Rural domestic sewage treatment system and treatment method

Abstract

The present application provides a kind of rural domestic sewage treatment system and treatment method, including solar power generation system, anaerobic tank, anoxic tank, photobioreactor A, sedimentation tank, photobioreactor B and ecological pond seven parts.Solar power generation, traditional A2O process, photobioreactor and ecological pond technology are coupled, and the oxygen tank in A2O is replaced by photobioreactor, oxygen production by algal photosynthesis is used to replace mechanical aeration, energy consumption and cost are reduced;Part of the algal cells are fermented and used as carbon source to improve the carbon-nitrogen ratio of wastewater and enhance the removal of total nitrogen;Residual algal cells are used to cultivate zooplankton to provide bait for fish and shrimp, thereby realizing the resource utilization of wastewater, reducing the amount of residual sludge and the cost of wastewater treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sewage treatment, and particularly relates to a rural domestic sewage treatment system and a treatment method. BACKGROUND

[0002] The pollutants in rural domestic sewage are mainly nitrogen, phosphorus and organic pollutants, and the types of pollutants and heavy metals and harmful substances are few. Random discharge of rural domestic sewage may cause water eutrophication or form black and odorous water body. Therefore, treatment of rural domestic sewage is an important part of rural environmental improvement.

[0003] A 2 The A / O process is one of the most commonly used sewage treatment processes and is also widely used for treatment of rural domestic sewage. 2 The A / O process mainly utilizes the action of microorganisms to efficiently remove nitrogen and organic matter in wastewater through anaerobic, anoxic and aerobic treatment stages. In the aerobic stage, mechanical aeration is required to maintain sufficient dissolved oxygen, which is the main source of high energy consumption of the process. In the anoxic stage, carbon source in the influent is used for denitrification and nitrogen removal. Phosphorus removal is mainly achieved through anaerobic phosphorus release and aerobic phosphorus uptake, and the remaining sludge is finally discharged to remove total phosphorus. The treatment of the remaining sludge greatly increases the operating cost of the treatment facility.

[0004] Rural domestic sewage generally has the characteristic of low carbon-nitrogen ratio. When the A 2 O process is used for treatment, the lack of carbon source often leads to difficulty in nitrogen removal, and the total nitrogen in the effluent does not meet the standard. The A 2 O process has high energy consumption, and a large amount of residual sludge needs to be treated, resulting in high operating cost and idle treatment facilities. In addition, rural domestic sewage mainly contains nitrogen, phosphorus and organic matter, and generally does not contain heavy metals and harmful substances, which has the potential for resource utilization. Therefore, the development of a low-cost rural domestic sewage treatment technology with resource utilization potential is the key to the treatment of rural domestic sewage. SUMMARY

[0005] Therefore, in order to solve the above problems in the prior art, the present application aims to provide a rural domestic sewage treatment system and a treatment method, which couples solar power generation, traditional A 2 O process, photobioreactor and ecological pond, replaces the aerobic tank in the A 2 O process with a photobioreactor, uses oxygen produced by algal photosynthesis to replace mechanical aeration, reduces energy consumption and cost, uses part of the algal cells as carbon source after fermentation treatment, improves the carbon-nitrogen ratio of the sewage, and enhances the removal of total nitrogen. The remaining algal cells are used to cultivate zooplankton to provide food for fish and shrimp, so as to realize resource utilization of the sewage and reduce the amount of residual sludge and the cost of sewage treatment.

