STEL: history and new prospects

UDK: 621.357

Bakhir V.M.1), Panicheva S.A. 2), Prilutsky V.I. 1), Shomovskaya N.Yu. 1)


1 ) The Russian Scientific & Research Institute for Medical Engineering (VNIIIMT MZ RF), Moscow, Russia; 2) Electrochemical Technologies Ltd. (ECT, Ltd.), St.Louis, USA

For the first time the name of the plants destined for electrochemically activated antimicrobial and washing agents synthesis – that is, STEL (descended from the words STerility and ELectro-chemistry) – was heard in the year of 1989. The name “STEL” was assigned to all the types of electrochemical plants which produce electrochemically activated washing, disinfecting and sterilizing solutions (ECA-solutions) and include electrochemical reactor made of FEM-3 flow electrochemical modular elements as one of the units of their construction. Owing to its design features, FEM-3 element, practically, has no alternatives as a reactor destined for application in ECA-solutions synthesis technology. Only in this reactor it is possible to create the conditions for simultaneous synthesis of chlorine-oxygen and hydroperoxide oxidants of the highest oxidation rates; and to provide the conditions for dense, electrically structured ion-hydrated sheathes generation in double electric layer located by anode surface, with these surfaces enveloping the newly-formed oxidants and preventing their subsequent quick mutual neutralization; and only there, within the shortest time during which liquid flows in cathodic chamber, practically all of the heavy metals ions could be transformed into insoluble hydroxides and a catholyte could be saturated with dissolved hydrogen; and hydrogen dissolved in catholyte could be forced to participate in anodic reactions of oxidants synthesis, as well.

The simplest technology of water processing in flow diaphragm reactors consists in simultaneous synthesis of approximately equal catholyte and anolyte volumes – that is, of water or solution exposed to cathodic or anodic processing, respectively. As far as this technology is concerned, perfection of reactor's structure manifests itself in the opportunity to obtain maximum possible values of anolyte oxidation-reduction potential (ORP), provided that its pH-factor value is minimal, with power inputs being minimal and with the maximum possible output capacity and the minimum possible level of parent solution or water mineralization provided, and to obtain minimum possible ORP-values for catholyte, with its pH-factor value being maximal, as well. That were these very conditions that were formerly considered to be the key conditions for “living” and “dead” water obtaining, but in many cases they were achieved at the expense of increased water mineralization level and prolonged time of electrochemical water treatment. As a matter of fact, in case one desires to obtain electrochemically activated water – that is, “living” water catholyte or “dead” water anolyte, – then it is necessary to ensure that each micro-volume of water being processed gets in touch with the surface of the respective electrode not dissolved in water, for a minimal period of time being estimated at integer-valued seconds or at fractions of a second, provided that water temperature changes are minimal (1 – 2 degrees) and that its mineralization level is equal to the minimum possible value not exceeding the level of salts content in standard drinking water. It is obvious that the major part of apparatuses destined for “living” and “dead” water generation manufactured in the early eighties, as well as of apparatuses of the similar destination being manufactured at the present time, didn't correspond and still do not correspond to these principals, as far as this branch of electro-chemistry hasn't ever been described in respective text-books and represents an independently developing scientific-and-technical archipelago.

Generation of disinfecting solution – that is, of acidic anolyte, – in STEL-plants doesn't represent any difficulties as regards to technical aspects; however, it is not expedient by the reason of its high corrosiveness level and pungent smell of chlorine. It is possible to avoid the strong chlorine smell presence only in case standard drinking water having no salt additives is used as a parent solution; however, anolyte obtained of sweet water does not possess sufficiently effective antimicrobial properties so as to be used in PCDPI/LPU (patient care and disease-prevention institution) as a disinfecting agent.

At the present time, there are the plants of STEL-AK-type destined for electrochemically activated anolyte and catholyte generation of sweet or distilled water manufactured in “NPO “Ekran”, OAO (Scientific-and-production association “Screen”, open JSC), with these plants having output capacity equal to 5 to 1000 litres/hour. Such ECA-solutions are used in various manufacturing processes implemented in agriculture, in industry and in medicine with the purpose of oxidation-reduction potential regulation in the human beings' organisms.

