India to grant rainwater harvesting systems to be used for collecting drinking water but our experts should understand its limitation.
Posted on January 14th, 2017

Lankaweb Science Editor

India and Sri Lanka today signed a Memorandum of Understanding (MoU) to construct 3000 rain water harvesting systems at a cost of Rs 300 million in Jaffna District.

According to Adaderana news report, the MoU was signed by Mr. Arindam Bagchi, Acting High Commissioner of India and Mr. V. Sivagnanasothy, Secretary, Ministry of National Integration and Reconciliation in the presence of A. H. M. Fowzie, State Minister of National Integration and Reconciliation.

The project envisages construction of 3000 rainwater harvesting systems for 3000 households in selected divisions of Jaffna District. The scope of the project also includes training of the households on operation and maintenance of the systems.

Beneficiaries will be identified by Government of Sri Lanka in consultation with the Government of India. The selected beneficiaries would include women headed families and recently resettled families, the High Commission of India said in a statement.

This grant project was approved by Government of India in response to a request received from the Office for National Unity and Reconciliation of Government of Sri Lanka, it said.

The project aims to assist people by supporting resettlement efforts focused on reintegrating internally displaced families in Jaffna by providing modern rain water harvesting systems to provide clean drinking water supply facility to households. The project will generate employment opportunities in Sri Lanka.”

Most of the developed countries like Australia and New Zealand promotes house builders, as part of the main construction scope, to construct rain water harvesting systems to be used exclusively for toilet flushing, car washing and other utility purpose only and never for drinking purposes.

This requirement is in line with the Guidelines for Drinking-water Quality FIRST ADDENDUM TO THIRD EDITION set by the World Health Organization publication ISBN 92 4 154696 4 wherein document clearly states rainwater which is a type of distilled or desalinated water may be considered bland, flavourless and unacceptable,and desalinated water is commonly treated by adding chemical constituents such as calcium and magnesium carbonate with carbon dioxide. Once such treatment has been applied, desalinated waters should be no more aggressive than waters normally encountered in the drinking-water supply.

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The long-term health effects of drinking rain water are deprived mineral intake that can affect our organs and functioning of our tissues and bones as also our immune system. So drinking desalinated water whether it is RO water or rain water is not advisable without further treatment.

We need re-mineralization to partly replace essential minerals removed from the water collected as rain water. Although this process has proved to be costly and not very convenient

The possible adverse consequences of low mineral content water consumption are discussed in the following categories:

  • Direct effects on the intestinal mucous membrane, metabolism and mineral homeostasis or other body functions.
  • Little or no intake of calcium and magnesium from low-mineral water.
  • Low intake of other essential elements and microelements.
  • Loss of calcium, magnesium and other essential elements in prepared food.
  • Possible increased dietary intake of toxic metals.

Even though food is a much richer source of calcium and magnesium intake than water, demineralized water can significantly affect the balance of these key minerals in the body.

One of the reasons for this is because the elements are usually present in water as free ions and, therefore, are more readily absorbed from water compared to food where they are mostly bound to other substances.”

Many studies throughout the world have reported that people drinking water that is low in calcium and magnesium (i.e., soft water) is tied to higher incidence of death from cardiovascular disease compared to those drinking regular water.

Recent studies also suggest that the intake of soft water may be associated with a higher risk of fracture in children and decreased bone density in adults.

In addition, studies found that cooking with demineralized water caused a huge loss of essential elements from most foods. In some cases, the loss of calcium and magnesium was as much as 60%.

Health of infants feeding powdered infant formula are significantly at high risk as infants consume drinking water from the day they are born owing to the fact that it is used to reconstitute the product. Their mineral intake only through the drinking water used for preparing infant formula up until complementary foods are introduced.


Frantisek Kozisek National Institute of Public Health Czech Republic
(Courtesy  WHO Publication


The composition of water varies widely with local geological conditions. Neither groundwater nor surface water has ever been chemically pure H2O, since water contains small amounts of gases, minerals and organic matter of natural origin. The total concentrations of substances dissolved in fresh water considered to be of good quality can be hundreds of mg/L. Thanks to epidemiology and advances in microbiology and chemistry since the 19th century, numerous waterborne disease causative agents have been identified. The knowledge that water may contain some constituents that are undesirable is the point of departure for establishing guidelines and regulations for drinking water quality. Maximum acceptable concentrations of inorganic and organic substances and microorganisms have been established internationally and in many countries to assure the safety of drinking water.

The potential effects of totally unmineralised water had not generally been considered, since this water is not found in nature except possibly for rainwater and naturally formed ice. Although rainwater and ice are not used as community drinking water sources in industrialized countries where drinking water regulations were developed, they are used by individuals in some locations. In addition, many natural waters are low in many minerals or soft (low in divalent ions), and hard waters are often artificially softened.

Awareness of the importance of minerals and other beneficial constituents in drinking water has existed for thousands years, being mentioned in the Vedas of ancient India. In the book Rig Veda, the properties of good drinking water were described as follows: Sheetham (cold to touch), Sushihi (clean), Sivam (should have nutritive value, requisite minerals and trace elements), Istham (transparent), Vimalam lahu Shadgunam (its acid base balance should be within normal limits)” (1). That water may contain desirable substances has received less attention in guidelines and regulations, but an increased awareness of the biological value of water has occurred in the past several decades.

