October 31, 2017 | Author: sajidahds | Category: Ammonia, Chemical Substances, Chemistry, Physical Sciences, Science
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To determine the amount of ammonia-nitrogen in a water sample....


Title: Ammonia-Nitrogen (NH3-N) Objectives: To determine the amount of ammonia-nitrogen in a water sample. Procedures: 1. For HACH DR 4000: Press the soft key under HACH PROGRAM Select the stored program for low range ammonia (NH3-N) by pressing 2400 with the numeric keys. Press ENTER. The display will show: HACH PROGRAM: 2400 N, Ammonia Nessler. The wavelength 425 nm, is automatically selected. For HACH DR 2800 or DR2500: Touch HACH PROGRAM, then select program 380 N, Ammonia, Ness. Touch START. 2. A 25 mL of mixing graduated cylinder was filled to the 25 mL mark with standard or sample. 3. Another 25 mL of mixing graduated cylinder was filled with (the blank) deionised water. 4. Three drops of mineral stabiliser was added to each cylinder. To mix, the mixing graduated cylinder was inverted (the reagent bottle was held vertically. Do no hold bottle at an angle). 5. Three drops of polyvinyl alcohol dispersing agent was added to each cylinder by holding the dropping bottle vertically. Inverted several times to mix. (hold the reagent bottle vertically. Do not hold bottle at an angle). 6. 1.0 mL of Nessler reagent was pipetted into each cylinder. Stopper. Inverted several times to mix. Notes: a. A yellow colour will develop if ammonia is present. The reagent will cause a faint yellow colour in the blank. b. Do not wait more than 15 minutes after reagent addition (Step 6) before performing Step 11. 7. The soft key under START TIMER was pressed. A 1-minute reaction period will begin. Step 8 was continued while timer is running. 8. Each solution was poured into a 10 mL sample cell. 9. When the timer beeps, the blank was placed into the cell holder. The light shield was closed. 10. The soft key under ZERO was pressed. The display will show: 0.000 mg/L N NH3. 11. The prepared sample was placed into the cell holder. The light shield was closed. Tesults in mg/L ammonia expressed as nitrogen (NH3-N) will be displayed.

Results: Sample Cell Blank Standard Sample 2 Sample 2 (blank) Sample 3 Sample 3 (blank)

Concentration (mg/L) 0.00 0.96 0.65 0.00 0.30 0.00

Discussion: Based on the result obtained, the standard reading is 0.96 mg/L which is closely to 1 ppm which has been prepared to be 1 ppm. The difference between the obtained value and the exact value is only 0.04 which did not seem to be very big and can be said the result for 0.96 mg/L is accepted. There is also a possibility of making error while adding reagent to standard before reading. The reagent might be added too much or too little and also the leaking of solution from the mixing measuring cylinder while shaking. All of these mistakes might be the reason why the reading is a bit far from the actual value. The result obtained for sample 2 is 0.65 mg/L which is lower than the standard reading. And for sample 3, the concentration of ammonia-nitrogen is 0.30 mg/L which give even more lower value. For the sample 2 (blank) and sample 3 (blank) shows the reading which is 0.00 mg/L is because the Nessler reagent, polyvinyl alcohol and mineral stabilizer was not added. But the sample 2 (blank) and sample 3 (blank) reading was taken into account is because these 2 were used for zeroing the machine every time to read sample. This step was done in order to reduce error and to calibrate the machine before taking measurement of ammonianitrogen concentration in each samples. Ammonia-nitrogen (NH3-N), is a measure for the amount of ammonia, a toxic pollutant often found in landfill leachate and in waste products, such as sewage, liquid manure and other liquid organic waste products. It can also be used as a measure of the health of water in natural bodies such as rivers or lakes, or in man-made water reservoirs. The term is used widely in water treatment and water purification systems. Ammonia can directly poison humans and upset the equilibrium of water systems. The ammonia-nitrogen levels can be lowered using a sequencing batch reactor. The values of ammonia-nitrogen in water are measured in milligram per litre and are used for specifying water treatment systems and facilities. The typical output of liquid manure from a dairy farm, after separation from the solids is 1600 mg NH3-N/L. Sewage treatment plants, receiving lower values, typically remove 80% and more of input ammonia and reach NH3-N values of 250 mg/L or less. The ammonium nitrogen value is also used in the context of properly designed landfill systems, where the leachate is being pumped to the surface and treated before it enters the ground water, testing the quality of the water exiting the treatment system.

Conclusion: Typical value for ammonia-nitrogen in water is 1.00 mg/L and this can be said that the value of ammonia-nitrogen for sample 2 and sample 3 is acceptable and harmless. Questions: 1. Identify the sources of ammonia in water. - The main sources of ammonia are natural: from decaying organic matter and from the excreta of humans and animals. Man-made sources such as from the use of fertilisers and waste disposal sites. 2. Are there alternative methods for determining ammonia in water? Compare the methods. - The alternative method is Phenate method which are ammonia reacts with phenol to form indophenol in presence of alkali and oxidising agent. Sodium nitroprusside acts as catalyst. The developed blue colour absorbs light of 640 nm wavelength. For this experiment, Nesslerization method was used which using Nessler reagent as reagent which will indicate yellow colour to signify that ammonia-nitrogen is presence in a water sample. 3. Why do you monitor nitrogen in a water treatment plant? - Ammonia and TKN are the major forms of nitrogen pollution, which if they are not removed cause oxygen depletion in streams. They are converted to nitrate, but nitrate itself can be a pollutant in large quantities in the river. 4. What are the typical ammonia values in water? How does your data compare with these values? - Typical ammonia values in water would be 1.00 mg/L which the sample 2 and sample 3 each reading were 0.65 mg/L and 0.30 mg/L which does not exceed the typical ammonia value indicating both samples were safe. References: 1. http://www.horizons.govt.nz/themes/horizons/images/waterqualitymatters/pdfs/Info% 20sheet-Water%20quality%20contaminants.pdf 2. http://www.env.gov.bc.ca/wat/wq/BCguidelines/nitrogen/nitrogen.html 3. http://hydrologyproject.gov.in/%5Cdownload%5Cmanuals%5CWaterQuality%5CWQTraining%5C39 HowtomeasureAmmoniaNirogen.pdf

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