CHARACTERISTICS OF
WATER
PHYSICAL PROPERTIES:
*
DENSITY - 1.0 at 4oC
*
Specific Heat - 4.18 Kj/kg at 0oC
*
Latent Heat - Fusion 79 kcal/kg
*
Latent Heat - Vaporization 539 kcal/kg
*
Viscosity 1.797 mPa.s at 0oC
*
Surface Tension 75.60 dynes/cm
*
Osmotic Pressure
p
= DCRT
p : Osmotic Pressure in Pa
DC
: Difference in Concentration in mol/m3
R : Constant of Ideal gases 8.314
J/mol/K
IMPURITIES OF WATER
*
BACTERIA & VIRUSES
*
MICRO-ORGANISMS
*
TURBIDITY
*
COLOUR
*
MINERALIZATION
*
METALLIC
*
DISSOLVED GASES
*
AMMONIA
*
ORGANIC MATTER
*
POLLUTANTS
SOURCES OF WATER FOR INDUSTRIAL APPLICATIONS
*
RIVER
*
SEA
*
PONDS
*
LAKES
*
IRRIGATION CANALS
*
BOREWELLS
*
RECYCLED WATER
*
RESERVOIRS
*
RECYCLED EFFLUENTS
APPLICATIONS OF WATER
IN POWER PLANTS
*
COOLING OF CONDENSATE
*
AUXILIARY COOLING
*
BOILER WATER
*
ASH HANDLING WATER
*
COAL DUST SUPPRESSION WATER
*
WASHING
*
DRINKING
*
SANITATION
*
FIRE WATER
*
SERVICE WATER
*
HVAC SYSTEM
MAKE - UP WATER TREATMENTS
*
CLARIFICATION - ALUM, PEs, PAC
*
FILTERATION
*
ULTRAFILTERATION
*
NANOFILTERATION
*
REVERSE OSMOSIS
*
ACTIVATED CHARCOAL
*
SOFTENING - LIME, ION EXCHANGE
*
ACID TREATMENT
*
INHIBITORS
*
OXYGEN REMOVAL
*
BIOCIDE ADDITION
EFFECT OF CLARIFICATION PROCESS
ON
CORROSION BEHAVIOUR OF COMPONENTS
*
ALUM REDUCES
pH, INCREASES SULPHATES
*
INCREASED
CORROSION
*
PAC - LESS
pH REDUCTION, LESS
CORROSION
*
POSSIBLE
LESS COST
INCREASED ALUM DOSING
*
QUICK RELIEF FROM PROBLEM
*
EXHAUSTING MACHINE AND CHEMICALS
*
INCREASE IN IONIC LOAD ON EXCHANGERS
*
FREQUENT BACKWASH OF FILTERS
*
CARRYOVER OF FINE FLOCS OF Al(OH)3
INTO CLARIFIED
WATER
*
FREQUENT DESLUDGING OPERATIONS
*
DELICATE PLANT OPERATIONS
*
DAMAGE CONCRETE STRUCTURES
*
HIGH Al CAUSE MENTAL DISORDERS
POLYELECTROLYTE DOSING
*
DECREASE ALUM DOSING EVEN BY 50 %
*
WORKS AT VERY LOW DOSAGES
*
REDUCES SLUDGE VOLUME BY 40 - 50 %
*
WORKS IN WIDE pH RANGE
*
LIME ADDITION CAN BE STOPPED
*
NON CORROSIVE
*
NO INCREASE IN IONIC LOAD ON RESINS
*
REDUCTION IN INDIRECT COST
*
NON-TOXICITY TO HUMANS
DETRIMENTAL EFFECT ON RESINS
REVERSE OSMOSIS
*
IT IS A PRESSURE ACTIVATED PROCESS BY WHICH
WATER FROM A HIGHLY
CONCENTRATED SOLUTION
PASSES THROUGH
SEMI-PERMEABLE MEMBRANE
LEAVING THE SOLUTES
BEHIND.
*
IT IS A CROSS-FLOW MEMBRANE PROCESS WHICH
REMOVES ALMOST ALL
ORGANIC COMPOUNDS
AND 90 - 99 % OF ALL
IONS.
*
SOLUTE PASSAGE CHARACTERISTICS ARE
DETERMINED BY
AFFINITY AND SOLUBILITY
PHENOMENA.
*
AN RO UNIT PRECEDING DM FOUND TO REDUCE
PRODUCTION COST OF
WATER BY ABOVE 50 %.
