Wastewater treatment system and method for treating kitchen waste wastewater

Abstract

The invention belongs to the technical field of environmental treatment, and particularly relates to a wastewater treatment system and a method for treating kitchen waste water. The sludge subjected to anaerobic fermentation modification in the sludge modification tank is used for adsorbing grease in the kitchen waste water, so that the grease removal rate is increased; effluent of the anoxic tank flows back to the anaerobic tank, sulfide generated by protein decomposition in the anaerobic tank is oxidized into sulfate, and the emission of malodorous gas is reduced; partial nitrate is reduced into nitrite through short-cut denitrification of the anoxic tank, and a substrate is continuously provided for anaerobic ammonia oxidation; and the total nitrogen removal rate is improved on the premise of not additionally adding a carbon source. The anaerobic tank is inoculated with hydrolytic acidification bacteria, refractory organic matters are hydrolyzed into biodegradable organic matters, denitrifying bacteria utilize the biodegradable organic matters to convert nitrite / nitrate into nitrogen, and phosphorus-accumulating bacteria synchronously complete anaerobic phosphorus release; and the aerobic tank uses nitrite / nitrate of the effluent of the anoxic tank as an oxidizing agent to promote phosphorus-accumulating bacteria to absorb phosphorus so as to realize phosphorus removal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental governance, and particularly relates to a wastewater treatment system and a method for treating kitchen wastewater. BACKGROUND

[0002] With the development of garbage classification treatment, a large amount of kitchen garbage is separately collected and disposed, and a small amount of oil, high-concentration organic matter and ammonia exist in the kitchen wastewater generated by the kitchen garbage, and the kitchen wastewater contains refractory organic matter. For the oil in the kitchen wastewater, an oil separation tank or air flotation is currently used for pretreatment. However, the oil separation tank is difficult to effectively treat the micro oil particles emulsified in the wastewater; the air flotation device can only remove 60-70% of the floating oil, and the removal rate of the emulsified micro oil particles (particle size <10 μm) is less than 30%, and the floating oil residue needs to be cleaned regularly, which is easy to cause secondary pollution. The residual oil is easy to wrap on the surface of sludge in the biochemical treatment system, which affects the mass transfer of pollutants in the biochemical process, and reduces the treatment efficiency. Secondly, the existing kitchen garbage is mostly treated by solid-liquid separation and full-mixing fermentation process for energy of organic matter, and the effluent after solid-liquid separation is high-ammonia wastewater with low ratio of degradable organic matter to total nitrogen. The traditional nitrification-denitrification process for denitrification not only needs a large amount of aeration, but also needs a large amount of additional carbon source for supplement, which increases the treatment cost. Overall, the existing process for treating kitchen wastewater has the disadvantages of low treatment efficiency and high operation cost. SUMMARY

[0003] Therefore, the present application provides a wastewater treatment system and a method for treating kitchen wastewater, and the wastewater treatment system provided by the present application can efficiently remove oil in the kitchen wastewater, improve the treatment efficiency, and reduce the wastewater treatment cost.

[0004] In order to solve the above technical problems, the present application provides a wastewater treatment system, which comprises an oil removal tank, an anaerobic tank, an anoxic tank, an anaerobic tank, an aerobic tank, a sedimentation tank and a sludge modification tank which are sequentially connected; The sedimentation tank is connected to the inlet of the anaerobic tank through a first backflow pipeline, and the sludge modification tank is connected to the inlet of the oil removal tank through a second backflow pipeline; The outlet of the anoxic tank is connected to the inlet of the anaerobic tank through a third backflow pipeline; The outlet of the anoxic tank is connected to the inlet of the aerobic tank through a cross-pipe.

[0005] Preferably, the oil removal tank contains a solid-liquid separation device; The anaerobic tank comprises an upflow anaerobic sludge blanket reactor or an internal circulation anaerobic reactor; The solid outlet of the oil removal tank is connected to the solid inlet of the sludge modification tank.

