Removal of nejayote contaminants with alginate and chitosan

Abstract

Nejayote is the residual water from the nixtamalization process characterized by an alkaline pH (pH > 10) as well as high concentrations of dissolved and suspended organic matter (COD > 10 200 mg/L). As for the above mentioned, nejayote is consid-ered within the more pollutants liquid effluents discharged into different water bodies. In this work, the effectiveness of sodium alginate and chitosan to reduce nejayote pollutants was tested. The application of alginate involved adsorption and gelation, which trapped suspended and dissolved material, and the use of chitosan implied an adsorption-precipitation phenomena. These polymers were used separately and sequen-tially. In the independent treatments, the alginate was more efficient than the chitosan, obtaining a COD removal of 61.43 ± 0.24 % and of 59.74 ± 0.36 % respectively. In sequential treatments, the removal efficiency of COD with alginate-chitosan was higher (70.19 ± 0.85 %) than that of the chitosan-alginate treatment (67.21 ± 0.24 %). On the other hand, the reduction in the amount of total solids allows that the effluent, after the processing, is within the maximum permissible limit established by the official Mexi-can standards NOM-002-SEMARNAT-1996 and NOM-001-SEMARNAT-1996.,This permits its discharge to urban or municipal sewerage systems and it can even be used for agricultural irrigation. The use of these biodegradable polymers is a viable option that has the potential to scale at the industrial level, contributing to the purification of discharges from the nixtamalization industry and to the benefit of the environment.