Black slag fixed bed for toluene, ethylbenzene and p-xylene (TEX) biodegradation and meiofauna development

In the past, black slag from an Electric Arc Furnace was dumped or stockpiled. Nevertheless, after much controversy, slag can no longer be considered a “waste”, and bearing in mind its positive properties, reuse alternatives are being sought. In this study, a black slag was used as an alternative packing material for toluene, ethylbenzene and p-xylene biofiltration, with these pollutants being fed both individually and jointly. Ethylbenzene recorded the highest elimination capacity when the ternary mixture was fed. The electrical conductivity of the leaching solution showed that the slag did not contribute to ion release or dissolution. The acid neutralizing capacity of the slag played a major role in preventing bed acidification. All the biofilters were invaded by mites, and other meiofauna including nematodes and rotifers also developed in the bed. Under these conditions, CO2 production was attributed not only to contaminant degradation but also to the metabolic processes of the meiofauna originating from the inoculum. Despite the favourable evolution of the operating parameters and the suitable performance of the slag bed, its high bulk density restricts the size of the bed. Slag is nonetheless recommended for use as a co-packing material.