Estudio de viabilidad de tratamiento de aguas residuales mediante foto-Fenton solar a diferentes pHs

Abstract

[ES] El proceso foto-Fenton es un proceso con alta capacidad para el tratamiento de aguas residuales. No obstante, su pH óptimo de trabajo (2.8) su pone un desventaja a la hora de aplicarlo a gran escala ya que los costes asociados a los ajustes de pH antes y después del tratamiento pueden ser elevados. Este pH de trabajo puede acercarse a valores más neutros mediante el empleo de agentes complejantes del hierro aunque el proceso resulta más lento y se aumenta el consumo de oxidante debido a la presencia de materia orgánica extra. Por ello resulta interesante estudiar la viabilidad tanto técnica como económica de este proceso a diferentes pHs cuando la carga orgánica es moderada.

[EN] In this project, a comparative study of both technical and economic feasibility of the treatment of contaminated water with high organic load has been carried out using the photo-Fenton process. On the one hand, the model water (100 mg / L of total organic carbon) has been treated by the photo-Fenton process in its optimum pH conditions; this is 2.8. On the other hand, the same treatment was carried out at pH 5 using humic substances as iron complexants. As is well known, iron ions precipitate in the form of hydroxides at pHs greater than 3.5 and their catalytic action is lost. In addition, and in order to get closer to real problems, tap water has been used as the matrix. In a first stage, laboratory-scale experiments have been carried out modifying the concentrations of iron, complexing agents and hydrogen peroxide in order to study the optimal proportions of humic substances and iron. While a certain amount of complexing is needed to keep the iron active at pH 5, an excess of complexing can compete for the generated radicals and even absorb some of the radiation. Once the most appropriate proportions have been determined, the pilot plant has been worked on calculating the consumption of reagents in both cases. At pH 2.8, the acid and base consumption increases but the treatment time and peroxide consumption decreases. At pH 5 the acid and base consumptions are much lower but the process is slower and more peroxide is consumed. When using all the data obtained to carry out the economic study in a plant that treats 4 m3 per day, it is observed that the process at optimal pH is 20% cheaper than if one works at pH 5 using complexing agents. Therefore, it is concluded that to treat water with high organic load it is preferable to use the process in its optimal conditions.