MATERIALS OF MEMBRANE
MATERIAL OF MEMBRANE IS CRUCIAL TO AVOID FOULING :
*
POLYSULPHONATE
*
POLYACRYLATE
*
POLYCARBONATE
*
POLYAMIDE
*
POLYOLEFIN
*
POLYVINYLLIDINE FLUORIDE
ADVANTAGES OF REVERSE OSMOSIS
*
CONTINUOUS OPERATION
*
NO REGENERATION NEEDED
*
CAN HANDLE WIDE RANGE OF TDS (700 - 60,000 ppm)
*
LOW OPERATING COST COMPARED TO DM
*
BULK STORAGE OF CHEMICALS (ACID AND ALKALI)
NOT REQUIRED
*
LESS FLOOR SPACE NEEDED FOR RO PLANT IN
COMPARISON TO DM
PLANT
*
EASY OPERATION AND MAINTENANCE
*
REDUCED EFFLUENT QUANTITY AND TREATMENT COST
*
COST OF TREATED WATER IS ALMOST HALF COMPARED
TO DM WATER.
TOPICS TO BE
COVERED
*
NEED FOR WATER TREATMENT
*
CLARIFLOCULATION PROCESS
*
CHLORINATION
*
ALTERNATIVES TO CHLORINATION WITH SPECIFIC
DISCUSSION ON OZONATION
*
REMOVAL OF COLLOIDAL SILICA AT PRETREATMENT
STAGE
*
REVERSE OSMOSIS
WHY PRETREATMENT
*
INCREASING POLLUTION IN WATER RESOURCES
*
INCREASING STRUCTURES BY REGULATORY BODIES ON
USE OF WATER
RESOURCES
*
FINE QUALITY REQUIREMENTS WITH INDUSTRIAL
GROWTH, IN
PARTICULAR POWER GENERATION
TECHNOLOGY
*
MORE AWARENESS IN PUBLIC
*
ECONOMIC USE OF DEMINERALISERS/MEMBRANES
BOILER FEED WATER
A PERFECT WATER FOR BOILER FEED IS
ONE
WHICH WILL
NOT DEPOSIT ANY SCALE FORMING
SUBSTANCES, WILL NOT CORRODE METAL OF
BOILERS AND WILL NOT RESULT
IN PRIMING OR FOAMING.
COMMON IMPURITIES IN WATER
AND THEIR EFFECTS IF USED FOR BOILER FEED
*
SUSPENDED SOLIDS : PRIMING, FOAMING, SLUDGE OR
SCALE
*
SILICA : DEPOSITION ESPECIALLY ON TURBINE BLADES
*
CARBONATES, BICARBONATES OF CALCIUM AND
MAGNESIUM :
DEPOSITION
*
CHLORIDE AND SULPHATE : SCALE AND CORROSION
*
FREE ACIDS : CORROSION
*
CARBONATE AND BICARBONATE OF SODIUM :
PRIMING, FOAMING, EMBRITTLEMENT
*
OXYGEN, CARBONIC ACID : CORROSION
*
OILS, GREASES : DEPOSITION, FOAMING, PRIMING
*
ORGANIC MATTER : CORROSION, FOAMING, PRIMING,
DEPOSITION
PRE-TREATMENT
TO MAKE WATER FREE FROM ALL IMPURITIES THAT
WILL ADVERSELY EFFECT THE FEED WATER
CHEMISTRY AND FURTHER WATER PURIFICATION
PROCESS.
*
SUSPENDED SOLIDS
*
ORGANIC MATTER
*
COLLOIDAL PARTICLES
*
NON REACTIVE SILICA
*
COLOUR AND ODOUR
*
EXCESS DISINFECTANTS
*
EXCESSIVE DISSOLVED IRON &
MANGANESE
CLARIFLOCULATION
REMOVAL OF SUSPENDED SOLIDS BY
*
COAGULATION/FLOCULATION
*
SETTLING
*
SEPARATION
ACHIEVED THROUGH
*
RETENTION TIME
*
ADDING COAGULANT
*
ADDING COAGULANT AID
*
CREATING SUITABLE pH & ENVIRONMENT FOR
PROPER
COAGULATION/FLOCULATION/SETTLING.
