Electrocoagulation treatment of rice grain based distillery effluent using copper electrode

Journal of Water Process Engineering 11 (2016) 1–7

Contents lists available at ScienceDirect

Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe

Electrocoagulation treatment of rice grain based distillery effluent using copper electrode Abhinesh Kumar Prajapati a,∗ , Parmesh Kumar Chaudhari b , Dharm Pal b , Anil Chandrakar c , Rumi Choudhary d a

Department of Chemical Engineering, Institute of Engineering and Science Indore, Indore 452001, India Department of Chemical Engineering, National Institute of Technology Raipur, Raipur 492001, India c Department of Chemical Engineering, Guru Ghasi Das University, Institute of Technology, Bilaspur 495009, India d Department of Chemical Engineering, C. V. Raman College of Engineering, Bhubaneswar, Odisha 752054, India b

a r t i c l e

i n f o

Article history: Received 29 October 2015 Received in revised form 13 March 2016 Accepted 16 March 2016 Keywords: Chemical oxygen demand Copper electrode Distillery effluent Electrocoagulation treatment Power consumption

a b s t r a c t This article reports the electro coagulation treatment (ECT) of rice grain based distillery effluent in a batch reactor using copper electrodes. ECT with copper electrode is a better alternative as compared to aluminum/iron electrode to treat rice grain based biodigester effluent (BDE), due to less power consumption at acidic pH which is the main attraction of the present work. The ECT in batch mode is conducted in a 1.5 L cubical shape electrocoagulation reactor using four-plate configurations. A current density of 89.3 A/m2 and pH 3.5 is found to be optimal, providing a maximum chemical oxygen demand (COD) and colour removal of 80% and 65%, respectively. At pH 3.5 electrode loss was 3.667 mg/L and power consumption was 11.42 WH/L. It is noted that treated slurry at pH 8 has shown best settling characteristic, which decreases with decrease in pH. Thermogravimetric analysis indicates that the residues obtained from the EC treated BDE may be used as fuel. © 2016 Elsevier Ltd. All rights reserved.

1. Introduction Ethanol has been considered as a renewable fuel that is better for the environment than traditional gasoline. In India, ethanol blended gasoline (5–10%) is used as a motor fuel in automobiles [1]. More than 75% of ethanol is produced from sugar cane molasses and sugar beet, which is not available throughout the year. Therefore other alternatives such as rice, wheat, corn etc. are also considered for ethanol production. Rice is one of the major crop and readily available India, and hence, could be used for production of ethanol. Ethanol is produced by fermentation of rice grain in fermentation broth, which contains 5–14% (v/v) of ethanol. The ethanol is separated from the top of the distillation column and the liquid obtained from the bottom is called spent wash (SW). Rice grain based SW contains high COD (10,000–40,000 mg O2 /L) and BOD (3000–15,000 mg O2 /L) [2]. Due to its high organic content it is first treated in an aerobic biodigester where 50–70% COD and 60–80% BOD is reduced. The effluent obtained from biodigester is called biodigester effluent (BDE), which still contains high COD (5000–15,000 mg O2 /L) and BOD (1000–5000 mg O2 /L) [2]. The high

∗ Corresponding author. E-mail address: [email protected] (A.K. Prajapati). http://dx.doi.org/10.1016/j.jwpe.2016.03.008 2214-7144/© 2016 Elsevier Ltd. All rights reserved.

COD and BOD of the distillery SW and BDE are due to the presence of a number of organic compounds like polysaccharides, reduced carbohydrate, proteins, melanoidin, waxes etc. BDE is often dark brown in colour and may be due to the presence of malanoidin. Colour is another serious problem, since the colour interferes with the absorption of sunlight are responsible to reduce the natural process of photochemical reactions for self purification of the surface water. Therefore, the removal of colour and COD from the rice grain based BDE acquires immense importance from the environmental point of view. Furthermore, regulatory agencies in India have notified discharge water quality standards for release into surface water (BOD < 30 mg O2 /L, COD < 100 mg O2 /L) and sewer (BOD < 100 mg O2 /L, COD < 300 mg O2 /L) [3], therefore, effective treatment method is needed to reduce pollution load of BDE. Various treatment methods reported to treat BDE includes coagulation [4], thermolysis [5], adsorption [6] and electrochemical treatment [2,7,8]. Among all these treatment methods, ECT is a better method due to its several advantages such as, less additional chemical (coagulant) requirement, easier installation, more cost effective, low value of secondary pollution, odor and colour removal, and lower residence time [9]. In our previous study [10] potential of elctrocoagulation process for the removal of colour and COD of rice grain based BDE was demonstrated. It was shown that under optimal initial pH (pH0 )

