CA2225261C - Treatment method for water containing nitrogen compounds - Google Patents
Treatment method for water containing nitrogen compounds Download PDFInfo
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- CA2225261C CA2225261C CA002225261A CA2225261A CA2225261C CA 2225261 C CA2225261 C CA 2225261C CA 002225261 A CA002225261 A CA 002225261A CA 2225261 A CA2225261 A CA 2225261A CA 2225261 C CA2225261 C CA 2225261C
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- waste water
- electrolysis
- nitrogen compounds
- peroxide
- catalyst
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- 229910017464 nitrogen compound Inorganic materials 0.000 title claims abstract description 63
- 150000002830 nitrogen compounds Chemical class 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims description 51
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title abstract description 85
- 239000002351 wastewater Substances 0.000 claims abstract description 73
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 69
- -1 chlorine ions Chemical class 0.000 claims abstract description 58
- 239000003054 catalyst Substances 0.000 claims abstract description 57
- 239000000460 chlorine Substances 0.000 claims abstract description 42
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 40
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Inorganic materials Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 claims abstract description 35
- 150000004972 metal peroxides Chemical class 0.000 claims abstract description 35
- 238000003860 storage Methods 0.000 claims abstract description 22
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 24
- 239000010457 zeolite Substances 0.000 claims description 24
- 229910021536 Zeolite Inorganic materials 0.000 claims description 22
- 229910001504 inorganic chloride Inorganic materials 0.000 claims description 16
- 229910052799 carbon Inorganic materials 0.000 claims description 15
- UPWOEMHINGJHOB-UHFFFAOYSA-N oxo(oxocobaltiooxy)cobalt Chemical compound O=[Co]O[Co]=O UPWOEMHINGJHOB-UHFFFAOYSA-N 0.000 claims description 14
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 10
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 8
- 229910052759 nickel Inorganic materials 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 6
- 239000010936 titanium Substances 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- 239000011780 sodium chloride Substances 0.000 claims description 5
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims description 4
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- LWBPNIJBHRISSS-UHFFFAOYSA-L beryllium dichloride Chemical compound Cl[Be]Cl LWBPNIJBHRISSS-UHFFFAOYSA-L 0.000 claims description 4
- YADSGOSSYOOKMP-UHFFFAOYSA-N dioxolead Chemical compound O=[Pb]=O YADSGOSSYOOKMP-UHFFFAOYSA-N 0.000 claims description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 4
- 239000012530 fluid Substances 0.000 claims description 3
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 2
- 229910001627 beryllium chloride Inorganic materials 0.000 claims description 2
- 239000001110 calcium chloride Substances 0.000 claims description 2
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- 229910052741 iridium Inorganic materials 0.000 claims description 2
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 2
- 229910001629 magnesium chloride Inorganic materials 0.000 claims description 2
- 239000001103 potassium chloride Substances 0.000 claims description 2
- 235000011164 potassium chloride Nutrition 0.000 claims description 2
- 229910000108 silver(I,III) oxide Inorganic materials 0.000 claims description 2
- 229910000859 α-Fe Inorganic materials 0.000 claims description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims 2
- 239000002198 insoluble material Substances 0.000 claims 1
- 229910052763 palladium Inorganic materials 0.000 claims 1
- 125000001309 chloro group Chemical group Cl* 0.000 abstract description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 43
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 24
- 238000012545 processing Methods 0.000 description 24
- 238000006243 chemical reaction Methods 0.000 description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 20
- 229910052757 nitrogen Inorganic materials 0.000 description 19
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 16
- 229910052760 oxygen Inorganic materials 0.000 description 16
- 239000001301 oxygen Substances 0.000 description 15
- 239000000126 substance Substances 0.000 description 10
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 9
- 239000010941 cobalt Substances 0.000 description 8
- 229910017052 cobalt Inorganic materials 0.000 description 8
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 8
- 239000007800 oxidant agent Substances 0.000 description 8
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 239000007864 aqueous solution Substances 0.000 description 6
- 150000002500 ions Chemical class 0.000 description 6
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- 230000015556 catabolic process Effects 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 5
- 229910001873 dinitrogen Inorganic materials 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- 150000001805 chlorine compounds Chemical class 0.000 description 4
- 229910001429 cobalt ion Inorganic materials 0.000 description 4
- XLJKHNWPARRRJB-UHFFFAOYSA-N cobalt(2+) Chemical compound [Co+2] XLJKHNWPARRRJB-UHFFFAOYSA-N 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- 101150114843 Mgll gene Proteins 0.000 description 3
- 101100009643 Papaver somniferum CODM gene Proteins 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000012670 alkaline solution Substances 0.000 description 3
- 229910021529 ammonia Inorganic materials 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 150000002897 organic nitrogen compounds Chemical class 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- CYSGHNMQYZDMIA-UHFFFAOYSA-N 1,3-Dimethyl-2-imidazolidinon Chemical compound CN1CCN(C)C1=O CYSGHNMQYZDMIA-UHFFFAOYSA-N 0.000 description 2
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 description 2
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 240000001987 Pyrus communis Species 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 2
- 239000004202 carbamide Substances 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 150000002894 organic compounds Chemical class 0.000 description 2
- 239000012286 potassium permanganate Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000003672 processing method Methods 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 230000007420 reactivation Effects 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- 101100060915 Haemophilus influenzae (strain ATCC 51907 / DSM 11121 / KW20 / Rd) comF gene Proteins 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical group [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000005708 Sodium hypochlorite Substances 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical group [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 229910000323 aluminium silicate Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910001919 chlorite Inorganic materials 0.000 description 1
- 229910052619 chlorite group Inorganic materials 0.000 description 1
- 150000001868 cobalt Chemical class 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 239000001023 inorganic pigment Substances 0.000 description 1
- 244000144972 livestock Species 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052680 mordenite Inorganic materials 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 238000006552 photochemical reaction Methods 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 102000004169 proteins and genes Human genes 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 102220047383 rs587777742 Human genes 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 235000010288 sodium nitrite Nutrition 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
- C02F1/4672—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation
- C02F1/4674—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation with halogen or compound of halogens, e.g. chlorine, bromine
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
- C02F1/46109—Electrodes
- C02F2001/46133—Electrodes characterised by the material
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S210/00—Liquid purification or separation
- Y10S210/902—Materials removed
- Y10S210/903—Nitrogenous
Abstract
Waste water containing nitrogen compounds is treated by first breaking the nitrogen compounds down by electrolysis in the presence of chlorine ions. The electrolysis step converts chlorine ions to hypochlorite ions. The partially treated water is returned to a storage container. The hypochlorite ions oxidize the nitrogen compounds and are reconverted to chlorine atoms. The partially treated water then may be returned to the electrolysis container to regenerate hypochlorite ions. In a second step, the partially treated waste water is passed over a metal peroxide catalyst. The metal peroxide catalyst further breaks down the nitrogen compounds, and removes the excess hypochlorite ions.
Description
03-18-1998 10:40 1-613-828-OeCA 02225261 1997-12-18~MS & ASSOO. F.02~24 TR>E;ATMFNT METHOD FOR WATER CONTAINING NITROGEN
COMPOUNDS
BAC.'KGROUND OF THE INVENTION
The present invention relates to a method for processing water which contClins nitrogen compounds. More specifically, the present invention relates to a treatment method for water which contains nitrogen compounds, wherein water is processed at normal temperature and pressure. Nitrogen compounds are removed by oxidative breakdown into nitrogen gas. At the same time, chemical oxygen demand (COD) is also reduced.
I0 Waste sources ofnitrogen compounds include proteins, which are used in livestock feed production industries; nitric acid, which is used in inorganic pigment production; ammonia, nitric acid, sodium nitrate, and sodium nitrite, which are used in surface processing steps in metal products production industries and electronic machinery appliance manufacturing; and the like.
When released into water, nitrogen compuunds are responsible for overnitrification. If these nitrogen compounds are released as nitrogen oxides into the atmosphere, they are dangerous to health as primary pollutants.
Furthermore, nitrogen oxides participate in a photochemical reaction and become one of the components of smog, a secondary combined pollution phenomenon. As a result, water which contains nitrogen compounds must be processed for denitrification. The dispersal of unprocessed nitrogen comF~ounds into the atmosphere during these processing steps must be prevented.
Waste water which contains nitrogen compounds can also contain 2$ organic compounds other than nitrogen compounds. Furthermore, the nitrogen compound itself can be organic or can be oxygen consuming. As a result, the ~rw~aurHUrnwo~r~mawm~W 7 03-18-1998 10:40 1-613-828-00CA 02225261 1997-12-18~MS & ASSOC. P.03/24 chemical oxygen demand (COD) of water containing nitrogen compounds can be great. In these cases as nitrogen compounds are broken down, there is also a need to reduce the COD.
Methods such as the activated carbon adsorption method and biological processing methods are well-known as conventional processing methods for nitrogen compounds in waste water. however, when using the activated carbon adsorption method, it is necessary to reactivate the activated carbon when adsorption equilibrium is reached. With reactivation, a highly concentrated nitrogen compound-containing reactivation waste solution is generated. The need for further processing of this waste is an additional probl<:m.
When water containing nitrogen is biologically processed, the breakdown time required is long because the reaction time is relatively slow.
A large-volume biological reaction container becomes necessary, and there is an additional problem of a large amomt of excess sludge being generated.
1n ,Tapanese Laid Open Patent Number 7-100466, a method is proposed ._ wherein waste water containing ammonia is processed by electrolysis in the presence of chloride ions, at a pH between 8 and 12. The ammonium ion and COD components in the water are efficiently degraded and removed.
