METHOD AND DEVICE FOR REMOVING ORGANIC MICROPOLLUTANTS (OMPS) IN WATER

Abstract

The present disclosure discloses a method and device for removing Organic Micropollutants (OMPs) in water, and belongs to the technical field of wastewater treatment. The method includes the following steps: S1: aerating residual sludge under a starvation condition to enrich starved-state microorganisms; and S2: treating wastewater containing OMPs under an aeration condition with sludge containing the starved-state microorganisms obtained in step S1, and periodically updating the sludge containing the starved-state microorganisms. According to the present disclosure, aerobic starvation treatment is performed on the sludge to gradually reduce the abundance of microorganisms that may use degradable organic matters only and enrich microorganisms that may use complex organic matters in the sludge, and the enriched sludge may degrade various OMPs and be used to remove OMPs in wastewater. The process is easy to operate and low in cost and has relatively high practical application value.

Claims

1. A method for removing Organic Micropollutants (OMPs) in water, comprising the following steps: S1: aerating residual sludge under a starvation condition to reduce the abundance of microorganisms that may use degradable organic matters only and enrich starved-state microorganisms that may use complex organic matters in the sludge; and S2: treating wastewater containing OMPs under an aeration condition with sludge containing the starved-state microorganisms obtained in step S1, and periodically updating the sludge containing the starved-state microorganisms.

2. The method for removing the OMPs in water according to claim 1, wherein aeration time in step S1 is 48 h to 72 h.

3. The method for removing the OMPs in water according to claim 2, wherein dissolved oxygen is at least kept greater than 1 mg/L in 48 h.

4. The method for removing the OMPs in water according to claim 2, wherein a replacement cycle of the sludge in step S2 is 5 days to 7 days.

5. The method for removing the OMPs in water according to claim 2, wherein a sludge concentration in step S1 is in a range of 7,000 mg/L to 10,000 mg/L; and/or, a sludge concentration in step S2 is controlled in a range of 2,000 mg/L to 3,000 mg/L.

6. The method for removing the OMPs in water according to claim 2, wherein hydraulic retention time for the treatment of the wastewater containing the OMPs in step S2 is 10 h to 15 h.

7. The method for removing the OMPs in water according to claim 1, a device is used for removing Organic Micropollutants (OMPs) in water, comprising: a sludge aeration tank (1) configured to periodically provide aerobic starved sludge, a wastewater aeration tank (2) configured to treat wastewater containing OMPs and a sedimentation tank (3), which are connected in sequence; a residual sludge pipe (4) configured to deliver residual sludge of a secondary sedimentation tank of an ordinary activated sludge process to the sludge aeration tank (1); an enriched sludge pipe (5) configured to periodically deliver sludge obtained by the sludge aeration tank (1) by aerobic starvation treatment to the wastewater aeration tank (2); a water inlet pipe (6) configured to deliver the wastewater containing the OMPs to the wastewater aeration tank (2) for treatment; and a wastewater aeration tank water outlet pipe (7) configured to discharge a sludge-wastewater mixture in the wastewater aeration tank (2) to the sedimentation tank (3).

8. The method for removing the OMPs in water according to claim 7, the device further comprising a sedimentation tank sludge return pipe (8) configured to cause sedimented sludge in the sedimentation tank (3) to return to the wastewater aeration tank (2); a sludge discharge pipe (10) configured to discharge the sludge sedimented by the sedimentation tank (3) from a system; and a water outlet pipe (9) configured to discharge a supernatant in the sedimentation tank (3) from the system.

9. The method for removing the OMPs in water according to claim 7, wherein a volume ratio of the wastewater aeration tank (2) to the sludge aeration tank (1) is less than 3.

10. The method for removing the OMPs in water according to claim 8, wherein a volume ratio of the wastewater aeration tank (2) to the sludge aeration tank (1) is less than 3.

11. The method for removing the OMPs in water according to claim 3, wherein hydraulic retention time for the treatment of the wastewater containing the OMPs in step S2 is 10 h to 15 h.

12. The method for removing the OMPs in water according to claim 4, wherein hydraulic retention time for the treatment of the wastewater containing the OMPs in step S2 is 10 h to 15 h.

13. The method for removing the OMPs in water according to claim 5, wherein hydraulic retention time for the treatment of the wastewater containing the OMPs in step S2 is 10 h to 15 h.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 is a schematic diagram of a device for removing OMPs in water according to the present disclosure.

