A method for treating domestic sewage

Abstract

This invention provides a method for treating domestic sewage, belonging to the technical field of sewage treatment methods. The invention involves filtering domestic sewage using a screen to remove floating impurities; adding a composite sewage treatment agent to the filtered sewage; subjecting the mixed sewage to ultrasonic treatment to obtain mixed sewage; discharging the mixed sewage into a sedimentation tank, where the settled sludge is used to produce biomass fertilizer; and discharging the supernatant clear water into a filtration tank, where the clear water filtered through an activated carbon layer and a quartz sand layer can be directly discharged. The composite sewage treatment agent comprises modified *Ichthyophthirius multifiliis* powder, a composite bacterial solution, polyacrylamide, water, and calcium oxide. This method for treating domestic sewage effectively removes COD, ammonia nitrogen, and heavy metal ion content from water bodies, achieving removal efficiencies of 99.6%, 99.9%, and 97.3%, respectively.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment methods, and more particularly to a method for treating domestic wastewater. Background Technology

[0002] Domestic sewage contains a large amount of organic matter, such as cellulose, starch, sugars, and fats and proteins; it also often contains pathogens, viruses, and parasite eggs; inorganic salts such as chlorides, sulfates, phosphates, bicarbonates, and sodium, potassium, calcium, and magnesium; and heavy metal ions such as copper and lead. Its general characteristics include high nitrogen, sulfur, and phosphorus content, and it easily produces foul-smelling substances under the action of anaerobic bacteria. Traditional methods for treating domestic sewage include biological treatment, physical treatment, and chemical treatment, but these methods suffer from low efficiency and high costs.

[0003] Chinese patent application CN111995172A discloses a method for treating domestic sewage, which involves filtering the sewage and then treating it in a grit chamber, oxidation tank, secondary sedimentation tank, coagulation tank, and denitrification deep bed filter. This technical solution can effectively reduce the nitrogen and phosphorus content in the sewage. However, the process is cumbersome and does not consider the treatment efficiency of organic matter and other heavy metal ions in the sewage. Chinese patent CN109851142B discloses a method for treating municipal domestic sewage, which involves adsorption, flocculation, and removal of heavy metal ions from municipal domestic sewage, while simultaneously applying a gradient magnetic field to assist adsorption. This technical solution uses chemical reagents, which are not very efficient at removing ammonia nitrogen, while ammonia nitrogen content (NH3-N) is often used as an important indicator for wastewater discharge.

[0004] Algae are a type of plant rich in chlorophyll and have a strong absorption capacity. Studies have found that some algae have a high adsorption capacity for harmful substances such as heavy metal ions, organic pollutants, and nutrients in wastewater. By adding algae to wastewater, the algae adsorb and accumulate harmful substances, thereby purifying the wastewater. Algae can also convert the adsorbed harmful substances into organic matter through photosynthesis, further reducing the pollution level of the wastewater.

[0005] However, using algae in wastewater treatment often requires cultivating the algae before application. Therefore, how to effectively utilize the adsorption properties of algae to obtain a simple process for treating domestic wastewater that is effective against heavy metals, ammonia nitrogen, and other organic pollutants is a technical problem that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method for treating domestic sewage, which solves the technical problem of low efficiency in treating ammonia nitrogen and heavy metal ions in existing sewage treatment methods.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for treating domestic sewage, comprising the following steps:

[0009] (1) The domestic sewage is filtered by a screen to remove floating impurities;

[0010] (2) Add composite sewage treatment agent to the filtered domestic sewage, and apply ultrasonic treatment to the mixed sewage to obtain mixed sewage;

[0011] (3) The mixed wastewater is discharged into the sedimentation tank, and the sludge after sedimentation is used to produce biomass fertilizer. The upper clear water is discharged into the filter tank, and the clear water after filtration through the activated carbon layer and the quartz sand layer can be discharged directly.

[0012] The composite wastewater treatment agent comprises modified black spore algae powder, composite bacterial solution, polyacrylamide, water, and calcium oxide.

