Journal of Environmental Treatment Techniques  
2021, Volume 9, Issue 1, Pages: 158-163  
J. Environ. Treat. Tech.  
ISSN: 2309-1185  
Journal web link:  
Treatment of Wastewater from Pulp and Paper Mill  
using Coagulation and Flocculation  
Balpreet Kaur *, Rajeev Kumar Garg , Anirudh Pratap Singh  
Department of Chemical Engineering, ShaheedBhagat Singh State Technical Campus, Ferozepur, Punjab, India  
Dean, Punjab Technical University, Jalandhar, Punjab, India  
Received: 10/06/2020  
Accepted: 21/10/2020  
Published: 20/03/2021  
In this work, an effluent sample from a local medium-scale paper mill has been treated using alum as a coagulant and chitosan (natural  
polymer) as a flocculant. Initially, the dose of alum has been optimized by adjusting the zeta potential to near zero for best coagulation  
results. The dose of 0.04 g/L was able to merely coagulate and unable to cause sweep flocculation of impurities. Then, at the optimised  
dose of 0.04 g/L various concentrations of chitosan in the range of 0.1-0.5 g/L were investigated for obtaining maximum flocculation of the  
suspended impurities. The physico-chemical parameters like pH, total suspended solids (TSS), chemical oxygen demand (COD),  
absorbance, and zeta potential were studied for comprehending the flocculation behavior. The observed results exhibited that the maximum  
flocculation was achieved at the chitosan concentration of 0.3 g/L. At the flocculant concentration of 0.3 g/L, 81% TSS removal and  
maximum 78% COD were reduced. Moreover, zeta potential value of the collected supernatant was close to zero (1.49 mV) which  
showed larger floc formation and easy settleability of the impurities. In all, it can be said that the utilization of chitosan along with alum  
may be a better option for the treatment of pulp and paper wastewater as well as other similar types of wastewater.  
Keywords: Pulp and paper mill waste water; coagulation-flocculation; chitosan; zeta potential; COD  
life of aquatic beings like zooplankton and fish is adversely  
affected due to release of toxic chemicals.  
The environmental pollution due to the activities of small  
The use of cleaner technologies and incorporating  
modifications in the process design can potentially reduce the  
pollutant load from industrial wastewater. Nevertheless, waste  
generation cannot be completely eliminated. Therefore,  
alternative techniques need to be introduced which can meet the  
prescribed discharge limits for most affecting pollutants like  
COD, BOD, AOX, color, turbidity, etc. [9, 10]. In this respect,  
chemical coagulation and flocculation offer a promising solution  
to waste water treatment facilities [11]. In this technique salts of  
selective metals are added to wastewater which initially  
neutralize the charge on impurities and subsequently  
agglomerate them into larger flocs which can be easily removed  
by settling. The factors affecting the effectiveness of these  
techniques are the nature of coagulating agent, dose of  
coagulant, pH of solution, concentration, and nature of  
impurities present in wastewater. Generally, the pulp and paper  
mill effluents consist of many non-biodegradable, hydrophobic,  
and polar compounds specifically phenols, lignin, long-chain  
fatty acids, resinous acids, and aromatic compounds [12].  
Almost all of these toxic compounds can be effectively removed  
through coagulation followed by flocculation.  
and medium-scale pulp and paper industries is  
multidimensional, causing serious problems not only to land  
fertility but also to the natural flora fauna as well as aquatic  
environment. The pulp and paper industry generates about 70-  
20 m of wastewater per metric ton of paper produced [1, 2].  
Pulping is the initial step in paper making involving mechanical  
or chemical treatment of raw material. It is widely used for the  
separation of cellulose/hemi-cellulose fibers for attaining  
improvement in its papermaking properties [3]. Further,  
bleaching is carried out in multistage processes to remove the  
residual lignin and hence achieve whiteness and brightness in  
the pulp [4]. Both these steps are highly energy-intensive  
consuming enormous volumes of freshwater and involving  
usage of large quantities of chemicals which consequently affect  
the properties of discharged effluents [5]. Various studies  
authenticate the harmful and undesirable impacts of these  
chemicals [6-8]. These effluents have been responsible for  
generating color problems, algal growth, and scum formation  
which hamperthe aesthetic looks of the environment.Also the  
In the past, many synthetic flocculants e.g. (PAM, HE, PEI)  
for precipitation of suspended impurities of paper mill waste  
water have been used [13]. The precipitated products obtained  
after the application of these flocculants have not been fully  
analyzed for degradation. It is expected that the precipitates are  
Corresponding author: Balpreet Kaur, Department of  
Chemical Engineering, Shaheed Bhagat Singh State Technical  
Campus, Ferozepur, Punjab, India. Email:  
Journal of Environmental Treatment Techniques  
2021, Volume 9, Issue 1, Pages: 158-163  
difficult to biodegrade as most of the flocculants are inorganic in  
nature or synthetic or polymeric materials which are itself  
difficult to biodegrade [14]. Chitosan a natural polymer obtained  
after partial deacetylation of chitin (biopolymer) has immense  
potential as a flocculant for wastewater treatment and sludge  
dewatering, as it is non-toxic, biodegradable, biocompatible and  
environment friendly [15-19]. Renault et al. [20] examined the  
flocculation behavior of cardboard mill wastewater collected  
after biological treatment with aerated lagoons using  
polyaluminium chloride (PAC) and chitosan solution.  
