suspended solids, 75% chemical oxygen demand and 84% biochemical oxygen
demand to tannery wastewater (Dixit et al. 2015).
Furthermore, in the course of tanning operation, a number of chemicals such as
tanning agents (organic and inorganic), dyes, acids, salts, and sulphonated oils were
applied to mutate animal skins into a persistent product. This makes leather withstand against thermal, chemical and microbial degradation, and due to the
non-biodegradability of tanned leather, management of sludge produced from tanneries is a challenging task (Lofrano et al. 2008). In addition to that, the implementation of such chemicals and their low biodegradability makes the effluent a severe
environmental and technological threat (Schrank et al. 2004).
The pre-tanning operations such as liming deliming are marked as alkaline in
nature as they impart high organic and sulphide contents, while the existence of a
high concentration of chromium, ammonium, sulphate and chloride salts in tanning
operations makes the effluent highly acidic with a high chemical oxygen demand
value (Saxena et al. 2016).
The existence of various toxic chemicals, for example, formaldehyde, resins,
chlorophenols, oils, chrome, phthalates and detergents categorized the tannery
wastewater as a substantial contributor of pollutants (Lofrano et al. 2013). The
poisoning potential of chemicals utilized during numerous tanning operations is
summarized in Table 11.2 (Saxena et al. 2016).
The partially treated tannery wastewater is of dark brown colour and is a prime
cause of harmful effects in water and soil; in addition to that, tannery wastewater
restricts sunlight insertion to water bodies resulting in a reduced photosynthetic
activity and thus causing a deleterious effect to aquatic system (Saxena et al. 2016).
Furthermore, the exhaustion of dissolved oxygen in water promotes anaerobic
conditions causing a rotten smell through water (Rai et al. 2005; Verma et al.
2008). Tannery wastewater restraint the nitrification process with the formation of
foam on the water surface, and the high organic and inorganic pollutant content leads
to the growth of an extensive range of pathogenic bacteria in water bodies (Saxena
et al. 2016).
Chandra et al. studied tannery wastewater collected from common effluent
treatment plant, with respect to seedling growth and seed germination on mung
bean, and they found that there was a presence of bacterial communities along with
various organic pollutants (Chandra et al. 2011).
The practice to discharge tannery wastewater (directly or indirectly) to rivers and
canals and their use in irrigation leads to a severe toxic effect on the plant, animals
and human (Saxena et al. 2016). Despite that, hexavalent chromium modulates the
structure of microbes present in soil and diminishes their growth to inhibit bioremediation process, and its input in food chain prompts ulceration, nasal irritation, lung
carcinoma and skin irritation in human being (Saxena et al. 2016).
Improper discharge of high salt content of tannery wastewater results in relevant
soil pollution; the presence of high sulphide in tannery wastewater creates inadequacy of micronutrients present in soil (Raj et al. 2014). The removal of azo dyes
present in tannery wastewater is one of the difficult tasks as they are complex and
xenobiotic in nature, and their discharge to water bodies gives rise to eye and skin
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A. Tripathi and S. Narayanan
demand to tannery wastewater (Dixit et al. 2015).
Furthermore, in the course of tanning operation, a number of chemicals such as
tanning agents (organic and inorganic), dyes, acids, salts, and sulphonated oils were
applied to mutate animal skins into a persistent product. This makes leather withstand against thermal, chemical and microbial degradation, and due to the
non-biodegradability of tanned leather, management of sludge produced from tanneries is a challenging task (Lofrano et al. 2008). In addition to that, the implementation of such chemicals and their low biodegradability makes the effluent a severe
environmental and technological threat (Schrank et al. 2004).
The pre-tanning operations such as liming deliming are marked as alkaline in
nature as they impart high organic and sulphide contents, while the existence of a
high concentration of chromium, ammonium, sulphate and chloride salts in tanning
operations makes the effluent highly acidic with a high chemical oxygen demand
value (Saxena et al. 2016).
The existence of various toxic chemicals, for example, formaldehyde, resins,
chlorophenols, oils, chrome, phthalates and detergents categorized the tannery
wastewater as a substantial contributor of pollutants (Lofrano et al. 2013). The
poisoning potential of chemicals utilized during numerous tanning operations is
summarized in Table 11.2 (Saxena et al. 2016).
The partially treated tannery wastewater is of dark brown colour and is a prime
cause of harmful effects in water and soil; in addition to that, tannery wastewater
restricts sunlight insertion to water bodies resulting in a reduced photosynthetic
activity and thus causing a deleterious effect to aquatic system (Saxena et al. 2016).
Furthermore, the exhaustion of dissolved oxygen in water promotes anaerobic
conditions causing a rotten smell through water (Rai et al. 2005; Verma et al.
2008). Tannery wastewater restraint the nitrification process with the formation of
foam on the water surface, and the high organic and inorganic pollutant content leads
to the growth of an extensive range of pathogenic bacteria in water bodies (Saxena
et al. 2016).
Chandra et al. studied tannery wastewater collected from common effluent
treatment plant, with respect to seedling growth and seed germination on mung
bean, and they found that there was a presence of bacterial communities along with
various organic pollutants (Chandra et al. 2011).
The practice to discharge tannery wastewater (directly or indirectly) to rivers and
canals and their use in irrigation leads to a severe toxic effect on the plant, animals
and human (Saxena et al. 2016). Despite that, hexavalent chromium modulates the
structure of microbes present in soil and diminishes their growth to inhibit bioremediation process, and its input in food chain prompts ulceration, nasal irritation, lung
carcinoma and skin irritation in human being (Saxena et al. 2016).
Improper discharge of high salt content of tannery wastewater results in relevant
soil pollution; the presence of high sulphide in tannery wastewater creates inadequacy of micronutrients present in soil (Raj et al. 2014). The removal of azo dyes
present in tannery wastewater is one of the difficult tasks as they are complex and
xenobiotic in nature, and their discharge to water bodies gives rise to eye and skin
364
A. Tripathi and S. Narayanan