LITERATURE REVIEW

The water quality parameters being studied by PCRWR for National Water Quality Monitoring Program are reviewed mainly focused on natural resources, contaminations and health effects in respect of various Physical & Aesthetic, Chemical, Trace & Ultra Trace Elements including Microbiological parameters.

In under developed and developing countries of the world; most of communicable diseases are water borne due to drinking of unsafe water and these diseases cause morbidity and mortality. In developing countries, the mortality rate especially in the infants is very high. This is due to lack of monitoring facilities of water quality as well as improving facilities like treatment plants. Unfortunately public and decision makers of the most developing world are not well aware of the gravity of the situation. In all developed countries drinking water quality is considered a very serious issue and improvement measures were taken about a century ago. For the evaluation of water pollution, water quality parameters are used for analytical purpose and also provision of safe drinking water to the citizens or public. The general public of these countries are aware of water quality impacts on human health, hence they are very conscience about it. For the reduction of pollution or improvement in quality of water used for human consumption depend on reliable analytical measurements. So analytical water quality parameters are utmost important and are playing a key role for water pollution assessment. The prime objective of this chapter is to know about natural sources, contaminations, health effects and guideline values of some basic drinking water quality parameters.

pH

The pH of an aqueous system is measure of acid-base equilibrium achieved by various dissolved compounds and in most natural water is controlled by the carbon dioxide-bicarbonate-carbonate equilibrium system. The pH of most raw water sources lies within the range 6.5-8.5. Chlorination tends to lower the pH, where as water softening using the excess lime/soda ash process raises the pH level. A direct relationship between human health and the pH of drinking water is impossible to ascertain because pH is so closely associated with other aspects of water quality. In so far as pH affects the various processes in water treatment that contribute to the removal of viruses, bacteria and other harmful organisms, it could be claimed that pH has an indirect effect on health. WHO Guideline (1984) recommended guideline value for pH is 6.5-8.5, although it is recognized that some problems could arise within a distribution system with pH level below 7.0. The efficiency of coagulation and flocculation process is markedly dependent on pH. Smith (1973) found that the metal ion stability and solubility in water solutions when they are in low concentration are affected very much by pH. EPA, USA (1977) claimed that at high pH levels drinking water acquires a bitter taste.

Electrical Conductivity (EC)

A measure of the ability of an aqueous solution to carry an electric current is called as conductivity. This ability depends on the presence of ions, their total concentration, mobility, and valence and on the temperature of measurement. Solutions of most inorganic compounds are relatively good conductors. Conversely molecules of organic compounds do not dissociate in aqueous solution. The determination of electrical conductivity provides a rapid and convenient means of estimating the concentration of electrolytes in water containing mostly mineral salts.

Turbidity

Turbidity in water is caused by the presence of suspended matter, such as clay, silt colloidal organic particles, Plankton and other microscopic organisms. Turbidity is an expression of certain light scattering and light-absorbing properties of water.  Turbidity is an important parameter for characterizing the water quality. Public health services drinking water standards (1962) documented that turbidity excess of the guideline value of 5 NTU is generally objectionable to consumers. The perception of higher turbidity in water at the consumer’s tap than in that entering the distribution system may indicate post-treatment contamination, corrosion, or other distribution problems. Consequently, as excessive turbidity can protect micro-organisms from the effects of disinfection, stimulate the growth of bacteria in the water and itself exert a significant chlorine demand, it is vitally important in producing safe drinking water.

Color

WHO (1984) and the Water Clinic (2003) reported that color in drinking water may be due to the presence of colored organic substances, usually humus, metals such as iron and manganese, colored industrial wastes. Danamenk (2003) reported that organic color and staining usually occur in areas with poor drainage, and sometimes it combines with iron to form “heme-iron” which is difficult to remove. Ronald (2003) found that USEPA and the Washington Administrative Code for Public Water Supplies has set limits for physical characteristics of water under general use color of drinking water should not exceed 15 units. WHO (1996) has recommended 15 TCU as the level, above which likely to give rise to consumer complaints because of appearance.

