Journal of Scientific & Industrial Research

Vol. 73, March 2014, pp. 195-198

Electrocoagulation process for textile wastewater treatment in continuous

upflow reactor
Neha Tyagi1*, Sanjay Mathur2 and Dinesh Kumar1
1
Centre for Environmental Science and Engineering, Indian Institute of Technology-Bombay, India
2
Department of Civil Engineering, Malaviya National Institute of Technology, Jaipur-302017, India
Received 23 July 2012; revised 04 April 2013; accepted 10 October 2013

This study investigates the influence of operating parameters (current density, detention time and time of electrolysis) on
COD and color removals from a simulated basic dyebath effluent using electrocoagulation (EC) with iron electrodes in
continuous flow mode. Till today, researchers are mainly focused on use of EC systems in batch processes. Looking to large
quantities of wastewater from textile Industry, continuous flow regime may offer a better solution. Firstly, the operational
parameters including current density (j), detention time (DT) and time of electrolysis were optimized. Then, total electric work
(E) and sacrificial weight of anode were calculated under optimum conditions. The size of electrode plate (5cm*5cm*0.5cm,
124cm2) was kept constant for all sets of experiments. Our results indicated that for a solution of 300mg/L basic red dye 5001 B,
almost 76% COD and 95% color were removed, when the pH was about 9, the DT was 20 min and the j was 14-17 mA/cm2.
Pseudo steady-state was achieved after passing 60 minutes of current in the solution. In addition, the result of our study
indicates that when the j and DT was increased above optimum level, charge reversal and surface saturation was occur due to
the excessive addition of coagulant.

Keywords: Electro coagulation, textile wastewater, up flow reactor, COD removal, current density.

Introduction treatment, chemical coagulation, activated carbon

Textile industries are among the most polluting adsorption, ultrafiltration, ozonation and electro-
industries in terms of the volume and complexity of coagulation–electroflotation4 (EC–EF). Each treatment
treatment of its effluent discharge. Textile industries method has its own advantages and disadvantages. EC
consume large volumes of water and chemicals for wet has been recently gained more interest when biological
processing of textiles. Textile mill effluents are also treatments fail, while it avoids the formation of
characterized by high levels of color caused by residual secondary pollutants5. The contaminants present in
dyes, COD, salt content, high temperature and broad wastewater are stabilized in solution by electrical
ranges of pH1. The colored wastewater released into charges. When metal ions (trivalent ions in most cases)
the ecosystem is also a dramatic source of aesthetic provided by EC are neutralized with ions of opposite
pollution and perturbation in the aquatic life2. electric charge of the suspended matters they become
Furthermore, dye effluents can contain chemicals, unstable and precipitate to solids of a high stability6. The
which are toxic, carcinogenic, or mutagenic to various electrochemical process appears as ideal to take
microbiological or animal species3. advantage of the combined production of polyvalent
Treatment of dyed wastewater can be take place by cations by oxidation of sacrificial anodes e.g. Fe and Al,
many types of conventional method such as biological and flotation of the pollutants to the solution surface
where it can be more easily collected and removed. The
Abbreviations metal ions can react with the OH− ions produced at the
COD Chemical Oxygen Demand cathode during gaseous H2 evolution, to yield insoluble
DT Detention time (min.)
EC Electrocoagulation
hydroxides which adsorb pollutants out of the solution.
EF Electroflotation It also contributes to coagulation by neutralizing the
I Current (A) negatively charged colloidal particles which have been
j Current density (mA/cm2) reported to be more compact than sludge obtained by
YCOD COD removal efficiency chemical methods.
_______________
*Author for correspondence The most widely used electrode materials in EC
Email: neha.tyagi107@gmail.com process are aluminum and iron1. In this study, basic
196 J SCI IND RES VOL 73 MARCH 2014

