Metal containing waste water treatment method and metal containing waste water treatment equipment

This metal containing waste water treatment method introduces a metal containing waste water from above into a submerged membrane separation tank 1 in which a reaction section 2, a submerged membrane section 3 having a submerged membrane 5 and a precipitation section 4 are arranged in order from top to bottom, causes a reaction by adding a pH adjuster to the reaction section 2, subsequently separates water from metal by the submerged membrane 5 of the submerged membrane section 3 and subsequently precipitates and concentrates the metal in the precipitation section 4. As described above, according to this treatment method, the pH adjuster is added to the reaction section 2, and therefore, solid-liquid separation can be effected by the submerged membrane 5 with a hydroxide formed. Moreover, the metal can be precipitated and concentrated by the action of gravity without using energy in the precipitation section 4.

What is claimed is:

1. A metal containing waste water treatment method for collecting metal from a metal containing waste water, comprising the steps of: separating a first metalhydroxide from the waste water by making the metal containing waste water pass through a first submerged membrane separation unit with a pH adjuster added; separating a concentrate brine that contains another metal dissolved in the waste water from the waste water by making the waste water pass through a reverse osmosis membrane separation unit; and sending the concentrate brine that contains said another metal back to the first submerged membrane separation unit and adding the concentrate brine to the waste water together with the pH adjuster.

2. The metal containing waste water treatment method as claimed in claim 1, wherein the metal containing waste water is made to pass through the second submerged membrane separation unit with a pH adjuster and a coagulant added to the metal containing waste water in a stage behind the first submerged membrane separation unit, the resulting liquid is made to pass through the reverse osmosis membrane separation unit with a pH adjuster added and further pass through an ultrapure water generating system arranged in a stage behind the reverse osmosis membrane separation unit, and the concentrate brine from the reverse osmosis membrane separation unit is sent back to the first submerged membrane separation unit and added to the waste water together with the pH adjuster.

3. The metal containing waste water treatment method as claimed in claim 2, wherein the water obtained from an electric deionization unit arranged behind the reverse osmosis membrane separation unit is recycled by being introduced into an ultrapure water generating system, and a concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit is sent back to the first submerged membrane separation unit, added to the waste water together with the pH adjuster and made to pass through the first submerged membrane separation unit.

4. The metal containing waste water treatment method as claimed in claim 3, wherein a pH adjuster, a coagulant and metal oxidizing bacterium are added in a stage behind the first submerged membrane separation unit and before the second submerged membrane separation unit.

5. A metal containing waste water treatment method comprising the steps of: introducing a metal containing compound semiconductor waste water from above into a first submerged membrane separation tank in which a reaction section, a submerged membrane section that has a submerged membrane and a precipitation section are arranged in order from top to bottom and adding a pH adjuster to the reaction section so as to cause a reaction; subsequently separating metal from the waste water by the submerged membrane of the submerged membrane section and subsequently precipitating and concentrating the metal in the precipitation section; treating a treated water obtained by the submerged membrane sequentially in an arsenic- and phosphorus-removing unit, an activated carbon adsorption unit, a reverse osmosis membrane unit and an electric deionization unit and thereafter introducing the resulting liquid into an ultrapure water generating system; and sending a concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit back to the reaction section.

6. The metal containing waste water treatment method as claimed in claim 5, wherein a concentrate concentrated in the first submerged membrane separation tank is further concentrated by being introduced into a second submerged membrane separation tank arranged below the first submerged membrane separation tank.

7. The metal containing waste water treatment method as claimed in claim 6, wherein a treated water from the submerged membrane of the first submerged membrane separation tank and the submerged membrane of the second submerged membrane separation tank are introduced into a reaction section of a third submerged membrane separation tank together with a pH adjuster and a coagulant, the precipitate in the third submerged membrane separation tank is further concentrated in a fourth submerged membrane separation tank, a treated water separated by the submerged membranes of the third submerged membrane separation tank and the fourth submerged membrane separation tank is meanwhile treated sequentially in an activated carbon adsorption unit, a reverse osmosis membrane unit and an electric deionization unit and thereafter introduced into an ultrapure water generating system, and a concentrate brine from the reverse osmosis membrane unit and the electric deionization unit is sent back to a reaction section of the first submerged membrane separation tank.

8. The metal containing waste water treatment method as claimed in claim 7, wherein an arsenic oxidizing bacterium is cultured and concentrated by introducing part of the metal containing waste water from compound semiconductor plant and a developer waste water into a fifth submerged membrane separation tank, and the arsenic oxidizing bacterium is introduced into the third submerged membrane separation tank.

9. The metal containing waste water treatment method as claimed in claim 8, wherein part of the concentrate brine precipitated in the third submerged membrane separation tank is sent back to the fifth submerged membrane separation tank.

10. The metal containing waste water treatment method as claimed in claim 9, wherein the arsenic oxidizing bacterium cultured in the fifth submerged membrane separation tank is introduced into the first submerged membrane separation tank and the third submerged membrane separation tank.

11. The metal containing waste water treatment method as claimed in claim 4, wherein the metal oxidizing bacterium is an arsenic oxidizing bacterium.

12. The metal containing waste water treatment method as claimed in claim 5, wherein metal is precipitated and concentrated in the precipitation section and thereafter further concentrated by an evaporator.

13. The metal containing waste water treatment method as claimed in claim 8, wherein the liquid precipitated and concentrated in the first submerged membrane separation tank is concentrated by being introduced into an evaporator, and the liquid precipitated and concentrated in the third submerged membrane separation tank is meanwhile concentrated by being introduced into an evaporator.

14. The metal containing waste water treatment method as claimed in claim 10, wherein the waste water from compound semiconductor plant is a waste water that contains hydrogen peroxide containing gallium arsenide.

15. A metal containing waste water treatment method for treating gallium, arsenic and water in a gallium arsenide waste water, separately collecting the gallium, arsenic and water, collecting the gallium and arsenic as valuable substances and meanwhile collecting the water as a raw water for an ultrapure water generating system, thereby establishing a completely closed treatment system.

16. The metal containing waste water treatment method as claimed in claim 15, wherein a microorganism is used for treating the arsenic.

17. The metal containing waste water treatment method as claimed in claim 16, wherein the microorganism is a metal oxidizing bacterium.

18. The metal containing waste water treatment method as claimed in claim 17, wherein the metal oxidizing bacterium is an arsenic oxidizing bacterium.

19. A metal containing waste water treatment method for collecting metal from a metal containing waste water, comprising the steps of: preliminarily adding a pH adjuster to the waste water so as to cause a reaction; making the resulting waste water pass through a multistage type submerged membrane separation unit including submerged membranes arranged vertically in a plurality of tiers, an adhesional precipitation section arranged below the submerged membranes for precipitating a reactant by making the reactant adhere to a filler and a diaphragm for vibrating the submerged membranes in order to separate a metalhydroxide from the waste water; separating a concentrate brine that contains another metal dissolved in the waste water from the waste water by making the treated water, from which the metalhydroxide has been removed, pass through a reverse osmosis membrane separation unit; and sending the concentrate brine that contains said another metal back to a stage before the multistage type submerged membrane separation unit and adding the concentrate brine to the waste water together with the pH adjuster.

20. The metal containing waste water treatment method as claimed in claim 19, wherein a pH adjuster and a coagulant are added in a stage behind the multistage type submerged membrane separation unit that serves as a first multistage type submerged membrane separation unit, next the resulting waste water is made to pass through a second multistage type submerged membrane separation unit, which has submerged membranes arranged vertically in a plurality of tiers, an adhesional precipitation section for precipitating a reactant by making the reactant adhere to a filler and a diaphragm for vibrating the submerged membranes, the resulting liquid is subsequently made to pass through a reverse osmosis membrane separation unit with a pH adjuster added, a treated water from the reverse osmosis membrane separation unit is further introduced into an ultrapure water generating system arranged in a stage behind the reverse osmosis membrane separation unit, and the concentrate brine from the reverse osmosis membrane separation unit is sent back to a stage before the first multistage type submerged membrane separation unit and the concentrate brine is added to the waste water together with the pH adjuster.

21. The metal containing waste water treatment method as claimed in claim 20, wherein the treated water obtained by the reverse osmosis membrane separation unit is made to pass through an electric deionization unit, a treated water obtained from the electric deionization unit is recycled by being introduced into an ultrapure water generating system, and a concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit is meanwhile sent back to the stage before the first multistage type submerged membrane separation unit and added to the waste water together with the pH adjuster.

22. The metal containing waste water treatment method as claimed in claim 21, wherein a pH adjuster, a coagulant and a metal oxidizing bacterium are added in a stage behind the first multistage type submerged membrane separation unit.

23. A metal containing waste water treatment method comprising the steps of: adding a pH adjuster to a waste water from compound semiconductor plant in a pH adjustment tank so as to cause a reaction; introducing the waste water from the pH adjustment tank upwardly in an upward flow into a multistage submerged membrane separation tank in which an upper portion where a pH meter is placed, a submerged membrane section that includes submerged membranes arranged vertically in a plurality of tiers and a diaphragm for vibrating the submerged membranes and an adhesional precipitation section for making a reactant adhere to a filler are arranged in order from top to bottom; primarily separating a metal from the waste water by physically catching and filtering the metal in the waste water in the adhesional precipitation section and secondarily separating the metal from the waste water by the submerged membranes in the submerged membrane section; treating a treated water obtained by the submerged membranes sequentially in an arsenic- and phosphorus-removing unit, an activated carbon adsorption unit, a reverse osmosis membrane unit and an electric deionization unit and thereafter introducing the resulting liquid into an ultrapure water generating system; and sending a concentrate brine from the reverse osmosis membrane unit and the electric deionization unit back to the pH adjustment tank.

24. The metal containing waste water treatment method as claimed in claim 23, wherein the treated water and the concentrate brine from the first multistage type submerged membrane separation unit is treated by being introduced into a second submerged membrane separation tank arranged below the multistage type submerged membrane separation tank that serves as a first submerged membrane separation tank.

