RU2370460C1 - Method of biological purification of natural water from organic compounds - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to biological purification of natural water from organic compounds with membrane separation. To realise the proposed method, natural water is subjected to mechanical purification, as well as activated sludge treatment in the presence of polycyclic aromatic hydrocarbons (PAH) with aeration with compressed air, membrane separation and subsequent disinfection. Activated sludge treatment of the water with addition of nitrogen and phosphorus salts is done while maintaining mass ratio permanganate demand: nitrogen: phosphorous, equal to 7.0:1.0:0.1 - 9.0:2.0:0.2. The natural water is purified while batching the PAH. ^ EFFECT: increased degree of purification, possibility of purifying natural water from organic compounds which are difficult to oxidise, as well as reduced cost of purification. ^ 2 tbl, 3 ex

Description

The invention relates to the field of biological treatment of natural waters from organic compounds with membrane separation.

A known method of biological purification of natural waters from organic compounds by treatment with activated sludge under aerobic conditions with the periodic introduction of hydrogen peroxide into biologically purified water until the concentration of the latter is 1-100 mg / l, followed by membrane separation of purified water (see JP patent No. 3221801 B2, IPC C02F 1/44, C02F 1/72, C02F 3/02, with priority dated 5.09.94, op. 22.10.02).

The disadvantage of this method is the low degree of purification from difficultly oxidized organic compounds due to the lack of the ability to extract from purified water oxidized organic compounds - metabolites.

A known method of biological purification of natural waters from organic compounds by first introducing finely dispersed activated carbon with a particle size of not more than 150 microns or fibrous activated carbon with a fiber length of not more than 150 microns into a purified water, treating a mixture of water with coal with activated sludge during aeration with solid separation and liquid phases by membrane separation. The activated sludge-activated carbon mixture separated in the separator is recycled to the biological treatment stage. Microorganisms of activated sludge and microorganisms immobilized on activated carbon contribute to the decomposition of organic compounds contained in water (see JP patent No. 3387311 B2 with priority dated April 22, 1996, published March 17, 2005, IPC C02F 1/44 (2006.1 )).

The disadvantage of this method is the low degree of purification from difficultly oxidized organic compounds - petroleum products, surfactants, etc., since with an insufficient content of nitrogen and phosphorus salts in water, the possibility of the formation of microorganisms oxidizing these substances is reduced.

A known method of biological treatment of natural water from organic compounds, the closest in purpose and technical essence to the claimed, by preliminary mechanical cleaning of coarse suspended solids, treatment with activated sludge in the presence of powdered activated carbon (PAH), which is continuously fed into the purified water in an amount of 10 -50 mg / l, by aeration with compressed air and separation of purified water from a mixture of activated sludge and PAHs on membranes with recirculation of one part of the sludge mixture with PAHs to the bio stage logical processing, and the other part of the sludge mixture with PAHs - at the stage of sedimentation with recirculation to the same stage of biological treatment. The purified water is subjected to disinfection (see JP patent No. 3168757 B2 with priority dated 02/01/93, publ. 05/21/01, IPC C02F 1/44 (2006.1)).

The disadvantages of this method are:

- low degree of purification from organic compounds and the inability to remove difficultly oxidized organic compounds, for example, petroleum products, surfactants, phenols, etc., due to the unsupported ratio of permanganate oxidizability to nitrogen and phosphorus, leading to a low rate of their oxidation, as well as the loss of sorption capacity continuously introduced activated carbon due to the fouling of its particles by microorganisms of activated sludge with the formation on the surface of the coal particles of a multilayer of activated sludge;

- the high cost of the cleaning process, due to both the continuous supply of irrationally used activated carbon, and the energy consumption for servicing recirculation cycle pumps.

According to data reproduced under comparable conditions, purified water had the following indicators: PO - 5.5 - 6.0 mg / l, petroleum products - 0.2-0.25 mg / l, SAS - 0.1-0.2 mg / l phenols - 0.01-0.02 mg / l, i.e. the quality of the purified water did not meet the requirements of SanPiN 2.1.4.1074-01 "Drinking water"; the oxidation rate was 2.0–2.5 mg / g of coal per day for PO, 0.08–0.085 mg / g of coal per day for petroleum products, and 0.9–1.0 mg / g of coal per day for surfactants and for phenols - 0.01-0.015 mg / g of coal per day. The duration of the process is 2.0-2.5 hours.

The technical result of the proposed method for the biological treatment of natural waters from organic compounds is to increase the degree of purification from organic compounds, the possibility of deep purification from difficultly oxidized organic compounds, as well as reducing the cost of the cleaning process.

The technical result is achieved by the fact that in the method of biological treatment of natural waters from organic compounds by mechanical treatment, treatment with activated sludge in the presence of powdered activated carbon (PAH) during aeration with compressed air and membrane separation, followed by disinfection, treatment of treated water with activated sludge with previously introduced into salts of nitrogen and phosphorus are carried out while maintaining the mass ratio: permanganate oxidizability: nitrogen: phosphorus - 7.0: 1.0: 0.1-9.0: 2.0: 0.2, and the process is conducted When a disposable loading of PAHs.