Artificially-produced demineralised waters, first distilled water and later also deionized or reverse osmosis-treated water, had been used mainly for industrial, technical and laboratory purposes. These technologies became more extensively applied in drinking water treatment in the 1960’s as limited drinking water sources in some coastal and inland arid areas could not meet the increasing water demands resulting from increasing populations, higher living standards, development of industry, and mass tourism. Demineralisation of water was needed where the primary or the only abundant water source available was highly mineralized brackish water or sea water. Drinking water supply was also of concern to ocean-going ships, and spaceships as well. Initially, these water treatment methods were not used elsewhere since they were technically exacting and costly

In this chapter, demineralised water is defined as water almost or completely free of dissolved minerals as a result of distillation, deionization, membrane filtration (reverse osmosis or nanofiltration), electrodialysis or other technology. The total dissolved solids (TDS) in such water can vary but TDS could be as low as 1 mg/L. The electrical conductivity is generally less than 2 mS/m and may even be lower (<0.1 mS/m). Although the technology had its beginnings in the 1960’s, demineralization was not widely used at that time. However, some countries focused on public health research in this field, mainly the former USSR where desalination was introduced to produce drinking water in some Central Asian cities. It was clear from the very beginning that desalinated or demineralised water without further enrichment with some minerals might not be fully appropriate for consumption. There were three reasons for this:

• Demineralised water is highly aggressive and if untreated, its distribution through pipes and storage tanks would not be possible. The aggressive water attacks the water distribution piping and leaches metals and other materials from the pipes and associated plumbing materials.

• Distilled water has poor taste characteristics.

• Preliminary evidence was available that some substances present in water could have beneficial effects on human health as well as adverse effects. For example, experience with artificially fluoridated water showed a decrease in the incidence of tooth caries, and some epidemiological studies in the 1960’s reported lower morbidity and mortality from some cardiovascular diseases in areas with hard water.

Therefore, researchers focused on two issues: 1.) what are the possible adverse health effects of demineralised water, and 2.) what are the minimum and the desirable or optimum contents of the relevant substances (e.g., minerals) in drinking water needed to meet both technical and health considerations. The traditional regulatory approach, which was previously based on limiting the health risks from excessive concentrations of toxic substances in water, now took into account possible adverse effects due to the deficiency of certain constituents.

At one of the working meetings for preparation of guidelines for drinking water quality, the World Health Organization (WHO) considered the issue of the desired or optimum mineral composition of desalinated drinking water by focusing on the possible adverse health effects of removing some substances that are naturally present in drinking water (2). In the late 1970’s, the WHO also commissioned a study to provide background information for issuing guidelines for desalinated water. That study was conducted by a team of researchers of the A.N. Sysin Institute of General and Public Hygiene and USSR Academy of Medical Sciences under the direction of Professor Sidorenko and Dr. Rakhmanin. The final report, published in 1980 as an internal working document (3), concluded that not only does completely demineralised water (distillate) have unsatisfactory organoleptic properities, but it also has a definite adverse influence on the animal and human organism”. After evaluating the available health, organoleptic, and other information, the team recommended that demineralised water contain 1.) a minimum level for dissolved salts (100 mg/L), bicarbonate ion (30 mg/L), and calcium (30 mg/L); 2.) an optimum level for total dissolved salts (250-500 mg/L for chloride-sulfate water and 250-500 mg/L for bicarbonate water); 3.) a maximum level for alkalinity (6.5 meq/l), sodium (200 mg/L), boron (0.5 mg/L), and bromine (0.01 mg/L). Some of these recommendations are discussed in greater detail in this chapter.

During the last three decades, desalination has become a widely practiced technique in providing new fresh water supplies. There are more than 11 thousand desalination plants all over the world with an overall production of more than 6 billion gallons of desalinated water per day (Cotruvo, in this book). In some regions such as the Middle East and Western Asia more than half of the drinking water is produced in this way. Desalinated waters are commonly further treated by adding chemical constituents such as calcium carbonate or limestone, or blended with small volumes of more mineral-rich waters to improve their taste and reduce their aggressiveness to the distribution network as well as plumbing materials. However, desalinated waters may vary widely in composition, especially in terms of the minimum TDS content. Numerous facilities were developed without compliance with any uniform guidelines regarding minimum mineral content for final product quality.

The potential for adverse health effects from long term consumption of demineralised water is of interest not only in countries lacking adequate fresh water, but also in countries where some types of home water treatment systems are widely used or where some types of bottled water are consumed. Some natural mineral waters, in particular glacial mineral waters, are low in TDS (less than 50 mg/l) and in some countries, even distilled bottled water has been supplied for drinking purposes. Otherbrands of bottled water are produced by demineralising fresh water and then adding minerals for desirable taste. Persons consuming certain types of water may not be receiving the additional minerals that would be present in more highly mineralized waters. Consequently, the exposures and risks should be considered not only at the community level, but also at the individual or family level.


Knowledge of some effects of consumption of demineralised water is based on experimental and observational data. Experiments have been conducted in laboratory animals and human volunteers, and observational data have been obtained from populations supplied with desalinated water, individuals drinking reverse osmosis-treated demineralised water, and infants given beverages prepared with distilled water. Because limited information is available from these studies, we should also consider the results of epidemiological studies where health effects were compared for populations using low-mineral (soft) water and more mineral-rich waters. Demineralised water that has not been remineralised is considered an extreme case of low-mineral or soft water because it contains only small amounts of dissolved minerals such as calcium and magnesium that are the major contributors to hardness.

The possible adverse consequences of low mineral content water consumption are discussed in the following categories:

• Direct effects on the intestinal mucous membrane, metabolism and mineral homeostasis or other body functions.

• Little or no intake of calcium and magnesium from low-mineral water.

• Low intake of other essential elements and microelements.

• Loss of calcium, magnesium and other essential elements in prepared food.

• Possible increased dietary intake of toxic metals.

1. Direct effects of low mineral content water on the intestinal mucous membrane, metabolism and mineral homeostasis or other body functions

Distilled and low mineral content water (TDS < 50 mg/L) can have negative taste characteristics to which the consumer may adapt with time. This water is also reported to be less thirst quenching (3). Although these are not considered to be health effects, they should be taken into account when considering the suitability of low mineral content water for human consumption. Poor organoleptic and thirst-quenching characteristics may affect the amount of water consumed or cause persons to seek other, possibly less satisfactory water sources.

