CA2231193A1 - Advanced oxidation of water using catalytic ozonation - Google Patents
Advanced oxidation of water using catalytic ozonation Download PDFInfo
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- CA2231193A1 CA2231193A1 CA002231193A CA2231193A CA2231193A1 CA 2231193 A1 CA2231193 A1 CA 2231193A1 CA 002231193 A CA002231193 A CA 002231193A CA 2231193 A CA2231193 A CA 2231193A CA 2231193 A1 CA2231193 A1 CA 2231193A1
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- catalyst
- ozone
- water
- waste water
- contaminants
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- 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
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
Abstract
Contaminants are removed from waste water (1) by an advanced oxidation process in which the waste water is contacted (7) with ozone (8) in the absence of a catalyst to oxidize-ozone-oxidizable contaminants and to dissolve ozone in the water, and the resultant ozone-containing water (3) is contacted with a solid ozone activating catalyst (5) to oxidize ozone refractory contaminants in the water. Effluent (6) from the catalyst treatment (5) can be contacted (7) with ozone and recycled (2) for further contact with the catalyst (5). The preferred catalyst is an undoped monolithic structure of gamma alumina having low surface area, high porosity and low pressure drop.
Description
CA 02231193 1998-03-0~
ADVANCED OXIDATION OF WATER TJSING C~TALYTIC OZONATION
c The present invention relates to the treatment o~
sur~ace water or aqueous e~luent to remove oryanic impurities there~rom.
Conventional microbiological waste water treatments are e~ective in removal o~ biodegradable oryanic cont~m;n~nts ~rom water. ~owever, recalcitrant organic cont~m;n~nts which are not biodegradable and/or are inhibitory to microbiological activity require chemical oxidation ~or removal. The extent o~ contamination is measured in terms o~ the amount o~ oxygen required to remove the cont~min~nts COD (Chemical Oxygen Demand) is the amount o~ oxygen required to oxidize all oxidizable cont~min~nts in the water to be treated; BOD (Biological Oxygen Demand) is the amount o~ oxygen required to oxidize the biodegradable cont~m;n~nts; and hard COD is the amount o~ oxygen required to oxidize the non-biodegradable cont~min~nts.
Chemical alternatives to microbiological waste water treatment are known. The most usual chemical treatment is the Zimmerman (or ZIMPRO) wet air oxidation process, in which waste water is contacted with air at elevated temperature and pressure, usually 200~C to 370~C at 20 to 200 Atmospheres (2 to 20 MPa). This method is only economical ~or waste water with an organics contents higher than 1~ or an oxidation heat value su~icient to maintain the elevated temperature required.
Various catalysts have been used in the Zimmerman process. These catalysts include noble or heavy metals such as palladium, platinum, cobalt or iron deposited on a CA 02231193 1998-03-0~
W 097tl4657 PCT/GB96/02525 carrier o~, ~or example, alumina, silica-alumina, silica gel, activated carbon, titania or zirconia (see JP-A-49-44556 (1974); JP-A-49-94157 (1974); and JP-A-58-64188 (1983)).
The use o~ ozone to treat water a~ter microbiologica bulk BOD removal is well known. Ozone is the strongest molecular oxidant ~or water treatment and it has been used since the beginning o~ this century in drinking water treatment to provide disin~ection, removal o~ colour, taste and odour, and destruction o~ organic compounds. However, ozone is very selective in its reactions; it predominantly reacts with compounds containing unsaturated bonds such as ole~ins, aromatic compounds and/or compounds cont~in;ng electron rich groups such as sul~ur and nitrogen. For other organic compounds such as saturated alkanes and chlorinated organics (most o~ pesticides and priority pollutants), the reactivity o~ ozone is limited. These ozone re~ractory cont~m;n~nts can be oxidized by hydroxyl radicals which are usually ~ormed by activating ozone with hydrogen peroxide or ultraviolet light ("advanced oxidation").
Hydrogen peroxide has an operation cost higher than ozone and ultraviolet light requires capital and operational costs at least equal to that o~ ozone generation. Accordingly, the activation o~ ozone to hydroxyl radicals by these two methods results in a large increase (50 - 200~) in the cost o~ water treatment.
Moreover, since hydroxyl radical reactions are much less speci~ic than those involving ozone alone, the hydroxyl radicals generated in solution by hydrogen peroxide or ultraviolet light activation o~ ozone can be wasted by reaction with non-target inhibitors or scavengers, such as carbonate and bicarbonate ions, which do not require CA 02231193 1998-03-0~
W O 97/146~7 PCT/GB96/02525 oxidation. Thus, a more cost e~ective method o~ ozone activation is needed.
PL-A-56775 (1969) reported that ozone-containing gas had been used in a continuous oxidation process to puri~y waste water ~rom coke ovens but that the treatment was uneconomic ~or industrial use. It was proposed in PL-A-56775 that the waste water should be continuously treated with ozone-cont~i n; ng gas in a ~roth phase by blowing the gas countercurrent to the waste water in a scrubber packed with Rashig rings, slag and~or oxides or silver, copper, aluminium, zinc, magnesium, tin, lead, iron, or manganese as catalysts.
US-A-4007118 (1977) discloses the ozonation o~ waste water using a transition metal catalyst, such as manganese trioxide, ~erric oxide, copper oxide or nickel oxide, which is present as a powder contained in ~abric bags, disposed on a substrate or dispersed within the waste water US-A-4040982 (1977) discloses a method o~ removing cont~m~n~nts ~rom waste water by treatment with ozone-containing gas in the presence o~ a catalyst comprising ~erric oxide supported on catalytically active alumina and having a sur~ace area o~ 150 to 450 m2/g and a pore volume o~ at least 0.3 C~3 . The exempli~ied alumina is gamma alumina but re~erence is made to eta alumina, amorphous alumina and activated alumina.