25. The metal containing waste water treatment method as claimed in claim 24, wherein the pH adjustment tank is served as a first pH adjustment tank, the treated water from the submerged membrane of the first submerged membrane separation tank and the submerged membrane of the second submerged membrane separation tank is introduced into a second pH adjustment tank together with a pH adjuster so as to cause a reaction, the treated water from the second pH adjustment tank is subsequently introduced upwardly in an upward flow into a multistage submerged membrane separation tank that serves as a third submerged membrane separation tank in which an upper portion where a pH meter is placed, a submerged membrane section that includes submerged membranes arranged vertically in a plurality of tiers and a diaphragm for vibrating the submerged membranes and an adhesional precipitation section for precipitating a reactant by making the reactant adhere to a filler are arranged in order from top to bottom, a metal is separated from the treated water, the metal is further concentrated in a fourth submerged membrane separation tank arranged below the third submerged membrane separation tank, the treated water separated by the submerged membranes of the third submerged membrane separation tank and the fourth submerged membrane separation tank is treated sequentially in an activated carbon adsorption unit, a reverse osmosis membrane unit and an electric deionization unit and thereafter introduced into an ultrapure water generating system, and a concentrate brine from the reverse osmosis membrane unit and the electric deionization unit is sent back to the first pH adjustment tank.

26. The metal containing waste water treatment method as claimed in claim 25, wherein an arsenic oxidizing bacterium cultured and concentrated in the fifth submerged membrane separation tank into which part of the waste water from compound semiconductor plant that contains a developer waste water and a metal are introduced into the third submerged membrane separation tank.

27. The metal containing waste water treatment method as claimed in claim 26, wherein part of the concentrate brine precipitated in the third submerged membrane separation tank is sent back to the fifth submerged membrane separation tank.

28. The metal containing waste water treatment method as claimed in claim 27, wherein an arsenic oxidizing bacterium cultured in the fifth submerged membrane separation tank is introduced into the first submerged membrane separation tank and the third submerged membrane separation tank.

29. The metal containing waste water treatment method as claimed in claim 22, wherein the metal oxidizing bacterium is an arsenic oxidizing bacterium.

30. The metal containing waste water treatment method as claimed in claim 23, wherein the resulting liquid is further condensed by being introduced into an evaporator after the metal is precipitated and condensed in the adhesional precipitation section.

31. The metal containing waste water treatment method as claimed in claim 26, wherein the liquid precipitated and concentrated in the first submerged membrane separation tank is concentrated by being introduced into an evaporator, and the liquid precipitated and concentrated in the third submerged membrane separation tank is concentrated by being introduced into an evaporator.

32. The metal containing waste water treatment method as claimed in claim 28, wherein an influent water is a waste water from compound semiconductor plant that contains hydrogen peroxide containing gallium arsenide.

33. A metal containing waste water treatment method for subjecting metal and water contained in a waste water from compound semiconductor plant to a physical treatment, a biological treatment and a chemical treatment to collect gallium and other metals by separation, thereby establishing a completely closed treatment system.

34. A metal containing waste water treatment method for subjecting metal and water contained in a waste water from compound semiconductor plant to a physical treatment, a biological treatment and a chemical treatment to collect gallium and other metals by separation, collecting the metal as a valuable substance and collecting the water as a raw water for an ultrapure water generating system, thereby establishing a completely closed treatment system.

35. A metal containing waste water treatment method for subjecting gallium, arsenic, phosphorus and water in a waste water that contains gallium arsenide and gallium phosphide to a physical treatment, a biological treatment and a chemical treatment, and separately collecting the substances as gallium and a mixture of arsenic and phosphorus, thereby establishing a completely closed treatment system.

36. A metal containing waste water treatment method for subjecting gallium, arsenic, phosphorus and water in a waste water that contains gallium arsenide and gallium phosphide to a physical treatment, a biological treatment and a chemical treatment, separately collecting the substances as gallium and a mixture of arsenic and phosphorus, collecting the gallium and the mixture of arsenic and phosphorus as valuable substances and collecting the water as a raw water for an ultrapure water generating system, thereby establishing a completely closed treatment system.

37. The metal containing waste water treatment method as claimed in claim 36, wherein a microorganism is used for treating the arsenic.

38. The metal containing waste water treatment method as claimed in claim 37, wherein the microorganism is a metal oxidizing bacterium.

39. The metal containing waste water treatment method as claimed in claim 38, wherein the metal oxidizing bacterium is an arsenic oxidizing bacterium.

40. A metal containing waste water treatment method for collecting metal from a metal containing waste water, comprising the steps of: preliminarily adding a pH adjuster to a waste water in a first pH adjustment tank so as to cause a reaction, thereafter introducing the generated metalhydroxide into a foam separation tank, making bubbles generated in the waste water in the foam separation tank adhere to the metaihydroxide and making the metaihydroxide surface, thereby subjecting the metaihydroxide to foam separation; making a treated water obtained after the separation of the metaihydroxide pass through a multistage type submerged membrane separation unit that has submerged membranes arranged vertically in a plurality of tiers, an adhesional precipitation section that is placed below the submerged membranes and precipitate a reactant obtained through the reaction by making the reactant adhere to a filler and a diaphragm for vibrating the submerged membranes, thereby further separating the metalhydroxide from the treated water; separating a concentrate brine that contains another metal dissolved in the treated water from the treated water by making the treated water pass through a reverse osmosis membrane separation unit and sending the concentrate brine that contains said another metal back to the first pH adjustment tank; introducing the metalhydroxide separated in the foam separation tank and the multistage type submerged membrane separation unit into an evaporator and concentrating the metalhydroxide; and cooling steam evaporated from the evaporator to restore water and introducing the resulting water into a second pH adjustment tank in a stage before the reverse osmosis membrane separation unit.

41. The metal containing waste water treatment method as claimed in claim 40, wherein the multistage type submerged membrane separation unit is served as a first multistage type submerged membrane separation unit, a reaction tank to which a pH adjuster and a coagulant are added is arranged in a stage behind the first multistage type submerged membrane separation unit and a treated water from the first multistage type submerged membrane separation unit is made to react, a treated water from the reaction tank is made to further pass through a second multistage type submerged membrane separation unit that has submerged membranes arranged vertically in a plurality of tiers, an adhesional precipitation section that is placed below the submerged membranes and precipitates a reactant obtained through the reaction by making the reactant adhere to a filler and a diaphragm for vibrating the submerged membranes, the resulting water is subsequently made to pass through a second pH adjustment tank to which a pH adjuster is added and a reverse osmosis membrane separation unit, a treated water from the reverse osmosis membrane separation unit is further introduced into an ultrapure water generating system arranged in a stage behind the reverse osmosis membrane separation unit, a concentrate brine from the reverse osmosis membrane separation unit is sent back to the first pH adjustment tank, a metalhydroxide separated by the foam separation tank, the first multistage type submerged membrane separation unit and the second multistage type submerged membrane separation unit is meanwhile introduced into an evaporator and concentrated, and steam evaporated from the evaporator is restored into water and utilized as a raw water for an ultrapure water generating system.

42. The metal containing waste water treatment method as claimed in claim 41, wherein the treated water from the reverse osmosis membrane separation unit is made to pass through an electric deionization unit arranged in a stage behind the reverse osmosis membrane separation unit, a treated water from the electric deionization unit is recycled by being introduced into an ultrapure water generating system, and a concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit is sent back to the first pH adjustment tank and introduced into the tank together with the pH adjuster.

43. The metal containing waste water treatment method as claimed in claim 42, wherein a pH adjuster, a coagulant and a ferrooxidans bacterium are added to a reaction tank arranged in a stage behind the first multistage type membrane separation unit.

44. A metal containing waste water treatment method, comprising steps of: introducing a compound semiconductor waste water that contains gallium arsenide, gallium phosphide and so on into a pH adjustment tank so as to cause a reaction with a pH adjuster added; thereafter introducing a waste water from the pH adjustment tank into a foam separation tank, making bubbles generated in the waste water in the foam separation tank adhere to a metalhydroxide obtained through the reaction so as to make the metalhydroxide surface, thereby subjecting the metalhydroxide to foam separation; introducing a treated water obtained after the separation of the metalhydroxide upwardly in an upward flow into a multistage type submerged membrane separation tank in which an upper portion where a pH meter is placed, a submerged membrane section that includes submerged membranes arranged vertically in a plurality of tiers and a diaphragm for vibrating the submerged membrane and an adhesional precipitation section for precipitating a reactant obtained through the reaction by making the reactant adhere to a filler are arranged in order from top to bottom; primarily separating a metal from the treated water by physically catching and filtering the metal in the treated water in the adhesional precipitation section; secondarily separating a metalhydroxide from the treated water by the submerged membranes of the submerged membrane section, treating the treated water obtained by the submerged membranes sequentially in an arsenic- and phosphorus-removing unit, an activated carbon absorption unit, a reverse osmosis membrane unit and an electric deionization unit, thereafter introducing the resulting liquid into an ultraviolet sterilizer, a cartridge polisher and an ultrafilter unit to produce an ultrapure water and supply the ultrapure water to each production unit and introducing a waste water from each production unit into the pH adjustment tank; sending and introducing a concentrate brine from the activated carbon absorption unit, the reverse osmosis membrane unit, the electric deionization unit and the ultrafilter unit back into the pH adjustment tank; and concentrating the metalhydroxide concentrated in the foam separation tank and the multistage type submerged membrane separation unit by introducing the metalhydroxide into an evaporator, cooling steam evaporated from the evaporator to restore water, making the water join the water separated in the multistage type submerged membrane separation tank and introducing the resulting liquid into the arsenic- and phosphorus-removing unit.

45. The metal containing waste water treatment method as claimed in claim 44, wherein the multistage type submerged membrane separation tank is served as a first multistage type submerged membrane separation tank, the metalhydroxide from the first multistage type submerged membrane separation tank is introduced into a second submerged membrane separation tank arranged below the first multistage type submerged membrane separation tank, and the metaihydroxide from the second submerged membrane separation tank is introduced into an evaporator so as to concentrate the metaihydroxide and steam obtained from the evaporator is cooled and restored into water and treated by being introduced into the arsenic- and phosphorus-removing unit.

46. The metal containing waste water treatment method as claimed in claim 45, wherein the water from the submerged membranes of the first submerged membrane separation tank and the submerged membrane of the second submerged membrane separation tank is introduced into a reaction tank together with a pH adjuster and a coagulant so as to cause a reaction, the resulting liquid is introduced upwardly in an upward flow into a third multistage submerged membrane separation tank in which an upper portion where a pH meter is placed, a submerged membrane section that includes submerged membranes arranged vertically in a plurality of tiers and a diaphragm for vibrating the submerged membranes and an adhesional precipitation section for precipitating a reactant obtained through the reaction by making the reactant adhere to a filler are arranged in order from top to bottom, thereby separating water from a metalhydroxide, the metalhydroxide is further concentrated in a fourth submerged membrane separation tank arranged below the third multistage type submerged membrane separation tank, the treated water separated by the submerged membranes of the third multistage type submerged membrane separation tank and the fourth submerged membrane separation tank is sequentially introduced into an activated carbon absorption unit, a reverse osmosis membrane separation unit and an electric deionization unit, thereafter the resulting liquid is introduced into an ultraviolet sterilizer, a cartridge polisher and an ultrafilter unit, a concentrate brine from the reverse osmosis membrane unit, the electric deionization unit and the ultrafilter unit is sent back to the pH adjustment tank, a metalhydroxide from the second submerged membrane separation tank is introduced into the evaporator so as to concentrate the metalhydroxide, steam obtained from the evaporator is cooled and restored into water, made to join the water separated in the second multistage type submerged membrane separation tank and introduced into the reaction tank, and a metalhydroxide from the fourth submerged membrane separation tank is introduced into an evaporator so as to concentrate the metalhydroxide, steam obtained from the evaporator is cooled and restored into water, made to join the water separated in the fourth multistage type submerged membrane separation tank and introduced into the activated carbon adsorption unit.