Williams (4) reported that distilled water introduced into the intestine caused abnormal changes in epithelial cells of rats, possibly due to osmotic shock. However, the same conclusions were not reached by Schumann et al. (5) in a more recent study based on 14-day experiments in rats. Histology did not reveal any signs of erosion, ulceration or inflammation in the oesophagus, stomach and jejunum. Altered secretory function in animals (i.e., increased secretion and acidity of gastric juice) and altered stomach muscle tone were reported in studies for WHO (3), but currently available data have not unambiguously demonstrated a direct negative effect of low mineral content water on the gastrointestinal mucous membrane.

It has been adequately demonstrated that consuming water of low mineral content has a negative effect on homeostasis mechanisms, compromising the mineral and water metabolism in the body. An increase in urine output (i.e., increased diuresis) is associated with an increase in excretion of major intra- and extracellular ions from the body fluids, their negative balance, and changes in body water levels and functional activity of some body water management-dependent hormones.Experiments in animals, primarily rats, for up to one-year periods have repeatedly shown that the intake of distilled water or water with TDS ≤ 75 mg/L leads to: 1.) increased water intake, diuresis, extracellular fluid volume, and serum concentrations of sodium (Na) and chloride (Cl) ions and their increased elimination from the body, resulting in an overall negative balance.., and 2.) lower volumes of red cells and some other hematocrit changes (3). Although Rakhmanin et al. (6) did not find mutagenic or gonadotoxic effects of distilled water, they did report decreased secretion of tri-iodothyronine and aldosterone, increased secretion of cortisol, morphological changes in the kidneys including a more pronounced atrophy of glomeruli, and swollen vascular endothelium limiting the blood flow. Reduced skeletal ossification was also found in rat foetuses whose dams were given distilled water in a one-year study. Apparently the reduced mineral intake from water was not compensated by their diets, even if the animals were kept on standardized diet that was physiologically adequate in caloric value, nutrients and salt composition.

Results of experiments in human volunteers evaluated by researchers for the WHO report (3) are in agreement with those in animal experiments and suggest the basic mechanism of the effects of water low in TDS (e.g. < 100 mg/L) on water and mineral homeostasis. Low-mineral water markedly: 1.) increased diuresis (almost by 20%, on average), body water volume, and serum sodium concentrations, 2.) decreased serum potassium concentration, and 3.) increased the elimination of sodium, potassium, chloride, calcium and magnesium ions from the body. It was thought that low-mineral water acts on osmoreceptors of the gastrointestinal tract, causing an increased flow of sodium ions into the intestinal lumen and slight reduction in osmotic pressure in the portal venous system with subsequent enhanced release of sodium into the blood as an adaptation response. This osmotic change in the blood plasma results in the redistribution of body water; that is, there is an increase in the total extracellular fluid volume and the transfer of water from erythrocytes and interstitial fluid into the plasma and between intracellular and interstitial fluids. In response to the changed plasma volume, baroreceptors and volume receptors in the bloodstream are activated, inducing a decrease in aldosterone release and thus an increase in sodium elimination. Reactivity of the volume receptors in the vessels may result in a decrease in ADH release and an enhanced diuresis. The German Society for Nutrition reached similar conclusions about the effects of distilled water and warned the public against drinking it (7). The warning was published in response to the German edition of The Shocking Truth About Water (8), whose authors recommended drinking distilled water instead of “ordinary” drinking water. The Society in its position paper (7) explains that water in the human body always contains 152 electrolytes (e.g. potassium and sodium) at certain concentrations controlled by the body. Water resorption by the intestinal epithelium is also enabled by sodium transport. If distilled water is ingested, the intestine has to add electrolytes to this water first, taking them from the body reserves. Since the body never eliminates fluid in form of “pure” water but always together with salts, adequate intake of electrolytes must be ensured. Ingestion of distilled water leads to the dilution of the electrolytes dissolved in the body water. Inadequate body water redistribution between compartments may compromise the function of vital organs. Symptoms at the very beginning of this condition include tiredness, weakness and headache; more severe symptoms are muscular cramps and impaired heart rate.

Additional evidence comes from animal experiments and clinical observations in several countries. Animals given zinc or magnesium dosed in their drinking water had a significantly higher concentration of these elements in the serum than animals given the same elements in much higher amounts with food and provided with low-mineral water to drink. Based on the results of experiments and clinical observations of mineral deficiency in patients whose intestinal absorption did not need to be taken into account and who received balanced intravenous nutrition diluted with distilled water, Robbins and Sly (9) presumed that intake of low-mineral water was responsible for an increased elimination of minerals from the body.

Regular intake of low-mineral content water could be associated with the progressive evolution of the changes discussed above, possibly without manifestation of symptoms or causal symptoms over the years. Nevertheless, severe acute damage, such as hyponatremic shock or delirium, may occur following intense physical efforts and ingestion of several litres of lowmineral water (10). The so-called “water intoxication” (hyponatremic shock) may also occur with rapid ingestion of excessive amounts not only of low-mineral water but also tap water. The “intoxication” risk increases with decreasing levels of TDS. In the past, acute health problems were reported in mountain climbers who had prepared their beverages with melted snow that was not supplemented with necessary ions. A more severe course of such a condition coupled with brain oedema, convulsions and metabolic acidosis was reported in infants whose drinks had been prepared with distilled or low-mineral bottled water (11).

2. Little or no intake of calcium and magnesium from low-mineral water Calcium and magnesium are both essential elements.

Calcium is a substantial component of bones and teeth. In addition, it plays a role in neuromuscular excitability (i.e., decreases it), the proper function of the conducting myocardial system, heart and muscle contractility, intracellular information transmission and the coagulability of blood. Magnesium plays an important role as a cofactor and activator of more than 300 enzymatic reactions including glycolysis, ATP metabolism, transport of elements such as sodium, potassium, and calcium through membranes, synthesis of proteins and nucleic acids, neuromuscular excitability and muscle contraction.

