The sources of water can include any aboveground collection such as rivers, lakes, ponds etc. Water contamination can be broadly categorized into three classes:
Chemical contaminants are elements or compounds. These contaminants may be naturally occurring or man-made. Examples of chemical contaminants include nitrogen, bleach, salts, pesticides, metals, toxins produced by bacteria, and human or animal drugs. Shraddha industries is pure water manufacturers and suppliers in vijayawada we do CDI technology for bore/ground water purification so that this water becomes healthy drinking water, we are best drinking water plants in vijayawada.
Salinity is typically used as an indicator to describe all dissolved chemical contamination.
Salinity is not just common salt as we know it as sodium chloride but can also be dissolved calcium, magnesium, sulphate, bicarbonate, boron, and other ions. It is assessed in terms of total dissolved solids(TDS) and measured in part per million or mg/litre.
Biological contaminants are organisms in water. They are also referred to as microbes or microbiological contaminants. Examples of biological or microbial contaminants include bacteria, viruses, protozoan, and parasites. Physical contamination typically refers to abnormal pH, excess sediment or turbidity or any other physical feature that makes the water undrinkable. Human Contamination sources.
Man-made contamination is mainly caused due to the socio-cultural factors such as untreated sewage from large-scale urbanization & industrialization and also as well as agricultural practices. India’s improving Standard of living among its fast growing urban population which is contributing to large amounts of solid and liquid waste.
Pure and crystal clear water is the lifeline of the universe. It is an essential component for the effective functioning of our body as 50 to 70% of it is made up of water including skin, tissues, cells and the organs so its very important that we drink clean water with the essential minerals for our body. As we have discussed about different contamination sources, we use CDI technology to remove the contaminants from water thus by providing you fresh and clean drinking water.
Capacitive Deionization(CDI) is a technology for removing salinity from water. This is a new generation of water treatment system that can treat ground or surface water containing high dissolved salts to produce clean drinkable water that meets WHO standards. It works on electrophoretic phenomenon to provide low TDS (Total Dissolved Solids) drinking water. Canals, tanks are converted to drinking water by using CDI technology that will decrease TDS.
CDI is an excellent alternative to RO technology. This is a high recovery system where water wastage is just 20% as against 70% from a RO system. It does not use any chemicals, consumes less power and has the lowest operating cost for treating water when compared to other systems.
Compared to conventional RO systems that waste more than 50% of water, the maximum water wastage is 20%. This results in long term conservation of ground water.
It uses no chemicals and has low consumables for operation. It consumes less power and the total cost of producing treated water .
It has a built in controller that automates the working of plant in typical Indian conditions. There is no major skill needed to operate the plant. The system can be managed and operated by local resources where it is installed.
This technology reduces all dissolved salts like calcium, magnesium, fluoride, nitrates, arsenic and other contaminants typically found in ground water but yet retains the desired levels of minerals required for human body.
This technology does not use any chemicals for treatment. The drain water coming from the system does not contain any chemicals that are hazardous to environment. This ensures safe release of water back to the environment.
CDI cells uses different coupled electrodes contained in a pressurized container, supplied with direct current at a potential difference of 1.6 Volt. The electrodes are placed at a distance at an order of magnitude of 0.1mm.
By powering the electrodes, an electrostatic field is created. The salts contained in the water, having an electric charge will be attracted by the electrode with opposite charge. Operating at low voltages, electrolysis and gas production will not occur. The result is the partial or total demineralization of the water as Step 1.
Once the electrodes are saturated with ions, the system will automatically short circuit the electrodes as step 2 releasing the ions and after that will reverse the polarity and move all the salts to the drain as step 3 in a small amount of water. At the end of step3, electrodes are regenerated, the polarity is reversed back to normal and the cycle starts again.
The whole process takes place automatically at a frequency of about one minute.
When water passes between the electrodes, the ions get attracted to opposite charged electrodes.
The water void of these salts and metals come out of the system.
With more and more ions sticking to the electrodes, they become saturated when this happens, the system automatically changes the polarity. The ions sticking to the electrodes fall off.
Water is then flushed between the electrodes and the wasted ions are flushed to drain. The polarity is reversed back and the ion removal process starts again.