Tiowever, this method generates hypochlorite ions as a by-product, which remain in the processed water and must be removed by further processing.
'rhe present inventors have proposed a method for treating waste water which contains an alkanolamine. In this method, an oxidant is added to waste water which contains an alkanolamine. The alkanolamine is oxidized and broken down in the presence of a metal catalyst and heat. By this method, monoethanolamine and the like can be e~ciently oxidized and broken down.
w~WiPI.tHOIUChwTO~T.ltutff:NW af).11 03-18-1998 10:41 1-613-828-eeCA 02225261 1997-12-18~MS & ASSOC. P.04/24 However, it is desirable to improve this method by eliminating the need for added oxidants or the need to heat to temperatures greater than 100 °C.
OBJECTS AND SUMMARY OF THE INVENTION
The object ofthe present invention is to provide a method for treating water containing nitrogen compounds which does not require added oxidants, and which can process water which contain nitrogen compounds at normal temperatures and pressure.
A further object is to provide a method for treating water which contains nitrogen compounds, wherein nitrogen compounds in the water are oxidized and broken down to nitrogen gas and removed, and the chemical oxygen demand (COD)is simultaneously reduced.
As a result of intensive research in order to achieve the above objects, it was found that nitrogen compounds are efficiently broken down and removed if; after electrolysis of the water which contains nitrogen compounds - 1 S and inorganic chloride compounds, the waste water is brought into contact with a metal peroxide catalyst. By the method of the present invention, no residual chlorine is left in the processed water.
Briefly stated, waste water containing nitrogen compounds is treated by first breaking the nitrogen compounds down by electrolysis in the presence of chlorine ions. The electrolysis step converts chlorine ions to hypochioritc ions. The partially treated water is returned to a storage container. The hypochlorite ions oxidize the nitrogen compounds and are reconverted to chlorine atoms. The partially treated water then may be returned to the electrolysis container to regenerate hypochlorite ions. In a second step, the partially treated waste water is passed over a metal peroxide w,ueannwcxwrom.mnwmu. n catalyst. The metal peroxide catalyst further breaks down the nitrogen compounds, and removes the excess hypochlorite ions.
According to one aspect of the present invention, a method for treating waste water containing nitrogen compounds and chlorine ions comprises the steps of supplying said waste water to a storage container; supplying a portion of said waste water from the storage container to an electrolysis chamber and performing electrolysis oz~ said waste water, such that said chlorine ions are oxidized to hypochlorite ions, and said nitrogen compounds are oxidized bysaidhypochlorite ions and therebybroken down; and returning waste water from the electrolysis chamber to the storage chamber; and contacting a portion of said waste water from the storage container with a metal peroxide catalyst after said step of performing electrolysis, such that hypochlorite ions are removed from said waste water.
According to another aspect of the present invention, a method for treating waste water containing nitrogen compounds comprising the steps of circulating said waste water between a storage container and an electrolysis container, adding a substoichiometric quantity of inorganic chlorides, performing electrolysis in said electrolysis chamber, such that said chlorine ions are oxidized to hypoehlorite ions, and sand nitrogen compounds are oxidized by said hypochlorite ions and thereby brolten down, and contacting said waste water with a metal peroxide catalyst after said step of performing electrolysis, such that said Iaypochlorite ions formed during said electrnlysis are removed from said waste water, said metal peroxide catalyst containing one of cobalt peroxide and nickel peroxide, said metal peroxide catalyst f~uther containing at least one member from the group consisting of aeolite, titanic, y--ahnnina, and a-alumhaa, said one of cobalt peroacide auxd nickel pero~cide being present in said metal peroxide catalyst at a concentration ofbetween about 0.01% by weight anal 10% byweight, said step of contacting occurring at an SV betweezt about 0.1 l~' and about 60 h~l, a temperature -03-18-1998 10:42 1-613-828-06CA 02225261 1997-12-184MS & ASSOC. P.06/24 between about 2f1 °C and about 80 °C, and a pressure substantially equal to atmospheric pressure.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in 5 conjunction with the accompanying drawings, in which like reference numerals designate the same elements.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a flow diagram illustrating the steps of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the method of the present invention, after waste water which contains nitrogen compounds and inorganic chlorides is first treated by electrolysis, the waste water is brought into contact with a metal oxide .-- catal yst.
Examples of nitrogen compounds which can be processed by the method of the present invention include itlorganic nitrogen compounds, such as ammonia, hydrazine, I,3-dimethyl-2-imidawlidinone, and the like; and organic nitrogen compounds, such as urea, ethanolarnine, aniline, and the like.
Waste water which contains such nitrogen compounds are typically discharged from, for example, dye factories, fertilizer factories, semiconductor factories, electric power plants, and chemical or pharmaceutical manufacturing factories.
In the Present invention, it is preferable that the electrodes used in electrolysis be of an electrode material which does not dissolve into water.
Examples include platinum-plated titanium electrodes, titanium electrodes WvN111l~lUCW W1DA1AW5141WIH117 03-18-1998 10:43 1-613-828-0~A 02225261 1997-IZ-IBAMS & ASSOC. P.07/24 which are coated with iridium or palladitun, lead dioxide electrodes, and ferrite electrodes.
In the present invention, inorganic chlorides which ure dissolved in the waste water generate chlorine ions. As a result of the electrolysis reaction, chlorine ions are oxidized to hypochlorite ions, as indicated in the following equation:
C1' -~ 20I~' ~ CIO' + H,O + 2e' Hypochlorite ions react with a wide variety of nitrogen compounds. A number of these reactions are set firth below.
1p 2NH, + 3C10- ~ N~ + 3H~0 + 3C1' NCH, + 2C10' ~ N~ + 2H~0 + 2C1 CO(NHz), + 3C10' - N, ~- 2H,0 + CO~ -~ 3C1 2N):-i.~CH,CHZOH + 13C10- ~ N~ + 7Hi0 + 4C02 i I 3C1' 2C6HSNH~ + 31 C10' °- NZ + 71-1,0 + 12COz + 31 Cl' If the nitrogen compound is an organic compound, nitrogen is converted into harmless nitrogen gas, and carbon is converted to carbon dioxide gas. As a result, the total organic carbon amount and the chemical oxygen demand of the processed water is reduced.
In the method of the present invention, chlorine ions, which are generated by inorganic chlorides dissolving in water, are oxidized to hypochlorite ions through electrolysis. Hypochlorite ions oxidize nitrogen compounds, and chlorine ions are regenerated. These chlorine ions again are oxidized to hypochlorite ions through electrolysis. A single chlorine ion alternates between chlorine ion and hypochlorite ion, and thus contributes to v:vU1F11.CN11fxW1U~TW nlwln117 03-18-1998 10:43 1-613-828-0~A 02225261 1997-12-18AMS & ASSOC. P.08/24 several cycles of the reaction. As a result, the amount of inorganic chloride required for treatment of the nitrogen compounds is less than the stoichiometric values indicated by the above equations.
If the waste water contains nitrogen compounds and sufficient levels of waste inorganic chloride compounds, it is possible to process by electrolysis directly. However, if the waste water does not already contain an adequate amount of inorganic chlorides, inorganic chlorides must be added before conducting electrolysis. There are no particular limitations to the inorganic chloride which is to be added so long as the inorganic chloride is water soluble. Examples include lithium chloride, sodium chloride, potassium chloride, beryllium chloride, magnesium chloride, and calcium chloride.
Electrolysis is conducted while circulating the water which contains nitrogen compounds and inorganic chlorides between a storage container and an electrolysis container. A portion of the water in the storage container is removed and is passed through a column filled with a metal peroxide catalyst to obtain the final form of the processed water. In this processing, an optimal amount of inorganic chloride can be maintained by controlling the speed with which the water circulates to the electrolysis reaction container, the speed of the water passage through the catalyst column, and the like.
In the method of the present invention, a portion of the nitrogen compounds is broken down by hypochlorite ions generated by electrolysis before contacting the metal peroxide catalyst. Thereafter, water containing the remaining nitrogen compounds and hypochlorite ions generated by electrolysis is brought into contact with the catalyst. Not only arc the remaining nitrogen compounds broken down at this step, but excess hypochlorite ions arc removed as well. When the water which contains nitrogen compounds and hypochlorite ions comes into contact with the metal peroxide catalyst, the roVIMIS~CMlIC1~W10ATAW 11flW IH>I1 03-18-1998 10:44 1-613-828-0~A 02225261 1997-12-18AMS & ASSOC. P.09/24 breakdown reactions of the nitrogen compounds proceed rapidly at normal temperature and pressure.
Examples of metal peroxide catalysts useful in the present invention include cobalt peroxide, nickel peroxide, copper peroxide, and silver peroxide.
Among these, cobalt peroxide and nickel peroxide are preferred. It is preferable that these metal peroxide catalysts be carried on zeolite, titania, y-alumina, a-alumina or the like. The preparation method for these are described below, using the example of zeolite as the carrier and cobalt peroxide as the carried catalyst.
Zeolite is an aluminosilicate which has uniform fine pores of molecular size. The structure of zeolite is a series of tetrahedrons of silicon atoms, with a portion substituted by aluminum atoms, which form a three dimensional mesh structure via oxygen atoms. Characteristic hollows and channels are formed. 'the size of these hollows or channels are determined by the size of the oxygen ring. Zeolite typically hay an ability to replace cations. In the present invention, natural zeolites, such a~ clinoptiololite or mordenite, or -- synthetic zeolites, such as zeolite A, zeolite X, or zeolite Y can be used with good results. These zeolites can be used singly, or two or more types can be mixed and used.
