Rag seeding in wastewater treatment systems

A wastewater treatment plant for domestic wastewater, having a series of process zones, comprising:

• the plant including a ragging zone for removal of hair and fibers in the wastewater stream, such hair and fibers tending to gather together to produce rags in the process zones,
• the ragging zone including a cartridge in the flow stream containing a multiplicity of fiber-gripping structures to which substantially the entire flow of wastewater is exposed as the wastewater flows through the cartridge,
• the fiber-gripping structures comprising hook structures with outer ends that curve or bend through more than 90°, the fixed structures being spaced apart no more than 20 mm and having a radius in the range of about 0.5 to 10 mm, and
• wherein the ragging zone includes a series a stages, each with at least one cartridge through which the flow stream penetrates, such that if a cartridge or cartridges of a first stage become blocked, the flow stream will overflow the cartridge and pass through the next stage, the cartridges being removable and replaceable,
• whereby the hair and fibers carried in the wastewater are caused to rag together on the fiber-gripping structures of the cartridges, so that the cartridges can be removed and changed as needed and fouling of the process zones by ragging is eliminated.