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A STUDY OF WASTE
WATER EVAPORATION
History
By Ronald G. Fink
Water evaporation was first used by the Phoenicians, Romans
and Chinese to obtain salt from seawater. Large flats
were filled with seawater and natural evaporation from the
sun evaporated the water and left behind dry salt. The first
boiling water evaporators in the U.S. are traced back to
the Onondaga Indians from the Syracuse, NY area in
1654. The Onondagas used iron pots to boil local brine
water down to a dry salt. Syracuse still has the nickname of
"Salt City". Hence, the first U.S. boiling water evaporators.
Without realizing it, they also discovered "severe corrosion"
and "evaporator meltdown", a problem that plagues traditional
boiling water reactors to this day. The combination of
water, salt and iron just doesn't mix well. Boiling water evaporators
have not changed much over the last 350 years. Industrial
wastewater evaporators are using boiling water
technology and are still plagued with corrosion problems.
Many applications utilizing evaporators assume and plan
for a less than one-year life. Corrosion and meltdown are
anticipated and accounted for. A new technology could
change the history of evaporators. It is a total novel approach:
no steel vessel, no pot of boiling water, no slurry
concentrate to dispose of, no corrosion, and no meltdown.
Definitions:
Evaporation
The process in which a liquid dissipates or emits vapor,
fumes or invisible minute particles into the air.
Distillation
The process of boiling a liquid then condensing and collecting
the vapor; used to purify liquids and to separate liquid
mixtures.
BTU's (British Thermal Unit)
Amount of Energy required to raise a 1 lb. mass of water 1°F
@ 1 atmosphere.
VOC's (Volatile Organic Compound)
Organic compound, which readily dissipates into the air at
room temperature, i.e., benzene, gasoline.
TDS (Total Dissolved Solids)
The amount of ionic matter dissolved in a fluid that can be
measured by electric current. Dissolved solids in water can
be deceiving. For example: seawater contains 35,000 ppm
of salt, yet it will appear crystal clear. 35,000 ppm is equivalent
to 3.5% of contaminants.
Thermal Oxidation
High temperature breakdown of contaminants to carbon
dioxide and water.
TSS (Total Suspended Solids)
Substances suspended in a fluid large enough to be visible
by the human eye and small enough to be kept in suspension
by the movement of the fluid molecules.
Condenser
An apparatus in which gas or vapor is condensed to liquid
form.
Slurry Concentrate
Boiling water evaporators leave a concentrated liquid slurry
Wastewater Evaporation From The Ancient
Phoenicians To Today’s Latest Technology
of the contaminants consisting of dissolved and suspended
solids.
Efficiency:
Boiling water evaporation efficiency is based on some basic
laws of physics:
•It takes 8,092 BTU's to evaporate one gallon of water
•Natural gas has a heating value of 1,000 BTU's per cubic
foot (1 Therm=100,000 BTU's)
•Approximate cost of natural gas is $0.50 per Therm
Based on this very basic formula, it should cost about $.04
of fuel to evaporate one gallon of water under ideal conditions.
Lab Analysis:
It is very important to completely understand the waste
stream so the proper technology, system and materials can
be utilized. The waste streams need to be analyzed for pH,
heavy metals, chlorides, dissolved solids and suspended
solids. Chlorides and pH will affect the corrosion rate of boiling
water evaporators, heavy metals and VOC's could affect
emissions, and dissolved and suspended solids will affect
pre-treatment and clean-out schedules.
Solids:
Both dissolved and suspended solids
can create numerous problems for a boiling
water evaporator:
•First, dissolved salts will raise the boiling
temperature. The higher the salt content,
the more heat and energy required to
bring the waste stream to a boil.
Dry Ash Residue from
Phosphatizing Plant
Dry Ash Residue from
Heavy Equipment Dealer
Dry Ash Residue from
Salt Truck cleaning
•Second, suspended solids tend to settle
to the tank bottom, creating a barrier factor
that insulates the heat source from the
wastewater, causing overheating of the
steel vessel and creating carbide precipitation
or carbon depletion of the steel. This
results in a general weakening and eventual
failure or meltdown.
•Third, dissolved and suspended solid volume.
