Lime-sulfur solution for enhancing effect of sulfur autotrophic denitrification and dephosphorization and application thereof

Abstract

The application discloses a lime-sulfur solution for enhancing the effect of sulfur autotrophic denitrification and phosphorus removal and application thereof, and is characterized in that sulfur and lime are mixed according to a mass ratio of 1-2:1, then the mixture is mixed with a calcium chloride-sulfide solution with a proper concentration and heated to make the sulfur basically dissolved, so as to obtain an alkaline lime-sulfur solution; the lime-sulfur solution is added into influent of a denitrification filter according to the demand of denitrification and phosphorus removal, dissolved reduced sulfur is used as an electron donor of autotrophic denitrification, and calcium ions are used as a precipitant for phosphorus removal. In the lime-sulfur solution prepared by the application, the dissolved sulfur added into wastewater promotes the electron transfer between sulfur and microorganisms, the alkalinity of the lime-sulfur solution helps to neutralize the sulfur autotrophic acid production and stabilize the pH value at 8-9, and promotes the growth of hydroxyapatite and the removal of phosphorus.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of simultaneous advanced denitrification and phosphorus removal of sewage in sewage treatment plants, and more particularly to a technical method for simultaneous denitrification and phosphorus removal by sulfur autotrophy. BACKGROUND

[0002] In recent years, with the increasing severity of water eutrophication, especially the widespread occurrence of urban black and odorous rivers, nitrate nitrogen and total nitrogen have been included in the pollution discharge and water control indicators, and more and more stringent nitrogen control standards have been formulated in various places.

[0003] Nitrification-heterotrophic denitrification has been the mainstream technology for wastewater denitrification. Through the aerobic biochemical process, organic nitrogen and ammonia nitrogen in water are converted into nitrate, and then the wastewater is returned to the anoxic tank, using the organic matter in the wastewater as an electron donor, and through heterotrophic denitrification microorganisms, nitrate nitrogen is converted into nitrogen gas. Heterotrophic denitrification denitrification technology also encounters some obstacles to meet the increasingly stringent total nitrogen water quality standards: first, a very high reflux ratio is required to make the total nitrogen meet the higher discharge standards, resulting in a large water treatment tank area, high energy consumption, and a substantial increase in cost; second, due to the long residence time of wastewater in the septic tank and drainage pipeline, there is a microbial degradation process of organic matter, which has consumed part of the carbon source, resulting in insufficient carbon source and low carbon-nitrogen ratio in wastewater entering the wastewater treatment plant, which cannot meet the demand of heterotrophic denitrification for organic carbon; third, in the case of insufficient carbon source, especially in high-nitrogen industrial wastewater, an anaerobic biological filter is generally added after the secondary sedimentation tank to add organic carbon for denitrification by heterotrophic denitrifying bacteria, but the addition of sodium acetate and other agents leads to high denitrification cost, and improper control of the addition amount also leads to high COD in the effluent, causing secondary pollution.

[0004] In order to make up for the deficiency of heterotrophic denitrification and meet the needs of advanced wastewater treatment, sulfur autotrophic denitrification technology has developed rapidly in recent years as a representative autotrophic denitrification technology. Sulfur autotrophic denitrification is a process in which denitrifying sulfur bacteria, a kind of facultative anaerobic microorganism, uses inorganic carbon as a carbon source to complete the synthesis metabolism, and uses sulfur and reduced sulfur compounds (thiosulfate, sulfite, sulfide, iron-sulfide minerals, sulfur) as electron donors to reduce nitrate to nitrogen gas. Iron-sulfide minerals such as pyrite and pyrrhotite are highly concerned because of their low cost and abundant output, but the main problem of iron-sulfide mineral autotrophic denitrification is that the reaction speed is very slow and the land area occupied is too large, which cannot meet the needs of wastewater treatment plant denitrification engineering. Sulfur as an electron donor has a faster denitrification reaction speed than iron-sulfide minerals, and is becoming the mainstream direction of sulfur autotrophic development.

