WO2018211504A1 - Method for decreasing the concentration of hydrogen sulfide - Google Patents

Abstract

A method and a system for the removal hydrogen sulfide (H2S) from a medium are disclosed. The method includes the steps of: maintaining the pH of the medium at a value of above 5.2; contacting the medium with an oxidant and applying a UV irradiation in the range of 200 to 270 nm on the medium.

Description

METHOD FOR DECREASING THE CONCENTRATION OF HYDROGEN

SULFIDE

FIELD OF INVENTION

[001] The present invention relates, inter-alia, to a method for decreasing hydrogen sulfide (H₂S) concentration in a medium.

BACKGROUND OF THE INVENTION

[002] Hydrogen sulfide (H₂S) is a hazardous contaminant found in well water, reclaimed water, sewage streams, effluent water, and pond water and also causes malodorous air pollution. H₂S is often produced in water by bacterial anaerobic reduction of sulfate in the presence of organic matter usually with the absence of oxygen. The solutions currently used such as evaporation by aeration towers or adsorption by activated carbon may cause air pollution and are expensive.

[003] Another solution for H₂S contamination is oxidation. H₂S can be oxidized by bacteria (phototropic, aerobic or anaerobic). However, the main drawbacks of biological oxidation of drinking water are the potential risk of microbial contamination of the treated water, excess waste biomass, and it is also an expensive technique. H₂S removal using oxidizing agents as Cl₂, KMn0₄, C10₂, H₂0₂, SO3^"2 ion, O3 and iron salts may need pre- or post-treatment and may generate many intermediate and end products.

[004] Other current technology available is oxidation of hydrogen sulfide in the presence of air. However, this method is very slow (weeks) and produces elemental sulfur (solid) which can cause clogging problems in the irrigation systems. Therefore, the complete oxidation of H₂S into sulfate, a soluble ion in water is desired.

SUMMARY OF THE INVENTION

[005] The present invention, in some embodiments thereof, relates to a method for decreasing hydrogen sulfide (H₂S) concentration in a medium.

[006] According to an aspect of some embodiments of the present invention, there is provided a method for decreasing H₂S concentration in a medium.

[007] In some embodiments, the method comprises the steps of:

a. maintaining the pH of the medium at a value of 5.2 or above;

b. contacting the medium with an oxidant, and c. applying ultraviolet (UV) irradiation in the range of 200 to 270 nm on said medium,

thereby decreasing the concentration of H₂S.

[008] In some embodiments, the UV irradiation is in the range of from 220 to 260 nm.

[009] In some embodiments, the oxidant is selected from: oxygen (0₂), Ozone (0₃), hypochlorite, hydrogen peroxide (H₂0₂), or a combination thereof. In some embodiments, the 0₂ is derived from air.

[010] In some embodiments, the pH is in the range of from 5.2 to 13. In some embodiments, the pH is in the range of from 5.2 to 8.0. In some embodiments, the pH is in the range of from 8.0 to 10.

[011] In some embodiments, the medium is selected from the group consisting of liquid, sludge, gas and soil. In some embodiments, the medium comprises water. In some embodiments, the medium comprises sewage. In some embodiments, the gas comprises air.

[012] In some embodiments, the decreasing H₂S concentration is at a rate of at least 8 % per minute.

[013] In some embodiments, the H₂S is present at an initial concentration of 0.001 to 500 ppm. In some embodiments, the H₂S is present at an initial concentration of 0.001 to 50 ppm. In some embodiments, the H₂S is present at an initial concentration of 1 to 30 ppm.

[014] In some embodiments, the oxidant is in an initial concentration in the medium of 0.2 x 10^"5 mol/liter to 1.5 x 10^~3 mol/liter. In some embodiments, the oxidant is in an initial concentration in the medium of 0.6xl0^"5 mol/liter to 0.7xl0^~3 mol/liter.

[015] In some embodiments, the UV irradiation has an intensity of least 0.5 watt per m³ of the medium. In some embodiments, the UV irradiation has an intensity of at least 25 watts per m³ of the medium. In some embodiments, the UV irradiation has an intensity of 0.5 to 100 watts per m³ of the medium. In some embodiments, the UV irradiation has an intensity of 0.5 to 50 watts per m³ of the medium. In some embodiments, the UV irradiation has an intensity of 1 to 25 watts per m³ of the medium.

[016] In some embodiments, the UV irradiation has an intensity of at least 1000 watt-sec per 1 gram of H₂S in the medium. In some embodiments, the UV irradiation has an intensity of at least 8000 watt-sec per 1 gram of H₂S in the medium. [017] According to another aspect of some embodiments of the present invention, there is provided a system comprising: (i) a container configured to maintain a medium comprising H₂S; (ii) an oxidizing agent inlet; (iii) at least one UV light source, configured to irradiate in the range of 200 to 270 nm on at least a portion of the medium; (iv) at least one sensor configured to measure one or more parameters selected from: a concentration of the H₂S in the medium; and a pH value of said medium.

[018] In some embodiments, the term "light source" refers to one or more lamps.

