Advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage by UV persulfate

Abstract

The present invention discloses an advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage by UV persulfate. The sewage flows to a secondary sedimentation tank by gravity, and sediments are precipitated and separated. Na.sub.2S.sub.2O.sub.8 solution is added therein, and a UV lamp is opened. Effluent result is analyzed after photooxidation. The sewage is transferred into a contact disinfection pool to react with ClO.sub.2 before discharging safely. The present invention uses a UV-based advanced oxidation process, which can effectively remove the nonsteroidal anti-inflammatory drugs in sewage, meets the requirements of sewage discharging, and decreases the environmental risk of nonsteroidal anti-inflammatory drugs. The method has some advantages such as simple equipments, easy operation, reasonable economy, as well as efficient treatment effect and high stability.

Claims

1. An advanced oxidation process of degrading nonsteroidal antiinflammatory drugs in sewage by UV persulfate, characterized in that it mainly comprises comprising the steps of: 1) separating supernatant from sediments from the sewage by settling and precipitating the sediments in a secondary sedimentary tank by gravity; 2) detecting and recording concentration of the nonsteroidal anti-inflammatory drugs remaining in the supernatant; 3) adding a NaS.sub.2O.sub.8 solution with mass concentration of 50-70% into the supernatant, forming a reaction solution, wherein the molar ratio of NaS.sub.2O.sub.8 and nonsteroidal anti-inflammatory drugs in the reaction solution is from 1:1 to 100:1; 4) transferring the reaction solution to an optical reactor for reacting, irradiating the reaction solution for 5-10 mins with UV light having a working power of 22 Watt, stirring the reaction solution, 5) analyzing the concentration of nonsteroidal anti-inflammatory drugs in the reaction solution after the step 4) using high performance liquid chromatography mass spectrometry (UPLC-MS), and calculating the drug removal rate and setting up dynamic simulation, and 6) transferring the reaction solution into a contact disinfection tank to react with ClO.sub.2 for disinfecting before discharging therefrom.

2. The advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage according to claim 1, characterized in that the secondary sedimentation tank is a vertical sedimentation tank with circular section, and the sewage flows from top to bottom with velocity of 15-25 mm/s, disposing spiral baffles at the bottom to distribute the sewage uniformly with rising speed of 0.6-0.8 mm/s at water passing section and settling time of 1.5-2.5 h; suspended solids sink into a cone sludge bucket, and clean water overflow from all around the bucket along a overflow weir, disposing baffles and scum tank above the weir to intercept scum; and disposing a sludge pipe with diameter of 300-400 mm near the tank wall, and discharging sludge regularly by hydrostatic pressure.

3. The advanced oxidation process of degrading nonsteroidal antiinflammatory drugs in sewage according to claim 1, characterized in that detecting method of the concentration of the nonsteroidal anti-inflammatory drugs comprises steps as follows: 1) sample extraction: sampling 500 mL water samples filtered with 0.22 pm mixed fibre membrane, and then storing the samples in a refrigerator of 4 C. for solid phase extraction and concentration detection of the nonsteroidal anti-inflammatory drugs afterward, and repeating each test three times and analyzing average valuesstandard deviation (SD); 2) sample purification: extracting solid phase extraction column of CNW HLB of aqueous phase (60 mg, 3 mL), i.e., organic balance column, and specific steps as follows: a. balancing the CNW HTB column by adding 3 mL methanol; b. washing the CNW HLB column with 3 mL pure water; c. 50 mL water samples passing through the CNW HLB column at a flow rate of 5 ml/min; d. washing the CNW HLB column again with 3 mL methanol (5%); e. eluting with 6 mL methanol solution, and drying liquid nitrogen to 1 mL, and storing in a refrigerator of 4 C. until subsequent machine inspection, 3) detecting the concentration of nonsteroidal anti-inflammatory drugs by UPLC-MS: the UPLC-MS being operated in electrospray negative (ESI) mode, data acquisition being performed by multiple reaction monitoring (MRM), separation being performed using a ACQUITY UPLC BEH-C18 column (2.1*50 mm, 1.7 pm,) at 30 C. with isocratic elution, the selected mobile phase being pre-ultrasonic degassed prior to use consisting of water (A) and methanol (B) at a flow rate of 0.1 mL/min, the isocratic elution being performed by 20% A phase and 80% B phase, isocratic elution for 5 mins and injection volume being 10 pL by an auto-injector.

