A system and method for defluorination and deamination of glass engraving wastewater

Abstract

This invention discloses a system and method for defluorination and ammonia removal from glass engraving wastewater. The defluorination and ammonia removal method includes the following steps: reacting glass engraving wastewater with an alkaline calcium-containing compound solution to produce a primary mixed liquid; reacting the primary mixed liquid with a fly ash suspension to obtain a secondary mixed liquid; subjecting the secondary mixed liquid to a flocculation reaction to produce a tertiary mixed liquid; filtering the tertiary mixed liquid to produce filtrate, neutralizing the filtrate with an oxalic acid solution, and then sequentially performing coagulation and flocculation reactions to produce a quaternary mixed liquid; subjecting the quaternary mixed liquid to sedimentation separation to produce a supernatant; and subjecting the supernatant to short-cut nitrification and denitrification treatment to produce a defluorinated and deammoniated supernatant. This invention uses fly ash to replace part of the slaked lime for defluorination, separates sludge and water through plate and frame filtration, adjusts the pH with oxalic acid, and adds coagulants and flocculants to achieve decalcification and hardening. The remaining oxalic acid provides a carbon source, and short-cut nitrification and denitrification are used for nitrogen removal, improving the defluorination and ammonia removal efficiency and reducing treatment costs.

Description

Technical Field

[0001] This application belongs to the field of wastewater treatment technology, and in particular relates to a system and method for defluorination and ammonia removal from glass engraving wastewater. Background Technology

[0002] In glass engraving, an etching solution composed of ammonium bifluoride is used to locally corrode the surface of glass products to create various patterns and designs. This process generates highly concentrated acidic wastewater containing fluoride and ammonia nitrogen, with fluoride ion concentrations reaching 1500-2000 mg / L and ammonia nitrogen concentrations approximately 300-600 mg / L, and a pH value of 2-3. Excessive fluoride levels in drinking water can harm human health, while excessive ammonia nitrogen can lead to eutrophication. Therefore, this wastewater requires defluorination and ammonia removal treatment.

[0003] For high-concentration acidic fluoride wastewater, the pH value must first be adjusted by adding alkali. Subsequently, physical or chemical methods are used for treatment, such as aluminum salt adsorption, membrane treatment, and calcium salt precipitation. Aluminum salt adsorption is only suitable for wastewater with fluoride ion concentrations below 10 mg / L; while membrane treatment is effective, its membrane modules are prone to scaling and producing difficult-to-treat concentrates, therefore calcium salt precipitation is the most commonly used method.

[0004] Calcium salt precipitation removes fluoride ions by adding lime or calcium chloride to the wastewater, causing fluoride ions to combine with calcium ions to form calcium fluoride precipitate. However, this method produces very fine calcium fluoride precipitates with a slow precipitation rate. Furthermore, calcium fluoride is only slightly soluble in water, often requiring multi-stage precipitation to achieve satisfactory removal. The precipitation process is time-consuming and inefficient, and the resulting sludge has a high water content (up to 99%), making it difficult to treat. In addition, calcium salt precipitation requires alkaline conditions, necessitating pH adjustment of the precipitated wastewater with inorganic acids. This process often accumulates large amounts of inorganic salts, adversely affecting subsequent treatment processes that require controlled salt concentrations.

[0005] There are various methods for removing ammonia nitrogen from wastewater, including stripping, air stripping, breakpoint chlorination, and biological methods.

[0006] Air stripping, also known as stripping, uses air or steam under alkaline conditions to convert free ammonia in water into gaseous ammonia, thus separating it from the water. The ammonia gas generated during the stripping process needs to be absorbed with dilute acid, and the resulting absorbent is difficult to treat or recover. Furthermore, stripping or air stripping methods are energy-intensive and are more suitable for treating wastewater with ammonia nitrogen concentrations higher than 2000 mg / L.

[0007] Breakpoint chlorination is a chemical denitrification method that oxidizes ammonia nitrogen into nitrogen gas by reacting chlorine gas or sodium hypochlorite with ammonia-containing wastewater. The disadvantages of this method are that it consumes large amounts of chlorine, resulting in high costs, and the treated wastewater contains a large amount of residual chlorine, which may react with organic matter to form toxic haloalkanes, thus requiring additional dechlorination treatment steps.

[0008] Traditional nitrification-denitrification biological nitrogen removal refers to the process by which microorganisms gradually oxidize ammonia nitrogen in wastewater to nitrite and nitrate under aerobic conditions, and then gradually reduce nitrate to nitrite and nitrogen gas under anoxic conditions. That is, ammonia nitrogen → nitrite nitrogen → nitrate nitrogen → nitrite nitrogen → nitrogen gas. This method has a long nitrogen removal process, requires a large amount of carbon source (C / N > 4), and has high operating costs. Because glass engraving wastewater contains very little organic matter (carbon source) that can serve as nutrients for microorganisms, and because large amounts of salt and scale are generated during pH adjustment and defluorination, affecting the normal operation of biological treatment methods, the application of traditional nitrification-denitrification biological nitrogen removal methods in glass engraving wastewater treatment is significantly limited. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this application aims to provide a defluoridation and ammonia removal system and method for glass engraving wastewater, solving the problems of poor removal efficiency and high operating costs associated with existing technologies. In the defluoridation process using calcium salt precipitation, this application partially replaces traditionally used quicklime or calcium chloride with high-calcium fly ash, replaces sedimentation separation with plate and frame filtration technology, and uses oxalic acid instead of inorganic acids for pH adjustment. For ammonia removal, a biological method replaces physicochemical methods, and a short-cut nitrification-denitrification biological nitrogen removal method (i.e., ammonia nitrogen → nitrite nitrogen → nitrogen gas) replaces the traditional nitrification-denitrification biological nitrogen removal method. Through these improvements, this application aims to achieve the goal of treating waste with waste, while reducing reagent dosage, lowering salt content, reducing sludge production, improving treatment efficiency, and reducing operating costs.

