Water treatment

Abstract

This article provides a method for treating water, wherein the water comprises a certain amount of at least one dissolved sulfide and at least one microorganism, the method comprising the following steps: i) reacting the water with Fe 2+ or Fe 3+ The process involves contacting an ion source to reduce the amount of at least one dissolved sulfide, and ii) contacting water with percarboxylic acid to provide disinfection against at least one microorganism; wherein step ii) is performed after step i). The reduction in the amount of at least one dissolved sulfide improves the disinfection performance of the percarboxylic acid.

Description

Technical Field

[0001] This disclosure generally relates to a method for treating water. This disclosure particularly, but not exclusively, relates to methods, apparatus, and systems for optimizing the disinfection performance of percarboxylic acids in water treatment processes. This disclosure also relates to Fe... 2+ ions or Fe 3+ The use of ions to improve the disinfection performance of percarboxylic acids in water. Background Technology

[0002] The demand for purified water is rapidly increasing worldwide. Efforts are underway to purify water using lower concentrations of chemical disinfectants without significantly increasing the cost of the purification process. Furthermore, there is a need for biodegradable or otherwise less harmful chemicals with fewer adverse health effects.

[0003] Chlorine-based disinfectants (such as hypochlorite, chlorine dioxide, and chloramine) have traditionally been used to disinfect water, including wastewater. While highly effective against bacteria, chlorine-based disinfectants are less effective against viruses, bacterial spores, and protozoan cysts. Furthermore, chlorine-based disinfectants produce potentially toxic and mutagenic byproducts, making them less than satisfactory for disinfection purposes.

[0004] Therefore, alternative disinfection methods were considered. Among these, ultraviolet (UV) irradiation is currently the most widely used alternative. It is typically effective against intestinal bacteria, viruses, parasite cysts, and bacterial spores without producing harmful byproducts. However, if the UV dose is too low, UV-damaged microorganisms can undergo photoreactivation or dark repair, leading to potential regrowth under favorable conditions. Furthermore, UV disinfection systems are highly dependent on upstream conventional treatment processes: UV is only effective when the treated water quality is high (i.e., low turbidity) because suspended solids can protect microorganisms from UV light. In addition, UV disinfection methods are relatively energy-intensive and expensive.

[0005] Other alternative sterilization methods, such as ozonation, ultrasound, and membrane filtration, have been investigated. However, these methods are generally more expensive and have their own drawbacks.

[0006] Recently, organic peroxides peracetic acid and performic acid have been considered as alternative disinfectants.

[0007] Peracetic acid (PAA or CH3COOOH) is a broad-spectrum disinfectant with a high redox potential. PAA is commercially available as an acidic quaternary equilibrium mixture of acetic acid, hydrogen peroxide (H2O2), and water as shown in the following reaction (1).

[0008]

[0009] PAA is active against a wide variety of microorganisms. The disinfection mechanism of PAA is based on the release of highly reactive oxygen species (ROS), such as hydroxyl radicals (HO·), alkoxy radicals (RO·), hydroperoxide radicals (HO2·), and superoxide radicals (O2·). - ROS can alter the metabolism of microorganisms and damage the structure of microbial cells due to chain reactions between ROS and biomolecules such as enzymes, lipids, structural proteins, and DNA. Advantageously, PAA produces little or no toxic / mutagenic byproducts after reacting with organic matter and degrades into acetic acid, hydrogen peroxide, and water.

[0010] Formic acid (PFA or HCOOOH) has been used to disinfect effluents from primary and secondary wastewater treatment plants (see the description of the wastewater treatment process below). PFA is typically applied in the form of an equilibrium mixture of PFA, water, hydrogen peroxide, and formic acid as shown in the following reaction (2).

[0011]

[0012] PFAs are highly unstable and typically need to be prepared on-site just before use. The sterilization mechanism of PFAs is considered similar to that of PAAs via ROS generation. PFAs are considered more effective than PAAs in sterilization (e.g., requiring lower doses and / or shorter contact times) to neutralize at least some microorganisms, including E. coli. E. coli ) and Enterococcus ( Enterococcus PFA is deactivated. This can be attributed to the higher redox potential of PFA, which provides a greater ability to oxidize pollutants. Similar to PAA, PFA produces little or no toxic / mutagenic byproducts after reacting with organic matter. PFA is completely biodegradable, and the degradation products of PFA include carbon dioxide and water (Gehr et al., 2009, Water Sci. Tech. 59, 89-96).

[0013] There is still a need to improve the disinfection performance of organic peroxides such as PAA and PFA in order to improve the overall efficiency of water treatment systems and reduce operating costs. Summary of the Invention

[0014] Therefore, in a first aspect, the present invention provides a method for treating water, wherein the water contains a certain amount of at least one dissolved sulfide and at least one microorganism, the method comprising the steps of:

[0015] i) Mix the water with Fe 2+ or Fe 3+ Ion source contact to reduce the amount of at least one dissolved sulfide, and

[0016] ii) Contact the water with percarboxylic acid to provide disinfection against the at least one microorganism;

[0017] Step ii) is performed after step i).

[0018] In a second aspect, the present invention provides an apparatus comprising:

[0019] At least one processor; and

[0020] At least one memory, the at least one memory including computer program code, the at least one memory and the computer program code together with the at least one processor, are configured to cause the device to perform the above-described method.

[0021] In a third aspect, the present invention provides a water treatment system comprising the aforementioned equipment, the system comprising:

[0022] The first quantitative feeding device is formulated to feed Fe 2+ or Fe 3+ An ion source is fed into the water.

[0023] The second quantitative feeding device is configured to feed percarboxylic acid into the water, and

[0024] A first measuring device is configured to measure the level of at least one dissolved sulfide in water and generate output data related to the measured level of dissolved soluble sulfides.

[0025] The device is configured and arranged to receive output data related to the measured level of the at least one dissolved sulfide from the first measuring device, monitor the measured level of the at least one dissolved sulfide in the water, and adjust the Fe content fed into the water by the first metering device based on the monitored level of the at least one dissolved sulfide. 2+ or Fe 3+ The amount of ion source and / or the amount of percarboxylic acid fed into the water by the second quantitative feeding device.

[0026] Preferred features of all aspects of the invention are defined by the dependent claims.