The processing of the zeolite carrier is conducted by bringing it into contact with aqueous solutions of sulfates, nitrates, or chlorides of cobalt, or mixture solutions of these. One method of contact involves soaking particles of zeolite in the solution. Alternatively, zeolite particles can be packed into a column and the aqueous solution can be passed through once or in a circulating manner. The concentration of cobalt salt and contact times are determined so that the necessary amount of cobalt is retained by the zeolite.
The amount of cobalt which is carried is preferably between about 0.01 % and 03-I8-1998 10:45 1-613-828-0~A 02225261 1997-12-18AMS & ASSOC. P.10/24 about 10% by weight. The thus-processed zeolite is then rinsed with water as needed after being separated from the aqueous solution, A rinsing step is desirable to remove all cobalt ions not present in the active sites of zeolite.
Generally, it is preferable to rinse until the color of cobalt ions disappear from the rinse water. By this procedure, it is possible to obtain an effective zeolite carrier hearing a small amount of cobalt.
Next, the zeolite carrier obtained as above is brought into contact with an alkaline aqueous solution which contains chlorine agents. As a method of contact, zeolite can be soaked in an alkaline solution which contains chlorine agents. Alternatively, zeolite can be packed into a colun2n, and the alkaline solution containing chlorine agents can be passed through once or in a circulating manner. In this manner, the cobalt peroxide catalyst used in the present invention is obtained. At the time of contact, a small amount of cobalt ions may separate from zeolite and generate fine precipitate in the peroxide, but the precipitate can be removed through final rinsing. Examples of chlorine agents include chemicals which generate free chlorine such as sodium hypochlorite, chlorine gas, chlorine generated by electrolysis, and the like.
Examples of the alkaline aqueous solution which is used in conjunction with the chlorine agent include aqueous solutions of sodium hydroxide, potassium hydroxide, and the like.
As an alternative method of formation of the cobalt peroxide catalyst, the zeolite may be heated after the rinsing step, causing the cobalt ion to change to cobalt oxide. Next, the zeolite carrier is brought into contact with an alkaline solution, and the same catalyst is obtained.
By the present invention, a portion of nitrogen compounds are oxidized and broken down by hypochlorite ions which are generated by electrolysis.
Furthermore, the water which contains remaining nitrogen compounds and ~,usa rwmurvro~r~mnwmfm 03-18-1998 10:45 1-613-B28-OLCA. X2225261 1997-12-18AMS & ASSOC. P.11/24 hypoChlorite ions i~ brought into contact writh a metal peroxide catalyst which is prepared as described above. This results in total breakdown of nitrogen enmpounds. The oxidation reaction regenerates chlorine ions, which are reoxidized by electrolysis to hypochlorite ions.
5 The catalyst, packed as particles of diameter about 0.3 to about l0 nun into a column, can be used as a fixed bed or a fluid bed. If particle diameter is less than 0.3 mm, the loss of pressure becomes too great in a fixed bed.
Similarly, if the particle diameter is less than 0.3 mm, there is a danger that the carrier will be destroyed and become mixed in with the processed water in a 10 fluid bed. The direction of water flow may be either upward or downward.
However, since nitrogen gas is generated in the reactions of the present invention, upward flow is preferred.
In the method of the present invention, the rate of water flow can be chosen so that it is appropriate for the contact method or the amount of metal peroxide held by the carrier. Typically, it is preferable to have an SV of between about 0.1 h-' and about 60 h-'. SV refers to space velocity, and is the ratio of the flow rate of the inflow to the volume of the treating device. For example, if the inflow has a flow rate of 2 liter/hr, and the volume of the treating device is one liter, the SV is 2 h''. It is even more prCfcrable to have an SV of between 0.5 h'' and 10 h-'. Even more preferable is an SV of between 1 by and about 10 h-'. The contact between the waste water containing nitrogen compounds and hypochlorite ions and the metal peroxide catalyst is typically conducted at a normal temperature between about 20 and °C. If the reaction is conducted at a temperature between about 40 and 25 °G, the reaction rate becomes higher, and the contact time can be shortened.
('Tenerally, if the nitrogen compound concentration in the water is high, it is preferable to have an extended contact time. Furthermore, if the contact time is too short, there is a danger that hypochlarite ions will remain in the processed water.
13y the present invention, oxidative breakdown of nitrogen compounds in water which contains nitrogen compounds is possible without the need for added oxidants, such as chlorlrae oxidants or hydrogen peroxide. Furthermore, the reaction can be performed at standard temperature and pressure. Because the reaction proceeds rapidly under normal temperature and pressure, the reaction device can be made more compact, and it is possible to obtain a processed water of a stable quality.
Referring to Figure 1, there is shown a process flow chart of one embodiment of the present invention. Waste water which contains nitrogen compounds is brought to a storage cantaiz~er 1 _ jnorganic chlorides aro added as needed with mining. Waste water is sent to an electrolysis reaction container 3 by a pump 2. After electrolysis, the wa fire water is circulated back to storage container 1. The waste water, which now contains nitrogezz compounds and hypochlorite ions generated by electrolysis, is then removed from storage container 1 by pump 4 and is sent to reaction column 5 which is packed with a metal peroxide catalyst.
Processed water is obtained by treating the waste water with the metal peroxide catalyst at normal temperature and pressure.
By the present invention, it is possible to remove nitragez~ compounds at a high rate with a small device, without adding oxidants such as chlorine oxidants or hydrogen peroxide.
In particular, with the present invention, no hypochlorite ions remain in the processed water because the metal peroxide catalyst is able to break dawn hypochlorite fans, Therefore, there is rio need for a separate residual chlorine removal process, as in the prior art. Furthermore, with the present invention, the hypachlorite iox~ which are 03-18-1998 10:47 1-613-828-0~A 02225261 1997-12-18AMS & ASSOC. P.13/24 12 M19S3-i2 generated are mire likely to react with nitrogen compounds than with metal peroxide catalysts, and so the ions will not be unnecessarily broken down.
With the present invention, inorganic nitrogen compounds or organic nitrogen compounds are hr~ken down to harmless nitrogen gas, carbon dioxide S gas, water, and the like. 1t is possible to reduce total nitrogen concentration and the chemical oxygen demand of the processed water. The method of the present invention can be applied to waste water which contains one of either inorganic nitrogen compounds or organic nitrogen compounds, or it can be applied to waste water which contains both.
Embodiment 1 Treatment of waste water which contained 1,000 mglliter of monoethanolamine, 375 mg/liter of ammonia nitrogen, and 8,000 mg/liter of sodium chloride was conducted. The initial water quality of this waste water was as follows: total nitrogen (T-N) = 60S mg/liter, ammonia nitrogen (NH4'-N) --- 37S mg/liter, total organic carbon (TOC) ~ 393 mg/liter, chemical oxygen demand by potassium permanganate at 100 °C (CODM") ----- 839 mg/liter, residual chlorine = 0 mg/liter, and pH -- 9.3.
1,250 ml of this waste water was placed in an electrolysis container.
The electrolysis container had S.0 cm x S.0 cm platinum-plated titanium plate electrodes. The waste water was processed by passage through a circulating system. The distance between the electrodes was 1.0 em. The between-electrode volume of the reaction container between the electrodes was 25.0 cm3. Current was 2.SA, and current density was l0A/dmz. The circulating solution passage rate was 1 10 ml/min.
W 71A1H:fKIVCIpW/pATA W I %7W I%11 !
03-18-1998 10:47 1-613-828-0~A 02225261 1997-12-l8AMS & ASSOC. P.14/24 The circulating reaction processing was conducted for six hour. The water quality after six hours was the following: total nitrogen ('f-N) -- 68 mg/liter, ammonia nitrogen (NhI,+ - N) - l mglliter, total organic carbon (TOC) = 72 mg/liter, oxygen demand (COD ,",~) --- 124 mg/liter, residual chlorine = 751 mg/liter, and pH 6.8.
Referring to Table l, the water quality analysis after each hour of circulating reaction time is shown.
Table 1 ProcessingStored Outflow time circulating from water catalyst (Comparison reaction 1) column (Embodiment 1) (hr) T-N NH,'-NTOC'r_n~~"ResidualpH T-N NH TO(:L()I)M"Residualrll m~ mgll mgJlmFJI Cl' mFll'-N mEllmFll CI-mgll mpJl 0 AUS :175 393 li3S)U 9.3 .-- -. -_ _-_ I SU'' :.J2 359 767 16 ti.tS- - - - - -p 4'2(i2'?7 340 635 l9 ?3..i- - -3 297 l 31 591 204 5.2 - - - - _ _ ~ 1b4 41 1y8 371 381 2.3 -9G 17 118 2? G72 3.9 l 6 68 1 72 124 751 G.8 - - - - -7 61 ND 53 92 8G3 G.9 48 ND 4.8 ?.G ND 7.4 8 57 ND 12 19 949 7.2 46 ND '2.7I.7 ND 7.b 9 57 NTJ 9.U 1'? y5~1 7.3 45 NU 2.1 1.6 NU 7.6 IU z7 ND 3.4 3.G 9G3 7.3 45 ND 1.5 I.G ND 7.G
N.D. = not detected After six hours, the electrolysis reaction was stopped. The solution in the electrolysis storage container was processed at a Speed of 15~ ml/hour through a reaction column packed with cobalt peroxide-carrying catalyst. 'The WWfa7r71IH.1(IW1DATAW11lIWIHYI3 03-IS-1998 10:48 1-613-828-OICA 02225261 1997-12-18AMS & ASSOC. P.15/24 catalyst was a cobalt peroxide at 2.5% by weight of cobalt in a spherical titania carrier having a diameter of 1.5 mm. The packing volume of the catalyst was S~ m1. The reaction column was processed at room temperature. Solution passage was continued for four hours. After each hour, the entire amount of processed water was collected, and tile water quality was analyzed. The processing time was added to the electrolysis processing time (six hours).