[0010] The objective of this application is achieved through the following technical solution:

[0011] A method for defluoridation and ammonia removal from glass engraving wastewater includes the following steps:

[0012] (1) The glass engraving wastewater and the alkaline calcium compound solution are stirred and mixed to carry out the alkali addition and fluoride fixation reaction to produce a primary mixed liquid;

[0013] (2) The primary mixture and the fly ash suspension are stirred and mixed to carry out an alkali-fixing fluoride reaction to produce a secondary mixture;

[0014] (3) The secondary mixture is stirred and mixed with flocculant to carry out flocculation reaction, producing a tertiary mixture;

[0015] (4) The three-stage mixture is filtered and separated to produce filtrate and filter cake;

[0016] (5) Add oxalic acid solution to the filtrate for neutralization reaction, and then add coagulant and flocculant in sequence for coagulation reaction and flocculation reaction respectively to produce a four-stage mixed liquid;

[0017] (6) Sedimentation separation is performed on the fourth stage mixed liquor to produce physicochemical supernatant and physicochemical sludge;

[0018] (7) The physicochemical supernatant is subjected to short-cut nitrification-denitrification biochemical reaction to produce defluorinated and deammoniated biochemical supernatant and biochemical sludge;

[0019] (8) After conditioning the physicochemical sludge and biochemical sludge with a conditioning agent, they are then processed in a dewatering equipment to produce dewatered filtrate and dried sludge cake. The dewatered filtrate is returned to the alkali-fixing fluoride reaction system described in step (2).

[0020] Preferably, in step (1), the concentration of the alkaline calcium-containing compound solution is 8-10%.

[0021] Preferably, the alkaline calcium-containing compound is calcium hydroxide or a mixture of calcium hydroxide and calcium chloride.

[0022] Preferably, in step (1), the amount of alkaline calcium compound solution added makes the pH of the reaction system 7-8.

[0023] Preferably, in step (1), the mixing is carried out by mechanical stirring, and the stirring speed is 60~70 rpm.

[0024] Preferably, in step (1), the reaction time between the glass engraving wastewater and the alkaline calcium-containing compound solution is 0.3~0.5h.

[0025] Preferably, in step (2), the fly ash in the fly ash suspension is high-calcium fly ash, that is, fly ash with a CaO content higher than 10%.

[0026] Preferably, in step (2), the concentration of the fly ash suspension is 15-20%.

[0027] Preferably, in step (2), the amount of fly ash suspension added is such that the pH of the reaction system is 9-10. Preferably, in step (2), the mixing is performed by mechanical stirring at a speed of 60-70 rpm.

[0028] Preferably, in step (2), the reaction time between the primary mixture and the fly ash suspension is 0.3~0.5h.

[0029] Preferably, in step (3), the flocculant is at least one of anionic polyacrylamide and sodium alginate.

[0030] Preferably, when the flocculant in step (3) is anionic polyacrylamide, it is prepared into a flocculant solution of 0.05~0.1% before use.

[0031] Preferably, when sodium alginate is used as the flocculant in step (3), it is prepared into a flocculant solution of 0.1~0.3% before use.

[0032] Preferably, in step (3), the mixing is carried out by mechanical stirring, and the stirring speed is 10~15 rpm.

[0033] Preferably, in step (3), the reaction time between the secondary mixture and the flocculant solution is 0.3~0.5h.

[0034] Preferably, in step (4), a plate and frame filter press is used to filter and separate the three-stage mixture to produce filtrate and filter cake. The working pressure of the plate and frame filter press is set to 0.6~1.0MPa.

[0035] Preferably, in step (5), the concentration of the oxalic acid solution is 8-10%.

[0036] Preferably, in step (5), the amount of oxalic acid solution added is such that the pH of the neutralization reaction system is 7-8.

[0037] Preferably, in step (5), the neutralization reaction is carried out by mechanical stirring, with a stirring speed of 55~65 rpm and a reaction time of 0.1~0.3 h.

[0038] Preferably, in step (5), the coagulation reaction is carried out by mechanical stirring, with a stirring speed of 15~20 rpm and a reaction time of 0.3~0.5 h.

[0039] Preferably, in step (5), the flocculation reaction is carried out by mechanical stirring, with a stirring speed of 10~15 rpm and a reaction time of 0.3~0.5 h.

[0040] Preferably, in step (5), the coagulant is at least one of polyaluminum, aluminum sulfate, polyferric sulfate, ferrous sulfate and ferric chloride.

[0041] Preferably, in step (5), the flocculant is at least one of anionic polyacrylamide and sodium alginate.

[0042] Preferably, the coagulant and flocculant in step (5) are prepared into solutions before use. The coagulant is prepared into a coagulant solution of 8-10%; when anionic polyacrylamide is used as the flocculant, it is prepared into a flocculant solution of 0.05-0.1%; when sodium alginate is used as the flocculant, it is prepared into a flocculant solution of 0.1-0.3%.

[0043] Preferably, in step (6), an inclined plate (tube) sedimentation tank is used to separate the four-stage mixed liquor.

[0044] Preferably, in step (6), the surface load of the inclined plate (tube) sedimentation tank is 1.0~1.5m³ / ㎡·h, and the effluent weir load is ≤2.0L / m·s.

[0045] Preferably, in step (8), the conditioning method of physical and chemical sludge is to mechanically stir and mix physical and chemical sludge and add conditioning agent for chemical conditioning.

[0046] Preferably, in step (8), a plate and frame filter press is used to separate the conditioned mixed sludge into sludge and water, producing dewatered filtrate and dried sludge cake. The working pressure of the plate and frame filter press is set to 0.6~1.0MPa.

[0047] The system used in the above-mentioned method for defluoridation and ammonia removal from glass engraving wastewater includes:

[0048] The primary reaction unit is used to stir and mix the glass engraving wastewater and the alkaline calcium-containing compound solution to carry out an alkali-addition and fluoride-fixing reaction, producing a primary mixed liquid;

[0049] The secondary reaction unit is used to stir and mix the primary mixture with the fly ash suspension to carry out an alkali-addition and fluorine-fixing reaction, thereby producing a secondary mixture.