[0027] In a third aspect, the present invention provides Fe 2+ or Fe 3+ The use of ions in methods for improving the disinfection performance of percarboxylic acids against at least one microorganism in water treatment, wherein the water contains a certain amount of at least one dissolved sulfide and at least one microorganism, and the use includes reacting the water with the Fe... 2+ or Fe 3+Ion contact is used to reduce the amount of at least one of the dissolved sulfides in water.

[0028] The methods, apparatus, systems, and applications defined herein are particularly useful in wastewater treatment. The inventors have discovered that by interacting with Fe... 2+ ions or Fe 3+ Ion contact reduces the amount of dissolved sulfides in water, which advantageously increases the disinfection efficiency of percarboxylic acid. Attached Figure Description

[0029] To aid in understanding this disclosure and to illustrate how embodiments can be implemented, reference is made to the accompanying drawings by way of example only, wherein:

[0030] Figure 1 This is a schematic block diagram illustrating a device according to an embodiment of the present invention.

[0031] Figure 2A This is a bar chart showing the effectiveness of PFA in wastewater samples with low dissolved sulfide content.

[0032] Figure 2B This is a bar chart showing the effectiveness of PFA in wastewater samples with high dissolved sulfide content.

[0033] Figure 3 A shows the use of Fe 2+ or Fe 3+ A bar chart showing the PFA efficacy in pretreated wastewater samples.

[0034] Figure 4A It uses 4.5 mg / L Fe 2+ (Left) or 7mg / l Fe 3+ (Right) Photograph of the treated wastewater sample.

[0035] Figure 4B It uses 9mg / l Fe 2+ (Left) or 14 Fe 3+ (Right) Photograph of the treated wastewater sample. Detailed Implementation

[0036] Regardless of the disinfection technology employed, disinfection performance is primarily controlled by the concentration of residual disinfectant. The term "residual disinfectant concentration" as used herein refers to the concentration of the disinfectant after a period of contact (or exposure) with the water to be treated. Therefore, consistent disinfection performance can be achieved by dynamically maintaining a threshold concentration of residual disinfectant during the disinfection process. However, for the specific use of percarboxylic acids (PFAs) as disinfectants in wastewater treatment systems, variations in water quality and quantity, as well as numerous side reactions between the disinfectant and water contaminants, can reduce the concentration of residual disinfectant and thus adversely affect disinfection performance. For example, when added to wastewater, PFAs and PAAs experience an initial rapid depletion (i.e., instantaneous disinfectant demand), followed by a more gradual decline. Poor water quality and water contaminants can accelerate both the initial depletion and subsequent decline. Consequently, quantitative feeding strategies that do not consider conditions affecting demand and / or decline can lead to inadequate disinfection performance and may violate regulatory microbiological restrictions.

[0037] As described above, the present invention provides a method for treating water, wherein the water contains a certain amount of at least one dissolved sulfide and at least one microorganism, the method comprising the steps of:

[0038] i) Mix the water with Fe 2+ or Fe 3+ Ion source contact is used to reduce the amount of at least one dissolved sulfide, and

[0039] ii) Contacting water with percarboxylic acid to provide disinfection against at least one of the said microorganisms;

[0040] Step ii) is performed after step i).

[0041] By reducing the amount of dissolved sulfides in the water to be treated, the disinfection performance of percarboxylic acid was unexpectedly improved. This, in turn, enabled the use of lower concentrations of percarboxylic acid to achieve satisfactory disinfection and meet microbial reduction targets, resulting in lower operating costs.

[0042] The term “dissolved sulfide” as used herein may also include any sulfide compound that is soluble in water or capable of dissolving in water.

[0043] Water to be treated

[0044] The water to be treated is not particularly limited and can be any water or aqueous solution that requires disinfection. Water to be treated can include raw water (e.g., surface water from lakes, oceans, or rivers), drainage, water used in agriculture, or wastewater. In some instances, the water can include industrial water. In this case, the term "industrial" can refer to the pulp and paper industry, the petroleum industry, the mining industry, the food industry, or any other applicable industry. Water to be treated typically includes one or more contaminants such as bacteria, viruses, and other non-living organic matter.

[0045] Wastewater treatment

[0046] In a preferred embodiment, the water to be treated includes wastewater. Therefore, the method for treating water according to the invention can be carried out within a wastewater treatment system or plant. The wastewater to be treated may include municipal wastewater, sewage, and / or industrial wastewater.

[0047] Municipal wastewater or sewage treatment typically involves the following sequential processes: preliminary treatment, primary treatment, secondary treatment, and tertiary treatment. These are wastewater treatment and water purification practices well known to those skilled in the art and are discussed further below.

[0048] Preliminary treatment can remove coarse and large suspended solids that can be easily collected from raw sewage or wastewater before they damage or clog any pumps and sewage lines of primary treatment equipment, for example by screening and / or crushing.

[0049] Primary treatment is designed to remove total suspended and floating solids from raw wastewater or sewage. Primary treatment may include screening to trap solids and gravity settling to remove suspended solids (which are removed and collected as sludge). The settling process can be accelerated by using chemicals. Total suspended solids concentration (TSS) is a key indicator of primary treatment. TSS represents the percentage by weight of fine particulate matter remaining suspended in a given volume of water. Primary treatment can reduce TSS concentrations by 40% to 50%.

[0050] Following primary treatment, wastewater can be directed to secondary treatment, which typically includes biological treatment steps and settling. Specifically, the primary effluent may undergo an activated sludge process, in which the effluent is aerated, and aerobic microorganisms metabolize organic matter into carbon dioxide and water and multiply to form a microbial community. Organic nitrogen compounds can be converted into ammonia, and subsequently into nitrates. Secondary settling tanks / vessels allow microorganisms and solid waste to aggregate and settle into sludge. At least a portion of the collected sludge (activated sludge) can then be recycled as inoculum for the biological treatment of further incoming wastewater.

[0051] Secondary treatment can reduce TSS levels to 10% to 15%. Biochemical oxygen demand (BOD) is a further indicator of secondary treatment. BOD is a measure of the amount of oxygen required by aerobic microorganisms to break down organic matter in a given water sample at a specific temperature over a given time period. Secondary treatment typically reduces BOD to 10% to 15%.

[0052] Alternative or additional processes that may be performed during secondary treatment can include biological filtration and oxidation ponds. Biological filtration requires the use of microorganisms immobilized on filters (such as sand filters, contact filters, or trickling filters) to break down organic matter and remove additional sediment. Oxidation ponds involve allowing wastewater to pass through a large body of water (such as lagoons) under sunlight for an extended period of time to allow microorganisms to decompose organic matter.

