**3. Results and discussion**

#### **3.1. Efficiency and reproducibility of the novel EC reactor**

The investigations of the best parameters have been discussed in our previous research [17]. The major EC operation in the textile wastewater was executed in triplicate to confirm the efficiency and reproducibility of the application when the best operating conditions (CD = 4 mA/cm<sup>2</sup> , temperature = 25°C, RT = 10 min, pH = 4. 57, rotation speed = 150 rpm and d<sup>e</sup> = 1 cm) are used. The performance of the novel EC system was investigated based on the levels of BOD, Al, color, phenols, turbidity, COD, G&O, TDS, DO, nitrates, sulfate, phosphate and TSS. The summary of the results of the parameters is shown in **Figure 2** and **Table 3**. The EC operation exhibited 97.1% total removal efficiency of COD. After the EC treatment process, the G&O and BOD5 in the wastewater had values of 0.1 and 5 mg/L, respectively. The hydrophobic capacity of G&O resulted in a higher affinity combining with the H<sup>2</sup> bubbles created at the cathode. The (G&O)-H2 complex gathered on the surface of the liquid, which could be skimmed with ease [18].

The proposed EC design enables superior efficiencies and simultaneously reduces energy consumption in comparison with other reports. Un and Aytac [12] studied textile wastewater treatment by EC process in a packed-bed electrochemical reactor. They reported 96.88% removal efficiency for COD and observed that the color was almost completely removed after 1 h of EC

operation. However, in this work, the 97% COD removal efficiency was obtained after 10 min reaction. Merzouk et al. [15] also studied the textile wastewater treatment using electro-flotation and EC using a batch reactor (electrode gap = 1 cm, conductivity = 2.1 μS/cm, pH = 7.6 and

**Table 3.** Efficiency and reproducibility of EC rotating anode in textile wastewater treatment using the best operating

TSS = 85.5%, color = 93%, COD = 79.7%, BOD5 = 88.9% and turbidity = 76.2%. Comparing with

). With the best operating conditions, the obtained results are as follow:

density = 11.55 mA/cm<sup>2</sup>

**Parameters Raw** 

Energy consumption (kwh/m<sup>3</sup>

Electrode consumption (kg/m<sup>3</sup>

Polymer consumption (kg/m<sup>3</sup>

Sludge production (kg/m<sup>3</sup>

BOD<sup>5</sup>

Chlorides Cl<sup>−</sup>

Electrical energy cost (US\$/m<sup>3</sup>

Sludge disposition cost (US\$/m<sup>3</sup>

Total operating cost (US\$/m<sup>3</sup>

conditions (CD = 4 mA/cm**<sup>2</sup>**

Polymer cost (US\$/m<sup>3</sup>

Electrode consumption cost (US\$/m<sup>3</sup>

**effluent**

) 1.44

DO (mg/L) 0.7 14.5 4.5–15

) 0.01

Electrical conductivity (μS/cm) 1455 2000 ID \_\_ Initial pH 4.57 4.57 — \_\_ Final pH \_\_ 6.92 6–8 \_\_

O&G (mg/L) 3 0.1 5–40 96.66

Sulfate (mg/L) 678 17.00 ID 97.50 Phosphate (mg/L) 7.2 0.23 ID 96.80 Nitrates (mg/L) 11 0.2 ID 98.18 Phenols (mg/L) 335 0.0065 10 99.99

Aluminum (mg/L) 1.50 6.00 — \_\_

(mg/L) 33 0.4 ID —

) \_\_ 0.072 — \_\_

) \_\_ 0.086 \_\_ \_\_

) \_\_ 0.283 — \_\_

, temperature = 25°C, rotation speed = 150 rpm, RT = 10 min, pH = 4.57, d<sup>e</sup> = 1 cm).

) \_\_ 0.030 \_\_ \_\_

) \_\_ 0.095 — \_\_

 (mg/L) 112.5 5.00 5–45.5 95.55 COD (mg/L) 988 28.65 20–500 97.10 TSS (mg/L) 3270 65.70 60–300 98.00 Color observance at 533 NM 0.3400 0.0051 ID 98.50 TDS (mg/L) 1250 80.00 5–180 93.60 Turbidity (NTU) 396 19.80 15–50 96.00

