UA122002C2 - METHOD OF CHROME-CONTAINING WASTEWATER TREATMENT - Google Patents

Abstract

The object of the invention: a method of purification of chromium-containing wastewater. Scope: for treatment of industrial sewage with the content of heavy metals, suspended solids, oils and oil products, mechanical impurity, etc. in systems of circulating and repeatedly circulating water supply. The essence of the invention: in the method of purification of chromium-containing wastewater at the end of the process of introduction of pre-reagents add ferrous sulfate in the form of 5-10% solution in the amount of 10-15 g / m3 / m3 - in the first case, 600… 1000 Cl / m3 - in the second case and 1000… 4000 Cl / m3 - in the third case, and also separate introduction of reagents which allows to create conditions for more effective sewage treatment that is important is provided. the condition of carrying out physical and chemical processes of sewage treatment in pressure flotation devices, especially with the introduction of reagents. EFFECT: conditions for more efficient treatment of chromium-containing wastewater are provided, electricity consumption is optimized and the reliability of operation of water treatment equipment of circulating water supply systems is increased.

Description

The invention belongs to the chemical industry, namely purification, neutralization and neutralization of industrial chromium-containing wastewater with an increased content of heavy metal ions, which are formed during the treatment of wastewater from enterprises of the machine-building complex of the country, ferrous and non-ferrous metallurgy, chemical and electrochemical processing of metals, alloys, etc.

A close technical solution is the method of purification of chromium-containing wastewater (A.s. Mo 1730045 and Mo 1730046 of the USSR, MKY СО2Е 1/46. Method of purification of chromium-containing wastewater / N.Y.

Bunin, S.M. Movchan; Melitopol Institute of Agricultural Mechanization. - Application

Mo4670283/26; statement 30.03.89; published 04/30/92. Bul. Mo 16). The method is performed according to the technological scheme, which includes the following operations in the following sequence: obtaining an iron-containing coagulant in an electrolyte solution, carrying out the electrolysis process using steel electrodes, mixing the obtained coagulant solution with treated wastewater, carrying out flotation by adding an electrolyte solution, containing: surfactant, sodium metasilicate (Mg5iOz), soda ash (Mao) and sodium tripolyphosphate (Ma5RzOio) with a total concentration of 50-100 mg/dmu, and electrolysis is carried out with specific electric current consumption, in two technological modes: 100-600 Kl /m3 - in the first case, 6000-4000 Kl/m: - in the second case.

The disadvantages of the analogue are the insufficient efficiency of wastewater treatment with the content of ions of heavy metals and oils and petroleum products, which form complex water-lubricant emulsions of a stable type, while a film forms on the surface of metal electrodes, which limits the functionality of water purification equipment.

A well-known method of wastewater treatment, adopted as a prototype, is the method of cascade wastewater treatment (Patent for a utility model Mo 94243 Ukraine, IPC" СО2Е 1/46 (2006.01).

The method of cascade wastewater treatment / S.I. Movchan - Application No. 201403882, application no. 04/14/2014; published 10.11.2014, Bull. Mo 21) in which wastewater is mixed with an electrolyte solution that is part of the complex of chemical components in a certain ratio to hexavalent chromium: Si:PAR:Maon:MaP2gO;:Ma»5iOz:Mag2COz:Ma5PzOio, while the spent washing solution contains small impurities of chemical components, which are gradually mixed with the total concentration of the electrolyte of 50...100 mg/dmu, and electrolysis is carried out using steel

From electrodes and pressure flotation. As an electrolyte, the spent washing solution of the electroplating process is used, and at the beginning of the process, surfactants, caustic soda (mMaon) and sodium pyrophosphate (MgRgO7) are added, then sodium metasilicate (MgBiOz) is introduced in the ratio of chemical components to Cg: (wt. parts) (Table 1).

Table 1

The ratio of chemical components to Art. 6: (wt. h) (6. Sodium tripolyphosphate (MaebRzOyu).