[0053] For many purposes, primary and secondary treatment are often sufficient, and not all wastewater treatment plants use tertiary treatment. Those that do use tertiary treatment achieve more stringent levels of cleanliness to meet the demanding standards governing water reuse, particularly in public water supplies. Tertiary treatment is also beneficial when facilities must discharge water into sensitive or fragile ecosystems, such as estuaries, low-flow rivers, coral reefs, etc. Tertiary treatment can include filtration, disinfection, and the removal of nitrogen and phosphorus.

[0054] Fe 2+ or Fe 3+ Ion source processing

[0055] Dissolved sulfide compounds in the water to be treated can originate from bacterial metabolism. In wastewater systems, dissolved sulfides can be present at various stages of the treatment process. Bacteria in water treatment systems (especially wastewater treatment systems) can utilize soluble oxygen, soluble nitrates, or soluble sulfates as energy sources. Soluble oxygen is typically present in fresh wastewater but is rapidly depleted by biological activity. Very little nitrate is usually present in wastewater, but sulfate is typically abundant. Therefore, in the absence of oxygen and nitrates, sulfate can be used as an energy source by bacteria. Dissolved sulfides can be generated from the reduction of sulfate during bacterial respiration and can subsequently combine with hydrogen ions to form hydrogen sulfide compounds. Therefore, in some embodiments, at least one dissolved sulfide compound comprises H₂S, HS₂, etc. - and / or S 2- .

[0056] Before adding percarboxylic acid, Fe can be added at at least one process location. 2+ or Fe 3+ An ion source is added to the water flow. In a continuous flow water treatment system, Fe can be added at at least one process location upstream of the percarboxylic acid source. 2+ or Fe 3+An ion source is added to the water flow. Fe can be added at several different locations. 2+ or Fe 3+ Ion sources. These can include, but are not limited to, any location along the water treatment system where dissolved sulfides are present. Preferably, Fe is applied at one, two, or more process locations adjacent to the location where dissolved sulfides are present or generated. 2+ or Fe 3+ An ion source is added to the water. In some instances, and specifically regarding wastewater treatment, the addition point can be located at the inflow or effluent of the primary or secondary treatment section. In other instances, Fe can be added. 2+ or Fe 3+ An ion source is added to at least the effluent from a wastewater treatment plant during primary and / or secondary treatment. In a preferred embodiment, Fe... 2+ or Fe 3+ Ion sources can be added after secondary treatment and before tertiary treatment, for example, at the effluent from secondary treatment. In some instances, the water entering the treatment plant can contain significant amounts of dissolved sulfides. In these instances, Fe... 2+ or Fe 3+ An ion source can be added to the water stream before it enters the treatment plant. Secondary wastewater treatment may also be particularly prone to generating dissolved sulfides. Therefore, in other instances, Fe is used compared to other stages of the wastewater treatment process. 2+ or Fe 3+ Ion source treatment can be more effective for secondary treatment effluents. After secondary treatment, most microorganisms may have settled and precipitated into sludge, and there may be no further significant production of dissolved sulfides.

[0057] The first quantitative feeding device can be configured to feed Fe 2+ or Fe 3+ An ion source is added to or fed into the water stream. The first metering device may include one or more pumps or valves that promote the Fe... 2+ or Fe 3+ The ion source is optionally delivered to the water via one or more pipelines. The first metering device can be operated manually or automatically, as described in further detail below. Fe 2+ or Fe 3+ The ion source can be added or fed into the water continuously or at regular intervals at a constant rate, or the feed can be adjusted quantitatively, as described below.

[0058] The rate of dissolved sulfide formation can depend on the concentration of sulfate ions, organic matter, and other factors such as pH, temperature, residence time, and flow rate. Therefore, in some embodiments, when water is mixed with Fe... 2+ or Fe 3+Before contacting the ion source, it is desirable to measure the concentration of dissolved sulfides in the water. The Fe2+ concentration can then be adjusted based on the obtained information about the dissolved sulfide concentration. 2+ or Fe 3+ Quantitative feeding of ions. According to another embodiment of the invention, Fe can be added... 2+ or Fe 3+ Downstream of the ion source or by adding Fe 2+ or Fe 3+ The concentration of dissolved sulfides is measured after the ion source. Therefore, it is possible to measure the concentration of dissolved sulfides in Fe. 2+ or Fe 3+ Before the ion source addition point and / or Fe 2+ or Fe 3+ The concentration of dissolved sulfides was measured after the ion source was added.

[0059] The concentration of dissolved sulfides in the water to be treated can be measured continuously. In the context of this invention, "continuously" means measuring the level of dissolved sulfides without interruption at regular, repetitive intervals. For example, the level of dissolved sulfides in the water can be measured at regular intervals from 1 minute to 5 minutes, or at regular intervals of 10 minutes, 20 minutes, 30 minutes, or hourly. 2+ or Fe 3+ The quantitative feeding of the ion source can be adjusted based on the measured concentration. This type of system enables the efficient delivery of Fe. 2+ or Fe 3+ The concentration of ions is used to reduce the desired amount of dissolved sulfides.

[0060] In order to maintain the concentration of dissolved sulfides at an acceptablely low level, Fe 2+ ions or Fe 3+ The molar ratio of the ion to at least one sulfide compound can be from 0.5:1 to 5:1, or from 1:1 to 3:1.

[0061] The concentration of dissolved sulfides can be measured using a first measuring device. In some instances, the concentration of dissolved sulfides is measured colorimetrically. In these instances, in Fe... 3+ In the presence of ions, water samples containing sulfides react with DPD (N,N-diethyl-p-phenylenediamine). The reaction of DPD with sulfides produces an intermediate compound, which is ultimately reacted with Fe. 3+ Ions are oxidized to methylene blue. The amount of methylene blue will be proportional to the amount of sulfide dissolved in the sample and can be quantified by comparison with a standard color chart or by spectrophotometry. Hach TMThe LCK653 Sulphide Cuvette Test is a commercially available absorption test for measuring dissolved sulfides. In other instances, the measuring device may include a sensor for directly determining the concentration of dissolved sulfides.

