Quality of Ground water

Transcription

1 Quality of Ground water Qualities of good water It should be free from bacteria which may cause disease Colourless and acceptable to public Tasty and odour less and cool It should not corrode pipes Free from all objectionable matter It should have dissolved oxygen and free carbonic acid so that it may remain fresh Impurities Suspended impurities which cause turbidity due to solid particles that are large enough to be filtered. Bacteria some cause disease Algae. Protozoa-cause odour, turbidity and colour Clay, silt, cause turbidity Colloidal impurities are very fine material electrically charged and cause epidemics. The colour of water is due to these colloidal material. The size of these fine material is between 1 micron to 1 milli micron (1 micron= mm and 1 milli micron= mm) Dissoloved impurities Organic inorganic, Salts Gases Physical Temp Colour Turbidity Taste and odor Chemical TDS Hardness PH Chloride Residual chlorine Iron Mg ph Dissolved gases Oxygen Carbon dioxide Nitrogen Nitrites, nitrates, Free ammonia Tests Dissolved metals Lead and Arsenic And other metals Biological Bacteria Algae Protozoa

2 Purpose To find major constituents of ground water Their relationship with different geological formations Graphical presentation of various constituents The impact of these constituents on human, cattle and agriculture in general Ground water pollution Total Dissolved Solids The TDS or total salt concentration of ground water varies from less than 100 ppm to more than ppm Broadly we can say <1000 Fresh Moderately saline Very saline >35000 Brine Calcium Ca is one of the principal cation in groundwater. Source of Ca are Igneous rock minerals like silicates, pyroxenes, feldspar minerals. Since the solubility of these minerals is low, water from igneous rocks or metamorophic rocks tend to be low in ca as well as TDS In sedimentary rock, ca occurs as carbonate ( calcite, aragonite) calcium magnesium carbonate (dolomite), Calcite (lime stone) and calcium sulphate (gypsium and anhydrite). Some calcium floride may also present. Some times caco3 is one of the main cementing agents for sandstones. Magnesium Mg is derived from igneous rock primarily from ferromagnesiam minerals like olivine, pyroxenes, dark coloured micas From metamorphic rocks, mg occurs in minerals like chlorite, montmorllonite, and sepentine. In sedementary rocks mg occurs as magnesite and other carbones some times mixed with calcium carbonate. Dolomite contains both ca and mg in equal ratio.

3 Sodium Sodium is primarily derived from feldspars in igneous rocks and its weathering products. Shale and clay layers often yield high sodium content. Other source of Na are leachate and deep percolation from upper soils layers. Contamination of fresh water with connate water Contamination of sea water and sea born evaporation. Potassium K is less common than sodium in igneous rocks. But more abundant is sedementary rocks as potassium feldspars. These nminerals however are very insoluble so that potassium levels in groundwater normally are much lower than sodium concentration. Hardness Hardness relates to its reaction with soap and to the scale and incrustations accumulating in containers or conduits where the water is heated or transported. Since soap is precipitated primarily by Ca and Mg ions hardness is defined as the sum of the concentrations of these ions expressed as ppm(mg/lt) of caco3 This hardness is also called as total hardness. This is calculated by (ca+mg)*50(ca and mg are in meq) Classsification hardness in mg/l Total hardness Soft <50 Moderately hard Hard Very hard >180 Carbonate and bicarbonate hardness( alkaline hard ness)hco3+co3 If Total hardness is greater than alkaline hardness, the excess is called non carbonate hardness

4 Carbonates and Bicarbonates. Irrigation water with a ph value (above 8.4) may indicate that the water contains high levels of carbonates and bicarbonates. Carbonates and bicarbonates tend to tie up calcium and magnesium during soil drying. This makes the sodium present potentially more damaging. High carbonates and bicarbonates in water essentially increases the sodium hazard Calcium carbonate (with a very low solubility) and soluble bicarbonates are usually in equilibrium with small quantities of carbon dioxide dissolved in water. If more carbon dioxide is present than the amount necessary for equilibrium, it could lower the ph of the environment. Above 3.5 mg/l CaCO3 and above 15 mg/l free CO2 (not in equilibrium with carbonate/ bicarbonate), Sulfates Sodium, magnesium and calcium (listed in the order of their solubility in water). The concentration in water at which sulfate ion is considered deleterious is about 1000 ppm and about 1100 ppm for magnesium ion. When sulfate is present in soils, predominantly as low soluble calcium salt, it is considered less dangerous than those containing sodium and magnesium sulfate at the same level of SO4 Other salts such as nitrate and nitrite will change the solubility of other salts and could have a substantial contribution in lowering the ph. Chloride Some ions like chloride can be directly absorbed into the leaves during sprinkler irrigation. Foliar damage from sprinkler irrigation is particularly acute during periods of high temperature and low humidity. Turfgrass is not particularly sensitive to high levels of chlorides, boron or sodium. However, many ornamental plants may be. Fluoride Sources of fluoride in groundwater are minerals like calcium fluoride (fluorite), apatite, cryolite (Igneous rocks and fluorspar in sedementary rocks. High concentration Is associated with high Ph

