Environmental Engineering Reference
In-Depth Information
Microbe-Mediated Degradation
of Synthetic Dyes in Wastewater
Maulin P. Shah
1 Introduction
In many parts of the world, the availability of clean water is today a crucial issue.
Moreover, water polluted by the textile industry discharges has received an
increased attention for several decades (Robinson et al.
2001
). Water pollution
mainly arises from the discharge of untreated or poorly treated ef
uents during
dyeing and
nishing processes. Wastewater resulting from these processes has
adverse impacts on the water quality in terms of total organic carbon (TOC),
biological oxygen demand (BOD), chemical oxygen demand (COD), suspended
solids, salinity, color, pH (5
12) and presence of recalcitrant synthetic compounds,
such as azo dyes (Faryal and Hameed
2005
; Savin and Butnaru
2008
; Akan et al.
2009
; Kuberan et al.
2011
). The ratio of BOD/COD ranges from 0.2 to 0.5 which
clearly indicates that these ef
-
uents contain a large proportion of non-biodegradable
organic matter (Yusuff and Sonibare
2004
; Savin and Butnaru
2008
). Usually,
0.6
150 l water are necessary to dye 1 kg of
cotton with reactive dyes which releases wastewater containing 20
0.8 kg NaCl, 30
60 g dyestuff and 70
-
-
-
30 % of the
-
applied un
xed reactive dyes, with an average concentration of 2,000 ppm, high
salt content and dyeing auxiliaries (Babu et al.
2007
). Worldwide, 280,000 tons of
textile dyes are discharged in industrial ef
uents every year (Jin et al.
2007
), which
have the adverse effects on the organisms in the environment, including their
inhibitory effect on aquatic photosynthesis, ability to deplete dissolved oxygen, and
toxicity to
ora, fauna and humans. If the dyes are broken down anaerobically,
aromatic amines are generated, which are very toxic, carcinogenic and mutagenic.
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