SPE
SPE 19759
A New Caustic Process for Softening
Produced Water for Steam Generation
II
R.J. Jan and T.G. Reed Jr., Mobil E&P U.S.
Copyright 1989. Society of Petroleum Engineers, Inc.
this paper was prepared for presentation at the 64th Annual Technlcsl Conference and Exhibition of the Society of Petroleum Engineers held In San Antonio, TX, October 8-11.1989.
This paper was selected for presentation by an SPE Program Committee following review of Information contained In an abstract submitted by the author(s). Contents of the paper
as presented. have not been reviewed by the Society 01 Petroleum Engineers and are aubJect to correction by the author(.). The material. as presented. does not necaasartly
any position 01 the Society 01 Petroleum Engineers. Its officers. or members. Papers presented at SPE meetings are aubJect to publication review by Editorial Commln_ 01 the Society
01 Petroleum Engineers. Permlsaion to copy I. _rieled to an abatreel 01 not more than 300 word•• 1lluatr>Jlion. may not be copied. Tho abstrac1 should contain conaptcuous acknowledgment
01 where and by whom tho paper la pre.ented. Write Publications Manager, SPE, P.O. Bo. 833836, Richardson. TX 75083-3836. rele•• 730989 SPEOAL.
raneci
ABSTRACT
Oilfield produced water containing a high concentration of total dissolved solids (TDS) and hardness
can successfully be softened for use as oilfield
~team generator feedwater.
At the Belridge field in
Kern County, California, the combination of caustic
softening and weak acid cation exchange have been
used to soften produced water containing 11,000 TDS
and 550 ppm hardness to less than 1 ppm hardness.
The resultant sludge containing calcium carbonate
and magnesium hydroxide is concentrated by centrifuging and is disposed of in a land fill. Compared
to the use of conventional strong acid ion exchange
followed by weak acid or weak acid followed by weak
acid ion exchange systems, the process offers the
benefits of lower capital and chemical costs,
partial silica removal and the elimination of liquid
waste discharge.
This paper gives design parameters, operating
conditions, and discusses future applications in
thermal recovery projects.
pressure to drive the oil toward producing wells.
A review of steam drive dynamics and project
descriptions are given by Ali(2)(3) and Chu.(4)
In California typically 0.2 to 0,5 barrel of oil is
produced for each water equivalent barrel of steam
injected. Therefore for a field producing 40,000
B/D of heavy oil, steam injection is 80,000 to ,(,4"
200,000 B/D. The availability of a large quantity
of suitable feed water is imperative.
In a conventiont<l boiler 100 , quality steam is
produced from WL\ter having a very low salt content.
The steam is used (or indirect heating or driving
turbines, and the condensate is returned to the
boiler for reuse. The only makeup water required i~
to replace the boiler blowdown which controls both
the suspended and dissolved solids content of the
boiler water. Hence, a large boiler requires only a
very small water treating plant.
For heavy oil recovery, steam is normally produced
in steam generators(5,6) , These generators are
horizontal fired heaters with a single pass tube
arrangement which produce only 70 - 80 , quality
steam. The steam together with the 20 - 30 , water
that stays in liquid phase are injected into the oil
formation. Since no condensate is returned for
reuse, full steam makeup of water are required to
feed the generators.
INTRODUCTION
The injection of steam for heavy oil recovery
started in the late 1950s and has become the
principal enhanced oil recovery method. In Kern
County, California, where the major U.S. efforts
have taken place, cyclic steam and steam drive
operations accounted for over 400,000 B/D(l) of
production. Thermal methods are also being used
in the heavy oils and tar sands of Canada and
Venezuela, with each country expecting 500,000
B/D by the year 2000.(1)
This feed water must be free of calcium and
magnesium to prevent scale formation in the steam
generator tubes or in the oil formation. Silica
at high concentration can also pose a precipitation problem. Since fresh water is not always
available or cannot be consumed for environmental
reasons, the softening of higher saline water
produced in the oil recovery process becomes
In a typical recovery process, high pressure steam
is injected at a rate sufficient to heat the formaation to reduce the oil viscosity and to provide
necessary.
A new process for softening of produced water for
steam generation has been developed and commerci-
References and illustrations at end of paper.
alized at the Mobil Oil South Belridge field.
519
The
SPEl
A NEW CAUSTIC PROCESS FOR SOFTENING PRODUCED WATER FOR STEAM GENERATION
Ion Exchange - Weak Acid FollOwed by Weak Asid
process is a variation of the hot lime process used
widely for boiler feedwater purposes.