[0050] The third-stage reaction unit is used to stir and mix the secondary mixture with the flocculant to carry out the flocculation reaction and produce the tertiary mixture.

[0051] The filtration and defluorination unit is used to filter and separate the three-stage mixture to produce filtrate and filter cake.

[0052] The neutralization and flocculation unit is used to receive the filtered liquid and sequentially perform neutralization, coagulation and flocculation reactions to produce a four-stage mixed liquid.

[0053] The decalcification and precipitation unit is used to precipitate and separate the four-stage mixed liquor, producing physicochemical supernatant and physicochemical sludge.

[0054] The short-cut nitrification-denitrification unit is used to perform short-cut nitrification-denitrification treatment on the physicochemical supernatant to produce a defluorinated and deammoniated biochemical supernatant.

[0055] The sludge dewatering unit is used to condition and dewater the physicochemical sludge and biochemical sludge to produce dewatered filtrate and dried sludge.

[0056] Compared with the prior art, the beneficial effects of this application include:

[0057] (1) High-calcium fly ash is an industrial waste that is alkaline when dissolved in water, which can reduce the amount of quicklime used to adjust the pH of wastewater to alkalinity. By partially replacing quicklime with high-calcium fly ash, the calcium ions in the solution can react with fluoride ions to form calcium fluoride precipitate. At the same time, the active alumina in the high-calcium fly ash further reduces the concentration of fluoride ions in the wastewater through adsorption. This method reduces the amount of quicklime used, achieves the purpose of waste treatment, and reduces operating costs.

[0058] (2) Calcium fluoride flocculants are relatively small and settle slowly during gravity sedimentation, resulting in low sedimentation efficiency and sludge in the effluent. By using plate and frame filtration technology, the loose and porous fly ash can form a sludge cake skeleton, allowing the fine calcium fluoride particles to fill the gaps in the skeleton. This not only prevents calcium fluoride from clogging the filter cloth but also improves filtration performance, thereby significantly improving the removal efficiency of fluoride ions.

[0059] (3) During gravity sedimentation, the water content of the settled sludge is as high as 99%. After using plate and frame filtration in this invention, the water content of the sludge can be reduced to about 60%, and the weight and volume of the sludge cake are significantly reduced, thereby greatly reducing the cost of sludge disposal. The dewatered sludge cake can be used as a cement admixture to realize the resource utilization of waste.

[0060] (4) This invention uses organic oxalic acid instead of commonly used inorganic acids such as sulfuric acid and hydrochloric acid to adjust the pH value of wastewater. At the same time, oxalic acid can react with calcium ions to form calcium oxalate with a low solubility product. Then, coagulants and flocculants are used to promote the formation of precipitate and separate it for removal, thereby achieving decalcification and hardening, and eliminating the adverse effects of scale on the short-cut nitrification-denitrification system. In addition, the residual oxalic acid in the wastewater can be used as a carbon source required for the short-cut denitrification process, thereby improving the biodegradability of the wastewater.

[0061] (5) Glass carving wastewater has a high ammonia nitrogen concentration and a low C / N ratio, making short-cut nitrification-denitrification biological methods particularly suitable for nitrogen removal. This method requires less oxygen and less carbon source, achieving energy conservation and consumption reduction. Because the reaction time is relatively short, the volume of the reaction tank can be reduced, thereby lowering investment costs.

[0062] (6) Use short-cut nitrification-denitrification process for biological nitrogen removal. By controlling the reaction conditions, the ammonia nitrogen oxidation process is mainly nitrification, which reduces the demand for alkalinity and dissolved oxygen during nitrification and the amount of carbon source added during denitrification, thereby significantly reducing operating costs. Attached Figure Description

[0063] Figure 1 This is a schematic flowchart of the glass engraving wastewater defluorination and ammonia removal method described in this invention.

[0064] Figure 2This is a schematic diagram of the system used in the glass engraving wastewater defluorination and deammoniation method of the present invention. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0066] First, see Figure 2 , Figure 2 This is a schematic diagram of the system used in the glass engraving wastewater defluorination and deammoniation method of the present invention, including:

[0067] Primary reaction unit 1 is used to mix and stir the glass engraving wastewater and calcium hydroxide solution to carry out an alkali-fixing fluoride reaction, producing a primary mixed liquid;

[0068] Secondary reaction unit 2 is used to mix and stir the primary mixture with the fly ash suspension to carry out an alkali-addition and fluorine-fixing reaction, thereby producing a secondary mixture;

[0069] The third-stage reaction unit 3 is used to mix and stir the second-stage mixture with the flocculant to carry out a flocculation reaction and produce a third-stage mixture.

[0070] The filtration and defluorination unit 4 is used to filter and separate the three-stage mixture to produce filtrate and filter cake.

[0071] Neutralization and flocculation unit 5 is used to receive the filtered liquid and sequentially perform neutralization reaction, coagulation reaction and flocculation reaction to produce a four-stage mixed liquid.

[0072] Decalcification precipitation unit 6 is used to precipitate and separate the four-stage mixed liquor to produce physicochemical supernatant and physicochemical sludge;

[0073] The short-cut nitrification-denitrification unit 7 is used to perform short-cut nitrification-denitrification treatment on the physicochemical supernatant to produce a defluorinated and deammoniated biochemical supernatant.

[0074] The sludge dewatering unit 8 is used to condition and dewater the physicochemical sludge and biochemical sludge to produce dewatered filtrate and dried sludge.

[0075] The primary reaction unit 1 includes a quicklime solution preparation and addition device 11, a primary reaction tank 12, a primary reaction mixer 13, and a first online pH meter 14. The quicklime solution preparation and addition device 11 is used to add a quicklime solution with a concentration of 8% to 10% to the primary reaction tank 12. The first reaction mixer 13 and the first online pH meter 14 are both installed in the primary reaction tank 12. The first reaction mixer 13 is used to rapidly mix and react the added quicklime solution with hydrogen ions and fluoride ions in the water. The stirring speed is 60 to 70 rpm, the pH value of the primary reaction tank 12 is controlled at 7 to 8, and the reaction time is 0.3 to 0.5 h. The first online pH meter 14 is used to control the amount of quicklime solution added in conjunction with the quicklime solution preparation and addition device 11.