[0013] Furthermore, both the activated carbon layer and the quartz sand layer are distributed at the bottom of the filtration tank, with the activated carbon layer distributed on top of the quartz sand layer; the particle size of the activated carbon in the activated carbon layer is 5-10 mm.

[0014] The quartz sand layer is divided into three layers: the upper layer has a particle size of 1-5 cm, the middle layer has a particle size of 5-10 mm, and the lower layer has a particle size of 1-5 mm.

[0015] Furthermore, the ratio of the modified black spore algae powder, the compound bacterial solution, polyacrylamide, water, and calcium oxide is 2-8g: 10-15mL: 20-30g: 50-80g: 15-28g.

[0016] Furthermore, the modified *Ichthyophthirius multifiliis* powder is prepared by: washing and drying *Ichthyophthirius multifiliis*, heat-treating it at 400–600°C for 10–30 minutes, and then crushing it into powder to obtain modified *Ichthyophthirius multifiliis* powder.

[0017] Furthermore, the preparation method of the compound bacterial liquid is as follows: after mixing kitchen waste with beet molasses and water, ferment at 25-30℃ for 15-20 days, and the filtered liquid is the compound bacterial liquid.

[0018] Furthermore, the mass ratio of the kitchen waste, beet molasses, and water is 1:0.1-0.3:6-8.

[0019] Furthermore, the frequency of the ultrasonic treatment is 100-200 Hz, and the duration of the ultrasonic treatment is 50-100 min.

[0020] Furthermore, the dosage of the composite wastewater treatment agent is 100–500 mg / L of domestic wastewater.

[0021] Furthermore, the thickness of the activated carbon layer is 1-5 cm, and the total thickness of the quartz sand layer is 10-20 cm.

[0022] The beneficial effects of this invention are:

[0023] This invention modifies *Ulva protozoa* through heat treatment, effectively increasing its surface area and improving its adsorption performance. Studies have shown that the modified *Ulva protozoa* powder can effectively adsorb Cu from water. 2+ and Pb 2+ Furthermore, through the filtration of the activated carbon layer and quartz sand layer in the filtration pool, all the black spore algae powder can be filtered out, making it convenient to use and more effective, and it can be used without cultivating the algae.

[0024] This invention combines modified *Ulva prostrata* powder, a composite bacterial solution, a flocculant, and an oxidant to achieve dual-function adsorption and chemical degradation of organic pollutants and heavy metal ions in wastewater. Ultrasonic-assisted degradation accelerates the contact rate between organic pollutants and the composite bacterial solution, thus increasing degradation efficiency. Polyacrylamide, acting as a flocculant, flocculates the *Ulva prostrata* powder colloidal particles adsorbed with organic pollutants and heavy metal ions into clusters in the wastewater, facilitating filtration and removal.

[0025] This invention sets up an activated carbon layer and a quartz sand layer at the bottom of the filter tank. The clear water separated by sedimentation first passes through the activated carbon layer to remove the yellow color from the water, and then passes through the quartz sand layer with particle sizes ranging from large to small. This can effectively perform deep filtration of tiny colloidal particles in the water. Utilizing the multi-stage particle size filtration layer of the quartz sand layer, a "backflow" phenomenon occurs between the tiny colloidal particles, causing the particles to pass back and forth through the quartz sand layer and be adsorbed on the surface of the quartz sand, thus achieving effective removal.

[0026] The domestic sewage treatment method of the present invention can effectively remove COD, ammonia nitrogen and heavy metal ion content from water bodies, with removal efficiencies of 99.6%, 99.9% and 97.3%, respectively. Detailed Implementation

[0027] This invention provides a method for treating domestic sewage, comprising the following steps:

[0028] (1) The domestic sewage is filtered by a screen to remove floating impurities;

[0029] (2) Add composite sewage treatment agent to the filtered domestic sewage, and apply ultrasonic treatment to the mixed sewage to obtain mixed sewage;

[0030] (3) The mixed wastewater is discharged into the sedimentation tank, and the sludge after sedimentation is used to produce biomass fertilizer. The upper clear water is discharged into the filter tank, and the clear water after filtration through the activated carbon layer and the quartz sand layer can be discharged directly.