red dye 5001 B was used which is basic in nature and temperature with water temperature varying in a close
iron electrode performs better EC at basic pH7. The range of 25-27C.
results of these works show that COD, color, turbidity
and even dissolved solids can be efficiently removed Preparation of simulated waste water
using EC4,5,7-12. The continuous regime of the EC Experiments were carried out on synthetic
process has however been less investigated, except in wastewater samples consists of 300mg/L basic red
a few studies13-16, especially in the case of COD dye 5001 B (commercial name of a direct dye used
reduction. extensively in the region), 3gm/L NaCl, 5.56 mg/L
Most of the studies available in the literature are hydrolyzed starch, 11.12 mg/L ammonium sulphate,
based on batch flow reactor. Textile industry is water 11.12 mg/L disodium hydrogen phosphate, 7-8 drops
based industry which discharges large quantities of liquid detergent. Synthetic wastewater was prepared
waste water. In our opinion, a batch flow reactor will by mixing all the chemicals in tap water and heated at
not offer feasible solution for such large quantity of 80°C for 1.5 hours to stimulate the actual wastewater,
wastewaters. The prime objective of this study was to which was then left to cool to room temperature9. The
determine the feasibility of EC in the continuous flow physicochemical characteristics of simulated
regime to treat a wastewater, which was simulated, wastewater were tabulated in Table. 1. All the
according to the wastewaters released from a chemicals used during experiment were purchased
Sanganer industrial area, Jaipur, India. The effluent from Merck. All experiments were done in duplicates
released from these industries slowly infiltrates into and average values were taken.
the land and finds its way to the ground water table, During the experiments, voltage was used as
thereby making it unsafe for drinking and other operating parameter and corresponding current was
domestic purposes. Further, effects of various recorded and on the basis of recorded current, j was
operating parameters on efficiency of EC process in calculated. The j was calculated through the equation
continuous flow regime were determined. as follows:

Materials and methods j = I (A) S.A. (cm2) … (1)

Reactor design
The experimental set up used in this study consists Where I = Current (A) and
of a beaker of 2.0 liters as a reactor to hold a sample of S = Surface area of the electrode (cm2)
1500 ml. A pair of rectangular iron plates was used as
anode and cathode at a spacing of 4 cm. Weight of COD of treated effluent was measured at an
electrodes was taken and by the help of this sacrificial interval of consecutive 10 minutes till the pseudo
weight of electrodes was calculated. EC unit was fed steady state was achieved. Pseudo steady state was
continuously with a peristaltic pump (Miclins, pp-20- characterized by variation of less than 5% in three
EX; 2ml/h to 10 L/hr) using the effluent from a consecutive readings of effluent COD. COD was
wastewater tank (Fig. 1). EC unit was connected to the measured by closed reflux calorimetric method with
DC linear power source (Testronix, 92-D; 30 V and 10 A). absorbance being measured at 600 nm using UV/VIS
All the experiments were conducted at room spectrophotometer (Schimadzu, UV-240). COD
removal efficiency (YCOD) was expressed as a
percentage removal.
Electrodes having an area of about 124.4 cm2 were
used to assess the feasibility of COD removal at
Table 1Physicochemical characteristics of simulated
wastewater
S.No. Parameter Average Values
1. pH 9
2. COD (mg/l) 600-650
3. Temperature (0C) 25-270C
Fig. 1Experimental setup of continuous EC cell (1: wastewater
tank; 2: peristaltic pump; 3: inlet of the first compartment; 4: 4. Color Dark orange
electrodes; 5: DC power supply; 6: treated effluent outlet; 7: sludge). 5. Conductivity ( mS cm-1) 4.7
 TYAGI et al: ELECTROCOAGULATION PROCESS FOR TEXTILE WASTE WATER 197

