8.1 Treatment with Fungi
Paper industry wastewater is mainly adequately treated by fungi (Yang et al. 2011)
because they produce extracellular ligninolytic enzymes (laccase, MnP, and LiP) and
are more effective in comparison to bacteria (Singhal and Thakur 2009). Among all
the fungal species, white rot fungi (Phanerochaete chrysosporium and Trametes
pubescens) have reported for the degradation of lignin or phenolic compounds by
ligninolytic enzymes (Zhang et al. 2012; Gonzalez et al. 2010; Chandra and Singh
2012; Freitas et al. 2009). In addition, kraft pulp and paper mill wastewater bioremediation was achieved by immobilized fungal consortium, which consists of two
basidiomycetes and deuteromycetous fungi such as Merulius aureus with an
unidentified genus and Fusarium sambucinum, respectively. In this study, after
4 days of incubation, reduction of color, lignin, and COD was 78.6%, 79.0%, and
89.4%, respectively (Malaviya and Rathore 2007). Freitas et al. (2009) have reported
that Pleurotus sajor-caju and Rhizopus oryzae are used for the reduction of color and
COD of wastewater discharged from the secondary treatment of a bleached kraft at
their relative absorbance. In this study, it was observed that after 10 days of
incubation period, reduction of color was 25–46% at 250 nm and 72–74% at
465 nm and COD was 74–81%. In laboratory-scale study at different optimized
conditions (3% inoculum, pH 6, shaking at 160 rpm, 30
C, and 60–72 h), pulping
effluent was treated with the help of Aspergillus niger. Further, it was observed that
reduction of color, COD, and turbidity was 43%, 60%, and 77%, respectively, while
methyl tertiary butylether (MTBE) was about 97% (Liu et al. 2011). Various
researchers reviewed that treatment of pulp and paper mill wastewater by using
various fungal species (Garg and Modi 1999; Garg and Tripathi 2011; Tripathi et al.
2007). However, the main constraint in using a fungal degrading system is the
requirement to maintain growth and/or enzymes (ligninases) activity at the
prevailing low pH (4–5). However, at low pH, the solubility of high molecular
weight fragments that are derived from lignin is reduced. Furthermore, the natural
pH of pulp and paper mill effluent is alkaline (pH ¼ 8–9). Therefore, any requirement to reduce the pH to the acidic range prior to fungal augmentation would be
uneconomical (Raj et al. 2007). There are several facts mentioned in this section, and
bacterial treatment systems that have an optimum pH (7–9) may play a key role in
biodegradation of pulp and paper mill wastewater, without any previous requirement
of pH modification. Due to this reason, studies on the bacterial decolorization/
degradation were more suitable for pulp and paper wastewater treatment, and on
the basis of available literature, production of bacterial ligninolytic enzymes has
been more demanding in recent years (Rahman et al. 2013; Raj et al. 2014a).
14 Pulp and Paper Mill Wastewater: Ecotoxicological Effects and. . .
349
Paper industry wastewater is mainly adequately treated by fungi (Yang et al. 2011)
because they produce extracellular ligninolytic enzymes (laccase, MnP, and LiP) and
are more effective in comparison to bacteria (Singhal and Thakur 2009). Among all
the fungal species, white rot fungi (Phanerochaete chrysosporium and Trametes
pubescens) have reported for the degradation of lignin or phenolic compounds by
ligninolytic enzymes (Zhang et al. 2012; Gonzalez et al. 2010; Chandra and Singh
2012; Freitas et al. 2009). In addition, kraft pulp and paper mill wastewater bioremediation was achieved by immobilized fungal consortium, which consists of two
basidiomycetes and deuteromycetous fungi such as Merulius aureus with an
unidentified genus and Fusarium sambucinum, respectively. In this study, after
4 days of incubation, reduction of color, lignin, and COD was 78.6%, 79.0%, and
89.4%, respectively (Malaviya and Rathore 2007). Freitas et al. (2009) have reported
that Pleurotus sajor-caju and Rhizopus oryzae are used for the reduction of color and
COD of wastewater discharged from the secondary treatment of a bleached kraft at
their relative absorbance. In this study, it was observed that after 10 days of
incubation period, reduction of color was 25–46% at 250 nm and 72–74% at
465 nm and COD was 74–81%. In laboratory-scale study at different optimized
conditions (3% inoculum, pH 6, shaking at 160 rpm, 30
C, and 60–72 h), pulping
effluent was treated with the help of Aspergillus niger. Further, it was observed that
reduction of color, COD, and turbidity was 43%, 60%, and 77%, respectively, while
methyl tertiary butylether (MTBE) was about 97% (Liu et al. 2011). Various
researchers reviewed that treatment of pulp and paper mill wastewater by using
various fungal species (Garg and Modi 1999; Garg and Tripathi 2011; Tripathi et al.
2007). However, the main constraint in using a fungal degrading system is the
requirement to maintain growth and/or enzymes (ligninases) activity at the
prevailing low pH (4–5). However, at low pH, the solubility of high molecular
weight fragments that are derived from lignin is reduced. Furthermore, the natural
pH of pulp and paper mill effluent is alkaline (pH ¼ 8–9). Therefore, any requirement to reduce the pH to the acidic range prior to fungal augmentation would be
uneconomical (Raj et al. 2007). There are several facts mentioned in this section, and
bacterial treatment systems that have an optimum pH (7–9) may play a key role in
biodegradation of pulp and paper mill wastewater, without any previous requirement
of pH modification. Due to this reason, studies on the bacterial decolorization/
degradation were more suitable for pulp and paper wastewater treatment, and on
the basis of available literature, production of bacterial ligninolytic enzymes has
been more demanding in recent years (Rahman et al. 2013; Raj et al. 2014a).
14 Pulp and Paper Mill Wastewater: Ecotoxicological Effects and. . .
349