AN-ANOLYTE – neutral anolyte

Employees of health care institutions performing practical tasks had a need for solution which would have a neutral pH-factor value. For the first time such an anolyte was obtained in STEL-MT-1-plant, the serial production of which was started in “Ekran”, NPO in the year of 1990. This anolyte was given the name of a neutral anolyte, having the “AN-anolyte” abbreviation, in contrast to formerly known acidic anolyte with the pH-factor value being lower than 5, and at the same time the latter anolyte was given the name of “A-anolyte”.

AN-anolyte is manufactured by only means of anodic processing of the parent sodium chloride solution carried out in RPE-reactor represented by a single or by several FEM-elements. The pH-factor value correction within the anodic processing procedure is performed by adjustment of the current share transferred by hydroxyl ions from cathodic chamber to anodic chamber, with sodium hydroxide concentration existing in cathodic chamber being maintained at increased level.

AN-anolyte proved to be a more strong antimicrobial solution than acidic anolyte. Moreover, in contrast to A-anolyte and thanks to some peculiarities of the technology that was used to obtain it, it possesses detergent properties, as well. However, AN-anolyte is characterized by high corrosiveness which is nearly the same as that of A-anolyte, but, in contrast to A-anolyte, it has less pungent smell of chlorine.

ANOLYTE ANK – neutral anolyte obtained using catholyte

The further improvement of AN-anolyte properties has resulted in significant changes in electrochemical synthesis technology and permitted to create a neutral anolyte of the new type in the year of 1995 ; this anolyte was given the “ANK-anolyte” reference name, which means “neutral anolyte obtained using catholyte”. Heavy metals ions elimination from the parent sodium chloride solution, dissolved hydrogen properties utilization in oxidants mixture, as well as the technology applied for correction of the pH-factor value of acidic anolyte solution are considered the most important aspects of the ANK-anolyte manufacturing technology.

As multiple experimental researches and wide experience of many years' practical application have shown, ANK-anolyte proved to be the solution which was the best to correspond with the needs of medicine: it possesses wide and universal spectrum of action, it is not toxic, it doesn't create toxic background after desiccation, it doesn't permit microorganisms to acquire resistance, and it has lower corroding ability than AN-anolyte.

There could be different hydraulic schemes applied for ANK-anolyte synthesizing. The most simple among them was used in all of the STEL-plants that were manufactured before the year of 2006. In accordance with this scheme, the quintessence of ANK-anolyte synthesis process consists in the whole parent solution volume feeding to cathodic chamber of RPE-reactor consisting of FEM-3 elements, where catholyte, during the flowing process, is enriched with metals cations (mainly with sodium cations) coming from anodic chamber, and where heavy metals ions transform into insoluble hydroxides as a result of the medium pH-factor value increase, as well. After that, hydrogen bubbles with the particles of insoluble hydroxides stuck to them and a certain quantity of catholyte are eliminated from the aggregate solution volume available in flotation reactor. Catholyte purified in such a manner is supplied to anodic chamber of the same reactor. As a rule, the pH-factor value of ANK-anolyte to be selected shall lie within the limits of 6,5 to 7,5 and is adjusted with the help of catholyte volume discharged into drainage from flotation reactor.

However, this scheme, as well as ANK-anolyte generated with its help, is not free from disadvantages. When anolyte is produced in accordance with this scheme, salt conversion factor doesn't exceed 13%, on the average, the latter fact results in necessity to retain the sodium chloride concentration in the parent solution at the level of not less than 5 grams/litre, in case the concentration of oxidants synthesized in ANK-anolyte lies within the limits of 500 – 600 milligrams/litre. When smooth shining surfaces are processed such an anolyte leaves the salt traces after its desiccation, with the latter fact calling forth the necessity of rinsing. Sporocidic activity retention cycle of ANK-anolyte doesn't exceed 5 days, the latter feature being conditioned on incomplete heavy metals ions elimination from the parent solution. This scheme doesn't permit to create technical electrochemical systems destined for long-term commercial operation (with the exception of medicine), as far as it is not able to provide favourable conditions for long-term service of FEM-elements anodic coating, in principle.