Referring to Tahle 1, there is shown the water quality between seven and ten hours of processing.
Between seven and ten hours of processing, total nitrogen (T-N) was at or below 50 mg/liter; ammonia nitrogen (NH4' - N} was not detected; total organic carbon (TOC) was at or below 5.0 mg/liter; oxygen demand (CORM") was Flt or below 3.0 mg/liter; and residual chlorine was not detected.
Comparison 1 Under the same conditions as Embodiment 1, electrolysis was conducted for ten hours continuously in a separate circulating processing system. After every hour, the water quality of the water in the electrolysis storage container was analyzed. The results are Shown in Table 1.
Up to six hours, the results of water quality analysis were the same as Embodiment 1. After eight hours, there were no changes in total nitrogen (T-N) (57 mg/litcr). Aftcr seven hours, ammonia nitrogen (Nl~~+ - N) was not detected. Total organic carbon (TOC) was below 5 mg/liter, and ten hours of electrolysis were required for the water quality to have an oxygen demand (CC>D",~ of below 5 mg/liter. From the seventh hour on there was a trend of increasing residual chlorine.
wwmraawmwrw~~wmW~~m 03-IS-1998 10:48 1-613-828-0~A.02225261 1997-IZ-IHAMS & ASSOC. P.16/24 It can be seen that treatment of waste water by contact with cobalt peroxide catalyst produces a processed water of superior quality to that obtained by electrolysis alone over many hours.
Embodiment 2 Processing of waste water which contained 1,000 mg/liter of 1,3-dimethyl-2-imidazolidinone was conducted. The initial water quality of this waste water was the following: total nitrogen (T-N) = 246 mg/liter, total organic carbon (TOC) = 526 mglliter, chemical oxygen demand by potassium permanganate at 100 °C (COD,H,~ = 950 mg/liter, residual chlorine = 0 mg/liter, sodium chloride = 10,000 mg/liter, and pH 9.7.
5(10 ml of the waste water was placed in the electrolysis container.
Under the same conditions as Embodiment l, electrolysis was conducted for three hours. After each hour, the water quality of the water in the electrolysis storage container was measured. Referring to Table 2, the results are shown.
WvUlhR1'CIRIGX~W/bw1'AWIHN.IW f11:
03-18-1998 10:49 1-613-828-0CA 02225261 1997-12-18~AMS & ASSOC. P.17/24 1~ M1953-12 Table 2 ProcessingStored Outflow time circulating from water catalyst (Comparison reaction 2) column (lmboditncnt 2) r-N TOC COD ResidunlpFi T-N TOC'COD ResidualpH
mg/1mg/1 mgJf"C'I rng/Imgllmglr''(.'I
mg/I
mg/l U 246 526 950 0 9.7 - - -1 183 400 718 108 9.2 _ _ _ _ 2 7 16S 308 540 7.9 - - - - -3 53.370 130 864 8.3 - - - -4 43.339 72 1150 8.5 28.1 5.7 9.4 N.D. 8.7 40.023 49 1490 8.9 26.3 4,2 6.7 N.D. 9.!
L f ~ .__f T1 J_~__ -av.u. uW W .WV.LV.U
Electrolysis was halted after three hours. As in Emhodiment 1, water from the electrolysis container was then passed at a rate of 150 ml/hour through a reaction column packed with cobalt peroxide catalyst. Solution passage was continued for two hours. After each hour, the entire amount of water was _ collected, and water quality analysis was conducted. 'I~he processing time was added to the electrolysis time (three hours). Referring to Table 2, the water quality for hours 4 and 5 are shown.
The water quality after three hours of electrolysis processing was as followsv total nitrogen (T-N) - 53.3 mg/liter, total organic carbon (TOC) = 70 mg/liter, oxygen demand (CODM~) = 130 mglliter, residual chlorine = 8fi4 mg/liter. The water quality after passage through the cobalt peroxide catalyst reaction column was as follows: total nitrogen (T-N) less than 3U mg/liter, total organic carbon (TOC) less than 10 mg/liter, oxygen demand (CODM,~ Less than mg/Iiter, and residual chlorine was not detected. Ammonia nitrogen (NH4' - N) was not measured.
r-w~au~wro~uwmmnm:
03-18-1998 10:49 1-613-828-0CA 02225261 1997-12-18~AMS & ASSOC. F~18~24 Comparison 2 Electrolysis with a separate circulating processing system was conducted continuously for five hours under the same conditions as embodiment 2. The water quality analysis results up to the third hour were the same as in embodiment 2. The water quality for the fourth and fifth hours is shown in Table 2.
Compared with passage through the catalyst reaction column of the present invention, total nitrogen (T-N) total organic carbon (TOC), and oxygen demand (COD,r,") values all were higher. In particular, residual chlorine at five hours was very high (1,490 mg/liter). The residual chlorine increased as the 1,3-dimethyl-2-imidazolidinone was broken down.
Embodiment 3 Processing of waste water containing 5,000 mg/liter of urea and 6,000 mglliter of sodium chloride was conducted. 'rhe water quality of the waste water was as follows: total nitrogen (T-N) = 2,330 mg/liter, ammonia nitrogen (NHQ' - I~ = 5.5 mg/1 iter, total organic carbon (TOC) = 1,000 mg/liter, residual chlorine = 0 mg/liter, and pH 1 I .9.
1,000 m1 of this waste water was placed in an electrolysis container.
Electrolysis was conducted for four hours under the same conditions as Embodiment 1. After four hours, electrolysis was terminated. As in Embodiment 1, the water in the electrolysis storage container was passaged at a rate of 150 mUhour through a reaction column packed with cobalt peroxide holding catalyst. Passage was continued for four hours. After each hour, the entire volume of the processing water was collected. and water quality was 'A"~tL1C47K71tId1vIDATAW I%T11I%111 03-18-1998 10:50 1-613-828-0CA 02225261 1997-12-18~AMS & ASSOC. F.19/24 analyzed. Processing time was added to the electrolysis time (four hours).
Referring to Table 3, the water quality between five and eight hours of processing are shown.
Table 3 ProcessingStored Outflow time circulating from water catalyst h (C'omparison reaction 3) column (Embodiment 3) ( r) T-N NH,'-NTOC ResidualpH r-trnrl,~.Nroc ResidualpH
mgll mg/I mgll CI- mgJlmg/l mgllCI' mg/I moll 0 2330 5.5 1000 0 11.9 - - - -1 _ ._ _ - 6.4 - _ _ _ _ 2 1260 26.8 554 668 6.3 ' - - - -3 _ _ _ 6.6 - _ _ -4 460 9.0 163 1790 6.4 - - - - -_.. _ _ 1~3 12.0 23 I8 8.7 6 137 N.D. I.5 2520 9.1 107 N.D. 1.1 7.2 9.3 7 _ _ _ - 101 N.D. 0.9 N.D. 9.5 8 143 N.1).1.4 2590 9.3 98 N.D. 0.5 N.D. y.6 m.ir. - mu uCrcc:lecr The water quality after four hours of electrolysis was as follows: total nitrogen (T-N) - 460 mg/liter, total organic carbon {TOC} = 163 mg/liter, residual chlorine - 1,790 mg/litcr. The water quality of the water samples passaged through the cobalt pero~cide holding catalyst between eve and eight hours were as follows: total nitrogen ('r-N) = between 123-98 mg/liter, and total organic carbon (TOC) = between 23-0.5 mg/liter. Residual chlorine after five hours of processing was 18 mg/liter, and after seven hours of processing, residual chlorine was not detectable.
W tILIpIfK11UC1ItWlpATAW tVf7W IH) 17 03-18-1998 10:51 1-613-828-eCA 02225261 1997-IZ-IB~AMS & ASSOC. P.20/24 Comparison 3 Electrolysis was conducted continuously for eight hours by a separate circulating processing system under the same conditions as in Embodiment 3.
Referring to Table 3, the water quality analysis results for hours 6 and 8 are shown. Total nitrogen (T-N) values were much higher, compared with passage through the catalyst reaction column of the present invention. Furthermore, residual chlorine values were very high (2,520-2,590 mg/liter).
The method of the present invention is effective against various nitrogen compounds. The present invention does not require additional oxidants, and can easily process waste water containing nitrogen compounds at normal temperahlre and pressure. With the present invention, it is possible to obtain high quality processed water which is low in total nitrogen concentration, total organic carbon concentration, and chemical oxygen demand. Furthermore, hyp~chlorite ions are broken down by metal peroxide catalysts and do not remain in the processed water. The water quality of the processed water is thereby further improved. Furthermore, the setup for embodiments of the present invention is compact. Because the necessary space for setup is reduced, the maintenance is easy.
Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.
wwaatS~L1111[~(111~pn1.tW H)w ~f f r ~7
COMPOUNDS
BAC.'KGROUND OF THE INVENTION
The present invention relates to a method for processing water which contClins nitrogen compounds. More specifically, the present invention relates to a treatment method for water which contains nitrogen compounds, wherein water is processed at normal temperature and pressure. Nitrogen compounds are removed by oxidative breakdown into nitrogen gas. At the same time, chemical oxygen demand (COD) is also reduced.