47. The metal containing waste water treatment method as claimed in claim 46, wherein part of a waste water from compound semiconductor plant that includes a developer waste water and a metal is introduced into a fifth submerged membrane separation tank, an arsenic oxidizing bacterium cultured and concentrated in the fifth submerged membrane separation tank is introduced into the third multistage type submerged membrane separation tank via the reaction tank.

48. The metal containing waste water treatment method as claimed in claim 47, wherein part of a concentrate brine precipitated in the third multistage type submerged membrane separation tank is sent back to the fifth submerged membrane separation tank.

49. The metal containing waste water treatment method as claimed in claim 48, wherein the arsenic oxidizing bacterium cultured in the fifth submerged membrane separation tank is introduced into the first multistage type submerged membrane separation tank and the third multistage type submerged membrane separation tank.

50. The metal containing waste water treatment method as claimed in claim 43, wherein the ferrooxidans bacterium is an arsenic oxidizing bacterium.

51. The metal containing waste water treatment method as claimed in claim 44, wherein not only the waste water from compound semiconductor plant that contains gallium arsenide, a pH adjuster to each production unit but also the developer waste water from each production unit are treated by being introduced into the pH adjustment tank.

52. The metal containing waste water treatment method as claimed in claim 44, wherein the concentrate brine precipitated and concentrated in the first multistage type submerged membrane separation tank and a floating substance that has surfaced and separated in the foam separation tank are concentrated by being introduced into an evaporator, the treated water from the submerged membrane of the first multistage type submerged membrane separation tank and the evaporator is introduced into a reaction tank together with a pH adjuster and a coagulant so as to cause a reaction, the resulting liquid is introduced upwardly in an upward flow into a third multistage type submerged membrane separation tank in which an upper portion where a pH meter is placed, a submerged membrane section that includes submerged membranes arranged vertically in a plurality of tiers and a diaphragm for vibrating the submerged membranes and an adhesional precipitation section for precipitating a reactant obtained through the reaction by making the reactant adhere to a filler are arranged in order from top to bottom, thereby separating water from a metalhydroxide, and the liquid precipitated and concentrated in the third multistage type submerged membrane separation tank is concentrated by being introduced into an evaporator.

53. The metal containing waste water treatment method as claimed in claim 49, wherein an influent water to the pH adjustment tank is a waste water from compound semiconductor plant that contains hydrogen peroxide and contains gallium arsenide, gallium phosphide and so on.

54. A metal containing waste water treatment method comprising the steps of: causing a reaction of gallium, arsenic, phosphorus and water in a waste water of gallium arsenide and gallium phosphide with a pH adiuster added in a pH adiustment tank, making bubbles generated in a waste water adhere to a metalhydroxide generated through the reaction in a foam separation tank so as to make the metalhydroxide surface in the waste water, thereby subjecting the metalhydroxide to foam separation; and making the treated water that has passed through the foam separation tank pass from below through a multistage type submerged membrane separation tank, which has submerged membranes arranged vertically in a plurality of tiers, an adhesional precipitation section that is placed below the submerged membranes and precipitates a reactant caused by the reaction by making the reactant adhere to a filler and a diaphragm for vibrating the submerged membranes, thereby further separating the metalhydroxide from the treated water, whereby the waste water is subjected to a physical treatment, a biological treatment and a chemical treatment, and the resulting liguid is thereafter treated in an evaporator so as to separately collect gallium, a mixture of arsenic and phosphorus and water, collecting the gallium and the mixture of arsenic and phosphorus as valuable substances and collecting the water as a raw water for an ultrapure water generating system, thereby establishing a completely closed treatment system, wherein a microorganism is used for the treatment of arsenic.

55. The metal containing waste water treatment method as claimed in claim 54, wherein the microorganism is a metal oxidizing bacterium.

56. The metal containing waste water treatment method as claimed in claim 55, wherein the metal oxidizing bacterium is an arsenic oxidizing bacterium.

BACKGROUND OF THE INVENTION

This invention relates to a metal containing waste water treatment method and treatment equipment, which collects gallium and arsenic from a waste water that contains gallium as a valuable metal and arsenic as a poisonous metal and recycles the substances. This invention further relates to a metal containing waste water treatment method and treatment equipment, which can constitute a completely closed treatment system of a (gallium arsenide) waste water or the like from compound semiconductor plant by carrying out pretreatment appropriate for the remaining treated water to recycle the resulting liquid as a raw water for an ultrapure water generating system. This invention further relates to a metal containing waste water treatment method for providing a completely closed treatment system of a (gallium arsenide, gallium phosphide and so on) waste water from compound semiconductor plant by separately collecting (1) gallium and (2) a mixture of arsenic and phosphorus from the waste water from compound semiconductor plant that contains gallium as a valuable metal, arsenic as a poisonous metal and so on, recycling the substances in another place and carrying out pretreatment optimum for the remaining water to recycle the resulting liquid as a raw water for an ultrapure water generating system.

Conventionally, it has been the most general way to treat the gallium arsenide containing waste water by the so-called neutralizing coagulation and sedimentation method for treating the waste water with ferric chloride as a coagulant, a neutralizer and a high molecular coagulant added. According to this neutralizing coagulation and sedimentation method, a sedimentation has been treated and disposed of as an industrial waste under the legal regulations.

On the other hand, there is a method for collecting a concentrate by evaporating and concentrating the gallium arsenide containing waste water, restoring the evaporated water into water by cooling and carrying out appropriate pretreatment to recycle the resulting liquid as a raw water for an ultrapure water generating system.

There is another prior art disclosed in Japanese Patent Laid-Open Publication No. 2000-117270. This prior art adjusts the pH of a metal containing waste water with an alkali agent of sodium hydroxide or the like, forms a metalhydroxide, thereafter makes the waste water pass through a membrane separation unit that has a pore diameter of 1 mm to 10 mm to thereby efficiently separate water from metalhydroxide and collect and recycle the valuable metal. Further, as a pretreatment process, the pH of the metal containing waste water is adjusted to 3 to 4, hydroxides of iron and chromium are separated and collected to selectively separate and collect the metals.

As shown in concrete in FIG. 58, this prior art treatment equipment disclosed in Japanese Patent Laid-Open Publication No. 2000-117270 is constructed of a pH adjustment tank 941, an MF membrane separation unit 942 filled with a ceramic membrane or the like, a pump 943, a pH readjustment tank 944, an RO membrane separation unit 945 and a redissolution tank 946.

Then, waste water, which contains heavy metals, is supplied so that a residence time in the pH adjustment tank 941 becomes 30 minutes. Subsequently, the pump 943 connected to the MF membrane separation unit 942 is operated.

The pump 943 of the treated water is interlocked with a liquid level switch placed in the pH adjustment tank 941 and controlled by the water level of the pH adjustment tank 941. The metalhydroxide generated in the pH adjustment tank 941 is concentrated by a film placed in the MF membrane separation unit 942.

On the other hand, the concentrated metalhydroxide is dissolved in the redissolution tank 946 and becomes a high-concentration nickel and zinc solution to be recycled in a plating bath and the like of the plant.

Another prior art disclosed in the aforementioned Japanese Patent Laid-Open Publication No. 2000-117270 will be described with reference to FIG. 59. This prior art treatment unit is constructed of a ferrooxidans bacterium reaction tank 1048, an MF membrane separation unit 1049, a pH adjustment tank 1041, an MF membrane separation unit 1042, a pH readjustment tank 1044, an RO membrane separation unit 1045 and so on.

Then, the pH of the waste water in the ferrooxidans bacterium reaction tank 1048 is adjusted to pH 3 with sulfuric acid and sodium hydroxide, while nitrogen and phosphorus are added as a nutrient. A ferrooxidans bacterium collecting MF membrane separation unit 1049 is placed inside this ferrooxidans bacterium reaction tank 1048. An MF membrane that is made of silica alumina-based ceramics and has a pore diameter of 10 .mu.m is employed for this MF membrane separation unit 1049. This MF membrane has its membrane surface continuously cleaned from inside the membrane by air.

Part of the concentrate brine of iron hydroxide, chromium hydroxide and the ferrooxidans bacterium, generated by this MF membrane, is sent back to the ferrooxidans bacterium reaction tank 1048, and another part is extracted, dried, granulated and thereafter recycled. Inside this ferrooxidans bacterium reaction tank 1048, iron hydroxide, chromium hydroxide and the ferrooxidans bacteria are accumulated and controlled within an MLSS (Mixed Liquor Suspended Solids) concentration from 100 to 200 mg/l (milligrams/liter). Further, the pH of the ferrooxidans bacterium treated water is adjusted to 9 by a sodium hydroxide solution in the pH adjustment tank 1041. Then, after stirring, a hydroxide of nickel and zinc is generated.

Subsequently, the water is made to pass from the pH adjustment tank 1041 to the MF membrane separation unit 1042 placed outside the pH adjustment tank 1041 by the pump 1043.

Yet another prior art (third prior art) is disclosed in Japanese Patent Laid-Open Publication No. HEI 9-285786. According to this third prior art, as shown in FIG. 60, mixed water 1175 obtained by preliminarily adding a chemical for precipitating arsenic or an adsorbent for adsorbing arsenic to raw water that, contains arsenic is flowed into a membrane filter tank 1174.

Otherwise, arsenic in the raw water is precipitated by making the raw water flow into the membrane filter tank 1174 and making mixed water by adding the aforementioned chemical or adsorbent. Otherwise, adsorption to the adsorbent is effected, and solid-liquid separation of mixed water 1176 inside the membrane filter tank 1174 is effected by a membrane filter 1173 (submerged membrane) placed inside the tank 1174. In the above case, the precipitation of arsenic is promoted by setting the amount of a membrane filtered water 1177 with respect to the amount of influent water into the membrane filter tank 1174 to 99% or more and maintaining the added chemical at high concentration inside the membrane filter tank 1174. In FIG. 60 are shown a raw water introducing pipe 1171, a coagulant loading pipe 1172, a treatment tank 1175 and a water tank 1188.