[0062] Detection / measurement of dissolved sulfides and Fe through the first metering feeder 2+ or Fe 3+ The addition or quantitative feeding of the ion source can be automated. Preferably, the measurement of dissolved sulfides is performed online. In other embodiments, the measurement of dissolved sulfides is performed in-line. Both in-line and online measurements are continuous, in-situ measurements. Online measurements are not performed directly in the main process line, but in a built-in branch or bypass (e.g., a sampling loop) into which a water sample containing dissolved sulfides is automatically fed. In-line measurements are performed directly in the main process line, which requires placing the probe or sampling interface directly into or co-linear with the process flow. For dissolved sulfide measurement methods that require additional reagents to measure dissolved sulfides (e.g., colorimetry as described above), an online measurement configuration is preferred.

[0063] The control equipment can control the Fe from the first quantitative feeding device. 2+ or Fe 3+ Quantitative feeding of the ion source. The control device may include a computing device configured to implement at least some of the features described herein. In one example, the invention provides a control device including at least one processor and at least one memory including computer program code, the at least one memory and the computer code being configured, together with the at least one processor, to cause the device to perform any of the methods described herein.

[0064] Figure 1 This is a block diagram of a control device (18) according to an embodiment of the present invention. The control device (18) is adapted to implement at least some of the operations described herein. See details. Figure 1 The control device (18) may include at least one processor (28), at least one memory (29), a communication interface (32), and a user interface (31). The control device may also include other internal circuitry and components necessary to perform the tasks described herein. The control device (18) may be configured and arranged to receive output data from a first measuring device (19) to monitor the level of dissolved sulfides present in water as measured by the first measuring device (19) and to adjust Fe... 2+ or Fe 3+ The ion source feeds water from the first quantitative feeding device (16).

[0065] The control device (18) may include a communication interface (32) for connecting the control device to a data communication system and enabling data communication with the device. The communication interface (32) may include wired and / or wireless communication circuitry, such as Ethernet, wireless LAN, Bluetooth, GSM, CDMA, WCDMA, LTE, 5G circuitry, and / or the like. The communication interface may be integrated into the control device (18) or provided as part of an adapter, card, etc., that can be attached to the control device (20). The communication interface (32) may support one or more different communication technologies. The control device (18) may also, or alternatively, include more than one communication interface (32).

[0066] The user interface (31) may include circuitry for receiving user input from the control device (18), for example via a keyboard, a graphical user interface displayed on the device's screen, voice recognition circuitry, or an accessory device such as headphones, and for providing output to the user via, for example, a graphical user interface or a speaker. The control device may be operated remotely.

[0067] At least one processor (28) may be coupled to at least one memory (29). At least one processor (28) may be configured to execute appropriate computer program code to implement one or more aspects described herein. At least one processor (28) may be a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a graphics processing unit, an application-specific integrated circuit (ASIC), a field-programmable gate array, a microcontroller, or a combination of such elements.

[0068] At least one memory (29) may include working memory (30) and persistent (non-volatile, N / V) memory (33) configured to store computer program code (34) and data (35). Memory (33) may include any one or more of the following: read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), random access memory (RAM), flash memory, data disk, optical storage, magnetic storage, smart card, solid-state drive (SSD), etc. Control device (18) may include other possible components for use in software and hardware-assisted execution of tasks designed to be performed.

[0069] The control device (18) may include multiple memories (33). The memories (33) may be configured as part of the control device (18) or as attachments to be inserted by a user, another person, or a robot into slots, ports, etc., of the device (18). The memories (33) may serve only the purpose of storing data, or may be configured as part of the device (18) for other purposes such as processing data.

[0070] Those skilled in the art will understand that, in addition to Figure 1 In addition to the components shown, the control device (18) may also include other components such as a microphone, a display, and additional circuitry such as input / output (I / O) circuitry, memory chips, application-specific integrated circuits (ASICs), and processing circuitry for specific purposes such as source encoding / decoding circuitry, channel encoding / decoding circuitry, encryption / decryption circuitry, etc. Furthermore, the control device (18) may include a disposable or rechargeable battery (not shown) to power the device (18) if an external power source is unavailable. It should also be noted that... Figure 1 Only one device (18) is shown, but some implementations can be similarly implemented in a cluster of the devices shown.

[0071] In some embodiments, the control device (18) may be configured to receive input of a specific parameter, such as a predefined threshold concentration of dissolved sulfides. This specific parameter may be input via a user interface (31). In these embodiments, based on output data received from a first measuring device (19), the control device (18) may detect an increase in the concentration of dissolved sulfides exceeding a predefined threshold concentration (e.g., when water quality is poor), and cause the first metering device (16) to increase the Fe content fed into the water to be treated within a given time period. 2+ or Fe 3+ The amount of ion source is adjusted to restore the sulfide concentration below a predefined threshold. This can be achieved, for example, by increasing the pump speed or by turning on an ion source that facilitates the extraction of Fe. 2+ or Fe 3+ The ion source is delivered to the water to be treated via a valve. Conversely, based on the output data received from the first measuring device (19), the control device (18) can detect a decrease in the concentration of dissolved sulfides below a predefined threshold and cause the metering device (16) to reduce the amount of Fe fed into the water to be treated within a given time period. 2+ or Fe 3+ The amount of ion source should be adjusted to avoid unnecessary reagent consumption. This can be achieved, for example, by reducing the pump speed or turning it off, which would otherwise help to ionize Fe. 2+ or Fe 3+ The ion source is delivered to the water to be treated via a valve. Appropriate computer program code (34), executed by the processor (28) and stored in the memory (29), can determine whether the measured level of dissolved sulfide is higher or lower than a predefined value, and the amount of Fe added to the water to be treated, based on output measurement data received from the first measuring device (19). 2+ or Fe 3+The required adjustment of the amount of ion source is as described herein. Therefore, the control device (18) may be constructed and arranged to compare the measured concentration of dissolved sulfide with a predefined concentration of sulfide, and may be constructed and arranged to adjust the performance of the first metering feed device (16).

[0072] In an embodiment of the invention, at least one processor (28) may include a proportional-integral-derivative (PID) controller. A PID controller employs a feedback control loop mechanism and is widely used in industrial control systems and various other applications requiring continuous modulation control. The PID controller continuously calculates an error value as the difference between a predefined set concentration of dissolved sulfide and a measured concentration of dissolved sulfide, and can subsequently apply corrections based on the proportional, integral, and derivative terms. The controller may attempt to adjust its output (e.g., by adjusting the delivery of Fe) by... 2+ or Fe 3+ The speed of one or more pumps in the ion source is used to minimize the error over time, ensuring that the concentration of dissolved sulfide does not exceed a predefined threshold concentration of dissolved sulfide. In another example, a PI (proportional, integral) based controller is used.

