Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
1999-11-22
2002-04-30
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S915000, C210S207000
Reexamination Certificate
active
06379548
ABSTRACT:
TECHNICAL FIELD
The present invention relates to apparatus for reclaiming industrial effluent water, i.e., acid-alkali effluent water containing organic matter, and more particularly to apparatus for reclaiming effluent water containing ammonia and organic matter at relatively low concentrations, fluorine as the case may be, and further phosphoric acid, especially the effluent water to be discharged from the wet process practiced with use of ultrapure water in plants for manufacturing semiconductors, liquid crystals or like electronic products or devices.
BACKGROUND ART
When acid-alkali effluent water containing several ppm of organic matter is to be reclaimed, the effluent water is first neutralized in a neutralizing tank and thereafter treated in a biological treatment tank to decompose and remove the organic matter as shown in FIG.
3
. The biologically treated water is subsequently supplied to an ultrafiltration (UF) circulation tank and then to a UF device to remove an SS component consisting mainly of microorganisms and contained in the treated water. The biologically treated water resulting from the removal of SS is fed to a regenerative ion exchange device for the removal of inorganic ions. The treated water free from inorganic ions is reused as recycled water from waste water or water for replenishing a cooling tower.
In the flow chart of
FIG. 3
, each reference numeral stands for as follows.
51
; collected effluent
52
; neutralizing agent
53
; oxygen dissolving tank
54
; UF circulation tank
55
; air
56
; regenerative ion exchange device
The other reference numerals are the same as those of FIG.
1
.
In the case of fluorine-containing effluent water, slaked lime is first added to the collected effluent water in a reactor for the primary treatment of the effluent water as shown in FIG.
4
. CaF
2
is formed according to the reaction formula:
Ca
2
+2F
−
→CaF
2
to precipitate in a settling tank, and sludge containing the precipitate is removed with a dehydrator. On the other hand, the water resulting from the primary treatment is treated in a biological treatment tank to decompose and remove organic matter. Aluminum sulfate serving as a coagulant is further added to the biologically treated water in a reactor for advanced treatment. Al(OH)
3
having a fluorine adsorbing property and formed according to the reaction formula:
Al
3+
+3OH→Al(OH)
3
is caused to adsorb the fluorine, followed by precipitation in a settling tank. The resulting sludge containing the Al(OH)
3
is removed with the dehydrator. The fluorine contained in a very small amount in the water subjected to the advanced treatment is removed by adsorption in a adsorption column packed with a chelate resin. The water treated is discharged from the column.
In the flow chart of
FIG. 4
, each reference numeral stands for as follows.
61
; flourine-containing collected effluent
62
; slaked lime
63
; settling tank
64
; dehydrator
65
; aluminum sulfate
66
; sludge
67
; discharge
The other reference numerals are the same as those of FIG.
1
.
The apparatus for reclaiming acid-alkali effluent water containing several ppm of organic matter includes a regenerative ion exchange device as described above. This device requires regeneration of the resin when ions are adsorbed to saturation. Usually 2 or 3 equivalent weights of a regenerant is used for removing one equivalent weight of ions and discharged from the device, while the regeneration discharges a large quantity of effluent. This gives rise to a need to suitably treat the effluent additionally.
The apparatus for reclaiming effluent water containing organic matter develops troubles such as clogging of the separation membrane device or ion exchange device disposed at a downstream location because the organic matter in the collected effluent permits active growth of microorganisms or because the metabolites of microorganisms, or fungi will leak.
On the other hand, slaked lime for use in treating fluorine-containing effluent water is in the form of fine particles and produces fine particles of CaF
2
through a liquid-phase reaction when dissolved in water. For a further advanced treatment of the effluent water, there is a need to add a coagulant to the water. The sludge produced by the use of these chemicals must be separated off by equipment such as a coagulation tank and thickener. The equipment then requires a large area for installation. To reduce the fluorine concentration of the treated water below the effluent regulation level, slaked lime serving as a neutralizing agent, aluminum sulfate as a coagulant, high-molecular-weight coagulant, etc. need to be used in excessive amounts, consequently producing a large quantity of sludge and adding to the amount of waste to be discarded. The sludge contains about 80% of water even when dewatered, and the CaF
2
content of the sludge is usually up to 10%.
The water recovered still remains to be treated for use as the raw water to be supplied to the pure water system resorting to conventional ion exchange and membrane separation.
An object of the present invention is to provide a compact effluent water reclamation apparatus which is minimized in the kinds and amounts of chemicals to be used for the recovery of water to thereby reduce the amount of waste and eliminate equipment, such as a thickener, which necessitates a large area for installation.
Another object of the invention is to provide an effluent water reclamation apparatus which is adapted for continuous treatment free of the likelihood of a membrane separation device or ion exchange device becoming clogged with microorganisms.
DISCLOSURE OF THE INVENTION
The present invention provides a first effluent water reclamation apparatus comprising a reverse osmosis device and adapted to treat acid-alkali effluent water containing organic matter but no fluorine. The first apparatus concentrates acid-alkali effluent water containing organic matter by reverse osmosis, evaporates the resulting concentrated water to dryness and collects the water permeating through a reverse osmosis membrane. The apparatus is characterized in that the apparatus comprises as arranged upstream from the reverse osmosis device a neutralizing device for neutralizing the effluent water to prevent a scale component from separating out from the effluent water in the process of reverse osmosis, and a biological treatment tank for biologically treating the neutralized effluent water.
With the first effluent water reclamation apparatus, fluorine-free effluent water is neutralized, for example, with an aqueous solution of caustic soda at a position upstream from the reverse osmosis device so as to render the effluent water unlikely to permit a scale component to separate out (to give high solubility) even if the water is concentrated to an extreme extent with the reverse osmosis device. The neutralized effluent water is treated in the biological treatment device to decompose and remove the organic matter. The biological treatment tank has an activated carbon packed layer which is fully supplied with oxygen or which is fluidized while being supplied with oxygen. Ammonia is digested in the biological treatment tank when contained in the effluent water. The pH of the effluent water drops during the process of digestion, so that the water is neutralized with an aqueous solution of caustic soda. The treated water flowing out from the biological treatment tank contains an SS component consisting predominantly of bacterial cells, so that the SS component is removed with an ultrafiltration (UF) device. The ultrafiltration (UF) membrane to be used is one having special spacers adapted to prevent adhesion of or clogging with bacterial cells, such as Preprox UF membrane, product of Kurita Water Industries, Ltd. Alternatively available is a method of conducting the biological treatment and removing the SS component in a single tank, by immersing a microfiltration (MF) membrane in a biological treatment tank wherein an activated carbon layer is fluidized with a supply of oxygen and suck
Inoue Shiro
Koba Kazunori
Kurokawa Masahiro
Momose Shoichi
Armstrong Westerman & Hattori, LLP
Barry Chester T.
Hitachi Zosen Corporation
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