JP-A-58-37039 (1983) discloses a method o~ removal o~
an aromatic organic compound ~rom waste water by mixing ~irst with a sur~actant, then with a transition metal or alkaline earth metal compound, and contacting the resultant mixture with ozone-containing gas to oxidatively decompose the organic compound.
CA 02231193 1998-03-0~
W O 9~/14657 PCT/G B96/02525 NL-A-9001721 (1991) discloses the treatment o~ iron-containing waste water by ~orming and L~L,Loving precipitated Fe(III) by mixing with hydrogen peroxidei then ~orming and L~L..o~ing precipitated carbonate by adding, ~or example, calcium hydroxide, calcium chloride and/or alkali metal hydroxidei and subsequently oxidation with, ~or example, ozone-containing gas alone or with a solid catalyst, to remove residual organic compounds. Speci~ied catalysts are activated carbon, alumina or silica. It is stated that the catalyst must have a sur~ace area o~ at least 50 m2/g and a pore volume o~ greater than 0.1 cm3jg and that its activity can be improved by addition o~ a transition metal such as copper, iron, molybdenum or cobalt. In the exempli~ied process, ozone-containing gas is passed through a bubble reactor countercurrently to li~uid e~luent ~rom a catalyst bed and the gas exiting the ~ubble reactor is passed through that catalyst bed cocurrently with the partially treated waste water. I~ required, additional ozone-containing gas can be added to supplement the ozone content o~ the gas exiting the bubble reactor.
US-A-5,145,587 (1992) discloses the treatment o~ waste water by wet oxidation with a molecular oxygen-containing gas in the presence o~ a solid catalyst comprising (i) titanium dioxide; (ii) an oxide o~ a lanthanide element;
and (iii) at least one metal selected ~rom manganese, iron, cobalt, nickel, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium or a water insoluble or sparingly soluble compound thereo~. The catalyst is ~ormed by adding component (iii) to a calcined mixture o~ (i) and (ii) and pre~erably is in the ~orm o~ an integral or monolithical structure, such as an extruded honeycomb (having straight through rhAnn~ls), o~ (i) and (ii) impregnated with (iii). The pre~erred oxidants are oxygen, ozone, hydrogen peroxide or mixtures o~ oxygen with ozone or hydrogen peroxide.
, CA 0223ll93 l998-03-OS
--5- 220PPCT05',22 . 08j97 US-A-5352369 (1994) discloses a method oi~ treating water to kill bacteria therein by contact with a silver catalyst in the presence o~ oxygen to ~orm an active oxidizer in the water. The silver catalyst is ~ormed by depositing elemental silver on an alumina matrix and heating to a temperature o~ at least 300~C. In the pre~erred embodiment ozone-containing gas is used as the source o~ oxygen but it is re~uired that the water be exposed to the silver catalyst as soon as the ozone-containing gas has been added to the water.
JP-A-5-228480 (1993) & JP-A-5-228481 (1993) disclose the removal o~ non-biodegradable contAm;n~nts ~rom raw water by ~irst contacting the water with ozonized air and then treating the ozonated water with at least one o~
hydrogen peroxide, ultrasound, ultraviolet light and a catalyst to generate hydroxyl radicals. In the process o~
JP-A-5-228480 the raw water ~lows in countercurrent to the ozonized air while in the process o~ JP-A-5-228481 the raw water and ozonized air ~low cocurrently. All o~ the exempli~ied processes use a combination o~ ultraviolet light, ultrasound and catalyst in the advanced oxidation section. The only speci~ied catalyst is alumina sur~ace treated with platinum or palladium.
It has now been ~ound that gamma alumina is such an e~ective catalyst ~or the catalytic ozonation o~ water that ozone re~ractory contAm;nAnts can more easily be removed even in the absence o~ hydrogen peroxide.
Thus, according to the present invention, there is provided a process ~or the removal o~ contAm;nAnts ~rom water which comprises contacting the water with ozone in the absence o~ a catalyst to oxidize ozone-oxidizable cont~m;nAnts and to dissolve ozone in the water, and contacting the resultant ozone-containing water with a gamma alumina ozone activation catalyst to oxidize ozone re~ractory contAm;n~nts in the water.
AMENDED SHEET
, CA 02231193 1998-03-0~
--6-- 220PPCT05~Z2. 08/9~
The process o~ the invention permits the use o~ some relatively inexpensive solid catalysts which are widely used in the chemical industry ~or chemical synthesis.
In this invention, the waste water ~irst reacts with ozone in a gas-liquid contactor and the easily oxidisable cont~m;n~nts are removed. The thus treated waste water (~ree ~rom gas bubbles but with residual dissolved ozone) passes through the ozone activation catalyst where the residual ozone is activated to secondary oxidants more reactive than ozone and which decompose cont~m;n~nts remaining a~ter treatment in the gas-liquid contactor. The e~luent ~rom the catalyst treatment can be re-injected to the gas-liquid contactor to absorb more ozone ~or reaction i~ the concentration o~ cont~m;n~nts is too high to reduce in a single pass through the catalyst (i.e. the oxidant demand o~ the waste water is higher than the m~;mnm ozone solubility in water under the operational conditions).