Taste

Taste refers only to gustatory sensations called bitter, salty, sour and sweet that result from chemical stimulation of sensory nerve endings located in the papillae of the tongue and soft palate as reported by APHA, et al., (1992). Taste threshold in distilled water for the major cations of drinking water i.e. calcium, magnesium, sodium and potassium have been reported to be approximately 100,30,100 and 300 mg/l respectively (National Academy of Sciences, 1973). Michael (1981) reported that there are only four true taste sensations; salty, sweet, bitter and sour.

Odor

Michael (1981) reported that a great number of organic and some inorganic substances contribute to the odor of waters. The non-specific fishy, grassy and musty odors normally associated with biological growth tend to occur most frequently in warm surface water in the warmer months of the year. Odor in potable water is almost invariably indicative of some form of pollution of the water source or of malfunction during water treatment or distribution. Drinking water should have no observable odor to any consumer (WHO, 1984).

Alkalinity (Alk)

The principal anions for producing Alkalinity of fresh water are bicarbonate, sulphate and chloride. The Alkalinity may be defined as, the capacity of some of its components to accept protons i.e. to bind an equivalent amount of a strong acid. The total contents of negative ions and other substances which react to neutralize the H⁺ ion. Jaffer et.al (1985) gave maximum permissible level/range of alkalinity as 50 to 500 mg/1 as CaCO₃.

Bicarbonates are the dominant anion in most surface and ground waters. The weathering of rocks contributes to bicarbonate content in water. Mostly bicarbonates are soluble in water and concentrations in water are related to the pH. Bicarbonates are usually less than 500 mg/l in groundwater. They also influence the hardness and alkalinity of the water. The good quality canal and tube-well water contains small amounts of NaHCO₃.

In Pakistan the sodic lands develop mainly under the influence of Na₂CO₃ and NaHCO₃ and saline sodic lands contain NaHCO₃ in medium to low amounts, Rafiq (1980) categorized the salt-affected lands into lands containing Na₂CO₃ and CaSO4; the presence of Na₂CO₃ indicated low amounts of Ca²⁺ and Mg²⁺ ions, Ansari et al. (1979) reported that the lands of the Punjab (Upper Indus Basin) had high concentrations of Na₂CO₃ and NaHCO3 but the lands of Sindh province (Lower Indus Basin) were mostly free from Na₂CO₃.

Saline waterlogged lands in Pakistan usually contain high levels of CaCO₃. Native CaCO₃ could be solubilized and convert to Ca(HCO₃)₂ and then soluble NaHCO₃.

(a)  CaCO₃ + CO₂ + H₂O                à        Ca(HCO₃)₂

(b)  Clay-2Na +Ca(HCO₃)₂  à        Clay-Ca+NaHCO₃

Calcite (CaCO₃) and dolomite are called rock-farming minerals on the earth. Calcite is the most common and widespread of the carbonate minerals. Great masses of calcite occur in limestone. Small crystal masses are present in rock openings. Calcite also occurs as a vein mineral in almost all rocks. Crystals are common. Cleavage is perfect.

Calcium (Ca)

Calcium is a mineral need for numerous functions, including blood clotting, the transmission of nerve impulses and the regulation of the hearts rhythm. The presence of calcium in water supplies results from deposits of limestone, dolomite, calcite, gypsum and gypsiferous shale. The Calcium minerals and compounds are not easily soluble in pure water, the presence of carbon dioxide readily increases their solubility and sources of water containing up to 100 mg of calcium per liter are fairly common in arid regions having pH above 7.0. WHO (1996) and PSI (1987) recommended 75 mg/l as permissible amount of calcium in drinking water, whereas PSQCA (2002) has recommended the revised water quality standard for calcium as 200 mg/l.

Magnesium (Mg)

The magnesium is a common constituent of natural water. Michael (1981) found that magnesium and calcium both produce the property of hardness in water. Acu-Cell (2003) had reported that about 19g of magnesium per 70kg human body weight is involved in the synthesis of protein as well as acts as co-factor in 300 enzymatic reactions.

