RU2083504C1 - Method of clearing turbid water via treatment with cationic flocculant in supplying pipeline - Google Patents

Abstract

FIELD: water purification. SUBSTANCE: invention refers to surface water sources. Flocculant is introduced into pipeline or into water before its feeding into pipeline, which is utilized for mixing flocculant with water and aggregating suspended materials. In this case, distance from flocculant introduction point to settlers is 500 to 60000 m, velocity gradient in pipeline 68 to 346 s^-1, and water treatment time 0.13 to 33 h. When pipeline comprises pumps for additionally lifting water, flocculant is introduced before one of them. EFFECT: optimized suspension aggregation process and improved settlement process. 2 cl, 2 tbl

Description

 The invention relates to methods for purifying water from surface water sources and can be used in the field of domestic, drinking or industrial water supply, in particular for treating troubled waters.

A known method of using a cationic flocculant is that it is introduced into the mixer, then the treatment is carried out in a flocculation chamber, settler or clarifier with suspended sediment and, finally, in the filter. The following hydraulic conditions for treating water with a focculant are recommended, for which ordinary wastewater treatment plants are designed:
rapid mixing in the mixer with a value of the rms gradient of the velocity 200 1000 s ^-1 , time 1 2 min;
slow mixing in a flocculation chamber with a speed gradient of 25 45 s ^-1 , mixing time 20 30 minutes

 The achievement of the technical result is hampered by the lack of optimal flocculation conditions, during which deep clarification of the water with the formation of a rapidly settling suspension would be carried out.

 A known method carried out by the Rostov Scientific Research Institute of AKH on water pipelines of the South of Russia for the treatment of turbid surface waters (Pyatigorsk, Neftekumsk, Cherkessk, etc.). Flocculant VPK-402 was introduced to the water treatment plant in front of the mixer; in it, as well as in the reaction chamber, the usual hydraulic conditions were maintained, the same as when treating water with mineral coagulants.

The achievement of the technical result is hindered by the fact that the standard hydraulic conditions during the flocculation process do not allow contaminants to aggregate into particles with sufficient hydraulic fineness for sedimentation in sedimentation tanks. The suspension of suspended solids occurred mainly in filters. The maximum effect of water clarification in sedimentation tanks did not exceed 30 - 50%
Attempts are known to improve the process of clarification of water treated with a flocculant, while settling were undertaken in the work. In the process of conducting experimental studies, the influence of the duration and intensity of mixing was simulated and shown when a foculant was added to the treated water of different turbidity.

 The achievement of the technical result is hampered by the lack of modeling in the flocculation mode. It is known that the sedimentation properties of the resulting flocculent suspension depend not only on maintaining the required mixing parameters, but also to a greater extent on the flocculation parameters.

A known method (1) of clarification of water, which consists in the fact that the water is brought into contact with the crushed mineral, in particular with clay. To accelerate flocculation, then a polyelectrolyte (flocculant), predominantly containing a polymer cation, is added to the water. In this case, a deeper clarification of water by settling is achieved than with the addition of one reagent, including the addition of one polyelectrolyte. So, acceptable clarification of water by settling to a turbidity of 0.22 1.3 NTU with feed water of 3 - 33 NTU was carried out with the following doses of reagents:
fine magnetite 10 mg / l;
cationic polyelectrolyte grades 7-810 or S-573 0.2 0.5 mg / l.

 The achievement of the technical result is hindered by the complexity of the processing - it is necessary to control the operation of the equipment for the preparation and input of two reagents simultaneously - a suspension of ground mineral and cationic polyelectrolyte. Of particular difficulty is the preparation and administration of a suspension of the mineral. Studies were conducted only in laboratory conditions. At industrial facilities, this method was not implemented, so there is no material confirming its effectiveness.

 Closest to the technical nature of the proposed object is a method (2) of using a cationic flocculant for water purification, implemented in the process of production testing. The flocculant Ba-2 was introduced into the pipeline immediately before the clarifier with a layer of suspended sediment.

 The achievement of the technical result is hampered by the fact that in the prototype the optimal hydraulic conditions of the flocculation process were not justified when using a flocculant. Tests were carried out at facilities for clarification of water, designed and intended for the use of mineral coagulants.

 To achieve a technical result, optimization of aggregation of suspended matter in troubled water is proposed to improve deposition.

The technical result is achieved by the fact that the method for purifying turbid waters involves treatment with a cationic flocculant in the supply pipe. In this case, the flocculant is introduced into the pipeline or into the water before it is fed into the pipeline used to mix and aggregate suspended solids at a distance of 500-6000 m from the settling tanks with a speed gradient in the pipeline reaching 68 346 s ^-1 and processing time 0.13 33 hours. If there are pumps on the pipeline for additional water rises, the flocculant is injected in front of one of them.