Having regard to the capacity and e~iciency o~
conventional waste water treatments, the waste water treated by the process o~ the invention usually will have a COD o~ at most 5000 mg/l. The extent o~ the advanced oxidation by the process will be determined mainly by environmental requirements, which presently require the COD
o~ waste water to be reduce to at most 125 mg/l be~ore discharge.
In addition to improving the ef~iciency o~ ozone usage in advanced oxidation, the use o~ a two phase catalysis (liquid/solid) instead o~ the conventional three phases (gas/liquid/solid) used in most prior art advanced oxidation catalysis improves the reaction rate and reduces catalyst erosion.
AMENDED ~H~
CA 02231193 1998-03-0~
Usually, the ozone-containing gas will be an ozone/oxygen or ozone/air mixture but pure ozone or ozone in admixture with any inert carrier gas can be used.
The catalyst can be in any solid ~orm but usually will be in the ~orm o~ granules, pellets or an integral or monolithic structure especially having a three ~;m~n~ional continuous pore phase. Pre~erably, the catalyst will be monolithic having a low sur~ace area (5 20 m2/g) and/or high porosity ( 2 5 pores per linear inch; 2 2 pores per cm). It is especially pre~erred that the catalyst is in the ~orm o~ ~oamed monolithic structure with high porosity and low pressure drop (5 0.1 bar g; ~ 10 kPa in a cylindrical reactor o~ 1000 mm high and 24 mm ID at a water ~low rate o~ 7 litre/min).
The catalyst pre~erably is a gamma-alumina catalyst, especially undoped gamma alumina optionally on a carrier, especially alpha alumina.
The following is a description by way o~ example only and with re~erence to the accompanying drawings o~
presently pre~erred embodiments o~ the invention. In the drawings:
Figure 1 is a graph of percentage COD removal (ordinate) against ozone consumed (abscissa) ~or a process o~ the invention using a gamma alumina catalyst (Catalyst C3; see Example 1 in~ra) and i~or a conventional (O3/ W ) advanced oxidation process;
AMENDED SHE~
CA 0223ll93 l998-03-0~
Figure 2 is a graph o~ percentage COD L~LI~ovcl (ordinate) against ozone consumed (abscissa) for a process o~ the invention using a monolithic catalyst o~ gamma alumina on an alpha alumina carrier (see Example 2 in~ra) and ~or a conventional (03/W) advanced oxidation process;
Figure 3 is a diagrammatic representation o~ apparatus ~or the removal o~ organic cont~m;n~nts ~rom high strength waste water using a process o~ the present invention; and Figure 4 is a diayL~LLLLuatic representation o~ apparatus ~or the removal o~ organic cont~m~n~nts ~rom low strength waste water using a process o~ the present invention.
Re~erring to Figure 3, a stream (1) o~ waste water which has been treated by conventional microbiological or chemical processes to reduce the COD to 5000 mg/l or less i5 mixed with a recycle stream (2) o~ water containing dissolved ozone. The resultant mixed stream (3) is pumped (4) upwardly through a ~ixed catalyst bed (5) and the bed e~luent (6) is passed to a gas-liquid contactor (7) in which it is thoroughly mixed with an ozone-containing gas (8) ~rom an ozone generator (not shown). The bulk o~ the ozonated water is LeL~Iuv~d in recycle stream (2) but a smaller portion is L~L"ov~d (9) ~or discharge or ~urther treatment. Undissolved gas is removed in a gaseous discharge stream (10) ~or reuse and/or return to the ozone generator.
The process o~ Figure 4 di~ers ~rom that o~ Figure 3 in that the waste water stream (1) is pumped (14) to the gas-liquid contactor (17) where it is mixed with ozone-cont~n;ng gas (8). All o~ the ozonated waste water ~rom the gas-liquid contactor (17) is passed upwardly through the catalyst bed (5). In this process, the spent ozone CA 02231193 1998-03-0~
containing gas is removed (10) ~rom the gas-liquid contactor (17) but the treated waste water discharge (19) is ~rom the catalyst bed (5).
ExamDle 1 Six water stable industrial catalysts in gr~n~ ~ or pellet ~orm were evaluated in a process o~ the present invention. The identity the catalysts is shown in Table 1 and their chemical compositions and geometric characteristics are shown in Table 2.
Table 1 Identitv o~ industrial catalysts evaluated Catalyst Re~ Manufacturer Trade Designation C1 Air Products 159Cp SiO~/Al?O~
C2 Air Products Co-ZSM5 C3 Harshaw Al-4126 C4 Harshaw Co-0502 C5 Engelhard MgO
C6 Harshaw Ag-0105 Table 2 Characteristics o~ industrial catalysts evaluated Re~ wt~ wt~ rpm~ining ~orm sur~ace pore A1~0~ SiO~ area ~olume m2/g cm3/g C~l2l 851 extrudate 300 C281 413~ CoOextrudate 285 C3>952 no addedextrudate 245 0.78 metal C4 18~ CoOpellet 49 0.38 C5 98~ MgOpellet 25 0.27 C6163 1113~ Ag~Opellet 1.5 0.07 1 amorphous (i.e. mixture o~ Al-O-Si bonds rather than Al 2 O3/Si ~2 mixture) 2 gamma alpha When treating a synthetic waste water (prepared by dissol~ing 1000mg/l glucose in tap water; COD 1000 mg/l) cont~;n;ng ozone by the process o~ the invention (O3 dissol~ed prior to contact o~ water with catalyst), these catalysts ~m~trated di~erent e~fectiveness in destruction o~ ozone re~ractory cont~m;n~nts as shown in the ~ollowing Table 3.
