Black water resourceful treatment method based on polytitanium-chitosan coagulation and nanofiltration
By combining polytitanium chloride and chitosan coagulation with nanofiltration, the problems of low efficiency and difficulty in resource recovery in black water treatment have been solved, and efficient resource utilization has been achieved, including the preparation of reclaimed water, liquid nitrogen fertilizer and solid organic fertilizer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-23
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional activated sludge processes for treating black water are inefficient, microorganisms are greatly affected by the environment, making resource recovery difficult. Furthermore, conventional coagulants can cause heavy metal residues and colloidal substances to clog nanofiltration membranes. Existing technologies are insufficient for efficiently treating black water and achieving resource utilization.
One-step coagulation using polytitanium chloride and chitosan as coagulants, combined with nanofiltration technology, separates and recovers carbon and phosphorus solid products and ammonia nitrogen from black water, and prepares reclaimed water, liquid nitrogen fertilizer and solid organic fertilizer, forming a resource-based closed loop.
It achieves the capture of more than 95% of COD and phosphate in black water, and the water quality after coagulation meets the standards for reuse. The concentrated liquid is enriched with ammonia nitrogen to prepare liquid nitrogen fertilizer, and the sludge is used to prepare organic fertilizer, thus constructing a complete resource recycling closed loop and solving the problems of low efficiency and difficulty in resource recycling in traditional methods.
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Figure CN121850139A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wastewater treatment and resource recovery technology, and in particular to a method for the resource recovery of black water based on polytitanium-chitosan coagulation and nanofiltration. Background Technology
[0002] Black water (toilet wastewater) accounts for only 5% of the total domestic sewage, but it contains 90% of the nutrients in domestic sewage. Traditional activated sludge processes have many drawbacks in treating this type of high-concentration black water. They are slow, microorganisms are greatly affected by the environment, and it is difficult to achieve effective resource recovery, making it difficult to treat black water efficiently.
[0003] In coagulation processes, conventionally used aluminum or iron salt coagulants often lead to heavy metal residues in sludge, with aluminum content exceeding 5 mg / kg. This negatively impacts the safety of subsequent agricultural applications of phosphate fertilizers. Furthermore, their removal rate of colloidal COD is typically below 70%, and residual colloidal substances further exacerbate membrane fouling. If nanofiltration is used directly to treat blackwater, colloidal organic matter rapidly clogs the membrane pores. Therefore, providing a novel method for the resource recovery of blackwater and achieving effective resource recycling is a pressing technical challenge in this field. Summary of the Invention
[0004] The purpose of this invention is to provide a black water resource recovery method based on polytitanium-chitosan coagulation and nanofiltration. Through the coagulation-nanofiltration coupling process, carbon / phosphorus solid products, ammonia nitrogen and reclaimed water are recovered simultaneously. It is suitable for rural areas, scenic spots and mobile facilities without pipe network coverage.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for the resource-based treatment of blackwater, comprising the following steps: Coagulant is added to black water for coagulation. The resulting mixture is then separated into solid and liquid components to obtain supernatant and sludge. The supernatant is separated by nanofiltration membrane to obtain reclaimed water and concentrate.
[0006] Optionally, the sludge is dewatered to produce phosphorus-containing organic fertilizer.
[0007] Optionally, a stabilizer is added to the concentrated solution to produce liquid nitrogen fertilizer.
[0008] Optionally, the coagulant is titanium polychloride and chitosan.
[0009] Optionally, the dosage of the polytitanium chloride is 350~400 mg / L (calculated as titanium); the dosage of the chitosan is 0.5~1 mg / L.
[0010] Optionally, the method of adding coagulant to black water includes: first adding polytitanium chloride to black water, and then adding chitosan; After adding polytitanium chloride, stir at 200-250 rpm for 30-60 seconds, then adjust the speed to 120-150 rpm and stir for 15-30 seconds; after adding chitosan, stir at 120-150 rpm for 30-60 seconds; finally, adjust the speed to 50-60 rpm and stir for 10-15 minutes.
[0011] Optionally, the nanofiltration membrane has a molecular weight cutoff of 200-300 Da and an operating pressure of 1.5-1.8 MPa.
