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Building Energy Efficient Technologies – ZLD
Mr. Pradeep Rathy
VAPCO Engineers Pvt. Ltd.
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• VAPCO Organization
• Why ZLD ?
• Effluent treatment
• Filtration
• Evaporation
• Drawing Schematic For Alchem
Presentation Outline
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Environment Systems
Process Equipment
EPC Division Bio Nutrients
Ethanol Plants Alcohol Plants
Starch Plants
Solvents Plants
Mechanical Separation
Process Equipment
Dairy Systems
Bio Effluent
Treatment
Filtration
Evaporation
ZLD
Enzymes
Yeast-Pro
VAPCO AT A GLANCE
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Wastewater Treatment Basis
• Disposal (under pollution Control Board Norms)
• Water Scarcity (need for recycle)
• Zero Discharge Norms (Government Regulation)
• Common effluent treatment Plants
• Process Products Recovery
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Study of wastewater Generation Areas
• Metal finishing/Automobile/steel mills /electroplating • Dying /Bleaching processes/tanneries/laundry-Textile
Industry • Acid-Alkali treatment- chemical industry/recovery of
chemical • Paper & pulp Industry, Leather Industry • Oily waste water- automobile/refineries • Pharmaceutical & food industry • Conventional STP • Thermal power/rubber industry/Fertilizers
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Effluent parameters to be analyzed
Parameters
mg/lit
as CaCO3
Color
Turbidity
TSS
TDS
Odor
Temp
pH
Oil & grease
Heavy metals
Free & emulsified oil
Phenols
Cyanides
Hardness
Alkalinity
Kjeldahl Nitrogen
Heavy metals
COD
BOD
Phosphates
Silica
Chlorides
Sulphate
Sodium
Magnesium
Calcium
Chromium
chlorine
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Heavy Metal Treatment
Effluent characteristics
Parameters
Unit
Variation limits
Ph
-
Acidic
Color
Hazen
Yellow – red depending on
metallic compounds
Zn
Mg/l
Variable
Hexavalent chromium
Mg/l
Variable
Chromium total
Mg/l
Variable
Cyanide
Mg/l
Variable
Copper
Mg/l
Variable
Nickel
Mg/l
Variable
Chlorides
Mg/l
Variable
Fluorides
Mg/l
Variable
Phosphates
Mg/l
Variable
COD
Mg/l
< 250 /100
BOD
Mg/l
< 25
TSS
Mg/l
Variable
TDS
Mg/l
Variable
Cadmium
Mg/l
Variable
Toxic chemical
Mg/l
Variable
Iron
Mg/l
Variable
Ammonical nitrogen
Mg/l
Variable
Oil & grease
Mg/l
< 25
Conductivity
Micro Siemen
Variable
Turbidity
NTU
Variable
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METAL TREATMENT BY HYDROXIDE PRECIPITATION Metals + Hydroxides metal Hydroxides. COMMON METHOD OF WASTEWATER TREATMENT FOR METAL REMOVAL - Metal hydroxide
Polymer Metal hydroxide trapped in polymer floc
Settled metal hydroxide
Inlet
Trapped solids
Filter media (sand)
Effluent
Sludge for dewatering
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Plating wastewater - Chromium reduction
• Wastewater containing hazardous hexavalent chromium is treated with chemical reduction process. Ph is reduced to 3.0 or less and Sulfur dioxide or SMBS or Sodium bisulfite or ferrous sulfate is added to reduce hexavalent chromium to trivalent form.
• A retention time of 45 minutes should be maintained to ensure adequate mixing and reaction with SO2 or other chemicals. This water then passed for next process of metal removal.
Hexavalent Chromium
Mixing tank or reactor
PH adjustment to 2-3 by adding Acid
SMBS solution
Trivalent Chromium.
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Plating wastewater –cyanide oxidation
• Electroplating industry using cyanide in process can treat this before metal treatment by alkaline oxidation
• Chlorine and caustic is added for oxidation of cyanide to cyanates.
