TWI534094B - Treatment method by using fluidized-bed crystallization technology to remove phosphate from phosphate-containing wastewater - Google Patents

Description

Method for removing phosphorus from phosphorus-containing wastewater by fluidized bed crystallization technology

The invention relates to a treatment method for removing phosphorus from waste water, in particular to a treatment method for removing phosphorus from phosphorus-containing wastewater by fluidized bed crystallization technology.

With the rapid development of science and technology over the past few years, serious environmental pollution, air pollution, and water pollution have caused serious damage to the ecology. The most serious of these is due to the rapid industrial development, a large amount of industrial wastewater is arbitrarily discharged. These industrial wastewaters contain a lot of heavy metals and inorganic pollutants, etc., if human consumption is too much, it may cause diseases and other problems.

The past phosphorus removal technologies mainly include chemical coagulation, adsorption, biological treatment and fluidized bed crystallization. Among them, the chemical coagulation technology uses metal salts as a precipitant, adding an alkali solution to adjust the appropriate pH value to react with the phosphate to form a solid precipitation solution, and with the addition of the polymer flocculant, the mechanism of coprecipitation is used to achieve the removal. Phosphorus purpose. Although the chemical coagulation sedimentation has the advantages of simple operation and good phosphorus removal effect, a large amount of chemicals need to be added in the phosphorus removal process, and the solid waste generated by the solid waste has high water content and low solid purity, which may cause troubles and increase of subsequent treatment. The cost of treating sludge. The adsorption method is to add an adsorbent to the phosphorus-containing solution, because the surface of the adsorbent is opposite to the adsorbed charge, They attract each other under the action of positive and negative charges, but do not directly link with the surface of the adsorbent, but are attached to the surface of the adsorbent by static electricity. Although the adsorption method has the advantages of simple operation, the adsorption material needs to be desorbed to extract concentration or transport after being saturated, and the number of regeneration of the adsorbent material is limited, so it is still in the development stage. Biological treatment is the main method of phosphorus removal in the sewage plant. By connecting the anaerobic tank and the aerobic tank in series, the microorganism can absorb the phosphorus in the water to achieve the purpose of phosphorus removal. The biological phosphorus removal method does not require additional additives, and the operation cost is relatively low. However, the biological phosphorus removal method cannot handle the high concentration of the phosphorus-containing solution, and a large amount of biological sludge is generated, which is still not a perfect phosphorus removal technology.

In recent years, fluidized bed crystallization technology has been paid attention to in phosphorus removal, and it has gradually been applied in sewage plants. In addition to the high efficiency advantages of chemical coagulation and sedimentation technology, fluidized bed crystallization and phosphorus removal technology can greatly reduce the use of chemicals because it operates at low supersaturation. In addition, the crystal beads produced by the fluidized bed crystallization technology have a large particle size and a low water content, so that there is no need to add a flocculant or a sludge re-dewatering process, which can save a lot of cost in the disposal of waste. The treatment device of the "fluidized bed crystallization technique" mainly comprises a reaction tank (i.e., a fluidized bed) having a support therein. The waste water to be treated flows upward from the bottom of the reaction tank, so that the support fluidizes at a certain upward flow speed, and the reaction tank is connected to the chemical inlet for feeding the medicament, so that the pollutant in the waste water is carried in the fluidized bed. Crystallization on the body to remove anions or metal ions from the wastewater and recover the reusable metal particles. However, the conventional "fluidized bed crystallization technology" requires the addition of a support (such as strontium sand, brick powder, etc.) to the reaction tank to cause crystallization, which causes the metal crystal body to contain a support component, and the purity of the crystal is not good, which affects it. The value of utilization.

Accordingly, the main object of the present invention is to provide a new fluidized bed crystallization technique. Phosphorus can be removed from phosphorus-containing wastewater. This treatment method can solve the problem of large space occupied by existing coagulation technology and large amount of sludge production, because it requires horizontally connected fast mixing tanks, slow mixing pools, Equipment such as sedimentation tanks and sludge dewatering machines. In addition, this treatment method does not require the addition of any heterogeneous support for crystallization, thereby improving the convenience of operation and improving the purity of the obtained crystal particles, and also increasing the benefits of recycling and recycling of the fluidized bed crystal particles. .

