RU2454373C2 - Method of air cleaning - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to centralised domestic water consumption, in particular, in treatment of low-turbidity blood waters. Proposed method comprises coagulating water dirt, flocculation, settling at continuous circulation of a portion of flakes, filtration through granular packing with cyclic washing, and recovery of washing waters. Note here that dirt washed from packing is dispersed and directed in zone of mixing treated water with circulated flakes.

EFFECT: stable high quality of treatment, reduced consumption of coagulant.

2 cl, 1 dwg, 2 tbl, 1 ex

Description

Technical field

The invention relates to methods for water purification and can be used in the field of centralized drinking water supply, in particular, in the treatment of surface low-turbid colored waters.

State of the art

A method of water purification is widely known, including its coagulation followed by flocculation, settling, filtering through a granular charge with periodic washing and disposal of washing water by returning it to the purified water before it enters the sedimentation [1].

The known method is ineffective, especially when cleaning low turbid colored water in the winter, when the coagulation process (in volumetric mode) proceeds very sluggishly, and the return of the wash water to the purified water leads to the fact that the removal of flakes after settling increases. As a result, the mud load coming to the filtration increases, thereby deteriorating the technical and economic indicators of the cleaning process.

The closest to the proposed technical essence and the achieved effect is a method of water purification, including coagulating it with subsequent flocculation, settling part of the flakes in continuous recirculation mode, filtering through a granular charge with periodic washing and disposal of washing water into the treated water before coagulating it [2 ].

This method, compared with the above, provides a significant improvement in the process, which in this case does not occur in volumetric mode, but in contact coagulation mode, which contributes to the formation of flakes with a greater hydraulic size (density) and, accordingly, their better separation from water by settling.

However, this method also has a number of disadvantages: in the case when the volume of washing water exceeds 20-25% of the volume of treated water, their return to it leads to a significant deterioration of the settling process. In addition, as the amount of washing water returned to the treated water increases, the dose of coagulant increases, which is necessary for high-quality water purification.

Description of the invention

The aim of the invention is to develop such a method of water purification in which the degree of purification corresponding to modern requirements is stably and reliably achieved while improving technical and economic indicators by reducing the consumption of coagulant and increasing the amount of wash water returned to the cleaning process (i.e. recyclable).

The goal is achieved according to the invention by the fact that when coagulating water with subsequent flocculation, settling in continuous recirculation of flakes, filtering through a granular charge with periodic washing and disposal of washing water by returning it to the water to be treated, the impurities washed out of the load by washing water are dispersed and sent to the mixing zone of purified water with recycled flakes.

Preferably, the method of water purification according to claim 1 is characterized in that the dispersion of the contaminants is carried out by turbolization of the wash water stream.

Brief Description of the Drawings

1 shows a method for purifying water according to the present invention.

Example

The water of the surface water source with a color of 75-80 degrees, turbidity of 4.8-5.0 mg / l, oxidizability of 9.6-10.1 mg O ₂ / l is purified in the installation, see figure 1, including mixer 1, sump 2 equipped with a continuous flake recirculation system, a filter with a granular charge 3, a clean water tank 4 and a wash water averaging tank 5. When the unit is in operation, the water to be purified is piped through A to mixer 1, where the coagulant is introduced. Next, the water goes to the settler 2, where in the first chamber there is an intensive formation of flakes, and in the second - their deposition. The water clarified in the sump 2 is transferred to the filters 3, where it is finally cleaned, after which it is sent to the tank 4.

The contaminated filter load 3 is washed with clean water entering through the pipe B, and then the washing water with the impurities washed from the load is sent to the averaging tank 5, from where it is pumped through the pipe D to the purified water before it enters the sedimentation tank.

Several series of experiments are carried out, in each of which the water is purified both in accordance with the known method (prototype), when the wash water is introduced into the water in front of the mixer, and with the proposed one, when the wash water is introduced into the mixing zone of the water to be treated with recycled flakes. The first series - rinsing water with impurities washed out of the filter load is sent to the purified water. In this case, the volume of wash water is changed from the volume of water being treated in the range from 20 to 45%.