[0076] The secondary reaction unit 2 includes a fly ash suspension preparation and addition device 21, a secondary reaction tank 22, a second reaction mixer 23, and a second online pH meter 24. The fly ash suspension preparation and addition device 21 is used to add a fly ash suspension with a concentration of 15-20% to the secondary reaction tank 22. The second reaction mixer 23 and the second online pH meter 24 are both installed in the secondary reaction tank 22. The second reaction mixer 23 is used to rapidly mix and react the added fly ash suspension with fluoride ions in the water. The stirring speed is 60-70 rpm. The pH value of the secondary reaction tank 22 is controlled at 9-10, and the reaction time is 0.3-0.5 h. The second online pH meter 24 is used to control the amount of fly ash suspension added in conjunction with the fly ash suspension preparation and addition device 21.

[0077] In some embodiments of the present invention, high-calcium fly ash, i.e., fly ash with a CaO content higher than 10%, is used. High-calcium fly ash is alkaline after dissolving in water, which can reduce the amount of quicklime used to adjust the pH of wastewater to 9-10. Due to its high calcium content, high-calcium fly ash can provide sufficient calcium ions, which then react with fluoride ions to form calcium fluoride precipitate.

[0078] The three-stage reaction unit 3 includes a first flocculant preparation and dosing device 31, a three-stage reaction tank 32, and a third reaction mixer 33; the first flocculant preparation and dosing device 31 is used to add a first flocculant solution (0.05%~0.1% anionic polyacrylamide or 0.1~0.3% sodium alginate or both) to the three-stage reaction tank 32, and the third reaction mixer 33 has a stirring speed of 10~15 rpm.

[0079] The filtration and defluorination unit 4 includes a filtration feed tank 41, a feed mixer 42, a feed level gauge 43, a filtration feed pump 44, and a plate and frame filter press 45. The filtration feed tank 41 is used to store the tertiary mixture after flocculation in the tertiary reaction tank 32. The feed mixer 42 is used to homogenize and stir the tertiary mixture to prevent sedimentation. The filtration feed pump 44 is used to pump the discharge from the filtration feed tank 41 into the plate and frame filter press 45. The feed level gauge 43 is used to control the start and stop of the filtration feed pump 44 according to the liquid level in the filtration feed tank. The tertiary mixture is separated into mud and water through pressure filtration to remove calcium fluoride precipitate from the tertiary mixture. The filtration feed pump 44 is a screw pump or a plunger pump, and the filtration pressure is 0.6~1.0MPa.

[0080] The neutralization and flocculation unit 5 includes an oxalic acid solution preparation and dosing device 51, a coagulant preparation and dosing device 52, a second flocculant preparation and dosing device 53, and a neutralization, coagulation, and flocculation reaction module 54.

[0081] The oxalic acid solution preparation and dosing device 51 is used to prepare oxalic acid into a solution with a concentration of 8% to 10%, and add the prepared oxalic acid solution to the neutralization, coagulation and flocculation reaction module 54.

[0082] The coagulant preparation and dosing device 52 is used to prepare a coagulant solution with a concentration of 8% to 10%, and add the prepared coagulant solution to the neutralization, coagulation and flocculation reaction module 54;

[0083] The second flocculant addition module 53 is used to prepare the second flocculant solution (0.05%~0.1% anionic polyacrylamide or 0.1~0.3% sodium alginate or both), and add the prepared second flocculant solution to the neutralization & coagulation & flocculation reaction module 54.

[0084] The neutralization, coagulation, and flocculation reaction module 54 includes a neutralization tank 541, a coagulation tank 542, a flocculation tank 543, a fast reaction mixer 544, a first slow coagulation mixer 545, a second slow flocculation mixer 546, and a third online pH meter 547. The fast reaction mixer 544 and the third online pH meter 547 are both located in the neutralization tank 541. The first slow coagulation mixer 545 and the second slow flocculation mixer 546 are respectively located in the coagulation tank 542 and the flocculation tank 543. The fast reaction mixer 544 is used to rapidly mix the added oxalic acid with the hydroxide ions in the wastewater and cause a neutralization reaction. The reaction is carried out in conjunction with the oxalic acid solution preparation and dosing device 51 to control the amount of oxalic acid solution added. The first slow coagulation mixer 545 and the second slow flocculation mixer 546 are used to react the remaining calcium ions in the neutralized wastewater with oxalic acid to form calcium oxalate precipitate and flocs. The stirring speed of the fast reaction mixer 544 is 55~65 rpm, the stirring speed of the first slow coagulation mixer 545 is 15~20 rpm, and the stirring speed of the second slow flocculation mixer 546 is 10~15 rpm. The pH value of the effluent from the neutralization tank 541 is controlled at 7~8.

[0085] In some embodiments of the present invention, the coagulant is selected from at least one of polyaluminum chloride, aluminum sulfate, polyferric sulfate, ferrous sulfate and ferric chloride. Among them, polyaluminum chloride is widely used in the water treatment industry as a highly efficient, economical and environmentally friendly coagulant, especially in the fields of drinking water treatment and wastewater treatment.

[0086] Both the first and second flocculants are selected from at least one of anionic polyacrylamide and sodium alginate. Anionic polyacrylamide exhibits excellent flocculation properties, promoting the formation of larger and more stable flocs from suspended particles, facilitating sedimentation or flotation and improving water treatment efficiency. Furthermore, anionic polyacrylamide is suitable for various water quality conditions, including high-turbidity and low-turbidity water, as well as water bodies with different pH values, enabling it to demonstrate good performance in diverse water treatment scenarios.

