AU702884B2 - Method of disinfecting water - Google Patents

Method of disinfecting water Download PDF

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Publication number
AU702884B2
AU702884B2 AU77150/96A AU7715096A AU702884B2 AU 702884 B2 AU702884 B2 AU 702884B2 AU 77150/96 A AU77150/96 A AU 77150/96A AU 7715096 A AU7715096 A AU 7715096A AU 702884 B2 AU702884 B2 AU 702884B2
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Australia
Prior art keywords
water
value
pool
added
ppm
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AU7715096A (en
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Lennart Olausson
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Priority claimed from SE9504176A external-priority patent/SE9504176D0/en
Priority claimed from SE9602284A external-priority patent/SE9602284D0/en
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    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/72Treatment of water, waste water, or sewage by oxidation
    • C02F1/722Oxidation by peroxides
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/30Treatment of water, waste water, or sewage by irradiation
    • C02F1/32Treatment of water, waste water, or sewage by irradiation with ultraviolet light
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/42Nature of the water, waste water, sewage or sludge to be treated from bathing facilities, e.g. swimming pools

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  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)
  • Mechanical Treatment Of Semiconductor (AREA)

Description

WO 97/19025 PCT/SE96/01506 1 METHOD OF DISINFECTING WATER TECHNICAL FIELD The invention relates to the water treatment technique and especially to a method of disinfecting water intended for baths, particularly for public baths, at which the water has a pH value >7.8 before the disinfection. However, in a wider perspective, it is possible that the invention can also be used to disinfect drinking water.
BACKGROUND OF THE INVENTION In general the disinfectant that is used for bathwater and drinking water is chlorine or certain active chlorine compounds. The chlorination is also used to facilitate the purification of the water by oxidation. In general chlorine gas, sodium hypochlorite, NaCO1, or calcium hypochlorite, Ca(CO1) 2 is used. Either chlorine gas, sodium hypochlorite or calcium hypochlorite is used, an equilibrium is reached in the water between the reactive species hypochlorous acid, HCIO, and hypochlorite ions, C10', that both are so called free active chlorine.
It is widely known that chlorination has a number of negative side effects: undesirable organic chlorine compounds are formed when free active chlorine reacts with organic compounds in the water, the chlorine can have an irritating effect on sensitive persons and chlorine has an unpleasant smell. Furthermore the handling of chlorine or active chlorine compounds is very dangerous for the staff who operate the purification plant.
Despite these disadvantages chlorination has been considered to be irreplaceable for disinfection ofbathwater and drinking water.
However, compounds and techniques have been developed to reduce the amount of added chlorine or chlorine compounds. Chlorination has e. g. been combined with addition of oxidizing agents. Among other things ozone and hydrogen peroxide have been used in combination with chlorine dosage. Furthermore UV-radiation in combination with addition of chlorinating agents have been used.
Since at least ten years another method in which is used hydrogen peroxide in combination with UV- radiation, is also known.This method, however, only has a limited disinfection potential, that among other things is shown in growth of organic matter on filters and in the boundary layer between water and air. Other inconveniences that WO 97/19025 PCT/SE96/01506 2 contribute to the fact that this method has not come into general use, are its high need of labour input and its high costs for installation and operation.
BRIEF DISCLOSURE OF THE INVENTION The purpose of the invention is to offer a method to disinfect water that has enough capacity of disinfection, that does not have high installation and operating costs and that does not require any contribution of chlorine or active chlorine compounds. This can be attained by the invention by adjusting the pH value to a value 7.8, suitably 7.6 and preferably and by adding hydrogen peroxide to the water in order to oxidize existing micro-organisms and other organic matter in the water at the mentioned lower pH value without presence of free active chlorine. Preferably the hydrogen peroxide is added in at least stoichiometric proportion to oxidize existing micro-organisms and other organic matter in the water.The pH value should not be lowered so much that the water gives an acid reaction. The lower pH limit is therefore set to 7.0, preferably to 7.1. The pH value should be adjusted to some value between 7.1 and 7.5, preferably between 7.3 and 7.4. The pH value is suitably adjusted by adding C0 2 'or carbonic acid.