2

A.K. Prajapati et al. / Journal of Water Process Engineering 11 (2016) 1–7

Table 1 Electrocoagulation used for treatment of distillery wastewater. Type of waste water

Current density or Current

Anode-Cathode

pH

time (time)

Removal efficiency

References

Distillery biodigester effluent Distillery biodigester effluent Distillery biodigester effluent Distillery spent wash Distillery spent wash Distillery spent wash Winery waste water Distillery spent wash

89.3 A/m2 156.25 A/m2 99 A/m2 14.285 mA/cm2 0.817 A/cm2 0.03 A/cm2 2A 6 A/dm2

Al-Al SS-SS Fe-Fe Rd-SS Al-Al, Al-Fe, Fe-Fe Al-Al Al-Al Graphite-Graphite

8 5 8 5.5 3 3 – 6.9–7.2

120 min 60 min 120 min 180 min 120 min 120 min 40 min 180 min

93 63.96 93 39.66 81.3, 71.8, 52.4 72.3 98.2 85.2

[2] [8] [10] [11] [12] [13] [14] [15]

of 8 and current density of 99 A/m2 , about 93% COD removal and 87% colour removal could be obtained. Optimum conditions of others related work and electrode used by different investigator is summarized in Table 1. In this background the present work aims to study the effect of pH, current density (CD) and electrolysis time (t) for the removal of COD and colour. The electrode loss and power consumption was calculated during ECT process. Besides, settling characteristics of the EC treated BDE is also reported. 2. Experimental 2.1. Effluent and its characterisation The BDE used in the present study was obtained from Chhattisgarh Distillery Pvt., Ltd., Kumhari, Chhattisgarh, India. To maintain constant characteristics of BDE, the sample was stored at 4 ◦ C in a deep freezer. Reactor was made up of Perspex glass and copper plate was used as electrode. The effluent was characterized in terms of various parameters namely, COD, colour, total solids, total dissolved solids, total suspended solids, reduced carbohydrate, sulphate, and chloride etc., as per standard method of analysis [16]. The main characteristic of the original and treated effluent studied in the present study is given in Table 2. 2.2. Experimental method The lab-scale batch experimental setup (Fig. 1) was used for the EC studies. In a 1.5 L reactor (made up of Perspex glass), 1.4 L of BDE was taken and its pH was maintained by using H2 SO4 (1 M) and NaOH (1 M) solutions. Four electrodes made up of copper plates (2 mm thickness having dimension of 8 cm × 7 cm) were used in the experiments hence the total effective surface area of each electrode was 56 cm2 . All electrocoagulation reactors (ECR), irrespective of their shape and size are basically electrochemical cells. All such reactors consist of a pair(s) of electrodes (of any desired shape)

in contact with the wastewater. The basic concept of ECT consists application of direct current from an external source between the sacrificial anode and the cathode (not necessarily made up of inert material) to enhance contact between the dispersed particles in the solution and promote in-situ coagulation. A distance of 2.0 cm was maintained between the two electrodes in the EC reactor. A distance of 1.5 cm was provided between the bottom of the electrodes and the reactor bottom for easy stirring. Mixing in the reactor was carried out by teflon coated stirring bar installed between pretreated plate and the bottom of the cell. The electrodes were cleaned with 10% dilute HCl solution after the completion of each run, followed by washing with tap water and drying at 50–60 ◦ C for further experiment. The current density was adjusted and kept constant by means of a digital direct current (D.C.) power supply (0–30 V, 0–5 A) source. During the experiments after certain time interval, samples were taken in a test tube and allowed for settling to remove sludge. At last the supernatant liquid obtained was used for various parameters (COD and colour) analysis.

