JP2006314863A - Phosphorus removal apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphorus removal apparatus which can carry out a crystallization process without using phosphate ore or the like as a seed crystal by generating fine particles of apatite working as a seed crystal from wastewater. <P>SOLUTION: The phosphorus removal apparatus for crystallizing and removing phosphorus contained at high concentration in wastewater comprises a solid-liquid separation means (a membrane separator 11) for extracting part of the wastewater to solid-liquid separate it, a seed crystal generation tank 12 for precipitating fine particles of an insoluble or sparingly soluble phosphorus compound by feeding a calcium compound to liquid separated by the solid-liquid separation means and reacting the calcium compound with phosphorus in the separated liquid, and a crystallization reaction tank 13 for reacting phosphorus contained in the wastewater with the calcium compound and crystallizing the phosphorus on the fine particles by feeding the fine particles of the phosphorus compound, generated in the seed crystal generation tank, and the calcium compound into the remainder of the wastewater and reacting them with each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dephosphorization apparatus, and more particularly to a dephosphorization apparatus that removes high-concentration phosphorus contained in sludge wastewater generated by biological treatment of sewage from wastewater by crystallization.

Sludge effluent generated from sewage treatment facilities that purify sewage by biological treatment contains a relatively high concentration of phosphoric acid phosphorus and a high SS concentration. As a method of removing phosphorus in wastewater with high SS concentration, by adding calcium compound to wastewater and adjusting pH, phosphorus and calcium compound are reacted to crystallize on the seed crystal as apatite and grow. A crystallization method is widely performed in which the coarse apatite crystals are separated from the SS component by gravity. (For example, refer to Patent Document 1).
JP 2002-307077 A

  However, although the ore is mainly used for the seed crystal used in the crystallization method, there is almost no production in Japan, and the reality is that it relies on imports. For this reason, if it becomes difficult to obtain the phosphate ore in the future, there is a problem that the process of the crystallization method cannot be established.

  Therefore, the present invention has an object to provide a dephosphorization apparatus capable of performing a crystallization method without using phosphate ore as a seed crystal by generating apatite fine particles as seed crystals from waste water. It is said.

  In order to achieve the above object, the dephosphorization apparatus of the present invention crystallizes phosphorus contained in sludge wastewater generated by biological treatment of sewage as an insoluble or sparingly soluble phosphorus compound and removes it from the wastewater. In the dephosphorization apparatus, by extracting a part of the waste water and separating it into solid and liquid, and by introducing a calcium compound into the separated liquid separated by the solid and liquid separating means and reacting with phosphorus in the separated liquid A seed crystal production tank for precipitating fine particles of insoluble or hardly soluble phosphorus compound, and the phosphorus compound fine particles and calcium compound produced in the seed crystal production tank are introduced into the remaining portion of the waste water and reacted. It comprises a crystallization reaction tank for reacting phosphorus contained therein with a calcium compound to crystallize on the fine particles.

  According to the dephosphorization apparatus of the present invention, the calcium compound is added to the separation liquid from which the SS component has been separated by the solid-liquid separation means, and the pH and the calcium compound in the separation liquid are adjusted as necessary. Apatite fine particles, which are insoluble phosphorus compounds, can be produced by reaction, and by introducing these fine particles into the waste water together with the calcium compound, phosphorus in the waste water can be crystallized using the fine particles as seed crystals. .

  FIG. 1 is a system diagram of a dephosphorization apparatus showing one embodiment of the present invention. This dephosphorization apparatus is an insoluble phosphorus compound obtained by reacting phosphorus in a separation liquid separated by the membrane separation apparatus 11 with a calcium compound, which is a solid-liquid separation means for performing solid-liquid separation of waste water. The seed crystal generation tank 12 for generating a certain apatite fine particles, and the fine particles generated in the seed crystal generation tank 12 and the calcium compound are introduced into the remaining portion of the waste water to react with each other, thereby causing phosphorus contained in the waste water to A crystallization reaction tank 13 for crystallization on fine particles is provided.

  Drainage (raw water) flowing from the raw water inflow path 14 into the dephosphorization device is partly branched into the branch path 15 and flows into the membrane separation device 11, SS components in the wastewater are separated into membranes, and SS components are concentrated. The wastewater in the state is returned to the raw water inflow path 14 through the return path 16, and the separated liquid from which the SS component has been separated and removed is introduced into the seed crystal production tank 12 through the path 17.

