METHODOLOGY

General methodology adopted for National Water Quality Monitoring Program consisted of establishing network for collection of water sample, monitoring stations, sample size and frequency of sample collection, details of analysis, recording of groundwater level etc. The details of these components are given below:

Grid Size and Number of Samples

A uniform site selection criterion was adopted and a grid size of 1 km² (for small cities) 4 and 9 km² (for medium cities) and 16 and 25 km² (for big cities) was established. Preference was given to permanent public points considering the long term monitoring requirement of the project. Geology and depth of aquifers was also considered. A minimum distance of 1 km was maintained between the two monitoring points. Site identification was marked on each city map according to the grid. Sample ID for monitoring purpose was marked on the basis of actual sampling visit sequence of various sites. Following identifications were also marked on every sample of each site:

Cross, field blank and replicate samples for quality control purposes were also collected. Sites for cross samples were selected owing to site number divisible by 10. Sites for Field Blank and Replicates were on the basis of site number divisible by 20. The details regarding grid size and sampling points (number) are shown in Table 4.1.

Table 4.1:  Details of Water Quality Monitoring Network

Monitoring Domains

The national water quality monitoring program covers twenty-one main cities, 11 in Punjab, 3 in Sindh, 4 in Balochistan, and 3 in NWFP. The detail of cities is available in section 1.3. For water quality data collection purposes, the country has been divided into six zones namely Capital Territory Area, Punjab (two zones), Sindh, Balochistan, and NWFP. The field teams of the sub offices were assigned the task in the respective zones of the country and were mobilized for field data collection. Details of the Monitoring Stations (MS) and their areas of responsibility for collection of water samples for water quality monitoring are as under:

·         Monitoring Station-I (WRRC, Islamabad)

Rawalpindi, Islamabad and Gujrat cities, Simly, Rawal and Khanpur dams, Tarbela, Mangla and Chashma reservoirs and Jhelum and Chenab Rivers.

·         Monitoring Station-II (Regional Office, Lahore)

Lahore, Sialkot, Sheikhupura, Gujranwala, Faisalabad and Kasur cities and Ravi River.

·         Monitoring Station-III (Regional Office, Bahawalpur)

Bahawalpur and Multan cities and Sutlaj River.

·         Monitoring Station-IV (Drainage Research Centre, Tandojam)

Hyderabad, Karachi and Sukkur cities, Manchar and Hamal lakes, LBOD, RBOD and Hub dam and Indus River.

·         Monitoring Station-V (WRRC, Quetta)

Quetta, Khuzdar, Loralai and Ziarat cities and Hanna Lake.

·         Monitoring Station-VI (WRRC, Peshawar)

Peshawar, Mardan and Mangora cities and Indus and Kabul Rivers.

 Sample Collection and Preservation

Water samples for physico-chemical analysis were collected in polystyrene bottles of 0.5 and 1.5 liter capacities. Before collecting the samples, the bottles were washed properly and rinsed thoroughly several times first with water and then with distilled water. For bacterial analysis, samples were collected in sterilized containers (200 ml). Hydrochloric acid and boric acid were used as preservatives in the sampling bottles for trace elements and nitrate nitrogen respectively before going to field. The first set of water samples was collected after monsoons rains. The sampling team comprised of a Deputy Director as Incharge assisted by a Laboratory Assistant, a supervisor, and a driver.

Following procedure and precautionary measures were followed while collecting samples from the field.

Tap Water

Un-rusted taps were selected for collection of water samples. These taps were properly cleaned and allowed to flow for a few minutes before collecting the sample.

     Sample Collection from Tap for Microbiological Analysis

Tubewell Water

The water samples from tube wells were collected after allowing them to flow for at least 10 minutes to get representative sample of the groundwater. Depth of groundwater level and location of the tubewell was properly marked on the topographic survey sheet.

Water from Distribution Network

The water samples from the distribution network were collected from the source of supply (as closely as possible) to minimize the effects of pollution in the distribution system and from consumers end to evaluate the actual quality of water being used. All water sample containers were filled slowly to avoid turbulence and air bubbles after flushing the system for sufficient time.

Measurement of Electrical Conductivity in the Field

pH Determination of Samples in the Field

Hand Pump/Dug Well Water

Water samples were collected from hand pumps or dug wells after purging of the hand pump or well. The purging was carried out by making one stroke for every foot of depth (A hand pump or dug well having 30 feet of depth, needs 30 strokes for its purging).

Stream Water

Water samples were collected from the centre by standing in the middle of the stream. Care was taken to keep the bottle well above the bed of the stream to avoid unwanted bed material going into the sample.

4.3.6    Spring Water

Water samples were collected directly from the spring in sterilized sampling bottles for microbiology and bottles used with or without preservatives for other water quality parameters.

