CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Serial No. 63/408,140, titled “SYSTEM AND METHOD TO REMOVE 1,4 DIOXANE FROM WATER” filed September 20, 2022, which is incorporated herein by reference in its entirety for all purposes.

FIELD OF TECHNOLOGY

Aspects and embodiments disclosed herein are generally related to water treatment systems and methods and, more specifically, to water treatment systems and methods capable of removing 1,4 dioxane from water.

SUMMARY

In accordance with one aspect, a system for treating contaminated water is disclosed.

The system includes at least three resin adsorbers, wherein a first and second resin adsorber are on-line and coupled in series, and a third resin adsorber is selectively off-line from the first and second on-line resin adsorbers, wherein the at least three resin adsorbers are fluidly couplable to a source of contaminated water having an initial concentration of at least one recalcitrant organic contaminant. The system also includes at least one heated recirculation tank fluidly coupled to an inlet of the third resin adsorber and configured to regenerate the third resin adsorber, and at least one air stripping unit fluidly coupled to an outlet of the third resin adsorber, wherein the at least one air stripping unit is configured to remove at least a portion of the at least one recalcitrant organic contaminant from heated water from the third resin adsorber.

In some embodiments, the system further includes at least one of a thermal or catalytic oxidizer fluidly coupled to the at least one air stripping unit.

In some embodiments, the at least one air stripping unit is coupled to at least one air supply. In some embodiments, water from the at least one heated recirculation tank supplied to the third resin adsorber is heated to not more than 160° F.

In some embodiments, the third resin adsorber is placed on-line with the first resin adsorber after completion of regeneration of the third resin adsorber.

In some embodiments, the second resin adsorber is taken off-line for regeneration after the third resin adsorber is placed on-line with the first resin adsorber.

In some embodiments, the second resin adsorber is returned on-line with the third resin adsorber after completion of regeneration of the second resin adsorber.

In some embodiments, the first resin adsorber is taken off-line for regeneration after the second resin adsorber is returned on-line with the third resin adsorber.

In some embodiments, the at least one recalcitrant organic contaminant is 1, 4-dioxane.

In accordance with another aspect, a system of regenerating at least one resin adsorber used for the removal of at least one recalcitrant organic contaminant from a water source is disclosed. The system includes at least one heated recirculation tank fluidly coupled to an inlet of the at least one adsorber and configured to regenerate the at least one resin adsorber. The system also includes at least one air stripping unit fluidly coupled to an outlet of the at least one resin adsorber, wherein the at least one air stripping unit is configured to remove at least a portion of the at least one recalcitrant organic contaminant from heated water from the at least one resin adsorber.

In some embodiments, the system further includes at least one of a thermal or catalytic oxidizer fluidly coupled to the at least one air stripping unit.

In some embodiments, the at least one air stripping unit is coupled to at least one air supply.

In some embodiments, water from the at least one heated recirculation tank supplied to the at least one resin adsorber is heated to not more than 160° F. In accordance with another aspect, a method of treating contaminated water having an initial concentration of at least one recalcitrant organic contaminant is disclosed. The method includes providing at least three resin adsorbers, wherein a first and second resin adsorber are online and coupled in series, and a third resin adsorber is selectively off-line from the first and second on-line resin adsorbers, wherein the at least three resin adsorbers are fluidly couplable to a source of contaminated water having an initial concentration of at least one recalcitrant organic contaminant. The method also includes providing at least one heated recirculation tank and fluidly coupling the at least one heated recirculation tank to the third resin adsorber, wherein the at least one heated recirculation tank is configured to supply heated water to the third resin adsorber to regenerate the third resin adsorber, and providing at least one air stripping unit fluidly coupled to the third resin adsorber, wherein the at least one air stripping unit is configured to remove at least a portion of the at least one recalcitrant organic contaminant from heated water from the third resin adsorber.

In some embodiments, the heated water supplied to the third resin adsorber does not exceed 160°F.

In some embodiments, the method further includes providing at least one of a thermal or catalytic oxidizer, wherein the at least one of the thermal or catalytic oxidizer is fluidly coupled to the at least one air stripping unit.

