Inclined tube is mainly used for water supply and drainage in the intake Sand, general industrial and domestic water sedimentation, sewage sedimentation, grease traps and tailings enrichment process can also transform the old pool. Its main features are: wet-week-old, hydraulic radius is small, a good state of laminar flow, particle deposition from turbulent flow interference. Straight pipe is mainly used for biological filter of the high-load biological filter, tower biological filter, Submerged Biological Aerated Filter (biochemical pool), and rotating biological contactors microbial carrier, for industrial organic wastewater and urban sewage biological treatment, the main feature is more efficient than activated sludge treatment, small footprint; aeration intensity lower than the activated sludge method, and does not require sludge return; sludge volume is small; adaptability, strong stability.