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Chemical Parameters in Basic Environmental Technology

Chemical Parameters in Basic Environmental Technology. Introduction. This session will briefly cover the following: Physical Parameters : Turbidity, Color, Taste and Odor. Chemical Parameters: Acid, Bases, pH, BOD,

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Chemical Parameters in Basic Environmental Technology

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  1. Chemical Parameters in Basic Environmental Technology

  2. Introduction This session will briefly cover the following: • Physical Parameters : Turbidity, Color, Taste and Odor. • Chemical Parameters: Acid, Bases, pH, BOD, Solids, Hardness, Pb, F, Cl, Chlorine, Sulfates, Nitrogen, Acidity, Alkalinity

  3. Introduction Cont’d The lab session will demonstrate the following analysis: • Pb • Turbidity • Color and Odor • DO, BOD • COD • Solids

  4. Color, Taste and Odor • Color • Taste • Odor

  5. Dissolved Oxygen (DO) • Important parameter of WS. Abbreviated as DO • Fish and other aquatic organisms need DO in the water to survive. The higher the DO is, The better the quality of water. • DO solubility depends on temperature and altitudes (E.g. 0 C--14.6ppm, 10 C --11.3ppm, 20 C --9.3ppm & 30 C--7.6 ppm) These values represent the solubility of oxygen at the saturation point. • DO can be measured by a wet chemical method or by membrance electrode meter.

  6. DO by Wet Method • Winkler Method: • Collect a water sample in 300ml glass-stoppered BOD bottle • Add 1ml of Magnesium Sulfate Heptahydrate & 1ml of Alkaline Azide Iodide solution • Immediately insert the stopper so that no air is trapped in the bottle. Invert several times to mix. • Wait until the floc in the solution has settled

  7. DO by Wet Method (Cont’d) • Remove the stopper and add Sulfamic acid. • Replace the stopper without trapping air in the bottle invert several times, and mix. • Pour 200ml of the solution into 250ml Erlenmeyer flask. • Fill a 25-ml buret to the zero mark with 0.025 N Sodium Thiosulfate solution

  8. DO by Wet Method (Cont’d) • Titrate the prepared sample with 0.025N SodiumThiosulfate to a pale yellow color. • Add starch indicator solution. Titrate until the solution changes from dark blue to colorless. • ml titrant used = mg/L DO

  9. DO by Membrane Electrode Meter • DO by Winkler Method is good for clean sample • Membrane Electrode Meter required to use for unclean sample. • Membrane Electrode Meter required to calibrated with known DO solution. • Known DO solution obtained by measuring DO with Winkler Method

  10. BOD BOD is a measure of the quantity of oxygen consumed by microorganisms during the decomposition of organic matter. BOD is most common parameter determined on the receiving water of municipal or industrial discharge. Water holds only limited supply of DO and it comes from the diffusion from atmosphere at the air/water interface, and as a byproduct of photosynthesis. Photosynthetic organisms , such as plants and algae, produce oxygen when there is sufficient light. During times of insufficient light, same organisms consume oxygen from DO of water. BOD samples degrade significantly during storage between collection and analysis. Sample should be store at 4 degree C and should be analyze within 6 hrs. The sample require to warm to 20 degree C. The BOD concentration in most waste-waters exceeds the concentration of DO available in an air-saturated sample. This require to dilute the sample before incubation to bring the oxygen demand and supply into appropriate balance. The bacteria growth required nutrients such as nitrogen, phosphorus, and trace metals. These nutrient added to buffered solution that the pH of the incubated sample remains in a range suitable for bacterial growth. The poor quality of dilution water will effect BOD results. .

  11. 5- Day BOD Test • The method consists of filling with sample, to overflowing , an airtight bottle of the specified size and incubating it at the specific temperature for 5days. DO is measured initially and after incubating using calibrated DO meter. • BOD bottles are of 300ml capacity. Bottles should be clean with detergent, rinse thoroughly, and drain before use. Keep water seals on BOD bottle to the flared mouth. Place plastic cup over flared mouth of bottle to reduce evaporation. • Sample temperature should be 20 degree C before making dilution. • Incubator: Thermostatically controlled at 20 degree C with + or – 1 degree to prevent photosynthetic production. • The seed solution should have sufficient microorganism population. The fresh seed solution from active waste water treatment plant is good choice. • Sample should be neutralized to pH 6.5 to 7.5 using sulfuric acid and sodium hydroxide such a way that quantity of the reagent does not dilute the sample more than 0.5%. • Check the sample for residual Chlorine. If residual chorine is present, then dechlorinate the sample and then add seed solution. • Residual Chlorine can be destroyed by adding sodium sulfite solution. • Sample containing toxic substance requires special study and treatment.

