The data introduces in detail the determination methods of 26 indexes encountered in the process of water treatment, as well as the common sense in the water treatment laboratory and the quality control of the laboratory, with some explanations of anaerobic terms.
Determination of pH value
PH is the negative logarithm of hydrogen ion activity in water. PH value can indirectly represent the acid-base strength of water. It is one of the most common and important test items in hydrochemistry.
Glass electrode method
Instrument: pH meter (with composite electrode), 250ml plastic beaker reagent: pH packaged buffer (potassium hydrogen phthalate, mixed phosphate, borax) temperature ℃, pH value 0.05m potassium hydrogen phthalate 0.025m mixed phosphate 0.01M borax
04.016.989.46 51.006.959.39 104.006.929.28 154.006.909.23
204.006.889.18 254.006.869.14 304.016.859.10 354.026.849.07
404.036.839.04 454.046.839.02
Experimental steps
(1) Preparation of buffer solution
Cut open the plastic bag, pour the powder into a 250ml volumetric flask, wash the inner wall of the plastic bag with a small amount of carbon dioxide free water, dilute to the scale, shake well and set aside.
(2) Calibration of instrument (phs-2c acidimeter)
a. Insert the electrode into the instrument, set the selector switch to pH, and adjust the slope at 100%;
b. Select two buffer solutions (the pH of the measured solution is between the two);
c. Put the electrode into the first buffer solution and adjust the temperature regulator to make the indicated temperature uniform with the solution.
d. After the reading is stable, adjust the pH value of the positioning regulator at the temperature shown in the upper table;
e. Then put it into the second buffer, mix well, and adjust the pH value of the slope regulator at the temperature shown in the table above.
(3) Sample determination
If the temperature of the sample is the same as that of the calibration, put the calibrated electrode directly into the sample and shake it well. When the reading is stable, it is the pH value of the sample; If the temperature is different, measure the sample temperature with the temperature, adjust the temperature regulator to indicate the temperature, keep the "positioning" unchanged, insert the electrode, shake well, and read after stabilization.
matters needing attention
(1) When the electrode is not used for a short time, soak it in distilled water; If it is not used for a long time, add a little electrode liquid into the electrode cap and cover the electrode cap.
(2) Timely supplement the electrode solution. The external reference supplement solution of the composite electrode is 3M potassium chloride solution
(3) The glass bulb of the electrode shall not contact with hard objects to avoid damage.
(4) Each time the water sample is measured, the electrode head shall be washed with distilled water and sucked dry with filter paper.
02
Determination of chemical oxygen demand
Chemical oxygen demand refers to the amount of oxidant consumed when treating water samples with strong oxidant under certain conditions, expressed in mg / L of oxygen.
Chemical oxygen demand reflects the degree of water pollution by reducing substances. These reducing substances include organic matter, nitrite, ferrous salt, sulfide, etc. It is one of the indicators of the relative content of organic matter in water.
Potassium dichromate method
1. Principle
In the strong acidic solution, a certain amount of potassium dichromate oxidizes (Ag + is used as the catalyst for this reaction) the reducing substances (organic matter) in the water sample, and the excess potassium dichromate is dripped back with ammonium ferrous sulfate solution with ferrolin as the indicator. Calculate the oxygen consumption of reducing substances in the water sample according to the dosage.
2. Interference and elimination
Chloride ions can be oxidized by dichromate and precipitate with silver sulfate, affecting the determination results. Therefore, mercury sulfate is added to the water sample before reflux to form a complex to eliminate interference.
3. Instruments
(1) Reflux device: all glass reflux device with 250ml conical bottle, including: grinded conical bottle, condenser tube, electric furnace or electric heating plate, rubber tube.
(2) 50ml acid burette
reagent
(1) Potassium dichromate solution (1 / 6k2cr2o7 = 0.2500mol/l): weigh 12.258g of standard or high-grade pure potassium dichromate dried at 120 ℃ for 2 hours, dissolve it in water, transfer it into a 1000ml volumetric flask and dilute it to the mark.
(2) Test ferrolin indicator solution: weigh 1.485g o-phenanthroline (C12H8N2. H2O), dissolve 0.695g ferrous sulfate in water, dilute to 100ml, and store in a brown bottle.
(3) Ammonium ferrous sulfate standard solution [(NH4) 2Fe (SO4) 2.6h2o ≈ 0.1mol/l]: weigh 39.5g ammonium ferrous sulfate and dissolve it in water. Slowly add 20ml concentrated sulfuric acid while stirring. After cooling, transfer it into a 1000ml volumetric flask, dilute it to the marking line and shake it well.