Plimmer Is A New Generation Of Water Treatment System That Can Treat Ground Or Surface Water Containing High Dissolved Salts To Produce Clean Drinkable Water That Meets Who Standards. This High Recovery System Does Not Use Any Chemicals, Consumes Very Low Power And Has The Lowest Operating Cost For Treating Water When Compared To Any System In The Market Today.
Plimmer Is Based On A Technology Called Capacitive Deionization. Capacitive Deionization Is A Technology For Removing Salinity Water. This Innovative Technology Is Used To Desalinate Water Without Using Resin Or Membrane Filters. It Does Not Require Chemicals To Treat Water And Uses Very Low Power To Separate Salts In Water.
The System Takes Out The Following Salts (Not Limiting) In A Single Process. By Controlling The Flow And Managing The Contact Time, It Is Possible To Ensure The Required Salts Be Retained In The Output Water That Is Good For Consumption. Table Below Shows Some Examples Of Salts And Metals Removed Using Plimmer
|Total Dissolved Solids||Chrome||Bacteria|
|Calcium Carbonate||Arsenic||Chromium 6|
CDI Cells Uses Different Coupled Electrodes Contained In A Pressurized Container, Supplied With Direct Current At A Potential Difference Of 1.6 Volt. The Electrodes Are Placed At A Distance At An Order Of Magnitude Of 0.1mm. By Powering The Electrodes, An Electrostatic Field Is Created. The Salts Contained In The Water, That Possess An Electric Charge, Will Be Attracted By The Electrode With Opposite Charge And Blocked Its Surface By The Electric Field.
Operating As Low Voltages, Electrolysis And Gas Production Will Not Occur. The Result Is The Partial Or Total Demineralization Of The Water (Step 1 In Picture Below) Once The Electrodes Are Saturated With Ions, The System Will Automatically ShortXCircuit The Electrodes (Step 2 Picture Below) Releasing The Ions And After That Will Reverse The Polarity And Move All The Salts To The Drain (Step 3 Picture Below) In A Small Amount Of Water (Around 20% Of Income Water). At The End Of Step 3, Electrodes Are Regenerated, The Polarity Is Reversed Back To Normal And The Cycle Starts Again. The Whole Process Takes Place Automatically At A Frequency Of About One Minute.
When Water passes between the electrodes, the ions get attracted to opposite charged electrodes. The water void of these salts and metals come out of the system
With more and more ions sticking to the electrodes, they become saturated - when this happens, the system automatically changes the polarity. The ions sticking to the electrodes fall off.
Water is then flushed between the electrodes and the wasted ions are flushed to drain. The polarity is reversed back and the ion removal process (Step 1) starts again.
Plimmer Is Ideally Suited To Operate In Rural Areas For The Following Reasons
Plimmer Is Highly Energy Efficient. It Can Operate In Single Phase, Low Voltage Situations That Are Typically Encountered In Villages. The Operating Voltage Ranges From 110 v X 230 v
Plimmer Comes In A Modular Fashion Starting From 100 Lph / 2000 Lpd To 2000 Lph / 48000 Lpd. This Will Ensures Adoption From Small Villages To Gram Panchayats
The Overall Reject From Plimmerf Is Less Than 20%. With This Small Quantity Of Reject We Can Manage It In Following Ways:
To Help Reduce O&M And Need For Skilled Resources, The Following Has Been Adopted In Plimmer
The Treated Water can be available at low cost.
Pre-treatment is a crucial component for water treatment. Proper pre-treatment is required to ensure smooth operation of the plant and lesser maintenance of the system.
Input from the sump/main lines enter the raw tank.
This is done to remove any bacteria and pathogens in water. Ozone or chlorine di-oxide is a very effective, safe and strong oxidizing agent that kills bacteria. It is environmentally safe, does not require any consumables and is produced freely onsite using oxygen available in atmosphere. By treating the inlet tank, we will ensure that the rest of the equipment in the process are bacteria free.
This is used to deliver suitable pressure to the sand filter and carbon filter and rest of the unit.
