WO2007057940A1

WO2007057940A1 - Water disinfecting apparatus and method

Info

Publication number: WO2007057940A1
Application number: PCT/IT2006/000804
Authority: WO
Inventors: Ralph Bohnstedt; Reinhard Bartsch
Original assignee: Idrovital Srl
Priority date: 2005-11-17
Filing date: 2006-11-17
Publication date: 2007-05-24
Also published as: ITRM20050572A1

Abstract

Completely automatic water disinfection system that, through the use of reactors, produces disinfecting liquids starting from aqueous solutions according to the electrochemical activation principal and injects these liquids into the existing water pipe network. The individual phases of the production are composed of the demineralisation (2) of the entry water (1), the temporary storage for the salt concentration (3) , the subsequent mixing (4) of the concentrated brine with the demineralised water, the treatment through the electrochemical reactors (5) and the temporary storage of the resulting product (6) that is then in¬ jected into the water supply network to be subjected to the treatment. After completion of a production cy¬ cle, a washing of the electrochemical reactors (5) is performed using a wash solution (7) ; all the process phases are controlled and monitored by an electronic programmable logic control (9) .

Description

"WATER DISINFECTING APPARATUS AND METHOD"

This invention concerns a completely automatic apparatus and method for disinfecting water and for the purification of drinking water and consumption water, including the elimination of biofilms in both the cold water pipes as well as hot water pipes, in open and closed systems for water supply and distribution, through a proportional dosing into the water supply network of an electrochemically activated aqueous solution of sodium hypochlorite that is produced and temporarily stored in the same apparatus for immediate use.

Technical field of the invention

Both the water supply networks and the fixed and stationary containers, which go under the name of wa- ter supply systems, are often contaminated with germs and do not satisfy the maximum limits on germ concentrations allowed by the Italian legislative decree N. 31 (implementation of the directive 98/83/EC on the quality of water intended for human consumption) . This is the cause of infections occurring among the water users (such as Legionnaires' disease) .

In addition to the micro-organisms that float freely in the water, the formation of the so-called biofilm is also significantly important, i.e., the formation of colonies of micro-organisms that colonize the internal surfaces of the pipes protecting themselves with a mucous layer that safeguards these colonies from various methods of disinfection. The waterworks provide hygienically impeccable drinking water up to the main water pipe, i.e., normally up to the user's water meter. The amendment of the European Directive on drinking water unquestiona- bly attributes to the user or to the building manager the responsibility for the observance of the maximum contamination values downstream from the water main. Therefore the user or building manager will also be liable - in the capacity of reseller of the drinking water - for any damages according to the current laws. It is for this reason that the disinfection carried out by the manager of a unit that consumes water is also denominated ' secondary disinfection of the water' . Technical state

Today, the usual systems recognised for secondary disinfection of the water can, for the most part, be divided into methods with an immediate effect and those with a deposit effect; they can also be sepa- rated into physical and chemical procedures. The secondary treatment, that is to say the treatment of the drinking water supplied to a building or complex of connected buildings, becomes even more important for public institutions, especially clinics, hospitals, and resting homes, in which the patients are subjected to a greater risk of nosocomial infection due to a weakened immune system. Due to a legal responsibility of the manager, this also holds for other types of lodgings, nurseries, other public institutions and housing structures subject to centralised administration. An additional fundamental point is the treatment of water for the food industry as well as the process and cooling water sector. The analyses carried out in the hospitals have disclosed frightening results which clearly demonstrate the urgent need to take action, and this. - contrary to public opinion - is also true in new buildings and new attached buildings.

One method that is often applied and quite widespread for the disinfection of infested water supply networks is the so-called thermal treatment, either applied as long-term heating at temperatures above 70 ⁰C or as periodic heating at partially higher temperatures. The disadvantages of this method are the high costs for energy, the heavy deposit of limescale due to thermal precipitation of the limescale, the danger of damaging pipes not suited to the high temperatures as well as any damages from corrosion. An additional important disadvantage of this method is that it is not applicable in the cold water pipes. Analyses carried out have demonstrated that even the cold water pipes can be infested just the same as the hot water pipes. Furthermore, this treatment denominated thermal shock' has no long-term effect. Thus this method must always be applied periodically.