[0031] The composite wastewater treatment agent comprises modified black spore algae powder, composite bacterial solution, polyacrylamide, water, and calcium oxide.

[0032] In this invention, both the activated carbon layer and the quartz sand layer are distributed at the bottom of the filtration tank, with the activated carbon layer distributed on top of the quartz sand layer; the particle size of the activated carbon in the activated carbon layer is 5-10 mm, preferably 6-8 mm.

[0033] In this invention, the quartz sand layer is divided into three layers: the upper layer of quartz sand has a particle size of 1-5 cm, the middle layer of quartz sand has a particle size of 5-10 mm, and the lower layer of quartz sand has a particle size of 1-5 mm; preferably, the upper layer of quartz sand has a particle size of 2-4 cm, the middle layer of quartz sand has a particle size of 6-8 mm, and the lower layer of quartz sand has a particle size of 2-4 mm.

[0034] In this invention, the ratio of modified *Ichthyophthirius multifiliis* powder, compound bacterial solution, polyacrylamide, water, and calcium oxide is 2-8g:10-15mL:20-30g:50-80g:15-28g, preferably 3-6g:11-14mL:22-28g:55-75g:20-26g, and more preferably 4-5g:12-13mL:25-28g:60-70g:20-24g.

[0035] In this invention, the modified *Ulva protozoa* powder is prepared by: washing and drying *Ulva protozoa*, then heat-treating it at 400–600°C for 10–30 min, and then crushing it into powder to obtain modified *Ulva protozoa* powder; preferably, heat-treating it at 450–550°C for 15–20 min.

[0036] In this invention, the preparation method of the compound bacterial liquid is as follows: after mixing kitchen waste with beet molasses and water, fermenting at 25-30℃ for 15-20 days, the filtered liquid is the compound bacterial liquid; preferably, fermenting at 28℃ for 15 days, the filtered liquid is the compound bacterial liquid.

[0037] In this invention, the mass ratio of kitchen waste, beet molasses and water is 1:0.1-0.3:6-8, preferably 1:0.2-0.3:7-8.

[0038] In this invention, the frequency of the ultrasonic treatment is 100-200Hz, preferably 120-180Hz, and more preferably 150Hz; the duration of the ultrasonic treatment is 50-100min, preferably 60-80min, and more preferably 70min.

[0039] In this invention, the dosage of the composite wastewater treatment agent is 100-500 mg / L of domestic wastewater, preferably 200-400 mg / L of domestic wastewater, and more preferably 300 mg / L of domestic wastewater.

[0040] In this invention, the thickness of the activated carbon layer is 1-5 cm, preferably 2-4 cm; the total thickness of the quartz sand layer is 10-20 cm, preferably 15 cm, with the upper, middle and lower quartz sand layers each being 5 cm thick.

[0041] 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.

[0042] Example 1

[0043] A method for treating domestic sewage includes the following steps:

[0044] (1) The domestic sewage is filtered by a screen to remove floating impurities;

[0045] (2) Add 400 mg / L of composite sewage treatment agent to the filtered domestic sewage, stir the sewage and apply ultrasonic vibration at 200 Hz for 60 min to obtain mixed sewage;

[0046] (3) The mixed wastewater is discharged into the sedimentation tank and allowed to settle for 2 hours. The sludge that is settled is used to produce biomass waste. The upper layer of clear water is discharged into the filter tank. The filter tank is arranged from top to bottom as follows: activated carbon layer (particle size 5-8 mm, thickness 3 cm), upper quartz sand layer (particle size 1-2 cm, thickness 5 cm), middle quartz sand layer (particle size 5-8 mm, thickness 5 cm) and lower quartz sand layer (2-4 mm, thickness 5 cm). The filtered clear water can be discharged directly.