PSF is used to remove any turbidity in water. The PSF is filled with a mixture of gravel at the bottom, followed by fine sand and then a layer of Anthracite for good turbidity removal from water.
Water then passes through activated carbon present in a pressurized vessel. ACF is used to take out any organics in water and it also takes out any residual ozone/chloride present in water restores taste.
UF ensures that there are no bacteria entering the system and will protect from Bio-fouling and also ensures treated water is void of any bacteria or viruses. This is a self-cleaning system suing water for back washing as in PSF and ACF.
Once water passes through the pre-treatment stages, it enters into CDI for treatment. These systems are built modularly and delivered as a box. Each of these boxes will have a suitable capacity to produce quality treated water complying to Indian standards. By building the system modularly we will ensure simpler maintenance and ease of installations.
Water coming out of CDI technology is directly sent to the output storage tank from where it will be discharged for consumption.
Post treatment ensures the electrodes in the cells are kept clean. This process is done automatically. CDI can programmed to run continuously for a period of 5/10/20 hours. After running for these durations, the system is programmed to rest for 1/2/4 hours respectively.
During the rest period, the system automatically sucks in a desired quantity of maintenance solution. The system then cleans the electrodes with this solution. The entire cleaning operation takes about 5 minutes after which the system rests till the rest cycle is complete. This cleaning extends the life of the cells.
The Complete System Works automatically and is web enabled, when connected through the net, the system can also be accessed from anywhere for monitoring and maintenance purposes.
Users will be able to access the system through a tab, smartphone or computer using the web interface. All Functionalities of the machine including setup, status and performance parameters can be viewed this screen.
IDROPAN'S is also enabled for an IoT architecture which will allow users to operate and maintain the plant from anywhere once it is connected to the local area network.
All parameters such as flow,conductivity, pressure and any errors caused by the system can be seen using this interface and suitable action at site can be planned accordingly.
Water contamination can be broadly categorized into three classes: chemical, biological and physical.
|Contaminant||Source||Health Consequences||Occurrence/Population affected in India|
|Arsenic||Geogenic (Underground Rock and Alluvial Formations)||Nausea and vomiting, decrease in red and white blood cells, abnormal heart rhythm, damage to blood vessels, darkening of the skin and the appearance of small “corns” or “warts” on the palms, soles, and torso8. High levels of arsenic can result in death.||Excess level of > 0.05 mg/L affects nearly 16 million people in five states.|
|Fluoride||Geogenic (Underground Rock and Alluvial Formations)||Denser bones in adults, but bones may be more fragile and brittle if exposure is excessive. Dental fluorosis8.||Excess levels > 1.5 mg/L fluoride is found in 199 districts of 19 states. Over 66 million people are at risk for fluorosis.|
|Heavy Metals||Untreated Industrial Waste||Cadmium: kidney damage. Lead: severe brain and kidney damage. Mercury: permanent damage to brain and kidneys8. Manganese: changes in nervous system and behavior, effects include slow and clumsy movements8.||Untreated (industrial and domestic) waste is contaminating water sources with heavy metals such as mercury, lead, nickel, chromium and manganese in various parts of the country2.|
|Iron||Geogenic (Underground Rock and Alluvial Formations)||Not considered harmful to the human body but Iron rich water is not considered desirable and can add biological contamination to the water.||Iron is found in 23 states and territories in India.|
|Nitrate||fertilizers, septic systems and manure||In animals, Nitrate alters thyroid function, amyloidosis of the liver, kidney, spleen, and adrenal glands, and affects lung and liver.||All of India’s fourteen major river systems are heavily polluted1. Nitrate is the most common contaminant. High levels of nitrate are found in all water sources where there is heavy usage of fertilizer and pesticides.|
|DDT (Dichlorodiphenyltric-hloroethane), HCH (Hexachlorocyclohex-ane)||Pesticides and Insectides||DDT affects the nervous system. 6-10 mg/kg leads to headache, nausea, vomiting, confusion, and tremors. The International Agency for Research on Cancer (IARC) has determined that DDT is possibly carcinogenic to humans. The IARC has also classified HCH (all isomers) as possibly carcinogenic to humans.||Pesticides and heavy metals detected in drinking and ground water in different parts of India. (Bouwer H, 1989; Dikshit TSS et al, 1990; Jani JP et al, 1991; Kumar S, 1995; Bansal OP et al, 2000; Ray PK, 1992). HCH and DDT were detected in different sources of water – wells, hand pumps and ponds in Bhopal.|
|Salinity||Over drafting of ground water aquifers, saline soil, seawater||Saline water cannot be used for drinking, bathing or cooking as it is not drinkable and causes skin lesions if used for bathing.||Affecting 13 out of 28 states5. In some areas of Rajasthan and Gujarat, salinity is so extreme that well water is used directly for salt manufacturing by solar evaporation.|
Much residential, office, rural and urban communities in India have turned to Reverse Osmosis technology as a means to purify the water. RO is heavily marketed as a household product in urban sectors while community level RO Systems are being installed in rural areas by various NGOs (Non Governmental Organizations) through state sponsored programs.
