thesis

1. Introduction
Textile production involves number of wet process like, finishing
,drying ,dyeing, printing, bleaching, washing, desizing etc. Each
process generates wastewater containing different type of pollutants
like dyes sizing agents, salts and dyeing auxiliaries . For fixing of dyes
different types of salt are used like sodium chloride,sodium
sulphate,sodium nitrate and sodium carbonate etc.scouring and
desizing process.azo dyes are mostly used in dyeing process.azo
dyes cause coloured wastewater.azo dyes have electron withdrawing
capacity due to n=n bond.in conventional treatment it is difficult to
decolourise the textile wastewater.for treatment of textile waste
water various physicochemicals(like coagulation,membrane
filtrationand adsorption)advanced oxidation process(fenton ultra
violet and h2o2 oxidation) biological processes(conventional activate
sludge and extended qeration activated sludge)
A combination of these processes can also be applied for treatment
of textile wastewater.
2 synthetic waste water composition:-
The composition of synthetic wastewater is as follows[muda et
al.2010]:-
Nh4cl 0.16 g/l ,kh2po4 0.23 g/l k2hpo4 0.58 g/l,
Cacl2.2h2o .07 g/l,mgso4.7h2o 0.09 g/l, edta 0.02 g/l and trace
solution 1 ml/l.
The carbon sources used were glucose 0.5 g/l.

2. The composition of trace elements was h3bo3 0.15g/l ,fecl3 1.5
g/l,zncl2 0.12 g/l mncl2.4h2o 0.12 g/l fecl3.4h2o 1.5 g/l zncl2 0.12 g/l
namoo4.2h2o 0.06 g/l,cocl2.6h2o 0.15 g/l
And ki 0.03 g/l . The ph of synthetic wastewater was approximate to
7
3 sludge
It is residual material left from industrial waste water or sewage
waste water processes. It consists of micro-organisms,non-living
organic matter & inorganic materials.
Physical properties of sludge
3.1.1 size
The avg. Dia of microbial granular slude is 2.3+_1.0mm according to
muda et al 2010.according to peng et al 1999,the diameter of
developed aerobic granules is in the range of 0.3-0.5 mm which is
smaller as compared to aneorbic granules that can be upto 2 to 3
mm.
3.1.2
Settling velocity
For seed sludge the avg. Settling velocity was 9.9+_0.7
M/l
And for seed anerobic granular sludge it was 42+_8 m/h

3. [muda et al 2010]. The avg settling velocity of the anerobic granular
seed is in range of 18-100m/h by schmit and ahring 1996.at the end
of experiment avg settling velocity for granular sludge was increased
from 17.8+_2.6 m/h to 80+_8m/h.
Developed microbial granular sludge posseses
High settling velocity.
This enabled the granules to escape from being flushed out.generally
as the no. Of operational days increases the bio mass concentration
and settling velocity also incresses.
3.1.3 granular strength
The granular strength of the granules was measured based on
integrity coefficient [ghangrekar et al 2005].if ic value is small ,then
strength will be higher.generally as the operation days increases as ic
value decreases. According to ghangrekar et al 2005 granules which
have ic value less than ware considered high strength granules.
The microbes in the granules were loosely linkes at the early stage of
granular development.as more microbes were linked together , the
granules increased in size. So the microbes produces more eps that
causes the granules to become denser and stronger.
3.1.4. Mineral content
There are some mineral present in sludge like na+ k + ca2+ mg2+ etc
Mechanism of colour removal
Yhe mechanisim of colour removal is adsorption of the dye onto the
biomass (brass et al 2001).
In during adsorption ,the dye is concentrated onto biomass.

4. Bio association b/w the dye and the bacterial cells tends to the
biological reduction of azo dyes .most of the azo dyes have
sulphonates substituents groups and a high molecular weight.
1 there are two mechanism for the decoloration of azo dyes as
terminal electron during bacterial catabolism connected to atp
generation
2 a gratuitons reduction of azo dyes by the end products of bacterial
catabolism not linked to atp generation.
Factors affecting colour removal
The composition of textile waste water include organics, nutrients,
salts, sulphur compound , toxicants and colour .
Any of these compounds may create inhibition to dye reduction
process.
1 oxygen
This is the most important factor to consider in color removal
process .it is the effect of oxygen on cell growth and dye reduction.in
aerobic condition during the reduction stage oxygen may inhibit the
dye reduction mechanism .because the electron doners by the cells
is used to reduce oxygen rather than the azo dye.for efficient colour
removal should be avoided[chang et al 2000]in aerobic condition
after reduction of azo bond there is no further reduction of yhe dye
molecule.
2temperature

5. In many system the rate of color removal increase with with
increasing temperature. The temperature required to produce the
max rate of colour removal tends to optimum cell culture growth
temperature of 35-45 c
3 ph
The optimum ph for colour removal is approximately 7 or slightly
alkaline value .the reduction of azo bond can increase the ph value
due to formation of the aromatic amines.
4 dye concentration
The concentration of dye can affect the efficiency of colour removal
4dye structure
Dyes those have simple structure and low molecular weight.they
exihibit higher rates of color removal but for highly substituted and
high molecular weight dyes , color removal is difficult.
In dyes when electron withdrawing group like –so3h -s02nh2 are in
the para position of the phenyl ring , relative to the azo bond their
causes an increase in the reaction rate.
Colour removal also depends on the no if azo bonds in the dye
molecule .the colour of the monoazo dye is removed faster than is
the colour of diazo or triazo dye according to hiltz et al
A acid dyes exihibit low colour removal due to a no of sulphonate
group in the dye