At the same time, electrolysis takes place with specific electric current consumption in two modes: 100...600 Kl/m3 - in the first case and 600...4000 Kl/m3 - in the second case.

The disadvantages of the prototype method are the impossibility of effective wastewater treatment, the formation of significant volumes of sludge and sediments, which causes low technical and economic indicators in the operation of treatment facilities and limitations in the treatment of certain types of wastewater containing fuel and lubricant impurities, suspended substances, etc. .

The invention is based on the task of improving the method of purifying chromium-containing wastewater by using chemical components in a specified sequence and their interaction with wastewater that is being treated, which allows for effective treatment of wastewater with high initial concentrations of heavy metal ions and increases the reliability of water treatment equipment in systems circulating and re-circulating water supply.

The problem is solved by the fact that in the method of purifying chromium-containing wastewater, which includes obtaining an iron-containing coagulant in the electrolyte using steel electrodes and mixing the resulting coagulant solution with the treated wastewater, flotation is carried out by introducing into the electrolyte a solution containing: surface - active substances, metasilicate, sodium pyrophosphate and tripolyphosphate, soda ash, as well as iron sulfate oxide with a total concentration of 50-100 mg/dmu, and as an electrolyte solution, used washing solution from the electroplating process is used in an amount that ensures the ratio of the components of the solution to of hexavalent chromium at the level of:

Si:PAR:MagbiOz:Ma«RgO;:Mag2COz:Ma5RzOto:RebOgh 7H2gO--1:(0.05-0.5):(0.05-0.5):(0.05-0.5) : (0.25-2.5):(0.15-1.5):0.10-0.15), (1) according to the proposed invention, at the end of the process of introducing the previous reagents, iron sulfate oxide is added, in the form 5-10 95 solution in the amount of 10-15 g/m3, and electrolysis is carried out with electric current consumption in three technological modes: 100...600 Kl/m3 - in the first case, 600...1000 Kl/m3 - in the second case and 1000...4000 Cl/m3 - in the third case.

In the examples of the specific implementation of the method of purification of chromium-containing wastewater, the technology provides for the separate introduction of reagents, which allows creating conditions for more effective wastewater treatment, and this is an important condition for conducting physical and chemical processes of wastewater treatment in pressure flotation devices, especially when reagents are introduced.

The use of chemical components in the specified sequence stabilizes the wastewater treatment process, increases the reliability of water treatment equipment and reduces the discharge of untreated or insufficiently treated wastewater into water bodies.

The use of chemical components at the level when their ratio to hexavalent chromium contributes to their effective removal by upward flows to the upper layer of the water treatment equipment, reduces the passivation of the electrode system, ensures high-quality treatment of chromium-containing wastewater by physical and mechanical methods.

The introduction of chemical components in the specified sequence allows you to subordinate the treatment of wastewater to the use of reagents, reduces the formation of liquid waste and ensures the reliability of water treatment equipment. The essence of the invention is explained by the drawings, where Fig. 1 shows a block diagram of the implementation of a complex system for the purification of chromium-containing wastewater in Fig. - 2 graphical dependences of the efficiency of wastewater treatment at

From the optimal concentration of chemical components to C of the spent washing solution (50-100 mg/dmu) when implementing the developed technical solutions with the following ratio, presented in Table 4.

The developed method of purification of chromium-containing wastewater is carried out on the equipment, which includes the following elements and constituent units: unit 1 for comparing chemical components with a reference solution, receiving tank 2, unit C for dosing reagents, reaction chamber 4, doser 5 for optimization of reagents, chamber 6 for electrochemical treatment of wastewater of water, block 7 of quality assessment, two chambers 8 and 9 for the accumulation of liquid waste, pipeline 10, valves 11, block 12 of correction of reagents, block 13 of determining the optimal ratio of chemical reagents to hexavalent chromium, block 14 of dosing the optimal amount of spent washing solution, block 15 of electrochemical processing, block 16 of wastewater efficiency control, block 17 of liquid waste treatment of galvanic production.

