**4. Tests of the biopolymers obtained**

After obtaining the biopolymers, we proceed to prepare solutions of these extracts, to perform jar tests, and thus to determine the coagulant and flocculant capacity of natural biopolymers.

The tests are carried out with water of natural characteristics with different types of solids, which include natural tannins, solids smaller than 0.2 mm, organic matter, and other substances typical of raw or residual waters.

#### **4.1. Preparation of the solutions for coagulation and flocculation of** *Melocactus* **sp.,**  *Opuntia dillenii***,** *Stenocereus griseus***,** *Cereus forbesii***,** *Aloe arborescens***, and** *Aloe vera*

After obtaining the biopolymers of the plants *Melocactus* sp., *Opuntia dillenii*, *Stenocereus griseus*, *Cereus forbesii*, *Aloe arborescens*, and *Aloe vera*, the preparation of the solutions is carried out to realize the tests of jars, which prove the action of coagulant and flocculant.

The flocculant preparation process was weighed 1 g of biopolymer, then 1000 ml of distilled water was added and manual agitation was carried out until completely diluted.

#### **4.2. Preparation of coagulation solutions of Kabuli chickpea (***Cicer arietinum* **L.)**

About 1% solution was prepared by adding 10 g of the anionic coagulant in 1000 ml with Milli-Q® water, obtaining a solution of 10,000 mg/l, after which stirring was carried out for 1 h to homogenize the mixture. In this solution, the tests were carried out to know the adequate doses to treat the synthetic water prepared in the laboratory.

To prepare the synthetic water, laboratory clay was used for the preparation of samples of turbid water for all the experiments. About 20 g of clay were added to 1 l of distilled water. The suspension was gently stirred for 1 h on a magnetic stirrer in order to achieve a uniform dispersion of the clay particles. The suspension was allowed to stand for 24 h to achieve complete hydration of the clay. This clay suspension served as a stock solution using distilled water to prepare water samples with a turbidity of 200 NTU.

#### **4.3. Control parameters in rockrose tests**

To test the coagulating and flocculating effect of the biopolymers of *Melocactus* sp., *Opuntia dillenii*, *Stenocereus griseus*, *Cereus forbesii*, *Aloe arborescens*, *Aloe vera*, and Kabuli chickpea (*Cicer arietinum* L.), jug tests were performed as provided in ASTM D2035: 08 [12].

The control parameters normally used in the efficiency of a coagulant are pH, turbidity, and color, which are governed by standardized methodologies [13], which determine the ability to remove solids from water based on their behavior, pH, and with its spectrophotometric absorbance, turbidity and color at different wavelengths.

In accordance with the regulations in force in Colombia, the tests were carried out taking into account the technical standards adopted by the country for each test [14].

The removal obtained is processed in terms of percentages, to be able to compare. In the case of pH, it is observed that it complies with the provisions of the national standard for this parameter [15]; and in the case of turbidity and color, the percentage of removal is taken into account, which is directly proportional to the decrease in absorbance in each test.