Although drinking water is not the major source of our calcium and magnesium intake, the health significance of supplemental intake of these elements from drinking water may outweigh its nutritional contribution expressed as the proportion of the total daily intake of these elements. Even in industrialized countries, diets deficient in terms of the quantity of calcium and magnesium, may not be able to fully compensate for the absence of calcium and, in particular, magnesium, in drinking water.

For about 50 years, epidemiological studies in many countries all over the world have reported that soft water (i.e., water low in calcium and magnesium) and water low in magnesium is associated with increased morbidity and mortality from cardiovascular disease (CVD) compared to hard water and water high in magnesium. An overview of epidemiological evidence is provided by recent review articles (12-15) and summarized in other chapters of this monograph (Calderon and Craun, Monarca et al.). Recent studies also suggest that the intake of soft water, i.e. water low in calcium, may be associated with higher risk of fracture in children (16), certain neurodegenerative diseases (17), pre-term birth and low weight at birth (18) and some types of cancer (19, 20). In addition to an increased risk of sudden death (21-23), the intake of water low in magnesium seems to be associated with a higher risk of motor neuronal disease (24), pregnancy disorders (so-called preeclampsia) (25), and some cancers (26-29).

Specific knowledge about changes in calcium metabolism in a population supplied with desalinated water (i.e., distilled water filtered through limestone) low in TDS and calcium, was obtained from studies carried out in the Soviet city of Shevchenko (3, 30, 31). The local population showed decreased activity of alkaline phosphatase, reduced plasma concentrations of calcium and phosporus and enhanced decalcification of bone tissue. The changes were most marked in women, especially pregnant women and were dependent on the duration of residence in Shevchenko. The importance of water calcium was also confirmed in a one-year study of rats on a fully adequate diet in terms of nutrients and salts and given desalinated water with added dissolved solids of 400 mg/L and either 5 mg/L, 25 mg/L, or 50 mg/L of calcium (3, 32). The animals given water dosed with 5 mg/L of calcium exhibited a reduction in thyroidal and other associated functions compared to the animals given the two higher doses of calcium.

While the effects of most chemicals commonly found in drinking water manifest themselves after long exposure, the effects of calcium and, in particular, those of magnesium on the cardiovascular system are believed to reflect recent exposures. Only a few months exposure may be sufficient consumption time effects from water that is low in magnesium and/or calcium (33). Illustrative of such short-term exposures are cases in the Czech and Slovak populations who began using reverse osmosis-based systems for final treatment of drinking water at their home taps in 2000-2002. Within several weeks or months various complaints suggestive of acute magnesium (and possibly calcium) deficiency were reported (34). The complaints included cardiovascular disorders, tiredness, weakness or muscular cramps and were essentially the same symptoms listed in the warning of the German Society for Nutrition (7).

3. Low intake of some essential elements and microelements from low-mineral water

Although drinking water, with some rare exceptions, is not the major source of essential elements for humans, its contribution may be important for several reasons. The modern diet of many people may not be an adequate source of minerals and microelements. In the case of borderline deficiency of a given element, even the relatively low intake of the element with drinking water may play a relevant protective role. This is because the elements are usually present in water as free ions and therefore, are more readily absorbed from water compared to food where they are mostly bound to other substances.

Animal studies are also illustrative of the significance of microquantities of some elements present in water. For instance, Kondratyuk (35) reported that a variation in the intake of microelements was associated with up to six-fold differences in their content in muscular tissue. These results were found in a 6-month experiment in which rats were randomized into 4 groups and given: a.) tap water, b.) low-mineral water, c.) low-mineral water supplemented with iodide, cobalt, copper, manganese, molybdenum, zinc and fluoride in tap water, d.) low-mineral water supplemented with the same elements but at ten times higher concentrations. Furthermore, a negative effect on the blood formation process was found to be associated with non-supplemented demineralised water. The mean hemoglobin content of red blood cells was as much as 19% lower in the animals that received non-supplemented demineralised water compared to that in animals given tap water. The haemoglobin differences were even greater when compared with the animals given the mineral supplemented waters.

Recent epidemiological studies of an ecologic design among Russian populations supplied with water varying in TDS suggest that low-mineral drinking water may be a risk factor for hypertension and coronary heart disease, gastric and duodenal ulcers, chronic gastritis, goitre, pregnancy complications and several complications in newborns and infants, including jaundice, anemia, fractures and growth disorders (36). However, it is not clear whether the effects observed in these studies are due to the low content of calcium and magnesium or other essential elements, or due to other factors.

Lutai (37) conducted a large cohort epidemiological study in the Ust-Ilim region of Russia. The study focused on morbidity and physical development in 7658 adults, 562 children and 1582 pregnant women and their newborns in two areas supplied with water different in TDS. One of these areas was supplied with water lower in minerals (mean values: TDS 134 mg/L, calcium 18.7 mg/L, magnesium 4.9 mg/L, bicarbonates 86.4 mg/L) and the other was supplied with water higher in minerals (mean values: TDS 385 mg/L, calcium 29.5 mg/L, magnesium 8.3 mg/L, bicarbonates 243.7 mg/L). Water levels of sulfate, chloride, sodium, potassium, copper, zinc, manganese and molybdenum were also determined. The populations of the two areas did not differ from each other in eating habits, air quality, social conditions and time of residence in the respective areas. The population of the area supplied with water lower in minerals showed higher incidence rates of goiter, hypertension, ischemic heart disease, gastric and duodenal ulcers, chronic gastritis, cholecystitis and nephritis. Children living in this area exhibited slower physical development and more growth abnormalities, pregnant women suffered more frequently from edema and anemia. Newborns of this area showed higher morbidity. The lowest morbidity was associated with water having calcium levels of 30-90 mg/L, magnesium levels of 17-35 mg/L, and TDS of about 400 mg/L (for bicarbonate containing waters). The author concluded that such water could be considered as physiologically optimum.

