RU2547114C1 - Method of clarifying and recycling conditionally clean water from filtration facilities of water treatment plants by treatment with polymer-colloidal complex reagent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes coagulation, settling in a two-section stabilisation tank and recycling purified water in a closed cycle. The coagulant used is a polymer-colloidal complex coagulant, which is obtained in advance by mixing a water-soluble polyelectrolyte - polydimethyldiallylammonium chloride, aluminium polyoxychloride and a copolymer of an acrylamide with a quaternary ammonium salt of dimethylaminoethyl methacrylate with molecular weight of 8-10 million units and degree of charge of 38-40 in molar ratio of 2:1:1.

EFFECT: high efficiency of aggregating suspended substances in settling tanks, high output and efficiency of clarifying and recycling conditionally clean water, environmental safety of a water treatment plant.

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Description

The invention relates to a technology for clarification and disposal of washing water of filter structures of water treatment plants. To implement the method, coagulation, sedimentation in a two-section averaging tank and reuse in a closed cycle are carried out. As the polymer colloidal complex reagent, a polymer colloidal complex coagulant is used, preliminarily obtained by mixing a water-soluble polyelectrolyte-polydimethyl diallylammonium chloride (PDDA), aluminum polyoxychloride (POA) and a copolymer of acrylamide with a quaternary ammonium salt of dimethylaminoaminoethylamine 10 ml. and a degree of charge of 38-40 with their mass ratio of 2: 1: 1.

The method provides an increase in productivity and technological efficiency of clarification and disposal of conditionally pure water, ensures the environmental safety of the water treatment plant.

A known method of clarification and disposal of washing water of filter structures of water treatment plants by their coagulation with a solution of aluminum oxychloride, settling in a two-section averaging tank and reuse in a closed cycle (2006, 107840/15 (008516) priority 13.03.06, IPC C02F 9/04, C02F 5/00).

A disadvantage of the known method of clarification and disposal of washing water of filter structures at water treatment plants by coagulation, settling and reuse in a closed cycle is the formation of loose sediment of low density and high humidity in them. Most of the sediment in the process of sedimentation of wash water floats up, and some of it is in the volume of sedimented water in the form of agglomerates of flakes in suspension. This creates the need for additional clarification of washing water after settling in the averaging tank by filtering on special filters to remove floating and suspended solids from them before reuse, which complicates the technology and reduces the economic efficiency of clarification and disposal of washing water from filter structures of water treatment plants.

There is a method of purifying turbid waters by treatment with a cationic flocculant in the supply pipe according to the application 9510773/26/013339, published 02/20/97. According to this method, the flocculant is introduced into the pipeline or into the water before it is fed into the pipeline.

The disadvantage of this method is that at no doses of the flocculant and processing parameters, pollution can not be removed before the turbidity after settling, below 3.0-2.5 mg / l - with the usual settling time for wastewater treatment plants, and for the next stage of treatment to work effectively, it is necessary to have water maximally clarified, with a turbidity of at least 2.0 mg / l.

To achieve the goal, a method is proposed according to which it is proposed to carry out additional water treatment with a mineral coagulant in the ratio of flocculant 40: 1 to 1: 1 (RF patent No. 2125540, IPC C02F 1/00, published January 27, 1999).

The disadvantage of this method is: the duration of the joint contact of the reactants with water in the pipeline from 02 to 16.7 hours with a velocity gradient in the pipeline G = 340 cm ^-1 , and the turbidity varies from 4.3 mg / l to 2.1 mg / l, not reaching the required indicator 2, 0 mg / l for maximally clarified water.

As a prototype, a method of clarification and disposal of washing water of filter structures of water treatment plants was taken (RF patent No. 2372297, IPC C02F 1/52, C02F 103/04, published 10.11.2009). To implement the method, coagulation, sedimentation in a two-section averager and reuse in a closed cycle are carried out, where a complex coagulant is used as a coagulant, which is a mixture of aqueous solutions of aluminum sulfate and oxychloride in a dose ratio of 2: 1 on aluminum oxide.

