydroxyl radical, OH . In neutral water the acid concentration equals the hydroxylconcentration and at room temperature they both are present at 107 gramequivalents (or moles) per liter.The "p" function is used in chemistry to handle very small numbers. It is the negativelogarithm of the number being expressed. Water that has 107 gram equivalents perliter of hydrogen ions is said to have a pH of 7. Thus, a neutral solution exhibits a pHof 7. Table 13 lists the concentration of H+ over 14 orders of magnitude. As it varies,the concentration of OH must also vary, but in the opposite direction, such that theproduct of the two remains constant.Table 13. pH relationships.

pHaH+

ConcentrationExponential

Notation, grammoles/L

H+ Concentration,Normality

OH Concentration,

Normality

OH Concentration,Exponential

Notation, grammoles/L

pOH

0 100 1 0.00000000000001 1014 14 1 101 0.1 0.0000000000001 1013 13 2 102 0.01 0.000000000001 1012 12 3 103 0.001 0.00000000001 1011 11 4 104 0.0001 0.0000000001 1010 10 5 105 0.00001 0.000000001 109 9 6 106 0.000001 0.00000001 108 8 7 107 0.0000001 0.0000001 107 7 8 108 0.00000001 0.000001 106 6 9 109 0.000000001 0.00001 105 510 1010 0.0000000001 0.0001 104 411 1011 0.00000000001 0.001 103 312 1012 0.000000000001 0.01 102 213 1013 0.0000000000001 0.1 101 114 1014 0.00000000000001 1 100 0

apH+pOH=14. Confusion regarding pH arises from two sources:

the inverse nature of the functionthe pH meter scale

It is important to remember that as the acid concentration increases, the pH valuedecreases (see Table 14).Table 14. Comparative pH levels of common solutions.

12 OH alkalinity 500 ppm as CaCO3

11OH alkalinity 50 ppm as CaCO3

Columbus. OH, drinking water, a

10 OH alkalinity 5 ppm as CaCO3

9 strong base anion exchanger effluents 8 phenolphthalein end point 7 neutral point at 25 °C 6 Weymouth, NIA, drinking water, a 5 methyl orange end point 4 FMA 4 ppm as CaCO3

3 FMA 40 ppm as CaCO3strong acid cation exchanger effluent

2 FMA 400 ppm as CaCO3

a Extremes of drinking water pHThe pH meter can be a source of confusion, because the pH scale on the meter islinear, extending from 0 to 14 in even increments. Because pH is a logarithmicfunction, a change of I pH unit corresponds to a 10 fold change in acidconcentration. A decrease of 2 pH units represents a 100 fold change in acidconcentration.AlkalinityAlkalinity tests are used to control limesoda softening processes and boilerblowdown and to predict the potential for calcium scaling in cooling water systems.For most water systems, it is important to recognize the sources of alkalinity andmaintain proper alkalinity control.Carbon dioxide dissolves in water as a gas. The dissolved carbon dioxide reactswith solvent water molecules and forms carbonic acid according to the followingreaction:CO2 + H2O = H2CO3

Only a trace amount of carbonic acid is formed, but it is acidic enough to lower pHfrom the neutral point of 7. Carbonic acid is a weak acid, so it does not lower pHbelow 4.3. However, this level is low enough to cause significant corrosion of systemmetals.If the initial loading of CO2 is held constant and the pH is raised, a gradualtransformation into the bicarbonate ion HCO3

occurs. This is shown in Figure 12.

The transformation is complete at pH 8.3. Further elevation of the pH forces asecond transformation into carbonate, CO3

2. The three species carbonic acid,bicarbonate, and carbonate can be converted from one to another by means of

bicarbonate, and carbonate can be converted from one to another by means ofchanging the pH of the water.Variations in pH can be reduced through "buffering" the addition of acid (or caustic).When acid (or caustic) is added to a water containing carbonate/bicarbonatespecies, the pH of the system does not change as quickly as it does in pure water.Much of the added acid (or caustic) is consumed as the carbonate/bicarbonate (orbicarbonate/carbonic acid) ratio is shifted.Alkalinity is the ability of a natural water to neutralize acid (i.e., to reduce the pHdepression expected from a strong acid by the buffering mechanism mentionedabove). Confusion arises in that alkaline pH conditions exist at a pH above 7,whereas alkalinity in a natural water exists at a pH above 4.4.Alkalinity is measured by a double titration; acid is added to a sample to thePhenolphthalein end point (pH 8.3) and the Methyl Orange end point (pH 4.4).Titration to the Phenolphthalein end point (the Palkalinity) measures OH and 1/2CO3

2; titration to the Methyl Orange end point (the Malkalinity) measures OH ,CO3

2 and HCO3 .

