WO2003036013A2

WO2003036013A2 - Method of and equipment for the rehabilitation of water wells

Info

Publication number: WO2003036013A2
Application number: PCT/ZA2002/000163
Authority: WO
Inventors: Gilbert Theo Hinze
Original assignee: Radical Waters (Ip) (Pty) Limited
Priority date: 2001-10-22
Filing date: 2002-10-21
Publication date: 2003-05-01
Also published as: AU2002336730A1; WO2003036013A3

Abstract

The invention relates to a method of rehabilitating a borehole or water well, the method comprising introducing an electrolytically activated, dilute aqueous saline solution into the water well, wherein the solution is either an anolyte or a catholyte or a mixture of anolyte and catholyte; and wherein the electrolytically activated, dilute aqueous saline solution is introduced either in a space above the water line or below the waterline. The invention also extends to a biocompatible and pollution free reagent adapted at least partially to eliminate biofilm in boreholes and waters wells, and to an electromechanical device for use in such a method.

Description

METHOD OF AND EQUIPMENT FOR THE REHABILITATION OF WATER WELLS

Introduction

This invention relates to a method of and equipment for the rehabilitation of water wells. More particularly, but not exclusively, the invention relates to a method of and equipment for increasing and maintaining yield and specific capacity of a water well, as well as eliminating biofouling by microbial organisms.

Background to the invention Background: Water well rehabilitation

Rehabilitation of water wells is often undertaken to increase its yield and specific capacity, as well as to eliminate the risk of biofouling of well water that may be caused by pathogenic microbes. Such biofouling may render the pumped water unsuitable for human or animal consumption. However, effective rehabilitation of a water well not only may restore and maintain lost well capacity and reduce or eliminate the risk of microbial contamination, but also has the added commercial advantages of reducing pump costs and extending the life of a water well.

The specific capacity (SC) of a water well is calculated in volumetric flow (Q) per minute per foot (or meter) drawdown (dd). "Drawdown" is defined as being the difference between the static water level (swl) and the pumping water level (pwl). Accordingly, drawdown is calculated according to the following equation: dd = (swl - pwl) whereas specific capacity is calculated as follows: SC = (Q / dd).

From the aforegoing it is apparent that specific capacity will decrease when the static water level decreases. The static water level may decrease as a result of dewatering of the aquifer, or due to a loss of permeability in porous media. The latter may be caused by the adherence of microorganisms and biofilm on the surfaces of the porous media. "Biofilm" generally refers to a conglomerate of microorganisms that are embedded in a structural matrix of macromolecules, such as exopolymers, wherein the matrix enables the colonizing cells to withstand normal treatment doses of biocides. High extraction rates (i.e. increased drawdown) expose the normally covered screens to oxygen by cascading water from above, which creates ideal conditions for the development of biofilm on the exposed areas. An increase of 1 milligram dissolved oxygen per litre increases the plugging rate by 10 times.

Three types of plugging or flow path blockage are recognized, namely chemical, biological and physical blockage.

(i) Chemical blockage

Chemical blockage is caused by the formation of mineral scale and encrustation on the porous media. Groundwater often includes high concentrations of dissolved minerals such as calcium, magnesium, iron and manganese. Dissolved natural carbon dioxide produces high concentrations of carbonic acid in some aquifers which helps keep minerals as ionic species in suspension. During pumping, however, a portion of the dissolved carbon dioxide is lost through increased velocity and decreased pressure causing an increase in the well water pH. This in turn results in an increase in the tendency for a portion of the dissolved mineral species, such as calcium and magnesium carbonates, to precipitate out. So, for example, when sulphate ions exceed 70 parts per million, they can precipitate as calcium and magnesium sulphates.