[019] In some embodiments, the H₂S is present at an initial concentration of 0.001 to 500 ppm in the medium.

[020] In some embodiments, the system further comprises a solution inlet.

[021] In some embodiments, the system further comprises a collecting unit in fluid communication with the container.

[022] In some embodiments, the system further comprises a pH control unit.

[023] In some embodiments, the system comprises an outlet line disposed in fluid communication with said container.

[024] Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

[025] Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description together with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

[026] In the drawings:

[027] Figure 1 presents a schematic illustration of H₂S full oxidation reaction. [028] Figure 2 presents a graph showing the three species of H₂S according to relevant pH levels.

[029] Figure 3 presents a graph showing the conversion of H₂S as a function of the acidity in the feed stream: percentage removal of H₂S (AH₂S) (compared to the initial concentration) according to relevant pH levels.

[030] Figure 4 presents a line graph of hydrogen sulfide absorbance at 6 different pH levels and between 200-350 nm.

[031] Figure 5 presents a line graph showing the removal of H₂S (AH₂S) according to the residence time of UV irradiation by 4 or 6 lamps.

[032] Figures 6A-C present a graph demonstrating the removal of H₂S from tap water containing dissolved hydrogen sulfide as a function of the concentration of H₂S in the inlet stream. Data is given for a retention time of 4.8 min, under illumination intensity of 4.1xl0¹⁹ photons sec^"1 (Figure 6A); the conversion of H₂S for different number of light bulbs (Figure 6B); and the quantum efficiency as a function of the initial concentration of hydrogen sulfide under illumination with one lamp (filled circles), two lamps (filled squares), three lamps (empty triangles) and four lamps (crosses; Figure 6C).

[033] Figure 7 presents a line graph showing the ratio between the molar formation of sulfate and the molar removal of H₂S (AH₂S) as a function of the retention time in a continuous flow reactor irradiated by 3 or 6 UV lamps.

[034] Figure 8 presents a schematic illustration of the experimental apparatus used for decreasing the concentration of H₂S.

[035] Figures 9A-B present the effect of retention time on the conversion of H₂S upon illumination with three (empty triangles) or six (filled circles) lamps at oxygen flow of 2.5 L min^"1 (Figure 9A); and at oxygen flow of 5 L min^"1 (Figure 9B).

[036] Figure 10 presents a graph showing the yield of sulfate ions in the field test experiments as a function of retention time upon illumination with three (empty triangles) or six (filled circles) lamps. The oxygen flow is 2.5 L min^"1.

[037] Figure 11 presents a graph showing the quantum efficiency in the field studies as a function of the initial concentration of hydrogen sulfide under illumination with three lamps (triangles) or six lamps (circles), under oxygen bubbling conditions of 2.5 L min^"1 (filled symbols) or 5 L min^"1 (empty symbols). DETAILED DESCRIPTION

[038] The present invention, in some embodiments thereof, relates to a method for decreasing the concentration of hydrogen sulfide (H₂S) in a medium.

[039] Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

[040] In some embodiments, the method for removal of H₂S in a medium, comprises the steps of: (i) maintaining the medium at a desired range of pH; (ii) contacting the medium with oxidant; and (iii) applying an ultraviolet (UV) irradiation on at least portion of the medium, thereby decreasing the concentration of the H₂S.

[041] In some embodiments, the medium is or comprises liquid, selected from, without being limited thereto, aqueous and non-aqueous solutions, water, groundwater, reclaimed water, effluent water, leachate, wastewater, sewage, blackwater, graywater, bilge water, ballast water, feed water, process water, industrial water, irrigation water, recreational water, pond water, lake water, well water, creek water, river water, rain water, runoff water, pool water, cooling water, non-potable water, potable water, drinking water, semi-pure water, and/or spent ultra-pure water, any or mixture thereof.

[042] In one embodiment, the medium is a gas or a mixture of gasses, such as, but not limited to air.

[043] In one embodiment, the medium is or comprises sludge.

[044] In one embodiment, the medium is in the form of gel.

[045] In some embodiments, the medium is or comprises waste, such as rubbish, trash, refuse, medical waste, radioactive waste, sweepings, scourings, rubble, debris, detritus, scum, grease, sludge, sewage, jetsam, and/or flotsam.

[046] In some embodiments, the medium is or comprises gas. In some embodiments, the medium is or comprises soil.

[047] In some embodiments, the pH value is 5.2 to 14, 5.2 to 10, or 5.5 to 12.

[048] In some embodiments, the pH value is 5.2 to 8. In some embodiments, the pH value is 8 to 10.

[049] In some embodiments, the pH value is 5.2, 5.3, 5.6, 5.8, 6, 7, 8, 9, 10, 11, 12, 13, or 14 including any value and range therebetween. In one embodiment, the pH is about 5.2. In one embodiment, the pH is about 6.0. In one embodiment, the pH is about 7.0. In one embodiment, the pH is about 7.5. In one embodiment, the pH is about 8.5. In one embodiment, the pH is about 9.0. In one embodiment, the pH is about 9.5. In one embodiment, the pH is about 9.7. In one embodiment, the pH is about 10.0. In one embodiment, the pH is about 11.0. In one embodiment, the pH is about 12.0. In one embodiment, the pH is about 13.0.