[0047] The composite wastewater treatment agent contains modified *Hydrilla verticillata* powder, composite bacterial solution, polyacrylamide, water, and calcium oxide in a ratio of 8g:15mL:25g:80g:20g. The modified *Hydrilla verticillata* powder is obtained by washing and drying *Hydrilla verticillata*, heat-treating it at 400℃ for 30 minutes, and then crushing it into powder.

[0048] The preparation method of the compound bacterial solution is as follows: mix kitchen waste with beet molasses and water, ferment at 25°C for 15 days, and filter the liquid to obtain the compound bacterial solution. The mass ratio of kitchen waste, beet molasses and water is 1:0.2:6.

[0049] Example 2

[0050] A method for treating domestic sewage includes the following steps:

[0051] (1) The domestic sewage is filtered by a screen to remove floating impurities;

[0052] (2) Add 450 mg / L of composite sewage treatment agent to the filtered domestic sewage, stir the sewage and apply ultrasonic vibration at 200 Hz for 60 min to obtain mixed sewage;

[0053] (3) The mixed wastewater is discharged into the sedimentation tank and allowed to settle for 2 hours. The sludge that is settled is used to produce biomass waste. The upper layer of clear water is discharged into the filter tank. The filter tank is arranged from top to bottom as follows: activated carbon layer (particle size 5-8 mm, thickness 3 cm), upper quartz sand layer (particle size 1-2 cm, thickness 5 cm), middle quartz sand layer (particle size 5-8 mm, thickness 5 cm) and lower quartz sand layer (2-4 mm, thickness 5 cm). The filtered clear water can be discharged directly.

[0054] The composite wastewater treatment agent contains modified *Hydrilla verticillata* powder, composite bacterial solution, polyacrylamide, water, and calcium oxide in a dosage ratio of 2g:10mL:25g:80g:20g. The modified *Hydrilla verticillata* powder is obtained by washing and drying *Hydrilla verticillata*, heat-treating it at 450℃ for 30 minutes, and then crushing it into powder.

[0055] The preparation method of the compound bacterial solution is as follows: mix kitchen waste with beet molasses and water, ferment at 25°C for 15 days, and filter the liquid to obtain the compound bacterial solution. The mass ratio of kitchen waste, beet molasses and water is 1:0.2:6.

[0056] Example 3

[0057] A method for treating domestic sewage includes the following steps:

[0058] (1) The domestic sewage is filtered by a screen to remove floating impurities;

[0059] (2) Add 500 mg / L of composite sewage treatment agent to the filtered domestic sewage, stir the sewage and apply ultrasonic vibration at 200 Hz for 60 min to obtain mixed sewage;

[0060] (3) The mixed wastewater is discharged into the sedimentation tank and allowed to settle for 2 hours. The sludge that is settled is used to produce biomass waste. The upper layer of clear water is discharged into the filter tank. The filter tank is arranged from top to bottom as follows: activated carbon layer (particle size 5-8 mm, thickness 3 cm), upper quartz sand layer (particle size 1-2 cm, thickness 5 cm), middle quartz sand layer (particle size 5-8 mm, thickness 5 cm) and lower quartz sand layer (2-4 mm, thickness 5 cm). The filtered clear water can be discharged directly.

[0061] The composite wastewater treatment agent contains modified *Hydrilla verticillata* powder, composite bacterial solution, polyacrylamide, water, and calcium oxide in a dosage ratio of 4g:15mL:25g:80g:20g. The modified *Hydrilla verticillata* powder is obtained by washing and drying *Hydrilla verticillata*, heat-treating it at 500℃ for 30 minutes, and then crushing it into powder.

[0062] The preparation method of the compound bacterial solution is as follows: mix kitchen waste with beet molasses and water, ferment at 25°C for 15 days, and filter the liquid to obtain the compound bacterial solution. The mass ratio of kitchen waste, beet molasses and water is 1:0.2:6.

