# US 6,719,893 B2 · Method for removing phosphorus from water to be treated using an electric field

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- Number: US 6,719,893 B2
- Document ID: US6719893B2
- Status: Granted
- Kind: B2
- Application number: 10/052,445
- Filed: 2002-01-23
- Published: 2002-12-12
- Granted: 2004-04-13
- Earliest claimed: 2001-06-11
- Assignees: Gunma University
- Inventors: Yutaka Sakakibara
- Web page: https://patentgrep.com/patent/US6719893B2

## CPC

- C02F 1/463: by electrocoagulation
- C02F 1/46114: {Electrodes in particulate form or with conductive and/or non conductive particles between them}
- C02F 2101/105: {Phosphorus compounds}
- Y02W 10/37: using solar energy
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

Phosphorus is removed from water to be treated by immersing electrodes into a tank filled with the water to be treated, applying a DC voltage between the electrodes to generate hydroxide ions through a cation migration in the water and/or an electrolysis, and precipitating phosphate ions in the water as a salt slightly soluble in water.

## Claims

### Claim 1

A method for removing phosphorus from water to be treated, which comprises immersing a multi-electrode system into a tank filled with the water to be treated, applying a DC voltage to the multi-electrode system to generate hydroxide ions through a cation migration in the water and/or an electrolysis, and precipitating phosphate ions in the water as a salt slightly soluble in water,
wherein the multi-electrode system is an operation system in which plural cathodes are arranged to a single anode, or plural anodes are arranged to a single cathode, and each electrode can be operated independently.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the tank is filled with granular solids.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the granular solids are sands, glass beads, or shells.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the cation migration and accumulation and/or the electrolysis are conducted while flowing the water to be treated through the tank.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the multi-electrode system is porous or meshed.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the water to be treated contains calcium ions and/or magnesium ions.

### Claim 7 (depends on 1)

The method according to claim 1, wherein a phosphorus compound removed from the water to be treated is recovered by back wash.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the multi-electrode system is an operation system in which plural cathodes are arranged to a single anode.

### Claim 9

A method for removing phosphorus from water to be treated, which comprises immersing a multi-electrode system into a tank filled with the water to be treated, applying a DC voltage to the multi-electrode system to generate hydroxide ions through a cation migration in the water and/or an electrolysis, and precipitating phosphate ions in the water as a salt slightly soluble in water,
wherein the multi-electrode system is an operation system in which plural cathodes are arranged to a single anode, or plural anodes are arranged to a single cathode, each electrode can be operated independently, and each electrode has openings capable of passing ions and water to be treated.

### Claim 10 (depends on 9)

The method according to claim 9, wherein the tank is filled with granular solids.

### Claim 11 (depends on 10)

The method according to claim 10, wherein the granular solids are sands, glass beads, or shells.

### Claim 12 (depends on 9)

The method according to claim 9, wherein the cation migration and accumulation and/or the electrolysis are conducted while flowing the water to be treated through the tank.

### Claim 13 (depends on 9)

The method according to claim 9, wherein the multi-electrode system is porous or meshed.

### Claim 14 (depends on 9)

The method according to claim 9, wherein the water to be treated contains calcium ions and/or magnesium ions.

### Claim 15 (depends on 9)

The method according to claim 9, wherein a phosphorus compound removed from the water to be treated is recovered by back wash.

### Claim 16 (depends on 9)

The method according to claim 9, wherein the multi-electrode system is an operation system in which plural cathodes are arranged to a single anode.