1-PURIFICATION ON A LARGE SCALE 2-PURIFICATION ON A SMALL SCALE

1. RAM NAIK. M 4 th Semester

11. Slow Sand Filtration

12. Removal Of The Vital Layer

13. Clean Slow Sad Filter Without Water

14. Mechanism of action of Slow Sand Filter: 1 .Sedimentation : The supernatant water acts as a settling reservoir. Settleable particles sink to the sand surface. 2. Mechanical straining : Particles too big to pass through the interstices between the sand grains are retained. 3 . Adhesion: The suspended particles that come in contact with the surface of the sand grains are retained by adhesion to the biological layer (Schmutzdecke) 4. Biochemical processes in the biological layer: Removes organic matter, holds back bacteria and oxidizes ammoniacal nitrogen in to nitrates Conversion of soluble iron and manganese compounds into insoluble hydroxides which attach themselves to the sand surfaces

17. RIVER In Mixing Chamber: Coagulation by Alum (5-40 mg/litre) Violent mixing of alum (minutes) In Flocculation Chamber: Slow stirring of water by paddles(30 minutes) at 2-4 rpm. Flocculent ppt. of Aluminium Hydroxide entangles all particulate, suspended matter along with bacteria In Sedimentation Chamber: Flocculent ppt. settle down (removal is done time to time) Clear water above goes for filtration Rapid Sand Filter: Remaining alum floc layer over sand bed. it holds back bacteria, oxidize organic matter Back washing-by air bubbles or water when floc layer becomes very thick

18. MIXING CHAMBER FLOCCULATION CHAMBER SEDIMENTATION TANK FILTERS CLEAR WATER STORAGE CONSUMPTION +ALUM COAGULATION PADDLES 30MIN 2-6hrs CHLORINATION

19. Paddles in a flocculation chamber

20. Properties Rapid sand filter Slow sand filter Area Small area Large area Rate of filtration(L/m2/hr) 4000-7500 100-400 Sand size (diameter) 0.4-0.7 mm 0.2-0.3 mm Pretreatment Coagulation and sedimentation Sedimentation Filter cleaning Backwashing Scraping Operation More skilled Less skilled Removal of colour Good Better Removal of bacteria 98-99% 99.9%-99.99% Prior water storage Storage needed No need

23. PRINCIPLES OF CHLORINATION 1. Water should be clear, free from turbidity 2. Chlorine demand : Chlorine needed to destroy bacteria, to oxidize organic matter and to neutralize the ammonia in water 3.Free residual chlorine for a contact period of 1 hour is essential 4. Breakpoint : P oint when chlorine demand of water is met and free residual chlorine appears 5 . Breakpoint chlorination: Chlorination beyond the breakpoint . The principle of break point chlorination is to add sufficient chlorine so that 0.5 mg/L free residual chlorine is present in the water after one hour of contact time 4. Dose of Chlorine = Chlorine demand + Free residual chlorine

38. Find volume of water in well (V in Liters) = 3.14 x h x d 2 x 1000 4 Find the amount of bleaching powder needed by Horrock’s apparatus Bleaching powder (max.100 g) mixed with water in a bucket Allow 10 minutes sedimentation Transfer supernatant chlorine solution to another bucket Deliver chlorine solution in to the well Allow 1 hour contact Do OTA test to measure free residual chlorine If free residual chlorine < 0.5 mg/L Add more bleaching powder

39. Inner pot (28 cm ht) Hole (1 cm dia) Polyethylene foil Hole of 1cm dia Bleaching powder 1kg + 2 kg coarse sand Moist mixture Outer pot (30X25 cm) Rope