5 Drinking water standards Physical Temp 10 to 15.6 deg c Odor 0 to 4 p0 value Colour 10 to 20 platinum cobalt scale Turbidity 5 to 10 ppm Taste no objectionable taste Biological B coli No B-coli in 100 ml Radiological a emitters 1 c/liter B emitters 10 c/liter Chemical(all are in PPM) TDS upto 500 Hardness 5 to 115 (expressed as Caco3 equivilant) Chlorides upto 250 Iron and Manganese upto0.3 PH 6.5 to 8 Lead 0.1 Arsenic Sulphate upto 250 Dissolved oxygen 5 to 6 BOD Nil Drinking water Standards(A few norms) Sr.No Substance Max allowable (mg/l) 1 Arsenic Barium 1 3 Cadmimum Calcium chloride Copper Fluoride Iron 1 9 Lead 1 10 Magnisium Mercury Nitrate 10 Contaminant Antimony Arsenic Asbestos Barium Maximum level mg/l 0.05 mg/l 7 million fibers/l 2 mg/l Inorganic Cyanide (as free cyanide) Flouride Lead Mercury (Inorganic) Nitrate (as N) 0.2 mg/l 4.0 mg/l mg/l TT mg/l 10 mg/l Alachlor Atrazine Benzene Organics mg/l mg/l mg/l Diquat Endothall Endrin Ethylbenzene 0.02 mg/l 0.1 mg/l mg/l 0.7 mg/l Beryllium mg/l Nitrite (as N) 1 mg/l Benzo(a)pyrene mg/l Ethylene dibromide mg/l Cadmium Chromium (total) mg/l 0.1 mg/l Selenium 0.05 mg/l Carbofuran 0.04 mg/l Glyphosphate 0.7 mg/l Copper 1.3 mg/l TT6 Thallium mg/l

6 Microorganisms Contaminant Contaminant level Foaming Agents 0.5 mg/l Beta particles and photon emitters Gross alpha particle activity Radium 226 and radium 228 (combined) Radionuclides 4 millirems /yr 15 picocuries/ liter (pci/l) 5 pci/l Giardia lamblia Heterotropic Plate count Legionella Total Coliforms (including fecal coliform and E. coli) Turbitity 5.0%10 Aluminum Chloride Color Copper Flouride mg/l* 250 mg/l 15 (color units) 1.0 mg/l 2.0 mg/l Iron 0.3 mg/l Manganese 0.05 mg/l Odor 3 (threshold odor #) ph Silver 0.1 mg/l Sulfate 250 mg/l Total Dissolved Solids 500 mg/l Viruses (enteric) Zinc 0.5 mg/l Classification of Ground Water Water class Electrical conductivity ds/m Salt concentration( TDS) mg/l Type of water Non-saline <0.7 <500 Drinking and irrigation water Slightly saline Moderately saline Highly saline Very highly saline Irrigation water Primary drainage water and groundwater Secondary drainage water and groundwater Very saline groundwater Brine >45 > Seawater Crop Water tolerance of Crops Low salt tolerance Medium tolerance High tolerance Fruits Lemon Date Date plam Grape Orange Apple Olive pomegranate Vegetable Green beans Cucumber Garden bean Radish Onions Spinach Celery Carrot, cabbage Asparagus Potato Field crops Filed beans sunflower Cotton Corn Sorghum Rice Wheat Sugar beet Barley Rape seed

7 TABLE 8 Representative yields (in %) by crop and irrigation water salinity in survey of Hissar area of Haryana, India (after Boumans et al. 1988) Crop Tubewell salinity, EC in ds/m Cotton Millet Wheat Mustard Average Rain Water (mg/l) Distanc Ca Mg Na Cl e from sea (sq.km) Graphical presentation of quality of water Well No TDS I/2 IA a a b b b c c c7 2072

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9 Chemical Quality of ground water in Banaskantha dt Irrigation water standards Dantivada(EPM %) Santalpur (EPM%) 60 Percentage HCO3 CL NO3 SO4 PO4 SIO2 CA MG NA K IRON F Constituents Piper s Diagram 1 Alkaline earths exceed alkalies 2. Alkalies exceed alkaline earths 3.Week acids exceed strong acids 4. Strong acids exceed week acids 5. Carbonate hardness exceeds 50% 6. Non carbonate hardness exceed 50% 7. Non carbonate alkali exceeds 50% 8. Carbonate alkali exceeds 50% 9. No one cationanion pair exceeds 50% Wilcox classification