[0006] The application further provides a method for treating kitchen waste water by using the wastewater treatment system. The kitchen waste water is introduced into the oil removal tank to be treated by oil absorption with the modified sludge backflow from the sludge modification tank, so as to obtain oil removal effluent; The oil removal effluent is introduced into the anaerobic tank to be subjected to anaerobic decomposition of organic matter, and the backflow liquid of the effluent from the anoxic tank is used to treat the anaerobic decomposition product of the organic matter, so as to obtain first anaerobic effluent; The first anaerobic effluent is introduced into the anoxic tank to be subjected to short-cut denitrification-nitrosation-anaerobic ammonia oxidation reaction, so as to obtain first anoxic effluent; Part of the first anoxic effluent is introduced into the anaerobic tank to be inoculated with hydrolytic acidification bacteria, denitrifying bacteria and phosphorus accumulating bacteria to be subjected to hydrolytic acidification, denitrification reaction and anaerobic phosphorus release respectively, so as to obtain second anaerobic effluent; The second anaerobic effluent and another part of the first anoxic effluent are introduced into the aerobic tank to be subjected to ammonia nitrogen reaction and phosphorus removal, and then are transferred to the sedimentation tank, so as to obtain effluent meeting the standard and sludge respectively; The sludge is transferred to the sludge modification tank to be subjected to anaerobic fermentation and then dehydration, so as to obtain dewatered sludge.

[0007] Preferably, the mass ratio of the kitchen waste water and the modified sludge backflow from the sludge modification tank in the oil absorption process is 1:1-2; The sludge concentration in the oil removal tank is above 10000 mg MLSS / L.

[0008] Preferably, the conditions in the anaerobic tank include that the temperature is 25-35℃, the pH value is 6.5-8.5, and the organic load is 1-5 kg COD / (m 3 .d); The concentration of free ammonia in the first anaerobic effluent is below 80 mg / L, and the concentration of sulfide in the first anaerobic effluent is below 1 mg / L.

[0009] Preferably, the conditions in the anoxic tank include that the temperature is 25-35℃, the dissolved oxygen concentration is 0.5-1 mg / L when the ammonia nitrogen concentration in the anoxic tank is below 100 mg / L, and the dissolved oxygen concentration is 1-2 mg / L when the ammonia nitrogen concentration in the anoxic tank is above 100 mg / L.

[0010] Preferably, the ratio of the COD concentration to the total phosphorus concentration in the first anoxic effluent is above 30; The ratio of the influent mass into the anaerobic tank to the influent mass into the aerobic tank is one tenth of the ratio of the COD concentration to the total phosphorus concentration in the first anoxic effluent.

[0011] Preferably, the conditions of the anaerobic tank include: temperature of 15-35℃, pH value of 6.0-7.5, sludge concentration of 3000-5000 mg MLSS / L.

[0012] Preferably, the conditions of the aerobic tank include: when the ratio of total nitrogen concentration to total phosphorus concentration in the influent of the aerobic tank is greater than 3, the dissolved oxygen is 2-3 mg / L; when the ratio of total nitrogen concentration to total phosphorus concentration in the influent of the aerobic tank is less than 3, the dissolved oxygen is 3-4 mg / L.

[0013] Preferably, the conditions of anaerobic fermentation in the sludge modification tank include: the concentration of oil in the sludge is 50-100 mg / L, and the sludge retention time is 7-15 days.