In some embodiments, the method further includes placing the third resin adsorber online with the first resin adsorber after completion of regeneration of the third resin adsorber.

In some embodiments, the method further includes taking the second resin adsorber offline for regeneration after the third resin adsorber is placed on-line with the first resin adsorber.

In some embodiments, the method further includes returning the second resin adsorber on-line with the third resin adsorber after completion of regeneration of the second resin adsorber.

In some embodiments, the method further includes taking the first resin adsorber off-line for regeneration after the second resin adsorber is returned on-line with the third resin adsorber. The disclosure contemplates all combinations of any one or more of the foregoing aspects and/or embodiments, as well as combinations with any one or more of the embodiments set forth in the detailed description and any examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing is not intended to be drawn to scale. In the drawing, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawing:

FIG. l is a process flow diagram of a water treatment system according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

The disclosure relates to systems and methods for the treatment of water. Water treatment systems, as used herein, may encompass any system for processing water, in particular, for removal of contaminants or undesired constituents. While the disclosure generally refers to municipal and industrial water treatment systems, other systems for water treatment are within the scope of the disclosure.

The motivation to clean contaminated sites has continued under government regulations which require the removal, reduction, destruction, or stabilization of environmentally hazardous chemical compounds. However, certain groundwater contaminants are difficult to treat in a cost- effective manner. These contaminants gain a reputation as being “recalcitrant”, primarily because of fundamental physicochemical properties that make treatment difficult.

One potential method for remediating such contamination, biodegradation, involves using indigenous or introduced (i.e., non-indigenous) bacteria or other microbes to degrade or digest organic chemicals transported across their cell membranes, thereby producing byproducts such as carbon dioxide gas and water. Although biodegradation works well for certain organic contaminants, it can be difficult or impossible to biodegrade recalcitrant organic contaminants. 1,4-dioxane is one example of a recalcitrant organic contaminant. 1,4-dioxane, sometimes referred to as simply “dioxane", is a clear liquid that easily dissolves in water. It is used primarily as a solvent in the manufacture of chemicals and as a laboratory reagent and has various other uses that take advantage of its solvent properties. 1,4-dioxane is an industrial synthetic chemical which has been used in numeral applications as a stabilizer for chlorinated solvents (mainly 1,1, 1 -tri chloroethane), and as an ingredient for production of cellulose acetate membranes, resins, printing inks, paints, adhesives, cosmetics, deodorants, fumigants, detergents, cleaning products, aircraft deicing fluids, etc. Many of the sites where 1,4-dioxane is found to contaminate drinking groundwater supplies are linked to industrial areas and hazardous waste landfills. Occurrence of 1,4-dioxane in groundwater has been reported throughout the U.S. because 1,4- dioxane is resistant to biological degradation and continues to be present in the environment. However, manufacturers now typically reduce 1,4-dioxane from these chemicals to low levels before these chemicals are made into products used in the home.

The challenge in treating 1,4-dioxane contaminated water is attributed to the complete miscibility of 1,4-dioxane in water, which makes it extremely difficult to treat using conventional treatment methods such as granular activated carbon (GAC) adsorption and air stripping. The Environmental Protection Agency (EP A) identifies the most serious hazardous waste sites in the nation. These sites are then placed on the National Priorities List (NPL) and are targeted for long-term federal clean-up activities. 1 ,4-dioxane has been found in at least 31 of the 1,689 current or former NPL sites. Although the total number of NPL sites evaluated for this substance is not known, the possibility exists that the number of sites at which 1,4-dioxane is found may increase in the future as more sites are evaluated. Since 1,4-dioxane is considered a hazardous material that contaminates ground water, there is a need for a process that will remove 1,4-dioxane from groundwater.

