SU831138A1 - Method of cleaning sewage - Google Patents

Description

(54) METHODS OF WASTEWATER TREATMENT

The invention relates to the treatment of water, in particular the treatment of waste and salt water through their successive clarification and desalination, and can be used both for drinking water supply and for technical purposes. Water purification methods are known by pre-flotation clarification and desalination by reverse osmosis. The use of flotation for water clarification instead of settling allows a 4-8-fold increase in the rate of water purification and, accordingly, a decrease in the volume of water clarification facilities 1} and 2. The disadvantage of these methods is incomplete clarification of the treated water and, as a consequence, the formation of deposits on the membranes of reverse osmosis apparatus. There is also known a method of purifying water from the precipitated and dissolved substances by successively coagulating it, clarifying with pressure fnation and filtering, desalting with reverse osmosis, introducing air into the water to be desalted, and obtaining a stream of purified water and a concentrate stream. The insoluble gens bubbles create in the reverse osmosis apparatus a turbulent mode of movement of desalted water, which significantly reduces the level of concentrated polarization and prevents accumulation of contaminants on the surface of membranes 3. The disadvantage of this method is the complexity caused by the presence of compressor equipment and an air saturation system, and the high cost is due to the presence of a system of water saturation with dissolved air under pressure when water is clarified by a nipor flotation. The purpose of the invention is to simplify the method and increase its efficiency. The goal is achieved by returning a part of the concentrate under pressure to the pressure flotation stage and throttling it with the clarified water before displacement. The essence of the proposed method is as follows. The water to be purified is subjected to a coagulation process. The concentrate from the reverse osmosis apparatus is injected into the coagulated water through a throttling device. By reducing the pressure to atmospheric air, the dissolved air is released in the form of fine bubbles, which carry out flotation clarification of water due to the adhesion of a coagulated suspension to them. Then the water is filtered through the sand filter and, together with the air supplied to it, is subjected to reverse osmosis desalination. The introduction of air with water into the reverse osmosis apparatus in an amount exceeding its solubility, along with the turbulization of desalinated water, also ensures that the concentrate is dissolved by dissolved air under a working pressure of 25-100 kgf / cm. To carry out the process of water clarification using pressure flotation, The entrained air released from it should be at least 1% of the volume of water being clarified. In order to keep the liver of this ratio, in the case of using as a water-air solution a waste concentrate inflated with air under pressure P, the amount of concentrate returned to the pressure flotation stage should be at least% of the amount of clarified water. This ratio is derived from the solubility of air in water at a normal pressure of 20 l / m. Example The purification of natural salt water by the proposed method is carried out. Water is coagulated by its rapid displacement with a coagulant of 60 mg / l) and subsequent smooth slow mixing for 10 minutes. The coagulated water through the throttling device is let in under pressure of 25 kgf / cm concentrate in the amount of 2%, which provides

Water flow.

Oxidation,

MG / LOD

20

3.2-4.5 0.8-t1.2

70

+0.

10.7 Sa, mg-ehv / l

10.4

0-1 6-7

3-4

0.01.5-3.0

3,026.1

10.7 its flotation clarification, in which coagulated contaminants of water are collected on its surface as a dense foam layer. Then the water is filtered at a speed of 5 m / h through a sand filter and, together with air, in a 1: 1 ratio (volume by volume under normal pressure) is subjected to reverse osmosis desalination at a pressure of 25 kgf / cm. The yield of purified water is 63%, the remaining water in the form of a concentrate is discharged into the drain. A small part of the concentrate of the reverse osmosis unit, which is 2% of the amount of source water, is returned to the pre-clarification stage under pressure, where it ensures the implementation of the flotation process. The lightening effect was 93.6-95.4%. At the same time, an increase in its salt content is insignificant and does not exceed 1%. The composition of natural saline water and the results of its purification by the proposed method are given in the table. The proposed method, in comparison with the known method, simplifies the process by eliminating the operation for preparing the water-air solution and the equipment necessary for this (pumps, compressors, saturators, etc.), which, on the one hand, greatly simplifies the technical implementation of the known water treatment method the other, due to the exclusion of the above equipment and the cost of its operation, increases the efficiency and reliability of this method of water purification.

mg-eq / l

6.4

Alkalinity, mEq / l

5.1

- a 50, mEq / l

6.0

17.5

C.I, mEq / l

Total salt content, mg / l

Claims (3)

1880 Claims The method of purification of wastewater from suspended and dissolved substances by successive coagulation, clarification by pressure flotation 35 and filtration, desalting by reverse osmosis with the introduction of air into the water to be desalted and obtaining a flow of purified water and a concentrate stream that differs from method and increase its efficiency, part ;. Table continuation 6,6 6,6 1.8 13.4 4.12 5.4-6.0 4.2 2.0 7,8 7,6 18.6 2.0 18.6 18.5 6.0 44.6 1970 4630 1970 633 of the concentrate is returned to the pressure flotation stage under pressure and throttled with water to be clarified before displacement. Sources of information taken into account in the examination 1.Paten ± Japan 52-78677, cl. 13 (7) D 41, 07.07.77. 2. The patent of France No. 2326980, cl. A 23 C 21/00, 06.05.77. 3.Desal i pation, 1977, No.1-3, p.19-26.