[0005] Sulfur autotrophic denitrification technology has the advantages of abundant sulfur resources, low cost, less sludge production, and low treatment cost, and is currently a hot spot in the field of denitrification research and engineering technology. The autotrophic denitrification process using sulfur as an electron donor produces water acidification, and limestone and other carbonates are usually used as a medium to stabilize the pH of the system. The existing sulfur-limestone autotrophic denitrification system is to mix limestone and elemental sulfur particles in a certain proportion as filler, or to granulate the mixture of limestone powder and sulfur as filler, and then load it into a reaction filter column for sewage treatment. Limestone dissolves continuously during the treatment process, thereby buffering the decrease in pH.

[0006] Currently, sulfur autotrophic denitrification technology still has the following outstanding problems:

[0007] (1) Slow denitrification rate of solid sulfur autotrophic denitrification material. Sulfur autotrophic denitrification materials, including sulfur, iron sulfide minerals, etc., can significantly reduce denitrification costs compared to sodium acetate, but the slow denitrification rate is a big problem. Because sulfur autotrophic denitrification materials are all insoluble solids, their interaction with microorganisms requires complex electron transfer mediators in the microbial metabolism process, which is the key factor restricting the denitrification reaction rate and the fundamental reason for the slow sulfur autotrophic denitrification rate. The heterotrophic denitrification anaerobic biological deep filter usually adds sodium acetate, and when the hydraulic retention time is 25-40 min, it can stably achieve the control requirements of nitrate nitrogen and total nitrogen. However, the existing sulfur autotrophic denitrification technology requires a hydraulic retention time of more than 100 min, and most natural iron sulfide autotrophic denitrification requires a hydraulic retention time of more than 4 h, which leads to high construction investment of sulfur autotrophic denitrification treatment tanks and poor economic efficiency. How to improve the biological reaction speed of sulfur autotrophic denitrification and make the denitrification reaction hydraulic retention time reach or approach the hydraulic retention time of heterotrophic denitrification is a key technical problem that needs to be solved urgently.

[0008] (2) Simultaneous denitrification and phosphorus removal. With the increasing emphasis on water environmental protection and the continuous improvement of discharge standards, many regions require the discharge of sewage treatment plants to meet the Class IV standard of surface water (dissolved oxygen 3 mg / L, COD 30 mg / L, total phosphorus 0.3 mg / L, and total nitrogen 1.5 mg / L). Sewage treatment plants not only face denitrification problems but also face phosphorus removal problems. Existing sewage treatment plants generally use iron and aluminum chemical precipitation-magnetic flocculation separation for phosphorus removal and heterotrophic denitrification deep bed filter for denitrification. Although iron sulfide minerals can simultaneously remove nitrogen and phosphorus, the denitrification rate is too slow to meet the requirements of sewage treatment plants for denitrification rate. Sulfur autotrophic denitrification has a faster denitrification rate than pyrite and pyrrhotite, but the denitrification method using sulfur as an electron donor does not have a significant phosphorus removal effect. How to achieve fast denitrification and simultaneous phosphorus removal in the same sulfur autotrophic denitrification filter is a difficult problem in water treatment.

[0009] Lime sulfur, also known as lime sulfur mixture, is prepared by lime, sulfur and water. The common ratio of sulfur, lime and water is 2:1:10. It is dark brown liquid with a smell and alkaline. It is easy to generate free sulfur and calcium sulfate in the air, and it must be stored in a sealed manner. It is used for sterilization, insecticide and acaricide, and is also used in gardening and veterinary. There is no report on its application in water treatment field. SUMMARY

[0010] The present application provides a preparation method of lime sulfur solution for enhancing the effect of sulfur autotrophic denitrification and phosphorus removal and application thereof through a large number of static and dynamic synchronous denitrification and phosphorus removal experimental researches, so as to solve the problems existing in the prior art and provide technical support for the application of sulfur autotrophic denitrification and phosphorus removal in the field of sewage treatment.