[0073] The predefined threshold concentration of dissolved sulfides can be 5 mg / L, 2 mg / L, 1 mg / L, or 0.5 mg / L. Therefore, a sufficient amount of Fe can be added. 2+ or Fe 3+ The ions reduce the concentration of sulfides dissolved in water to less than 5 mg / L, less than 2 mg / L, less than 1 mg / L, or less than 0.5 mg / L. In a preferred embodiment, a sufficient amount of Fe is added. 2+ or Fe 3+ The ions reduce the concentration of sulfides dissolved in water to less than 0.5 mg / L. The inventors have found that percarboxylic acid exhibits optimal disinfection performance when the concentration of sulfides dissolved in water is less than 0.5 mg / L. In some instances, ferric chloride (II) or ferric chloride (III) provides Fe, respectively. 2+ and Fe 3+ Ion source. Capable of ionizing Fe at concentrations of at least 5 mg / L, at least 10 mg / L, at least 15 mg / L, or at least 20 mg / L. 2 + or Fe 3+ Ions are added to water. Particularly effective Fe... 2+ or Fe 3+ The ion concentration can be from 5 mg / L to 15 mg / L or from 10 mg / L to 15 mg / L. Fe can be added at the above baseline concentrations. 2+ or Fe 3+ An ion source is added to the water. The Fe content can then be adjusted according to the level of dissolved sulfides, as detailed in this article.2+ or Fe 3+ The concentration of ions.

[0074] For Fe 2+ or Fe 3+ The ion source is not particularly limited and may include any water-soluble ferrous or ferric salt such that, upon contact with water, Fe... 2+ or Fe 3+ The ions can be used to react with dissolved sulfides. In some instances, Fe... 2+ or Fe 3+ The ion source includes one or more of ferric sulfate (Fe2(SO4)3), ferric chloride (FeCl3), ferrous chloride (FeCl2), and ferrous sulfate (FeSO4). In a preferred embodiment, Fe... 2+ or Fe 3+ The ion source may include ferrous chloride and / or ferric chloride.

[0075] It is believed that in Fe 2+ and Fe 3+ When Fe ions combine with dissolved sulfide ions, they form insoluble sulfide precipitates, thereby reducing the amount of dissolved sulfide. 2+ and Fe 3+ Insoluble elemental sulfur can also be formed during ion treatment. Insoluble sulfide precipitates and sulfur can be removed from water by sedimentation or precipitation. In some embodiments, sulfide precipitates / sulfur are allowed to settle in a sedimentation tank, where they can be removed from the water. In the method of the present invention, Fe... 2+ or Fe 3+ Ions can also neutralize the charge on other suspended particles in the water, causing them to settle. Furthermore, the precipitate formed can trap additional particles, promoting flocculation and further clarifying the water. In some instances, the pH of the water can be adjusted to optimize the precipitation of dissolved sulfides. In some instances, a pH range of 5-11 provides optimal removal of dissolved sulfides. In preferred instances, a pH range of 6-7 provides optimal removal of dissolved sulfides.

[0076] The inventors unexpectedly discovered that Fe... 2+ ionic ratio Fe 3+ Ions are more effective. We don't want to be bound by theory, Fe... 2+ Ions can be more effective at precipitating sulfide ions and promoting the aggregation of suspended particles. This can lead to a reduction in total suspended solids (TSS), resulting in reduced microbial growth in the water and a lower microbial load in the effluent, as well as enhanced disinfection performance of percarboxylic acids.

[0077] Disinfection by percarboxylic acid

[0078] Using Fe 2+ or Fe 3+ After ion source treatment, a disinfectant containing percarboxylic acid is brought into contact with water or fed into water to provide disinfection against at least one microorganism.

[0079] The percarboxylic acid may include peracetic acid (PAA), performic acid (PFA), or a combination thereof. In a preferred embodiment, the percarboxylic acid includes PFA.

[0080] The second metering device can be configured to add or feed percarboxylic acid into the water stream. This metering device may include one or more pumps or valves that facilitate the optional delivery of the percarboxylic acid into the water via one or more lines. The second metering device can be operated manually or automatically, as described in more detail below.

[0081] PAA is commercially available as an acidic quaternary equilibrium mixture of acetic acid, hydrogen peroxide (H2O2), and water as shown in reaction (1) below. Therefore, it can be fed into water as an equilibrium mixture.

[0082]

[0083] Due to the greater instability and faster decomposition time of PFA, it may be necessary to generate PFA immediately before use. Preferably, PFA is generated in situ (i.e., at the water treatment site). Therefore, the second metering device may contain the reaction vessel in which PFA is generated. In other embodiments, PFA is generated outside the water treatment system and directly and rapidly transferred to the metering device for feeding into the water. A preferred method for preparing PFA involves mixing formic acid with hydrogen peroxide according to reaction (2) below, optionally in the presence of an acid catalyst such as sulfuric acid, ascorbic acid, or boric acid. If the molar ratio of formic acid to hydrogen peroxide is increased, or by removing water from the reaction, the equilibrium of reaction (2) below can shift in favor of PFA formation.

[0084]

[0085] Percarboxylic acid can be fed into the water continuously (i.e., without interruption) or at regular, predetermined time intervals. Percarboxylic acid can also be fed into the water at a constant rate. Alternatively, the amount of percarboxylic acid fed into the water can be adjusted based on the measured levels of dissolved sulfides and / or the measured levels of residual percarboxylic acid. As mentioned above, the level of residual percarboxylic acid in the water provides an indication of disinfection effectiveness.

[0086] In some instances, the feeding of percarboxylic acid into water is automated. In these instances, and further reference... Figure 1The aforementioned control device (18) can be operatively connected to the second metering feeder (16a). The control device (18) can be configured and arranged to receive output data from the first measuring device (19) relating to the concentration of dissolved sulfides, and to adjust the feed of percarboxylic acid from the second metering feeder (16a) into the water based on such output data. This ensures that any variation in the concentration of dissolved sulfides on the disinfection performance of the percarboxylic acid is minimized or offset by adjusting the amount of percarboxylic acid fed into the water for disinfection.

