TWI576317B - Method of treating suspended solids and heavy metal ions in sewage - Google Patents

Description

Method for treating suspended solids and heavy metal ions in sewage

The invention relates to a method for treating sewage, in particular to a method for treating suspended solids and heavy metal ions in sewage

Removal of suspended solids and heavy metal ions from water is a very important part of improving water quality. In general, contaminants such as suspended solids and heavy metal ions in the sewage are uniformly distributed in the water body without a proper chemical addition, or only settle at a relatively slow speed, and it takes a long time to separate from the water. Therefore, in the conventional sewage treatment method, an appropriate chemical agent is generally added to precipitate suspended solids or other pollutants in the form of sludge.

In order to accelerate the precipitation and to combine the suspended solids into a dense sludge, a conventional method such as a hydroxide precipitation method is to accelerate the suspension solids by adding a chemical such as sodium hydroxide, lime and magnesium hydroxide. precipitation. In addition, with the combination of other programs and pharmaceuticals, many other commercially available technologies have been developed. However, in the above-described accelerated precipitation method, there are still common disadvantages such as high sludge moisture content, inability to recover, and purification.

As described above, the use of chemical coagulation precipitation to remove suspended solids and heavy metal ions in water is a fairly widely used technique for water treatment. However, its long-standing problem is that the moisture content of the sludge is too high (>98%). To further reduce the water content in the sludge, the traditional way of treating sludge is pressure filtration. Dehydration procedure, however, the water content of the filter cake formed by this procedure is still more than 50%. Up to 50% moisture content will result in high processing costs when shipping and handling filter cakes.

On the other hand, in 1970, researchers such as Kostenbader and Haines invented the High Density Sludge (HDS) program to increase the solids content in the sludge, so that the solids content in the sludge could be increased to 10~30%. The water content of the filter cake can be reduced to 30-50% by dewatering by pressure filtration. The operation step is to recover the generated sludge and mix it with the slaked lye, and then inject it back into the water treatment tank to react with the newly formed sludge to achieve the effect of densification. However, the main disadvantages of this technology are as follows: 1. It is necessary to additionally set up a reaction tank for large-scale sludge recovery and alkali treatment; 2. The moisture content of the treated filter cake is still high; 3. Recycling pollution If the amount of mud is too large, it will reduce the efficiency of water treatment; 4. It is impossible to reduce the volume of sludge that has already produced low solid content.

Other related wastewater treatment methods, for example, TW 438725 discloses a wastewater treatment method for removing harmful ions by coagulation sedimentation, which mainly uses an aluminum compound and polypropylene decylamine as a coagulant, and reuses the sediment as a coagulant. TW I228104 discloses a zero sludge wastewater treatment method and apparatus, which converts copper-containing wastewater treatment into valuable heavy metal raw materials, and the residue can be recycled as a coagulant; TW I280951 discloses a fluidized bed process aqueous solution treatment system, The system mainly mixes the treatment liquid and the reactants with the reflux water to form a reaction crystal through the arrangement of the nozzles on the piping; and US Pat. No. 7,738,513 discloses a solid-liquid fluidized bed for simultaneously removing carbon, nitrogen and phosphorus. A wastewater treatment system that uses a biological fluidized bed technology to simultaneously remove carbon, nitrogen and phosphorus using a wastewater treatment system with two fluidized beds.

However, in the above-mentioned prior art, an effective solution has been proposed for how to effectively solve the problems of excessive water treatment equipment, excessive water content of the filter cake, poor processing efficiency, and inability to reduce the volume of the sludge.

In order to solve the above-mentioned defects in the prior art, the present invention provides a method for treating suspended solids and heavy metal ions in sewage, in order to solve the conventional treatment method, the water treatment equipment covers an excessively large area, the moisture content of the filter cake is too high, and the treatment Inefficiency and the inability to reduce the volume of sludge.