With regard to the physical systems, for the most part ultraviolet radiation is applied in order to disinfect hot and cold running water. Nevertheless, this radiation does not allow for treatment of the biofilms in the pipes upstream and downstream. The ultraviolet light has effect exclusively on the water that is about to flow through the glass tube. The biofilm in the pipes downstream will, however, contaminate the water again.

Chemical systems for secondary treatment of the water mainly make use of applications of chlorine, hy- drogen peroxide, ozone, silver and copper.

The concentrated use of chlorine, ozone and hydrogen peroxide means that the water pipes are not use- able for the entire duration of the intervention. Thus this method is not always applicable in the buildings subject to continuous use; moreover, it must be repeated continuously.

A continuous treatment with chlorine or ions of silver or copper does not allow a successful intervention that would guarantee, at the same time, the ob- servance of the maximum values of these substances allowed for drinking water. Moreover, continuous treatment with high additions of chlorine, even if limited over time, increases the danger of trihalogen methane formation and favours problematic contaminations such as, for example, Legionella since these are not reached and eliminated in their habitat, in other words inside the amoebae located in the biofilm.

Another way to proceed is the production of chlorine dioxide on site which uses two reagents, an acid and a chlorite. This method requires, however, the storage of chemical substances as well as the observance of the relative directives concerning safety, workplace safety and building safety.

In addition, it is possible to use various tech- niques of electrolytic oxidation that disinfect the running water, the entire quantity of water introduced or a part of this in by-pass. These systems allow for a remarkable decrease in the contamination of bacteria since they are also able to eliminate the biofilms, but they are not authorised since they have the seri- ous drawback of not preventing or controlling either the chemical reactions caused by the various substances contained in the water or the creation of un- desired and harmful secondary products.

The disadvantages of the systems and methods cited above and available today on the market are thus such that it can be reasonably stated that no system exists which can simultaneously fulfil in a long-lasting manner the conditions set by a modern water disinfection system. These conditions are the following: • Observance of the maximum values according to the Italian legislative decree N. 31 (implementation of the directive 98/83/EC on the quality of water intended for human consumption) . • No harmful chemical substances.

• Both immediate and long-term effect of the disinfecting agent.

• Elimination of the so-called biofilm, in other words the resistant layer of various micro-organisms inside the water pipes.

• No alteration of the acidic-basic equilibrium of the water and no damage that would result, such as corrosion for example.

• Convenient application without the need for particular safety measures in order to use the relative water pipes and without the need to completely close the pipes to public access, even if only for a limited period. Description of the invention

The task of this invention is that of realising a disinfection apparatus that satisfies the conditions listed above and at the same time is effective, environmentally compatible and has an efficient price- performance ratio.

According to the invention, this objective is achieved by the use in the water supply network of electrolytically activated disinfection solutions and integrating this fundamental technology in a compact apparatus which is easy to produce. Many detailed studies have demonstrated a strong bactericidal and fungicidal effect of the solutions produced with electrochemical activation systems. This technology, of Russian origin, involves the electrochemical treatment of lean brine through highly developed reactors in which the chamber of the anode and the chamber of the cathode are separated by a membrane. A solution is obtained which is highly activated and metastable, the active ingredient of which is sodium hypochlorite. It can be produced either as an acidic substance or neutral substance. The secondary product - an alkaline solution - is normally discarded.

This sodium hypochlorite solution is characterised by a very high oxidation-reduction potential but is intended - due to subsequent loss of effectiveness - to immediate use. In order to rectify this drawback, according to this discovery, this disinfecting agent is produced and injected in a totally automatic manner into the water supply network to be disinfected, through a dosing pump that collects the disinfecting agent from a temporary storage container in a quantity set by a programmable logic control unit.