4.3.7    Dams, Rivers and Lakes

It is difficult to obtain a truly representative sample when collecting surface water samples. Sampling point was selected carefully (near to bank in case of river) to avoid any kind of debris in the water. Considerable variations like seasonal stratification, runoff, rainfall and wind were also documented while collecting water sample especially from lake.

4.3.8    Microbiological Samples

The water samples for microbiological contamination were collected in clean, sterile plastic bottles (200 ml). The care was taken to ensure that no accidental contamination occurs during sampling. Samples were not taken from those taps, which were leaking between the spindle and gland to avoid outside contamination. The samples were kept cool and in the dark while transporting to the laboratory.

     Microscopic Examination of Isolated Micro-organisms              Inoculation of Water Samples in the Laboratory

4.3.9    Type of Water Samples and Preservatives

Samples were collected for microbiological analysis, for trace elements, for Nitrate (N) and general water quality parameters. The details of these samples and preservative used for each sample are given below:

·         Type A – All sites – Sterilized sampling bottles for microbiological analysis;

·         Type B – All sites – 2+10 ml/litre HNO₃ as preservative for trace elements;

·         Type C – All sites – 1 ml/100 ml, 1 M Boric acid as preservative for Nitrate (N); and

·         Type D – All sites – No preservative for other water quality parameters.

Types of Samples (A, B, C, D) from Single Source

4.3.10  Check List of Items/Activities Needed before Going to Field

·         Number of bottles required for sampling.

·         An appropriate preservative filling in the sampling bottles.

·         Calibration of field equipment (if necessary).

·         General items required for sampling e.g., sampling forms, equipment, markers, ballpoints, distilled water, paint, pH-meter and EC-meter.

4.3.11  Check List of Items/Activities Needed During Collection of Samples

·         City map with grids and identified ID site. During site finalization, ensure that site selection meets the criteria of representative sample. Filling site and sample ID in the form.

·         Sample bottle with date and sample ID with indelible ink.

·         Sample bottles preserved with appropriate preservative.

·         Finalization of method for sample collection.

·         Ensuring at four water quality samples.

·         Confirm cross, field blanks and replicate samples from suitable sites.

·         Marking of (P) on site after collecting sample for future reference and use red paint.

4.3.12  Check List Items/Activities after Collection of Samples

·         Samples are transported to the laboratory within the recommended time period.

·         That the water samples are not filtered.

·         Purpose of water testing to the communities is properly explained.

4.4              Quality Control Measures

Quality control measures were started from the filed. Standard sampling methods were adopted to collect the samples. Four types of samples were collected for monitoring purpose where as three kinds of samples were collected for quality control. The detail of these samples is as under:

(i)         Samples for Monitoring Purposes

a)      Samples for microbiological examination in sterile bottle.

b)      Samples for the analysis of trace elements by addition of HNO₃ as preservative.

c)      Samples for the analysis of Nitrate (N) by addition of boric acid as preservative.

d)      Samples without preservative for the analysis of EC, pH, Hardness, Ca, Mg, Na, K and HCO₃ etc.

(ii)        Samples for Quality Control Purposes.

a)      Samples for cross analysis (10%).

b)      Samples to check reproducibility (10%).

c)      Samples for field blank (10%).

Field blank and replicate samples were planned to be analyzed in the same laboratory to see the quality of distilled water and reproducibility in analytical readings. Cross samples were planned to be sent to some reputable laboratories for comparison. However, due to constraint of time, cross samples could not be carried out in any other laboratory. Therefore, all analysis of field blank, replicate and cross samples for water quality purposes was carried out in PCRWR water quality laboratory at Islamabad by two different teams are shown at Annexure-VII.

Moreover, PINSTECH is now a days analyzing the cross samples of NWQMP (Phase-II) to see the accuracy in analytical results of both laboratories. The comparison of these results will be given in the next report.

4.5              Analytical Methods

The water samples were analyzed for physical, chemical and bacteriological parameters by using standard methods (Table 4.2). The details of the parameters and methods used for their analysis are given below:

Table 4.2: Water Quality Parameters and Methods used for Analysis

Continued-

Table 4.2- (Contd.)

4.5.1    Alkalinity

Alkalinity of water is its acid-neutralizing capacity. The measured value may vary significantly with the end point pH used. The alkalinity is primarily a function of carbonate, bicarbonate and hydroxide contents. The measured values may also include contributions from borates, phosphate, silicates or other bases if present. Alkalinity measurements are used in the interpretation and control of water and waste water treatment processes. Raw domestic waste water has an alkalinity less than or slightly greater than that of the water supply. The method used for this analysis was 2320 Standard Method (1992). The chemicals used for this analysis included:

i)                    Carbon dioxide free distilled water;

ii)                   Sodium carbonate solution, 0.05 mol/l;

iii)                 HCl 0.02 M;

iv)                 Phenolphthalein indicator; and

v)                  Methyl orange indicator.