There were either the advantages or the accumulated problems connected with the technology and technique of ANK-anolyte manufacturing and practical application revealed and studied within the period covering the years of 2000 – 2001.

The main advantages of ANK-anolyte are as follows:

•  ANK-anolyte proved to be the most powerful and the most universal substance among all of the well-known liquid antimicrobial agents, with its toxicity being the lowest and with absolute environmental safety provided.

•  Many years' experience of ANK-anolyte practical application in PCDPI has proved that there are no microorganisms' strains resistant to ANK-anolyte originating at all.

•  STEL-plants equipped with electrochemical reactors consisting of FEM-3 elements and destined for ANK-anolyte manufacturing managed to provide thousands of PCDPI with inexpensive high-performance antimicrobial solutions that were harmless for patients, personnel and for surrounding environment, as well.

•  By this time, ANK-anolyte obtained in STEL-plants manufactured by “NPO “Ekran”, OJSC has been recognised as a therapeutic agent (anti-infective agent) destined for skin coverlets, mucous membranes and suppurating wounds disinfection, and for the other purposes, as well. There has been the respective pharmacopoeia paper (article) obtained.

There should be the following facts revealed within the period covering the years of 2000 – 2001 referred to disadvantages and problems of the technology and technique of electrochemically activated ANK-anolyte manufacturing and practical application in PCDPI:

•  ANK-anolyte possesses corrosiveness and is not recommended for cleansing of instruments manufactured of alloys which do not possess corrosion-resistance properties.

•  The effectiveness of objects disinfection with ANK-anolyte considerably decreases in the albuminous contaminating agents presence.

•  After its desiccation ANK-anolyte leaves the salt traces on smooth shining surfaces of objects .

•  The companies which are illegally manufacturing and distributing STEL-plants and are also involved in counterfeit FEM-elements manufacturing have caused ideological harm to original electrochemical activation technology and actual damage to customers.

Within the years of 2001 – 2005 the main ANK-anolyte disadvantages were successfully surmounted through the efforts of the group of specialists representing Electrochemical Medical Technique Department of “NPO “Ekran”, OJSC, Vitold Bakhir's Electrochemical Systems and Technologies Institute, American company “Electrochemical Technologies, Ltd.” and the Russian Academy of Medical and Technical Sciences, as well.

1. There has been a plant of STEL-ANK-type created, this plant ensuring ANK-anolyte manufacturing according to the new technological scheme. ANK-anolyte obtained in the plants of STEL-ANK-type is characterised by low mineralization level (that is, total content of dissolved inorganic electrolytes), even if the concentration of metastable mixture of chlorine-oxygen and hydroperoxide oxidants is increased. Particularly, while the mineralization level of ANK-anolyte manufactured in the plants of STEL-10N-120-01-type makes 2 to 5 grams/litre, provided that the oxidants concentration is equal to 200 to 500 mg/litre, the mineralization level of ANK-anolyte manufactured in the plants of STEL-ANK-type makes 0,5 to 2,0 grams/litre, with the same oxidants concentration provided. Low level of ANK-anolyte mineralization is the reason for its decreased corrosiveness rate and for simultaneously provided advanced antimicrobial properties, these characteristics being conditioned on more intensive osmotic transfer of energetically acting substances (EAS) to the micro-organisms' internal environment. Furthermore, ANK-anolyte generated in the plants of STEL-ANK-type is characterised by longer antimicrobial activity retention cycle (up to 7 days), the latter fact being connected with advanced quality of the parent solution purification from heavy metals ions achieved within the process of ANK-anolyte synthesising in the plants of STEL-ANK-type.