4. High loss of calcium, magnesium and other essential elements in food prepared in low-mineral water

When used for cooking, soft water was found to cause substantial losses of all essential elements from food (vegetables, meat, cereals). Such losses may reach up to 60 % for magnesium and calcium or even more for some other microelements (e.g., copper 66 %, manganese 70 %, cobalt 86 %). In contrast, when hard water is used for cooking, the loss of these elements is much lower, and in some cases, an even higher calcium content was reported in food as a result of cooking (38-41).

Since most nutrients are ingested with food, the use of low-mineral water for cooking and processing food may cause a marked deficiency in total intake of some essential elements that was much higher than expected with the use of such water for drinking only. The current diet of many persons usually does not provide all necessary elements in sufficient quantities, and therefore, any factor that results in the loss of essential elements and nutrients during the processing and preparation of food could be detrimental for them.

5. Possible increased dietary intake of toxic metals

Increased risk from toxic metals may be posed by low-mineral water in two ways: 1.) higher leaching of metals from materials in contact with water resulting in an increased metal content in drinking water, and 2.) lower protective (antitoxic) capacity of water low in calcium and magnesium.

Low-mineralized water is unstable and therefore, highly aggressive to materials with which it comes into contact. Such water more readily dissolves metals and some organic substances from pipes, coatings, storage tanks and containers, hose lines and fittings, being incapable of forming low-absorbable complexes with some toxic substances and thus reducing their negative effects.

Among eight outbreaks of chemical poisoning from drinking water reported in the USA in 1993-1994, there were three cases of lead poisoning in infants who had blood-lead levels of 15 µg/dL, 37 µg/dL, and 42 µg/dL. The level of concern is 10 µg/dL. For all three cases, lead had leached from brass fittings and lead-soldered seams in drinking water storage tanks. The three water systems used low mineral drinking water that had intensified the leaching process (42). First-draw water samples at the kitchen tap had lead levels of 495 to 1050 µg/L for the two infants with the highest blood lead; 66 µg/L was found in water samples collected at the kitchen tap of the third infant (43).

Calcium and, to a lesser extent, magnesium in water and food are known to have antitoxic activity. They can help prevent the absorption of some toxic elements such as lead and cadmium from the intestine into the blood, either via direct reaction leading to formation of an unabsorbable compound or via competition for binding sites (44-50). Although this protective effect is limited, it should not be dismissed. Populations supplied with low-mineral water may be at a higher risk in terms of adverse effects from exposure to toxic substances compared to populations supplied with water of average mineralization and hardness.

6. Possible bacterial contamination of low-mineral water

All water is prone to bacterial contamination in the absence of a disinfectant residual either at source or as a result of microbial re-growth in the pipe system after treatment. Re-growth may also occur in desalinated water. Bacterial re-growth within the pipe system is encouraged by higher initial temperatures, higher temperatures of water in the distribution system due to hot climates, lack of a residual disinfectant, and possibly greater availability of some nutrients due to the aggressive nature of the water to materials in contact with it. Although an intact desalination membrane should remove all bacteria, it may not be 100 % effective (perhaps due to leaks) as can be documented by an outbreak of typhoid fever caused by reverse osmosis-treated water in Saudi Arabia in 1992 (51). Thus, virtually all waters including desalinated waters are disinfected after treatment. Non pathogenic bacterial re-growth in water treated with different types of home water treatment devices was reported by Geldreich et al. (52) and Payment et al. (53, 54) and many others. The Czech National Institute of Public Health (34) in Prague has tested products intended for contact with drinking water and found, for example, that the pressure tanks of reverse osmosis units are prone to bacterial regrowth, primarily do to removal of residual disinfectant by the treatment. They also contain a rubber bag whose surface appears to be favourable for bacterial growth.


The corrosive nature of demineralised water and potential health risks related to the distribution and consumption of low TDS water has led to recommendations of the minimum and optimum mineral content in drinking water and then, in some countries, to the establishment of obligatory values in the respective legislative or technical regulations for drinking water quality. Organoleptic characteristics and thirst-quenching capacity were also considered in the recommendations. For example, human volunteer studies (3) showed that the water temperatures of 15-350 C best satisfied physiological needs. Water temperatures above 350 or below 150 C  resulted in a reduction in water consumption. Water with a TDS of 25-50 mg/L was described tasteless (3).

1. The 1980 WHO report

Salts are leached from the body under the influence of drinking water with a low TDS. Because adverse effects such as altered water-salt balance were observed not only in completely desalinated water but also in water with TDS between 50 and 75 mg/L, the team that prepared the 1980 WHO report (3) recommended that the minimum TDS in drinking water should be 100 mg/L. The team also recommended that the optimum TDS should be about 200-400 mg/L for chloride-sulphate waters and 250-500 mg/L for bicarbonate waters (WHO 1980). The recommendations were based on extensive experimental studies conducted in rats, dogs and human volunteers. Water exposures included Moscow tap water, desalinated water of approximately 10 mg/L TDS, and laboratory-prepared water of 50, 100, 250, 300, 500, 750, 1000, and 1500 mg/L TDS using the following constituents and proportions: Cl- (40%), HCO3 (32%), SO4 (28%) / Na (50%), Ca (38%), Mg (12%). A number of health outcomes were investigated including: dynamics of body weight, basal and nitrogen metabolism, enzyme activity, water-salt homeostasis and its regulatory system, mineral content of body tissues and fluids, hematocrit, and ADH activity. The optimal TDS was associated with the lowest incidence of adverse effect, negative changes to the human, dog, or rat, good organoleptic characteristics and thirst-quenching properties, and reduced corrosivity of water.

In addition to the TDS levels, the report (3) recommended that the minimum calcium content of desalinated drinking water should be 30 mg/L. These levels were based on health concerns with the most critical effects being hormonal changes in calcium and phosphorus metabolism and reduced mineral saturation of bone tissue. Also, when calcium is increased to 30 mg/L, the corrosive activity of desalinated water would be appreciably reduced and the water would be more stable (3). The report (3) also recommended a bicarbonate ion content of 30 mg/L as a minimum essential level needed to achieve acceptable organoleptic characteristics, reduced corrosivity, and an equilibrium concentration for the recommended minimum level of calcium.