[0014] The sludge modified by the sludge modification tank (the proportion of lipids and hydrophobic proteins is increased to more than 65%, and the contact angle is >95°) is used to adsorb the oil (emulsified oil particles) in the kitchen wastewater, and the adsorption rate is more than 96%, so that the concentration of oil in the oil-removed effluent is <5 mg / L, which is reduced by more than 80% compared with the prior art; at the same time, the sludge adsorbing oil can be transported to the sludge modification tank for anaerobic fermentation, realizing "waste treatment with waste", solving the pain point of "difficult oil residue disposal" in the existing process, and improving the problem of methane yield reduction caused by oil pollution in the anaerobic tank. At the same time, the amount of water flowing back from the anoxic tank to the anaerobic tank is controlled, the sulfide produced by the decomposition of protein in the anaerobic tank is oxidized to sulfate, and the emission amount of malodorous gas (H2S) is reduced by more than 90%. Through short-cut denitrification in the anoxic tank, part of the nitrate is reduced to nitrite (nitrite accumulation rate >80%), which continuously provides substrate for anaerobic ammonia oxidation; finally, the total nitrogen removal rate is more than 90%, without additional carbon source, the aeration energy consumption is reduced by 40%, and the sludge production is reduced by 35%, breaking through the limitation of "high consumption and high carbon source dependence" in the prior art. The present application inoculates hydrolytic acidification bacteria in the anaerobic tank, hydrolyzes the refractory organic matter into biodegradable organic matter (such as small molecular organic acid); at the same time, denitrifying bacteria convert nitrite / nitrate into nitrogen gas using biodegradable organic matter, and phosphorus-accumulating bacteria complete anaerobic phosphorus release (phosphorus release amount >20 mgP / gVSS) simultaneously; the aerobic tank uses nitrite / nitrate in the effluent of the anoxic tank as an oxidant to promote the phosphorus uptake of phosphorus-accumulating bacteria (phosphorus uptake amount >30 mgP / gVSS), and finally the total phosphorus removal rate is more than 98%, and the hydrolysis rate of refractory organic matter is up to 90%, without chemical agents, solving the problem of "high cost and high chemical sludge" in the existing phosphorus removal technology. Through modification of the sludge in the sludge modification tank, the adsorption capacity of the sludge for oil pollution is improved, the consumption of reagents in the oil removal process is reduced, and the problem of low organic matter removal rate caused by oil pollution wrapping microorganisms in the anaerobic methanation process is strengthened. The wastewater treatment system provided by the present application can efficiently treat kitchen wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1A structural schematic diagram of a wastewater treatment system used in an embodiment of the present application. DETAILED DESCRIPTION

[0016] The present application provides a wastewater treatment system, comprising an oil removal tank, an anaerobic tank, an anoxic tank, an anaerobic tank, an aerobic tank, a sedimentation tank and a sludge modification tank connected in sequence. The sedimentation tank is connected to the inlet of the anaerobic tank through a first reflux pipeline; the sludge modification tank is connected to the inlet of the oil removal tank through a second reflux pipeline. The outlet of the anoxic tank is connected to the inlet of the anaerobic tank through a third reflux pipeline. The outlet of the anoxic tank is connected to the inlet of the aerobic tank through a cross-pipeline.

[0017] As a specific embodiment of the present application, the oil removal tank contains a solid-liquid separation device; the present application can use the solid-liquid separation device to separate the system after oil removal. As a specific embodiment of the present application, the solid outlet of the oil removal tank is connected to the solid inlet of the sludge modification tank, so that the sludge after oil removal in the oil removal tank can be transported into the sludge modification tank for modification (anaerobic fermentation).

[0018] As a specific embodiment of the present application, the anaerobic tank can include an upflow anaerobic sludge bed reactor or an internal circulation anaerobic reactor.

[0019] Figure 1 A structural schematic diagram of a wastewater treatment system used in an embodiment of the present application.

