Saturday 26 May 2012

CHARACTERISTICS OF WATER and its uses


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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