Stormwater treatment device
A stormwater treatment device includes a tank defining an internal volume and having an inlet and an outlet, a rotatable screen unit mounted within the tank, the rotatable screen unit being barrel-shaped to define a through path with an inlet end and an outlet end. The rotatable screen unit includes a screen structure with a plurality of screening openings for allowing passage of at least some water from the through path outwardly through the screen structure while inhibiting passage of trash items through the screen structure such that trash items move along the through path from the inlet end to the outlet end. The rotatable screen unit includes a plurality of external drive paddles that rotate with the screen structure and that interact with water that has been screened by passing outwardly through the screen structure interacts with the external drive paddles to cause rotation of the rotatable screen unit.
1. A stormwater treatment device, comprising:
a tank defining an internal volume and having an inlet and an outlet;
a rotatable screen unit mounted within the tank, the rotatable screen unit being barrel-shaped to define a through path with an inlet end and an outlet end, the rotatable screen unit includes a screen structure with a plurality of screening openings for allowing passage of at least some water from the through path outwardly through the screen structure while inhibiting passage of trash items through the screen structure such that trash items move along the through path from the inlet end to the outlet end;
wherein the rotatable screen unit includes a plurality of external drive paddles that rotate with the screen structure and that drive rotation of the screen structure by interacting with water that has been screened by passing outwardly through the screen structure.
2. The stormwater treatment device of claim 1 , wherein the rotatable screen unit further includes a plurality of internal blades, within the through path, and which rotate with the screen structure, wherein the internal blades are configured to direct at least some water moving along the through path upwardly along the screen structure.
3. The stormwater treatment device of claim 2 , wherein each internal blade runs in a helical pattern along an internal surface of the screen structure, wherein each external drive paddle is configured as a trough structure.
4. The stormwater treatment device of claim 3 , wherein the trough structure has a V-shaped end profile.
5. The stormwater treatment device of claim 2 , wherein each internal blade is configured to push trash items along the through path and out of the outlet end of the through path.
6. The stormwater treatment device of claim 1 , further comprising:
an insert within the tank, the insert configured to define:
an inlet bay into which water from the inlet of the tank flows, the inlet bay including an outlet opening positioned such that the inlet end of the through path is open to the inlet bay for water entry;
an outlet bay for delivering water to the outlet of the tank;
a trash bay located at the outlet end of the through path;
a support housing for the rotatable screen unit, wherein the support housing defines a path at an external surface side of the screen structure for allowing at least some water that passes through the screening openings to move to the outlet bay without such water passing through the outlet end of the rotatable screen unit into the trash bay;
wherein trash items that pass along the through path and out of the outlet end of the rotatable screen unit are captured within the trash bay.
7. The stormwater treatment device of claim 6 , wherein the insert further comprises a flow path from the trash bay to the outlet bay, with at least one trash bay screen located along the flow path to maintain captured trash debris within the trash bay while allowing water that enters the trash bay to flow to the outlet bay.
8. The stormwater treatment device of claim 7 , wherein the trash bay screen is located at a height to permit water level equalization between the trash bay and the outlet bay during lower flow conditions.
9. The stormwater treatment device of claim 1 , further comprising:
an insert within the tank, the insert configured to define:
a support housing for the rotatable screen unit, the support housing carrying a plurality of bearing assemblies to permit rotation of the rotatable screen unit.
10. The stormwater treatment device of claim 9 , wherein at least some of the bearing assemblies include a thrust bearing for limiting axial movement of the rotatable screen unit and a track bearing to support rotation of the rotatable screen unit.
11. The stormwater treatment device of claim 1 , further comprising:
an insert within the tank, the insert configured to define:
an inlet bay into which water from the inlet of the tank flows, the inlet bay including an outlet opening positioned such that the inlet end of the through path is open to the inlet bay for water entry;
an outlet bay for delivering water to the outlet of the tank;
a trash bay located at the outlet end of the through path.
12. The stormwater treatment device of claim 11 , wherein the insert is further configured to define a path at an external surface side of the screen structure for delivering at least some water that passes through the screening openings to the outlet bay and toward the outlet of the tank without such water passing through the outlet end of the rotatable screen unit into the trash bay, wherein at least part of that path extends under the rotatable screen unit in a direction to continue to drive the rotatable screen unit as the water moves toward the outlet of the tank.
13. The stormwater treatment device of claim 1 , wherein the rotatable screen unit is a first rotatable screen unit, and the device further comprises a second rotatable screen unit, the second rotatable screen unit being barrel-shaped to define a second through path with an inlet end and an outlet end, the second rotatable screen unit having a second screen structure with a plurality of screening openings for allowing passage of water therethrough while inhibiting passage of trash items through the screening openings of the second screen structure such that trash items move along the second through path from the inlet end to the outlet end, wherein the second rotatable screen unit includes a plurality of external drive paddles that rotate with the second screen structure and that interact with water that has been screened by passing outwardly through the second screen structure interacts with the external drive paddles to cause rotation of the second rotatable screen unit.
14. The stormwater treatment device of claim 1 , wherein the rotatable screen unit is oriented such that a rotation axis of the rotatable screen unit runs transverse to an inlet flow direction of water flowing into the inlet of the tank.
15. The stormwater treatment device of claim 14 , wherein the rotation axis runs substantially perpendicular to the inlet flow direction.
16. The stormwater treatment device of claim 14 , further comprising a wall member that deflects water entering the inlet of the tank to dissipate energy.
17. A stormwater treatment device, comprising:
a tank defining an internal volume and having an inlet and an outlet;
a rotatable screen unit mounted within the tank, the rotatable screen unit being barrel-shaped to define a through path with an inlet end and an outlet end, the rotatable screen unit having a plurality of screening openings for allowing passage of water therethrough while preventing passage of trash items through the screening openings so that trash items within the through path move from the inlet end to the outlet end;
wherein the rotatable screen unit has a rotation axis that runs transverse to an inlet flow direction of water entering the inlet;
wherein a wall is located in the tank and configured and positioned such that stormwater flowing in the inlet flow direction into the tank impinges on the wall to dissipate energy and divert the stormwater toward the inlet end of the rotatable screen unit.
18. The stormwater treatment device of claim 17 , wherein the rotation axis runs substantially perpendicular to the inlet flow direction.
19. The stormwater treatment device of claim 17 , wherein the rotatable screen unit includes:
(i) at least one internal blade within the through path such that water entering the inlet end of the through path interacts with the internal blade to move upward along a height of the rotatable screen unit; and
(ii) a plurality of external paddles that are oriented such that screened water that passes through the screening openings drives rotation of the rotatable screen unit.
20. The stormwater treatment device of claim 17 , wherein:
the wall is part of an insert that includes structure that supports the rotatable screen unit; or
the wall is solid without any openings therethrough.
21. The stormwater treatment device of claim 17 , wherein:
the wall is part of an insert that includes structure that supports the rotatable screen unit; and
the wall is solid without any openings therethrough.
22. A method of treating stormwater, comprising:
flowing stormwater into a tank in which a rotatable screen unit is located, the rotatable screen unit shaped to define an axial through path with an inlet end and an outlet end, the rotatable screen unit having a plurality of screening openings for allowing passage of stormwater therethrough while preventing passage of trash items through the screening openings;
flowing the stormwater into the inlet end of the rotatable screen unit, wherein at least some stormwater passes through the screening openings for screening and interacts with externally located drive blades of the rotatable screen unit to drive rotation of the rotatable screen unit.