Calibrate with potassium dichromate before use.
Calibration method:
Accurately suck 10.00ml of potassium dichromate standard solution into a 250ml conical flask, dilute it with water to about 110ml, slowly add 30ml of concentrated sulfuric acid and mix well. After cooling, add 3 drops of Triadimefon indicator solution and titrate with ammonium ferrous sulfate solution. The end point is the color of the solution from yellow to blue-green to reddish brown.
C-Concentration of ammonium ferrous sulfate standard solution (mol / L)
V-dosage of ammonium ferrous sulfate standard solution (ML)
(4) Sulfuric acid - silver sulfate: add 5g silver sulfate to 500ml concentrated sulfuric acid and dissolve it in 1 ~ 2 days.
(5) Mercuric sulfate: crystal or powder.
4. Experimental steps
(1) Take 20ml of mixed water sample and put it into a reflux conical flask;
(2) Add about 0.4g mercury sulfate;
(3) accurately add 10.00ml potassium dichromate standard solution and small glass beads;
(4) Then slowly add 30ml sulfuric acid silver sulfate solution;
(5) Shake well, connect the condensing pipe, heat and boil and reflux for 2 hours;
(6) After cooling, add 90ml distilled water from the condenser tube;
(7) Take down the conical flask, add 3 drops of Triadimefon indicator solution, titrate with ammonium ferrous sulfate standard solution, and the end point is from yellow to blue-green to reddish brown. Record the dosage of ammonium ferrous sulfate standard solution.
5. Precautions
(1) Glass beads must be added before adding h2so4-agso4 to avoid boiling.
(2) Three significant figures shall be reserved for COD results.
(3) When the COD is greater than 500, it shall be diluted roughly as follows:
COD value 8001500-25003000-15000 > 20000
Dilution ratio 23-610-50 > 100
※ the above dilution ratios are for reference only
(4) Check the quality and operation level of the reagent with potassium hydrogen phthalate standard solution. Since the theoretical COD value of each gram of potassium hydrogen phthalate is 1.176g, dissolve 0.4251g of dried potassium hydrogen phthalate (hoocc6h4cook) in heavy distilled water, transfer it into a 1000ml volumetric flask, dilute it to the mark, and make it a 500mg / lcodcr standard solution.
(5) The reflux device can also be replaced by COD constant temperature heater, and air condensation can replace water condensation.
(6) Cod quick tester can also be used for colorimetric determination.
(7) Introduction to relevant data: 20 ~ 80mg / L nitrite in water sample will make cod unable to be determined accurately according to conventional methods. Generally, aminosulfonic acid and ammonium aminosulfonate can be used to eliminate interference, mainly due to the action of amino group in it:
The reaction can take place at room temperature or under heating conditions, releasing ammonia, so as to achieve the purpose of removing NO2 -.
The experimental results show that 10mg masking agent can almost completely mask 1mg NO2 -; The masking agent has little effect on the blank in the range of 0 ~ 15mg, and has a great effect on the determination when it exceeds 15mg.
The above instructions are for reference only.
03
Determination of biochemical oxygen demand (BOD5)
Domestic sewage and industrial wastewater contain a large amount of organic matter, which consumes a large amount of dissolved oxygen when decomposed in the water body, which destroys the oxygen balance in the water body and worsens the water quality. Biochemical oxygen demand (BOD) is the oxygen consumed by organic matter in water under certain conditions. It is an important biochemical index used to express the content of organic matter in water. The classic method for measuring oxygen demand is dilution inoculation method.
Dilution inoculation
1. Method principle
Biochemical oxygen demand refers to the amount of dissolved oxygen consumed in the biochemical process of microbial decomposition of some oxidizable substances in water, especially organic substances under certain conditions.
Incubate in a constant temperature incubator at 20 + / - 1 ℃ for 5 days, and measure the dissolved oxygen of the samples before and after culture respectively. The difference between the two is BOD5 value, expressed in mg / L of oxygen.
This method is applicable to the determination of BOD5 range: 2mg / L6000, which will bring errors due to dilution.
2. Instrument:
(1) Constant temperature incubator
(2) 5-20l fine mouth glass bottle
(3) 1000-2000ml measuring cylinder
(4) Glass rod: 50ml. A 10 rubber plug with several small holes is fixed at the bottom of the rod.
