Engineering Excellence Awards 2013

“Reverse Osmosis in Aluminium Smelter for Effluent Treatment”

Vedanta Aluminium Limited, Jharsuguda

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Domestic Aluminium Smelter Scenario

Next 5 years Forecast

Production Projections:

Aluminium demand remains healthy

As per the current greenfield projects, Aluminium Production is set to be doubled by next 5 years

Water consumption rate is approximately 1m3/MT of Al produced. Efficient recycling techniques required

The raw effluent coming from the plant contains up to 50 ppm fluorideVedanta Plant1

Vedanta Plant2

Mahan Aluminium

Renukoot (Hindalco)

Muri (Hindalco)

Hirakud (Hindalco)

Lapanga (Hindalco)

Nalco

Balco

Balco (expansion)

020

040

060

080

010

0012

00

500

1100

359

400

359

213

359

460

245

325

Production in KTPA

Production in KTPA

2

In Production – 1918 KTPA

Greenfield – 2402 KTPA

Raw Material +

Power

Raw Material

+

Power

Raw Effluent

Raw Material

Alumina: Al2O3

Carbon Anode: C

Cryolite: Na3AlF6

Aluminium Fluoride: AlF3

Smelter Process Scenario

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Major Objectives of Effluent Treatment

Treating effluents to fresh water levels. Hence Conservation of water

Zero discharge of rejected effluents to ambient water

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Nalgonda Technique Adsorption Technique Ion Exchange Method

Reverse Osmosis Distillation Process

Types of Effluent Treatment Techniques

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Fluoride removal efficiency > 99%

Membrane Separation Technology without using Chemicals

Less area for operation

Removes other biological impurities

RO

Why Reverse Osmosis ??

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Process flow diagram of Effluent Treatment Plant

50

50

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Preliminary Treatment

Rated Capacity: 100m3/hour x 3

The effluent recycling plant is designed to treat 250 m3/day of effluent.

The rejects of the ETP are disposed of to a sludge drying bed by back flush in the system. The sludge is further disposed off in SLF area.

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9

Sand Filtration and Iron Removal

Pressure Sand Filter

Rate : 50 m3/hour

It is used to remove the suspended solids in the effluent

Iron Removal Filter

Rate : 50 m3/hour

It is used to remove the iron particles in the effluent

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Ultrafiltration & Double Stage RO

Ultra Filtration

Rate: 50 m3/hour

The mesh size of RO membrane is 0.01 microns

UF consists of hydranautics membrane fitted with PLC based system for automatic service.

The main function of this system is to reduce BOD, COD, biological impurities, suspended solids and oil from the effluent.

Treatment by Reverse Osmosis

Principle of Reverse Osmosis

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Double Stage RO

Reverse Osmosis

Rate: 50 m3/hour

The mesh size of RO membrane is 0.0001 microns

RO typically operates at 10-12 bar for reverse high pressure.

The membranes of RO are semi-permeable.

It consists of double stage membrane to reduce dissolve impurities and fluoride from the effluent.

RO Membranes

RO membranes are cellulose acetate, aromatic polyamide and thin film composite (TFC). In general all TFC membranes are placed in series in a pressure vessel

Cellulose acetate is resistant to small concentration of chlorine and is therefore kept free from bacteria and its subsequent re-growth.

Aromatic polyamide cannot tolerate chlorine but is resistant to bacteria. It is useful in treating over a wider pH range (4-11) of effluent.

Maximum Operating Temperature –

30 – 35 oC

Life Span – 3 Years

Sand & Iron Removal Ultra Filtration Reverse Osmosis

TSS < 1255ppm

pH 7.3 – 8.1

BOD < 30 ppm

COD < 100 ppm

O & G < 35 ppm

TDS < 500 ppm

Fluoride < 50 ppm

Iron < 2.4 ppm

Hardness < 120 ppm

TSS < 5.0 ppm

pH 7.0 – 7.5

BOD < 20 ppm

COD < 90 ppm

O & G < 5 ppm

TDS < 500 ppm

Fluoride < 7 ppm

Iron < 0.3 ppm

Hardness < 120 ppm

TSS < 1.0 ppm

pH 7.0 – 7.5

BOD < 5 ppm

COD < 30 ppm

O & G < 2 ppm

TDS < 500 ppm

Fluoride < 5 ppm

Iron < 0.2 ppm

Hardness < 120 ppm

TSS < 0.1 ppm

pH 7.0 – 7.5

BOD < 5 ppm

COD < 20 ppm

O & G < BDL

TDS < 50 ppm

Fluoride < 1ppm

Iron < 0.1 ppm

Hardness < 5 ppm

Effluent

Raw Effluent ETP + PSF + IRF After Ultra Filtration After Reverse Osmosis

Treated Effluent Quality

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2008-09 2009-10 2010-11 2011-12 2012-13 2013-14 (YTD)0

1

2

3

0

100000

200000

300000

400000

500000

600000

700000

0

90553

410563

598907 584141

303833

2.64

2.13

1.74

1.231.3

0.85

Recycled Water SWC

Water Consumption Scenario

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Handling of RO Rejects – Solar Pond

Specifications of Solar Pond

Surface Area – 2000 m2

Tank Depth – 2 meters

Free Board – 0.25 meters

Evaporation rate – 5m3/hour

Solar pond is used for forced evaporation of rejected RO effluents

It consist of rectangular concrete tank fitted with specially designed solar air heating system and mist fans

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Solar Panels & Atomizers

Solar Heating Panels

They are used to blow hot air to the solar pond

It ensures faster evaporation in spite of being spread over a small surface area.

Solar Heating PanelsMist Fans (atomizers)

Mist Fans

The RO reject gets converted into mist by mist fans.

It is then evaporated by blowing hot air with solar air heating system

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HAZARDOUS WASTES

Disposal of Rejected Effluents

SLF

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Power Consumption

Total Power connected load is 93.2 KWTotal Power consumption is 2236.8 KWH per day

Evaporation Rate

Benefits of Advanced Solar Pond

Multiple Effect Evaporator Normal Solar Pond Advanced Solar Pond

- 19200 m2 2000 m2 with a depth of 2m

Rs 43/m3 Rs 28.9/m3 Rs 10/m3

3.2 m3/hour 3.3 m3/hour 5 m3/hour

O & M cost

Surface area

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Key Benefits

100% recycling of water coming in to the system

Consistency in output quality even with varying inputs

It reduces fluoride to < 1 ppm as well as other pollutants significantly

Can be used to treat any fluoride contaminated water

If adopted by all smelter plants as per present scenario, this can reduce approximately 2 Mt fluoride load to Environment over conventional treatment

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Our Vision is to become the Benchmark in Environmentally Sustainable Aluminium

Smelter22