Hardness

Hard water forms precipitates on boiling or when soap is added to it. Hardness is due to the presence of calcium, magnesium or ferrous (iron salts) as chloride, sulphate or bicarbonates. The terms “hard water” and “soft water” are still in use. The degree of hardness is equivalent to CaCO₃ concentration and designated as soft (0-60 mg/1), medium hard (60-120 mg/1), hard (120-180 mg/1), very hard (>180 mg/1). Bokina (1965) found increased incidence of urolithiasis due to hard water in the USSR where the local tap water contained 300-500 mg of calcium per litre. Guidelines for Canadian drinking water quality (1979) documented that there is no firm evidence that water hardness causes ill effects in man. Marier (1979) observed that there is a close association between death rates from stocks and the acidity of river derived drinking water. Since that time, a number of studies in various parts of the world have demonstrated that there is high statistically significant negative association between water hardness and cardiovascular disease. In most studies, the Calcium concentration has shown the strongest co-relation. The co-relation with hardness and the calcium content of water was high, although other water parameters, many of which are Interco-related with hardness, also provided strong statistical associate ion. Very hard water can cause household pipes choking, scaling, incrustations on kitchen utensils and increasing soap consumption. Hard water can create both nuisance and economic burden to community. A hardness level of about 100 mg of CaCO₃ per litre provides an acceptable balance between corrosion and the problems of incrustation, although, from aesthetic considerations 500 mg/1 is recommended as a guideline value.

Sodium (Na)

Sodium is present in abundance or in less quantity in natural waters. Seawater contains relatively high levels of sodium about 10 g of sodium per litre (WHO, 1979). The sodium salts are highly soluble in water and found abundance in mineral deposits. Sodium is the principal cation (Na⁺) in the extra-cellular fluid (ECF) and it has several physiological roles including maintaining acid-base balance, generating transmembrane gradients (which allow cells to take up nutrients) maintenance of ECF volume and osmotic pressure and in the electro-physiology of nerve and muscle cells (Healthnet, 2003). Acu-Cell (2003) reported that deficiency of sodium in the body may appear as mental apathy, low blood pressure, fatigue, depression, seizures, dehydration etc., whereas overdose can cause edema, hypertension, stroke, headaches, kidney damages, stomach problems and nausea.  WHO (1984) reported that in most countries, the majority of water supplies contain less than 20 mg of sodium per liter but in some countries sodium levels can exceed 250 mg/l. According to WHO (1979) water treatment chemicals such as sodium fluoride, sodiumsilico fluoride, sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium hypochlorite can add significant amounts of Na (30 mg/l) in drinking water. WHO (1996) recommended the 200 mg/l as the guideline value for sodium in drinking water.

Potassium (K)

The potassium content of drinking water varies greatly depending on its source and it tends to be larger in mineral and seawaters than ordinary tap water. However, on average the daily water consumption by adults, the K intake is less than 0.1%. Potassium abundance in drinking waters can reach upto 20 mg/l (APHA, et al., 1992). The potassium is very significant body mineral important to both cellular and electrical function. The total potassium in the body and blood serum varies from 4-5 mg/100 ml. An amount of 1600 to 3500 mg of potassium consumption per day has been recommended by Anderson & Young (2002). Potassium deficiency causes irregular and rapid heart beat, hypertension, muscle weakness, bladder weakness, kidney disease and asthma whereas over dose may appear as irregular/rapid heart beat, cystitis, bladder infection, ovarian cysts, and weakened immune system (Acu-Cell, 2003). An increased level of potassium in the blood is known as hyper-kalemia appear as reduced renal function, an abnormal breakdown of protein and severe infection (Aparna, 2001).

Chloride (Cl)

Chloride high concentration occurs from chloride containing geological formation, pollution by sewage, industrial waste, intrusion of seawater and other saline water. It is widely distributed in nature in the form of NaC1, KCl and CaCl₂ salts. Chloride is present at low concentration in natural surface water as compared to ground water. Chloride is the abundant anion in human body and contributes significantly, along with its associated cations for maintaining the osmotic activity of extra cellular fluids (88%). A normal 70 kg human body weight contains about 81 g of chloride in 45 liters of drinking water. One gram table salt (NaCl) per person per day is essential for normal health. For children up to 18 years of age, a daily dietary intake of 45 mg chloride per kg of body weight is sufficient. The salty taste produced by chloride depends on the chemical composition of the water. The salty taste with concentration of 250 mg/1 may be detectable in water containing sodium ions. On the other hand, the typical salty taste may be absent in water containing 1000 mg/1 chloride when calcium and magnesium ions are predominant. A high chloride content has a deleterious effect on metallic pipes and structures. WHO (1984) had recommended 250 mg/1 as guideline value.