[0087] Therefore, based on the output data received from the first measuring device (19), the control device (18) can detect an increase in the concentration of dissolved sulfides above a predetermined threshold concentration, and cause the second metering device (16a) to increase the amount of percarboxylic acid fed into the water to be treated within a given time period until the concentration of dissolved sulfides returns to the predetermined threshold. This can be achieved, for example, by increasing the pump speed or opening a valve that facilitates the delivery of percarboxylic acid from the second metering device (16a) to the water to be treated. Conversely, based on the output data received from the first measuring device (19), the control device (18) can detect a decrease in the concentration of dissolved sulfides below a predetermined threshold, and cause the second metering device (16b) to reduce the amount of percarboxylic acid fed into the water to be treated within a given time period to avoid unnecessary depletion of percarboxylic acid and an increase in the residual percarboxylic acid concentration exceeding regulatory limits. This can be achieved, for example, by decreasing the pump speed or closing a valve that would otherwise facilitate the delivery of percarboxylic acid from the second metering device (16b) to the water to be treated.

[0088] As described above, the appropriate computer program code (34) executed by the processor (28) and stored in the memory (29) can determine, based on the output measurement data received from the first measuring device (19), whether the measured level of dissolved sulfide is higher or lower than a predetermined threshold, and the necessary adjustment of the amount of percarboxylic acid fed into the water to be treated, as described herein. Therefore, the control device (18) can be configured and arranged to compare the measured dissolved sulfide concentration with a predetermined threshold sulfide concentration, and can be configured and arranged to adjust the performance of the second metering device (16a).

[0089] In a further example, the metering of percarboxylic acid may also be adjusted additionally or alternatively based on the concentration of residual percarboxylic acid. In these examples, a second measuring device (19a) may be provided to measure the concentration of residual percarboxylic acid. A control device (18) may be configured and arranged to receive output data from the second measuring device (19a) relating to the concentration of residual percarboxylic acid, and to adjust the feed of percarboxylic acid from the second metering device (16a) to the water based on such output data. Thus, for example, based on the output data received from the second measuring device (19a), the control device (18) may detect an increase in the concentration of residual percarboxylic acid above a predetermined threshold concentration, and cause the second metering device (16a) to reduce the amount of percarboxylic acid fed into the water to be treated within a given time period to avoid unnecessary depletion of percarboxylic acid and an increase in the concentration of residual percarboxylic acid exceeding regulatory limits, and to restore the concentration of residual percarboxylic acid to the predetermined threshold. This can be achieved, for example, by reducing the pump speed or closing valves that otherwise facilitate the delivery of percarboxylic acid from the second metering device (16a) to the water to be treated. Conversely, based on the output data received from the second measuring device (19a), the control device (18) can detect that the concentration of residual percarboxylic acid has decreased below a predetermined threshold, and cause the second metering device (16a) to increase the amount of percarboxylic acid fed into the water to be treated within a given time period to maintain the required disinfection efficacy. This can be achieved, for example, by increasing the pump speed or opening a valve that facilitates the delivery of percarboxylic acid from the second metering device (16a) to the water to be treated. In the example of in-situ synthesis of percarboxylic acid, the change in the metering of percarboxylic acid can be achieved by changing the corresponding percarboxylic acid production rate (e.g., by changing the amount of reactants available to produce percarboxylic acid).

[0090] The predetermined threshold concentration of residual percarboxylic acid can be determined based on applicable regulatory limits in the area where the water treatment system is located. In some embodiments, the predetermined threshold concentration of percarboxylic acid may be 2 mg / L to 5 mg / L, 0.3 mg / L to 1 mg / L, or 0.4 mg / L to 0.6 mg / L.

[0091] In some embodiments, the method for treating water according to the present invention is a continuous method. In one example of the invention, a percarboxylic acid solution (preferably a PFA solution) is contacted with water at a base concentration of 0.5 to 50 mg / L, or 0.8 to 25 mg / L, or 1 to 10 mg / L based on the amount of active percarboxylic acid (i.e., the concentration of percarboxylic acid at the point of addition to the water before it is consumed). The percarboxylic acid can be continuously fed into the water to be treated from a second metering device (16a) in which percarboxylic acid can be generated at the above-mentioned active concentration. The metering of the percarboxylic acid can be adjusted as described above in response to changes in the concentration of dissolved sulfides and / or the concentration of residual percarboxylic acid.

[0092] As described above, the PID controller continuously calculates the error value as the difference between the predetermined set concentration of residual percarboxylic acid and the measured concentration of percarboxylic acid, and can subsequently apply corrections based on proportional, integral, and derivative terms. The controller may attempt to minimize this error over time by adjusting its output (e.g., by adjusting the speed of the pump delivering the percarboxylic acid) so that the concentration of percarboxylic acid does not exceed a predetermined threshold concentration.

[0093] Percarboxylic acid can be added with Fe 2+ or Fe 3+ Percarboxylic acid is added to water at at least one process location after the ion source, such that the amount of dissolved sulfide at the point of addition is reduced. This ensures that the disinfection performance of the percarboxylic acid is minimized by the presence of dissolved sulfides. In continuous flow systems, the percarboxylic acid is preferably added at the point of Fe... 2+ or Fe 3+ The ion source is added downstream of the process location. In wastewater treatment, percarboxylic acid can be added to the water as a final treatment step, for example, as a tertiary treatment following primary and secondary treatment.

[0094] Measurement of percarboxylic acid

[0095] In the water treatment method according to the invention, the level of residual percarboxylic acid is preferably measured and monitored continuously and in real time to detect any fluctuations in concentration deviating from the threshold concentration of residual PFA. In the context of this invention, "continuous" means measuring the level of percarboxylic acid at regular, repetitive intervals without interruption. For example, the level of residual percarboxylic acid can be measured and monitored at regular intervals (e.g., every 2 minutes, every 3 minutes, every 4 minutes, every 5 minutes, every 10 minutes, every 30 minutes, or every hour). Measurements can be performed online or in-line as described above with respect to the measurement of dissolved sulfides.

[0096] Percarboxylic acids can be measured manually or automatically. Standard methods, including amperometric techniques and colorimetric methods such as the widely used DPD (N,N-diethyl-p-phenylenediamine) method, can be used to measure them. DPD kits and photometers are commercially available. Examples of DPD analyzers that can be used for percarboxylic acid measurements include Hach. ® CL-17 analyzer, Hach ® CL-17sc analyzer or Xylem ® The 3017M analyzer can also be used to measure percarboxylic acids using the standard Reflectoquant peracetic acid test.

