Journal of Chemical and Natural Resources Engineering, Vol.4(1):43-53
FKKKSA, UNIVERSITI TEKNOLOGI MALAYSIA
COAGULATION AND FLOCCULATION TREATMENT OF WASTEWATER
IN TEXTILE INDUSTRY USING CHITOSAN
MOHD ARIFFIN ABU HASSAN1, TAN PEI LI1, ZAINURA ZAINON NOOR1
Aluminum sulfate (alum), ferrous sulfate, ferric chloride and ferric chloro-sulfate were
commonly used as coagulants. However, a possible link of Alzheimer’s disease with
conventional aluminium based coagulants has become an issue in wastewater treatment.
Hence, special attention has shift towards using biodegradable polymer, chitosan in
treatment, which are more environmental friendly. Moreover, chitosan is natural
organic polyelectrolyte of high molecular weight and high charge density which
obtained from deacetylation of chitin. Experiments were carried out on textile industry
wastewater by varying the operating parameters, which are chitosan dosage, pH and
mixing time in order to study their effect in flocculation process by using chitosan. The
results obtained proved that chitosan had successfully flocculated the anionic suspended
particles and reduce the levels of Chemical Oxygen Demand (COD) and turbidity in
textile industry wastewater. The optimum conditions for this study were at 30 mg/l of
chitosan, pH 4 and 20 minutes of mixing time with 250 rpm of mixing rate for 1 minute,
30rpm of mixing rate for 20 minutes and 30 minutes of settling time. Moreover,
chitosan showed the highest performance under these conditions with 72.5% of COD
reduction and 94.9% of turbidity reduction. In conclusion, chitosan is an effective
coagulant, which can reduce the level of COD and turbidity in textile industry
Chitosan; textile wastewater; coagulation; flocculation; wastewater
Textile dyeing processes are among the most environmentally unfriendly industrial
processes, because they produce colored wastewaters that are heavily polluted with
dyes, textile auxiliaries and chemicals . Besides, textile finishing’s wastewaters,
especially dye-house effluents, contain different classes of organic dyes, chemicals and
auxiliaries. Thus they are coloured and have extreme pH, COD and BOD values, and
they contain different salts, surfactants, heavy metals, mineral oils and others.
Therefore, dye bath effluents have to be treated before being discharged into the
environment or municipal treatment plant .
Textile dyes are structurally different molecules themselves with low or no
biodegradability. The removal of color is associated with breakup of the conjugated
unsaturated bonds in molecules. For this reason, many chemical treatment processes
have been used extensively to treat textile wastewaters. Most of the studies, such as
chemical precipitation, adsorption by activated carbon photocatalytic oxidation,
ozonation and Fenton’ oxidation focusing on color removal although effective, are
Department of Chemical, Faculty of Chemical and Natural Resources Engineering,
Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia.
Correspondence to : Mohd. Ariffin (firstname.lastname@example.org)
MOHD. ARIFFIN, TAN PEI LI, ZAINURA
expensive or can cause further secondary pollution . In most water treatment plants,
the minimal coagulant concentration and the residual turbidity of the water are
determined by the Jar-Test technique. Besides, physical-chemical treatment allows
reducing dissolved, suspended, colloidal and non settable matter as well as colouring
from dyes. Depending on the wastewater characteristics, COD of a textile effluent can
be reduced between 50% and 70% after optimizing the operating conditions such as
pH, coagulant and flocculants concentrations .
Coagulation or flocculation process was conducted for the treatment of
industrial wastewater to achieve maximum removal of COD, TP and TSS. Therefore,
Amudaa and Amoob  investigated the effect of coagulant dose, polyelectrolyte dose,
pH of solution and addition of polyelectrolyte as coagulant aid and found to be
important parameters for effective treatment of beverage industrial wastewater. Colloid
particles are removed from water via coagulation and flocculation processes
.Besides, Guibal and Roussy , pointed that the coagulation and the flocculation of
suspended particles and colloids result from different mechanisms including
electrostatic attraction, sorption (related to protonated amine groups) and bridging
(related to polymer high molecular weight).
Aluminum sulfate (alum), ferrous sulfate, ferric chloride and ferric chlorosulfate were commonly used as coagulants . Additionally, high COD removal
capacities have been observed during the combined action of alum and lime for the
treatment of stabilized leachates. However, it has been stated out recently that there
may be a possibility for aluminium-based coagulants to link with Alzheimer’s disease
. Hence, a special attention has been given to the environmental friendly coagulant
or flocculent, chitosan.
Chitin is cellulose like biopolymer widely distributed in nature, especially in
marine invertebrates, insects, fungi, and yeasts. Its deacetylated product, chitosan, is
readily soluble in acidic solutions, which makes it more available for applications.
Chitosan is a biodegradable, non-toxic, linear cationic polymer of high molecular
weight. Besides, chitosan was an effective agent for coagulation of suspended solids
from various food processing wastes . Moreover, chitin extraction also does not
cause any disturbance to the ecosystem, its embraces all advantages provided by
polysaccharides, considering it as the source of chitosan, and both are biocompatible
biopolymers for animal tissues with low toxicities and significant biomedical
applications . Chitosan coagulation produced flocs of better quality, namely larger
flocs and faster settling velocity. The effectiveness of chitosan for coagulating mineral
suspensions was improved due to the presence of inorganic solutes or due to addition
of materials extracted from soils at high pH .
Apparently, no major studies have been done to clarify the textile wastewater
by using chitosan in coagulation and flocculation process. Therefore, this study was
carried out to analyze the effect of chitosan in clarifying textile wastewater in
flocculation process in different experimental conditions. The optimum pH, dosage and
mixing time needed to achieve t...