[050] Herein, the terms "oxidant" or "oxidizing agent" are used interchangeably and, in some embodiments, refer to any suitable oxidizing agent including any substance, which will readily take on electrons.

[051] In some embodiments, the oxidizing agent is selected from, but is not limited to, oxidizing agents or oxidation agents in any suitable form, such as a liquid, semi- liquid, semi-solid, solid, gaseous, semi-gaseous, pure oxidizing agent, oxidizing agent or oxidizing agent precursor as part of a formulation, ore mixtures of more than one oxidizing agent.

[052] In some embodiments, the oxidizing agent is selected from but is not limited to: oxygen (0₂), ozone (O3), peroxides such as hydrogen peroxide (H2O2) and benzoyl peroxide; elemental halogen species, as well as oxygenated halogen species, such as perchlorate, chlorine dioxide, hypochlorite ions and perchlorite species; hydroxyl radicals, free radicals, fluorine, potassium permanganate, quinones, or any mixture thereof.

[053] In one embodiment, the oxidizing agent is O2. In one embodiment, O2 is obtained from a container. In one embodiment, O2 is obtained from an air flow.

[054] In one embodiment, the term "decreasing", or any grammatical derivative thereof, indicates that:

(a) the concentration of ¾S is decreased by at least 20 %, at least 30 %, at least 40 %, at least 50 %, at least 60 %, at least 70 %, at least 80 %, or at least 90 %, including any value therebetween, compared to a situation of lacking the presence of oxidants and applied UV irradiation; and in some embodiments: (b) the ¾S is further oxidized to an oxidized species as described herein below.

[055] In another embodiment, "decreasing", or any grammatical derivative thereof, indicates that the concentration of ¾S is decreased by at least 15 %, at least 10 %, or at least 5 % of the initial concentration of ¾S, including any value therebetween, compared to situation lacking the presence of oxidants and the applied UV irradiation. Methods for determining a level of H₂S are known in the art, e.g., iodometric method, as described in the Examples section below.

[056] In another embodiment, "decreasing", or any grammatical derivative thereof, indicates that the decreasing of the concentration of H₂S is at a rate of at least 1 % per min to 10% per min, or at least 5 % per min to 8% per min.

[057] In another embodiment, "decreasing", or any grammatical derivative thereof, indicates that the decreasing of the H₂S concentration is at a rate of at least 1 % per min, at least 2 % per min, at least 3 % per min, at least 4 % per min, at least 5 % per min, at least 6 % per min, at least 7 % per min, at least 8 % per min, at least 9 % per min, or at least 10 % per min, including any value and range therebetween.

[058] In some embodiments, by "oxidized", it means that the H₂S is fully or almost fully (e.g., at least 70%, or at least 80%) oxidized to S0₄ ^2" species e.g., as shown in Figure 1. In some embodiments, by "fully oxidized" it is meant to refer to less than 20%, or less than 10%, of the H₂S molecules being partially oxidized (e.g., to species such as S, SO3^2", or S₂03^2") upon completing the disclosed method.

[059] In some embodiments, the initial concentration of H₂S is decreased (e.g., oxidized) at a desired rate (also referred to as: "rate of decrease" or "decrease rate").

[060] As used herein, the term "rate of decrease", or any grammatical derivative thereof, indicates that the concentration of H₂S is decreased.

[061] In some embodiments, the decrease rate is at least 5 % per 1 minute, at least 5 % per 2 minutes, at least 5 % per 5 minutes, at least 5 % per 6 minutes, or at least 5 % per 10 minutes.

[062] In some embodiments, the decrease rate is at least 6 % per 1 minute, at least 6 % per 2 minutes, at least 6 % per 5 minutes, at least 6 % per 6 minutes, or at least 6 % per 10 minutes. In some embodiments, the decrease rate is at least 8 % per 1 minute, at least 8 % per 2 minutes, at least 8 % per 5 minutes, at least 8 % per 6 minutes, or at least 8 % per 10 minutes.