A 100 ml sample was mixed with 2 or 3 drops of phenolphthalein indicator in a conical flask. The phenolphthalein alkalinity of the sample was determined by titrating with standard acid (HCl 0.02 M) until the disappearance of pink colour. The alkalinity to phenolphthalein was considered to be zero in case no colour was produced after addition of few drops of phenolphthalein. The methyl orange alkalinity of the sample was determined by titrating with standard acid (HCl 0.02 M) until the colour changes from yellow to orange.

Total alkalinity as CaCO₃ (m.mol/l)= 1000xBxC

                                                V

where:

B=  ml of standard acid solution to reach the end point of methyl orange;

C=  Concentration of acid in mol/l; and

V=  ml of sample.

Using 100 ml of sample and 0.1 mol/l standard acid solutions, the numerical value of alkalinity is directly expressed in m.mol/l by the number of ml of titrant consumed.

4.5.2    Arsenic

Arsenic is a non-metallic element, present naturally in surface and ground water due to erosion of rocks. It is concentrated in shale, clays, phosphorites, coals, sedimentary iron ore and manganese ores.  Aqueous arsenic in the form of arsenite, arsenate and organic arsenicals may result from mineral dissolution, industrial discharges or the application of herbicides. The chemical form of arsenic depends on its source. Inorganic arsenic may originate from minerals, industrial discharges and insecticides, whereas organic arsenic may come from industrial discharges, insecticides and biological action on inorganic arsenic. The toxicity of arsenic depends on its chemical form.

Merck Test Kit, Cat No. 1.17926.0001, Germany (0.01-0.5 mg/l) was used for arsenic analysis. When zinc and sulfuric acid are added to compounds of arsenic-III and arsenic-V, arsenic hydride is liberated, which in turn reacts with mercury-II bromide contained in the reaction zone of the analytical test strip to form yellow-brown mixed arsenic mercury halogenides. The concentration of arsenic-III and arsenic-V are measured semi quantitatively by visual comparison of the reaction zone of the analytical test strip with the fields of colour scale. The concentrations of foreign substances given in Table 4.3 lies below the limit at which the determination is interfered with.

Table 4.3: Concentration Levels of Foreign Substance

One analytical test strip was removed and the tube was closed immediately. The test strip was inserted with the reaction zone first about halfway through the slot in the stopper of the reaction vessel. A sample of 10 ml was transferred to the reaction vessel by a syringe and added 2 spoonfuls of reagent arsenic-I. Then added 10 drops of reagent arsenic-II rapidly and closed the reaction vessel with the stopper immediately. The sample solution should not come in contact with the test strip while swirling. After 30 minute, the strip was removed and compared the colour on the label/concentration value in mg/l arsenic.

4.5.3    Bicarbonates

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. No guidelines values are recommended by WHO. The method used for this analysis was 2320 Standard Method (1992).

Determination of Bicarbonates by Titration Method

The reagent used for this analysis included:

i)                    Methyl orange indicator; and

ii)                   Standard acid (HCl) 0.02 N.

A 50 ml of sample was taken in flask and added one drop of methyl orange. Then titrated it against the standard acid until the colour changed from yellow to orange and recorded the volume of acid used as “R₂”.

Bicarbonate mg/l= R₂ x20-R₁x20x2

where:

R₁= Volume of acid used for phenolphthalein alkalinity.

4.5.4    Calcium

The presence of calcium in water supplies results from passage through or over deposits of limestone, dolomite, gypsum and gypsiferous shale. The calcium content may range from zero to several hundred milligrams per litre, depending on the source and treatment of the water. Small concentrations of calcium carbonate combat corrosion of metal pipes by laying down a protective coating. Appreciable calcium salts, on the other hand, precipitate on heating to form harmful scale in boilers, pipes and cooking utensils. Chemical softening, reverse osmosis, electro dialysis, ion exchange is used to reduce calcium and the associated hardness.

Samples were collected in plastic bottles without the addition of preservative. The samples were re-dissolved by the addition of nitric acid in case of precipitation of calcium carbonate produced during sample storage before analysis. The method used for this analysis was Disodium Ethylenediaminetetraacetate dehydrate (EDTA) titration method (reference method). When EDTA is added to water containing calcium and magnesium ions, soluble EDTA chelates are formed. The stability constant for the calcium chelates is larger than that for the magnesium chelate consequently, in a titration, calcium reacts before the magnesium. Calcium can be determined in the presence of magnesium by EDTA titration when an indicator is used that reacts with calcium only e.g. Murexide gives a colour change when all of the calcium has been complex by EDTA at a pH of 12 to 13.

Orthophosphate precipitates calcium at the pH of the test and, therefore, produces low results. Strontium and barium interfere with the calcium determination by virtue of the fact that they also form EDTA chelates and alkalinity in excess of 30 mg/l may cause an indistinct endpoint with hard water. The concentration levels of ions which cause interference with the calcium hardness are given in Table 4.4.