(ii) Biological blockage

Biological blockage is caused by at least three major groups of micro-organisms, namely slime-forming, iron-reducing bacteria and sulphate-reducing bacteria. These are naturally occurring bacteria that are commonly present in soil, either in an aerobic or anaerobic form. Iron-reducing bacteria produce a stalk-like structure, often filled with slime-producing bacteria, which increases plugging. Sulphur- reducing bacteria are anaerobic and may be found underneath scale, which provides a low oxygen environment. They consume sulphate by releasing a corrosive organic acid and hydrogen sulphide gas, which smells like rotten eggs and produces ferrous sulphate or oxide scales. Iron and sulphate reducing organisms also produce bacterial corrosion of casings and pumping equipment. Such pumping equipment has to be replaced frequently unless bacteria causing corrosion are eliminated.

(iii) Physical blockage

The migration of fines from numerous sources requires an effective dispersant to disperse the clay/silt aggregate. Well rehabilitation procedure The current well rehabilitation procedure involves pre-treatment of the well with mechanical tools to dislodge mineral encrustations and bacterial deposits within easy to reach areas, whereafter chemical treatment is applied, using Muriatic, Sulfamic, Phosphoric or Glycolic acids individually or in combination. The most recent technology involves the heating of acids mentioned above as well as the application of heated caustic soda thereafter for the removal of slime and encrustations from the screens below. The hazardous nature of the chemicals not only poses a real danger to the operators, but also requires special permission for the subsequent disposal thereof during post-treatment pump test and until water parameters have normalized in respect of conductivity, pH and special chemical detection procedures. This is an unsafe, costly and time-consuming procedure. Redevelopment is then employed by the removal of all debris and dislodged deposits using mechanical means such as jetting, airlifting or bailing. The final step involves chlorination using either sodium hypochlorite or calcium hypochlorite.

Background: Electrolysis of fluids It has long been known that electrolysis of fluids, for example saline solutions, results in the production of useful products, such as chlorine and ozone, which are especially useful as in-vitro microbicides for cleaning hard surfaces. So, for example, USA patent no. 5,462,644 discloses a method of sterilising and disinfecting equipment that are contaminated with biofilm by killing the microorganisms in the biofilm. The method includes the steps of suspending the contaminated equipment in a bath of electrically conductive electrolyte solution and applying an electric field to the solution so as to kill the microorganisms. The electrolyte solution optionally may include an effective amount of a sterilant or disinfectant.

A disadvantage associated with this method is that a suitable electric current must be applied to the bath continuously to effect working of the invention.

USA patent no. 6,117,285 also discloses a system for sterilizing hard surfaces. Particularly, the invention discloses an apparatus for producing an electrolysed fluid, such as a saline solution, that can be used for disinfecting and sterilising medical and dental equipment. More particularly, the apparatus comprises a container for holding a fluid to be electrolysed, power supply means to provide a source of electric current, and a first and second electrode immersed in the fluid and connected to the power supply means, the arrangement being such that the fluid is electrolysed as the current is passed there through. The invention also discloses a system for disinfecting and/or sterilising health care equipment that includes at least one conduit through the equipment, where the equipment are bathed in the electrolysed saline solution and where the system provides for through flow of electrolysed solution through the conduit and over the surfaces of the equipment.

A disadvantage associated with this system is that the resultant electrolysed solution is produced in relatively small quantities on a batch or discontinuous basis. Further, the products produced at the anode and the cathode are intricately mixed so that the electrolysed solution comprises a mixture of anolyte and catholyte in a single solution. This is a disadvantage since the respective effectiveness of the catholyte and anolyte is at least partially neutralised when they are produced and harvested as a single solution.

Electrolytically activated water and treatment of biofilm The applicant, in accordance with the requirements of this invention, utilised a cylindrical electrolytic device, having at least one electrolytic cell, in which a permeable membrane separates an anodic chamber from a cathodic chamber. The specific design permits the harnessing of two distinct, separate and electrochemically different product streams of activated water in a process known as electrolytic activation (EA) or electrochemical activation (EGA).

The product streams remain active for a limited period of time. During this period of increased activity, these meta-stable product streams have been shown to have applications in a diverse array of technological processes, often as a substitute for traditional chemical agents. Irrespective of the characteristics of the specific solution, where activation status can extend from hours to days, the resultant meta-stable product streams following decay of the state of activation revert to benign water with the composition of the feed.