[063] In some embodiments, the decrease rate is to at least 10 % per 1 minute, at least 10 % per 2 minutes, at least 10 % per 5 minutes, at least 10 % per 6 minutes, or at least 10 % per 10 minutes. In some embodiments, the decrease rate is at least 20 % per 1 minute, at least 20 % per 2 minutes, at least 20 % per 5 minutes, at least 20 % per 6 minutes, or at least 20 % per 10 minutes. In some embodiments, the decrease rate is at least 30 % per 1 minute, at least 30 % per 2 minutes, at least 30 % per 5 minutes, at least 30 % per 6 minutes, or at least 30 % per 10 minutes. In some embodiments, the decrease rate is at least 40 % per 1 minute, at least 40 % per 2 minutes, at least 40 % per 5 minutes, at least 40 % per 6 minutes, or at least 40 % per 10 minutes. In some embodiments, the decrease rate is at least 45 % per 1 minute, at least 45 % per 2 minutes, at least 45 % per 5 minutes, at least 45 % per 6 minutes, or at least 45 % per 10 minutes. In some embodiments, the decrease rate is at least 50 % per 1 minute, at least 50 % per 2 minutes, at least 50 % per 5 minutes, at least 50 % per 6 minutes, at least 50 % per 10 minutes. In some embodiments, the decrease rate is at least 60 % per 1 minute, at least 60 % per 2 minutes, at least 60 % per 5 minutes, at least 60 % per 6 minutes, or at least 60 % per 10 minutes. In some embodiments, the decrease rate is at least 70 % per 1 minute, at least 70 % per 2 minutes, at least 70 % per 5 minutes, at least 70 % per 6 minutes, or at least 70 % per 10 minutes. In some embodiments, the decrease rate is at least 80 % per 1 minute, at least 80 % per 2 minutes, at least 80 % per 5 minutes, at least 80 % per 6 minutes, or at least 80 % per 10 minutes. In some embodiments, the decrease rate is at least 90 % per 1 minute, at least 90 % per 2 minutes, at least 90 % per 5 minutes, at least 90 % per 6 minutes, or at least 90 % per 10 minutes.

[064] Methods for determining a level of H₂S in a medium are described in the Example section that follows.

[065] In one embodiment, the oxidizing agent comprises 0₂. In one embodiment, the oxidizing agent comprises 0₃. In one embodiment, the oxidizing agent comprises a combination of 0₂ and O3. In some embodiments, combining both 0₂ and O3 provides an enhancing or an additive effect in decreasing the concentration of the H₂S.

[066] In one embodiment, the term "ultraviolet irradiation" refers to electromagnetic radiation with a wavelength shorter than human visible light, in a wavelength of about 10 nm to about 400 nm.

[067] In some embodiments, UV irradiation is in a wavelength of 200, 210, 220, 230, 240, 250, 260, or 270 nm, including any value and range therebetween. In one embodiment, the UV irradiation is in a wavelength of about 210 nm. In one embodiment, the UV irradiation is in a wavelength of about 220 nm. In one embodiment, the UV irradiation is in a wavelength of about 230 nm. In one embodiment, the UV irradiation is in a wavelength of about 240 nm. In one embodiment, the UV irradiation is in a wavelength of about 250 nm. In one embodiment, the UV irradiation is at about 260 nm. [068] In exemplary embodiments, the UV irradiation is performed by a lamp with power of 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 watts per m³ of a treated medium, including any value and range therebetween. In one embodiment, the UV irradiation is performed by a lamp with power of about 0.5 watt per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 1 watt per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 5 watts per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 8 watts per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 10 watts per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 20 watts per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 25 watts per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 40 watts per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 50 watts per m³ of a treated medium. In one embodiment, the UV irradiation is performed by a lamp with power of about 60 watts per m³ of a treated medium.

[069] In some embodiments, the UV irradiation has an intensity of at least 1000, at least 2000, at least 3000, at least 4000, at least 5000, at least 6000, at least 7000, at least 8000, at least 9000, or at least 10,000 watt-sec per 1 gram of H₂S in a treated medium, including any value and range therebetween.

[070] In one embodiment, the UV irradiation has an intensity of at least 1000 watt- sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 2000 watt-sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 3000 watt-sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 4000 watt-sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 5000 watt-sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 6000 watt-sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 7000 watt-sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 8000 watt-sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 9000 watt-sec per 1 gram of H₂S in a treated medium. In another embodiment, the UV irradiation has an intensity of at least 10,000 watt-sec per 1 gram of H₂S in a treated medium.

[071] In some embodiments, the method is characterized by quantum efficiency ranges from 2% to 70%.

[072] In some embodiments, the quantum efficiency ranges from 10% to 60%. In some embodiments, the quantum efficiency ranges from 20% to 50%.

[073] The term "quantum efficiency" refers to the ratio of oxidized H₂S molecules to the number of photons emitted e.g., by the lamps.

[074] The terms "medium" and "treated medium" are used herein throughout interchangeably.

[075] In some embodiments, the initial H₂S concentration in the medium is 0.001 to 500 ppm, 0.01 to 500 ppm, 1 to 400 ppm, 1 to 100 ppm, or 1 to 30 ppm.

[076] In some embodiments, the initial H₂S concentration in the medium is 0.001, 0.01, 0.1, 0.5, 1, 1.5, 2, 3, 4, 5, 10, 15, 20, 25, 30, 40, 50, 100, 250, or 500 ppm, including any value and range therebetween.

[077] In some embodiments, the term "initial concentration" refers to the concentration of a species, e.g., H₂S before applying intentional removal or oxidation of the species. In some embodiments, by "removal or oxidation of the species" it is meant to refer to applying the disclosed method in an embodiment thereof.