4. The advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage according to claim 1, characterized in that the drug removal rate of the nonsteroidal anti-inflammatory drugs equals to (1C.sub.t/C.sub.0)100%, wherein C.sub.0 is the concentration prior to treatment, and C.sub.t is the concentration of the nonsteroidal anti-inflammatory drugs at reaction time of t, and wherein the concentration unit of the nonsteroidal anti-inflammatory drugs is ug/L.

5. The advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage according to claim 1, characterized in that the optical reactor is made of quartz glass, and a quartz sleeve is vertically disposed in the center of the optical reactor; and an ultraviolet lamp is placed in the quartz sleeve for irradiation.

6. The advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage according to claim 1, characterized in that the reaction is irradiated using an ultraviolet lamp comprising a quartz tube, wherein the ultraviolet lamp is a low pressure mercury lamp which emits monochromatic ultraviolet light of 254 nm, and the intensity of the ultraviolet light from the outer wall of the quartz tube is 1.35 mW/cm.sup.2.

7. The advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage according to claim 1, characterized in that a ClO.sub.2 generator is connected with the contact disinfection tank, and the reaction with ClO.sub.2 can disinfect and kill pathogenic microorganisms in the sewage.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an operation flowchart of an advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage by UV persulfate;

(2) FIG. 2 illustrates influences of irridation time ondegradation effects of nonsteroidal anti-inflammatory drugs in accordance with the advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage by UV persulfate of the present invention;

(3) FIG. 3 illustrates influences of oxidant dose ondegradation effects of nonsteroidal anti-inflammatory drugs in accordance with the advanced oxidation process of degrading nonsteroidal anti-inflammatory drugs in sewage by UV persulfate of the present invention;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) For further illustrating the invention, examples are given bellow.

Example 1

(5) Secondary biological effluent from a municipal sewage treatment plant in a city of Nanjing was taken as an example. An advanced oxidation process for degrading nonsteroidal anti-inflammatory drugs in sewage by UV persulfate mainly comprises steps that:

(6) 1) the sewage flows to a secondary sedimentation tank by gravity, and sediments are precipitated and separated therein. The secondary sedimentation tank is a vertical sedimentation tank with circular section. Sewage flows from top to bottom with the velocity of 15 mm/s. Spiral baffles are disposed at the bottom to distribute the sewage uniformly in the tank with rising speed of 0.6 mm/s at water passing section and settling time of 1.5 h. Suspended solids sank into a cone sludge bucket, and clean water overflows out from all around the bucket along a overflow weir. Baffle and scum are disposed above the weir to intercept scum and ensure water quality. A sludge pipe with diameter of 300 mm is disposed near the tank wall. Sludge is discharged regularly by hydrostatic pressure from the sludge pipe. Separated supernatant is extracted for detecting and recording the concentration of nonsteroidal anti-inflammatory drugs remaining therein using high performance liquid chromatography;

(7) 2) NaS.sub.2O.sub.8 solution separated in the secondary sedimention tank with mass concentration of 50-70% is added into the supernatant, so that the molar ratio of NaS.sub.2O and, nonsteroidal anti-inflammatory drugs is 60:1, and reaction solution is obtained. The reaction solution is then transferred to an optical reactor for reacting to irradiate the solution for 5 mins with UV light having a working power of 22 Watt, and keeping all the components of the reaction solution with a uniform concentration by electromagenic stirring. The optical reactor is made of quartz glass. A quartz sleeve is vertically disposed in the center of the optical reactor. An ultraviolet lamp is placed in the quartz sleeve for irradiation. The ultraviolet lamp is low pressure mercury lamp, which emits monochromatic ultraviolet light of 254 nm. The intensity of the ultraviolet light from the outer wall of the quartz tube is 1.36 mW/cm.sup.2.