In order to achieve the above and other objects, the method for treating suspended solids and heavy metal ions in the sewage of the present invention utilizes a tank to use the sludge formed by the purified sewage as a filler as a purification aid to freshly inject. Sewage and chemicals can be combined on the surface of the filled sludge, including adsorption, agglutination, crystallization and dehydration.

The method for treating suspended solids and heavy metal ions in the sewage of the present invention comprises the following steps: Step 1: adding iron sulfate-based reagent to some sewage to be treated, and initially precipitating suspended solids in water, and initially separating the sewage into lower turbidity. Primary treatment sewage and low-density sludge; Step 2: filling the low-density sludge separated in step 1 into a tank, wherein the tank body has at least a first inlet and a first outlet, and the first outlet is Located above the first inflow port; and step 3: injecting other sewage or primary treated sewage to be treated into the first inflow port, so that other sewage or primary treated sewage to be treated passes through the low density sludge in the trough to fluidize The low-density sludge combines the suspended solids in the water with the low-density sludge, and the treated water passing through the low-density sludge flows out through the first outlet.

In the above treatment method, the iron sulfate-based reagent described in the step 1 may be iron sulfate, ferrous sulfate or polyferric sulfate.

In the above treatment method, the alkaline earth metal hydroxide is further added to the sewage in the step 1.

In the above treatment method, the ratio of the iron sulfate-based reagent to the alkaline earth metal hydroxide in the sewage of the step 1 is between 1:2 and 1:4.

In the above treatment method, before the step 2, calcium hydroxide Ca(OH) ₂ or barium hydroxide Ba(OH) _{2 is} further added to the low-density sludge separated in the step 1.

In the above treatment method, the step 3 further directs the treated water flowing out from the first outlet to the first inlet and then returns it to the tank to repeatedly bind the suspended solids in the water to the sludge in the tank. When the agglomerated sludge can no longer be fluidized or the treated water has been sufficiently purified, the water in the tank is released.

In the above treatment method, in the step 2, the alkaline earth metal hydroxide is further added to the sewage and injected into the inflow port.

In the above treatment method, the iron sulfate-based reagent is further added to the sewage in the step 2, and is injected into the inflow port.

In the above processing method, the tank further includes a second inflow port and a second outflow port located above the second inflow port, the second inflow port and the second outflow port being located below the first outflow port In step 3, the sludge flowing out from the second outlet is further guided to the second inlet and then injected back into the tank.

The method for treating suspended solids and heavy metal ions in the sewage of the invention uses the fluidized bed technology to continuously combine the suspended solids in the sewage with the sludge in the tank, so that the density of the sludge in the tank rises, densifies, and continuously The circulation continues to reduce suspended solids and heavy metal ions in the sewage. Finally, the dense sludge that can no longer be fluidized can be taken out of the tank. The invention can reduce the volume of solid waste, the dosage of the medicament, and convert the sludge in the reaction tank into crystal grains to facilitate solid-liquid separation and reduce the load of the subsequent processing unit.

100‧‧‧ tank

110‧‧‧First entrance

120‧‧‧first exit

130‧‧‧ Fluidized sludge

140‧‧‧ treated water

200‧‧‧ tank

210‧‧‧First entrance

220‧‧‧First-rate exit

230‧‧‧ Fluidized sludge

240‧‧‧ treated water

250‧‧‧Second inflow

260‧‧‧Secondary exit

270‧‧‧ third-rate exit

1 is a schematic view showing a tank body and an operation state used in a method for treating suspended solids and heavy metal ions in sewage according to Embodiment 1 of the present invention.

Fig. 2 is a schematic view showing the tank body and the operation state used in the method for treating suspended solids and heavy metal ions in the sewage of Example 2 of the present invention.

