Bioloop filter (braided cord made of vinylidene chloride thread) was used for the biological treatment of sewage. In this study, the aeration tank (1.8 m3) was divided into 4 portions across the flow direction and bioloop filter (30 or 45 m·m-3) was submerged in each tank. Amount of biomass attached to the filter was determined after 60 to 100 days operational periods and were regarded as mixed liquor suspended solids (MLSS).
The amount of biomass attached on the filter was ranged from 0.4 to 0.6 kg·m-3 (bioloop 30 m·m-3) and from 0.4 to 0.8 kg·m-3 (bioloop 45 m·m-3). Acoordingly, BOD loadings in this study were kept in the range from 0.15 to 0.35 kg-BOD·kg-MLSS-1·d-1. Effluent BOD was stabilized with the decrease of BOD loading and effluent containing BOD<5 mg·l-1 was obtained even in winter season at a loading under 0.24 kg-BOD·MLSS-1·d-1. Though dissolved oxygen concentration in bulk liquid was maintained at suficiently high level, biomass contained sulfide ion upto 0.4 mg-S2-·g-biomass-1. As a result of anaerobic degradation inside the biomass, the excess sludge production ratio of this process was less than that of conventional activated sludge.