(8) 3) The result of the solution after the reaction, of step 2) is analyzed. The concentration of nonsteroidal anti-inflammatory drugs is detected with high performance liquid chromatography. The removal rate is calculated and dynamic simulation is set up. Then the effluent is transferred into a contact disinfection tank to react with ClO.sub.2 for disinfecting. A ClO.sub.2 generator is connected with the contact disinfection tank, which is a multilevel combined ClO.sub.2 generator. The ClO.sub.2 generator includes a tank reactor composed of acid proof conduit and water jet vacuum set. The tank reactor is a two-stage or multistage reactor. An air distributor is disposed in the main tank reactor, and a balance tube is disposed in the auxiliary tank reactor, so that the reaction is more complete and the discharging of reacted raffinate can meet the requirement of the standard. Aqueous solution or stable ClO.sub.2 solution is obtained by the generated ClO.sub.2. The reaction principle is that: NaClO.sub.3+2HCl=ClO.sub.2+Cl.sub.2+NaCl+H.sub.2O. The reaction with ClO.sub.2 can disinfect and kill pathogenic microorganisms in the sewage, and discharge the effulant of the contact disinfection tank eventually.

Example 2

(9) Secondary biological biological effluent from a municipal sewage treatment plant in a city of Nanjing was taken as an example. An advanced oxidation process for degrading nonsteroidal anti-inflammatory drugs in sewage by UV persulfate mainly comprises steps that:

(10) 1) The sewage flows to a secondary sedimentation tank by gravity, and sediments are precipitated and separated therein. The secondary sedimentation tank is a vertical sedimentation tank with circular section. Sewage flows from top to bottom with the velocity of 15 mm/s. Spiral baffles are disposed at the bottom to distribute the sewage uniformly in the tank with rising speed of 0.6 mm/s at water passing section and settling time of 1.5 h. Suspended solids sank into a cone sludge bucket, and clean water overflows, out from all around the bucket along a overflow weir. Baffle and scum are disposed above the weir to intercept scum and ensure water quality. A sludge pipe with diameter of 300 mm is disposed near the tank wall. Sludge is discharged regularly by hydrostatic pressure from the sludge pipe. Separated supernatant is extracted for detecting and recording the concentration of nonsteroidal anti-inflammatory drugs remaining therein using high performance liquid chromatography;

(11) 2) NaS.sub.2O.sub.8 solution with mass concentration of 60% is added into the supernatant after separated in the secondary sedimention tank, so that the molar ratio of NaS.sub.2O.sub.8 and nonsteroidal anti-inflammatory drugs is 50:1, and reaction solution is obtained. The reaction solution is then transferred to an optical reactor for reacting to irradiate the solution for 7.5 mins with UV light having a working power of 22 Watt, and keeping all the components of the reaction solution with a uniform concentration by electromagenic stirring. The optical reactor is made of quartz glass. A quartz sleeve is vertically disposed in the center of the optical reactor. An ultraviolet lamp is placed in the quartz sleeve for irradiation. The ultraviolet lamp is low pressure mercury lamp, which emits monochromatic ultraviolet light of 254 nm. The intensity of the ultraviolet light from the outer wall of the quartz tube is 1.35 mW/cm.sup.2.

(12) 3) The result of the solution after the reaction of step 2) is, analyzed. The concentration of nonsteroidal anti-inflammatory drugs is detected with high performance liquid chromatography. The removal rate is calculated and dynamic simulation is set up. Then the effluent is transferred into a contact disinfection tank to react with ClO.sub.2 for disinfecting, A ClO.sub.2 generator is connected with the contact disinfection tank, which is a multilevel combined ClO.sub.2 generator. The ClO.sub.2 generator includes a tank reactor composed of acid proof conduit and water jet vacuum set. The tank reactor is a two-stage or multistage reactor. An air distributor is disposed in the main tank reactor, and a balance tube is disposed in the auxiliary tank reactor, so that the reaction is more complete and the discharging of reacted raffinate can meet the requirement of the standard. Aqueous solution, or stable ClO.sub.2 solution is obtained by the generated ClO.sub.2. The reaction principle is that: NaClO.sub.3+2HCl=ClO.sub.2+Cl.sub.2+NaCl+H.sub.2O. The reaction with ClO.sub.2 can disinfect and kill pathogenic microorganisms in the sewage, and discharge the effulant of the contact disinfection tank eventually.