In a preferred evolutionary plan of the invention, the disinfection apparatus which is described has an inlet for the water that ensures the arrival of cold water to be subjected to the treatment. This in- let is designed with suitable technical devices, for example, check valves to prevent the water from flowing back into the collection point.

The added water is demineralised through suitable treatments in conformity with its composition. This normally occurs through a simple exchange of ions that eliminates the harmful ions (damaging) of calcium and magnesium in the apparatus. The presence of these elements would result in damage, or at least the continuous periodic replacement of the membranes or other parts subject to obstruction and formation of plaque inside the electrochemical reactors, for example, the support mesh, electrodes and channels. The softening would be regulated at zero French degrees of hardness, which is equivalent, in more modern units, to zero mmol/1, a value which is difficult to reach with equipment currently available on the market. With regard to this problem of a minimum permanence of calcium or magnesium, there is also provided a self- purification phase which is described below. Under ^' certain conditions, it may also be necessary to elimi- nate iron and manganese or even to use a process of reverse osmosis.

The demineralised water treated with this method (hereafter also denominated process water) is stored in a first container equipped with hydrostat. In this first container the water is balanced in a saturated state of about 28%, adding tablets of table salt by hand. This water brought to the maximum salt concentration is used for the regeneration of the aforesaid ion exchanger, as well as for the additional salting of the process water.

If necessary, the true production of the disinfectant is activated through an information request on the filling level of the tank where the same disinfec- tant is stored once produced and that is equipped with a hydrostat. If the level is insufficient and must be integrated, fixed quantities of process water, in line with the dimensions of the system, are salted with concentrated brine through suitable equipment, nor- mally diaphragm pumps.

The lean brine produced in this manner is, then, sent to the reactors that operate on the basis of the electrochemical activation principal in order to undergo the electrochemical treatment that transforms it into a powerful disinfectant that is collected in the storage tank referred to above. The concentration of this brine depends on the power absorption of the reactors and normally amounts to 0.4% - 0.5% NaCl content. This value corresponds with an electrical con- ductance of approximately 6.5 mS . The solution thus produced is injected, by means of the dosing pump, into the water supply network to be disinfected. The quantity dosed is controlled either exclusively in a manner proportional to the volume (flow-rate) or exclusively based on the measured values of the level of free chlorine, or on the basis of a combination of these two methods.

All the phases of the process are controlled by a programmable logic control (PLC) . Through special pro- grams, it can be connected to existing computer systems, tele-control systems and LAN networks.

This water disinfection apparatus and process that has been invented satisfies, among other things, the following functions and obtains the following advan- tages:

• low chlorine pollution with simultaneous effectiveness

• neutral Ph value, thus no corrosive effect

• cost-savings due to a possible lowering of the delivery temperature of the sanitary hot water

• the storage of chemical substances and the observance of related safety regulations

(building safety and work safety) are not necessary

• elimination of the biofilm

• deposit effect and barrier effect of the disinfection

• treatment of both hot and cold water • secondary product (alkaline solution) still useable The invention would be clearer referring to the attached design tables that illustrate, by way of non-restrictive example, the preferred realisation form. In the tables: fig.l illustrates the water disinfection apparatus according to the invention through a schematic representation of the sequences of processes and fig.2 illustrates the water disinfection apparatus according to the invention representing its hy- draulic and electric components as well as their connection.

With reference to figure 1, the main phases of the process covered by the discovery are: the deminerali- sation 2 of the water that is introduced into the ap- paratus through the inlet 1, the temporary storage for the concentration of salt, 3, the subsequent mixing 4 of the concentrated brine with the added demineralised water, the treatment through the electrochemical reactors 5 and the temporary storage of the resulting product 6.

After completion of a process cycle, a washing of the electrochemical reactors 5 is performed using a wash solution 7.