It is also suitable that the alkalinity of the water is kept at a value between 50 and 100, suitably at a value between 60 and 80 mg HCO3" 1 water, in which case the method of the invention is used for disinfection of water in a swimming-pool.
The pH value and the alkalinity can be adjusted to the desired levels by adjusted addition of CO 2 (herein is in the following also included carbonic acid) and H202 that preferably is added into a pipe parallel to the main pipe in a circular flowpath, that also includes the swimming-pool. If only CO 2 is added, the alkalinity expressed as the amount of HC0 3 1 water decreases. On the other hand if both CO 2 and H 2 0 2 are added at the same time into the pipe, HCO3" will be produced, ie. the alkalinity increases. For the best control and regulation of both pH value and alkalinity it is appropriate that CO. H202 and CO 2
HO
2 are added at different periods that do not overlap. A control sequence can thus comprise a first period when CO 2 but no H202 is added to the pipe, a second period when H202 but no CO 2 is added into the pipe and a third period when both CO 2 and H202 are added into the pipe.
In the case the invention refers to disinfection of water in baths, water is continuously lost by evaporation. This water, together with other water that can vanish or divert from the system, is compensated by fresh water. Normally fresh water contains metals which can be in a soluble state as metal ions or as complex ions. If these metals are not WO 97/19025 PCT/SE96/01506 3 removed before fresh water is added into the water in the pool, the metals will gradually be accumulated in the water. Some metals, as aluminium, copper, iron and manganese, can have a great disturbing effect on the disinfecting process by stimulating the decomposition of the hydrogen peroxide, i.e. that it does not fulfil the purpose, or the amount of added H 2 0 2 has to increase considerably to have the desired purification effect. To avoid these problems, incoming fresh water should be purified from such metals which can decompose the hydrogen peroxide. The incoming fresh water should be cleaned so that the water in the pool will contain maximum 0.20 ppm Al, preferably maximum 0.09 ppm Al, maximum 0.10 ppm and preferably maximum 0.005 ppm of each of the metals Cu, Fe and Mn. The purification of the incoming fresh water from the mentioned metals can be carried out by an ion exchanger.
BRIEF DESCRIPTION OF DRAWING The drawing shows schematically the water purification system for a swimming-pool that works in accordance with the method of the invention.
DESCRIPTION OF A PREFERRED EMBODIMENT In the drawing a swimming-pool is designated 1. From the bottom of the pool an outlet waterpipe 2 leads to a coarse screen 3. From the pool 1 also surface water is directed through a pipe 4 to a compensation tank 5 and from there through a pipe 6 to the already mentioned outlet pipe 2, after which the joined flows are directed to the coarse screen 3.
Fresh water can be directed through a pipe 7 to the compensation tank 5. In the pipe 7 there are two ion exchange columns 30 and 31 connected in series of which one is an anion exchange column and the other a cation exchange column, to remove aluminium, copper, iron and manganese from the water.
From the coarse screen 3 the water is circulated further by means of a pump 10 to three filters 11, 12, 13 connected in parallel and through these. After the filters 11, 12, 13 the liquid flow is divided into two flows. One by-pass that represents 5-25% of the total circulating flow is led through a branch pipe 14 while the main part is directed through a mainpipe 15 which is parallel to the branch pipe 14. Both flows in the pipes 14 and are joined in an inlet pipe 16, through which treated water is directed into the pool 1. For measurement of the content of hydrogen peroxide and the pH value of the water in mainpipe 15, a very little flow is at the measuring points directed through a pipe 17 for analysis of H 2 0 2 in the measure equipment 18 and for analysis ofpH in the measure equipment 19 and then back to outlet pipe 2.
WO 97/19025 PCT/SE96/01506 4 The branch pipe 14 goes through a safety cabin 21. In this safety cabin there is one or several containers 22 containing H202. From a container 22 hydrogen peroxide is dosed into the water in branch pipe 14 by means of a pump 32 which pumps hydrogen peroxide from the container 22 and directs it into the branch pipe 14 at a point in the safety cabin 21. After, before and/or simultaneously with the addition of hydrogen peroxide, carbon dioxide is added to the water in the branch pipe 14 from one or several carbon dioxide bottles 24 via a pipe 25 with a valve 34.
