! 0', ! . • : ~' ..

~ n .. u t;;,;: 1

~)1 I ( i

I o· I

I

~ c ·: -· _,

o I I ~ 1~ 1 ~ u

I i 0 l ~. r1 ~ u

I L 1

!

~

L

I L r

.,. I . ~., ......

. !

I

I

·f I

I

,. l

[}:{]/A\00~& 0 §rn3&®©@ Susitna Joint Venture

Document Number -------~-· -----~-""""-"''--"''--------·~. ,J' 1?... ~'~-·. •/. --· .... .,.·;, !. ....

Please Return To DOCUMENT CONTROL

WATER AND WASTEWATER MANAGEMENT AT FOSSIL-FUELED POWER GENERATING STATIONS

Kenneth B. Kim Emil F. Dul

John N. Brogard

Principal Environmental Engineers £basco Services Inc. New York, New York

On October 8, 1974, the Final Effluent Limitation Guidelines (ELG) for power plants were promulgated pursuant to the requirements of Public Law 92-500.

In accordance with that law, compliance with the chemical provisions of the guidelines is re­quired by 1977 and 1983, respectively, for Best Practicable Control Technology Currently

• Available (BPCTCA) and Best Available Technology Economically Achievable (BATEA). This paper will identify the features of W A TER/W ASTE\V ATER MANAGEMENT

PLANS which, if developed for existing and planned fossil-fut;!led power plants, could serve as a basis for developing ELG compliance programs.

The purpose of a water and wastewater management plan is to develop an optimized pro­gram of water supply, use and re-use and effluent treatment, and disposal that achieves the fo~~nwing four objectives:

1. water conservation 2. adherence to legal requirements concerning discharge standards and limitations 3. minimized operation and maintenance problems 4. minimized investment and annual costs associated with the use and ultimate disposal of

plant waters. Begause the plan will vary among plants, this paper intends only to provide an overview of

the subject based. on the authors' experience at various fossil-fueled plants about the United States. The specific objectivel:i of this paper are to:

-identify the factors that affect the development of a plan for water and wastewater manage­ment programs;

-identify major water use locations at fossil-fueled power plants~ -identify and qualitatively evaluate wastewater sources and characteristics in fossil-fueled power plants;

-identify high impact systems requiring managemen~ and. .--present a discussion of two cases where water and wastewater management plans have been developed. The cases concern coal-fired fossil-fueled power plants located in the Northeast (Case I) and in the Southwest (Case II).

FOSSIL-FUEL PO\VER PLANT COMPONENTS

The major components of a fossil-fueled power plant are identified in Figure 1 and consist of: ·

1. Boiler. generates the heat that is ultimately used to convert water to steam. 2. Turbine-Generator. where potential energy of the steam is converted to mechanical and

thence electrical energy. 3. Condenser. where the steam is condensed b'y circulating cooling water. The condensation

step produces the pressure differential across the turbine that causes the turbine to sptn. 4. Cooling System. where power plant rejected heat is conveyed back to the air or water en­

virom. '.enl·

I t .§ 3 "t At ...... @1'/WAP. f4 0 4( .QS¥4 § .A

. ·--· ~-------~- ...... --~ ... ,....,_....,..,t"~·· ...._....,..~··-~~·-'"':"

.. :.. ii

1.

I

I· 1:.

I l l l L r l l r r· )

I l ! ' l 1 l l \

1

J I , I ~ l.

l I i i

l I j l i i ~ ' t

,, ... ,

i I I

I ~~ ~ I t.J

l

I ~ ~ ! L.J

1 ! \

I r~ L,;

~ fi 1t t

~ c ~c i

~[J

I

~ I! I u I

~L ~L 1

~L I

f L I I ' t..J l

I I ~ . .J

IL

I

!

j t $

' ,·

,

' ' • '

1 f . '

t i j

l ~

l

~'

· -. o· H t·. , ,

~ ... - __ .., ___ ,__..__~_..--~- .... ....:...--··---~ ·--~~- ._;L ________ ..___.....:, __ _.. ___ ~~--~;~.-..'.:;~

·-······- .. __: --·.. .. .. --·------... ·-----•~"'-'""",..,w .... · ..... _ .. __ e_e ......... --... __ _..... -· .... w-·.oo.·· . ..,, ......,..., • ..,.._,,_. _ • ..._ .... ·.~··-..re=-·'*'e.;.,;..;io;i·"""'•-.o" ... ffillllll;ji·fi-=•·llll=tO.w.._.._