Principles of EA technology

Water of varying mineralisation is passed through the cylindrical electrolytic cell, the specific design of which permits the production of two distinct and electrochemically different product streams, which are electrolytically activated, low concentration saline solutions. The design of the specific cylindrical cell utilised by the applicant for this invention is characterised therein that it ensures a uniformly high voltage electrical field through which each micro-volume of water must pass. This electric field created in the cylindrical cell has a high potential gradient and results in the creation of solutions of which the pH, oxidation reduction potential (ORP) and other physico-chemical properties lie outside of the range that can normally be achieved by conventional chemical or most electrolytic means.

Two separate streams of activated solutions are produced, namely anolyte and catholyte. Depending on the production methods used and conditions of operation of the electrolytic cell, the anolyte typically can have a pH range of 1.5 to 9 and an oxidation-reduction potential (ORP) of +150 mV to +1200 mV. The anolyte is oxidizing, due to the presence of a mixture of oxidising free radicals, and has an antimicrobial effect. The catholyte that is produced typically can have a pH range of 8.5 to 13 and an ORP of about -150 mV to - 900mV. The catholyte has reducing and surfactant properties and is an antioxidant.

One of the advantages of the design of the specific cylindrical cell utilised by the applicant for this invention is that the chemical composition of the two solutions can be altered by utilizing various hydraulic flow arrangements, linking electrolytic cell modules in various configurations in order optimally to address the requirements of specific areas of application. Some other variables are flow rate, hydraulic pressure, concentration, temperature, current density, and voltage on the electrodes. Aside from its distinctive attributes, the negatively charged anti-oxidant solution (the

catholyte) can also be channelled back into the anode chamber, thereby modulating the quality of the positively charged oxidant solution (the anolyte) that is produced. Depending on the specifications of the required application, variations in the design of the hydraulic systems can be effected to meet the requisite objectives.

Properties of Electrolytically Activated Solutions

The properties of electrolytically activated solutions are dependent upon a number of

factors. These factors comprise the solution flow rate through the electrolytic cell, type of salt, voltage and current applied, temperature, inter-flow dynamics of the solutions between the anode and cathode chambers such as the degree of feedback of catholyte into the anolyte chamber, the design and geometry of the cell, and the degree of mineralisation of the water.

During the process of electrolytic activation in the electrolytic cell utilised by the applicant,

three broad classes of products are believed to be produced, namely stable products,

highly active unstable products and quasi-stable structures.

(i) Stable products: These are acids (in the anolyte) and bases (in the catholyte) that influence the pH of the solution in question, as well as other active species.

(ii) Highly active unstable products: These include free radicals and other active ion

species with a half-life of typically less than 48 hours. Included here are electrically

and chemically active micro-bubbles of electrolytic gas, 0.2 to 0. 5 micrometer in diameter and with concentrations of up to 10⁷ ml^"1, distributed uniformly through the solution. All these species serve to enhance the ORP of the anolyte and catholyte.

(iii) Quasi-stable structures: These are structures formed at or near the electrode surface as a consequence of the very high voltage gradient (10⁶ V cm^"1) in those regions. These are free structural complexes of hydrated membranes around ions, molecules, radicals and atoms. The size of these water clusters is reduced from about 13-18 to approximately 5-6 molecules per cluster. All these features enhance the diffusion, catalytic and biocatalytic properties of the water.

It is important to note that the level of mineralisation of input water required to generate optimally metastable solutions is insignificantly different from the composition of potable water. However, the heightened electrical activity and altered physico-chemical attributes of the solutions differ significantly from the inactivated state, yet they remain non-toxic to mammalian tissue and the environment. Without maintenance of the activated state, these diverse products degrade to the relaxed state of benign water and the anomalous attributes of the activated solutions such as altered conductivity and surface tension similarly revert to pre-activation status.