The method of purification of chromium-containing wastewater is as follows.

During electrolysis in an electrolyte solution containing small impurities of surface-active substances, soda ash, metasilicate, sodium pyrophosphate and tripolyphosphate, as well as ferrous sulfate (Table 2).

Table 2

The ratio of chemical components to Sb" and the efficiency of wastewater treatment

"Bemnnih PARO 0001 May"

Sow active sodium sodium calcined)| sodium will oxidize substances of iron

Table 2 (continued) ratio. -X33110X2 THEIR | H. | XX | ХХ micaceous Geo» 7НгО components to the surface: pyrophosphate) metasilicate| sodium tripolyphosphate, sulfuric acid, active ingredients. and oxidized sodium calcified)| sodium and iron substances 98.5 95 98.0 95 98.5 95 98.5 95 98.0 95 98.5 95 98.5 95 98.5 95 97.5 Zo

According to the data (Table 2), the surface of the steel electrodes is activated and the rate of transport of the iron-containing coagulant to the waste water with the content of chromium Sb: and Si ions increases. Chemical additives make it possible to obtain a more concentrated solution of the coagulant, as well as smaller bubbles of the gas phase.

When the iron-containing coagulant is further mixed with wastewater, the oxidation-reduction reaction is accelerated (Table 2), flotation complexes are formed, and the efficiency of the process of flotation of hydroxides to the foam layer is several times higher compared to known methods (Table 3). This allows to increase the degree of wastewater treatment.

Table C

Comparative indicators of the efficiency of wastewater treatment and the amount of sediment and sludge formation when using chemical components and additives

Mo |Formula of chemical components n/p OMR Additives wasp flotosh

PU | llama

Si:PAR:Mag»biOz:MagSOz: Labomid-203 (TU-

Te MahRo; 38107-38-73 0.01 |Fo15 12 0.5 oz og Mama Labomid-201 boi |oot| ovB | 110 odv-ovo

From "Ma5RzOto 38107-38-73 0.01 10.011 | 0.65 11.0. 10.45-0.50

Si:PAR:Maon:Ma»5iOz: Labomid-201 (TU- 4MaeR2Ou MabSOz:avRzOto 38107-38-73 0.01 0.012 0.70 | 175 oo

PAR:Maon:mMa»5iOz:Ma«P2O;: |Labomid-203 (TU- Y

Sg epAR: Beer obina maon:Ma25103:Mag«RgO;: konsovana 0.01 10.011| 0.80 10.0 10.40-0.45 "MagSOz:MazRzO o y

Si PAR:Maon:Mag5iOz: . 7. | Ma«ReO7MagSOz:MavReOcho: ZVT) (TU 001 |0.012| 075 | 10.5 |YUAB-0.5O "Be5Ogh 7NgO

When purifying chromium-containing wastewater with an iron-containing coagulant obtained from the electrolyte by the proposed method, the total concentration of chemical components introduced into the electrolyte should be within 50-100 mg/dm3 and are represented by graphical dependencies (Fig. 2) and in Table. 4.

Table 4

The efficiency of wastewater treatment with the optimal concentration of chemical components to Cg: spent washing solution (50-100 mg/dm) in the implementation of developed technical solutions with the following ratio: n/p washing solution input to solution of components , , , 1. Consecutively 1 |Sib :PAR:MagbiOz:MagSOz:MagR2O»7 1:0.0570.5)X0.2572.5)0.15- 2. Gradually 0.5):(0.05-0.5):(0.15 -1.5) - 3. Slowly. . ex Y 1. Slowly 2.) St: PAR:Ma»biOz:Mag2SOz:MagR2O? 1:0.0570.5):0.25 2.5)(0.15 2. Withstanding 0.5):(0.05-0.5):(0.15-1.5) : tighter limits concentrations o Y o Y o |1. Consistently 3. | Art MadR2O;7:Ma25iOz:Mag2COz:Ma5RzoO at 150.05 0.5): (0.05-0.5)(0.25 2. Gradually 2.5):0.15-1.5) - 3 Slowly o Y o Y o Y 1. Consistently