According to the present invention, a method for removing phosphorus from a phosphorus-containing wastewater by a fluidized bed crystallization technique, firstly providing a fluidized bed reaction tank having a lower section and an upper section, the lower section being provided with a wastewater inlet port And a medicament inlet port, the upper section is provided with a water outlet, and a circulation line is provided between the lower section and the upper section; then, the phosphorus-containing wastewater and the crystallizing agent are separately introduced from the wastewater inlet port and the medicament inlet port Mixing in the fluidized bed reaction tank, wherein the crystallization agent contains calcium ions and the molar concentration ratio of calcium ions to the phosphate ions in the phosphorus-containing wastewater is controlled between 1.0:1.0 and 2.0:1.0, and the inflowing wastewater is The pH value is controlled between 6 and 9; then, the phosphorus-containing wastewater mixed with the crystallization agent flows from the lower portion of the reaction tank to the upper portion of the reaction tank and is returned to the lower portion via the reflux line for circulation The phosphate ions in the phosphorus-containing wastewater are reacted with calcium ions in the crystallization agent to form calcium phosphate crystal particles.

According to the present invention, the influent phosphate ion concentration also directly affects the efficiency of the phosphorus removal treatment. In a preferred embodiment, the influent phosphate ion concentration is controlled between 1000 mg/L and 1500 mg/L.

In a preferred embodiment, the molar ratio of calcium ions to phosphate ions in the phosphorus-containing wastewater is about 2.0:1.0, and the pH of the influent wastewater is between 7 and 9, the influent phosphate The ion concentration was 1500 mg/L.

In a preferred embodiment, the molar ratio of calcium ions to phosphate ions in the phosphorus-containing wastewater is about 1.4:1.0, and the pH of the influent wastewater is between 7 and 9, the influent phosphate The ion concentration was 1500 mg/L.

Other objects, advantages and features of the present invention will become apparent from

10‧‧‧Reaction tank

12‧‧‧ lower section

14‧‧‧上段

16‧‧‧ Wastewater inlet

18‧‧‧Pharmaceutical inflow

20‧‧‧Water outlet

22‧‧‧Return line

24‧‧‧pH detector

26‧‧‧

28‧‧‧

30‧‧‧Fluorine-containing wastewater

32‧‧‧Crystal Pharmacy

1 is a schematic view of a fluidized bed reaction tank in accordance with an embodiment of the present invention.

Figure 2 (a), (b) and (c) individually show the influent concentration of 1500 ppm phosphate ion (PO ₄ ^-3 ) and the molar concentration ratio of calcium ion to phosphate ion (Ca ⁺² : PO ₄ ^{- 3} )=1.0:1.0 operating conditions, different pH values (pH6, pH9) of influent wastewater relative phosphorus removal rate (phosphate removal%), phosphorus conversion rate (phosphate conversion%) and the amount of collected particles (mass of Diagram of granules).

Figure 3 (a), (b) and (c) individually show different pH values (pH 6, pH 7) under operating conditions of 1500 ppm phosphate ion influent concentration and Ca ⁺² : PO ₄ ^-3 = 1.0: 1.0. , pH9, pH11) of the influent wastewater relative phosphorus removal rate, phosphorus conversion rate and the amount of collected particles.

Figure 4 (a), (b) and (c) individually show the Mohr concentration ratio of different calcium ions to phosphate ions under the operating conditions of 1500 ppm phosphate ion influent concentration and pH 9 influent wastewater (Ca ^{+ 2} : PO ₄ ^-3 = 1.0: 1.0, 1.2: 1.0, 1.4: 1.0) A plot of relative phosphorus removal rate, phosphorus conversion rate, and amount of collected particles.

Figures 5(a), (b) and (c) show the phosphate ion concentration of different influent (500mg) under the operating conditions of influent wastewater with Ca ⁺² : PO ₄ ^-3 = 1.2:1.0 and pH9. /L, 1000 mg/L, 1500 mg/L PO ₄ ^-3 ) A plot of relative phosphorus removal rate, phosphorus conversion rate and amount of collected particles.

The present invention is directed to a treatment method for removing phosphorus from phosphorus-containing wastewater by a fluidized bed crystallization technique, which utilizes crystallization granulation to remove phosphorus from the phosphorus-containing wastewater, and the obtained crystalline particles can be further Reuse. In the treatment method, a fluidized bed reaction tank 10 (see Fig. 1) is first provided, the reaction tank 10 having a tubular lower section 12 and a tubular upper section 14, the upper section 14 having an outer diameter larger than the outer diameter of the lower section 12. The lower section 12 is provided with a waste water inlet 16 and a medicament inlet 18, the upper section 14 is provided with a water outlet 20, and the lower section 12 and the upper section 14 have a return line 22. In the present embodiment, the bottom portion of the lower portion 12 of the reaction tank 10 has a conical shape to facilitate uniform dispersion of the return flow force. A pH value detector 24 is provided at the water outlet 20 to monitor the pH of the flow port while collecting water samples for water quality analysis.

