|Title of Invention||
AN ELECTRONIC DEVICE FOR ON-LINE DRINKING WATER DISINFECTION
|Abstract||An electronic device for on line drinking water disinfection, which comprises a known pump (3) connected to a suspended particulate free water source, characterized in that the output of the said pump being connected to the input of a reactor cell (11) through a control valve (5), the said reactor cell (11) essentially consisting of one or more rotatable and cyclically polarity interchangeable crossed pair low leaching electrodes (30), the said electrodes being connected to an electronic control unit (1) which supplying modulated DC current, the output of the said reactor cell (11) being connected through a control valve (12) and a non return valve (20) to the bottom of a storage tank (17), the said storage tank (17) being provided with an overflow outlet (22) at its top portion and a pipe (21) having water outlet tap (23) fixed below the level of the said overflow outlet (22).|
|Full Text||The present invention relates to an electronic device for on-line drinking water disinfection.
The device of the present invention is particularly useful for on-line treatment of microbially contaminated drinking water supplies to disinfect pathogenic microorganisms such as E.coli and provide safe drinking water to communities as per World Health Organisation (WHO) /Environmental Protection Agency ( EPA, USA) standards prescribed for potable drinking water. It shall support the basic human need of leading a comfortable life, free from water borne diseases at much cheaper cost as compared to hitherto known technologies. Potable and fresh water once an abundant resource in most parts of the world, is increasingly becoming a scarce commodity in recent-times mainly for two reasons, firstly, due to greater net consumption by industries and for irrigation and secondly due to microbial and chemical contamination. In India, the water quality analyses undertaken in several states under societal mission programmes have shown that a significant number of drinking water sources are contaminated with microorganisms such as bacteria, viruses and protozoans, making them unfit for consumption. Since water is basic unit of life, it is very much required by every body for a variety of purposes, including drinking. Since good quality water already has become a scarce commodity, and therefore, attempts to obtain potable water by disinfecting various water sources without addition of harmful chemicals has always been undertaken.
In order to check and control the water quality acceptable for drinking purpose several devices and techniques have been used from time to time.
Reference may be made to the earliest recorded knowledge of water treatment in the Sanskrit Medical Lore and Egyptian Wall inscriptions wherein Sanskrit writings dating about 2000 B.C. tell how to purify foul water by boiling in copper vessels, exposure to sunlight, filtration through charcoal and cooling in earthen vessels. The earliest known apparatus for clarifying water was pictured on Egyptian walls in the 1500 and 1300 B.C. showing siphoning of water using wick siphons.
Reference may be made to the most prevalent method for water purification which is boiling. The major drawbacks associated with boiling are that it is slow and fuel consuming and above all impairs the natural taste of the water. Disease causing micro-organisms may
survive in water that has been boiled for less than 15 minutes. Hence this method cannot be used for bulk application for community water supply systems.
Reference may be made to yet another method of water purification wherein filtration technique using silver impregnated activated alumina is also used for disinfection of bacteria in the drinking water. But this technique is again very slow and pores of the filter get choked over a period of time and if the candle is not replaced, the blocked pores themselves become the breeding pockets for micro-organisms. Moreover, this technique does not remove all micro-organisms present in water.
Reference may be made to the most common method wherein chlorination of drinking water is done to destroy bacterial contamination. Though chlorination kills the bacteria and effectively controls the water borne diseases, and many a diseases have been practically eliminated in the industrialised countries, but in the developing countries because of high costs of chlorination system, lack of funds, skilled scientific manpower and proper distribution system, such water borne diseases continue to affect the population particularly those residing in rural and remote areas. The main drawback of this method is that chlorine in presence of organic impurities in water produces trihalohydrocarbons which are reported to be carcinogenic to humans. On this account chlorination of water used for drinking purpose has been banned in some of the developed countries including USA. Added, chlorination also ruins the taste of the drinking water if the dose is not strictly controlled.
Reference may be made to still another method of water purification wherein ozonization technique is used for water treatment, wherein the ozone is generated right at site of water source meant for disinfection. The major drawback of this technique is that ozone is , however, known to be very poisonous, costly and, therefore, not feasible for developing countries specially where large populations reside in villages and remote areas and many of them live below the poverty line. Added, the organisms propagate in the distribution system which requires follow up treatment and chlorination as a measure of safety.