The disadvantage of this method is the lack of technological and economic efficiency of clarification and utilization of natural waters, which does not fully ensure environmental safety. With the introduction of a mixture of aqueous salts of sulfate and aluminum oxychloride in an amount of 15 mg / l, the content of salts in water increases significantly, a loose layer of sediment of low density and high humidity is formed.

The achievement of the technical result is hampered by the lack of optimal flocculation conditions for the aggregation of suspended pollutants during joint contact of water with reagents, during which deep clarification of water would be carried out with the formation of a rapidly settling and aggregated suspension. Hence the insufficient efficiency of water clarification due to the frequently changing composition of the treated water, the underdeveloped surface of the complex, and the weak flocculating effect.

The aim of the invention is to increase the efficiency of aggregation of suspended solids of conditionally pure water in the tanks.

To achieve the goal, it is proposed to treat conditionally pure waters with a polymer colloidal complex coagulant (PAC).

The objective of the proposed technical solution is to develop a method for clarifying and recycling conditionally clean water from filter structures of water treatment plants, which involves treating with a polymer colloidal complex reagent, coagulating them, settling in a two-section averaging tank and reusing in a closed loop, where the polymer colloid complex reagent is used polymer-colloidal complex coagulant previously obtained by mixing water-soluble lielektrolita polydimethyldiallylammonium chloride (PDDAHA) polyoxychloride aluminum (Pohang) and a copolymer of acrylamide with a quaternary ammonium salt of dimethylaminoethyl (ASDMAEM) with a molecular weight of 8-10 MU and the degree of ionic charge 38-40 with a mass ratio of reactants 2: 1: 1, respectively.

The technical result is achieved by the fact that the method of clarification and disposal of conditionally pure water from the filter structures of water treatment plants is carried out by treating with a polymer-colloidal complex coagulant, coagulating them, settling in a two-section averaging tank and reusing in a closed loop, previously obtained by mixing a water-soluble polyelectrolylamide (polydimethyldialyl chloride) PDDAH), aluminum polyoxychloride (POHA) and a copolymer of acrylamide with quaternary ammonium salt w dimethylaminoethyl (ASDMAEM) with a molecular weight of 8-10 MU and the degree of ionic charge 38-40 with their mass ratio of 2: 1: 1, respectively.

Clarification of conditionally pure wash water is carried out by sedimentation of the suspension in the averaging tank. Two sections of the averaging tank operate alternately: in one section of the tank, conditionally clean cleaned wastewater is collected, purified from sedimentation by flocculation by treatment with a polymer-colloidal complex coagulant under static conditions and reused for washing filter structures of water treatment plants, the empty section is washed into the other, and the wash water is discharged during the next flush. Sludge containing impurities is pumped to thickeners, thickened at a water treatment plant, transported to a sewage treatment plant and disposed of as a reagent for dewatering sewage sludge.

Polymercolloid complex coagulant in the form of a solution of three polymers taken in a ratio of components 2: 1: 1, suitable for clarification of conditionally pure waters, it is corrosive inactive, has a pH of 6.9-7.0, has a bactericidal effect, inhibits the growth of phytoplankton, increases the flocculating effect.

The polymeric colloidal complex coagulant has a developed surface and high sorption activity compared to aluminum oxychloride and sulfate, which are used at water treatment plants and in clarification sites.

The use of a polymer-colloidal complex coagulant consisting of PDDAH, POHA polyelectrolyte and ASDMAEM copolymer taken in a ratio of 2: 1: 1, respectively, with PAC being administered in an amount of 1.0-4.0 mg / l, which ensures the quality of clarified wash water that meets the regulatory requirements for the waters used repeatedly for flushing the filter structures of water treatment plants. No additional filtering is required. The quality of the wash water exceeds the quality of the water clarified both in a known manner and in a manner according to the prototype.

At the same time, the introduction of the reagents can be carried out in the form of a mixture prepared in advance in the indicated range of the quantitative ratio, which is a polymer-colloidal complex coagulant.