[0034] In the figure: 1—sludge aeration tank; 2—wastewater aeration tank; 3—sedimentation tank; 4—residual sludge pipe; 5—enriched sludge pipe; 6—water inlet pipe; 7—wastewater aeration tank water outlet pipe; 8—sedimentation tank sludge return pipe; 9—water outlet pipe; and 10—sludge discharge pipe.

[0035] FIG. 2 illustrates a kinetic curve of degradation of bisphenol AF by sludge in a sludge aeration tank according to embodiment 1.

[0036] FIG. 3 illustrates a kinetic curve of degradation of gabapentin by sludge in a sludge aeration tank according to embodiment 1.

[0037] FIG. 4 illustrates a removal effect of a continuous flow reactor taking enriched sludge as seeding sludge on wastewater containing micropollutants bisphenol AF and gabapentin according to embodiment 2.

[0038] FIG. 5 illustrates a change rule of a sludge concentration in an aerobic starvation process according to embodiment 3.

DETAILED DESCRIPTION

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person skilled in the technical field of the present disclosure. The term “and/or” as used herein includes any and all combinations of one or more related listed items.

[0040] If specific conditions are not indicated in the embodiments, it shall be carried out in accordance with the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments for which no manufacturers are noted are all common products commercially available from the market.

[0041] As used herein, the term “about” is used to provide flexibility and imprecision related to a given term, metric, or value. A person skilled in the art may easily determine the degree of flexibility of specific variables.

[0042] The concentrations, amounts, and other values are presented in a range format herein. It should be understood that such a range format is used only for convenience and brevity, and should be flexibly interpreted as including not only the values explicitly stated as the limits of the range, but also all individual values or subranges covered within the range, as if each value and subrange are explicitly stated. For example, a numerical range of about 48 to about 72 should be explained as not only including the clearly described limit values 48 to about 72 but also including independent numbers (e.g., 50, 55 and 70) and sub-ranges (e.g., 50 to 70). The same principle is suitable for describing a range involving only one numerical value. For example, “less than about 72” should be explained as including all abovementioned values and ranges. In addition, this explanation is suitable for all ranges or features regardless of the breadths thereof.

[0043] The present disclosure will be further described below with reference to specific embodiments.

[0044] As shown in FIG. 1, a device for removing OMPs in wastewater consists of a sludge aeration tank 1, a wastewater aeration tank 2 and a sedimentation tank 3, which are connected through a pipeline. A residual sludge pipe 4 delivers residual sludge of a secondary sedimentation tank to the sludge aeration tank 1. Sludge containing starved-state microorganisms obtained by the sludge aeration tank 1 by aeration under a starvation condition is periodically delivered to the wastewater aeration tank 2 by an enriched sludge pipe 5. A water inlet pipe 6 delivers wastewater containing OMPs to the wastewater aeration tank 2. A sludge-wastewater mixture in the wastewater aeration tank 2 is discharged to the sedimentation tank 3 by a wastewater aeration tank water outlet pipe 7 after the wastewater is treated with the starved-state microorganisms in the wastewater aeration tank 2 under an aeration condition and stays for specific time. Sedimented sludge in the sedimentation tank 3 periodically returns to the wastewater aeration tank 2 through a sedimentation tank sludge return pipe 8, and a supernatant is discharged by a water outlet pipe 9. After a replacement cycle of the sludge in the wastewater aeration tank 2 is reached, the sludge is discharged from a system by a sludge discharge pipe 10 after sedimented by the sedimentation tank 3. A sludge discharge cycle is the same as a cycle of periodically delivering sludge from 1.

[0045] The residual sludge is aerated by the sludge aeration tank 1 under the starvation condition to obtain seeding sludge of the wastewater aeration tank 2, and the wastewater containing the OMPs is treated by the wastewater aeration tank 2 to remove the OMPs in the wastewater. Since an organic load of the wastewater containing the OMPs is usually low and cannot keep the sludge in the wastewater aeration tank 2 available for long, the sludge aeration tank 1 is required to regularly provide starved sludge to replace the sludge in the wastewater aeration tank 2.

[0046] A sludge concentration in the sludge aeration tank 1 is controlled in a range of 7,000 mg/L to 10,000 mg/L. Aeration time in the sludge aeration tank 1 is required to be controlled in a range of 48 h to 72 h. Dissolved oxygen in the sludge aeration tank 1 is required to be controlled to be 1 mg/L or greater. If the dissolved oxygen concentration is too low, the sludge may enter an anaerobic state, and the degradation effect of the obtained enriched sludge is relatively poor. If the dissolved oxygen concentration is too high, energy may be wasted. A sludge concentration in the wastewater aeration tank 2 is controlled in a range of 2,000 mg/L to 3,000 mg/L.