[0020] The present application also provides a method for treating kitchen wastewater by using the wastewater treatment system described in the above technical solution, comprising the following steps: The kitchen wastewater is introduced into the oil removal tank for oil absorption treatment by using the modified sludge refluxed from the sludge modification tank, to obtain oil removal effluent; The oil removal effluent is introduced into the anaerobic tank for organic matter anaerobic decomposition, and the reflux liquid of the anoxic tank effluent is used to treat the organic matter anaerobic decomposition product to obtain first anaerobic effluent; The first anaerobic effluent is introduced into the anoxic tank for short-cut denitrification-nitrosation-anaerobic ammonia oxidation reaction to obtain first anoxic effluent; Part of the first anoxic effluent is introduced into the anaerobic tank to inoculate hydrolytic acidification bacteria, denitrifying bacteria and phosphorus accumulating bacteria for hydrolytic acidification, denitrification reaction and anaerobic phosphorus release, respectively, to obtain second anaerobic effluent; The second anaerobic effluent and another part of the first anoxic effluent are introduced into the aerobic tank for ammonia nitrogen reaction and phosphorus removal, and then transferred to the sedimentation tank to obtain effluent meeting the standard and sludge, respectively. The sludge is transferred to the sludge modification tank for anaerobic fermentation and then dewatered to obtain dewatered sludge.

[0021] As one of the specific embodiments of the present application, the mass concentration of oil in the kitchen waste water can be 85-190 mg / L, which can be specifically 90 mg / L, 100 mg / L, 115 mg / L, 130 mg / L, 140 mg / L, 160 mg / L or 180 mg / L; the COD in the kitchen waste water can be 3200-5800 g / L, which can be specifically 3500 mg / L, 3800 mg / L, 4000 mg / L, 4500 mg / L, 5000 mg / L or 5500 mg / L; the ammonia nitrogen content in the kitchen waste water can be 220-430 mg / L, which can be specifically 250 mg / L, 280 mg / L, 300 mg / L, 350 mg / L or 400 mg / L; the total phosphorus in the kitchen waste water can be 18-38 mg, which can be specifically 22 mg / L, 25 mg / L, 30 mg / L or 35 mg / L; the ratio of the refractory organic matter (humic acid) to the COD in the kitchen waste water can be 28-36%, which can be specifically 30%, 32%, 33% or 35%.

[0022] As one of the specific embodiments of the present application, the mass ratio of the kitchen waste water to the modified sludge of the sludge modification tank reflux in the oil absorption process can be 1:1-2, which can be specifically 1:1.2 or 1:1.5; the sludge concentration in the oil removal tank can be 10000 mgMLSS / L or more, which can be specifically 11500 mgMLSS / L or 13000 mgMLSS / L.

[0023] The modified sludge of the sludge modification tank reflux can efficiently adsorb and remove the oil in the kitchen waste water, and the oil removal rate is 96% or more.

[0024] After obtaining the oil removal effluent, the present application passes the oil removal effluent into an anaerobic tank for organic matter anaerobic decomposition, and uses the reflux liquid of the anoxic tank effluent to treat the organic matter anaerobic decomposition product to obtain the first anaerobic effluent. As one of the specific embodiments of the present application, the conditions in the anaerobic tank include: the temperature can be 25-35℃, which can be specifically 30℃ or 32℃; the pH value can be 6.5-8.5, which can be specifically 7.2 or 7.8; the organic load can be 1-5 kgCOD / (m 3 .d), which can be specifically 2 kgCOD / (m 3 .d), 3.2 kgCOD / (m 3 .d) or 4 kgCOD / (m 3d); the present application does not have special requirements for the oxygen content in the anaerobic tank, and the oxygen concentration can be set according to the conventional anaerobic condition. As a specific embodiment of the present application, the concentration of free ammonia in the first anaerobic effluent can be 80 mg / L or less, and can be 72 mg / L or 78 mg / L; the concentration of sulfide in the first anaerobic effluent can be 1 mg / L or less, and can be 0.9 mg / L or 0.8 mg / L. The return amount of the return flow of the anoxic tank effluent is determined according to the concentration of free ammonia and sulfide in the first anaerobic effluent, as long as it can meet the above concentration range.

[0025] The present application can oxidize more than 80% of the degradable organic matter methane gas in the kitchen waste water under the above conditions, and the present application returns the anoxic tank effluent to the anaerobic tank to oxidize the sulfide (such as H2S) produced in the process of protein decomposition in the anaerobic tank into sulfate using nitrate or nitrite in the anoxic tank, reducing the toxicity of hydrogen sulfide to microorganisms and the generation of malodorous gas in the methanation process.