[078] In one embodiment, the initial H₂S concentration is at least 0.001 ppm. In one embodiment, the initial H₂S concentration is at least 0.01 ppm. In one embodiment, the initial H₂S concentration is at least 0.1 ppm. In one embodiment, the initial H₂S concentration is at least 1 ppm. In one embodiment, the initial H₂S concentration is at least 1.5 ppm. In one embodiment, the initial H₂S concentration is at least 2 ppm. In one embodiment, the initial H₂S concentration is at least 3 ppm. In one embodiment, the initial H₂S concentration is at least 4 ppm. In one embodiment, the initial H₂S concentration is at least 5 ppm. In one embodiment, the initial H₂S concentration is at least 10 ppm. In one embodiment, the initial H₂S concentration is at least 15 ppm. In one embodiment, the initial H₂S concentration is at least 20 ppm. In one embodiment, the initial H₂S concentration is at least 25 ppm. In one embodiment, the initial H₂S concentration is at least 30 ppm. In one embodiment, the initial H₂S concentration is at least 40 ppm. In one embodiment, the initial H₂S concentration is at least 50 ppm. In one embodiment, the initial H₂S concentration is at least 100 ppm. In one embodiment, the initial H₂S concentration is at least 250 ppm. In one embodiment, the initial H₂S concentration is at least 500 ppm.

[079] In some embodiments, the initial oxidant concentration is 10^"6 to 10^"5 mol/liter. In some embodiments, the initial oxidant concentration is O.lxlO^"5 to 1.5xl0^~3 mol/liter. In some embodiments, the initial oxidant concentration is 0.2xl0^"5 to 1.5xl0^~3 mol/liter. In some embodiments, the initial oxidant concentration is 0.6xl0^"5 to lxlO^"3 mol/liter. In some embodiments, the initial oxidant concentration is 0.6xl0^"5 to 0.7xl0^"3 mol/liter.

[080] In some embodiments, the initial oxidant concentration is 0.002, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1, or 1.5 millimol/liter liquid, including any value and range therebetween.

[081] In one embodiment, the initial oxidant concentration is at least 0.002 millimol/liter. In one embodiment, the initial oxidant concentration is at least 0.02 millimol/liter. In one embodiment, the initial oxidant concentration is at least 0.05 millimol/liter. In one embodiment, the initial oxidant concentration is at least 0.1 millimol/liter. In one embodiment, the initial oxidant concentration is at least 0.2 millimol/liter. In one embodiment, the initial oxidant concentration is at least 0.3 millimol/liter. In one embodiment, the initial oxidant concentration is at least 0.4 millimol/liter. In one embodiment, the initial oxidant concentration is at least 0.5 millimol/liter. In one embodiment, the initial oxidant concentration is at least 0.6 millimol/liter. In one embodiment, the initial oxidant concentration is at least 1 millimol/liter. In one embodiment, the initial oxidant concentration is at least 1.5 millimol/liter.

[082] In some embodiments, by "initial oxidant concentration" it is meant to refer to the initial concentration of the oxidant in the medium prior to the onset of the reaction of the oxidant with H₂S.

[083] In some embodiments, the method is characterized by turbidity increase of the treated water by less than 1 Nephelometric Turbidity Unit (NTU). In one embodiment, the turbidity of the treated water is increased by less than 0.8 NTU. In one embodiment, the turbidity of the treated water is increased by less than 0.6 NTU. In one embodiment, the turbidity of the treated water is increased by less than 0.5 NTU. In one embodiment, the turbidity of the treated water is increased by less than 0.4 NTU. In one embodiment, the turbidity of the treated water is increased by less than 0.2 NTU.

[084] The term "turbidity" means the cloudiness or haziness of a fluid caused by suspended particles (e.g., suspended solids). The turbidity may be measured by any method known in the art, e.g., can be measured by using Hach 2100P turbidity meter as described in the Examples section below.

[085] In another embodiment, the invention provides a kit for application of the disclosed methods and systems at various sites such as, for example, water treatment sites.

[086] In some embodiments, the kit may comprise: (i) a sensor for measuring sulfate/H₂S concentration in the medium; (ii) a solution (e.g., a buffer) for maintaining the pH at a desired basic range; and optionally (iii) a source (e.g., a lamp) allowing to provide UV irradiation.

[087] In some embodiments, there is provided a system comprising:

(i) a container configured to maintain a medium comprising H₂S;

(ii) an oxidizing agent inlet;

(iii) at least one UV light source;

[088] In some embodiments, the term "inlet" refers to an inlet port. Optionally, the inlet is disposed on the container body.

[089] In some embodiments, the term "inlet" may mean a type of opening, a plurality of openings, or any type of pipe leading into the container.

[090] Optionally, the oxidizing agent inlet allows the oxidizing agent to enter the container.

[091] In some embodiments, by "oxidizing agent" it is meant to refer to liquid comprising an oxidizing agent. In some embodiments, by "oxidizing agent" it is meant to refer to a gas comprising an oxidizing agent.

[092] In some embodiments, the oxidizing agent inlet comprises a material resistant to oxidation (also referred to as: "oxidation resistant material") by oxidizing agents.

[093] In some embodiments, the term "oxidation resistant material" refers to a material that is not itself oxidized upon the contact with the oxidizing agent.