( В. А. Клячко, И.Э. Апельцин.Очистка природных вод. М.Стройиздат,1971, с. 101 104),
где W удельный расход мощности на 1 м³ емкости камеры хлопьеобразования, которая представляет собой трубопровод;
m абсолютная вязкость воды.The speed gradient is calculated by the well-known formula:

(V. A. Klyachko, I.E. Apeltsin. Purification of natural waters. M. Stroyizdat, 1971, p. 101 104),
where W is the specific power consumption per 1 m ³ capacity of the flocculation chamber, which is a pipeline;
m absolute viscosity of water.

где q расход воды по трубопроводу, м³с;
H потери напора, м;
V объем воды в трубопроводе, м³.For the pipeline:

where q is the water flow through the pipeline, m ³ s;
H pressure loss, m;
V is the volume of water in the pipeline, m ³ .

Therefore, the speed gradient depends on:
loss of water pressure in the pipeline,
water consumption
viscosity, which in turn depends on the temperature of the water,
the volume of water in the conduit, which in turn depends on its length and diameter.

 Losses of water depend on the speed of movement of water, the state of the internal walls of the pipeline, its surface, the presence of fouling, local resistance (narrowing, bends, etc.).

 In many cases, the supply of water from surface water sources to water treatment plants is carried out through pipelines over significant distances. The proposed method is based on the process of mixing and aggregation in the feed pipe, or the process of mixing the flocculant with water in the pump, and aggregation of suspended matter in the feed pipe.

The main reason for the improvement of flocculation conditions during processing in the pipeline is the presence of two zones in it, which differ sharply in hydraulic conditions:
parietal zone with intense turbulent pulsations,
the central zone is relatively calm, with moderate ripples.

 In the central zone, aggregates from suspension particles are formed by binding them with polymer bridges, and in the near-wall zone, partial destruction of unstable aggregates or separation of the weakest links occurs. The constant exchange of masses of water between these zones contributes to the multiple occurrence of the processes of formation and partial destruction of aggregates and the final formation of particles with the most durable polymer bridges, capable of further strengthening and settling in sedimentation tanks.

 The rationale for the selected limits is as follows. The boundary parameters of water treatment in the pipeline indicated in the application materials are determined by modeling on a special device (see materials of application No. 95100022 of January 5, 1995), as well as by calculation. The main criterion for choosing the boundary parameters was the turbidity of the separated water obtained during the simulation.

 The simulation results for various operating conditions of steel pipelines are given in table. one.

Below values: processing time 0.13 h (8 min), pipeline length 500 m
turbidity of settled water is not reached 8 12 mg / l, which is acceptable according to SNiP 2.04.02-84 "Water supply. External networks and structures" for supplying water to quick filters.

 When the values of these parameters are higher than the upper limits: processing time 33 h (2000 min), the length of the pipeline is 60,000 m, the deterioration of water quality due to turbidity begins as a result of the destruction of the aggregate suspension from prolonged transportation through the pipeline.

With a smaller velocity gradient (<68 s ^-1 ), the specified clarification effect is not achieved. The upper limit of this indicator is not possible to determine, although it should exist, but lies behind the real values of flow rates for water supply pipelines.

 In the table. 1, the calculated values of the velocity gradients are calculated for new pipelines, without fouling. In this case, pressure losses in pipelines were taken into account (for calculating velocity gradients) according to the data of reference materials (see nomogram for calculating steel water pipes, Kurgan A.M. Fedorov N.F. "Handbook for hydraulic calculations of water supply and sewage systems. L. Stroyizdat, 1978, p. 347).

The upper limit of the velocity gradient in this application is not accepted as the limit after which there is an increase in turbidity of the treated water, but as the maximum obtained during the experimental verification of the proposed method in the production test process. According to the above example 2, it is 346 s ^-1 . Values of the velocity gradient of more than 346 s ^{-1 were} not achieved in real water supply systems, since they will not be economically justified in terms of the loss of water pressure in the pipeline and, consequently, in energy costs.

The difference between the present invention and the prototype is the introduction of a flocculant into the pipeline or water before being fed into the pipeline used to mix and aggregate suspended solids at a distance of 500-60,000 m. In it, the processing should go on for 0.13 33 hours with a speed gradient of 68 346 s ^{- 1} .

 If there are pumps for additional lifting of water, the flocculant is introduced in front of one of them, and, for example, the distance after the flocculant's inlet point, the processing time in the pipeline, and the velocity gradient must be observed the same.