RO is the opposite of the natural process of osmosis. During osmosis, pure water will flow through a semi-permeable membrane from the dilute side to the concentrated side until both sides have reached the same level of concentration. In Reverse Osmosis, the natural process of osmosis is reversed: by using high pressure, pure water is forced to flow through the membrane from the concentrated side to the more dilute side.
A RO system has a very selective semi-permeable membrane which typically rejects 99% of the impurities from source water resulting in very pure water on the other side of the membrane. The rest of the water which has all the impurities is sent down the drain as reject. A typical RO operates at a recovery rate of 15% to 60%. The recovery rate is defined as:
For example, if 100L (Liters) of contaminated feed water is fed into a RO system operating at 60% recovery rate, that system will provide 60 Liters of purified water. This means for a RO system that has 60% recovery rate, for every 100 Liters of feed water, 40 Liters of water is discarded as waste to achieve 60 Liters of purified water.
The principle limitations of RO technology are its environmental impact: the power requirement of running the high pressure pump, disposing of highly concentrated waste water and capital plus disposal cost associated with membranes and filters.
In comparison to conventional distillation water purification technologies such as ME (Multi Effect) or MSF (Multi Stage Flash), a RO system consumes 48% more energy10 (RO Requires= 7.6 K-Wh/m3 per kg purified water, ME/MSF utilizes 3.6 K-Wh/m3 per kg of purified water). However, the power issue can be mitigated using renewable energies such as Solar or Wind Power. Furthermore, most RO membranes have pre-filters which need to be replaced on regular intervals. The used pre-filters have to be thrown away after single use which adds to the environmental cost associated with solid waste generation.However, the biggest challenge to operating a RO system in water stressed regions is dealing with the amount and pollution level of the reject waste water which can be substantial depending on the recovery rate of the RO system.
Figure 3 shows differences in reject waste water generation to produce 75 Liters of purified water at various recovery rates.As seen in Figure 3, in a higher recovery RO system, less water is rejected. However, the concentration of pollutants increases with increasing the recovery rate.
Figure 5 illustrates the adverse effect of high TDS and high volume of reject water at various recovery rate scenarios. Concentration of the reject waste water TDS was calculated using the following formula
at lower recoveries, more waste water is generated which is either the same pollution level as source water or starts to increase in pollution concentration as recovery is increased. Thus, at higher recoveries (> 60%) the effluent pollution concentrations have more than doubled.
|15% Recovery||25% Recovery||40% Recovery||60% Recovery|
|Source Water Flow (Liters Per Minute)||500||300||187.5||125|
|Reject Flow (Liters Per Minute)||425||225||112.5||50|
|Product Water Flow (Liters Per Minute)||75||75||75||75|
|Source Water TDS (ppm)||3000||3000||3000||3000|
|Product Water TDS (ppm)||500||500||500||500|
|Reject Wastewater TDS (ppm)||3029||3500||4500||7000|
At present, India has no regulatory policy for the safe disposal of concentrated rejected water; it is common to discharge the rejected water back into the environment.Long term discharge of untreated rejected water into the environment will render the soil and ground water contamination to irreparable levels. The situation may come that it will not be possible to purify the water even via RO. Increasing salinity in the soil and water will also negatively affect the agricultural productivity levels.