This third prior art oxidizes trivalent arsenic into pentavalent arsenic by either one of a method for adding an oxidizer or a method for carrying out ozone treatment, thereafter introduces the mixed water to which the chemical or the adsorbent has been added into the membrane filter tank 1174 in which the submerged membrane is placed and separates arsenic by promoting the precipitation or adsorption of arsenic.

Still another prior art (fourth prior art) is disclosed in Japanese Patent No. HEI 3-61514. This fourth prior art is a waste water treatment method for removing arsenic from a waste water that contains gallium and arsenic and collecting gallium.

In concrete, soluble ferric salt is added to the waste water that contains gallium and arsenic, and gallium and arsenic are coprecipitated with the precipitation of ferric hydroxide by adjusting the pH with an alkali agent.

Then, the precipitate is suspended in water, and gallium is eluted from the precipitate by adjusting the pH to the alkali side with sodium hydroxide, or an alkali agent added. After separation from the precipitate, water is evaporated and hardened by drying to collect gallium.

The aforementioned prior art of Japanese Patent Laid-Open Publication No. 2000-117270 describes the "metal containing waste water treatment and valuable metal collecting method characterized by forming a metalhydroxide by adjusting the pH of the metal containing waste water, thereafter making the resulting liquid pass through a membrane separation unit that has a pore diameter of 1 mm to 10 mm, thereby separating water from metalhydroxide".

In contrast to this, according to the gallium arsenide process in a semiconductor plant, the liquid is circulated in the unit using a filter that has a pore diameter of not greater than 1 .mu.m (pore diameter of 0.4 .mu.m, for example) in a back polishing unit, or production equipment in the plant. Therefore, particles of not smaller than 0.4 .mu.m are discharged in the waste water. In order to catch the particles of not smaller than 0.4 .mu.m, it is required to make the water pass through a membrane separation unit that has a pore diameter of 0.4 .mu.m.

On the other hand, it is required to carefully examine the pore diameter of the MF membrane to be adopted considering the fact that the general MF membrane has a pore diameter of about 1 .mu.m to 10 .mu.m and the fact that the pump power is increased when the pore diameter is reduced, also in consideration of energy saving.

Moreover, there are availed on the market UF's (Ultra Filter: ultrafiltration membrane) that have a pore diameter of about 0.002 .mu.m to 0.4 .mu.m. Therefore, it is proper to select the model conforming to the purpose and construct an energy-saving system.

The prior art disclosed in Japanese Patent Laid-Open Publication No. 2000-117270 cannot collect metal at high concentration (10% or more) and discharges metal ions collected by a reverse osmosis membrane in the waste water without recycling the metal ions. In the MF membrane separation unit of Japanese Patent Laid-Open Publication No. 2000-117270, the electrical energy consumed by the pump is large.

The aforementioned prior art (Japanese Patent Laid-Open Publication No. 2000-117270) describes the "metal containing waste water treatment and valuable metal collecting method characterized by forming a metalhydroxide by adjusting the pH of the metal containing waste water, concurrently loading a high molecular coagulant or a liquid chelating agent to form a flock of metalhydroxide and thereafter making the resulting liquid pass through a membrane separation unit that has a pore diameter of 50 .mu.m to 200 .mu.m, thereby separating water from the flock of metalhydroxide".

Although a concession is made to the fact that this description is intended for hydroxide, it is desired that the impurities of coagulant and so on should not be included, in order to collect gallium, or the valuable metal. In concrete, although only the gallium hydroxide is desired to be included, the high molecular coagulant or the liquid chelating agent is concurrently loaded to form a flock of metalhydroxide according to this prior art.

Furthermore, the aforementioned prior art (Japanese Patent Laid-Open Publication No. 2000-117270) describes the "metal containing Waste water treatment and valuable metal collecting method characterized by forming a hydroxide of chromium and iron from the metal containing waste water that contains ions of trivalent chromium and bivalent iron through the oxidation of the bivalent iron to trivalent iron with pH adjusted to 3 to 4 in the first stage, thereafter making the resulting liquid pass through a membrane separation unit that has a pore diameter of 1 .mu.m to 10 .mu.m to thereby separate water from the hydroxides of iron and chromium and next separating and collecting the remaining metals from the treated water in the second stage according to the methods claimed in claim 1 or 2".

If the gallium arsenide waste water is treated by applying this prior art, there is the problem that the arsenic is oxidized from trivalent arsenic to pentavalent arsenic and easily precipitated and becomes a mixture of hydroxides of arsenic and gallium as a precipitate, causing a trouble in refining and collecting gallium.

There is a cost merit when the gallium hydroxide and the pentavalent arsenic are independently separately collected to the utmost.

Moreover, the aforementioned prior art (Japanese Patent Laid-Open Publication No. 2000-117270) describes the "metal containing waste water treatment and valuable metal collecting method as claimed in claim 3, characterized in that a ferrooxidans bacterium is used in oxidizing the bivalent iron to the trivalent iron". In contrast to this, there is the problem that the ferrooxidans bacterium is not useful when treating the gallium arsenide waste water.

Moreover, the aforementioned prior art (Japanese Patent Laid-Open Publication No. 2000-117270) describes the "metal containing waste water treatment and valuable metal collecting method characterized in that, when metals are separated and collected from the metal containing waste water that contains ions of nickel, zinc, trivalent chromium and bivalent iron according to the method as claimed in claim 3 or 4, hydroxides of nickel and zinc are formed by adjusting the pH to 8 to 10 in the second stage, separating water from the hydroxides of nickel and zinc.

However, in contrast to the requirement of the formation of a precipitate by adding a coagulant after the oxidation of arsenic in the second stage, i.e., after arsenic is made to be a stable insoluble salt in the case of the gallium arsenide waste water, the aforementioned prior art has the problem that no oxidation process exists.

Moreover, the aforementioned prior art (Japanese Patent Laid-Open Publication No. 2000-117270) describes the "metal containing waste water treatment and valuable metal collecting method as claimed in any one of claims 1 through 5, characterized in that a membrane made of ceramics is employed as a membrane separation unit". However, the membrane separation unit made of ceramics is generally expensive.

Moreover, the aforementioned prior art (Japanese Patent Laid-Open Publication No. 2000-117270) describes the "metal containing waste water treatment and valuable metal collecting method as claimed in any one of claims 1 through 6, characterized in that the metal of the concentrate of the metalhydroxide that has been separated and collected is re-dissolved by adjusting the pH to 0.5 to 3 by sulfuric acid, and the concentrate brine of the metal is collected and recycled.

However, there is a further problem that a concentration and precipitation process is needed after the membrane separation of the prior art since there is required a gallium slurry of which the gallium concentration is as high as possible when gallium is refined from the gallium arsenide waste water.

Moreover, the aforementioned prior art (Japanese Patent Laid-Open Publication No. 2000-117270) describes the "metal containing waste water treatment and valuable metal collecting method as claimed in any one of claims 1 through 7, characterized in that the treated water from which the metalhydroxide has been separated and collected is recycled by making the treated water pass through a reverse osmosis membrane."

However, in contrast to the necessity of a pretreatment system before the gallium arsenide waste water is made to pass through the reverse osmosis membrane, the prior art has no pretreatment process.

Moreover, the aforementioned prior art (Japanese Patent Laid-Open Publication No. 2000-117270) has the problem that the power of the pump (pump 1043 and pump 1050) related to the MF membrane separation unit is great now that energy saving is valued.

The third prior art (Japanese Patent Laid-Open Publication No. HEI 9-285786) discloses in the claim 1 the "water treatment equipment operating method by means of an immersion type membrane filter unit characterized in that the precipitation or adsorption of arsenic is promoted by flowing a mixed water obtained by preliminarily adding a chemical for precipitating arsenic or an adsorbent for adsorbing arsenic to a raw water that contains arsenic into a membrane filter tank or by flowing the raw water into the membrane filter tank then forming a mixed water with the added chemical or adsorbent, thereby precipitating the arsenic in the raw water or adsorbing the arsenic to the adsorbent, and effecting solid-liquid separation of the mixed water inside the membrane filter tank by the immersion type membrane filter unit placed in the tank and setting the amount of membrane filtered water with respect to the amount of influent water into the membrane filter tank to 99% or more when the membrane filtered water that has passed through the membrane surface of the immersion type membrane filter unit is unloaded from the tank, thereby maintaining the chemical or the adsorbent at high concentration in the membrane filter tank".

In this claim 1, although arsenic can be treated, there is no process for separating two metals apart from each other as in the case of the gallium arsenide waste water. Moreover, the claim 2 claims the "water treatment equipment operating method by means of the immersion type membrane filter unit claimed in claim 1, characterized in that the arsenic in the raw water is oxidized to the pentavalent arsenic ion by either adding an oxidizer to the raw water or treating the raw water with ozone". This claim 2, which employs the chemical for oxidizing the arsenic in the raw water to the pentavalent arsenic ion, requires a chemical cost.

SUMMARY OF THE INVENTION

Accordingly, the object of this invention is to provide a metal containing waste water treatment method and treatment equipment capable of establishing a completely closed treatment system of the waste water by efficiently and stably treating the metal containing waste water discharged from a compound semiconductor plant, saving-energy and collecting and recycling valuable metals from the waste water as valuable substances.

Another object of this invention is to provide a metal containing waste water treatment method capable of establishing a completely closed treatment system of the waste water by recycling the sodium ions of the added sodium hydroxide and recycling by treatment the waste water as a raw water for an ultrapure water generating system.

In order to achieve the above objects, there is provided a metal containing waste water treatment method comprising the steps of:

introducing a metal containing waste water from above into a submerged membrane separation tank in which a reaction section, a submerged membrane section that has a submerged membrane and a precipitation section are arranged in order from top to bottom;

adding a pH adjuster to the reaction section so as to cause a reaction with the metal containing waste water;

separating the metal containing waste water into water and metal by the submerged membrane of the submerged membrane section; and

precipitating and concentrating the separated metal in the precipitation section.

According to the treatment method of this invention, the pH adjuster is added to the reaction section. Therefore, a hydroxide can be formed and subjected to solid-liquid separation by the submerged membrane. Moreover, the metal can be precipitated and concentrated in the precipitation section by the action of gravity without using energy.

Also, there is provided metal containing waste water treatment equipment comprising:

a submerged membrane separation tank in which a reaction section, a submerged membrane section that has a submerged membrane and a precipitation section are arranged in order from top to bottom and into which a metal containing waste water is introduced from above, whereby

a pH adjuster is added to the reaction section so as to cause a reaction with the metal containing waste water,

the metal containing waste water is separated into water and metal in the submerged membrane section, and

the separated metal is precipitated and concentrated in the precipitation section.