I0 Waste sources ofnitrogen compounds include proteins, which are used in livestock feed production industries; nitric acid, which is used in inorganic pigment production; ammonia, nitric acid, sodium nitrate, and sodium nitrite, which are used in surface processing steps in metal products production industries and electronic machinery appliance manufacturing; and the like.
When released into water, nitrogen compuunds are responsible for overnitrification. If these nitrogen compounds are released as nitrogen oxides into the atmosphere, they are dangerous to health as primary pollutants.
Furthermore, nitrogen oxides participate in a photochemical reaction and become one of the components of smog, a secondary combined pollution phenomenon. As a result, water which contains nitrogen compounds must be processed for denitrification. The dispersal of unprocessed nitrogen comF~ounds into the atmosphere during these processing steps must be prevented.
Waste water which contains nitrogen compounds can also contain 2$ organic compounds other than nitrogen compounds. Furthermore, the nitrogen compound itself can be organic or can be oxygen consuming. As a result, the ~rw~aurHUrnwo~r~mawm~W 7 03-18-1998 10:40 1-613-828-00CA 02225261 1997-12-18~MS & ASSOC. P.03/24 chemical oxygen demand (COD) of water containing nitrogen compounds can be great. In these cases as nitrogen compounds are broken down, there is also a need to reduce the COD.
Methods such as the activated carbon adsorption method and biological processing methods are well-known as conventional processing methods for nitrogen compounds in waste water. however, when using the activated carbon adsorption method, it is necessary to reactivate the activated carbon when adsorption equilibrium is reached. With reactivation, a highly concentrated nitrogen compound-containing reactivation waste solution is generated. The need for further processing of this waste is an additional probl<:m.
When water containing nitrogen is biologically processed, the breakdown time required is long because the reaction time is relatively slow.
A large-volume biological reaction container becomes necessary, and there is an additional problem of a large amomt of excess sludge being generated.
1n ,Tapanese Laid Open Patent Number 7-100466, a method is proposed ._ wherein waste water containing ammonia is processed by electrolysis in the presence of chloride ions, at a pH between 8 and 12. The ammonium ion and COD components in the water are efficiently degraded and removed.
Tiowever, this method generates hypochlorite ions as a by-product, which remain in the processed water and must be removed by further processing.
'rhe present inventors have proposed a method for treating waste water which contains an alkanolamine. In this method, an oxidant is added to waste water which contains an alkanolamine. The alkanolamine is oxidized and broken down in the presence of a metal catalyst and heat. By this method, monoethanolamine and the like can be e~ciently oxidized and broken down.
w~WiPI.tHOIUChwTO~T.ltutff:NW af).11 03-18-1998 10:41 1-613-828-eeCA 02225261 1997-12-18~MS & ASSOC. P.04/24 However, it is desirable to improve this method by eliminating the need for added oxidants or the need to heat to temperatures greater than 100 °C.
OBJECTS AND SUMMARY OF THE INVENTION
The object ofthe present invention is to provide a method for treating water containing nitrogen compounds which does not require added oxidants, and which can process water which contain nitrogen compounds at normal temperatures and pressure.
A further object is to provide a method for treating water which contains nitrogen compounds, wherein nitrogen compounds in the water are oxidized and broken down to nitrogen gas and removed, and the chemical oxygen demand (COD)is simultaneously reduced.
As a result of intensive research in order to achieve the above objects, it was found that nitrogen compounds are efficiently broken down and removed if; after electrolysis of the water which contains nitrogen compounds - 1 S and inorganic chloride compounds, the waste water is brought into contact with a metal peroxide catalyst. By the method of the present invention, no residual chlorine is left in the processed water.
Briefly stated, waste water containing nitrogen compounds is treated by first breaking the nitrogen compounds down by electrolysis in the presence of chlorine ions. The electrolysis step converts chlorine ions to hypochioritc ions. The partially treated water is returned to a storage container. The hypochlorite ions oxidize the nitrogen compounds and are reconverted to chlorine atoms. The partially treated water then may be returned to the electrolysis container to regenerate hypochlorite ions. In a second step, the partially treated waste water is passed over a metal peroxide w,ueannwcxwrom.mnwmu. n catalyst. The metal peroxide catalyst further breaks down the nitrogen compounds, and removes the excess hypochlorite ions.
According to one aspect of the present invention, a method for treating waste water containing nitrogen compounds and chlorine ions comprises the steps of supplying said waste water to a storage container; supplying a portion of said waste water from the storage container to an electrolysis chamber and performing electrolysis oz~ said waste water, such that said chlorine ions are oxidized to hypochlorite ions, and said nitrogen compounds are oxidized bysaidhypochlorite ions and therebybroken down; and returning waste water from the electrolysis chamber to the storage chamber; and contacting a portion of said waste water from the storage container with a metal peroxide catalyst after said step of performing electrolysis, such that hypochlorite ions are removed from said waste water.
According to another aspect of the present invention, a method for treating waste water containing nitrogen compounds comprising the steps of circulating said waste water between a storage container and an electrolysis container, adding a substoichiometric quantity of inorganic chlorides, performing electrolysis in said electrolysis chamber, such that said chlorine ions are oxidized to hypoehlorite ions, and sand nitrogen compounds are oxidized by said hypochlorite ions and thereby brolten down, and contacting said waste water with a metal peroxide catalyst after said step of performing electrolysis, such that said Iaypochlorite ions formed during said electrnlysis are removed from said waste water, said metal peroxide catalyst containing one of cobalt peroxide and nickel peroxide, said metal peroxide catalyst f~uther containing at least one member from the group consisting of aeolite, titanic, y--ahnnina, and a-alumhaa, said one of cobalt peroacide auxd nickel pero~cide being present in said metal peroxide catalyst at a concentration ofbetween about 0.01% by weight anal 10% byweight, said step of contacting occurring at an SV betweezt about 0.1 l~' and about 60 h~l, a temperature -03-18-1998 10:42 1-613-828-06CA 02225261 1997-12-184MS & ASSOC. P.06/24 between about 2f1 °C and about 80 °C, and a pressure substantially equal to atmospheric pressure.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in 5 conjunction with the accompanying drawings, in which like reference numerals designate the same elements.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a flow diagram illustrating the steps of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the method of the present invention, after waste water which contains nitrogen compounds and inorganic chlorides is first treated by electrolysis, the waste water is brought into contact with a metal oxide .-- catal yst.
Examples of nitrogen compounds which can be processed by the method of the present invention include itlorganic nitrogen compounds, such as ammonia, hydrazine, I,3-dimethyl-2-imidawlidinone, and the like; and organic nitrogen compounds, such as urea, ethanolarnine, aniline, and the like.
Waste water which contains such nitrogen compounds are typically discharged from, for example, dye factories, fertilizer factories, semiconductor factories, electric power plants, and chemical or pharmaceutical manufacturing factories.
In the Present invention, it is preferable that the electrodes used in electrolysis be of an electrode material which does not dissolve into water.
Examples include platinum-plated titanium electrodes, titanium electrodes WvN111l~lUCW W1DA1AW5141WIH117 03-18-1998 10:43 1-613-828-0~A 02225261 1997-IZ-IBAMS & ASSOC. P.07/24 which are coated with iridium or palladitun, lead dioxide electrodes, and ferrite electrodes.
In the present invention, inorganic chlorides which ure dissolved in the waste water generate chlorine ions. As a result of the electrolysis reaction, chlorine ions are oxidized to hypochlorite ions, as indicated in the following equation:
C1' -~ 20I~' ~ CIO' + H,O + 2e' Hypochlorite ions react with a wide variety of nitrogen compounds. A number of these reactions are set firth below.
1p 2NH, + 3C10- ~ N~ + 3H~0 + 3C1' NCH, + 2C10' ~ N~ + 2H~0 + 2C1 CO(NHz), + 3C10' - N, ~- 2H,0 + CO~ -~ 3C1 2N):-i.~CH,CHZOH + 13C10- ~ N~ + 7Hi0 + 4C02 i I 3C1' 2C6HSNH~ + 31 C10' °- NZ + 71-1,0 + 12COz + 31 Cl' If the nitrogen compound is an organic compound, nitrogen is converted into harmless nitrogen gas, and carbon is converted to carbon dioxide gas. As a result, the total organic carbon amount and the chemical oxygen demand of the processed water is reduced.
In the method of the present invention, chlorine ions, which are generated by inorganic chlorides dissolving in water, are oxidized to hypochlorite ions through electrolysis. Hypochlorite ions oxidize nitrogen compounds, and chlorine ions are regenerated. These chlorine ions again are oxidized to hypochlorite ions through electrolysis. A single chlorine ion alternates between chlorine ion and hypochlorite ion, and thus contributes to v:vU1F11.CN11fxW1U~TW nlwln117 03-18-1998 10:43 1-613-828-0~A 02225261 1997-12-18AMS & ASSOC. P.08/24 several cycles of the reaction. As a result, the amount of inorganic chloride required for treatment of the nitrogen compounds is less than the stoichiometric values indicated by the above equations.
If the waste water contains nitrogen compounds and sufficient levels of waste inorganic chloride compounds, it is possible to process by electrolysis directly. However, if the waste water does not already contain an adequate amount of inorganic chlorides, inorganic chlorides must be added before conducting electrolysis. There are no particular limitations to the inorganic chloride which is to be added so long as the inorganic chloride is water soluble. Examples include lithium chloride, sodium chloride, potassium chloride, beryllium chloride, magnesium chloride, and calcium chloride.