[0011] In order to solve the technical problems, the present application adopts the following technical solutions:

[0012] The present application discloses a preparation method of lime sulfur solution for enhancing the effect of sulfur autotrophic denitrification and phosphorus removal, which comprises the following steps:

[0013] (1) Selecting sulfur raw material with dry basis elemental sulfur content not less than 70%, including any one or more of industrial desulfurization by-product sulfur powder, natural sulfur, desulfurization hydrogen by-product sulfur paste, liquid sulfur purification by-product sulfur residue cake and solid waste rich in sulfur.

[0014] (2) Selecting lime raw material: calcium oxide content not less than 90%.

[0015] (3) Preparing calcium chloride-sulfide solution: preparing calcium chloride-sulfide solution with calcium chloride (solid calcium chloride or high-concentration calcium chloride solution) and solid calcium sulfide or solid sodium sulfide, so as to obtain calcium chloride-sulfide solution with calcium chloride mass concentration of 1-5% and sulfur ion mass concentration of 0-2%.

[0016] (4) Preparing ingredients: adding sulfur raw material and lime raw material into the reaction container according to the mass ratio of 1-2:1, and then adding calcium chloride-sulfide solution according to the solid-liquid mass ratio of 1:15-20.

[0017] (5) Dissolving: stirring the materials in the reaction container and heating to boiling, and then keeping warm for more than 20 min to dissolve sulfur, so as to obtain alkaline lime sulfur solution (pH=10-11).

[0018] (6) Storage: transferring the lime sulfur solution in the reaction container to the storage tank by pump for standby.

[0019] The lime-sulfur solution prepared by the preparation method can be used for enhancing the effect of sulfur autotrophic denitrification and phosphorus removal: according to the concentration of nitrate nitrogen and phosphate in wastewater and the demand for denitrification and phosphorus removal, the lime-sulfur solution is metered and added to the influent of an anaerobic denitrification and denitrification tank, and the nitrate nitrogen is reduced to nitrogen by the denitrifying microorganisms in the denitrification tank, the elemental sulfur is used as the electron donor for autotrophic denitrification and denitrification, the calcium ions are used as the precipitant for phosphorus removal, the alkalinity of the lime-sulfur solution helps to neutralize the sulfur autotrophic acid production, the pH is stabilized at 8-9, the growth of hydroxyapatite and the phosphorus removal are promoted.

[0020] Further, the present application proposes a starting and operating method of a lime-sulfur enhanced sulfur autotrophic denitrification and phosphorus removal reaction tank constructed by using the lime-sulfur solution, which is Method One or Method Two.

[0021] Method One includes the following steps:

[0022] (1) The electronic donor is replaced in the heterotrophic denitrification and denitrification filter tank of a normally operated sewage treatment plant, and the organic carbon source solution (such as sodium acetate, glucose, and methanol) is directly replaced by the lime-sulfur solution in a gradient, that is, according to the concentration of nitrate nitrogen and phosphate in wastewater and the demand for denitrification and phosphorus removal, the organic carbon source solution is gradually reduced to zero in 15 days, the addition amount of the lime-sulfur solution is gradually increased from zero to 100% of the demand, and the microbial community in the denitrification filter tank is gradually evolved from heterotrophic denitrification microorganisms to sulfur autotrophic denitrification microorganisms.

[0023] (2) After the sulfur autotrophic denitrification microbial membrane on the surface of the filler is matured, the lime-sulfur solution is added to the influent of the denitrification filter tank according to the mass ratio of nitrate nitrogen to elemental sulfur in the influent of 1:1-2.

[0024] (3) The lime-sulfur solution is added according to the metering ratio of step (2) for 1-2 weeks of denitrification and denitrification operation, and the nitrate, total nitrogen, total phosphorus, calcium ion, and pH in the effluent are monitored, the addition amount of the lime-sulfur solution is slightly adjusted according to the denitrification effect, and finally the total nitrogen in the effluent is stably reached to the discharge standard.

[0025] (4) Under the premise of stable denitrification effect, the amount of lime used in the preparation of the lime-sulfur solution is adjusted according to the pH monitoring result of the effluent, so that the pH of the effluent is stably kept at 8-9.

[0026] (5) Under the premise of stable denitrification effect and effluent pH, the concentration of calcium chloride in the preparation of the lime-sulfur solution is adjusted, and the concentration of calcium chloride is as low as possible under the premise of meeting the phosphorus removal effect.