[0006] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0007] A rural domestic sewage treatment system, comprising: an anaerobic tank, an anoxic tank, a photobioreactor A, a sedimentation tank, a photobioreactor B and an ecological pond connected in sequence,

[0008] One end of the anaerobic tank is connected with a municipal sewage inlet pipe, and the anaerobic tank is used for anaerobic fermentation to mineralize macromolecular organic matter and algal cells into small molecular organic matter and inorganic matter, and the anaerobic tank introduces the generated carbon dioxide-containing waste gas to the photobioreactor A through a pipeline for discharge;

[0009] The effluent of the anaerobic tank flows into the anoxic tank, and the anoxic tank is used for denitrification to reduce nitrate nitrogen in the sewage to nitrogen by using carbon-containing organic matter in water as a carbon source through internal denitrifying bacteria to achieve denitrification;

[0010] The photobioreactor A is a bacteria-algae symbiotic system, the inside of the reactor is filled with biological fillers, bacteria adhere to the biological fillers to grow and form a biofilm, and the reactor is inoculated with algae with high nitrogen and phosphorus removal rates and no biological toxicity, the effluent of the anoxic tank enters the photobioreactor A, part of ammonia nitrogen in the water is oxidized to nitrate nitrogen under the action of nitrifying bacteria, and part of ammonia nitrogen, nitrate nitrogen and phosphorus are absorbed by algal cells to be removed;

[0011] The effluent of the photobioreactor A enters the sedimentation tank, part of the algal cells in the sewage will be precipitated, and the bottom of the sedimentation tank is also connected with the anaerobic tank through a pipeline and controls the backflow through a sludge pump, the precipitated algal cells are backflowed to the anaerobic tank through the pipeline for hydrolysis and fermentation, and the other part of the high-activity algal cells flow out to the photobioreactor B with the effluent;

[0012] After the effluent of the sedimentation tank enters the photobioreactor B, the nitrogen and phosphorus nutrients in the water are further absorbed by the algal cells in the photobioreactor B, the algal cells are fed by zooplankton in the reactor B, and algae-water separation is achieved;

[0013] The ecological pond is used for breeding fish that feed on zooplankton, the effluent of the photobioreactor B carries a large amount of zooplankton, and the zooplankton are fed by the fish after entering the ecological pond, so that the substances and energy in the sewage flow to the fish through the food chain of algae and zooplankton, and the goal of resource utilization is achieved while the sewage is treated to meet the standard.

[0014] Optionally, the biological fillers of the photobioreactor A are biological ropes or suspended fillers with high specific surface area, and the filling rate is 10-50%. The filling rate refers to the proportion of the biological fillers in the volume of the reactor cavity.

[0015] Optionally, the photobioreactor A is a rectangular cuboid made of organic glass with an open top and is transparent, a lighting lamp is arranged at the top, the lamp is powered by a solar power generation system, and the reactor is provided with a light source at night and when the light is insufficient during the day.

[0016] Optionally, the hydraulic retention time of the photobioreactor A is 12-72 hours, and the algae biomass lost with the effluent water is 30-80% of the total biomass in the photobioreactor A.

[0017] Optionally, the anaerobic tank is a glass fiber reinforced plastic structure which is sealed and light-proof, and the glass fiber reinforced plastic structure is connected with a pipeline through a gas permeation hole, and the other end of the pipeline is arranged at the bottom of the photobioreactor A.

[0018] Preferably, the hydraulic retention time of the anaerobic tank is 20-72 hours, and the sludge is cleaned once every 0.5-1 year.

[0019] Optionally, the photobioreactor B is a transparent cuboid made of organic glass, and the top of the photobioreactor B is open, and natural light is used for illumination, and the photobioreactor B is inoculated with daphnia.

[0020] Optionally, the photobioreactor A and the photobioreactor B are both formed by connecting a plurality of reactors of the same type in series.

[0021] Optionally, the anoxic tank is filled with biological ropes or suspended fillers, and the filling rate is 30-80%.

[0022] The application further provides a treatment method of the rural domestic sewage treatment system.

[0023] (1) After the system is started, the sewage and the backflow algae cells first enter the anaerobic tank to perform anaerobic fermentation and remove part of the organic matter.

[0024] (2) The effluent water of the anaerobic tank enters the anoxic tank, and the nitrate nitrogen in the water is converted into nitrogen gas under the action of denitrifying bacteria to achieve denitrification.

