Electro-Fenton systems for “on-site” sanitary wastewater treatment: Towards an off-grid technology for developing countries

Abstract

Nowadays, 2.3 billion people in the world (almost a third of the planet´s population) live in communities that lack a sewer system and the financial resources for its installation. In this work, two electrochemical reactors based on the Fenton reaction were evaluated as a tertiary treatment for real sanitary wastewater which was obtained from a pre-treatment using biological processes. The evaluated systems were solar-powered, modular, off-grid operated and tested for open use. The processes consist on treating real sanitary wastewater with an anaerobic biodigester followed by a biological anoxic-aerobic stage and finally using the electrochemical reactors. The solid waste is stabilized using a solar heater and the outcoming aqueous effluent has an average organic matter concentration measured as chemical oxygen demand of 30.6 ± 10.1 mgO2 L−1, biological chemical demand of < 10 mgO2 L−1, total organic carbon of 14.8 ± 3.6 mgC L−1, total suspended solids of < 7.96 mg L−1 and total nitrogen of 36.2 ± 12.1 mgN L−1. The treated water falls below the limits established by the Mexican regulations on concentration of organic matter, total suspended solids, helminth eggs (HE) (< 1 HE L−1) and is close to the limit concentration for fecal coliforms. The goal of this study was to verify the functionality of the prototypes under realistic conditions so that these findings can contribute to the development of a technology for on-site sanitary wastewater treatment systems.