Color of wastewater from paraquat production

The raw wastewater from the production of paraquat by cyanide method is generally dark brown or dark brown, with a deep chroma.

1. production process and pollutant emission analysis

1. 1 cyanidation method

Cyanidation process is the main basis for the formulation of standards, and the setting of main indicators is also determined according to cyanidation process.

1. 1. 1 process wastewater

Cyanide process produces process wastewater in the filtration part. The wastewater contains pyridine, paraquat, cyanide ion, ammonia nitrogen, sodium chloride, alcohol, organic solvent and so on. The wastewater is strongly alkaline and has high chroma.

1. 1.2 Waste gas discharged from production process

The production process of cyanide method involves the emission of tail gas during the use of chlorine, liquid ammonia, pyridine, methyl chloride and other raw materials.

1. 1.3 waste water incineration treatment

After the waste water is burned, the exhaust stream discharged into the atmosphere from the exhaust pipe contains water vapor, smoke dust, sulfur dioxide, nitrogen oxides and so on. The residue discharged during incineration contains cyanide ions.

1.2 sodium method

Sodium method includes middle and high temperature sodium method and low temperature sodium method, and the middle and high temperature sodium method has been strictly prohibited. The characteristic tripyridine isomers, mainly 2,2' ∶ 6', 2'- tripyridine, produced in the process of medium/high temperature sodium process are set as control items, and the medium/high temperature sodium process can be prohibited from being used from the perspective of environmental protection.

2. Determination of pollutant emission control indicators

2. 1 Determination principle of control index

According to the characteristics of pesticide industry, the emission standard not only controls conventional factors, but also controls characteristic pollution factors according to the characteristics of pesticide production. These characteristic pollution factors may be intermediates or final products of pesticide production. These characteristic pollution factors are often highly toxic and harmful. If they are not controlled, they will pose a serious threat to the ecological environment, food safety and human health. The screening of characteristic pollution factors will comprehensively consider the following factors: (1) high yield; (2) It is highly toxic to human body and environment or harmful to ecological environment; (3) easy to control; (4) Effective detection and monitoring means. (5) Too many control factors should not be set at the beginning, and the control factors can be continuously adjusted or increased in the future.

2.2 Determination of control indicators

Above all, the production technology of paraquat and the discharge of three wastes in China are analyzed. On this basis, according to the above principles, the pollutant emission control index of paraquat pesticide production is determined, as shown in table 1.

Table 1 Standard Control Index of Pollutant Emission from Paraquat Pesticide Production

Waste water, waste gas, waste liquid and waste residue

Conventional pollutant characteristic pollutant

PH value, CODcr, chromaticity, ammonia nitrogen, cyanopyridine, paraquat, 2,2': 6', 2 '- tripyridine chloride, ammonia, pyridine, methyl chloride and cyanide-containing waste.

2.3 Applicability of control indicators

According to the actual investigation results, there is no production device using low temperature sodium method in China at present. Considering the implementation cost and technical problems, it is unlikely that the domestic low-temperature sodium process plant will be put into operation in a short time. Therefore, the control items that set the characteristics for the low-temperature sodium method alone are not considered. However, it cannot be completely ruled out that some enterprises have made leap-forward progress in technology, and at the same time, it cannot be ruled out that some enterprises "claim" to adopt the low-temperature sodium method. If this happens, we think: firstly, the setting of Tripyridine Project excludes the possibility that the medium/high temperature sodium method "impersonates" the low temperature sodium method; Secondly, other conventional control projects such as wastewater are not only aimed at cyanide process, but also have certain universality, and can also be applied to the possible low-temperature sodium process.

3. Determination of standard values in emission standards

3. 1 Basis for determining standard value

The determination of the standard value is mainly based on:

(1) Current pollution control technology level. Emission standards are different from environmental quality standards, which are based on environmental reference values and are the target values for protecting public health and maintaining ecological environment safety. The goal of pollution control is to meet environmental quality standards, and its means is to limit the emission of pollution sources, and the core of emission limitation is emission standards. The formulation of emission standards must be based on technology, because emission standards are to be implemented by enterprises and the principle of "technical coercion" should be embodied. That is, by formulating emission standards, polluters are forced to adopt advanced pollution control technologies. The standard value we set should be the level that enterprises can reach after adopting advanced production technology and pollution control measures. Instead of blindly pursuing the advanced nature of standards, it is better to break away from the technical level of pollution control in the current industry.