3. Result and discussion It has been reported that the distillery effluent contains carbohydrate, proteins and melonoidin [17]. Carbohydrate contains negatively charged carboxylic and hydroxyl functional groups. The melonoidin and colloidal surfaces also have negative charges. All these take part in the electrocoagulation reduction process. Data investigated for BDE are presented in Table 1. During the EC process involving copper electrode, (Cu2+ ) were released at the anode, while at the cathode, typical H2 production occurs. Many reactions take place in the EC reactor with copper electrodes as shown below [18]: At copper anode

2Cu → 2Cu2+ + 4e−

Table 2 Typical composition of biodigester effluent before and after treatment by EC at CD = 89.3 A/m2 , electrode distance = 2 cm. Parameters

Biodigester effluent

EC treated BDE at optimum condition (pH 3.5)

COD TDS TSS TS Reduced carbohydrate Protein Chlorine Phosphate Total hardness Sulphate pH Colour Absorbance at wavelength = 475 nm Colour (PCU)

11,500 43,245 39,331 82,576 517 165 161 0.05 10,220 4718 7.8 Blackish brown 0.831 398

2300 1523 4515 6038 Not found 79 55 nil 244 613 8.0 Light yellow (transparent) 0. 299 139.3

*All value in mg/dm3 except pH and colour.

(1)

A.K. Prajapati et al. / Journal of Water Process Engineering 11 (2016) 1–7

3

Fig. 1. Schematic diagram of the experimental setup used for the electrocoagulation study.

2Cu + 4H+ → 2Cu2+ + 2H2

(2)

At cathode 4H2 O + 4e− → 2H2 + 4OH− Cu2+

(3)

Cu3+

The and ions hydrate and hydrolyse to form monomeric and polymeric species: Cu(OH)2 + , CuOH2+ , Cu2 (OH)2 4+ , Cu(OH)4 − , Cu(H2 O)2 + , Cu(H2 O)5 OH2+ , Cu(H2 O)4 (OH)2 + etc. [19]. The colloidal particles have net negative charges which are entrapped in amorphous ions hydroxides and get neutralized and settled due to its heavy mass. Organic pollutants are also removed through sweeping, when it comes in the way of settling heavy mass. 3.1. Effect of pH

(a) 90 Percentage COD reduction

In the acidic pH range, the electrode is attacked by H+ and this process enhances its dissolution, and following reaction occurs:

pH 1.5 pH 5 pH 8

80

pH 3.5 pH 6.5 pH 9.5

70 60 50 40 30 20 15

35

55

(b)

75 Time (min)

95

115

Percentage color reduction

80 It has been reported that the pH of the solution influence the electrocoagulation treatment of effluent [20]. The effect of pH on treatment of BDE was investigated at a constant current density (CD) 89.3 A/m2 . The results are shown in Fig. 2(a and b). The COD and colour reduction of BDE solution was increased with increase in pH from 1.5 to 6.5. The effect was decreased when the pH was increased further up to 9.5. It was also observed that COD and colour reduction of BDE solution increases with increase in electrolysis time (t). The COD reduction of 22%, 35%, 39%, 42%, 25%, and 23% is obtained in 20 min at pH values of 1.5, 3.5, 5, 6.5, 8, and 9.5, respectively, which increased to 46, 80, 83, 85, 63, and 57% in 120 min. Similar effects were also observed by different investigators [2,10]. It can be seen that BDE provided best COD reduction at pH 6.5 and less reduction at pH > 6.5 and pH < 9.5. The different values of COD reduction at different pH were probably due to the quality and quantity of copper hydroxide ions generated at particular pH. It is also reported that, at pH > 6.5and pH < 9.5, part of the solution get reduced to H2 and the proportion of the hydroxide ion

70 60 50 40 30 20

pH 1.5

pH 3.5

pH 5

pH 6.5

pH 8

pH 9.5

10 15

35

55

75 Time (min)

95

115

Fig. 2. Effect of pH on (a) percentage COD reduction and (b) percentage colour reduction (CD 89.3 A/m2 , electrode distance = 2 cm, CODi = 11500 mg/dm3 , colouri = 398 PCU).