Table 4.4:  Recommended Level of Concentrations of Ions for Non-Interference of Calcium

            The reagents used for this analysis included:

i)                    Sodium hydroxide (NaOH), 1N;

ii)                   Murexide indicator; and

iii)                 Standard EDTA titrant, 0.01 M.

            A sample of 50 ml was used, or a smaller portion diluted to 50 ml so that the calcium content was about 5-10 mg. Then added 2 ml of NaOH solution or a volume sufficient to obtain a pH of 12-13. After stirring well, 0.1-0.2 gm of the Murexide indicator was added. Then EDTA titrant was added slowly, with continuous stirring until the proper end point reached.  

            Concentration of Ca (mg/l) = AxBx400.8

                           V

            where:

            A= ml of EDTA titrant used for titration of sample:

                        B= ml of standard calcium solution; and

                        ml of EDTA titrant

V=  ml of sample.

4.5.5    Carbonate

The method used for this analysis again was 2320 Standard Method (1992). The reagents used for this analysis included:

i)                    Standard solution 0.02 N HCL; and

ii)                   Phenolphthalein indicator.

A 50 ml of sample was taken in flask and added one drop of phenolphthalein indicator. The carbonate was considered to be zero in case of no pink colour. If the sample turned into pink colour, the sample was titrated against the standard acid until it became colourless. The volume of acid used was noted as “R₁”.

Concentration of carbonate mg/l= R₁x20x2.

4.5.6    Chloride

Chloride (Cl) ion is one of the major inorganic anions in water and waste water. In potable water, the salty taste produced by chloride concentrations is variable and dependent on the chemical composition of water. Some waters containing 250 mg Cl/ l may have a detectable salty taste if the cation is sodium. On the other hand the typical salty taste may be absent in water containing as much as 1000 mg/l when the predominant cations are calcium and magnesium. The chloride concentration is higher in waste water than in raw water. Along the seacoast, chloride may be present in high concentration because of leakage of saline water into water bodies directly or indirectly. Industrial processes may also increase chloride. High chloride content can harm metallic pipes and structures, as well as growing plants. The method used for this analysis was Titration (silver nitrate) standards method.

Representative samples were collected in clean and chemically resistant plastic bottles. The maximum sample portion required was 100 ml. No special preservative was necessary for the storage of samples. Chloride is determined in a natural or slightly alkaline solution by titration with standard silver nitrate using potassium chromate as indicator. Silver chloride quantitatively precipitates before red silver chromate is formed.

Bromide, iodide and cyanide are measured as equivalents of chloride ion. Main interferences are the contents of thiosulfate, thiocyanate, cyanide, sulfite, sulfide, Iron (if present >10 mg/l) and orthophosphate (if present >25 mg/l.) The pretreatment of highly colored or turbid samples is required. The reagents used for this analysis included:

·         Standard silver nitrate solution (0.02 M);

·         Potassium chromate indicator; and

·         Aluminum hydroxide suspension.

A 20 ml sample was taken in a conical flask and adjusted the pH range 7 to 10 with H₂SO₄ or NaOH. A few drops of K₂CrO₄ indicator solution was added and titrated against standard solution of AgNO₃ (titrant) up to pinkish yellow end point. 100 ppm NaCl standard was used to confirm accuracy.

Concentration of Cl mg/l =         (A-B) xMx35.45x1000

                        V

where:

A and B are the volumes of silver nitrate solution required by the sample and blank respectively;

M= Concentration (mol/lit) of AgNO₃; and

V=  ml of sample.

4.5.7    Chromium

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 litre is allowed in drinking water in the USA and a similar limit is allowed by WHO. The method used for this analysis was 1.5-Diphenylcarbohydrozide Method (HACH-8023) by Spectrophotometer. The measurements can be made within the accuracy range of 0.0 to 0.60 mg/l.

Hexavalent chromium is determined by the 1, 5 Diphenylcarbohydrozide method using chromium reagent (chroma ver 3). This reagent contains an acidic buffer combined with 1,5- Diphenyl-carbohydrozide when reacts to give a purple colour, which is proportional to the amount of hexavalent chromium present.

Samples were collected in clean plastic bottles, stored at 4^oC and analyzed within 24 hours after collection. The contents of one chroma ver 3-reagent powder pillow were added in 10 ml of deionized water. After swirling thoroughly, blank solution was taken in cullet and placed in cell holder of spectrophotometer adjusted at wavelength of 540 nanometer (nm). Standard chromium solutions of 0.005, 0.02, 0.04, 0.06, 0.08 and 0.1 mg/l were prepared and treated in the same way as deionized water and absorbance were noted. Similarly absorbance of samples was taken and the concentration of chromium was determined with the help of calibrated graph.

4.5.8    Conductivity

Conductivity is a measure of the ability of an aqueous solution to carry an electric current. This ability depends on the presence of ions, their total concentration, mobility, 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. The apparatus used for this analysis was EC meter, HACH-44600, USA.

