the analysis in the sewage treatment plant is a very important operation method. the analysis result is the basis of the sewage adjustment. therefore, the accuracy of the analysis is very high. the accuracy of the analysis value must be ensured to ensure the correct and reasonable means of the normal operation of the system.
i. determination of chemical oxygen demand (codcr)
chemical oxygen demand: refers to the amount of oxidant consumed in the treatment of water samples with potassium dichromate as the oxidant under strong acid and heating conditions, and the unit is mg/l. in china, potassium dichromate method is generally used as a basis.
1, method principle
in a strongly acidic solution, a certain amount of potassium dichromate is used to oxidize the reducing material in the water sample, and excess potassium dichromate is used to test the ferrioxide as an indicator, and the solution is dribbled with ammonium ferrous sulfate solution. the amount of oxygen consumed by the reducing substances in the water sample was calculated from the amount of ammonium ferrous sulfate.
2, the instrument
(1) backflow device: all-glass return device with 250 ml erlenmeyer flask (full glass reflux device with a sample volume of 30 ml or more and a 500 ml erlenmeyer flask).
(2) heating device: hot plate or variable group electric furnace.
(3) 50 ml acid titrant.
3, reagent
(1) potassium dichromate standard solution (1/6 = 0.2500mol/l:) weigh 12.258g of reference or superior grade pure potassium dichromate that has been previously dried at 120°c for 2h, dissolved in water, and transferred to a 1000ml volumetric flask. diluted to the mark, shake.
(2) test titrione indicator solution: weigh 1.485 g of phenanthroline, dissolve 0.695 g of ferrous sulfate in water, dilute to 100 ml, and store in a brown bottle.
(3) ammonium ferrous sulfate standard solution: weigh 39.5g of ferrous ammonium sulfate dissolved in water, and slowly add 20ml of concentrated sulfuric acid while stirring. after cooling, move into a 1000ml volumetric flask, dilute to the mark with water, and shake. before use, calibrate with potassium dichromate standard solution.
calibration method: accurately absorb 10.00ml of potassium dichromate standard solution and 500ml conical flask, dilute with water to about 110ml, slowly add 30ml concentrated sulfuric acid, and mix. after cooling, three drops of test triathine indicator solution (approximately 0.15 ml) was added and titrated with ammonium ferric sulfate. the color of the solution was from yellow to blue-green to reddish-brown and the end point.
c[(nh4)2fe(so4)2]=0.2500×10.00/v
in the formula, the concentration of c-ammonium ferrous sulfate standard solution (mol/l); the amount of ammonium ferrous sulfate standard titration solution (ml).
(4) sulfuric acid-silver sulfate solution: 25 g of silver sulfate is added to 2500 ml of concentrated sulfuric acid. place 1-2d, shake from time to time to dissolve it (if no 2500ml container, add 5g silver sulfate in 500ml concentrated sulfuric acid).
(5) mercury sulfate: crystal or powder.
4, matters needing attention
(1) the maximum amount of chloride ion complexed with 0.4 g of mercury sulfate can reach 40 ml. if 20.00 ml of water sample is used, that is, the water sample with the highest concentration of chloride ion of 2000 mg/l can be complexed. if the chloride ion concentration is low, less mercury sulfate may be added, keeping the mercury sulfate: chloride ion = 10:1 (w/w). the presence of a small amount of mercury chloride precipitation does not affect the assay.
(2) the volume of water sample to be used can be in the range of 10.00-50.00ml, but the amount and concentration of reagents can be adjusted accordingly, and satisfactory results can also be obtained.
(3) for samples with a chemical oxygen demand of less than 50 mol/l, a standard solution of potassium dichromate 0.0250 mol/l should be used. when dropping back, use 0.01/l ferrous ammonium sulfate standard solution.
(4) after the sample is heated and refluxed, the remaining amount of potassium dichromate in the solution should be a small amount of 1/5-4/5.
(5) when the quality and operation technique of the potassium stannous hydrogen dihydroxide standard solution were tested, the theoretical codcr per gram of potassium hydrogen disulphate was 1.167 g, so 0.4251 l of potassium stannous hydrogenate and double distilled water were dissolved. into a 1000 ml volumetric flask, dilute to the mark with double-distilled water to make 500 mg/l codcr standard solution. when used with new.
(6) three valid figures should be retained for the measurement results of codcr.
(7) in each experiment, the standard titration solution of ammonium ferrous sulfate should be calibrated. when the room temperature is high, the concentration of ferrous sulfate should be particularly noticed.
5, the measurement step
(1) shake the recovered water samples and effluent samples.