In order to fully understand the objects, features and advantages of the present invention, the present invention will be described in detail by the accompanying drawings. And the effect of the present invention will be explained in detail by the following specific embodiments, together with the accompanying drawings, and the following:

Example 1

The method for treating suspended solids and heavy metal ions in the sewage of the present embodiment comprises the following steps:

Step 1: Adding iron sulfate-based reagent to some of the sewage to be treated to precipitate the suspended solids in the water, and initially separating the sewage into primary treated sewage with low turbidity and low-density sludge. In step 1, after the preliminary precipitation of suspended solids in the water, the upper liquid portion can be regarded as the primary treated sewage, and the precipitated low-density sludge is used in the subsequent step 2.

Step 2: The low-density sludge separated in the step 1 is filled into a tank body, wherein the tank body has at least a first inflow port and a first outflow port located above the first inflow port. In the step 2 of the first embodiment and the subsequent step 3, the tank system used has at least a first inflow port 110 and a first outflow port 120 located above the first inflow port 110, as shown in FIG.

Step 3: Inject other sewage or primary treated sewage to be injected into the first inlet, and let other sewage or primary treated sewage to pass through the low-density sludge in the tank to fluidize the low density. The sludge is combined with the low-density sludge in the water, and the treated water passing through the low-density sludge flows out through the first outlet. Referring to FIG. 1 , in step 3 of the embodiment, a sewage pump is used to inject sewage from the first inlet 110, and the injected sewage fluidizes the low-density sludge in the tank 100 to form a fluidized sludge. 130. The treated water 140 of the fluidized sludge 130 forms a liquid surface above the fluidized sludge 130. When the liquid level rises to the height of the first outlet 120, the sludge is fully treated. The water 140 will flow out from the first outflow port 120.

In the early stage of injecting sewage, it is preferred to control the flow rate of sewage injection to a lower range to avoid sludge loss in the tank. As shown in FIG. 1, it is preferable to control the flow rate of the sewage injection so that the interface between the fluidized sludge 130 and the treated water 140 is located below the first outlet 120. The hydraulic retention time can be as long as 30 min to 5 hours, and the flow rate of the treated water in the tank is about 10 cm/nin.

Preferably, when the solid particles form crystal particles, the flow rate of the sewage injection can be gradually increased, so that the hydraulic retention time is 5 to 15 minutes.

Preferably, the pH of the treated water can be further monitored, and the measured pH should be greater than 7.0 to ensure complete reaction of iron, calcium/strontium ions in the water. When the measured pH value is less than 7.0, the alkaline earth metal hydroxide may be further added to the sewage and injected into the inflow port to maintain the pH of the treated water in a range of more than 7.0.

Example 2

The treatment method of suspended solids and heavy metal ions in the sewage of Example 2 is substantially similar to that of Example 1, but steps 1 to 3 of the adjustment of Example 1 are as follows to further improve the efficiency of sewage treatment.

Step 1: Adding iron sulfate-based reagent and alkaline earth metal hydroxide to some of the sewage to be treated to precipitate the suspended solids in the water, and initially separating the sewage into primary treated sewage with low turbidity and low-density sludge. In the first step, after the preliminary precipitation of suspended solids in the water, the upper liquid portion can be regarded as the primary treated sewage, and the low-density sludge of the lower solid portion is taken for the subsequent step 2.

In comparison with Example 1, in Example 2, an alkaline earth metal hydroxide was further added to the sewage. The ratio of the iron sulfate-based reagent to the alkaline earth metal hydroxide is between 1:2 and 1:4.

Step 2: adding calcium hydroxide Ca(OH) ₂ or barium hydroxide Ba(OH) _{2 to} the low-density sludge separated in step 1, forming a denser sludge, and filling the denser sludge into one In the tank body, the tank body has a first inlet and a first outlet located above the first inlet, and a second inlet and a second outlet above the second inlet, the second flow The inlet and the second outlet are located below the first outlet. In step 2 of the second embodiment and the subsequent step 3, the tank system used is as shown in FIG. 2, the tank body 200 has a first inlet 210 and a first outlet 220 located above the first inlet 210. The second inflow port 250 and a second outflow port 260 above the second inflow port 250, and a third outflow port 270 above the first outflow port 220. Compared with Embodiment 1, the tank body of Embodiment 2 further includes a second inflow port 250 and a second outflow port 260 located above the second inflow port 250, and a third portion above the first outflow port 220. Outflow port 270.