Measurement of EC in the Laboratory

The samples were shaken thoroughly before starting measurements and allowed to stabilize till removal of attain air bubbles. EC meter was standardized with the help of standard solution of potassium chloride, 0.01 M at a constant temperature of 25 ^oC. Then conductivity cell was thoroughly rinsed with distilled water as well as a small amount of sample. The cell was then completely filled with sample. The EC of the samples was noted from the screen of EC meter. Temperature affects conductivity that varies by about 2% per 1 ^oC. The temperature of 25 ^oC is taken as standard. Dissolved carbon dioxide increases conductivity without increasing the mineral salt content. The same is true for a sample with a low pH value, owing to the high equivalent conductivity of the hydrogen ion. However, the effect is not large and the removal of carbon dioxide from hard water cannot be achieved without a risk of precipitating calcium carbonate.

4.5.9    Fluoride

A fluoride concentration of approximately 1.0 mg/l in drinking water effectively reduces dental caries without harmful effects on health. Fluoride may occur naturally in water or it may be added in controlled amounts. Some fluorosis may occur when the fluoride level exceeds the recommended limits. The method used for analyzing was 8029, SPADNS (Hach) by Spectrophotometer. The range of analysis is about 0.0 to 2.00 mg/l. Samples were collected without preservative in polythene bottles and analyzed within 28 days.

The SPADNS colorimetric method is based on the reaction between fluoride and a zirconium-dye lake. Fluoride reacts with the dye lake, dissociating a portion of it into a colorless complex anion (ZnF₆^-2) and the dye. As the amount of fluoride increases, the color produced becomes progressively lighter. Thus bleaching the red color is an amount proportional to the fluoride concentration.

A 10 ml sample and deionized water was measured into two dry sample cells. Then two ml of SPADNS reagent was added into each cell and swirled to mix. After one-minute reaction period, the blank was placed into the cell holder of spectrophotometer adjusted at 580 nm and pressed the zero button. Then the prepared sample was placed into the cell holder and their absorbance was noted. Similarly, all the samples were treated and their absorbances were noted. The concentration of fluoride in samples was determined with the help of regression model. Concentration of F^-ion mg/l equals Abs.x6.9364+0.0425.

4.5.10  Hardness

Originally, water hardness was understood as a measure of the capacity of water to precipitate soap. In conformity with current practice, total hardness is defined as the sum of the calcium and magnesium concentrations, both expressed as calcium carbonate, in milligram per litre. The hardness may range from zero to hundreds of milligrams per litre, in terms of calcium carbonate, depending on the source and treatment to which the water has been subjected. Samples were collected in plastic bottles without the addition of preservative. The method used for this analysis was EDTA Titration Standard Method (1992).

EDTA forms soluble chelates of calcium and magnesium ions. When a small amount of Eriochrome Black T indicator is added to a solution containing calcium and magnesium ions at pH 10.0+ 0.1, the solution became wine-red in colour. When the solution is titrated with EDTA the calcium and magnesium are complexed and at the end point the colour of the solution changes from wine-red to blue. Several metal ions can interfere with the titration by producing fading or indistinct endpoints. To minimize these interferences, sodium sulfide solution is added. The approximate concentration of various ions can be tolerated if sodium sulfide is added. Interfering substances are aluminum 20 mg/l, cadmium 10 mg/l, cobalt 0.3 mg/l, copper 20 mg/l, ferrous ions 5 mg/l, lead 20 mg/l, manganese ion 1 mg/l, nickel 0.3 mg/l, polyphosphate 10 mg/l, zinc 200 mg/l.

A 25 ml of sample was taken and diluted to 50 ml with distilled water in a conical flask. One ml of buffer solution and 1-2 drop of Eriochrome Black T indicator was added. Then the standard EDTA titrant was added slowly with continuous stirring, until last radish tinge colour disappeared from the solution. The end point of the solution was normally blue. The duration of the titration was not extended beyond 5 minutes measured from the time of addition of buffer.

Hardness as CaCO₃ (mg/l)=      (A-B) xCx1000

                                 V

where:

A= ml of EDTA for titration of sample;

B= ml of EDTA for titration of blank; and

C can be calculated from the standardization of the EDTA titrant and equivalent to

ml of standard calcium solution; and

                        ml of EDTA titrant

V= ml of sample.

4.5.11  Iron

Iron is an abundant element in the earth’s crust, but exists generally in minor concentrations in natural water system. Surface water in a normal pH range of 6 to 9 rarely carries more than 1 mg of dissolved iron per liter. The formation of hydrated ferric oxide makes iron-laden waters objectionable. This ferric precipitate imparts an orange stain to any setting surface including, laundry articles, cooking and eating utensils and plumbing fixtures. Additionally, iron imparts a yellowish colour and bitter taste to water. This coloration along with associated taste and odors can make the water undesirable for domestic use. WHO has established 0.3 mg/l as the highest desirable level for iron in water and 1.0 mg/l as the maximum permissible level in water intended for domestic use.