2. Recent recommendations

More recent studies have provided additional information about minimum and optimum levels of minerals that should be in demineralised water. For example, the effect of drinking water of different hardness on the health status of women aged from 20 to 49 years was the subject of two cohort epidemiological studies (460 and 511 women) in four South Siberian cities (55, 56). The water in city A water had the lowest levels of calcium and magnesium (3.0 mg/L calcium and 2.4 mg/L magnesium). The water in city B had slightly higher levels (18.0 mg/L calcium and 5.0 mg/L magnesium). The highest levels were in city C (22.0 mg/L calcium and 11.3 mg/L magnesium) and city D (45.0 mg/L calcium and 26.2 mg/L magnesium). Women living in cities A and B more frequently showed cardiovascular changes (as measured by ECG), higher blood pressure, somatoform autonomic dysfunctions, headache, dizziness, and osteoporosis (as measured by X-ray absorptiometry) compared to those of cities C and D. These results suggest that the minimum magnesium content of drinking water should be 10 mg/L and the minimum calcium content should be 20 mg/L rather than 30 mg/L as recommended in the 1980 WHO report (3).

Based on the currently available data, various researchers have recommended that the following levels of calcium, magnesium, and water hardness should be in drinking water:

• For magnesium, a minimum of 10 mg/L (33, 56) and an optimum of about 20-30 mg/L (49, 57);

• For calcium, a minimum of 20 mg/L (56) and an optimum of about 50 (40-80) mg/L (57, 58);

• For total water hardness, the sum of calcium and magnesium should be 2 to 4 mmol/L (37, 50, 59, 60).

At these concentrations, minimum or no adverse health effects were observed. The maximum protective or beneficial health effects of drinking water appeared to occur at the estimated desirable or optimum concentrations. The recommended magnesium levels were based on cardiovascular system effects, while changes in calcium metabolism and ossification were used as a basis for the recommended calcium levels. The upper limit of the hardness optimal range was derived from data that showed a higher risk of gall stones, kidney stones, urinary stones, arthrosis and arthropathies in populations supplied with water of hardness higher than 5 mmol/L.

Long-term intake of drinking water was taken into account in estimating these concentrations. For short-term therapeutic indications of some waters, higher concentrations of these elements may be considered.


The WHO in the 2nd edition of Guidelines for Drinking-water Quality (61) evaluated calcium and magnesium in terms of water hardness but did not recommend either minimum levels or maximum limits for calcium, magnesium, or hardness.The first European Directive (62) established a requirement for minimum hardness for softened or desalinated water (≥ 60 mg/L as calcium or equivalent cations). This requirement appeared obligatorily in the national legislations of all EEC members, but this Directive expired in December 2003 when a new Directive (63) became effective. The new Directive does not contain a requirement for calcium, magnesium, or water hardness levels. On the other hand, it does not prevent member states from implementing such a requirement into their national legislation. Only a few EU Member States (e.g. the Netherlands) have included calcium, magnesium, or water hardness into their national regulations as a binding requirement. Some EU Member States (e.g. Austria, Germany) included these parameters at lower levels as unbinding regulations, such as technical standards (e.g., different measures for reduction of water corrosivity). All four Central European countries that became part of the EU in May 2004 have included the following requirements in their respective regulations but varying in binding power;

• Czech Republic (2004): for softened water ≥ 30 mg/L calcium and ≥ 10 mg/L magnesium; guideline levels of 40-80 mg/L calcium and 20–30 mg/L magnesium (hardness as Σ Ca + Mg = 2.0 – 3.5 mmol/L).

• Hungary (2001): hardness 50 – 350 mg/L (as CaO); minimum required concentration of 50 mg/L must be met in bottled drinking water, new water sources, and softened and desalinated water.

• Poland (2000): hardness 60–500 mg/L (as CaCO3).

• Slovakia (2002): guideline levels > 30 mg/L calcium and 10 – 30 mg/L magnesium.

The Russian technical standard Astronaut environment in piloted spaceships – general medical and technical requirements (64) defines qualitative requirements for recycled water intended for drinking in spaceships. Among other requirements, the TDS should range between 100 and 1000 mg/L with minimum levels of fluoride, calcium and magnesium being specified by

a special commission separately for each cosmic flight. The focus is on how to supplement recycled water with a mineral concentrate to make it physiologically valuable” (65).


Drinking water should contain minimum levels of certain essential minerals (and other components such as carbonates). Unfortunately, over the two past decades, little research attention has been given to the beneficial or protective effects of drinking water substances. The main focus has been on the toxicological properties of contaminants. Nevertheless, some studies have attempted to define the minimum content of essential elements or TDS in drinking water, and some countries have included requirements or guidelines for selected substances in their drinking water regulations. The issue is relevant not only where drinking water is obtained by desalination (if not adequately re-mineralised) but also where home treatment or central water treatment reduces the content of important minerals and low-mineral bottled water is consumed.

Drinking water manufactured by desalination is stabilized with some minerals, but this is usually not the case for water demineralised as a result of household treatment. Even when stabilized, the final composition of some waters may not be adequate in terms of providing health benefits. Although desalinated waters are supplemented mainly with calcium (lime) or other carbonates, they may be deficient in magnesium and other microelements such as fluorides and potassium. Furthermore, the quantity of calcium that is supplemented is based on technical considerations (i.e., reducing the aggressiveness) rather than on health concerns. Possibly none of the commonly used ways of re-mineralization could be considered optimum, since the water does not contain all of its beneficial components. Current methods of stabilization are primarily intended to decrease the corrosive effects of demineralised water.