[0025] (3) The effluent water of the anoxic tank enters the photobioreactor A, and part of the ammonia nitrogen in the water is oxidized into nitrate nitrogen under the action of nitrifying bacteria, and part of the ammonia nitrogen, the nitrate nitrogen and the phosphorus and other nutrient salts are removed by being absorbed by the algae cells.

[0026] (4) The effluent water of the photobioreactor A enters the sedimentation tank, part of the cells are precipitated and backflow to the anaerobic tank, and another part of the high-activity algae cells flow out with the effluent water, part of the effluent water of the sedimentation tank is backflow to the anoxic tank to perform denitrification, and another part of the effluent water of the sedimentation tank enters the photobioreactor B.

[0027] (5) After the effluent water of the sedimentation tank enters the photobioreactor B, the nitrogen and phosphorus nutrient salts in the water are further absorbed by the algae cells, and the algae cells are eaten by the zooplankton in the photobioreactor B to realize algae-water separation.

[0028] (6) The effluent of the photobioreactor B enters the ecological pond, and the zooplankton in the effluent is eaten by aquatic animals such as fish and shrimps, and the nitrogen and phosphorus nutrients in the sewage are ultimately used through the algae-zooplankton-fish and shrimp food chain.

[0029] By adopting the technical scheme, the present application has the following beneficial effects: oxygen produced by algal photosynthesis is used to replace mechanical aeration, thereby reducing energy consumption and cost; part of the algal cells are fermented and used as a carbon source, thereby improving the carbon-nitrogen ratio of the sewage and strengthening the removal of total nitrogen; the remaining algal cells are used to cultivate zooplankton, thereby providing bait for fish and shrimps, so that the resource utilization of the sewage is realized, and the amount of residual sludge is reduced, thereby reducing the cost of sewage treatment. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The figure is a structural schematic diagram of the rural domestic sewage treatment system of the present application. DETAILED DESCRIPTION

[0031] The present application provides a rural domestic sewage treatment and resource utilization method, which comprises a solar power generation system, an anaerobic tank, an anoxic tank, a photobioreactor A, a sedimentation tank, a photobioreactor B and an ecological pond. The specific steps are as follows:

[0032] S1: After the system is started, the sewage and the backflow algal cells first enter the anaerobic tank, and anaerobic fermentation is performed to mineralize macromolecular organic matter and algal cells into small-molecule organic matter and inorganic matter. The anaerobic tank is made of light-proof material or is light-proof treated, is closed, and the carbon dioxide-containing waste gas generated by the anaerobic tank is introduced by a pipeline to the bottom of the photobioreactor A for discharge. The hydraulic retention time of the anaerobic tank is 20-72 hours, and the sludge is cleaned once every 0.5-1 year.

[0033] S2: The effluent of the anaerobic tank and part of the effluent of the sedimentation tank enter the anoxic tank for denitrification. The backflow water of the sedimentation tank contains a large amount of nitrate nitrogen, and under the action of denitrifying bacteria in the anoxic tank, the organic matter in the effluent of the anaerobic tank is used as a carbon source to carry out denitrification, so that the nitrate nitrogen is reduced to nitrogen gas, and denitrification is realized. The anoxic tank is internally filled with biological ropes or suspended fillers, and the filling rate is 30-80%, which provides a carrier for the growth of denitrifying bacteria and avoids the loss of denitrifying bacteria with the effluent. The hydraulic retention time of the anoxic tank is 4-24 hours.

[0034] S3: The effluent of the anoxic tank enters the photobioreactor A, and part of the ammonia nitrogen in the water is oxidized to nitrate nitrogen by nitrifying bacteria, and part of the ammonia nitrogen, nitrate nitrogen and phosphorus are absorbed by algal cells to be removed. The photobioreactor A is a bacteria-algae symbiotic system, which can be connected in series by 1-5 reactors of the same type. The reactor is made of material with good light collecting effect, and is provided with a lamp inside or outside, which is powered by a solar power generation system. During the day, sunlight provides light source for algal growth, and at night and during the day with insufficient light, the lamp is used to supplement the light source. The reactor is filled with biological filler, and biological ropes or suspended fillers with high specific surface area are selected, and the filling rate is 10-50%, which provides a carrier for the growth of biofilm. Algae are selected from diatoms, green algae and other algae with high nitrogen and phosphorus removal rate and no biological toxicity. The hydraulic retention time of the photobioreactor A is 12-72 hours, so that the algal biomass lost with the effluent is 30-80% of the total biomass in the photobioreactor A.