Despite the intrinsic shortcomings of RO, many domestic and government supported installations are put precisely in regions which have severe problems of water quality and availability. In Punjab where ~95% (112 out of 118 blocks5) of the ground water aquifers are over their recharge limit (extraction is greater than recharge) and ground water salinity is affecting 35% of the state (6 out of 17 districts5), the Punjab State Government is pursuing community run RO systems to meet rural water needs. With the collaboration of NGOs, the Punjab government has installed 120 water service centers, a combination of RO and UV units, that service 600 villages. More service centers are in the pipeline.
Similarly, in the state of Haryana, where 66% (71 out of 108 blocks5) of the ground water aquifers are over their recharge limit and ground water salinity is affecting 55% of the state (11 out of 20 districts5); the Haryana government has installed over 63 RO based systems. The state of Gujarat suffers from over 80%5 saline water sources and the adoption rate of RO technology is very prevalent due to the need for good quality drinking water. Hundreds of RO plants ranging from 5-10 Liters per hour to 5000 Liters per hour have sprung up all over the state to meet the demand.
In Gujarat alone, this is leading to ~ 0.5 Million Liters Per Day of high TDS (TDS>1000 mg/L) reject water into the ground and surface water sources of a state already struggling with issues of water salinity and availability. The Water and Sanitation Management Organization (WASMO) of Gujarat is embarking on a rural water treatment programs throughout the state. It is planning to install RO plants in villages through a variety of management options.
India needs aggressive water conservation techniques and alternative water purification technologies to cope with the demand for good quality water for its growing population and their increasing needs. The lack of regulatory policy for ground water mining as well as the availability \of government subsidized electricity provides individuals and communities with inexpensive ground water. With rejected water doubling in concentration and being discharged (untreated) back into the environment will lead to a rise in the overall TDS of the ground water and soil salinity over the course of time. Long term effect may include decline in agricultural productivity and hindering of manufacturing capabilities due to lack of fresh water. This paper is calling for a longer and more extensive study to be conducted to examine long term effects of discharging RO reject water and its safe disposal in water stressed regions of India. Further research should also be carried out to develop eco-friendly technology alternatives to RO filtration.
Lalit Mohan Sharma is Group Leader (Natural Resource Management Center) at Institute of Rural Research and Development (IRRAD) an initiative of Sehgal Foundation. He is a graduate civil engineer and holds a Masters of Technology (Management & Systems) from Indian Institute of Technology, Delhi. Under his leadership IRRAD’s water management program has been recognized widely. The organization has won UNESCO-Water Digest ‘Best Water NGO’ award for ‘Revival of Rural Water Resources’ in 2009 and 2010 and ‘Best Water NGO’ for ‘Rain Water Harvesting’ 2008 and Ministry of Water Resources, Government of India ‘Ground Water Augmentation Award-2010’. He has presented several papers on issues related to integrated and sustainable development of water resources and sanitation.
Chemistry Department, SMDRSD College
Pathankot, 14500, Punjab, India
The popularity of reverse osmosis (RO) water has been steadily increasing since it was first introduced as a home water purification system in the 1970s. Even the bottle water companies are also using reverse osmosis water these days. Reverse Osmosis (RO) is a membrane based process technology used for desalination of water to make it drinkable. The RO water purification method involves the process of forcing the water through a semipermeable membrane, which filters out contaminants larger in size than water molecules. The most mineral particles that are required by our body such as sodium, magnesium and iron are larger in size than water molecules and get removed from water by semipermeable membrane of the RO system thus render water unhealthy for consumption. The World Health Organisation has conducted a study which exposes some of the health risks associated with demineralised drinking water. Some of the health risks associated with consuming reverse osmosis water are discussed here.
Drinking water supply comes from ground and surface water sources. As per drinking water regulations municipalities are required to treat and disinfect drinking water before distributing it to public due to the possibility of the presence of micro-organisms, toxic minerals, metals, organic chemicals, pesticides etc. Improperly treated drinking water is responsible for causing a number of diseases. The guidelines about drinking water standards are given by Word Health Organisation and European Union .