**Treated effluent**

) \_\_ 0.966 — \_\_

) \_\_ 0.038 \_\_

**Allowable limit (EPA)** 

http://dx.doi.org/10.5772/intechopen.76876

**Removal (%)**

119

**1996**

Treatment of Textile Wastewater Using a Novel Electrocoagulation Reactor Design

**Figure 2.** The removal efficacy of several parameters of the textile wastewater using the best operating condition.


**Table 3.** Efficiency and reproducibility of EC rotating anode in textile wastewater treatment using the best operating conditions (CD = 4 mA/cm**<sup>2</sup>** , temperature = 25°C, rotation speed = 150 rpm, RT = 10 min, pH = 4.57, d<sup>e</sup> = 1 cm).

operation. However, in this work, the 97% COD removal efficiency was obtained after 10 min reaction. Merzouk et al. [15] also studied the textile wastewater treatment using electro-flotation and EC using a batch reactor (electrode gap = 1 cm, conductivity = 2.1 μS/cm, pH = 7.6 and density = 11.55 mA/cm<sup>2</sup> ). With the best operating conditions, the obtained results are as follow: TSS = 85.5%, color = 93%, COD = 79.7%, BOD5 = 88.9% and turbidity = 76.2%. Comparing with

**Figure 2.** The removal efficacy of several parameters of the textile wastewater using the best operating condition.

(electricity received by the cathode and the anode because of DC power supply). The values

The investigations of the best parameters have been discussed in our previous research [17]. The major EC operation in the textile wastewater was executed in triplicate to confirm the efficiency and reproducibility of the application when the best operating conditions (CD = 4 mA/cm<sup>2</sup>

perature = 25°C, RT = 10 min, pH = 4. 57, rotation speed = 150 rpm and d<sup>e</sup> = 1 cm) are used. The performance of the novel EC system was investigated based on the levels of BOD, Al, color, phenols, turbidity, COD, G&O, TDS, DO, nitrates, sulfate, phosphate and TSS. The summary of the results of the parameters is shown in **Figure 2** and **Table 3**. The EC operation exhibited 97.1% total removal efficiency of COD. After the EC treatment process, the G&O and BOD5

the wastewater had values of 0.1 and 5 mg/L, respectively. The hydrophobic capacity of G&O

The proposed EC design enables superior efficiencies and simultaneously reduces energy consumption in comparison with other reports. Un and Aytac [12] studied textile wastewater treatment by EC process in a packed-bed electrochemical reactor. They reported 96.88% removal efficiency for COD and observed that the color was almost completely removed after 1 h of EC

complex gathered on the surface of the liquid, which could be skimmed with ease [18].

, tem-

in

bubbles created at the cathode. The (G&O)-H2

were determined from Eq. (5).

of (Cenergy)

118 Wastewater and Water Quality

<sup>M</sup> and (Cenergy)

**3. Results and discussion**

S

resulted in a higher affinity combining with the H<sup>2</sup>

**3.1. Efficiency and reproducibility of the novel EC reactor**

the above results, this study utilizes only EC under the best operating conditions and exhibits superior removal efficiencies: TSS 98%, color >98%, BOD5 = 95.55%, COD 97% and turbidity = 96%. In recent time, El-Ashtoukhy et al. [19] examined phenol removal from wastewater generated from oil refinery using a fixed-bed anode electrochemical reactor consisting random Al raschig rings. At pH = 7, CD = 8.59 mA/cm<sup>2</sup> and concentration of NaCl = 1 g/L, around 80% phenol reduction was observed after 2 h using 40 mg/L as the primary phenol concentration.

EC model with rotating anode was lower than the conventional model with static electrodes

Electrochemical impedance spectroscopy is one of the most effective methods for investigation of electrochemical constraints of the electrolyte/electrode interface [22–24]. The impedance method was employed to study the effect of color adsorption on the Al anode and rotation speed (rpm) of the electrode on electrode passivity. The electrolyte was real textile effluence, and the potential of 0 V vs. Ag/AgCl, and frequency ranging from 0.01 to 105 Hz, was used for performance evaluation of the electrolyte/anode interface. **Figure 3(a)** presents the Nyquist plot for the anode at varying speed of rotation (0, 75, 100 and 150 rpm). Two semicircles were detected at low frequencies and high frequencies. **Figure 3(b)** presents the best fits for the Al electrode impedance spectra. The fitting parameters comprise the solution resistance (R<sup>s</sup>

parallel with a combination of the double-layer capacitance (Cdl) and impedance of the faradic reaction. On the other hand, the faradic reaction impedance comprises passivation resistance (Rct), accompanied by adsorption capacitance (Cads) and adsorption resistance (Rads) [25–28]. **Table 5** summarizes the impedance parameters. Temporarily, the first semicircle diameter signifies the values of Rct, and the diameter of the second semicircle signifies the values of Rads.