[0026] After obtaining the first anaerobic effluent, the present application passes the first anaerobic effluent into the anoxic tank for short denitrification-nitrification-anaerobic ammonia oxidation reaction to obtain the first anoxic effluent. As a specific embodiment of the present application, the conditions in the anoxic tank include: the temperature can be 25~35℃, and can be 30℃ or 32℃; when the ammonia nitrogen concentration in the anoxic tank is 100 mg / L or less, the dissolved oxygen concentration can be 0.5~1 mg / L, and when the ammonia nitrogen concentration in the anoxic tank is greater than 100 mg / L, the dissolved oxygen concentration can be 1~2 mg / L; the present application increases the concentration of dissolved oxygen to promote the conversion of excessive ammonia nitrogen into nitrite or nitrate, to provide more nitrite or nitrate for the anaerobic tank, and to improve the ability of the entire system to resist nitrogen load impact.

[0027] The present application makes full use of the small amount of degradable organic matter remaining in the anaerobic tank effluent (first anaerobic effluent) to reduce part of the nitrate produced in the denitrification-anaerobic ammonia oxidation process to nitrite, to continuously provide substrate for the anaerobic ammonia oxidation process, and to reduce the total nitrogen concentration of the effluent.

[0028] After the first anoxic effluent is obtained, part of the first anoxic effluent is introduced into an anaerobic tank to inoculate hydrolytic acidification bacteria, denitrifying bacteria and phosphorus accumulating bacteria to respectively perform hydrolytic acidification, denitrification and anaerobic phosphorus release, and a second anaerobic effluent is obtained. In the present application, the hydrolytic acidification bacteria can be Clostridium. As a specific embodiment of the present application, the ratio of COD concentration to total phosphorus concentration in the first anoxic effluent is 30 or more, which can be specifically 31, 35 or 38, and the ratio of COD concentration to total phosphorus concentration in the first anoxic effluent is limited in the above range, so that no additional carbon source is needed; the ratio of the influent mass of the anaerobic tank to the influent mass of the aerobic tank can be one tenth of the ratio of COD concentration to total phosphorus concentration in the first anoxic effluent. The present application can provide hydrolytic acidification bacteria, denitrifying bacteria and phosphorus accumulating bacteria by the way of returning sludge in the sedimentation tank to the anaerobic tank.

[0029] As a specific embodiment of the present application, the conditions of the anaerobic tank include: the temperature can be 15-35℃, which can be specifically 20℃, 25℃ or 30℃; the pH value can be 6.0-7.5, which can be specifically 6.5, 6.8 or 7; the sludge concentration can be 3000-5000 mg MLSS / L, which can be specifically 4000 mg MLSS / L, 4200 mg MLSS / L, 4500 mg MLSS / L or 4800 mg MLSS / L; the present application has no special requirements for the oxygen content in the anaerobic tank, and the oxygen concentration can be set according to the conventional anaerobic conditions.

[0030] In the present application, the anaerobic tank inoculates hydrolytic acidification bacteria to hydrolyze and acidify 50-80% of the refractory organic matter in the anoxic tank effluent into biodegradable organic matter, while the denitrifying bacteria convert nitrite and nitrate in the anoxic tank effluent into nitrogen gas by using the biodegradable organic matter, and the phosphorus accumulating bacteria complete the anaerobic phosphorus release process by using the biodegradable organic matter.

[0031] After the second anaerobic effluent is obtained, the second anaerobic effluent and another part of the first anoxic effluent are introduced into an aerobic tank to perform ammonia nitrogen reaction and phosphorus removal, and then transferred to a sedimentation tank to obtain effluent water and sludge respectively. As a specific embodiment of the present application, the mass ratio of the other part of the first anoxic effluent to the total amount of the first anoxic effluent can be 0.8-0.9:1; the conditions of the aerobic tank include: when the ratio of total nitrogen (nitrite and nitrate) concentration to total phosphorus concentration in the influent of the aerobic tank is 3 or more (which can be specifically 3.5 or 4), the dissolved oxygen can be 2-3 mg / L, which can be specifically 2 mg / L or 2.5 mg / L; when the ratio of total nitrogen concentration to total phosphorus concentration in the influent of the aerobic tank is less than 3, the dissolved oxygen can be 3-4 mg / L.