20, 30 and 40 minutes of DT. Before each run of During electrolysis, the positive electrode
experiment, electrodes were washed with acetone to undergoes anodic reactions while cathodic reactions
remove surface grease, and the impurities from the occur on the negative electrode. The released ions
iron electrode surfaces was removed by dipping them neutralize the particle charges and thereby initiate
for 5 min in a solution freshly prepared by mixing 100 coagulation. The YCOD depends directly on the
cm3 HCl solution (35%) and 200 cm3 of concentration of ions produced by the electrodes as
hexamethylenetetramine aqueous solution (2.8%)7. the time of electrolysis increases. After passing 60
Sacrificial weight of electrodes were calculated by minutes of current in the solution almost stable
measuring their weight before and after of EC pseudo steady state was achieved in different j and
process. thereafter only ± 5% YCOD was achieved (Fig. 2).
Effect of detention time on COD removal efficiency
Results and Discussions
Effect of current density and operating time on COD removal In order to find out the optimum DT for treatment of
efficiency simulated wastewater at which maximum COD
It is well known that j is the major operating variable removal was achieved-the inlet flow rates were
directly affecting the performance of electro progressively varied to achieve designated DT of 20,
coagulation and operating costs. It is clearly evident 30 and 40 minutes. The continuous EC process
that as the value of j increases from 7.55-17 mA/cm2 a provided an YCOD higher than 50% for all the studied
substantial increment in the YCOD was observed (Fig. 2). DT at 14-17mA/cm2 of j (Fig. 3). Although, it was
Highest removal efficiency was achieved at 14-17 reported in this study as the DT increases, YCOD
mA/cm2. This may be due to as the value of j increases, decreases and there may be two possible reasons. First,
the amount of Fe3+ cations released by the anode the excessive addition of counter ions from coagulant
increases and therefore formation of monomeric ions (iron) may result in restabilization by a charge reversal;
and hydroxyl complexes increases1. These hydroxides the net charge on the particles may be reversed by the
complexes have strong affinity with dispersed, adsorption of an excess of counterions. Second, the
dissolved as well as counter ions to cause coagulation particles restabilization, if there was an insufficient
and adsorption. But, it doesn’t mean that YCOD was number of a colloidal particle available for bridging or
directly proportional to j. The decrement in YCOD with due to surface saturation or sterical stabilization17. In
increased j was also observed at 20.0-23.0 mA/cm2. studied process, complete decolurization was achieved
This may be attributed to the adsorption of the within 20 minutes at all the considered detention time
hydrogen bubbles produced by the electrodes, although (data not shown here). In comparison for the complete
the cathode was perforated, hydrogen bubbles adsorb decolourization and 85 % of COD removal, Fenton
on the lower face of cathode and remain blocked on process takes 40-120 min18. Although, Fenton process
this area1. This technical problem induces a reduction was highly sensitive to pH change and reagent dosage
in the YCOD as the j was increases. Another limitation but electrocoagulation was not. Thus, it concluded that
of working at high j was that no increment observed in maximum COD removal was achieved at about 20 min
the YCOD. Indeed, electrode material consumption DT at 14-17mA/cm2 of j.
increases as a factor of j while energy consumption
rises as j2 and induces heating by joule effect1.

Fig. 2COD removal profile at different current density (j): Ci = 300 Fig. 3Effect of detention time on COD removal profile: j = 14-17
mg/L, influent pH=9, k = 4.7 mS/cm. mA/cm2, Ci = 300 mg/L, influent pH=9, k = 4.7 mS/cm
198 J SCI IND RES VOL 73 MARCH 2014