-CA 02231193 1998-03-0~
Table 3 COD destruction bv catalytic ozonation process O~ Consumed Re~idual COD (mg/l) mg/l Cl C2 C3 C4 C5 C6 o 990 10271015 970 10401050 As can be seen ~rom Table 3, Catalyst C3, an undoped gamma alumina, had the highest activity ~or COD destruction by the catalytic ozonation treatment. Surprisingly, the catalytic activity was in the order C3 > C5 > C4 > C2.
Catalysts Cl and C6 did not present any signi~icant catalytic e~ect in the catalytic ozonation treatment.
The combination o~ ozone with Catalyst C3 o~ers advantages over the current 03 /W advanced oxidation process in the destruction o~ COD as indicated by the comparative results in Figure 1. The removal o~ COD was much higher with the Catalyst C3 catalytic ozonation than the 03/W process at the same ozone dosages. The ozone required ~or the same degree o~ COD removal by the Catalyst C3 catalytic ozonation is less than 50~ o~ that by the O3/ W process, representing a signi~icant reduction in treatment cost.
Catalyst C3 maint~i ne~ its catalytic activity a~ter 100 hours operation. Municipal secondary e~luent, CA 02231193 1998-03-0~
land~ill leachate, and waste water ~rom a hospital sewer were all satis~actorily treated using this catalyst.
Exam~le 2 The procedure o~ Example 1 was repeated using, as catalyst, a ~oamed monolithic material of 92~ alpha alumina (low sur~ace area) and coated with 5~ gamma alumina (RETI OE L HPA washcoat reticulated ceramic) sold as a ~ilter media. The base material has a pore density o~ 10 pores per linear inch (4 pores per cm) and a calculated sur~ace area o~ 2290 m2/m3 (< 5x10-3 m~/g). The 5~ washcoat increases the sur~ace area to 15 m-/g.
This material achieved similar COD removal rate as the 03/ W process with little back-pressure (see Figure 2).
For example, when a laboratory reactor (1000 mm high and 24 mm ID) is packed with the monolithic material, a pressure drop o~ 0 02 bar g (2 kPa) was recorded at a water ~low rate o~ 7 litre/min compared with 0 8 bar g (80 kPa) ~or Catalyst 3 (in granular ~orm) under the same conditions.
It will be appreciated that the invention is not restricted to the exempli~ication above but that numerous modi~ications and variations can be made without departing ~rom the scope o~ the ~ollowing claims.
ADVANCED OXIDATION OF WATER TJSING C~TALYTIC OZONATION
c The present invention relates to the treatment o~
sur~ace water or aqueous e~luent to remove oryanic impurities there~rom.
Conventional microbiological waste water treatments are e~ective in removal o~ biodegradable oryanic cont~m;n~nts ~rom water. ~owever, recalcitrant organic cont~m;n~nts which are not biodegradable and/or are inhibitory to microbiological activity require chemical oxidation ~or removal. The extent o~ contamination is measured in terms o~ the amount o~ oxygen required to remove the cont~min~nts COD (Chemical Oxygen Demand) is the amount o~ oxygen required to oxidize all oxidizable cont~min~nts in the water to be treated; BOD (Biological Oxygen Demand) is the amount o~ oxygen required to oxidize the biodegradable cont~m;n~nts; and hard COD is the amount o~ oxygen required to oxidize the non-biodegradable cont~min~nts.
Chemical alternatives to microbiological waste water treatment are known. The most usual chemical treatment is the Zimmerman (or ZIMPRO) wet air oxidation process, in which waste water is contacted with air at elevated temperature and pressure, usually 200~C to 370~C at 20 to 200 Atmospheres (2 to 20 MPa). This method is only economical ~or waste water with an organics contents higher than 1~ or an oxidation heat value su~icient to maintain the elevated temperature required.
Various catalysts have been used in the Zimmerman process. These catalysts include noble or heavy metals such as palladium, platinum, cobalt or iron deposited on a CA 02231193 1998-03-0~
W 097tl4657 PCT/GB96/02525 carrier o~, ~or example, alumina, silica-alumina, silica gel, activated carbon, titania or zirconia (see JP-A-49-44556 (1974); JP-A-49-94157 (1974); and JP-A-58-64188 (1983)).
The use o~ ozone to treat water a~ter microbiologica bulk BOD removal is well known. Ozone is the strongest molecular oxidant ~or water treatment and it has been used since the beginning o~ this century in drinking water treatment to provide disin~ection, removal o~ colour, taste and odour, and destruction o~ organic compounds. However, ozone is very selective in its reactions; it predominantly reacts with compounds containing unsaturated bonds such as ole~ins, aromatic compounds and/or compounds cont~in;ng electron rich groups such as sul~ur and nitrogen. For other organic compounds such as saturated alkanes and chlorinated organics (most o~ pesticides and priority pollutants), the reactivity o~ ozone is limited. These ozone re~ractory cont~m;n~nts can be oxidized by hydroxyl radicals which are usually ~ormed by activating ozone with hydrogen peroxide or ultraviolet light ("advanced oxidation").
Hydrogen peroxide has an operation cost higher than ozone and ultraviolet light requires capital and operational costs at least equal to that o~ ozone generation. Accordingly, the activation o~ ozone to hydroxyl radicals by these two methods results in a large increase (50 - 200~) in the cost o~ water treatment.
Moreover, since hydroxyl radical reactions are much less speci~ic than those involving ozone alone, the hydroxyl radicals generated in solution by hydrogen peroxide or ultraviolet light activation o~ ozone can be wasted by reaction with non-target inhibitors or scavengers, such as carbonate and bicarbonate ions, which do not require CA 02231193 1998-03-0~
W O 97/146~7 PCT/GB96/02525 oxidation. Thus, a more cost e~ective method o~ ozone activation is needed.