4

A.K. Prajapati et al. / Journal of Water Process Engineering 11 (2016) 1–7

1 0.9

100 0.8

80 0.7

60

Height (H/Ho)

Energy consumption (Wh/dm3)

(a) 120

40 20 0

0.5 pH 3.5

0.4

pH 5

pH 6.5

pH 8

0.3

0

2

4

6

8

10 0.2

pH

(b) 6 Anode consumption (mg/dm3)

0.6

0.1 0

5

0

20

40

60 80 Time (min)

100

120

140

4 Fig. 4. Settling characteristic of the electrochemical treated slurry.

3 2 1

(a)

100

0 4

6

8

10

pH Fig. 3. Effect of pH on (a) electrode energy consumption (b) anode consumption (CD = 89 A/m2 , electrode distance = 2.0 cm, treatment time = 120 min, CODi = 11500 mg/dm3 , colouri = 398 PCU).

produced is less; consequently, less COD removal efficiency [21]. However, pH 3.5 was considered as optimum pH due to less power consumption and electrode loss. The colour reduction is expressed as the percent decrease in the absorbance of the BDE sample from the untreated sample at a wavelength () = 475 nm. In 20 min of EC treatment, colour reduced to 23%, 30%, 33%, 35%, 20%, and 16% at pH 1.5, 3.5, 5, 6.5, 8, and 9.5, respectively, which further reduced to 51%, 65%, 70%, 73%, 49.3%, and 42% in 120 min. It is observed that the colour reduction follows the trend of the COD reduction in the pH range of 3.5–9.5. The decolourization is due to the removal of melanoidin and other organic components that separates out from the effluent during electro coagulation. The electrical energy consumption was also calculated using the following equation [22]. P

 WH  dm

3

=

Vc It



Treatedvolume dm3



(4)

Fig. 3(a) shows the energy consumption as a function of pH at CD = 89.3 A/m2 , g = 20 mm, time = 120 min, and stirring speed = 120 rpm. At pH 1.5, 3.5, 5, 6.5, 8, and 9.5, respectively the P is found to be 9.2, 11.42, 28.82, 45.13, 97.14, and 114.28 WH/L of BDE. It is observed that as the pH is increased, the power consumption also increases. This may depend on three parameters includes (i) conductivity of the metal (ii) temperature of the solution, and (iii) pH of the solution. Electrical conductivity in metals is a result of the movement of electrically charged particles. The atoms of metal elements are characterized by the presence of valence electrons. It is ‘free electrons’ that allow metals to conduct an electric current. The value of conductivity (6.30 × 107 S/m at 20 ◦ C) of copper is high with less resistivity (1.59 × 10−8  m at 20 ◦ C). The transfer

90

Percent COD reduction

2

80 70 60 j=44.6 A/m2 j=89.3 A/m2

50

J=111.6 A/m2 40

J=133.9 A/m2

30 15

35

55

75

95

115

Time (min)

(b) 90

j=44.6 A/m2 j=89.3 A/m2 j=111.6 A/m2 j=133.9 A/m2

80 Percent color reduction

0

70 60 50 40 30 20 15

35

55

75 Time (min)

95

115

Fig. 5. Effect of current density on (a) percentage COD (b) colour reduction (pH 3.5, electrode distance = 2 cm, CODi = 11500 mg/dm3 , colouri = 398 PCU).

