Method for wastewater treatment in fluidized bed biological reactors

Claim 1

The method of carrying out a fluidized bed biological reaction for advanced treatment of wastewater, in which there is provided within a confined upwardly-extending treatment zone an upflow bed of solid particulate carrier having the biological reaction bacteria cells growing thereon, said wastewater to be treated being passed upwardly through said bed at a velocity at least sufficient to fluidize said bed; wherein the improvement comprises: (a) restraining the top of said bed with a perforated plate to maintain a smaller uppermost portion of said bed as a fixed bed with a larger portion of said bed therebeneath being in fluidized condition, the perforations in said plate being of smaller size than said carrier so as to retain said carrier in said treatment zone while permitting the treated water to pass therethrough; (b) continuing to pass the wastewater to be treated through said bed for initial biological reaction in said fluidized bed portion and final biological reaction in said fixed bed portion until said fixed bed portion has become clogged with cellular material; (c) discontinuing said treatment and raising said plate to a level out of contact with said bed when fully fluidized and above an outlet from said confined space which is located at a level normally above said plate during said treatment; and (d) passing wash water upwardly through said bed at a velocity sufficient to fully fluidize said bed while removing wash water together with excess cellular material through said outlet, the fixed portion of said bed being broken up and fluidized to release cellular material therefrom.

Claim 2

The method of carrying out a fluidized bed biological reaction for advanced treatment of wastewater, in which there is provided within a confined upwardly-extending treatment zone an upflow bed of solid particulate carrier having the biological reaction bacteria cells growing thereon, said wastewater to be treated being passed upwardly through said bed at a velocity at least sufficient to fluidize said bed; wherein the improvement comprises: (a) restraining the top of said bed with a perforated plate to maintain a smaller uppermost portion of said bed as a fixed bed with a larger portion of said bed therebeneath being in fluidized condition, the perforations in said plate being of smaller size than said carrier so as to retain said carrier in said treatment zone while permitting the treated water to pass therethrough; (b) continuing to pass the wastewater to be treated through said bed for initial biological reaction in said fluidized bed portion and final biological reaction in said fixed bed portion until said fixed bed portion has become clogged with cellular material; (c) discontinuing said treatment and raising said plate to a level out of contact with said bed when fully fluidized and above an outlet from said confined space which is located at a level normally above said plate during said treatment; and (d) passing wash water upwardly through said bed at a velocity sufficient to fully fluidize said bed while removing wash water together with excess cellular material through said outlet, the fixed portion of said bed being broken up and fluidized to release cellular material therefrom.

Claim 7

The method of carrying out a fluidized bed biological reaction for advanced treatment of wastewater, in which there is provided within a confined upwardly-extending treatment zone an upflow bed of solid particulate carrier having the biological reaction bacteria cells growing thereon, said wastewater to be treated being passed upwardly through said bed at a velocity at least sufficient to fluidize said bed; wherein the improvement comprises: (a) passing said wastewater upwardly through said bed at an upward velocity greater than the minimum fluidization velocity for said bed when unrestrained; (b) restraining the upper surface of said bed with a perforated plate to maintain a smaller uppermost portion of said bed as a fixed bed with a larger portion of said bed therebeneath being in fluidized condition, said upper fixed bed portion being of relatively small size compared to said fluidized bed portion, the perforations in said plate being of smaller size than said carrier so as to retain said carrier in said treatment zone while permitting the treated water to pass therethrough; (c) continuing to pass the water to be treated through said bed for initial biological reaction in said fluidized bed portion and final biological reaction in said fixed bed portion until said fixed bed portion has become clogged with cellular material, said water being treated varying substantially in flow rate, said variation being by a factor of at least 5% with reference to the average daily (24 hrs) flow rate, said fixed bed portion increasing in size and downward extent when said water flow rate substantially increases; (d) discontinuing said treatment and raising said plate to a level out of contact with said bed when fully fluidized and above an outlet from said confined space which is located at a level normally above said plate during said treatment; and (e) passing wash water upwardly through said bed at a velocity sufficient to fully fluidize said bed while removing wash water together with excess cellular material through said outlet, the fixed portion of said bed being broken up and fluidized to release cellular material therefrom.

Claim 8

The method of carrying out a fluidized bed biological reaction for advanced treatment of wastewater, in which there is provided within a confined upwardly-extending treatment zone an upflow bed of solid particulate carrier having the biological reaction bacteria cells growing thereon, said wastewater to be treated being passed upwardly through said bed at a velocity at least sufficient to fluidize said bed; wherein the improvement comprises: (a) passing said wastewater upwardly through said bed at an upward velocity greater than the minimum fluidization velocity for said bed when unrestrained; (b) restraining the upper surface of said bed with a perforated plate to maintain a smaller uppermost portion of said bed as a fixed bed with a larger portion of said bed therebeneath being in fluidized condition, said upper fixed bed portion being of relatively small size compared to said fluidized bed portion, the perforations in said plate being of smaller size than said carrier so as to retain said carrier in said treatment zone while permitting the treated water to pass therethrough; (c) continuing to pass the water to be treated through said bed for initial biological reaction in said fluidized bed portion and final biological reaction in said fixed bed portion until said fixed bed portion has become clogged with cellular material, said water being treated varying substantially in flow rate, said variation being by a factor of at least 5% with reference to the average daily (24 hrs) flow rate, said fixed bed portion increasing in size and downward extent when said water flow rate substantially increases; (d) discontinuing said treatment and raising said plate to a level out of contact with said bed when fully fluidized and above an outlet from said confined space which is located at a level normally above said plate during said treatment; and (e) passing wash water upwardly through said bed at a velocity sufficient to fully fluidize said bed while removing wash water together with excess cellular material through said outlet, the fixed portion of said bed being broken up and fluidized to release cellular material therefrom.