Biocidal properties of anolyte and mixed anolyte and catholyte

Most of the earlier technologies that have employed electrolytic activation to generate biocidal solutions have not been capable of separating the anolyte and catholyte solutions during generation in the cell. In these earlier technologies, the two opposing solutions have greatly neutralised each other with regard to potential electrical activity. One of the advantages of the more modern EGA systems is that the biocidal activity of hypochlorous acid generated in these systems is up to 300 times more effective than the sodium hypochlorite generated by earlier systems. Additionally, comparison of neutral anolyte (pH=7) with alkaline gluteraldehyde (pH=8.5) showed that the latter required a concentration of 2% versus 0.05% of the former, in order to achieve the same biocidal efficacy. Similarly, it has been shown that a 5% solution of sodium hypochlorite ("Jik") can only be used for purposes of disinfection, whilst a 0.03% solution of neutral anolyte has both disinfecting and sterilising properties. In general, the biocidal activity of non- activated neutral anolyte (only stable products and no electrical charge) is 80 times the potential activity of the hypochlorite solution, but still exhibits only one third of the full biocidal potential of the optimally activated EGA solution.

Thus, using non-toxic salts, these activated solutions have been shown conclusively to exceed chemically derived "equivalents" both in low dosage effectiveness as well as physico-chemical properties. This heightened biocidal capacity relative to traditional chemical solutions permits the incorporation of activated solutions at substantially lower dose rates, eliminating the risk of toxicity and adverse environmental impact, while providing cost effective resolutions.

Acidic anolyte solutions in dental units

The use of electrolytically activated low concentration saline solutions as biocides in dental unit water lines (DUWL) is proposed and disclosed in numerous documents, including international patent application PCT/US99/29013, published under WO 00/33757. This application, PCT/US99/29013 proposes the use of acidic electrolysed water having a pH of 2.5-6.5 in continuous contact with the interior surfaces of the DUWL's during operation of the dental appliances, both as biocide for the biofilm and as operating fluid for the dental appliances.

PCT/US99/29013 focuses on two types of electrolytic systems, both producing its acidic anolyte from a plate reactor-type, electrolytic cell, and proposes that it is incorporated into dental systems for disinfecting and reducing of biofilm in DUWL's. The first system makes use of a membrane to generate and separate distinct anolyte and catholyte solutions. This system generates very acidic anolyte at a pH 2 - 3,5. The second system does not use a membrane and generates only one stream of solution. PCT/US99/29013 proposes the addition of HCI (hydrochloric acid) into the feed of the second system, so as to increase the concentration of chloride ions and, in order to increase the microcidal efficacy of the anolyte, to lower the pH even further.

A material disadvantage of the acidic anolyte solutions proposed in PCT/US99/29013 is their toxicity, due to their relatively high chlorine and sodium hypochlorite content. In fact, it is believed that there is relatively little difference between the acid anolyte solutions as proposed and household bleach, with the latter being substantially simpler and cheaper to procure.

A further disadvantage of the acidic anolyte solutions proposed in PCT/US99/29013 is that they are advocated merely to reduce biofilm, and thus their apparent inability to eliminate biofilm, potentially allowing the DUWL's to develop resistant strains of biofilm, with the accompanying implication of serious health risks. More particularly, PCT/US99/29013 only proposes the disinfection of the DUWL's with reference to the cited microbial results, but does not propose the sterilisation of the DUWL's nor does it disclose any evidence of the removal of biofilm from the inner surfaces of the DUWL's. In fact, it is common knowledge that disinfection of water does not show/prove elimination or even reduction in biofilm.

In addition, PCT/US99/29013 makes reference to the use of Japanese electrolyzers, which, as reported in a scientific paper published by Horiba et al in Oral Surgery, Oral Medicine, Oral Pathology, Volume 87, No.1 , January 1999, proved ineffective against Bacillus subtilis, thus supporting the belief that the different electrolytic devices produce different solutions with varying levels of efficacy.

Further, and with reference to the adding of a dilute HCI solution to the electrolyzer to increase the chlorine concentration resulting in additional chlorine ions which increases the cleansing effect, it is believed that the acidic solutions without the added HCI is sub- optimally effective. It has been well documented that HCI, although a very effective biocide, has proven sub-optimal efficacy against biofilm. Thus, by adding HCI to the process water, one may improve the microcidal efficacy of the product to some extent but not the removal and elimination of the biofilm.