A.K. Prajapati et al. / Journal of Water Process Engineering 11 (2016) 1–7

5

Fig. 6. TG, TGA, and DTA of EC-treated BDE sludge. Air rate, 200 mL/min.

of energy is strong when there is little resistance. Copper is a good conductor because it contain more free electron like other metals. Each copper atom provides a single free electron, so there are many free electrons. Free electron concentration in copper is as high as 8.5 × 1028 /m3 . During ECT the temperature of the solution rises up to 10 ◦ C. Temperature of the solution is another parameter which influences the conductivity of copper as the electrical conductivity of a conductor will decrease with an increase in temperature. pH is also an important parameter which is the measurement of the H+ ions present in the solution. Since it is a weak electrolyte. Therefore in acidic pH value of I and V is decreased. By Ohm’s law at less resistivity value of voltage does not change with change in current; therefore, value of P is less at acidic pH. The electrode loss (EL) at different pH was also noted. The values are shown in Fig. 3(b). At similar operating conditions and at pH values of 1.5, 3.5, 5, 6.5, 8, and 9.5, respective electrode losses were found to be 2.9, 3.667, 5.2207, 4.35, 4.328, and 1.905 mg/L of treated BDE. Electrode loss in case of copper was less as compared to Al and Fe electrodes. Maximum COD reduction (85%) is obtained at pH 6.5 at the cost of 45.13 mg electrode loss and 45.13 WH energy consumption in BDE treatment. This may be due to the availability of much OH− for the formation of Cu(OH)2 through the reaction between Cu2+ and OH− . Increase in EL with change in pH has been reported by Anto-Ponselvan et al. [23]. It was reported that at pH 8, maximum COD reduction was 93% with power consumption 22 WH/L and electrode loss of 19.7 mg/L using iron electrode [10]. In an another study by Prajapati and Chaudhari [2], maximum COD reduction of 93% was achieved with power consumption of

31 WH/L and electrode loss of 16.85 mg/L using aluminum electrode. In this study optimum COD reduction was observed to be 80% at pH 3.5 with power consumption of 11.2 WH/L and electrode loss of 3.667 mg/L using copper as a sacrificial electrode. To analyze the separation characteristic by settling, after the EC process the treated BDE sample was slowly mixed and taken in a 0.5 dm3 capacity cylinder having 46 mm diameter. The supernatant and solid interface was noted at different times. Fig. 4 shows the time vs height graph of settling sludge of effluent treated at different pH. The settling rate is found in the order of pH 3.5 > pH 5 > pH 6.5 > pH 8. Settling characteristic was found good in between pH 6.5 to pH 8. This may be due to the formation of heavy flocks which settles down at this pH value. The method proposed by Richardson et al. [24] is most suitable to design a continuous thickener based on batch studies [25]. 3.2. Effect of current density The current density (CD) has been found to have strong influence on the efficiency of the EC process, as reported by several authors [26–28]. To observe its effect, experiments were conducted at various CDs (44.6–178.5 A/m2 ) at constant pH 5 and the observations are shown in Fig. 5(a and b). At CDs 44.6, 89.3, 133.8 and 178.5 A/m2 ; COD reduction of 73%, 80%, 86%, and 89.8%; and colour reduction of 48%, 67%, 79%, and 86%, respectively were obtained in a time period of 120 min. The removal of COD and colour increases with increase in CD. Significant COD and colour removal is obtained after 100 min of treatment at all current densities. By increasing the EC time to

6

A.K. Prajapati et al. / Journal of Water Process Engineering 11 (2016) 1–7

Table 3 Analysis of residue and foam obtained after EC at different pH. Parameter

At pH 5.0

At pH 6.5

At pH 8.0

At pH 9.5

Analysis of residue obtained after EC at different pH 10.53 Weight of residue (kg/m3 ) Colour Blue Nature Bulky mass, difficult to grinding Approximated drying period 15 80 % convertible COD

At pH 3.5

40.7 Blue Bulky mass, difficult to grinding 21 83

45.12 Blue Bulky mass, difficult to grinding 14 85

33.13 Blue Bulky mass, difficult to grinding 20 63

28.2 Blue Bulky mass, difficult to grinding 13 57

Analysis of foam obtained after EC at different pH Colour Blue Nature Soft mass, easy to grinding 80 % convertible COD

