HJ/T 70-2001 PDF in English
HJ/T 70-2001 (HJ/T70-2001, HJT 70-2001, HJT70-2001)
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High-chlorine wastewater. Determination of chemical oxygen demand. Chlorine emendation method
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Standards related to: HJ/T 70-2001
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HJ/T 70-2001: PDF in English (HJT 70-2001) HJ/T 70-2001
ENVIRONMENTAL PROTECTION INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
High-chlorine wastewater - Determination of chemical
oxygen demand - Chlorine emendation method
ISSUED ON: SEPTEMBER 11, 2001
IMPLEMENTED ON: DECEMBER 01, 2001
Issued by: State Environmental Protection Administration
Table of Contents
Foreword ... 3
1 Scope ... 4
2 References ... 4
3 Definitions ... 4
4 Principle ... 5
5 Reagents ... 5
6 Instruments ... 7
7 Sampling and samples ... 8
8 Steps ... 9
9 Representation of results ... 10
High-chlorine wastewater - Determination of chemical
oxygen demand - Chlorine emendation method
1 Scope
This method applies to the determination of chemical oxygen demand (COD)
in high-chlorine wastewater with a chloride ion content of less than 20 000 mg/L.
The detection limit of the method is 30 mg/L. It applies to the determination of
COD in wastewater from oil fields, coastal refineries, oil depots, chlor-alkali
plants, and deep-sea discharge wastewater.
2 References
The following document contains the provisions which, through reference in this
Standard, become the provisions of this Standard, and have the same effect as
this standard.
GB 11914-89 Water quality - Determination of the chemical oxygen demand
- Dichromate method
When the above standard is revised, the latest version shall be used.
3 Definitions
3.1 High-chlorine wastewater
It refers to wastewater with chloride ion content greater than 1 000 mg/L.
3.2 Apparent COD
It refers to the corresponding mass concentration of oxygen converted from the
amount of potassium dichromate consumed by the water sample under certain
conditions.
3.3 Chloride ion emendation value
It refers to the mass concentration of oxygen corresponding to the chlorine
generated by the oxidized chloride ions in the water sample.
Meet the requirements of 4.5.1 in GB 11914-89.
5.8 Ammonium ferrous sulfate [(NH4)2Fe(SO4)2] standard titration solution
Meet the requirements of 4.6 in GB 11914-89.
5.9 Sodium thiosulfate (Na2S2O3) standard titration solution
5.9.1 Sodium thiosulfate standard titration solution of which the concentration
is c(Na2S2O3) ≈ 0.05 mol/L
WEIGH 12.4 g of sodium thiosulfate (Na2S2O3 • 5H2O) in water that is freshly
boiled and covered for cooling, ADD 1.0 g of anhydrous sodium carbonate
(Na2CO3), TRANSFER to a 1000 ml brown volumetric flask, DILUTE to the
mark with water, and SHAKE well. After standing for one week, CALIBRATE its
exact concentration. If the solution becomes cloudy, it must be filtered.
5.9.2 Calibration method
In a 250 ml iodine volumetric flask, ADD 1.0 g of potassium iodide (KI) and 50
ml of water, ADD 5.00 ml of potassium dichromate standard solution (6.7),
SHAKE until completely dissolved, ADD 5 ml of sulfuric acid solution (6.3), and
immediately PLUG with a plug and SHAKE well. After placing in the dark place
for 5 min, TITRATE with sodium thiosulfate standard titration solution to be
calibrated until the solution is light yellow, ADD 1 ml of starch solution, and
CONTINUE titration until the blue color just disappears, which is the end point.
RECORD the amount of sodium thiosulfate standard titration solution
consumed. MAKE a blank titration at the same time.
5.9.3 Calculation of the concentration of sodium thiosulfate standard titration
solution:
where: V1 - the volume of sodium thiosulfate standard titration solution
consumed in the titration of potassium dichromate standard
solution, ml;
V2 - the volume of sodium thiosulfate standard titration solution
consumed in the titration of blank solution, ml.
5.10 Starch solution (1 g/100 ml)
WEIGH 1.0 g of soluble starch, MAKE a paste with a small amount of water,
slowly POUR 100 ml of boiling water, continue to BOIL until the solution is clear,
and STORE in a reagent bottle after cooling. Prepare before use.
8 Steps
8.1 PIPETTE 20.0 ml of water sample (or take an appropriate amount of water
sample and add water to 20.0 ml) in a 500 ml inline conical flask. According to
the chloride ion concentration in the water sample, ADD different volumes of
mercury sulfate solution (5.5) according to the ratio of HgSO4: Cl- = 10: 1 (see
Table 1 for details), and SHAKE well. ADD 10.0 ml of potassium dichromate
standard solution (5.7) and 3 ~ 5 bumping-proof glass beads (5.13).
8.2 When determining a batch of water samples with different chloride ion
concentrations at the same time, in order to reduce the number of
determinations of blank value, they can be appropriately grouped according to
the level of chloride ion concentration. The amount of mercury sulfate added is
determined by the highest chloride ion concentration in the group, and the ratio
is HgSO4: Cl- = 7.5: 1.
8.3 CONNECT the inline conical flask to the lower end of the condensing tube,
and CONNECT the condensate. Slowly ADD silver sulfate-sulfuric acid solution
(5.6) from the upper end of the condensing tube through a funnel (see Table 1
for the added volume), and continuously ROTATE the inline conical flask to
make them mix uniformly.
8.4 ADD 20.0 ml of sodium hydroxide solution (5.11) to the absorption bottle,
and DILUTE to 200 ml with water.
8.5 CONNECT the device according to Figure 1, and INSERT the outlet tube
under the liquid surface of the absorption bottle.
8.6 PASS IN nitrogen (5 ~ 10 ml/min), HEAT, and REFLUX for 2 h after the
solution boils. After stopping heating, INCREASE the nitrogen flow (30 ~ 40
ml/min), taking care not to suck the solution back. Continue to PASS IN nitrogen
for 30 ~ 40 min.
8.7 REMOVE the absorption bottle, COOL to room temperature; ADD 1.0 g of
potassium iodide, and then ADD 7.0 ml sulfuric acid (5.4) to adjust the pH of
the solution to about 3 ~ 2; LEAVE it for 10 min; TITRATE to light yellow with
sodium thiosulfate standard titration solution; ADD starch indicator to continue
to titrate until the blue just disappears, which is the end point. RECORD the
milliliters V3 of sodium thiosulfate standard titration solution consumed.
8.8 After the inline conical flask is cooled, ADD a certain amount of water from
the upper end of the condensing tube. See Table 1 for the amount of water
added. REMOVE the inline conical flask. After the solution is cooled to room
temperature, ADD 3 drops of 1,10-phenanthroline indicator solution (5.12), and
TITRATE with ammonium ferrous sulfate standard titration solution (5.8) until
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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