[0087] The decalcification sedimentation unit 6 includes an inclined plate (tube) sedimentation tank 61 and a sludge pump 62. The inclined plate (tube) sedimentation tank 61 is used to separate the calcium oxalate flocs in the flocculation tank 543 into precipitates and water. The sludge pump 62 is used to discharge the sludge from the bottom of the inclined plate (tube) sedimentation tank. The surface loading rate of the inclined plate (tube) sedimentation tank 61 is 1.0~1.5 m³ / m. 2 The outlet weir load is ≤2.0L / m·s.

[0088] The short-cut nitrification-denitrification unit 7 includes main structures such as anoxic tank 701, nitrification tank 702, and secondary sedimentation tank 703, and is equipped with auxiliary facilities such as submersible mixer 704, blower aeration device 705, carbon source addition device 706, alkalinity addition device 707, phosphate addition device 708, mixed liquor return pump 709, sludge return pump 710, online dissolved oxygen meter 711, and fourth online pH meter 712.

[0089] The anoxic pool 701 is equipped with a submersible mixer 704 with a power of 8~10W / m. 3 The horizontal flow velocity of the mud-water mixture in the tank is 0.3-0.5 m / s to ensure thorough mixing of mud and water and prevent sludge deposition. The carbon source addition device 706 provides the carbon source required for denitrification, using glucose or methanol as the carbon source, with a C / N ratio of 2.5-3 as the addition control condition. The phosphate addition device 708 adds potassium dihydrogen phosphate as a nutrient salt for microorganisms to the anoxic tank, making the BOD5 / TP ratio 18:1.

[0090] The sludge concentration in the nitrification tank 702 is 3.5~5 g / L, and the total nitrogen loading rate is ≤0.05 kgTN / (kgMLSS·d). An aeration device 705 is installed in the tank. The air supply is adjusted by linking the blower in the aeration device 705 with an online dissolved oxygen meter 711, controlling the dissolved oxygen level in the tank to a low level of 1.0~1.5 mg / L. This inhibits the growth of nitrifying bacteria, making nitrite-oxidizing bacteria the dominant species, achieving ammonia nitrogen nitrite oxidation, and creating conditions for short-cut denitrification. An alkalinity dosing device 707 provides alkalinity for the ammonia nitrogen nitrite oxidation and nitrification processes, using sodium carbonate to neutralize the acidity generated during nitrite oxidation and nitrification, with a residual alkalinity >70 mg / L as the dosage. Control indicators: The fourth online pH meter 712 is linked with the oxalic acid dosing pump 512 and the alkalinity dosing device 707 to regulate the pH value of the nitrification tank 702 to maintain it at 7~8.5; the mixed liquor return pump 709 returns the mixed liquor after nitrification to the anoxic tank 701 for denitrification and nitrogen removal, and the mixed liquor return ratio is 350%-400%; the blower in the aeration device 705 is used to provide oxygen required for the growth and reproduction of nitrifying bacteria in the nitrification tank 702, and the aerobic aerator is used to make air form microbubbles in the water to improve oxygen transfer and utilization efficiency.

[0091] The secondary settling tank 703 is used for sedimentation and separation of the sludge-water mixture from the nitrification tank 702, and the surface loading of the secondary settling tank 703 is 0.6~1.0 m³. 3 / m 2 •h, the secondary sedimentation tank 703 is equipped with a sludge return pump 710, which is used to return the sludge after sedimentation and separation to the inlet of the anoxic tank 701 to replenish the biomass of the anoxic tank and maintain the sludge balance of the system. The sludge return ratio is 80%-100%.

[0092] Furthermore, it also includes a sludge dewatering unit 8, which includes a sludge conditioning tank 81, a conditioning agent preparation and dosing device 82, a sludge feed pump 83, and a sludge dewatering machine 84. The sludge conditioning tank 81 is used to condition the physicochemical sludge discharged from the decalcification and precipitation unit 6 and the biochemical sludge discharged from the short-cut nitrification and denitrification unit 7. The conditioning agent preparation and dosing device 82 is used to prepare the conditioning agent solution and add the conditioning agent solution to the sludge conditioning tank 81 to condition the sludge particles and improve the dewatering performance. The conditioning agent used in the conditioning process is a cationic polyacrylamide solution or a combination of cationic polyacrylamide solution and ferric chloride solution. When the cationic polyacrylamide solution and ferric chloride solution are added together, each of the conditioning agent stirring and dissolving tanks is an independent set. The cationic polyacrylamide solution is prepared to a concentration of 0.08-0.12%; the ferric chloride solution is prepared to a concentration of 8-10%. The sludge feed pump 83 is a screw pump or plunger pump used to pump the conditioned sludge to the sludge dewatering machine 84, which is used to dewater the conditioned and modified sludge.

[0093] In some embodiments of the present invention, the sludge dewatering machine 84 is a plate and frame filter press with a filtration pressure of 0.6~1.0 MPa.

[0094] Secondly, see also Figure 2 The specific implementation steps of the glass engraving wastewater defluorination and deammoniation method of the present invention are as follows:

[0095] After the glass engraving wastewater enters the primary reaction tank 12, a quicklime solution with a concentration of 8-10% is added to it, the pH value is controlled at 7-8, and the mixture is continuously stirred to ensure a full reaction. The stirring speed is 60-70 rpm, and the reaction time is 0.3-0.5 h. After the reaction is completed, the effluent flows by gravity to the secondary reaction tank 22.

[0096] Add a high-calcium fly ash mixture with a concentration of 15-20% to the secondary reaction tank 22, control the pH value at 9-10, and continuously stir to ensure full reaction. The stirring speed is 60-70 rpm, and the reaction time is 0.3-0.5 h. After the reaction is completed, the effluent enters the tertiary reaction unit 3.

[0097] Add 0.05%~0.1% anionic polyacrylamide to the three-stage reaction tank 32, and stir continuously to ensure a full reaction. The stirring speed is 10~15 rpm, and the reaction time is 0.3~0.5 h. After the reaction is completed, the three-stage mixture enters the filtration and defluorination unit 4.