In addition, the relatively high concentrations of sodium hypochlorite generated result in the generation of relatively high levels of tri-halomethanes, thus increasing the carcinogenic potential of the solutions. PCT/US99/29013 thus proposes the use and incorporation of a sodium hypochlorite generator, which has contingent disadvantages and which defeats the whole purpose of using electrolytically activated saline solutions as biocides.

Object of the invention It is accordingly an object of the present invention to provide a safe and relatively inexpensive, but effective method of and equipment for the rehabilitation and maintenance of water wells by the removal of biofilm and the reduction of microorganisms.

Further, it is also an object of this invention to provide a reagent for eliminating biofilm in boreholes.

Summary of the invention

According to the invention there is provided a method of rehabilitating a borehole or water well, the method comprising the step of introducing an electrolytically activated solution into the water well, wherein the solution is either an anolyte or a catholyte or a mixture of anolyte and catholyte, and wherein the solution is introduced into the borehole or water well either as free flowing liquid, a fog or a high- or low-pressure spray, and wherein the solution is introduced either in the space above the water line or below the waterline.

More particularly, the method may provide first introducing the catholyte so as to loosen and suspend attached matter, including at least some of the biofilm, and to reduce and precipitate at least some of the salts that may be present in solution, such as iron, and then secondly using the anolyte to kill the biofilm, other suspended organisms and to oxidise some of the reduced species. Depending on the conditions of the particular well or borehole, a mixture of catholyte and anolyte may be used as a singular treatment solution. Intermittent introduction of activated solutions may be employed to maintain inflow by preventing biofilm formation and rendering water potable at the same time. In particular, after a well has been rehabilitated, activated solutions may be used periodically to remove newly formed slime layers, preventing production loss and rendering water potable by the elimination of pathogens from the water.

The water used for activation may be obtained from the same well to be rehabilitated, eliminating transportation and storage cost of materials to be used in the rehabilitation process.

According to another aspect of the invention, there is provided an electrochemical device for generating the anolyte and catholyte solutions, the device including an electrochemical activation reactor, which is equipped with an on-board electrical generator; and a submersible pump that can be lowered into the water well or borehole to extract water.

According to a further aspect of the invention there is provided a biocompatible and pollution free reagent adapted at least partially to eliminate biofilm in boreholes and water wells, the reagent comprising an electrolytically activated solution of anolyte, or a solution of catholyte, or a solution of anolyte and catholyte, and characterised therein that it is completely safe for human and animal consumption and for on-site disposal without any threat of polluting groundwater or the environment. Specific embodiment of the invention

Without limiting the scope thereof, the invention will now further be described by means of the following example.

The basic electrolytic cells that were used to generate the electrolytically activated solutions utilised in this specification are substantially as disclosed in U.S. Patent No 5,635,040. The cells are modular units and, in various reactor configurations or devices, form the basis of the equipment disclosed in this specification, with the operational specifications for the reactors being optimised for each specific application. Particularly, the electrochemical reactor may be a so-called Flow-through Electrolytic Module (FEM) as described by Bakhir in USA patent no 5,427,667.

The cell includes a cylindrical metal vessel which is typically about 210mm long and 16mm in diameter, having a central rod anode (positive electrode) located within a concentric ceramic tube membrane. The outer tubular wall of the cell reactor acts as the cathode (negative electrode). Provision is made for inlet and outlet ports for the passage of the fluid through it.

Effectively, the ceramic membrane divides the cell into two compartments, namely the anode compartment and the cathode compartment. Water enters the cell and exits from these compartments as two streams, the anolyte and the catholyte, respectively. If so desired, some or all of the catholyte may be returned to the anode compartment so as to vary the properties of the anolyte being produced. A number of other hydraulic system configurations also exist, all of which are designed to achieve specific objectives. The design of the cell is such as to ensure a very high uniform electric field through which each micro volume of water must pass. In so doing, the molecules of water in the anolyte and catholyte acquire special properties which cannot be reproduced by other, more conventional chemical means. This electrolytic treatment results in the creation of anolyte and catholyte solutions whose pH, oxidation-reduction potentials (ORP) and other physico-chemical properties lie outside of the range that can be achieved by conventional chemical means.