Previously, attempts have been made to treat water contaminated by 1,4 dioxane using either a combination of hydrogen peroxide (H2O2) and ultraviolet light (UV) or ozone (O3) and UV light. 1,4-dioxane can be destroyed by advanced oxidation processes (AOPs) using a combination of hydrogen peroxide (H2O2), ozone (O3), and ultraviolet light (UV) such as H2O2/UV, O3/UV, H2O2/O3, and H2O2/O3/UV. These AOPs involve the use of powerful oxidative hydroxyl free radicals to destroy organic compounds. However, there are several disadvantages associated with AOPs. Color, turbidity, and fouling constituents such as iron and manganese must be removed prior to the treatment processes to relatively low levels to allow sufficient UV transmission and prevent fouling onto UV light bulbs. Constituents such as carbon, bicarbonate, reduced metal ions, TOC, and nitrite may scavenge hydroxyl free radicals and inhibit target organic destruction. Residual oxidative H2O2 and O3 from the treatment process must be removed to prevent corrosion to treatment and distribution systems downstream or damage to aquatic environment after discharge. Harmful byproducts may be produced from incomplete destruction of 1,4-di oxane and other constituents in water. Additionally, O3 reacts directly with bromide ions to form bromate, which has a low drinking water standard of 10 ug/L. Materials of construction must be resistant to corrosive H2O2 and O3. Furthermore, operational costs associated with UV energy consumption can be very high.

Another process previously used to treat water contaminated with 1,4 dioxane was utilizing a regenerable charred resin material that will adsorb 1,4-dioxane. However, this process results in a waste stream that contains concentrated 1,4-dioxane that requires another means to destroy the 1,4-dioxane such as incineration.

As another known treatment option, a synthetic resin may possess an adsorptive capacity for 1,4-dioxane several times higher than GAC, and the treatment process may include on-site regenerability of the synthetic resin with steam and solvents such as methanol. However, steam regeneration requires high temperature resistant materials of construction, high energy consumption, and complex process safety controls. Additionally, resin at high temperatures above the water boiling point after steam regeneration must be cooled down to ambient levels prior to the next adsorption cycles, resulting in a significant amount of energy waste. Steam laden with 1,4-dioxane requires condensation and disposal or further treatment. The resin can also be regenerated with methanol. However, methanol with a low flash point poses a potential explosion risk. Residual methanol on the resin after regeneration may not be completely rinsed away and may not be acceptable for discharge or drinking water standards. Accordingly, the present disclosure pertains to systems and methods of water treatment to remove recalcitrant contaminants such as, e.g., 1,4 dioxane while avoiding the above-referenced disadvantages.

In one embodiment of the present disclosure, a system and method for removal of 1,4- dioxane involves resin adsorption followed by on-site regeneration using hot water (rather than, e.g., high temperature steam). The use of hot water at temperatures at or below 160° F may enable on-site resin regeneration without operating under hazardous conditions that are associated with, e g., steam and methanol. Some other advantages of resin regeneration using hot water include lower energy consumption, materials of construction with lower temperature resistance capacities, and simultaneous removal of 1,4-dioxane during regeneration.

FIG. 1 illustrates a water treatment system 10 for removal of 1,4 dioxane with on-site resin regeneration in accordance with an aspect of the present disclosure. The system 10 comprises three resin vessels/adsorbers 12a, 12b, 12c. The adsorbers 12a, 12b, 12c may each contain any appropriate adsorbent resin such as, e.g., activated carbon-based resins, polymeric adsorbent resins, macroporous adsorbent resins, etc. In the embodiment shown in FIG. 1, two adsorbers 12a, 12b are operated in series during adsorption cycles, while the third adsorber 12c is regenerated. The lead adsorber in the adsorption cycle (adsorber 12b) will be taken off-line for regeneration once the effluent 1,4-dioxane concentration from the lead adsorber 12b has been found to exceed a treatment objective. The lag adsorber 12c will then be repositioned as a lead adsorber followed by the regenerated adsorber 12a in the next adsorption cycle.

