A domestic sewage treatment system for bulk cargo terminals

Abstract

The present invention belongs to the technical field of sewage treatment, and relates to a domestic sewage treatment system for bulk cargo terminals, including a water collection sedimentation tank, a pre-reaction tank, a biochemical tank, an intermediate water tank, a filter, and a disinfection water tank; the pre-reaction tank includes a modified walnut shell. The modified walnut shell prepared by the present invention has a good removal effect on the difficult-to-biodegrade substances in the domestic sewage of the bulk cargo terminal, and can increase the biodegradability of the sewage entering the subsequent treatment process; the modified walnut shell allows the difficult-to-biodegrade suspended substances in the sewage to be fully precipitated, avoiding entering the biochemical tank to affect the sludge biochemical effect and microbial activity, thereby greatly improving the treatment capacity and stability of the subsequent reactor; by combining N, P, and K elements, nutrients are provided to microorganisms, the biodegradability of sewage is increased, and the problem of high content of difficult-to-biodegrade chemical substances suspended in domestic sewage, poor biodegradability, and low sludge content is solved to the greatest extent.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a domestic sewage treatment system for a bulk cargo terminal. Background Art

[0002] Sewage treatment is the process of purifying sewage to meet the water quality requirements for discharge into a water body or reuse. Sewage treatment is widely used in various fields. With the continuous acceleration of urbanization, the discharge of various domestic sewage is increasing. If no measures are taken to treat it, it will lead to serious pollution of water resources or even make it unusable, affecting the balance of the ecosystem and reducing the quality of human production and life.

[0003] Domestic sewage from bulk cargo terminals contains a large amount of mineral powder, coal powder, sand and other particulate matter, and domestic sewage from the front-line production area is mostly domestic sewage generated for cleaning, containing a large amount of daily chemical products and detergents, with low sludge content, high chemical oxygen demand (COD), low biochemical oxygen demand (BOD), and poor biodegradability. If it is discharged directly into the water environment, it will cause serious pollution to the water environment and damage the aquatic ecosystem. Therefore, it is necessary to treat domestic sewage from bulk cargo terminals to reduce water pollution, ensure water quality safety, and achieve the purpose of protecting the environment and improving resource utilization efficiency. Although many ports are equipped with ship domestic sewage treatment equipment, the effect of treating domestic sewage in the terminal operation area is not good. Summary of the invention

[0004] In view of the deficiencies of the above-mentioned prior art, the present invention provides a domestic sewage treatment system for bulk cargo terminals, and the specific technical scheme is as follows: A domestic sewage treatment system for a bulk cargo terminal comprises a water collection sedimentation tank, a pre-reaction tank, a biochemical tank, an intermediate water tank, a filter, and a disinfection water tank connected in sequence; The pre-reaction tank includes modified walnut shells, and the preparation method of the modified walnut shells includes the following steps: Step (1): crush the walnut shells, place them in boiling deionized water for 10-20 minutes and then vacuum dry them; Step (2): placing the walnut shells treated in step (1) into a mixed solution of polyaluminium chloride and aluminium sulfate, stirring at 30-40°C for 60-70 minutes, and then vacuum drying; Step (3): placing the walnut shells treated in step (2) into a mixed solution of polyacrylamide and activated silicic acid, stirring at 30-40° C. for 150-200 minutes, and then vacuum drying; Step (4): slowly drip a mixed solution of potassium nitrate solution and diammonium hydrogen phosphate solution onto the walnut shells treated in step (3) until the walnut shells are submerged, let stand for 2-4 hours, and then vacuum dry.

[0005] In the preparation of the modified walnut shell of the present invention, the crushed walnut shell is first heated in deionized water to remove non-carbon components, the surface is fully eroded, a microporous structure extending in all directions is generated, and the specific surface area and porosity are increased; the walnut shell is then subjected to a series of treatments to obtain a modified walnut shell that has a good removal effect on difficult-to-biodegrade substances in domestic sewage from bulk cargo terminals and can increase the biodegradability of sewage. The modified walnut shell adsorbs the surface active components in the sewage through hydrophilic properties, electrostatics and hydrogen bonds; by loading flocculants and coagulants, the suspended matter that is difficult to biodegrade in the sewage can be fully precipitated to avoid entering the biochemical pool to affect the biochemical effect of sludge and the activity of microorganisms, thereby greatly improving the processing capacity and stability of the subsequent reactor; by combining N, P, and K elements, nutrients are provided to microorganisms, the biodegradability of sewage is increased, and the problem of high content of difficult-to-biodegrade chemical substances suspended in domestic sewage, poor biodegradability, and low sludge content is solved to the greatest extent.