2. There has been the technology of all-purpose ECA-solution – that is, of ALOKS-anolyte, – manufacturing developed (“all-purpose” means that it is destined for disinfection, pre-sterilisation cleansing and sterilisation); the latter anolyte is manufactured by means of ethyl alcohol infusing in the amount of 1 volume percent into ANK-anolyte synthesised in the plants of STEL-ANK-type only, with the ANK-anolyte oxidants concentration being equal to 500 mg/litre. EAS of ALOKS-anolyte represent the mixture of metastable inorganic (chlorine-oxygen and hydroperoxide) and organic (peroxy-compounds) oxidants. Moreover, the major part of metastable organic oxidants is represented by per-acetic acid which is generated by means of progressive alcohol oxidation with inorganic oxidants of ANK-anolyte. Within 3 minutes after alcohol is infused and mixed with ANK-anolyte volume ALOKS-anolyte is considered to be ready for application and it will retain its functional properties within 6 hours. In case 6 hours have passed ALOKS-anolyte is not recommended for application; and after the expiration of 24 hours the acting substances of ALOKS-anolyte almost completely neutralize each other. ALOKS-anolyte antimicrobial activity which has been proved by a number of authoritative foreign scientific research centres exceeds the analogous properties of ANK-anolyte by 1000 – 10 000 times, with the latter fact permitting to reduce the time of products processing with this solution to 1 – 3 minutes. ALOKS-anolyte doesn't provoke metals corrosion in case the immersion method is applied for processing and it demonstrates high performance under the high organic load conditions.

3. There have been the technology and technical facilities destined for all-purpose ECHA-solution – that is, for PEROX-anolyte, – manufacturing developed; PEROX-anolyte is manufactured in the plants of STEL-PEROX-type by means of its electrochemical synthesis of sodium carbonate aqueous solution. The acting substances of PEROX-anolyte – that is, sodium peroxy-carbonates, per-carbonic acid and hydroperoxide electron-acceptor compounds, their state being metastable, – are all oxidants. The PEROX-anolyte mineralization level lies within the limits of 0,5 to 1,0 g/l; the oxidants content measured with the help of iodometric titration method in the active chlorine compounds equivalent makes 40 to 50 mg/l; the pH-factor value stays within the bounds of 6 to 7. This solution is characterised by minimal toxicity with no corrosiveness feature detected at all and is recommended for application not only as an agent destined for disinfection, pre-sterilisation cleansing and sterilisation of medical-purpose products but also as sterile water possessing antimicrobial properties which can retain for 20 days. With the abovementioned functions provided, PEROX-anolyte could be used for the medical-purpose products rinsing during the technological procedures of their preparation for application.

Furthermore, during the PEROX-anolyte synthesis there is PEROX-catholyte simultaneously synthesised in the plants of STEL-PEROX-type; PEROX-catholyte can be used as a washing solution, and as a medium for insecticides solutions preparation, as well. The level of PEROX-catholyte mineralization doesn't exceed 1 g/l, even if the pH-factor value exceeds 10 and the oxidation-reduction potential is lower than minus 500 mV. Sodium hydroxide, hydrogen peroxide and other hydroperoxide electron-donor compounds, their state being metastable, – with all of them being oxidants – are the acting substances of PEROX-catholyte. PEROX-catholyte application as a medium for insecticide preparations dissolution permits to improve functional properties of insecticides solutions, with the acting substances concentration being simultaneously reduced by 50 – 70 % owing to intensification of the processes of acting substances transfer through the insects' external integuments.

4. There have been the new technical systems developed, as well; the reactors consisting of FEM-3 elements that are used in these systems can operate for no less than 50 000 hours without anodic coatings changed and with the shutoff performed with the only purpose of electrode chambers cleaning. The salt conversion level obtained in these new technical systems destined for ANK-anolyte manufacturing mounts to 45% ; however, these systems have retained the “STEL-plants” name as the basic name; this was done so as not to violate the succession scheme ensuring that the electrochemical medical technique is perceived in accordance with its destination; however, there have been such prefixes as “ANK” (for example, STEL-ANK), “PEROX” (for example, STEL-PEROX) added to this name, depending on the type of hydraulic scheme applied for ANK-anolyte synthesis.

