Aplicación de la tecnología de electroxidación al tratamiento y reutilización de agua en la acuicultura: estudio de la formación de subproductos

Abstract

Aquaculture, as a technique for growing aquatic plants and animals, is an important source of high protein foods, and hence economical profits [1]. On the other hand, aquaculture has a negative effect in environmental due to its wastewater rich in nitrogen compounds and organic matter [2]. Electrochemical oxidation with boron doped diamond (BDD) electrodes is a potential technology to remove pollutants from water, including total nitrogen ammonia the main aquaculture seawater contaminant. Previous studies in the research group have developed applications in treatment of leachate [3], wastewater [4] and waste streams in aquaculture [5]. Concerning the latter application and as a result of this electrochemical oxidation, bromide contained in seawater is turned into bromate, a carcinogenic chemical. An investigation about the generation of this hazardous by-product is required, so formation pattern of bromate during aquaculture seawater electroxidation with boron doped diamond (BDD) electrodes was evaluated in this work. In order to determine generation of bromates, several experiments were carried out with water from a fish-culturing facility located in Cantabria at different current densities (10 and 50 A m-2) and constant temperature (25ºC). Ion chromatography was used for bromide, bromate and chloride quantification and spectrophotometry for total ammonia nitrogen (TAN) determination. As a result, electrochemical oxidation technology using boron doped diamond (BDD) electrodes was successfully tested as an efficient alternative to treat aquaculture seawater removing total ammonia nitrogen (TAN), being 4 mg/l the maximum concentration of bromate achieved in the range of current densities applied. It has been found current density has a large effect on % TAN removal and time needed to reach it. Bromate formation is influenced by current density too, and its formation begins when total ammonia nitrogen (TAN) has been practically eliminated.