[0035] S4: The effluent of the photobioreactor A enters the sedimentation tank, part of the cells are precipitated and then returned to the anaerobic tank, and the other part of the high-activity algal cells flow out with the effluent. Part of the effluent of the sedimentation tank is returned to the anoxic tank, and the other part enters the photobioreactor B. The return flow of the sedimentation tank effluent is 100-400%. The hydraulic retention time of the sedimentation tank is 24-120 hours, so that the algal cell return flow is 20-60% of the algal cell quantity in the photobioreactor A effluent. The sedimentation tank is subjected to light shielding treatment.

[0036] S5: The effluent of the sedimentation tank enters the photobioreactor B, and the nitrogen and phosphorus nutrients in the water are further absorbed by algal cells, and at the same time, the algal cells are fed by zooplankton in the photobioreactor B, so as to realize the separation of algae and water. The photobioreactor B is an algae-zooplankton symbiotic system, which can be connected in series by 1-5 reactors of the same type. The reactor mainly uses natural light, and can also use a lamp to supplement light, which is powered by a solar power supply system. The reactor is inoculated with branchiopods and copepods zooplankton which feed on algae without biological toxicity. The hydraulic retention time of the photobioreactor B is 12-72 hours, so that the zooplankton biomass lost with the effluent is 30-80% of the total biomass in the reactor.

[0037] S6: The effluent of the photobioreactor B enters the ecological pond, and the zooplankton in the effluent is fed by aquatic animals such as fish and shrimp, and the nitrogen and phosphorus nutrients in the sewage are finally utilized through the algae-zooplankton-fish and shrimp food chain.

[0038] The application will be further described in combination with the drawings and examples. Example

[0039] A rural domestic sewage treatment and resource utilization method, which comprises a solar power generation system, an anaerobic tank, an anoxic tank, a photobioreactor A, a sedimentation tank, a photobioreactor B and an ecological pond, and specifically comprises the following parts:

[0040] Anaerobic tank is glass steel structure, sealed, light-tight, air permeable hole connected pipeline, pipeline outlet is set in the bottom of photobioreactor A.

[0041] Anoxic tank is glass steel structure, internal hanging biological rope, filling rate is 80%.

[0042] Photobioreactor A is transparent organic glass made of rectangular box, open top, set the lighting tube at the top, the lighting tube is powered by solar power system, turn on the lighting tube at sunset, turn off the lighting tube at sunrise. The reactor is filled with biological rope, the filling rate is 30%. The reactor is inoculated with chlorella.

[0043] The sedimentation tank is a inclined plate sedimentation tank with a cover plate, which is light-tight.

[0044] Photobioreactor B is a transparent organic glass rectangular box, open top, using natural light, the reactor is inoculated with daphnia magna.

[0045] Ecological pond is a common pond, breeding fish such as hypophthalmichthys nobilis, crucian carp and aramichthys pellegrini.

[0046] Wastewater treatment steps:

[0047] System start: first in photobioreactor A using sewage acclimation culture chlorella, chlorella biomass reaches 0.3-0.5 g / L, 10-30% of the water and algae mixture in photobioreactor A is transferred to photobioreactor B, acclimation culture daphnia magna, the reduced part of photobioreactor A is supplemented with equal amount of sewage, when the density of daphnia magna reaches 20-60, start the system water, control the initial water quantity is 20-50% of the target treatment capacity, under the premise that the system effluent quality reaches the first level B standard of "municipal wastewater treatment plant pollutant discharge standard" (GB 18918-2002), gradually increase the water quantity to the target treatment capacity, the start-up process is about 21-45 days.