Dissolved sulphate is considered to be permanent solute of water. The majority of sulphate compounds are soluble in water, the exception being the sulphates of lead, barium and strontium. It may however be reduced to sulfide, volatilized to the air as H₂S precipitated as an insoluble salt or incorporated in living organisms. Sulphates are used in the manufacturing of numerous chemicals, dyes, glass, paper, soaps, textiles, fungicides, insecticides, astringents and cosmetics. Sulphate levels in Canadian lakes range from 3 to 30 mg/l Katz (1977). Finding of National Water Quality Monitoring Program (NWQMP) have revealed that water samples of various cities of Punjab and Balochistan provinces have sulphate concentration exceeding WHO limits (Kahlown, et al., 2001). No symptoms of sulphate deficiency have been reported in humans. No optimum dietary intake for inorganic sulphate has been suggested. Fingl (1980) reported the dehydration as a common side effect due to the ingestion of large amounts of magnesium or sodium sulphate. The taste threshold concentrations of sulphate salts are 250-500 mg/l for sodium sulphate, 250 to 900 mg/l for calcium sulphate and 400 to 600 mg/l for magnesium sulphate NRC (1977). WHO (1996) has set the sulphate level of 250 mg/l in drinking water above which consumer may feel problem in taste.

Nitrate is a very important water quality parameter regarding health point of view. It comes into water from fertilizer use, decayed vegetable and animals matter, domestic effluent, sewage sludge, industrial discharges, farm leachates, atmospheric washout. U.S. EPA (1977) documented that water supply in some countries containing high levels of nitrate have been responsible for cases of infantile Methaemoglobinaemia and death. Xu Guang Wei (1981) had diagnosed gastric cancer in China in the areas where high levels of both nitrate and nitrite were found in drinking water and found the high mortality rate from this disease. Data showed that in this area the levels of both nitrate and nitrite in drinking water and in vegetables were higher than in the low-risk areas. WHO (1978) has documented that the pregnant women are at greater risk than the general adult population due to nitrate induced Methaemoglobinaemia. Guidelines for drinking water by WHO (1984) recommended 10 mg/1 as nitrate nitrogen.

Methaemoglobinaemia:

The extent of the worldwide problem has been reviewed by WHO (1984). It has been well documented that in some countries water supplies containing high levels of nitrates were responsible for cases of infant Methaemoglobinaemia and death. It was recommended that water supplies containing high levels of nitrate should not be used by child and for the preparation of infant foods. The problem of Methaemoglobinaemia does not arise in adults. Increased sensitivity may also occur when infants suffer from gastrointestinal disturbances which increase the number of bacteria that can convert nitrate to nitrite. Prolonged boiling of water may increase the problem by increasing the nitrate levels owing to evaporation. Cases of infant Methaemoglobinaemia have not been reported in areas where the drinking water contains less than 10 mg of nitrate-N per litre, only 2.3% of all cases appear to be associated with nitrate levels between 10-20 mg of nitrate-N per litre of water.

Carcinogenicity of Nitrosamines: Nitrosamines will be produced which may be carcinogenic. It has been shown that the formation of nitrosamines may be increased in individuals with bladder infections which would be ultimately absorbed into the blood. Although tests on animals have shown that a number of nitrosamines are carcinogenic, there is no direct evidence of their carcinogenicity in man. In a review of gastric cancer in China, the Putian Prefecture of the Fujian Province was found to have the highest mortality from this disease. The levels of both nitrate and nitrite in drinking water and in vegetables were higher in this area. Evidences of carcinogenicity from nitrate via the formation of nitrosamines rests with epidemiological studies (WHO 1984).

Phosphorus occurs in natural waters and in wastewaters almost solely as “phosphates” classified as orthophosphates, condensed phosphates (pyro, meta, and polyphosphates) and organic phosphates. Water Sheds (2003) reported that phosphorus plays a role in deoxyribonucleic acid (DNA), ribonucleic acid (RNA), adenosine di-phosphate (ADP) and adenosine tri-phosphate (ATP) and required for these necessary components of life to occur. Generally, phosphorus (as orthophosphate) is the limiting nutrient in freshwater and aquatic system. The natural total phosphorus are generally less than 0.03 mg/l whereas the natural levels of orthophosphate usually range from 0.005 to 0.05 mg/l. No guideline values suggested by WHO for drinking water, however the EPA water quality criteria state that phosphates should not exceed 0.05 mg/l if streams discharge into lakes or reservoirs, 0.25 mg/l within a lake or reservoir and 0.1 mg/l in streams or flowing waters (USEPA, 1986).