(5) Dissolved oxygen bottle (iodine measuring bottle): 250-300ml
Reagent:
(1) Phosphate buffer solution
Dissolve 8.5g potassium dihydrogen phosphate (KH2PO4), 21.75g potassium hydrogen phosphate (K2HPO4), 33.4g disodium hydrogen phosphate heptahydrate (Na2HPO4 · 7H2O), and 1.7g ammonium chloride (NH4Cl) in water and dilute to 1000ml. The pH value of this solution is 7.2
(2) Magnesium sulfate solution
Dissolve 22.5g magnesium sulfate heptahydrate (MgSO4 · 7H2O) in water and dilute to 1000ml
(3) Calcium chloride solution
Dissolve 27.5g anhydrous calcium chloride in water and dilute to 1000ml.
(4) Ferric chloride solution
Dissolve 0.25g ferric chloride hexahydrate (FeCl3 · 6H2O) in water and dilute to 1000ml.
(5) Hydrochloric acid solution (0.5mol/l)
Dissolve 40ml concentrated hydrochloric acid in water and dilute to 1000ml.
(6) Sodium hydroxide solution (0.5mol/l)
Dissolve 20g sodium hydroxide in water and dilute to 1000ml.
(7) Glucose glutamate standard solution
After drying glucose and glutamic acid in 103 for 1 hour, weigh 150mg each and dissolve them in water, transfer them into a 1000ml volumetric flask, dilute them to the mark, and prepare them before use.
(8) Dilution water
Fill a certain amount of water into a 5-20l glass bottle, control the water temperature at about 20 ℃, and aerate with an aerator for 2-8 hours to make the dissolved oxygen in the diluted water close to saturation. The bottle cap is covered with two layers of gauze and placed in a 20 ℃ incubator for several hours to make the dissolved oxygen content in the water reach about 8mg / L. Before use, add 1ml of calcium chloride, magnesium sulfate, ferric chloride and phosphoric acid buffer to each liter of water and mix well.
(9) The following kinds of inoculant can be selected:
1. For general domestic water, place it for one day and night and take it from the clear night.
2. Surface soil water: take 100g of garden or plant growing soil, add 1 liter of water, let it stand for 10 minutes, and take the clear night.
3. Effluent from sewage treatment plant
4. River or lake water containing urban sewage
(10) Inoculation dilution water
Dosage of inoculation per liter of diluted water: 1-10ml of domestic sewage; Surface soil water 20-30 ml; River or lake water 10-100 ml.
The pH value of inoculation dilution water is 7.2, which should be used immediately after preparation.
3. Determination of water samples
(1) Determination of undiluted water samples
① Transfer the mixed water sample into two dissolved oxygen bottles (there shall be no bubbles in the transfer), overflow a little and plug it. There should be no bubbles in the bottle.
② One bottle was immediately tested for dissolved oxygen, and the other bottle was put into the incubator after being sealed with saliva and cultured at 20 ± 1 ℃ for 5 days
③ After 5 days, dissolved oxygen was measured.
④ Calculation:
C1 - dissolved oxygen concentration of water sample before culture
C2 - dissolved oxygen concentration of water sample after culture
(2) Determination of diluted water sample:
Water sample type reference value dilution coefficient remarks
Permanganate index of surface water < 5 --- the product of permanganate and a certain coefficient is the dilution multiple. When using dilution water, the COD value is multiplied by the coefficient, which is the dilution multiple. When using inoculation dilution water, it is only multiplied by the coefficient
5—100.2，0.3
10—200.4，0.6
>200.5, 0.7 ,1.0
Industrial wastewater potassium dichromate dilution water 0.075,0.15,0.225
Inoculation dilution water 0.075,0.15,0.25
(1) general dilution method
① According to the selected dilution ratio, introduce some dilution water into a 1000ml measuring cylinder; ② Add the required amount of mixed water sample, and then introduce dilution water (or inoculation dilution water) to 800ml;
③ Mix up and down with a glass rod with rubber plate. During mixing, the rubber plate shall not be exposed to the water to prevent bubbles;
④ Put the water sample into two dissolved oxygen bottles and measure the dissolved oxygen on the same day and after 5 days of culture.
⑤ Dilute water was also cultured for blank experiment, and the dissolved oxygen before and after 5 days was measured.
4. Precautions
(1) The pH value of the water sample should be in the range of 6.5-7.5. If it exceeds the range, the pH value can be adjusted by hydrochloric acid or sodium hydroxide to be close to 7.
(2) There shall be no bubbles in the water sample during collection, storage and operation
(3) When the dilution ratio of water sample exceeds 100, dilute it with distilled water in a volumetric flask in advance, and then take an appropriate amount for dilution culture.