[0006] Furthermore, the particle size of the crushed walnut shell is 0.8-1.3 mm; and the vacuum drying temperature is 60-80°C.

[0007] Furthermore, in the mixed solution in step (2), the mass fraction of polyaluminium chloride is 2-5%, the mass fraction of aluminium sulfate is 1-6%, and the mass ratio of walnut shell to the mixed solution is 1:5.5.

[0008] Furthermore, in the mixed solution in step (3), the mass fraction of polyacrylamide is 0.2-1.5%, the mass fraction of activated silicic acid is 0.5-4%, and the mass ratio of walnut shell to mixed solution is 1:4.8.

[0009] Furthermore, in the mixed solution in step (4), the mass fraction of potassium nitrate is 15-20%, and the mass fraction of diammonium hydrogen phosphate is 10-20%.

[0010] Furthermore, the water collection sedimentation tank includes a filter screen and a mechanical screen cleaner installed in sequence.

[0011] The water collection sedimentation tank is filtered through a filter screen and a mechanical grille cleaning machine to remove large particles of impurities and pollutants; and small and medium-sized easily sedimentable mineral powder, coal powder, sand and other particles are separated through gravity sedimentation.

[0012] Furthermore, the biochemical pool is an SBR biochemical pool, comprising a lift pump, an SBR reactor and a decanter connected in sequence.

[0013] The SBR biochemical pool divides the process in chronological order. It is based on the sequencing batch activated sludge process and is a sewage biochemical treatment process that integrates functions such as regulation, primary sedimentation, denitrification, biodegradation, and final sedimentation. There is no need to set up a sludge return system. During operation, the sewage is lifted by a lifting pump and regularly enters the SBR reactor in the SBR biochemical pool. The aerobic microorganisms in the activated sludge decompose the organic matter to purify the sewage. After sedimentation, the mud and water are separated, and the purified water is discharged from the pool by the decanter.

[0014] The operation process of the SBR biochemical pool is generally divided into a water inlet period, an aeration period, a sedimentation period, a drainage period and an idle period.

[0015] Water inlet period: The process of the reactor accepting sewage. Before the water inlet begins, it is the idle period of the previous cycle. At this time, the water level is low, and there is a high concentration of activated sludge mixed liquid in the reactor. The denitrification time is about 2 hours. During the water filling process, there is a mixture of pollutants in the SBR reactor and the pollutants are adsorbed, absorbed, and oxidized by the activated sludge in the pool. As the concentration of liquid pollutants continues to increase, the rate of adsorption, absorption, and oxidation continues to accelerate. During the water filling period, anoxic stirring is carried out in the reactor, which has the function of denitrification.

[0016] Aeration period: After the SBR pool is filled with water, aeration is carried out to achieve the purpose of removing BOD and nitrification and denitrification. In the reaction stage, the activated sludge microorganisms are periodically in an environment of high and low concentration substrates, and the reactor also forms an anaerobic-anoxic-aerobic alternating process accordingly, which not only has good organic matter treatment efficiency, but also has good phosphorus removal and denitrification effects. During the operation of the SBR reactor, as the reaction time of the reactor increases, its substrate concentration also changes from high to low. The microorganisms experience a logarithmic growth period, a decelerated growth period, and a decay period. The rate of degradation of organic matter also transitions from a zero-order reaction to a first-order reaction. The concentration of pollutants in each part of the reactor is uniform. The use of a complete mixing reaction can dilute the pollutants in the reactor to the greatest extent and limit the inhibition of pollutants on microorganisms.

[0017] Sedimentation period: After aeration is stopped in the sedimentation process, the activated sludge flocs are subjected to gravity sedimentation and supernatant separation. The SBR tank body is used as a sedimentation tank. There is no phenomenon of flocculated activated sludge being broken. Moreover, the process is carried out under stopped conditions, which is close to an ideal sedimentation tank and is minimally affected by the outside world. It has the advantages of short sedimentation time, high sedimentation efficiency, and no sludge swelling.

