SU814878A2 - Method of flotational purification of water - Google Patents

Description

(54) METHOD OF FLOTATION WATER TREATMENT

The invention relates to chemical technology, in particular to the treatment of natural and waste waters, and can be used to clean natural and waste waters with a high concentration of pollutants, as well as to seal excess activated sludge.

According to the main auth. No. 715496, a method of flotation water purification is known, which includes saturating the purified recirculating water under pressure with air, additional ejection of air into it, mixing with the water being cleaned and subsequent separation of the mixture under atmospheric pressure ll.

The disadvantage of this method is the relatively low rate of flotation separation and the degree of water purification from finely dispersed soils is not high enough. This is due to the fact that the purified recirculating water contains both small air bubbles (50-150 microns which are released from the supersaturated solution, as well as large bubbles (200-500 microns) formed with additional ejection of air into it. At the same time time in the treated water there are particles of pollution

varying degrees of dispersion (large and small). In the process of flotation, a part of small air bubbles adheres to large particles of pollution, which leads to a decrease in the rate of flotation separation. In addition to the 6th, that part of the small bubbles, which is fixed on the large particles, does not participate in the flotation of the small particles. As is known, the small particles are most effectively floated by the small bubbles. Therefore, the quality of water purification from finely dispersed soils is not high enough.

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The purpose of the invention is to increase the degree of purification.

This goal is achieved by the fact that before additional ejection of air into the purified recirculating water, a part of it is removed and sent to the additional flotation of the purified water.

Selection and use of part of the recirculating water before additional

5 ejection of air into it for additional flotation of the purified water allows only small air bubbles to be introduced into it. Small air bubbles are introduced into the cleaned

0 water after flotation cleaning it

recirculated water into which water was additionally ejected. This allows you to first extract large particles of contaminants from the treated water using large air bubbles, which ensures a high rate of flotation separation, and then the remaining small particles using the bubbles introduced for additional flotation. The flotation of small particles in this case occurs at a high rate, which is explained by the small weight of the small particles. In addition, due to the high efficiency of adhering of small air bubbles to small particles, impurities, the quality of purified water is improved.

The proposed flotation water purification method is carried out according to the following flow chart.

The water to be purified is fed to a flotation cell where it is mixed with purified recirculating water, which is saturated with pressurized air using an ejector, a pump, a pressure tank and an additional ejector. The floater separates the mixture under atmospheric pressure and removes large particles of contamination with large bubbles. Then, the water purified in the floater enters the other flotation device, where a part of the purified recirculating water is simultaneously taken and sent without additional ejection of air into it. In the second floater, the final separation of the mixture under atmospheric pressure and the removal of small particles of contaminants by small bubbles occurs.

Example. Excess sludge is subjected to flotation compaction with initial moisture content of 99.3-99.5%. Sludge consumption 10 l / h. Compaction is performed using purified recirculating water in an amount of 10 l / h, saturated with air under an excess pressure of 0.3-0.4 MPa. After saturation under an excess pressure, the recirculated water is divided into two streams (respectively, 7 l / h

3 l / h). Air is additionally ejected into the first stream in the amount of 4-6%. After displacing the treated water with the first stream of recirculating water and separating the mixture for 30 minutes, the moisture content of the compacted sludge is 95-96%, and the amount of suspended solids in the sub-water is 50-75 mg / l. This run-down water is mixed with the second stream and the final separation is carried out within 20 minutes. The total flotation separation time is 50 min. As a result of the additional flotation, the concentration of suspended solids in the sub-water decreases to 10-20 mg / l.

In a known method, flotation sludge compaction takes 1 hour, which is associated with a lower separation rate. At the same time, the quality of drinking water is 2-3 times worse.

The application of the proposed method allows to intensify the process of flotation separation and reduce the size of flotation units. Improving the quality of purification allows the use of purified water for reuse or recycling of water without the additional use of other methods of cleaning from highly dispersed soils. Reducing the size of flotation plants and improving the quality of treatment will save capital and operating costs.

Claims (1)

1. USSR author's certificate No. 715496, cl. C 02 C 5/00, 09/20/7G.