Electrolysis is conducted while circulating the water which contains nitrogen compounds and inorganic chlorides between a storage container and an electrolysis container. A portion of the water in the storage container is removed and is passed through a column filled with a metal peroxide catalyst to obtain the final form of the processed water. In this processing, an optimal amount of inorganic chloride can be maintained by controlling the speed with which the water circulates to the electrolysis reaction container, the speed of the water passage through the catalyst column, and the like.
In the method of the present invention, a portion of the nitrogen compounds is broken down by hypochlorite ions generated by electrolysis before contacting the metal peroxide catalyst. Thereafter, water containing the remaining nitrogen compounds and hypochlorite ions generated by electrolysis is brought into contact with the catalyst. Not only arc the remaining nitrogen compounds broken down at this step, but excess hypochlorite ions arc removed as well. When the water which contains nitrogen compounds and hypochlorite ions comes into contact with the metal peroxide catalyst, the roVIMIS~CMlIC1~W10ATAW 11flW IH>I1 03-18-1998 10:44 1-613-828-0~A 02225261 1997-12-18AMS & ASSOC. P.09/24 breakdown reactions of the nitrogen compounds proceed rapidly at normal temperature and pressure.
Examples of metal peroxide catalysts useful in the present invention include cobalt peroxide, nickel peroxide, copper peroxide, and silver peroxide.
Among these, cobalt peroxide and nickel peroxide are preferred. It is preferable that these metal peroxide catalysts be carried on zeolite, titania, y-alumina, a-alumina or the like. The preparation method for these are described below, using the example of zeolite as the carrier and cobalt peroxide as the carried catalyst.
Zeolite is an aluminosilicate which has uniform fine pores of molecular size. The structure of zeolite is a series of tetrahedrons of silicon atoms, with a portion substituted by aluminum atoms, which form a three dimensional mesh structure via oxygen atoms. Characteristic hollows and channels are formed. 'the size of these hollows or channels are determined by the size of the oxygen ring. Zeolite typically hay an ability to replace cations. In the present invention, natural zeolites, such a~ clinoptiololite or mordenite, or -- synthetic zeolites, such as zeolite A, zeolite X, or zeolite Y can be used with good results. These zeolites can be used singly, or two or more types can be mixed and used.
The processing of the zeolite carrier is conducted by bringing it into contact with aqueous solutions of sulfates, nitrates, or chlorides of cobalt, or mixture solutions of these. One method of contact involves soaking particles of zeolite in the solution. Alternatively, zeolite particles can be packed into a column and the aqueous solution can be passed through once or in a circulating manner. The concentration of cobalt salt and contact times are determined so that the necessary amount of cobalt is retained by the zeolite.
The amount of cobalt which is carried is preferably between about 0.01 % and 03-I8-1998 10:45 1-613-828-0~A 02225261 1997-12-18AMS & ASSOC. P.10/24 about 10% by weight. The thus-processed zeolite is then rinsed with water as needed after being separated from the aqueous solution, A rinsing step is desirable to remove all cobalt ions not present in the active sites of zeolite.
Generally, it is preferable to rinse until the color of cobalt ions disappear from the rinse water. By this procedure, it is possible to obtain an effective zeolite carrier hearing a small amount of cobalt.
Next, the zeolite carrier obtained as above is brought into contact with an alkaline aqueous solution which contains chlorine agents. As a method of contact, zeolite can be soaked in an alkaline solution which contains chlorine agents. Alternatively, zeolite can be packed into a colun2n, and the alkaline solution containing chlorine agents can be passed through once or in a circulating manner. In this manner, the cobalt peroxide catalyst used in the present invention is obtained. At the time of contact, a small amount of cobalt ions may separate from zeolite and generate fine precipitate in the peroxide, but the precipitate can be removed through final rinsing. Examples of chlorine agents include chemicals which generate free chlorine such as sodium hypochlorite, chlorine gas, chlorine generated by electrolysis, and the like.
Examples of the alkaline aqueous solution which is used in conjunction with the chlorine agent include aqueous solutions of sodium hydroxide, potassium hydroxide, and the like.
As an alternative method of formation of the cobalt peroxide catalyst, the zeolite may be heated after the rinsing step, causing the cobalt ion to change to cobalt oxide. Next, the zeolite carrier is brought into contact with an alkaline solution, and the same catalyst is obtained.
By the present invention, a portion of nitrogen compounds are oxidized and broken down by hypochlorite ions which are generated by electrolysis.
Furthermore, the water which contains remaining nitrogen compounds and ~,usa rwmurvro~r~mnwmfm 03-18-1998 10:45 1-613-B28-OLCA. X2225261 1997-12-18AMS & ASSOC. P.11/24 hypoChlorite ions i~ brought into contact writh a metal peroxide catalyst which is prepared as described above. This results in total breakdown of nitrogen enmpounds. The oxidation reaction regenerates chlorine ions, which are reoxidized by electrolysis to hypochlorite ions.
5 The catalyst, packed as particles of diameter about 0.3 to about l0 nun into a column, can be used as a fixed bed or a fluid bed. If particle diameter is less than 0.3 mm, the loss of pressure becomes too great in a fixed bed.
Similarly, if the particle diameter is less than 0.3 mm, there is a danger that the carrier will be destroyed and become mixed in with the processed water in a 10 fluid bed. The direction of water flow may be either upward or downward.
However, since nitrogen gas is generated in the reactions of the present invention, upward flow is preferred.
In the method of the present invention, the rate of water flow can be chosen so that it is appropriate for the contact method or the amount of metal peroxide held by the carrier. Typically, it is preferable to have an SV of between about 0.1 h-' and about 60 h-'. SV refers to space velocity, and is the ratio of the flow rate of the inflow to the volume of the treating device. For example, if the inflow has a flow rate of 2 liter/hr, and the volume of the treating device is one liter, the SV is 2 h''. It is even more prCfcrable to have an SV of between 0.5 h'' and 10 h-'. Even more preferable is an SV of between 1 by and about 10 h-'. The contact between the waste water containing nitrogen compounds and hypochlorite ions and the metal peroxide catalyst is typically conducted at a normal temperature between about 20 and °C. If the reaction is conducted at a temperature between about 40 and 25 °G, the reaction rate becomes higher, and the contact time can be shortened.
('Tenerally, if the nitrogen compound concentration in the water is high, it is preferable to have an extended contact time. Furthermore, if the contact time is too short, there is a danger that hypochlarite ions will remain in the processed water.
13y the present invention, oxidative breakdown of nitrogen compounds in water which contains nitrogen compounds is possible without the need for added oxidants, such as chlorlrae oxidants or hydrogen peroxide. Furthermore, the reaction can be performed at standard temperature and pressure. Because the reaction proceeds rapidly under normal temperature and pressure, the reaction device can be made more compact, and it is possible to obtain a processed water of a stable quality.
Referring to Figure 1, there is shown a process flow chart of one embodiment of the present invention. Waste water which contains nitrogen compounds is brought to a storage cantaiz~er 1 _ jnorganic chlorides aro added as needed with mining. Waste water is sent to an electrolysis reaction container 3 by a pump 2. After electrolysis, the wa fire water is circulated back to storage container 1. The waste water, which now contains nitrogezz compounds and hypochlorite ions generated by electrolysis, is then removed from storage container 1 by pump 4 and is sent to reaction column 5 which is packed with a metal peroxide catalyst.
Processed water is obtained by treating the waste water with the metal peroxide catalyst at normal temperature and pressure.
By the present invention, it is possible to remove nitragez~ compounds at a high rate with a small device, without adding oxidants such as chlorine oxidants or hydrogen peroxide.
In particular, with the present invention, no hypochlorite ions remain in the processed water because the metal peroxide catalyst is able to break dawn hypochlorite fans, Therefore, there is rio need for a separate residual chlorine removal process, as in the prior art. Furthermore, with the present invention, the hypachlorite iox~ which are 03-18-1998 10:47 1-613-828-0~A 02225261 1997-12-18AMS & ASSOC. P.13/24 12 M19S3-i2 generated are mire likely to react with nitrogen compounds than with metal peroxide catalysts, and so the ions will not be unnecessarily broken down.
With the present invention, inorganic nitrogen compounds or organic nitrogen compounds are hr~ken down to harmless nitrogen gas, carbon dioxide S gas, water, and the like. 1t is possible to reduce total nitrogen concentration and the chemical oxygen demand of the processed water. The method of the present invention can be applied to waste water which contains one of either inorganic nitrogen compounds or organic nitrogen compounds, or it can be applied to waste water which contains both.
Embodiment 1 Treatment of waste water which contained 1,000 mglliter of monoethanolamine, 375 mg/liter of ammonia nitrogen, and 8,000 mg/liter of sodium chloride was conducted. The initial water quality of this waste water was as follows: total nitrogen (T-N) = 60S mg/liter, ammonia nitrogen (NH4'-N) --- 37S mg/liter, total organic carbon (TOC) ~ 393 mg/liter, chemical oxygen demand by potassium permanganate at 100 °C (CODM") ----- 839 mg/liter, residual chlorine = 0 mg/liter, and pH -- 9.3.
1,250 ml of this waste water was placed in an electrolysis container.
The electrolysis container had S.0 cm x S.0 cm platinum-plated titanium plate electrodes. The waste water was processed by passage through a circulating system. The distance between the electrodes was 1.0 em. The between-electrode volume of the reaction container between the electrodes was 25.0 cm3. Current was 2.SA, and current density was l0A/dmz. The circulating solution passage rate was 1 10 ml/min.