[0098] The feed mixer 42 homogenizes and stirs the three-stage mixture to prevent sedimentation. The filter feed pump 44 then pumps the three-stage mixture into the plate and frame filter press 45 for pressure filtration to achieve mud-water separation. The filtration working pressure is set to 0.6~1.0MPa, producing filtrate and filter cake. The filtrate flows by gravity into the neutralization and flocculation unit 5, and the filter cake is used as cement admixture to realize the resource utilization of waste.

[0099] A 10% oxalic acid solution is added to the neutralization tank 541 of the neutralization and flocculation unit 5. The wastewater is continuously and rapidly stirred to control the pH value at 7-8. Then, it is introduced into the coagulation tank 542 and the flocculation tank 543 in sequence and stirred slowly. An 8%-10% polyaluminum chloride solution is added to the coagulation tank 542, and an 0.05%-0.1% anionic polyacrylamide solution is added to the flocculation tank 543. The calcium oxalate produced by the neutralization reaction forms flocs. The flocculent liquid produced by the flocculation tank 543 flows by gravity to the decalcification and precipitation unit 6.

[0100] Calcium oxalate flocs form sedimented sludge at the bottom of the inclined plate (tube) sedimentation tank 61 and are separated from the wastewater. The sedimented sludge is discharged through the sludge pump 62 to form physicochemical sludge. The physicochemical supernatant formed by the effluent from the inclined plate (tube) sedimentation tank 61 flows by gravity into the short-cut nitrification and denitrification unit 7.

[0101] In the short-cut nitrification-denitrification unit 7, wastewater first enters the anoxic tank 701. Inside the anoxic tank 701, a submersible mixer 704 homogenizes and agitates the wastewater, creating anoxic conditions. Denitrifying bacteria utilize the unreacted oxalic acid from the neutralization and flocculation unit and the carbon source added by the carbon source dosing device 706 to reduce nitrite and nitrate nitrogen in the mixed liquor returned from the nitrification tank 702 and the sludge returned from the secondary sedimentation tank 703 to nitrogen gas. The effluent from the anoxic tank 701 then enters the nitrification tank 702, where the aeration device 7... 05 provides oxygen to form aerobic conditions, microorganisms remove organic pollutants (BOD) brought into the wastewater, nitrifying bacteria convert ammonia nitrogen in the wastewater into nitrite nitrogen, mixed liquor return pump 709 returns the mixed liquor at the end of nitrification tank 702 to the front end of anoxic tank 701, the effluent from nitrification tank 702 enters secondary sedimentation tank 703 for sludge-water separation, the biochemical supernatant is discharged after meeting the standards, and the settled sludge is returned to anoxic tank 701 to replenish the system microorganisms, or is discharged to sludge dewatering unit 8 as the remaining biochemical sludge.

[0102] The physicochemical sludge discharged from the decalcification and precipitation unit 6 and the biological sludge discharged from the short-cut nitrification and denitrification unit 7 enter the sludge conditioning tank 81 in the sludge dewatering unit 8. The agitator in the sludge conditioning tank 81 mixes the physicochemical sludge and the biological sludge. The conditioning agent preparation and addition device 82 adds 0.1% cationic polyacrylamide to the sludge conditioning tank 81 to condition the mixed sludge. The sludge feed pump 83 pumps the conditioned mixed sludge into the sludge dewatering machine 84 for dewatering, producing dewatered filtrate and dried sludge. The dewatered filtrate is returned to the secondary reaction tank 22 in the second reaction unit 2 for treatment. The dried sludge is used as cement admixture, realizing the resource utilization of waste.

[0103] Comparative Example 1

[0104] A certain industrial park primarily manufactures glass engraving products. During production, these companies generate acidic wastewater containing high concentrations of ammonia nitrogen and fluoride ions. To ensure the wastewater meets direct discharge standards after treatment, a comprehensive wastewater treatment plant has been constructed within the park. Wastewater from each company is collected through a separate pipe and discharged to the treatment plant, which has a designed capacity of 1500 m³. 3 The water quality of the comprehensive equalization tank is shown in Table 1 below: / d

[0105] Table 1. Summary of Design Influent Water Quality (Unit: mg / L, pH dimensionless)

[0106]

[0107] After treatment, the wastewater must meet the direct discharge standards shown in Table 2:

[0108] Table 2. Summary of Design Effluent Water Quality (Unit: mg / L, pH dimensionless)

[0109]

[0110] The original treatment process of this wastewater treatment plant was "homogenization and equalization adjustment → primary coagulation and sedimentation → secondary coagulation and sedimentation → tertiary coagulation and sedimentation → pH adjustment → breakpoint chlorination → sand filtration and activated alumina adsorption". During normal and stable operation, the F in the equalization tank... - Sampling and testing of NH3-N and TN were conducted twice daily for 10 consecutive days, and the average concentration of each indicator was recorded. Among them, F - The average concentrations were 1482 mg / L, NH3-N 197 mg / L, TN 219 mg / L, and calcium ion 119 mg / L. The effluent from the equalization tank entered the primary coagulation reactor. A 10% slaked lime solution and a 0.05% anionic polyacrylamide solution were sequentially added to the primary coagulation sedimentation tank. The sedimentation tank used a radial flow design with a surface loading rate of 0.55 m³ / m². 2The sedimentation time is 5.5 hours. For secondary coagulation sedimentation, a 10% calcium chloride solution, a 10% PAC (polyaluminum chloride) solution, and a 0.05% anionic polyacrylamide solution are added sequentially. The sedimentation tank is a radial flow type with a surface loading rate of 0.55 m³ / m². 2 The sedimentation time is 5.5 hours. The three-stage coagulation sedimentation process involves sequentially adding a 10% composite defluorinating agent solution (main components are calcium chloride and calcium hydroxide, manufactured by Jiangxi Shengen Energy Saving and Environmental Protection Technology Co., Ltd.), a 10% PAC solution, and a 0.05% anionic polyacrylamide solution. The sedimentation tank is a radial flow type with a surface loading rate of 0.55 m³ / m². 2 The sedimentation time is 5.5 hours; the pH adjustment tank uses 98% concentrated sulfuric acid; the breakpoint chlorination uses 10% sodium hypochlorite solution; the sand filtration and activated alumina adsorption unit uses sand filter tanks with a diameter of φ×H=2.0×3.05m (2 in operation, 1 on standby) and activated alumina adsorption tanks with a diameter of φ×H=2.2×3.45m (2 in operation, 1 on standby), along with one set of activated alumina regeneration device and related supporting equipment. After analyzing the F in the effluent at the end of the above process... - Sampling and testing of NH3-N and TN were conducted twice daily for 10 consecutive days, and the average concentration of each indicator was recorded. Among them, the effluent F - The average concentrations were 9 mg / L, 16 mg / L for NH3-N, 20 mg / L for TN, and 316 mg / L for calcium ions. None of the control indicators met the emission requirements.