Total Dissolved Solids (TDS)

Total dissolved solids (TDS) in water are inorganic salts and small amounts of organic matter. The principal ions contributing to TDS are carbonate, bicarbonate, chloride, sulphate, nitrate, sodium, potassium, calcium and magnesium. TDS in water may be originated from natural sources, sewage effluent discharges, urban runoff and industrial discharges. TDS is linked to taste, hardness, corrosion properties and tendency to incrustation. There is no evidence of deleterious physiological reactions have TDS levels in excess of 1,000 mg/1 Dufor (1972). TDS in drinking water may even have beneficial health effects. Bruvold et al., (1967) have rated the palatability of drinking water due to the TDS level i.e. Excellent (<300 mg/1), Good (300-600 mg/1), Fair (600-900 mg/1), Poor (900-1200 mg/1, Unacceptable (>1200 mg/1). Water with extremely low TDS levels may also be unacceptable because of its flat, insipid taste. WHO recommended 1000 mg/l TDS as guideline values.

Lead (Pb)

The main sources of lead are paints, pipes, wastes of batteries, manufacturing industries and gasoline. Lead is a serious cumulative body poison. The natural lead content of lake and river water worldwide has been estimated to be 1-10 µg/l WHO (1973). Michael (1981) had reported 0.03 µg/l in seawater but near the surface and shore the concentration may be as much as 10 times more. SDWF (2003) had given the possible chronic health effects as brain and nerve damage, kidney damage, digestive disturbances, blood disorders and hypertension. The symptoms of acute poisoning i.e. tiredness, lassitude, slight abdominal discomfort, irritability, anemia and children, behavioral changes were also diagnosed. Guideline value for lead is 0.01 mg/l or 10 µg/l (10 ppb) recommended by WHO (1984).

Arsenic (As)

Arsenic (As) is an inorganic element has no taste, smell, color in water. As is a naturally occurring element found in soils, surface water and groundwater, highest in areas of geothermal activity. As is used for the production of pesticides and herbicides. As is ingested by drinking contaminated water. As is known carcinogenic and poisoning element either acute or chronic. It can enter the metabolic system of unborn babies. Ingestion of large quantities resulting in stomach pain, nausea, vomiting, diarrhea which may lead to shock, coma and even death. Higher rates are linked to produce cancer of the lungs, bladder, kidney, liver and skin, particularly in young age children and elder old age human. The unborn babies and people with long illnesses are at greater risk of As poisoning (USDI, 2001). The permissible limits of WHO (1984) are 10 ppb to As concentration in drinking water.

Iron (Fe)

Iron is also an abundant element by weight on the earth’s crust. In water it occurs in the divalent and trivalent (ferrous and ferric) forms. The solubility in natural waters is dependent upon the pH and the oxidation-reduction potential. In reducing conditions; iron exists in the ferrous state. On exposure to air oxidized to the ferric form and with water hydrolyzes to insoluble hydrated ferric oxide that makes iron-laden waters objectionable. Iron in water can cause staining of laundry and porcelain, deposit a slimy coating on the piping. A bittersweet astringent taste is detectable at level above 1 mg/l. Iron is an essential element in human nutrition. It is contained in a number of biologically significant proteins as hemoglobin and cytochromes. Iron also promotes the growth of “iron bacteria” which derive their energy from the oxidation of ferrous iron to ferric iron. Iron deficiency causes anemia and symptoms of fatigue appeared. The higher iron intake through drinking water/food may produce symptoms of anorexia, dizziness, nausea, vomiting, headache, weight loss, shortness of breath and possibly a graying color to the skin. WHO (1996) have recommended the guideline value for iron in drinking water as 0.3 mg/l.

