Building Energy Efficient Technologies – ZLD

Mr. Pradeep Rathy

VAPCO Engineers Pvt. Ltd.

• VAPCO Organization

• Why ZLD ?

• Effluent treatment

• Filtration

• Evaporation

• Drawing Schematic For Alchem

Presentation Outline

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

Why ZLD ?

5

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

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

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

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

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

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.

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

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

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 .

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Filtration

30

• Types of Filtration • Microfiltration • How it works?

• Ultrafiltration • How it works?

• Microfiltration vs. Ultrafiltration

Types of Filtration

2 Examples:

1. Cross Flow

2. Dead End Flow

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)

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)

Microfiltration

Separates soluble contaminants remaining within the supernatant

Supernatant may include: Other proteins

Bio-molecules

Un-used growth media

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)

Ultrafiltration

Usually used to further separate any contaminants able to pass through the microfiltration membrane using a pressure gradient

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

Microfiltration vs. Ultrafiltration

Microfiltration:

Proteins act as the permeate

Ultrafiltration

Proteins act as the retentate

Pradeep Rathy

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

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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

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PROCESS DESCRIPTION

• OBJECTIVES

– CONCENTRATE SOLUTE

– RECOVER SOLVENT

– FORM CRYSTALS

• MECHANISM

– HEAT EXCHANGE WITH PHASE CHANGE

– BATCH OR CONTINUOUS

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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

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EVAPORATION DESIGN FACTORS

• HIGH TEMPERATURE REACTIONS

• FOAMING

• SCALING AND CORROSION

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OTHER DESIGN FACTORS

• SPECIFIC HEAT

• HEAT OF CONCENTRATION

• FREEZING POINT VS. CONCENTRATION

• GAS LIBERATION

• TOXICITY

• EXPLOSION HAZARDS

• NEED FOR STERILITY

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EVAPORATION COMPARED WITH DISTILLATION

• SOLUTE IN EVAPORATION IS GENERALLY NON-VOLATILE, RELATIVE TO SOLVENT

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EVAPORATION EQUIPMENT

• SUMMARIZED IN FIGURE 8.2-1

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EVAPORATOR EQUIPMENT

• PLATE & FRAME - CRYSTALLIZERS

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OSLO TYPE CRYSTALLIZERS

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OTHER CRYSTALLIZERS

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THIN FILM EVAPORATORS

• USED FOR VISCOUS AND THERMALLY SENSITIVE MEDIA

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INTEGRATED PLANT

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EVAPORATOR CONFIGURATION

• SINGLE STAGE EVAPORATORS

• HEAT TRANSFER )12.8()( 1 TTUAq s

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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