Treatment of Wastewater from Pulp and Paper Mill using Coagulation and Flocculation

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 158-163

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

https://doi.org/10.47277/JETT/9(1)163

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

Abstract

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.

Introduction

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 affec ting 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:

balpreet_kaur@yahoo.com

158

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

Parameters

COD (mg/L)

Value

2816

6.51

TSS (mg/L)

2029

-40

0.8

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

solids.

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

Wastewater

AlK(SO .12H

[24]. sulfate

Aluminum

potassium

)

(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

159