[0018] Drainage period: After the sedimentation period, drainage and sludge discharge are carried out. The surface clear liquid is removed through the decanter as the water level changes until the lowest water level is reached. Most of the settled activated sludge at the bottom of the reaction tank is used as the activated sludge for the next cycle, and the excess sludge is led out and discharged. The remaining part of the treated water in the reaction tank can serve as circulating water and dilution water.

[0019] Idle period: Idle period is to restore the activity of microorganisms through static state, and play a certain role in denitrification to remove nitrogen, creating conditions for the next operation cycle. After the idle period, the activated sludge is in a state of nutrient starvation. The unit weight of activated sludge has a large adsorption surface area. Therefore, when entering the water inlet period of the next operation cycle, the activated sludge can give full play to its strong adsorption capacity and effectively play its initial removal role.

[0020] Furthermore, two intermediate water pumps are arranged in the intermediate water tank to regulate the water volume during the process.

[0021] Furthermore, the filter uses quartz sand as filter material to filter and adsorb sewage.

[0022] Furthermore, the disinfection pool adjusts the chloride ions in the sewage by adding sodium hypochlorite, and collects the treated water for reuse as reclaimed water.

[0023] The beneficial effects of the present invention are: The modified walnut shell prepared by the invention has a good effect of removing the difficult-to-biodegrade substances in the domestic sewage of bulk cargo terminals, and can increase the biodegradability of the sewage; the modified walnut shell adsorbs the surface active components in the sewage through hydrophilicity, electrostatic and hydrogen bonding; by loading flocculants and coagulants, the suspended matter that is difficult to biodegrade in the sewage is fully precipitated to avoid entering the biochemical pool to affect the sludge biochemical effect and microbial activity, thereby greatly improving the processing capacity and stability of subsequent reactors; by combining N, P and K elements, nutrients are provided to microorganisms, the biodegradability of the sewage is increased, and the problems of high content of difficult-to-biodegrade chemical substances suspended in domestic sewage, poor biodegradability and low sludge content are solved to the greatest extent. DETAILED DESCRIPTION

[0024] The principles and features of the present invention are described below in conjunction with embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0025] The preparation of modified walnut shells comprises the following steps: Step (1): crushing the walnut shells to a particle size of 0.8-1.3 mm, placing the crushed walnut shells in deionized water and heating them, boiling the crushed walnut shells in deionized water for 15 minutes, and then vacuum drying them at 70° C. for 2 hours; Step (2): placing the walnut shells treated in step (1) into a mixed solution of polyaluminium chloride and aluminium sulfate, stirring at 35°C for 65 minutes, and then vacuum drying at 70°C for 2 hours; the mass fraction of polyaluminium chloride in the mixed solution is 2%, the mass fraction of aluminium sulfate is 1%, and the mass ratio of the walnut shells to the mixed solution is 1:5.5; Step (3): placing the walnut shells treated in step (2) into a mixed solution of polyacrylamide and activated silicic acid, stirring at 35°C for 180 minutes, and then vacuum drying at 70°C for 2 hours; the mass fraction of polyacrylamide in the mixed solution is 0.2%, the mass fraction of activated silicic acid is 1%, and the mass ratio of the walnut shells to the mixed solution is 1:4.8; Step (4): slowly dripping a mixed solution of potassium nitrate solution and diammonium hydrogen phosphate solution onto the walnut shells treated in step (3) until the walnut shells are immersed, leaving the solution to stand for 4 hours and then vacuum drying at 70° C. for 2 hours; the mass fraction of potassium nitrate in the mixed solution is 18%, and the mass fraction of diammonium hydrogen phosphate is 15%.

[0026] Example 1 A bulk cargo terminal domestic sewage treatment system comprises a water collection sedimentation tank, a pre-reaction tank, a biochemical tank, an intermediate water tank, a filter, and a disinfection water tank connected in sequence; the system is used to treat domestic sewage from a bulk cargo terminal of bauxite.

[0027] (1) Domestic sewage flows into the water collection and sedimentation tank through the pipe network. The water collection and sedimentation tank includes a filter screen and a mechanical screen cleaning machine. The water collection and sedimentation tank is filtered through the filter screen and the mechanical screen cleaning machine to remove large particles of impurities and pollutants; small and medium-sized particles such as ore powder, coal powder, sand and soil that are easy to settle are separated by gravity sedimentation. The water level difference before and after the screen is 500mm. When the water level difference reaches 300mm, the slag needs to be cleaned. The time required for the water level difference to reach 300mm is recorded. The screen cleaning cycle is set based on this time. The effluent of the water collection and sedimentation tank is lifted into the pre-reaction tank, and the water pump makes the effluent flow rate at 40t / h.