Reference may be made to still another method of water disinfection wherein disinfection of microbialy contaminated water is carried out under controlled UV source of energy which can completely eliminate bacteria and viruses without adding anything to the
water or removing the essential nutrients and minerals. UV- light has germicidal properties and at proper intensities of the UV- source, can render bacteria and other pathogens harmless by inactivating their DNA. The drawbacks of this technique is that the process is costly and uneconomical because of high cost of equipment for a community supply and distribution system. The process of course has instant bactericidal effect, but unlike chlorine, which remains in solution while water is being transported and stored, killing most organisms that enter the water after treatment, UV-light has no long term residual disinfecting power and is effective only in UV-C wavelength range 220-280 nm). Photo reactivation of organisms and effect of turbidity on efficiency of the UV-technology are other major drawbacks. Added UV-irradiation technique for drinking water treatment is reported to be ineffective on bacterial cysts and biofilm bacteria and hence offers a very restricted scope for complete disinfection of such types of microbial contaminations present in the drinking water supplies..
Reference may be made to still another method of water treatment known to have been in vogue in some selected cities of USA during late 1960's and patented by Pat. No. US3669857, 6/1972 Kirkham et al .In this method the Oxidation & Reduction Potential (ORP) is continuously measured at a sensing position and a reducing agent is fed to the water in response to the measured ORP to neutralise the oxidising agent and maintain a desired concentration of reducing agent residuals in the water at the second sensing position. This technique being very cumbersome, involves specialized and costly equipment and qualified operators to monitor ORP and to maintain the optimum concentration of the reducing agent and hence is not easily affordable by developing and under developed countries where literacy rate is very low particularly in rural areas.
Reference may be made to the product profile of the "Super Aqua System" utilising an advanced process wherein electrolytically generated copper and silver ions are dispersed into water system for the purpose of microbiological and algae control .A direct current is applied across specially formulated copper and silver electrodes at a dose rate that is automatically maintained by a solid state control unit. The disinfection action is attributed to the positively charged ions which form electrostatic bonds to the negatively charged sites on microorganisms and then undergo reaction at the cell surface, crossing the cell membrane and beginning the inactivation process. The main drawbacks of this system are:
1. The technique is only useful for swimming pool waters as indicated in the product information available on internet web-site under category of US-patents.
2. High cost of silver electrodes for larger electrolytic reactor cells if the system is used for on line water disinfection particularly for community supplies. Such a system is not feasible as such.
Reference may also be made to electrochemical disinfection of bacteria in drinking water using activated fibers by Tadashi Matsunaga et al, Biotechnology and Bio Engineering Vol. 43 page No. 429-433; 1994. In this technique E.coli is adsorbed on to activated carbon fiber and were killed electrochemically when a potential of 0.8 volts vs saturated calomel electrode (SCE) was applied. Drinking water was passed through the reactor in stop-flow mode : 2ml/min. for 12 hours and 1 ml/min. for 6 hours. In absence of applied potential bacteria grew to a maximum concentration of 9.5x10 cells/ml while it reduced to 30 cells/ml after applying potential of 0.8 volts vs SCE. The major drawback of such a system as reported in the paper itself is that this system is capable of treating only a small amount of water, because carbon filter cannot adsorb bacteria effectively.
Reference may also be made to ( Patent No. 178683 dated June 18,1997 ) a technology invented by Industrial Toxicology Research Centre Lucknow (India), a constituent laboratory of Council of Scientific & Industrial Research (CSIR ). It is known for effective disinfection of bacteria (E.coli) from the drinking water. The technology is based upon the principle of anodic oxidation of water in which electric energy is converted into chemical energy which produces oxidants with extra high potential and act on bacteria and other micro-organisms and destroy them.
In spite of the fact that this invention has been reported to be one of the most effective technologies of disinfection available in the world today, it suffers from the following major drawback: :
The use of this invention is restricted to a small section of the society particularly the urban families who could utilise the device of the invention in their homes since its scope of application was limited to treatment of only a few litres (10 Itr) of contaminated water at a
time in 10 minutes time and hence cannot be utilised for community water supplies particularly in nursing homes, hospitals, schools, community centres, multi storied buildings and for rural community living in villages and remote areas.
Another drawback of this technology being its limitation to disinfect microbial contamination beyond 2500 MPN/100 ml of E.coli within specified period of 10 minutes without affecting the water quality. In case higher contamination, is desired to be disinfected, either treatment timing or treatment energy shall have to be increased which implies fair chances of enhanced leaching of toxic metals such as Cr, Ni, Pb, Fe etc. from stainless steel electrodes and an ample possibility of exceeding their concentration in water under treatment beyond WHO safe limits for drinking water. Enhanced leaching of these toxic metals ; specially Cr and Ni may pose health hazards to the consumer of such water if used for drinking. Leaching of Fe also leads to enhanced turbidity and development of palish colour and thus affecting the astheticity of water quality which necessitates post filteration through activated charcoal powder filter after the water has been treated followed by iron removal by suitable techniques.