Demineralised water that has not been remineralized, or low-mineral content water – in the light of the absence or substantial lack of essential minerals in it – is not considered ideal drinking water, and therefore, its regular consumption may not be providing adequate levels of some beneficial nutrients. This chapter provides a rationale for this conclusion. The evidence in terms of experimental effects and findings in human volunteers related to highly demineralised water is mostly found in older studies, some of which may not meet current methodological criteria. However, these findings and conclusions should not be dismissed. Some of these studies were unique, and the intervention studies, although undirected, would hardly be scientifically, financially, or ethically feasible to the same extent today. The methods, however, are not so questionable as to necessarily invalidate their results. The older animal and clinical studies on health risks from drinking demineralised or low-mineral water yielded consistent results both with each other, and recent research has tended to be supportive.

Sufficient evidence is now available to confirm the health consequences from drinking water deficient in calcium or magnesium. Many studies show that higher water magnesium is related to decreased risks for CVD and especially for sudden death from CVD. This relationship has been independently described in epidemiological studies with different study designs, performed in different areas, different populations, and at different times. The consistent epidemiological observations are supported by the data from autopsy, clinical, and animal studies. Biological plausibility for a protective effect of magnesium is substantial, but the specificity is less evident due to the multifactorial aetiology of CVD. In addition to an increased risk of sudden death, it has been suggested that intake of water low in magnesium may be associated with a higher risk of motor neuronal disease, pregnancy disorders (so-called preeclampsia), sudden death in infants, and some types of cancer. Recent studies suggest that the intake of soft water, i.e. water low in calcium, is associated with a higher risk of fracture in children, certain neurodegenerative diseases, pre-term birth and low weight at birth and some types of cancer. Furthermore, the possible role of water calcium in the development of CVD cannot be excluded.

International and national authorities responsible for drinking water quality should consider guidelines for desalination water treatment, specifying the minimum content of the relevant elements such as calcium and magnesium and TDS. If additional research is required to establish guidelines, authorities should promote targeted research in this field to elaborate the health benefits. If guidelines are established for substances that should be in deminerialised water, authorities should ensure that the guidelines also apply to uses of certain home treatment devices and bottled waters.


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9 Responses to “India to grant rainwater harvesting systems to be used for collecting drinking water but our experts should understand its limitation.”

  1. Christie Says:

    Human batteries.

  2. Ananda-USA Says:

    I made the following estimate for a rainwater collection system using the roof of a small home in Gampola Sri Lanka. The roof is made of Amana cetamic-coated aluminum metal sheet and has gutters and downspouts on two opposing sides of the roof ridge. The water will be collected in two plastic tanks from the downspouts and pumped to the point of use.

    Average rainfall in Gampola = 5mm/d
    Roof rainwater catchment area (10m×10m) = 100m^2
    Average volume of rainwater collected = (5/1000)×100 = 0.5m^3/d
    = 500 lpd = 500/3.785 gpd = 132 gpd

    I have given the details of an under-the-kitchen-sink RO water purification unit with a capacity of 50 gpd elsewhere at LankaWeb. That system costs about 31SLR/day for 50 gpd throughput.

    Therefore, it appears that the above roof-based rainwater collection system can supply the water volume required by that RO system.

    The collected rainwater would have to be pumped to a water storage tank at a suitable height to satisfy that pressure requirements of the RO system, but that can be met very easily.

  3. Dilrook Says:

    I must say that this is a very unwise “scientific” analysis that fails to take into account ground realities.

    Jaffna people will not drink rain water alone. They also drink well water and pipe water. It is a fact that mineral content of Jaffna well water and pipe water is extremely high. Therefore they will not suffer any health problems by drinking rain water along with it. In fact, it will massively improve their health as drinking high mineral containing well water is causing various problems.

    I don’t mean this is a good project. On the contrary. All I say is this will improve the health condition of Jaffna people enormously and Jaffna will be able to house many more people. It will certainly be ominous for Sri Lanka.

    India is once again colonizing Sri Lanka with a massive South Indian population to ease its problem and export Hindu expansionism.

  4. NeelaMahaYoda Says:


    This is not a just scientific analysis. This is something recommended by WHO. This will be incorporated into the next Guide Line on Drinking Water by WHO.

    It is accepted in US and UK. Demineralised drinking water bottles are illegal in UK and US. There is a minimum Ca and Mg level should be maintained if you need to sell these water bottles in UK, Europe and US.

    This is something You never consume in US, and why do you want to recommend that to poor Sri Lankans?


    I agree with Aloy that the best solution is to give water to NCP farmers through the Moragahakanda project being constructed as a result of the Prez effort. Let them get another ‘loan’ and help all the farmers in those affected areas and solve the problem once and for all. may be the Chinese could be persuaded to spend the $200m that is earmarked for the research programme for this useful work instead.

    What Ananda has never noticed is that when you remove Arsenic, barium, cadmium, hexavalent chromium, trivalent chromium, copper, fluoride, lead, radium through a RO membrane, inevitably it removes useful minerals like magnesium and calcium down to zero.

    If we continuously drink water that are derived of these two minerals, there will be long term negative impacts on our overall health, which is actually the opposite of what we want to achieve via filtered water

    Carbon block is apparently not a re-mineraliser. Re-mineralisation is the process of dissolving calcium and magnesium salts in the water to raise the pH to an acceptable level and give ‘taste’. it is achieved by flowing the water through a bed of an approved proprietary material

    To explain in simpler language, demineralized water isn’t the safest drinking water for you health for these 4 reasons:
    1. Negatively effects various aspects of our biology,
    2. Does not provide minerals essential to our health,
    3. Strips foods of essential minerals when used for cooking, making juice, baby formula, etc.,
    4. Attacks metal surfaces such as copper and lead plumbing and fittings, tanks and even bottles, dissolving metals and other impurities into the water.

    “Sufficient evidence is now available to confirm the health consequences from drinking water deficient in calcium or magnesium. Many studies show that higher water magnesium is related to decreased risks for CVD and especially for sudden death from Cardiovascular Disease (CVD). This relationship has been independently described in epidemiological studies with different study designs, performed in different areas, different populations, and at different times.

