Advanced Oxidation of Pulp and Paper Industry Effluent
Parveen Kumar, Satish Kumar, Nishi K. Bhardwaj
+
and Ashutosh Kumar Choudhary
Department of Paper Technology, Indian Institute of Technology Roorkee, Saharanpur Campus,
Saharanpur, U. P., India
Abstract. The advanced photocatalytic oxidation of the pulp and paper industry effluent (primary clarified
and biotreated) has been studied with UV/TiO
2
and UV/TiO
2
/H
2
O
2
treatment processes for environmental
load reduction. The photo-oxidation experiments are performed under UV radiation in a slurry-type of
reactor with optimized treatment conditions i.e. pH 7.0, 0.5 g/L of TiO
2
and 15 mM/L of H
2
O
2
for 4 hours.
The BOD (Biochemical Oxygen Demand)/ COD (Chemical Oxygen Demand) ratio of the effluents is low i.e.
0.25 and 0.12 for primary clarified and biotreated effluents, respectively, indicating that biorefractory
organics are present. Addition of hydrogen peroxide to the UV/TiO
2
system enhances the photoprocess
performance. The treatment for 4 hrs with UV/TiO
2
/H
2
O
2
removes the organic load of the primary clarified
effluent by 57.9 % in COD, 42.9 % in BOD, and 89.2 % in color and of biotreated effluent by 74.8 % in
COD, 52.7 % in BOD, and 95.4 % in color, which is higher as compared to UV/TiO
2
process. Higher COD,
BOD, and color reduction is obtained for biotreated effluent as compared to primary clarified one. The
BOD/COD ratio of the effluents improved after photocatalytic oxidation, i.e. 0.09 and 0.11 points for
biotreated effluent and 0.06 and 0.09 points for primary clarified effluent with UV/TiO
2
and UV/TiO
2
/H
2
O
2
treatment processes, respectively.
Keywords: Advanced oxidation, paper mill effluent, biodegradability, UV/TiO
2
, UV/TiO
2
/H
2
O
2
.
1. Introduction
The pulp and paper industry effluents contain a variety of toxic organic compounds that may cause
deleterious environmental impacts to receiving water bodies if discharged untreated. Among the various
sections, the effluents from pulp bleaching are responsible for most of the color, organic matter, and toxicity
of the water discharges of this industry [1]. The pulp produced by chemical pulping requires bleaching to
produce bright pulps. The use of chlorine gas and chlorine compounds as bleaching chemicals is known to
generate various toxic and bio-refractory chlorinated organics (phenols, resin and fatty acids, dioxins and
furans) in the paper mill effluent [2]. Some of them are toxic, mutagenic, and resistant to biodegradation. The
conventional effluent treatment processes are not effective for their complete degradation. Hence, treatment
with some advanced oxidation processes (AOP’s) is needed [3].
TiO
2
photocatalysis, an AOP, is an important alternative because it can cause the complete
mineralization of a wide range of organics without any harmful environmental impact [4]. When a photon of
light strikes the catalyst surface, an electron is raised from the valence band to the conduction band leaving
behind a hole (h
+
vb
), eqn. (1) [1]. h
+
vb
can either directly oxidize a wide range of adsorbed pollutants or by
producing OH
radicals (from H
2
O/OH
−
ion), eqn. (2 and 3), which can also oxidize organics non-selectively,
eqn. (7). Electron (e
-
cb
) is readily taken by adsorbed O
2
to produce superoxide ion (O
2
.-
), eqn. (4), thus
prevents the electron-hole recombination. O
2
.-
can further participate in contaminants degradation reactions
[5]. Addition of H
2
O
2
to the photocatalytic system increases the degradation efficiency positively because it
can additionally form OH
radicals either by direct radiation absorption or by accepting conduction band
electrons, eqn. (5 and 6) [6].
+
Corresponding author. Tel.: +91-132-2714350; fax: +91-132-2714311.
E-mail address: nishifpt@iitr.ernet.in.
170
2011 International Conference on Environmental and Agriculture Engineering
IPCBEE vol.15(2011) © (2011) IACSIT Press, Singapore