Systems and methods for controlling waterborne pathogens

Abstract

Systems and methods to control colonization, amplification and/or growth of waterborne aerobic heterotrophic bacteria within potable water plumbing of a premises are provided, the premises having potable water plumbing having at least one point of use within the premises, the potable water plumbing being adapted to receive a potable water supply from a municipal water source. The systems and methods to control colonization, amplification, and/or growth of waterborne aerobic heterotrophic bacteria within cooling towers and evaporative condensers, recirculates system water through a deoxygenation device to reduce dissolved oxygen levels and prevent bacterial respiration within the heat exchanger and pressurized lines.

Claims

1. A method to prevent colonization, amplification and/or growth of waterborne aerobic heterotrophic bacteria within a potable water plumbing system of a premises comprising: (i) supplying potable water to the potable water plumbing system of the premises from a municipal potable water source having a dissolved oxygen content from 8 to 15 mg/L and containing established colonies of waterborne aerobic heterotrophic bacteria; (ii) passing the supply of potable water from the municipal potable water source through a hollow fiber membrane deoxygenation device operatively associated with the potable water plumbing system to deoxygenate the supply of potable water from the municipal potable water supply to at least hypoxic dissolved oxygen concentrations of less than 2.0 mg/L to thereby provide a downstream supply of deoxygenated water to the potable water plumbing system of the premises sufficient to prevent colonization, amplification and/or growth of the waterborne aerobic heterotrophic bacteria supplied to the potable water plumbing system by the potable water from the municipal potable water source.

2. The method according to claim 1, wherein step (ii) is practiced by deoxygenating the supply water to anoxic dissolved oxygen concentrations of less than 0.5 mg/L.

3. The method according to claim 1, wherein the potable water plumbing system comprises at least one of a fire suppression system, a cooling tower, a boiler, a water heater, a sink faucet, an ice machine, a drinking fountain and a hose bib.

4. The method according to claim 1, which further comprises passing the supply of potable water through a water-pretreatment system positioned upstream of the hollow fiber membrane deoxygenation device.

5. The method according to claim 4, wherein the water-pretreatment system comprises a sediment filter, an activated carbon filter and/or a water softener.

6. The method according to claim 1, wherein the potable water plumbing system of the premises comprises: a water heater to provide a source of potable heated water, and a water discharge for discharging the potable heated water from the water heater, and wherein the method further comprises providing an aerator at the water discharge to aerate the potable heated water and re-oxygenate the potable heated water discharged through the water discharge to a dissolved oxygen concentration of greater than 2.0 mg/L.

7. The method according to claim 6, wherein the aerator re-oxygenates the potable heated water discharged through the water discharge to a dissolved oxygen concentration of between about 5 mg/L to about 15 mg/L.

8. The method according to claim 6, wherein the aerator re-oxygenates the potable heated water discharged through the water discharge to a dissolved oxygen concentration of between of between about 8 mg/L to about 10 mg/L.

Description

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

(1) The disclosed embodiments of the present invention will be better and more completely understood by referring to the following detailed description of exemplary non-limiting illustrative embodiments in conjunction with the drawings of which:

(2) FIG. 1 is a schematic diagram showing an exemplary embodiment in accordance with the present invention;

(3) FIG. 2 is a schematic diagram showing another exemplary embodiment in accordance with the present invention; and

(4) FIG. 3 is a schematic diagram showing an exemplary embodiment of a cooling tower/evaporative condenser installation in accordance with the present invention.

DETAILED DESCRIPTION

(5) In general, the embodiments disclosed herein will necessarily include a membrane contactor to remove oxygen from an incoming municipal water supply before it is distributed to fire-suppression systems, cooling towers, evaporative condensers, potable cold-water service, and water heaters or boilers so as to create at least a hypoxic (<2.0 mg/L dissolved oxygen) or anoxic (<0.5 mg/L dissolved oxygen) aqueous water source downstream of the contactor. Established bacterial biofilms and aerobic heterotrophic bacterial colonies will cease amplification, cellular respiration, and eventually become non-viable in such a hypoxic or anoxic water source. Aerobic heterotrophic bacteria, including Legionella and Pseudomonas, that are introduced from the incoming municipal water supply will thus not be able to colonize, amplify, metabolize, or establish biofilms within premise plumbing systems by virtue of the hypoxic or anoxic conditions of the water source downstream of the contactor. According to certain embodiments, the contactor will effect a downstream anoxic (<0.5 mg/L dissolved oxygen) water condition such that aerobic bacteria already in the plumbing systems will become metabolically dormant under such conditions.

(6) Water with reduced dissolved oxygen concentrations may then be treated and used as untreated water would normally be. Installation of aerators at the point of water use (e.g., at water supply faucets where the water is discharged to the consumer) can re-introduce dissolved oxygen to improve perceived taste if desired. The aerator may therefore re-oxygenate the otherwise previously deoxygenated water at the point of discharge so that the discharged water has a dissolved oxygen concentration of greater than 2.0 mg/L, for example between about 5 mg/L to about 15 mg/L or between about 8 to about 10 mg/L. To ensure that membrane contactor performance is achieving desired results, an in-line real-time dissolved oxygen sensor can be installed in cold-water plumbing lines, hot water distribution lines, and recirculating utility water lines.

(7) Accompanying FIG. 1 shows a system 10 which embodies the present invention. As shown, the system 10 will include a deoxygenation device 12 positioned to receive potable water from the municipal potable water supply 14. The deoxygenation device 12 thereby delivers deoxygenated water having a dissolved oxygen concentration of less than 2.0 mg/L to achieve hypoxic water conditions, or less than 0.5 mg/L to achieve anoxic water conditions to the potable water supply system (noted generally by reference numeral 16) within the premise building 18.

(8) The system 10 depicted in FIG. 2 is similar to that depicted in FIG. 1 (and thus the same reference numerals have been employed for the same features) with the principal exception being that a water-pretreatment system 20 which may include a sediment filter, an activated carbon filter and/or a water softener, is installed in the potable water conduit from the municipal water supply 14 upstream of the deoxygenating device 12. The pretreatment system 20 may thus be advantageously employed so that sediment and/or other dissolved particulates do not affect the deoxygenation functions of the deoxygenation device 12.

(9) A cooling tower/evaporative condenser installation 10 is depicted schematically in accompanying FIG. 3. As shown, the installation 10 is provided with a condenser 30 which is operatively supplied with cold water from a cooling tower 32. The condenser 30 is in heat-exchange relationship with an evaporator 34 positioned within a cooling loop 34a circulation of chilled water providing a heat-exchange medium to remove heat from the heat load 36. A chilled water pump 38 is provided so as to circulate the chilled water within the cooling loop 34a.

(10) As is conventional, the cooling tower 32 operates to provide cold water in the basis 32a which provides a supply of cold water that is circulated within the loop 40 by the cold water pump 42. Make-up water is supplied to the basin 32a from the municipal water supply MWS through a sediment filter 44a and an activated carbon filter 44b. A deoxygenation device 46 is positioned in the circulation loop 40 so as to receive the cold water from the basin 32a of the cooling tower 32. The deoxygenation device 46 thereby delivers deoxygenated cold water having a dissolved oxygen concentration of less than 2.0 mg/L to achieve hypoxic water conditions, or less than 0.5 mg/L to achieve anoxic water conditions to the condenser 30 and thereby ensures that deoxygenated cold water circulates within the loop 40. If desired, a sedimentation filter 46a may be positioned upstream of the deoxygenation device 46 to remove particulates that may be present in the cold water within the loop 40.

(11) Various modifications within the skill of those in the art may be envisioned. Therefore, while the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope thereof.