KR100466280B1 - Suspended solid removing method of wastewater by electrofloatation and sedimentation - Google Patents

Abstract

An object of the present invention is to propose a method for economically and efficiently removing suspended solids in wastewater by electrolytic flotation and precipitation.

To this end, the waste water is neutralized and coagulated, and then sent to the floating part 3 of the electrolytic flotation and the settling tank 1, and the suspended solids having a low specific gravity are lifted by the scraper 6 when they are injured by the bubbles generated in the electrolytic cell 11. Scum hopper (10) by the transfer to remove, the heavy gravity is sent to the sedimentation section (2), if settled through the sludge pit (Sludge pit; 9), the solid water is removed from the water (1) The secondary treated water) is flowed into Weir (4) and sent to the next (secondary) process through the ditch 15.

It is expected that it will be widely used in the wastewater treatment field because the efficiency of removing suspended solids is much higher than the conventional single sedimentation or flotation process, and the treatment process is simple, the facility cost and operation cost are low, and the operation is easy. .

Description

Suspended solid removing method of wastewater by electrofloatation and sedimentation

The present invention separates and removes suspended solids from the waste water by electrolytic flotation and precipitation method, and removes and removes heavy ones by sedimentation by separating heavy weights, improving facility removal efficiency and operating costs. It is to propose a method that is cheaper than the prior art.

Solid materials in waste water have a problem in that the suspended solids cannot be separated and removed efficiently when only a single precipitation process or a single flotation process is applied because the specific gravity is a mixture of light and heavy specific gravity.

In order to solve this problem, in Korea Patent Registration No. 0173968, the floating solids in the wastewater were treated by flotation, sedimentation, and concentration process, and the treatment efficiency was significantly improved compared with the case of applying a single precipitation process or flotation process. A part of the water is dissolved by pressurizing pump, pressure tank and air compressor into water and then decompressed to generate fine bubbles while decompressing the floating solid material. For example, the solid material with heavy specific gravity was sludge concentrated in the thickening part after sedimentation, and the sludge was discharged, but the residence time of the precipitated sludge was long. Sludge rises, resulting in a decrease in treatment efficiency. There is a problem with the needs of skilled operating personnel and facility cost because operating costs are high, such as driving at high pressure operation difficult.

In the case of Korean Patent Publication No. 1994-0003858 and Registration No. 10-0319022, the electrode is installed in contact with the wastewater, and in the case of the wastewater having a low electrolyte concentration, it is necessary to supply a neutral electrolyte such as NaCl, Na ₂ SO _4, and so on. In this case, when the electrolyte concentration is relatively low, the applied voltage must be increased, so the power cost is a problem, and thus the overall operating cost may be much higher than that of the pressurized part.

In addition, when the electrode is in direct contact with the wastewater, metal ions such as Ca ⁺⁺ , Al ⁺⁺⁺ , Fe ⁺⁺ , Fe ⁺⁺⁺ in the water precipitate on the cathode to form a scale and thus hydrogen polarization. Because of the phenomenon, the resistance may be increased and operation may be impossible, so the pole switching should be performed every certain time. If the pole switching is frequent, there is a problem of shortening the life of the electrode because it cannot solve the problem of oxidation corrosion of the anode. .

In the case of Korean Patent Publication No. 2002-0031121, an oxo-compound salt (NaCl) such as Cl ^- ion is supplied to the electrolyte to generate chlorate ions such as ClO ^- by electrolysis to produce organic substances in wastewater, In the case of floating by the generated bubbles while oxidatively decomposing NH ₄ ⁺ ions or the like, there is a problem that it is not feasible because there is no economical efficiency because of high power cost and electrolyte cost.

In other words, in the case of wastewater treatment by electrolysis, a Faraday current of 26,800 Ah is applied to electrolyze 1 kg equivalent material, so that the power consumption is high and the electrolyte concentration is about 0.5% or less. In this case, since it is necessary to supply the electrolyte separately, the operating cost is much higher than other methods, so it is not realized.

And, Korean Unexamined Patent Publication No. 194-0003858, Japanese Patent Publication No. Hei 05-212385, Hei 09-029260, Hei 10-305282, Hei 10-305283 No. 2000-117260 can also cause problems such as electrolyte consumption, power ratio, cathode scale and hydrogen polarization by bringing electrodes into contact with wastewater, and it is difficult to remove heavy solids in the wastewater. There is a problem falling.

An object of the present invention is to solve the above problems, in order to separate the suspended solids in the waste water, economical and efficient separation of the suspended solids by electrolytic flotation and sedimentation, which is easy to operate and low in operation cost and operation cost. It is the purpose of the present invention to eliminate it.