[0032] In the present application, 20-50% of the nitrite or nitrate in the anoxic tank effluent is used as an oxidizing agent in the aerobic tank to promote phosphorus accumulating microorganisms to complete phosphorus removal.

[0033] The present application returns part of the sludge to the anaerobic tank after separating the sludge and water in the sedimentation tank, and the rest of the sludge enters the sludge modification tank.

[0034] After obtaining the sludge, the present application transfers the sludge to the sludge modification tank for anaerobic fermentation and dehydration to obtain the dewatered sludge. As one specific embodiment of the present application, the conditions for anaerobic fermentation in the sludge modification tank include that the concentration of oil in the sludge can be 50-100 mg / L, which can be specifically 80 mg / L or 90 mg / L; the sludge retention time can be 7-15 days, which can be specifically 8 days, 10 days or 13 days. In the present application, the oil can include vegetable oil and / or clear oil; additional addition is needed when the concentration of oil in the sludge is insufficient (less than 50 mg / L); in the present application, the sludge is induced by oil during the anaerobic fermentation process at a specific oil concentration, which promotes the sludge to secrete more hydrophobic EPS, thereby increasing the surface contact angle of the modified sludge and improving the selective adsorption of the modified sludge to oil, so as to realize efficient oil removal of the modified sludge in the oil removal tank.

[0035] As one specific embodiment of the present application, the dehydration can be pressure filtration.

[0036] The present application promotes the microorganisms in the sludge to secrete more hydrophobic EPS (such as lipids and hydrophobic proteins) through anaerobic fermentation, replaces the original hydrophilic EPS (such as polysaccharides), continuously improves the hydrophobicity of the sludge surface, and the surface contact angle of the sludge is > 90°, thereby improving the selective adsorption of the modified sludge to oil.

[0037] The kitchen wastewater treatment method provided by the present application uses the modified sludge to adsorb oil and grease, recovers energy by methanation of organic matter, and realizes low-carbon denitrification and efficient hydrolysis of refractory organic matter through short-cut denitrification-nitrosation-anaerobic ammonia oxidation integrated reaction.

[0038] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0039] Example 1 Residential kitchen wastewater treatment project Project background: The kitchen wastewater of a certain city residential area contains a large amount of emulsified oil, high concentration of organic matter and ammonia nitrogen, and the water quality fluctuates greatly. The water quality indexes of the influent are as follows: oil 115 mg / L, COD 3800 mg / L, ammonia nitrogen 280 mg / L, total phosphorus 22 mg / L, and refractory organic matter (humic acid) accounting for 28% of COD.

[0040] Utilize Figure 1 The key parameters of the wastewater treatment system shown in the figure for treating kitchen wastewater are as follows: Oil removal tank: the mass ratio of modified sludge return flow to influent is 1.2, and the sludge concentration is 11500 mg MLSS / L; Anaerobic tank: temperature 30℃, pH 7.2, organic load 3.2 kgCOD / (m 3 .d), the effluent of the anoxic tank controls the free ammonia in the effluent of the anaerobic tank to be 72 mg / L and the sulfide to be 0.8 mg / L; the conditions of the anoxic tank: temperature 30℃, dissolved oxygen concentration 0.8 mg / L; the COD of the effluent of the anaerobic tank is 810 mg / L, and the total phosphorus is 20 mg / L; the influent ratio of the anaerobic tank to the aerobic tank is 3.5:1; Anaerobic tank: temperature 25℃, pH 6.8, sludge concentration 4200 mg MLSS / L, influent COD / total phosphorus = 35>30, no need for additional carbon supplement; Aerobic tank: (nitrite + nitrate) / total phosphorus = 3.5, dissolved oxygen 2.0 mg / L; Anaerobic fermentation in the sludge modification tank: the concentration of oil is 100 mg / L, and the residence time is 10 days.

