**1. Introduction**

Conventional water treatment processes include coagulation and flocculation, especially that which is chemically assisted, for both drinking water and wastewater. The removal capacity of these operations is effective and with a speed that could have been used, especially with waters that have high concentrations of organic matter, for this purpose, reagents have been used such as aluminum sulfate, which is usually obtained from the reaction of aluminum hydroxide with sulfuric acid [1]. Another reagent used is ferric chloride, which is obtained by the reaction of

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

chlorine gas on heated iron [2]; and a reagent used in recent years is the aluminum polychloride obtained by the reaction of aluminum with hydrochloric acid in aqueous solution [1].

**2. Selection of plants with the potential to produce biopolymers for** 

**Figure 1.** *Stenocereus griseus*. Source: http://cactiguide.com/cactus/?genus=Stenocereus&species=griseus.

**Figure 2.** Cereus forbesii. Source: http://www.kakteensammlungholzheu.de/en/cereus\_forbesii.html.

Plants with the capacity to generate biopolymers with coagulant and flocculant uses have been under study during the last decades, especially *Moringa oleifera*, *Opuntia* spp., *Cicer arietinum* [5], and others that have demonstrated coagulant capacity, as part of the traditional

Extraction and Use of Plant Biopolymers for Water Treatment

http://dx.doi.org/10.5772/intechopen.77319

371

**coagulation and water flocculation**

empirical knowledge of indigenous communities [6].

The reactions associated with the coagulants are determined by some parameters such as the pH, the temperature of the water, and the concentrations of the solids that are going to be complexed to form flocs that can be separated by density difference inside the mixture. When the flocs are separated from the mixture, sludge is generated that must be thickened and then disposed of, within a waste management plan; these residues will have a high concentration of aluminum and iron, respectively, according to the type of coagulant used, whether it be aluminum sulfate, aluminum polychloride, or ferric chloride. The final disposal of these sludges is usually difficult, because of the load of aluminum or iron as they are considered toxic for the soil in high concentrations[3].

These disposal problems of the sludge, which generally has a high concentration of organic matter, generate environmental impacts when they are discharged into soils or bodies of water, changing the natural microbiota and affecting the species that have contact with high concentrations of aluminum and iron. To overcome this difficulty, different products of vegetable origin have been studied, which have properties similar to those of aluminum or iron compounds, generate coagulation and flocculation, but with organic compounds, are part of the natural components of plants come, as is the case of *Melocactus* sp., *Opuntia dillenii*, *Stenocereus griseus*, *Cereus forbesii*, *Aloe arborescens*, *Aloe vera*, and Kabuli chickpea (*Cicer arietinum* L.). These plants have shown an activity for the flocculation of substances with small particle size, below 0.2 mm, which generally cannot be separated by natural sedimentation [3].

The sludge derived from the coagulation and flocculation processes with plant extracts has a completely organic composition, which means that they can be digested by microorganisms and transformed into carbon, nitrogen, and phosphorus substances that can be incorporated into the corresponding biogeochemical cycles, with absence of toxic metals for the soil [4], or with safe concentrations for this vital resource. This technological alternative transforms water treatment into a less aggressive process with the environment, taking into account that most of the waste generated in drinking water and domestic waste treatment is sludge.

The extraction systems of plant biopolymers have different methodologies, which are easy to apply, proven, and are part of already standardized unit operations. Taking into account that different parts are harvested from each plant, we must understand that for most of the plants, their use is of the majority of the biomass, whereas when we speak of Kabuli chickpea (*Cicer arietinum* L), we are using only their seed, which diminishes its use, taking into account the weight ratio of the plant and the mass used for the preparation of the coagulant.

The operations developed to determine the efficiency of each plant extract in the coagulation and flocculation are defined within the established for jar tests and some of them have Z potential measurements (measure of the magnitude of the repulsion or attraction between the particles).
