**1. Introduction**

The problems of water availability have their origin in the physiographic and climatic distribution, the contamination of surface and underground waters and the accelerated increase in demand for the different uses. For example, the reuse of water in agriculture is a well-known practice in the world; however, reuse in industry, municipal services, secondary uses, and aquifer recharge is only practiced to a limited extent. Given the imminent shortage of the resource in some areas of the country, the reuse of water is considered as an alternative supply; however, to reuse the water it is necessary to meet a certain quality.

Among the main parameters that define water quality are turbidity and color, attributed to the presence of colloidal particles and dissolved organic matter. These particles remain in suspension for a long time and can even pass through a very fine filter medium [1] since they do not have the tendency to agglomerate.

In particular, coagulation and flocculation processes have shown their usefulness in eliminating colloidal particles in water. On one hand, coagulation aims to neutralize the surface charges of suspended particles, and thus facilitate their agglomeration. In practice, this procedure is characterized by the injection and rapid dispersion of both chemical and organic products [2]; on the other hand, flocculation aims to favor, with the help of slow mixing, the contact between destabilized particles. Thus, the particle agglomerate forms a "floc" that can be easily eliminated by the decantation and filtration procedures [3].

Polymers have been used in coagulation-flocculation processes for water purification for at least four decades [4]; compared to alum, some of the advantages derived from the use of polymers in water treatment are:


The polymers used in water treatment are soluble in water and mainly synthetic in nature, although some natural products may be of interest. Polymers are widely characterized by their ionic nature: cationic, anionic, and non-ionic. Strictly ionic polymers are called polyelectrolytes [5].

The most important characteristics of polymeric flocculants are their molecular weight (MW) and, in the case of polyelectrolytes, their charge density. All polymers used as flocculants in water treatment must be soluble in water.

In an aqueous solution, polymers very often assume a random folded configuration. The length of the polymer depends on the interaction between its segments, if there is an appreciable repulsion between segments then the polymer expands a little.

The best-known example is polyelectrolytes, where the segments are charged. In this case, the polymer can expand significantly and there are significant effects on ionic strength. At higher ionic strength, the repulsion between charged segments is "filtered" by ions in solution, so the expansion of the molecule would not be as great [6].

Due to this aspect, the polyelectrolytes are suitable for use in the coagulationflocculation process and their use as coagulants in water treatment and sludge thickening. Thus, it is proposed to study the influence of bio-polyelectrolytes (BP), in the aggregation of particles of organic matter dispersed in water. The intention is to eliminate the contamination matrix that is generated in fish packing plants that currently lack water treatment systems. As an additional benefit, it is proposed that the residual sludge does not become waste for special handling, but rather has a reuse value taking advantage of its content. In this work, the performance of biopolyelectrolytes as a sustainable alternative for the sanitation and reuse of treated wastewater is evaluated. The main factors that affect the performance of chitosan in destabilizing and aggregating colloidal particles of organic matter is discussed.