In the formulation of standards, new sources and existing sources are based on different technical levels. The new source emission standard is formulated according to the most advanced technical level in China at present, and the current source emission standard is formulated according to the more advanced technical level in China at present.

(2) Environmental quality requirements and ecological impact of pollutants: In the process of formulating emission standards, in addition to the current level of pollution control technology, we should also fully consider the impact of pollutant emissions on human health and even the entire ecological environment. When formulating pesticide discharge standards, ADI value (daily allowable intake per kilogram of body weight), MRL value (maximum allowable residue limit of crops) and LC50 value (semi-lethal concentration) of pesticides are comprehensively considered, which makes the formulated standards not only technically and economically feasible, but also fully protect human health and ecological environment.

(3) Existing relevant standards at home and abroad: The existing relevant standards (including domestic standards and foreign standards) must have considered many factors in the formulation process, and have been tested in practice for a certain period of time, which can be used as a reference for us to formulate this standard.

3.2 Determination of discharge standard value of water pollutants

(1) Maximum allowable displacement

According to the investigation, at present, the enterprises producing paraquat by cyanide process produce paraquat 1 ton (100%), and the amount of raw wastewater discharged by production equipment is between 2 ~ 8m3. See Table 2 for the original wastewater discharge of some enterprises.

Table 2 Discharge of raw wastewater from some paraquat production enterprises

Enterprise Name Waste Water Discharge in Production Process (m3/ ton of API)

Syngenta cyanamide method 4

2.5 ~ 3 cyanamide process in Salonda Company

Shandong dongfang science and technology company cyanamide method 3

Ammonium Cyanide Process 3 of Hubei Xianlong Company

Cyanohydrin method of Shanghai Taihe Company 6

Alcohol Cyanidation of Zhejiang Yongnong Company 7.5

Sublimation Baker Company Cyanide Method 7

Alcohol cyanidation method of Shijiazhuang Baofeng Company II

Generally speaking, the output of wastewater per unit product is relatively low, about 4m3, by using the cyanamide process. Using cyanohydrin process, the output of wastewater per unit product is relatively high, about 7m3. However, some enterprises use alcohol cyanidation process, and the output of wastewater per unit product is very low. This shows that there is still much room for improvement in cyanohydrin process, and the amount of wastewater can be reduced through appropriate measures.

Therefore, for the current source enterprise, it is estimated that the wastewater output per unit product is 7m3 for the new source enterprise, and the wastewater output per unit product is 4m3. The equipment and ground washing water for paraquat production 1 ton (100%) is 0.5m3 Because the concentration of paraquat production wastewater is usually very high, it is allowed to be 4 times of its dilution capacity during the treatment. Therefore:

Maximum allowable displacement = (unit product wastewater output+equipment and ground washing water) × dilution multiple

Therefore, for the maximum allowable displacement, the standard limit of Xinyuan enterprise is 18m3, and that of the current source enterprise is 30m3.

(2) Chemical oxygen demand

The COD index is the first-class standard 100mg/L/L stipulated in the Integrated Wastewater Discharge Standard (GB 8978- 1996). See Table 3 for the treatment level that the enterprise can achieve at present:

Table 3 COD concentration of raw wastewater and final discharge of some enterprises

The enterprise name adopts the COD(mg/L) of process raw wastewater and the COD(mg/L) of final drainage.

Syngenta cyanamide method 20000

Cyanidation method of Zhejiang Yongnong Company 22000100 ~110

Sublimation Baker Company Cyanide Process 25000

Cyanohydrin method of Shanghai Qinhe Company 78000

Shandong Oriental Science and Technology Company's Melamine Law 1000 50

According to the provisions of Integrated Wastewater Discharge Standard (GB 8978- 1996) and the treatment level that enterprises can reach, the limit value of COD discharge is100 mg/L/L. ..

For the pretreatment standard, the COD limit can be set according to the specific requirements of the sewage treatment plant and the load capacity of the biochemical treatment device of the enterprise, but the maximum value cannot exceed 500 mg/L.

(3) pH value

The raw wastewater produced by cyanidation method contains cyanide ions, so the raw wastewater is strongly alkaline, generally between pH 10 ~ 13. See Table 3 for the pH value of raw wastewater from some enterprises.