Step 3: Injecting other sewage or primary treated sewage mixed with alkaline earth metal hydroxide and iron sulfate-based reagent into the first inflow port 210, and passing the sewage through the denser sludge in the trough 200 to fluidize the When the sludge is denser, the fluidized sludge 230 flowing out from the second outlet 260 is led to the second inlet 250 and injected back into the tank 200, so that the suspended solids in the water are combined with the low-density sludge. The treated water 240 passing through the sludge flows out through the first outlet 220. Wherein, the treated water 240 flowing out from the first outflow port 220 is further guided to the first inflow port 210 and injected back into the trough body 200 to repeatedly bind the suspended solids in the water to the solid particles in the fluidized sludge 230. When the agglomerated sludge can no longer be fluidized, the water in the tank 200 is released. Referring to FIG. 2, in step 3 of Embodiment 2, the sewage to be treated is injected from the first inlet 210 by a metering pump, and the injected sewage fluidizes the densely densified sludge in the tank 200 to form Fluidized sludge 230. Passing through the fluidized sludge 230 The water is formed above the fluidized sludge 230 to form a liquid surface. When the liquid level rises to the height of the first outlet 220, the treated water sufficiently interacting with the sludge 230 will flow out from the first outlet 220. .

Compared with the first embodiment, in step 3 of the second embodiment, the fluidized sludge 230 flowing out from the second outlet 260 is further guided to the second inlet 250 and injected back into the tank 200 to ensure the tank. The fluidized sludge 230 in 200 can uniformly react with the sewage. Furthermore, in step 3 of Embodiment 2, the treated water 240 flowing out from the first outflow port 220 is further guided to the first inflow port 210 and injected back into the trough body 200 to repeatedly bind the suspended solids in the water to the trough body. On the sludge in 200, when the agglomerated sludge can no longer be fluidized or the treated water 240 has been sufficiently purified, the water in the tank 200 is discharged from the third outlet 270 to ensure the water. The suspended solids are fully excluded. Further, in the step 3 of the second embodiment, the sewage to be treated is mixed with an alkaline earth metal hydroxide and an iron sulfate-based reagent before being injected into the tank 200.

Similar to the first embodiment, in the second embodiment, before the sewage is injected, it is preferred to control the flow rate of the sewage injection to a lower range to avoid sludge loss in the tank. As shown in FIG. 2, it is preferable to control the flow rate of the sewage injection so that the interface between the fluidized sludge 230 and the treated water 240 is located between the first outlet 220 and the second outlet 260 to avoid The fluidized sludge 230 flows out of the first outlet 220, and the fluidized sludge 230 can flow out from the second outlet 260 to the second inlet 250 and be injected back into the tank 200. The hydraulic retention time can be as long as 30 min to 5 hours, and the flow rate of the treated water in the tank 200 is about 10 cm/min.

Preferably, a valve is provided in the third outflow port 270, and the discharge of the treated water 240 is controlled by the valve. In the second embodiment, after the sewage is injected into the first inflow port 210 for about one hour, the valve disposed in the third outflow port 270 is opened, and the time at which the valve disposed in the third outflow port 270 is opened is not particularly limited. The operation can be appropriately adjusted depending on the degree to which the treated water 240 is purified. By the arrangement of the third outflow port 270, the upper portion of the treated water 240 that is sufficiently purified can be discharged from the third outflow port 270, and the lower portion of the treated water 240 that is not sufficiently purified is from the first outflow port. 220 flows out and is directed to the first inflow port 210 and back into the trough 200 to ensure that the treated water 240 discharged from the third outflow port 270 has been sufficiently purified.

In the second embodiment, the agglutination reagent such as iron sulfate or polyferric sulfate is used to treat the sewage with calcium hydroxide or barium hydroxide, and the produced low solid content sludge is pretreated with the alkali solution to form a denser one. The sludge is then filled into the tank. Preferably, the treated water and the fluidized sludge are refluxed by a certain amount of pumps.