[0063] Example 4

[0064] A method for treating domestic sewage includes the following steps:

[0065] (1) The domestic sewage is filtered by a screen to remove floating impurities;

[0066] (2) Add 300 mg / L of composite sewage treatment agent to the filtered domestic sewage, stir the sewage and apply ultrasonic vibration at 200 Hz for 60 min to obtain mixed sewage;

[0067] (3) The mixed wastewater is discharged into the sedimentation tank and allowed to settle for 2 hours. The sludge that is settled is used to produce biomass waste. The upper layer of clear water is discharged into the filter tank. The filter tank is arranged from top to bottom as follows: activated carbon layer (particle size 5-8 mm, thickness 3 cm), upper quartz sand layer (particle size 1-2 cm, thickness 5 cm), middle quartz sand layer (particle size 5-8 mm, thickness 5 cm) and lower quartz sand layer (2-4 mm, thickness 5 cm). The filtered clear water can be discharged directly.

[0068] The compound wastewater treatment agent contains modified black spore algae powder, compound bacterial solution, polyacrylamide, water and calcium oxide in a dosage ratio of 6g:15mL:25g:60g:15g. The modified black spore algae powder is obtained by washing and drying black spore algae, heat-treating it at 550℃ for 30 minutes, and then crushing it into powder.

[0069] The preparation method of the compound bacterial solution is as follows: mix kitchen waste with beet molasses and water, ferment at 25°C for 15 days, and filter the liquid to obtain the compound bacterial solution. The mass ratio of kitchen waste, beet molasses and water is 1:0.2:6.

[0070] Example 5

[0071] A method for treating domestic sewage includes the following steps:

[0072] (1) The domestic sewage is filtered by a screen to remove floating impurities;

[0073] (2) Add 100 mg / L of composite sewage treatment agent to the filtered domestic sewage, stir the sewage and apply ultrasonic vibration at 200 Hz for 60 min to obtain mixed sewage;

[0074] (3) The mixed wastewater is discharged into the sedimentation tank and allowed to settle for 2 hours. The sludge that is settled is used to produce biomass waste. The upper layer of clear water is discharged into the filter tank. The filter tank is arranged from top to bottom as follows: activated carbon layer (particle size 5-8 mm, thickness 3 cm), upper quartz sand layer (particle size 1-2 cm, thickness 5 cm), middle quartz sand layer (particle size 5-8 mm, thickness 5 cm) and lower quartz sand layer (2-4 mm, thickness 5 cm). The filtered clear water can be discharged directly.

[0075] The composite wastewater treatment agent contains modified *Hydrilla verticillata* powder, composite bacterial solution, polyacrylamide, water, and calcium oxide in a dosage ratio of 8g:15mL:25g:80g:20g. The modified *Hydrilla verticillata* powder is obtained by washing and drying *Hydrilla verticillata*, heat-treating it at 600℃ for 30 minutes, and then crushing it into powder.

[0076] The preparation method of the compound bacterial solution is as follows: mix kitchen waste with beet molasses and water, ferment at 25°C for 15 days, and filter the liquid to obtain the compound bacterial solution. The mass ratio of kitchen waste, beet molasses and water is 1:0.2:6.

[0077] Comparative Example 1

[0078] The technical solution is the same as in Example 1, except that the composite wastewater treatment agent does not contain modified black spore algae powder.

[0079] Comparative Example 2

[0080] The technical solution is the same as in Example 2, except that the heat treatment temperature of the modified *Ichthyophthirius multifiliis* powder is 900°C.

[0081] Comparative Example 3

[0082] The technical solution is the same as in Example 3, except that only an activated carbon layer and a single layer of quartz sand (particle size 1-2 cm, thickness 5 cm) are set in the filter tank.

[0083] Comparative Example 4

[0084] The technical solution is the same as in Example 3, except that only an activated carbon layer is set in the filtration tank.

[0085] Comparative Example 5

[0086] The technical solution is the same as in Example 5, except that the composite sewage treatment agent does not contain composite bacterial solution.

[0087] Experimental Example

[0088] Taking the domestic sewage of a certain town as an example, the water quality of the domestic sewage was tested, and the results are shown in Table 1 below.