216

SUCK

STUNt

..... QUAliTY CONTROL SYSl[NI

IOILlll

fU[l STORAGE AHO TR .. N\PORT

sYSTlM

COIIDEN~AT[

II[TUIIN

Figure 1. Fossil fueled power plant features

CII!CULATINC WATtll

C£NRIIATOII

SOLID WAST[ OIS,OSAL

Treatment and Reuse

TO TIIAIISMISIIOII

.-AT£11 SU,L'I' SYSTEM

5. Fuel Storage and Transport System. where the fossil fuel is transferred from the incom­ing transport system to a point of storage prior to use in the boiler, and then transported to the boiler i tse!f .

6. Air Quality Control System. where the control of ~,articulate and sulfur oxide poilutants (AQCS) is effected.

7. Solid Waste Disp_osal System. where solids generated in plant operations are treated and stored or processed for reuse or resale.

FACTORS AFFECTING W ATER/W ASTEW A TER MANAGEMENT AT FOSSIL­FUELED POWER PLANfS

As previously noted, the features of water and wastewater management plans vary among plants. The primary factors influencing these variations are:

1. Generic Fuel Type. The use of gas, oil, lignite or coal will affect the number of water use operations and wastewater sources in the plant. The lignite and coal fired plants will have sig­nificantly greater management requirements than either gas or oil fired plants.

2. Specific Fuel Quality. Once a fuel type is selected, significant variations in the fuel characteristics still remain. For example, depending on the coal source, the ash, moisture and sulfur content will vary drastically and cause significantly different water use requirements and wastewater sources, quantity and quality. Similarly with fuel oil, the fuel number (i.e. 2-5), source and ~ansportlstorage methods will influence water use and wastewater genera­tion. (Attention is brought to the process of fuel washing, for example, which is required for fuel oil contmninated with salt water added in the transportation qperation). .

3. Heat Dissipation System. Depending on the type system in usc or planned, variations in chemical addition, tlow volume. etc. results. Variations among sy!:items will be reflected in the potential opportunities for water management

4. Location. The location l~lctor will cause variations in water availability and quality, water quality stand.1rds, meteorology, air quality control systems required, etc. which, in turn, effect water mallagcment considerations and opportuni tics.

•

------~-· _.,.,__..,_....,....to .. '• ........ '""'~ .-.-<; -rr-~•;~ ...

-

---

r

I t, !

...... ~~.....,_

I ~· ; RL~( \ !

I r • t .: !

~ r LJ

•

___ _....._...._. _____________ , __________________________ _ n~rer and Wastewaier Management 217

s. Market/Plant Betterment Factors. Economic, metallurgical, and plant water chemistry affect the plan as well as the potential for marketing process wastes. For example, when the op­portunity exists to market flyash, dry collection systems are used in the plant in favor of wet systems. The problems of wet sludge transport and ponding are thus obviated.

WATER/WASTES MANAGEMENT GAS AND OIL FIRED PLANTS (Figure 2)

Gas and oil fired power plants result in fewer water use locations and significantly fewer wastewater sources than coal fired plants and are thus briefly addressed in the following.

Features Common to Gas and Oil Fired Plants

The major water use .IGCation at such plants is the cooling system, whereas low volume waste sources L'"tat occur in a semi-continuous mode or batch nature include:

-Boiler blowdown --~-

.water treat.rn~nt wastes -Cooling system cieanout w~~ -Boiler cleaning wastes

Features Unique to Oil Fired Plants

Depending on fuel quality characteristics, the following unique wastes management systems may be required:

-Particulate removal -S~ scrubbing -Fuel washing These operations require a water supply and result in polluted streams. Also, as required

under 10-CFR 110 and 112, Spill Prevention, Control and Countermeasure (SPCC) plans are required to insure that oily waste discharges to the receiving water body are prevented.