(2) take 3 grinding conical flasks, numbered 0, 1, 2; add 6 glass beads to each of the 3 conical flasks.
(3) add 20 ml of distilled water to the #0 erlenmeyer flask (using a plump pipette); add 5 ml of water sample to the #1 erlenmeyer flask (use a 5 ml pipette to rinse with water.) tube 3 times), then add 15ml of distilled water (using a plump pipette); add 20ml of water sample to erlenmeyer no. 2 (use plump pipette, use water to rinse the pipette 3 times ).
(4) add 10 ml of potassium dichromate non-standard solution to 3 erlenmeyer flasks (10 ml of non-standard potassium dichromate solution pipette, use potassium dichromate non-standard solution to rinse the pipette 3 times).
(5) place the erlenmeyer flask on the electronic universal furnace, and then open the water pipe to fill the condenser with water (do not open it too much, based on experience).
(6) add 30 ml of silver sulfate (using a 25 ml graduated cylinder) from the upper part of the condenser tube to each of the 3 conical flasks, and then shake 3 conical flasks.
(7) plug in the plug of the electric multi-purpose furnace and start timing by boiling. heat for 2 hours.
(8) after the heating is completed, unplug the plug of the electric multi-purpose furnace and cool it for a period of time (how long depends on experience).
(9) add 90ml distilled water from the upper part of the condensing tube to the 3 conical flasks respectively. (addition of distilled water causes: 1. add water from the condensing tube so that the residual water sample on the inner wall of the condensing tube flows into the conical flask during the heating process, reducing the error 2. add a certain amount of distilled water to make the color reaction more apparent during the titration).
(10) after the addition of distilled water, the heat will be released and the conical flask will be cooled.
(11) after thoroughly cooling, add 3 drops of test ferrioxide indicator to each of the 3 conical flasks, and then shake 3 conical flasks.
(12) titration with ferrous ammonium sulfate. the color of the solution is from yellow to blue-green to reddish brown. (note the use of an automatic burette. remember to take a reading after one titration and raise the autoburette level to the highest point for the next titration).
(13) record readings and calculate results.
ii. determination of biochemical oxygen demand (bod5)
domestic sewage and industrial waste water contain large amounts of various organic substances. when they contaminate waters, these organics consume a large amount of dissolved oxygen when decomposing in the water, thereby destroying the oxygen balance in the water and deteriorating the water quality. the lack of oxygen in water causes the death of fish and other aquatic organisms. the organic matter contained in the water body is complex and it is difficult to measure its composition one by one. people often use the oxygen consumed by organic matter in water under certain conditions to indirectly express the content of organic substances in water. biochemical oxygen demand is an important indicator of this type.
the classic method for determining biochemical oxygen demand is dilution inoculation.
water samples for biochemical oxygen demand should be filled and sealed in bottles during collection. store at 0-4 degrees celsius. should generally be analyzed within 6h. if you need long-distance transport. in any case, storage time should not exceed 24h.
1, method principle
biochemical oxygen demand refers to the amount of dissolved oxygen consumed by biochemical processes carried out by microorganisms to decompose certain oxidizable substances, especially organic substances, in the presence of water under specified conditions. this biooxidation process takes a long time. if cultured at 20 degrees celsius, it takes more than 100 days to complete the process. at present, it is generally regulated at home and abroad to culture for 5 days at 20 degrees plus or minus 1 degree celsius, and the dissolved oxygen before and after the culture of the sample is measured. the difference between the two is the bod5 value, expressed in milligrams of oxygen per liter.
for some surface waters and most industrial waste waters, due to the presence of more organic matter, it is necessary to dilute and then culture the assay to reduce its concentration and ensure that there is sufficient dissolved oxygen. the degree of dilution should be such that the dissolved oxygen consumed in the culture is greater than 2 mg/l while the remaining dissolved oxygen is above 1 mg/l.
in order to ensure that there is enough dissolved oxygen after the dilution of the water sample, the dilution water is usually blown into the air for aeration, and the dissolved oxygen in the dilution water is nearly saturated. a certain amount of inorganic nutrient salts and buffer substances should also be added to the dilution water to ensure the growth of microorganisms.
for industrial waste water containing no or less microorganisms, including acidic waste water, alkaline waste water, high-temperature waste water, or chlorinated waste water, inoculation of bod5 should be carried out to introduce microorganisms that can decompose organic matters in the waste water. when there is organic matter in the wastewater that is difficult to be degraded by microorganisms in general domestic sewage at a normal speed or contains highly toxic substances, the domesticated microorganisms should be introduced into water samples for inoculation. this method is suitable for the determination of water samples with a bod5 greater than or equal to 2 mg/l and a maximum of 6000 mg/l. when the water sample bod5 is greater than 6000mg/l, there will be a certain error due to dilution.