In the treatment equipment of this invention, the metal containing waste water is introduced from above into the submerged membrane separation tank, and the pH adjuster is added to the reaction section to cause a reaction, separating water and the metal from each other in the submerged membrane section and precipitating and concentrating the metal in the precipitation section. Through these processes, a hydroxide can be formed and subjected to solid-liquid separation by the submerged membrane. Moreover, the metal can be precipitated and concentrated in the precipitation section by the action of gravity without using energy.

In one embodiment of the present invention, the submerged membrane is an ultrafiltration membrane,

a pH meter and a filler are placed in the reaction section, pH in the reaction section is adjusted to 4 to 5 and an air diffusion pipe is placed below the submerged membrane owned by the submerged membrane section.

In this embodiment, the submerged membrane is an ultrafiltration membrane, and the pH meter and the filler are placed in the reaction section, by which the pH in the reaction section is adjusted to 4 to 5. Therefore, it is enabled to efficiently generate gallium hydroxide and thereafter effect solid-liquid separation with high accuracy by the submerged membrane, or the ultrafiltration membrane.

In this embodiment, air is discharged from the air diffusion pipe placed below the submerged membrane, and the filler for stirring use is existing in the reaction section. Therefore, in the reaction section, the stirring of the waste water is promoted to ensure the reaction of the waste water with the pH adjuster, efficiently generating gallium hydroxide. Moreover, since the pH in the reaction section is adjusted to 4 to 5, the gallium in the waste water is selectively generated as gallium hydroxide.

In one embodiment of the present invention, the filler is a reaction promoting member of a line mixer or the like that has a stirring structure.

In this embodiment, the filler is a reaction promoting material such as a line mixer. Therefore, the stirring of the waste water is further promoted by air discharged from the air diffusion pipe and the filler in the reaction section. Even with a residence time of a few minutes, the reaction of the waste water with the pH adjuster is further ensured.

In one embodiment of the present invention, the water separated in the submerged membrane section is pretreated by being introduced into a pretreatment system and recycled as a raw water for an ultrapure water generating system.

In this embodiment, the water separated in the submerged membrane section is introduced into the pretreatment system to carry out pretreatment and recycled as a raw water for an ultrapure water generating system. Therefore, the effective use of water can be achieved, completing a closed treatment system.

Also, there is provided metal containing waste water treatment equipment comprising:

a first submerged membrane separation tank in which a first reaction section, a first submerged membrane section that has a first submerged membrane and a first precipitation section are arranged in order from top to bottom and into which a metal containing waste water is introduced from above; and

a second submerged membrane separation tank in which a second reaction section, a second submerged membrane section that has a second submerged membrane and a second precipitation section are arranged in order from top to bottom and into which a treated water from the first submerged membrane section of the first submerged membrane separation tank is introduced from above, whereby

the first submerged membrane separation tank serves to add a pH adjuster to the first reaction section so as to cause a reaction with the metal containing waste water, subsequently separate water and metal from the metal containing waste water by the first submerged membrane of the first submerged membrane section and subsequently precipitate and concentrate the metal in the first precipitation section located in a lowermost portion, and

the second submerged membrane separation tank serves to add a coagulant and a pH adjuster to the second reaction section so as to cause a reaction, subsequently separate water and metal by the second submerged membrane of the second submerged membrane section and subsequently precipitate and concentrate the metal in the second precipitation section located in a lowermost portion.

The waste water treatment equipment of this invention is provided with the first submerged membrane separation tank and the second submerged membrane separation tank. Therefore, the precipitates of two groups can be separated, concentrated and precipitated.

In the first submerged membrane separation tank, the hydroxide formed by the pH adjuster can be concentrated, precipitated and separated. In the second submerged membrane separation tank, the coagulant and the pH adjuster are added to the treated water (separated water) that has undergone separation by the membrane in the first submerged membrane separation tank. Through this process, a larger precipitate such as a flock can be formed, enabling the hydroxide to be concentrated, precipitated and separated.

In one embodiment of the present invention, the water separated in the second submerged membrane section is pretreated by being introduced into the pretreatment system and recycled as a raw water for an ultrapure water generating system.

In this embodiment, the water separated in the second submerged membrane section is introduced into the pretreatment system to carry out pretreatment and recycled as a raw water for the ultrapure water generating system. Therefore, the water treated by the membranes of two stages is to be pretreated. Therefore, the load of the pretreatment system is reduced and easily recycled as a raw water for the ultrapure water generating system.

Also, there is provided metal containing waste water treatment equipment comprising:

a first submerged membrane separation tank in which a first reaction section, a first submerged membrane section that has a first submerged membrane and a first precipitation section are arranged in order from top to bottom and into which a metal containing waste water is introduced from above, the first submerged membrane separation tank serving to add a pH adjuster to the first reaction section so as to cause a reaction with the metal containing waste water, subsequently separate water and metal from the metal containing waste water by the first submerged membrane of the first submerged membrane section and subsequently precipitate and concentrate the metal in the first precipitation section located in a lowermost portion;

a second submerged membrane separation tank in which a second reaction section, a second submerged membrane section that has a second submerged membrane and a second precipitation section are arranged in order from top to bottom and into which a treated water from the first submerged membrane of the first submerged membrane separation tank is introduced from above, the second submerged membrane separation tank serving to add a coagulant and a pH adjuster to the second reaction section so as to cause a reaction, subsequently separate water and metal by the second submerged membrane of the second submerged membrane section and subsequently precipitate and concentrate the metal in the second precipitation section located in a lowermost portion; and

a third submerged membrane separation tank that has a third submerged membrane.

In the treatment equipment of this invention, the treated water from the first submerged membrane and the precipitate from the third submerged membrane separation tank are introduced from above into the second submerged membrane separation tank. Therefore, in this second submerged membrane separation tank, the mixed waste water is treated while receiving the influence of the precipitate from the third submerged membrane separation tank. Moreover, in the second reaction section, the coagulant and the pH adjuster are added. Therefore, in the second reaction section, a larger precipitate such as a flock is formed and able to be concentrated, precipitated and separated.

In one embodiment of the present invention, the metal containing waste water is a waste water that contains a compound semiconductor, and the pH adjuster is sodium hydroxide.

In this embodiment, the metal containing waste water is the waste water from compound semiconductor plant, and the pH adjuster is sodium hydroxide. Therefore, with the metal related to the compound semiconductor plant, a hydroxide can be formed by sodium hydroxide.

In one embodiment of the present invention, the waste water that contains the compound semiconductor is a waste water that contains gallium arsenide.

In this embodiment, the waste water from compound semiconductor plant is the waste water that contains gallium arsenide. Therefore, gallium can be collected as gallium hydroxide.

In one embodiment of the present invention, the ultrafiltration membrane has a pore diameter of 0.1 .mu.m to 1.0 .mu.m.

In this embodiment, the pore diameter of the ultrafiltration membrane is 0.1 .mu.m to 1.0 .mu.m. Therefore, a minute solid matter can reliably be separated.

In one embodiment of the present invention, the pretreatment system is any one or a combination of an activated carbon absorption unit, an ion exchange unit and a reverse osmosis membrane unit.

In this embodiment, the pretreatment system is any one or a combination of the activated carbon absorption unit, the ion exchange unit and the reverse osmosis membrane unit. Therefore, even if some organic matter, ions, minute particles and so on are existing in the treated water to the pretreatment system, the substances can reliably be removed resulting in pretreated as a raw water for the ultrapure water generating system.

In one embodiment of the present invention, the metal containing waste water is a waste water that contains gallium arsenide, and the metal precipitated and concentrated in the precipitation section is gallium hydroxide.

In this embodiment, the metal containing waste water is the waste water that contains gallium arsenide, and the precipitated concentrated metal is gallium hydroxide. Therefore, the gallium hydroxide can be received as a valuable substance by the gallium manufacturer, and this enables the recycling of gallium.

In one embodiment of the present invention, the coagulant is ferric chloride, and the pH adjuster is sodium hydroxide.

Also, in one embodiment of the present invention, the coagulant is ferric chloride, and the pH adjuster is sodium hydroxide.

According to the embodiment, the coagulant is ferric chloride, and the pH adjuster is sodium hydroxide. Therefore, arsenic can be made to be an insoluble salt as iron arsenate.

In one embodiment of the present invention, the metal containing waste water is a waste water that contains gallium arsenide,

the precipitated concentrated metal in the first submerged membrane separation tank is gallium hydroxide, and

the precipitated concentrated metal in the second submerged membrane separation tank is iron arsenate.

In this embodiment, the metal containing waste water is the waste water that contains gallium arsenide, the precipitated concentrated metal in the first submerged membrane separation tank is gallium hydroxide, and the precipitated concentrated metal in the second submerged membrane separation tank is iron arsenate. Therefore, two kinds of metals can separately be collected, and this allows the easy refinement by the manufacturer.

In one embodiment of the present invention, a developer waste water discharged through a gallium arsenide process and a waste water that contains arsenic are introduced into the third submerged membrane separation tank.

In this embodiment, the developer waste water discharged from the gallium arsenide process that contains developer and arsenic is introduced into the third submerged membrane separation tank. Therefore, the arsenic oxidizing bacterium can be cultured and bred in the third submerged membrane separation tank using nitrogen in the developer contained in the waste water as a nutrient.

In one embodiment of the present invention, a slurry precipitated and concentrated in the second precipitation section located in the lowermost portion of the second submerged membrane separation tank is sent back to the third submerged membrane separation tank.

In this embodiment, the slurry precipitated and concentrated in the precipitation section located in the lowermost portion of the second submerged membrane separation tank is sent back to the third submerged membrane separation tank. Therefore, the necessary amount of arsenic oxidizing bacterium can be secured by being sent back to the third submerged membrane separation tank, and this can be utilized for oxidizing trivalent arsenic to pentavalent arsenic again in the second submerged membrane separation tank.

In one embodiment of the present invention, a developer waste water and an arsenic containing waste water are introduced into the third submerged membrane separation tank so as to culture an arsenic oxidizing bacterium, and the cultured arsenic oxidizing bacterium is introduced into the second submerged membrane separation tank.

In this embodiment, the developer containing waste water and the arsenic containing waste water are introduced into the third submerged membrane separation tank so as to culture the arsenic oxidizing bacterium, and the cultured arsenic oxidizing bacterium is introduced into the second submerged membrane separation tank. Therefore, the nitrogen component in the developer contained in the waste water can be utilized for culturing and breeding the arsenic oxidizing bacterium. Moreover, by utilizing the cultured arsenic oxidizing bacterium, the oxidation from trivalent arsenic to pentavalent arsenic in the second submerged membrane separation tank can efficiently be carried out at low cost.

