Process for producing reclaimed water and system for producing reclaimed water

• US 9,028,695 B2
• Filed: 09/22/2011
• Issued: 05/12/2015
• Est. Priority Date: 03/27/2009
• Status: Active Grant

• Current Assignee: Metawater Company Limited
• Original Assignee: Metawater Company Limited
• Inventors: Noguchi, Motoharu, Kozono, Hideki, Aoki, Michiko
• Primary Examiner(s): BASS, DIRK R
• Application Number:
  US13/240,543
• Publication Number:
  US 20120031838A1
• Time in Patent Office: 1,328 Days
• Field of Search: None
• US Class Current: 210/636
• CPC Class Codes: B01D 2321/168 Use of other chemical agents
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration
• CPC Class Codes: C02F 1/281 using inorganic sorbents
• CPC Class Codes: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 1/5236 using inorganic agents
• CPC Class Codes: C02F 1/56 Macromolecular compounds
• CPC Class Codes: C02F 1/78 with ozone C02F1/4672 takes precedence
• CPC Class Codes: C02F 2103/20 from animal husbandry
• CPC Class Codes: C02F 2209/03 Pressure
• CPC Class Codes: C02F 2209/11 Turbidity
• CPC Class Codes: C02F 2303/16 Regeneration of sorbents, filters
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage

Abstract

The process includes operation as follows: putting ozone generated by an ozone generator into raw water, in a normal mode, to subject the raw water to ozone treatment; injecting a flocculant into the raw water before or after the ozone treatment; filtering the raw water by a separation membrane after the ozone treatment and the injection of the flocculant; and intermittently setting cleaning mode to put a larger quantity of cleaning ozone than that in the normal mode into the raw water so as to intermittently increase the concentration of dissolved ozone, thereby cleaning the filtration membrane.

Claims

1. A process for producing reclaimed water, comprising the operations of:

in a normal mode, putting ozone generated by an ozone generator into raw water to subject the raw water to ozone treatment;

injecting a flocculant into the raw water after the ozone treatment;

filtering the raw water by a separation membrane after the ozone treatment and the injection of the flocculant;

measuring a transmembrane pressure, which is a pressure difference between an upstream side and a downstream side of the separation membrane, by measuring a gauge pressure and correcting the measured gauge pressure for at least one of a water temperature and an installed height difference of a pressure gauge,

intermittently setting a cleaning mode to put a larger quantity of cleaning ozone than in the normal mode into the raw water so as to intermittently increase the concentration of a dissolved ozone, thereby cleaning the filtration membrane,

determining a transmembrane rising speed by periodically measuring the transmembrane pressure immediately after backwashing the separation membrane and plotting the measured transmembrane pressure over time to determine when to inject the larger quantity of cleaning ozone in the cleaning mode,

wherein when the transmembrane rising speed exceeds a first predetermined value, the ozone processor sets the cleaning mode to inject one of a first larger quantity of the ozone for a first predetermined time period and a second larger quantity of the ozone for a second predetermined time period, where the first larger quantity of the ozone is less than the second larger quantity of the ozone and the first predetermined time period is longer than the second predetermined time period.

2. The process for producing reclaimed water according to claim 1, wherein the turbidity of the raw water is measured, and in the case where the turbidity exceeds a predetermined value, the cleaning mode is not set.

3. The process for producing reclaimed water according to claim 1, wherein the quantity of input ozone or ozone consumption in the normal mode is measured, and in the case where the quantity of the input ozone or the ozone consumption exceeds a predetermined value, the cleaning mode is not set.

7. The process for producing reclaimed water according to claim 2, wherein the quantity of input ozone or ozone consumption in the normal mode is measured, and in the case where the quantity of the input ozone or the ozone consumption exceeds a predetermined value, the cleaning mode is not set.

4. A system for producing reclaimed water, comprising:

an ozone processor with an ozone generator that generates ozone, for putting the ozone into raw water, in a normal mode, to carry out ozone treatment of the raw water, and for intermittently setting a cleaning mode to put a larger quantity of cleaning ozone than in the normal mode into the raw water so as to intermittently increase the concentration of dissolved ozone;

a flocculant injection unit for injecting a flocculant into the raw water after the ozone treatment;

a membrane filtration unit located at the downstream of the ozone processor and the flocculant injection unit, and for carrying out membrane filtration of the raw water by a separation membrane, and

means for measuring a transmembrane pressure, which is a pressure difference between an upstream side and a downstream side of the separation membrane, wherein a transmembrane rising speed is determined by periodically measuring a transmembrane pressure immediately after backwashing the separation membrane and plotting the measured transmembrane pressure over time to determine when to inject the larger quantity of cleaning ozone in the cleaning mode,

wherein when the transmembrane rising speed exceeds a first predetermined value, the ozone processor sets the cleaning mode to inject one of a first larger quantity of the ozone for a first predetermined time period and a second larger quantity of the ozone for a second predetermined time period, where the first larger quantity of the ozone is less than the second larger quantity of the ozone and the first predetermined time period is longer than the second predetermined time period, and

wherein the means for measuring the transmembrane pressure measures a gauge pressure, and corrects the measured gauge pressure for at least one of a water temperature and an installed height difference of a pressure gauge.

5. The system for producing reclaimed water according to claim 4, further comprising a turbidity measuring unit for measuring the turbidity of the raw water, wherein the cleaning ozone is not put into the raw water when the turbidity measured by the turbidity measuring unit exceeds a predetermined value.

6. The system for producing reclaimed water according to claim 4, wherein the ozone processor does not set the cleaning mode by said means for measuring a transmembrane pressure when the quantity of the input ozone or the ozone consumption in the normal mode exceeds a predetermined value.

8. The system for producing reclaimed water according to claim 5, wherein the ozone processor does not set the cleaning mode by said means for measuring a transmembrane pressure when the quantity of the input ozone or the ozone consumption in the normal mode exceeds a predetermined value.

9. The system for producing reclaimed water comprising:

an ozone processor with an ozone generator that generates ozone, and for to putting the ozone into raw water, in a normal mode, to carry out ozone treatment of the raw water, and for intermittently setting a cleaning mode to put a larger quantity of cleaning ozone than in the normal mode into the raw water so as to intermittently increase the concentration of dissolved ozone;

a flocculant injection unit for injecting a flocculant into the raw water after the ozone treatment;

a membrane filtration unit located at the downstream of the ozone processor and the flocculant injection unit, and for carrying out membrane filtration of the raw water by a separation membrane, and

means for measuring a transmembrane pressure, which is a pressure difference between an upstream side and a downstream side of the separation membrane, wherein a transmembrane rising speed is determined by periodically measuring a transmembrane pressure immediately after backwashing the separation membrane and plotting the measured transmembrane pressure over time to determine when to inject the larger quantity of cleaning ozone in the cleaning mode,

wherein when the transmembrane rising speed exceeds a first predetermined value, the ozone processor sets the cleaning mode to inject one of a first larger quantity of the ozone for a first predetermined time period and a second larger quantity of the ozone for a second predetermined time period, where the first larger quantity of the ozone is less than the second larger quantity of the ozone and the first predetermined time period is longer than the second predetermined time period, and

wherein a dissolved concentration of the ozone in the ozone treated raw water is measured and an amount of the flocculant injected by the flocculant injection unit is determined on a basis of the measured dissolved ozone concentration.