· MAJOR \VATER USE LOCATIONS AND WASTEWATER CONSIDERATIONS AT COAL FIRED PLANTS

The key water use locations and associated wastewater considerations at a ••typical" 600 MWe coal fired power plant include the following (Figures 3, 4, 5):

! . Boiler Makeup. A 350 gpm design capability is typically provided for the boiler makeup water system although actual water use is considerably less. Because a high, purity makeup water is required, treatment utilizing sedimentation, filtration and demineralization is pro­\'idcd. 'These operations result in the production of sludges, backwash and regenerant wastes, respectively, which require treatment and disposal.

2. Bottom Ash Hopper Sealing and Cooling. In this operation, 200 to 600 gpm of water is trpically used to cool the metal walls of the bottom ash hopper and maintain a water seal be­tween the boiler and ash hopper walls to prevent gas escape. In many older, existing plants, this water is discharged without any re-use, whereas, in fact, it is quite suitable as supply to other plant systems such as ash sluicing or Air Quality Control System (AQCS) makeup. The drscharge stream is typically at a temperature of about 150 +oF, contains a high settleable solids load and may be acid to neutral in pH.

3. &uom Ash Sluicing. This operation is highly variable in water demand depending on: ·Cool type and ash content · · -Ash accumulation rate -Frt-quency of sluicing ·Duration of sluicing operation

... .,., ........ ,, .... -

i:f I

1

I I

I l I

j

I

• l i ,! .J

M t l ' . ._j

Pt. I, l lJ

n,· A ~ ~ -~ , LJ !

I n " LJ

~ 0 l

~D i

i r·: l .. J

~ fl ~ lJ

,. II

~w

i l~ I

I L I l

1 J u i

I l I

i i

.l.J i

i

I t 1.

b

IU 1

• I

__ ......... ..........._.-~·---- .. ··- ___ .____. .. ~ -~ .. ~ ._... ___ • .J..-

218

GAS OR Oll:_FIRJ_D PLANT WASTES

• COOLING TOWER SLOWDOWN

• LOW VOLUME WASTE SOURCES

BOILER SLOWDOWN WATER TREATMENT WASTES COOLING TOWER BASIN CLEANOUT WASTES

BOtl.ER CLEANING WASTES

• DOMESTIC WASTES

UNIQUE OIL·FIRED PLANT WASTES

· Treatment and Reuse

..

• PRECiPITATOR/SCRUBBER WASTES (DEPENDENT ON FUEL QUALITY)

PARTICULATE WASTES

S02 WASTES

• FUEL HANDLING WASTES

SALT WATER REMOVAL • SPILL PREVENTION, CONTROL & COUNTERMEASURE (SPCC) PLAN (10 CFR 110 & 112)

FUEL STORAGE AREA WASTES

FUEL HANDliNG AREA WASTES

Figure 2. Water and wastewater. management areas at gas and oil fired power plants

• PROCESS WATER

BOILER MAKEUP

ASH COOLING AND SEALING

BOTTOM ASH SLUICING

FLY ASH SLUICING

S02 SC~UBBER SYSTEM

• COOLING WATER

CONDENSER COOLING (1 cfs/MW)

AUXILIARY (SEALS, BEARINGS, PUMPS: 0.01-0.1 cfs/MWe)

• POTABLE/PLANT SERVICE WATER

WASHDCWN

SINKS

fiRE PROTECTION

HVAC

Figure 3. Major water usc locations a·.t coal fired power plant

_.-.-' " .. - .- l, S # ~~ I ¥9t46!i ,Qj@ Q$ Q J»UUJI'(Aqll FC ..... iCNI ___ _.. .... --..~- ~~-:_,..,.., ____ ,....., ...... ...,..~~ .....

{ ,,

•

r,)

l !. 0

} !'

t

I

i

In ~ _.LJ

;,

II ~

' '.

