RU2264993C1 - Method of purification of oily waste waters - Google Patents

Abstract

FIELD: methods of oily waste waters purification.

SUBSTANCE: the invention is pertaining to the processes of oily waste waters purification and may be used for purification of the waste waters up to requirements of maximum permissible concentration (MPC) standard. The method provides for in series purification of the waste waters by sedimentation, an electrochemical filtration, a sorption with removal of oil products into a collector and the suspended substances - onto the sludge drying beds. At that the sedimentation is conducted in two stages: at the first stage they separate the film-type and the low-dispersed drips of petroleum, at the second stage for extraction of the highly dispersive solid and liquid fragments apply a reagent-settler possessing a high density, a bio-coagulant - active sludge, then the water is purified by a pressure flotation, and for an afterpurification of water perform a coalescence of the fine drips of petroleum on the surface of the hydrophobic grainy material. Extraction of the drips of petroleum conduct by filtration through a layer of an oil product, in which an electrical field is formed in direction of the electric field lines. Then conduct a water filtration through the cathode with the following deep purification by the electrochemical filtration, a sorption, a natural afterpurification in ponds. It is preferable in the capacity of the reagent-settler to use sediments from a tailing dump of a mining-and-dressing combine works. The method ensures reduction of time of a water purification due to combination of in time and space of separate stages of the multistage process, a decreased metal input in equipment realizing the method, an increased effectiveness of purification and stabilization of quality of the purified waste waters.

EFFECT: the invention ensures reduction of time of a water purification, a decreased metal input in equipment realizing the method, an increased effectiveness of purification and stabilization of quality of the purified waste waters.

5 cl, 1 dwg, 1 tbl

Description

The invention relates to processes for the purification of oily wastewater and can be used for wastewater treatment LPPS to the requirements of the MPC. Waste oily water can be purified from oil products and suspended solids that can be extracted by oxidation or coagulation.

Known ship installation for the purification of oily water, including a sump, hydrophobic filter, electroflotator, contact filters loaded with granular material (burnt rock) [1]. Before filtering, coagulant produced by the coagulator is introduced into contact filters. The disadvantages of the device is that the filtration of water is carried out in a mineral granular material, which does not provide the sorption of fine particles.

The closest technical solution is the method of purification of oily wastewater [2]. The method consists in purifying oil-containing water in a sump, a three-product hydrocyclone, a polymer-loaded filter, an electrochemical filter, and a sorption filter.

The disadvantages of this method is that sedimentation is carried out in one step without precipitating reagents and a bio-coagulant, the absence of pressure flotation and a combined device with hydrophobic filtration, the application of an electric field and coalescence does not prevent the passage of negatively charged and highly dispersed drops of oil, increases the intensity of the equipment, and the absence natural tertiary treatment in ponds does not provide for stabilization of the quality of treated wastewater.

The problem solved by the invention is to reduce the time of water treatment by combining in time and space the individual stages of a multi-stage process, reducing the metal consumption of the equipment that implements the method, increasing the treatment effect and stabilizing the quality of treated wastewater.

This problem is solved by the fact that in the method of purification of oily wastewater, including sequential wastewater treatment by sedimentation, electrochemical filtration, sorption with the removal of petroleum products in the accumulator, suspended solids - to sludge sites, according to the invention, sedimentation is carried out in two stages, and the first stage is separated film and low-dispersed oil droplets; in the second stage, a high-density precipitating reagent, bioco, is used to extract highly dispersed solid and liquid particles shulant, which is used as activated sludge from biological sewage facilities, then water is purified by pressure flotation from fine solid and liquid particles, and for water purification, coalescence of small droplets and liquid filtration in an electric field is carried out with the extraction of oil droplets moving in the direction of the electrode plates, connected to a positive source of current and water passing through the gap between the negatively polarized plates, and subsequent deep cleaning by electrochemical filtration, sort btsiya, natural tertiary treatment in ponds.

The advantage of the proposed method compared to the prototype is the reduction of metal equipment and stabilization of the quality of treated wastewater.

The present invention meets the criterion of "industrial applicability", confirmed by a combination of the following conditions:

The invention is intended for use in industry in the treatment and disinfection of wastewater LPPS (linear pumping booster stations).

The drawing shows a schematic diagram of the water technology of the proposed method.

The scheme contains a sewage pumping station (SPS) of industrial wastewater 1 (LSW), a sump 2 (OTS), a sump 3 (OTS), a storage tank converted into a sump 4 (OTS), a flotator 5, a coalescing-hydrophobic filter 6, an electrochemical filter 7, sorption filter 8, four-section settling pond 9, three-section sludge pits 10, reagent farm 11 (PX), oil sludge collector 12, sewage pumping station for domestic wastewater 13 (SPS), biological treatment facilities 14 (BF), contact chamber 15 pure water tank 16 (RF C), a sewage pumping station for treated wastewater 17, a reagent farm 20, a pumping station 21.

Purification of industrial oily water is as follows. Pump station 1 sends wastewater to sedimentation tanks 2, 3, where preliminary separation of oil and suspended solids by sedimentation takes place. The oil accumulated in the upper part is removed by oil gathering device by gravity to the reservoir of captured oil 12, the sediment is removed under hydrostatic pressure to the sludge pads 10.

Next, water is supplied to a sump with a thin-layer module 4. To accelerate the sedimentation process of the finely dispersed particles remaining in the water, bio-coagulation with activated sludge from secondary sumps BOS 14 and the use of a precipitating reagent are provided. As a biocoagulant, activated sludge from secondary settling tanks of biological sewage treatment plants at a concentration of 1 ... 4 g / l is used. Sludge from the tailings of the mining and processing plant at a concentration of 1 ... 2 g / l with a density of about 6000 kg / m ^{3 of the} following composition is used as a precipitating reagent:

iron oxides - 50-60%

zinc oxides - 2-5%

copper oxides - 1-2%

calcium carbonate - the rest.