[094] Further embodiments of the oxidizing agent are described hereinabove.

[095] In some embodiments, the system further comprises a second inlet, also referred to as "solution inlet". [096] In some embodiments, the solution inlet may allow an alkali solution to enter the container. In some embodiments, the solution inlet may allow a buffer solution to enter the container.

[097] In some embodiments, the term "alkali solution" is used herein to refer to a solution having a pH value greater than 7, greater than 7.5, greater than 8, greater than 8.5, greater than 9, greater than 9.5, or greater than 10.

[098] In some embodiments, the term "buffer solution", "buffer", or "pH buffer", as used herein refers to a solution containing both a weak acid and its conjugate weak base. In some embodiments "pH buffer" is a buffered solution that resists changes in pH by the action of its acid- base conjugate components.

[099] In some embodiments, the system further comprises a control unit.

[0100] In some embodiments, the control unit comprises a pH control unit.

[0101] In some embodiments, the pH control unit may allow to maintain the pH of the medium. In some embodiments, by "maintain the pH" it is meant that a pH value of the medium is maintained within pH value higher than 5, higher than 5.2, higher than 5.5, or higher than 6. In some embodiments, by "maintain the pH" it is meant that a pH value of the medium is maintained within less than 10.

[0102] In some embodiments, by "maintain the pH" it is meant that a pH absolute value of the medium varies within a range of less than +3, less than +2.5, less than

+2, less than +1.5, less than +1, or less than +0.5, including any value and range therebeween.

[0103] In some embodiments, maintaining the pH of the medium is obtained by allowing an alkali solution or a buffer solution to enter the container, e.g., via the solution inlet.

[0104] In some embodiments, the light source is configured to irradiate in a wavelength range of 150 to 300 nm, 180 to 280 nm, 200 to 270 nm, on at least a portion of the medium.

[0105] In some embodiments, the term "portion" refers to a specific volume of the medium, for example, 1%, 10%, 20%, 50%, 60%, 70%, 80%, 90%, or in some embodiments, even 100% of the medium, including any value and range therebetween.

[0106] In some embodiments, the system further comprises: (iv) at least one sensor for measuring one or more parameters selected from: a concentration of a compound comprising sulfur in the medium; and a pH value of the medium. [0107] In some embodiments, by "compound comprising sulfur" it is meant to refer to H₂S. In some embodiments, by "compound comprising sulfur" it is meant to refer to a compound comprising sulfate.

[0108] In some embodiments, the container can be of any shape or size. Thus, as used herein, the term "container", in some embodiments thereof, encompasses, for example, tubes, flasks, water tanks, and reactors of any size and shape, including, but not limited to, small and even microscopic vessels and containers such as, but not limited to, pipette tips.

[0109] In some embodiments, the system further comprises an outlet line disposed in fluid communication with the container.

[0110] As used hereinthroughout, the term "fluid communication" means fluidically interconnected, and refers to the existence of a continuous coherent flow path from one of the components of the system to the other if there is, or can be established, liquid and/or gas flow through and between the ports even if there exists a valve between the two conduits that can be closed, when desired, to impede fluid flow therebetween. In some embodiments, the term "port" refers to a path for distributing liquid or gas, either on or above ground surface or underground, which may include but is not limited to one or more ducts, pipes, channels, tubes, troughs or other means for distribution.

[0111] According to some embodiments, the system further comprises at least one pipe attached to, or integrally formed with the container. In some embodiments, the pipe is configured to lead one or more of: a liquid, or an oxidizing agent to the container. In some embodiments, the pipe is configured to lead one or more of: a liquid, or an oxidizing agent out of the container.

[0112] In some embodiments, the H₂S is present at an initial concentration of 0.001 to 500 ppm in the medium. In some embodiments, the initial H₂S concentration in the medium is 0.01 to 500 ppm, 1 to 400 ppm, 1 to 100 ppm, or 1 to 30 ppm.

[0113] In some embodiments, the system further comprises a collecting unit which defines a part of, or is disposed in fluid communication with the container.

[0114] The sensor, the control unit, e.g., a monitoring device, or a controller (e.g., computer) may be used to monitor, control and/or automate the operation of the various components of the systems disclosed herein, such as valves, sensors, weirs, blowers, fans, dampers, pumps, etc. [0115] The present invention may be a system, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.

[0116] The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD- ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiberoptic cable), or electrical signals transmitted through a wire. Rather, the computer readable storage medium is a non-transient (i.e., not-volatile) medium.

[0117] Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. [0118] Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction- set- architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state- setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field- programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.

[0119] Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions.

[0120] These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks.

[0121] The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks.

[0122] General

[0123] As used herein the term "about" refers to ± 10 %.

[0124] The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to". The term "consisting of means "including and limited to". The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0125] The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

[0126] The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". Any particular embodiment of the invention may include a plurality of "optional" features unless such features conflict.

[0127] As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

[0128] Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0129] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

[0130] As used herein the term "method" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.

[0131] As used herein, the term "treating" includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition.