CHEMICALS USED IN WATER
CLARIFLOCULATION
*
ALUM/FERROUS SULPHATE/FERRIC SULPHATE, SODIUM
ALUMINATE, PAC: AS
COAGULANT
*
ACTIVATED SILICA, POLY ELECTROLYTES: COAGULANT
AID
*
LIME, SODIUM CARBONATE: pH ADJUSTMENT
*
BENTONITE : FLOC WEIGHTING AGENT
CHANGES IN WATER QUALITY
BY ADDITION
OF 1 PPM OF PRETREATMENT CHEMICALS
CHANGES IN WATER QUALITY
BY ADDITION OF 1 PPM OF PRETREATMENT CHEMICALS
*
ALUMINIUM SULPHATE : CHANGE IN ALKALINITY
BY
-0.45, SULPHATE BY
0.45
*
FERROUS SULPHATE : CHANGE IN ALKALINITY BY
-0.36,
SULPHATE BY 0.36
*
FERRIC SULPHATE : ALKALINITY BY -0.75, SULPHATE
BY
0.75
*
CHLORINE : ALKALINITY BY -1.4, CHLORIDE BY 1.4
*
HYDRATED LIME : ALKALINITY BY 1.26, HARDNESS BY
1.26
SODA ASH : ALKALINITY BY 0.5
TIPS TO ACHIEVE BETTER
CLARIFLOCULATION
*
KEEP RETENTION TIME AS PER YOUR REQUIREMENT OF
WATER QUANTITY
*
FOR ALUM, THE FLOCULATION pH is 5.5 - 7.5
FOR FERRIC ALUM, pH
5.5 - 7.5
FOR NON FERRIC ALUM,
pH 5.5 - 6.2
*
MAINTAIN PROPER MIXING RATES AT THE CLARIFLOCULATORS.
*
FOR EXTREME LOW TURBID WATERS, USE BENTONITE
CLAY OR FUELLERS EARTH ALONGWITH COAGULANT IF NECESSARY/POSSIBLE GO FOR SLUDGE CIRCULATION CLARIFLOCULATION
IMPROVES WITH TEMPERATURES
*
MAINTAIN PROPER SLUDGE BLANKET
*
WHEREVER POSSIBLE/NECESSARY GO FOR
COAGULANT
AID INSTEAD OF EXCESS ALUM.
*
SODIUM ALUMINATE, WHICH IS HIGHLY ALKALINE CAN
BE USED ALONGWITH ALUM IN COAGULATION OF LOW
pH WATERS
*
USE PROPER QUANTITY OF WATER DISINFECTANTS FOR
BETTER CLARIFLOCULATION
*
GO FOR BETTER INSTRUMENTATION, IF POSSIBLE ON-
LINE FOR CHECKING AND OPTIMISING PRETREATMENT.
*
PURITY OF LIME AND ITS SHELF LIFE ARE CRUCIAL
FOR
PROPER CLARIFLOCULATION
*
DO NOT LOOK PRETREATMENT AND DEMINERALISATION
IN ISOLATION
CHLORINATION PROCESS
*
DESTROYING THE ORGANIC MATTER (BOTH CHEMICAL,
BIOLOGICAL) THROUGH OXIDATION USING CHLORINE.
*
Cl2
+ H2O HClO
+ HCl (5<pH<10)
HClO ClO- + H+
(pH>10)
PROBLEMS WITH CHLORINATION
*
CHLORINE IS A POISONOUS GAS SUPPLIED IN
CYLINDERS/TONNERS
*
CHLORINATED WATERS WITH EXCESS RESIDUAL
CHLORINE ARE
HAZARDOUS TO PLANT AND ANIMAL
LIFE
*
ASSOCIATED WITH PROBLEMS LIKE COPPER TUBE
LEAKS, CORROSION OF
ASSOCIATED PIPINGS, etc.
*
TO REMOVE EXCESS CHLORINE IN TREATED WATER, WE
HAVE TO USE
ACTIVATED CARBON, SODIUM SULPHITE
DOSING RESULTING IN
EXCESS O&M COST
*
MANGANESE, IRON, H2S AND ORGANICS WITH
UNSATURATED LINKAGES
INCREASE CHLORINE DEMAND,
MICROBIOLOGICAL DISINFECTION WILL BE
EFFECTIVE ONLY AFTER REMOVAL OF THESE IONS.
*
EFFECT OF CHLORINE ON VIRUS IS VERY LITTLE
*
PHENOL IN WATERS REACT WITH CHLORINE TO FORM
CHLOROPHENOLS HAVING
BAD ODOR AND TASTE
*
CHLORINATION MAY RESULT IN FORMATION OF TRI
HALO METHANES WHICH
ARE TOXIC
*
CHLORINATION INCREASES IONIC LOAD ON FURTHER
TREATMENT SYSTEMS
ALTERNATIVES TO CHLORINATION
*
BLEACHING POWDER DOSING : SOLID, HAVING LESS
AVAILABLE CHLORINE,
CAUSING MORE SLUDGE AND
EXCESS LOAD ON ION
EXCHANGERS
*
SODIUM HYPOCHLORIDE ADDITION : LIQUID, NOT COST
EFFECTIVE FOR LARGE
QUANTITIES OF WATER
*
BROMINATION : SUITABLE FOR WATERS THAT HAVE pH
7.5 OR GREATER AND
EXCESS AMMONIA. MOST
COMMONLY USED IS
NaBr. EFFECTIVE AT A WIDER pH
RANGE.