**Parameters EC rotating anode EC static electrode EC-EO static electrode**

) 5 12 12

) 0.038 0.1 0.087

) 0.966 8.49 9.00

) 1.44 3.50 2.88

) 0.283 1.76 1.69

**Table 4.** Comparison of the EC rotating anode with the conventional model static electrode (EC alone and EC-EO) at

) No add 1.26 1.20

) No add 0.1 No add

Materials Al-Al Mp Al-Bp Al Mp Ti-Bp Al

COD removal (%) 97.10 92.60 93.50 TSS removal (%) 98.00 96.40 97.00 Color removal (%) 98.50 96.50 97.50 Initial pH Natural 6.00 6.00 Conductivity (μS/cm) 2000 1980 1910 Current/volume ratio (A/L) 0.2 0.2 0.2

RT (min) 10 90 90

, while conventional static electrode including EC = 1.76

http://dx.doi.org/10.5772/intechopen.76876

Treatment of Textile Wastewater Using a Novel Electrocoagulation Reactor Design

) in

121

(EC rotating anode = 0.283US\$/m<sup>3</sup>

Surface area/volume ratio (m<sup>2</sup>

Electrode consumption (kg/m<sup>3</sup>

Energy consumption (kwh/m<sup>3</sup>

Sludge production (kg/m<sup>3</sup>

Operation cost (US\$/m<sup>3</sup>

optimal conditions.

NaOH (kg/m<sup>3</sup>

NaCl (kg/m<sup>3</sup>

/m<sup>3</sup>

and EC-EO =1.69 US\$/m<sup>3</sup>

**3.3. Passivation and adsorption phenomenon**

).

US\$/m<sup>3</sup>

In this study, the concentration of primary phenol is 350.0 mg/L, and after 10 min, about 99.99% was extracted, while 0.009 mg/L of phenol remains with the cured wastewater. Furthermore, Martinez-Delgadillo et al. (2012) investigated Cr (VI) reduction to Cr (III) with the aid of Fe (II) in a rotating ring iron electrode. Their report shows up to 99.9% removal of Cr (VI) between 22 and 42 min contact time at an angular velocity ranging from 0 to 230 rpm (at 5 A). In the current study, the optimal reaction time and current were 10 min and 2 A, to confirm the reduction in power consumption and low cost of operation. Moreover, this work also reports high TDS removal efficiency (93.6%) when the best set of operating parameters were used, and the phosphate concentration was decreased to 0.23 from 7.2 mg/L. The Al electrode suspension displayed a rise in the whole dissolved concentration to 6.00 from 1.5 mg/L during the operation. In comparison with the quality standards of global textile wastewater [20, 21], the findings support the analysis of the efficacy of the EC system for treatment of textile wastewater for various usages. The outcomes show that the COD, turbidity, TDS, BOD and DO are all lower than the acceptable limit. Conversely, the generally pH level of the treated effluence was basic (6.9 ± 0.04) to some extent, which is under the acceptable limit. Similarly, the oil and grease, as well as the total phenols, fall under the acceptable limit. Under optimal conditions, the real electrode consumption was 0.038 kg/m<sup>3</sup> , while the energy consumption was 0.966 kWh/m<sup>3</sup> , 0.9 kWh/m<sup>3</sup> for DC power supply consumption and 0.066 kWh/m<sup>3</sup> for DC motor of rotating anode. For settling metallic sludge study after adding 0.01 kg/m<sup>3</sup> LPM3135 polymers, a 5% sludge dryness and 63 mL/g SVI were noted in the course of the analysis. The sludge production was 1.44 kg/m<sup>3</sup> . Furthermore, the SRF utilized in these investigations was (4.6×1012m/kg). The results revealed that the main cost of the treatment operation per m3 [Eq. (4)] of wastewater, using the best set of operating parameters, is roughly 0.283 US\$.