Due to the introduction of a polymer-colloidal complex coagulant, suspended particles of contaminants are bound by the polymer bridges of the complex coagulant and aggregates are formed that can settle in sedimentation tanks.

The main reason for the increase in the effect of flocculation is the introduction of a complex coagulant, the joint participation of all the components of PDDA, POHA, and ASDMAEM copolymer with a molecular weight of 8-10 million units. and the degree of ionic charge 38-40 with a mass ratio of components 2: 1: 1, respectively. At the same time, a synergistic effect of agglomeration of the smallest particles into relatively “large aggregates” is observed, given that we are talking about relatively pure waters, i.e. the combined effect of flocculants and coagulants is observed, which exceeds the action exerted by each of them individually.

The technical result is an increase in the sorption characteristics of the polymer colloidal complex coagulant and, as a result, achievement of the required turbidity index, less than 2.0 mg / l, of conditionally pure water with an optimal consumption of polymer colloidal complex coagulant.

The volume of supplied POHA reagent decreased by 10 times, the price decreased by 3.3 times the treatment of 1 m ^{3 of} water. There is an economic and technological effect.

Aluminum polyoxychloride is a colloidal particle of polymer nature in an aqueous solution and when mixed with an aqueous solution of polyelectrolytes - polydimethylallylammonium chloride and a copolymer of acrylamide with a quaternary ammonium salt of dimethylaminoethyl methacrylate PDDAH: POHA: ASDMEAEM in a ratio of 1: 1: 1: Moreover, PACs are administered in an amount of 1.0–4.0 mg / L; interpolymer complexes are formed due to cooperative donor – acceptor interactions. Essentially, such interpolymer complexes are a polymer-colloidal complex of PACs of an organomineral nature, which is quite large, combined with a large total positive charge and acts as a cationic polymer flocculant.

Characterization of the components of the polymer colloidal complex coagulant.

Polyelectrolyte polydimethyldiallylammonium chloride PDDAH.

Chemical formula: n (C8H16) NCl.

Appearance: Colorless to yellow, homogeneous in consistency, liquid without impurities.

Non-combustible, non-explosive, low toxicity, has no unpleasant odor. The reagent is a water-soluble cationic polymer, mixes with water in any proportion, is characterized by a very high cationic charge with a relatively low molecular weight - from 10 thousand to 1 million, can be used as a coagulant and flocculant for the treatment of industrial wastewater from mineral contaminants, to ensure effective treatment of turbid highly contaminated waters, for the treatment of drinking water in domestic water supply systems. The molecular weight of the polymer is approximately 3 * 10 ⁵ units.

Obtaining: A high molecular weight strongly basic cationic polymer with a linear cyclic structure, obtained by radical polymerization of a dimethyl diallylammonium chloride monomer, which, in turn, is made from allyl chloride and dimethylamine by heating in an alkaline medium.

Specifications

Name of indicator:

Mass fraction of the main substance,%, not less than 25-35

Mass fraction of sodium chloride,%, no more than 10

Viscosity, mm ² / s, not less than 2

PH value, pH 5-8

ALUMINUM POLYOXYCHLORIDE (hereinafter - the LUNCH) STO 14175996-25-2010

Appearance: The solution is colorless to yellow (opalescence is allowed).

The analytical data of the POHA solution are presented in table 1.

Table 1 No. p / p The name of indicators Norm for POHA-18 Actually one. Mass fraction of alumina (Al ₂ O ₃ ),% 16.5-17.5 16.6 2. Mass fraction of chlorides,% 19.0-23.0 22.0 3. Mass fraction of residue insoluble in water,%, no more 0.1 Less than 0.1 four. Density (at 20 degrees C), g / cm3 0.34-1.38 1.37 5 The activity of hydrogen ions (pH) 0.5-4.5 6. Mass fraction of iron (Fe),%, no more 00017

APPLICATION

It is a coagulant and is intended for the purification and treatment of water in domestic, drinking and industrial water supply, swimming pool water, sewage in industry and agriculture, for use in technological cycles of paper, leather, textile and other industries.