A St :PAR:Maon: Mag2g5iOz:MagRgO»: ooo o OB- 2. Gradually "| Mag2bOz:Ma»vRzO1o 05). " MU ' ' 3. Slowly and 4. Clear dosage o Y o Y o Y 1. Consistently

PAR:Maon:Mg5iOz:Ma«RgO;:Ma»bOz: 150.05 0.5)0.05 0.5), With 2. Gradually 5. 0.5):0.15-0.5): (0.05-0.5) (0.05- .

MaBRzOcho 05) 3. Slow and 4. Clear dosage 1. Consecutively.

St PAR:MaON:MagviOz:MahR»O»: in My field In Gradually.

MagSOz:Ma5RzOcho:RebO» 7NhO ,9):(0,195-0,5)0,05-0,5)0,05- 3. . keeping 0.5): (0.10-0.15) concentration limits: 5 tab

The ratio of chemical components to Si: in the treatment of wastewater from electroplating departments at the declared technical level is presented in the table. 5.

Table 5

The ratio of chemical components to Stib-

SibPAR:Ma»biOz:MagSOz:Ma»P2O;-1 (0.05-0.5)(0.05-0.5)(0.25-2.5):(0.15-0.5 ):(0.05- ' 0.5):(0.15-1.5

Ste:Mg«P2O;:MgbiOz:Mg2COz:MazRzOto-1:(0.05-0.5):(0.05-0.5):(0.25-2.5):(0.15- 1.5

A Sg: PAR:MaonN:Ma»5iOz:Ma«:RgO;:Mag2COz:MavRzOchto-1:(0.05-0.5):(0.05-0.5):(0.15-0, 5):(0.15-

T0.5):0.05-0.5)(0.05-0.5 5 surfactant: Mmaon:Ma»5iOz:Ma»PrO7;:Mag2COz:MavRzOto-1:(0.05-0.5) :(0.05-0.5):(0.15-0.5):(0.15-

T0.5): (0.05-0.5):0.05-0.5

St :PAR:Maon:Ma»5zoOz:MgRhO;:MgSOz:MavRzOto-1:(0.05-0.5):(0.05-0.5):(0.15-0.5):( 0.15-0.5):0.05-0.5):(0.05-0.5

St: PAR:Maon:MagbiOz: / Mag«RgO;:MagSOz:Ma5RzOiyuBebOi oh /7H2gO-1:(0.05-0.5):(0.05- "T10.5):0.15-0, 5):0.15-0.5):0.5-0.5):(0.05-0.5):(0.10-0.10

When treating wastewater, with a total concentration of less than 50 mg/dmU, the method does not allow obtaining a high degree of wastewater treatment, due to the fact that the rate of flotation of suspended substances to the upper layers of the water treatment equipment decreases, the steel electrodes are passivated by the falling sediment. The latter circumstance leads to an increase in the consumption of electric current and, in the end, the process of wastewater treatment deteriorates.

In the case of a total concentration of additives of more than 100 mg/dmu, significant volumes of foam product are formed in the upper layers of wastewater from water treatment equipment, which prevents effective mixing of iron-containing coagulant and wastewater, and this, in turn, reduces the degree of purification chromium-containing wastewater.

The degree of purification of chromium-containing wastewater depends on the specific consumption of electric current (Table 6), taking into account the concentration of the iron-containing reagent, the efficiency of flotation and the degree of passivation of the electrodes.

Table 6

Indicators of the efficiency of wastewater treatment depending on the cost of electrical energy when using chemical components of the spent washing solution poet et tet netnnnn JJ» UK, city 2. Efficiency.