Next, the phosphorus-containing wastewater 30 and the crystallization agent 32 are separately introduced into the lower stage 12 of the reaction tank 10 from the wastewater inlet port 16 and the chemical inlet port 18 by means of the pumps 26 and 28.

Next, the phosphorus-containing wastewater 30 mixed with the crystallization agent 32 is caused to flow from the lower stage 12 to the upper stage 14 and is returned to the lower stage 12 via the return line 22 for circulation, so that the phosphate ions and crystals in the phosphorus-containing wastewater 30 are crystallization. The agent 32 reacts. In the present embodiment, the crystallization agent 32 is a calcium ion-containing agent (for example, a calcium chloride agent), and calcium ions are reacted with phosphate ions in the phosphorus-containing wastewater 30 to produce calcium phosphate crystal particles, and the supersaturation is controlled appropriately. In the range, the phosphorus-containing wastewater 30 is subjected to a granulation reaction in the fluidized bed reaction tank 10 to remove phosphate ions in the phosphorus-containing wastewater 30.

According to the treatment method of the present invention, the pH value of the influent wastewater (pH value), the molar ratio of calcium ions to phosphate ions (Ca ⁺² : PO ₄ ^-3 ), and the influent phosphate ion concentration will The phosphorus removal rate and the phosphorus conversion rate (liquid to solid state) in the phosphorus-containing wastewater 30 are respectively affected. According to the test results, the pH value of the influent wastewater is preferably controlled between 7 and 9, and the molar ratio of calcium ions to phosphate ions (Ca ⁺² : PO ₄ ^-3 ) is preferably controlled at 1.0:1.0 to Between 1.4 and 1.0, the influent phosphate ion concentration is preferably controlled between 1000 and 1500 mg/hr.

Referring to FIG. 2(a) and FIG. 2(b), respectively, the phosphorus removal rate and the phosphorus conversion rate of the influent wastewater with different pH values after the particle growth stability are respectively compared, and the operating conditions are the pH values of the influent wastewater respectively. 6 and 9, the molar concentration of the calcium ion of the crystallizing agent 32 relative to the phosphate ion of the phosphorus-containing wastewater 30 (Ca ⁺² : PO ₄ ^-3 ) is fixed at 1.0:1.0, and the influent phosphate ion concentration is 1500 mg. /L. The phosphorus removal rate is a comparison of the total phosphate ion concentration consumed in the reaction tank with different pH values and the filtered concentration of the outflow water. It can be seen from Fig. 2(a) that after the end of the 60-hour operation time, the phosphorus removal rate of pH 6 is 49.62%, and the phosphorus removal rate of pH 9 is 73.39%; from Fig. 2(b) It can be seen that the phosphorus conversion rate of pH 6 is 53.01%, and the phosphorus conversion rate of pH 9 is 73.36%; from Fig. 2(c), it can be seen that the amount of particles collected at pH 6 is 17.47 g, and the pH value is 9 The amount of particles collected was 61.03 g. Figure 2 (a), (b), (c) shows that when the pH is increased from 6 to 9, the phosphorus removal rate, the phosphorus conversion rate, and the amount of collected particles all increase sharply. Therefore, the pH of the influent wastewater is greatly increased. Affects the phosphorus removal rate and the amount of crystal particles obtained. That is, increasing the pH of the influent wastewater will cause more hydrogen phosphate (HPO ₄ ^-2 ) and phosphate (PO ₄ ^-3 ) to react with calcium ions to form more calcium phosphate compounds, and not only Increasing the amount of particulate form also encourages crystal growth, for example, the maximum size of the particles obtained at pH 9 is greater than 0.840 mm, while the maximum size of particles collected at pH 6 is about 0.590 mm.