[0132] In those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B." [0133] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0134] Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

EXAMPLES

[0135] Reference is now made to the following examples which, together with the above descriptions, illustrate the invention in a non-limiting fashion.

[0136] Materials and Methods

[0137] H₂S preparation: Sodium sulfide nonahydrate (Na₂S'9H₂0) was used to prepare standard solution of 1000 mg/L H₂S. A concentrated solution of HCl 37% was used to prepare a 3% HCl solution for maintaining a desired pH level. Water samples collected from the experimental setup were analyzed as received or were stored frozen for up to 2 weeks after sampling (sulfate, hydrogen sulfide).

[0138] The concentration of H₂S was determined by standard method 4500-S2-F Iodometric method and the concentration of sulfate was determined by standard method 4500-SO₄ ^2~E using a turbidimetric method. Turbidity was measured by using Hach 21 OOP turbidity meter.

[0139] The oxygen concentration and pH levels were tested by using appropriate electrodes.

[0140] In exemplary procedures, the experiments were conducted by UV emission at 254 nm with residence time of 10 seconds to 20 minutes using one or more low- pressure mercury lamps. EXAMPLE 1

LABORATORY EXPERIMENTS

[0141] In exemplary procedures, H₂S was oxidized into sulfate by 3 steps:

a) adjusting the pH above 7 and hence HS^" is the major derivative in the medium, as shown in Figure 2.

b) addition of oxidant in order to oxidize HS^" ion into sulfate (see Figure i);

c) applying a UV irradiation for efficient oxidation process and improved removal of HS7H₂S.

[0142] The pH of the medium was maintained at a desired range. As shown in Figure 3, the percentage removal of H₂S (AH₂S) is above 60 % when the pH is above 6.5.

[0143] As shown in Table 1 below, 0₃ was more reactive oxidant than 0₂ (columns 2 and 4). In addition, Table 1 indicates that the UV irradiation increases the efficiency of HS7H₂S oxidation. AH₂S was larger when applying UV irradiation with 0₂ (columns 1 and 4) or O3 (columns 2 and 3).

[0144] As shown in Figure 4, HS^" ion absorbs UV in the range of 200-270 nm and therefore the UV irradiation wavelength used is therebetween that range, while the peak absorbance is at -230 nm.

Table 1

[0145] The intensity of UV irradiation shown to impact the oxidation reaction. Six lamps showed more reactive oxidation of H₂S than 3 lamps, as summarized in Table 2. However, Figure 5 illustrates no difference between UV irradiation of 4 or 6 lamps. [0146] Figure 5 also demonstrates that the increased residence time of UV irradiation improved the oxidation reaction, and 56% of the initial concentration of H₂S was oxidized after 6 minutes of UV irradiation.

Table 2

[0147] Without being bound by any particular theory, it is assumed that the removal rate of H₂S was found to correlate linearly with the initial concentration of H₂S (i.e. approximately first order with respect to H₂S), as shown in Figure 6A.

[0148] Figure 6B shows the effect of light intensity on the conversion of H₂S. The measurements were performed at a retention time of 4.8 min, and at an inlet pH of

7.5.

[0149] Figure 6B presents the quantum efficiency (defined herein as the ratio between the number of oxidized H₂S molecules and the number of photons emitted by the lamps) as a function of the initial concentration of hydrogen sulfide. This Figure reveals quantum efficiency (QE) values ranging between a few percent up to 70%. Generally, for a given initial concentration, increasing the number of lamps decreased the quantum efficiency, while at a given light intensity, the higher the initial concentration of H₂S was, the higher was the quantum efficiency.

[0150] Figure 7 presents a graph demonstrating the effect of retention time on the ratio of the amount of formed sulfate to the amount of consumed H₂S upon illumination with three (triangles) or six (diamonds) lamps.

[0151] Figure 8 presents a schematic illustration of the experimental apparatus used for decreasing H₂S concentration. EXAMPLE 2

FIELD TESTS

[0152] In additional exemplary procedures, the treated water were naturally H₂S- containing well-water, characterized by their high H₂S content (20 ppm) and by their high temperature of 38 °C. The results show the effectiveness of the disclosed method also for water containing H₂S at concentrations that are higher than the concentration of oxygen at its solubility limit. Herein, the lack in oxygen was overcome by supplying extra oxygen (or alternatively air).

[0153] In exemplary procedures, the tested water was untreated water containing not only H₂S but also high concentration of other chemicals, i.e. 560 ppm of sulfate ions, 360 ppm chlorides and Total Dissolved Solids (TDS) concentration value of 1500 ppm.

[0154] Figures 9A-B present the effect of retention time on the conversion of H₂S upon illumination with three (empty triangles) or six (filled circles) lamps at oxygen flow of 2.5 L min ¹ (Figure 9A); and at oxygen flow of 5 L min ¹ (Figure 9B).

[0155] Further exemplary experiments were performed to test the effect of retention time on the yield of sulfate in the field test experiments.

[0156] Figure 10 presents the yield of sulfate ions in the field test experiments as a function of retention time upon illumination with three (empty triangles) or six (filled circles) lamps. The oxygen flow was 2.5 L min^"1.

