TECHNOLOGICAL OPTIONS FOR THE

MANAGEMENT OF SALINE STREAMS

Dr. G. Sekaran Chief Scientist& Cluster Chairman

IWWA 2014

Environmental Technology Division

CSIR- Central Leather Research Institute

Adyar, Chennai

24TH MARCH , 2014

Leather manufacturing and wastes

Soaking

Liming

Unhairing

Reliming

Deliming including washing

Pickling

Tanning

Wastewater Major issue

Soak liquor

Lime liquor

Lime liquor

Delime liquor

Pickle liquor

Tan liquor

Ammonia

H2S

Hair

High TDS, COD, BOD

High COD, BOD ,Sulphide,fleshing

High TDS

High TDS

Dusting of salt Salt

Leather manufacturing and wastes

Retanning

Neutralization including washing

Wet-finishing

Trimming

Buffing

Wastewater Major issues

Shavings

Waste water

Waste water

Trimmings

Shaving

Finishing

Waste water

Buffing dust

High COD, Low BOD , Low BOD/COD

High COD, Low BOD , Low BOD/COD

Inorganic TDS

Sodium chloride is the major contributor of TDs

Sodium sulphide

Chromium

Calcium hydroxide

Zinc chloride

Mercuric Chloride

Magnesium salt, phosphate , nitrate

Organic TDS in tannery wastewater [natural organics and synthetic organics]

• Organic compounds employed in the tanning process

• Synthetic tanning agents, Sulphonated polyphenols,Modified Glutardialdehyde

• Acrylic acid condensates Anionic surfactants aliphatic sulfonates

• Aliphatic sulphates Non ionic surfactants Aromatic ethoxylates

• Aliphatic ethoxylates Preservatives

• Benzo azol- derivatives Hologenated alkanes

• Chlorinated fatty acids, Aliphatic thiols

• Dyes

Parameters Raw

effluent

pH 8.5

Turbidity, NTU 850

Total Dissolved Solids , mg/l 16000

Total Suspended Solids , mg/l 4200

Chemical Oxygen Demand , mg/l 4750

Biochemical Oxygen Demand, mg/l 1100

Total hardness , mg/l 1600

Chromium , mg/l 180

Sulphide , mg/l 120

Chloride , mg/l 9500

Characteristics of wastewater discharged from leather industry

OBJECTIVES OF BIOLOGICAL TREATMENT

To reduce the BOD and COD To reduce the refractory organic compounds To reduce foulants in the treated wastewater To reduce reject volume in the R.O unit To increase rate of evaporation in evaporator

Impact of TDS on secondary Biological treatment The raw wastewater contains large amounts of easily degradable aliphatic biogenic orgnaic matter which might be prefrentially degraded in the anaerobic step The degradation of aromatic compounds is energetically and kinetically less favourable under anaerobic conditions The organic removal efficiency decreased with increased in sodium chloride content in the influent wastewater.

Effluent turbidity increased significantly when the sodium chloride concentration in the wastewater was increased.

High concentration of salts cause cell plasmolysis and death of micro organisms due to the increase in osmotic pressure

The flux decline profile becomes more prominent with increasing Ca2+ concentration

The flux profiles become more significant when the ionic strength of the feed solution is increased to 10 mM

Membrane fouling results in an increase in feed pressure and requires frequent cleaning of membranes. This leads to a reduction in overall facility efficiency and a shorter membrane life.

The increase in effluent turbidity could be caused by the release of nondissolved cellular components due to plasmolysis of microorganisms

Distribution of TDS in sectional streams of wastewater

Soak Liquor –

47.1 %

Pickilng - 12.5 %

Chrome Tanning -

13.7 %

Others - 26.66 %

0

5000

10000

15000

20000

25000

R R - S R - (S + P) R - (S + P +C)

R - (P + C)

21000

15857 12962

9122

16923

R - Raw; S - Soak; P - Pickle; C - Chrome

Total Dissolved solid(mg/L) content of wastewater after segregation

0

2000

4000

6000

8000

10000

12000

14000

R R - S R - (S + P) R - (S + P +C)

R - (P+C)

12500

5000

3585 1836

11095

R - Raw; S - Soak; P - Pickle; C - Chrome

Chloride(mg/L) content of wastewater after segregation

Option 1

Management of soak

liquor

Conventional Method: segregation and solar evaporation

Issues: The evaporated residue is poor in quality It lacks reusable option due to the presence of dissolved organics ( derived from the raw material) suspended impurities ( derived during solar evaporation )

Magnified issue: Disposal onto secured land fill is not recommended due to difficulty in handling the leachate . The salt is heaped in industries [for how long?]