In one embodiment of the present invention, a slurry precipitated and concentrated in the second precipitation section located in the lowermost portion of the second submerged membrane separation tank contains an arsenic oxidizing bacterium.

In this embodiment, the arsenic oxidizing bacterium adheres to the slurry precipitated and concentrated in the precipitation section in the lowermost portion of the second submerged membrane separation tank. Therefore, it is enabled to construct an optimum system by circulating necessary amount of the slurry within the system.

Also, there is provided a metal containing waste water treatment method for carrying out waste water treatment by microorganically oxidizing trivalent arsenic in the arsenic containing waste water to pentavalent arsenic by an arsenic oxidizing bacterium.

According to the treatment method of this invention, the waste water treatment is carried out by microorganically oxidizing trivalent arsenic in the arsenic containing waste water into pentavalent arsenic by the arsenic oxidizing bacterium. This obviates the need for using a chemical as an oxidizer and allows the reduction of the running cost.

In one embodiment of the present invention, the waste water treatment is carried out by changing the trivalent arsenic in the arsenic containing waste water into the pentavalent arsenic by the arsenic oxidizing bacterium and adding a coagulant and a pH adjuster.

In this embodiment, the waste water treatment is carried out by changing trivalent arsenic in the arsenic containing waste water into pentavalent arsenic by the arsenic oxidizing bacterium with the coagulant added. Therefore, arsenic as an insoluble salt is caught and formed into a large flock by the coagulant and the pH adjuster.

Also, there is provided a metal containing waste water treatment method for collecting metal from a metal containing waste water, comprising the steps of:

separating a first metalhydroxide from the waste water by making the metal containing waste water pass through a first submerged membrane separation unit with a pH adjuster added;

separating a concentrate brine that contains another metal dissolved in the waste water from the waste water by making the waste water pass through a reverse osmosis membrane separation unit; and

sending the concentrate brine that contains said another metal back to the first submerged membrane separation unit and adding the concentrate brine to the waste water together with the pH adjuster.

According to the treatment method of this invention, when the metal containing waste water is made to pass through the first submerged membrane separation unit after the formation of a metalhydroxide through the reaction with the pH adjuster added, then the metalhydroxide can be concentrated in the first submerged membrane separation unit.

Moreover, another metal, which has passed through the first submerged membrane separation unit, is made to pass through the reverse osmosis membrane separation unit. Because of the reverse osmosis membrane separation unit used this time, the metal moves to the concentrate brine side. By sending again the concentrate brine that contains another metal as a new pH adjuster back to the waste water so as to be added, the amount of use of the new pH adjuster can be reduced. That is, the running cost can be reduced.

In one embodiment of the present invention, the metal containing waste water is made to pass through the second submerged membrane separation unit with a pH adjuster and a coagulant added to the metal containing waste water in a stage behind the first submerged membrane separation unit,

the resulting liquid is made to pass through the reverse osmosis membrane separation unit with a pH adjuster added and further pass through an ultrapure water generating system arranged in a stage behind the reverse osmosis membrane separation unit, and

the concentrate brine from the reverse osmosis membrane separation unit is sent back to the first submerged membrane separation unit and added to the waste water together with the pH adjuster.

According to this embodiment, the pH adjuster is added to the waste water so as to generate water and a first metalhydroxide. The water and the first metalhydroxide are separated into water and the concentrate of the first metalhydroxide by the first submerged membrane separation unit.

Subsequently, the pH adjuster (sodium hydroxide, for example) and the coagulant (ferric chloride, for example) are added to the waste water in the stage behind the first submerged membrane separation unit. Subsequently, the waste water in which the second metal (arsenic) is dissolved can be separated into water and a second metallic concentrate by the second submerged membrane separation unit.

Further, the metal (sodium ions) concentrated by the reverse osmosis membrane separation unit in the stage behind the second submerged membrane separation unit is sent back and added to the stage before the initial first submerged membrane separation unit and able to be recycled as a pH adjuster.

According to this embodiment, the two kinds of first and second metals can be separated and collected by the first and second submerged membrane separation units. At the same time, the metal (sodium) included in the pH adjuster added initially can be recycled as a pH adjuster, and this produces the effect of reducing the running cost.

In one embodiment of the present invention, the water obtained from an electric deionization unit arranged behind the reverse osmosis membrane separation unit is recycled by being introduced into an ultrapure water generating system, and

a concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit is sent back to the first submerged membrane separation unit, added to the waste water together with the pH adjuster and made to pass through the first submerged membrane separation unit.

According to this embodiment, the water quality of the ultrapure water generating system can be improved by placing the electric deionization unit behind the reverse osmosis membrane separation unit, effecting electric deionization and reducing the load of the ultrapure water generating system in the subsequent stage.

The electric deionization unit is not required to be reproduced by acid or alkali as in the case of the ion exchange resin, and, of course, no waste liquid is generated. Therefore, the waste water treatment equipment can be obviated. That is, since the electric deionization unit is used, the system can be completed without using a chemical substance as a chemical nor generating a waste liquid, producing the effect of providing an environment-friendly system.

In one embodiment of the present invention, a pH adjuster, a coagulant and metal oxidizing bacterium are added in a stage behind the first submerged membrane separation unit and before the second submerged membrane separation unit.

According to this embodiment, the pH adjuster, the coagulant and the metal oxidizing bacterium are added in the stage behind the first submerged membrane separation unit. Therefore, the metal in the waste water can be oxidized by this metal oxidizing bacterium, allowing the metal to be stabilized.

According to this embodiment, the metal is oxidized not by the oxidizer as a chemical but by using the metal oxidizing bacterium. Therefore, the chemical cost can be saved, and the running cost can be reduced.

Also, there is provided a metal containing waste water treatment method comprising the steps of:

introducing a metal containing compound semiconductor waste water from above into a first submerged membrane separation tank in which a reaction section, a submerged membrane section that has a submerged membrane and a precipitation section are arranged in order from top to bottom and adding a pH adjuster to the reaction section so as to cause a reaction;

subsequently separating metal from the waste water by the submerged membrane of the submerged membrane section and subsequently precipitating and concentrating the metal in the precipitation section;

treating a treated water obtained by the submerged membrane sequentially in an arsenic- and phosphorus-removing unit, an activated carbon adsorption unit, a reverse osmosis membrane unit and an electric deionization unit and thereafter introducing the resulting liquid into an ultrapure water generating system; and

sending a concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit back to the reaction section.

According to the treatment method of this invention, gallium as a metal can be collected, and arsenic and phosphorus in the separated water are removed by the is arsenic- and phosphorus-removing unit and further pretreated to recycle the water for the ultrapure water generating system. Therefore, a completely closed treatment system of the waste water that contains gallium, arsenic and phosphorus can be completed.

Moreover, by sending the concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit back to the reaction section of the first submerged membrane separation tank, the metal (sodium ions) in the concentrate brine can be sent back and recycled. This enables the reduction in the amount of use of sodium hydroxide as a pH adjuster and the reduction in the running cost.

In one embodiment of the present invention, a concentrate concentrated in the first submerged membrane separation tank is further concentrated by being introduced into a second submerged membrane separation tank arranged below the first submerged membrane separation tank.

According to this embodiment, the second submerged membrane separation tank is arranged below the first submerged membrane separation tank. Therefore, the metal in the waste water can be concentrated by the physical means in two steps without consuming a vast amount of energy like that of the evaporator, and this allows the concentration of the concentrate brine to be increased.

In one embodiment of the present invention, a treated water from the submerged membrane of the first submerged membrane separation tank and the submerged membrane of the second submerged membrane separation tank are introduced into a reaction section of a third submerged membrane separation tank together with a pH adjuster and a coagulant,

the precipitate in the third submerged membrane separation tank is further concentrated in a fourth submerged membrane separation tank,

a treated water separated by the submerged membranes of the third submerged membrane separation tank and the fourth submerged membrane separation tank is meanwhile treated sequentially in an activated carbon adsorption unit, a reverse osmosis membrane unit and an electric deionization unit and thereafter introduced into an ultrapure water generating system, and

a concentrate brine from the reverse osmosis membrane unit and the electric deionization unit is sent back to a reaction section of the first submerged membrane separation tank.

According to this embodiment, after the separation of gallium and arsenic, gallium and arsenic can be each concentrated by the two-stage submerged membrane separation tank (second submerged membrane separation tank and fourth submerged membrane separation tank) without consuming a vast amount of energy like that of the evaporator. Therefore, according to this embodiment, gallium and arsenic can be concentrated while saving energy as far as possible.

In one embodiment of the present invention, an arsenic oxidizing bacterium is cultured and concentrated by introducing part of the metal containing waste water from compound semiconductor plant and a developer waste water into a fifth submerged membrane separation tank, and the arsenic oxidizing bacterium is introduced into the third submerged membrane separation tank.

According to this embodiment, the arsenic oxidizing bacterium cultured and concentrated in the fifth submerged membrane separation tank is introduced into the third submerged membrane separation tank. Therefore, in this third submerged membrane separation tank, trivalent arsenic can be concentrated and separated as stable pentavalent arsenic by the arsenic oxidizing bacterium. Moreover, since no oxidizer is used as a chemical, the running cost can be reduced.

Moreover, the arsenic oxidizing bacterium propagates using the organic matter in the developer contained in the waste water discharged from the compound semiconductor fabricating process as a nutrient in fifth submerged membrane separation tank and propagates on the basis of the arsenic included in the waste water. For this reason, there is no need for using the costing nutrient in culturing the arsenic oxidizing bacterium, and the running cost can be reduced.

In one embodiment of the present invention, part of the concentrate brine precipitated in the third submerged membrane separation tank is sent back to the fifth submerged membrane separation tank.

According to this embodiment, part of the concentrate brine precipitated in the third submerged membrane separation tank is sent back to the fifth submerged membrane separation tank. Therefore, the arsenic oxidizing bacterium in the concentrate brine can be recycled, and the speed of culturing the arsenic oxidizing bacterium in the fifth submerged membrane separation tank can be increased.

In one embodiment of the present invention, the arsenic oxidizing bacterium cultured in the fifth submerged membrane separation tank is introduced into the first submerged membrane separation tank and the third submerged membrane separation tank.