.w.tmD
COMMERCIAL WATER TREATING SYSTEMS
Ion Exchange - Strong Acid Followed by Strong Mid
~
Ion exchange techniques have been extensively used
and documented in several California alkaline
floods and steamflood operations(7,8,9,lO). Most
common systems consist of two beds of strong acid
ion exchange resin in series with the first bed
removing the bulk of the hardness and the second
acting as a polisher to remove the last traces of
calcium and magnesium. The chemical structure of
the strong acid cation exchange resins is usually
a sulfonated copolymer of styrene and divinybenzene. The resin functions by exchanging sodium
ions for calcium and magnesium ions. It is
regenerated with sodium chloride brine. The low
cost of brine regenerant makes the system
economically attractive.
The system works well on oil free water with total
dissolved solids (TDS) of less than 5000 ppm. In
cases where the TDS of the water is higher, sodium
in the produced water competes for sites on the
resin with the calcium and magnesium. This makes
the softening of water to less than the required
1 ppm hardness very difficult. Further, brine
regenerant waste usually amounts to 10-15 % of of
the total soft water produced. Disposal of this
quantity of waste brine poses additional problems.
In the event that the TDS of the
in excess of 8,000 ppm, strong acid resin i.
effective in hardness removal. The use of a
strong acid followed by a weak acid system be,co.e,.
impractical. An alternative is to employ a weak
acid followed by weak acid system(7,8,9).
This technique can reduce the hardness of a high
TDS produced water to less than 1 ppm. However,
the regeneration costs are high. To soften a
large volume of water with a significant hardness
say 350 ppm or higher, by this technique would
be economically practical.
While ion exchange processes work well to remova
the calcium and magnesium values from water,
neither strong acid resins nor weak acid resins
have any noticeable effect on removing scalecausing silica from the water. Further. when ion
exchange resins are regenerated, the calcium and
magnesium ions from the resins are entrained in
the regenerative liquid, (e.g., brine or acid)
which, is routinely disposed of by injection into
a subterranean formation. Unfortunately, the
calcium and magnesium iona in the spent
regenerative liquid can plug the formation th.!re,by
severely restricting the injection of the waste
liquid into the formation. In strong acid resin
systems, as much as 10-15 , of the treated water,
and in weak acid resin systems, 5-10 , of the
product water, may be lost due to regenerant
make-up, backwashing, and rinsing of the resin.
Lime-Soda process followed by Ion Exchange
Ion Exchange '- Strong Acid Followed by Weak Acid
System
One of the oldest methods of water softening is
lime-soda softening. (11,12,13,14) The calcium
and magnesium salts constituting the hardness
content of a water are chemically precipitated and
removed through the use of lime (calcium
hydroxide) to raise the pH and soda ash (sodium
carbonate) to supply the carbonate ion. This
process may be carried out at normal raw water
temperatures, in which case it is referred to as
"cold lime process" or at temperatures near or
above the boiling point, referred to as "hot lime
process" . The principal difference between these
two processes is the faster reaction rate and the
reduced solubility of calcium and magnesium salts
at elevated temperatures, which result in the hot
process having a higher efficiency than the cold
Because of the limitation stated above, the strong
acid followed by weak acid system is used for
produced water with TDS between 5000 - 8000 ppm.
The chemical structure of the weak acid cation
exchange resins is usually a carboxylic acid group
within an acrylic divinylbenzene matrix. This
type of resin exhibits a very strong selectivity
for calcium and magnesium ions. Hence, it can
effectively remove the hardness in a system where
the strong acid resin cannot. The resin is
considerable more costly to purchase, and requires
two steps in regeneration; first, it is treated
with hydrochloric acid to remove the calcium and
magnesium and then with caustic soda to convert
the resin back to the sodium form. Compared to
the cost of brine regenerant (for strong acid
resin), the cost of acid and caustic (for weak
acid resin) is several times higher.
process.
The hot process can reduce the hardness of the
water down to 15-25 ppm. The cold process is
limited to 30-50 ppm. Since by itself, neither
process can meet the requirements of less than 1
This system utilizes strong acid resin as primary
softener to remove majority of the hardness and
minimize the regenerant cost. It is followed with
ppm hardness, ion exchange softeners are used for
final polishing. The polishing softener could be
a strong acid resin or a weak acid ion exchange
resin depending on the TDS of the water.
a weak acid resin as polisher to ensure the final
softness of the product water meets the 1 ppm
specification.