SRIOM

PROCESS

[CLRI PATENTED

PROCESS]

R.O Salt

NaCl

HCl

H2O

Neutralisation

Ca SO4 (solid lumps)

OPTION FOR SPECIATION OF SALT FROM REJECT

CO2

Ca (OH)2

Ca Cl2 (crystals)

Sand

filter

Organic

destruction

Semi Pilot plant for SRIOM Process

in Envt. Tech. Division, CLRI

Option 2

Management of soak

liquor

Conventional Method: segregation and solar evaporation

Issues: Poor rate of evaporation due to microbial mat ( cynobacteria and thiobacillus) on the surface of water preventing the diffusion of thermal and light radiations Rate is very much reduced during winter

and Rainy season Spill over around solar evaporation pan Causing ground water pollution. Recommendation: Mechanical evaporation Bottleneck : Presence of natural organic compounds (

protein , fat, muco poly saccharides, blood,

dirt , dung )

S.No.

Parameters

Min

Max

Ave.

Standard

Deviation

1

pH

5.72

7.25

6.56

0.439

2

BOD

360

720

460

108.16

3

COD

882

1581

1327

269.30

4

TOC

164

328

273

62.30

5

Dissolved protein

470

916

709

128.86

6

Total Dissolved

Solids

14390

31250

23452

6406.98

7

Bacterial count

6X104

1.12X108

2.13X107

-

Characteristics of clarified soak wastewater

All the values except pH and Bacterial count are expressed in mg/l

Bacterial count is expressed in CFU/ml

Molecular oxygen has low oxidation

potential and thus difficult to degrade

synthetic orgnics In tannery

wastewater.

Hence, oxidants with high oxidation

potential for the oxidation of

inorganics may improve the

environmental management in Leather

sector.

Compound Oxidation Potential

(V)

Relative Power of

Chlorine

Fluorine 3.06 2.25

Hydroxyl Radical 2.80 2.05

Ozone 2.07 1.52

Hydrogen

Peroxide

1.77 1.30

Permanganate 1.67 1.23

Hypochlorous acid 1.49 1.10

Chlorine 1.36 1.10 Hydroxyl radical may be considered as the oxidising agent with oxidation potential of 2.8V Reduction potential O2 + 4H+ + 4e- --> 2H2O (l) ; 1.23 V

insitu generation of highly

potent chemical oxidant

hydroxyl radical (OH•)

with a high electrochemical

oxidation potential

(2.8V versus normal hydrogen

electrode)

for the destruction of wide

range of organic compounds in

soak wastewater FACCO technology in

TNPL, Karur, Tamilnadu

Fenton’s reagent , releases hydroxyl radicals on mixing with wastewater facilitating the oxidation of organics. During the Fenton reaction , hydrogen peroxide is catalysed by ferrous ions to produce hydroxyl radicals

Fe2+ + H2O2 Fe3+ + OH- + HO (k176.5 mol-1 s-1)

The generated Fe3+ can react with H2O2 to regenerate

back Fe2+ to sustain the reaction

Fe3+ + H2O2 Fe2+ + H+ + HO2 (k2 1 x 10-2 mol-1 s-1)

The OH• species formed through Eq (1) attack the organic substrates present in the wastewater.

FACCO technology for refractory laden

wastewater

Hydroxy radicals are

generated by Fenton’s reagent, a mixture of Ferrous iron and hydrogen peroxide

Hydroxy radicals react with organics and break them down gradually into smaller fragments .

FACCO technology

in CETP, VAPI

Nano Porous Activated carbon has been proved

to generate hydroxyl radicals using molecular

oxygen

S.no Parameters Values

1 SBET (m2/g) 438.9

2 Smic (m2/g) 214.9

3 Smeso (m2/g) 224.0

4 Vmeso /Vtot (%) 69.23

5 Average pore diameter (nm ) 3.528

6 Carbon (%) 37.96

7 Hydrogen (%) 2.40

8 Nitrogen (%) 0.50

9 Moisture (%) 13.56

10 Ash (%) 45.58

11 Decolorizing power (mg/g) 69.32

12 Point of zero charge (PZC) 7.1

13 Apparent density (g/cm3) 0.32

Characteristics

of the

Nanoporous

carbon

SBET: BET surface

area;

Smic: micropore

surface area;

Smeso: mesopores

surface area.