2, the instrument
(1) incubator
(2) 5 - 20l fine glass bottles.
(3) 1000 - 2000ml cylinder
(4) glass stir bar: the length of the bar should be 200 mm longer than the cylinder height used. at the bottom of the rod, a hard rubber plate with a diameter smaller than the bottom of the cylinder and with several small holes is fixed.
(5) dissolved oxygen bottle: between 250ml and 300ml, with a ground glass stopper and a bell-shaped mouth for water supply.
(6) siphon, for water sampling and dilution water addition.
3, reagent
(1) phosphate buffer solution: 8.5 potassium dihydrogen phosphate, 21.75 g of dipotassium hydrogen phosphate, 33.4 sodium phosphate dibasic heptahydrate, and 1.7 g of ammonium chloride were dissolved in water and diluted to 1000 ml. the ph of this solution should be 7.2
(2) magnesium sulfate solution: 22.5 g of magnesium sulfate heptahydrate was dissolved in water and diluted to 1000 ml.
(3) calcium chloride solution: 27.5 anhydrous calcium chloride was dissolved in water and diluted to 1000 ml.
(4) ferric chloride solution: 0.25 g of ferric chloride hexahydrate is dissolved in water and diluted to 1000 ml.
(5) hydrochloric acid solution: dissolve 40 ml hydrochloric acid in water and dilute to 1000 ml.
(6) sodium hydroxide solution : dissolve 20g sodium hydroxide in water and dilute to 1000ml
(7) sodium sulfite solution: dissolve 1.575 g of sodium sulfite in water and dilute to 1000 ml. this solution is unstable and needs to be prepared daily.
(8) glucose-glutamic acid standard solution: after drying glucose and glutamic acid at 103 degrees celsius for 1 hour, weigh each 150ml into water, transfer it to a 1000ml volumetric flask, and dilute it to the marking line and mix well. this standard solution was prepared just before use.
(9) diluent: the ph of the dilution water should be 7.2, and its bod5 should be less than 0.2 ml/l.
(10) inoculation solution: the domestic sewage is generally used. it is left overnight at room temperature and the supernatant is used.
(11) inoculation of dilution water: divide appropriate amount of inoculum, add diluted water, and mix. the amount of inoculum added per liter of diluted water is 1 to 10 ml of domestic sewage, or 20 to 30 ml of surface soil exudates, and the ph of inoculated dilution water should be 7.2. the bod value is preferably between 0.3 and 1.0 mg/l. the inoculation dilution water should be used immediately after preparation.
4, calculation
1. water samples directly cultured without dilution
bod5(mg/l)=c1-c2
in the formula: c1—dissolved oxygen concentration (mg/l) of water sample before culture;
c2 - dissolved oxygen concentration (mg/l) remaining after 5 days of incubation.
2, diluted after the cultivation of water samples
bod5(mg/l)=[(c1-c2)-(b1-b2)f1]∕f2
in the formula: c1—dissolved oxygen concentration (mg/l) of water sample before culture;
c2 - dissolved oxygen concentration (mg/l) after incubation for 5 days;
b1—dilute water (or inoculum dilution water) dissolved oxygen concentration before culture (mg/l);
b2 - dilution water (or inoculated dilution water) dissolved oxygen concentration after incubation (mg/l);
f1 - the proportion of diluted water (or inoculated dilution water) in the culture fluid;
f2 - the proportion of water in the culture fluid.
b1 - dissolved oxygen before dilution of the water;
b2 - dissolved oxygen after dilution of the water;
f1 - the proportion of dilution water in the culture fluid;
f2 - the proportion of water sample in the culture fluid.
note: calculation of f1, f2: for example, the dilution ratio of the culture solution is 3%, that is, 3 samples of water and 97 dilutions of water, then f1=0.97, f2=0.03.
5, matters needing attention
(1) the biological oxidation of organic matter in water can be divided into two stages. the first stage is the carbon and hydrogen in the organic matter, and the oxidation produces carbon dioxide and water. this phase is called the carbonization stage. it takes about 20 days to complete the carbonization stage at 20 degrees celsius. the second stage is the nitrogenous material and part of the nitrogen, oxidized to nitrite and nitrate, known as the nitrification stage. it takes about 100 days to complete the nitrification stage at 20 degrees celsius. therefore, in the general determination of bod5 in water samples, nitrification is very low or no nitrification occurs at all. however, the effluent from the biological treatment tank contains a large amount of nitrifying bacteria. therefore, part of the oxygen demand of nitrides was also included in the measurement of bod5. for such water samples, nitrification inhibitors may be added to inhibit the nitrification process. for this purpose, 1 ml of propylene thiourea at a concentration of 500 mg/l or a certain amount of 2-chloro-6-trichloromethylpyridine immobilized on sodium chloride can be added to each liter of the diluted water sample, so that tcmp is the concentration in the diluted sample is approximately 0.5 mg/l.
