A method for calculating the optimal dosage concentration of oxidant in ultraviolet advanced oxidation process based on energy consumption (EE / O)

Abstract

The present invention belongs to the field of environmental engineering water treatment, and particularly relates to a method for calculating the optimal dosage concentration of oxidant in ultraviolet advanced oxidation process based on energy consumption (EE / O). It mainly includes: two simple formulas for calculating the optimal dosage concentration of oxidant in ultraviolet advanced oxidation process (based on energy consumption). The present invention provides a simple calculation method for the optimization of the dosage concentration of oxidant in ultraviolet-based advanced oxidation process in engineering applications, and provides theoretical guidance for the popularization and application of ultraviolet-based advanced oxidation process in engineering.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic degradation of organic micropollutants, and particularly relates to a method for calculating the optimal dosage concentration of oxidants in an ultraviolet advanced oxidation process based on energy consumption (EE / O). Background Art

[0002] The threats of organic micropollutants such as pharmaceutical pollutants, odorants, endocrine disruptors, disinfection by-products, and algal toxins to the quality of drinking water have received wide attention. These organic micropollutants not only have a serious impact on the water ecosystem, but also seriously endanger human health. Ultraviolet-based advanced oxidation processes (UV-based AOPs) have received extensive attention because they can effectively remove organic pollutants in water.

[0003] UV-based AOPs usually use chemical oxidants such as hydrogen peroxide (H2O2), free available chlorine (FAC), peroxydisulfate (PDS), monochloramine (NH2Cl), etc., combined with ultraviolet irradiation, to generate highly reactive free radicals that can effectively reduce pollutants in water. The optimization of energy consumption is an important topic for UV-based advanced oxidation processes in the field of water treatment, where the EE / O (kWh·L -1 ) value is the most commonly used evaluation index for UV-based AOPs in engineering applications. In engineering applications, EE / O is usually optimized based on both the dosage of oxidant and the dosage of electrical energy consumption to achieve the treatment target with the lowest operating cost. However, due to the lack of theoretical research on process optimization, the engineering applications of UV-based AOPs are generally optimized one by one according to the requirements of water treatment plants, which limits their large-scale popularization and application in engineering.

[0004] In summary, there is an urgent need for a simple and efficient method to optimize the dosage concentration of oxidants in the ultraviolet advanced oxidation process in engineering applications based on energy consumption (EE / O). Summary of the Invention

[0005] The purpose of the present invention is to provide a method for calculating the optimal dosage concentration of oxidants in an ultraviolet advanced oxidation process based on energy consumption (EE / O), derive a formula, provide a simple calculation method for optimizing the dosage concentration of oxidants in the ultraviolet-based advanced oxidation process in engineering applications, and provide theoretical guidance for the popularization and application of UV-based AOPs in engineering.

[0006] The first technical solution proposed by the present invention to solve the technical problems raised in the prior art is: to provide a method for calculating the optimal dosage concentration of oxidants in an ultraviolet advanced oxidation process based on energy consumption (EE / O), including the following steps:

[0007] In engineering applications, EE / O generally consists of two parts: the consumption of oxidant (EE / O Oxidant ) and the consumption of electric energy (EE / O UV ):

[0008]

[0009] Among them, P (kWh·s -1 ) is the energy input of the ultraviolet lamp, t (s) is the reaction time, V (L) is the reaction volume, C i and C f (M) are the initial and final concentrations of the pollutant respectively, C oxidant (mM) is the dosing concentration of the oxidant; α (kWh·mmol -1 ) is the conversion coefficient of the oxidant into energy consumption.

[0010] 1. First, taking UV / H2O2 that only generates ·OH as a single PRS as an example, a formula for calculating the optimal dosing concentration of oxidant for UV / H2O2 is derived based on EE / O:

[0011] The removal effect of UV / H2O2 on pollutants in water is determined by the steady-state concentration of ·OH in the system ([·OH] ss ):

[0012]

[0013] In the system, [·OH] ss is jointly determined by the generation rate of free radicals (Generation Rate, G.R.) and the scavenging rate of free radicals (ScavengingEffect, S.E.). In engineering applications, [·OH] ss in the UV / H2O2 system can be expressed as:

[0014]

[0015] Substituting Equations 2 and 3 into Equation 1, we can get:

[0016]

[0017] Among them, β is the conversion coefficient that converts the output energy of the ultraviolet lamp into UV light intensity (I, Einstein·L -1 ·s -1 ).