W 71A1H:fKIVCIpW/pATA W I %7W I%11 !
03-18-1998 10:47 1-613-828-0~A 02225261 1997-12-l8AMS & ASSOC. P.14/24 The circulating reaction processing was conducted for six hour. The water quality after six hours was the following: total nitrogen ('f-N) -- 68 mg/liter, ammonia nitrogen (NhI,+ - N) - l mglliter, total organic carbon (TOC) = 72 mg/liter, oxygen demand (COD ,",~) --- 124 mg/liter, residual chlorine = 751 mg/liter, and pH 6.8.
Referring to Table l, the water quality analysis after each hour of circulating reaction time is shown.
Table 1 ProcessingStored Outflow time circulating from water catalyst (Comparison reaction 1) column (Embodiment 1) (hr) T-N NH,'-NTOC'r_n~~"ResidualpH T-N NH TO(:L()I)M"Residualrll m~ mgll mgJlmFJI Cl' mFll'-N mEllmFll CI-mgll mpJl 0 AUS :175 393 li3S)U 9.3 .-- -. -_ _-_ I SU'' :.J2 359 767 16 ti.tS- - - - - -p 4'2(i2'?7 340 635 l9 ?3..i- - -3 297 l 31 591 204 5.2 - - - - _ _ ~ 1b4 41 1y8 371 381 2.3 -9G 17 118 2? G72 3.9 l 6 68 1 72 124 751 G.8 - - - - -7 61 ND 53 92 8G3 G.9 48 ND 4.8 ?.G ND 7.4 8 57 ND 12 19 949 7.2 46 ND '2.7I.7 ND 7.b 9 57 NTJ 9.U 1'? y5~1 7.3 45 NU 2.1 1.6 NU 7.6 IU z7 ND 3.4 3.G 9G3 7.3 45 ND 1.5 I.G ND 7.G
N.D. = not detected After six hours, the electrolysis reaction was stopped. The solution in the electrolysis storage container was processed at a Speed of 15~ ml/hour through a reaction column packed with cobalt peroxide-carrying catalyst. 'The WWfa7r71IH.1(IW1DATAW11lIWIHYI3 03-IS-1998 10:48 1-613-828-OICA 02225261 1997-12-18AMS & ASSOC. P.15/24 catalyst was a cobalt peroxide at 2.5% by weight of cobalt in a spherical titania carrier having a diameter of 1.5 mm. The packing volume of the catalyst was S~ m1. The reaction column was processed at room temperature. Solution passage was continued for four hours. After each hour, the entire amount of processed water was collected, and tile water quality was analyzed. The processing time was added to the electrolysis processing time (six hours).
Referring to Tahle 1, there is shown the water quality between seven and ten hours of processing.
Between seven and ten hours of processing, total nitrogen (T-N) was at or below 50 mg/liter; ammonia nitrogen (NH4' - N} was not detected; total organic carbon (TOC) was at or below 5.0 mg/liter; oxygen demand (CORM") was Flt or below 3.0 mg/liter; and residual chlorine was not detected.
Comparison 1 Under the same conditions as Embodiment 1, electrolysis was conducted for ten hours continuously in a separate circulating processing system. After every hour, the water quality of the water in the electrolysis storage container was analyzed. The results are Shown in Table 1.
Up to six hours, the results of water quality analysis were the same as Embodiment 1. After eight hours, there were no changes in total nitrogen (T-N) (57 mg/litcr). Aftcr seven hours, ammonia nitrogen (Nl~~+ - N) was not detected. Total organic carbon (TOC) was below 5 mg/liter, and ten hours of electrolysis were required for the water quality to have an oxygen demand (CC>D",~ of below 5 mg/liter. From the seventh hour on there was a trend of increasing residual chlorine.
wwmraawmwrw~~wmW~~m 03-IS-1998 10:48 1-613-828-0~A.02225261 1997-IZ-IHAMS & ASSOC. P.16/24 It can be seen that treatment of waste water by contact with cobalt peroxide catalyst produces a processed water of superior quality to that obtained by electrolysis alone over many hours.
Embodiment 2 Processing of waste water which contained 1,000 mg/liter of 1,3-dimethyl-2-imidazolidinone was conducted. The initial water quality of this waste water was the following: total nitrogen (T-N) = 246 mg/liter, total organic carbon (TOC) = 526 mglliter, chemical oxygen demand by potassium permanganate at 100 °C (COD,H,~ = 950 mg/liter, residual chlorine = 0 mg/liter, sodium chloride = 10,000 mg/liter, and pH 9.7.
5(10 ml of the waste water was placed in the electrolysis container.
Under the same conditions as Embodiment l, electrolysis was conducted for three hours. After each hour, the water quality of the water in the electrolysis storage container was measured. Referring to Table 2, the results are shown.
WvUlhR1'CIRIGX~W/bw1'AWIHN.IW f11:
03-18-1998 10:49 1-613-828-0CA 02225261 1997-12-18~AMS & ASSOC. P.17/24 1~ M1953-12 Table 2 ProcessingStored Outflow time circulating from water catalyst (Comparison reaction 2) column (lmboditncnt 2) r-N TOC COD ResidunlpFi T-N TOC'COD ResidualpH
mg/1mg/1 mgJf"C'I rng/Imgllmglr''(.'I
mg/I
mg/l U 246 526 950 0 9.7 - - -1 183 400 718 108 9.2 _ _ _ _ 2 7 16S 308 540 7.9 - - - - -3 53.370 130 864 8.3 - - - -4 43.339 72 1150 8.5 28.1 5.7 9.4 N.D. 8.7 40.023 49 1490 8.9 26.3 4,2 6.7 N.D. 9.!
L f ~ .__f T1 J_~__ -av.u. uW W .WV.LV.U
Electrolysis was halted after three hours. As in Emhodiment 1, water from the electrolysis container was then passed at a rate of 150 ml/hour through a reaction column packed with cobalt peroxide catalyst. Solution passage was continued for two hours. After each hour, the entire amount of water was _ collected, and water quality analysis was conducted. 'I~he processing time was added to the electrolysis time (three hours). Referring to Table 2, the water quality for hours 4 and 5 are shown.
The water quality after three hours of electrolysis processing was as followsv total nitrogen (T-N) - 53.3 mg/liter, total organic carbon (TOC) = 70 mg/liter, oxygen demand (CODM~) = 130 mglliter, residual chlorine = 8fi4 mg/liter. The water quality after passage through the cobalt peroxide catalyst reaction column was as follows: total nitrogen (T-N) less than 3U mg/liter, total organic carbon (TOC) less than 10 mg/liter, oxygen demand (CODM,~ Less than mg/Iiter, and residual chlorine was not detected. Ammonia nitrogen (NH4' - N) was not measured.
r-w~au~wro~uwmmnm:
03-18-1998 10:49 1-613-828-0CA 02225261 1997-12-18~AMS & ASSOC. F~18~24 Comparison 2 Electrolysis with a separate circulating processing system was conducted continuously for five hours under the same conditions as embodiment 2. The water quality analysis results up to the third hour were the same as in embodiment 2. The water quality for the fourth and fifth hours is shown in Table 2.
Compared with passage through the catalyst reaction column of the present invention, total nitrogen (T-N) total organic carbon (TOC), and oxygen demand (COD,r,") values all were higher. In particular, residual chlorine at five hours was very high (1,490 mg/liter). The residual chlorine increased as the 1,3-dimethyl-2-imidazolidinone was broken down.
Embodiment 3 Processing of waste water containing 5,000 mg/liter of urea and 6,000 mglliter of sodium chloride was conducted. 'rhe water quality of the waste water was as follows: total nitrogen (T-N) = 2,330 mg/liter, ammonia nitrogen (NHQ' - I~ = 5.5 mg/1 iter, total organic carbon (TOC) = 1,000 mg/liter, residual chlorine = 0 mg/liter, and pH 1 I .9.
1,000 m1 of this waste water was placed in an electrolysis container.
Electrolysis was conducted for four hours under the same conditions as Embodiment 1. After four hours, electrolysis was terminated. As in Embodiment 1, the water in the electrolysis storage container was passaged at a rate of 150 mUhour through a reaction column packed with cobalt peroxide holding catalyst. Passage was continued for four hours. After each hour, the entire volume of the processing water was collected. and water quality was 'A"~tL1C47K71tId1vIDATAW I%T11I%111 03-18-1998 10:50 1-613-828-0CA 02225261 1997-12-18~AMS & ASSOC. F.19/24 analyzed. Processing time was added to the electrolysis time (four hours).
Referring to Table 3, the water quality between five and eight hours of processing are shown.
Table 3 ProcessingStored Outflow time circulating from water catalyst h (C'omparison reaction 3) column (Embodiment 3) ( r) T-N NH,'-NTOC ResidualpH r-trnrl,~.Nroc ResidualpH
mgll mg/I mgll CI- mgJlmg/l mgllCI' mg/I moll 0 2330 5.5 1000 0 11.9 - - - -1 _ ._ _ - 6.4 - _ _ _ _ 2 1260 26.8 554 668 6.3 ' - - - -3 _ _ _ 6.6 - _ _ -4 460 9.0 163 1790 6.4 - - - - -_.. _ _ 1~3 12.0 23 I8 8.7 6 137 N.D. I.5 2520 9.1 107 N.D. 1.1 7.2 9.3 7 _ _ _ - 101 N.D. 0.9 N.D. 9.5 8 143 N.1).1.4 2590 9.3 98 N.D. 0.5 N.D. y.6 m.ir. - mu uCrcc:lecr The water quality after four hours of electrolysis was as follows: total nitrogen (T-N) - 460 mg/liter, total organic carbon {TOC} = 163 mg/liter, residual chlorine - 1,790 mg/litcr. The water quality of the water samples passaged through the cobalt pero~cide holding catalyst between eve and eight hours were as follows: total nitrogen ('r-N) = between 123-98 mg/liter, and total organic carbon (TOC) = between 23-0.5 mg/liter. Residual chlorine after five hours of processing was 18 mg/liter, and after seven hours of processing, residual chlorine was not detectable.
