CVL100 Leather Industry

8/11/2019 CVL100 Leather Industry

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Leather Industry

-Tanneries

CVL100:Environmental

Science


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Introduction

One of the ten largest foreign exchange earners in the country!S "#$% &illion'$

Indian leather industry is the second largest (roducer of leather foot)ear and

leather garments in the )orld* em(loying +$% million (eo(le$

,easons for the gro)th of the Indian leather industry include:

Easy availa&ility of raw materials

Easy availa&ility of skilled manpower

ro)ing domestic demand due to burgeoning fashion industry and local

population

Common leather (roducts include:

.oot)ear

arments

Leather accessories

/utomo&ile interiors

.urniture


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Industry S(read

The industry is located mainly in orth and South India

North India:

un2a& 3alandhar and Ludhiana'

4aryana /m&ala * urgaon* 5arnal'

!ttar radesh 5an(ur */gra* Saharan(ur*oida'

South India:

Tamil adu Chennai* Vellore and Trichy'

5erala Calicut and 5ochi'

The industries are almost e6clusively found nearrivers/lakes or areas )ith easy ground)ater accessdue to the water-intensive nature of (rocesses$


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Tanneries of 5an(ur-7here the anges dies

5an(ur is home to a&out400 big and smalltanneries

8illions of liters ofuntreated )aste fromtanneries reaches theanges daily$

The highly to6ic )aste*containing sul(hides*chromium salts* animal

fats and othercarcinogenic materialsrenders the )ater uselessfor all do)nstream users$


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rocessing Leather

anningis the most common o(eration needed to (roduceleather* that can &e later used for ma9ing foot)ear*garments* other accessories or ra) leather for direct e6(ort$

Tanning ma9es the leather !exibleand resistant to

putrefying$ Tanning com(ounds form lin9s &et)een layersof collagenanimal fat'* allo)ing them to slide )$r$t eachother* 2ust li9e gra(hite$

In order to carry out tanning* )e need to pre-processleather and remove un)anted animal fat* hair and e6cess

moisture ost (rocessing of leather de(ends u(on the desired

(ro(erties and mode of usage glossy/hard/extra !exibleor coloured'


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re-(rocessing

uring the (re(aratory stages* many of the un)anted ra) s9incom(onents are removed$ 8any o(tions for (retreatment ofthe s9in e6ist$ ot all of the o(tions may &e (erformed$re(aratory stages may include:

Skinning: O&taining ra) materials; s9ins from animals$

"uring# ,emoving moisture from s9ins to (revent (utrefaction

Soaking: use of en


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Summary of Chemicals!sed

(rocesses Involved "hemicals %sed

S9inning /

Curing Conc$ &rine solutions

Soa9ing 4igh @uantities of clean )ater

Liming 8il9 of lime&asic' and sodiumsul(hides* cyanides and amines

!nhairing and Scudding Sodium sul(hides and sodiumhydro6ide

eliming and ?ating /mmonium sul(hate* chloride

ic9ling Common salt and sul(huric acid


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Tanning

They are of t)o ty(es: )egetable tanningusingtannin o&tained from tree &ar9s' or "hrometanningusing CrAB or CrB'

The aim is to &ind and coat the natural

protein*collagen+)ith tannin; chromium salts*ma9ing the leather )ater* &acteria resistant and=e6i&le$

The (rocess needs very lo) (4* ensured &y (ic9ling$

/fter satisfactory (enetration of tannin;chromium*the hides undergo &asiDcation and are (re(ared forthe Dnishing touches$


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Common (ollutants

/ll the (rocesses involved in leather (rocessing arechemical intensive$

In the a&sence of automation and necessary chec9s*human a((ro6imation is used to estimate doses of )ater

and chemicals in India$ Su&se@uently* )aste from Indian tanneries is laden )ith

far more (ollutants )hen com(ared to other countries$

Common (ollutants include cations li9e sodium*(otassium* calcium* chromiumhe6avalent' anionsli9e

sul(hates* sul(hides* chlorides* cyanides organicproducts li9e en


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5an(ur-/ ictorial ,ecce


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EFects

8ost tanneries in India are unregulated$

O(erating on limited &udgets* they are inca(a&le oftreating their )aste and directly dum( them intonear&y rivers* eg$ anga