Blue Soft mass, easy to grinding 83

Blue Soft mass, easy to grinding 85

Blue Soft mass, easy to grinding 63

Blue Soft mass, easy to grinding 57

Table 4 Material balance for the metal and sludge at different pH. Experimental pH

Actual metal loss treated effluent (mg/dm3 )

Metal in sludge (mg/dm3 )

Metal in filtrate (mg/dm3 )

Total metal in the sludge (mg/dm3 )

% Error

3.5 5 6.5 8 9.5

3.667 5.2207 4.35 4.328 1.905

2.021 3.1207 3.05 3.048 1.405

1.5 2.1 1.30 1.28 0.5

3.521 5.124 4.221 4.25 1.811

3.98 1.85 2.96 1.80 4.93

120 min, it is observed that only 4% more COD reduction and 5% more colour reduction were achieved. The data reflects that 10% increase in COD reduction was found when CD was increased to 89 A/m2 from 44.6 A/m2 . By further increasing CD from 89.3 A/m2 to 133.9 A/m2 only 11% increase in COD reduction was obtained. Increase in CD increases the cost of processing. The removal of colour and COD increases with increase in current density. This is in accordance with Faraday’s law (Eq. (5)) which provides a relationship between current density and the amount of anode material that dissolves in the sample [29]. m=

M (CD) t ZF

(5)

where m is the theoretical amount of ion supplied per unit surface area by current density (CD) provided for a time duration (t). The number of electrons participating in the oxidation/reduction reaction are expressed by electrocoagulation equivalent (Z); for Cu, Z = 2. M is the atomic weight of anode material, for Cu, M = 63 g/mol; and F is the Faraday’s constant (96,487 C/mol). In EC process, when current density increases, number of Cu2+ ions also increases because m is directly proportional to CD. At higher CD, higher rate of formation of copper hydroxides results into the higher COD removal efficiency, because of occurrence of precipitation and sweep coagulation. 3.3. Analysis of scum and residue For the analysis of solid residues and scum, it was first separated from the treated BDE and later on dried at 110 ◦ C, until its weight became constant. Characteristics of foam and solid residues were also determined. Analysis data are presented in Table 3. It can be seen that the weight of residue and foam obtained at pH 6.5 have highest mass. Drying period lies between 13 and 21 h. Residues of EC treated BDE are hard and difficult to grind, whereas, scum has soft and easy grindable mater. Perhaps these residues organics have good heating value as presented by various authors [30,31]. After incineration, the ash may be blended with soil to make bricks (having good strength), which can be used as building material. Thermal degradation (oxidation) characteristics of BDE sludge obtained after EC treatment were studied by means of thermogravimetric (TG), differential thermogravimetric (DTG), and differential

thermal analysis (DTA) tests in oxidative (air) environment. To determine the thermal characteristics of EC treated BDE, it was heated to 110 ◦ C and a dry solid mass was obtained. The dried mass was kept for DTG-DTA-TG analysis. Thermal degradation (oxidation) characteristics of sludge obtained after EC of BDE are presented in Fig. 6. This curve indicates a weight loss of 31.05% of its original weight up to 300 ◦ C. Between 300 ◦ C and 700 ◦ C, the sludge gets further oxidized and has a weight loss of 3.53% of its original weight. On further heating to 1000 ◦ C, only 60.05% weight left for ECT treated sludge. The DTG curve displays a maximum rate of weight loss of 5.3 mg/min at 259 ◦ C for this sludge. Thermal degradation is an exothermic reaction with a heat evolution of 1.74 kJ/g at a temperature of 259 ◦ C (DTA curve). The broad spectrum of DTA and DTG demonstrates the presence of different organic molecules which oxidized over a wide temperature range. 3.4. Copper balance in treated effluent and their management The residue obtained was dried and dissolved in aquarezia with slow heating at about 80 ◦ C until the entire residue dissolved completely. After suitable dilution, the metal content of the residue and the filtrate was determined by atomic absorption spectrometer. The material balance for copper is given in Table 4. Central Pollution Control Board of India [3] has fixed the waste water discharge limits of treated effluent in surface and sewer to (<4 mg/L). Copper may be recovered through adsorption or by other physicochemical treatment methods. 4. Conclusion EC process for treatment of BDE of rice grain-based distillery resulted as an effective treatment method to reduce COD and colour. COD reduction of 46, 80, 83, 85, 63, and 57%; and colour reduction of 51%, 65%, 70%, 73%, 49.3%, and 42% were obtained at pH 1.5, 3.5, 5, 6.5, 8, and 9.5, respectively at constant CD of 89.3 A/m2 . The COD and colour reduction was found to increase with increase in current density. At pH 5, COD reduction of 73%, 80%, 86%, and 89.8%; and colour reduction of 48%, 67%, 79%, and 86% was obtained at CD 44.6, 89.3, 133.8, and 178.5 A/m2 , respectively. At pH 1.5, 3.5, 5, 6.5, 8, and 9.5 the 9.2, 11.42, 28.82, 45.13, 97.14 and 114.28 WH with energy consumed per liter treatment of BDE. The weigh losses