So, almost all the hitherto known technologies of drinking water disinfection suffer from one drawback or the other besides having their own limitations and scope of application. Considering the immense necessity of an on- line drinking water disinfection and distribution system for community water supplies and specially to meet the requirements of nursing homes, small schools, guest houses, community centres, housing societies and other public places, and also to lend support to the government of India's goal of "Health for all by 2000 AD", extensive research was carried out by Industrial Toxicology Research Centre, Lucknow, a constituent laboratory of CSIR which has led to the device of the present invention.
The main object of the present invention is to provide an electronic device for on-line drinking water disinfection which obviates the drawbacks of the hitherto known prior art devices and methods.
Another object of the present invention is to provide safe drinking water that can be stored without recontamination up to 30 hours after its treatment.
Still another objective of the present invention is to provide a low cost water disinfection
system that can even treat brackish or turbid water unlike UV-technology.
Yet another objective of the present invention is to cut down health care costs of the public by way of better health through use of safe drinking water at almost negligible operating cost of the device.
Another object of the present invention is to provide a device capable of removing a large bacterial contamination of the order of 2.6x103 colony forming units per ml (CPU) at a high flow rate of the order of 500 liters / hour from contaminated drinking water sources without altering physico- chemical properties of the feed water and at the same time maintaining its taste and astheticity.
In the drawings accompanying the specifications;
Fig.l represents the block diagram of the device of the present invention. The main parts are :
1. Electronic control unit.
2. Electronic timer.
5. Motorised / solenoid valve.
6. Temperature sensor for feed water.
7. Turbidity sensor for feed water.
8. pH sensor for feed water.
9. Conductivity sensor for feed water.
10. Feed water sampling outlet tap.
11. Electrochemical reactor with cross pair electrode.
12. Motorised / solenoid valve.
13. Turbidity sensor for treated water.
14. Temperature sensor for treated water.
15. Conductivity sensor for treated water.
16. pH sensor for treated water.
17. Storage reservoir.
18. Micro switch.
19. Float valve.
20. non return valve.
21. Water outflow pipe.
22. Over flow outlet pipe.
23. Water out put tap.
24. Electrical aspirator.
25. Selector switches SW 1,2,3,4.
Fig.2 represents schematic embodiments of the device of the present invention. The various
26. Motorised / solenoid valve
28. Motorised / solenoid valve.
29. Reactor cell.
30. Crossed pair electrode.
31. Vent for waste gases.
32. Over flow drain pipe.
33. Electronic control unit and electronic timer.
34. Electrical aspirator.
35. Back flow check valve.
36. Storage reservoir.
37. Float valve.
38. Bush and guide rod mechanism.
39. Micro switch.
41. Drain taps for reactor cell.
42. Drain tap for storage reservoir.
43. Activated charcoal powder filter.
44. Water outlet pipe.
45. Water outlet tap.
An electronic device for on line drinking water disinfection, which comprises a known pump (3) connected to a suspended particulate free water source, characterized in that the output of the said pump being connected to the input of a reactor cell (11) through a control valve (5), the said reactor cell (11) essentially consisting of one or more rotatable and cyclically polarity interchangeable crossed pair low leaching electrodes (30), the said electrodes being connected to an electronic control unit (1) which supplying modulated DC current, the output of the said reactor cell (11) being connected through a control valve (12) and a non return valve (20) to the bottom of a storage tank (17), the said storage tank (17) being provided with an overflow outlet (22) at its top portion and a pipe (21) having water outlet tap (23) fixed below the level of the said overflow outlet (22).
In an embodiment of the present invention the control valves (5) and (12) used may be such as motorized or solenoid type.
In another embodiment of the present invention the control valve (5) and (12) may be connected to an electronic control unit (1) through an electronic timer (2).
In yet another embodiment of the present invention the rotatable crossed pair electrodes may by connected to a variable speed prime mover such as an electric motro.
In still another embodiment of the present invention the low leaching electrodes used may be such as paltinised Titanium, stainless steel with or without sintering.
In yet another embodiment of the present invention sensors (6), (7), (8), (9), (130, (14), (15), (16) connected to respective measuring instruments for monitoring various physicochemical parameters such as pH, conductivity, Turbidity and Temperature may be provided at the reactor cell (11) inlet and reservoir (17) outlet.
In another embodiment of the present invention the reservoir (17) may be provided with an automatic water overflow controller (19), (18) through a relay (4) capable of controlling the main power supply input of the electronic control unit (1). In yet another embodiment of the present invention a feed water sampling outlet tap (10) may be provided at the input of the reactor cell (11).
In still another embodiment of the present invention the dwell time of the reactor treated water in the storage reservoir may be for a period of at least 15 minutes.
In still another embodiment of the present invention an electrical aspirator (24) may be provided between the outlet of the reactor cell and inlet of the storage reservoir.