• In next tank again chlorine is added to convert cyanate to CO2 & nitrogen with Detention time of 45 minutes
Cyanide
Sodium Hypo chlorite
Caustic for pH 9.5 to 10.0
Mixing tank 1 Mixing tank 2
Sodium Hypo chlorite
Caustic for pH 8.0
Cyanates Effluent for metal treatment
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Metal treatment
Simply adjusting pH to 8.6 can effectively precipitate all the metals. Since all metals display similar effect, it is clear that pH adjustment is critical in case
of metal removal.
Metal solubility are on the basis of theoretical wastewater, but in actual number varies by presence of cyanide and ammonia in wastewater, which can inhibit the removal of heavy metal from wastewater. So in general pH
should be adjusted to 9.0
Wastewater collection tank
Mixing tank
PH adjustment to 9.0 by adding caustic.
Polymer addition
Sedimentation
Dewatering of sludge
Backwash water containing heavy metals
Wastewater
Sludge
Discharge
Adjust pH to discharge
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Dosage calculation after Jar Test
• Chemical dosages- ml of chemical X conc. X 10 ppm dosage
liter of sample
• Kg of chemical/day = ppm dosage x flow (m3/day)
Volume of solution Liters /day = kg of chemical / % of solution
• Per hrs. dosage(liters/hr) = solution Liters/ No. of hrs. dosage required
• Pump capacity (LPH) = per hrs dosage + 10 % extra capacity .
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Sludge Collection tank
Filter Press
Treated water
SMBS Acid
Treated water storage tank
M G F
A C F
NaOCl dosing
Polymer & lime dosing in SMFT
Lamella clarifier
AUTOMOBILE INDUSTRY EFFLUENT TREATMENT
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Textile Industry Effluent
Parameters
Unit
Variation limits
Ph
-
Highly alkaline
Color
Hazen
Variable
Zn
Mg/l
less
Chlorides
Mg/l
High
Sodium
Mg/l
High
Phosphates
Mg/l
High
COD
Mg/l
500-10000
BOD
Mg/l
High
TSS
Mg/l
Variable
TDS
Mg/l
Variable
Sulphide
Mg/l
Variables
Toxic chemical
Mg/l
Less
Iron
Mg/l
Less
Ammonical nitrogen
Mg/l
Nil
Oil & grease
Mg/l
Nil
Conductivity
Micro Siemen
Variable
Turbidity
NTU
Variable
Temperature
Degree
50- 150
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Treatment of effluent
• Temperature reduction
• Color reduction
• Suspended solids reduction
• Organic matter reduction
• Sulphide , inorganic less harmful compound reduction
Raw Effluent
Aeration Tank
Sludge sump
AIR BLOWER
FeSO4 LIME POLYMERS
HRSCC
SECONDARY CLARIFIER
Collection Tank
AIR BLOWER
Discharge
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Suspended solids & Inorganic compound reduction
• Dosing chemicals- Alum , Lime/ Caustic for pH –7-8,Ferrous and ferric salts.
• Polymer anionic dosages for floc formation and fast settlement
• Fluoride & phosphate removal-
• Alum ( Ferrous )dosage with ph 7- 9.0- molar ratio varies 2: 1 to 12.7 : 1
• Lime + CaCl2 – pH 8-8.5
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Chemical Industry
• Neutralization
• Alkalinity reduction
• Suspended solids reduction
• Silica reduction
• Metal and organic matter reduction
• TDS reduction
• Inorganic compound reduction
Parameters
Unit
Variation limits
Ph
-
Variable
Color
Hazen
Variable depending on compounds
Zn
Mg/l
Variable
Chlorides
Mg/l
High
Sodium
Mg/l
High
Phosphates
Mg/l
High
COD
Mg/l
Variables
BOD
Mg/l
Variable
TSS
Mg/l
variable
TDS
Mg/l
Variable
Sulphide
Mg/l
high
Toxic chemical
Mg/l
Variables
Iron
Mg/l
Variable
Ammonical nitrogen
Mg/l
Nil
Oil & grease
Mg/l
Nil
Conductivity
Micro Siemen
Variable
Turbidity
NTU
Variable
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Alkalinity & Silica Reduction
• Data required- alkaline hardness, EMA, anions, alkalinity, silica.