[0041] Treatment effect: Effluent indicators: oil 3.1 mg / L (removal rate 97.3%), COD 175 mg / L (removal rate 95.4%), ammonia nitrogen 7.5 mg / L (removal rate 97.3%), total phosphorus 0.7 mg / L (removal rate 96.8%), and the hydrolysis rate of refractory organic matter reaches 76%; Cost comparison: compared with the existing "oil removal tank + traditional nitrification and denitrification + chemical phosphorus removal" process, the aeration energy consumption of the treatment method in the embodiment is reduced by 42%, there is no carbon source and chemical agent cost, and the sludge production is reduced by 40%.

[0042] Example 2 Restaurant centralized area kitchen waste wastewater treatment project Project background: a city restaurant centralized area produces kitchen waste wastewater, and the wastewater has high oil content and high refractory organic matter content.

[0043] Influent water quality indicators: oil 190 mg / L, COD 5200 mg / L, ammonia nitrogen 430 mg / L, total phosphorus 38 mg / L, and refractory organic matter (long-chain fatty acids) accounting for 33% of COD.

[0044] Utilize Figure 1 The key parameters of the wastewater treatment system shown in the figure for treating kitchen waste wastewater are as follows: Oil removal tank: the mass ratio of modified sludge return flow to influent is 1.5, and the sludge concentration is 13000 mg MLSS / L; Anaerobic tank: temperature 32℃, pH 7.8, organic load 4.0 kgCOD / (m 3d), the anoxic tank effluent return flow control anaerobic tank free ammonia 78 mg / L, sulfide 0.9 mg / L; the anoxic tank conditions: temperature 30℃, dissolved oxygen concentration is 0.8 mg / L; anaerobic tank effluent COD is 1100 mg / L, total phosphorus is 35 mg / L, anaerobic tank and the aerobic tank influent ratio is 3.1:1; Anaerobic tank: temperature 30℃, pH 7.2, sludge concentration 4800 mgMLSS / L, influent COD / total phosphorus=31>30, no need for additional carbon supplement; Aerobic tank: (nitrite + nitrate) / total phosphorus=4.0, dissolved oxygen 2.5 mg / L.

[0045] Anaerobic fermentation in sludge modification tank: oil concentration is 100 mg / L, residence time is 10 days.

[0046] Treatment effect: Effluent indicators: oil 4.3 mg / L (removal rate 97.7%), COD 210 mg / L (removal rate 96.0%), ammonia nitrogen 9.8 mg / L (removal rate 97.7%), total phosphorus 0.9 mg / L (removal rate 97.6%), and hydrolysis rate of refractory organic matter 73%. Cost comparison: the treatment method of the embodiment reduces the operation cost by 55% (membrane replacement cost saving + reagent cost saving) compared with the existing "air flotation + membrane separation + traditional denitrification + chemical phosphorus removal" process, and shortens the treatment cycle by 30% (from 12h to 8.4h).

[0047] Although the above embodiment has made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and people can also obtain other embodiments according to the embodiment without creativity, which all belong to the protection scope of the present application.

Claims

1. A wastewater treatment system, characterized in that, It includes an oil removal tank, an anaerobic tank, an anoxic tank, an anaerobic tank, an aerobic tank, a sedimentation tank, and a sludge modification tank connected in sequence. The sedimentation tank is connected to the inlet of the anaerobic tank via a first return pipe; the sludge modification tank is connected to the inlet of the oil removal tank via a second return pipe. The outlet of the anoxic tank is connected to the inlet of the anaerobic tank via a third reflux pipe. The outlet of the anoxic tank is connected to the inlet of the aerobic tank via a bypass pipe.