[0157] The results show that it was possible to obtain approximately 100% of sulfate yield (the yield is defined herein as the moles ratio of the formed to the removed H₂S).

[0158] The QE for the field tests experiments was also tested, and the results showed that the QE obtained in the field tests was similar to the QE measured with "synthetic water" (as shown in Example 1) i.e. that contained only H₂S (at lower concentration; see Figure 11).

EXAMPLE 3

EFFECT OF 0₂ + UV, AND OZONE

[0159] In additional exemplary procedures, the possible additive effect of 0₂+short UV together with ozone was studied both under laboratory conditions and in field tests. For comparison, the oxidation by ozone alone was measured as well. [0160] Table 3 presents the average conversion of H₂S under three modes of operation: ozone, UV/0₂ and ozone+UV/0₂. The presented values were obtained in laboratory experiments (retention time of 4.8 min), as well as in field tests and represent average values over inlet concentrations of 4.4-6 ppm H₂S in the inlet stream (laboratory studies), and 20-21 ppm (field studies).

[0161] The results were obtained under illumination with three lamps (3.06 xlO¹⁹ photons S^"1) as well as under illumination with six lamps.

[0162] Combining the two techniques yielded an increase in the overall removal of H₂S. The performance of the combined process was compared with the calculated conversion assuming ozone treatment followed by UV/0₂ treatment (each technique with its stand-alone performance). The results of the calculated conversion are also given in Table 3 (right column). These results were in very good agreement with the measured performance of the combined process. The results show that the two techniques do not mutually interfere. This lack of negative or positive interference suggest that the two techniques operate via different, non-coupled, mechanisms. This conclusion can be important, since it suggests that in cases where, for any reason, both techniques are in use, there is no need for two different reactors so that one reactor should be sufficient.

Table 3

[0163] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. [0164] All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

Claims

WHAT IS CLAIMED IS:

1. A method for decreasing hydrogen sulfide (H₂S) concentration in a medium, comprising the steps of: a. maintaining pH of said medium at a value of 5.2 or above; b. contacting said medium with an oxidant, and c. applying ultraviolet (UV) irradiation in the range of 200 to 270 nm on said medium, thereby decreasing the concentration of said H₂S.

2. The method of claim 1, wherein said UV irradiation is in the range of from 220 to 260 nm.

3. The method of any one of claims 1 or 2, wherein said oxidant is selected from: oxygen (0₂), Ozone (0₃), hypochlorite, hydrogen peroxide (H₂0₂), or a combination thereof.

4. The method of claim 3, wherein said oxidant comprises 0₂.

5. The method of any one of claims 1 to 4, wherein said pH is in the range of 5.2 to 13.

6. The method of claim 5, wherein said pH is in the range of 5.2 to 8.0, or 8.0 to 10.

7. The method of any one of claims 1 to 6, wherein said medium is selected from the group consisting of: liquid, sludge, gas, and soil.

8. The method of any one of claims 1 to 7, wherein said medium comprises water.

9. The method of any one of claims 1 to 7, wherein said medium comprises sewage.

10. The method of claim 7, wherein said gas comprises air.

11. The method of any one of claims 1 to 10, wherein said decreasing H₂S concentration is at a rate of at least 8 % per minute.

12. The method of any one of claims 1 to 11, wherein said H₂S is present at an initial concentration of 0.001 to 500 ppm.

13. The method of claim 12, wherein said initial concentration is 0.001 to 50 ppm.

14. The method of claim 13, wherein said initial concentration is 1 to 30 ppm.

15. The method of any one of claims 1 to 14, wherein said oxidant is in an initial concentration in said medium of 0.2 x 10^"5 mol/liter to 1.5 x 10^~3 mol/liter.

16. The method of any one of claims 1 to 14, wherein said oxidant is in an initial concentration in said medium of 0.6xl0^"5 mol/liter to 0.7xl0^~3 mol/liter.

17. The method of any one of claims 1 to 16, wherein said UV irradiation has an intensity of at least 0.5 watt per m³ of said medium.

18. The method of any one of claims 1 to 16, wherein said UV irradiation has an intensity of at least 25 watts per m³ of said medium.

19. The method of any one of claims 1 to 18, wherein said UV irradiation has an intensity of at least 1000 watt-sec per 1 gram of H₂S in said medium.

20. A system comprising:

(i) a container configured to maintain a medium comprising H₂S;

(ii) an oxidizing agent inlet;

(iii) at least one UV light source, configured to irradiate in the range of 200 to 270 nm on at least a portion of said medium; and

(iv) at least one sensor configured to measure one or more parameters selected from: a concentration of the H₂S in the medium; and a pH value of said medium.

21. The system of claim 20, wherein the H₂S is present at an initial concentration of 0.001 to 500 ppm in the medium.

22. The system of any one of claims 20 or 21, further comprising a solution inlet.

23. The system of any one of claims 20 to 22, further comprising a collecting unit in fluid communication with the container. The system of any one of claims 20 to 23, further comprising a pH control unit.