(2) glassware should be thoroughly cleaned. soak it with detergent and then dip it with dilute hydrochloric acid, and then wash it with tap water and distilled water.
(3) in order to check the quality of dilution water and inoculum and the operator's operation level, 20 ml of glucose-glutamic acid standard solution can be diluted to 1000 ml with inoculation dilution water, according to the procedure for determination of bod5. the measured value of bod5 should be between 180-230 mg/l. if not, check the quality of the inoculum solution, dilution water, or operating technique for problems.
(4) when the dilution of the water sample is more than 100 times, it should be diluted with water in a volumetric flask in advance, and then take the appropriate amount for final dilution culture.
third, the determination of suspended solid material (ss)
suspended solids represent the amount of undissolved solid matter in water.
1, method principle
the built-in measurement curve converts the absorbance at a specific wavelength of the sample to the concentration value of the parameter to be measured and displays it on the lcd.
2, the measurement step
(1) shake the recovered water samples and effluent samples.
(2) take a colorimetric tube and add 25ml of water sample, then add it to the mark with distilled water (because the inlet ss is larger, if you do not dilute it may exceed the maximum of the suspended material tester, so that the result is not accurate. of course water sampling is not fixed. if the water is too dirty, take 10ml. add distilled water to the mark.)
(3) turn on the suspended substance tester, add distilled water to the small box similar to the cuvette to 2/3, wipe the outer wall, press the selection key while shaking, then quickly put it into the suspension tester, then press press the down-read button. if it is not zero, press the clear button to clear the instrument (measure once).
(4) incoming water ss: pour the influent sample in the colorimetric tube into the small box for 3 times, then add the influent sample to 2/3, dry the outer wall, and press the selection key while shaking. then quickly into the suspension tester, then press the read key, measured three times, to obtain the average value.
(5) measuring the water ss: shake out the water sample and rinse the small box three times. (the method is the same as above)
3, calculation
the result of the influent ss is: dilution multiple* the measured water sample reading the result of the outflow ss is the measured water sample instrument reading.
iv. determination of total phosphorus (tp)
1, method principle
under acidic conditions, orthophosphoric acid reacts with ammonium molybdate and potassium cerium tartrate to form a phospho-molybdenum heteropoly acid, which is reduced by the reducing agent ascorbic acid and becomes a blue complex, usually incorporating molybdophosphoric blue.
the minimum detection concentration of this method is 0.01mg/l (the corresponding concentration when the absorbance a=0.01); the upper limit of determination is 0.6mg/l. it can be applied to the determination of orthophosphate in industrial wastewater such as surface water, domestic sewage and daily chemical, phosphate fertilizer, surface phosphating of machined metal, pesticide, steel, coking, etc.
2, the instrument
spectrophotometer
3, reagent
(1) 1 1 sulfuric acid.
(2) 10% (m/v) ascorbic acid solution: dissolve 10 g of ascorbic acid in water and dilute to 100 ml. the solution was stored in a brown glass bottle and was stable for several weeks in a cold place. if the color turns yellow, dispose it again.
(3) molybdate solution: dissolve 13 g of ammonium molybdate [(nh4)6mo7o24·4h2o] in 100 ml of water. dissolve 0. 35 g of potassium oxo barium tartrate [k(sbo)c4h4o6·1/2h2o] in 100 ml of water. under constant stirring, slowly add ammonium molybdate solution to 300 ml (1 1) sulfuric acid, add potassium antimony tartrate solution and mix well. the reagents were stored in brown glass bottles and kept in a cold place. at least 2 months stable.
(4) turbidity-chromaticity compensator: mix two volumes of (1 1) sulfuric acid and one volume of 10% (m/v) ascorbic acid solution. this solution was prepared on the same day.
(5) phosphate stock solution: potassium dihydrogen phosphate (kh2po4) was dried at 110[deg.] c. for 2 h and allowed to cool in a desiccator. weigh 0.217 g in water and transfer it to a 1000 ml volumetric flask. add (1 1) sulfuric acid 5ml and dilute to the mark with water. this solution was 50.0 ug of phosphorus per ml.