The )aste is e6tremely rich in undecom(osed organicmatter and minerals* thus (ossessing high ',&and",&

They )rea9 havoc )ith the river>s ecosystem*

reducing availa&le o6ygen for other river organisms$ ChromiumVI' is a 9no)n carcinogen* 9no)n to

cause lung cancer. liver failure. kidney damageand early dementia


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EFects

/ 1GG# study conducted &y the CC? on theground)ater @uality in 5an(ur revealed CrVI' levelsof mg/$ the Indian government (laces the limitat 01 mg/$This is 1+0 times the allo)ed limit$

'io-accumulation: This is common in organismsli9e Dsh* )hich on su&se@uent human consum(tion*an cause cancer and other deadly diseases$

ot only organisms* even cro(s start accumulating

these chemicals* due to continuous usage of river)ater for irrigation$

The 2angetic dolphin* found only in the anges* isseverely threatened &y this )ater (ollution$


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Control;8itigation: 7aterollution

Steps for treatment (ossibilities

re-treatment settling 8echanical screening

rimary treatment Sul(hide removal from &eamhouseeHuents* chromium removal fromtanning eHuents* (hysical-chemicaltreatment for ?O removal

Secondary treatment ?iological treatment * activated sludge*

lagooning

Tertiary treatment itriDcation and denitriDcation

Sedimentation and sludgehandling

iFerent sha(es and dimensions oftan9s and &asins


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Control;8itigation: /irollution

/ir (ollution from tanneries fall under three categories:

,dours: ?iological decom(osition of organic matter *sul(hideand ammonia emissions from )aste)aters are res(onsi&le forthe characteristic o&2ectiona&le odours arising from tanneries$,eduction of these odours is more a @uestion of

operationalmaintenance than of technology$

Solvent )apours: Solvent and other va(ours from theDnishing o(erations vary )ith the ty(e of chemicals used andthe technical methods em(loyed to reduce their generationand release$ !( to 0 of the solvent used may &e )astedthrough emissions* )hile modern processes are availa&le toreduce this to around in many cases$

Incineration of wastes : This (ractice &y many tanneriesraises the im(ortance of ado(ting good incinerator designand follo)ing careful operating practices$


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7aste 8anagement

Sludges of organic com(osition* if free from chrome orsul(hides* have value as a soil conditioner as )ell as asmall fertili3er eect from nitrogenous com(oundscontained therein$

rimmings and !eshings can &e converted into various&y-(roducts li9e gelatin* glue* leather&oard and tallo)grease* giving good economic returns to the tannery o)ners$

Tannery )astes should not react )ith other industrialresidues* such as acidic )astes* )hich react to create toxichydrogen sulphide gas$

To avoid leachate generation and odour* only solids andde)atered sludges should &e dis(osed of at landDll sites$

Incineration under uncontrolled conditions may lead tounacce(ta&le emissions and is not recommended$


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ollution revention

7ater use eJciency can &e im(roved throughtechni@ues li9e increased volume control of (rocessing)aters* K&atch versus Krunning )ater )ashes* lo)=oat modiDcation of e6isting e@ui(ment re-use of)aste)ater in less critical (rocesses and recycling of

individual (rocess li@uors$

Traditional soa9ing and unhairing account for over %0

of the ?O and chemical o6ygen demand CO' loadsin ty(ical tanning eHuents$ Various methods can &eem(loyed to su&stitute for sul(hide* to recyclelime;sul(hide li@uors and to incor(orate hair-savingtechni@ues$


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ollution revention

7e need to reduce the chromium that is K&ledout from tanning (rocesses$ 7e can carry outdirect recycling of used chrome li5uors )hichalso reduces salinity of )aste eHuent' and the

treatment of collected chrome-&earing li@uors)ith al9ali to (reci(itate the chromium ashydroxide* )hich can then &e recycled$

CVL100 Leather Industry

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