The method is as follows.

After mechanical treatment, the source of natural water with indicators: permanganate oxidizability (PO) - 7.0-9.0 mg / l, petroleum products - 0.25-0.5 mg / l, SAS - 0.5-0.7 mg / l, phenols - 0.04-0.06 mg / l, suspended solids - 20-30 mg / l, ammonium nitrogen - 0.01-1.9 mg / l, phosphorus - 0.05-0.19 mg / l with the introduced salts of nitrogen and phosphorus (for example, ammonium chloride, ammonium sulfate, aqueous ammonia, trisodium phosphate) in terms of nitrogen and phosphorus while maintaining the mass ratio PO: nitrogen: phosphorus - 7.0: 1.0: 0.1 - 9.0: 2.0: 0.2 is treated in a biological reactor with activated sludge in the presence of oshkoobraznogo activated carbon (PAC) provided a disposable loading it in an amount of 15-25 kg / m ³ reactor with aeration of compressed air and membrane separation. The process is carried out within 1.0-1.25 hours. The combination of the above features provides an oxidation rate of 3.5–4.5 mg / g of coal per day for PO, 0.2–0.25 mg / g of coal per day for petroleum products, and 1.5–2.5 mg / g for SAS coal per day and phenols 0.04-0.05 mg / g of coal per day.

Thus, conditions are created for the development of microorganisms immobilized on coal and on the outside of the membranes, forming a monolayer of activated sludge, not limiting the diffusion of organic hardly oxidizable substances to the surface of coal and adsorption on it. Concentration and adsorption on the surface of coal of organic compounds and difficultly oxidized organic compounds lead, due to selection and auto-selection, to the development of microorganisms with a low growth rate but intensive metabolism and, therefore, capable of deep oxidation of organic difficultly oxidized compounds adsorbed on coal. Due to the oxidation of adsorbed organic compounds, including difficultly oxidized ones, biological regeneration of coal occurs, which eliminates the need for its continuous introduction into the reactor; a high degree of purification of natural water is achieved, which meets the requirements of SanPiN 2.1.4.1074-01 "Drinking water" (see table 1, p.1-3).

While maintaining the mass ratio PO: nitrogen: phosphorus below the claimed 7.0: 1.0: 0.1, the oxidation rate of organic compounds by PO is 3.0 mg / g of coal per day, oil products - 0.15 mg / g of coal in day, surfactants - 1.2 mg / g of coal per day, phenolam - 0.03 mg / g of coal per day, respectively, the degree of purification from organic compounds and hardly oxidizable organic compounds increases, but capital and operating costs are unreasonably increased due to increase the duration of the process (see table 1, p. 4).

While maintaining the mass ratio of PO: nitrogen: phosphorus above the claimed 9.0: 2.0: 0.2, they provide an oxidation rate of PO of 5.0 mg / g of coal per day, oil products - 0.3 mg / g of coal per day, SPAS -2.6 mg / g of coal per day, phenolam - 0.06 mg / g of coal per day, there is a decrease in the degree of water purification from organic compounds and hardly oxidizable organic compounds (see table 1, p. 5), the quality of drinking water does not meet the requirements of SanPiN 2.1.4.1074-01 "Drinking water".

The water purified from organic compounds and hardly oxidizable organic compounds is separated from the mixture of activated sludge and PAHs by microfiltration on hollow fiber membranes and, after disinfection, is sent to the consumer.

Purified water has the following indicators:

Permanganate oxidizability - 4.0-5.0 mg / l, petroleum products - 0.03-0.05 mg / l; SPAS - 0.02-0.05 mg / l; phenols - 0.0008-0.001 mg / l.

Next, the purified water is subjected to disinfection.

Data indicating the advantage of the claimed parameters of the method of biological treatment of natural waters from organic compounds are shown in table 1.

From table 1 it follows that the claimed parameters ensure the quality of purified natural water corresponding to SanPiN 2.1.4.1074-01 "Drinking water", and avoiding the claimed parameters leads to a deterioration of the required parameters or significant, 1.5-1.8 times, increase in capital and operating costs.

Data indicating the advantage of the proposed method for the biological treatment of natural waters from organic compounds in comparison with the known, are shown in table 2.