In the sampling and storage process, iron in solution may undergo changes due to oxidation and it can readily precipitate on the sample container walls or a partially settle-able solid suspension. For total iron measurement, precipitation can be controlled in the sample containers by the addition of 1.5 ml of concentrated nitric acid per liter of sample immediately after collection. The method used for this analysis was Photometric Phenanthroline Method.

Ferrous (iron) chelates with 1, 10-phenanthroline to form an orange-red complex. Colour intensity is proportional to iron concentration. A pH between 2.9 and 3.5 ensures rapid colour development in the presence of an excess of phenanthroline. The interfering substances are cyanide, nitrate, phosphate, chromium, zinc, iron, cobalt and copper (in excess of 5 mg/l), nickel (in excess of 2 mg/l), Bismuth, cadmium, mercury, molybedate and silver.

The concentration of iron was measured at 510 nanometer on Spectrophotometer, Model U-1100, HITACHI. The reagents used for this analysis included:

i)                    Iron standard solutions;

ii)                   Phenanthroline solution; and

iii)                 Ammonium acetate buffer solution.

A 5 ml of deionized water was taken in a beaker. Its pH was adjusted between 3 and 4 and 1 ml of buffer solution with 0.2 ml of phenanthroline solution was added. After 10-15 minute, the contents of beaker were taken in a culet and placed in cell holder of the spectrophotometer at wavelength of 510 nm and the zero button was pressed. The standard solutions from 0.1 to 1.0 mg/l were prepared and their absorbances were taken. Similarly the absorbance of samples was taken and their concentrations were determined with the help of calibrated graph.

Determination of Iron on Spectrophotometer

4.5.12  Magnesium

Magnesium ranks eighth among the elements in order of abundance and is the common constituent of natural water. Waters associated with granite or siliceous sand may contain less than 5 mg of magnesium per litre. Water containing dolomite or magnesium-rich limestone may contain 10-50 mg/l and several hundred mg/l may be present in water that has been in contact with deposits containing sulfates and chlorides of magnesium. Magnesium by a similar action to calcium, imparts the property of hardness to water. This may be reduced by chemical softening or ion exchange methods. The method used for analyzing magnesium concentration was 2340-C, Standard Method (1992). Magnesium was estimated as the difference between hardness and calcium as CaCO₃.

Concentration of Mg (mg/l) = [total hardness (as CaCO₃ mg/l)–Calcium hardness (as mg CaCO₃/l) x 0.243].

4.5.13  Nitrate-N

Nitrate, highly oxidized form of nitrogen is commonly present in natural water due to end product of the aerobic decomposition of organic nitrogenous matter. Significant sources of nitrate are fertilizers from cultivated land, drainage from livestock feed lots and domestic and some industrial waste water. Unpolluted natural water usually contains only minute amounts of nitrate. Excessive concentrations in drinking water are considered hazardous for infants. In their intestinal tract nitrates are reduced to nitrites, which may cause methaemoglobinaemia.

Samples were collected in plastic bottles with the addition of boric acid (2 ml/l sample) and stored at 4^oC. Before analysis, the samples were warmed to room temperature and neutralized with 5.0N sodium hydroxide standard solution. The method used for this analysis was Cadmium Reduction Method (HACH-8171) by Spectrophotometer.

The range of measurement for Nitrate (N) in drinking waters falls between 0 to 4.5 mg/l (NO₃-N). The possible interferences are strong oxidizing and reducing substances. Ferric (iron) causes high results and must be absent. Chloride conc. above 100 mg/l may also cause low results.

Cadmium metal reduces nitrate presence in the sample to nitrite. The nitrite ion reacts in an acidic medium with sulfamilic acid to form an intermediate diazonium salt, which couples to gentisic acid to form an amber-coloured product.

A 25 ml of deionized water was taken in a beaker. The contents of 1 NitraVer 5-nitrate reagent pillow were added and swirled to dissolve. The beaker was placed undisturbed for 5 minutes to allow for the chemical reaction to complete. The contents of beaker were taken in a reference cell and placed into the cell holder of UV Visible spectrophotometer adjusted at wavelength of 400 nm. The zero button was pressed to display zero reading. Then the standard nitrate (N) solutions of 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mg/l were prepared in separate beakers and their absorbance were noted. Similarly absorbances of samples were measured and the concentrations of nitrate (N) were determined with the help of calibrated graph.

4.5.14  pH

For most practical purposes the pH of an aqueous solution can be taken as the logarithm to the base 10 of the reciprocal of the hydrogen ion concentration (more precisely, of the hydrogen ion activity) in moles/litre. The practical pH scale extends from 0 to 14 with the middle value of 7 corresponding to exact neutrality at 25^oC. The pH of natural waters is usually governed by the carbon dioxide/bicarbonate/ carbonate equilibrium and lies in the range between 4.5 and 8.5. Humic substances may affect it by changes in the carbonate equilibrium due to bioactivity of plants, in some cases by hydrolysable salts etc. Waste waters and polluted waters may have pH values much lower or higher.