[0028] (2) The pre-reaction tank mainly regulates the non-biodegradable chemical substances suspended in the sewage, and adds modified walnut shells to react under aeration conditions to increase the biodegradability of the sewage. The fan is used as the power to distribute it to each aerator through the air duct, and tiny bubbles are released from the micropores on the aerator to increase the solubility of oxygen in the water and ensure that the dissolved oxygen is above 2 mg / L. The sewage and modified walnut shells are mixed in a mass ratio of 15:2 and aerated for 3 hours. The pre-reaction tank is equipped with a mixing belt. According to the water temperature control, the heating power is turned off when the water temperature is higher than 25°C, and the heating power is turned on when the water temperature is lower than 20°C. The effluent from the pre-reaction tank enters the SBR biochemical tank through the lifting pump, and the water pump makes the effluent flow rate at 40t / h.

[0029] (3) The SBR biochemical pool system is divided into water intake, aeration, sedimentation, decanting, and stagnation (sludge discharge) according to the set program. The amount of water intake each time is controlled according to the liquid level of the SBR biochemical pool. The times are 30 min, 330 min, 70 min, 30 min, and 20 min respectively. The SBR biochemical pool is equipped with a mixing belt. According to the temperature control of the SBR biochemical pool, the heating power is turned off when the water temperature is higher than 25°C, and it is automatically heated when it is less than 15°C. After each program of the decanter is started, it is controlled according to the liquid level. The decanting time is set to 30 minutes. When the decanter of the SBR biochemical pool reaches the low liquid level, it is delayed for 3 minutes and the decanter returns to the working high liquid level. The upper opening of the exhaust pipe of the decanter should be 200mm above the water surface, and there should be no blockage in the pipe. The sludge discharge electric valve discharges sludge for 2 minutes per cycle, and the sludge discharge valve automatically opens and closes. The SBR biochemical pool is operated in two cycles per day during this period, and the water treatment volume in each cycle is 60m 3 .

[0030] (4) The effluent from the SBR biochemical pool is decanted from the decanter to the intermediate water tank. The intermediate water tank has the function of regulating the water volume in the process and is equipped with two intermediate water pumps. When the intermediate water pump is started, the outlet valve should be adjusted to an outlet flow rate of about 7-15t / h. The water pump in the intermediate water tank lifts the sewage into the filter.

[0031] (5) The filter is fed with coagulant PAC through a tubular mixer, which causes small suspended solids and large organic matter in the water to condense into larger particles, and then further filters and adsorbs the sewage through quartz sand as filter material in the filter. Automatic filter processing capacity: 10-15t / h, automatic gravity operation.

[0032] Ratio and dosage of flocculant: The designed dosage of biochemical effluent flocculant is 20PPm, and the filter water inlet is 15t / h. The dosage of flocculant is 15t / h×20PPm÷1000=0.3kg / h. The concentration of liquid polyaluminium chloride is 10%, and the actual dosage of the metering pump is 3L / h.

[0033] (6) The water from the filter enters the disinfection pool. The disinfection pool sterilizes and disinfects by adding sodium hypochlorite, so that the microorganisms and water indicators of the filtered water meet the water quality standards for domestic miscellaneous water. The dosage (in terms of available chlorine) is 2 mg / L. The treated water is collected and reused as reclaimed water.

[0034] The indicators of domestic sewage from bauxite bulk cargo terminal before and after treatment are shown in Table 1.

[0035] Table 1 Various indicators before and after domestic sewage treatment

[0036] Example 2 A domestic sewage treatment system for bulk cargo terminals comprises a water collection sedimentation tank, a pre-reaction tank, a biochemical tank, an intermediate water tank, a filter, and a disinfection water tank; the domestic sewage of bulk cargo terminals of iron ore and coal powder is treated.

[0037] (1) Domestic sewage flows into the water collection sedimentation tank through the pipe network. When the water level difference before and after the screen reaches 500mm, the slag needs to be cleared. The time required for the water level difference to reach 300mm is recorded, and the screen cleaning cycle is set based on this time. The effluent from the water collection sedimentation tank is lifted into the pre-reaction tank, and the water pump makes the effluent flow rate at 40t / h.