W tILIpIfK11UC1ItWlpATAW tVf7W IH) 17 03-18-1998 10:51 1-613-828-eCA 02225261 1997-IZ-IB~AMS & ASSOC. P.20/24 Comparison 3 Electrolysis was conducted continuously for eight hours by a separate circulating processing system under the same conditions as in Embodiment 3.
Referring to Table 3, the water quality analysis results for hours 6 and 8 are shown. Total nitrogen (T-N) values were much higher, compared with passage through the catalyst reaction column of the present invention. Furthermore, residual chlorine values were very high (2,520-2,590 mg/liter).
The method of the present invention is effective against various nitrogen compounds. The present invention does not require additional oxidants, and can easily process waste water containing nitrogen compounds at normal temperahlre and pressure. With the present invention, it is possible to obtain high quality processed water which is low in total nitrogen concentration, total organic carbon concentration, and chemical oxygen demand. Furthermore, hyp~chlorite ions are broken down by metal peroxide catalysts and do not remain in the processed water. The water quality of the processed water is thereby further improved. Furthermore, the setup for embodiments of the present invention is compact. Because the necessary space for setup is reduced, the maintenance is easy.
Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.
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Claims (14)
1. A method for treating waste water containing nitrogen compounds and chlorine ions, comprising the steps of:
supplying said waste water to a storage container;
supplying a portion of said waste water from the storage container to an electrolysis chamber and performing electrolysis on said waste water, such that said chlorine ions are oxidized to hypochlorite ions, and said nitrogen compounds are oxidized by said hypochlorite ions and thereby broken down; and returning waste water from the electrolysis chamber to the storage chamber;
and contacting a portion of said waste water from the storage container with a metal peroxide catalyst after said step of performing electrolysis, such that hypochlorite ions are removed from said waste water.
supplying said waste water to a storage container;
supplying a portion of said waste water from the storage container to an electrolysis chamber and performing electrolysis on said waste water, such that said chlorine ions are oxidized to hypochlorite ions, and said nitrogen compounds are oxidized by said hypochlorite ions and thereby broken down; and returning waste water from the electrolysis chamber to the storage chamber;
and contacting a portion of said waste water from the storage container with a metal peroxide catalyst after said step of performing electrolysis, such that hypochlorite ions are removed from said waste water.
2. A method for treating waste water according to claim 1, wherein said waste water is circulated between a storage container and an electrolysis chamber before said step of contacting said waste water with a metal peroxide catalyst.
3. A method for treating waste water according to claim 1, further comprising adding at least one inorganic chloride to said waste water.
4. A method for treating waste water according to claim 1, wherein said step of electrolysis includes two or more electrodes made from a substantially water-insoluble material.
5. A method for treating waste water according to claim 4, wherein said electrodes are a member selected from the group consisting of platinum-plated titanium electrodes, iridium-coated titanium electrodes, palladium-coated titanium electrodes, lead dioxide electrodes, and ferrite electrodes.
6. A method for treating waste water according to claim 3, wherein said at least one inorganic chloride includes at least one member selected from the group consisting of lithium chloride, sodium chloride, potassium chloride, beryllium chloride, magnesium chloride, and calcium chloride.
7. A method for treating waste water according to claim 1, wherein a metal peroxide in said metal peroxide catalyst is at least one member selected from the group consisting of cobalt peroxide, nickel peroxide, copper peroxide, and silver peroxide.
8, A method for treating waste water according to claim 7, wherein said metal peroxide catalyst includes a carrier, said carrier being a member selected from the group consisting of zeolite, titania, .gamma.-alumina, and .alpha.-alumina.
9. A method for treating waste water according to claim 8, wherein said metal peroxide is between about 0.01% and about 10% by weight of said carrier.
10. A method for treating waste water according to claim 1, wherein said metal peroxide catalyst includes catalyst particles, said catalyst particles having a diameter between about 0.3 mm to about 10 mm.
11. A method for treating waste water according to claim 10, wherein said catalyst particles are arranged in a column in one of a fixed bed and a fluid bed.
12. A method for treating waste water according to claim 1, further comprising flowing said waste water over said metal peroxide catalyst at a flow rate such that said method has an SV of between about 0.1 h -1 and 60 h -1.
13. A method for treating waste water according to claim 1, wherein said process is performed at a temperature between about 20°C and about 80°C, and at a pressure that is substantially equal to atmospheric pressure.
14. A method for treating waste water containing nitrogen compounds, comprising the steps of:
circulating said waste water between a storage container and an electrolysis container, adding a substoichiometric quantity of inorganic chlorides;
performing electrolysis in said electrolysis chamber, such that said chlorine ions are oxidized to hypochlorite ions, and said nitrogen compounds are oxidized by said hypochlorite ions and thereby broken down; and contacting said waste water with a metal peroxide catalyst after said step of performing electrolysis, such that said hypochlorite ions formed during said electrolysis are removed from said waste water;
said metal peroxide catalyst containing one of cobalt peroxide and nickel peroxide;
said metal peroxide catalyst further containing at least one member from the group consisting of zeolite, titanic, .gamma.-alumina, and .alpha.-alumina;
said one of cobalt peroxide and nickel peroxide being present in said metal peroxide catalyst at a concentration of between about 0.01% by weight and 10% by weight;
said step of contacting occurring at an SV between about 0.1 hr -1 and about 60 hr -1, a temperature between about 20°C and about 80°C, and a pressure substantially equal to atmospheric pressure.
circulating said waste water between a storage container and an electrolysis container, adding a substoichiometric quantity of inorganic chlorides;
performing electrolysis in said electrolysis chamber, such that said chlorine ions are oxidized to hypochlorite ions, and said nitrogen compounds are oxidized by said hypochlorite ions and thereby broken down; and contacting said waste water with a metal peroxide catalyst after said step of performing electrolysis, such that said hypochlorite ions formed during said electrolysis are removed from said waste water;
said metal peroxide catalyst containing one of cobalt peroxide and nickel peroxide;
said metal peroxide catalyst further containing at least one member from the group consisting of zeolite, titanic, .gamma.-alumina, and .alpha.-alumina;
said one of cobalt peroxide and nickel peroxide being present in said metal peroxide catalyst at a concentration of between about 0.01% by weight and 10% by weight;
said step of contacting occurring at an SV between about 0.1 hr -1 and about 60 hr -1, a temperature between about 20°C and about 80°C, and a pressure substantially equal to atmospheric pressure.
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| JP8-354063 | 1996-12-18 | ||
| JP35406396A JP4003016B2 (en) | 1996-12-18 | 1996-12-18 | Nitrogen compound-containing water treatment method |
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| EP (1) | EP0849227B1 (en) |
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| US7947185B2 (en) * | 1998-07-06 | 2011-05-24 | Grott Gerald J | Water sanitation methods |
| DE19853182A1 (en) * | 1998-11-19 | 2000-05-25 | Univ Dresden Tech | Removal of ammonium and/or ammonia from saline aqueous solution, e.g. sewage or other waste liquor, involves electrolysis at constant pH in a divided cell in the presence of chloride |
| DE19925534A1 (en) * | 1999-06-04 | 2000-12-07 | Degussa | Treatment of waste waters containing (in)organic compounds involves the use of hydroxyl producers in the presence of titanium-containing silicates as catalyst |
| US6761827B2 (en) | 2001-10-26 | 2004-07-13 | Zodiac Pool Care, Inc. | Method and apparatus for purifying water |
| US7238278B2 (en) * | 2001-10-26 | 2007-07-03 | Zodiac Pool Care, Inc. | Apparatus for purifying water |
| JP2003230883A (en) * | 2002-02-08 | 2003-08-19 | Sanyo Electric Co Ltd | Wastewater treatment method and wastewater treatment system |
| US6994793B2 (en) * | 2002-04-19 | 2006-02-07 | Hydro-Trace Incorporated | Process for remediating ground water containing one or more nitrogen compounds |
| JP2004181363A (en) * | 2002-12-03 | 2004-07-02 | Sanyo Electric Co Ltd | Water treatment method |
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1996
- 1996-12-18 JP JP35406396A patent/JP4003016B2/en not_active Expired - Lifetime
-
1997
- 1997-12-17 US US08/991,818 patent/US6132627A/en not_active Expired - Lifetime
- 1997-12-18 EP EP97122357A patent/EP0849227B1/en not_active Expired - Lifetime
- 1997-12-18 CA CA002225261A patent/CA2225261C/en not_active Expired - Fee Related
- 1997-12-18 DE DE69705485T patent/DE69705485T2/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| DE69705485D1 (en) | 2001-08-09 |
| EP0849227A2 (en) | 1998-06-24 |
| DE69705485T2 (en) | 2002-05-29 |
| EP0849227A3 (en) | 1998-09-30 |
| JP4003016B2 (en) | 2007-11-07 |
| JPH10174976A (en) | 1998-06-30 |
| CA2225261A1 (en) | 1998-06-18 |
| EP0849227B1 (en) | 2001-07-04 |
| US6132627A (en) | 2000-10-17 |
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