In an embodiment of the present invention there is provided an improved on-line electronic water disinfection and distribution device for community water supplies which comprises an electrochemical reaction cell of around 200 litres capacity made from high grade stainless steel sheet type AISI St.304. At the bottom end of this reactor cell is fixed a feed water pipe having water flow rate control valves and a pre-filter fixed on it to remove any suspended impurities in the feed water prior to being treated through one or more pair of crossed electrodes made from low leaching stainless steel sheet grade AISI-St-304 or platinised titanium. The electrodes are powered through an electronic control unit which is capable of supplying wide range constant DC modulated current that can be adjusted from 0 to 6 amperes or more depending upon the bacterial load and required flow rate to be obtained from the device when the feed water comes in contact with the electrodes. The electronic control unit also comprises cyclically polarity interchangeable electronic circuit for electrodes. The top of the reaction cell is covered with stainless steel lid. The electrode pair is suspended by tightening it to the top cover through stainless steel nuts & bolts, which are suitably insulated individually and so also from the reaction cell. The nuts and bolts are connected to electrical terminals which are used to connect electrodes to electronic control unit through suitable cable for supply of electrical energy. The reaction cell is also provided with a vent, an over flow drain pipe and a drain tap to respectively discharge waste gases, excessive water, and draining out of the unused water from the electrolytic cell when not in use or during periodic maintenance. An electrical aspirator whose inlet pipe dips into feed water in the reaction cell through top cover just above the top edge of cross-electrode pair and operable from 220 V/AC supply is used to transfer the treated water from the reactor cell to storage reservoir through G.I. pipe. The open end of the G.I. pipe is fixed near the bottom end of the storage reservoir and a back flow check valve is fitted at its end to prevent back flow of treated water from the storage reservoir to the reaction cell through aspirator. The storage reservoir is made from stainless steel sheet type AISI St 304 and having water handling capacity of 1000 litres with conical base. A drain tap is fitted at its bottom for purpose of draining out treated water when the device of the present invention is not in use or during its maintenance. A water outlet pipe is clamped inside the storage tank along its walls. On the top end of this pipe an activated charcoal filter is placed which is used to remove any colour or hue from the water. On the second end of this pipe an
outlet tap is fixed for drawing the treated water when the device of the present invention is in routine use. A float valve is positioned on the top cover of the storage tank through a bush and guide rod mechanism. The free end of the guide rod being protruding out from the top cover of the storage tank and its upward movement through bush mechanism during rise of the water level in the storage tank, activates a normally closed micro-switch being positioned just above the free end of the guide rod. The triggering action of the micro-switch automatically disconnects the electric supply to electronic control unit and hence to (i) Crossed-pair electrodes (ii) Flow control valves and (iii) Electrical aspirator. This system provides a fool proof safety to the device of the present invention. The float valve, bush and guide rod mechanisms also restore the normal operation of the device as soon as the treated water is drawn out for use and its level in the storage reservoir is lowered to a position such that the float valve and the guide rod are pushed down under their own weights to facilitate release of the lever of the micro-switch and hence restoring the normal electrical supply through normally closed contacts, via the electronic control unit and relay. The electronic control unit is also capable of synchronous monitoring of the electric supply to flow control valves and electric aspirator with respect to the rise and fall in the treated water level in the storage reservoir. The electronic control unit is suitably protected against electrical overloading, mains supply variations and accidental short circuiting of the electrodes. In order to intensify the exchange reaction of the oxidants in the reactor cell the crossed pair electrodes are continuously rotated at slow speed by using a conventional DC electric motor and gear attachment. Suitable water quality measuring electronic on-line equipments such as (i) pH meter (ii) Electrical conductivity meter (iii) Temperature indicator & (iv) Turbidity meter and their respective sensors/electrodes are placed at suitable points for monitoring these parameters both for pre and post treated water.
In the device of the present invention the electrochemical reactions during anodic oxidation take place mainly on the anode surface interface. Intensification of the exchange between organisms and material i.e. transporting of the reaction partners (microorganisms) to the anodic phase boundary and dissipation of reaction products e.g. CO2 and O2 has been achieved by using rotatable and cyclically polarity interchangeable crossed pair electrodes.
In the device of the present invention, the leaching of the toxic heavy metals from the stainless steel electrodes has been contained to within WHO safe limits for drinking water by precisely controlling the treatment timings and then allowing a rest time ( dwell time ) to the
treated water thereby achieving complete disinfection of the microorganisms in the after phase of anodic oxidation reactions.
In the device of the present invention, the electronic control unit is capable of supplying a wide range modulated constant DC current enabling the handling of a variety of feed waters with conductivity ranges varying between 300 - 3000 micro Siemens cm and provides threshold energy to decontaminate microbial load even up to 2.6X 10 CPU / ml or more irrespective of water level in the reaction cell.
