JPH0137983B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a method for removing phosphorus and SS contained in sewage, human waste, or industrial wastewater. "Prior art" Wastewater containing phosphorus is brought into contact with fluidized phosphate mineral (phosphate rock) in the presence of calcium and alkali, and the phosphorus in the wastewater is converted to apatite Ca ₁₀
The method of crystallizing (OH) ₂ (PO ₄ ) ₆ on the mineral filter medium is a known technique and is expected to be an effective method since it generates a small amount of sludge that is difficult to treat. ``Problems to be Solved by the Invention'' In the conventional method, most of the phosphorus contained in wastewater can be fixed on the filter medium, but since the filter mediums collide with each other in a fluidized state, reactants on the filter medium are If a part of the filter material peels off, or if fine apatite generated in the liquid or SS in the wastewater leaks into the treated water, and if a sand filtration is installed in the latter stage, the filter layer will become clogged in a short period of time and the problem will be reversed. The frequency of washing increased, and the disposal of solids discharged by backwashing was also troublesome. The present invention aims to solve these problems. "Means for Solving the Problems" The present invention provides a fluidized bed dephosphorization method in which phosphorus-containing wastewater is brought into contact with solid particles having phosphorus removal ability in the presence of calcium and alkali. Below is a method for treating phosphorus-containing wastewater characterized by bringing it into contact with the solid particles, which was developed as a result of the inventor's repeated studies to solve the problems of the conventional technology described above. The present invention relates to a method for efficiently removing phosphorus and SS present in wastewater by contacting a reaction solution with a filter medium in the presence of an anionic polymer in a reaction tank in which the filter medium is fluidized. The process flow of an embodiment of the present invention will be explained using FIG. 1. Phosphorus-containing wastewater (raw water) 1 to which calcium salt 2 or alkali agent 3 has been added, and reaction tank 9
Part of the effluent water is mixed with circulating water 4 to which calcium salt 5 or alkali agent 6 has been added, and the water is passed into reaction tank 9. Here, the anionic polymer 7 is injected into the reaction tank, and the solid particles 8 having phosphorus removal ability are fluidized in the presence of the anionic polymer.
By contacting with water, some of the phosphorus and SS in the wastewater are removed. A part of the reaction tank outflow water is circulated water 4, and the rest is passed through a filter tank 12 filled with a filter medium 11 such as sand, which mainly removes SS phosphorus and remaining SS.
remove. Calcium chloride, gypsum, and slaked lime can be used as calcium salts, and slaked lime and caustic soda can be used as alkaline agents. Methods for injecting calcium and alkaline agents include: injecting a calcium agent into raw water and then injecting the alkaline agent into circulating water; injecting an alkaline agent into raw water and then injecting a calcium agent into circulating water; There is a method in which calcium and alkaline agents are injected into the circulating water, and calcium and alkaline agents insufficient for the reaction are injected into the circulating water, and there is a method in which a calcium agent and an alkaline agent are injected into the circulating water. It is desirable to inject the alkaline agent while detecting the pH of the liquid in the reaction tank. The mixing ratio of raw water and circulating water is preferably 1:1 to 1:3. The anionic polymer injected into the reaction tank is
Sodium polyacrylate, polyacrylamide, maleic acid copolymer, etc. are good, and the injection amount is
0.2 to 1 mg/is good. The anionic polymer is preferably injected into the reaction tank. The flow rate of the liquid in the reaction tank is the rate necessary for fluidizing the solid particles having phosphorus removal ability, and is determined by the particle size and density of the solid particles. Note that the solid particles are those having phosphorus removal ability, such as phosphate rock, bone charcoal, Kanuma soil, and lightly burnt magnesia. As described above, in the present application, in the fluidized bed dephosphorization method, a solution in which Ca ²⁺ and OH ^- have been adjusted is brought into contact with a filter medium having phosphorus removal ability in the presence of an anionic polymer, thereby increasing the mutual interaction between the filter media. Since SS generated during mutual collisions and reactions can be fixed on the filter medium, the phosphorus removal rate (phosphorus fixation rate) of fluidized bed dephosphorization can be significantly improved, and the frequency of backwashing in the subsequent filtration process can be reduced. , the filtration step can be omitted. Example 1 Crushed and sieved phosphate rock (direct diameter 0.4 mm, uniformity factor 1.4) was placed in a 1000 mm thick dephosphorization tower with an inner diameter of 100 mm and an effective depth of 2.5 m, with an inverted conical bottom. Filled. Secondary treated water obtained by treating factory wastewater with activated sludge is used as raw water, and 200 mg/(50 mg/as Ca) of CaSO ₄ 2H ₂ O is added to it, and circulating water (twice the flow rate of raw water) is added with slaked lime. Mix and flow into the dephosphorization tower. Injection of slaked lime reduces the pH of the treated water to 9.5.
I made it so that The liquid flow rate in the reaction tank is such that the phosphate rock becomes fluidized.
The speed was 30m/h. Further, 0.5 mg of anionic polymer was injected into the lower part of the reaction tank and brought into contact with phosphate rock. A part of the water flowing out of the dephosphorization tank was filled with 800 ml of anthracite (effective diameter 0.8 mm, uniformity factor 1.5) with an inner diameter of 200 mm.
It was filled to a thickness of mm and water was passed through at a LV of 200 m/day. Water passage 2
Table 1 shows the average values for 3 months, and also shows the cases where anionic polymer was not added and where it was directly injected into raw water as a comparative example.

[Table] Example 2 In Example 1, the amount of anionic polymer injected was changed and the changes in SS and phosphorus concentration of the dephosphorization tower effluent were measured.

[Table] The injection rate of the anionic polymer was good at 0.2 mg/or more, but at 1 mg/or more, the filter media coalesced together at the bottom of the reaction tank, a uniform fluidized bed was not formed, and the water quality deteriorated. "Effects of the Invention" As described above, according to the present invention, in a fluidized bed dephosphorization method, a solution in which Ca ²⁺ and OH ^- have been adjusted can be mixed with a filter medium having phosphorus removal ability in the presence of an anionic polymer. By bringing them into contact, fine SS generated during collisions and reactions between the filter media can be fixed onto the filter media, which can significantly improve the phosphorus removal rate (phosphorus fixation rate) of the fluidized bed dephosphorization method.
The frequency of backwashing in the subsequent filtration process can be reduced, or the filtration process can be omitted. Furthermore, since the removed phosphorus is reliably fixed in the form of calcium phosphate on the filter medium, so-called floc-like sludge that is difficult to treat is not discharged, and the amount of sludge generated can be reduced.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the process flow of one embodiment of the present invention. 1...Drainage (raw water), 2,5...Calcium salt,
3, 6... Alkaline agent, 4... Circulating water, 7... Anionic polymer, 8... Solid particles having phosphorus removal ability, 9... Reaction tank (fluidized bed), 10... Fluidized bed treated water, 11...filter material, 12...filter tank,
13... Treated water.

Claims (1)

[Claims] 1. In a fluidized bed dephosphorization method in which phosphorus-containing wastewater is brought into contact with solid particles having phosphorus removal ability in the presence of calcium and alkali, the wastewater is brought into contact with the solid particles in the presence of an anionic polymer. A method for treating phosphorus-containing wastewater characterized by contacting the wastewater. 2. The method for treating phosphorus-containing wastewater according to claim 1, wherein the solid particles having phosphorus removal ability are selected from phosphate rock, bone charcoal, Kanuma soil, and light burnt magnesia.