2. The wastewater treatment system according to claim 1, characterized in that, The oil removal tank contains a solid-liquid separation device; The anaerobic tank includes an upflow anaerobic sludge bed reactor or an internal circulation anaerobic reactor. The solids outlet of the oil removal tank is connected to the solids inlet of the sludge modification tank.

3. A method for treating kitchen wastewater using the wastewater treatment system described in claim 1 or 2, characterized in that, Includes the following steps: The kitchen wastewater is fed into the oil removal tank and the modified sludge returned from the sludge modification tank is used for oil absorption treatment to obtain oil-removed effluent. The oil-removed effluent is fed into an anaerobic tank for anaerobic decomposition of organic matter. The reflux liquid from the anoxic tank is used to treat the anaerobic decomposition products of the organic matter to remove sulfides, thus obtaining the first anaerobic effluent. The first anaerobic effluent is fed into an anoxic tank to undergo a short-cut denitrification-nitrification-anaerobic ammonium oxidation reaction to obtain the first anoxic effluent. A portion of the first anoxic effluent is fed into an anaerobic tank and inoculated with hydrolytic acidifying bacteria, denitrifying bacteria, and polyphosphate-accumulating bacteria to carry out hydrolytic acidification, denitrification, and anaerobic phosphorus release reactions, respectively, to obtain the second anaerobic effluent. The second anaerobic effluent and another part of the first anoxic effluent are fed into the aerobic tank for ammonia nitrogen reaction and phosphorus removal, and then transferred to the sedimentation tank to obtain qualified effluent and sludge, respectively. The sludge is transferred to a sludge modification tank for anaerobic fermentation and then dewatered to obtain dewatered sludge.

4. The method for treating kitchen wastewater according to claim 3, characterized in that, The mass ratio of kitchen wastewater to modified sludge returned from the sludge modification tank during the oil absorption process is 1:1~2. The sludge concentration in the oil removal tank is above 10,000 mg MLSS / L.

5. The method for treating kitchen wastewater according to claim 3, characterized in that, The conditions in the anaerobic digester include: a temperature of 25-35℃, a pH of 6.5-8.5, and an organic loading rate of 1-5 kg ​​COD / (m³). 3 .d); The concentration of free ammonia in the first anaerobic effluent is below 80 mg / L, and the concentration of sulfide in the first anaerobic effluent is below 1 mg / L.

6. The method for treating kitchen wastewater according to claim 3, characterized in that, The conditions in the anoxic tank include: a temperature of 25~35℃; a dissolved oxygen concentration of 0.5~1mg / L when the ammonia nitrogen concentration in the anoxic tank is below 100mg / L, and a dissolved oxygen concentration of 1~2mg / L when the ammonia nitrogen concentration in the anoxic tank is above 100mg / L.

7. The method for treating kitchen wastewater according to claim 3, characterized in that, The ratio of COD to total phosphorus concentration in the first anoxic effluent is greater than 30; The ratio of the mass of the first anoxic effluent entering the anaerobic tank to the mass of the effluent entering the aerobic tank is one-tenth of the ratio of COD to total phosphorus concentration in the first anoxic effluent.

8. The method for treating kitchen wastewater according to claim 3 or 7, characterized in that, The conditions of the anaerobic tank include: temperature of 15~35℃, pH value of 6.0~7.5, and sludge concentration of 3000~5000mgMLSS / L.

9. The method for treating kitchen wastewater according to claim 3, characterized in that, The conditions for the aerobic tank include: when the ratio of total nitrogen concentration to total phosphorus concentration in the influent of the aerobic tank is greater than 3, the dissolved oxygen is 2~3 mg / L; when the ratio of total nitrogen concentration to total phosphorus concentration in the influent of the aerobic tank is less than 3, the dissolved oxygen is 3~4 mg / L.

10. The method for treating kitchen wastewater according to claim 3, characterized in that, The conditions for anaerobic fermentation in the sludge modification tank include: the concentration of oil in the sludge is 50~100mg / L, and the sludge retention time is 7~15 days.

Images