The ASDMAEM copolymer of acrylamide with a quaternary ammonium salt of dimethylaminoethyl methacrylate is a cationic flocculant having a molecular weight of 8-10 ppm. and a high degree of cationic charge 38-40.

PAC for clarification of conditionally pure waters based on a polymer, which is a three-dimensional matrix consisting of a polymer composition of the composition: a water-soluble polyelectrolyte polydimethyl diallylammonium chloride, aluminum polyoxychloride and a copolymer of acrylamide and quaternary ammonium salt DMAEM (dimethylaminoethyl methacrylate) with a molecular weight of 8 million molecular weight . and the degree of charge 38-40, taken in the following ratio of components 2: 1: 1, and the PAC is administered in an amount of 1.0-4.0 mg / L.

The characteristic of the purified water.

The treated water is a mixture of slightly chemically contaminated wastewater that undergoes hydrobiobotanical treatment in a channel of conditionally clean wastewater and enters the clarification station with the following indicators, presented in table 2.

table 2 Min-max July 2012 pH 6.5-8.4 7.15 Suspended substances, mg / DM ³ 5.9-48.0 17.0 The total salt content, mg / DM ³ 400-750 450.5 Hardness, mol / dm ³ * equiv. 2.95-5.8 5.4 Alkalinity, mol / dm ³ * equiv. 2.1-3.5 2.84 Chlorides, mg / dm ³ 65-150 98.6 Sulfates, mg / dm 50-160 82.0 COD, mg O ₂ / dm ³ 20-75 25.4 Transparency "across the cross", cm 10-50 fifteen Turbidity, mg / dm ³ 1.5-12.5 17.3

In the period from April to October in relatively clean water there is a large amount of phytoplankton, which contributes to an increase in turbidity parameters.

Determination of the optimal dose of PAC in laboratory tests.

In laboratory conditions, the working dose of PAC was preliminarily selected. In a series of cylinders with a volume of 250 cm ³ filled with test water, a PAC solution of 0.1–5.0 cm ³ was introduced. Intensive mixing was not carried out, deposition was fixed after 30 minutes. The speed and effectiveness of coagulation was evaluated visually by comparing the thickness of the supernatant layer and turbidity in the samples.

The results are presented in table 3.

Table 3 PAC The dose of PAC in mg / l of purified water Observation results 0.4 No reaction 1.2 Start flocculation, small flakes 2.0 Fast flocculation, medium flocs 4.0 The process begins quickly after entering the reagent large flakes, the turbidity in 30 minutes decreased from 10.2 mg / l to 2.0 mg / l.

The invention is illustrated by the following examples.

Example 1. In this example, the influence of the composition of the PAC on the degree of purification of conditionally pure water is presented, which is used as real filter system constructions of water treatment plants having a neutral and slightly alkaline reaction with the following characteristics: pH - 7.15, turbidity - 270 mg / l, color , hail - 14, sludge time - 30 min.

100 ml of a 1% solution of the polymer-colloidal complex coagulant is prepared by mixing a water-soluble polyelectrolyte of polydimethyldiallylammonium chloride (PDDA), aluminum polyoxychloride (POHA) and a copolymer of acrylamide with a quaternary ammonium salt of dimethylaminoethyl methacrylate (АСДМАЭМ. and the degree of ionic charge 38-40 at their various mass ratios, then diluted with water to a concentration of the working solution of 0.1% of the mass.

1. (1: 2: 1), 2. (0.5: 1: 1.5), 3. (2.5: 1.5: 1), 4. (2: 1: 1), 5. (2.0: 0.5: 1), 6. (2.0: 0.5: 0.5), 7. (2.0: 1: 1.5).

Further, turbidity, color, volume of a precipitate of relatively pure water after 2 minutes stirring and 30 minutes settling at room temperature were determined.

The data are presented in table 4.