[0027] Method Two includes the following steps:

[0028] (1) The filter material is filled in the newly built anaerobic denitrification filter tank, and the filter material is preferably 3-6 mm collophanite particles.

[0029] (2) Fill the denitrification filter with the wastewater to be treated, and add commercially available or on-site enriched autotrophic denitrification bacteria solution at 1-5% of the water volume in the filter.

[0030] (3) Use a water pump to drive the effluent from the denitrification filter back to the inlet. The hydraulic retention time is 2-6 hours for water circulation to promote the formation of microbial biofilm on the surface of the packing material.

[0031] (4) During the biofilm formation process of water circulation microorganisms, nitrates are continuously or intermittently added to the influent to maintain the nitrate nitrogen concentration in the influent at 20-50 mg / L. At the same time, lime sulfur solution is added to the influent to maintain the mass ratio of elemental sulfur to nitrate nitrogen in the influent at 1.5-2.5.

[0032] (5) Monitor the pH of the effluent and adjust the amount of lime-sulfur solution added to stabilize the pH of the filter effluent at 8-9. Allow the biofilm to form in the water circulation for 5-15 days. When the nitrate nitrogen removal rate in the effluent reaches more than 70%, the biofilm formation of denitrifying thiobacillus is considered to be basically mature.

[0033] (6) Use the wastewater to be treated as influent and operate in an open circuit with a hydraulic retention time of 20-60 minutes (i.e., direct discharge of effluent). Add lime-sulfur solution to the influent of the filter bed according to the mass ratio of nitrate nitrogen to elemental sulfur in the influent of 1.9:1. Monitor the nitrate, total nitrogen, total phosphorus, calcium ions and pH in the effluent. Adjust the amount of lime-sulfur solution added slightly according to the denitrification effect, so that the total nitrogen in the effluent can stably meet the discharge standard.

[0034] (7) Under the premise of stabilizing the denitrification effect and the pH of the effluent, adjust the concentration of calcium chloride when preparing the lime-sulfur solution. Under the premise of satisfying the phosphorus removal effect, select the lowest possible concentration of calcium chloride.

[0035] The inventiveness and beneficial effects of this invention are reflected in:

[0036] (1) The traditional method for preparing lime sulfur involves mixing sulfur, lime, and water in a ratio of 2:1:50-75 and heating the mixture in a container to boiling for at least 40 minutes. In the heated alkaline lime solution, elemental sulfur undergoes a disproportionation reaction to generate sulfide ions and thiosulfates (Equation 1). The sulfide ions further react with elemental sulfur to form polysulfides (Equation 2), thus forming a lime sulfur solution rich in elemental sulfur, sulfide ions, and thiosulfates, which is used for insecticidal and sterilization purposes in landscaping or veterinary medicine industries. The method of this invention uses calcium chloride and sulfide solutions in the preparation of lime sulfur. The sulfide ions in these solutions can promote the conversion of solid elemental sulfur into soluble polysulfides, reducing the lime sulfur preparation temperature or shortening the boiling time, reducing energy consumption, and avoiding excessively high pH levels in the effluent during water treatment due to excessive lime addition.

[0037] S+OH - ------S 2- +S2O3 2-+ 3H2O (1)

[0038] (n-1)S + S 2- -----S n 2- (n=2~5) (2)

[0039] (2) The sulfur autotrophic simultaneous denitrification and phosphorus removal agent is prepared by using the principle of heating dissolution of sulfur in lime alkaline solution and sulfur ion promoting dissolution of sulfur, and the lime sulfur solution is used for sulfur autotrophic denitrification for the first time. The soluble reduced sulfur species in lime sulfur is the electron donor for autotrophic denitrification, which can migrate more easily in aqueous solution, and can directly cross the cell membrane of Thiobacillus denitrificans to occur denitrification reaction in the cell, thereby overcoming the obstacles existing in the interaction and electron transfer between solid sulfur and denitrifying microorganisms, greatly improving the rate of sulfur autotrophic denitrification, and providing a new technical scheme for solving the problem of sulfur autotrophic denitrification rate.