PL-A-56775 (1969) reported that ozone-containing gas had been used in a continuous oxidation process to puri~y waste water ~rom coke ovens but that the treatment was uneconomic ~or industrial use. It was proposed in PL-A-56775 that the waste water should be continuously treated with ozone-cont~i n; ng gas in a ~roth phase by blowing the gas countercurrent to the waste water in a scrubber packed with Rashig rings, slag and~or oxides or silver, copper, aluminium, zinc, magnesium, tin, lead, iron, or manganese as catalysts.
US-A-4007118 (1977) discloses the ozonation o~ waste water using a transition metal catalyst, such as manganese trioxide, ~erric oxide, copper oxide or nickel oxide, which is present as a powder contained in ~abric bags, disposed on a substrate or dispersed within the waste water US-A-4040982 (1977) discloses a method o~ removing cont~m~n~nts ~rom waste water by treatment with ozone-containing gas in the presence o~ a catalyst comprising ~erric oxide supported on catalytically active alumina and having a sur~ace area o~ 150 to 450 m2/g and a pore volume o~ at least 0.3 C~3 . The exempli~ied alumina is gamma alumina but re~erence is made to eta alumina, amorphous alumina and activated alumina.
JP-A-58-37039 (1983) discloses a method o~ removal o~
an aromatic organic compound ~rom waste water by mixing ~irst with a sur~actant, then with a transition metal or alkaline earth metal compound, and contacting the resultant mixture with ozone-containing gas to oxidatively decompose the organic compound.
CA 02231193 1998-03-0~
W O 9~/14657 PCT/G B96/02525 NL-A-9001721 (1991) discloses the treatment o~ iron-containing waste water by ~orming and L~L,Loving precipitated Fe(III) by mixing with hydrogen peroxidei then ~orming and L~L..o~ing precipitated carbonate by adding, ~or example, calcium hydroxide, calcium chloride and/or alkali metal hydroxidei and subsequently oxidation with, ~or example, ozone-containing gas alone or with a solid catalyst, to remove residual organic compounds. Speci~ied catalysts are activated carbon, alumina or silica. It is stated that the catalyst must have a sur~ace area o~ at least 50 m2/g and a pore volume o~ greater than 0.1 cm3jg and that its activity can be improved by addition o~ a transition metal such as copper, iron, molybdenum or cobalt. In the exempli~ied process, ozone-containing gas is passed through a bubble reactor countercurrently to li~uid e~luent ~rom a catalyst bed and the gas exiting the ~ubble reactor is passed through that catalyst bed cocurrently with the partially treated waste water. I~ required, additional ozone-containing gas can be added to supplement the ozone content o~ the gas exiting the bubble reactor.
US-A-5,145,587 (1992) discloses the treatment o~ waste water by wet oxidation with a molecular oxygen-containing gas in the presence o~ a solid catalyst comprising (i) titanium dioxide; (ii) an oxide o~ a lanthanide element;
and (iii) at least one metal selected ~rom manganese, iron, cobalt, nickel, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium or a water insoluble or sparingly soluble compound thereo~. The catalyst is ~ormed by adding component (iii) to a calcined mixture o~ (i) and (ii) and pre~erably is in the ~orm o~ an integral or monolithical structure, such as an extruded honeycomb (having straight through rhAnn~ls), o~ (i) and (ii) impregnated with (iii). The pre~erred oxidants are oxygen, ozone, hydrogen peroxide or mixtures o~ oxygen with ozone or hydrogen peroxide.
, CA 0223ll93 l998-03-OS
--5- 220PPCT05',22 . 08j97 US-A-5352369 (1994) discloses a method oi~ treating water to kill bacteria therein by contact with a silver catalyst in the presence o~ oxygen to ~orm an active oxidizer in the water. The silver catalyst is ~ormed by depositing elemental silver on an alumina matrix and heating to a temperature o~ at least 300~C. In the pre~erred embodiment ozone-containing gas is used as the source o~ oxygen but it is re~uired that the water be exposed to the silver catalyst as soon as the ozone-containing gas has been added to the water.
JP-A-5-228480 (1993) & JP-A-5-228481 (1993) disclose the removal o~ non-biodegradable contAm;n~nts ~rom raw water by ~irst contacting the water with ozonized air and then treating the ozonated water with at least one o~
hydrogen peroxide, ultrasound, ultraviolet light and a catalyst to generate hydroxyl radicals. In the process o~
JP-A-5-228480 the raw water ~lows in countercurrent to the ozonized air while in the process o~ JP-A-5-228481 the raw water and ozonized air ~low cocurrently. All o~ the exempli~ied processes use a combination o~ ultraviolet light, ultrasound and catalyst in the advanced oxidation section. The only speci~ied catalyst is alumina sur~ace treated with platinum or palladium.
It has now been ~ound that gamma alumina is such an e~ective catalyst ~or the catalytic ozonation o~ water that ozone re~ractory contAm;nAnts can more easily be removed even in the absence o~ hydrogen peroxide.
Thus, according to the present invention, there is provided a process ~or the removal o~ contAm;nAnts ~rom water which comprises contacting the water with ozone in the absence o~ a catalyst to oxidize ozone-oxidizable cont~m;nAnts and to dissolve ozone in the water, and contacting the resultant ozone-containing water with a gamma alumina ozone activation catalyst to oxidize ozone re~ractory contAm;n~nts in the water.