[0018] Generally, the EE / O value based on the UV advanced oxidation process is usually optimized according to the oxidant dosage concentration and the energy consumption of the ultraviolet lamp. However, in domestic water treatment plants, ultraviolet is one of the most widely used disinfection technologies. But for the already built water plants, the distribution of UV lamps and the hydraulic retention time are fixed. Therefore, the EE / O value mainly depends on the oxidant dosage concentration. Equation 4 is a function of the oxidant dosage concentration. As the oxidant dosage concentration increases, EE / O shows a trend of first increasing and then decreasing. The concentration of the oxidant that produces the minimum EE / O value is the optimal oxidant dosage concentration (C opt-EE / O ). Therefore, take the derivative of Equation 4 and set its value to zero:

[0019]

[0020] In engineering applications, the concentration of H2O2 is generally 10 -3 M or less. Therefore, (C 2 ·β·I·t + 2·C 3 ·α)·ε << A b ·C 2 α, Equation 5 can be simplified to

[0021] 2.303·(A b ·C 2 α·k ·OH / Oxidant +C 2 ·S c ·α·ε - A b ·I·S c ·β·t) = 0 (6)

[0022] Furthermore, the formula for calculating C opt-EE / O is obtained:

[0023]

[0024] 2. Generalize to other ultraviolet-based advanced oxidation processes

[0025] In this invention, the [OH] -7 under different oxidant concentrations in the UV / H2O2 system was fitted through a kinetic model under the conditions of a specific treatment process (I = 1×10 -1 Einstein·L -1 ·s ss , hydraulic retention time = 300 s), and the corresponding EE / O value was obtained by substituting it into Equation 4. The results show that the EE / O value corresponding to the oxidant dosage concentration calculated by C opt-EE / O (Equation 7) is the smallest ( Figure 1), this result verifies the accuracy of our formula. Applying the same method, we found that the C derived from UV / H2O2 opt-EE / O formula (Formula 7) can be extended and applied to other UV-based advanced oxidation processes (including UV / free chlorine, UV / persulfate)( Figure 1 ). For UV / chloramine, (C 2 ·β·I·t + 2·C 3 ·α)·ε and A b ·C 2 α values are in the same order of magnitude, so Formula 5 can be simplified to

[0026] 2.303·(2·A b ·C 2 α·k ·OH / Oxidant +C 2 ·S c ·α·ε - A b ·I·S c ·β·t) = 0 (8)

[0027] Furthermore, the formula for calculating C opt-EE / O is obtained:

[0028]

[0029] It is verified by the same kinetic model method that the EE / O value corresponding to the oxidant dosage concentration calculated by applying Formula 9 in the UV / NH2Cl system is the smallest ( Figure 1 ).

[0030] In summary, using Formula 7 (applicable to UV / H2O2, UV / FAC, UV / PDS) or Formula 9 (applicable to UV / NH2Cl) can calculate the optimal dosage concentration of the oxidant based on energy consumption (C opt-EE / O ).

[0031] Beneficial effects:

[0032] The beneficial effects of the present invention are as follows:

[0033] 1) The present invention proposes a method for calculating the optimal dosage concentration of the oxidant in the UV-based advanced oxidation process based on energy consumption (EE / O). The formula derived by applying this method can measure the optimal dosage concentration of the oxidant that generates the minimum energy consumption (EE / O) in the UV-based advanced oxidation process, providing guidance for the application of UV-based advanced oxidation in water treatment.

[0034] 2) The formula for calculating C opt-EE / OThe formula can be extended and applied to other UV-based advanced oxidation processes (such as UV / FAC, UV / PDS, UV / NH2Cl), providing a simple method for optimizing their energy consumption in engineering.

[0035] 3) The formula for calculating the optimal oxidant concentration based on EE / O derived in the present invention provides a simple method for comparing different ultraviolet advanced oxidation processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a graph showing the changes in EE / O values corresponding to different oxidants. DETAILED DESCRIPTION

[0037] The present invention will be further described below by way of specific examples and accompanying drawings. The examples of the present invention are provided to help those skilled in the art better understand the present invention and are not intended to limit the present invention in any way.

[0038] Example 1

[0039] The present invention is further described through embodiments with reference to the accompanying drawings.

[0040] In this example, lake / river water samples were selected and geosmin (GSM), a common odor pollutant in water, was used as the target pollutant. The C of this water sample in different UV advanced oxidation processes was determined by the formula. opt-EE / O , the specific steps are as follows:

[0041] 1) Pass lake / river water samples through a 0.45 μm water filter membrane for later use.