This cleaning is indispensable for the operation of the equipment, in order to prevent obstructions inside the electrochemical reactor and guarantee its operation. The injection into the water supply network to be disinfected is marked with the number 8. It should be noted that the phases illustrated under the numbers 1 and 8 do not necessarily have to refer to the same water system. Additional details and the respective effects are described below referring to the water disinfection apparatus illustrated schematically in figure 2, where the references are the following: 1. Water inlet

2. Demineralisation

3. Storage of brine

4. Mixing unit

5. Electrochemical reactors 6. Storage of the product

7. Storage of the wash solution

8. Injection unit

9. Electronic control / PLC control 10. Opening and closing instruments 11. Level control sensors

12. Wash liquid and salt dosage

13. Process water control unit

14. Product control unit

15. Discharge of the alkaline product 16. Water meter

17. Chlorine measurement

The water made available at the inlet 1 of the apparatus, which is normally collected from the water system to be subjected to the treatment, must have chemical and physical properties such as to be suitable for the subsequent phases . The attachment to the existing water pipe systems is equipped with suitable technical devices such as for example the check valve, Ia, that prevents undesired backflow. Within the pro- duction and use of disinfectants, the legislation requires the assembly of this check valve. In the event of the supply of drinking water, it is normally presumed that it does not contain contaminations that can cause damage to systems downstream, as for example a high iron content. Therefore it is sufficient to re- move any calcium and magnesium content through a customary softener in order to satisfy the requirements for completely desalinated process water. If the added water should have characteristics different from those cited above, it will be necessary to take appropriate technical measures for the conditioning of the water, as for example the use of a system based on reverse osmosis .

Phase 2 is generally described as the deminerali- sation; the demineralised (completely desalinated) wa- ter provided is sent both into a storage container 3 as well as the mixing unit 4 through the activation of the opening and closing instruments 10 controlled by the electronic control 9. This equipment is normally composed of electromagnetic valves, pneumatic systems and groups of electromagnetic valves.

The container 3 for the storage of the concentrated brine is equipped with level sensors that regulate - through the electronic control unit - the automatic filling and that, moreover, transmit an impulse used for the signalling of alarms in case of anomalies or the attainment of a level which is lower than that allowed.

The salt used for the concentration of the brine must be added by hand; the size of the storage is con- ceived so as to allow a sufficiency of the contents of at least one week. The added salt must certainly sat- isfy the purity requirements prescribed in accordance with the corresponding regulations in order to prevent undesired substances from be introduced into the system. The request for production, which is communicated to the electronic control 9 by the level control in the product storage tank 6, starts the true production process. For this purpose the instrument 10 is activated to add the process water 2, collecting it from the mixing unit 4 while a pump 12 or different dosing devices, such as Venturi check valves for example, add to this water, in preset proportions, a concentrated salt solution collecting it from the storage container 3; in this manner an addition of approximately 4 gr/1 of sodium chlorite is normally performed.

The resulting solution passes through a device to completely mix the components; this can be a container with specially designed ram mixer or other device that guarantees a homogenous mixing of the liquids through vortex mixing.

The correct ratio between flow-rate and salt addition is measured and controlled by means of the control 13. For this purpose it uses a flow-rate meter with regulation of the quantity or an analog and digi- tal pressure reducer for the quantification and regulation of the water quantity as well as a conductivity measuring instrument, which allows the measurement and regulation of the salt content through the electrical conductivity attained. In the mixing unit 4 there is also incorporated the admission of the wash liquid that is collected from a container 7, which can be filled by hand, in a semi-automatic manner with float valve or automatic manner in relation to the liquid chosen. This unit is used to inject or fill the reactor group 5 with water without the brine - after the end of the production cycle - and contains the wash liquid to remove any residue and prevent encrustation caused by the escape of small parts of calcium and magnesium in phase 2 of the demineralisation or caused by the still salt wa- ter.