• Composition of compounds according to nature and its availability
• Requirement of lime , soda ash & dolomite
• Dosage required and pump capacity
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Paper and Pulp Industry
• Temperature reduction
• Suspended solids reduction
• Color reduction
• COD reduction
Parameters
Unit
Variation limits
Ph
-
Variable
Color
Hazen
Variable depending on compounds
COD
Mg/l
Variables
BOD
Mg/l
Variable
TSS
Mg/l
Very high
TDS
Mg/l
Variable
Conductivity
Micro Siemen
Variable
Turbidity
NTU
Variable
temperature
degree
High
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Treatment scheme
Sludge Collection tank
Filter Press
Treated water
M G F
A C F
Final treated water tank
NaOCl Dosage
Equalization Tank
Lime dosing T3
T2
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Oily Wastewater treatment
• Floating oil removal
• Emulsified oil removal
• Suspended solid removal
• BOD removal
Reverse Osmosis
Equalisation Tank
Feed Pump
Cleaning & Process tank
UF feed pump and UF
Filter Paper Oil Skimmer
Rotameter
RO PRODUCT TO STORAGE TANK. (May be used for gardening, toilet flushing, car washing etc.)
RO REJECT TO SOLAR POND
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Existing Waste water Collection tank
Oil Skimmer
DAF
Primary Clarifier
Equalization Tank
Aeration Tank
Secondary Clarifier
Filter feed Sump
Final Treated Water Tank
RCC
Sludge Sump
CONVENTIONAL OILY WASTEWATER TREATMENT
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Food Industry & pharmaceutical
• There should not be any toxic or antibiotic compounds in effluent , otherwise it has to be disinfected before treatment
• Reduction BOD & COD
• Reduction in SS
• Reduction in oil & grease
• Neutralization
Parameters
Unit
Variation limits
Ph
-
variabl
COD
Mg/l
Variables & high
BOD
Mg/l
Variable & high
TSS
Mg/l
Variable & high
TDS
Mg/l
Variable
Oil & grease
Mg/l
Variable
Phenols
Mg/l
Variable
Acid & alkali
Mg/l
Variable & high
Toxic chemical
variables
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Treatment Scheme
Oil skimmer
Aeration Tank SECONDARY CLARIFIER
AIR BLOWER
Sludge sump
AIR BLOWER
Primary settlment
Filter press
M G F
A C F
Treated water
NaOCl Dosage
Discharge
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Sewage treatment plant -Conventional
Treated water
M G F
A C F Settling
Tank
Final Treated water.
Sludge Collection tank / SDB
Filter Press
Aeration tank NaOCl Dosage
Parameters
Unit
Variation limits
Ph
-
neutral
COD
Mg/l
< 650
BOD
Mg/l
< 350
TSS
Mg/l
<100
Oil & grease
Mg/l
< 20
Toxic chemical
Nil
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Equalization tank
Primary treatment
Collection tank Aeration tank Secondary treatment MGF
ACF
Treated W Tank
Solid separation
Solid Incineration
Basket strainers
UF Collection tank CF RO
Solar ponds / Evaporators
Solids
UV/UF
Sludge digestion
- discharge
- Recycle - Zero Discharge - process reuse
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Filtration
30
• Types of Filtration • Microfiltration • How it works?
• Ultrafiltration • How it works?