The mechanism of the device of the present invention can be explained with respect to the principle of anodic oxidation. Active oxygen species are produced in water under influence of modulated constant DC current supplied from the electronic control unit through a specially designed crossed pair electrode kept immersed in the contaminated water under treatment in the electrochemical reaction cell where the electrical energy is changed to chemical energy. The oxidants produced due to electron reaction and ion migration mechanism have an extra high potential and act on bacteria and other microorganisms more effectively as compared to other oxidant producing agents such as chlorine, hypochlorite, mono-chloroamine, UV & gamma-radiations, ozonation etc. commonly used for drinking water disinfection. These oxidants thus produced, destroy the microbial cell membrane and kill them. The phenomenon ensures a sustained after effect which lasts over a period between several minutes to hours and brings about complete disinfection. The long duration of the microbicidal action as a result of anodic oxidation ensures no fresh growth of the microorganisms up to the point of distribution of treated water especially for on-line system.
The strength of the oxidation process in the device of the present invention was checked by a non-specific test of free oxidants in the treated water by means of a DPD ( Di-Phenyl Di-Oxy Toluene) test. The oxidant concentration was adjusted by varying the operating modulated DC current level and was optimised between 0.3 ppm to 0.6 ppm. Since the speed of extermination of microorganisms is dependent upon individual water parameters, hence to ensure complete disinfection, a short waiting period of 10-15 minutes (dwell time) was allowed between the outflow of water from the reactor cell to the outlet tap. In the present device, this dwell time was provided by coupling the reactor cell to a storage tank and maneuvering the flow rate of the feed water by appropriate process engineering design
The following reactions take place during anodic oxidation ofwater:-
A. Reaction at Anode
B. Reaction at cathode
C. Final Reaction
The device of the present invention is explained with reference to processing of contaminated feed water for purpose of disinfection of pathogenic bacteria. Referring to fig.2 wherein an embodiment of the device of the present invention is shown : the feed water being pumped into the device being routed through an electrically operated flow regulating valve (26) and filtered through a pre-filter (27) to remove suspended impurities, if any, after pre-filtration it is passed on to reaction cell (29) through another flow regulating valve (28) which governs the flow rate of feed water to the reaction cell. The flow rate is so optimised that the contact time of feed water with the electrodes (30) shall be 25-30 minutes before it is aspirated to the storage reservoir (36) by an electrical aspirator (34). The electrical aspirator (34) is supplied the electric power through electronic control unit (33). The treated water is led to the storage reservoir (36) via a back flow check valve (35) which is fitted near the base of the storage reservoir (36). The treated water is provided a dwell time of the order of 10-15 minutes in process of its rise within the storage reservoir (36) before it is drawn for use through outlet tap (45). The activated charcoal filter (43) is used to remove any colour of the feed water if developed at all.
The operation of the device can be explained as follows systematically :
1. Connect the running water tap to the feed water pipe of the device.
2. Adjust the opening of the flow control valves (26) & (28) corresponding to flow rate
of 500 liter/hour, manually pr through electronic control unit (33).
3. Operate the electronic control unit (33) and adjust the treatment current by using
control marked (A) to 6.0 Amps (threshold current for 500 litres/hour flow rate) as soon
as the water level rises in the reaction cell and touches the crossed pair electrode (30)
as must be indicated on the panel meter (M) fixed on the electronic control unit (33).
4. Operate the electric aspirator (34)
5. As the water level rises, it gets continuously treated under the influence of modulated
constant DC current supply through crossed pair electrodes and transferred to storage
reservoir (36) through back flow check valve (35) till the level rises to the activated
charcoal filter (43) and thence to outlet tap (45).
6. When the treated water is not being drained out for use, a foolproof fail safe float valve
(37), and guide rod and bush mechanism (38) actuate the normally closed micro
switch (39) which in turn cuts off supply to electronic control unit (33) and hence to
flow control valves (26) & (28); the electrode (30) and aspirator (34). The input feed
water supply is stopped and possible over flow of water from the storage reservoir
7. As soon as the treated water is drawn from either outlet tap (45) or the drain tap (42) and
water level falls below from a set level, the float valve, (37), guides down through guide
rod and bush mechanism (38) releases the micro switch (39) and normally closed
contact of the micro switch (39) restores back to its normal state.
8. The continuous water treatment cycle is then restored back.
The principle of the electronic device for on-line drinking water disinfection is based on anodic oxidation of contaminated drinking water for inactivation and destruction of microorganisms.
The device comprises of an electrolytic reactor cell fitted with one or more low leaching crossed pair electrodes from highly stable metal sheets such as stainless steel, platinised titanium etc. and powered through cyclically interchangeable polarity modulated constant DC current supplied through an electronic control unit, suitable water flow regulating valves such as
motorised or solenoid type, a conventional DC motor and gear attachment for rotating the electrode, a float valve and bush & guide rod mechanism, and a water outlet tap for supply of treated water.