[0040] (3) The lime sulfur prepared by the present application is used for sulfur autotrophic denitrification, which is helpful for simultaneous denitrification and phosphorus removal. The appropriate alkalinity of lime sulfur helps to neutralize the sulfur autotrophic acid production and stabilize the pH at 8-9, so as to meet the pH requirement of wastewater discharge, promote the growth of hydroxyapatite and phosphorus removal. The production rate of apatite is affected by the supersaturation degree, and the higher the pH and calcium ion concentration of the solution (equation 3), the higher the supersaturation degree, the faster the growth of apatite, and the lower the residual phosphate concentration in water. Under the premise of not affecting the metabolic rate of microorganisms and not exceeding the discharge standard, it is beneficial to improve the pH as much as possible to remove phosphates. In the process of preparing lime sulfur solution, calcium chloride is added to improve the calcium ion concentration in lime sulfur and promote the removal of phosphorus, and the requirements of sulfur autotrophic denitrification and phosphorus removal for reduced sulfur species concentration, pH and calcium ion concentration in the process of simultaneous denitrification and phosphorus removal are coupled.

[0041] 3HPO4 2- + 5Ca 2+ + 4OH - ---Ca5 (PO4) 3 (OH) + 3H2O (3)

[0042] (4) Preferably, collophanite is used as the filter material of the denitrification filter to overcome the nucleation barrier of apatite on the surface of the phosphorus removal filter material, and to improve the denitrification rate. Collophanite is a sedimentary phosphorite composed of nanometer apatite, micro-fine quartz, dolomite or calcite, and has large particle strength, porosity and good water resistance. As the denitrification filter material, the apatite in the collophanite can induce the growth of apatite, so as to simultaneously remove phosphorus in depth during the denitrification process. Generally, in the aqueous solution, when the concentrations of hydroxyl ions, calcium ions and phosphate are lower than the solubility product of apatite, it is difficult to form apatite, which is attributed to the nucleation barrier of apatite crystals. When the collophanite is used as the filter material for denitrification, due to the existence of nanometer apatite crystals and intergranular voids, the phosphate ions, calcium ions and hydroxyl ions in the water can diffuse to the surface of the apatite crystals to be fixed and grown, so as to overcome the nucleation barrier of the crystals, provide appropriate hydroxyl ions (increase pH) and calcium ions to the water, promote the growth of apatite and consume phosphate, and thus achieve deep phosphorus removal. DETAILED DESCRIPTION

[0043] The embodiments of the present application are described in detail below, which are implemented on the premise of the technical solutions of the present application, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present application is not limited to the following embodiments.

[0044] Embodiment 1

[0045] Commercially available sulfur powder is purchased, and the content of elemental sulfur is 99%. Commercially available lime powder is purchased, and the content of calcium oxide is 95%. Anhydrous calcium chloride is purchased, and 20 g of the anhydrous calcium chloride is weighed and added to 1 L of water to prepare a 2% calcium chloride solution. 40 g of the sulfur powder and 20 g of the lime powder are weighed and added to a 1 L glass beaker, and 900 mL of the 2% calcium chloride aqueous solution is added. The beaker is placed on an electric heating magnetic stirrer, and the sulfur is dissolved by heating and boiling for 40 min to obtain an alkaline lime-sulfur solution (pH = 10.5), which is poured into a 1 L container bottle and sealed with a rubber plug for standby use.

[0046] Tap water is used to prepare simulated secondary sedimentation tank effluent as experimental water by adding nitrate, dipotassium hydrogen phosphate and glucose, wherein the nitrate nitrogen is 20 mg / L, the COD is 30 mg / L, and the TP is 2 mg / L.

[0047] A plastic pipe with a diameter of 80 mm and a height of 400 mm is used to prepare a simulated sulfur autotrophic deep denitrification filter, and the filter is filled with collophanite particles with a particle size of 3-5 mm.