Sludge from sump 4 is discharged to sludge pads 10.

Water from the sump 4 is fed by gravity to the pressure flotator 5 for fine cleaning. The flotator is equipped with a clarified liquid recirculation system, a saturator, a reagent farm for dosing coagulant into the purified water, and a system for removing sludge. To increase the effect of water treatment, the flotator is made three-section with sequential treatment of water in each section. The input of recirculated water saturated with air is carried out in each section. Sludge is removed to the sludge pads 10, oil sludge to the collected oil reservoir 12.

Filters 6, 7, 8 are made in the pressure version, so the water after the flotator is pumped by the pump station 21. The coalescing-hydrophobic filter 6 is a combined device. It combines the methods of coalescence and liquid filtration in an electric field. Water is supplied to the central cylindrical part of the apparatus, coaxial to the housing, filled with a coalescing granular charge. As a hydrophobic granular material, granular polystyrene or a fluoroplast of a fraction of 2 ... 5 mm is used. In a coalescing charge, oil droplets are deposited on the hydrophobic surface of the granular material, their coalescence, the formation of film oil on the grain surface, the flow of oil from grain to grain in the vertical direction under the action of hydrodynamic forces, the coalescence of film oil with a layer of oil filling the upper part of the apparatus. In the oil layer (hydrophobic liquid layer) are electrode plates connected to the positive pole of the DC power source. Negative electrode plates are located in water. Electric field strength 300 ... 600 V / m.

The oil-water emulsion emerging from the coalescing charge passes through the gap between the negatively polarized plates. In this case, negatively charged drops of oil are inhibited by the electric field and do not pass together with the filtrate into the annular gap formed by the apparatus body and the coalescing chamber.

The clarified water is further treated in an electrochemical filter 7 and a sorption filter 8. The filter 7 is filled with three layers of granular materials. The upper layer consists of electronegative aluminum granules, the middle layer consists of granules of mineral filtering material, for example calcite, and the lower layer consists of electropositive activated carbon granules. When water is filtered from top to bottom due to the electrochemical current arising due to the potential difference between the upper and lower layers, aluminum dissolves and hydrolyzes. When filtering water in a mineral granular material, contact coagulation occurs, and water is purified from residual pollutants.

Post-treatment of water from dissolved hydrocarbon oil fractions occurs in a sorption filter, where the oil concentration reaches the MPC _px .

The purified water is discharged into the biological pond 9, which is a buffer structure. In it, water is saturated with oxygen. At the exit from the biological pond, the water is mixed with purified household water, after which it undergoes post-treatment in natural conditions in biological ponds 9, is disinfected in the contact chamber 15, accumulates in the RFC 16, and is pumped to the outlet by the pumping station 17.

Dehydrated sludge from sludge sites 10 is transported by road to compost site 19, where they are stabilized and composted.

Examples of the method.

Model solutions containing suspended solids and crude oil were purified. The content of petroleum products in the treated water according to the purification steps is given in table 1.

Table 1.
The content of petroleum products in the treated water according to the stages of purification (the content of petroleum products in the source water is 500 mg / l, the suspended matter content is 700 mg / l) Sampling point Concentration Concentration petroleum products, mg / l suspended solids mg / l Sump No. 1 250 350 Sump No. 2 100 140 Flotator 40 56 Coalescing hydrophobic 4 6 filter Electrochemical 0.4 0.6 filter Sorption filter <0.05 <0.5

The table shows that the quality of the treated wastewater at the outlet of the treatment plant reaches MPC _px .

Literature

1. RF patent 2091132, MKI B 01 D 36/04. Ship installation for the purification of oily waters / Nazarov V.D., Shapensky A.M., Nasyrov Yu.N. et al. / B.I. No. 27 - 1997.

2. RF patent 2156740, MKI C 02 F 1/40. The method of purification of oily wastewater. / Nazarov V.D. / B.I. No. 27 - 2000.

Claims (5)

1. The method of purification of oily wastewater, including sequential wastewater treatment by sedimentation, electrochemical filtration, sorption with the removal of petroleum products in the accumulator, suspended solids - to sludge sites, characterized in that the sedimentation is carried out in two stages, and at the first stage, film and low-disperse are separated drops of oil, at the second stage, a high-density precipitating reagent, a biocoagulant, which is used as a precipitate, is used to extract highly dispersed solid and liquid particles activated sludge from biological sewage facilities, then water is purified by pressure flotation from fine particulate and liquid particles, and for the purification of water, small droplets of oil are coalesced on the surface of a hydrophobic granular material and liquid filtration is carried out in an electric field to extract oil droplets moving in the direction of the electrode plates, connected to a positive source of current and water passing through the gap between the negatively polarized plates, and the subsequent deep cleaning of the electrochemical th filtration, sorption, additional purification in natural ponds. 2. The method according to claim 1, characterized in that as a reagent-precipitator used precipitation from the tailings of the mining and processing plant in a concentration of 1-2 g / l of the following composition: Iron oxides 50-60% Zinc oxides 2-5% Copper oxides 1-2% Calcium carbonate Rest 3. The method according to claim 1, characterized in that as a biocoagulant use activated sludge from the secondary settling tanks of biological sewage structures in a concentration of 1-4 g / l. 4. The method according to claim 1, characterized in that granular polystyrene and a fluoroplastic fraction of 2-5 mm are used as a hydrophobic granular material. 5. The method according to claim 1, characterized in that they create an electric field with a strength of 300-600 V / m