The lime processes reduce bicarbonate and silica
in feedwater in addition to the hardness. For
softening of large volumes of water With high
hardness and high TDS, it is an economically
Several operators in Kern County have chosen this
option.
attractive process, however, it requires
handling/storage facilities for lime,
520
produc~s
SPE 19759
RAYMOND J. JAN
large volumes of sludge for disposal snd is
susceptible to operating upsets due to lime scale
or plugging. Further, in most processes using
lime, the feed water is routinely heated to
above its boiling point (212 - 220 F) to
enhance the chemical reactions between the lime
and the hardness ions. These high temperature
"hot lime" processes require expensive pressure
vessels, additional energy for heating, and
present delicate handling and safety problems, all
of which add substantially to the overall costs of
the water softening operation.
Esso in Canada is operating several large hot lime
softening units with weak acid polishing. No
producers in the heavy oil field of Kern County,
California are utilizing this process at this
time.
Ihermosoft/Ihermosludge Process
If water containing significant quantities of
bicarbonate is heated under pressure to above 400
F, the bicarbonate will decompose, liberating C02
and causing the pH to increase. This increase in
pH will precipitate the calcium and magnesium.
The sludge thus produced will absorb some of the
silica content as well. At this high temperature
the hardness can be reduced to less than 1 ppm and
some silica is removed in the sludge.
A number of years ago, "thermosludge" boilers
which use a related process, were built which
generated 100 , steam from produced water(15).
Both softening and steam generation took placa in
the same equipment. The high cost of the equipment and operating difficulties restricted its
use.
Work is continuing, primarily in Canada, to
develop a commercial process "Thermosoft"
utilizing this chemistry to soften produced water
for feed to steam generators.
3
given in Table 1. Because of its high TDS
(10,500 ppm), one could not expect the existing
strong acid softeners to be able to soften the
produced water to less than I ppm hardness.
One of the first options considered was to install
new weak acid softeners which would function as
polishers and remove any hardness leakage from the
existing strong acid softeners. Such a system is
schematically shown in Figure 1.
A second option investigated was lime softening
followed by weak acid resin. Laboratory tests
confirmed that lime process would be about two
cents per barrel lower in operating costs when
compared to the strong acid followed by weak acid
system. Howeyer, the quantity of solid prd'duced
by the precipitation of the calcium and magnesium
would present a significant disposal problem. It
was therefore decided to investigate the use of
caustic soda instead of lime to effect the
precipitation of calcium and magnesium.
CAUSTIC PRECIPITATION PROCESS AT BELRIDGE
Chemistry
Caustic (NaOH) is known to elevate the pH of a
solution and when carbonate in sufficient
quantity is present will cause the calcium and
magnesium hardness to precipitate just as the
lime (Ca(OH)2) does. However, the cost of
caustic versus lime, on an equivalent hydroxyl
ion ( OH- ) basis is at least six times higher.
For this rea~on, lime has been commonly used for
large scale commercial water softening purpose.
There is not another known water softening plant
which uses the caustic precipitation process.
The chemical reactions that take place for a lime
and a caustic precipitation reaction are as follows:
Ca(OH)2
SOUTH BELRIDGE FIELD
The South Belridge field is located in western Kern
County, California approximately 50 miles west of
Bakersfield. The overall structure of the field is
a broad southeasterly plunging anticline, about nine
miles long and two miles wide. Mobil has for years,
operated a steam drive at the south end of the
field. Current steam injection rate is about
110,000 BID or about 1,650,000 pounds per hour.
Ca(OH)2
+ 2 NaHC03'" CaC03#
+ 2 H20 + Na2C03
Caustic Soda
For many years, steam generator feed water was
prepared by blending produced water with fresh water
from the California Aqueduct in about a 50-50 ratio.
The blend resulted in a water of about 4000 - 5000
ppm TDS and was softened in a strong acid resin
system which consisted of eight trains of primary
and polishing vessels. The use of the fresh water
meant that significant quantities of produced water
had to be disposed of each day. With ever
increasing difficulties in produced water disposal,
and potential restrictions on fresh water supply, a
decision was made in 1987 to convert the generator
feed water system to 100 % produced water.