Table 3 pH value of raw wastewater from some enterprises

Enterprise name pH value of raw wastewater

Syngenta 12.6

Shandong Lvba Company 9.4

Shijiazhuang Baofeng Company 13.3

Shanghai Taihe Company 12.7

Whether the raw wastewater is directly discharged into the environment after treatment or after biochemical treatment after pretreatment, the pH value should be adjusted to be close to neutral. According to the limit value of Integrated Wastewater Discharge Standard (GB 8978- 1996), the limit value of discharge standard and pretreatment standard is set at 6 ~ 9.

(4) Chromaticity

The raw wastewater from the production of paraquat by cyanide method is generally dark brown or dark brown, with a deep chroma. See Table 4 for the chromaticity of raw wastewater from some enterprises.

Table 4 Chromaticity of raw wastewater from some enterprises

The enterprise name adopts the method of measuring process chromaticity (chromaticity).

Syngenta cyanamide method 75000 platinum and cobalt standard colorimetric method

Shijiazhuang Baofeng Company 300,000 yuan by alcohol cyanidation

Cyanamide method of Jinan Lvba Company 62500

Cyanohydrin method of Shanghai Qinhe Company 600000

If the original wastewater is directly discharged into the environment after treatment, the chromaticity index should be controlled. At present, the domestic enterprises that adopt advanced wastewater treatment technology can reach the chromaticity index below 50. At the same time, according to the provisions in the Integrated Wastewater Discharge Standard (GB 8978- 1996), the limit value of the discharge standard is set at 50.

For the pretreatment standard, further biochemical treatment is needed, and finally all discharge indexes (including chromaticity indexes) of sewage treatment plants are reached. Therefore, all indexes can meet the requirements of biochemical treatment as long as the substances affecting biochemical treatment are removed from wastewater. For chromaticity index, it is not a highly sensitive factor affecting biochemical treatment, so there is no pretreatment standard.

(5) Ammonia nitrogen

In the process of producing paraquat by cyanamide method, ammonia only plays a catalytic role. With the filtration and washing operations, a large amount of ammonia nitrogen will enter the raw wastewater. At present, enterprises generally adopt stripping to recover ammonia water, and then reuse ammonia water in the process. This technology is a mature method widely used in China. By stripping, the recovery rate of ammonia in wastewater can reach 97~98%, and the ammonia concentration in wastewater after stripping is about 200 mg/L. Considering that the dilution capacity is allowed to be 4 times in further biochemical treatment, the ammonia concentration in diluted wastewater can be reduced to about 50 mg/L. Because ammonia nitrogen is easily removed by nitrification-denitrification of microorganisms, the standard limit of ammonia nitrogen in pretreatment standard is 50 mg/L.

If the original wastewater is directly discharged into the environment after treatment, the limit value of the discharge standard is set to 15mg/L with reference to the Integrated Wastewater Discharge Standard (GB 8978- 1996).

(6) Cyanide ion

Cyanide ion is a harmful pollutant in cyanide process wastewater. The concentrations of cyanide ions in raw wastewater and treated wastewater of some enterprises are as follows:

Table 5 Cyanide ion concentration in raw wastewater and treated wastewater of some enterprises

Enterprise name: concentration of cyanide in treated wastewater (mg/L).

Syngenta cyanamide method 7870

Shandong Dongfang Science and Technology Company Ammonia Cyanidation Method 2000.08

Ammonium cyanide method of Hubei Xianlong Company 600 0.5

Cyanohydrin Method of Shijiazhuang Baofeng Company 1500

Cyanidation method of biochemical encyclopedia company 1000 ~ 1500 0.5

Cyanohydrin method of Zhejiang Yongnong Company 18000 60 ~ 80

After the primary treatment of 8000 cyanohydrin process in Shanghai Qinhe Company:

After secondary treatment:

Because cyanide is very toxic and harmful to the biochemical treatment process, the discharge standard and pretreatment standard of cyanide ions are set at 0.5mg/L with reference to the provisions in Integrated Wastewater Discharge Standard (GB 8978- 1996) and the treatment level that enterprises can reach.

(7) pyridine

Pyridine is the most important raw material in paraquat production. Because of its strong irritation, volatility, certain toxicity and non-biodegradability, it is listed as a characteristic pollution factor that needs to be monitored in wastewater. See Table 6 for pyridine content in raw wastewater and final drainage of some enterprises.