Example No. 1

After mechanical cleaning into natural water with indicators: PO - 7.0 mg / L, petroleum products - 0.25 mg / L, SAS - 0.5 mg / L, phenols - 0.04 mg / L, ammonium nitrogen - 0, 01 mg / l; phosphorus - 0.05 mg / L; ammonium chloride in terms of nitrogen in the amount of 0.99 mg / L and trisodium phosphate in terms of phosphorus in the amount of 0.05 mg / L are introduced. The resulting mixture is treated in a biological reactor with activated sludge in the presence of PAHs provided that it is loaded once in an amount of 15 kg / m ^{3 of the} reactor and the mass ratio PO: nitrogen: phosphorus is 7.0: 1.0: 0.1. Aeration of the mixture is carried out with compressed air followed by membrane separation. The process is carried out within 1.0 hour. The oxidation rate for PO is 3.5 mg / g of coal per day, for petroleum products - 0.2 mg / g of coal per day, for SAS - 1.5 mg / g of coal per day and phenols - 0.04 mg / g of coal per day.

Purified water has the following indicators: permanganate oxidizability - 4.0 mg / l; petroleum products - 0.03 mg / l; SPAS - 0.02 mg / l; phenols - 0.0008 mg / l.

The purified water is subjected to disinfection.

Example No. 2

The process is carried out analogously to example 1: natural water with PO indicators - 8.0 mg / l, petroleum products - 0.35 mg / l, SAS - 0.6 mg / l, phenols - 0.05 mg / l, ammonium nitrogen - 1 , 0 mg / l; phosphorus - 0.1 mg / l, with pre-added ammonium chloride in terms of nitrogen in an amount of 0.5 mg / l and trisodium phosphate in terms of phosphorus in an amount of 0.05 mg / l is treated in the presence of PAHs in an amount of 20 kg / m ³ reactors, while maintaining the mass ratio PO: nitrogen: phosphorus - 8.0: 1.5: 0.15. The process is carried out within 1.2 hours. According to PO, the oxidation rate is 4.0 mg / g of coal per day, oil products - 0.22 mg / g of coal per day, SAS - 2.0 mg / g of coal per day, phenolam - 0.045 mg / g of coal per day.

Purified water has the following indicators: permanganate oxidizability - 4.5 mg / l; petroleum products - 0.04 mg / l; SAS - 0,035 mg / l; phenols - 0.0009 mg / l.

The purified water is subjected to disinfection.

Example No. 3

The process is carried out analogously to example 1: natural water with PO indicators - 9.0 mg / l, petroleum products - 0.5 mg / l, SAS - 0.7 mg / l, phenols - 0.06 mg / l, ammonium nitrogen - 1 , 9 mg / l, phosphorus - 0.19 mg / l, together with the introduced ammonium chloride in terms of nitrogen in an amount of 0.1 mg / l and trisodium phosphate in terms of phosphorus - 0.01 mg / l is treated in the presence of PAHs in the amount of 25 kg / m ^{3 the} reactor while maintaining the mass ratio PO: nitrogen: phosphorus - 9.0: 2.0: 0.2. The process is carried out within 1.25 hours. The oxidation rate for PO is 4.5 mg / g of coal per day, for petroleum products - 0.25 mg / g of coal per day, for SAS - 2.5 mg / g of coal per day and for phenols - 0.05 mg / g coal per day.

Purified water has the following indicators: permanganate oxidizability - 5.0 mg / l; petroleum products - 0.05 mg / l; SPAS - 0.05 mg / l; phenols - 0.001 mg / l.

The purified water is subjected to disinfection.

Only a combination of factors such as maintaining the mass ratio of permanganate oxidizability: nitrogen: phosphorus in the range of 7.0: 1.0: 0.1-9.0: 2.0: 0.2, provided by the preliminary introduction of salts of nitrogen and phosphorus and disposable loading powdered activated carbon (PAH), allows you to solve the problem - to increase the degree of purification of natural water from organic compounds and difficultly oxidized organic compounds (petroleum products, surfactants and phenols), reduce the cost of the process due to energy savings while eliminating Circulation cycles, requiring pumps, and due to the irrational use of expensive activated carbon for continuous feeding it (PAH cost to date is 105 thousand rubles per ton).

An additional advantage is the simplification of the process (as a consequence of the foregoing) and a reduction in its duration from 2.5 to 1.25 hours.

The proposed method for the biological treatment of natural waters from organic compounds and difficultly oxidized organic compounds in comparison with the known provides:

- increasing the degree of purification to indicators that meet the requirements of SanPiN 2.1.4.1074-01 "Drinking water", by ensuring unhindered diffusion of both organic and hardly oxidizable organic compounds through a monolayer of activated sludge to the surface of activated carbon with their simultaneous oxidation by microorganisms immobilized on this surface with intense metabolism;

- reducing the cost of the process by 1.5-1.8 times.

Claims (1)

The method of biological treatment of natural waters from organic compounds by mechanical treatment, treatment with activated sludge in the presence of powdered activated carbon - PAHs with aeration by compressed air, membrane separation and subsequent disinfection, characterized in that the treatment of purified water with activated sludge with nitrogen salts previously introduced into it and phosphorus is carried out while maintaining the mass ratio of permanganate oxidizability: nitrogen: phosphorus equal to 7.0: 1.0: 0.1-9.0: 2.0: 0.2, and the process is carried out with a single charge Pauz.