The wash cycle is freely programmable, but is normally composed of two phases: in the first phase there occurs the addition of the wash liquid, in the event it concerns a concentrate, hydrochloric acid for example, or the filling if it concerns a solution, for example saturated citric acid, the second phase is without this addition with the result that during the production pauses the reactors are exclusively filled with demineralised water. After the concentration of salt and the mixing in 4, the process water thus produced is now subjected to the true treatment and is transformed through the electrochemical treatment in the reactor group 5 into a valuable disinfectant that is made available in con- tainer 6 for future use.

This method using electrochemical reactors includes a refined form of the well-known electrolysis. With a separatory membrane between the anode chamber and the cathode chamber, it is possible to separate the products dissociated through the electrochemical activation obtaining, in this manner, on one side - depending on the execution - an acidic or neutral solution with high oxidation-reduction potential for purposes of disinfection and, on the other side, a basic solution that is normally discarded, even though it could be used for cleaning purposes.

These reactors are powered by specially developed transformers that allow to ensure high current-voltage ratios with high constant amperages in order to guarantee constant quality of the electrochemically acti- vated product. For technical safety reasons, it operates with direct current . Normally the correct operation of the reactors is controlled by the observance of the amperage, but it can also be checked through the control unit 14 by means of the measurement of the Ph value, the chlorine concentration and the oxidation-reduction voltage.

The reactors unit, therefore, has two outlets in which the first transports the product to be used during the production cycle into the container 6 and the second is directly connected to a discharge outlet 15. Immediately after the end of production, an instrument 10 interrupts the first connection and another instrument 10 opens a connection that allows the liquid, which is passing through the reactor in the wash cy- cle, to be delivered to the second outlet connected with the discharge outlet 15.

Now, if necessary, a pump 8 - normally a dosing diaphragm pump that forms an integral part of the injection unit - collects the product from the storage container 6 and injects it into the water supply network to be subjected to the treatment. The pump can be controlled by impulses issued from an especially inserted water meter in electrical contact 16 or, also, through the measurement of the level of free chlorine 17 or even a combination of these two methods. An electronic control 9 has the function of coordinating all the components involved in the production process and ensuring a correct operation of all the phases of production, washing and stand-by. With the aid of suitable computer instruments, the use of a programmable logic control (PLC) also allows the display and recording of all the measurable parameters. Both the state of the system as well as the notification of operation errors can be transmitted to the display of the keyboard or be sent via telephone con- nection or even transmitted to a LAN network.

Up to this point the preferred evolution plan of the invention has been described. However, it is obvious that numerous modifications and variations may be made by the experts in the field without going beyond the scope of protection of this invention as defined by the claims that follow.

Claims

1) Process for the disinfection of water and for the decontamination of drinking and industrial water in open and closed water systems, including the elimina- tion of biofilms, characterised by the fact that it includes the following phases: a) demineralisation of cold water coming from the water system to be subjected to the disinfection treatment or from another source; b) temporary storage of part of the demineralised water obtained in this manner in a storage container, where the concentration of salt is increased by the addition of salt until obtaining concentrated brine; c) mixing of the concentrated brine with the deminer- alised water in preset proportions; d) treatment of the lean brine resulting from phase c) by means of membrane electrochemical reactors of a well-known type, that operate on the basis of the electrochemical activation principal in order to ob- tain an acidic or neutral solution with high oxidation-reduction potential to be used as a disinfecting agent; e) wash cycle of the reactors cited in phase d) f) temporary storage of said disinfecting agent in a storage tank; g) collection of said disinfecting agent from its storage tank and injection into the water supply network to be subjected to the treatment;

2) Process as described in claim 1 characterised by the fact that all the phases of the process are controlled and monitored by an electronic programmable logic control that works in combination with suitable instruments for detection of the level of brine in the container for the brine storage, instruments to control the ratio between the flow-rate of the demineral- ised water and the brine, instruments for detection of the level of the disinfecting agent in the storage tank of the disinfecting agent, and instruments to control the correct ratio between the flow-rate of the water supply network and the addition of the disin- fecting agent.