The measurement test results of the H202 and the pH registered by the measuring equipment 18 and 19, are processed in a computer 33 in accordance with a control program that has been programmed into the computer for controlling the pump 32 for supply of H 2 0 2 as well as the valve 34 for supply of CO 2 to the branch pipe 14. A control sequence can consist of the following parts. First the valve 34 is opened for adding of C02 and is kept open during a certain period of time, depending on pH value registered by the measuring equipment 19, after the valve 34 once again is closed at command from the computer 33. The pump 32 is during this first period inactive. Then the pump 32 starts and a certain amount of H202 is pumped into the pipe 14 from the bottle 22 depending on the content ofH 2 02 registered in the measuring equipment 18 and in accordance with the program in the computer 33, after which the pump 32 is stopped once again. During the third period the pump 32 is once again active and is pumping H202 from the container 22 into the pipe 14, simultaneously as the valve 34 is open, so that also CO 2 is led into the pipe 14 to rise the alkalinity to the desired level.
Alternatively the second and third period can follow directly after each other, i. e. the pump 32 has to work continuously during the mentioned second and third periods. It should be realized that this control sequence can be varied, so during certain control sequences only some of the mentioned periods are active. It is also possible during each control sequence to lead in H202 first and then CO 2 The essential point is that CO 2 and H202 can be added separately as well as simultaneously for deliberate and controlled mixing of CO 2 and H202, so that it is possible to regulate during a control sequence either the pH value, the value of H 2 0 2 or the alkalinity.
ACHIEVED RESULTS The invention has been developed primarily for disinfecting water for public baths.
Normally such water has a pH value over 8 and there are pH values right up to about pH 9. In the experiments which the invention is based on, the above described equipment, was used, and the treatment was in the way that immediately is evident from the description of the equipment. The volume of the pool 1, see figure, was 30 m3. The pH WO 97/19025 PCT/SE96/01506 value was lowered by addition of carbonic acid, CO 2 Before the adjustment ofpH the water had a pH value of 8.6. Hydrogen peroxide was added in varying amounts as a disinfectant. In each experiment was investigated how much hydrogen peroxide that had to be added, at different pH values, to keep the concentration of H202 in the water at 90 ppm, after it had been contaminated by 30 persons. It was presumed that 30 persons is a big enough population to give an acceptable statistic mean value of the whole contamination of the water in form of bacteria, other micro-organisms and other organic matter. The results are shown in the following table.
pH value after adding CO 2 Added amount ofH 2 0 2 litres 8.2 7.8 7.6 4.2 7.30-7.40 -2.1 7.28 4.2 It is evident from the table that the capacity of the hydrogen peroxide to oxidize organic matter in water and thus its capacity to destroy micro-organisms, in other words its disinfecting capacity, was strongly dependent on the pH value. While 40 litres of H 2 0 2 were required to maintain a concentration of H202 of 80 90 ppm in the water at pH 8.2, which indicates a very high consumption of H202 to maintain the intended oxidation effect, only approximately 2.1 litres ofH 2
O
2 were required to maintain the same effect at pH 7.30 to 7.40. At pH values under 7.30 the filters started to silt up with organic matter, which required increased addition of HzO2.
Successful operation tests with a lowering of the pH-value in bathwater to approximately 7.4 by adding CO 2 and using H202 as the only disinfectant, have verified the reliability of the method. The optimum pH in the plant in question was 7.37. The reliability of the method indicates that the concentration of H202 in water can be kept at a level lower than 80 ppm. According to this conceivable development H202 is added in such amount that the concentration of H 2 2 in water is maintained within the interval 10 70 ppm, preferably within the interval 10 50 ppm.
It should be realized that the invention is not limited to the use of CO 2 or carbonic acid to lower the pH-value. Other acids may probably also be used. However, other oxidation agents, e.g. ozone, should not supplement the addition of hydrogen peroxide, since it can disturb the integrated process. On the other hand nothing obstructs that e.g. UV- WO 97/19025 PCT/SE96/01506 6 radiation in a manner known per se, supplements the disinfection by means of hydrogen peroxide and eventually other chemical disinfectants, provided that chlorine or chlorine compounds are not used. It can also be suitable to add chemicals directly to the swimming-pool 1, e.g. sodium bicarbonate, to increase the alkalinity in the water in question, which does not contain active chlorine. This can simply be made by throwing the chemicals into the pool at the end of the day to let it mix and work during the night.
It is suitable that the alkalinity is at alevel corresponding to 60 and 80 mg HC0 3 O/1 water.