6. B direct dye exihibit high level of colour removal
C reactive dye eihibit low levels of colour removal
Electron donor
According to bras et al ,the addition of electron donor such as
glucose or acetate ions increases the reduction cleavage of azo bond.
Coenzyme reducing equivalents act as the electron donors for azo
dye reduction
Redox potential as rate determining step involves a redox
equilibrium b/w/ the dye and reducing agent.so colour removal
depends on the redox poentialof the electron donor and electron
acceptors.if the redox potential of the system is at most negative
then colour removal rate will be highest.if we increases redox
potential of the system , the colour removal rate decreases.
Technologies available for colour removal
There are two possible location :-
1 at the dye house ,to remove colour
2 at the sewage works to treat colour
Methods of treatment of waste water

7. 1 physical/chemical methods
Oxidation
Adsorption
Membrane technologies
Coagulation/flocculation
2
Conventional active sludge
Entended aeration activated sludge
Oxidation
Oxidative process representes a widely used chemical method for
the treatment of textile wastewater treatment.the main oxidizing
agent is h2o2.hydrogen peroxide is added to an cidic solution (ph =2-
3) containing fe2+ ions.it is called fenton reaction .it mainly used in
pre-treatment. The reaction is exothermic and it takes place at high
temperature.the great amount of total cod removes to fe(oh)3 co-
precipitation .the main drawback of this method are the significant
addition of acid and alkali to reach required ph , to high discharge in
final effuluent.
The ozone oxidation is also a very effective decolourising process
ozone can easily vreak the double bond of the dyes. It can oxidize a
significant portion of cod.
The –ve effect carcinogenic aromatic amines, i.e toxic.
Adsorption

8. In this process the mixing of waste water and the porous material
powder orgranules occurs.in this method ,the pollutants in the waste
water are removed on the surface of the porous material of filter
commonly used adsorbents are activated carbon ,silicon polymers nd
kaolin
Membrane separation process
In this method the membrane’s micropores are used to filter and to
separate certain substance in wastewater .this method is based on
membrane pressure some of the methods are reverse osmosis
ultrafiltration ,nano filtration and microfiltration.
Coagulaton flocculation sedimentation
Colloidal type of very small type material have electrical changes
.these changes give repulsion and prevent their aggeration by adding
water electrolytic products,ployelectrolyte can eliminate the surface
charges of the colloids .this effect is known as coagulation.
Biologica wastewater treatment
According to different oxygen demand biological treatment methods
can be divided into aerobic and anaerobic treatment.
Aerobic biological treatment
According to the oxygen demand of different bacteria , the bacteria
can be divided into aerobic bacteria . Anaerobic bacteria an
dfacultative bacteraia.

9. Aerobic biological treatment can be divided into major categoried :-
activated sludge process-
Activate sludge is a kind of floc which is mainly comprised of many
microorganisms and has strong ddecomposition .in present the
oxidation ditch and sbr process are commonly used activated sludge
process
Oxidation ditch
The oxidation ditch is generally consisted of the ditch body of ring
shape. Wastewater activated sludge and various micro organisms are
mixed in a loop ditch oxidation ditch has a long hrt; low organic
loading and long sludge age . It has high purification stable reliable
,simple,easy,low investment and energy consumption.
Sequencing batch reactor activated sludge process
Its operation is mainly composed of five processes-
1 inflow
2 reaction
3 sedimentaton
4 outflow
5 standby.
Sbr process have high removal rate of cod as well as high removal
efficiency of colour.

10. Anaerobic biological treatment
In this method the anaerobic bacteria used. This is a good method
for treatment of waste water .the uasb reactor is used for treatment
of simulated textile wastewater.
As azo dyes have n=n bond in structure ,thereore their
biodegradation are impossible under aerobic condition .in aerobic
condition oxygen are used as electron acceptor instead of azo dye .
In anaerobic condition azo dye are used as electron acceptor ,so
breakdown of n=n bond occurs .thus decolouration is possible.
Conclusion
The salt concentration of 32g/l was optimum for 82.5% removal of
cod at a hrt of 20 h . At 128 g/l cod removal efficiency decreased to
18.5% in vasb reaction generally as nacl concentratioion of usab
reaction increases cod removal efficiency decreases [isik,2004],state
operation is possible with salt concentration up to 27-30g nacl .clolur
removal efficiencies were not affected with ncreasing salt
concentration in usabreactor.
After the ssalt concentration of 32g/l , the methanogenic bacteria
could be inhibited. The high salt concentration reduces methane
percentage.
it si possible to obtain high decolouration yields of
azo dyes in methanogenic usab reactor (bras et al 2005).higher
decolouration yield is obtained for diazo than monoazo (bras et al
2005).

11. Combines anaerobic – arobic usab reation a method for complete
removal of azo dyes from wastewater.at higher hydraulic retention
time. The colour removal efficiency can be used in both aerobic &
anaerobic.