AMENDED SHEET
, CA 02231193 1998-03-0~
--6-- 220PPCT05~Z2. 08/9~
The process o~ the invention permits the use o~ some relatively inexpensive solid catalysts which are widely used in the chemical industry ~or chemical synthesis.
In this invention, the waste water ~irst reacts with ozone in a gas-liquid contactor and the easily oxidisable cont~m;n~nts are removed. The thus treated waste water (~ree ~rom gas bubbles but with residual dissolved ozone) passes through the ozone activation catalyst where the residual ozone is activated to secondary oxidants more reactive than ozone and which decompose cont~m;n~nts remaining a~ter treatment in the gas-liquid contactor. The e~luent ~rom the catalyst treatment can be re-injected to the gas-liquid contactor to absorb more ozone ~or reaction i~ the concentration o~ cont~m;n~nts is too high to reduce in a single pass through the catalyst (i.e. the oxidant demand o~ the waste water is higher than the m~;mnm ozone solubility in water under the operational conditions).
Having regard to the capacity and e~iciency o~
conventional waste water treatments, the waste water treated by the process o~ the invention usually will have a COD o~ at most 5000 mg/l. The extent o~ the advanced oxidation by the process will be determined mainly by environmental requirements, which presently require the COD
o~ waste water to be reduce to at most 125 mg/l be~ore discharge.
In addition to improving the ef~iciency o~ ozone usage in advanced oxidation, the use o~ a two phase catalysis (liquid/solid) instead o~ the conventional three phases (gas/liquid/solid) used in most prior art advanced oxidation catalysis improves the reaction rate and reduces catalyst erosion.
AMENDED ~H~
CA 02231193 1998-03-0~
Usually, the ozone-containing gas will be an ozone/oxygen or ozone/air mixture but pure ozone or ozone in admixture with any inert carrier gas can be used.
The catalyst can be in any solid ~orm but usually will be in the ~orm o~ granules, pellets or an integral or monolithic structure especially having a three ~;m~n~ional continuous pore phase. Pre~erably, the catalyst will be monolithic having a low sur~ace area (5 20 m2/g) and/or high porosity ( 2 5 pores per linear inch; 2 2 pores per cm). It is especially pre~erred that the catalyst is in the ~orm o~ ~oamed monolithic structure with high porosity and low pressure drop (5 0.1 bar g; ~ 10 kPa in a cylindrical reactor o~ 1000 mm high and 24 mm ID at a water ~low rate o~ 7 litre/min).
The catalyst pre~erably is a gamma-alumina catalyst, especially undoped gamma alumina optionally on a carrier, especially alpha alumina.
The following is a description by way o~ example only and with re~erence to the accompanying drawings o~
presently pre~erred embodiments o~ the invention. In the drawings:
Figure 1 is a graph of percentage COD removal (ordinate) against ozone consumed (abscissa) ~or a process o~ the invention using a gamma alumina catalyst (Catalyst C3; see Example 1 in~ra) and i~or a conventional (O3/ W ) advanced oxidation process;
AMENDED SHE~
CA 0223ll93 l998-03-0~
Figure 2 is a graph o~ percentage COD L~LI~ovcl (ordinate) against ozone consumed (abscissa) for a process o~ the invention using a monolithic catalyst o~ gamma alumina on an alpha alumina carrier (see Example 2 in~ra) and ~or a conventional (03/W) advanced oxidation process;
Figure 3 is a diagrammatic representation o~ apparatus ~or the removal o~ organic cont~m;n~nts ~rom high strength waste water using a process o~ the present invention; and Figure 4 is a diayL~LLLLuatic representation o~ apparatus ~or the removal o~ organic cont~m~n~nts ~rom low strength waste water using a process o~ the present invention.
Re~erring to Figure 3, a stream (1) o~ waste water which has been treated by conventional microbiological or chemical processes to reduce the COD to 5000 mg/l or less i5 mixed with a recycle stream (2) o~ water containing dissolved ozone. The resultant mixed stream (3) is pumped (4) upwardly through a ~ixed catalyst bed (5) and the bed e~luent (6) is passed to a gas-liquid contactor (7) in which it is thoroughly mixed with an ozone-containing gas (8) ~rom an ozone generator (not shown). The bulk o~ the ozonated water is LeL~Iuv~d in recycle stream (2) but a smaller portion is L~L"ov~d (9) ~or discharge or ~urther treatment. Undissolved gas is removed in a gaseous discharge stream (10) ~or reuse and/or return to the ozone generator.
The process o~ Figure 4 di~ers ~rom that o~ Figure 3 in that the waste water stream (1) is pumped (14) to the gas-liquid contactor (17) where it is mixed with ozone-cont~n;ng gas (8). All o~ the ozonated waste water ~rom the gas-liquid contactor (17) is passed upwardly through the catalyst bed (5). In this process, the spent ozone CA 02231193 1998-03-0~
containing gas is removed (10) ~rom the gas-liquid contactor (17) but the treated waste water discharge (19) is ~rom the catalyst bed (5).
ExamDle 1 Six water stable industrial catalysts in gr~n~ ~ or pellet ~orm were evaluated in a process o~ the present invention. The identity the catalysts is shown in Table 1 and their chemical compositions and geometric characteristics are shown in Table 2.