Table 6 pyridine content in raw wastewater and final drainage of some enterprises

The name of the enterprise adopts pyridine (mg/L) as the process raw wastewater and pyridine (mg/L) as the final drainage.

Syngenta cyanamide method 146.28 was not detected.

Jinan green bully cyanamide method 16.00-

Shijiazhuang Baofeng Cyanohydrin Method 8 16.28-

Sublimation bakanol cyanide method can't detect it.

* The data in Syngenta, Balu and Baofeng in the above table are measured data; The data of Sublimation Baike is provided by the enterprise.

At present, there is no provision about pyridine in China's national emission standards, which is only reflected in environmental quality standards. However, pyridine has been included in the control project in the emission standards formulated in some places.

Table 7 Relevant standards of pyridine in water

Standard name standard limit value

Environmental Quality Standard for Surface Water (GB 3838-2002) 0.2 mg/L.

Shanghai local sewage discharge standard (DB 31199-1997) Class I standard: 2.0 mg/L.

Secondary standard: 2.0 mg/L.

Grade III standard: 5.0 mg/liter.

Class I waters in Sichuan Environmental Pollutant Emission Standard (Trial): Class A1.0 mg/L; Grade B 2.0 mg/L

Class ii water body: class a 2.0 mg/l; Grade B 3.0 mg/L

Three types of water: Grade A 3.0 mg/L; Grade B 5.0 mg/L

Referring to the local sewage discharge standards in Shanghai and Sichuan Province, the discharge standard limit of Xinyuan enterprise is 2.0mg/L, and that of current source enterprise is 5.0 mg/L. ..

(8) Paraquat ion

Paraquat ion is the most important characteristic pollutant in standard formulation. Because it is a pollutant only involved in paraquat production, it has strong particularity, so there is no relevant discharge standard at home and abroad, but some countries such as the United States have drinking water quality standards for paraquat. Therefore, for the determination of paraquat ion emission limit, several different estimation models in the multi-media environmental target value (MEG) method complement each other and confirm each other.

Emission Standard of Pollution Source Enterprises —— Estimation of Multimedia Environmental Target Value (MEG)

Multimedia environmental goal (Meg) is the limit value of the content and emission of chemicals or their degradation products in environmental media calculated by EPA Industrial Environment Laboratory in the United States. It is estimated that when the amount of chemicals does not exceed MEG, it will not have harmful effects on the surrounding people and the ecosystem. MEG includes ambient environment target value (AMEG) and emission environment target value (DMEG). AMEG stands for the maximum allowable concentration of chemicals in environmental media (it is estimated that organisms will not be adversely affected by the concentration of such chemicals for life). DMEG refers to the maximum allowable concentration of chemicals in the discharge flow when the organism is in short-term contact with the discharge flow. It is expected that pollutants with a concentration not higher than this will not have irreversible harmful effects on human body or ecosystem. At the same time, the industrial environment laboratory has also proposed a variety of estimation models of magnetoencephalogram values.

Table 8 Data required for estimating MEG value of paraquat ion

Data description data value

The allowable concentration of paraquat in workplace air recommended by NIOSH is 1.5mg/m3.

US Federal Drinking Water Guide 30 μ g/L

The lowest ecotoxicity data value (IC50 of crescent moon algae is the lowest in the existing data) is1.8 mg/L.

Rats were given LD 50 65 438+0 55 ~ 203 mg/kg orally.

(a) NIOSH recommended value estimation model:

DMEGWH (μ g/L) = 15×DMEGAH=22.5 μ g/L.

(2) drinking water standard estimation model:

DMEGWH (μ g/L) =5× drinking water standard =150μ g/L.

(c) Estimation model based on ecological environment:

DMEGWE (μ g/L) = 100× minimum ecotoxicity data value (mg/L) =180μ g/L.

(D)LD50 estimation model:

Dimethyl glycol monomethyl ether (μ g/L) = 0.675× LD50 =104.625 ~137.025 μ g/L.

* The corner mark in the above formula indicates: W- water; H- health; Electronic ecology.

In the above estimation model, there is no data estimated by NIOSH recommended value model, because NIOSH recommended value is the limit value of workplace ambient air, and the inhalation toxicity of paraquat is considered more. Paraquat is highly toxic by inhalation and moderately toxic by contact and oral administration. The formulation of this standard will be mainly based on contact and oral toxicity.