The formula for the use of chemical components of the waste. electrical in sewage treatment. washing solution about energy, kW of water, 90 h./m3 -1:0.05...0.5):(0.05...0.5):(0.25 2.5):(0 ,15...1.5)

StbMaBrzoOzo:Mag P2gO;:Ma»viOz:Mag2COz:-1:(0.15...0.5): o 0.15...0.5):(0.05...0.5) :(0.05...0.5

St. MagR2gO;: Mag»5iOz:

MagSOz:Mav5RzOcho-1:(0.05...0.5):(0.05...0.5):(0.25...2.5): 99.6-99.9 96 5.4-6.8 (0.15...1.5)

Stb PAR: maon:ma»5iOz:Ma«eRgO;:Mag2COz:Ma5RzOcho-1:(0.15...0.5): 99.7-99.9 95 5.0-6.35 (0, 05...0.53:00.15...0.5): 0.15...0.53:0.05...0.5):(0.05...0.5

Mmaon:Mag5iOz:Ma«P2O7;:Mag2COz:MavRzOcho-1:(0.15...0.5): o 0.05...0.5):(0.15...0.5) :(0.15...0.5):(0.05...0.5):(0.05...0.5)

SteMagR2O;:MagziOz:Mag2COz:Ma5RzOzo:RezOxx 7Ng2O- 1: o

When the specific consumption of electric current is less than 600 Kl/dm3, the concentration of the iron-containing reagent in the electrolyte, the degree of saturation with the gas phase does not allow to achieve a high degree of purification. In addition, with specific electric current consumption less than 600 K/dmU, complete destruction of the washing solution is not ensured.

At specific consumption of electric current, which is in the range: more than 600 Kl/dm" and less than 1000 Kl/dm", the instability of the highly concentrated wastewater treatment process occurs. At the same time, it is advisable to determine the sequence of introduction of chemical reagents (Table 5) and to observe the time of wastewater treatment, which extends the functionality of the proposed system for the treatment of chromium-containing wastewater.

In the case when the specific consumption of electric current is within the range of more than 1000 Kl/dm" and less than 4000 Kl/dm3, there is a decrease in the ecological and economic indicators of the wastewater treatment process, as a result of which the concentration of the iron-containing coagulant in the electrolyte reaches its maximum value and subsequently passivates the sediment surface of steel electrodes.

The second significant feature of the proposed method is that as an electrolyte, the spent washing solution of the galvanic coating process is used in the amount that ensures the ratio of the chemical components of the solution to Si" at the level of the weight part is given in Table 7.

Table 7

The ratio of the chemical components of the solution to Si?" at the level of the weight part

When the concentration of each of the components of the spent washing solution is less than the minimum weight part (Table 8) to the weight part Si?", the degree of wastewater treatment decreases due to a decrease in the efficiency of flotation of heavy metal hydroxides.

Table 8

The ratio of the chemical components of the solution to Si" at the level of the minimum weight part 0.15...0.5 caustic sodium (MaOH 0.05...0.5 sodium pyrophosphate (MgRgO; 0.15...0.5 sodium metasilicate (Mag5iOz 0.15...0.5, soda ash (MagSO» 0.05...0.5 sodium tripolyphosphate (MazRzOcho 0.05...0.5, iron sulfate oxide (He5O4x7H2gO 5-10 95 solution in amount of 10-15 g/m3

When the concentration of each of the components of the spent washing solution is more than

Sib: at the level of the maximum weight part (Table 9) to the weight part Sib-, the passivation of the electrodes increases, which contributes to an increase in the consumption of electric current.

Table 9

The ratio of the chemical components of the solution to Si" at the level of the maximum weight part 0.15...0.5 caustic soda (MaOH) 0.05...0.5 sodium pyrophosphate (MgRgO; 0.15...0, 5 sodium metasilicate (Mag5iOz 0.15...0.5 soda ash (Ma?COz 0.05...0.5 sodium tripolyphosphate (Ma5RzOcho 0.05...0.5, 5-10 95 solution in the amount 10-15 g/m?