SilicaWhen not properly controlled, silica forms highly insulating, difficult to removedeposits in cooling systems, boilers, and turbines. An understanding of some of thepossible variations in silica testing is valuable.Most salts, although present as complicated crystalline structures in the solid phase,assume fairly simple ionic forms in solution. Silica exhibits complicated structureseven in solution.Silica exists in a wide range of structures, from a simple silicate to a complicatedpolymeric material. The polymeric structure can persist when the material isdissolved in surface waters.The size of the silica polymer can be substantial, ranging up to the colloidal state.Colloidal silica is rarely present in groundwaters. It is most commonly present insurface waters during periods of high runoff.The polymeric form of silica does not produce color in the standard molybdate basedcolorimetric test for silica. This form of silica is termed "nonreactive". The polymericform of silica is not thermally stable and when heated in a boiler reverts to the basicsilicate monomer, which is reactive with molybdate.

As a result, molybdate testing of a boiler feedwater may reveal little or no silica,while boiler blowdown measurements show a level of silica that is above controllimits. High boiler water silica and low feedwater values are often a first sign thatcolloidal silica is present in the makeup.One method of identifying colloidal silica problems is the use of atomic emission orabsorption to measure feedwater silica. This method, unlike the molybdatechemistry, measures total silica irrespective of the degree of polymerization.

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Concern for the environment is not a new issue, as evidenced by thenotice printed in the January, 1944 issue of The Betz Indicator. (Figure 21)In the 1960's it became evident that there could be a dark side to theeconomic development that resulted from the decades of rapid industrialgrowth following World War II. During this period the general publicbecame aware of the consequences of improper waste material handlingand industrial accidents. Frightening incidents at Love Canal, Seveso,and Bhopal in the 1970's and 1980's had tragic effects on members ofthe general public beyond the fence line of the facilities. In the past fewdecades, public awareness has grown concerning many other importantenvironmental issues:

acid rain

global warming ("greenhouse effect")stratospheric ozone depletiontropical deforestationthe urban trash crisispesticides in groundwaterhazardous waste disposalnatural and synthetic carcinogens

Focus on environmental considerations has shifted from a singlemediumapproach (air, water, land) to a holistic approach. Early regulationspermitted the removal of a solvent, such as trichloroethane (methylchloroform), from contaminated groundwater by counter current airstripping. It was soon realized that while the water was no longercontaminated, an air pollutant had been created in the process. Today'sregulations address the fact that moving a pollutant from one medium toanother does not eliminate the problem. In the example given above, thesolvent removed from the water must he condensed or adsorbed byactivated carbon and recovered or incinerated.Another change is a recognition that city sewers are an appropriatemeans of disposal only for those industrial wastes that are removed ordegraded to environmentally compatible products in the municipaltreatment plant. Industrial wastes that cause a degradation of effluentwater quality or render the sewage sludge hazardous must be managedin ways that are environmentally acceptable. The accomplishment of thisgoal will require the continuing, longterm efforts of all concerned.The cost of manufacturing a product now includes factors for wastedisposal and pollution prevention. Often, it is more economical to alter

Page 2

disposal and pollution prevention. Often, it is more economical to alterprocesses to produce less waste or more benign wastes, and to recoverusable materials from waste streams, than to make a contaminatedwaste stream suitable for disposal.THE INDUSTRIAL USE OF WATER It is becoming increasingly apparent that fresh water is a valuableresource that must be protected through proper management,conservation, and use.Although twothirds of the Earth's surface is covered by water, most of itis seawater, which is not readily usable for most needs. All fresh watercomes from rainfall, which percolates into the soil or runs off into riversand streams. The hydrologic cycle is dynamic, as shown in Chapter 1.In order to ensure an adequate supply of high quality water for industrialuse, the following practices must he implemented :

purification and conditioning prior to consumer (potable) or industrialuseconservation (and reuse where possible)wastewater treatment