(6) phosphate standard solution: pipette 10.00 ml phosphate stock solution into a 250 ml volumetric flask and dilute to the mark with water. this solution contains 2.00 ug of phosphorus per milliliter. when you are using it,
4, the determination step (only to measure into the water sample as an example)
(1) shake the recovered water sample and effluent sample. (the water sample on the biochemical pool should be shaken and left for a period of time to take the supernatant solution).
(2) take 3 sets of plug scale tube, the first set of plug scale tube plus distilled water to the upper scale line; the second set of plug scale tube add 5ml of water sample, and then add distilled water to the upper scale line; immerse the calibration tube with hydrochloric acid for 2 hours, or scrub with a phosphate-free detergent.
(3) after the cuvette is used, dilute nitric acid or chromic acid lotion should be soaked for a while to remove the adsorbed molybdenum blue color.
v. determination of total nitrogen (tn)
1, method principle
potassium persulfate is dissolved in an aqueous solution at a temperature of 60°c or more as follows to produce hydrogen ions and oxygen. k2s2o8 h2o→2khso4 1/2o2 khso4→k hso4_hso4→h so42-
sodium hydroxide is added to neutralize the hydrogen ions and potassium persulfate is completely decomposed. in alkaline media at 120°c-124°c, using potassium persulfate as an oxidizing agent can not only oxidize ammonia nitrogen and nitrite nitrogen in the water sample to nitrate, but also oxidize most of the organic nitrogen compounds in the water sample to nitrate. then absorbance was measured at a wavelength of 220 nm and 275 nm by ultraviolet spectrophotometry, and the absorbance of nitrate nitrogen was calculated by the following formula: a=a220-2a275 to calculate the total nitrogen content. its molar absorptivity is 1.47×103
2, interference and elimination
(1) when hexavalent chromium and trivalent iron ions are contained in the water sample, 5% by weight of 5% hydroxylamine hydrochloride solution may be added to eliminate the effect on the measurement.
(2) iodide and bromide ions interfere with the measurement. there was no interference when the iodide ion content was 0.2 times the total nitrogen content. there was no interference when the bromide ion content was 3.4 times relative to the total nitrogen content.
(3) the effect of carbonate and bicarbonate on the determination can be eliminated by adding a certain amount of hydrochloric acid.
(4) sulfate and chloride have no effect on the determination.
3, the scope of application of the method
this method is mainly applicable to the determination of total nitrogen in lakes, reservoirs and rivers. the lower limit of detection was 0.05 mg/l; the upper limit of determination was 4 mg/l.
4, the instrument
(1) ultraviolet spectrophotometer.
(2) pressure steam sterilizers or domestic pressure cookers.
(3) corrosion tube with a glass stopper.
5, reagent
(1) without ammonia water, add 0.1ml concentrated sulfuric acid per liter of water and distill. collect the effluent in a glass container.
(2) 20% (m/v) sodium hydroxide: weigh 20g of sodium hydroxide, dissolved in ammonia-free water, and dilute to 100ml.
(3) alkaline potassium persulfate solution: weigh 40g of potassium persulfate, 15g of sodium hydroxide, dissolved in ammonia-free water, diluted to 1000ml, the solution is stored in a polyethylene bottle, can be stored for one week.
(4) 1 9 hydrochloric acid.
(5) potassium nitrate standard solution: a. standard stock solution: 0.7218 g of potassium nitrate dried at 105-110° c. for 4 h is dissolved in ammonia-free water and transferred to a 1000 ml volumetric flask for constant volume. this solution contains 100 mg of nitrate nitrogen per ml. add 2 ml of chloroform as a protector and stabilize it for at least 6 months. b. potassium nitrate standard solution: the stock solution is diluted 10 times with ammonia-free water. this solution contains 10 mg of nitrate nitrogen per ml.
6, the measurement step
(1) shake the recovered water samples and effluent samples.
(2) take 3 25 ml colorimetric tubes (note that it is not a large colorimetric tube). the first colorimetric tube plus distilled water was added to the lower scale line; the second colorimetric tube was filled with 1ml of water sample, and then added to the lower scale line with distilled water; the third colorimetric tube was added with 2ml of water sample, and then distilled water was used. add to the lower tick mark.
(3) add 5 ml of basic potassium persulfate to 3 colorimetric tubes
(4) place the 3 colorimetric tubes in a plastic beaker and heat them in a pressure cooker. digestion.
(5) after heating, disassemble the gauze and let it cool naturally.
(6) after cooling, add 1 ml of 1 9 hydrochloric acid to each of the three colorimetric tubes.
(7) add distilled water to each of the 3 colorimetric tubes to the upper scale line and shake well.
(8) use two wavelengths and measure with a spectrophotometer. first, use a 275nm, 10mm quartz cuvette (slightly older) to measure the blank, water, and water samples and count; use a 220nm, 10mm quartz cuvette (slightly older) to measure the blank. water, water samples and count.