Unless otherwise stated, the pH, oxidation-reduction potential (ORP) and concentration values of chlorine, chlorides and other dissolved salts were determined as per standard methods of examination of water and effluents.

Also, the annotation used for the various electrolytically generated solutions identified in this specification is as found in the Russian literature and patents of Bakhir et al and are as follows:

Anolyte:

1.1 A - electrically activated acidic anolyte pH: <5,0 ORP: +800 ..+1200 mV CSE active species: Cl₂, HCIO, HCI, HO*₂ This solution results when there is no catholyte feedback and the mineralisation level is high (>5 g/l). Chlorine gas is evolved, the solution is highly oxidizing, corrosive and microcidal. The products are mostly stable.

1.2 AN - electrically activated neutral pH anolyte pH: 5,0 - 7,0 ORP: +600...+900 mV active species: HCIO, 0₃, HO*, HO*₂

Here some catholyte is re-circulated to the anode compartment and the mineralisation is generally low (<3 g/l). Under these conditions, the formation of highly active but unstable species is favoured. The solution is microcidal but not corrosive and harmless to human or animal tissue.

1.3 ANK - electrically activated neutral pH anolyte pH: 7,2 - 8,2 ORP: +250- +800 mV active species: HCIO, CIO^", HO₂ ^", HO*₂, HO*, H₂O₂, ¹O₂, CI^"

Here a larger flow of catholyte is re-circulated resulting in a higher pH. The solution is still oxidizing and has similar properties to AN, but with a greater degree of short-term activation.

1.4 AND - electrically activated neutral pH anolyte pH: 6,8 - 7,8 ORP: +700- +1100 mV active species: HCIO, CIO^", HO^" ₂, HO*₂, H₂O₂, ¹O₂, CI*, HCI0₂, CI0₂, O₃, HO*, O*

The solution has a rather high positive ORP and can be used for disinfection.

2. Catholyte:

2.1 K - electrically activated alkaline catholyte pH: >9,0 ORP: -700- -820 mV active species: NaOH, O^" ₂, HO*₂, H0._2l OH^", OH*, HO₂ ^", O^2" ₂

This solution usually has a pH of 11-12 and is highly reducing. It is very active, but the relaxation times are significantly shorter than for anolyte solutions.

2.2 KN - electrically activated neutral catholyte pH: <9,0

ORP: -300 - -500 mV active species: O^" ₂, HO*₂, HO^" ₂, H₂O₂, H*, OH*

When mixed together, post production and extrinsically to the generating device in the "as produced" ratios, the anolyte and catholyte form a unique solution, which has both microcidal as well as surfactant properties. The capacity of a single solution possessed of both these attributes concurrently cannot be replicated with currently available chemical formulations. The dual attributes of this mixture have also been shown to be non-toxic for human tissue, as well as having a low corrosion potential profile. The mixture, with its strong oxidation-reduction potential has the capacity to effect the necessary electron transfer between the metastable radical species of the solution and the specific electrical charges present on the biofilm surface, thus destabilising the electrolytic forces at the interface of the gluco-calyx matrix (GCM) and the exposed (non-biofilm coated) conduit surface. This results in the reduced adherence and hence dislodging of the biofilm matrix.

The ability consistently to produce two or more distinct, separate and electrochemically different product streams of activated water of specific quality, as well as unique and proven attributes on a demand driven basis, with no adverse environmental consequences, significantly differentiates the electrolytic technology applied in this invention from the method for the rehabilitation of water wells commonly used

It will be appreciated that many variations in detail are possible without departing from the scope or spirit of the invention as set out in the claims.