#### **3.2. Comparison performance of the EC rotating anode with the conventional model**

**Table 4** shows a comparative study between EC rotating anode and the conventional static electrodes in two-phase EC process alone and EC-EO process depending on the results of each model at the optimal conditions. Each model has the same optimal applied current to volume ratio (0.2 A/L). Although the EC model with rotating anode has the lowest surface area to volume ratio (5 m<sup>2</sup> /m<sup>3</sup> ), it can be seen that this reactor model obtained the best removal efficiency of contaminant textile wastewater (COD, TSS and the color). The minimum reaction time (10 min) was achieved by EC model with rotating anode compared with a conventional model in two phases (90 min) which demonstrated the activity of electrodes for the treatment and reduced significantly the energy consumption to 0.966 kwh/m<sup>3</sup> . Furthermore, the rotation speed of anode affects the energy consumption by reducing the main voltage and passivation films. The EC process with rotating anode showed excellent treatment without setting the initial pH or using supporting electrolyte. The electrode consumption and sludge production were less than the conventional model with static electrodes. As for the operating costs, the EC model with rotating anode was lower than the conventional model with static electrodes (EC rotating anode = 0.283US\$/m<sup>3</sup> , while conventional static electrode including EC = 1.76 US\$/m<sup>3</sup> and EC-EO =1.69 US\$/m<sup>3</sup> ).

## **3.3. Passivation and adsorption phenomenon**

the above results, this study utilizes only EC under the best operating conditions and exhibits superior removal efficiencies: TSS 98%, color >98%, BOD5 = 95.55%, COD 97% and turbidity = 96%. In recent time, El-Ashtoukhy et al. [19] examined phenol removal from wastewater generated from oil refinery using a fixed-bed anode electrochemical reactor consisting random

phenol reduction was observed after 2 h using 40 mg/L as the primary phenol concentration.

able limit. Under optimal conditions, the real electrode consumption was 0.038 kg/m<sup>3</sup>

, 0.9 kWh/m<sup>3</sup>

tigations was (4.6×1012m/kg). The results revealed that the main cost of the treatment operation

**Table 4** shows a comparative study between EC rotating anode and the conventional static electrodes in two-phase EC process alone and EC-EO process depending on the results of each model at the optimal conditions. Each model has the same optimal applied current to volume ratio (0.2 A/L). Although the EC model with rotating anode has the lowest surface

efficiency of contaminant textile wastewater (COD, TSS and the color). The minimum reaction time (10 min) was achieved by EC model with rotating anode compared with a conventional model in two phases (90 min) which demonstrated the activity of electrodes for the treatment

speed of anode affects the energy consumption by reducing the main voltage and passivation films. The EC process with rotating anode showed excellent treatment without setting the initial pH or using supporting electrolyte. The electrode consumption and sludge production were less than the conventional model with static electrodes. As for the operating costs, the

**3.2. Comparison performance of the EC rotating anode with the conventional model**

[Eq. (4)] of wastewater, using the best set of operating parameters, is roughly 0.283 US\$.

for DC motor of rotating anode. For settling metallic sludge study after adding

), it can be seen that this reactor model obtained the best removal

LPM3135 polymers, a 5% sludge dryness and 63 mL/g SVI were noted in the course of

In this study, the concentration of primary phenol is 350.0 mg/L, and after 10 min, about 99.99% was extracted, while 0.009 mg/L of phenol remains with the cured wastewater. Furthermore, Martinez-Delgadillo et al. (2012) investigated Cr (VI) reduction to Cr (III) with the aid of Fe (II) in a rotating ring iron electrode. Their report shows up to 99.9% removal of Cr (VI) between 22 and 42 min contact time at an angular velocity ranging from 0 to 230 rpm (at 5 A). In the current study, the optimal reaction time and current were 10 min and 2 A, to confirm the reduction in power consumption and low cost of operation. Moreover, this work also reports high TDS removal efficiency (93.6%) when the best set of operating parameters were used, and the phosphate concentration was decreased to 0.23 from 7.2 mg/L. The Al electrode suspension displayed a rise in the whole dissolved concentration to 6.00 from 1.5 mg/L during the operation. In comparison with the quality standards of global textile wastewater [20, 21], the findings support the analysis of the efficacy of the EC system for treatment of textile wastewater for various usages. The outcomes show that the COD, turbidity, TDS, BOD and DO are all lower than the acceptable limit. Conversely, the generally pH level of the treated effluence was basic (6.9 ± 0.04) to some extent, which is under the acceptable limit. Similarly, the oil and grease, as well as the total phenols, fall under the accept-