• Microfiltration vs. Ultrafiltration
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Types of Filtration
2 Examples:
1. Cross Flow
2. Dead End Flow
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Type 1: Cross Filtration
Flow parallel to membrane surface
Does not cause buildup, therefore does not suffer from reduced flow overtime
F = feed; M = membrane; P = permeate;
R = retentate (components that do NOT pass through the membrane)
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Type 2: Dead End Flow
Flow perpendicular to membrane surface
Causes build up of filter cake on membrane
F = feed; M = membrane; P = permeate (components that pass through membrane)
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Microfiltration
Separates soluble contaminants remaining within the supernatant
Supernatant may include: Other proteins
Bio-molecules
Un-used growth media
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How does Microfiltration work?
Pressure driven process
Separates: Components in a solution or
suspension based on molecular size
Particles size range:
10mm (starches) to aprx. 0.04mm (DNA, Viruses, and globular proteins)
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Ultrafiltration
Usually used to further separate any contaminants able to pass through the microfiltration membrane using a pressure gradient
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How does Ultrafiltration work?
Separates:
Particle size range: 0.1mm to 0.001mm
Usually based on molecular weight
Typical range: 200 to 300,000 g/mole
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Microfiltration vs. Ultrafiltration
Microfiltration:
Proteins act as the permeate
Ultrafiltration
Proteins act as the retentate
Pradeep Rathy
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Microfiltration vs. Ultrafiltration
Microfiltration: Separates larger particles
For example-
Colloids
Fat globules
Cells
Located upstream to reduce load and fouling capacity on ultrafiltration membrane downstream
Ultrafiltration Separates smaller particles
For example-
Macromolecules
However, processes are basically identical
Pradeep Rathy
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EVAPORATION
Feed water Vaporised
tank feed water
Tank Volume out to
0.92 litre/cm atmosphere
Overflow
to drain Water
main
Steam in
Constant
level Sight
device glass
Steam
trap
Condensate
out
Condensate
tank
Tank Volume
1.31 litre/cm
Figure 1. The Evaporator
Pradeep Rathy
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PROCESS DESCRIPTION
• OBJECTIVES
– CONCENTRATE SOLUTE
– RECOVER SOLVENT
– FORM CRYSTALS
• MECHANISM
– HEAT EXCHANGE WITH PHASE CHANGE
– BATCH OR CONTINUOUS
Pradeep Rathy
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DESIGN FACTORS
• SOLUTION FLUID VISCOSITY
– HEAT TRANSFER COEFFICIENTS
– PRESSURE DROPS
• SOLUTE SOLUBILITY
– SUPERSATURATED CONDITION
• MATERIALS (BIO-MATERIALS) MAY BE HEAT SENSITIVE
– DEGRADATION TEMPERATURE • ELEVATED PRESSURE
• BOILING POINT ELEVATION
Pradeep Rathy
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EVAPORATION DESIGN FACTORS
• HIGH TEMPERATURE REACTIONS
• FOAMING
• SCALING AND CORROSION
Pradeep Rathy
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OTHER DESIGN FACTORS
• SPECIFIC HEAT
• HEAT OF CONCENTRATION
• FREEZING POINT VS. CONCENTRATION
• GAS LIBERATION
• TOXICITY
• EXPLOSION HAZARDS
• NEED FOR STERILITY
Pradeep Rathy
