**4. Conclusions**

The wastewater generated by industries is becoming more complex and difficult to treat to restore its quality and reuse it. The coagulation-flocculation process has become one of the 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 maximize the recovery of cellulose fiber and obtain the best quality of treated water.