In order to achieve the above object, the present invention is to install a floating part inside the sedimentation tank to separate and remove the suspended solids having a low specific gravity from the waste water by the first injury, and then settle the suspended solids with a heavy specific gravity at the sedimentation section. The process is simpler compared to the DAF (Dissolved air floatation) method, which floats and removes lightly suspended suspended solids by the bubbles generated by decompression of conventional air in pressurized water while improving the removal efficiency of suspended solids. in applying the floatation method, was reducing the electrolyte consumption and power ratio by installing the electrode in the scale and the electrolytic bath (chamber) in order to solve the hydrogen polarization of the negative electrode isolated from the Oh and waste water, the electrolyte is Glauber's salt of the weak acid (Na ₂ SO _4), while improving the above-mentioned problems by using the aqueous solution of facility cost and operation cost are inexpensive and effective in the suspended solids How would you suggest can.

1 is a wastewater treatment process diagram by electrolytic flotation and precipitation

2 is a plan view of the electrolytic flotation and the settling tank

3 is an electrolytic flotation and a settling tank front view

4 is a top view of the electrolyzer

5 is an electrolytic cell front view

<Explanation of symbols for main parts of drawing>

1: electrolytic flotation and precipitation tank 2: precipitation section

3: Injured part 4: Weir

5: Skimmer 6: Scraper

7: Center well 8: Drive reduction gear

9: Sludge pit 10: Scum hopper

11: electrolytic cell 12: positive electrode plate

13: negative electrode plate 14: rectifier

15: Ditch 16: Hand Rail

17: Walk way 18: Rotation axis

19: porous membrane

Since suspended solids in wastewater are often mixed with suspended solids and heavy solids, which are lighter than the specific gravity of water, when only the sedimentation tank is applied, the suspended solids, which are light in weight, are floated on top of the sedimentation tank and discharged together with the water. Even when floating flotation tanks are applied, solid materials with heavy specific gravity precipitate and are discharged together with the water of water, which reduces the efficiency of separation and removal of suspended solids.In addition, floating solids are injured by bubbles generated by dissolving air in pressurized water and decompressing air. The separation DAF method is complicated and the operation process is difficult, there is a defect in the high facility cost and operating cost in the present invention proposes a method for economically and efficiently treating the suspended solids in the waste water by the electrolytic flotation and precipitation method. will be.

Hereinafter, described in detail by the accompanying drawings as follows.

When the wastewater enters the sump, it is transferred to the neutralization tank, and caustic soda is stirred by injecting a flocculant of polycation metal salts such as alumina, poly aluminum chloride (PAC), iron sulfate (FeSO₄), and ferric chloride (FeCl₃). Neutralizing agents such as (NaOH) and slaked lime (Ca (OH) ₂) are injected to neutralize the pH around 7 and then flocculate suspended solids with negative charges by electrical attraction and then send them to the flocculation tank for electrolytic flotation and precipitation. In 1), floc (Floc) is formed by slow stirring while injecting organic polymer coagulant to float and settle, and then it is sent to electrolytic flotation and precipitation tank (1).

Wastewater injected into the center well (7) of the electrolytic flotation and the settling tank (1) is floated by the bubbles generated in the electrolyzer (11) installed in the lower portion of the suspended solid material with a light specific gravity rises to the top of the floating portion (3) When it is sent to the scum hopper (Scum hopper; 10) by a rotary skimmer (Skimmer 5) and then sent to the sludge and scum storage tank to remove, the heavy material is settled in the settling section (2) scraper (Scrapper; 6) is sent to the sludge pit (9) to be discharged to the scum and sludge storage tank to remove, at this time sludge deposited in the sedimentation section (3) to improve the solids removal efficiency, the middle of the outside of the center well (7) Form a blanket layer to the extent that the water flows through the second layer, while the solid material is filtered and passed through the fish water in the state that the solids are removed as much as possible (Weir; 4) to the ditch (Ditch) Through 15) Liver) sends process twos.

The electrolyzer 11 is a quadrangular tube as shown in Figs. 4 and 5, and the body is a polyvinyl chloride (PVC), an polyethylene (PE), and an engineering plastic (Engineering plastic), which is an insulating material. Produced by using bakelite, etc., the anode 12 and the cathode 13 are installed alternately at regular intervals, and the electrolyte inside the electrolytic cell 11 is disposed at the top with wastewater and For isolation, a porous membrane 19 such as asbestos or synthetic resin, which is a corrosion resistant material, is provided for the electrolyte.

Since the positive electrode plate 12 is highly corroded during the electrolytic reaction, the DSA coated with TiO₂-RuO₂ on the titanium plate, which is a corrosion-resistant material and has a low oxygen generation overvoltage, is coated. (Dimensionally stable anode) electrode is used, and the material of the negative electrode plate 13 is made of platinum plated plate or titanium plate which has low hydrogen generation overvoltage and excellent corrosion resistance to the electrolyte during cease-fire. .