(4) Check the quality of dilution water and inoculation solution and the level of laboratory personnel. Dilute 20ml glucose glutamate standard solution to 1000ml with dilution water and operate according to the steps of BOD. The measured value should be between 180-230mg / L. otherwise, find out the cause.
(5) In the process of culture, pay attention to add sealing saliva in time.
04
Determination of dissolved oxygen
The molecular oxygen dissolved in water is called dissolved oxygen. The saturation content of dissolved oxygen is closely related to the partial pressure of oxygen in the air, atmospheric pressure and water temperature. The dissolved oxygen in clean surface water is generally close to saturation, and the dissolved oxygen content in wastewater is generally low.
1. Method selection
Iodometry and its correction method are commonly used to determine dissolved oxygen in water, and dissolved oxygen meter can also be used to determine it. Oxidizing substances can make iodide free of iodine and produce positive interference; Reducing substances can reduce iodine to iodide, resulting in negative interference. Most of the polluted surface water and industrial wastewater adopt the modified iodometry and electrode method.
2. Collection and preservation of water samples
The water sample shall be collected in the dissolved oxygen bottle without bubbles. Pour the water sample directly along the bottle wall to about 1 / 3-1 / 2 of the overflow bottle volume. After collection, it shall be fixed at the sampling site and coexisted in the dark.
Iodometry:
1. Principle
Manganese sulfate and basic potassium iodide are added to the water sample. The dissolved oxygen in the water oxidizes the low valence manganese into high valence manganese to form the hydroxide precipitation of tetravalent manganese. After adding acid, the hydroxide precipitates and dissolves and reacts with iodine ions to release iodine. The content of dissolved oxygen can be calculated by titrating iodine with sodium thiosulfate with starch as indicator.
2. Reagent
(1) Alkaline potassium iodide sodium azide solution: weigh 250g sodium hydroxide and dissolve it in 200ml water; Weigh and dissolve 75g potassium iodide in 100ml water and 5g sodium azide in 20ml water. After sodium hydroxide is cooled, mix the three solutions and dilute them to 500ml. Store in a brown bottle, stopper tightly with a rubber stopper and keep away from light.
(2) 40% (M / V) potassium fluoride: weigh 40g of potassium fluoride (KF · 2H2O) and dissolve it in water, dilute it to 100ml, and store it in a polyethylene bottle.
(3) The experimental procedure is the same as that of iodometry. Only replace basic potassium iodide with basic potassium iodide sodium azide solution. If it contains Fe3 + interference, insert it under the liquid level and first add 1ml of 40% potassium fluoride solution.
matters needing attention
(1) Sodium azide is a highly toxic and explosive reagent. Alkaline potassium iodide sodium azide solution cannot be acidified directly, otherwise toxic smoke will be produced.
(2) The water sample is strongly acidic or alkaline, and can be adjusted to neutral with sodium hydroxide or sulfuric acid.
(3) Do not generate bubbles during operation.
(4) The concentration of sodium thiosulfate should be calibrated easily every time it is used.
And then
Determination of suspended solids (SS)
Determination of ammonia nitrogen (NH3-N)
Determination of nitrite nitrogen
Determination of nitrate nitrogen
Determination of Kjeldahl nitrogen (KTN)
Determination of total nitrogen (TN)
Determination of phosphorus (total phosphorus, phosphate)
Determination of sulfate
Determination of sulfide
Determination of total salt content
Determination of volatile fatty acids (VFA)
Determination of alkalinity
Determination of chloride
Determination of total hardness
Determination of calcium ion
Determination of chromaticity
Determination of turbidity
Determination of total solids and volatile solids
Determination of total suspended solids, volatile suspended solids and ash
Determination of methanogenic activity of anaerobic sludge
Measurement of sludge particle size distribution and sedimentation rate
Evaluation index of activated sludge performance and quantity
Laboratory knowledge
1、 Experimenter's code
2、 Management rules for drugs and reagents
3、 Washing of glassware
4、 Preparation of pure water
5、 Expression of general solution concentration
6、 Collection and preservation of water samples
Quality control of laboratory
1、 Five characteristics of monitoring data
2、 Detection limit
3、 Determination limit
4、 Optimum determination range
5、 Calibration curve
Anaerobic noun interpretation
1、 Upstream velocity
2、 Hydraulic retention time
3、 Organic load of reactor
4、 Sludge volume index
5、 Residence time of sludge in reactor