NaOH
+ Ca( HC0 3) 2 .. CaC03+
+
H20 + NaHC03
2 NaOH
+ Mg( HC0 3) 2 .. Mg(OH) 2+ +
H20 + Na2C03
NaOH
+
NaHC03 -- Na2C03
+
H2 0
The chemical reactions show that
a).
To precipitate each mole of calcium ion, two
moles of hydroxyl ion are required with lime
while only one mole is needed with caustic. In
preCipitating each mole of calcium hardness,
two moles of calcite (CaC03) sludge are formed
with lime, while only one mole is formed with
caustic.
A typical Belridge produced water analysis is
521
4
b).
A NEW CAUSTIC PROCESS FOR SOFTENING PRODUCED WATER FOR STEAM GENERATION
To precipitate each mole of magnesium hardness,
four moles of hydroxyl ions are required with
lime while only two moles are needed with
caustic. In precipitating each mole of
magnesium hardness, two
mol~s
The treated water from the reactor/clarifier, with
its hardness reduced from 514 ppm to about 10 - SO
ppm, is processed in sand filters where any
entrained solids are removed from the water.
of calcite and
After filtration, the water enters the ion exchange
polisher vessels. Weak acid resin having a
carboxylic functional group is used in this step
where substantially all of the remaining hardness
ions, i.e., calcium and magnesium, are removed from
the produced water. The soft water, having a final
hardness of less than 1 ppm is supplied as feed
one mole of magnesium hydroxide sludge are
formed with lime, while only one mole of
magnesium hydroxide is generated with the
caustic process.
c).
SPE 19759
Neutralizatio~of sodium bicarbonate, which is
required in order to raise the pH. consumes
hydroxyl ions. The neutralization generates
calcite sludge for the lime process but no
solid precipitant is formed for the caustic
water to steam generators.
process.
Further, lime has such a low solubility in water
that a significant portion of it is not dissolved
and thus not used in the precipitation process. The
undissolved lime is included in the resultant
sludge.
These theoretical observations were confirmed in
laboratory tests conducted with Belridge produced
water. The sludge formed in a caustic process is
five times less than for the lime reaction. The
operating cost is less than one cent per barrel
of soft water higher than for the lime system.
The precipitate from the reactor/clarifier is dewatered in a centrifuge and these solids, which
constitute the only substantial waste in the
operation, are removed as a sludge and are ready for
disposal as landfill materials.
Liquid wastes due to filter backwashing and ion
exchange regeneration are recycled to the reactor/
clarifier where they are processed along with the
produced water. This results in no liquid waste
which must be injected or otherwise be disposed of.
BELRIDGE OPERATING RESULTS
Caustic soda had additional advantages. First it
could be added to the system as a liquid which made
control easy as opposed to metering solid lime.
Second, caustic is used for weak acid resin regeneration, its supply and storage are needed anyway.
Third, lime sludge is very susceptible to scaling
and plugging which makes lime based softeners less
reliable. Caustic sludge is fluffy and flows like a
thick paint.
Conceptual design of the Belridge water plant
started in July, 1987. Detailed engineering,
equipment procurement and construction were
completed in October, 1988 and the new water plant
was placed in service one month later.
The plant has a design capacity of 120,000 BID with
feed of only produced water. Typical operating data
is given in Table 2.
The reactor/clarifier effectively reduces the
produced water hardness from about 500 ppm down to
about 35 ppm at a pH of 9.3. Over half of the
silica is also removed, possibly as magnesium
silicate. This is an added benefit for the
precipitation process as conventional ion exchange
alone woulc not have reduced any of the silica
Based on these factors. a decision was made to
develop a caustic precipitation system followed by
weak acid ion exchange to soften the produced water
at Belridge.
The rate of reaction between the caustic and the
dissolved hardness ions in the water is strongly
dependent upon time, temperature, pH and the
sludge recirculation. At Belridge, the water
being treated is produced as part of the production
of a steam recovery operation and is already at a
temperature of 160 - 180 F. This relatively high
temperature greatly benefits the caustic precipitation reactions. The clarifier was sized, based on
laboratory tests. to give a 1 gpm/sq. ft. for
reaction and settling. A pH of 9.3 was found to be
content.
Also, heavy metals such as barium. iron,
manganese and strontium are practically all removed
at the clarifier. Overall quality of the feed water
to the steam generators improved significantly
compared to the original strong acid ion exchange
system.