Cooling systems are being modified in industrial applications to reducethe use of fresh water makeup. The operation of cooling towers at highcycles of concentration and the reuse of waste streams (includingmunicipal plant effluent for cooling tower makeup) can contributesignificantly to reduced water consumption.Both groundwater and surface waters can become polluted as a result ofthe improper management of wastes (Figure 23). Because of theincreasing demands for fresh water, there is a continuing need to shareresources. Regulations will require the increasing treatment of alldomestic and industrial wastewaters in order to remove industrial andpriority pollutants and restore the effluent water to the quality required bythe next user. Facilities that treat domestic waste must also control themore conventional pollutants, such as BOD (biological oxygen demand),ammonia, and nitrates, and restore the pH if it is out of the neutral zone.Concerns about the safety of drinking water supplies are widespread.Although there are many pollutants that degrade water quality (includingnatural pollutants), those that attract the greatest public attention resultfrom industrial activity and the use of agricultural pesticides andfertilizers.Environmental regulations establish quality criteria for both industrial anddomestic waste treatment discharges. Although some countries havemore comprehensive laws and permit regulations than others, stringentpollution control standards will probably be adopted globally in thecoming years.AIR QUALITYGeographic boundaries are not recognized by the winds. Air qualityissues are complicated by the fact that they are usually of multinationalconcern. Significant issues such as acid rain, stratospheric ozonedepletion, and the greenhouse effect require a degree of internationalcooperation that is difficult to achieve (see Figure 24). Technologiesavailable today can have a positive and measurable impact on theseissues. Several chapters in this handbook describe technologies thatincrease boiler and industrial cooling efficiency. In paper mills, generatingplants, steel mills, refineries, and other major energy consumers, eachincremental increase in energy efficiency represents a reduction inrequired fuel. As a result of reduced fuel consumption, less carbondioxide is produced, and where coal or other sulfur containing fuels areused there is also a decrease in sulfur oxide emissions. Fluidized bedboilers are being used increasingly to reduce the presence of acidic

boilers are being used increasingly to reduce the presence of acidicgasses (SOx and NOx ) in the boiler flue gas.

One of the problems faced by governments is the amount of energyrequired to accomplish wet scrubbing (to remove acid gases) andelectrostatic precipitation of particulates. These processes, combined,consume up to 30% of the energy released by the burning of coal . Whilethese processes reduce the contaminants thought to cause acid rain,they increase the amount of coal burned and thereby increase theproduction of carbon dioxide, one of the gases thought to cause the"greenhouse effect."

Many of the air pollutants of concern could be greatly reduced throughthe use of alternative energy sources, such as nuclear fission (and atsome point, probably nuclear fusion), geothermal, wind, hydroelectric,photovoltaic, biomass, and solar. At this time, many of the alternativesare significantly more expensive than the use of fossil fuels, and eachhas its own problems. There are no clear and simple solutions; no sourceof energy has been developed that is both economically attractive andwithout environmental drawbacks.Over the past several years, most industrialized countries have passedlaws addressing air pollution concerns and industrial and power plantemissions. Nations have begun to come together in a cooperativefashion to formulate agreements and protocols to deal with globalatmospheric concerns. There has been a multinational agreement tophase out the use of certain chloro fluorocarbon compounds (used asrefrigerant gases and for other purposes) because they have been linkedwith a reduction of ozone in the stratosphere. There is reason to believethat a reduction in stratospheric ozone will allow a higher level of UVradiation to reach the earth's surface, and this is expected to cause anincrease in the incidence of skin cancer along with other undesirableeffects.There are movements to establish multinational agreements that provideincentives to allow economic progress to occur in developing countrieswithout the destruction of their rain forests. The rain forests should bepreserved not only for the sake of conservation but also because theyremove vast quantities of atmospheric carbon dioxide throughphotosynthesis and thus have a favorable effect on global warming andthe greenhouse effect.Human understanding of atmospheric chemistry is far from complete. Asour understanding grows there will undoubtedly be many changes indirection and emphasis regarding atmospheric pollutants. Because asizeable amount of atmospheric pollution results from industrial activityand power generation, the scope and stringency of industrial air pollutionregulations will continue to increase.INDUSTRIAL WASTE REDUCTION AND ENERGY CONSERVATION In the 20th century, industrialized nations evolved from exploiters ofbountiful natural resources to conservators of scarce resources. In theearly 1900's, the consumption of industrial products was modest andnatural resources appeared to he limitless. As the demand for electricpower and industrial products grew, the limitations of the Earth's naturalresources became an increasing concern. Today, even developingcountries are very interested in the controlled development and utilizationof their resources.In addition to producing a desired output at a certain cost, industrialproducers must now consider the following objectives:

to consume a minimum of raw materials and energyto minimize waste through efficient use of resourcesto recover useful materials from production waste

to treat any residual waste so that it can be converted to anenvironmentally acceptable form before disposal

In addition to concerns about the depletion of natural resources, thereare widespread concerns about waste disposal practices. The burying ofuntreated industrial wastes, whether classified as hazardous ornonhazardous, is no longer an acceptable practice. Landfill of stabilizedresidues from the incineration, thermal treatment, or biologicaloxidation/degradation of industrial wastes is the approach accepted bymost countries today.Certain materials that are the waste products of one process can berecovered for reuse in another application. For example, boiler blowdownmay be used as cooling tower makeup in certain instances. Other wasteproducts may contain valuable components that can be extracted. As thecost of waste disposal has escalated, it has become economicallyfeasible to use alternative raw materials and to alter processes so thatless waste or less hazardous waste is produced. The treatment of wasteand wastewater so that it can be successfully reused is an increasingneed .The most efficient driving force for the selection of alternative, wastereducing raw materials and processes is the marketplace. Because of thehigh cost of waste treatment and disposal, certain processes can offsethigher initial costs with reduced operating expenses. For example,membrane systems (reverse osmosis, electro dialysis reversal, etc.)have been used successfully to treat boiler makeup water and reduce thetotal level of contamination in the waste discharge in comparison with ionexchange systems. Membrane treatment of cooling tower blowdown hasalso been used to reduce the total quantity of wastewater. The strippingof carbon dioxide and ammonia from process condensate streams hasmade it feasible to reuse them as boiler feedwater. The reduction ofcooling tower blowdown by the use of side stream softeners and/orfilters, along with effective deposit control and corrosion inhibitionprograms, is also increasing.Although global efforts are being made to ensure that the wastes fromindustrial processes are properly managed, the cost of remedying thedamage from past practices must also be addressed. Injudicious burial ofindustrial wastes in the past has resulted in significant groundwatercontamination (leaching) problems. Because the underground movementof chemicals leaching from dumping areas is extremely difficult to monitorand track, this form of pollution is of major concern to the general public.A large percentage of the world's population relies on groundwater fromwells or springs for its potable water supply.Because the turnover of an aquifer can take years, or even decades, anycontamination can be serious. Fortunately, certain natural processes,including microbiological digestion, may break down leaching pollutantsto nonharmful materials. One remedy that is gaining acceptance is theaddition of certain nutrients and inoculum cultures to contaminated soilsto accelerate the biological degradation of pollutants. This process isreferred to as bioremediation and has many useful variants.

Industrial and commercial producers have an obligation to minimizeconsumption of the Earth's natural resources and to generate a minimumof pollutants and waste.The term "zero risk" is often used to represent the ultimate goal ofgenerating products without any possibility of producing environmentaleffects. As zero risk is approached (although in most cases it can neverbe fully attained), the cost to the producer and to society in generalbecomes increasingly larger for each increment of risk avoided (seeFigure 27).

It has become clear to all nations that the protection of the environment isan immediate and ongoing concern. It will take a great deal of time andeffort to redesign industrial processes to minimize wastes produced.Deposit and corrosion control treatments that are effective underdemanding conditions and also environmentally acceptable arenecessary. Efficient treatment. handling, feeding, and control systemsare essential to ensure optimum system performance with minimumimpact on the environment.

Previous Table of Contents Next(Chapter 01 Water

Sources, Impurities andChemistry)

(Chapter 03 ApplyingQuality Methods)

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Conditions | Library

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