L.J ':e

ll ~ . : I

l_J I

-~j~. PI ~ i ' Lj \ I

-~. r::;::J ij ( 1

\ {

l

i

___ -._..:....-_..... _____ ....... -...... ~--·-·· --- _.....:~-------~---~·- ··---~--· .. -··-· ..... --·-~~

Water and Wastewater Management

• BOILER MAKEUP 350 GPM DESIGN CAPABILITY (TYPICAL)

SEDIMENT ATION/FI L TRATioN/OEMINERALIZATION

(PRODUCES WATER TREATMENT WASTES)

• BOTTOM ASH COOLING & SEALING TYPICALLY 200-600 gpm

150° F+ HIGH SETTLEABLE SOLIDS

pH : 2-7 (RE-USE IN S02 AND PARTICULATE REMOVAL SYSTEMS)

• BOn'OM ASH SLUICING WATER VOLUME IS FUNCTION OF:

COAL TYPE AND ASH CONTENT ASH ACCUMULATION RATE/FREQUENCY OF SLUICE

NUMBER OF SLUICES/DAY NEED TO PRODUCE A 3-8% SLURRY

POND WASTES (HIGH SUSPENDED SOLIDS)

__ _.......,....,..,__ .. ·- .. -

219

RECYCLE TO ASH/S02/PARTICULATE SYSTEMS (LOW QUALITY WATER USES)

"TYPICALLY" ONCE PER SHIFT; 45-90 MINUTE DURATION

Figure.;_ Process water considerations (600 MWe)

• F~ Y ASH SLUICING

PRECIPITATION PREFERRED

WET PARTICULATE SCRUBBEn iCa IN ASH+ S02 + H20 RESULTS IN SCALING I PLUGGING

PROBLEMS)

IF MARKET POTENTIAL (DRY PRECIPITATOR}

W::T SLUICING (PRODUCE 5-10% SLURRY)

• S02 SCRUBBER SYSTEM

LIME SLURRY FEED (OR POWDERED LIMESTONE SLURRY FEED. PACKED BED)

5-10% CaS04 SLUDGE PRODUCED

THICKENING TO' 40% SOLIDS

POND SLUDGE (LINERS)

POTENTIAL "CHANNELING'' PROBLEMS IN PACKED TOWEPS (PRODUCES VARIABLE pH)

. Figure 5. Process water considerations (600 MWe}

I

l· l

\ t I

\'

l \,,

l l t

\' I I I l

r

.

'

l I ~ I ~ L J 1 ..

I ~ r I ! I

l L:J ' l

l ,RI1 i· I t \ LJ

~ ~ ~ ; ' '

! ~-.J

~ n

u (, ~

1 .1 1- 1

i J..~ ~.s

~ n ,. l L ~

~ 1 !

... _ ....

I n ~ t

! u

i fl i ' i u l

j rl f

lJ I

I r1 u

i' fl f• ' E

Ll ' '

l: r1 L_j

I

~. u

{ ; l ' !

i s l . • .

' ~ l • {

I

t , ;

_ .. --.---- ·--·-- --------~-~- -----'!::.~--. .-.....--

. Treatment and Reuse 220

Typically, the sluicing operation is de•igned to produce a 5 to 8 percent ash slurry. Obviously, water demand in the opemtion is reduced as the solids content" is i ncrc.ast~d. although pumping · constraints must be considered before a slurry solids content is fixed. Ash sluicing wasteS are normally ponded on-site and pond supernatant can be re-used within the plant.

4. Fly Ash Sluicing. In order to meet source standards for air quality co~ntrol, tlue gas partic-ulate (i.e. flyash) removal is required. Current engineering practice incorporates the use of electrostatic precipitators in this context although wet scrubbers have betm used in the past. Wet scrubbers have inherent maintenance problems associated with scale formation caused by the precipitation of CaS04 due to the complexing of calcium (present in the flyash) and flue gas S02 in the presence of water. Unless the precipitated flyash has a market, precipitator par­ticulate accumulations are sluiced wi.th water (in a 5 to 10 percent slurry) to on-site ponds .

5. S02 Scrubber System. When flue gas desulfurization is required, major water use, and wastewater and solid waste sources are created. Typically, lime or limestone based slurry systems are utilized. A 5 to 10 percent calcium sulfate/sulfite sludge is produced that is then thickened (i.e. to about 40 percent solids) and subsequently ponded, on or off-site.