The device can be operated both on 220 V AC mains supply or a suitable generator set.
The device is capable of providing 5001itres/hour or more of safe drinking water free from pathogenic bacteria (E.coli.) of the order of 2.6X 103 CFU/ml or more present in the contaminated water.
The device requires low capital investment and the running cost is also negligibly low. The net electric consumption calculated for 8 hours a day running of the device shall be close only to 2-units of electric power.
The device is easy to operate and almost maintenance free.
The device is capable of catering the needs for providing safe drinking water for community water supplies.
The treated water can be collected and stored for use without recontaniination up to 30 hours.
The novelty of the device of the present invention is in its capability to disinfect high pathogenic bacterial contamination of the order of 2.6 X 103 CFU/ml or more at high flow rate of the order of 500 litres / hour or more in continuous mode without altering any physico-chemical characteristics of the feed water. Further, water treated by the device of the present invention can be stored without recontaniination up to 30 hours.
The inventive steps of the device of the present invention primarily resides in the low leaching one or more crossed pair, rotatable and cyclically polarity interchangeable electrodes used in the reaction cell.
Another inventive step of the device of the present invention is to contain the leaching of toxic metals from stainless steel crossed pair electrode during treatment process to within WHO
safe limits for drinking water by treating the contaminated water in the reactor cell against gravity during its controlled flow as set by the flow control valve, the treatment time and energy required for disinfection of given bacterial load being automatically set by the electronic control unit and remaining constant for a given bacterial load till the water is aspirated and transferred to the storage reservoir tank through check valve.
Yet another step of the device of the present invention is to make the system fool proof and safe from accidental over flow of water in the storage reservoir tank by using bush and guide rod mechanism fitted atop the reservoir tank that controles the entire electric operation of the system through activation & deactivation action of a single micro-switch.
Another inventive step is in the storage reservoir wherein dwell time of at least 15 minutes allows the residue oxidants present in the treated water to completely disinfect the pathogenic bacteria.
The following examples are given by way of illustration and therefore, should not be construed to limit the scope of the present invention:
Studies on testing of the disinfection efficacy of the device due to bacterial contamination.
In a series of experiments, an overhead tank filled with tap water was contaminated with laboratory cultured E.coli bacteria strain . Contaminated water samples were drawn for quantification of bacteria (Control) , This water was then pumped through motorised /solenoid valve in to the reactor cell at varying flow rates (160 -570 litres /hour for different experiments) where it was treated at different electric currents in the range of 4 to 6 Amp. After treatment this water was aspirated in to a storage reservoir through a back flow check valve fitted near its bottom. The treated water rose up in the storage reservoir continuously at the same rate as that of feed water. A dwell time of 15 minutes was achieved automatically before it was drawn through outlet tap in pre-sterilized conical flask for the purpose of quantification of bacteria.
The experimental results are shown in Tables-1 & la.
Table 1. Influence of current, flow rate and bacterial load on disinfection efficiency (Online mode).
* CPU = Colony forming units.
Table la. Evaluation of disinfection efficacy under optimum electric current of 6.0 Amp. and flow rate of 470 litres/hr
Plate count of E.coli (faecal coliform) was observed in water samples collected before (control) and after (treated) the disinfection process for 30 minutes of drinking water 400 liter/hour flow rate at 6 amp. 0.1 ml of each sample was spread over the pre-prepared MacConkey agar plates. The plates were incubated at 37°C for about 24 hrs. Number of red colonies were enumerated to calculate the E.coli count as CFU/ml (CFU= colony forming units). The counts/ml in control and treated samples of 12 experiments are as give above.
Results shown in the table 1 indicate complete disinfection of bacteria in the contamination range from l.lxlO2 to 3.Ox 103 CFU/ml and flow rate range of 400 to 570 litres/ hour when the contaminated water is treated at modulated DC current in the range of 4.0 to 6.0 Amps.
Studies on metal analysis in the treated water to check possible leaching of metals from the stainless steel electrodes during treatment.
The metal constituents in the electrodes of the device have the tendency to leach out in water under influence of electric current field. But if the leaching is within the safe limits as prescribed by WHO for drinking water, the treated water is considered potable. Metal analysis studies were, thus, carried out on the treated water and samples analysed for leaching of toxic elements from the electrode such as Cd , Cr , Fe. Mn , Ni, Pb, and Zn using atomic absorption spectrophotometer and Induced Plasma Emission Spectro-photometer. Table (2) below shows the results of such studies.