[0012] Optionally, the chemical oxygen demand of the black water is 1500~1800 mg / L, the ammonia nitrogen content is 230~250 mg / L, and the total phosphorus content is 31~35 mg / L.
[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes polytitanium chloride and chitosan for one-step coagulation, capturing over 95% of COD and over 95% of phosphate in black water. The coagulated water is then nanofiltered to obtain reclaimed water that meets the "Water Quality Standard for Urban Wastewater Reuse for Miscellaneous Uses" (GB / T 18920-2020), which can be used for toilet flushing / greening. The nanofiltration concentrate enriches ammonia nitrogen and, after adding stabilizers, is prepared into liquid nitrogen fertilizer. The sludge obtained from coagulation is dewatered and then anaerobically digested to produce biogas, hydrothermally pyrolyzed, or dried and used directly as a soil conditioner. This linkage of "solid carbon and phosphorus recovery → liquid nitrogen enrichment → water regeneration" constitutes a complete resource utilization closed loop, realizing the resource utilization of black water. Attached Figure Description
[0014] Figure 1 This is a flowchart for the resource utilization treatment of blackwater. Detailed Implementation
[0015] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0016] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0017] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0018] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.
[0019] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0020] The room temperature described in this invention is 25±2℃.
[0021] All raw materials used in this invention can be obtained commercially or prepared using existing technologies.
[0022] This invention provides a method for the resource-based treatment of blackwater, comprising the following steps: Coagulant is added to black water for coagulation. The resulting mixture is then separated into solid and liquid components to obtain supernatant and sludge. The supernatant is separated by nanofiltration membrane to obtain reclaimed water and concentrate.
[0023] In this invention, polytitanium chloride (PTC)-chitosan (CTS) is responsible for the efficient capture of carbon and phosphorus (achieving solid-state recovery), while a nanofiltration membrane of specific specifications is responsible for water regeneration and liquid enrichment of nitrogen. This three-pronged approach of "solid-state carbon and phosphorus recovery + liquid nitrogen enrichment + water regeneration" constitutes a complete resource recovery loop and is the key technology.
[0024] In this invention, the COD of the supernatant is <105 mg / L and the TP is <0.5 mg / L.
[0025] In this invention, the sludge is dewatered to produce phosphorus-containing organic fertilizer.
[0026] In some embodiments of the present invention, the phosphorus-containing organic fertilizer is used directly as a soil conditioner after anaerobic digestion to produce biogas, hydrothermal pyrolysis, or drying.
[0027] In this invention, a stabilizer is added to the concentrated liquid to produce liquid nitrogen fertilizer.
[0028] In some embodiments of the present invention, after the concentrated liquid is enriched with ammonia nitrogen (200~500 mg / L), a stabilizer is added to prepare a liquid nitrogen fertilizer.
[0029] In this invention, the coagulant is titanium polychloride and chitosan.
[0030] In this invention, the dosage of the polytitanium chloride (PTC) is 350~400 mg / L based on titanium, for example, it can be 350 mg / L, 360 mg / L, 380 mg / L or 400 mg / L, etc.; the dosage of the chitosan (CTS) is 0.5~1 mg / L, for example, it can be 0.5 mg / L, 0.6 mg / L, 0.8 mg / L or 1 mg / L, etc.
[0031] In this invention, the method of adding coagulant to black water includes: first adding titanium polychloride to black water, and then adding chitosan; After adding titanium polychloride, stir at room temperature at a speed of 200-250 rpm (e.g., 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, or 250 rpm) for 30-60 seconds (e.g., 30 seconds, 40 seconds, 50 seconds, or 60 seconds). Then adjust the speed to 120-150 rpm (e.g., 120 rpm, 130 rpm, 140 rpm, or 150 rpm) and stir for 15-30 seconds (e.g., 15 seconds, 20 seconds, 25 seconds, or 30 seconds). After adding chitosan, stir at room temperature at a speed of 120-150 rpm. Stir at 120 rpm (e.g., 120 rpm, 130 rpm, 140 rpm, or 150 rpm) for 30-60 seconds (e.g., 30 seconds, 40 seconds, 50 seconds, or 60 seconds); finally, adjust the speed to 50-60 rpm (e.g., 50 rpm, 55 rpm, or 60 rpm) and stir for 10-15 minutes (e.g., 10 minutes, 12 minutes, 14 minutes, or 15 minutes).
