The characteristics and application of grain-slag media in a biological aerated filter (BAF)

Novel filter media-grain slag particles were prepared using waste material-grain slag, clay and pore-forming material with a mass ratio of 3:2:1. Compared with haydite, grain-slag had higher total porosity, larger total surface area and lower bulk and apparent density. Tests of heavy metal elements in lixivium proved that grain-slag were safe for wastewater treatment. In order to ascertain the application of grain-slag, grain-slag and haydite were applied as the media of biological aerated filters (BAF) to treat municipal wastewater in two lab scale upflow BAFs. The results showed that grain-slag reactor brought a relative superiority to haydite reactor in terms of chemical oxygen demand (CODcr) and ammonia nitrogen (NH3-N) removal at the conditions of water temperature ranging from 20 °C to 26 °C and DO ≥4.00 mg L−1 when hydraulic retention time (HRT) ranging from 1 h to 5 h. In addition, the detection of the amount of hetero bacteria and nitrobacteria of two biological aerated filters in three HRTs also showed that grain-slag medium was more suitable to the attached growth of nitrobacteria, which is helpful to the improvement of nitrification performance in grain-slag BAF. Therefore, grain-slag application in BAF, as a novel process of treating wastes with wastes, provided a promising way in grain slag waste material utilization.