Please refer to FIG. 3( a ) and FIG. 3( b ) respectively, which respectively illustrate another embodiment of the phosphorus removal rate and phosphorus conversion rate of the inflow wastewater with different pH values after the particle growth is stabilized, and the operating conditions are The pH values of the flowing wastewater were 6, 7, 9, and 11, respectively, and the molar concentration of the calcium ion of the crystallizing agent 32 relative to the phosphate ion of the phosphorus-containing wastewater 30 (Ca ⁺² : PO ₄ ^-3 ) was fixed at 1.2:1.0. The influent phosphate ion concentration was 1500 mg/L. It can be seen from Fig. 3(a) that after the end of the 60-hour operation time, the lowest phosphorus removal rate and conversion rate are at pH 6, wherein the phosphorus removal rate of pH 6 is 56.40%, and the phosphorus removal rate of pH 7 is 85.95%; the phosphorus removal rate of pH 9 was 88.37%, while the phosphorus removal rate of pH 11 was highest during the operation period of 9 to 18 hours, but decreased to 73.39% after 24 hours. It can be seen from Fig. 3(b) that the phosphorus conversion rate of pH 6 is 59.80%, the phosphorus conversion rate of pH 7 is 90.31%, the phosphorus conversion rate of pH 9 is 90.80%, and the phosphorus conversion of pH value 11 is obtained. The rate is 74.81%. It can be seen from Fig. 3(c) that the amount of particles collected at pH 6 is 23.91 g, the amount of particles collected at pH 7 is 71.29 g, and the amount of particles collected at pH 9 is 76.43 g, while pH 11 The amount of particles collected dropped to 59.79 grams. In Figures 3(a), (b), and (c), when the pH is increased from 6 to 9, the phosphorus removal rate, phosphorus conversion rate, and amount of collected particles also increase sharply (because there is more phosphoric acid). Root ions can react with calcium ions), however, as the pH increases from 9 to 11, the phosphorus removal rate, phosphorus conversion rate, and amount of collected particles decrease (because there are more nucleation sites present) at this pH. The value is not dominated by crystal growth to dominate the phosphorus removal rate, which is dominated by the nucleation site.

Please refer to FIG. 4(a) and FIG. 4(b), respectively, which illustrate the Mohr concentration ratio of different calcium ions to phosphate ions (Ca ⁺² : PO ₄ ^-3 = 1.0: 1.0, 1.2: 1.0, 1.4: 1.0) The phosphorus removal rate after the particle growth is stabilized is compared with the phosphorus conversion rate (liquid to solid state). The operating conditions were such that the pH of the influent wastewater was fixed at 9, and the influent phosphate ion concentration was 1500 mg/L. The phosphorus removal rate is a comparison of the total phosphate ion concentration consumed in the reaction tank with different pH values and the filtered concentration of the outflow water. It can be seen from Fig. 4(a) and Fig. 4(b) that after the end of the 60-hour operation time, the phosphorus removal rate and the phosphorus conversion rate of Ca ⁺² : PO ₄ ^-3 = 1.0: 1.0 are about 72.39%. The phosphorus removal rate and phosphorus conversion rate of Ca ⁺² :PO ₄ ^-3 = 1.2:1.0 are about 88.37%, and the phosphorus removal rate and phosphorus conversion rate of Ca ⁺² :PO ₄ ^-3 = 1.4:1.0 are about 97.09%. It can be seen that as the molar ratio of calcium ions to phosphate ions increases, the phosphorus removal rate and phosphorus conversion rate increase (because more calcium ions can react with phosphate ions). It can be seen from Fig. 4(c) that the amount of particles collected by Ca ⁺² :PO ₄ ^-3 =1.0:1.0 is 61.03 g, and the amount of particles collected by Ca ⁺² :PO ₄ ^-3 =1.2:1.0 is 76.43. Grams, while Ca ⁺² : PO ₄ ^-3 = 1.4: 1.0 The amount of particles collected was 136.86 grams, and the largest size of the particles was greater than 1.00 mm. Since more calcium ions are present, the amount of collected particles increases as the molar ratio of calcium ions to phosphate ions increases.

