Process and apparatus for removal of nitrate from surface and ground water, in particular drinking water

Claim 2

A process for removing nitrates from surface and ground water and from drinking water by biological denitrification comprising reducing said nitrates to gaseous nitrogen by contacting said water with a biocatalyst comprising a core of immobilized denitrifying organism cells trapped and cross-linked in an ionophoric gel or polymer and surrounded by an additional cell-free protective layer, said layer being impermeable to cells and consisting of a gel or polymer.

Claim 3

A process according to claim 1 further including a step of catalytic deoxidation of the water by oxidation with added hydrogen in the presence of a precious metals catalyst performed before the biological denitrification.

Claim 4

A process according to claim 1, wherein the strain "micrococcus denitrificans" is present in the biocatalyst.

Claim 5

A process according to claim 1, wherein the biological denitrification is performed in two or more stages.

Claim 6

A process according to claim 1, wherein the pH of the water in the biological denitrification is adjusted to 7 by the addition of acid.

Claim 7

Apparatus for removing nitrates from natural waters comprising, in combination: means for supplying water to be denitrified; a source of hydrogen; a first static mixer for oxidizing said water and including means for receiving said water from said means and hydrogen from said source; a first reactor receiving said water from said first static mixer and containing a bed of precious metal catalyst; hydrogen supply means connected operatively to said first reactor; a catalytic bed in said reactor having an upper section receiving said water; an outlet for said water communicating with said first reactor; a second static mixer including means for receiving water from said reactor and means for receiving hydrogen from said hydrogen supply means; a second reactor vessel constituting the first stage of denitrification; conduit means connecting said second mixer to said second reactor; said second reactor containing a biocatalyst bed consisting of immobilized cells trapped in an ionophoric gel of polymer and surrounded by an additional cell-free protective polymeric layer; a third reactor forming the second denitrification stage of said apparatus and fluidly communicating with and surmounted by said second reactor; said third reactor also containing a biocatalyst bed and a discharge line wherein connected with said third reactor are a recirculating pump, a pH meter, a first hydrogen meter and a flow meter; means for measuring the residual nitrate content of water discharging from said third reactor; and a collecting vessel communicating therewith.

Claim 8

Apparatus for removing nitrates from natural waters comprising, in combination: means for supplying water to be denitrified; a source of hydrogen; a first static mixer for oxidizing said water and including means for receiving said water from said means and hydrogen from said source; a first reactor receiving said water from said first static mixer and containing a bed of precious metal catalyst; hydrogen supply means connected operatively to said first reactor; a catalytic bed in said reactor having an upper section receiving said water; an outlet for said water communicating with said first reactor; a second static mixer including means for receiving water from said reactor and means for receiving hydrogen from said hydrogen supply means; a second reactor vessel constituting the first stage of denitrification; conduit means connecting said second mixer to said second reactor; said second reactor containing a biocatalyst bed consisting of immobilized cells trapped in an ionophoric gel of polymer and surrounded by an additional cell-free protective polymeric layer; a third reactor forming the second denitrification stage of said apparatus and fluidly communicating with and surmounted by said second reactor; said third reactor also containing a biocatalyst bed and a discharge line wherein connected with said third reactor are a recirculating pump, a pH meter, a first hydrogen meter and a flow meter; means for measuring the residual nitrate content of water discharging from said third reactor; and a collecting vessel communicating therewith.

Claim 9

Apparatus according to claim 6, having by-pass lines and associated values bypassing said biological denitrification reactors and/or the first reactor.

Claim 10

Apparatus according to claim 6 said means for measuring residual nitrate content comprising measuring devices for NO 3 NO X and NO 2 contents.

Claim 11

The apparatus of claim 6, having conduit means for introducing hydrogen directly into said second and third reactors.

Claim 12

The apparatus of claim 6, having by-pass means for flowing water directly from said second reactor to said collecting vessel without flowing through said third reactor.

Claim 13

The apparatus of claim 10, further including a second hydrogen meter between the third reactor and the collecting vessel.

Claim 14

The apparatus of claim 10, further including a water seal and gas lines connecting said reactors to said collecting vessel; a source of supply of oxygen supplying oxygen to said collecting vessel; controllable circulating systems for controlling the degree of denitrification of each of said denitrification stages; said systems consisting each of a conduit connecting the upper part of said second and third reactors thereto to vent gases from the apparatus.

Claim 15

The apparatus of claim 6, wherein the collecting vessel includes a splash overflow of enriching the water issuing from said third reactor with oxygen.