Table 1 Identitv o~ industrial catalysts evaluated Catalyst Re~ Manufacturer Trade Designation C1 Air Products 159Cp SiO~/Al?O~
C2 Air Products Co-ZSM5 C3 Harshaw Al-4126 C4 Harshaw Co-0502 C5 Engelhard MgO
C6 Harshaw Ag-0105 Table 2 Characteristics o~ industrial catalysts evaluated Re~ wt~ wt~ rpm~ining ~orm sur~ace pore A1~0~ SiO~ area ~olume m2/g cm3/g C~l2l 851 extrudate 300 C281 413~ CoOextrudate 285 C3>952 no addedextrudate 245 0.78 metal C4 18~ CoOpellet 49 0.38 C5 98~ MgOpellet 25 0.27 C6163 1113~ Ag~Opellet 1.5 0.07 1 amorphous (i.e. mixture o~ Al-O-Si bonds rather than Al 2 O3/Si ~2 mixture) 2 gamma alpha When treating a synthetic waste water (prepared by dissol~ing 1000mg/l glucose in tap water; COD 1000 mg/l) cont~;n;ng ozone by the process o~ the invention (O3 dissol~ed prior to contact o~ water with catalyst), these catalysts ~m~trated di~erent e~fectiveness in destruction o~ ozone re~ractory cont~m;n~nts as shown in the ~ollowing Table 3.
-CA 02231193 1998-03-0~
Table 3 COD destruction bv catalytic ozonation process O~ Consumed Re~idual COD (mg/l) mg/l Cl C2 C3 C4 C5 C6 o 990 10271015 970 10401050 As can be seen ~rom Table 3, Catalyst C3, an undoped gamma alumina, had the highest activity ~or COD destruction by the catalytic ozonation treatment. Surprisingly, the catalytic activity was in the order C3 > C5 > C4 > C2.
Catalysts Cl and C6 did not present any signi~icant catalytic e~ect in the catalytic ozonation treatment.
The combination o~ ozone with Catalyst C3 o~ers advantages over the current 03 /W advanced oxidation process in the destruction o~ COD as indicated by the comparative results in Figure 1. The removal o~ COD was much higher with the Catalyst C3 catalytic ozonation than the 03/W process at the same ozone dosages. The ozone required ~or the same degree o~ COD removal by the Catalyst C3 catalytic ozonation is less than 50~ o~ that by the O3/ W process, representing a signi~icant reduction in treatment cost.
Catalyst C3 maint~i ne~ its catalytic activity a~ter 100 hours operation. Municipal secondary e~luent, CA 02231193 1998-03-0~
land~ill leachate, and waste water ~rom a hospital sewer were all satis~actorily treated using this catalyst.
Exam~le 2 The procedure o~ Example 1 was repeated using, as catalyst, a ~oamed monolithic material of 92~ alpha alumina (low sur~ace area) and coated with 5~ gamma alumina (RETI OE L HPA washcoat reticulated ceramic) sold as a ~ilter media. The base material has a pore density o~ 10 pores per linear inch (4 pores per cm) and a calculated sur~ace area o~ 2290 m2/m3 (< 5x10-3 m~/g). The 5~ washcoat increases the sur~ace area to 15 m-/g.
This material achieved similar COD removal rate as the 03/ W process with little back-pressure (see Figure 2).
For example, when a laboratory reactor (1000 mm high and 24 mm ID) is packed with the monolithic material, a pressure drop o~ 0 02 bar g (2 kPa) was recorded at a water ~low rate o~ 7 litre/min compared with 0 8 bar g (80 kPa) ~or Catalyst 3 (in granular ~orm) under the same conditions.
It will be appreciated that the invention is not restricted to the exempli~ication above but that numerous modi~ications and variations can be made without departing ~rom the scope o~ the ~ollowing claims.
Claims (12)
1. A process for the removal of contaminants from water which comprises contacting the water with ozone in the absence of a catalyst to oxidize ozone-oxidizable contaminants and to dissolve ozone in the water, and contacting the resultant ozone-containing water with a gamma alumina ozone activating catalyst to oxidize ozone refractory contaminants in the water.
2. A process as claimed in Claim 1, wherein the water to be treated has a COD of at most 5000 mg/l.
3. A process as claimed in any one of the preceding claims, wherein the ozonation treatments reduce the COD of the water to at most 125 mg/l.
4. A process as claimed in any one of the preceding claims, wherein effluent from the catalyst treatment is contacted with ozone and recycled for further contact with the catalyst.
5. A process as claimed in Claim 4, wherein the recycled effluent is mixed with fresh waste water prior to recycle through the catalyst.
6. A process as claimed in any one of the preceding claims, wherein the catalyst is a foamed monolithic structure with a pressure drop of at most 10 kPa (0.1 bar g) in a cylindrical reactor of 1000 mm high and 24 mm ID at a water flow rate of 7 litre/min.
7. A process as claimed in Claim 6, wherein the catalyst has a surface area of at most 20 m2/g.
8. A process as claimed in Claim 6 or Claim 7, wherein the catalyst has a porosity of at least 2 pores per linear cm (5 pores per inch).
9. A process as claimed in any one of the preceding claims, wherein the catalyst is undoped gamma alumina optionally on a carrier.