[0048] The anaerobic sludge from a sewage treatment plant is used as a strain of autotrophic denitrifying bacteria, and the bacteria are enriched by directional culture in a sodium thiosulfate liquid medium (medium composition (g / L): Na2S2O3·5H2O, 5.0; KH2PO4, 2.0; KNO3, 2.0; NaHCO3, 1.0; NH4Cl, 0.5; MgCl2·6H2O, 0.5; FeSO4·7H2O, 0.01) to obtain a liquid of autotrophic denitrifying bacteria.

[0049] The denitrification filter is filled with the simulated secondary sedimentation tank effluent, and a 3-mm plastic tube is used to connect the outlet of the denitrification filter, a peristaltic pump, a bacteria liquid bottle, and the inlet of the denitrification filter. The peristaltic pump is used to inject 100 mL of the enriched and cultured autotrophic denitrifying bacteria liquid into the denitrification filter, and water circulation is performed at a hydraulic retention time of 3 h to promote the biofilm formation on the surface of the filler.

[0050] During the water circulation biofilm formation, nitrate is intermittently added to the influent to maintain a nitrate nitrogen concentration of 50 mg / L in the influent, and lime sulfur solution is added to the influent to maintain a mass ratio of elemental sulfur to nitrate nitrogen of 2.0:1 in the influent. The pH of the effluent is monitored, and the effluent pH is stabilized at 8.5-9. After 7 days of water circulation, the biofilm of the denitrifying bacteria is basically mature.

[0051] The prepared simulated wastewater is delivered to the denitrification filter by using a peristaltic pump, and the filter is operated in an upflow mode with a hydraulic retention time of 30 min. The peristaltic pump is used to add lime sulfur solution to the denitrification influent according to a mass ratio of nitrate nitrogen to elemental sulfur of 1.9:1 in the influent. The nitrate, total nitrogen, total phosphorus, calcium ion, and pH in the effluent are monitored. The amount of lime sulfur solution is slightly adjusted according to the denitrification effect, and finally the total nitrogen in the effluent is stabilized to meet the discharge standard.

[0052] Under the premise of stabilizing the denitrification effect and the effluent pH, the concentration of calcium chloride in the preparation of the lime sulfur solution is adjusted. Under the premise of meeting the phosphorus removal effect, the concentration of calcium chloride is selected to be as low as possible.

[0053] Under the experimental conditions of 20 mg / L of nitrate nitrogen, 2 mg / L of phosphate phosphorus, 30 mg / L of COD in the influent, a hydraulic retention time of 30 min, and a water temperature of 25℃, the experimental results show that the nitrate nitrogen concentration in the effluent is <4 mg / L, and the phosphate phosphorus concentration is <0.2 mg / L, which meets the surface water quality standard III and achieves the purpose of simultaneous denitrification and phosphorus removal of wastewater by sulfur autotrophy.

[0054] Example 2

[0055] Sulfur powder was purchased with 99% of elemental sulfur. Lime powder was purchased with 95% of calcium oxide. Anhydrous calcium chloride and calcium sulfide were purchased. 20 g of anhydrous calcium chloride and 10 g of calcium sulfide were weighed and added to 1 L of water to prepare a calcium chloride-calcium sulfide solution. 40 g of sulfur powder and 20 g of lime powder were weighed and added to a 1 L beaker. 900 mL of the calcium chloride-calcium sulfide solution was added to the beaker. The beaker was placed on an electric magnetic stirrer and heated at 60°C for 30 min to dissolve the sulfur, obtaining an alkaline lime-sulfur solution (pH = 10.5). The solution was poured into a 1 L container bottle and sealed with a rubber plug for later use.

[0056] Tap water was used to prepare simulated secondary sedimentation tank effluent by adding nitrate, dipotassium hydrogen phosphate and glucose. The simulated secondary sedimentation tank effluent contained 20 mg / L of nitrate nitrogen, 30 mg / L of COD and 2 mg / L of TP.

[0057] A plastic pipe with a diameter of 80 mm and a height of 400 mm was used to simulate a sulfur autotrophic deep denitrification filter. The pipe was filled with collophane particles with a particle size of 3-5 mm.