Because over 90 , of the hardness is removed in the
reactor/clarifier, the weak acid ion exchange
columns are able to operate without needing a regeneration step for five to seven days. In the
absence of a clarifier, the ion exchange system
would need to be regenerated at about once every
twelve hours. Significant chemical savings and ease
of operations are realized.
optimum.
Process Block Diagram
The process block diagram developed for the Belridge
water plant is given in Figure 2.
OPERATING PROBLEHS AND SOLUTIONS
In operation, the produced water enters a reactor/
clarifier where it is mixed with an aqueous solution
of caustic. In the reactor/clarifier, a large
volume of dense slurry of previously precipitated
solids is recirculated and mixed with the incoming
produced water. This sludge recirculation provides
The new water plant has been in service for over
six months treating all produced water. The
efficiency and smoothness of operation have
exceeded the original expectations. Over this
period, there were two shut downs related to the
reactor/clarifier. Deflection of the rake shaft
seed crystals and encourages the completion of the
precipitation reactions.
522
SPE 19759
RAYMOND J. JAN
5
caused the rake arms to cateh the sample line in one
instanee and eon tact with the tank floor in other
instanee. Corrective action is underway to add a
lower support member to restrain the shaft from
moving.
his valuable advice and test work on ion exchange
system and to E. R. Fieler, Mobil Exploration and
Producing Serviee Inc. for her review and valuable
comments of the manuscript.
Scaling and plugging problems which eommonly occur
in a lime proeess have not been observed even when
sludge is left standing for over a week.
REFERENCES
The centrifuge is eoncentrating the elarifier sludge
to over 50 , solids, whieh were subjected to the
State of California "Criteria for Identifieation of
Hazardous and Extremely Hazardous Waste" tests and
deemed not hazardous.
1.
Kuuskraa, V.A.: "The Status and Potential of
Enhanced Oil Recovery". SPE/DOE No. 14951,
Paper presented at the SPE/DOE Fifth Symposium
on Enhanced Oil Recovery, Tulsa, OK., April
20-23, 1986.
For produced waters with even higher hardness and
TDS than those of Belridge, the proeess would be
even more attractive. The higher capital and
operating eosts of ion exchange systems make them
impractical.
2.
Farouq Ali, S.M.: "Current Status of Steam
Injection as a Heavy Oil Recovery Method". J.
Cdn. Pet. Tech., Jan-March, 1974, pp. 1-15.
3.
Farouq Ali, S.M. and Meldau, R.F.: "Current
Steamflood Technology". J. Pet. Tech., Oct.,
1979, pp. 1332-1342.
4.
Chu, C.: "State-of-the-Art Review of Steamflood
Field Projects". SPE No. 11733, Paper
presented the 1983 California Regional
Meeting, Ventura, California, April 23-25, 1983.
5.
Bradley, B.Y. and Gatzke, L.R.: "Steamflood
Heater Scale and Corrosion". J. Pet. Tech.,
Feb., 1975, pp. 171-178.
6.
Burns, W.C.: "Water Treatment for Once-Through
Steam Generators". J. Pet. Tech., April, 1965,
pp.417-421.
7.
Reyes, R.B.: "Softening of Oilfield Produced
Water by Ion Exchange for Alkaline Flooding and
Steamflooding", SPE 11706, presented at 53rd
Annual California Regional Meeting of SPE,
Ventura, CA., 1983.
8.
Hart, R.A. and Thomas, S.A.: "Design and
Implementation of Softening Process for High TDS
Oil Field Produced Water", International Water
Conference, IWC-86-9, 1986, pp. 72-80.
9.
Lange, P.M., Martinola F.B. and Soest H.K.: "New
Technology in the Softening of Produced
Water in Enhanced Oil Recovery Systems",
International Water Conference, Pittsburg,
Penn., IWC-87-36, 1987.
10.
Bradley, B.W.: "Influence of Salt Dosage and
Hardness on Series Softener Performance", SPE
1951, Presented at 42nd Annual Fall Meeting of
SPE, Houston, Tx., Oct., 1967.
11.
Harden, J.E. and Hull, G.R.: "Operating
Experiences with a Large Hot Lime-Zeolite System
for 1500 PSI boilers'", Proceedings, Am. Power
Conf., Vol. XIX, 1957, pp. 672-684.
12.
Lane, M. and Duff, J.H.: "Some Chemical Aspects
of Hot Process-Hot Zeolite Plant Performance", .