Claims (14)

1. P:\OPER\AXD\77150-96.SPE 23/12/98 -7-THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. Method for disinfection of water that has a pH value 7.8, characterized in that pH value is adjusted to a value between 7.0 and 7.6, and that hydrogen peroxide is added to the water at the said lower pH value in sufficient amount to maintain a level of H 2 02 of 50-150 ppm in the water in order to oxidize, without presence of free active chlorine and without presence of ozone, any micro-organisms and other organic matter existing in the water.
2. Method according to claim 1, characterized in that the pH value is adjusted to at least
7.1 but less than 3. Method according to claim 2, characterized in that the pH value is adjusted to between 7.3 and 7.4. 4. Method according to any of claims 1-3, characterized in that the pH value is adjusted by means of carbon dioxide or carbonic acid. 5. Method according to any of the claims 1-4, characterized that hydrogen peroxide, H202, is added in a sufficient amount to maintain a level of H 2 0 2 of 80-90 ppm. 6. Method according to any of the claims 1-4, characterized in that hydrogen peroxide, H202, is added in a sufficient amount to maintain a level of H 2 0 2 of 50-70 ppm in the water. 7. Method according to any of the claims 1-6, to disinfect water that is circulated in a path in which is included a swimming-pool 1, characterized in that the hydrogen peroxide is added to the water in a shunt or branch pipe (14) through which is led 5-25% of the total water flow to the pool.
8. Method according to claim 7, characterized in that the addition of CO 2 or carbonic acid to the water is done in the same shunt or branch pipe (25) to which the hydrogen 8/'>7 P\ P:\OPER\AXD\77150-96.SPE 23/12/98 -8- peroxide is added.
9. Method according to claim 7, characterized in that the addition of C0 2 or carbonic acid to the water is done in another shunt or branch pipe than to which the hydrogen peroxide is added. Method according to any of the claims 7-9, characterized in that the pH value is measured in the water in the said path at a point after the pool but before the addition of hydrogen peroxide and, whenever appropriate, before the addition of the carbon dioxide or the carbonic acid.
11. Method according to any of the previous claims, characterized in that the alkalinity of the water in the pool is maintained at a value corresponding to a value between 50 and 150, suitably at a value corresponding to a value between 60 and 80 mg HC03-/1 water.
12. Method according to any of the claims 7-8 or 10-11, characterized in that CO 2 or carbonic acid and hydrogen peroxide are added at the same time into the same pipe leading to the pool in order to increase the alkalinity of the water in the pool, so that it is kept at a level corresponding to at least 50, suitably at least 60 mg HCO 3 water.
13. Method according to any of the claims 7-8 or 10-12, characterized in that CO 2 or °o carbonic acid is added without simultaneous addition of hydrogen peroxide into a pipe leading :to the pool in order to decrease the alkalinity so that it is kept at a level corresponding to maximum 100, suitably to maximum 80 mg HCO-/1 water.
14. Method according to the claims 12 and 13, characterized in that CO 2 or carbonic acid, as well as hydrogen peroxide, and also CO 2 or carbonic acid together with hydrogen peroxide are added in said pipe during different periods, so that during each such period regulated amounts of said chemicals are added in order to keep the alkalinity of the water at a level corresponding to between 50 and 100, suitably between 60 and 80 mg HC03-/1 water. r 0 7 0 U 9 P:\OPER\AXD\77150-9.SPE 23/12/98 -9- Method according to the claims 7-14, characterized in that fresh water is added to said path to replace water that leaves the path, including water that evaporates, at which the fresh water, before it is led into the path, is cleaned with reference to at least some of the metals belonging to the group of metals consisting of aluminium, copper, iron and manganese.
16. Method according to claim 15, characterized in that incoming fresh water is cleaned with reference to aluminium, so that the amount of aluminium in the water in the pool does not exceed 0.20 ppm, preferably does not exceed 0.09 ppm.
17. Method according to claim 15, characterised in that incoming fresh water is cleaned with reference to copper, so that the amount of copper in the water in the pool does not exceed 0.10 ppm, preferably does not exceed 0.05 ppm.
18. Method according to claim 15, characterised in that incoming fresh water is cleaned with reference to iron, so that the amount of iron in the water in the pool does not exceed 0.10 ppm, preferably does not exceed 0.05 ppm.
19. Method according to claim 15, characterised in that incoming fresh water is cleaned with reference to manganese, so that the amount of manganese in the water in the pool does not exceed 0.10 ppm, preferably does not exceed 0.05 ppm. o
20. Method substantially as hereinbefore described with reference to the accompanying drawings. S.DATED this 23rd day of December, 1998. LENNART OLAUSSON By his Patent Attorneys: DAVIES COLLISON CAVE
AU77150/96A 1995-11-23 1996-11-20 Method of disinfecting water Ceased AU702884B2 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
SE9504176A SE9504176D0 (en) 1995-11-23 1995-11-23 Ways to disinfect water
SE9504176-0 1995-11-23
SE9602284A SE9602284D0 (en) 1996-06-10 1996-06-10 Ways to disinfect water
SE9602284-3 1996-06-10
PCT/SE1996/001506 WO1997019025A1 (en) 1995-11-23 1996-11-20 Method of disinfecting water