 Thus, the proposed invention meets the requirement of novelty.

The following can serve as evidence of the compliance of the invention under consideration with the requirement of an inventive step: the introduction of a flocculant into the pipeline or into the water before feeding it into the pipeline at a specified distance first leads to the mixing of the flocculant with water, and then along its main part along the length to aggregate suspended solids. These processes occur at a processing time of 0.13 33 h and a velocity gradient of 68 346 s ^-1 . When a flocculant is introduced in front of the pump, mixing occurs in the pump, and aggregation of suspended solids in the pipeline. The aggregation of suspended solids in troubled water in this way will lead to their more efficient sedimentation in the sump. And all taken together allows you to reduce the content of suspended solids in settled water.

 Thus, the present invention meets the requirement of inventive step.

 The possibility of carrying out the invention is confirmed by the following information.

Example 1. At industrial water treatment plants during comparative production tests, water was clarified with the following characteristics: suspended solids 8 120 mg / l, alkalinity 3 mEq / l, temperature 1.5 10 ^o C, total hardness 5.5 6 mg -eq / l, pH 8-8.2. The cationic flocculant VPK-402 was introduced with a pipeline with a diameter of 1000 mm at a distance of 3 km from the settlers. The indicators of the regime of movement of water in the pipeline for calculating the conditions defined by the claims: supply 2500 m ³ h 690 l / s, speed 0.9 m / s, length of the pipeline 3000 m, pressure loss 16.2 m, the volume of water in the pipeline 2440 m ³ .

Время обработки в трубопроводе 3000 м 0,9 м/с 3333 с=0,9 ч.

Processing time in the pipeline 3000 m 0.9 m / s 3333 s = 0.9 hours

 In sedimentation tanks, water was sedimented for 1.5 hours, suspended solids in the source and clarified water were determined by the weight method.

 The results of clarification of water in the sumps when introducing flocculant into the pipeline are given in table. 2.

 They show that the use of a flocculant according to the proposed method allows to obtain a degree of clarification of water, acceptable for supplying to quick filters (5.0 mg / l and below).

Example 2. At industrial water treatment facilities No. 2 of Rostov-on-Don (Aleksandrovka village), water was clarified according to the proposed method with the following indicators: suspended solids 53 mg / l, total hardness 5 mEq / l, alkalinity 3 mg equiv / l, pH 8.0. The cationic flocculant VPK-402 was introduced into the pipeline with a diameter of 1000 m at a distance of 1.9 km from the settlers. The indicators of the mode of movement of water in the pipeline for calculating the conditions defined by the claims: feed 800 l / s, the diameter of the pipeline 1000 mm, the length of the pipeline 1900 m, the speed of water 1.02 m / s, the pressure loss in the pipeline 29 m, the absolute viscosity of the water at t = 10 ^o C, μ0.013 Pz. the volume of water in the pipeline 1900 • 0.785 = 190 m ³ , the processing time in the pipeline 0.52 hours

Время обработки в трубопроводе: 1900:1,02=1870 с=0,52 ч. В осветленной воде содержание взвешенных веществ составляло 2,5 мг/л.The specific energy consumption for mixing water in the flocculation chamber, which is a water conduit:

Processing time in the pipeline: 1900: 1.02 = 1870 s = 0.52 hours. In clarified water, the content of suspended solids was 2.5 mg / L.

 Thus, at these values of the parameters of water treatment in the pipeline, a sufficiently deep clarification of water in the sumps is provided. High pressure losses in the pipeline and, accordingly, the velocity gradient is explained by high hydraulic resistance due to significant deposits and fouling of the walls of the pipeline by the shell.

 The proof of compliance of the proposed invention with the requirement of industrial applicability may be as follows.

 The proposed method can be used in the treatment of turbid waters to obtain drinking water or technical quality.

 The possibility of implementing the invention in its implementation is reflected in the information section of the application, confirming the possibility of implementing the method.

 The proposed method in its implementation ensures the achievement of a technical result, which consists in optimizing the process of aggregation of suspended water in muddy water and improving its deposition in sedimentation tanks.

 Thus, the present invention meets the requirement of industrial applicability.

Claims (2)

1. A method for treating turbid waters by treatment with a cationic flocculant in a feed pipe, characterized in that the flocculant is introduced into the pipe or into the water before it is fed into the pipe used to mix and aggregate suspended solids at a distance of 500-60,000 m from the settling tanks with a speed gradient of pipeline 68 346 s ^{- 1} and processing time 0.13 33 hours  2. The method according to claim 1, characterized in that if there are pumps on the pipeline for additional water rises, the flocculant is introduced in front of one of them.

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