10. A process as claimed in Claim 9, wherein the carrier is alpha alumina.
11. A process as claimed in Claim 10, wherein the catalyst is a foamed monolithic alpha alumina substrate coated with undoped gamma alumina
12. A process as claimed in any one of the preceding claims, wherein contact with the catalyst is conducted in the absence of added hydrogen peroxide.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9521359.1 | 1995-10-17 | ||
| GBGB9521359.1A GB9521359D0 (en) | 1995-10-17 | 1995-10-17 | Advanced oxidation of water using catalytic ozonation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2231193A1 true CA2231193A1 (en) | 1997-04-24 |
Family
ID=10782519
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002231193A Abandoned CA2231193A1 (en) | 1995-10-17 | 1996-10-16 | Advanced oxidation of water using catalytic ozonation |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0859746A1 (en) |
| CA (1) | CA2231193A1 (en) |
| GB (1) | GB9521359D0 (en) |
| TW (1) | TW414783B (en) |
| WO (1) | WO1997014657A1 (en) |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ATE243558T1 (en) * | 1997-10-21 | 2003-07-15 | Karsten Pedersen | CATALYTIC PROCESS FOR THE REMOVAL OF ORGANIC POLLUTANTS IN WATER |
| US6129849A (en) * | 1998-10-23 | 2000-10-10 | Kansai Electric Power Co., Inc. | Process for accelerating reaction of ozone with AM catalyst |
| TW590789B (en) | 2001-09-14 | 2004-06-11 | Ind Tech Res Inst | Method of treating an air stream containing VOCs |
| US8808550B2 (en) * | 2010-03-18 | 2014-08-19 | Air Products And Chemicals, Inc. | Apparatus and method for dissolution of ozone in water and catalytic oxidation |
| US8871098B2 (en) | 2011-09-22 | 2014-10-28 | Air Products And Chemicals, Inc. | Gas dispersion apparatus for improved gas-liquid mass transfer |
| CN105712466B (en) * | 2014-12-01 | 2018-11-06 | 大连福瑞普科技有限公司 | A kind of ozone catalytic wet oxidation method of phenol wastewater |
| CN104986848A (en) * | 2015-07-24 | 2015-10-21 | 天津万峰环保科技有限公司 | Electromagnetic (EM) advanced catalytic oxidation sewage deep treatment process |
| US11124439B2 (en) | 2015-12-07 | 2021-09-21 | The University Of North Carolina At Charlotte | Devices, systems, and methods for heterogeneous catalytic quenching of hydrogen peroxide in a water source |
| US11434153B2 (en) | 2018-03-28 | 2022-09-06 | L'Air Liquide, Société Anonyme pour l'Etude et l'Exploitation des Procédés George Claude | Separation of ozone oxidation in liquid media into three unit operations for process optimization |
| US11084744B2 (en) | 2018-03-28 | 2021-08-10 | L'Air Liquide, Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude | Method for mixing gas-free liquid oxidant with process liquid |
| US10858271B2 (en) | 2018-03-28 | 2020-12-08 | L'Air Liquide, SociétéAnonyme pour l'Etude et l'Exploitation des Procédés Claude | Methods for producing high-concentration of dissolved ozone in liquid media |
| CN110639491B (en) * | 2018-06-26 | 2022-09-16 | 宁波市雨辰环保科技有限公司 | Catalyst for harmless treatment of highly toxic wastewater and preparation method and application thereof |
| CN111646561A (en) * | 2020-06-13 | 2020-09-11 | 深圳市创飞格环保技术有限公司 | Ozone catalytic oxidation reactor for sewage treatment and sewage circulation treatment method |
| CN111792751A (en) * | 2020-06-18 | 2020-10-20 | 神马实业股份有限公司 | Treatment method of caprolactam production wastewater |
| CN112569946A (en) * | 2020-12-28 | 2021-03-30 | 广西柳钢环保股份有限公司 | Ozone catalyst for organic wastewater treatment and preparation method thereof |
| CN112919616A (en) * | 2021-02-18 | 2021-06-08 | 科盛环保科技股份有限公司 | High-efficient ozone catalytic oxidation reactor for advanced treatment of chemical industry park sewage tail water |
| CN113289614B (en) * | 2021-06-03 | 2023-03-17 | 上海庞科环境技术有限公司 | Preparation method of three-dimensional alumina coating ozone catalyst for antibiotic wastewater |
| CN113184975A (en) * | 2021-06-10 | 2021-07-30 | 青岛派尼尔环保技术有限公司 | Advanced catalytic oxidation process for ozone |
| GR1010508B (en) | 2022-05-20 | 2023-07-20 | Αριστοτελειο Πανεπιστημιο Θεσσαλονικης-Ειδικος Λογαριασμος Κονδυλιων Ερευνας, | Method of removing micropollutants by use of heterogenous catalytic ozonation from water |
| CN115228482B (en) * | 2022-08-15 | 2023-09-12 | 广州桑尼环保科技有限公司 | Ozone catalyst taking aluminum sludge as raw material and preparation method and application thereof |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2655641B1 (en) * | 1989-12-07 | 1992-04-24 | Anjou Rech | PROCESS OF OZONATION OF WATER WITH ACTIVATION BY HETEROGENEOUS CATALYSIS. |
| NL9200508A (en) * | 1992-03-19 | 1993-10-18 | E M Engineering F T S B V | METHOD AND APPARATUS FOR CLEANING WATER. |
| JPH06335690A (en) * | 1993-05-31 | 1994-12-06 | Kubota Corp | Ozone catalytic reaction tank |
-
1995
- 1995-10-17 GB GBGB9521359.1A patent/GB9521359D0/en active Pending
-
1996
- 1996-04-19 TW TW85104678A patent/TW414783B/en active
- 1996-10-16 EP EP96935002A patent/EP0859746A1/en not_active Ceased
- 1996-10-16 WO PCT/GB1996/002525 patent/WO1997014657A1/en not_active Application Discontinuation
- 1996-10-16 CA CA002231193A patent/CA2231193A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1997014657A1 (en) | 1997-04-24 |
| EP0859746A1 (en) | 1998-08-26 |
| GB9521359D0 (en) | 1995-12-20 |
| TW414783B (en) | 2000-12-11 |
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