Publications (2)

Publication Number Publication Date
AU7715096A AU7715096A (en) 1997-06-11
AU702884B2 true AU702884B2 (en) 1999-03-11

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AU77150/96A Ceased AU702884B2 (en) 1995-11-23 1996-11-20 Method of disinfecting water

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EP (1) EP0956270A1 (en)
JP (1) JP2000500395A (en)
AU (1) AU702884B2 (en)
CA (1) CA2236375A1 (en)
NO (1) NO982317D0 (en)
WO (1) WO1997019025A1 (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3574400B2 (en) 2000-12-04 2004-10-06 株式会社 高千穂 Building Rainwater Utilization System
ES2528396B1 (en) * 2013-08-07 2015-11-19 Metalast S.A.U. Carbon dioxide injection system for water treatment
ES2434140B1 (en) * 2013-08-07 2014-10-07 Metalast S.A.U. Carbon dioxide supply system for water treatment

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0495707A1 (en) * 1991-01-16 1992-07-22 OTV (OMNIUM de TRAITEMENTS et de VALORISATION) Method and device for the oxidation of organic micropollutants in water by O3/H2O2 coupling

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH605421A5 (en) * 1976-04-02 1978-09-29 Schweizerische Sodafabrik Disinfecting water using hydrogen peroxide
DE2852475C2 (en) * 1978-12-05 1980-05-22 Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler, 6000 Frankfurt Process for the automatically controllable detoxification of wastewater containing nitrite ions

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0495707A1 (en) * 1991-01-16 1992-07-22 OTV (OMNIUM de TRAITEMENTS et de VALORISATION) Method and device for the oxidation of organic micropollutants in water by O3/H2O2 coupling

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CA2236375A1 (en) 1997-05-29
WO1997019025A1 (en) 1997-05-29
EP0956270A1 (en) 1999-11-17
NO982317L (en) 1998-05-20
JP2000500395A (en) 2000-01-18
AU7715096A (en) 1997-06-11
NO982317D0 (en) 1998-05-20

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