Flocculation tests indicated a drop of about 45% in COD and  
Table 1: Chemical Characteristics of the wastewater collected  
from the paper mill  
COD (mg/L)  
TSS (mg/L)  
Zeta Potential (mV)  
Dissolved Oxygen (ppm)  
.1.1 Preparation of chitosan (bio-flocculant) solution  
Chitosan powder (0.125 g) was accurately weighed in a 250  
ml volumetric flask and mixed thoroughly with 12.5 ml HCL  
0.1M) solution and kept for one hour. The dissolution was slow  
and some amount of chitosan remained in the form of a thin gel.  
It was then diluted to 250 ml with water to obtain a 0.5 g/L  
chitosan (CH) solution. After further dilutions five different  
concentrations (0.1, 0.2, 0.3, 0.4 and 0.5 g/L) of chitosan  
solution were prepared. The solutions were freshly prepared  
before each set of experiments.  
65% in turbidity with PAC flocculant. On the other hand,  
flocculation using chitosan dissolved in acetic acid displayed a  
comparatively higher drop in COD (~80%) and turbidity  
~85%). Picos-Corrales et al. [21] studied the effect of chitosan  
and bean straw flour as bio-flocculants in the treatment of  
agricultural wastewater. Results from jar tests confirmed the  
higher efficiency of chitosan in the removal of pollutants and  
reducing the concentration of undesirable metals like manganese  
and iron from wastewater. However, both the materials  
performed better than the commercially available  
polyaluminium chloride coagulant. Altaher et al. [22] studied the  
effect of chitosan as a supporting coagulant along with  
conventional alum for sea water treatment. The combination of  
both (chitosan 5 mg/L and alum 13.5 mg/L) was effective in  
.2 Analytical methods  
COD tests were conducted on the supernatant collected after  
treatment of water sample with chitosan solution of various  
concentrations using closed reflux titrimetric method based on  
the APHA manual. To measure the charge on colloidal particles  
in waste water solutions NICOMP 380 ZLS (NICOMP Zeta  
potential/Particle Sizer, Santa Barbara, CA, USA) was used.  
The absorbance of various samples was recorded on UV-Vis  
double beam spectrophotometer (UV 5704SS), by Electronics  
Corporation of India. Samples were filtered with a glass filter  
before analysis using a quartz cuvette. pH meter (Eutech,  
Singapore) was used to measure the pH of all solutions. pH  
meter was calibrated with buffer solutions of pH 4, pH 7, and  
pH 9 before actual measurements. Magnetic stirrer model Remi,  
India was used for proper mixing of solutions. The total  
suspended solids (TSS) were evaluated with the use of standard  
filter paper (Whatman 42) and the residue retained on the filter  
was dried to a constant weight at 103 to 105 °C for 1 hr. The  
increase in weight of the filter represented the total suspended  
reducing the turbidity from 1×10 to 10 NTU. Meraz et al. [23]  
investigated the behavior of two different molecular weights of  
chitosan on the coagulation-flocculation efficiency of tortilla  
industry waste water. Both the variants with dose less than 3 g/L  
were successful in lowering the turbidity of water by 80% with  
pH of 5.5 maintained in the solution.  
In the present study, chitosan is being used as a flocculant  
along with alum as a coagulant for the removal of suspended  
impurities from pulp and paper mill waste water. For a particular  
dose of alum, varying concentrations of bio-flocculant chitosan  
were examined for maximum removal of suspended and  
colloidal impurities from wastewater. Zeta potential of the  
supernatant before and after treatment with alum/chitosan was  
used as  
a yardstick for evaluating each procedure and  
understanding the colloidal behavior of suspended particles  
there in. Further, the reduction in the COD of waste water with  
addition of different concentrations of chitosan was determined.  
Also, the TSS, absorbance and pH of each solution before and  
post treatment with chitosan solution was investigated.  
Experimental section  
Five conical flasks of 250 ml capacity with 100 ml of  
wastewater sample in each were arranged for experimental  
study. Alum dose of 0.04 g/L was added to each flask. To ensure  
uniform mixing the mixtures were stirred at 140 rpm for 2  
minutes. Then, 100 ml of chitosan solution of different  
concentrations (0.1, 0.2, 0.3, 0.4, and 0.5 g/L) was respectively  
added to five flasks and stirred thoroughly for 30 minutes at 40  
rpm. It was kept undisturbed for half an hour for the settling of  
flocs. The pH was determined at this stage for each treated water  
sample. The supernatant was analyzed for investigating the  
various physico-chemical characteristics such as pH, COD, zeta  
potential, absorbance, and TSS.  
Materials and methods  
.1 Materials  
Wastewater was collected from the water treatment plant of  
a medium scale, agro residue, and recycle based paper mill in  
Punjab, India (details are not given due to confidentiality) with a  
production capacity of 200 tons/day. The major products  
produced by the mill are mechanical pulp, paper and board. The  
waste water samples collected were characterized and the results  
are given in Table 1. The measurement of these parameters was  
based on Standard Methods for the Examination of Water and  
AlK(SO .12H  
[24]. sulfate  
(purity 99.9%, AR grade), used as  
Results and discussion  
The mechanism involved in coagulation by alum follows  
coagulant in the study was purchased from CDH Pvt Ltd., India.  
Chitosan powderwas sourced from India Sea Foods, Cochin  
with ash content of 0.05%.  
two steps. Firstly, the positively charged hydroxyl groups  
attached to aluminum neutralize negatively charged particles