WATER QUALITY

Water is the most vital resource for all kinds of life on this planet and is affected both qualitatively and quantitatively by varieties of activities on land, water & air. Water quality has a vital role in assessing the impacts in an around the streams & lakes. Basic physico-chemical studies reveal the status of water and the nature of the catchment responsible for the flow. Polluted state of water resources can lead to a steady decline in wildlife & fishes and often has miscellaneous effects on the environment. Some of the basic Physico-chemical parameters are:

pH: This indicates the extent and nature of the water, how acidic or basic the water is? Natural water usually has pH values between 5.0 and 8.5. These values are typical with slight seasonal variations; a sudden change would indicate industrial pollution. Many chemical reactions are controlled by pH and biological activity is usually restricted to a fairly narrow pH range of 6.0 to 8.0. Highly acidic or highly alkaline waters are undesirable because of corrosion hazards and possible difficulties in treatment.

Temperature:  It is expressed in ^oC or ^oF. Many of the industries use the natural water for cooling the boilers and release the water in the streams again but at an elevated temperature. The abnormal increase in temperature can cause decline in the dissolved oxygen concentration and in turn affect the survival of aquatic organisms

Salinity:  Expressed in mg/l or ppm it represents the total concentration of salt present in the water body.

Electrical Conductivity:  Conductivity of solution depends upon the quantity of dissolved salts present. It is related to TDS content. Its value becomes greater with the increase of the degree of pollution.

Turbidity: The presence of colloidal solid gives liquid a cloudy appearance, which is aesthetically unattractive and may be harmful. Turbidity in water may occur due to clay and silt particles, discharge of sewage or industrial waste or to the presence of large number of microorganisms.

Total Dissolved Solids (TDS): The total dissolved solids in the water are measured in mg/liter or ppm. The value of TDS is higher in rainy season because of the mud dissolved in the water. Run off generally increases the TDS in streams.

Total Hardness as CaCO₃ This is the property of water, which prevents lather formation with soap and produces scales in boilers. It is mainly due to the dissolved calcium and magnesium salts. There is no health hazard but economic disadvantages of hard water include increased soap consumption and higher fuel costs.

Chloride: It enters into the surface water due to the weathering of some sedimentary rocks, from sewerage, industrial or agricultural runoff. It is responsible for the brackish taste in water and is an indicator of sewage pollution because of the chloride content in urine.

Nitrogen - Nitrate (NO₃ - N): Nitrogen - Nitrate is the final oxidation product of nitrogen. Natural sources of nitrate to surface waters include igneous rocks, land drainage and plant and animal debris. Natural levels, which seldom exceed 0.1mg/L NO₃ - N, may be enhanced by municipal and industrial wastewater, including lechates from waste disposal sites and sanitary landfills. In rural and suburban areas the use of inorganic nitrate fertilizers can be a significant source.

Phosphate: Phosphate is essential for the growth of organisms and can be nutrient that limits the primary productivity of a body of water. In instances where phosphate is a growth - limiting nutrient, the discharge of raw or treated wastewater, agricultural drainage, or certain industrial wastes to that water may stimulate the growth of photosynthetic aquatic micro- and macro- organisms in nuisance quantities.

Biochemical Oxygen Demand (BOD): BOD is a measurement of the Oxygen required for microorganisms whilst breaking down organic matter to stable inorganic forms such as CO₂, NO₃, and H₂O. So the water with high BOD indicates the organic pollution.

Chemical Oxygen Demand (COD): COD is used as a measurement of the Oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidant. Usually the concentrations of COD in surface water ranges from 20mg/L or less in unpolluted water to greater than 20 mg/L in water receiving effluents.

Table 7 lists the parameters, which shows that the parameters are well below the permissible limits for surface water given by Bureau of Indian Standards. The Nagzari Valley having the most suitable & pristine water followed by the stream near the Syke’s point followed by reservoir near the Kulgi Camp.

Table 7: Analysis of some Basic Water Quality Parameters

Water Sampling Protocol:

1. Shore samples are to be collected from the surface of water, by gently putting the thoroughly washed container into the water which is free flowing (for the river samples) or from a clear place (in lake samples) taking into account that no other substances enter the container.
2. The on-site parameters which should be measured at the sampling point are the water temperature which can be either done by the help of a thermometer or with the help of a probe.
3. pH can be determined either through pH paper or by pH probes (for better accuracy).
4. Total dissolved solids can be measured with the help of probes which will give the idea of the total dissolved ions in the water sample.
5. The salinity & conductivity can also be done using the probe.
6. Dissolved oxygen estimation:
7. DO is analyzed at the spot by Winkler’s method in which the BOD (Niskin bottle sampler or van Dorn sampler) bottle has to be gently put into the water & should be slightly tilted so that water slowly enters the bottle as soon as the bottle is filled put the cap & close the bottle when it is still inside the water. Be careful not to allow any air bubbles to be entrapped, as it will significantly change the results. If bubbles are there after inserting the cap, remove and start the process again.
8. Add 1 ml of the manganese reagent (Winkler’s A) and 1 ml of the alkali-iodide solution (Winkler’s B) making sure no air is entrained into the bottles. It is important to just immerse the tips of the dispensers without immersing them completely. This avoids contamination while eliminating air entrainment at the same time. Shake the contents well by inverting the bottle repeatedly. Keep the bottle for some time to settle down the precipitate.
9. Add 1 ml of Conc. H₂SO₄ and shake well to dissolve the precipitate.
10. Remove a part of the content into a conical flask for titration and Titrate against Sodium Thiosulphate solution using starch as an indicator.

Dissolved oxygen (ppm) = (Normality of Na₂S₂O₃ (0.025N)* Burette Reading* 8000)/ ml of sample taken for titration
Prerequisites & Precautions while sampling & analysis of Water samples

1. The sampling bottles or containers should be washed with non-phosphate detergent, rinsed thoroughly with running water, and finally rinsed with demonized water. (Traces of chemicals or detergent can interfere with the analysis.)
2. The inner portion of the sample bottle & caps should not be touched with bare hands.
3. Sample should be never permitted to stand in the sun; they should be stored in cool place.
4. The glasswares should be properly washed & rinsed with distilled water.