Conclusion 4 Kobya M, Can O T & Bayramoglu M, Treatment of textile

Day by day regulations becoming increasing wastewaters by electrocoagulation using iron and aluminum
electrodes, J Haz Mater, 100 (2003) 163-178.
stringent, industrial users are searching for more 5 Alinsafi A, Khemis M, Pons M N, Leclerc J P, Yaacoubi A,
advanced method to solve their wastewater treatment Benhammou A & Nejmeddine A, Electro-coagulation of
problems. EC is one of the most promising techniques reactive textile dyes and textile wastewater, Chem Eng Process,:
for the treatment of wastewater containing color and Proc Intens, 44 (2005) 461-470.
6 Merzouk B, Gourich B, Sekki A, Madani K, Vial Ch. &
organic pollutants. The COD and color removal of Barkaoui M, Studies on the decolorization of textile dye
dye solution of basic red dye 5001 B was affected by wastewater by continuous electrocoagulation process, Chem Eng
j, DT and time of electrolysis. Our results showed that J, 149 (2009) 207-214.
unilateral increase in j, DT, and time of electrolysis 7 Kim T H, Park C, Shin E B & Kim S, Decolorization of disperse
would not assure higher COD removal, and an and reactive dyes by continuous electrocoagulation process,
Desalin, 150 (2002) 165-175.
optimization of these parameters must determine to 8 Slokar Y M & Majcen L M A, Methods of decoloration of
achieve the optimum COD removal for a given type textile wastewaters, Dyes Pigm, 37 (1998) 335-356.
of wastewaters. For a solution with dye concentration 9 Chen X, Chen G & Yue P L, Investigation on the electrolysis
of 300mg/L, COD and color elimination of 76% and voltage of electrocoagulation, Chem Eng Sci, 57 (2002) 2449-
2455.
95%, respectively were reported, when the pH was 10 Chen X, Chen G & Yue P L, Separation of pollutants from
about 8.5, the DT 20 min and the j 14-17 mA/cm2. In restaurant wastewater by electrocoagulation, Sep Pur Tech, 19
addition of these, the result of our findings indicates (2000) 65-76.
that when the DT and j was increased above optimum 11 Mansour L B, Ksentini I & Elleuch B, Treatment of wastewaters
level, charge reversal and surface saturation were of paper industry by coagulation-electroflotation, Desalin, 208
(2007) 34-41.
occur due to the excessive addition of coagulant. 12 Mameri N, Yeddou A R, Lounici H, Belhocine D, Grib H &
Complete color removal was achieved after 15-20 min Bariou B, Defluoridation of septentrional Sahara water of north
of detention time. Africa by electrocoagulation process using bipolar aluminium
electrodes, Water Res, 32 (1998) 1604-1612.
13 Daneshvar N, Ashassi S H & Tizpar A, Decolorization of orange
II by electrocoagulation method, Sep Pur Tech, 31 (2003)
Acknowledgement 153-162.
We would like to thanks the Malaviya National 14 Daneshvar N, Ashassi S H & Kasiri M B, Decolorization of dye
Institute of Technology Jaipur, for funding. solution containing Acid Red 14 by electrocoagulation with a
comparative investigation of different electrode connections, J
Haz Mater, 112 (2004) 55-62.
References 15 Mollah M Y A, Pathak S R, Patil P K, Vayuvegula M, Agarwal
1 Mohan N, Balasubramanian N & Subramanian V, T S, Gomes J A G, Kesmez M & Cocke D L, Treatment of
Electrochemical Treatment of Simulated Textile Effluent, Chem orange II azo-dye by electrocoagulation (EC) technique in a
Eng & Tech, 24 (2001) 749-753. continuous flow cell using sacrificial iron electrodes, J Haz
2 Sevimli M F & Sarikaya H Z, Ozone treatment of textile Mater, 109 (2004) 165-171.
effluents and dyes: effect of applied ozone dose, pH and dye 16 Metcalf & Eddy, Wastewater Engineering Treatment and Reuse,
concentration, J Chem Tech & Biotech, 77 (2002) 842-850. Washington, Seattle, 4th ed, (Tata McGraw-Hill) 2003,
3 Greaves A J, Phillips D A S & Taylor J A, Correlation between 478-493.
the bioelimination of anionic dyes by an activated sewage sludge 17 Kang S F, Liao C H & Chen M C, Pre-oxidation and coagulation
with molecular structure. Part 1: Literature review, Color Tech, of textile wastewater by the Fenton process, Chemosphere, 46
115 (1995) 363-365. (2002) 923-928.