Fluoride (F)

Traces of fluorides occurrence are widespread in waters and higher concentrations are often associated with groundwater sources in areas where fluoride-bearing minerals are common. Edmunds and Smedley (1996) have found high fluoride concentrations in groundwater from calcium-poor aquifers and where exchange of sodium for calcium occurs. In areas that are rich in fluoride containing minerals e.g. flourapatite, the groundwater may contain up to 10 mg of fluoride per liter or even more (Bulusu et al, 1979). According to WHO (1970) most of the waters contain below 1 mg of fluoride per liter. Drinking water is typically the largest single contributor to the daily fluoride intake (WHO, 1986). However, this is not necessarily true in every case. British Geological Survey (2003) has found a significant mitigating effect against dental caries as minor concentrations in drinking water is beneficial. Optimal concentrations are 1 mg/l, however, chronic ingestion greater than 1.5 mg/l (WHO guideline value) is linked with development of dental flourosis and in extreme cases, skeleton fluorosis. High doses have been linked to cancer.

Chromium (Cr)

Chromium concentrations in natural waters are usually very small. Elevated chromium concentrations can result from mining and industrial processes. An upper limit of 0.05 mg of chromium per liter is allowed in drinking water in the USA and a similar limit is allowed by WHO. Natural water contains only traces of chromium as cation. Chromium under strongly oxidizing conditions may be converted to hexavalent state and occurs as chromate anion. Its presence indicates pollution by industrial wastes. Liver necrosis, nephritis, G.I. mucosa irritation, prostrate, digestive track and lung cancers are reported in the literature due to excessive intake of chromium. The WHO has recommended 50 mg/l as the maximum permissible limit for this element. Chromium exists in trivalent state, which is stable form, and other one is hexavalent chromium, which is readily reduced by a variety of organic species. Trivalent form rarely occurs in potable water. According to APHA, et al., (1992), the hexavalent chromium concentration of U.S drinking waters has been reported to vary between 3 and 40 µg/l with a mean of 3.2 µg/l. The hexavalent chromium (at 10 mg/l of body weight) could cause liver necrosis, nephritis and death in man, lower doses also cause irritation in gastrointestinal mucosa. Liver, kidney and lungs damage as the possible chronic health effects. The levels in water are usually low (9.7 mg/l) because of the low solubility of chromium. He also determined that the drinking water normally contains very low concentrations of chromium (5 µg/l or less) and the chromium levels as high as 20 g/l in tap water are found very rare. Chromium plays a vital role in glucose metabolism through its influence on glucose tolerance. Chromium in water is absorbed at approximately 5% of the dose as compared to food which is 0.5-1% (WHO, 1973).

Manganese (Mn)

The manganese is a mineral that naturally occurs in rocks and soil and is the normal constituent of the human diet. Manganese may become noticeable in water at concentrations greater than 0.05 mg/l of water by imparting a color, odor or taste to the water. APHA, et al., (1992) found that there is evidence that manganese occurs in surface waters both in suspension in the quadrivalent state and in the trivalent state in a relatively stable, soluble complex. Manganese intake through drinking water can vary considerably, normally being substantially lower than intake from food. Available data indicate that exposure via this source would normally be less than 0.1 mg/day, but can be an order of magnitude higher, exposure to high concentrations of manganese over the course of years has been associated with toxicity to the nervous system (USEPA, 1977). Acu-Cell (2003) reported that manganese deficiency in the body may appear as hypoglycemia, joint discolorations, asthma, migraine, osteoporosis and gastrointestinal disorders whereas manganese toxicity due to over dose cause muscle tremors, dizziness, liver disease, high risks to several cancers, fibroid tumors, edema and colitis. WHO (1996) has recommended 0.1 mg/l as the guideline value for drinking water.

Molybdenum (Mo)

Molybdenum is generally present at very low concentrations in water. It’s concentration in surface water is normally less than 7 µg/l. The molybdenum plays a vital role in everyday life, particularly in relation to many aspects of the protection of human health and the environment. The essential metal is found mainly in the liver, kidney and adrenal gland. Its functions in the body as a component of three main enzymes such as sulphate oxidase, xanthine oxidase and aldehyde oxidase. Deficiency of this element is very rare. In the body deficiency will manifest as abnormal excretion of sulphur metabolities, low concentration of uric acid in the urine and increased excretion of hypoxanthine and xanthine excretion. The molybdenum in drinking water has been recommended 0.07 mg/l by WHO (APHA et al., 1992; WHO, 1996)