Example 3

(13) Secondary biological effluent from a municipal sewage treatment plant in a city of Nanjing was taken as an example. An advanced oxidation process for degrading nonsteroidal anti-inflammatory drugs in sewage by UV persulfate mainly comprises steps that:

(14) The sewage flows to a secondary sedimentation tank by gravity, and sediments are precipitated and separated therein. The secondary sedimentation tank is a vertical sedimentation tank with circular section. Sewage flows from top to bottom with the velocity of 15 m/s. Spiral baffles are disposed at the bottom to distribute the sewage uniformly in the tank with rising speed of 0.6 mm/s at water passing section and settling time of 1.5 h. Suspended solids sank into a cone sludge bucket, and clean water overflows out from all around the bucket along a overflow weir. Baffle and scum are disposed above the weir to intercept scum and ensure water duality A sludge pipe with diameter of 300 mm is disposed near the tank wall. Sludge is discharged regularly by hydrostatic pressure from the sludge pipe. Separated supernatant is extracted for detecting and recording the concentration of nonsteroidal anti-inflammatory drugs remaining therein using high performance liquid chromatography;

(15) 2) NaS.sub.2O.sub.8 solution separated in the secondary sedimention tank with mass concentration of 70% is added into the supernatant so that the molar ratio of NaS.sub.2O.sub.8 and nonsteroidal anti-inflammatory drugs is 100:1, and reaction solution is obtained. The reaction solution is then transferred to an optical reactor for reacting to irradiate the solution for 10 mins with UV light having a working power of 22 Watt, and keeping all the components of the reaction solution with a uniform concentration by electromagenic stirring. The optical reactor is made of quartz glass. A quartz sleeve is vertically disposed in the center of the optical reactor. An ultraviolet lamp is placed in the quartz sleeve for irradiation. The ultraviolet lamp is low pressure mercury lamp, which emits monochromatic ultraviolet light of 254 nm. The intensity of the ultraviolet light from the outer wall of the quartz tube is 1.35 mW/cm.sup.2.

(16) 3) The result of the solution after the reaction of step 2) is analyzed. The concentration of nonsteroidal anti-inflammatory drugs is detected with high performance liquid chromatography The removal rate is calculated and dynamic simulation is set up. Then the effluent is transferred into a contact disinfection tank to react with ClO.sub.2 for disinfecting, A ClO.sub.2 generator is connected with the contact disinfection tank, which is a multilevel combined ClO.sub.2 generator. The ClO.sub.2 generator includes a tank reactor composed of acid proof conduit and water jet vacuum set. The tank reactor is a two-stage or multistage reactor. An air distributor is disposed in the main tank reactor, and a balance tube is disposed in the auxiliary tank reactor, so that the reaction is more complete and the discharging of reacted raffinate can meet the requirement of the standard. Aqueous solution, or stable ClO.sub.2 solution is obtained by the generated ClO.sub.2. The reaction principle is that: NaClO.sub.3+2HCl=ClO.sub.2+Cl.sub.2+NaCl+H.sub.2O. The reaction with ClO.sub.2 can disinfect and kill pathogenic microorganisms in the sewage, and discharge the effulant of the contact disinfection tank eventually.

(17) It should be noted that the value range involved in the above examples can be realized. Other values will not be listed hereby because of limited description.

(18) 1. result interpretation of embodiments

(19) 1) 500 mL water sample is filtered with 0.22 m mixed fibre membrane, and then stored in a refrigerator of 4 C. for solid phase extraction and concentration detection of the nonsteroidal anti-inflammatory drugs afterward. Each test is repeated three times, and average valuesstandard deviation (SD) is analyzed. A simple test flowchart is shown in FIG. 1.

(20) 2) enrichment and purification of three nonsteroidal anti-inflammatory drugs solid phase extraction column of CNW HLB of aqueous phase (60 mg, 3 mL), i.e., organic balance column, is extracted. The specific steps are as follows:

(21) a. balancing the CNW HLB column by adding 3 mL methanol;

(22) b. washing the CNW HLB column with 3 mL pure water;

(23) c. 50 mL water sample passing through the CNW HLB column at a flow rate of 5 mL/min;

(24) d. washing the CNVV HLB column again with 3 mL methanol (5%);

(25) e. elutanting with 6 mL methanol solution, and drying liquid nitrogen to 1 mL, and storing in a refrigerator of 4 C. until subsequent machine inspection.