(9) calculation result.
6. determination of ammonia nitrogen (nh3-n)
1, method principle
classical mercury and alkaline potassium alkaline solutions react with ammonia to produce a reddish-brown colloidal compound that absorbs strongly in the wide wavelength range of the teaching width. the usual measurement wavelength is in the range of 410-425 nm.
2. preservation of water samples
water samples are collected in polyethylene bottles or glass bottles and should be analyzed as soon as possible. if necessary, add sulfuric acid and acidify to ph<2 and store at 2-5°c. acidified samples should be protected from contamination by absorbing ammonia from the air.
3, interference and elimination
organic compounds such as aliphatic amines, aromatic amines, aldehydes, acetone, alcohols, and organic nitrogen amines, and inorganic ions such as iron, manganese, magnesium, and sulfur, cause interference due to generation of a different color or turbidity, and the color and turbidity of water also affect colorimetric. to this end, flocculation precipitation filtration or distillation pretreatment, volatile reducing interfering substances, and heating under acidic conditions to remove interference with metal ions may also be added by adding an appropriate amount of masking agent.
4, the scope of application of the method
the minimum detectable concentration of this method is 0.025 mg/l (photometric method) and the upper limit of determination is 2 mg/l. visual colorimetry is used. the minimum detection concentration is 0.02 mg/l. after appropriate and pretreatment of water samples, this law can be applied to surface water, groundwater, industrial wastewater and domestic sewage.
5、instrument
(1) spectrophotometer.
(2) ph meter
6. test agent
the water used for preparation of the reagent should be anhydrous ammonia.
(1) nessler's reagent can be prepared by one of the following methods:
1. weigh 20g of potassium iodide dissolved in about 25ml of water, and add a small amount of mercury dichloride (hgcl2) crystal powder (about 10g) while stirring until the reddish-red precipitate does not dissolve easily. this is a drop of saturated dioxide. mercury solution, and fully stirred, vermilion precipitation does not dissolve, stop adding mercury chloride solution.
in addition, 60g of potassium hydroxide was dissolved in water and diluted to 250ml. after cooling to room temperature, the above solution was slowly stirred into potassium hydroxide solution, diluted with water to 400ml, and mixed. after overnight, the supernatant was transferred to a polyethylene bottle and stored in a stopper.
2. weigh 16 g of sodium hydroxide, dissolve in 50 ml of water and allow to cool to room temperature.
another said to take 7g of potassium iodide and 10g of mercury iodide (hgi2) dissolved in water, and then the solution was slowly injected into the sodium hydroxide solution under stirring, diluted with water to 100ml, stored in a polyethylene bottle, tampons preserved.
(2) potassium sodium solution
weigh 50g of sodium potassium tartrate (knac4h4o6.4h2o) dissolved in 100ml of water, heat boiling to remove ammonia, cooling, set to 100ml.
(3) ammonium standard stock solution
weigh 3.819 g of ammonium chloride (nh4cl) dried at 100 degrees celsius in water, transfer to a 1000 ml volumetric flask, and dilute to the mark. this solution contains 1.00 mg ammonia nitrogen per ml.
(4) ammonium standard use solution
pipette 5.00 ml of amine standard stock solution into a 500 ml volumetric flask and dilute to the mark with water. this solution contains 0.010 mg of ammonia nitrogen per ml.
7, calculation
ammonia nitrogen content (mg) from the calibration curve
ammonia nitrogen (n, mg/l) = m*1000
in the formula, m—amount of ammonia nitrogen (mg) determined by calibration, and v—volume of water sample (ml).
8, matters needing attention
(1) the ratio of sodium iodide to potassium iodide by sodium reagent has a great influence on the sensitivity of color development. the precipitate formed after quiescence should be removed.
(2) traces of ammonium salts are contained in the filter paper. use caution when using ammonia-free water. all glassware should be free of ammonia contamination in the laboratory air.
9, the measurement step
(1) shake the recovered water samples and effluent samples.
(2) pour the influent and effluent samples into a 100 ml beaker.
(3) add 1 ml of 10% zinc sulfate and 5 drops of sodium hydroxide to each of the two beakers and mix them with two glass rods.
(4) start filtration after standing for 3 minutes.
(5)pour the still water sample into the filter hopper, filter the part and drain the filtrate from the bottom beaker, and then use this beaker to connect the remaining water in the funnel until it is filtered again. the filtrate is drained. (in other words, wash the beaker twice with a funnel of filtrate)
(6) filter the remaining water in the beaker separately.