A.K. Prajapati et al. / Journal of Water Process Engineering 11 (2016) 1–7

obtained at pH 1.5, 3.5, 5, 6.5, 8, and 9.5 are 2.9, 3.667, 5.2207, 4.35 4.328, and 1.905 mg, respectively per liter of BDE treated. The settling characteristic of treated BDE was found best at the pH 8. The foams and residues obtained from the EC treated BDE sample may be used as a fuel after incineration in a furnace. References [1] Ministry of Petroleum & Natural Gas, Indian government, www.petroleum. nic.in, 2015. [2] A.K. Prajapati, P.K. Chaudhari, Electrochemical treatment of rice grain based distillery effluent: chemical oxygen demand and color removal, Environ. Technol. 35 (2014) 242–248. [3] Central Pollution Control Board (CPCB), Pollution Control Acts, Rules and Notifications Issued There Under, Central Pollution Control Board, Delhi, 2006. [4] A.K. Prajapati, R. Choudhary, K. Verma, P.K. Chaudhari, A. Dubey, Decolorization and removal of chemical oxygen demand (COD) of rice grain based effluent (BDE) using inorganic coagulants, Desalin. Water Treat. 53 (2015) 2204–2214. [5] A.K. Prajapati, P.K. Chaudhari, B. Mazumdar, R. Choudhary, Catalytic thermal treatment (catalytic thermolysis) of a rice grain-based biodigester effluent of an alcohol distillery plant, Environ. Technol. 36 (2015) 2548–2555. [6] Y. Satyawali, M. Balakrishnan, Performance enhancement with powdered activated carbon (PAC) addition in a membrane bioreactor (MBR) treating distillery effluent, J. Hazard. Mater. 170 (2009) 457–465. [7] M. Kumar, F. Infant, A. Ponselvan, J.R. Malviya, V.C. Srivastava, I.D. Mall, Treatment of bio-digester effluent by electrocoagulation using iron electrodes, J. Hazard. Mater. 165 (2009) 345–352. [8] C. Thakur, V.C. Srivastava, I.D. Mall, Electrochemical treatment of a distillery waste water: parametric and residue disposal study, Chem. Eng. J. 148 (2009) 496–505. [9] B. Nasr, G. Abdelatif, Electrochemical treatment of wastewaters containing 4-chlororesorcinol using boron doped diamond anodes, Can. J. Chem. Eng. 87 (2009) 78–84. [10] A.K. Prajapati, P.K. Chaudhari, Electrochemical treatment of rice grain based distillery biodigester effluent, Chem. Eng. Technol. 37 (2014) 65–73. [11] R.K. Prasad, S.N. Srivastava, Electrochemical degradation of distillery spent wash using catalytic anode: factorial design of experiments, Chem. Eng. J. 146 (2009) 22–29. [12] V. Khandegar, A.K. Saroha, Electrochemical treatment of distillery spent wash using aluminum and iron electrodes, Chin. J. Chem. Eng. 20 (3) (2012) 439–443. [13] B.M. Krishna, U.N. Murthy, B.M. Kumar, K.S. Lokesh, Electrochemical pretreatment of distillery wastewater using aluminum electrode, J. Appl. Electrochem. 40 (2010) 663–673.