The table given below represents the characteristics of new electrochemically activated solutions compared with that of existing chemical reagents solutions and of ANK-anolyte manufactured in the plants of STEL-10N-120-01-type.

Comparative characteristics of chemically stable and electrochemically activated disinfecting solutions

Indices
Chemically stable disinfecting solutions
Electrochemically activated solutions obtained in STEL-pants
STEL-10N-120-01
STEL-ANK-40-01
STEL-PEROX-20-01
Acting substances
Quaternary ammonium compounds, phenols, chlorine-isocyanurates, aldehydes
Meta-stable chlorine-oxygen and hydroperoxide compounds
Meta-stable chlorine-oxygen and hydroperoxide compounds
Peroxy-carbonates, per-carbonic acid, hydroperoxide compounds in meta-stable state
Acting substances concentration in working solution
0,1 – 2,5%
0,02 – 0,05%
0,02 – 0,05%
0,004 – 0,005%
(in active chlorine equivalent)
Antimicrobial activity spectrum
Wide – for 10% of known agents, limited – for 90% of them
Wide
Wide
Wide
Toxicity for human beings and animals
Yes
No
No
No
Degradation products toxicity for human beings and animals
Yes
No
No
No
Necessity of neutralisation prior to discharging into sewerage system
Yes
No
No
No
Necessity of medical instruments rinsing after disinfection
Yes
Yes
No
No
Antimicrobial properties combination with detergent power
Yes – for 10% of known agents
Yes
Yes
Yes
Traces presence on smooth surfaces after desiccation
Yes
Yes
Feebly marked
Practically unnoticeable

 

Examination of infringing products (of STEL-plants, of counterfeited electrochemical reactors manufactured by such foreign companies as “ AQUASTEL ”, “ENVIROLIGHT”, “STERILOX” ( now called “PURICORE”), as the Russian company “IZUMRUD” (EMERALD) from Saint-Petersburg, for instance) which appear in the Russian market and abroad has shown that neither of the counterfeited electrochemical reactors imitating FEM-3 elements, and neither of the diaphragm reactors having the structure differing from that of FEM-3 elements, permits to ensure that chlorine-oxygen and hydroperoxide compounds are generated in the ANK-anolyte synthesis scheme in proportions necessary for imparting of the required antimicrobial activity parameters to ANK-anolyte and does not permit to provide the conditions ensuring long-term simultaneous presence of chlorine-oxygen and hydroperoxide compounds in ANK-anolyte, as well. As a rule, the counterfeit STEL-plants are equipped with either unoriginal reactors or with reactors consisting of standard FEM-3 elements manufactured by their only legal manufacturer existing in the world – that is, by the Russian company “Laboratory of Electrotechnology” (“LET”, LLC), – with their quantity still being much lower than the quantity required for achieving of the plant output capacity stated in the respective documentation.

There are multiple violations of ANK-anolyte manufacturing technique, of its generation technology and of its practical application methods committed by different companies which are not considered the authorised representatives of their devisers. In order to give the STEL-plants consumers – that is, the responsible employees of PCDPI, – an opportunity not to expose to risk the health of those people who have entrusted themselves to them as their patient there has been a system of the author's information provision to interested persons and organisations developed ( www.vbinstitute.org) , the abovementioned author's information covers all the problems of electrochemical technique and technology. This system has been created on the basis of information database provided by the group of enterprises considered to be the leaders in the sphere of electrochemical systems and technologies of electrochemically activated solutions manufacturing and application and includes databases of the group of enterprises authorised by the devisers being the owners of the greater part of patents issued in the field being discussed here; the latter fact permits to provide the customers with reliable information and high-quality products on their demands.

 

Published in the journal Meditsinskiy alfavit, N 11, 2006, pp. 32-36.