[0058] The denitrification filter was filled with the simulated secondary sedimentation tank effluent. A 3 mm plastic pipe was used to connect the outlet of the denitrification filter, a peristaltic pump, a bacteria solution bottle and the inlet of the denitrification filter. 100 mL of the autotrophic denitrifying bacteria solution (same as in Example 1) was injected into the denitrification filter using the peristaltic pump. Water circulation was carried out at a hydraulic retention time of 3 h to promote the formation of a microbial biofilm on the surface of the filler.

[0059] During the water circulation process for microbial biofilm formation, nitrate was intermittently added to the influent to maintain a nitrate nitrogen concentration of 50 mg / L. Lime-sulfur solution was also added to the influent to maintain a mass ratio of elemental sulfur to nitrate nitrogen of 2.0:1. The pH of the effluent was monitored and stabilized at 8.5-9. After 7 days of water circulation, the denitrifying sulfur bacteria biofilm was basically mature.

[0060] The prepared simulated wastewater was delivered to the denitrification filter using a peristaltic pump. The filter was operated in an upflow mode with a hydraulic retention time of 30 min. Lime-sulfur solution was added to the influent using the peristaltic pump at a mass ratio of nitrate nitrogen to elemental sulfur of 1.9:1. The nitrate, total nitrogen, total phosphorus, calcium ion and pH in the effluent were monitored. The amount of lime-sulfur solution added was adjusted slightly based on the denitrification effect. Finally, the total nitrogen in the effluent was stabilized to meet the discharge standard.

[0061] Under the premise of stable denitrification effect and effluent pH, the concentration of calcium chloride in the preparation of lime-sulfur solution was adjusted. Under the premise of meeting the phosphorus removal effect, the lowest possible concentration of calcium chloride was selected.

[0062] Under the experimental conditions that the influent nitrate nitrogen is 20 mg / L, the influent phosphate phosphorus is 2 mg / L, the influent COD is 30 mg / L, the hydraulic retention time is 30 min and the water temperature is 25 ℃, the experimental results show that the effluent nitrate nitrogen concentration is less than 4 mg / L, the effluent phosphate phosphorus concentration is less than 0.2 mg / L, the surface water quality standard III is met, and the purpose of simultaneous denitrification and phosphorus removal of wastewater sulfur autotrophy is achieved.

[0063] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for starting up and operating a lime-sulfur enhanced autotrophic denitrification and phosphorus removal reactor constructed using a lime-sulfur solution, characterized in that, Includes the following steps: (1) In the heterotrophic denitrification filter of the sewage treatment plant in normal operation, the electron donor is replaced and the organic carbon source solution is directly replaced by lime-sulfur solution gradient. That is, according to the concentration of nitrate nitrogen and phosphate in the wastewater and the requirements for denitrification and phosphorus removal, the amount of organic carbon source solution added is gradually reduced to zero within 15 days, and the amount of lime-sulfur solution added is gradually increased from zero to 100% of the required amount. The microbial community in the denitrification filter gradually evolves from heterotrophic denitrification microorganisms to sulfur autotrophic denitrification microorganisms. (2) After the sulfur autotrophic denitrification microbial film on the packing surface matures, lime sulfur solution is added to the influent of the denitrification filter according to the mass ratio of nitrate nitrogen to elemental sulfur in the influent water of 1:1~2. (3) Add lime-sulfur solution according to the metering ratio in step (2) and run the denitrification process for 1-2 weeks. Monitor the nitrate, total nitrogen, total phosphorus, calcium ions and pH in the effluent. Adjust the amount of lime-sulfur solution added according to the denitrification effect, so that the total nitrogen in the effluent can be stably met the discharge standard. (4) Under the premise of stabilizing the denitrification effect, adjust the amount of lime used in the preparation of lime-sulfur solution according to the pH monitoring results of the effluent, so that the pH of the effluent is stabilized at 8-9; (5) Under the premise of stabilizing the denitrification effect and the pH of the effluent, adjust the concentration of calcium chloride when preparing the lime-sulfur solution, and select the lowest possible concentration of calcium chloride while meeting the phosphorus removal effect; The method for preparing the lime-sulfur solution includes the following steps: (1) Select sulfur raw materials with a dry basis elemental sulfur content of not less than 70%; (2) Select lime raw materials with a calcium oxide content of not less than 90%; (3) Preparation of calcium chloride-sulfide solution: Add water to calcium chloride and solid calcium sulfide or solid sodium sulfide to prepare calcium chloride-sulfide solution with a calcium chloride mass concentration of 1-5% and a sulfide ion mass concentration of 0-2% and not 0. (4) Ingredients: Add sulfur raw material and lime raw material to the reaction vessel at a mass ratio of 1~2:1, and then add calcium chloride-sulfide solution at a solid-liquid mass ratio of 1:15~20; (5) Dissolving: Stir the materials in the reaction vessel and heat to boiling, keep warm for more than 20 minutes to dissolve the sulfur and obtain an alkaline lime-sulfur solution; (6) Storage: Transfer the lime-sulfur solution in the reaction vessel to a storage tank using a pump for later use.