According to this embodiment, the arsenic oxidizing bacterium is introduced into the first submerged membrane separation tank and the third submerged membrane separation tank, allowing trivalent arsenic to be changed into stable pentavalent arsenic and allowing the organic matter in the waste water to be resolved by utilizing the organic matter resolving power possessed by the arsenic oxidizing bacterium. Consequently, the load on the ultrapure water generating system by the raw water quality can further be reduced.

In one embodiment of the present invention, the metal oxidizing bacterium is an arsenic oxidizing bacterium.

According to this embodiment, the metal can be oxidized without using an oxidizer as a chemical, and this produces the effect of reducing the running cost.

In one embodiment of the present invention, metal is precipitated and concentrated in the precipitation section and thereafter further concentrated by an evaporator.

According to this embodiment, the metal is precipitated and concentrated in the precipitation section and thereafter further concentrated by the evaporator, and therefore, the metal can be concentrated in a short time. Moreover, since the evaporator is used, the concentration can easily be increased to the desired level.

In one embodiment of the present invention, the liquid precipitated and concentrated in the first submerged membrane separation tank is concentrated by being introduced into an evaporator, and

the liquid precipitated and concentrated in the third submerged membrane separation tank is meanwhile concentrated by being introduced into an evaporator.

According to this embodiment, different metals can be concentrated to the desired concentration level in a short time in the first submerged membrane separation tank and the third submerged membrane separation tank.

In one embodiment of the present invention, the waste water from compound semiconductor plant is a waste water that contains hydrogen peroxide containing gallium arsenide.

According to this embodiment, the hydrogen peroxide in the waste water is resolved by the anaerobic microorganism and becomes easily recycled as a raw water for the ultrapure water generating system.

Also, there is provided a metal containing waste water treatment method for treating metal and water contained in a waste water from compound semiconductor plant and separately collecting the metal and water, thereby establishing a completely closed treatment system.

According to the treatment method of this invention, a completely closed treatment system is established by treating and separately collecting the metal and water included in the waste water from compound semiconductors plant. This produces the effect of minimizing the influence exerted on the environment.

Also, there is provided a metal containing waste water treatment method for treating metal and water contained in a waste water from compound semiconductor plant, separately collecting the metal and water, collecting the metal as a valuable substance and meanwhile collecting the water as a raw water for an ultrapure water generating system, thereby establishing a completely closed treatment system.

According to the treatment method of this invention, a completely closed treatment system is established by treating and separately collecting the metal and water included in the waste water from compound semiconductors plant, collecting the metal as a valuable substance and collecting the water as a raw water for the ultrapure water generating system. Therefore, the influence exerted on the environment can be minimized, and the metal is collected as a valuable substance, allowing the economical efficiency to be improved.

Also, there is provided a metal containing waste water treatment method for treating gallium, arsenic and water in a gallium arsenide waste water and separately collecting the gallium, arsenic and water, thereby establishing a completely closed treatment system.

According to the treatment method of this invention, a completely closed treatment system is established by treating and separately collecting the gallium, arsenic and water included in the waste water. Therefore, the influence exerted on the environment can be minimized.

Also, there is provided a metal containing waste water treatment method for treating gallium, arsenic and water in a gallium arsenide waste water, separately collecting the gallium, arsenic and water, collecting the gallium and arsenic as valuable substances and meanwhile collecting the water as a raw water for an ultrapure water generating system, thereby establishing a completely closed treatment system.

According to the treatment method of this invention, a completely closed treatment system is established by treating and separately collecting the gallium, arsenic and water included in the waste water, collecting the metal as a valuable substance and collecting the water as a raw water for the ultrapure water generating system. Therefore, the influence exerted on the environment can be minimized, and the metal is collected as a valuable substance, allowing the economical efficiency to be improved.

In one embodiment of the present invention, a microorganism is used for treating the arsenic. According to this embodiment, arsenic can be treated by the power of the microorganism, and the running cost be reduced in comparison with the treatment with a chemical.

In one embodiment of the present invention, the microorganism is a metal oxidizing bacterium. According to this embodiment, the metal can be oxidized at low cost.

In one embodiment of the present invention, the metal oxidizing bacterium is an arsenic oxidizing bacterium. According to this embodiment, trivalent arsenic can be oxidized to pentavalent arsenic at low cost.

Also, there is provided a metal containing waste water treatment method for collecting metal from a metal containing waste water, comprising the steps of:

preliminarily adding a pH adjuster to the waste water so as to cause a reaction;

making the resulting waste water pass through a multistage type submerged membrane separation unit including submerged membranes arranged vertically in a plurality of tiers, an adhesional precipitation section arranged below the submerged membranes for precipitating a reactant by making the reactant adhere to a filler and a diaphragm for vibrating the submerged membranes in order to separate a metalhydroxide from the waste water;

separating a concentrate brine that contains another metal dissolved in the waste water from the waste water by making the treated water, from which the metalhydroxide has been removed, pass through a reverse osmosis membrane separation unit; and

sending the concentrate brine that contains said another metal back to a stage before the multistage type submerged membrane separation unit and adding the concentrate brine to the waste water together with the pH adjuster.

According to the treatment method of this invention, the waste water is made to react with the pH adjuster added to form a metalhydroxide and thereafter made to pass through the submerged membrane separation unit in which the submerged membranes are placed vertically in a plurality of tiers. Through these processes, a large amount of metalhydroxide can efficiently be concentrated by this submerged membrane separation unit. That is, the treatment capability can be improved.

Moreover, another metal (sodium ions, for example) attributed to the pH adjuster, which has passed through the submerged membrane separation unit in which the submerged membranes are placed vertically in a plurality of tiers, is made to pass through the reverse osmosis membrane separation unit. Due to the reverse osmosis membrane separation unit used this time, the metal moves to the concentrate brine side. The concentrate brine that includes the metal is sent again back to the waste water together with the pH adjuster so as to be recycled, by which the amount of use of a new pH adjuster can be reduced.

In one embodiment of the present invention, a pH adjuster and a coagulant are added in a stage behind the multistage type submerged membrane separation unit that serves as a first multistage type submerged membrane separation unit,

next the resulting waste water is made to pass through a second multistage type submerged membrane separation unit, which has submerged membranes arranged vertically in a plurality of tiers, an adhesional precipitation section for precipitating a reactant by making the reactant adhere to a filler and a diaphragm for vibrating the submerged membranes,

the resulting liquid is subsequently made to pass through a reverse osmosis membrane separation unit with a pH adjuster added,

a treated water from the reverse osmosis membrane separation unit is further introduced into an ultrapure water generating system arranged in a stage behind the reverse osmosis membrane separation unit, and

the concentrate brine from the reverse osmosis membrane separation unit is sent back to a stage before the first multistage type submerged membrane separation unit and the concentrate brine is added to the waste water together with the pH adjuster.

According to this embodiment, the pH adjuster is added to the waste water, and a large amount of water and a large amount of metalhydroxide are efficiently separated into water and a concentrate by the submerged membrane separation unit in which the submerged membranes are placed vertically in a plurality of tiers. Subsequently, the pH adjuster (sodium hydroxide) and the coagulant (ferric chloride) are added, by which the metal (arsenic) dissolved in the water can be separated from a large amount of water as a large amount of concentrate. That is, the treatment capability can be improved.

Moreover, the metal (sodium ions) concentrated by the reverse osmosis membrane separation unit can be recycled by being sent back to the stage before the first submerged membrane separation unit in which the submerged membranes are placed vertically in a plurality of tiers.

In one embodiment of the present invention, the treated water obtained by the reverse osmosis membrane separation unit is made to pass through an electric deionization unit, a treated water obtained from the electric deionization unit is recycled by being introduced into an ultrapure water generating system, and

a concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit is meanwhile sent back to the stage before the first multistage type submerged membrane separation unit and added to the waste water together with the pH adjuster.

According to this embodiment, the water quality of the ultrapure water generating system can be improved by arranging the electric deionization unit in the stage behind the reverse osmosis membrane separation unit and effecting electric deionization to reduce the load of the ultrapure water generating system in the subsequent stage. This electric deionization unit is not required to be reproduced by acid or alkali as in the case of the ion exchange resin, and, of course, no waste liquid is discharged by the reproduction. Therefore, the waste water treatment equipment can be obviated.

Moreover, the concentrate brine (concentrate brine containing sodium ions) from the electric deionization unit is sent back and made to pass through the first submerged membrane separation unit in which the submerged membranes are arranged vertically in a plurality of tiers. Therefore, the metal (sodium) ions can be recycled.

In one embodiment of the present invention, a pH adjuster, a coagulant and a metal oxidizing bacterium are added in a stage behind the first multistage type submerged membrane separation unit.

According to this embodiment, the pH adjuster, the coagulant and the metal oxidizing bacterium are added in the stage behind the first submerged membrane separation unit in which the submerged membranes are arranged vertically in a plurality of tiers. Therefore, concurrently with the improvement of the treatment capability of the submerged membranes arranged vertically in a plurality of tiers, the metal in the waste water can be oxidized by the metal oxidizing bacterium for the stabilization of the metal.

In particular, the oxidation is effected by means of the metal oxidizing bacterium without oxidizing the metal with the oxidizer as a chemical. Therefore, the chemical cost can be saved, and the running cost can be reduced.

Also, there is provided a metal containing waste water treatment method comprising the steps of:

adding a pH adjuster to a waste water from compound semiconductor plant in a pH adjustment tank so as to cause a reaction;

introducing the waste water from the pH adjustment tank upwardly in an upward flow into a multistage submerged membrane separation tank in which an upper portion where a pH meter is placed, a submerged membrane section that includes submerged membranes arranged vertically in a plurality of tiers and a diaphragm for vibrating the submerged membranes and an adhesional precipitation section for making a reactant adhere to a filler are arranged in order from top to bottom;

primarily separating a metal from the waste water by physically catching and filtering the metal in the waste water in the adhesional precipitation section and secondarily separating the metal from the waste water by the submerged membranes in the submerged membrane section;

treating a treated water obtained by the submerged membranes sequentially in an arsenic- and phosphorus-removing unit, an activated carbon adsorption unit, a reverse osmosis membrane unit and an electric deionization unit and thereafter introducing the resulting liquid into an ultrapure water generating system; and

sending a concentrate brine from the reverse osmosis membrane unit and the electric deionization unit back to the pH adjustment tank.

According to the treatment method of this invention, the waste water from the pH adjustment tank is introduced from below into the multistage submerged membrane separation tank constructed of the upper portion where the pH meter is placed, the submerged membrane section where the diaphragm and the submerged membranes arranged vertically in a plurality of tiers and the adhesional precipitation section. Through this process, the pH inside the water tank can be first adjusted by the pH meter. Moreover, the treatment capability of the submerged membrane section can be improved by applying vibrations to the submerged membranes arranged vertically in a plurality of tiers to flake off the accretion to the submerged membranes.

