TRATAMIENTO DE AGUAS RESIDUALES EMPLEANDO POLÍMEROS NATURALES Y BIODEGRADABILIDAD DE LOS LODOS GENERADOS

Abstract

There are many methods to treat wastewater, either of municipal or industrial type. One is the coagulation-flocculation which aim is to eliminate colloidal particles than other methods can not remove. Currently, iron or aluminum salts and synthetic polymers have been employed, which generate less biodegradable sludges. Biopolymers such as guar gum, carob, mesquite and cactus mucilage have coagulant and flocculant properties, so they can be used in the treatment of municipal and industrial wastewater. These biopolymers can show equal or better removal efficiencies than synthetic products. In addition, their use will generate more biodegradable sludges. The aim of this work was to study the wastewater treatment using natural polymer and determine the biodegradability of generated sludges, compared with those generated by using ferric chloride. Methods were developed for extraction of cactus mucilage and mesquite bean gum. The biopolymers were characterized in terms of rheological parameters and metal content. Municipal wastewater and wastewater generated from a cosmetics industry were used. These samples were characterized in terms of physicochemical parameters, zeta potential and the effect of pH over sedimentation. It was performed an experimental design with 3 factors (i.e., type of biopolymer, biopolymer dose and initial COD wastewater), each with 3 levels. The response variables evaluated were final pH, removals of COD, turbidity, salinity and the sludge was analyzed in terms of volume, weight, density, BOD/COD ratio and metal contents. In municipal wastewater biopolymers worked best with the lowest dose (25 mg/L), removing between 44 and 52% of the initial COD. The biopolymers showed similar behavior among themselves, removing 25 to 20 mg COD per mg of biopolymer. The galactomannans (guar and carob gums) worked better (when treating industrial wastewaters) with the medium dose (300 mg/L) with COD removal between 22 and 25%. They were able to remove 10 and 11 mg COD per mg of biopolymer. The cactus mucilage worked better with the lower dose (150 mg/L), reaching 21 mg COD / mg, twice the amount reached when using the galactomannans. The volume of produced sludge is directly related to the initial organic load of wastewater. The higher the initial load, the higher the produced sludge. Densities of the generated sludge from municipal wastewater showed a significant difference for all experiments, while in the sludge generated by industrial wastewater no significant differences were observed. The biopolymers have the potential to replace the use of inorganic salts and synthetic polymers in the treatment of municipal wastewater and a high load-wastewater from cosmetic industry through coagulation and flocculation.