  The seed crystal generation tank 12 is provided with a calcium compound addition path 18 for introducing a calcium hydroxide aqueous solution as a calcium compound. From the calcium compound addition path 18, depending on conditions such as drainage pH and phosphorus concentration. An aqueous solution containing a certain amount of calcium hydroxide is added. In the seed crystal production tank 12, phosphoric acid phosphorus in the separation liquid reacts with calcium hydroxide, and insoluble calcium phosphate is precipitated to form fine particles (hereinafter referred to as seed crystals) composed of apatite crystals mainly composed of calcium phosphate. Formed in the separation liquid. The produced seed crystal is separated by an appropriate solid-liquid separation means such as gravity sedimentation or filtration, and is introduced into the crystallization reaction tank 13 through the seed crystal path 19. In addition, the liquid from which the seed crystal has been separated is extracted from the outflow path 20.

  Raw water from the raw water inflow path 14, seed crystals from the seed crystal path 19, and calcium hydroxide aqueous solution from the calcium compound addition path 21 flow into the crystallization reaction tank 13, and phosphorus contained in the raw water is contained in the crystallization reaction tank 13. Acidic phosphorus and calcium hydroxide react and crystallize on the surface of the seed crystal to grow apatite crystals. Apatite crystals grown to a predetermined size are drawn out from the crystal recovery path 22 at the bottom of the tank, and the drainage (treated water) from which phosphorus has been removed flows out from the treated water path 23 at the top of the tank.

  The crystallization reaction tank 13 can adopt the same structure as a conventional crystallization reaction tank, and fluidizing means for effectively bringing a seed crystal or a growing crystal in contact with the liquid in the tank, A crystal separation unit or the like can be provided for gravity separation of crystals grown in the size of. Further, the crystal extracted from the crystal recovery path 22 may be classified and a small crystal may be circulated in the crystallization reaction tank 13.

  The solid-liquid separation in the membrane separation device 11 and the generation of seed crystals in the seed crystal generation tank 12 can be performed continuously or in a batch mode, and the apatite crystals from the crystallization reaction tank 13 can be produced. What is necessary is just to make it throw a seed crystal into the crystallization reaction tank 13 according to the drawing-out amount. Further, it is possible to cause the entire amount of the separation liquid containing the seed crystals to flow into the crystallization reaction tank 13 without separating the produced seed crystals from the separation liquid.

  Further, it is preferable to add an aqueous calcium hydroxide solution to the seed crystal production tank 12, but other calcium compounds such as calcium chloride and a pH adjuster such as sodium hydroxide are preferably added at an appropriate ratio. May be. It is also possible to add another substance that forms an insoluble or hardly soluble compound by reaction with phosphorus, such as a magnesium compound.

  In this way, wastewater containing high-concentration phosphoric acid phosphorus and high-concentration SS components is solidified by solid-liquid separation means such as the membrane separation device 11 like sludge wastewater generated by biological treatment of sewage. After the liquid separation, the apatite in a state that can be used as a seed crystal in the crystallization reaction tank 13 by reacting high concentration phosphorus and calcium compounds in the separation liquid in a predetermined pH range in the seed crystal production tank 12. Fine particles can be deposited. Thereby, it is not necessary to separately prepare a seed crystal such as phosphorus ore, and the dephosphorization apparatus can be operated in a stable state.

It is a systematic diagram of the dephosphorization apparatus which shows one example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Membrane separator, 12 ... Seed crystal production tank, 13 ... Crystallization reaction tank, 14 ... Raw water inflow path, 18 ... Calcium compound addition path, 19 ... Seed crystal path, 21 ... Calcium compound addition path, 22 ... Crystal recovery Route, 23 ... treated water route

Claims (1)

  In a dephosphorization apparatus that crystallizes phosphorus contained in sludge effluent generated by biological treatment of sewage as an insoluble or hardly soluble phosphorus compound and removes it from the effluent, a part of the effluent is extracted and solid liquid Solid-liquid separation means for separation, and seed crystal generation in which fine particles of insoluble or sparingly soluble phosphorus compounds are precipitated by adding calcium compounds to the separation liquid separated by the solid-liquid separation means and reacting with phosphorus in the separation liquid The phosphorus contained in the waste water is reacted with the calcium compound by introducing into the remainder of the waste water and reacting the fine particles of the phosphorus compound produced in the tank and the seed crystal production tank and the calcium compound. A dephosphorization apparatus comprising: a crystallization reaction tank for crystallization.

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