[0111] In addition, due to the high operating cost of this process (approximately 55-60 yuan per ton of water treated), and the inability to ensure that the fluoride ions, ammonia nitrogen, and total nitrogen in the effluent consistently meet the standards, the treatment facilities suffer from severe scaling during operation, which has seriously affected the normal and stable operation of the system.

[0112] Example 1

[0113] To ensure that the effluent consistently meets standards and that all units of the system operate normally, the park organized the renovation of the wastewater treatment plant, adopting the technical methods provided in this invention.

[0114] The method for defluoridation and ammonia removal from glass engraving wastewater described in this invention comprises the following steps:

[0115] During normal and stable operation, the F in the equalization tank - Sampling and testing of NH3-N and TN were conducted twice daily for 10 consecutive days, and the average concentration of each indicator was recorded. Among them, F -The average concentrations were 1490 mg / L, NH3-N 196 mg / L, TN 222 mg / L, and calcium ion 110 mg / L. After homogenization and equalization, the wastewater entered the existing primary coagulation tank. A 10% slaked lime solution was added to the primary coagulation sedimentation tank for pH adjustment, maintaining the pH at 7-8. The reaction time was 0.4 h. The effluent from the primary reaction did not enter the primary sedimentation tank. Instead, the effluent from the primary reaction entered the existing secondary coagulation tank. During the secondary reaction, a 10% high-calcium fly ash suspension was added instead of the calcium chloride solution, maintaining the pH at 9-10. Continuous stirring was maintained to ensure a full reaction, and the reaction time was 0.5 h. The effluent from the secondary reaction did not enter the secondary sedimentation tank but entered the existing tertiary coagulation tank for storage and stirring. It was then directly fed into a plate and frame filter press for filtration at a pressure of 0.7 MPa. The filtrate from the plate and frame filter press was sampled and tested twice daily for 10 consecutive days, and the F... - The average concentration of calcium ions was 2.3 mg / L, and the average concentration of NH3-N was 211 mg / L. After the filtrate entered the neutralization and flocculation unit, a 10% oxalic acid solution was added to the neutralization tank. The agitator speed was 60 rpm to control the pH of the effluent from the neutralization tank at 7-8. A 10% PAC solution and a 0.08% anionic polyacrylamide solution were added to the coagulation tank and flocculation tank, respectively. The agitator speed for slow coagulation was 15 rpm, and the agitator speed for slow flocculation was 10 rpm, forming a large amount of flocculants. The effluent entered the decalcification and sedimentation unit, and the sludge-water separation effect was obvious. The supernatant of the inclined plate sedimentation tank was sampled and tested twice a day for 10 consecutive days. The average concentration of calcium ions was 65 mg / L, the average concentration of NH3-N was 190 mg / L, and the average concentration of TN was 213 mg / L. The wastewater then entered the short-cut nitrification and denitrification unit. After biological treatment in the nitrification tank, appropriate amounts of glucose, sodium carbonate, and potassium dihydrogen phosphate are added via carbon source addition, alkalinity addition, and phosphate addition devices, respectively, to maintain a C / N ratio of 2.8, a BOD5 / TP ratio of 18:1, a pH of 7-8.5, and a low dissolved oxygen level of 1.0-1.5 mg / L in the nitrification tank. This ensures that nitrifying bacteria become the dominant species, achieving ammonia nitrogen nitrification. The system is designed with a BOD5 sludge loading rate (Ls) of 0.06 kgBOD5 / kgMLSS·d, a total nitrogen loading rate of 0.04 kgTN / (kgMLSS·d), a biological tank retention time of 2.5 days, a nitrification tank sludge concentration of 4 g / L, a mixed liquor recirculation ratio of 400%, a sludge recirculation ratio of 100%, and a secondary sedimentation tank surface loading of 0.8 m³. 3 / m 2 ·h, the same testing measures were applied to the effluent from the secondary sedimentation tank, and F was measured. - The average concentration was 2.1 mg / L, the NH3-N concentration was 3 mg / L, and the TN concentration was 13 mg / L. All control indicators met the emission requirements.

[0116] After adopting the technical method provided by this invention, the fluoride, ammonia nitrogen, and total nitrogen levels in the wastewater effluent met the discharge standards. A cost analysis was conducted before and after the upgrade. Specifically: the amount of quicklime used was reduced by approximately 11%; by weight, the amount of high-calcium fly ash powder increased by approximately 8 times compared to calcium chloride powder, resulting in a cost reduction of approximately 18% for this agent; because a short-cut nitrification-denitrification process was used instead of breakpoint chlorination to remove ammonia nitrogen, although this increased construction costs slightly and required the addition of a certain amount of sodium carbonate to maintain alkalinity and potassium dihydrogen phosphate as a phosphorus source, this method requires less oxygen and less glucose as a carbon source, thus reducing the overall cost of ammonia nitrogen removal by approximately 61%; furthermore, the sludge cake generated during filtration and sludge dewatering was used as a cement admixture, achieving resource recycling and significantly reducing sludge disposal costs, lowering the cost per ton of water treated by the wastewater treatment plant to 35-38 yuan; in addition, due to the use of oxalic acid to adjust the pH, no calcium salt scaling problems occurred in the various treatment units of the wastewater treatment plant, allowing for normal and stable operation.

