**3. Results and discussion**

**Tables 1** and **2** show the physicochemical characterization of the six types of industrial wastewater. The values of the main residual water quality parameters such as BOD5 , COD, alkalinity, hardness, pH, electrical conductivity, content of dissolved and suspended solids, settleable solids, temperature, turbidity, nitrogen and total phosphorus, heavy metals are shown. Of these normative parameters, the environmental legislation dictates which ones must comply, considering the type of industry and body of discharge of residual water. Additionally, other non-regulated parameters, which are fundamental to understand and operate the coagulationflocculation process, such as particle size, turbidity, total organic carbon, biodegradability and zeta potential [21]. The measurement of these parameters is key to implement the design and sequence of an industrial wastewater treatment train to achieve the best quality of treated water.

In all types of wastewater, the regulated parameters exceed the maximum permissible limits, both for their discharge to the water receiving bodies and for their reuse. One of the main pollutants present in industrial wastewater is the content of dissolved and suspended solids, where these can be organic and inorganic depending on the source of the wastewater. Generally, the first stage of a wastewater treatment train consists of the elimination of the suspended particles; this is where the coagulation-flocculation processes are applied. Considering the main interactions that occur between the suspended particles and the coagulant-flocculant agents, the zeta potential is a key parameter to determine the surface charge density of the suspended particles and the polyelectrolytes, as well as the optimum dose to perform the solid-liquid separation of the suspended particles.

**Figure 1** shows the ζ = f (pH) profiles of each type of industrial wastewater, metalworking, candy factory, nejayote, recycled oils, recycled cellulose and paper. These profiles show that all the wastewater has negative zeta potential values at pH > 5, while at pH <5, zeta potential values are close to neutrality or positive. With exception, the wastewater from the electroplating processes shows positive zeta potential values at pH <6.0, and at pH > 7.0 presents negative zeta potential values. As expected, in order to carry out a coagulation-flocculation process in an efficient way, it is necessary to add a polyelectrolyte with a positive charge to neutralize the negative charge of the wastewater from the pulp and paper industry. The monitoring of the zeta potential value with respect to the polyelectrolyte dose in the wastewater allows to construct the coagulation-flocculation operation curves, and this ensures that the operators of the wastewater treatment plants avoid the problem of overdosing of coagulant-flocculant agents and save on the consumption of chemical substances [22]. In this chapter, the capacity of a biopolyelectrolyte extracted from the shrimp waste for the clarification of wastewater from the cellulose and paper recycling industry was evaluated. This was done with the aim of increasing the reuse potential of the treated water and improving the efficiency of solid-liquid separation processes for the recovery of cellulose fiber present in industrial wastewater.

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After each addition of chitosan, the mixture of residual water with chitosan was stirred at 200 rpm for 2 min and subsequently at 50 rpm for 20 min. For the evaluation of the quality of

**Tables 1** and **2** show the physicochemical characterization of the six types of industrial waste-

ity, hardness, pH, electrical conductivity, content of dissolved and suspended solids, settleable solids, temperature, turbidity, nitrogen and total phosphorus, heavy metals are shown. Of these normative parameters, the environmental legislation dictates which ones must comply, considering the type of industry and body of discharge of residual water. Additionally, other non-regulated parameters, which are fundamental to understand and operate the coagulationflocculation process, such as particle size, turbidity, total organic carbon, biodegradability and zeta potential [21]. The measurement of these parameters is key to implement the design and sequence of an industrial wastewater treatment train to achieve the best quality of treated water.

In all types of wastewater, the regulated parameters exceed the maximum permissible limits, both for their discharge to the water receiving bodies and for their reuse. One of the main pollutants present in industrial wastewater is the content of dissolved and suspended solids, where these can be organic and inorganic depending on the source of the wastewater. Generally, the first stage of a wastewater treatment train consists of the elimination of the suspended particles; this is where the coagulation-flocculation processes are applied. Considering the main interactions that occur between the suspended particles and the coagulant-flocculant agents, the zeta potential is a key parameter to determine the surface charge density of the suspended particles and the polyelectrolytes, as well as the optimum dose to