[0047] Since a low organic load cannot keep the sludge in the wastewater aeration tank 2 available for long, the sludge in the wastewater aeration tank 2 is required to be periodically replaced. A replacement cycle of the sludge is 5 days to 7 days. In order to achieve a relatively good micropollutant removal effect, hydraulic retention time in the wastewater aeration tank 2 is controlled in a range of 10 to 15 h. In order to meet the requirement of the wastewater aeration tank 2 on the sludge concentration, a volume ratio of the wastewater aeration tank 2 to the sludge aeration tank 1 is less than 3.

Embodiment 1

[0048] In this embodiment, residual sludge of a wastewater treatment plant (a municipal wastewater treatment plant in Nanjing) at a sludge concentration of about 7,500 mg/L is aerated as seeding sludge of a sludge aeration tank 1 without any additional nutrient, with the dissolved oxygen kept at 1.5 mg/L or greater. The sludge at different time points (days 0, 1, 2, 3 and 4, namely when aeration time reaches 0 h, 24 h, 48 h, 72 h and 96 h) in an aeration treatment process is selected for OMP degradation kinetics experiments. The sludge concentration in a wastewater aeration tank 2 is made 2,000 mg/L to 3,000 mg/L. Bisphenol AF and gabapentin are used as an only carbon source respectively, at the concentration of 10 mg/L. Other ingredients are further included: 5 mg L−1 KH.sub.2PO.sub.4, 5 mg L−1 NH.sub.4Cl, 22.5 mg L−1 MgSO.sub.4.7H.sub.2O and 27.5 mg L−1 CaCl.sub.2).

[0049] Experimental results are shown in FIG. 2 (bisphenol AF, 10 mg/L) and FIG. 3 (gabapentin, 10 mg/L). The sludge obtained by aeration for 2 days (Day 2, 48 h) in the sludge aeration tank 1 has the highest degradation capacity for bisphenol AF and gabapentin, and the sludge obtained by aeration for 3 days (Day 3, 72 h) has the second highest degradation capacity for bisphenol AF and gabapentin. This is probably because sludge obtained by enriching bacteria taking complex nondegradable organic matters in the sludge as a carbon source under the starvation condition has a relatively high OMP degradation capacity for bisphenol AF and gabapentin. Aerobic starvation remarkably improves the degradation capacity of the sludge for some micropollutants, but requires the aeration time of the sludge to be controlled because limited organic matters in the sludge may be used for microorganisms and excessively long starvation time may cause the death of functional floras. The experimental results show that relatively appropriate aeration time is usually about 48 h to 72 h, and if retention time is 10 h to 15 h or greater under this condition, the concentrations of bisphenol AF and gabapentin may be reduced to be 1 mg/L or less respectively.

Embodiment 2

[0050] The sludge obtained by aeration for 2 days in the sludge aeration tank 1 is selected as seeding sludge in the wastewater aeration tank 2 (the sludge concentration is about 2,500 mg/L) to continuously treat wastewater containing OMPs to research the OMP removal effect of sludge enriched by aeration. As shown in FIG. 4, experimental results show that the sludge enriched by aeration has a relatively good removal effect on the OMPs in the wastewater, but the effect may be kept for only about 7 days. The sludge in the wastewater aeration tank 2 may be regularly replaced according to the requirement on the concentration of the OMPs under a practical working condition. A suggested replacement cycle is 5 days to 7 days.

Embodiment 3

[0051] The residual sludge of the wastewater plant in embodiment 1 is aerated under the starvation condition, with the dissolved oxygen concentration kept at 1 mg/L or greater. Sludge amount data obtained in 60 days is shown in FIG. 5. Results show that starvation aeration treatment gradually reduces the sludge concentration and the sludge concentration is kept at about 4,000 mg/L after 25 days. Therefore, starvation aeration may reduce the amount of the sludge to a certain extent to further reduce the treatment cost of the residual sludge. The reduction of the amount of the sludge indicates that complex organic matters in the sludge may be used for microorganisms, thereby implementing the acclimation enrichment of the microorganisms. This is also probably because a starvation aeration process may improve the OMP degradation capacity of the sludge.

[0052] The foregoing description is merely a schematic description of the present disclosure and implementations thereof, and is not restrictive. The accompanying drawings merely show one of the implementations of the present disclosure, and the actual structure/implementation is not limited thereto. Therefore, similar structures and embodiments designed by a person of ordinary skill in the art as inspired by the disclosure herein without departing from the spirit of the present disclosure and without creative efforts shall fall within the protection scope of the present disclosure.