InDENSE technology screens out heavy sludge particles from ordinary sludge by adding a sludge filter and returns them to the biochemical system, while discharging light sludge outside the system through sludge discharge. By using this technology, the sewage treatment system can enrich dense sludge. Dense sludge has the characteristics of fast settling speed and easier synchronization of nitrification and denitrification pathways, making it a more advanced granular sludge.