**Figure 1** shows the ζ = f (pH) profiles of each type of industrial wastewater, metalworking, candy factory, nejayote, recycled oils, recycled cellulose and paper. These profiles show that all the wastewater has negative zeta potential values at pH > 5, while at pH <5, zeta potential values are close to neutrality or positive. With exception, the wastewater from the electroplating processes shows positive zeta potential values at pH <6.0, and at pH > 7.0 presents negative zeta potential values. As expected, in order to carry out a coagulation-flocculation process in an efficient way, it is necessary to add a polyelectrolyte with a positive charge to neutralize the negative charge of the wastewater from the pulp and paper industry. The monitoring of the zeta potential value with respect to the polyelectrolyte dose in the wastewater allows to construct the coagulation-flocculation operation curves, and this ensures that the operators of the wastewater treatment plants avoid the problem of overdosing of coagulant-flocculant agents and save on the consumption of chemical substances [22]. In this chapter, the capacity of a biopolyelectrolyte extracted from the shrimp waste for the clarification of wastewater from the cellulose and paper recycling industry was evaluated. This was done with the aim of increasing the reuse potential of the treated water and improving the efficiency of solid-liquid separation processes for the recovery of cellulose fiber present in industrial wastewater.

, COD, alkalin-

water. The values of the main residual water quality parameters such as BOD5

the treated water, a sample of the supernatant was extracted [21].

perform the solid-liquid separation of the suspended particles.

**3. Results and discussion**

130 Wastewater and Water Quality



**Table 1.** Physicochemical characterization of industrial wastewater: Nixtamalization, recycled cellulose and paper and recycled oils wastewater.

**Figure 1.** ζ = f (pH) profiles from industrial wastewater: Candy factory, metalworking, recycled oils, nejayote, electro-

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133

**Figure 2.** ζ = f (pH) profiles of recycled cellulose and paper wastewater and chitosan.

plating and recycled cellulose and paper.


**Table 2.** Physicochemical characterization of industrial wastewater: Electroplating and metalworking wastewater.

Innovation of Coagulation-Flocculation Processes Using Biopolyelectrolytes and Zeta Potential… http://dx.doi.org/10.5772/intechopen.75898 133

**Figure 1.** ζ = f (pH) profiles from industrial wastewater: Candy factory, metalworking, recycled oils, nejayote, electroplating and recycled cellulose and paper.

**Parameter Electroplating** 

Total Phosphorus, TP (mg P/L) 16

COD (mg O<sup>2</sup>

COD (mg O<sup>2</sup>

(mg O<sup>2</sup>

132 Wastewater and Water Quality

Biodegradability (BOD5

recycled oils wastewater.

BOD5

(mg O<sup>2</sup>

Biodegradability (BOD5

BOD5

**wastewater**

**Parameter Recycled cellulose and** 

/COD) 0.5

Temperature (°C) 25 Temperature (°C) 32 Sn (mg/L) 4854 Zn (mg/L) 7.78 Pb (mg/L) 1044 Ni (mg/L) 41.57 Fe (mg/L) 683 Cr (mg/L) 7.44 TSS (mg/L) 4510 Cd (mg/L) 0.47 Turbidity (FAU) 2990 SS (mg/L) 9 EC (mS/cm) 74 Fats and oils (mg/L) 465.66 ζ (mV) 26 TSS (mg/L) 3352.63 Particle size (nm) 346 Turbidity (FAU) 2990 Color (Pt-Co) 6742 EC (mS/cm) 327 pH 0.8 ζ (mV) −10.0

**paper wastewater**

/L) 8000 COD (mg O<sup>2</sup>

/L) 4000 BOD5

Total Nitrogen, TN (mg N/L) 88 Biodegradability (BOD5

Particle size (nm) 500 Particle size (nm) 750 Color (Pt-Co) 3000 Color (Pt-Co) 2340 pH 5.4 pH 7.63

TOC (mg C/L) 1890 TOC (mg C/L) 5200

**Table 1.** Physicochemical characterization of industrial wastewater: Nixtamalization, recycled cellulose and paper and