[0038] (2) The pre-reaction tank mainly regulates the non-biodegradable chemical substances suspended in the sewage, and adds modified walnut shell adsorption surfactant products to react under aeration conditions to increase the biodegradability of the sewage. The fan is used as the power to distribute it to each aerator through the air duct, and tiny bubbles are released from the micropores on the aerator to increase the solubility of oxygen in the water and ensure that the dissolved oxygen is above 2 mg / L. The sewage and modified walnut shell are mixed in a mass ratio of 10:1 and aerated for 2 hours. The pre-reaction tank is equipped with a mixing belt. According to the water temperature control, the heating power is turned off when the water temperature is higher than 25°C, and the heating power is turned on when the water temperature is lower than 20°C. The effluent from the pre-reaction tank enters the SBR biochemical tank through the lifting pump. The water pump makes the effluent flow rate at 40t / h.

[0039] (3) The SBR biochemical pool system runs according to the set program: water intake, aeration, sedimentation, decanting, and stagnation (sludge discharge). The amount of water intake each time is controlled according to the liquid level of the SBR biochemical pool. The times are 30 min, 330 min, 70 min, 30 min, and 20 min respectively. The SBR biochemical pool is equipped with a mixing belt. According to the temperature control of the SBR pool, the heating power is turned off when the water temperature is higher than 25°C, and it is automatically heated when it is less than 15°C. After each program of the decanter is started, it is controlled according to the liquid level. The decanting time is set to 30 minutes. When the decanter of the SBR biochemical pool reaches the low liquid level, it is delayed for 3 minutes and the decanter returns to the working high liquid level. The upper opening of the exhaust pipe of the decanter should be 200 mm above the water surface, and there should be no blockage in the pipe. The sludge discharge electric valve discharges sludge for 2 minutes per cycle, and the sludge discharge valve automatically opens and closes. The SBR biochemical pool is operated in two cycles per day during this period, and the water treatment volume in each cycle is 60 m 3 .

[0040] (4) The effluent from the SBR biochemical pool is decanted from the decanter to the intermediate water tank. The intermediate water tank has the function of regulating the water volume in the process and is equipped with two intermediate water pumps. When the intermediate water pump is started, the outlet valve should be adjusted to an outlet flow rate of about 7-15t / h. The water pump in the intermediate water tank lifts the sewage into the filter.

[0041] (5) The filter is fed with coagulant PAC through a tubular mixer, which causes small suspended solids and large organic matter in the water to condense into larger particles, and then further filters and adsorbs the sewage through quartz sand as filter material in the filter. Automatic filter processing capacity: 10-15t / h, automatic gravity operation.

[0042] Ratio and dosage of flocculant: The designed dosage of biochemical effluent flocculant is 20PPm, and the filter water inlet is 15t / h. The dosage of flocculant is 15t / h×20PPm÷1000=0.3kg / h. The concentration of liquid polyaluminium chloride is 10%, and the actual dosage of the metering pump is 3L / h.

[0043] (6) The water from the filter enters the disinfection pool. The disinfection pool sterilizes and disinfects by adding sodium hypochlorite, so that the microorganisms and water indicators of the filtered water meet the water quality standards for domestic miscellaneous water. The dosage (in terms of available chlorine) is 1~3mg / L. The treated water is collected and reused as reclaimed water.

[0044] The indicators before and after the treatment of domestic sewage from the iron ore and coal powder bulk cargo terminal are shown in Table 2.

[0045] Table 2 Various indicators before and after domestic sewage treatment

[0046] Comparative Example 1 The difference from Example 1 is that the modified walnut shells are replaced with unmodified walnut shells.

[0047] The indicators of domestic sewage from bauxite bulk cargo terminal after treatment are shown in Table 3.

[0048] Table 3 Various indicators after domestic sewage treatment

[0049] Comparative Example 2 The difference from Example 2 is that the modified walnut shells are replaced with unmodified walnut shells.

[0050] The indicators of domestic sewage from iron ore and coal powder bulk cargo terminal after treatment are shown in Table 4.