Actually all substances present in water are not harmful to our health, some of them are not harmful to our health. Some of them are health improving too. The water almost or completely free of dissolved minerals as a result of deionisation, distillation, reverse osmosis or other technologies is called demineralised water. There are many pros and cons on drinking demineralised water. The arguments favouring drinking demineralised water is that the minerals present in water interfere with our body functions. Many articles written by doctors or nutritionists claim that the presence of minerals in drinking water cause diseases like occurrence of cardiovascular diseases, diabetes, cancer, respiratory diseases etc. The argument against drinking demineralised water are that by distilling or reverse osmosis we have lost a primary source of necessary minerals in our diet and that the water has lost its own minerals will attract and absorb minerals in our body resulting in deficiency of minerals.
The importance of minerals and other beneficial constituents in drinking water is even mentioned in Rig Veda in which properties of good drinking water are described as, “ Sheetham (cold), Sushihi(clean), Sivam(should have nutritive value and required minerals), Istham(transparent), Vimalam Lahu Shadgunam(its acid base balance should be within normal limits). Initially demineralised water, first distilled water, later deionised or reverse osmosis treated water had been used for laboratory, technical and industrial purposes. These technologies became more extensively used for obtaining drinking water in 1960s due to limited drinking water sources in coastal and inland areas, the increasing drinking water demands resulting from increasing populations, higher living standards, development of industries and mass tourism. Demineralisation of water was also required in the areas where the water sources are sea water or highly mineralised brackish water. Demineralised water was also used in ocean going ships and spaceships where this was the only source of drinking water.
Initially these water treatments were not used at homes since they were costly, but with improvement of economic status, these days RO system has become an essential gadget at the homes of even middle class in India in addition to higher class. Demineralised water is defined as water almost or completely free of dissolved minerals, obtained by distillation, deionisation, reverse osmosis or Nano filtration etc. The total dissolved solids (TDS) in this water is quite low approximately 1mg/l. From the beginning it was clear that demineralised water without further addition with some minerals might not be fully suitable for consumption due to following reasons.
The potential for adverse health effects from long term consumption of demineralised water is of concern not only in countries which lack adequate fresh water, but also in countries where such types of home water treatment systems or bottled water are widely used. So the exposures and risks should be considered not only at community level but also at the individual or family level.
Review of some experimental facts obtained from the experiments conducted on laboratory animals and human volunteers and observations obtained from populations supplied with demineralised water and infants given beverages prepared in distilled water, the possible harmful effects of reverse osmosis water consumptions are discussed here.
Calcium and magnesium are essential elements for our body. Calcium is part of our bones and teeth. It is also important in conducting myocardial system, heart and muscle contractibility, blood clotting etc. The most common disease caused by calcium deficiency is osteoporosis. Its deficiency has also been proved to cause hypertension .
Magnesium plays an important role in glycolysis, ATP metabolism, transport of elements such as potassium, sodium and calcium through membranes, synthesis of proteins and nucleic acids, muscle contraction etc. Its deficiency increases the risks to humans of developing various pathological conditions such as hypertension, cardiovascular diseases, vasoconstrictions, diabetes and osteoporosis etc. .
It has been found that drinking water low in magnesium for long term can cause increased morbidity and mortality from cardiovascular diseases, risks of motor neuronal disease, pregnancy disorder etc. Water low in calcium taken for long duration of time causes high risk of fracture in children, certain neurodegenerative diseases, preterm and low weight birth etc. Deficiency of both magnesium and calcium in drinking water can also cause some types of cancers .
It has been reported by WHO and other studies that drinking of demineralised water can cause electrolyte imbalance in body as all the minerals from such water are filtered off by semipermeable membrane in reverse osmosis or removed by distillation in distilled water. So this mineral free water in our body leaches electrolytes from our tissues, so that our body can function normally and can eliminate waste. If water redistribution process in our body is not functioning properly, one may feel fatigue, muscle cramps, weakness, headache and abnormal heart rate. In the past, acute health problems were reported in mountain climbers who used to drink water from melted snow that was not supplemented with necessary ions. More severe health problems arising from such condition are brain oedema, convulsions, metabolic acidosis etc. 