/L) 1432 Particle size (nm) 678

/L) 30 pH 7.36

/COD) 0.02 TOC (mg C/L) 3858 BOD5

**Table 2.** Physicochemical characterization of industrial wastewater: Electroplating and metalworking wastewater.

(mg O<sup>2</sup>

Biodegradability (BOD5

TOC (mg C/L) 125 Color (Pt-Co) 2500

TN (mg N/L) 50.6 COD (mg O<sup>2</sup>

**Parameter Metalworking** 

(mg O<sup>2</sup>

**Parameter Recycled oils** 

/L) 43,650

/L) 17,500

/COD) 0.4

**wastewater**

/L) 64,800

/L) 2857

/COD) 0.04

TN (mg N/L) 316.8

**wastewater**

**Figure 2.** ζ = f (pH) profiles of recycled cellulose and paper wastewater and chitosan.

most used technologies to remove suspended particles, dyes and heavy metals; however, one of the trends consists of the substitution of synthetic coagulant-flocculant agents with biopolyelectrolytes. This leads to the development of environmentally friendly technologies, and take advantage of the waste that contains biodegradable polymeric materials and with high potential for its application in the elimination of toxic pollutants from industrial wastewater. In this chapter, the wastewater treatment of the cellulose and paper industry was carried out through a coagulation-flocculation process using a dose of 10 mg/L chitosan at pH 5.4. Through the zeta potential measurements, the pH = 5.4 at which the chitosan and the wastewater have an opposite electric charge was determined, and the best dose of chitosan to

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135

maximize the recovery of cellulose fiber and obtain the best quality of treated water.

The authors thank the Autonomous University of Baja California for the financing granted for

\* and Mercedes T. Oropeza-Guzmán<sup>2</sup>

1 Faculty of Chemical Sciences and Engineering, Autonomous University of Baja California,

[1] Muralikrishna IV, Manickam V, editors. Environmental Management: Science and

[2] Cahoon LB, Mallin MA. Water quality monitoring and environmental risk assessment in a developing coastal region, southeastern North Carolina. In: Ahuja S, editor. Monitoring

[3] Suthar S, Sharma J, Chabukdhara M, Nema A. Water quality assessment of river Hindon at Ghaziabad, India: Impact of industrial and urban wastewater. Environmental

2 Graduate and Research, Center of the Technical Institute of Tijuana, Tijuana, México

Engineering for Industry. United States: Elsevier; 2017. pp. 295-336

Water Quality. Amsterdam: Elsevier; 2013. pp. 149-169

Monitoring and Assessment. 2010;**165**:103-112

**Acknowledgments**

**Conflict of interest**

**Author details**

Tijuana, Mexico

**References**

Eduardo A. López-Maldonado1

the development of this project (UABC-PTC-668).

The authors state that there is no conflict of interest.

\*Address all correspondence to: elopez92@uabc.edu.mx

**Figure 3.** ζ = f (chitosan dose) in coagulation-flocculation tests from recycled cellulose and paper wastewater.

**Figure 2** shows the variation of zeta potential with respect to the pH of the wastewater and chitosan. The zeta potential value of the wastewater shows that the suspended particles have a negative surface charge density at pH 5–9. The ζ = f (pH) profile shows that at pH = 4.0 and pH > 10.0, the wastewater has two isoelectric points (ζ = 0). The stability of the particles to remain suspended is due to the value of the negative zeta potential (ζ = −25.5 mV). In order to destabilize the dispersion of cellulose fiber particles, the addition of a cationic coagulantflocculant agent that allows the neutralization of the negative surface charge is necessary. The wastewater at pH 5.4 has a ζ = −25.5 mV and the chitosan ζ = 15.0 mV, the dosage of chitosan at this pH by pure electrostatic interaction ensures its reaction.

In **Figure 3**, it is shown that the zeta potential value of the wastewater from cellulose and paper industry increases linearly as the dose of chitosan increases (ζ = −25.5 mV to ζ = −5.1 mV), reaching the isoelectric point at a dose of 10 mg/L chitosan. The water treated at pH 5.4 with chitosan has a value of BOD5 = 150 mg O<sup>2</sup> /L, turbidity = 5 FAU, TSS = 2 mg/L, COD = 200 mg/L and hardness = 250 mg CaCO<sup>3</sup> /L, and the treated water with these physicochemical characteristics can be discharged into the municipal sewer system or reused as process water.