As a result of the analysis of the obtained data, it can be concluded that the best results for the purification of conditionally pure waters were obtained by treating water with a polymer-colloidal complex coagulant in the composition and ratios: PDDAH: POHA: ASDMLEM = 2: 1: 1.

Table 4 The influence of the composition of the PAC on the degree of purification of relatively pure water The designation of the reagents and their ratio PDDA: POHA: ASDMAEM * The volume of sediment,% Turbidity after 30 minutes, mg / l The degree of purification,% 1. (1: 2: 1) PKK-1 1.15 2.2 98.5 2. (0.5: 1: 1.5) PKK-2 1.15 2.3 98.8 3. (1.5: 1.5: 1) PKK-31 1.15 2.4 98.0 4. (2: 1: 1) PKK-4 1.0 2.0 99.3 5. (2: 0.5: 1) PKK-5 1.0 2.1 99.2 6. (2: 0.5: 0.5) PKK-6 1.1 2.1 99.0 7. (2: 1: 1.5) PKK-7 1.2 2.1 99.1 8. (1: 1.5: 2) PKK-8 1.15 L 2-2 98.0 * - dose of the reagent 2.9 mg / l according to ASDMAEM, the content of pollutants in relatively clean water - 280 mg / l.

Determining the optimal dose of PAC during production tests.

The procedure for determining the dose of PAC is regulated by the requirements of TU 38303-06-2001 "Technical water" in terms of turbidity, as well as the degree of contamination of the source water. The minimum dose is selected at which the process proceeds efficiently, the flakes are large and quickly settle, and the turbidity of the clarified water should be no more than 6.0 mg / l (norm according to TU).

A 1% solution was used as the PAC working solution; the coagulation efficiency was estimated by the turbidity determined by the method using measuring instruments, a centrifuge, and a FC2 photocolorimeter. Tests were conducted from July 24 to July 30, 2012 at the clarification station. 0.7 tons of PAC were consumed, with 369600 m ^{3 of} water being purified.

The results are presented in table 5.

Table 5 Date of testing PAC dose, mg / l The turbidity of the source water, mg / l Turbidity after 20 minutes of sediment Turbidity after 30 minutes of sediment 07/24/2012 1.8 13.2 4.0 2.0 07/25/2012 0.8 12.9 6.3 6.2 07/30/2012 1.4 12.8 5.5 5.1

Production tests showed:

- PAC - an effective reagent for clarification of conditionally pure water;

- PAC - has a bactericidal effect, inhibits the growth of phytoplankton and is relevant for water recycling systems;

- the absence of corrosive activity in the PAC (pH of the aqueous solution of the PAC is 6.9-7.0, in contrast to POCA (used in practice) 0.5 and above);

- the volume of supplied POHA reagent decreased by 10 times, the treatment of 1 m ^{3 of} water at a price decreased by 3.3 times;

- reduced time to reach a minimum turbidity of 2.0 mg / l from 120 minutes to 30.

The technical result is an increase in the sorption characteristics of the PAC and, as a result, the achievement of the required turbidity index of conditionally pure waters, reduction of the time to reach the turbidity index.

The PAC can be used to clarify water, which is a mixture of slightly contaminated wastewater that has undergone hydrobiobotanical treatment in a channel of conditionally clean wastewater and arrives at the clarification station.

As can be seen from table 5, the dose of 1.8 mg / l PAC for water purification is excessive with the initial turbidity of 19.2 mg / l, because the obtained turbidity values of clarified water in 2.0 mg / l after 20 minutes of sedimentation are 3 times higher than normal. The norm according to TU 38303-06-2001 "Technical water". A dose of 0.8 mg / L is clearly insufficient. The turbidity after 30 minutes of sediment is above normal and equal to 6.2 mg / L. At a dose of PAC 1.4 mg / l, the required turbidity value of the purified "clarified" water 5.5 mg / l is achieved.