3) Process as described in the preceding claims, characterised by the fact that after completion of a production cycle, a washing of the electrochemical reactors is performed using a wash solution.

4) Process as described in the preceding claims characterised by the fact that said washing occurs in two phases: in the first phase there occurs the addition of the wash liquid, in the second phase only the washing is carried out so that during the production pauses the reactors are exclusively filled with demin- eralised water.

5) Process for the disinfection of water according to claim 2, characterised by the fact that the temporarily stored disinfecting agent is injected into the water supply network in quantities dosed in a manner proportional to the flow-rate of the water or based on measured values of the level of free chlorine or a combination of these two methods.

6) Process as described in any of the preceding claims characterised by the fact that it is applicable to both cold water pipes as well as hot water pipes.

7) Automated apparatus for the disinfection of water and for the decontamination of drinking and industrial water in open and closed water systems, including the elimination of biofilms, characterised by the fact that it includes : instruments for the entry of the water (1) that ensure the supply of cold water; instruments (2) in order to completely demineralise said water; a container (3) for temporary storage where part of the demineralised water is collected and mixed with salt in order to obtain a concentrate brine of sodium hypochlorite, said tank being equipped with level sensors; a mixing unit (4) where demineralised water is mixed with the brine coming from the container (3) in preset proportions under the control of a control device (13) in order to obtain a lean brine; at least one membrane electrochemical reactor of a well-known type, that operates on the basis of the electrochemical activation principal, where said lean brine is treated to obtain an acidic or neutral solution with high oxidation-reduction potential to be used as a disinfecting agent; a storage container (6) where said disinfecting agent is temporarily stored; an injection unit (8) suitable to collect the disinfecting agent from the storage container (6) in order to inject it into the water supply network to be sub- jected to the disinfection treatment; instruments (16) to regulate the quantity of disinfecting agent that the injection unit 8 injects; an electronic control (9) having the function of coordinating all the components involved in the production process and ensuring a correct operation of all the phases of production, washing and stand-by.

8) Automated apparatus as described in claim 7 characterised by the fact that the demineralised water is sent both into the storage container (3) as well as the mixing unit (4) by means of the activation of the opening and closing mechanisms (10) controlled by the electronic control (9).

9) Automated apparatus as described in the preceding claim characterised by the fact that said opening and closing mechanisms (10) are composed of electromagnetic valves and/or pneumatic systems and/or groups of electromagnetic valves.

10) Automated apparatus as described in claim 7 characterised by the fact that the level sensors of the container (3) for the storage of the concentrated brine regulate, through the electronic control unit

(9), the filling of the same container and are able to transmit a pulse used for the signalling of alarms in case of anomalies or the attainment of a low level of brine in the container (3) .

11) Automated apparatus as described in claim 7 characterised by the fact that in the mixing unit (4) there is incorporated the injection of the wash liquid that is collected from a container (7) . 12) Automated apparatus as described in claim 7 characterised by the fact that the electrochemical reac- tors (5) are powered by transformers that ensure high current-voltage ratios with high _.constant amperages in order to guarantee constant quality of the electro- chemically activated product. 13) Automated apparatus as described in claim 7 characterised by the fact that the correct operation of the reactors is controlled by a control unit (14) by means of the measurement of the PH value_r the chlorine concentration and the oxidation-reduction voltage. 14) Automated apparatus as described in claim 7 characterised by the fact the reactor or reactors have two outlets of which the first transports the product to be used during the production cycle into the container (6) and the second is directly connected to a dis- charge outlet.

15) Automated apparatus as described in claim 7 characterised by the fact that the injection unit (8) includes a dosing diaphragm pump suitable to collect the disinfecting agent from the storage container (6) in order to inject it into the water supply network.