2. A method for starting up and operating a lime-sulfur enhanced autotrophic denitrification and phosphorus removal reactor constructed using a lime-sulfur solution, characterized in that, Includes the following steps: (1) Fill the newly built anaerobic denitrification filter with filter media, which are 3-6mm phosphate rock particles; (2) Fill the denitrification filter with the wastewater to be treated, and add commercially available or on-site enriched autotrophic denitrification bacteria solution at 1-5% of the water volume in the filter. (3) Use a water pump to drive the effluent from the denitrification filter back to the inlet, and run the water circulation for a hydraulic retention time of 2-6 hours to promote the formation of microbial biofilm on the surface of the packing material. (4) During the biofilm formation process of water circulation microorganisms, nitrates are continuously or intermittently added to the influent to maintain the nitrate nitrogen concentration in the influent at 20-50 mg / L. At the same time, lime sulfur solution is added to the influent to maintain the mass ratio of elemental sulfur to nitrate nitrogen in the influent at 1.5-2.5:

1. (5) Monitor the pH of the effluent and adjust the amount of lime-sulfur solution to stabilize the pH of the filter effluent at 8-9. Allow the biofilm to form in the water circulation for 5-15 days. When the nitrate nitrogen removal rate in the effluent reaches more than 70%, the biofilm formation of denitrifying thiobacillus is considered to be basically mature. (6) Use the wastewater to be treated as influent, and run the filter in the open circuit according to the hydraulic retention time of 20-60 minutes. Add lime-sulfur solution to the influent of the filter according to the mass ratio of nitrate nitrogen to elemental sulfur in the influent of 1.9:

1. Monitor the nitrate, total nitrogen, total phosphorus, calcium ions and pH in the effluent. Adjust the amount of lime-sulfur solution added according to the denitrification effect, so that the total nitrogen in the effluent can be stably met the discharge standard. (7) Under the premise of stabilizing the denitrification effect and the pH of the effluent, adjust the concentration of calcium chloride when preparing the lime-sulfur solution, and select the lowest possible concentration of calcium chloride while meeting the phosphorus removal effect; The method for preparing the lime-sulfur solution includes the following steps: (1) Select sulfur raw materials with a dry basis elemental sulfur content of not less than 70%; (2) Select lime raw materials with a calcium oxide content of not less than 90%; (3) Preparation of calcium chloride-sulfide solution: Add water to calcium chloride and solid calcium sulfide or solid sodium sulfide to prepare calcium chloride-sulfide solution with a calcium chloride mass concentration of 1-5% and a sulfide ion mass concentration of 0-2% and not 0. (4) Ingredients: Add sulfur raw material and lime raw material to the reaction vessel at a mass ratio of 1~2:1, and then add calcium chloride-sulfide solution at a solid-liquid mass ratio of 1:15~20; (5) Dissolving: Stir the materials in the reaction vessel and heat to boiling, keep warm for more than 20 minutes to dissolve the sulfur and obtain an alkaline lime-sulfur solution; (6) Storage: Transfer the lime-sulfur solution in the reaction vessel to a storage tank using a pump for later use.