[0032] In this invention, the nanofiltration membrane has a molecular weight cutoff of 200-300 Da, preferably 200 Da, and an operating pressure of 1.5-1.8 MPa, preferably 1.5 MPa.
[0033] In some embodiments of the present invention, the nanofiltration membrane is of model NF90.
[0034] In this invention, the selection of nanofiltration membrane is the key to achieving effective separation of small molecule organic matter and ions (ammonium ions), thereby simultaneously producing qualified reclaimed water and high-concentration nitrogen liquid fertilizer.
[0035] In this invention, the reclaimed water has a COD < 30 mg / L and NH4 < 30 mg / L.+ -N concentration <5 mg / L, meets urban miscellaneous water standards, and can be used for toilet flushing or landscaping.
[0036] In this invention, the black water mainly consists of feces, urine, and toilet flushing water, typically originating from wastewater generated during toilet flushing. Its typical characteristics include significantly higher concentrations of organic matter, nitrogen, phosphorus, and suspended solids compared to general domestic sewage or greywater; specifically, in embodiments of this invention, its chemical oxygen demand (COD) is typically 1500-1800 mg / L; ammonia nitrogen (NH4)... + The content of phosphorus (N) is usually 230~250 mg / L; the content of total phosphorus (TP) is usually 30~35 mg / L.
[0037] In some embodiments of the present invention, the black water may originate from urban residential buildings, public toilets, rural household toilets, the sewage collection systems of mobile transportation vehicles such as trains / airplanes / ships, as well as septic tanks or sewage storage facilities in areas without sewers.
[0038] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0039] Example 1 according to Figure 1 The flowchart for black water treatment: The blackwater first enters the blackwater equalization tank, where the COD concentration is adjusted to 1500 mg / L, the TP concentration to 35 mg / L, and the NH4+ concentration to... + The -N concentration is 235 mg / L, and the adjusted black water enters the black water coagulation tank. PTC (350 mg Ti / L) from the chemical storage tank was added to the blackwater coagulation tank. After addition, the mixture was stirred at 200 rpm for 1 min at room temperature, then the speed was adjusted to 150 rpm and stirred for 30 s. Then, CTS (0.5 mg / L) was added, and the mixture was stirred at 150 rpm for 30 s at room temperature. Finally, the speed was adjusted to 60 rpm and stirred for 10 min. The resulting coagulated liquid was subjected to solid-liquid separation to obtain a solid and a supernatant. The COD concentration of the supernatant decreased to 105 mg / L, the TP concentration decreased to 0.4 mg / L, and the NH4+ concentration decreased. + -N concentration is 180 mg / L; solids enter the sludge storage and recovery unit, and after treatment, solid phosphorus-containing organic fertilizer is obtained; supernatant enters nanofiltration equipment; Using a nanofiltration membrane with a molecular weight cutoff of 200 Da (NF90 model), the supernatant is deeply separated at an operating pressure of about 1.5 MPa. The purified water from the product side enters the purified water storage tank, while the concentrated liquid from the concentrate side enters the concentrate recovery tank unit as liquid nitrogen fertilizer.
[0040] Tests showed that the COD concentration in the clear water storage tank was 22 mg / L, TP was below 0.1 mg / L (below the detection limit, meeting the reuse water standard), and NH4 was... + The -N concentration is 3.8 mg / L, which meets the requirements of the "Water Quality Standard for Urban Wastewater Reuse for Miscellaneous Uses" (GB / T 18920-2020) and is suitable for use in toilet flushing / greening.