(7) take 3 colorimetric tubes. the first colorimetric tube is added with distilled water and added to the mark; the second colorimetric tube is added with 3--5ml of water sample filtrate, and then added to the mark with distilled water; the second colorimetric tube is added with 2ml of water sample filtrate. then add distilled water to the mark. (the amount of filtrate taken in and out of the water sample is not fixed)
(8) separately add 1 ml potassium sodium tartrate and 1.5 ml nessler's reagent to each of the 3 colorimetric tubes.
(9) shake well and time for 10 minutes. using a spectrophotometer, use a 420nm, 20mm cuvette. calculate.
(10) calculation results.
vii. determination of nitrate nitrogen (no3-n)
1, method principle
water sample in alkaline medium, nitrate can be reduced to ammonia by reducing agent (dai's alloy) under the condition of heating. after being distilled, it is absorbed in boric acid solution and measured by nessler reagent or acid titration. .
2, interference and elimination
nitrite is also reduced to ammonia under this condition and needs to be removed beforehand. ammonia and ammonia salts in water samples can also be pre-distilled to remove them prior to the addition of the teller alloy.
this method is particularly suitable for the determination of nitrate nitrogen in heavily contaminated water samples. it can also be used as a measure of nitrite nitrogen in water samples (determination of nitrous acid after removal of ammonia and ammonium salts by alkaline predistillation from water samples. the total amount of salt, minus the amount of nitrate separately determined, is the amount of nitrite).
3, the instrument
nitrogen fixed distillation device with nitrogen ball.
4, reagent
(1) sulfamic acid solution: 1 g of sulfamic acid (hoso2nh2) was dissolved in water and diluted to 100 ml.
(2) 1 1 hydrochloric acid
(3) naoh solution: weigh 300g of sodium hydroxide dissolved in water and dilute to 1000ml.
(4) dai's alloy (cu50:zn5:al45) powder.
(5) boric acid solution: weigh 20g of boric acid (h3bo3) into water and dilute to 1000ml.
5, the measurement step
(1) shake the sample of the retrieved no. 3 point and reflow point and clear it for a while.
(2) take 3 colorimetric tubes. the first colorimetric tube plus distilled water to the mark; the second colorimetric tube plus 3ml3 spotted supernatant, and then added to the mark with distilled water; the third colorimetric tube plus 5ml reflux point what supernatant? and then add distilled water to the mark.
(3) take three evaporating dishes and drop the liquids in the three colorimetric tubes into corresponding evaporating dishes.
(4) add 0.1 mol/l sodium hydroxide to each of the three evaporating dishes to adjust the ph to 8. (use precision ph test paper, the range is between 5.5-9.0. each need about 20 drops of sodium hydroxide)
(5) turn on the water bath and place the evaporating dish on the water bath. the temperature is set to 90°c until evaporated. (about 2 hours)
(6) after evaporation, remove the evaporating dish and cool it.
(7) after cooling, add 1 ml of phenol disulfonic acid to each of the three evaporating dishes and grind them with a glass rod so that the reagents are in full contact with the residue in the evaporating dish. after standing still for a while, polish them again. after 10 minutes of standing, about 10 ml of distilled water was added.
(8) add 3 to 4 ml of ammonia to the evaporating dish while stirring, and then move it to the corresponding colorimetric tube. add distilled water separately to the mark.
(9) shake well and measure with a spectrophotometer, using a cuvette with a wavelength of 410 nm and 10 mm (ordinary glass, slightly newer). and count.
(10) calculation results.
viii. determination of dissolved oxygen (do)
molecular oxygen dissolved in water is called dissolved oxygen. the dissolved oxygen content in natural water depends on the balance between the oxygen in the water and the atmosphere.
iodometric method is generally used to measure dissolved oxygen
1, method principle
manganese sulphate and basic potassium iodide are added to the water sample. the dissolved oxygen in the water oxidizes the low-cost manganese to high-priced manganese, producing a brown precipitate of the tetravalent manganese hydroxide. after the acid is added, the hydroxide precipitate is dissolved and reacted with iodide ions to release free iodine. starch was used as an indicator and iodine was titrated with sodium thiosulfate to calculate the dissolved oxygen content.
2, the measurement step
(1) samples of point 9 retrieved from the wide-mouth bottle are allowed to stand for more than ten minutes. (note that the jar is used, and note the sampling method)
(2) insert the glass elbow into the jar sample, and inhale the supernatant into the dissolved oxygen bottle by siphoning. first suck a little, rinse the dissolved oxygen bottle three times, and then inhale the supernatant solution and fill it with dissolved oxygen. bottle.