Example 1

Fact sheet Borehole number: KG 1 - Calitzdorp

Farm Name: Kleinberg

Borehole Depth: 190m (19 / 07 / 2002)

Static Water Level: 32,67m (24 / 07 / 2002) Casing: 203mm uPVC from surface to 140m below surface, with 2 stainless steel Johnson screen sections inserted. Borehole reduces in diameter at 146m below surface to 165mm. No casing from 140m to 165m. Slotted 165mm uPVC casing from 165m to 190m below surface. Screened sections: 117m to 119,5m below surface

137m to 139m below surface

Coordinates: 33°32'56,189"S

21°39'26,158"E (Cape Datum)

Example 2

Fact sheet

Borehole number: DL 16 - Calitzdorp Farm Name: Daniels Kraal

Borehole Depth: 165,2m (14 / 08 / 2002) Static Water Level: 43,60m (29 / 07 / 2002)

Casing: 203mm uPVC from surface to 165,2m below surface, with 2 stainless steel Johnson screen sections inserted. Screened sections: 97,5m to 99,2m below surface

146,25m to 148,0m below surface Coordinates: 33°33'57,627"S

21°38'36,253"E (Cape Datum) Example 3

Fact sheet

Borehole number: DP 28 - Dysselsdorp Farm Name: Bokkraal Borehole Depth: 223,5m (19 / 07 / 2002) Static Water Level: 99,7m (19 / 07 / 2002) Casing: 203mm uPVC from surface to 223,5m below surface, with 4 stainless steel Johnson screen sections inserted. Screened sections: 153,0m to 155,0m below surface 158,0m to 160,0m below surface

201 ,0m to 203,0m below surface

212,8m to 214,5m below surface Coordinates: 33°34'52,6"S

22°27'24,2"E (Cape Datum)

22

Specific Capacity = Q / s

Q (m3/dav) Sw (m) Spec Cap (L/s/m)

66.528 0.42 158.4

486.432 2.83 171.8840989

Pre 958.176 5 98 160.2301003

1440.288 10.01 143.8849151

2331.072 17.5 133.2041143 767.6032286

Q (m3/dav) Sw (m) Spec Cap (L/s/m)

68.256 0.32 213.3

490.752 1.81 271.1337017

Post 963.36 4.2 229.3714286

1432.512 6.68 214.4479042

2344.896 12.09 193.9533499 1122.206384

Result: 46.196 % Improvement

Claims

1. A method of rehabilitating a borehole or water well, the method comprising introducing an electrolytically activated, dilute aqueous saline solution into the water well, wherein the solution is either an anolyte or a catholyte or a mixture of anolyte and catholyte; and wherein the electrolytically activated, dilute aqueous saline solution is introduced either in a space above the water line or below the waterline.

2. The method as claimed in claim 1 wherein the solution is introduced into the borehole or water well either as free flowing liquid, or is plunged, surged, fogged or introduced as a high- or low-pressure spray.

3. The method as claimed in claims 1 and 2 comprising first introducing the catholyte into the water well until attached matter, including at least some biofilm, is loosened and suspended and at least some of those salts that may be present in solution, such as iron, are reduced and precipitated; and then subsequently introducing the anolyte into the water well so as to kill the biofilm and other suspended organisms, and to oxidise some of the reduced species.

4. The use of an electrochemically activated, dilute aqueous saline solution in a method of rehabilitating a borehole or water well, wherein the electrochemically activated dilute aqueous saline solution includes separable catholyte and anolyte, which are introduced into the borehole or water well either separately or simultaneously.

5. A biocompatible and pollution free reagent adapted at least partially to eliminate biofilm in boreholes and water wells, the reagent comprising an electrolytically activated, dilute aqueous saline solution of anolyte, or of catholyte, or of anolyte and catholyte.

6. An electrochemical device for generating anolyte and catholyte solutions, the device including an electrochemical activation reactor, which is equipped with an on-board electrical generator; and a submersible pump dimensioned to be lowered into a water well or borehole to extract water.

7. A method of rehabilitating a borehole or water well substantially as hereinbefore described.