Table 2. Studies on metal concentration(ppm) at optimised Treatment current (6.0 Amp.) and flow rate (4701/hr) Untreated Water sample (control)
ND- Not detectable Experimental Conditions:
1. pH of water sample : 7.85
2. Conductivity : 375 micro Siemens cm.
3. Treatment Current : 6 Amps.
4. Temperature : 27.8°C
The concentrations of the metals analysed in water after treatment reveal that their level was within the WHO permissible limits for safe drinking water.
Studies on pH measurement of the treated water samples
A number of treated and untreated water samples were tested for pH values to assess whether the treatment alters the pH of the feed water? pH of the feed and treated water samples were measured using a known pH meter that has been standardised using standard buffer solutions of 4.0 ; 7.0 ; & 9.2 pH values.
Table (3) shows the results of such studies.
Table 3. pH analysis on the treated water through On-Line Electronic Water Disinfection System.
Permissible limits: 6.5 - 9.2 pH
Flow rate of feed water : 470 litres/hr
Treated current : 6.0 Amps
Dwell time : 15.0 minutes
The results show that there was no significant change in pH values of the reactor treated water as compared to those from the feed water.
Studies on the specific conductivity measurement of the treated water samples
These studies were undertaken to ascertain the effect of water treatment on the electrical conductivity of the feed water. Electrical conductivity was measured both for feed and treated water samples using a known conductivity meter and conductivity cell.
Table (4) shows the results of such studies.
Table 4. Studies on possible change in the specific conductivity of water during the Anodic oxidation
1. Water samples: Raw water samples taken from dug tube well at ITRC Gheru Campus and
stored in the overhead sintex water tank.
2. Contaminant: Gomti river water with bacterial load of 2.60xl03 counts per ml.
3. Flow rate: 470 litres per hour.
4. Water Temperature: 35.4°C
5. pH of the raw feed water: 8.10
The data (table -4) shows that the conductivity of the treated water does not show any significant change. This is understandable since leaching of metal ions from the electrodes during the treatment of water are also insignificant.
Studies on temperature measurement of the treated water samples
These studies were carried out to ascertain the effect on temperature of feed water during
its treatment in the device. This is significant, since abnormal increase in the temperature leads to
change in the taste of the water particularly if used for drinking purposes.
The results of these studies are tabulated in Table (5)
Table 5. Effect of treatment on temperature
shown in table -5 reveal that there is no significant change in the temperature of the water during its treatment in the reactor cell of the device.
Studies on turbidity measurement of the treated water samples The objective of these studies was to observe any change in turbidity of the feed water after it has been treated in the reactor cell of the device. Turbidity measurements were made using a known Nephelo-Turbidity Meter which was standardised by using standard turbid solutions of known turbidity values of 10,0 & 100.0 Nicholson Turbidity units (NTU) prepared from Formazine,.
The results of these studies are tabulated in table -(6)
Table 6. Studies on turbidity measurements of the feed and treated water
Permissible limits 10-28 NTU/mg/L Conditions:
1. Mode of operation : Batch & On-Line modes
2. Flow rate of feed water : 470 litres/hrs (on-line mode)
3. Treatment time : 30 minutes(Batch mode)
4. Treatment current : 6.0 Amps
5. Standards used : Standard solutions of Formazine of 10 & 100 NTU (Nicholson
Turbidity units) used for standardisation of turbidity meter.
The data shown in table -6 indicate that there is no significant change in the turbidity of
the treated water as compared to that of feed water.
Studies on total dissolved and suspended solids of the treated water samples Water with high IDS values due to concentration of calcium, magnesium, chloride and/or sulphate are of generally inferior palatability and may induce an unfavourable physiological reaction in the transient consumer. Water high in suspended solids may be esthetically unsatisfactory. The objective of these studies was to ascertain any change in the amount of TDS & SS during treatment of feed water in the reactor cell and to ensure that the water quality does not change on account of possible change in TDS & SS values during treatment in the device of the invention. Such studies were carried out using known analytical methods and results are tabulated in Table-(7)
Table 7. Studies on total dissolved solids(TDS) and suspended solids (SS) -
Permissible limits as per B.I.S. IS-10500, 1991:
1. TDS: 2000 mg/L; SS: NA
2. Desirable limits for TDS: 500 mg/L;
Permissible limits for TDS: 2000 mg/L
1. Flow rate : 4351tr/hr
2. pH of feed water. : 7.85
3. Conductivity : 620.0 micro-siemens cm
4. Treatment Current : 6 Amps
5. Temperature : 27.8°C
Studies on spectrophotometeric analysis of treated water samples The objective of these studies was to observe any change in the clarity of the treated water. The observation of water clarity were made using spectrophotometeric analysis technique at wavelength 500nm in the visible range of the spectrum (maximum light energy) and using untreated feed water as reference blank. The results of these studies are tabulated in Table (8)
Table 8. Spectrophotometeric studies on water samples
1. Flow rate : 435 L/hr2. pH of feed water : 7.85
3. Conductivity of feed : 375 micro-Siemens cm
4. Treatment current : 6 Amps.
5. Wavelength selected : 550nm
6. Temperature : 27.8°C
The data shown in table (8) indicates that the change in transmittance is less than 1.0% in a series of studies carried out and suggests that there is very negligible change in clarity of the feed water samples after it has been treated in the reactor cell of the device of the invention.