When demineralised water is used for cooking, it results in a great loss of essential elements from food i.e. about 60% magnesium and calcium, 70% manganese, 86% cobalt, 66% copper etc. However these losses in metal contents are not reported when the cooking is done in natural water. Since some nutrients are only ingested with food, low mineral water used for cooking may take away these nutrients from food and results in a striking deficiency in these elements. So any factor that causes the loss of essential elements and nutrients during cooking and processing of food should be avoided as the diet these days taken by us already do not provide necessary elements in sufficient quantities [14-15].
Demineralised water is highly aggressive to materials it comes into contact with. So it readily dissolves metals and organic substances from the pipes, storage tanks, containers and other plumbing materials and thus it becomes contaminated. Thus the act of cleaning water with RO may end in addition of more harmful substances. Calcium and magnesium present in water and food have been found to have antitoxic activity and hence they can prevent the absorption of some toxic elements from the intestine into blood [16, 17].
In reverse osmosis process bacteria get filtered out by semipermeable membrane because of their usually larger size than the pores of the semi-permeable membrane and thus are drained out with waste water which is then rejected by the system. But, it is significant to point out that reverse osmosis drinking water systems are not bacteria proof. The system may have exposure to some bacteria prevailing in the environment. Bacterial contamination may occur during the actual processing of water in the system. The RO membrane can have defects making bacteria able to pass through it. Bacteria may sometimes enter the water through the seal that holds the RO membrane which then flourish in low mineral RO water due to the lack of a residual disinfectant present in natural water and great availability of leached nutrients. The regrowth of bacteria is encouraged in RO water due to the lack of a residual disinfectant present in natural water and great availability of leached nutrients in aggressive water particularly when it has high temperature [18, 19]. So in addition to reverse osmosis, we should also use ultraviolet purification system to eliminate bacteria completely from our water. There are reverse osmosis/ultraviolet combined systems that are these days designed to confirm that no bacteria enter into drinking water.
As demineralised water contains no minerals, it absorbs other elements very easily. Theoretically, demineralised or reverse osmosis water should be neutral with pH value of 7. But, such water isunstable in nature and hence readily absorbs carbon dioxide in the air when it comes in contact with air which makes the water acidic, hence more corrosive to pipes and storage tanks. Freshly demineralised water may reach pH as low as 5.5 in a short time. Acidic water is not healthy for drinking as it can lead to imbalance of pH in blood, which should be alkaline.
In the natural health and medical communities, acidosis in the body is considered an underlying cause for most of the degenerative diseases . Dr. Otto Warburg won the Nobel Prize, in 1931 for discovering the cause of cancer. According to him cancer was caused by a lack of cellular oxygenation due to acidosis in the body. It has also been determined in various medical researches that drinking acidic water as well as other acidic beverages often cause an imbalance of minerals in the body. Low mineral water increased diuresis i.e. the production of urine by the kidneys by 20% on average and significantly increased the elimination of sodium, potassium, calcium magnesium and chloride ions from the body as reported by WHO in a study.
Low mineral water or reverse osmosis water has low TDS so it tastes bitter. The demineralised water with a TDS of 25-50 mg/l has been described as tasteless by the World Health Organisation (WHO) in 1980, based on a study report. (WHO 2004 paper). RO water purifier manufacturers have become aware of this problem so these days some RO water purifiers have been fitted with a Cartridge called a remineraliser cartridge which is filled with purified alkali essential mineral salts of Calcium and Magnesium, through which the pure RO water is made to pass. As a result the pure RO water dissolves some of the essential minerals from this remineralisation cartridge to give RO water which does not taste bitter, have some essential minerals and is alkaline. However even this remineraliser cartridge cannot add all the essential nutrients present in natural water.
Demineralised or reverse osmosis water is less effecting in satisfying thirst than water rich in minerals. (WHO 2004 paper) As a result lesser amount of water is consumed and hence tempts consumers to take other less healthy beverages such as soft drinks, carbonated water, tea, coffee etc. which adds to their calorie intake leading to obesity and in turn to many diseases.