An indication of the variation in water volumes, pollutant loads, and sludge quantities that can occur depending on fuel type is available from inspection of the following typical

analyses: Item

Moisture,% Ash,% Sulfur,% Heating Value (BTU/lb)

WATlll SOURCE

MAlt[ UP

Wyoming Coal

20 6.0 0.5

9000

lVAPOJIATION

tttAT

CHEMICAl TIIUlMtNl

Pennsylvania Bituminous

5 20

2 11,500

COND[NS£11

TYPES OF SYSTEMS

COOLING POND/LAKE

SPRAY POND MECHANICAL DRAFT TOWER NATURAl. DRAFT TOWER

DAY TOWER

Texas Lignite

24 12.0

1.0 7800

WE.T/DAY TOWER (PLUME ABATEMENT VS. WATER CONSERVATION)

Figure 6. Recirculating cooling system components .

-

i l

1\ ~' i i I t J I -- ..,.._

II ~. j ' ' ' t 1

t J 1

~ r:~ ~LJ 1

I' , .. ,

' ; .u

i ! ~ ·LJ

IL I I t :L I t ~

LJ

~ I ijl.J

iL IL IL I ' i 6

,........--

---~---...,...__....- ... -.- --·--·"'- .... ~#-4. ... --... <0:·-·' -- ........ __ ..... ~- --- --·-··--...... --""-~-----.. -----·tz'zp------A-

Water and Wastewater Management 221

• PROCESS WATER RECOVERY/RE-USE

ASH SEALING/COOLING WATER

BOTTOM ASH SLUICING WATER

AOC SYSTEM SLUDGE SUPERNATANT

BOILER f. LOWDOWN

• COOLING SYSTEM RE-USE

SLOWDOWN

• OTHER

STORMWATER DURING CONSTRUCTION; TREATED SANITARY EFFLUENT

Figure 7. Potential areas for wa~er management

Simplistically, it can be seen that on a "per unit available BTU basis," Texas lignite will have a greater impact than Wyoming Coal in:

-the quantity of ash requiring transport and disposal -air quality control requirements -water use -wastewater treatment -economics of water and wastes management With res~ct to the ~·solig wastes" aspect of the management plan. it may be of interest to

note that for a 600 M\V unit. equipped with a pulverized coal type boiler and using a "'1 per­cent sulfur coal," the wastes production level is as follows:

Flyash -0.40 acre-ft/day (assumed dry weight = 60 pet) Bottom Ash -0.12 acre-ft/day (assumed dry weight= 50 pet) S0

2 Sludge -0.50 acre-ft/day (assumed moisture content- 60°)

Total = 1.0 acre-ftlday Therefore, based on a 40 year plant life and an assumed average sludge pond depth of 20

f~t, the resulting areal requirement is about 750 acres.

CONDENSER COOLING SYSTEM CO~SIDERATIO~S

Typical recirculating cooling water system components are identified in Figure 6 whereas water use ~md treatment considerations are presented below:

1. Typk.1l Fossil-Fueled Power Plant Heat Rejection Rate = 4.5 x 1 O~> BTU/MW-hr. 2. 600 MW Heat Rejection Rate = 2.7 x 10'~ BTU/hr 3. Condenser Rise:

-Once through lake, pond system - 20° F (Average) -Mechanical System- 1 ~-26" F

4. Circulating V'later Flow (CWI--1 Rate = 1 cfs/M\V (@ 20° F condenser rise)

--. """"~-..... ..... ~------ ...... ,.___ f41•V" • .. , • ......-.' .............. ~ :owur .... ....--..-- ..... ...,_......,., ..... c:: 1!,.. ·-.. ···'¥"" .... ,;.c ua;u ..,...:.-..,-... _..-

~ ~ r-~

t f I

l. f r

l)

l

I I l

i.,~¥ ·-•'-·"'·c ____ ~_,.~_.,_~_' __ "'" ___ ".,'_'_"' .. "-''"'-"-''J_-- '·'.--.c~~==·-~~ : .. ~.· ·~~~~=-3---~~l--__ -"- :_ ------·--- _,, ... ___ jL _____ ,~---~---" ___ ,.: __ ~,~"~---~--' ____ : __ j~_.C:;;;,,~ ~J. -- -~- --- .~-.,..__,_i

I' ~ ) i

l ' I , j , 1- ~

L )

~ R l .. !

~ ~

~ r!

~ ' '

' ' 1-< ~.J

I L.J

I f' f : L;

! ! I I! u

I .f ' j

i G

I l ! i ' LJ

1 i LJ

I

I i

L.