The electrolyte solution may be a mineral acid such as sulfuric acid (H₂SO₄), hydrochloric acid (HCl), or an electrolyte such as manganese (NaSO₄) or salt (NaCl), but hydrochloric acid or salt with Cl ^- ion is used for electrolytic reaction. when hypochlorite ions (ClO ^-) considering the oxo compound (oXO-compounds) are as generated forgoing possible since the anode corrosion snarled, hydrogen in the cathode polarization, and the scale (scale) occurs as such subjected to sulfuric acid in the Glauber's salt solution pH Use weakly acidic aqueous solution adjusted to about 5.

When a direct current is applied from the rectifier 14 while supplying weakly acidic aqueous solution to the electrolyzer 11, oxygen (O2) is generated at the anode 12 and the cathode (13) while the following electrochemical reaction is known at the electrolyzer 11. ), Hydrogen (H₂) bubbles are generated.

Anodic reaction in acidic aqueous solution

2H₂O → O₂ (g) + 4H + + e -, E 0 = 1.227V

Cathodic Reaction in Acidic Aqueous Solution

^{4H + + e - → 2H₂ (} g), E 0 = OV

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Overall reaction 2H₂O → O₂ (g) + 2H₂ (g), E ⁰ = 1.227V

In the above-described electrolytic reaction, the bubble generation amount is proportional to the applied current amount, and the size of the particles of the generation bubble depends on the applied voltage.

If the applied voltage is low, the particle size of the generated bubbles is small, while the size of the bubble particles generated at a high applied voltage is large.

The current applied at a constant voltage changes depending on the concentration of the electrolyte in the electrolytic cell 11. When the concentration of the electrolyte is increased, the amount of bubbles generated increases as the applied current increases. On the contrary, when the concentration of the electrolyte decreases, the applied current also decreases. The outbreak is reduced.

In the case of small bubbles generated due to the applied voltage being low, the floating speed is slowed to prevent floating solid matters. On the other hand, if the applied voltage is too high, bubbles of large particles are generated and the floating speed of the bubbles is too fast. As the stirring occurs, the floating efficiency decreases.

Therefore, an optimum voltage should be applied by installing a voltage indicating controller (VOC), and the amount of bubble generation is performed by installing an amper indicating controller (AIC) while applying an optimum applied voltage. Adjust the injection volume so that the optimal current is applied.

Then, the scum generated from the scum hopper 10 of the floating part 3 and the sludge discharged from the sludge fit 9 of the sedimentation part 2 are sent to the sludge and the scum storage tank, and then sent to a dewatering process for dehydration treatment. The fish water flowed to the upper part of the precipitation part 2 is sent to the primary (middle) treatment tank, and then sent to the secondary biological treatment process or other post-treatment process.

As is apparent from the above description, the present invention has a much higher treatment efficiency compared to the case of separating and removing the suspended solids from the wastewater in a single sedimentation tank or flotation tank, and the process cost and operation cost are considerably lower than those of the conventional pressurization tank. Because of its simplicity, it is expected to be widely used to remove suspended solids in wastewater treatment because it is easy to operate and maintain.

Claims (3)

Suspended solids contained in the waste water are neutralized and aggregated, and then supplied to the center well (7) of the electrolytic flotation and the settling tank (1), and to the bubbles generated by the electrolytic cell (11) installed at the bottom. Floating solid material having a light specific gravity is lifted to the upper part of the floating part (3), and then transported to the scum hopper (Scum hopper; 10) by a skimmer (5). 2) When settled, it is sent to the sludge pit by a scraper (6) to be discharged and removed, and the waste water from which the suspended solids are removed is fed into the weir (4) above the settling section (2). To remove suspended solids from wastewater. The method according to claim 1, wherein the positive electrode plate 12 and the negative electrode plate 13 are provided inside the electrolytic cell 11, and the porous membrane 19 is provided on the upper side, so that the electrode plate and the electrolyte of the electrolytic cell 11 are separated from the waste water. A method of reducing power consumption and minimizing the negative electrode scale and hydrogen polarization to facilitate operation. The method of claim 2, wherein sulfuric acid (H 2 SO ₄) is added to the aqueous solution of NaSO 해서 using a weakly acidic aqueous solution having a pH of 4 to 5 as the electrolyte, the material of the positive electrode has a low oxygen generation overvoltage and corrosion of the anode A titanium-dioxide-stable anode (DSA) coated with TiO₂-RuO₂-coated on a titanium plate with excellent corrosion resistance.The cathode has a low hydrogen generation overvoltage and a power failure. Method to improve corrosion problems with low power consumption by using platinum plated or titanium plate with excellent corrosion resistance in electrolyte.