Stormwater treatment system/apparatus

A stormwater treatment apparatus comprising,

• a lightweight watertight sedimentation tank module, said sedimentation tank module having a central sedimentation tank with an open top within it, including an annular perimeter basin, also within said sedimentation tank module,
• said central sedimentation tank having a removable watertight cover at said open top,
• said annular perimeter basin having a wetland formed of sand and gravel deposited within it, said central sedimentation tank including an inlet port from outside said basin for carrying stormwater into said covered central sedimentation tank and having an infiltration section in the wall between it and the annular perimeter basin, said infiltration section being transmissive of water, but generally not transmissive of particulate materials, and located to pass water into said perimeter basin in the subsurface area of wetland,
• said central sedimentation tank being formed with a plurality of bulkheads each extending radially from the center of said central sedimentation tank to the perimeter thereof, said bulkhead dividing said central sedimentation tank into a series of adjacent chambers, a first one of said bulkheads adjacent to said infiltration section being formed to be water impermeable, a second one of said bulkheads adjacent to said inlet port being water impermeable except for an oil and grease trap which passes water into the next chambers while blocking oil and grease from passing, said first and second ones of said bulkhead forming a first chamber coupled to said inlet port, at least one additional water impermeable bulkhead forming at least one additional chamber,
• means positioned in at least one of said additional chambers for transferring water from the surface of the water in said additional chamber to the next chamber near the bottom thereof,
• an outlet port located near the bottom of said annular perimeter basin, said outlet port including valve means which can be adjusted to control the throughput of water entering said sedimentation tank and exiting said annular perimeter basin at said outlet port.

A storm water treatment apparatus comprising,

• a lightweight watertight sedimentation tank module, said sedimentation tank module having a central sedimentation tank within it, including with an annular perimeter basin, also within said sedimentation tank module,
• said central sedimentation tank having a removable watertight cover,
• said annular perimeter basin having a wetland formed of sand and gravel deposited within it, said central sedimentation tank including an inlet port from outside said basin for carrying stormwater into said covered central sedimentation tank and having an infiltration section in the wall between it and the annular perimeter basin, said infiltration section being located generally diametrically opposite to said inlet port, said sedimentation tank comprising filter means between said inlet port and said infiltration section being transmissive of water, but generally not transmissive of particulate materials and said infiltration section being located to pass water into said perimeter basin in the subsurface area, and;
• an outlet port located near the bottom of said annular perimeter basin, said outlet port including valve means which can be preset to control the throughput of water entering said sedimentation tank and exiting said annular perimeter basin at said outlet port.