Thus, the optimal ratio of the PAC dosage and the “turbidity index” of 5.5 mg / L for 20 minutes of sedimentation was found with a high turbidity index of the initial water — 12.8 mg / L.

Comparative indicators of the quality of wash water clarified by the proposed method, the method according to the prototype and analogue, as well as the volume of sludge obtained are presented in table 6.

As can be seen from table 6, the turbidity of the source water according to the claimed method reached a value of 2.0 in 30 minutes, which is 2-3 times faster than according to the prototype and analogue 4.3 mg / l and 7.4 mg / l, respectively.

Rinsed the filters. Waste wastewater is collected in one section of the averaging tank and, under laboratory conditions, is tested in a test coagulation and flocculation unit. The turbidity in the wash water was 270 mg / l, the color - 14 degrees. The optimal doses of PDDAH, POHA, and ASDMAEM reagents have been established for their separate and combined use. The optimal dose of PDDAH was 35.0 mg / l, POHA - 15 mg / l and ASDIAEM - 15 mg / l when administered separately.

The turbidity of the settled wash water in this case exceeded the norm - 7 mg / l.

Table 6 Measured parameters Types of PAC (a mixture of three polymers) Injectable Prototype (a mixture of aluminum sulfate and aluminum oxychloride solutions) Reagents Analog (107840, aluminum oxychloride) one 2 3 four Source Wash Water Quality Turbidity, mg / l 270 270 270 Color, hail. fourteen fourteen fourteen The dose of reagents, mg / l fourteen fifteen fifteen The quality of the separated water Color, hail. 1.0 1.0 2.0 Turbidity, mg / l 2.5 4.0 13 The total volume of sediment (including floated from the volume of wash water,%, during sedimentation) 480 min 1.0 2.1 2.6 120 min 1.5 2.8 3.4 30 minutes 2.0 4.3 7.4

The introduction of a polymer-colloidal complex coagulant from a mixture of PDDAH, POHA, ASDMAEM aqueous solutions with doses of 7.0, 3.5, 3.5 mg / L, respectively (dose ratio 2: 1: 1) ensured the normative quality of clarified wash water. The introduction of only one aluminum polyoxychloride into water led to the formation of rapidly settling flakes of aluminum hydroxide. Most of the sediment in the process of settling the wash water surfaced (39%), and some of it was suspended in the amount of sediment in the form of large aggregates of flakes. This created the need for additional purification of wash water by filtration to remove floating and suspended solids from them before reuse. A similar separation of the precipitate occurred with the separate introduction of the components. After introducing into the wash water a polymer-complex colloid coagulant from aqueous solutions of the PDDAX + POHA + ASDMAEM mixture with doses of 7.0, 3.5, 3.5 mg / L, respectively, the normative quality of clarified waters with respect to turbidity was obtained. In this case, the formation of small dense flakes of aluminum hydroxide occurred, they were compactly packed in the sediment without separation and the sediment volume was reduced by more than 2.5 times.

Taking into account the established doses, clarification of the used filter wash water by coagulation and sedimentation in one section of the averaging tank was carried out. The clarified water was used to wash the filters after the next filter cycle. At the same time, the spent wash water was discharged into the second section of the averaging tank for cleaning and reuse. The wash water sludge was thickened and used as a reagent in the experimental sludge dewatering of a sewage treatment plant.

Thus, the proposed method allows to increase the technological and economic efficiency of clarification and disposal of washing water of filter structures of water treatment plants.

Claims (1)

The method of clarification and disposal of conditionally pure water from the filter structures of water treatment plants is carried out by treatment with a complex reagent, their coagulation, settling in a two-section averaging tank and reuse in a closed cycle, characterized in that the polymer reagent is used as a complex reagent, obtained by mixing water-soluble polyelectrolyte - polydimethyldiallylammonium chloride, aluminum polyoxychloride and acryl copolymer and a quaternary ammonium salt of dimethylaminoethyl methacrylate with a molecular weight of 8-10 MU and the degree of ionic charge 38-40 with a mass ratio of components 2: 1: 1.