In this series of experiments, the residence time of water in the sump was 1.6 hours; the dose of coagulant introduced into the water is 10.0 mg / l (Al ₂ O ₃ ). The criterion for the effectiveness of the experiments was the condition that the turbidity of the water coming from the sump to the filter does not exceed 3.0 mg / L. The results of the experiments are summarized in table 1.

Table 1 Efficiency of water sedimentation at different volumes of flushing water returned to the treated water Cleaning method Turbidity of water (mg / l), sent from the sump to the filter at various% ratio of the volume of wash water returned to the treated twenty% 25% thirty% 35% 40% 45% one 2 3 four 5 6 7 famous 2.2 2,8 3.6 5,4 7.5 10.1 proposed 1.4 1,5 1.8 2.2 2,8 3.2

As follows from the results of the first series of experiments, when returning the washed water to the purified, namely to the mixing zone of the treated water with recirculated flakes, ceteris paribus, the possibility of a larger return increases significantly. This fact seems to be very important for large water treatment plants, consisting of several treatment units, since in this case it becomes possible to collect wash water from all units and direct it to mix with the treated water supplied to one unit.

The second series - the contaminants washed out of the load by washing water, either specially dispersed (the proposed method) or not dispersed, are sent to the mixing zone of the treated water with recirculated sludge. In this case, the coagulant dose is varied in the range from 10.0 mg / L to 7.0 mg / L (according to Al ₂ O ₃ ).

In this series of experiments, the residence time of water in the sump was 1.6 hours. The volume of wash water from the volume of purified water was 40%. The criterion for the effectiveness of the experiments was the condition that the turbidity of the water coming from the sump to the filter does not exceed 3.0 mg / L. The results of the experiments are summarized in table 2.

table 2 The effectiveness of water sedimentation at various doses of coagulant administered Cleaning method Turbidity of water (mg / l), directed from the sump to the filter at various doses of coagulant in mg / l (according to Al ₂ O ₃ ) 10 9 8 one 2 3 four Method without dispersing flakes in wash water 2,8 5.9 12.1 Dispersion Method 1.9 2,3 2.9

As follows from the results of the second series of experiments, the dispersion of contaminated (essentially coagulant flakes with sorbed substances extracted from water) washed out of the load with wash water and then sent to the mixing zone of the treated water with recirculated flakes contributes to the possibility of a significant reduction in the required degree of purification doses of coagulant.

Apparently, this is due to the fact that when dispersing contaminants, the destroyed flakes entering the recirculation zone contribute to a more intensive contact coagulation process (the degree of effectiveness of which directly depends on the different sizes of the particles interacting) and, accordingly, the formation of flakes with a larger hydraulic size .

The latter circumstance, in turn, ensures their best recovery from water by sedimentation.

At the same time, it was found that the most rational dispersion of contaminants washed from the load is carried out by turbolization of the wash water stream during its transportation for mixing with purified water.

Thus, the advantage of the claimed method is the intensification of the process, which improves the technical and economic indicators both by reducing the consumption of coagulant and by increasing the amount of wash water returned to the cleaning process.

Information sources

1. Building norms and rules water supply, external networks and structures, SNiP 2.04.02-84 by the USSR State Committee for Construction, M., 1985, p. 45.

2. “Utilization of washing water of filtering facilities at water treatment plants”, team of authors, St. Petersburg magazine “Water and Ecology. Problems and solutions ”, No. 1, 2000, pp. 12-13 (prototype).

Claims (2)

1. A method of purifying water, including coagulating it, followed by flocculation, settling part of the flakes in continuous recirculation mode, filtering through a granular charge, periodically washing it and disposing of the wash water by returning it to the purified water before it enters the sedimentation process, characterized in that it is contaminated washed from the load with wash water, dispersed and sent to the mixing zone of the purified water with recycled flakes. 2. The method of water purification according to claim 1, characterized in that the dispersion of contaminants is carried out by turbulization of the wash water stream.

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