and concentration of NaCl = 1 g/L, around 80%

for DC power supply consumption and

. Furthermore, the rotation

. Furthermore, the SRF utilized in these inves-

, while the

Al raschig rings. At pH = 7, CD = 8.59 mA/cm<sup>2</sup>

120 Wastewater and Water Quality

energy consumption was 0.966 kWh/m<sup>3</sup>

the analysis. The sludge production was 1.44 kg/m<sup>3</sup>

/m<sup>3</sup>

and reduced significantly the energy consumption to 0.966 kwh/m<sup>3</sup>

0.066 kWh/m<sup>3</sup>

area to volume ratio (5 m<sup>2</sup>

0.01 kg/m<sup>3</sup>

per m3

Electrochemical impedance spectroscopy is one of the most effective methods for investigation of electrochemical constraints of the electrolyte/electrode interface [22–24]. The impedance method was employed to study the effect of color adsorption on the Al anode and rotation speed (rpm) of the electrode on electrode passivity. The electrolyte was real textile effluence, and the potential of 0 V vs. Ag/AgCl, and frequency ranging from 0.01 to 105 Hz, was used for performance evaluation of the electrolyte/anode interface. **Figure 3(a)** presents the Nyquist plot for the anode at varying speed of rotation (0, 75, 100 and 150 rpm). Two semicircles were detected at low frequencies and high frequencies. **Figure 3(b)** presents the best fits for the Al electrode impedance spectra. The fitting parameters comprise the solution resistance (R<sup>s</sup> ) in parallel with a combination of the double-layer capacitance (Cdl) and impedance of the faradic reaction. On the other hand, the faradic reaction impedance comprises passivation resistance (Rct), accompanied by adsorption capacitance (Cads) and adsorption resistance (Rads) [25–28]. **Table 5** summarizes the impedance parameters. Temporarily, the first semicircle diameter signifies the values of Rct, and the diameter of the second semicircle signifies the values of Rads.


**Table 4.** Comparison of the EC rotating anode with the conventional model static electrode (EC alone and EC-EO) at optimal conditions.

solution pH to increase the solution temperature and the addition of any chemicals (Na2

The optimal energy and electrode consumptions were 0.038 kg/m<sup>3</sup>

\*, Mohammed A. Ajeel<sup>2</sup>

\*Address all correspondence to: ahmednamesamir@yahoo.com

2 Al-Karkh University of Science, Baghdad, Iraq

Universiti Teknologi Malaysia, Malaysia

enhanced the EC process performance and validated the novel reactor design.

led to the lower cost of operation (0.283US\$/m<sup>3</sup>

**Acknowledgements**

**Conflict of interest**

**Author details**

Ahmed Samir Naje<sup>1</sup>

Nigeria

Shreeshivadasan Chelliapan<sup>4</sup>

Almuthana Governorate, Iraq

research.

NaCl) is not required. The economic viability of the operation of the reactor is influenced by the parameters. The energy and electrode consumption of the EC increases as the CD increases.

nificantly enhanced the textile wastewater treatment by improving the pollutant removal rate, reducing reaction time of treatment, without any additional chemicals during the process, and reducing the operation cost compared to conventional model (EC and EC-EO). It was found that the passivation phenomenon reduced with the increased rotation speed of anode, which

The authors thank Babylon Textile Plant, Iraq, for supplying the textile wastewater. They also thank for Almuthana University Iraq and Ministry of Higher Education Iraq for funding this

The authors whose names are listed in the beginning of this chapter certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership or other equity interest; and expert testimony or patent-licensing arrangements) or nonfinancial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) on the subject matter or materials discussed in this manuscript.

1 Department of Architect Engineering, College of Engineering, Almuthana University,

3 Department of Chemical Engineering, Covenant University, Sango-Ota, Ogun-State,

4 Department of Engineering, Razak Faculty of Technology and Informatics,

, Peter Adeniyi Alaba3

and

SO<sup>4</sup> or 123

, which

and 0.966 kWh/m<sup>3</sup>

http://dx.doi.org/10.5772/intechopen.76876

). The novel EC reactor with rotating anode sig-

Treatment of Textile Wastewater Using a Novel Electrocoagulation Reactor Design

**Figure 3.** (a) Nyquist plots of the Al anode in an aqueous textile wastewater solution at 25°C temperature and varying electrode speed of rotation. (b) Equivalent circuits utilized to fit the Nyquist plots.


**Table 5.** Electrochemical impedance data extracted from the Nyquist plots at varying speed of rotation (rpm).

From **Table 5** and **Figure 3(a)**, it is clear that the values of Rct and Rads significantly declined with a rise in the rotation speed of the Al anode from 0 attaining the lowest value at 150 rpm. Therefore, the fouling rate of the anode was lessened, and the rate of adsorption of color to the interface of the anode increased at 150 rpm. Conversely, the highest values of the adsorption capacitance and double-layer capacitance were observed at 150 rpm. This elucidates the improvement in the rate of removal upon rotating the anode at 150 rpm as the EC experiment proceeds. It also confirms that the designed model can be a panacea to the limitation of the previous model.