I t t:..;, I I

l l-"'1

I !

l4l

i I ! I ~

. . t t J r

!

l I l ~

i 4 ~ ;

. . . f i "' l 1 ' .

~ t

' i

.. ···---~ ... -·- ... -~~... _ _... __________ __.-..~---.. ·-- ----- ' ,_ .....

~-....... --

222 Treatment and Reuse

5. Treatment Needs: -Biological Foulant Control (Chemical/ Mechanical) -Corrosion control or Scale Pievention

6. Evaporative loss - 1 percent CWF/1 oo F Condenser Rise 7. Drift Rate- 0.003 percent- 0.005 percent CWF 8. Blowdown controlled by:

-Water Cpemistry (cycles of concentration) -MetallurJSY -Econorrucs of chemical treatment

These data are provided only as a guide to the nature of the quantities of water transported through condenser cooling systems and potential system consumptive water uses. Chemical treatment techniques are so varied that no generalized information is offered.

The key feature associated with cooling system operation is the potential for re.:use and recy­cle of cooling system blowdown in plant operations such as ash sluicing, AQCS makeup and ash hopper cooling and sealing.

POTENTIAL FOR WATER MANAGEME~T"f

The key locations within the coal fired power plant where water is available for reuse and recycle inck1de (Figure 7):

Ash Hopper Sealing/Cooling Water Bottom Ash Sluicing \Vater AQC System Sludge Supernatant :poi ler BlQWdQwn Cooling System Blowdown The nature of water management plans is demonstrated in the following cases .

Case 1- Coal Fired Plant- Northeast US (Figure 8) This plant is located on a stream that can easily supply abundant water to the plant.

However, because of the intluence of acid mine drainage, the water quality is poor and pre­treatment is required. In order to minimize the costs of pre-treatment, a water management plan has been developed that emphasizes:

-Minimizing intake water volume -Maximizing recycle and reuse. The intake water is initially aerated. Lime is added to neutralize the acidity of the makeup

and a polyelectrolyte is added to form a floc that is settk_' ~\lt in a clarifier. · Some of the pre-treated intake water serves as make-up .o the cooltng tower. Cooling tower

blowdown is, in turn, used as make-up water to the S01 absorber and for economizer ash sluic-ing. Excess water is discharged to the creek via a clarifier. ·

Water removed from the sludge discharged from the S02 absorber is recycled to the absor-ber for reuse.

Water contained in the slurry that results from ash sluicing is removed in hydrobins and ash ponds, and used for ash hopper cooling and sealing, ash bin cleaning and fuel unloading. This water is then reused. for nsh sluicing.

The remainder of the pretreated intake water is sent through gravity sand filters. One stream is conveyed w the potable water system, with sewage treatment plant eft1uent being reused in the ash sluice l<mp.

The ot.hcr stream originaung in the l!ruvity sand filters is conveyed to a demineralizer for additional treatment prior to usc as boiler makeup water.

Rcgencr;.mt and botlcr ch:amn!:! wastes an: ClltJaliJcd ~mLl neutraltzeLl and then afforded ad­vanced waste treatment for hc~tvy metals and dissolved sui iLls removal. WJtcr is then recycled to the polishing cxdHtngcr.

•snb,.

l

I t I I

I !,

~~ : ".: ~ '!;.;'""' • • • - • ft I o • • ' •

. . ' ~· . ~ ' , I

1 """" 'f ~ I -r~

li .. r. u

""'1.

~ ,_...,

i

~ j~ tl '

~~ .. -j

' ' ;~ ~;~

l\._.J

i

I ;"-··:

L__.~

J

I r·~, L-J

ri Jj

~ t-~

i

I ,.

. ' -..___.

I' L.J

I ) ' ". ' L..J

~ I

d - ' L-<

r· l s ~

"' .. ,, ~

i r~ i I j l

i \ L.;;..,.,_,

'1 I .i ' ·I

:1 ~

'I J ·j :

I I . ...., l !

·~........-....f-•o!