[0051] Table 4 Various indicators after domestic sewage treatment

[0052] Comparative Example 3 The difference from Example 1 is that the modified walnut shell is replaced by "no substance for adsorption or reaction is used in the pre-reaction tank".

[0053] The indicators of domestic sewage from bauxite bulk cargo terminal after treatment are shown in Table 5.

[0054] Table 5 Various indicators after domestic sewage treatment

[0055] 1. The removal rates of various test items in Example 1 and Example 2 are shown in Table 6.

[0056] Table 6 Removal rates of various test items in Example 1 and Example 2

[0057] The difference between COD and BOD5 indicates the organic matter in sewage that is difficult to be decomposed by microorganisms. The BOD5 / COD ratio is used to indicate the biodegradability of sewage. When BOD5 / COD < 0.3, it is considered that the biodegradability of sewage is poor and it is not suitable to use biological treatment methods. Example 1 The sewage BOD5 / COD = 0.29 < 0.3, Example 2 The sewage BOD5 / COD = 0.27 < 0.3, the biodegradability of sewage is poor, and the effect of treating wastewater only by activated sludge method is not ideal. Example 1 and Example 2 add a pre-reaction tank before the SBR reactor. It can be seen from the removal rates of various parameters in Example 1 and Example 2 that the removal rates of BOD5 and COD are both above 94%, and the removal rates of ammonia nitrogen and total phosphorus are both above 98%. It can be seen that the pre-reaction tank pre-treats the suspended chemical substances that are not easy to biodegrade in sewage, and the effect of increasing the biodegradability of sewage under aeration conditions by adding modified walnut shells is obvious. Compared with Example 2, Example 1 has a larger mass fraction of the modified walnut shell adsorption surfactant product added, and the aeration time is also longer. Judging from the removal rate of various indicators, Example 1 has a better effect. It can be seen that the walnut shell adsorption surfactant product has a good effect in this process.

[0058] 2. The removal rates of various test items in Example 1 and Comparative Example 1 are shown in Table 7.

[0059] Table 7 Removal rates of various test items in Example 1 and Comparative Example 1

[0060] Comparative Example 1 treats the same wastewater as Example 1, but replaces the modified walnut shell with an unmodified ordinary walnut shell; it can be seen from the removal rates of various parameters in Example 1 and Comparative Example 1 that the removal rates of BOD5, COD, ammonia nitrogen, and total phosphorus in Comparative Example 1 are all lower than 60%. It was found in the process that the sludge activity in the SBR reactor during the treatment of Comparative Example 1 was low; the subsequent filter was easily clogged, reducing the service life of the filter material. It can be seen that the pre-reaction tank pre-treats the suspended non-biodegradable chemical substances in the sewage, and the effect of increasing the biodegradability of the sewage under aeration conditions by adding modified walnut shells is obvious.

[0061] 3. The removal rates of various test items in Example 2 and Comparative Example 2 are shown in Table 8.

[0062] Table 8 Removal rates of various test items in Example 2 and Comparative Example 2

[0063] Comparative Example 2 treated the same wastewater as Example 2, but replaced the modified walnut shell with an unmodified ordinary walnut shell; the removal rates of various parameters in Example 2 and Comparative Example 2 showed that the removal rates of BOD5, COD, ammonia nitrogen, and total phosphorus in Comparative Example 2 were all lower than 60%. It was found that the sludge activity in the SBR reactor during the treatment of Comparative Example 2 was low; the subsequent filter was easily clogged, reducing the service life of the filter material. The addition of the modified walnut shell adsorption surfactant product under aeration conditions increased the biodegradability of the sewage significantly.

[0064] 4. The removal rates of various test items in Example 1 and Comparative Example 3 are shown in Table 9.

[0065] Table 9 Removal rates of various test items in Example 1 and Comparative Example 3

[0066] Comparative Example 3 treats the same wastewater as Example 1. No adsorption or reaction substances are used in the pre-reaction tank of Comparative Example 3. The removal rates of various parameters in Example 1 and Comparative Example 3 show that the removal rates of BOD5, COD, ammonia nitrogen and total phosphorus in Comparative Example 3 are all lower than 50%. It was found that the sludge activity in the SBR reactor during the treatment of Comparative Example 3 was low; the subsequent filter was easily clogged, reducing the service life of the filter material. It can be seen that the effect of increasing the biodegradability of sewage under aeration conditions by adding the modified walnut shell adsorption surfactant product is obvious.