  12. COD: Chemical Oxygen Demand • COD used as a measure of the oxygen equivalent to the organic matter content of sample that susceptible to oxidation by strong chemical oxidant. • COD and BOD can be related empirically to BOD if the sample source is the same. • Dichromate solution is superior oxidizing agent and applicable to wide variety of samples. Pyridine and related compounds resist oxidation. • Ammonia is not oxidized in the absence of significant concentration of free chloride. Mercuric sulfate and silver sulfate should be added in dichromate solution. Silver sulfate reacts with halide and free halide are not available. Now ammonia oxidized because Halide free ion are not available. Mercuric sulfate act as catalyst to finish oxidizing process fast. • Closed Reflux, Colorimetric Method. Homogenize sample for 2 minutes. Turn on the COD reactor, pre heat to 150 oC. Place the plastic shield in front of the reactor Remove the cap of COD digestion reagent vial for appropriate range. Sample conc range COD Digestion Reagent 0-150 Low range 0-1500 High range 0-15000 High range plus 1. Hold the vial at 45 oC angle. Pipet 2.0 ml of sample into vial.

  13. COD: Chemical Oxygen Demand 2. Replace the vial cap tightly. Rinse the COD vial with deionized water and wipe the vial clean with a paper towel. 3. Hold the the vial by the cap and over a sink. Invert gently several times to mix the contents. Place the vial in the preheated COD reactor. 4. Prepare a blank by repeating step 1 to 3, substituting 2 ml deionized water for the sample. Also run 50 ppm, 100 ppm, 150 ppm, 500 ppm, 1000 ppm, 1500 ppm, 5000 ppm, 10000 ppm and 15000 ppm of COD standard. Take reading on UV/VIS spectroscopy using 420 nm wave length. Use 1 cm cell. Plot graph for low range-blank, 50 ppm, 100 ppm, and 150 ppm. Plot graph for high range-blank, 500 ppm, 1000, ppm and 1500 ppm. Plot graph for high range plus-blank, 5000 ppm, 10000 ppm and 15000 ppm. 5. Heat the vials for 2 hours. 6. Turn the reactor off. Wait about 20 minutes for the vials to cool to 120 oC or less. 7. Invert each vial several times while still warm. Place the vials in to a rack. Wait until the vital have cooled to room temperature. 8. Use one of the following analytical technique to determine the sample concentration:

  14. COD: Chemical Oxygen Demand • COD • Immediate results • Sample can be preserved with sulfuric acid. • Vial should be tightly sealed and kept behind plastic seal as a safety. • Enough time to run sample and maintain the temperature. • Dichromate solution should be equally in concentration and volume for each vial. This is possible. Different Dichromate conc required different range of COD. • BOD • Consume long time • Sample should be immediately checked. • BOD bottle required to tight and sample water should be kept on flared mount. • Sample required to store at 4 oC and requited to analyze at 20 oC, which require some time. • Require fresh and good seed solution

  15. COD: Chemical Oxygen Demand • COD • Sample should be precisely homogenous due to use 2 ml of sample. • COD method for different range should be stored in UV/VIS spectroscopy. • It is required to run check standard only. • BOD • Sample required to be neutralized at the time BOD analysis. • Required to check Chlorine of samples and if necessary it is required to dechlorinate sample. • Sample containing toxic substance required special study and treatment. • DO meter required to calibrate every time. • Incubator should work properly.

  16. COD Chemical Oxygen Demand COD is used as a measure of the oxygen equivalent to the organic matter content of sample that susceptible to oxdidation by strong chemical oxidant.

  17. Where to Get More Information • Other training sessions • List books, articles, electronic sources • Consulting services, other sources

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