[0041] Example 2 The blackwater first enters the blackwater equalization tank, where the COD concentration is adjusted to 1800 mg / L, the TP concentration to 35 mg / L, and the NH4+ concentration to... + The -N concentration is 235 mg / L, and the adjusted black water enters the black water coagulation tank. PTC (400 mg Ti / L) from the chemical storage tank was added to the blackwater coagulation tank. After addition, the mixture was stirred at 200 rpm for 1 min, then the stirring speed was increased to 150 rpm for 30 s. Next, CTS (1 mg / L) was added, and the mixture was stirred at 150 rpm for 30 s. Finally, the stirring speed was increased to 60 rpm for 10 min. The resulting coagulated liquid was subjected to solid-liquid separation to obtain a solid and a supernatant. The COD concentration of the supernatant decreased to 98 mg / L, the TP concentration decreased to 0.2 mg / L, and the NH4+ concentration decreased. + -N concentration is 178 mg / L; solids enter the sludge storage and recovery unit, and after treatment, solid phosphorus-containing organic fertilizer is obtained; supernatant enters nanofiltration equipment; Using a nanofiltration membrane with a molecular weight cutoff of 200 Da (NF90 model), the supernatant is deeply separated at an operating pressure of about 1.5 MPa. The purified water from the product side enters the purified water storage tank, while the concentrated liquid from the concentrate side enters the concentrate recovery tank unit as liquid nitrogen fertilizer.
[0042] Tests showed that the COD concentration in the clear water storage tank was 20 mg / L, TP was below 0.1 mg / L (below the detection limit, meeting the reuse water standard), and NH4 was... + The -N concentration is 3.5 mg / L, which meets the requirements of the "Water Quality Standard for Urban Wastewater Reuse for Miscellaneous Uses" (GB / T 18920-2020) and is suitable for use in toilet flushing / greening.
[0043] Comparative Example 1 The blackwater first enters the blackwater equalization tank, where the COD concentration is adjusted to 1500 mg / L, the TP concentration to 35 mg / L, and the NH4+ concentration to... + The -N concentration is 235 mg / L, and the adjusted black water enters the black water coagulation tank. CTS (0.5 mg / L) from the chemical storage tank was added to the blackwater coagulation tank, followed by stirring at 150 rpm for 30 seconds; then the stirring speed was adjusted to 60 rpm for 10 minutes; then PTC (350 mg Ti / L) was added, and the mixture was stirred at 200 rpm for 1 minute, followed by stirring at 150 rpm for 30 seconds. The resulting coagulated liquid was subjected to solid-liquid separation to obtain a solid and a supernatant. The COD concentration of the supernatant decreased to 231.5 mg / L, the TP concentration decreased to 4.5 mg / L, and the NH4+ concentration decreased. + The -N concentration is 215 mg / L, and the supernatant enters the nanofiltration device; Using a nanofiltration membrane with a molecular weight cutoff of 200 Da (NF90 model), the supernatant is deeply separated at an operating pressure of about 1.5 MPa, and the purified water from the product side enters the purified water storage tank.
[0044] Tests showed that the COD concentration in the clear water storage tank was 80.2 mg / L, TP was below 0.1 mg / L, and NH4+ was... + The -N concentration was 80.5 mg / L.
[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for the resource-based treatment of blackwater, characterized in that, Includes the following steps: Coagulant is added to black water for coagulation. The resulting mixture is then separated into solid and liquid components to obtain supernatant and sludge. The supernatant is separated by nanofiltration membrane to obtain reclaimed water and concentrate.
2. The method according to claim 1, characterized in that, The sludge is dewatered to produce phosphorus-containing organic fertilizer.
3. The method according to claim 1, characterized in that, A stabilizer is added to the concentrated liquid to produce liquid nitrogen fertilizer.
4. The method according to claim 1, characterized in that, The coagulant is titanium polychloride and chitosan.
5. The method according to claim 4, characterized in that, The dosage of the polytitanium chloride is 350~400 mg / L (calculated as titanium); the dosage of the chitosan is 0.5~1 mg / L.
6. The method according to claim 5, characterized in that, Methods for adding coagulants to black water include: first adding titanium chloride to the black water, and then adding chitosan; After adding polytitanium chloride, stir at 200-250 rpm for 30-60 seconds, then adjust the speed to 120-150 rpm and stir for 15-30 seconds; after adding chitosan, stir at 120-150 rpm for 30-60 seconds; finally, adjust the speed to 50-60 rpm and stir for 10-15 minutes.
7. The method according to claim 1, characterized in that, The nanofiltration membrane has a molecular weight cutoff of 200~300 Da and an operating pressure of 1.5~1.8 MPa.
8. The method according to claim 1, characterized in that, The black water has a chemical oxygen demand of 1500~1800 mg / L, an ammonia nitrogen content of 230~250 mg / L, and a total phosphorus content of 31~35 mg / L.