(26) 3) The concentrations of nonsteroidal anti-inflammatory drugs are detected by UPLC-MS selected from US Waters Company. The UPLC-MS is operated in an electrospray negative (ESI) mode, and data acquisition is performed by multiple reaction monitoring (MRM), Table 1 shows the monitoring parameters of the multi-reaction.

(27) TABLE-US-00001 TABLE 1 Monitoring parameters of multi-reacton of nonsteroidal anti-inflammatory drugs Parent Cone ion Daughter- Voltage Collision Compound (m/z) ion (m/z) (V) energy (V) Diclofenac 295.9 214 21 30 Ibuprofen 204.7 160.8 40 6.5 Naproxen 231.2 170 36 22

(28) Separation is performed by a ACQUITY UPLC BEH-C18 chromatographic column (2.1*50 mm, 1.7 m) at 30 C. with isocratic elution. The mobile phase consists of water and methanol at a flow rate of 0.1 mL/min. The isocratic elution is performed by 20% A phase and 80% B phase, isocratic elution for 5 mins and injection volume is 10 L by an auto-injector.

(29) 2. Analysis of the removal rate of nonsteroidal anti-inflammatory drugs The concentration unit of nonsteroidal anti-inflammatory drugs in the present invention is g/L.

(30) The removal rate of nonsteroidal anti-inflammatory drugs=(1Ct/C.sub.0)100%, C.sub.0the concentration at beginning, C.sub.tthe concentration of nonsteroidal anti-inflammatory drugs at reaction time of t. The nonsteroidal anti-inflammatory drugs to be detected are diclofenac, ibuprofen and naproxen.

(31) According to the results:

(32) 1) Influence of irridation time of UV on degrading of target pollutants

(33) FIG. 2 shows the influence of irridation time on degradation effects of three nonsteroidal anti-inflammatory drugs. Diclofenac, ibuprofen and naproxen can be degraded tiredly under the Irradiation of ultraviolet, and they satisfy first order reaction kinetics, and the kinetic constants are 5.0410.sup.3s.sup.1, 0.29110.sup.3s.sup.1, and 0.20810.sup.3s.sup.1.

(34) 2) Influences of molar ratio of Na.sub.2S.sub.2O.sub.8 to nonsteroidal anti-inflammatory drugs on degrading of target pollutants.

(35) FIG. 3 shows, under 5 mins irridation of low pressure mercury lamp having a working power of 22 Watt and the molar ratio 1:1-100:1 of Na.sub.2S.sub.2O.sub.8 to nonsteroidal anti-inflammatory drugs, the removal rates of all target polluents increase with oxidant concentration. In general, productivity of SO.sub.4.sup. increases when the concentration of NaS.sub.2O.sub.8 is too large, accordingly the reaction rate increases continually. The removal rate of the three nonsteroidal anti-inflammatory drugs increases with the increasing consumption of oxidant in the embodiment. Considering the removal effects in practical process, the input amount of 100:1 is selected as the best input amount. The degrading rates of the three drugs improve significantly when a UV/NaS.sub.2O.sub.8 process is used as the process of degrading nonsteroidal anti-inflammatory drugs. The removal rate can reach 95% in 5 mins.

(36) 3) influences of intensity of light sources on degrading of to pollutants

(37) Two common ultraviolet light sources UV/AOP used in the process are selected by the test, which are respectively mercury lamp having a working power of 22 Watt and mercury lamp having a working power of 300 Watt. Removal rates of the target pollutants in condition of molar ratio (oxidant: pollutants) 100:1, irridation for 5 min are illustrated in Table 2. When the mercury lamp having the working power of 22 Watt is adopted, the removal effect of the nonsteroidal anti-inflammatory drugs is very good. Considering of energy consumption, 22 Watt UV lamp is selected as light resource.

(38) TABLE-US-00002 TABLE 2 Comparison of degradation effects of nonsteroidal anti-inflammatory drugs by using two light resources Power of mercury lamp Diclofenac Ibuprofen Naproxen 22 W 99.64 0.1% 96.68 2.95% 97.16 1.34% 300 W 99.91 0.01% 99.38 0.1% 99.61 0.55%

(39) In summary, the method of the present invention is effective to degrade the nonsteroidal anti-inflammatory drugs in sewage. It also demonstrated from the treatment results that the components and the parameters are both best choices to realize the method of the present invention.

(40) Unless otherwise indicated, the numerical ranges involved in the invention include the end values. While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.