In addition, the reuse of spent washing solution for the treatment of chromium-containing wastewater allows to increase the efficiency of the process and create environmentally safe operating conditions of the electrochemical wastewater treatment system.

The wastewater treatment system creates conditions for obtaining a 2.0-2.5 times smaller volume of sediment compared to known analogues (Table 10), due to the fact that the predominant process of extracting hydroxides is the flotation process.

Table 10

Indicators of liquid waste generation in the developed method in comparison with the existing one

Volume | Volume Additives, which

The method of sediment | flotoshlam is used

Proposed Labomid-203 (TU-38107-38- method 4-6 0.5 0.01 0.5 ov 73

Proposed Labomid-201 (TU-38107-38- method 4-6 0.5 0.01 0.5 ov 73 (Prototype | 870 | 25 | 001 | 05 | 0.8 | SDB-OST-13-183-83

In comparison with known developments, the proposed method works when dosing spent washing solutions to the electrolyte, in which iron-containing coagulant is obtained at high consumption of electric current. This allows to increase and stabilize a higher degree of wastewater treatment. At the same time, used washing solutions from the electroplating process are reused.

In the proposed method of purification of chromium-containing wastewater, the following stages of physical and chemical processes are performed, the sequence of which is presented in the table. 11.

Table 11

Comparative indicators of the main parameters and characteristics of the spent washing solution

The ratio of chemical components to Stgbsho. with. South Africa: Ma»5iOz: o o

Stages of roce in PARMaeRgOg Mag MaeRoOu MagbiO»: / MahRO: man in

СОз:Ма5РзОчо | Mag2bOz:Ma5RzO1o Ma»Soz: St. 3 -Lo

Eeb5Ox«u7NgO

Ma5RzOcho 1. Redox reaction: 120...140 sec. 140...60 sec. 130...190 sec. 150...210 sec. carrying out the reaction 90...95 96 92...95 925 95...96 925 95...96 925 150...240 sec. | 125...180 sec. | 150...240 sec. 125...180 sec. 3. Efficiency of extraction of hydroxides 70...80 95 75...80 95 75...82 95 75...80 95 heavy metals with a foam layer, 90 4. Efficiency of purification from ions 95...97 90 94. ..98 90 96...98 90 94...98 90 heavy metals 5. Volume of formation 2.0...2.5 22.25 22..25 2.2...2.5 volume liquid waste

The method of cleaning chromium-containing wastewater by using chemical components in a certain ratio to hexavalent chromium allows to increase the level of intensification in the work of circulating water supply systems.

Claims (2)

FORMULA OF THE INVENTION 1. The method of purifying chromium-containing wastewater, which includes obtaining an iron-containing coagulant in the electrolyte using steel electrodes and mixing the obtained coagulant solution with treated wastewater, while flotation is carried out by introducing into the electrolyte a solution containing surface-active substances, metasilicate, sodium pyrophosphate and tripolyphosphate, soda ash, and as an electrolyte solution, the spent washing solution of the galvanic coating process is used, in the amount that ensures the ratio of the components of the solution to hexavalent chromium at the level: St:PAR:Ma»biOz:Ma»P2O;:Mag2bOz: Ma5RzOito: / RebOgh7H2gO-1:0.05-0.5):0.05-0.5): (0.05-0.5): (0.25-2.5): (0.15- 1.5): (0.10-0.15) (1), which differs in that at the end of the process of introducing the previous reagents, iron sulfate oxide is added in the form of a 5-10 95 solution in the amount of 10-15 g/mU, and electrolysis are carried out with electric current consumption in three technological modes: 100...600 Cl/m3 - in the first case, 600...1000 Cl/m3 - in the second case, and 1000...4000 Cl/m3 - in the third case. 2. The method according to claim 1, which differs in that separate introduction of reagents is provided.