Reverse osmosis is effective for removing most of the contaminants from water but it alone does not remove volatile organic compounds (VOC), chlorine, chloramines, pharmaceuticals and other chemicals found in municipality water. The RO’s efficiency to remove contaminants from water depends upon the concentration and chemical nature of contaminant, nature of membrane and the operating conditions. But these days R.O. systems have multistage filtration media, such as activated carbon, in addition to R.O. membrane which removes chlorine, VOC and certain pesticides .
Reverse Osmosis also removes fluoride that natural water contains. Lack of fluoride in drinking water causes tooth decay and cavities in children. Some dentists relate the lack of fluoride in drinking water as a cause of an increased number of cavities in young children who consume distilled, RO or demineralised water .
Epidemiological studies in many countries all over the world since the early 1960’s, have reported that water low in minerals especially calcium and magnesium is responsible for rise in morbidity and mortality from cardiovascular disease. Epidemiological studies were conducted among Russian populations, in the Ust-llim region of Russia in 1992 . People in these two regions were provided with either low-mineral water or normal water. The study mainly focused on the morbidity and physical development of 7,658 adults, 562 children, 1,582 pregnant women and their infants and new-borns (WHO 2004 paper).
People who were provided with low-mineral water suffered from higher risks of hypertension, coronary heart diseases, chronic gastritis, goitre, gastric and duodenal ulcers, pregnancy complications and many types of complications in new-borns and infants including anaemia, jaundice, fractures and growth disorders. (WHO 2004 paper) Effect of short-term consumption of low mineral water were observed in the Czech and Slovak populations who started using reverse osmosis-based systems for final treatment of drinking water at their home taps in 2000-2002. Various health problems indicative of acute magnesium and calcium deficiency were reported within several weeks or months. Among these were cardiovascular disorders, weakness, tiredness and muscular cramps .
It was reported in a multi-city study that the women living in cities supplied with low-mineral water showed cardiovascular changes in their ECG, higher blood pressure, headache, dizziness, and osteoporosis more frequently as compared to those living in cities which were supplied with higher mineral content water [24-25]. It was reported by the researchers in Israel that low-mineral water used for agricultural irrigation has harmful effects on crops. Israel is a world innovator in using desalinated water in farming. Calcium deficiency has been observed to cause physiological defects, whereas magnesium shortage harms plant development. The predominantly significant harmful effects are found to be to the crops such as tomatoes, basil and certain species of flower are.
After analysing several scientific studies regarding demineralised or reverse osmosis water, the World Health Organization released a report stating that such water “has a definite adverse influence on the animal and human organism.” Thus provided various norms about the safe drinking water .
At these concentrations no adverse health effects were observed. The recommended magnesium levels were based on cardiovascular system effects, while changes in calcium metabolism and ossification were used as a basis for the calcium levels (WHO paper 2004).
RO systems are doing a great work of removing impurities/ contaminants from the water but the problem with RO systems is that they do not discriminate between the good and bad minerals as they remove everything. So the need is to remineralise the water once it has passed through the RO membrane. So adding back the calcium and magnesium in proper concentration solves the problem. RO industry has become aware of the reality that long term consumption of demineralised water is not good for health. They are also trying to find solutions to make their RO filtered water healthy.
Initially some industries offered corosex and calcite solutions. Though corosex and calcite will remineralize water but they were not designed to work with the aggressive acidic water produced by RO system. Hence corosex and calcite minerals can dump more minerals into water than our kidneys can digest and end up in the formation of kidney stones. So corosex and calcite are not the right solution for remineralization of aggressive acidic water produced by RO machines. These days Nano filtration and ultrafiltration is gaining the rapport as these filters are cost effective, much smaller and allow faster flow of water.
The filter required depends upon the source of your water. For the water supplied by municipality does not require to be cleaned by RO system unless the municipality adds fluoride to it. There is a new water filter ( made in America) which is consist of two types of filters, activated carbon and zeolite minerals bound with polymers to form a carbon block. It removes 85% of fluoride at the rate of water flow rate 2 litres per minute and 95% if flow rate of water is reduced to 1 litre per minute. So problem of mixing of fluoride by municipality in water supply can be solved.