Environmental Engineering Reference
In-Depth Information
White rot fungi is another group of widely
exploited microorganism in distillery effluent
bioremediation. White rot fungi produce vari-
ous isoforms of extracellular oxidases including
laccases, manganese peroxidases and lignin per-
oxidase, which are involved in the degradation of
various xenobiotic compounds and dyes. Another
important mechanism involved in decolorization
of the distillery mill effluent by fungi is adsorp-
tion.
(
2001
) explored the possibility of using a marine
cyanobacterium for decolorization of distillery
spent wash and its ability to use melanoidins as
carbon and nitrogen source. A marine filamen-
tous, nonheterocystous form
Oscillatoria bory-
ana
BDU 92181 used the recalcitrant biopolymer
melanoidin as nitrogen and carbon source lead-
ing to decolorization. The mechanism of color
removal is postulated to be due to the production
of hydrogen peroxide, hydroxyl anions, and mo-
lecular oxygen, released by the cyanobacterium
during photosynthesis.
2.4.2
Decolorization of Effluent
by Bacteria
2.5
Role of Bioreactors in Effluent
Treatment
Different bacterial cultures capable of both bio-
remediation and decolorization of distillery spent
wash have been isolated. Different research-
ers have reported isolation of various bacterial
strains acclimatized on higher concentrations
of distillery mill effluent. These are
Lactobacil-
lus hilgardii
(Ohmomo et al.
1988
),
Bacillus
sp.
(Kambe et al.
1999
; Kaushik and Thakur
2009b
),
Pseudomonas putida
(Ghosh et al.
2002
),
Bacil-
lus thuringiensis
(Kumar and Chandra
2006
),
and
Pseudomonas aeruginosa
(Mohana et al.
2007
). Some researchers carried out melanoidin
decolorization by using immobilized whole cells.
These strains were able to reduce significant lev-
els of BOD and COD. The major products left
after treatment were biomass, carbon dioxide,
and volatile acids.
Besides fungi and bacteria, yeast (Moriya
et al.
1990
; Sirianuntapiboon et al.
2003
) and
algae (Valderrama et al.
2002
; Kumar and
Chandra
2004
) have also been utilized widely
since long back for biodegradation of complex,
toxic, and recalcitrant compounds present in dis-
tillery spent wash.
a.
Anaerobic Reactors
Wastewater treatment using anaerobic process
is a very promising reemerging technology,
produces very little sludge, requires less en-
ergy, and can become profitable by cogenera-
tion of useful biogas (Mailleret et al.
2003
).
However, these processes have been sensi-
tive to organic shock loadings, low pH, and
show slow growth rate of anaerobic microbes
resulting in longer hydraulic retention times
(HRT). This often results in poor performance
of conventional mixed reactors. Biomethana-
tion using biphasic system is most appropriate
treatment method for high strength wastewa-
ter because of its multiple advantages viz.,
possibility of maintaining optimal conditions
for buffering of imbalances between organic
acid production and consumption, stable per-
formance, and higher methane concentration
in the biogas produced (Seth et al.
1995
). In
recent years, the UASB process has been suc-
cessfully used for the treatment of various
types of wastewaters (Lettinga and Hulshoff
Pol
1991
). Jhung and Choi (
1995
) performed
a comparative study of UASB and anaerobic
fixed film reactors for treatment of molasses
wastewater. The UASB technology is well
suited for high strength distillery wastewaters
only when the process has been successfully
started up and is in stable operation. How-
ever, the conventional UASB reactors showed
2.4.3
Decolorization of Effluent by
Algae
Cyanobacteria are considered ideal for treatment
of distillery effluent as they apart from degrading
the polymers also oxygenate water bodies, thus
reduce the BOD and COD levels. Kalavathi et al.
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