Clean out schedules will be dictated
by the volume of solids in the waste
stream. A waste stream containing 50,000
ppm of suspended and dissolved solids is
equivalent to 5% solids. One thousand
gallons of wastewater weighs approximately
8,400 lbs. If 5% is solids, that is the equivalent of 420
lbs of solids. Even using advanced Thermo Oxidation Dry
Chamber Flash Evaporation that will process the solids to a
completely dry ash, you will have a pile of 420 lbs of solids
as a dry ash. This is usually easily disposed of through normal
waste channels. With a boiling water evaporator, these
solids must be removed as slurry, usually three parts of
water to one part of solids, to create a flowable slurry mixture.
This slurry contains all the contaminants in the waste

stream and usually must be handled by a licensed hauler to
a licensed waste processer.
Traditional Wastewater
Evaporation Methods:
Natural Evaporation Ponds rely on
the combination of solar heat and
wind to naturally evaporate water.
This method requires a great deal
of area, is slow and is subject to
the weather.
Concerns
•Very slow
•Takes up a lot of space
•Requires large land mass and pond liner
•Odor problems
Forced Air Evaporators utilize blowers to force air in a
counter current to a spray of water pumped to the top of a
column and free falling downward. The evaporation rate is
largely dependent on the water temperature
and the dew point. This method is cost effective
and highly efficient when the waste stream
to be evaporated is preheated by another
process and the wastewater does not contain
volatile compounds (VOC's) that would be
readily transferred to the air, and thereby create
air pollution. Not recommended for water
high in dissolved or suspended solids as they
will deposit on the internals and block the water
and airflow. This design has no method of removing dried
solids. Cost estimates depend on the temperature of the
waste stream.
Concerns
•Efficiency is dependent on the relative humidity and water
temperature
•Air permitting may be required. VOC's will create air pollution
Boiler Blow-Off Evaporators can evaporate
large volumes (2-4 gpm) at a low cost and are
effective on pretreated waste streams. They
have no method of collecting or removing suspended
solids. Most of the dissolved solids
are vaporized in the steam at 212°F and
blown off into the atmosphere. VOC will
be vaporized and will create air pollution.
Therefore, all VOC's and solids must be
removed from this system. Efficiency is 70%-85%.
Concerns
•VOC's will vaporize and create air pollution
•Not suitable for distillation or water reuse
TRADITIONAL BOILING WATER EVAPORATORS
(GENERAL)
A. The fuel cost of bringing the entire wastewater reservoir
(50-300 gal.) up to boiling (usually over 212°F).
B. The higher the salts or chloride in the dissolved solids, the
higher the temperature must go before boiling occurs; the
higher the TDS, the higher the temperature
C. Suspended solids are usually heavier than water and
tend to settle, forming an insulation barrier, which tends to
overheat the steel vessel while depriving the wastewater of
the heat. Excessive heat builds up in the vessel bottom resulting
in carbide precipitation, which is the carbon scale
seen on overheated steel. This results in loss of strength,
buckling, and eventually failure of the tank bottom, fire tube
or melt down.
D. The ability to transfer as much heat to the water as possible.
Systems that vent flue gas are generally less efficient
than systems that utilize the flue gases for additional heating
of the wastewater.
The key to fuel efficiency is to maximize the BTU value
of the heat source. A poor efficiency system can still
have good fuel efficiency if the waste heat is used for
another source, such as water or air heating. A safety
concern with overuse of waste heat is the cooling of the
waste heat gases. If they are cooled to the point they no
longer vent properly, a back up of flue gases can occur. A
flue gas exhaust fan can be used to alleviate this problem.
Basic Boiling Water Tank Evaporators basically
heat the water to its boiling point 212°F and exhaust
the steam via an exhaust pipe. This method has no
way to remove dried solids other than baking the tank
contents down to a cake, which insulates the
heat and holds it into the steel, causing early
tank failure. Efficiency is usually 65%-75%
depending on design. With the addition of a
condenser you can distill the water for reuse.
Concerns
•VOC's vaporize to atmosphere as air pollution
•Acids and salts will attack the steel
•Cost of energy to heat the entire tank of wastewater to over
212°F
•Cost of extra energy to bring high salt content water to a
boil
•Dissolved solids and suspended solids are periodically
drained off in a slurry solution and this highly
concentrated liquid waste must be disposed of
•Cost of extra energy to overcome the insulation caused by
suspended solids build up on vessel bottom
•Risk of system running dry resulting in melt down
A
B
C
D

Steam Tube with Water Exhaust
Boiling Water Evaporator is basically
the same concept as a Boiling
Water Evaporator. However, the hot
exhaust gases are bubbled through
the wastewater to improve heat
transfer efficiency. VOC's will be vaporized
and air pollution will result.