In Example 1 and Example 2, the injected sewage acts on the surface of the high surface area solid particles in the fluidized sludge to increase the density of solid particles in the fluidized sludge. In the first embodiment and the second embodiment, the suspended solids or heavy metal ions in the sewage are precipitated by the solid particles in the fluidized sludge to continuously treat the sewage containing suspended solids or heavy metal ions, and continue in the fluidized sludge. Growing on solid particles. Thereby, the solid particles are formed into crystal particles and the water content thereof is lowered to 5 to 20%. The crystal particles can be easily subjected to solid-liquid separation without the use of conventional micro-aperture film technology. The principle of the present invention is similar to the conventional High Density Sludge (HDS) program, but the sewage treatment method of the present invention is carried out in the same tank as compared to the conventional high density sludge (High Density Sludge, The HDS) program does not require an additional reaction tank for sludge recovery and alkali adjustment, and has the advantage of saving space.

The method for treating suspended solids and heavy metal ions in the sewage of the invention, wherein the reagent of the sulfuric acid-based iron salt is used as a coagulant to fully mix with the sewage, the alkali can be utilized, such as slaked lime, barium hydroxide, phosphate or sodium hydroxide. And the formation of a precipitate, which can remove pollutants in the water such as suspended solids, uranium or ultra-uranium ions.

On the other hand, since the sulfate ion can form a sparingly soluble or insoluble sulfate with a cation such as calcium or barium, the conductivity in the water is not too high. Therefore, the solid formed in the tank contains iron hydroxide (contains heavy metal or sewage suspended solids) and sulfate.

The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of protection of the present invention is defined by the scope of the patent application.

100‧‧‧ tank

110‧‧‧First entrance

120‧‧‧first exit

130‧‧‧ Fluidized sludge

140‧‧‧ treated water

Claims (6)

The invention relates to a method for treating suspended solids and heavy metal ions in sewage, comprising the following steps: Step 1: adding iron sulfate-based reagent to some sewage to be treated, preliminary precipitation of suspended solids in water, preliminary separation of the sewage into primary treatment with low turbidity Sewage and low-density sludge; Step 2: Filling the low-density sludge separated in the step 1 into a tank, wherein the tank body has at least a first inlet and a first outlet, and the first outlet is located at the same Above the first inflow port; and step 3: injecting other sewage or primary treated sewage to be treated into the first inflow port, so that other sewage or primary treated sewage to be treated passes through the low density sludge in the trough to fluidize the low Density sludge, the suspended solids in the water are combined with the low-density sludge, and the treated water passing through the low-density sludge flows out through the first outlet; wherein the low density is further separated in step 1 before performing step 2. Calcium hydroxide Ca(OH) ₂ or barium hydroxide Ba(OH) ₂ is added to the sludge. The method of claim 1, wherein the iron sulfate-based reagent according to step 1 is iron sulfate, ferrous sulfate or polymeric ferric sulfate. The method of claim 2, wherein the alkaline earth metal hydroxide is further added to the sewage in the step 1. The method of claim 3, wherein the ratio of the ferric sulfate-based reagent to the alkaline earth metal hydroxide in the wastewater of the step 1 is between 1:2 and 1:4. The processing method of any one of the items 1 to 4, wherein the step 3 further directs the treated water flowing out of the first outflow port to the first inflow port and then returns it to the trough body to repeat The suspended solids in the water are bound to the sludge in the tank, and when the agglomerated sludge can no longer be fluidized or the treated water has been sufficiently purified, the water in the tank is released. The processing method of claim 5, wherein the tank further comprises a second inflow port and a second outflow port located above the second inflow port, the second inflow port and the second outflow port are located in the first Below the first-class outlet, in step 3, the sludge flowing out of the second outlet is further guided to the second inlet and injected back into the tank.