Referring still to FIG. 1, the exhausted lead adsorber from the adsorption cycle may be regenerated using hot water (i.e., water not exceeding 160° F) in a recirculation mode through a heated recirculation tank 20, while 1,4-dioxane is simultaneously removed from the hot water through an air stripping unit 14 coupled to an air supply 16. The air stripping unit 14 may be any appropriate air stripper enabling the transfer of contaminants from a liquid phase to a gas phase in order to effectively decontaminate the water. Air stripping typically involves passing contaminated water through a packed column or tower, where air is introduced at the bottom of the column and allowed to rise counter-current to the water flow. Volatile organic compounds (VOCs) transfer from the water into the air due to the concentration gradient, and the VOC-laden air is then treated separately to remove or destroy the contaminants. A commercial example of an air stripper used for decontaminating water is the QuickStrip™ Air Stripping System from QED Environmental Systems.

As detailed above, the volatile nature of 1,4-dioxane is significantly enhanced at the elevated temperature. Accordingly, in some embodiments, off-gas from the air stripping unit 14 may be sent to a thermal or catalytic oxidizer 18 in the event that air treatment is required to mitigate the volatility of the off-gas containing 1,4 dioxane. A commercial example of a thermal oxidizer commonly used for industrial emissions treatment is the Regenerative Thermal Oxidizer (RTO) from Anguil Environmental Systems. RTOs are designed to destroy VOCs and hazardous air pollutants (HAPs) through high-temperature combustion, operating on the principle of regenerative heat exchange. In some embodiments, RTOs use a bed of ceramic media or heat exchange media to preheat the incoming polluted air stream and recover heat from the combustion process. RTOs typically operate at very high temperatures (e.g., above 1500° F (815° C)) to ensure the complete oxidation of VOCs and HAPs into carbon dioxide (CO2) and water vapor. Catalytic oxidizers, on the other hand, use catalysts to promote the oxidation of pollutants at lower temperatures compared to thermal oxidizers. One commercial example of a catalytic oxidizer is the Catalytic Oxidation System by Anguil Environmental Systems. Catalytic oxidizer systems are designed to efficiently control emissions of VOCs, HAPs, and other air pollutants through catalytic reactions.

The systems and methods described herein are possible because the resin regeneration cycle performed at an elevated temperature requires a shorter duration than that in the adsorption cycle. The actual resin regeneration time may vary and will depend upon various factors such as, e.g., the loading of 1,4-dioxane and other constituents onto the resin, the precise temperature of the hot water, and/or the desired level of contaminant removal. Different adsorbent resins have varying affinities for specific contaminants. Some resins may adsorb contaminants more strongly than others, and this can affect the contact time needed for desorption. Additionally, higher temperature water generally increases the desorption rate, but excessively high temperatures can damage a particular resin or degrade the contaminant. Thus, the specific contact time needed for extracting a recalcitrant contaminant from an adsorbent resin can vary from minutes to hours or even longer, depending on the specific circumstances. In some embodiments, a plurality of resin adsorbers can be added to prolong the adsorption cycle duration, and/or additional air stripping units may be added to shorten the regeneration cycle duration. In such embodiments, the lead adsorber may be taken off-line once it has been partially loaded with 1,4-dioxane at a concentration up to or slightly above the treatment objective, and not completely exhausted with the influent concentration, resulting in a shorter required regeneration duration. 1,4-dioxane will be released from the resin by hot water at a slower rate than that by steam, resulting in a much lower off-gas concentration. Accordingly, while off-gas treatment by way of thermal or catalytic oxidation is shown and described above with respect to FIG. 1, it is to be understood that systems and methods according to some embodiments of the present disclosure may not require such off-gas treatment.

The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the term “plurality” refers to two or more items or components. The terms “comprising,” “including,” “carrying,” “having,” “containing,” and “involving,” whether in the written description or the claims and the like, are open-ended terms, i.e., to mean “including but not limited to.” Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. Only the transitional phrases “consisting of’ and “consisting essentially of,” are closed or semi-closed transitional phrases, respectively, with respect to the claims. Use of ordinal terms such as “first,” “second,” “third,” and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

Having thus described several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Any feature described in any embodiment may be included in or substituted for any feature of any other embodiment. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only. Those skilled in the art should appreciate that the parameters and configurations described herein are exemplary and that actual parameters and/or configurations will depend on the specific application in which the disclosed methods and materials are used. Those skilled in the art should also recognize or be able to ascertain, using no more than routine experimentation, equivalents to the specific embodiments disclosed.