Rag seeding in wastewater treatment systems
In a wastewater treatment plant a rag seeding tank is included in a process drain to collect hair and fibers which have passed through headworks of the plant. The hair and fibers tend to join together into large masses downstream of the headworks and can be damaging to process zones, particularly membrane zones. The rag seeding tank includes cartridges filled with surfaces that fibers and hair will attach to, so that hair/fiber rags grow in the seeding tank and are removed therefrom rather than causing problems downstream.
1. 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.
2. A wastewater treatment plant as in claim 1 , wherein the ragging zone is a part of one of the process zones.
3. A wastewater treatment plant as in claim 1 , wherein the ragging zone stands as a separate zone upstream of at least some of the process zone.
4. A wastewater treatment plant as in claim 1 , wherein the outer ends of the hook structures curve through at least 180°.
5. A wastewater treatment plant as in claim 1 , wherein the outer ends of the hook structures curve according to a radius no greater than about 5 mm.
6. A wastewater treatment plant as in claim 1 , wherein the fiber-gripping structures are spaced apart no greater than about 10 mm.
7. A wastewater treatment plant as in claim 1 , wherein each stage includes a liquid level indicator to indicate to an operator that the level in the stage has risen to overflow the cartridge, and thus a cartridge has become clogged and needs replacement.
8. A wastewater treatment plant as in claim 1 , with a series of said cartridges, each being replaceable when clogged.
9. A wastewater treatment plant as in claim 1 , wherein the hook structures comprise natural burs from plants.