Nickle (Ni)

The nickel compounds are found in many ores and minerals and nickel salts are quite soluble, may contribute to water pollution through municipal or industrial waste discharges. About 1 mg/l level of nickel in surface water has been reported in the literature. The nickel is relatively non toxic to man. The toxicity of nickel to aquatic life varies generally with the species, pH and water hardness. Plasma nickel is a constituent of the circulating proteins nickeloplasmin and albumin and it is thought to be factor in hormone, lipid and cell-membrane metabolism. Skin reactions such as itching, burning, redness or other rashes are the most common symptoms of nickel sensitivity; however asthma attacks are another but less frequent possibility. WHO has recommended guideline value for nickel as 0.02 mg/l (Acu-Cell, 2003; WHO 1996; USEPA, 1977).

Aluminum (Al)

Aluminum is distributed widely in nature and is a constituent of all soils, plants and animal tissues. As a consequence of this wide natural distribution and the activities of man, aluminium is present in air, food and water, both natural and polluted. The salts of aluminum are used extensively in water treatment for the removal of color and turbidity. The level of aluminum in water varies considerably and may exceed 10 mg/l in the vicinity of aluminum processing plants. The aluminum has been associated with certain neurological disorders such as dialysis, dementia and Alzheimer’s disease. Aluminium present in drinking water contributes only a small proportion of the estimated daily human intake i.e. less than 4% of the normal daily intake. Aluminum does not appear to be an essential nutrient in man. The chronic use of large quantities of aluminum hydroxide in the form of “antacids” can lead to excessive loss of phosphate from the system. However, it is not clear, whether the presence of aluminum causes such conditions or is simply an indicator of other factors (APHA et al., 1992; WHO, 1996).

Selenium (Se)

The selenium concentrations usually found in water are of the order of a few micrograms per liter, but may reach 50-300 µg/l in seleniferous areas and have been reported to reach 1 mg/l in drainage water from seleniferous irrigated soils. The data from different parts of the world indicated that the selenium contents in most surface water samples analyzed was well below 10 µg/l. It is reported that the sources of contamination of selenium are discharges from petroleum refineries, corrosion deposits and discharge from mines. The selenium concentration of most drinking waters and natural waters is less than 10 µg/l. According to Acu-Cell (2003) deficiency of selenium leads to lowered glutathione peroxidase activity and it is implicated with a higher risk for cancer of the liver lungs, colon, rectum and prostate. Whereas over dose or selenium toxicity may appear as nerve degeneration, osteoporosis, cystadenoma, shingles, loss of hair, garlic breath and death (NRC, 1977; National Academy of Sciences, 1973; USEPA, 1986; APHA, et al., 1992). Possible chronic health effects produce by selenium toxicity reported by USEPA (1986) as growth inhibition, skin discoloration, dental and digestion problems, liver damage and psychological disorders and possible heath effects may be the hair or fingernail loss, numbness of fingers or toes and circulatory problems. According to WHO (1984) guideline value for selenium in drinking water is 0.01 mg/l.

Coliform

Total coli form   bacteria, a particular group of waterborne microbiological contaminants is the most common indicator organism applied to drinking water. Total coliform bacteria and fecal coli form Escherichia Coli (E.Coli) are two types of fecal indicator bacteria. Several bacteria can be classified as coliform, and are commonly found in soil, on the surface of leaves, in decaying matter, and can grow in water distribution mains. These types of coliform bacteria aren’t fecal contamination related and do not necessarily indicate unsafe water. Almost all surface waters contain some bacteria while groundwater’s are generally free of bacteria unless under the direct influence of surface water. Surface and groundwater contamination can occur as a result of surface runoff through urban areas, pastures, feedlots, on-site septic tank/sewage disposal system leakage, sewage treatment plant/disposal system overload, raw sewage deep well injection, improper coagulation, use of recycled, concentrated backwash water. Distribution system contamination can occur as a result of cross-connection, broken or leaking waterlines, or back-siphonage. Effects of bacterial ingestion include abdominal cramps and diarrhea. WHO standards require zero Coliform to be found per 100 ml of safe drinking water (USDI; 2001).