[0048] System operation:

[0049] (1) Sewage and backflow algae cells first enter anaerobic tank, anaerobic fermentation, large molecular organic matter and algae cells are mineralized into small molecular organic matter and inorganic matter, hydraulic retention time is 36 hours, sludge is cleaned once every half year.

[0050] (2) Anaerobic tank effluent and part of the sedimentation tank effluent enter anoxic tank for denitrification, hydraulic retention time is 6 hours.

[0051] (3) The effluent from the anoxic tank is fed into the photobioreactor A, in which a part of the ammonia nitrogen in the water is oxidized into nitrate nitrogen by nitrifying bacteria, and a part of the ammonia nitrogen, nitrate nitrogen and phosphorus are absorbed by the algal cells to be removed. The hydraulic retention time of the photobioreactor A is 36 hours, and the algal biomass lost with the effluent accounts for 45-60% of the total algal biomass in the photobioreactor A.

[0052] (4) The effluent from the photobioreactor A is fed into the sedimentation tank, in which a part of the cells are precipitated and then backflowed into the anoxic tank, and another part of the high-activity algal cells are lost with the effluent. A part of the effluent from the sedimentation tank is backflowed into the anoxic tank, and another part is fed into the photobioreactor B. The backflow amount of the effluent from the sedimentation tank is set to 200%, and the hydraulic retention time is 36 hours. The backflow amount of the algal cells is 20-40% of the algal cell amount in the effluent from the photobioreactor A.

[0053] (5) The effluent from the sedimentation tank is fed into the photobioreactor B, in which the nitrogen and phosphorus nutrients in the water are further absorbed by the algal cells, and the algal cells are eaten by the zooplankton in the photobioreactor B to realize the separation of the algae and water. The hydraulic retention time is 24 hours, and the zooplankton biomass lost with the effluent accounts for 30-45% of the total zooplankton biomass in the photobioreactor.

[0054] (6) The effluent from the photobioreactor B is fed into the ecological pond, in which the zooplankton in the effluent is eaten by aquatic animals such as fish and shrimp, and the water quality of the effluent from the ecological pond is superior to the first level B standard.

[0055] The specific embodiments of the present application are described above, but the present application is not limited thereto. Various changes can be made to the present application without departing from the spirit of the present application.

Claims

1. A rural domestic wastewater treatment system, characterised in that, It comprises: sequentially connected anaerobic tank, anoxic tank, photobioreactor A, sedimentation tank, photobioreactor B and ecological pond, One end of the anaerobic tank is connected with the municipal sewage inlet pipe, and the anaerobic tank is used for anaerobic fermentation to mineralize macromolecular organic matter and algal cells into small molecular organic matter and inorganic matter. The anaerobic tank introduces the generated carbon dioxide-containing waste gas to the photobioreactor A through a pipeline for discharge. The effluent of the anaerobic tank flows into the anoxic tank, and the anoxic tank is used for denitrification. The internal denitrifying bacteria reduce the nitrate nitrogen in the sewage to nitrogen gas by taking the carbon-containing organic matter in the water as carbon source, thereby achieving denitrification. The photobioreactor A is a bacteria-algae symbiotic system, the inside of the reactor is filled with biological filler, bacteria adhere to the biological filler to grow and form a biofilm, and the reactor is inoculated with algae with high nitrogen and phosphorus removal rate and no biological toxicity. The effluent of the anoxic tank enters the photobioreactor A, part of the ammonia nitrogen in the water is oxidized to nitrate nitrogen under the action of nitrifying bacteria, and part of the ammonia nitrogen, nitrate nitrogen and phosphorus are absorbed by algal cells to be removed. The effluent of the photobioreactor A enters the sedimentation tank, part of the algal cells in the sewage will be precipitated, and the bottom of the sedimentation tank is also connected with the anaerobic tank through a pipeline and controlled by a sludge pump to return flow. The precipitated algal cells return to the anaerobic tank through the pipeline for hydrolysis and fermentation, and the other part of the high-activity algal cells flow out with the effluent to the photobioreactor B. After the effluent of the sedimentation tank enters the photobioreactor B, the nitrogen and phosphorus nutrients in the water are further absorbed by the algal cells in the photobioreactor B, and the algal cells are fed by the zooplankton in the reactor B, thereby realizing algae-water separation. The ecological pond is used for breeding fish that feed on zooplankton. The effluent of the photobioreactor B carries a large amount of zooplankton, which is fed by fish after entering the ecological pond. Finally, the substances and energy in the sewage flow to the fish through the food chain of algae and zooplankton, thereby achieving the goal of resource utilization while completing the standard treatment of sewage.

