PHOSPHOROUS MITIGATION FOR GREEN FILTER BEDS

1 . A stormwater filtration system comprising:

a vault forming a bay having a filtration bed with live plant matter therein, an inlet for delivering stormwater into the bay, an outlet flow system in a lower part of the bay for receiving stormwater filtered through the filtration bed and delivering the filtered stormwater out of the bay, wherein the filtration bed comprises a filtration layer overlying an adsorption layer wherein said adsorption layer comprises a phosphorus adsorptive granular media.

2 . The stormwater filtration system of claim 1 , wherein the phosphorus adsorptive granular media comprises expanded perlite thermally impregnated with at least one active material.

3 . The stormwater filtration system of claim 2 , wherein said active material comprises activated alumina.

4 . The stormwater filtration system of claim 2 wherein the average particle size of the phosphorus adsorptive granular media is about 0.5 mm to about 12.5 mm.

5 . The stormwater filtration system of claim 1 wherein the filtration layer comprises a media mixture comprising inorganic components and organic components wherein the inorganic components account for a majority of the volume of said filtration layer.

6 . The stormwater filtration system of claim 5 wherein the inorganic components are selected from the group consisting of sand, pumice, zeolite, perlite and combinations thereof.

7 . The stormwater filtration system of claim 5 wherein the organic components are selected from the group consisting of peat, compost, mulch and combinations thereof.

8 . The stormwater filtration system of claim 5 wherein the organic and inorganic components are in the form of pellets or granules.

9 . The stormwater filtration system of claim 5 wherein the media mixture comprises pelletized leaf compost, sand, zeolite and pumice.

10 . The stormwater filtration system of claim 9 wherein the media mixture comprises about 7-13% by volume of pelletized leaf compost, about 60-80% by volume pelletized pumice or zeolite, and about 10-25% by volume sand.

11 . The stormwater filtration system of claim 10 wherein the media mixture further comprises water absorbent crystal material in an amount of less than 1% by volume.

12 . The stormwater filtration system of claim 5 wherein the media mixture comprises coarse sand and peat granules.

13 . The stormwater filtration system of claim 12 wherein the media mixture comprises about 85-95% by volume of coarse sand and about 5-15% by volume peat granules.

14 . The stormwater filtration system of claim 1 wherein the filtration layer has a depth of about 6-30 inches and the adsorption layer has a depth of about 2-6 inches.

15 . The stormwater filtration system of claim 1 wherein the filtration bed includes a drainage layer beneath the adsorption layer wherein the drainage layer comprises gravel.

16 . The stormwater filtration system of claim 1 wherein the bay is a first bay of the vault and the vault includes a second bay alongside the first bay, the second bay including at least one stormwater filtration device and an inlet for receiving excess stormwater from the first bay.

17 . The stormwater filtration system of claim 1 wherein the live plant matter is a tree and the filtration bed includes an upper layer formed by a plurality of permeable pavers disposed about a trunk of the tree.

18 . A method for treating stormwater, the method comprising:

receiving stormwater into a treatment bay including a filtration bed having live plant material planted therein, wherein the filtration bed comprises a filtration layer overlying an adsorption layer wherein said adsorption layer comprises a phosphorus adsorptive granular media;

filtering some of the stormwater downward through the filtration bed; and

directing the stormwater filtered by the filtration bed away from the treatment bay.

19 . The method of claim 18 , wherein the phosphorus adsorptive granular media comprises expanded perlite thermally impregnated with activated alumina.

20 . The method of claim 18 wherein the average particle size of the phosphorus adsorptive granular media is about 0.5 mm to about 12.5 mm.

21 . The method of claim 18 wherein the filtration layer includes a media mixture which comprises about 7-13% by volume of pelletized leaf compost, about 60-80% by volume pelletized pumice or zeolite, and about 10-25% by volume sand.

22 . The method of claim 18 wherein the filtration layer includes a media mixture which comprises about 85-95% by volume of coarse sand and about 5-15% by volume peat granules.

23 . A stormwater filtration system comprising:

a vault forming a bay having a filtration bed with live plant matter therein, an inlet for delivering stormwater into the bay, an outlet flow system in a lower part of the bay for receiving stormwater filtered through the filtration bed and delivering the filtered stormwater out of the bay, wherein the filtration bed comprises a plurality of layers and an uppermost layer comprises permeable pavers.

24 . The stormwater filtration system of claim 23 wherein the permeable pavers have a permeability of not less than 10 gallons per minute per square foot.

25 . A stormwater filtration system comprising:

a vault forming a bay having a filtration bed with live plant matter therein, an inlet for delivering stormwater into the bay, an outlet flow system in a lower part of the bay for receiving stormwater filtered through the filtration bed and delivering the filtered stormwater out of the bay, and an absorption area comprising a phosphorus adsorptive granular media

26 . The stormwater filtration system of claim 25 wherein the absorption area comprises a permeable sock.

27 . The stormwater filtration system of claim 26 wherein the permeable sock is located in the outlet flow system.

28 . The stormwater filtration system of claim 25 wherein the absorption area comprises a removable media polishing vessel.

29 . The stormwater filtration system of claim 28 wherein the outlet flow system delivers filtered stormwater to the removable media polishing vessel.