*
CHLORINE DIOXIDE ADDITION : SUITABLE WHEN WATER
CONTAINS EXCESS
AMINES, EFFECTIVE IN pH RANGE OF
8 - 11.
OZONATION
*
GETTING IMPORTANCE IN EUROPEAN COUNTRIES AS
ALTERNATIVE TO CHLORINE
*
PREPARED AT DOSING SITE BY SILENT ELECTRIC
DISCHARGE OF DRY AIR
(WITH DEW POINT<-70oC), OR
DRY OXYGEN (WITH DEW
POINT<-60oC)THROUGH SERIES
OF ELECTRODES AND AT
A VOLTAGE OF 17.5 KV.
*
OZONE GENERATORS WITH OUTPUT OF EVEN 10 % BY
WEIGHT ARE AVAILABLE
*
THERMAL DESTRUCTION AND CATALYTIC DESTRUCTION
METHODS ARE
AVAILABLE FOR DESTROYING EXCESS
OZONE GASES
ADVANTAGES OF OZONE
*
REMOVAL OF IRON AND MANGANESE CAN BE
EFFECTIVELY DONE AT
NEUTRAL pH. (WITH
*
CHLORINATION pH ABOVE 9 IS NEEDED.
*
REMOVAL OF COLLOIDS AND ORGANICS IS MORE
EFFECTIVE WITH
OZONE.
*
POLYMERS AND ORGANIC MACRO MOLECULES IN
WATER GET EASILY
BROKEN INTO SMALLER ORGANIC
ACIDS WITH
PROPERTIES OF COAGULATANT AIDS. THIS
REDUCES THE
FLOCULATING AGENT CONSUMPTION
DURING
CLARIFLOCULATION
*
RESPONSE OF OZONE ON ORGANIC CELLS EXCEEDS
CHLORINE BY A FACTOR
OF > 10.
*
CHLORINE ATTACKS ENZYMES THAT EFFECT CELL
MULTIPLICATION WHILE
OZONE RUPTURE CELL WALL
MAKING IT VERY
EFFECTIVE EVEN FOR VIRUS.
*
NO ADDITION OF DISSOLVED SOLIDS AS LOAD TO
FURTHER ION
EXCHANGERS
*
HEALTH HAZARDOUS NATURE COMPOUNDS ARE NOT
FORMED
*
NOT HAZARDOUS IN HANDLING
*
OZONE IS EFFECTIVE AT ALL pH
*
EFFECTIVE IN REDUCING FUNGI GROWTH
*
OPERATING COST IS VERY LESS.
PROBLEMS WITH OZONE
*
CAPITAL
COST IS VERY HIGH
*
GAS IS UNSTABLE
TO BE
PREPARED AT SITE ONLY
*
MAINTENANCE OF RESIDUALS IS NOT POSSIBLE.
CHEMISTRY OF SILICA IN WATER
*
REACTIVE FORM
*
SILICON DI OXIDE DISSOLVED IN WATER RESULTING IN
MONOSILICIC ACID
*
SiO2
+ 2H2O H4SiO4
*
RESPONDS TO STANDARD SILICO MOLYBDATE TEST
SUSPENDED PARTICLE FORM – SAND
*
COLLOIDAL SILICA
*
INSOLUBLE & INSEPARABLE
*
NON-IONIC IN THE FORM OF
*
SILICON POLYMERISED WITH SiO2
*
SILICON LOOSELY BOUND WITH ORGANICS
*
SILICON LOOSELY BOUND WITH INORGANICS
*
(Al2O3/CaO)
*
CHEMICALLY NON - REACTIVE
*
C(SURFACE WATER > WELL WATER)
*
CONC. VARIES WITH LOCATION AND SEASON.
WHAT HAPPENS WHEN COLLOIDAL
SILICA ENTERS BOILER?
*
RESPOND TO ALL CHEMICAL TESTS
*
FORCE PRESSURE REDUCTIONS, GENERATION
LOSSES.
*
SEVERE BLOW DOWNS
AND HEAT LOSSES.
*
LONG START-UPs.
WHAT HAPPENS IF BOILERS ARE
OPERATED WITH HIGH SILICA
*
GETS CARRIED OVER TO THE TURBINE.
*
DEPOSITS ON VARIOUS STAGES OF TURBINE BLADES
DURING STEAM EXPANSION.
*
DEPOSITS ARE HARD TO REMOVE.
*
CAUSE VIBRATIONS IN THE TURBINE.
*
REDUCE OPERATING EFFICIENCY.
*
REQUIRE TURBINE BLADE WASHING/SHUT DOWN
FOR CLEANING.
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