7

[14] F. Kirzhner, Y. Zimmels, Y. Shraiber, Combined treatment of highly contaminated winery wastewater, Sep. Purif. Technol. 63 (2008) 38–44. [15] P. Manisankar, C. Rani, S. Viswanathan, Effect of halides in the electrochemical treatment of distillery effluent, Chemosphere 57 (8) (2004) 961–966. [16] L. Clesceri, L.A. Greenberg, R. Trussell, Standard Methods for Water and Waste Water Examination, APHA, New York, 1989. [17] P.K. Chaudhari, I.M. Mishra, S. Chand, Decolorization and removal of chemical oxygen demand (COD) with energy recovery: treatment of biodigester effluent of a molasses-based alcohol distillery using inorganic coagulants, Colloids Surf. A: Physicochem. Eng. Asp. 296 (2007) 238–247. [18] A.K. Prajapati, P.K. Chaudhari, Physicochemical treatment of distillery wastewater—a review, Chem. Eng. Commun. 202 (2015) 1098–1117. [19] O.P. Sahu, B. Mazumdar, P.K. Chaudhari, Treatment of wastewater by electrocoagulation: a review, Environ. Sci. Pollut. Res. 21 (2014) 2397–2413. [20] S. Mahesh, B. Prasad, I. Mall, I.M. Mishra, Electrochemical degradation of pulp and paper mill wastewater. Part 1 COD and color removal, Ind. Eng. Chem. Res. 45 (2006) 2830–2859. [21] A.K. Golder, A.N. Samanta, S. Ray, Removal of trivalent chromium by electrocoagulation, Sep. Purif. Technol. 53 (2007) 33–41. [22] R. Sridhar, V. Sivakumar, V. Prince, J. Prakash, Treatment of pulp and paper industry bleaching effluent by electrocoagulant process, J. Hazard. Mater. 186 (2011) 1495–1502. [23] F.I. Anto-Ponselvan, M. Kumar, J.R. Malviya, V.C. Srivastava, I.D. Mall, Elelectrocoagulation studies on treatment of biodigester effluent using aluminum Electrodes, Water Air Soil Pollut. 199 (2009) 371–379. [24] J.F. Richardson, J.H. Harker, J.R. Backhurst, Coulson and Richardson’s Chemical Engineering, Particle Technology & Separation Processes, vol. 2, 5th ed., Elsevier, Amsterdam, 2002. [25] R. Font, Calculation of the compression zone height in continuous thickeners, AIChE J. 36 (1990) 3–12. [26] N. Modirshahla, M.A. Behnajady, S. Kooshaiian, Investigation of the effect of different electrode connections on the removal efficiency of Tartrazine from aqueous solutions by electrocoagulation, Dyes Pigment 74 (2007) 249–257. [27] E.S.Z. El-Ashtoukhy, N.K. Amin, O. Abdelwahab, Treatment of paper mill effluents in a batch-stirred electrochemical tank reactor, Chem. Eng. J. 146 (2009) 205–210. [28] C. Barrera-Díaza, B. Bilyeu, G. Roa, L. Bernal-Martinez, Physicochemical aspects of electrocoagulation, Sep. Purif. Rev. 40 (2011) 1–14. [29] M.Y.A. Mollah, R. Schennach, J.R. Parga, D.L. Cocke, Electrocoagulation (EC)—science and applications, J. Hazard. Mater. 84 (2001) 29–41. [30] S. Mahesh, B. Prasad, I.D. Mall, I.M. Mishra, Electrochemical degradation of pulp and paper mill wastewater. Part 2. Characterization and analysis of sludge, Ind. Eng. Chem. Res. 45 (2006) 5766–5774. [31] R. Katal, H. Pahlavanzadeh, Influence of different combinations of aluminum and iron electrode on electrocoagulation efficiency: application to the treatment of paper mill wastewater, Desalination 265 (2011) 199–205.