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EVAPORATION COMPARED WITH DISTILLATION
• SOLUTE IN EVAPORATION IS GENERALLY NON-VOLATILE, RELATIVE TO SOLVENT
Pradeep Rathy
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EVAPORATION EQUIPMENT
• SUMMARIZED IN FIGURE 8.2-1
Pradeep Rathy
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EVAPORATOR EQUIPMENT
• PLATE & FRAME - CRYSTALLIZERS
Pradeep Rathy
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OSLO TYPE CRYSTALLIZERS
Pradeep Rathy
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OTHER CRYSTALLIZERS
Pradeep Rathy
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THIN FILM EVAPORATORS
• USED FOR VISCOUS AND THERMALLY SENSITIVE MEDIA
Pradeep Rathy
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EVAPORATOR CONFIGURATION
• SINGLE STAGE EVAPORATORS
• HEAT TRANSFER )12.8()( 1 TTUAq s
Pradeep Rathy
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MULTI-EFFECT EVAPORATORS
• STEAM FROM ONE EFFECT IS THE HEAT SOURCE FOR THE SECOND EFFECT
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MULTI-EFFECT COUNTERFLOW CONFIGURATION
• FIGURE 8.2-3 FEED-FOREWARD – PRESSURE IS
REDUCED IN EACH STAGE
– FEED & STEAM ENTER THE SAME STAGE IN THE TRAIN
• FIGURE 8.2-4 – FEED-BACKWARD – PRESSURE IS
INCREASED IN EACH STAGE
– FEED & STEAM ENTER FROM OPPOSITE ENDS OF THE TRAIN
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PARALLEL FEED
• SOLAR EVAPORATION SYSTEM
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EVAPORATOR HEAT TRANSFER
• OVERALL HEAT TRANSFER COEFFICIENTS – SEE TABLE 8.3-1
• NEED TO KNOW RANGE TO REVIEW DESIGNS
• PLATE & FRAME CAN HAVE HIGHER COEFFICIENTS THAN SHELL & TUBE.
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CHANGE OF PHASE HEAT TRANSFER
• SECTION 4.8 FOR SUMMARY OF MECHANISMS
• FIGURE 4.8-1
– CONVECTION
– NUCLEATE
– TRANSITION
– FILM
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HEAT TRANSFER COEFFICIENTS
• BASED ON ΔT
NUCLEATE BOILING
CONFIGURATION EQUATION RANGE REFERENCE
HORIZONTAL 3/1
2)(1043 KT
Km
Wh
q/A, kW/m2 < 16 (4.8-1)
HORIZONTAL 3
2)(56.5 KT
Km
Wh
16 < q/A, kW/m2
< 240 (4.8-2)
VERTICAL 7/1
2)(537 KT
Km
Wh
q/A, kW/m2 < 3 (4.8-3)
VERTICAL 3
2)(95.7 KT
Km
Wh
3 < q/A, kW/m2 < 63
(4.8-4)
FORCED CONVECTION IN TUBES
15513
2)(55.2
sysP
eKTKm
Wh
Psys = kPa (4.8-5)
FILM BOILING
HORIZONTAL TUBE
4/13
2
4.0()(62.0
TD
Tchgk
Km
Wh
vtube
Pvvapvlvv
m
(4.8-6)
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SINGLE STAGE MODELS
• MASS AND ENERGY BALANCES
STEAMCONDENSATE
FEED SOLUTIONPRODUCT VAPOR
PRODUCT LIQUID
F, TF,xF,hF V,TBP,yV,HV
L, TBP,xL,hL
S,TS,HS
C,TC,hC
CSVLF
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MASS & ENERGY BALANCES
• COMPONENT MASS BALANCE
• SYSTEM HEAT BALANCE
VAPORINSOLUTENOLxFx LF
)84.8(
)74.8(
)64.8(
Sq
HVHLhSFh
ShVHLhSHFh
vapVLF
SVLSF
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OTHER DESIGN FACTORS
• LOWER EVAPORATION PRESSURE
– WILL INCREASE EFFECTIVE ΔT
– LOWER EVAPORATOR AREA
– INCREASED SOLVENT CONDENSER AREA
– HIGHER VELOCITIES MIST ELIMINATION
• BOILING POINT ELEVATION
– REDUCES EFFECTIVE ΔT WITH INCREASING CONCENTRATION
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BOILING POINT ELEVATION
• DÜRING’S RULE – SOLUTION BOILING POINT IS LINEARLY RELATED TO PURE WATER NBPt AT PSYS
• FIGURE 8.4-2
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ENTHALPY-CONCENTRATION
• HEAT OF MIXING EFFECTS
• NON-IDEAL
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104 Pradeep Rathy