[0067] The modified walnut shell prepared by the invention absorbs the non-biodegradable substances in sewage through excellent hydrophilicity, electrostatic and hydrogen bonding, and increases the nutrients required by microorganisms, thereby solving the problems of high content of non-biodegradable chemical substances suspended in domestic sewage, poor biodegradability and low sludge content to the greatest extent.

[0068] The modified walnut shells prepared by the present invention have a good removal effect on the difficult-to-biodegrade substances in the domestic sewage of bulk cargo terminals, and can increase the biodegradability. This is because the modified walnut shells prepared by the present invention adsorb the difficult-to-biodegrade substances in the sewage through hydrophilicity, electrostatic and hydrogen bonding, and combine N, P, and K elements through chemical bonds, provide nutrients to microorganisms, and increase the biodegradability of sewage. Provide a more favorable living environment for microorganisms, help the sewage treatment ecosystem composed of various microbial components such as bacteria, fungi, and protozoa, and have various types of microbial systems such as suspended aerobic, attached aerobic, attached facultative anoxic, and attached anaerobic, thereby greatly improving the processing capacity and stability of the subsequent SBR reactor.

[0069] The above detection methods, basis and instruments used are shown in Table 10.

[0070] Table 10 Detection methods, basis and instruments used

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A domestic sewage treatment system for bulk cargo terminals, characterized in that: It includes a water collection sedimentation tank, a pre-reaction tank, a biochemical tank, an intermediate water tank, a filter, and a disinfection water tank connected in sequence; The pre-reaction tank includes modified walnut shells, and the preparation method of the modified walnut shells includes the following steps: Step (1): crush the walnut shells, place them in boiling deionized water for 10-20 minutes and then vacuum dry them; Step (2): placing the walnut shells treated in step (1) into a mixed solution of polyaluminium chloride and aluminium sulfate, stirring at 30-40°C for 60-70 minutes, and then vacuum drying; Step (3): placing the walnut shells treated in step (2) into a mixed solution of polyacrylamide and activated silicic acid, stirring at 30-40° C. for 150-200 minutes, and then vacuum drying; Step (4): slowly drip a mixed solution of potassium nitrate solution and diammonium hydrogen phosphate solution onto the walnut shells treated in step (3) until the walnut shells are submerged, let stand for 2-4 hours, and then vacuum dry.

2. The bulk cargo terminal domestic sewage treatment system according to claim 1 is characterized in that: The particle size of the crushed walnut shell is 0.8-1.3 mm; the vacuum drying temperature is 60-80°C.

3. The bulk cargo terminal domestic sewage treatment system according to claim 1, characterized in that: The mass fraction of polyaluminium chloride in the mixed solution in step (2) is 2-5%, the mass fraction of aluminium sulfate is 1-6%, and the mass ratio of walnut shell to the mixed solution is 1:5.

5.

4. The bulk cargo terminal domestic sewage treatment system according to claim 1, characterized in that: The mass fraction of polyacrylamide in the mixed solution in step (3) is 0.2-1.5%, the mass fraction of activated silicic acid is 0.5-4%, and the mass ratio of walnut shell to the mixed solution is 1:4.

8.

5. The bulk cargo terminal domestic sewage treatment system according to claim 1, characterized in that: The mass fraction of potassium nitrate in the mixed solution in step (4) is 15-20%, and the mass fraction of diammonium hydrogen phosphate is 10-20%.

6. The bulk cargo terminal domestic sewage treatment system according to claim 2, characterized in that: The water collection sedimentation tank comprises a filter screen and a mechanical grid cleaning machine which are installed in sequence.

7. The bulk cargo terminal domestic sewage treatment system according to claim 2, characterized in that: The biochemical pool comprises a lift pump, an SBR reactor and a decanter which are connected in sequence.

8. The bulk cargo terminal domestic sewage treatment system according to claim 1, characterized in that: Two intermediate water pumps are arranged in the intermediate water tank.

9. The bulk cargo terminal domestic sewage treatment system according to claim 1, characterized in that: The filter uses quartz sand as filter material to filter and adsorb sewage.

10. The bulk cargo terminal domestic sewage treatment system according to claim 1, characterized in that: The disinfection pool adjusts the chloride ions in the sewage by adding sodium hypochlorite, and collects the treated water for reuse as reclaimed water.

Images