Escherichia Coli (E.Coli)

Fecal bacteria are single-celled microorganisms, virtually always associated with fecal contamination of water, but not always harmful. Fecal indicator bacteria are used in determining (indicating) the microbial quality of water. Fecal coliform known as Escherichia Coli (E.Coli) are fecal indicator bacteria. Escherichia Coli (E.Coli) is the fecal coliform group of bacteria contaminated in much higher level than coliforms. E.Coli appears as straight rods, single or in pairs forms, can grow on simple nutrient media. Chiang (2003) found that Escherichia coli is a specific subset of thermotolerant coliform bacteria which possess the enzymes B-galactosidase, B-glucuronidase and hydrolyzes 4-methyl-umbelliferyl-B-D-glucuronidase. Waite (1985) had estimated that 95% of all coliform found in human feces could be E.Coli. Sewage, treated effluents, all natural water which was subjected to recent fecal contamination from humans or wild animals will contain E.Coli. Usually E.Coli cannot multiply in any natural water environment and they are, therefore, used as specific indicator for fecal contamination (WHO, 1996). The presence of E.Coli can cause diarrhea, nausea and other problems especially for infants, children and those with weak immune systems, cause infantile diarrhea and acute diarrhea that may be fatal. Hemorrhagic colitis (HC) is the acute disease caused by E-Coli. HC results in severe abdominal cramps, watery diarrhea, and lower intestinal bleeding; with occasional vomiting and fever. In some cases, hemolytic uremic syndrome or renal failure can occur. Although not life threatening to healthy adults, these diseases can be fatal to young children. E-Coli is transmitted through fecal-oral ingestion of the bacteria by direct ingestion (i.e. drinking), primary contact recreation (i.e. swimming), or secondary contact (i.e. fishing). WHO standards require zero E.Coli to be found per 100 ml of safe drinking water (USDI; 2001).

Leakage of pipe lines:

The water at the source is usually potable, fit and good quality for human consumption but got contaminated and polluted when pipelines were cut for illegal connections. The old and rusted distribution pipeline system was the main cause of micro holes and crakes and mixing of sewerage water.

Location of pipelines:

The authorities responsible for supply of potable water to the public in cities, usually layout the freshwater pipes at parallel or beneath the sewerage pipes or channels. The seepage of sewerage polluted water is towards lower levels causing the mixing of waste effluent in freshwater.

Clogging of sewerage system:

In most of the cities, more than 50% of sewerage channels and pipelines are overloaded and remained in most cases blocked due to poor maintenance and plugging with plastic bags & bottles and, therefore, much of the sewage overflows into surface drains and natural water channels.

Mixing of untreated contaminated water:

The overall cities in Pakistan are producing wastewater estimated at 4.43 billion cubic meters. The total wastewater finding its way to the major rivers is estimated at about 1.782 billion cubic meters, which includes municipal and industrial effluents. The river Indus and its tributaries have been heavily polluted with agricultural, human, hospital and industrial wastes. About 60% of the Karachi city’s untreated sewage is being flushed into the Arabian Sea. It means that over 300 million gallons of untreated water going in the sea daily (Dawn, March 18-24, 2004) (Dawn, March 16, 2004).

Growing of field crops and vegetables:

It is common practice in urban adjoining agricultural fields to irrigate the field crops and vegetables with untreated wastewater because of its high fertility and reliable supply in spite of the health risks involved. Farmers prefer to use untreated wastewater when there is opportunity for direct economic benefits and especially in cases when there is lack of access to other sources of irrigation water.

Groundwater pollution in:

• Consolidated Rocks:

The polluted and contaminated poor quality water can percolate and mix in the groundwater sources even in areas of hard rock formations. Because even the hard rocks zones are capable of producing joints, fractures, fissures, lineaments, caverns, cavities, splitting, broken layers, fault zones, curved faces, cleavages, cracks, cones, pores, openings, veins, capillaries etc. These open spaces acts as water movement capillaries facilitating the mixing of surface and groundwater.

• Unconsolidated Rocks:

If the land surface contains layers of loess it can store a huge amount of contaminated and polluted water and can release it slowly toward the aquifer even in the dry periods. At the land surface, the layers of gravels, pebbles, boulders, course grained sands, loamy soils, fine sands, sandy loam, silt are permeable enough to produce acceptable infiltration rates for mixing of polluted water into the fresh aquifers.