[0097] The level of residual percarboxylic acid can be measured by a second measuring device (19a) at any process location after the percarboxylic acid is fed into the water. Preferably, the measurement begins after a sufficient contact time (i.e., the time between the addition of the percarboxylic acid to the water and the measurement) has elapsed. A contact time of at least 5, 10, 20, or 30 minutes is desired. In some instances, a contact time of at least one or two hours is provided. In a continuous flow system, this means performing the measurement at a flow distance of at least 5, 10, 20, 30 minutes, one hour, or two hours downstream of the point where the percarboxylic acid is fed into the water.

[0098] Fe was also provided 2+ or Fe 3+ The use of ions to enhance the disinfection performance of percarboxylic acids against at least one microorganism in a water treatment method, wherein the water contains a certain amount of at least one dissolved sulfide and at least one microorganism, and the use includes reacting the water with Fe... 2+ or Fe 3+ Ion contact reduces the amount of at least one dissolved sulfide in water.

[0099] This method can be as defined in this paper.

[0100] Although at least some aspects of the embodiments described herein with reference to the accompanying drawings include computer processes executed in a processing system or processor, the invention also extends to computer programs, particularly computer programs on or in a carrier suitable for carrying out the invention. The program may be non-transitory source code, object code, code between source code and object code (e.g., in a partially compiled form), or any other non-transitory form suitable for implementing the process according to the invention. The carrier may be any entity or device capable of carrying the program. For example, the carrier may include storage media such as solid-state drives (SSDs) or other semiconductor-based RAM; ROMs such as CD-ROMs or semiconductor ROMs; magnetic recording media such as floppy disks or hard disks; conventional optical storage devices, etc.

[0101] The following are merely examples and do not limit the scope of this disclosure.

[0102] Example

[0103] Example 1 - Dissolved sulfide content in wastewater

[0104] The sulfide content of various wastewater (WW) samples before and after biological (secondary) treatment was determined using a Hach tester LCK 653. The results are shown in Table 1 below. The dates and times of sample collection before and after secondary (biological) treatment are indicated.

[0105] Table 1

[0106]

[0107] As can be seen from Table 1, the content of dissolved sulfides in the incoming wastewater (WW) and in the secondary treatment influent is significantly lower than that in the secondary treatment effluent.

[0108] Example 2 - PFA efficacy and dissolved sulfide content

[0109] Evaluation of PFA against Escherichia coli in wastewater (WW) samples E. coli The disinfection efficacy of total coliforms and total aerobic bacteria was measured. Testing was conducted immediately after sulfide content measurement at the wastewater treatment plant. The first wastewater (WW) sample had a sulfide content of 2.84 mg / ml, and the second wastewater (WW) sample had a sulfide content of 5.08 mg / ml. The quality of the wastewater (WW) samples was similar in other respects.

[0110] Wastewater (WW) samples were quantitatively fed with different concentrations of PFA to determine disinfection efficacy after a set 12-minute contact time. After this time, Escherichia coli and total coliforms were quantified using Compact Dry EC bacterial culture plates (Nissui Pharma, Japan). Total aerobic bacterial colonies were counted using 3M Petrifilm aerobic count plates. All bacteria were incubated at +37°C for 24 hours.

[0111] from Figure 2A It can be seen that when the sulfide content in the wastewater (WW) was 2.84 mg / L, incubation with 20 mg / L PFA resulted in a significant reduction in Escherichia coli, total coliforms, and total aerobic bacteria. 34 mg / L PFA eradicated both total coliforms and total aerobic bacteria. Figure 2B As shown, the effectiveness of PFA decreases when the sulfide content in wastewater (WW) increases (5.08 mg / L). Even the highest dose of PFA at 34 mg / L is insufficient to kill total coliforms and total aerobic bacteria.

[0112] Example 3 - PFA in Fe 2+ / Fe 3+ The effects after treatment

[0113] Wastewater (WW) samples were taken from the effluent of the secondary (biological) treatment and treated using the following protocol with 13.5 mg / L Fe. 2+ (Provided with ferrous chloride (II) solution), 14 mg / L Fe 3+ (Provided as ferric chloride (III) solution) or 21 mg / L Fe 3+(Using ferric chloride (III) solution) Incubate: 30 seconds of rapid mixing, 10 minutes of slow mixing, and 10 minutes to allow settling. 2+ / Fe 3+ The treatment reduced the dissolved sulfide content in the water to less than 0.005 mg / L. Samples were then incubated with various concentrations of PFA for 12 minutes, and E. coli and total coliform counts were subsequently determined.

[0114] like Figure 3 As shown, when using 13.5 mg / L Fe 2+ (ferrous chloride (II) solution), 14 mg / L Fe 3+ (ferric chloride (III) solution) and 21 mg / L Fe 3+ Treatment with ferric chloride (III) solution resulted in a reduction of *E. coli* and total coliforms at 3 mg / L. 20 mg / L PFA completely eliminated *E. coli* and total coliforms. These data suggest that at higher sulfide concentrations (2.84 mg / L and 5.08 mg / L, respectively), 20 mg / L PFA is insufficient to kill bacteria to an acceptable level. Figure 2A and 2B A rough comparison.

[0115] Example 4 - Using Fe 2+ and Fe 3+ Remove dissolved sulfides

[0116] Fe 2+ and Fe 3+ The effect of removing dissolved sulfides from wastewater (WW) samples was evaluated visually. Wastewater (WW) samples obtained from the secondary treatment effluent were treated at room temperature with 50 ppm ferrous chloride (II) (providing 4.5 mg / L Fe). 2+ ion)( Figure 4A (Left), 50ppm ferric chloride (III) (providing 7mg / l Fe) 3+ ion)( Figure 4A (Right), 100ppm ferrous chloride (II) (providing 9mg / l Fe) 2+ ion)( Figure 4B (Left) or 100ppm ferric chloride (III) (providing 14mg / l Fe) 3+ ion)( Figure 4B (Right) Incubation. Visual evaluation is performed after slow mixing for 10 minutes and settling for 10 minutes.