(3) add 1 ml of manganese sulfate and 2 ml of basic potassium iodide to a full dissolved oxygen bottle. (note the precautions when adding, join from the middle)
(4) cover the bottle with the dissolved oxygen bottle and shake it up and down. shake it again every few minutes and shake it up three times.
(5) add 2ml concentrated sulfuric acid to the dissolved oxygen bottle and shake well. leave it for five minutes in a dark place.
(6) into a basic burette (with rubber tube, glass beads. note the difference between acid, basic burette) into sodium thiosulfate to the mark, ready for titration.
(7) after standing for 5 minutes, remove the dissolved oxygen bottle placed in the dark place, pour the liquid in the dissolved oxygen bottle into a 100 ml plastic cylinder, and rinse three times. finally pour to the graduated cylinder 100ml tick.
(8) pour the liquid in the cylinder into an erlenmeyer flask.
(9) titrate to a colorless flask with sodium thiosulfate, then add a drop of starch indicator and titrate with sodium thiosulfate until it fades. record the reading.
(10) calculation results.
dissolved oxygen (mg/l)=m*v*8*1000/100
m is sodium thiosulfate solution concentration (mol/l)
v is the volume of sodium thiosulfate solution consumed when titrating (ml)
nine, the total alkalinity
1, the measurement step
(1) shake the recovered water samples and effluent samples.
(2) the influent sample was filtered (no filtration was needed if the water was clean), and 100 ml of the filtrate was taken in a 100 ml erlenmeyer flask. using a 100 ml graduated cylinder, take 100 ml of the shake sample and transfer it to another 500 ml erlenmeyer flask.
(3) add 3 drops of methyl red-methylene blue indicator to two erlenmeyer flasks, respectively, in light green.
(4) into a basic burette (with rubber tube, glass beads, 50ml. the basic burette used in the determination of dissolved oxygen is 25ml, pay attention to distinguish) pour 0.01mol/l hydrogen ion to the scale line.
(5) lavender with hydrogen ions in two erlenmeyer flasks, and record the volume reading used. (remember to take a reading after titration, and fill up and titrate the other one. about 40 milliliters of water sample is needed. the water sample needs about 10 milliliters)
(6) calculation results. the amount of hydrogen ions used in the standard fluid * 5 is the volume.
x. determination of sludge deposition ratio (sv30)
1, the measurement step
(1) take a 100 ml graduated cylinder.
(2) shake the sample of the recovered oxidation ditch no. 9 and pour it into the measuring cylinder to the upper mark line.
(3) 30 minutes after the start of the timer, read the scale reading of the interface and record it.
11. determination of sludge volume index (svi)
svi is determined by dividing the sludge settling ratio (sv30) by the sludge concentration (mlss). but pay attention to the conversion unit. the unit for svi is ml/g.
xii. determination of sludge concentration (mlss)
1, the measurement step
(1) shake the sample of the retrieved no. 9 point and the reflow point.
(2) take 100 ml of each sample from point 9 and the reflow point into a graduated cylinder. (the sample of point 9 can be obtained by measuring the settlement ratio of sludge)
(3) using a rotary vane vacuum pump to separately filter the point 9 sample and reflow point sample in the measuring cylinder. (note that the choice of filter paper, filter paper is used in advance called good filter paper. if the day of the 9th sample to be measured mlvss, filter 9 spotted sample filter must be selected, anyway, the use of qualitative filter paper. also pay attention to quantitative filter paper and qualitative filter paper the difference
(4) take out the filtered filter mud sample and put it into the electric blast drying oven. the temperature of the drying oven will rise to 105°c and start drying for 2 hours.
(5) take out the dried filter paper and place it in a glass dryer to cool it for half an hour.
(6) after cooling, use a precision electronic balance to weigh and count.
(7) calculation results. sludge concentration (mg/l) = (balance reading - filter paper weight) * 10000
xiii. determination of volatile organic compounds (mlvss)
1, the measurement step
(1) after weighing the filter paper on the 9th point with a precision electronic balance, put the filter paper sludge into a small porcelain crucible.
(2) open the box resistance furnace, adjust the temperature to 620 °c, and put the small porcelain crucible into the box resistance furnace for about 2 hours.
(3) after two hours, close the box type resistance furnace and after cooling for 3 hours, open the door of the box type resistance furnace to a small joint and cool again for about half an hour to ensure that the temperature of the porcelain crucible does not exceed 100°c.
(4) take out the porcelain crucible and place it in the glass drier. re-cool it for about half an hour, place it on a precision electronic balance, and record the reading.
(5) calculation results.
volatile organic matter (mg/l) = (filter paper sludge weight small mortar weight - balance reading) * 10000.
article source: new environmental protection classroom
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