On site determination of pH of the samples was done in most of the cases. In other cases where pH meter was not available samples were collected and transferred in a completely filled, well stopper bottles to prevent changes in its composition especially in carbon dioxide. The method used for this analysis was Electrometric Method (Reference method). The pH meter was standardized according to the manufacturer’s instructions. Before measuring the pH of the test samples, the electrode was washed thoroughly first with distilled water and then with the sample water. Then the electrode was dipped into the sample and system was allowed to stabilize before making the final reading. Determination was made in unstirred solutions to avoid loss of carbon dioxide or other volatile components.

4.5.15  Sulfate

Sulfate is an abundant ion in the earth’s crust and light concentrations may be present in water due to leaching of gypsum, sodium-sulfate and shale. High concentrations of sulfate may be due to oxidation of pyrite and mine drainage. Sulfates also come from sulfur containing organic compounds and industrial waste discharge. Sulfate concentrations in natural water range from a few mg to several hundred mg per litre. The WHO has established 200 mg/l as the highest desirable level of sulfate and 400 mg/l as the maximum permissible level in water for domestic use. Samples were collected in clean plastic bottles and were stored at 4^oC in order to reduce the possibility of bacterial reduction of sulfate to sulfide in polluted or contaminated samples. The method used for this analysis was Sulfa Ver 4 HACH Method (8051) (powder pillows). The range of measurement was 0 to 70 mg/l.

Sulfate ions in the sample react with barium in the sulfa ver 4-sulfate reagent and form insoluble barium-sulfate turbidity. The amount of turbidity formed is proportional to the sulfate concentration. The following elements interfere at levels above those concentrations listed below:

UV-VIS Spectrophotometer (U-1100), HITACHI apparatus was used for analysis.

A 25 ml of deionized water was taken in a beaker. The contents of sulfa ver 4 sulfate reagent powder pillows were added and swirled to dissolve. The beaker was placed undisturbed for 5 minute to reach its reaction period. The contents of beaker were taken in a reference cell and placed into the cell holder of UV-VIS spectrophotometer adjusted at wavelength of 450 nm. The button zero was pressed to display zero reading. Then the standard solutions of 5,10,20,30,40,50,60 and 70 mg/l sulfate were prepared into separate beakers and the contents of sulfa ver 4-sulfate reagent powder pillows were added and swirled to dissolve. After 5 minutes (reaction period) the absorbance were taken and a graph was plotted between concentration of the sulfate standard solution and their representative absorbance. Similarly the water samples were treated and their absorbance was compared with graph in order to determine their concentrations.

4.5.16  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 plate. Flavour refers to complex of gustatory, olfactory and trigeminal sensations resulting from chemical stimulation of sensory nerve endings located in the tongue, nasal cavity and oral cavity. Water samples taken into the mouth for sensory analysis always produce a flavor, although taste, odor or mouth-feel may predominate, depending on the chemical substances present. Taste tests were performed only on samples that were known to be sanitarily acceptable for ingestion. The method used for this analysis was that sample taste was carried out at the original temperature of the sample after rinsing the mouth with a portion of sample for some seconds on the tongue. The result of a sample test was described only qualitatively. The person tasting water must avoid eating, drinking or smoking before making a test. Only 4 true taste sensations, salty, sweet, bitter and sour were used for reporting taste results.

4.5.17  Turbidity

Turbidity is an expression of the optical property that causes light to be scattered and absorbs rather than transmitted in straight line through the sample. Suspended matter such as clay, silt, fine organic, inorganic substances, soluble coloured organic compounds, plankton and other microscopic organisms causes turbidity in water. Correlation of turbidity with the weight concentration of suspended matter is difficult to derive due to the size, shape and refractive index of the particulates that affect the scattering properties of the light in the suspension. Optically black particles (activated carbon) may absorb light and effectively increase turbidity measurements. The turbidity is of interest for two main reasons. First, turbidity is an important parameter for characterizing the water quality. Water treatment plants need its values for the treatment of surface water. Secondly, knowledge of the turbidity allows an estimate to be made of the concentration of un-dissolved substances.

The samples were collected in plastic bottles. Turbidity of the samples was measured just after their collection as irreversible changes may occur in turbidity as a result of long period storage. The method used for this analysis was Nephelometric method. The apparatus consisted of Turbidity meter, Lamotte, Model 2008, USA. This turbidity method is based on a comparison of the intensity of light scattered by the sample under defined conditions with the intensity of light scattered by a standard reference suspension under the same conditions. The higher the intensity of scattered light, the higher the turbidity. Formazin polymer is used as the reference turbidity standard suspension. Turbidity determination is applicable to a water sample that is free from debris and rapidly settling coarse sediments. Dirty glassware, the presence of air bubbles, and the effects of vibrations that disturb the surface visibility of the sample will give false results. “True colour” (water colour) due to dissolved substances may absorb light and cause low turbidity values. This effect usually is however not significant in the case of treated water.

a)      Measurement of Turbidity Less Than 40 NTU.