Please refer to FIG. 5( a ) and FIG. 5( b ) respectively, which respectively show the phosphoric acid ion concentration (500 mg/L, 1000 mg/L, 1500 mg/L PO ₄ ^-3 ) of different inflows after the particle growth is stable. The removal rate is compared to the phosphorus conversion rate (liquid to solid). The operating conditions were such that the pH of the influent wastewater was fixed at 9, and the molar concentration ratio of calcium ions to phosphate ions (Ca ⁺² : PO ₄ ^-3 ) was fixed at 1.2:1.0. It can be seen from Fig. 5(a) and Fig. 5(b) that after the end of the 60-hour operation time, the phosphate removal rate and the phosphorus conversion rate of the phosphate ion concentration of 500 mg/L are about 46.16%, and the phosphate ion concentration is 1000 mg. The phosphorus removal rate and phosphorus conversion rate of /L are about 64.84%, and the phosphorus removal rate and phosphorus conversion rate of phosphate ion concentration 1500 mg/L are about 88.37%. As the concentration of phosphate ions increases, the phosphorus removal rate and phosphorus conversion rate increase (because more calcium ions can react with phosphate ions). It was found from the experiments of the examples that the ions in the range of the minimum phosphate ion concentration are difficult to react with each other and eventually escape to the fluidized bed reactor in a dissolved or unreacted form, resulting in a relatively high phosphorus removal rate and phosphorus conversion rate. low. It can be seen from Fig. 5(c) that the amount of particles collected by the phosphate ion concentration of 500 mg/L is 5.06 g, the amount of particles collected by the phosphate ion concentration of 1000 mg/L is 23.90 g, and the phosphate ion concentration is 1500 mg/L. The amount of particles collected was 76.43 grams. Thus, increasing the phosphate ion concentration will increase the amount of collected particles while having a higher phosphorus removal rate.

From the above results, the treatment method of the present invention can be used to effectively remove phosphorus from phosphorus-containing wastewater and reduce the use of chemicals; moreover, the treatment method does not require the use of a support in a fluidized bed reaction tank. Therefore, the treatment efficiency obtained is high and the purity of the crystal particles is high, and the utilization potential is high. Furthermore, the treatment method of the present invention utilizes changes in operating conditions and reaction tank design to form crystals in a fluidized bed reaction tank, wherein the pH of the influent wastewater is controlled between 6 and 9, and calcium is The molar concentration ratio of ions to the phosphate ions in the phosphorus-containing wastewater is controlled between 1.0:1.0 and 1.4:1.0, and thus, more phosphate ions react with more calcium ions, thereby increasing phosphorus removal. Efficiency and crystallization granulation rate.

In the foregoing specification, the invention has been described in terms of a particular embodiment, and various changes or modifications may be made in accordance with the features of the invention. Therefore, obvious substitutions and modifications may be made by those skilled in the art, and will still be incorporated in the scope of the claimed invention.

10‧‧‧Reaction tank

12‧‧‧ lower section

14‧‧‧上段

16‧‧‧ Wastewater inlet

18‧‧‧Pharmaceutical inflow

20‧‧‧Water outlet

22‧‧‧Return line

24‧‧‧pH detector

26‧‧‧

28‧‧‧

30‧‧‧Fluorine-containing wastewater

32‧‧‧Crystal Pharmacy

Claims (4)

A method for removing phosphorus from a phosphorus-containing wastewater by a fluidized bed crystallization technique, comprising: providing a fluidized bed reaction tank having a lower section and an upper section, wherein the lower section is provided with a wastewater inlet and a medicament a flow port, the upper section is provided with a water outlet, and a return line is provided between the lower section and the upper section, the reaction tank does not have a support; the phosphorus-containing wastewater and the crystallizing agent are separately from the waste water inlet and the medicament The flow port is introduced into the fluidized bed reaction tank, wherein the influent phosphate ion concentration is controlled between 1000 mg/L and 1500 mg/L, and the crystallizing agent contains calcium ions and calcium ions are phosphate ions in the phosphorus-containing wastewater. The molar concentration ratio is controlled between 1.0:1.0 and 1.4:1.0, the pH value of the influent wastewater is controlled between 7 and 9; and the phosphorus-containing wastewater mixed with the crystallization agent is used in the reaction tank The lower portion flows to the upper portion of the reaction tank and is returned to the lower portion via the reflux line for circulation, so that phosphate ions in the phosphorus-containing wastewater react with calcium ions in the crystallizing agent to form crystal particles. The treatment method according to claim 1, wherein the crystallization agent is calcium chloride. The treatment method according to claim 1, wherein the calcium ion concentration ratio of the phosphate ion in the phosphorus-containing wastewater is 1.2:1.0, the pH of the influent wastewater is 9, and the inflowing phosphate The ion concentration was 1500 mg/L. The treatment method according to claim 1, wherein the calcium ion concentration ratio of the phosphate ion in the phosphorus-containing wastewater is 1.4:1.0, and the pH of the influent wastewater is 9 The influent phosphate ion concentration was 1500 mg/L.