Water Pollution Lecture Notes PDF

WATER POLLUTION Water pollution is the contamination of water bodies like lakes, rivers, oceans and ground water etc.in such away as to affect the life of living organisms who are in its contact in any way. WATER POLLUTION •Water contains impurities of various kinds–natural and manmade •The natura...

WATER POLLUTION Water pollution is the contamination of water bodies like lakes, rivers, oceans and ground water etc.in such away as to affect the life of living organisms who are in its contact in any way. WATER POLLUTION •Water contains impurities of various kinds–natural and manmade •The natural impurities are not essentially dangerous. These comprise • Dissolved gases • Dissolved minerals • Suspended impurities • Microscopic organisms. •A more serious aspect of water pollution is that caused by human activity – urbanization and industrialization. The sources of pollution resulting from these are: a) Sewage, which contains decomposable organic matter and pathogenic agents. b) Industrial and trade waste, which contain toxic agents ranging from metal salts to complex synthetic organic chemicals. c) Agricultural pollutants, which comprise fertilizers and pesticides . d) Physical pollutants, that is heat and radioactive substances. Types Point sources • Discharge pollutants from specific locations • • • • Factories Sewage treatment plants Oil tankers can be monitored and regulated. Non point sources • Run off water containing pesticides and fertilizers from areas of agricultural land • Difficult to monitor and control. WATER BORNE DISEASE CAUSED BY CHEMICALS Arsenic Cancer, vascular disease, liver disease, skin lesions, neurological diseases Fluoride Fluorosis Chlorine Toxic & causes sufficient cell damage in the human body Iodine Enlargement of thyroid gland & mental retardation Nitrates High level of nitrate in water can lead to blood poisoning & death, methemoglobinemia •Wash hands with soap and water before handling food. Purification ➢Storage ➢Filtration ● Slow sand filter ● Rapid sand filter ➢Disinfection ● Chlorination ● Superchlorination ● Ozonization ● Ultraviolet Irradiation STORAGE Natural purification ➢ Physical : ➢ Chemical : organic matter in the water oxidized by 90% suspended impurities settle down by gravity in 24 hrs. rendering clear water aerobic bacteria with the help of dissolved o2 ➢ Biological : drop in bacterial count by 90% in 5-7 days. Optimum storage 7-10 days thereafter chance of algal growth causing change in color & odor. Purification on Small Scale (Domestic method) ➢ BOILING: • • • Must be brought to rolling boil for 10-20 minutes. Also removes temporary hardness No “residual protection” ➢ CHEMICAL DISINFECTION: •Bleaching powder •Chlorine solution •High test hypochlorite •Chlorine tablets- 0.5mg tablet for 20 litres of water •Iodine- 2 drops of 2% ethanol sol of Iodine for 1litre of water Microfibre Mesh Removes visible dirt to give safe drinking water. Compact Carbon Trap Removes harmful parasites and pesticides to give clean drinking water. Germkill Processor Uses 'programmed chlorine release technology' to target and remove invisible harmful viruses and bacteria and provide pure drinking water. Polisher Removes chlorine and other contaminants to make water clear, odourless and great tasting CHLORINATION ➢ Chlorine kills bacteria no effect on spores and certain viruses except in high doses ➢Oxidizes Iron, manganese and H2S ➢ Destroys some color & odor producing constituent ➢Controls Algae and slime organisms ➢Aids coagulation ACTION OF CHLORINE H2O + Cl2 HOCL HCL + HOCL H + OCL HCL neutralized by alkalinity of water •Disinfectant action mainly due to HOCL (Hypochlorous acid). PRINCIPLES OF CHLORINATION Water should be clear and free from turbidity 1. Chlorine demand should be estimated 2. Free residual Chlorine should be present for at least one hour i.e. the contact period. 3. Minimum of 0.5 mg/L (0.5ppm) of free Chlorine should be present METHOD OF CHLORINATION Chlorine can be applied either as Chlorine gas : cheap, quick in action, efficient and easy to apply. Applied with chloronomes Chloramines : Loose compounds of cl2 and NH3 Less tendency to produce chlorinous taste more persistent type of residual cl2 , gives more persistent type of residual cl2 . Slow in action hence not used. Perchloron (HTH) ca compound with 60-70% available Cl2 . Solution of HTH also used. Gas is first choice