[0117] Use 9 mg / L Fe 2+ ion( Figure 4B The treatment (left) resulted in a dissolved sulfide concentration <0.005 mg / L. Using 14 mg / L Fe...3+ ion( Figure 4B The treatment (right) resulted in a dissolved sulfide concentration of 0.325 mg / L. This indicates that Fe... 2+ Ions relative to Fe 3+ Improved efficiency of ions. Compared with 14 mg / L Fe 3+ ion( Figure 4B Compared to the water sample treated with 9 mg / L Fe, the water sample treated with 9 mg / L Fe 2+ ion( Figure 4B The increased turbidity of the treated water sample (left) can be attributed to precipitated iron sulfide that did not settle to the bottom of the container. Similar considerations apply. Figure 4A Among them, it was observed that with 7 mg / L Fe 3+ Compared to ion treatment (right), treatment with 4.5 mg / L Fe 2+ Turbidity increases after ion treatment (left).

[0118] Once the disclosure herein is given, other variations or uses of the technology disclosed will become apparent to those skilled in the art. This disclosure is not limited to the described embodiments, but only to the appended claims.

Claims

1. A method for treating water, wherein the water contains a certain amount of at least one dissolved sulfide and at least one microorganism, the method comprising the following steps: i) contacting the water with Fe 2+ or Fe 3+ ion source to reduce the amount of the at least one dissolved sulfide; and ii) Contacting water with percarboxylic acid to provide disinfection against at least one of the said microorganisms; Step ii) is executed after step i).

2. The method according to claim 1, wherein the percarboxylic acid comprises performic acid and / or peracetic acid.

3. The method according to claim 2, wherein the percarboxylic acid comprises performic acid.

4. The method of any one of claims 1 to 3, wherein step i) comprises contacting the water with Fe 2+ an ion source.

5. The method according to any of the preceding claims, wherein the dissolved sulfide comprises H2S, HS - and / or S 2- .

6. The method according to any one of the preceding claims, wherein the method comprises measuring the amount of the at least one dissolved sulphide prior to performing step ii), optionally wherein in step i) the Fe 2+ or Fe 3+ ion source is contacted with water in an amount determined based on the measured amount of the at least one dissolved sulphide compound.

7. The method of claim 6, wherein the percarboxylic acid in step ii) is contacted with water in an amount determined based on the measured amount of at least one dissolved sulfide compound.

8. The method according to any one of the preceding claims, wherein prior to step ii), the amount of the at least one dissolved sulfide is reduced to less than 5 mg / L, or less than 2 mg / L, less than 1 mg / L, or less than 0.5 mg / L.

9. The method of claim 8, wherein the amount of the at least one dissolved sulfide is reduced to less than 0.5 mg / L.

10. The method according to any one of the preceding claims, wherein the percarboxylic acid in step ii) is contacted with water in an amount of 0.5 to 50 mg / L based on the active percarboxylic acid.

11. The method of claim 10, wherein the percarboxylic acid in step ii) is contacted with water in an amount of 1-10 mg / L based on the active percarboxylic acid.

12. The method according to any one of the preceding claims, wherein in step i) Fe 2+ or Fe 3+ ions are sourced from contact with water to provide 5 mg / l to 15 mg / l of Fe 2+ or Fe 3+ ions.

13. The method according to any one of the preceding claims, wherein the method further comprises measuring the amount of residual percarboxylic acid in the water, optionally wherein the percarboxylic acid in step ii) is contacted with the water in an amount determined based on the measured amount of residual percarboxylic acid.

14. The method according to any one of the preceding claims, wherein the method further comprises settling the precipitate formed in step i).

15. The method according to any one of the preceding claims, wherein the water comprises wastewater.

16. The method of claim 15, wherein the method comprises performing primary and / or secondary treatment of wastewater, optionally wherein step i) is performed on the inflow of secondary sedimentation.

17. The method of claim 15 or claim 16, wherein the method further comprises performing tertiary treatment of the wastewater, optionally wherein step ii) is performed during the tertiary treatment.

18. The method according to any one of the preceding claims, wherein Fe 2+ or Fe 3+ Ion sources include ferric sulfate, ferric chloride, ferrous chloride, and ferrous sulfate.

19. The method of claim 18, wherein Fe 2+ or Fe 3+ Ion sources include ferrous chloride or ferric chloride.

20. The method according to any one of the preceding claims, wherein in step i), Fe is used in a ratio of 0.5:1 to 5:1 or 1:1 to 3:

1. 2+ ions or Fe 3+ The molar ratio of ions to at least one dissolved sulfide compound makes Fe 2+ Ion source or Fe 3+ The ion source is in contact with water.

21. An apparatus comprising: At least one processor; as well as At least one memory, the memory including computer program code, the at least one memory and the computer program code being configured together with the at least one processor to cause the device to perform the method of any one of claims 1-20.

22. A water treatment system comprising the apparatus of claim 21, the system comprising: The first quantitative feeding device is configured to feed Fe into the water. 2+ or Fe 3+ Ion source The second quantitative feeding device is configured to feed percarboxylic acid into the water, and A first measuring device is configured to measure the level of at least one dissolved sulfide in water and generate output data relating to the measured level of dissolved sulfide. The device is configured and arranged to receive output data relating to the measured level of the at least one dissolved sulfide from the first measuring device, monitor the measured level of the at least one dissolved sulfide in the water, and adjust the Fe content fed into the water by the first metering device based on the monitored level of the at least one dissolved sulfide. 2+ or Fe 3+ The amount of ion source and / or the amount of percarboxylic acid fed into the water by the second quantitative feeding device.

23. The system of claim 22, wherein the system further comprises: A second measuring device is configured to measure the level of percarboxylic acid in water and generate output data related to the measured level of percarboxylic acid. The device is configured and arranged to receive output data relating to the measured level of percarboxylic acid from the second measuring device, monitor the measured level of percarboxylic acid in the water, and adjust the amount of percarboxylic acid fed into the water by the second metering device based on the monitored level of percarboxylic acid. 24.Fe 2+ ions or Fe 3+ The use of ions to improve the disinfection performance of percarboxylic acids against at least one microorganism in a water treatment method, wherein the water comprises a certain amount of at least one dissolved sulfide and at least one microorganism, and the use includes reacting the water with Fe... 2+ ions or Fe 3+ Ion contact is used to reduce the amount of at least one dissolved sulfide in water.

25. The use according to claim 24, wherein the method is as defined in any one of claims 1-20.

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