FENTON ACTIVATED

CARBON CATALYTIC

OXIDATION

[FACCO]

Hydroxyl radicals are generated from molecular oxygen and adsorb

onto the MAC800 through the following sequential reactions. The free

electrons present in the MAC800 (this was confirmed using ESR

spectroscopy, the value reported was calculated by spin density of the

carbon = 16.052 x 1021 spins/g) initiate reaction

-C (e-cb) + O2 -C (O2

●)ads

-C (O2●)ads + H+

(aq) -C(HO2●)ads

The adsorbed hydro peroxyl radicals are converted into hydroxyl

radicals and remain adsorbed on the surface of MAC800

-C(HO2●)ads + H+

aq -C(2OH●)ads

The positive charged centers in MAC 800 serves to adsorb the

organic substrate as expressed interms of COD (The existence of

energy gap in MAC800 was confirmed through UV-Reflectance

spectroscopy and the value was found to be 1.55eV conforming

to extrinsic semiconductor grade).

-C(h+vb) + (COD) -C (COD)ads

FACCO technology saline (3% TDS)

wastewater

Karthikeyan et al ., Environ Sci

Pollut Res, 2012.

The adsorbed COD and hydroxyl radicals present at the proximate position

undergo constructive overlapping to produce CO2 and H2O and regenerating

back to bare nano activated carbon surface.

(COD)ads

H2O + CO2 + -C (h+vb) + e-

cb

-C (2OH●)ads

where

h+vb - electron hole in the valence band

e-cb - electron in the conduction band

-C - refers to the excited carbon active site

FACCO technology in CETP, VAPI

Sekaran et al., Environmental Chemistry Letters 9 ( 2011) ,

Concentration of pollution parameters after treatment using

extreme halophiles after immobilization in mesoporous activated carbon

S.No

Pollution

Parameters

Concentration (mg/l)

Initial

Final

1

COD

2559

67-148

2

BOD

720

15-51

3.

Protein

Nil

709

Segregation , Treatment and Reuse of Soak liquor

Reject volume

50%

Treated soak wastewater

Water

recovery

Option 3

Integrated solid waste

and

soak liquor

Management

MAJOR ISSUE WITH OPTION 2 IS

ENERGY REQUIREMENT FOR MECHANICAL

EVAPORATION OF SALINE STREAM IS VERY

HIGH

RECOMMENDATION:

EXTRACTION OF ENERGY FROM HAZARDOUS

SOLID WASTE THROUGH PYROLYSIS PROCESS

MSPM

hopper

Residual ash

Condensate oil

Condenser

Wet scrubb

er

Dehydration

Unit, Silica gel

Gas pump

O2 cylinder

Clean gas

Gate valve

Pyrolytic gas

Energy recorder

Temperature programmer

O2 flow controller

Gas sampling port

Screw conveyer

Induction Furnace

Oxygen

MSPM

Road

application

materials

Evaporation

of saline

streams

using energy

from solid

waste

Option 2

Management of Spent

Chrome Liquor

[low COD and High TDS]

0

1000

2000

3000

4000

5000

6000

7000

R R - S R - (S + P) R - (S + P +C)

R - (P+C)

5300

6271 5841

4933

3863

R - Raw; S - Soak; P - Pickle; C - Chrome

Sulphate(mg/L) content of wastewater after segregation

Segregation of chrome liquor to reduce sulphate

content in the composite stream and to increase

COD/SO4

Anaerobic digestion is improved by

suppressing SRB and promoting the activity MB

PUMP

collection

TANK

Liquor

Chrome

Recovery of Chromium hydroxide from spent chrome liquor S

pe

nt

ch

rom

e

liq

uo

r MgO

H2SO4

Issues:

Management of supernatant

liquor ( Magnesium sulphate)

in chromium precipitation .

Increases TDS content of

treated wastewater

Retards evaporation rate in

evaporators due to

hygroscopic nature [ hydration

energy is -91.2 kj/mole)

PUMP

AIRBLOWER

PRESSURE

SAND

FILTER

CACCO

REACTOR

AA

EXCESS

AIR

TREATED

MgSO4 solution

For resale AA: AIR AQUA SYSTEM

collection TANK

Liquor

Chrome

MgSO4 + COD

Recovery of Chromium hydroxide and MgSO4 from spent

chrome liquor S

pe

nt

ch

rom

e liq

uo

r

MgO

H2SO4

Textile industry

The bottlenecks in adopting the technology are high cost of operation

for MEE and maintenance of RO membrane module.

Multi effect evaporation is a costly system for concentration of the

effluents before crystallization.

It requires more maintenance in terms of consuming more fuel

The recovered salt has poor purity and market value of salt is also very

less.

When the availability of land has become constraint, the MEE would be

preferable.

A common MEE set-up as joint ventures may be an economical

recommendation.

Proper preliminary treatments should be followed to reduce the

maintenance cost of RO membrane.

CONCLUSIONS The saline streams have to be segregated for the

better management of other streams in biological

treatment .

The saline streams have to be treated for reuse

purpose to overcome the solid waste disposal

issues.

Pyrolysis integrated saline water management

could be a better choice to manage both liquid and

solid wastes