2. The rural domestic wastewater treatment system according to claim 1, characterized in that, The biological filler of the photobioreactor A is biological rope or suspended filler with high specific surface area, and the filling rate is 10-50%.

3. The rural domestic wastewater treatment system according to claim 1, characterized in that, The photobioreactor A is a rectangular cuboid made of transparent organic glass with an open top, and a lighting lamp is arranged at the top. The lamp is powered by a solar power generation system, which provides light source for the reactor at night and when the light is insufficient during the day.

4. The rural domestic wastewater treatment system according to claim 1, characterized in that, The hydraulic retention time of the photobioreactor A is 12-72 hours, so that the algal biomass lost with the effluent is 30-80% of the total biomass in the reactor A.

5. The rural domestic wastewater treatment system according to claim 1, characterized in that, The anaerobic tank is a glass steel structure that is sealed and light-tight. The glass steel structure is connected with a pipeline through a gas permeation hole, and the other end of the pipeline is arranged at the bottom of the photobioreactor A. The hydraulic retention time of the anaerobic tank is 20-72 hours, and the sludge is cleaned once every 0.5-1 year.

6. The rural domestic wastewater treatment system according to claim 1, characterized in that, The photobioreactor B is a rectangular cuboid made of transparent organic glass with an open top, and uses natural light. The reactor is inoculated with daphnia magna.

7. The rural domestic wastewater treatment system according to claim 1, characterized in that, The photobioreactor A and the photobioreactor B are both composed of multiple reactors of the same type connected in series.

8. The rural domestic wastewater treatment system according to claim 1, characterized in that, The anoxic tank is filled with biological rope or suspended filler, and the filling rate is 30-80%.

9. A method of treating rural domestic wastewater by the system according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: (1) After the system is started, the sewage and the backflow algae cells first enter the anaerobic tank to carry out anaerobic fermentation and remove part of the organic matter; (2) The effluent of the anaerobic tank enters the anoxic tank, and the nitrate nitrogen in the water is converted into nitrogen gas under the action of denitrifying bacteria to achieve denitrification; (3) The effluent of the anoxic tank enters the photobioreactor A, part of the ammonia nitrogen in the water is oxidized to nitrate nitrogen under the action of nitrifying bacteria, and part of the ammonia nitrogen, nitrate nitrogen and phosphorus are removed by being absorbed by the algae cells; (4) The effluent of the photobioreactor A enters the sedimentation tank, part of the cells are precipitated and backflow to the anaerobic tank, and the other part of the high-activity algae cells flow out with the effluent, part of the effluent of the sedimentation tank is backflow to the anoxic tank for denitrification, and the other part enters the photobioreactor B; (5) After the effluent of the sedimentation tank enters the photobioreactor B, the nitrogen and phosphorus nutrients in the water are further absorbed by the algae cells, and the algae cells are eaten by the zooplankton in the reactor B to realize algae-water separation; (6) The effluent of the photobioreactor B enters the ecological pond, and the zooplankton in the effluent is eaten by fish, and the nitrogen and phosphorus nutrients in the sewage are finally used through the algae-zooplankton-fish food chain.

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