The remaining four data include the estimated values of drinking water standard model and LD50 model based on health and toxicological effects, and the estimated values based on ecological environment model. Moreover, the four data values are close, which can well confirm each other. The maximum value of the four data is180μ g/L, and the minimum value is104.625μ g/L. In order to ensure emission safety, 100μg/L is conservatively taken as the current emission standard limit of the source enterprise. It is predicted that if the concentration of paraquat ions in the discharge flow does not exceed 100μg/L, it will not have irreversible harmful effects on human body or ecosystem under the condition of short-term contact.

Emission Standard of Xinyuan Enterprise —— Total Control: Considering Cumulative Effect

Assuming that the degradation process of paraquat ion in environmental system conforms to the first-order reaction kinetics, there are:

dC/dt=kC

C- paraquat ion concentration in the environment

Test launch time

K- degradation coefficient

The above formula shows that the degradation rate of paraquat ion depends on the degradation coefficient when the concentration of paraquat ion in the environment is constant.

The change of paraquat ion concentration in the environment can be expressed as:

Ct=C0e-kt

C0—— the initial concentration of paraquat ions;

Paraquat ion concentration at CT- time t;

logarithmic

kt=lnC0/Ct

When the degradation is half, that is, Ct=C0/2.

T 1/2=ln2/k

T 1/2- degradation half-life

In the environment, the average degradation half-life of paraquat ion is 65,438+0,000 days, and T65,438+0/2 = 65,438+0,000 days can be considered:

k=6.9× 10-4d- 1

The degradation coefficient obtained is very small, which shows that paraquat ion is difficult to degrade in the environment and has obvious cumulative effect.

Therefore, although the concentration limit of paraquat ion in the federal drinking water guide formulated by EPA in the United States is set at 30μg/L, some states in the United States and some countries such as Britain and Australia have implemented stricter drinking water standards. See Table 9 for the standards of paraquat in some countries and regions.

Table 9 Paraquat Standards in Some Countries and Regions

Standard name restriction

Arizona drinking water standard is 3 micrograms per liter.

The water quality standard of British water supply regulations is 0. 1μg/L (the total amount of pesticides is less than 0.5ug/L).

Australian Health and Medicine Commission standard 0.03 μ g/L..

Of course, there is a difference between drinking water standard and discharge standard, but considering the long-term cumulative effect, it is appropriate to set the discharge standard of paraquat ion in Xinyuan enterprise as relatively safe 30μ g/L, and from the current situation of domestic enterprise governance, some enterprises with better pollution control have been able to meet or even lower this standard, so from the perspective of technical feasibility, this standard can also be achieved.

(9) 2,2': 6', 2''- Tripyridine

2,2': 6', 2''- tripyridine is one of the characteristic pollutants in paraquat wastewater produced by sodium method at medium and high temperature. Some data show that 2,2': 6', 2 '- tripyridine is the main isomer, but 2,2' can't be detected in cyanide wastewater and low temperature sodium wastewater. At the same time, 2,2': 6', 2''- Tripyridine has a strong carcinogenic effect. Therefore, 2,2': 6', 2 '- Tripyridine is set as one of the characteristic pollution factors in wastewater, and it is not allowed to be detected, so as to eliminate the medium/high temperature sodium treatment process that has been explicitly prohibited by the state from the perspective of environmental protection.

3.3 Determination of standard values of air pollutants

3.3. 1 Waste gas from production process

The waste gas emissions in the production process include chlorine, ammonia, pyridine and methyl chloride.

(1) chlorine gas

In China's Comprehensive Emission Standard of Air Pollutants (GB 16297- 1996), the secondary emission standard of chlorine gas of Xinyuan enterprise is as follows:

Table 10 Provisions on Chlorine in Comprehensive Emission Standard of Air Pollutants

Maximum allowable discharge concentration of pollutants mg/m3 Maximum allowable discharge rate kg/h

Exhaust pipe height m level 2

Chlorine gas 65 25

30

40

50

60

70

80 0.52

0.87

2.9

5.0

7.7

1 1

15

Referring to the above standards, it is stipulated that the height of the exhaust pipe shall not be less than 30m, and the specific limits are as follows:

Table 1 1 chlorine emission limit

Maximum allowable emission concentration of pollutants mg/m3 Vent height m Maximum allowable emission rate kg/h

Chlorine 65 30 0.87

(2) Ammonia gas

The Comprehensive Emission Standard for Air Pollutants (GB 16297- 1996) has no provisions on ammonia, but the Emission Standard for Odor Pollutants (GB 14554- 1993) has the following provisions:

Table 12 Provisions on Ammonia in Odor Pollutant Emission Standard

Control the height m of the project exhaust pipe and the discharge amount kg/h.