Dissolved and suspended solids removed
periodically by draining a
slurry. Efficiency is 75%-85%.
Concerns
•VOC's will be exhausted as air pollution
•Acids and salts will attack the steel, shorten vessel and
steam tube life
•Cost of extra energy to bring high salt content water to a
boil
•Dissolved solids and suspended solids are periodically
drained off in a slurry solution and this highly concentrated
liquid waste must be disposed of
•Cost of energy to bring the entire tank of wastewater to over
212ºF
•Cost of extra energy to overcome the insulation caused by
suspended solids build up on vessel bottom
•Risk of system running dry resulting in melt down
Heat Exchanger Boiling Water Evaporators heat a coil
filled with a high temperature oil, which is pumped to another
coil inside a tank containing the waste. The advantage of
this system is that the tank can be
made of non-corrosive polypropylene
with no direct flame contact.
The vapor can be distilled, efficiency
is 70%-80%.
Concerns
•VOC's will be exhausted as air
pollution
•Coil failure due to corrosion
•Acids and salts will attack the steel, shorten coil life
•Cost of extra energy to bring high salt content water to a
boil
•Dissolved solids and suspended solids are periodically
drained off in a slurry solution and this highly concentrated
liquid waste must be disposed of.
•Cost to bring the entire tank of wastewater to over 212ºF
Steam Tube Boiling Water Evaporators utilize a hot tube
as a heat source. The flame is directed inside a steel tube
thereby saving the tank from flame impingement and early
failure. The tube will fail, however, it is easily replaceable
and considerably less expensive than the tank. Efficiency is
70%-80%. The water is heated to
212ºF. The vapor can be distilled
and reused.
Concerns
•VOC will be vaporized and will
create air pollution
•Acids and salts will attack steel
vessel
•Low tube life expectancy
•Cost of extra energy to bring high salt content water to a
boil
•Cost of energy to heat the entire tank of wastewater to over
212ºF
•Dissolved solids and suspended solids are periodically
drained off in a slurry solution and this highly concentrated
liquid waste must be disposed of
•Cost of extra energy to overcome the insulation caused by
suspended solids build up on vessel bottom
•Risk of system running dry resulting in melt down
New Technology:
Thermo Oxidizer - Flash Evaporation utilizes a ceramic
chamber to flash evaporate atomized wastewater in a dry
chamber. The atomized wastewater is heated in a chamber
of hot gases to 800ºF - 1400ºF resulting in a complete flash
evaporation of the water, leaving behind all the contaminants
as a dry ash. All volatiles in the wastewater are burned and
actually add BTU value. The heat source can be oil, gas,
diesel, or used oil. A secondary chamber thermally oxidizes
the flue gases to eliminate any air pollution.
Thermal
Oxidation
Chamber
Ceramic
Dry Chamber
Flash
Evaporator
Thermally Oxidized
Combustion Gases
And Water Vapor
Hot Gases
Wastewater
Atomizer
Dry Ash Containing
Contaminants
Considerations
•No steel for acids and salts to corrode
•No steel vessel to replace
•No cost associated with bringing high salt content water
to a boil
•No cost associated with energy needed to overcome
slurry solution and suspended solids insulating heat
source from the water
•No cost associated with disposal of concentrated slurry
•No VOC air pollution worries
•No cost of energy to heat an entire vessel of wastewater
to 212ºF
•No risk of system running dry, resulting in meltdown
•No cost to haul off waste oil if waste oil burner is utilized
Future Technology: The future may be in microwave
wastewater evaporation technology!
Ron Fink President, CEO, Founder of RGF Environmental Group, Inc.
Mr. Fink holds a BSME and has been active in Nuclear Weapon detection
for the DIA and Nuclear Power Industry. He holds numerous patents and
authored over 70 articles.
RGF Environmental Group, Inc. founded in 1985 manufactures over 500
products involving Advanced Oxidation Technology.