[0042] 2) Use UV spectrophotometer to measure the A of water sample b (cm -1 ) are 0.13 respectively.

[0043] 3) The S of the water sample was measured experimentally c (s -1 ) are 3.39×10 5 .

[0044] 4) The molar absorption coefficients ε (M -1 cm -1 ) are 18.6, 62, 382, and 22 respectively.

[0045] (5) The secondary reaction rate constants k(M) of H2O2, FAC, NH2Cl, PDS and ·OH were obtained by consulting the literature. -1- s -1 ) are: 2.70×10 7 , 2.00×10 9, 5.10×10 8 , 1.40×10 7 .

[0046] (6) By consulting the literature and calculation, α (2.27×10 -4 H2O2, 6.03×10 -4 FAC, 1.19×10 -3 NH2Cl and 1.64×10 -3 PDS, kWh·mmol -1 ); β is 0.523.

[0047] (7) By consulting the literature, the second-order reaction rate constants of GSM and ·OH, ·Cl and ·SO4 - are 1.10×10 10 , 2.74×10 9 , 9.99×10 8 M -1 ·s -1

[0048] (8) Substituting the above values into Formulas 7 and 9, the optimal dosing concentrations of oxidants in the water sample based on energy consumption for H2O2, FAC, NH2Cl, and PDS can be obtained as 5.56×10 -4 , 3.17×10 -5 , 4.72×10 -5 , 2.14×10 -4 M, and their corresponding EE / O values are 7.13×10 -3 , 8.07×10 -3 , 1.40×10 -2 , 2.86×10 -2 kWh·L -1 .

[0049] The results of this implementation plan are as follows:

[0050] Calculate the optimal dosing concentrations of oxidants in the selected water samples in different ultraviolet advanced oxidation processes according to the formulas, as Figure 1 shown: The optimal oxidant dosing concentrations of the same water sample in different ultraviolet advanced oxidation processes generally follow the following rule: HOCl < NH2Cl < PDS < H2O2.

[0051] It should be understood that the implementation plans and examples discussed here are only for illustration. For those skilled in the art, improvements or transformations can be made, and all these improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for calculating the optimal dosage concentration of oxidant in ultraviolet advanced oxidation process based on energy consumption (EE / O), mainly including: Two formulas for calculating the optimal dosage concentration of oxidants in the ultraviolet advanced oxidation process: 1) First, taking ultraviolet / hydrogen peroxide (UV / H2O2) that generates only hydroxyl radicals (·OH) as a single primary reactive species (PRS) as an example, a formula for calculating the optimal dosage concentration (C opt-EE / O ) of the UV / H2O2 oxidant is derived based on EE / O: In formula (1), A b (cm -1 ) is the absorbance of the water quality measured by the ultraviolet spectrophotometer, S c represents the consumption capacity of the water quality for free radicals, β is the conversion coefficient for converting the output energy of the ultraviolet lamp into UV light intensity, I (Einstein·L -1 ·s -1 ) is the light intensity, t (s) is the reaction time, α (kWh·mmol -1 ) is the conversion coefficient for converting the oxidant into energy consumption in the UV / H2O2 system, k ·OH / Oxidant (M -1 ·s -1 ) is the second-order reaction rate constant of ·OH with the oxidant, ε (M -1 ·cm -1 ) is the molar absorption coefficient of the oxidant; 2) Generalize the simple formula derived based on the steady-state concentration of ·OH ([·OH] ss ) in the system to other UV-based advanced oxidants (UV-based AOPs) that generate multiple PRSs, including UV / free chlorine (UV / FAC), UV / peroxydisulfate (UV / PDS); 3) Based on [·OH] ss The simple formula derived is transformed and then extended and applied to ultraviolet / monochloramine (UV / NH2Cl) to obtain the formula: In formula (2), A b (cm -1 ) is the absorbance of the water quality measured by the ultraviolet spectrophotometer, S c represents the consumption capacity of the water quality for free radicals, β is the conversion coefficient for converting the output energy of the ultraviolet lamp into UV light intensity, I (Einstein·L -1 ·s -1 ) is the light intensity, t (s) is the reaction time, α (kWh·mmol -1 ) is the conversion coefficient for converting the oxidant into energy consumption in the UV / NH2Cl system, k ·OH / Oxidant (M -1 ·s -1 ) is the second-order reaction rate constant of ·OH with the oxidant, ε (M -1 ·cm -1 ) is the molar absorption coefficient of the oxidant.

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