Statistical analysis of the treated water samples
The efficacy of the device of the present invention was cross-classified according to flow rate (litres/hour) and current (Amp.) passed in the system. Significance of the efficiency rates were compared at different current levels and av different time intervals using Chi-square test.
Leaching of different metals in treated water at different levels of current were analysed using Analysis of Variance.
Data obtained from the above experimental studies are given in tables 9.1; 9.2; 9.3. Table 9.1. Flow rate Vs Current Vs Efficiency (n)
Table 9.2. Current Vs Efficiency (n)
Table 9.3. Flow rate vs Efficiency (n)
The data in the tables 9.1; 9.2 ; & 9.3 show that the device is found to be efficient in 5.5 to 6.0 amperes current as the efficiency rate (100%) of disinfection was significantly higher ( p The main advantages of the present invention are: -
1. Highly innovative technology arising out of human needs and striving to support a
comfortable life for man at much cheaper costs as compared to the hitherto known
technologies including chlorination & UV-irradiation used for treatment of
contaminated drinking water sources.
2. 100% disinfection of pathogenic microorganisms achieved even in highly contaminated
drinking water supplies (as compared to other hitherto known devices) in a very short
duration of time (E.coli up to 2.6xl03 CFU/ml have been disinfected at a flow rate of
about 500 litres/hour.
3. No exogenous chemical added in water during treatment if the feed water has
electrical conductivity between 300-3000 microsiemen cm w.r.t. the prototype
device of the present invention
4. Prolonged microbiocidal effect protects the treated water against recontamination up
to 30 hours.
5. The treated water even disinfects the pipelines, if used for distribution at a distance.
6. No health or operating hazards involved.
7. No change in taste, colour or other physico-chemical parameters of the treated
water e.g. pH, temp., conductivity, temperature, turbidity, suspended solids etc. In
other words the astheticity of the drinking water source does not alter.
8. Quick and low cost technology as compared to other hitherto known technologies.
9. Almost free from maintenance problems.
10. No contamination on account of leaching etc. of potentially toxic elements if operated
strictly under optimised conditions.
11. Highly simple and flexible technology that can find applications in many scientific
areas other than water treatment.
12. National fiscal savings on account of reduced health care costs by use of safe drinking
water from the device of the present invention.
1. An electronic device for on line drinking water disinfection, which comprises a known
pump (3) connected to a suspended particulate free water source, characterized in
that the output of the said pump being connected to the input of a reactor cell (11)
through a control valve (5), the said reactor cell (11) essentially consisting of one or
more rotatable and cyclically polarity interchangeable crossed pair low leaching
electrodes (30), the said electrodes being connected to an electronic control unit (1)
which supplying modulated DC current, the output of the said reactor cell (11) being
connected through a control valve (12) and a non return valve (20) to the bottom of
a storage tank (17), the said storage tank (17) being provided with an overflow
outlet (22) at its top portion and a pipe (21) having water outlet tap (23) fixed below
the level of the said overflow outlet (22).
2. An electronic device as claimed in claim 1 wherein the control valves (5) and (12)
used are selected from motorized or solenoid type.
3. An electronic device as claimed in any of the claims 1-2 wherein the control valves
(5) & (12) are connected to an electronic control unit (1) through an electronic timer
4. An electronic device as claimed in any of the claims 1-3 wherein the rotatable crossed
pair electrodes are connected to a known variable speed prime mover.
5. An electronic device as claimed in any of the claims 1-4 wherein low leaching
electrodes used are selected from Platonized titanium, stainless steel with or without
6. An electronic device as claimed in any of the claims 1-5 wherein the feed water
sampling outlet tap (10) is provided at the input of the reactor cell.
7. An electronic device as claimed in any of the claims 1-6 wherein an electrical
aspirator is provided between the outlet of the reactor cell an inlet of the storage
8. An electronic device for on-line drinking water disinfection substantially as herein
described with reference to the examples and drawings accompanying this
|Indian Patent Application Number||697/DEL/2000|
|PG Journal Number||13/2009|
|Date of Filing||31-Jul-2000|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001, INDIA.|
|PCT International Classification Number||C02F 5/00|
|PCT International Application Number||N/A|
|PCT International Filing date|