Ammonia 15

20

25

30

35

40

60 4.9

8.7

14

20

27

35

75

In occupational exposure limits of Hazardous Factors in Workplace (GBZ2-2002), the maximum allowable concentration of ammonia is 30mg/m3. Because the height of the exhaust pipe is limited to 30m, the allowable discharge concentration is 300mg/m3 according to air dilution 10 times. Therefore, the ammonia emission limits are specified as follows:

Table 13 ammonia emission limit

Maximum allowable emission concentration of pollutants mg/m3 Vent height m Maximum allowable emission rate kg/h

Ammonia 300 30 20

(3) pyridine and methyl chloride

In the Comprehensive Emission Standard for Air Pollutants and Emission Standard for Odor Pollutants, there are no regulations on the emission limits of these two gases. However, the allowable concentrations of these two substances in workplace air in occupational exposure limits (GBZ2-2002) are as follows:

Table 14 Provisions on Pyridine and Chloromethane in occupational exposure limits (mg/m3)

Chinese name English name MAC TWA STEL

Pyridine -4 10

Methyl chloride -60 120

* MAC-in the table-maximum allowable concentration; Twa-time-weighted average allowable concentration; Stel-allowable concentration for short-time contact.

Generally speaking, the concentration of harmful gases discharged from the exhaust pipe after diffusion through the atmosphere shall not exceed the first maximum allowable concentration stipulated by the atmospheric quality standard or the sanitary standard. According to the Sutton model of the turbulent diffusion of harmful substances, we can know that:

Among them:

Cmax- the maximum concentration of landing.

M- pollutant discharge per unit time

U- wind speed

He-height of exhaust pipe

That is to say, when the wind speed and the height of the exhaust pipe are fixed, the maximum ground concentration is directly proportional to the pollutant discharge per unit time. Namely:

Here, the same conditions as the chlorine emission standard are adopted. It is known that the maximum allowable concentration of chlorine in occupational exposure limits of Hazardous Factors in Workplace is 1mg/m3. By calculating the above formula, it can be concluded that in this case:

K= 1. 149

Because we only care about the proportional relationship, there is no unified unit in the calculation here, but the original unit of each quantity is directly selected, which will not affect the subsequent results.

For pyridine and chloromethane, under the same conditions as chlorine, the maximum allowable concentrations of pyridine and chloromethane are known to be 4 mg/m3 and 60 mg/m3, respectively, so the maximum allowable emission rate limits of these two substances can be obtained as follows:

Table 15 Maximum allowable emission rate limits of pyridine and methyl chloride

Maximum allowable discharge rate of pollutants kg/h

Pyridine 3.48

Methyl chloride 52.2

For the concentration limit of these two substances, the enterprise standard of Jielikang Company in Britain stipulates that pyridine is 90mg/m3 and chloromethane is 200mg/m3. It is recommended to adopt the same standards, and the emission regulations of pyridine and methyl chloride are as follows:

Table 15 Emission Limits of Pyridine and Chloromethane

Maximum allowable emission concentration of pollutants mg/m3 Vent height m Maximum allowable emission rate kg/h

Pyridine 90 30 3.48

Methyl chloride 200 30 52.2

3.3.2 Waste gas generated by incineration treatment of process wastewater

Incineration is used to treat process wastewater. During the treatment, waste gas is discharged into the atmosphere from the exhaust pipe of the incinerator. Considering the composition of process wastewater and the analysis of incineration process, it is known that the main component of the waste gas is water vapor, and it also contains pollutants such as particulate matter, nitrogen oxides and sulfur dioxide. The emission standards of these pollutants can be implemented according to the Control Standard for Hazardous Waste Incineration (GB 18484-200 1).

3.4 Basis for setting the limit value of solid waste discharge project

For cyanide processes, solid waste usually comes from the following sources:

(1): for example, cyanide recovery process in cyanohydrin or cyanohydrin process.

(2) Produced in the process of incineration treatment of wastewater: Burning residual salt will be produced in the process of incineration treatment of wastewater, and the output is related to the specific incineration process.