    In addition to an increased risk of sudden death, it has been suggested that intake of water low in magnesium may be associated with a higher risk of motor neuronal disease, pregnancy disorders (so-called preeclampsia), sudden death in infants, and some types of cancer.

    Recent studies suggest that the intake of soft water, i.e. water low in calcium, is associated with a higher risk of fracture in children, certain neurodegenerative cardiovascular diseases, pre-term birth and low weight at birth and some types of cancer.”

    Health of infants feeding powdered infant formula are are in great danger as infants consume drinking water from the day they are born owing to the fact that it is used to reconstitute the milk. Their mineral intake only through the drinking water used for preparing infant formula up until complementary foods are introduced.

    There are many RO systems now available in the US and UK market with re-mineraliser unit incorporated in the system. A few of them are ; Home Master, Aquasana AQ RO3 ,and Abundant Water Flow ro system

    Another way to remineralise osmosis water is to add an water ionizer in your current reverse osmosis system set up. It is basically a time based filter that will release minerals into your drinking water at pre specified timing. It is the only way to enable remineralization for RO systems that don’t have a built this being built in.

    However, adding a water ionizer is not cheap. Most will cost around USD140+. Hence, this is why I insist on buying a reverse osmosis water system that have this being built in. It is way cheaper and saves you time on doing further installation.

  5. Ananda-USA Says:


    Thank you for bringing up the issue of the need to remineralize rainwater or RO water with Ca and Mg elements, but there are simple ways of offsetting that deficiency as I describe below.

    In my write up on an inexpensive 4-stage RO system elsewhere I also mentioned my having installed a much more expensive whole-house RO system. That system has the remineralization feature that you referred to.

    This issue of remineralization is not always important, because the simple act of taking a daily vitamin pill, with more than the RDA of not only vitamins but also essential minerals, can offset any deficiencies in a person’s dietary and liquid intakes.

    If a person can afford to buy an RO unit with the remineralization feature built in, that is good, but I happen to think that EVERYBODY, especially in SL where people don’t pay attention to eating a balanced diet, should take a daily vitamin+mineral pill while paying more attention to the more important issue of avoiding drinking and cookinh use of contaminated water.

    It would be useful if you present for us at LankaWeb the specifications and cost data on the 3 brands of RO units with remineralization that you presented. Please be sure to specify both the list of contaminants removed and the water purification capacity in gpd.

  6. Dilrook Says:


    If they consume rain harvested water only, then it is very harmful. I agree with you on that. But that is not the case.

    Lack of minerals in rain harvested water is more than compensated by well and pipe water in the north which is very heavy in minerals. People use both.

    In fact, the biggest water problem in the very north is it has too much of calcium and other minerals in it. People spend money on bottled water. The poor cannot afford it. If they drink a mix of rain harvested water with no minerals and well/pipe water loaded with minerals, they will have a balanced water and mineral intake. The overall consumed water quality will enormously improve and there will be more water in this arid zone.

    I see this as part of Indian sponsored Tamil colonization schemes in the north (and Upcountry) to change the nation’s demographic balance in favour of India.

  7. Ananda-USA Says:


    You correctly pointed out

    “1. Negatively effects various aspects of our biology,
    2. Does not provide minerals essential to our health,
    3. Strips foods of essential minerals when used for cooking, making juice, baby formula, etc.,
    4. Attacks metal surfaces such as copper and lead plumbing and fittings, tanks and even bottles, dissolving metals and other impurities into the water.”

    biuut are these issues significant for the RO unit I presented and its mode of use, and can these effects be simply alleviated?

    Items 1 & 2: These are easily addressed through taking vitamin and mineral supplements in pill form, given that the main issue is protecting yourself from ingesting harmful contaminated water.

    Item 3: The problem of stripping of essential minerals from food and drinks REMAINS an issue, but can be partially offset by taking vitamin and mineral supplements in pill form as for Items 1 & 2.

    Item 4: The problem of electrochemical degradation of metal surfaces does not arise in the case of the RO system I presented because the produced RO water does not generally come into contact with such surfaces. This unit uses plastic and stainless steel fittings that are resistant to such attack, and the water will usually be accessed in a stainless or porcelain kitchen sink setting and used in plastic or glass vessels.

    However, if the water remains in contact with aluminum (usually protected by a chemically resistant Al2O3 oxide coating) or cast iron pans without teflon or ceramic coatings, leaching of metal into the water could become a problem. For the very restricted mode of use of this RO system, I think this issue is not significant.

    I don’t think that attempting to remedy nutritional deficiencies through the water supply is the best approach. Due to variability in the nutritional content of food and drink due to personal and community habits, locations, and indeed wealth of each consumer, there are many unaddressed nutritional vitamin and mineral deficiencies.

    These deficiencies may be best addressed by simply taking a vitamin and mineral supplement pill every day, rather than attempting to do it through the water supply.

    What is MORE IMPORTANT may be to provide a clean uncontaminated water supply, free of toxic chemicals, carcinogens, and heavy metals that may cause neurological disorders, in an inexpensive and cost effective way to each family.

    That was the thrust of my submission.

  8. Dilrook Says:

    If they plan to extend this project beyond Jaffna and Batticaloa districts, it must be opposed on the basis of ill effects of RO water.

    Jaffna and Batticaloa (coastal) are unique cases where water naturally contains a very high level of minerals. Consuming this water and RO water minimises the ill effects of drinking RO water. However, other areas are different. Their water contains little minerals. They must not be confined to drinking RO water and ground water with little mineral content.

  9. Lorenzo Says:


    All of you have got the WRONG END OF THE STICK.

    Why are you worried? IF this is bad it will affect TNA voters, LTTE families (women headed families are LTTE Mahaveer families. The man was in the LTTE and killed in war). Truth to be told it is NOT BAD for SL.

    I’m surprised NO Tamil scientist has cried over this.

    Endia will NEVER do anything bad for Endians including Tamils.

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