With ever increasing limitations on produeed water
disposal and fresh water supply, other existing
water plants are under study for conversion.
CONCLUSIONS
1.
2.
3.
A new process for softening of high TDS
produced water for steam generation using
caustic has been developed and commercially
demonstrated.
The use of caustic preeipitation redueed
the calcium and magnesium hardness from
about 500 ppm to less than 50 ppm. Residual
hardness was polished to less than 1 ppm by
weak acid ion exchange resins.
For. high TDS and high hardness produced
water, this process offers a signifieant
operating cost reduction over the conventional weak acid ion exchange systems with
the additional benefit of psrtial silica
removal.
4.
5.
This process concentrates the calcium and
magnesium hardness from the produced water
as calcite and magnesium hydroxide solids
and generates no liquid waste.
Compared to the lime system, this process is
cost competitive, operationaly more reliable
and produces only about 20 , of the solid
sludge volumes. Caustic precipitation
sludge is fluffy and not susceptible to
scaling and plugging as does the lime
process sludge.
ACKNOWLEDGEHENTS
The authors wish to thank Mobil Exploration and
Producing U.S. for permission to publish this paper.
Thanks are due R. B. Reyes, Dow Chemical U.S.A. for
523
A NEW CAUSTIC PROCESS FOR SOFTENING PRODUCED WATER FOR STEAM GENERATION
6
Presented before the 16th Annual Meeting of the
Am. Power Conf., Mar. 24-26, 1954.
13.
Liang, L.S., Wei, I.W. and Siderrpou10s H.G.:
"Simulation of Lime-Soda Softening", J. Envir.
Eng. Div., Oct., 1980, pp. 935-945.
14.
Owen, T.E. and Humenick, M.J.: "The Effect of
Water Treatment Alternatives on Water Demands
for In Situ Production of Bitumen", University
of Wyoming, Dept. of Civil Eng., 1985.
15.
Hull, R.J.: "The Thermos1udge Water Treating and
Steam Generation Process", J. Pet. Tech., Dec.,
1967, pp. 1537-1540.
TABLE 2
TABLE 1
OPERATING RESULTS OF THE BELRIDGE CAUSTIC
SOFTENING PLANT (12/6/88)
TYPICAL BELRIDGE PRODUCED WATER ANALYSIS
CONSTITUENTS
CALCIUM, AS Ca
AS CaC03
MAGNESIUM, AS Mg
AS CaC03
TOTAL HARDNESS, AS CaC03
CONSTITUENTS
PPM
CONCENTRATION, PPM
PRODUCED
WATER
CLARIFIER
OVERFLOW
SOFT .
WATER
103
pH, unit
7.0
9.3
9.3
257
HARDNESS, AS CaC03
407
35.4
0.6
SILICA, AS Si02
202
88
78
257
IRON, AS Fe
0.5
0.1
0.1
514
BARIUM, AS Ba
2
0.5
0.5
MANGANESE, AS Mn
0.2
0.05
0.05
STRONTIUM, AS Sr
3.1
0.1
0.1
63
SODIUM, AS Na
3,900
BICARBONATE, AS HC03
1,362
CHLORIDE, AS Cl
5,300
SULFATE, AS S04
76
SILICA, AS Si02
242
TDS
SP! 19759
... _.----------------_ ..... _---------_._._-_._---_._.--
10,500
pH, unit
7.0
TEMPERATURE, F
170
524
.
SPE 197 C; 9
,
FILTERED WATER
ElCISTINel mONel ACID SOFTENERS
,.,
NEW WEAK ACID SOF'TENERS
REGENERATED WITH .. " HCL AND
.. " NaOH SOLUTIONS
.
TO SOFT WATER TANK
FIGURE 1: SCHEMATIC DIAGRAM or A STRONG ACID rOLLOWED
BY A WEAK ACID SYSTEt.I
I'IIODUCED WATER
II
_
SOUDS
,
SOUII/UGUID
SEPAIIA)'ION
_SUJDOE
...-
UQUIDS
NaOH IN
IlEACTOR
CUIUFIER
•
BACKWASH
IN ~
~
OVERF\.OW
FILTERS
fw:t;ASH
OUT
~
1IlIIOIERA11ON
WEAK ACID
CHtII1CALS IN
IX
IIEGOIEIWITS
OUT
1 SOFT WATER
FIGURE 2:
BELRIDGE WATER PLANT BLOCK DIAGRAM
525