Moreover, the waste water from the pH adjustment tank is first introduced into the adhesional precipitation section, and therefore, the solid matter in the waste water can be removed by being stuck to the filler of the adhesional precipitation section. It is to be noted that the solid matter in the waste water means the solid matter originally included in the waste water and the solid matter of hydroxide and so on formed by adding the pH adjuster.

The solid matter stuck to the filler, which includes the hydroxide, gradually grows with a lapse of time. As a result, the solid matter becomes easily precipitated and is able to be unloaded to the outside of the tank.

Moreover, by sending the concentrate brine from the reverse osmosis membrane separation unit and the electric deionization unit back to the pH adjustment tank, the metal (sodium, as one example) ions in the concentrate brine can be sent back and recycled.

It is to be noted that the compound semiconductor is the generic term of the substances that play the role of a semiconductor constructed by combining a plurality of elements, which are exemplified by gallium arsenide, gallium phosphide, indium phosphide, gallium nitride and zinc sulfide. The compound semiconductor can obtain high-frequency high-speed characteristics and a light-emitting characteristic superior to those of silicon.

In one embodiment of the present invention, the treated water and the concentrate brine from the first multistage type submerged membrane separation unit is treated by being introduced into a second submerged membrane separation tank arranged below the multistage type submerged membrane separation tank that serves as a first submerged membrane separation tank.

According to this embodiment, the waste water can be concentrated in two steps in the second submerged membrane separation tank arranged below the first submerged membrane separation tank, and the concentration level of the concentrate brine can be increased.

In one embodiment of the present invention, the pH adjustment tank is served as a first pH adjustment tank,

the treated water from the submerged membrane of the first submerged membrane separation tank and the submerged membrane of the second submerged membrane separation tank is introduced into a second pH adjustment tank together with a pH adjuster so as to cause a reaction,

the treated water from the second pH adjustment tank is subsequently introduced upwardly in an upward flow into a multistage submerged membrane separation tank that serves as a third submerged membrane separation tank in which an upper portion where a pH meter is placed, a submerged membrane section that includes submerged membranes arranged vertically in a plurality of tiers and a diaphragm for vibrating the submerged membranes and an adhesional precipitation section for precipitating a reactant by making the reactant adhere to a filler are arranged in order from top to bottom, a metal is separated from the treated water, the metal is further concentrated in a fourth submerged membrane separation tank arranged below the third submerged membrane separation tank,

the treated water separated by the submerged membranes of the third submerged membrane separation tank and the fourth submerged membrane separation tank is treated sequentially in an activated carbon adsorption unit, a reverse osmosis membrane unit and an electric deionization unit and thereafter introduced into an ultrapure water generating system, and

a concentrate brine from the reverse osmosis membrane unit and the electric deionization unit is sent back to the first pH adjustment tank.

According to this embodiment, the waste water treatment capability can be improved. At the same time, after the separation of two kinds of metals (gallium and arsenic, as one example) in the first and third submerged membrane separation tanks, the two kinds of metals (gallium and arsenic, as one example) can also be concentrated by the two-stage submerged membrane separation tanks (second submerged membrane separation tank and fourth submerged membrane separation tank). According to this invention, the two kinds of metals can be concentrated saving the energy as far as possible.

In one embodiment of the present invention, an arsenic oxidizing bacterium cultured and concentrated in the fifth submerged membrane separation tank into which part of the waste water from compound semiconductor plant that contains a developer waste water and a metal are introduced into the third submerged membrane separation tank.

According to this embodiment, the arsenic oxidizing bacterium cultured and concentrated is introduced into the third submerged membrane separation tank. Therefore, trivalent arsenic can be concentrated and separated as stable pentavalent arsenic by the arsenic oxidizing bacterium in this third submerged membrane separation tank. Moreover, since no oxidizer is used as a chemical, the running cost can be reduced.

Moreover, the arsenic oxidizing bacterium propagates using the organic matter in the developer contained in the waste water discharged from the compound semiconductor fabricating process as a nutrient in fifth submerged membrane separation tank and propagates on the basis of the arsenic included in the waste water. Therefore, the running cost can be reduced without using the costing nutrient for culturing the bacterium.

In one embodiment of the present invention, part of the concentrate brine precipitated in the third submerged membrane separation tank is sent back to the fifth submerged membrane separation tank.

According to this embodiment, part of the concentrate brine precipitated in the third submerged membrane separation tank is sent back to the fifth submerged membrane separation tank. Therefore, the arsenic oxidizing bacterium in the concentrate brine can be recycled, and the speed of culturing the arsenic oxidizing bacterium in the fifth submerged membrane separation tank can be increased.

In one embodiment of the present invention, an arsenic oxidizing bacterium cultured in the fifth submerged membrane separation tank is introduced into the first submerged membrane separation tank and the third submerged membrane separation tank.

According to this embodiment, the arsenic oxidizing bacterium is introduced into the first submerged membrane separation tank and the third submerged membrane separation tank. The organic load on the ultrapure water generating system by the raw water quality can further be reduced by not only changing trivalent arsenic into stable pentavalent arsenic but also resolving the organic matter in the waste water utilizing the organic matter resolving power possessed by the arsenic oxidizing bacterium.

In one embodiment of the present invention, the metal oxidizing bacterium is an arsenic oxidizing bacterium. According to this embodiment, the metal is oxidized without using a oxidizer as a chemical, resulting in a reduction of the running cost.

In one embodiment of the present invention, the resulting liquid is further condensed by being introduced into an evaporator after the metal is precipitated and condensed in the adhesional precipitation section.

According to this embodiment, the metal is precipitated and condensed in the adhesional precipitation section and thereafter further concentrated by being introduced into the evaporator. Therefore, the concentration can be achieved in a short time. Furthermore, since the evaporator is used, the concentration can easily be increased to the desired concentration level.

In one embodiment of the present invention, the liquid precipitated and concentrated in the first submerged membrane separation tank is concentrated by being introduced into an evaporator, and

the liquid precipitated and concentrated in the third submerged membrane separation tank is concentrated by being introduced into an evaporator.

According to this embodiment, the concentrate brine from the first submerged membrane separation tank and the third submerged membrane separation tank are introduced into the respective evaporators, and different metals can be concentrated to the desired concentration level in a short time.

In one embodiment of the present invention, an influent water is a waste water from compound semiconductor plant that contains hydrogen peroxide containing gallium arsenide.

According to this embodiment, hydrogen peroxide in the waste water, which serves as an oxidizer, is treated by being resolved by the reducibility possessed by the anaerobic microorganism generated attendant on culturing the arsenic oxidizing bacterium at high concentration. Through this process, a treated water, which can easily be recycled as a raw water for the ultrapure water generating system, is obtained. Moreover, since the hydrogen peroxide in the waste water is treated by being resolved by the anaerobic microorganism, the running cost can be reduced in comparison with the method of using a chemical.

Also, there is provided a metal containing waste water treatment method for subjecting metal and water contained in a waste water from compound semiconductor plant to a physical treatment, a biological treatment and a chemical treatment to collect gallium and other metals by separation, thereby establishing a completely closed treatment system.

According to the treatment method of this invention, the metal and water included in the water from compound semiconductor plant are treated physically, biologically and chemically, i.e., subjected to all of the three treatment processes (physical treatment, biological treatment and chemical treatment). Therefore, the water quality of the treated water can be improved.

Moreover, the metal included in the waste water is collected by being separated into gallium and other metals. Therefore, the refinery manufacturer can easily recycle gallium, and other metals can also easily be recycled.

Moreover, a completely closed treatment system is established by separately collecting gallium and other metals. Therefore, the influence exerted on the environment can be minimized.

Also, there is provided a metal containing waste water treatment method for subjecting metal and water contained in a waste water from compound semiconductor plant to a physical treatment, a biological treatment and a chemical treatment to collect gallium and other metals by separation, collecting the metal as a valuable substance and collecting the water as a raw water for an ultrapure water generating system, thereby establishing a completely closed treatment system.

According to the treatment method of this invention, a completely closed treatment system is established by physically, biologically and chemically treating the metal and water included in the waste water, separately collecting the substances, collecting the metal as a valuable substance and collecting the water as a raw water for the ultrapure water generating system. As described above, according to this invention, the waste water is subjected to the three treatment processes. Therefore, the treatment is reliable, and the influence exerted on the environment can concurrently be minimized. Moreover, since the metal is collected as a valuable substance, the economic efficiency can be improved. Moreover, if the metal is collected as a valuable substance, there is no subjection to the law on waste disposal, and there are many merits including system control.

Also, there is provided a metal containing waste water treatment method for subjecting gallium, arsenic, phosphorus and water in a waste water that contains gallium arsenide and gallium phosphide to a physical treatment, a biological treatment and a chemical treatment, and

separately collecting the substances as gallium and a mixture of arsenic and phosphorus, thereby establishing a completely closed treatment system.

According to the treatment method of this invention, the gallium arsenide and the gallium, arsenic, phosphorus and water contained in the gallium phosphide waste water are treated physically, biologically and chemically, and therefore, the treatment is reliable. Moreover, (1) gallium and (2) a mixture of arsenic and phosphorus, which are separately collected, can easily be recycled by the refinery manufacturer. Moreover, since a completely closed treatment system is established, the influence exerted on the environment can be minimized.

Also, there is provided a metal containing waste water treatment method for subjecting gallium, arsenic, phosphorus and water in a waste water that contains gallium arsenide and gallium phosphide to a physical treatment, a biological treatment and a chemical treatment,

separately collecting the substances as gallium and a mixture of arsenic and phosphorus,

collecting the gallium and the mixture of arsenic and phosphorus as valuable substances and collecting the water as a raw water for an ultrapure water generating system, thereby establishing a completely closed treatment system.

According to the treatment method of this invention, the gallium arsenide and the gallium, arsenic, phosphorus and water contained in the gallium phosphide waste water are subjected to the aforementioned three treatment processes, and therefore, the waste water can reliably be treated. Moreover, in this embodiment, the gallium and the mixture of arsenic and phosphorus, which are separately collected, can easily be recycled by the refinery manufacturer. Moreover, since the metals are collected as valuable substances, the economic efficiency can be increased. At the same time, the metals, which are not wastes, are not subjected to the law on waste disposal, and there is the merit that the statutory regulations are totally reduced. Moreover, a completely closed treatment system is established by collecting water as a raw water for the ultrapure water generating system. Therefore, the influence exerted on the environment can be minimized.

In one embodiment of the present invention, a microorganism is used for treating the arsenic.

According to this embodiment, the arsenic can be treated by the power of the microorganism, a