: "

,, I ·~ ~ ... -~..,.;;.._ ""'~ '"-~····~---~~""-····---- ..... ·- ·-,~~------·-·'"'-~-..._--.--..__::_ _____ . ..::.. ____ ~.-_.._ .... ,_· -· . :.-~--~i:.: .. ~~---~~ ·~(~.:~ &:;;:f

-----.... .. ------~·· . -···- •--. ----------· .. ~- ... ---------------_,._ ·---. Water and U'astewater Management

~ ..... .. 1-_...,.....;-------.,1------4] ·~;!· ...... [1-__ ... _ ... _~----

COOi.""•UCa ,_, T.Ut ... •t

ln.T!atD ... ,. l'"'OIUCl u •• ,

••K PUilf "OUtlll•I•U

l()UALtll'ltOtt ... llll~.tl1J&l,.U1t(\ll

io1\1('W

•owatttto ..,,, 1•(UW£11t

1ono ... ••• ..,..,,u ac.a .. o•·uA .. , ... "n'",.

COO\.tlt-C .tiiO HA\.I"C,

Figure 8. Water management plan for coal fired plant in Northeast

ucua

'"""'"lilt "OUI!ItC.

Ci.U••••C.I UIM.O&DIItC

223

c::J IIIOCUU \DUOOC:U 01' .... UJ,.U&.U WUIII

Plant oily wastes. originating from equipment leaks and floor washdown, are conveyed to an oil-water separator and thence to the desilting basin.

Plant area runoff flows to a desilting basin and then to the receiving stream Acidic. coal pile runoff is neutralized prior to discharge via the desilting basin. The extensive degree of tleatment of discharge water is required to meet extremely strict

water quality standards set by the state environmental control agency.

Case II- Coal Fired Plant Southwest US (Figure 8)

fn water-short areas such as the southwestern United States, strict water conservation and reuse are necessary for effective fossil fueled plant operation. Here, the water uses are often

. assigned on a priori\\y basis. For example, the water use systems requiring the highest quality water (i.e. the boiler

makeup water system). would receive a supply directly f:,.om the raw water source. Other units in this category would include:

1. Condenser water 2. Plant service water 3. Equipment cooling water 4. Potable water

The water discharged from these initial users would scrn.~ as the water supply for the sec­ondary users. In this case, equipment cooling discharp:e and boiler hlowdnwn could be used to supply makeup water to the cooling towers anu suifur uio'\td\.~ wet scrubhtng systems. Users with the lc~Ist critical water qu.llily rcqwr!.!m:.!nts (i.e. ash slllldng and. cooling and seal water for the bottom ash hoppers) \\ouiJ n~cet \'C water from the cooling tower discharge.

------------

or+

I j·

I

I r

I l

I I I

I l

I _J··'

• • • ~ • . 4 . . . .

I ~

i I I

i ?

. ! ..

224

e ... .

lot. I'D\ to OIS,DUI.- POliO

. ·-· ~--·- _.._. ___ ,__

Treatment and Reuse

IDUI')tt a\M Ot\~'l\1\. ....

--------,

UtU*'tAIIID 411Dlllll"

SI.LIDC( PO.;)

I UloiD I

.!!.~

I I 1

' I I 1 I I I I

~ LJ

::::::J lloOICITll \OUOC:l, Of at • UILULI WUI~

Figure 9. Water management plan for coal fired plant in Southwest

Plant runoff will be conveyed to a settling basin for removal of settleable solids. Plant oily wastes ,.,_·ill be sent to an oil-water separator system. The treated effluents would be collected in a treated effluent pond that will serve as a source

of additional make-up for the cooling system. Sludge is discharged from the lime or limestone wet S02 scrubbing system in the form of a

solids slurry that is approximately 10 percent by weight. This stream i.' thickened and solids are conveyed to a lined sludge pond. The \Vater iemoved from the thickener is returned to the :S02 scrubbing system.

In the arid southwestern U.S. where there is a high natural evaporation rate, scrubber sludge and ash transport water can be contained in a lined pond and iemoved by evaporation. This would also make it possible to comply with zero pollutant discharge requirements, if required or desired.

...... ..._ __ ,.,.._...,_"" ......... __ ,_, ..... -... .....,.. __ , .. _ .. _~· ........... .....,, ...... ______ _ ...--....... -~»• ..,..... .. -....,........,... -4 $ $ 4 ' ..

-w