The samples were vigorously shaken till the disappearance of air bubbles. The sample was then poured into the turbidity meter tube. The turbidity was read directly from the instrument scale.

b)   Turbidity Exceeding 40 NTU

The samples were diluted with one or more volumes of turbidity free water to fall below 40 NTU. Then calculated the turbidity values by using following equation:

Nephelometric turbidity units (NTU) = Ax (BxC)

                                                                                         C

where;

A=   NTU found in diluted samples;

B=   Volume of dilution water, ml; and

C=   Sample volume taken for dilution, ml.

4.6              Water Table Depth Measurements

Water level measurements are made to monitor changes in the piezometeric surface under different conditions. Records are required of continuous measurements such as those supplied by an automatic water stage recorder or of periodic measurements with a time interval extending from less than a minute (for a pump test) to 6 months. However, the frequency of measurements should be adjusted to the circumstances. In some instances, only a few measurements over a long period of time may be required. The possibility of error in interpretation decreases as the frequency of measurement and length of record increases. Water level may be measured with a number of different devices. The general procedures used are:

4.6.1    Chalked Steel Tape

Probably the most common device for measuring static water level is the chalked steel tape which has a weight attached on the lower end. The weight keeps the tape tight and aids in lowering it into the well. The tape is chalked with carpenter’s chalk, ordinary blackboard chalk, or dry soil, which changes shade upon becoming wet. The line of the colour change denotes the length of tape immersed in water. Subtracting this length from the reading at the measuring point gives the depth to water. Cascading water in a well may mask the mark of the true water level on the tape, however, this usually occurs only in a well that is being pumped. When this condition is encountered, another method of measuring is used. In small-diameter wells, the volume of the weight may cause the water level to rise in the pipe, and the measurements may need correction.

4.6.2    Electric Sounder (Water Level Indicator)

Electric sounders are also used to measure the depth to water in wells. There are a number of commercial models available, none of which is entirely reliable. Many sounders use brass or other metal indicators clamped around a conductor wire at 5 ft intervals to indicate the depth to water when the metal indicates contact. The spacing of these indicators should be checked periodically with a surveyor’s tape to assure accurate and reliable readings. Some electric sounders use a single-wire line and probe, and rely on grounding to the casing to complete the circuit, others use a two wire line and double contacts on the electrode. Most sounders are powered with flashlight batteries and the closing of the circuit by immersion in water is registered on a milliammeter. Experiences have shown the two-wire circuits with a battery are the most satisfactory. Electric sounders are generally more suitable than other devices for measuring the depth to water in wells that are being pumped because they generally do not require removal from the well for each reading. However, when there is oil on the water, water cascading into the well, or turbulent water surface in the well, measuring with an electric sounder may be difficult.

4.6.3    Steel Tape

A simple and reliable method for measuring the depth to water in observation holes between 1¹/₂ and 6 inches in diameter is a steel tape with a popper. The popper is a metal cylinder of 1 to 1¹/₂ inches in diameter and 2 to 3 inches long with a concave under surface fastened to the end of a steel tape. The popper is raised a few inches and then dropped to hit the water surface, where it makes a distinct “pop”. By adjusting the length of tape, the point at which the popper just hits the surface is rapidly determined. Poppers generally are not satisfactory for measuring pumping wells because of the operating noise and lack of clearance. Permanent pump installations should always be required with an access hole for probe insertion or an airline and gauge, or preferably both, to measure draw down during pumping. An airline is accurate only to about 0.5 ft unless calibrated against a tape for various draw downs, but is sufficiently accurate for checking well performance.

4.6.4.   Mercury Gauge

Artesian wells with piezometeric heads above the ground surface are conveniently measured by capping the well with a cap that has been drilled, tapped and fitted with a plug which is removed for the insertion of a Bordon gauge or mercury manometer stem. The static level is determined from the gauge reading of manometer reading after the pressure has stabilized. For continuous records, a recording pressure gauge may be used.

During the present study, the water levels were measured using Water Level Indicator because of its simple and easy use. Secondly the water levels were measured sufficiently after the pumping was stopped to obtain static conditions.

4.7              Data Base

The water quality database is being launched for the consumer’s awareness and emphasis on water quality issues and analytical results including physico-chemical and microbiological examination. Remedial measures and guidance regarding the protection of source will also be provided in detail about any potential hazard, if present in the source of surveyed area.

The website will be updated periodically to improve the effectiveness of information and its easy access on the suggestions of website visitors and researchers in the field of water sector.