[0089] Table 1. Results of domestic sewage testing in a certain town

[0090]

[0091] The water quality of the treated samples from Examples 1 to 5 and Comparative Examples 1 to 5 was tested, and the results are shown in Table 2 below.

[0092] Table 2. Test results of examples and comparative examples.

[0093]

[0094] As can be seen from the above embodiments, the present invention provides a method for treating domestic sewage. As can be seen from embodiments 1-5 above, increasing the concentration of the composite sewage treatment agent in sewage can effectively improve the removal efficiency of organic pollutants, heavy metal ions, and total phosphorus content in sewage; as can be seen from Comparative Example 1, the modified *Ulva lactuca* powder has a significant effect on the removal of Cu... 2+ and Pb 2+ The removal effect is obvious; as can be seen from Comparative Example 2, high-temperature heat treatment of *Ulva prolifera* is actually not conducive to increasing the surface area of ​​*Ulva prolifera*. This is because as the temperature rises, the micropores on the surface of *Ulva prolifera* biomass collapse, reducing the surface area of ​​*Ulva prolifera* powder and thus decreasing the adsorption performance; as can be seen from Comparative Examples 3 and 4, the multi-stage particle size setting in the filter tank of this invention can effectively reduce the color of the water and at the same time reduce the content of tiny colloidal particles in the water; as can be seen from Comparative Example 5, the composite bacterial solution also plays an important role in the composite wastewater treatment agent. It can cooperate with the modified *Ulva prolifera* powder to produce dual adsorption-degradation characteristics, playing a key role in the degradation of organic pollutants in wastewater.

[0095] 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 treating domestic sewage, characterized in that, Includes the following steps: (1) Use a screen to filter domestic sewage to remove floating impurities; (2) Add composite sewage treatment agent to the filtered domestic sewage, and apply ultrasonic treatment to the mixed sewage to obtain mixed sewage; (3) The mixed wastewater is discharged into the sedimentation tank, and the sludge after sedimentation is used to produce biomass fertilizer. The upper clear water is discharged into the filter tank, and the clear water after filtration through the activated carbon layer and the quartz sand layer can be discharged directly. The composite wastewater treatment agent comprises modified *Hydrilla verticillata* powder, composite bacterial solution, polyacrylamide, water, and calcium oxide; Both the activated carbon layer and the quartz sand layer are distributed at the bottom of the filtration tank, with the activated carbon layer distributed on top of the quartz sand layer; the particle size of the activated carbon in the activated carbon layer is 5~10mm. The quartz sand layer is divided into three layers: the upper layer of quartz sand has a particle size of 1-5 cm, the middle layer of quartz sand has a particle size of 5-10 mm, and the lower layer of quartz sand has a particle size of 1-5 mm. The ratio of modified *Hydrilla verticillata* powder, compound bacterial solution, polyacrylamide, water, and calcium oxide is 2-8g: 10-15mL: 20-30g: 50-80g: 15-28g; The modified *Ulva prolifera* powder is prepared by: washing and drying *Ulva prolifera*, heat-treating it at 400-600℃ for 10-30 minutes, and then crushing it into powder to obtain modified *Ulva prolifera* powder. The method for preparing the compound bacterial solution is as follows: mix kitchen waste with beet molasses and water, ferment at 25-30℃ for 15-20 days, and the filtered liquid is the compound bacterial solution.

2. The method for treating domestic sewage according to claim 1, characterized in that, The mass ratio of the kitchen waste, beet molasses, and water is 1:0.1~0.3:6~8.

3. The method for treating domestic sewage according to claim 1 or 2, characterized in that, The ultrasonic treatment frequency is 100~200Hz, and the ultrasonic treatment time is 50~100min.

4. The method for treating domestic sewage according to claim 3, characterized in that, The dosage of the composite wastewater treatment agent is 100~500 mg / L of domestic wastewater.

5. The method for treating domestic sewage according to claim 1 or 2, characterized in that, The thickness of the activated carbon layer is 1-5 cm, and the total thickness of the quartz sand layer is 10-20 cm.

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