[0117] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Any other corresponding changes and modifications made based on the technical concept of this application should be included within the scope of protection of the claims of this application.

Claims

1. A method for defluoridation and ammonia removal from glass engraving wastewater, characterized in that, Includes the following steps: (1) The glass engraving wastewater and the alkaline calcium compound solution are stirred and mixed to carry out the alkali addition and fluoride fixation reaction to produce a primary mixed liquid; (2) The primary mixture is stirred and mixed with the fly ash suspension to carry out an alkali-fixing and fluorine-fixing reaction to produce a secondary mixture; (3) The secondary mixture is stirred and mixed with flocculant to carry out flocculation reaction, producing a tertiary mixture; (4) The three-stage mixture is filtered and separated to produce filtrate and filter cake; (5) Add oxalic acid solution to the filtrate for neutralization reaction, and then add coagulant and flocculant in sequence for coagulation reaction and flocculation reaction respectively to produce a four-stage mixed liquid; (6) The four-stage mixed liquor is subjected to sedimentation and separation to produce physicochemical supernatant and physicochemical sludge; (7) The physicochemical supernatant is subjected to short-cut nitrification-denitrification biochemical reaction to produce a defluorinated and deammoniated biochemical supernatant and biochemical sludge; (8) After conditioning the physicochemical sludge and biochemical sludge with a conditioning agent, they are then processed in a dewatering equipment to produce dewatered filtrate and dried sludge cake. The dewatered filtrate is returned to step (2) for alkali addition and fluoride fixation reaction. In step (4), a plate and frame filter press is used to filter and separate the three-stage mixture to produce filtrate and filter cake. The working pressure of the plate and frame filter press is set to 0.6~1.0MPa. The filter cake described in step (4) is used as a cement admixture to realize the resource utilization of waste; The fly ash in the fly ash suspension in step (2) is high-calcium fly ash; The fly ash suspension described in step (2) partially replaces the calcium hydroxide solution; The concentration of the fly ash suspension in step (2) is 15-20%; The amount of fly ash suspension added in step (2) is such that the pH of the reaction system is 9-10; The mixing in step (2) is carried out by mechanical stirring at a speed of 60-70 rpm; The reaction time between the primary mixture and the fly ash suspension in step (2) is 0.3~0.5h.

2. The method for defluoridation and ammonia removal from glass engraving wastewater according to claim 1, characterized in that, The concentration of the alkaline calcium-containing compound solution in step (1) is 8-10%; the alkaline calcium-containing compound is calcium hydroxide or a mixture of calcium hydroxide and calcium chloride; The amount of alkaline calcium-containing compound solution added in step (1) is such that the pH of the reaction system is 7-8; The mixing in step (1) is carried out by mechanical stirring at a speed of 60-70 rpm; The reaction time between the glass engraving wastewater and the alkaline calcium compound solution in step (1) is 0.3~0.5h.

3. The method for defluoridation and ammonia removal from glass engraving wastewater according to claim 1, characterized in that, The flocculant in step (3) is at least one of anionic polyacrylamide and sodium alginate; When the flocculant used in step (3) is anionic polyacrylamide, it should be prepared into a flocculant solution of 0.05~0.1% before use; When sodium alginate is used as the flocculant in step (3), it should be prepared into a flocculant solution of 0.1-0.3% before use; The mixing in step (3) is carried out by mechanical stirring at a speed of 10-15 rpm; The reaction time between the secondary mixture and the flocculant solution in step (3) is 0.3~0.5h.

4. The method for defluoridation and ammonia removal from glass engraving wastewater according to claim 1, characterized in that, The concentration of the oxalic acid solution in step (5) is 8-10%; The amount of oxalic acid solution added in step (5) is such that the pH of the neutralization reaction system is 7-8; The neutralization reaction in step (5) is carried out by mechanical stirring at a speed of 55-65 rpm for a reaction time of 0.1-0.3 h. The coagulation reaction in step (5) is carried out by mechanical stirring at a speed of 15-20 rpm for a reaction time of 0.3-0.5 h. The flocculation reaction in step (5) is carried out by mechanical stirring at a speed of 10-15 rpm and a reaction time of 0.3-0.5 h.

5. The method for defluoridation and ammonia removal from glass engraving wastewater according to claim 4, characterized in that, The coagulant mentioned in step (5) is at least one of polyaluminum, aluminum sulfate, polyferric sulfate and ferric chloride; The flocculant in step (5) is at least one of anionic polyacrylamide and sodium alginate; Before use, the coagulant and flocculant in step (5) are prepared into solutions respectively. The coagulant is prepared into a coagulant solution of 8~10%; when anionic polyacrylamide is used as the flocculant, it is prepared into a flocculant solution of 0.05~0.1%; when sodium alginate is used as the flocculant, it is prepared into a flocculant solution of 0.1~0.3%.

6. The method for defluoridation and ammonia removal from glass engraving wastewater according to claim 1, characterized in that, In step (6), the four-stage mixture is separated using an inclined plate or inclined tube sedimentation tank; In step (6), the surface loading of the inclined plate or inclined tube sedimentation tank is 1.0~1.5 m³ / m. 2 •h, outlet weir load ≤2.0L / m·s.

7. The method for defluoridation and ammonia removal from glass engraving wastewater according to claim 1, characterized in that, In step (8), the conditioning method for physical and chemical sludge is to mechanically mix physical and chemical sludge and add conditioning agent for chemical conditioning; In step (8), a plate and frame filter press is used to separate the conditioned mixed sludge into sludge and water, producing dewatered filtrate and dried sludge cake. The working pressure of the plate and frame filter press is set to 0.6~1.0MPa. The dried mud cake described in step (8) is used as a cement admixture to realize the resource utilization of waste; The conditioning agent in step (8) is a cationic polyacrylamide solution or a combination of cationic polyacrylamide solution and ferric chloride solution; Before using the conditioning agent described in step (8), it is prepared into a solution, and the cationic polyacrylamide solution is prepared into a solution of 0.08~0.12%; Ferric chloride solution is prepared to a concentration of 8-10%.

Images