(3) Cyanide packaging: the remaining packaging after cyanide is used, including bags, bags, boxes, etc. The material is usually paper or plastic.

No matter what kind of solid waste, it may contain cyanide and must be treated effectively. Therefore, solid waste can be controlled according to the requirements of Pollution Control Standard for Cyanide-containing Wastes (GB 12502-90).

Table 16 Relevant regulations in the pollution control standard of cyanide-containing waste.

The first and second levels of the project

The cyanide content in the waste (calculated by CN-) is ≤1.0 mg/L ≤1.5 mg/L.

* The cyanide content of waste refers to the total cyanide concentration of waste in leachate.

* The first level refers to the standards that should be implemented from the date of implementation of this standard for newly built, expanded and rebuilt enterprises and institutions; The second level refers to the standards that have been implemented by enterprises and institutions before the implementation of this standard.

According to the above standards, the limit value of cyanide (calculated by CN-) in solid waste is ≤ 1.0 mg/L, where the cyanide content of waste refers to the total cyanide concentration of waste in leachate.

4. Standard monitoring

In order to improve the operability of monitoring of each control project, the position of sampling points and the provisions of sampling frequency are defined. At the same time, the requirements for continuous on-line monitoring of waste gas produced by incineration process wastewater are stipulated. This is because, firstly, the continuous on-line monitoring technology of waste gas emitted by incinerators is relatively mature at present; Secondly, for the waste gas discharged from incinerators, there are often problems such as difficulty in sampling, untimely manual monitoring, and great interference from human factors. If manual monitoring is adopted, it will inevitably lead to excessive discharge and affect the effectiveness of standard implementation; Thirdly, continuous online monitoring can effectively improve the monitoring level, reduce the labor intensity of operators, and accumulate experience for further promotion in other fields. The sampling frequency is set according to the production cycle of different enterprises.

5. Control project analysis method

5. 1 Control items of existing national standard analysis methods

The existing national standard analysis method of control projects, according to the standard method. See table 17 for details:

Table 17 Control Project Analysis Method

Source of project analysis method

COD potassium dichromate method GB11914-89

PH glass electrode method GB6902-96

Colorimetric dilution multiple method GB 1 1903-89

Distillation and titration of ammonia nitrogen GB7478-87

Cyanide ion titration GB7486-87

Pyridine gas chromatography GB/T 14672-93

Chloromethyl orange spectrophotometry HJ/T30-99

Anna's reagent colorimetry GB/T 14688-93

Pyridine barbituric acid spectrophotometry GB/T16116-95

Chloromethane gas chromatography GB/T 16078-95

Toxicity leaching method of cyanide (calculated by CN- in leaching solution) Horizontal oscillation method

Determination of total cyanide-silver nitrate titration GB5086.2-97

GB7486-87

5.2 There is no national standard analysis method for the analysis of paraquat ions and 2,2': 6', 2 '- tripyridine.

For paraquat ions and 2,2': 6', 2 '- tripyridine which have no national standard analytical methods, the analytical methods were established through experiments and literature review.

5.2. 1 paraquat ion analysis method

For paraquat ions, liquid chromatography was used. The method is briefly described as follows:

A certain volume of paraquat wastewater was filtered by needle filter, and paraquat ions in wastewater were separated and determined by liquid chromatography. The mobile phase was sodium octane sulfonate-acetonitrile-buffer solution, the chromatographic column was Spherisorb Pheny and 5μm, and the detector was ultraviolet variable wavelength detector.

This method is suitable for the determination of paraquat ions in industrial wastewater and surface water. The minimum detection amount (based on S/N=2) is 10- 12g, and the minimum detection concentration is10.21μ g/L. Repeat the water sample with paraquat ion concentration of16 ~ 76 μ g/L.

5.2.2 Analytical Method of 2,2': 6', 2' '- Tripyridine

For 2,2': 6', 2 '- tripyridine, the water sample was treated with sodium hydroxide and ethyl acetate, and then it was identified by gas chromatography-mass spectrometry.

This method is suitable for the determination of 2,2': 6', 2 '- tripyridine in industrial wastewater and surface water. The minimum detection limit (S/N=2) of this method is 8×10-1g, and the detection limit is 0.08 mg/L. The water samples with 2,2': 6' and 2'-tripyridine concentrations less than 1.0mg/L were determined repeatedly. The relative standard deviation of this method was less than 30%, and the recovery rate was 70- 138.