RU2351551C1 - Method for purification of sewage from organic compounds, nitrogen and phosphorus - Google Patents

Abstract

FIELD: sewage treatment facilities.

SUBSTANCE: invention is related to the field of biological purification of sewage from organic compounds, nitrogen and phosphorus. To realise the method, the following hydraulically communicated stages - anaerobic, anoxic, aerobic - are performed for treatment with activated sludge with membrane separation, stage of deaeration that precedes stage of anaerobic treatment, stage of powdered activated carbon (PAC) treatment with membrane separation. Method also includes recirculation of sludge mixture from the aerobic treatment stage to stage of deaeration and recirculation of sludge mixture from anoxic stage to anaerobic stage. Purified water after serial anaerobic stage at load on activated sludge by "БПК" of 2.0-4.0 mg/g·hr and anoxic stage at load on activated sludge by nitrogen of 3.5-4.5 mg/g·hr, "БПК" of 8-13 mg/g·hr is supplied directly to the stage of aerobic treatment with membrane separation. At that load on activated sludge by nitrogen makes 0.8-1.2 mg/g-hr, by oil products - 0.5-0.7 mg/g·hr, according to synthetic surfactants - 0.16-0.22 mg/g·hr and by phenols - 0.18-0.25 mg/g·hr. At the stage of anoxic treatment 80-90% of recirculated sludge mixture is supplied from deaeration stage. Water purification with PAC is carried out at concentration of dissolved oxygen to 4.0 mg/l due to supply of compressed air and PAC concentration of 20-30 g/l at its single charging. At that load on PAC by oil products makes 0.35-0.45 mg/g·hr, by synthetic surfactants - 0.06-0.07 mg/g·hr and by phenols - 0.02-0.024 mg/g·hr.

EFFECT: method provides for increased degree of purification from nitrogen and phosphorus, wider range of removed organic compounds, process simplification and reduction of its duration.

2 tbl, 3 ex

Description

The invention relates to the field of biological wastewater treatment from organic compounds, nitrogen and phosphorus compounds by treatment with activated sludge with separation by membrane filtration.

A known method of biological treatment of wastewater from organic compounds, nitrogen and phosphorus, which consists in treating wastewater with activated sludge in three stages: the stage of anaerobic treatment of water with stirring, the stage of aerobic treatment using suspended microorganisms immobilized on a coarse polymer carrier, the membrane filtration stage on hollow fiber membranes. At the same time, the chambers where the anoxic, aerobic processes and the membrane filtration process occur are interconnected. It is planned to recirculate activated sludge from the membrane filtration stage to the anaerobic treatment stage to achieve a certain concentration of activated sludge (see patent EP No. 1484287 A1 dated January 31, 2003, published on August 7, 2003, ISM 038 dated December 8, 2004. IPC C02F 3/12).

The disadvantage of this method is the insufficiently high degree of purification from difficultly oxidized organic compounds due to the lack of a stage of purification, nitrate and phosphorus nitrogen due to the lack of separation of the process into anaerobic - to remove phosphorus and anoxic - to remove nitrate nitrogen and an increased concentration of dissolved oxygen at the anoxic stage because it is on it that the sludge mixture from the aerobic stage is saturated with oxygen, which leads to inhibition of the denitrification process.

A known method of biological treatment of domestic wastewater from organic compounds, nitrogen and phosphorus compounds in the presence of a finely divided carrier with immobilized microorganisms; purified water is treated in the denitrification zone in the presence of a finely divided carrier with denitrifying microorganisms and in the subsequent nitrification zone in the presence of a finely divided carrier with nitrifying microorganisms. The water thus treated is subjected to membrane separation. The sludge mixture from the nitrification zone is recycled to the denitrification zone (see JP patent No. 3385306 B2, with priority 02/26/98, publ. 03/10/2003, IPC С02Р 3/10, 3/34).

The disadvantage of this method is the low degree of purification from difficultly oxidized organic compounds due to the lack of a post-treatment stage, phosphorus due to the lack of an anaerobic stage designed specifically for its removal, nitrate nitrogen due to the increased concentration of dissolved oxygen in the denitrification zone, which leads to inhibition of the process denitrification.

A known method of biological treatment of domestic wastewater from organic compounds and suspended solids, which consists in preliminary removal of large mechanical impurities from the effluent from the drains, aerobic treatment of the purified water in an aeration tank with air supply to it and maintaining the concentration of activated sludge 5-50 g / l. The sludge mixture from the aeration tank is fed into the membrane separation chamber on hollow fiber membranes with a pore diameter of 0.01-1.0 μm or on membranes installed directly in the aeration tank. The sludge mixture is recycled to the head of the process. The treated wastewater is filtered through sand filters and activated carbon and then UF-irradiated for final disinfection (see patent DE No. 10105221 A1, priority 02.02.2001, published 08.08.2002, IPC C02F 3 / 12).

The disadvantage of this method is the insufficiently high degree of purification from compounds of nitrogen and phosphorus due to the lack of anaerobic and anoxic stages, designed specifically to remove these contaminants.

A known method of biological treatment of wastewater from organic compounds and suspended solids, as well as nitrogen and phosphorus compounds, which consists in the stepwise treatment of treated water with activated sludge in a biological reactor, where (depending on the composition of the wastewater) anaerobic, anoxic and aerobic conditions are maintained with varying in the direction of decreasing the load on the BOD of 0.01-1.0 kg / kg of sludge per day (mainly 0.02-0.6 kg / kg of sludge per day). The duration of the biological treatment process is 2-120 minutes (mainly 20-90 minutes). A mixture of water and activated sludge is subjected to membrane separation on hollow fiber membranes with recirculation of 5-300% of the volume of activated sludge at the stage of treatment with activated sludge and the removal of purified water (see application RU No. 2004136167 of 04/23/03 with a priority of DE of 05/10/02 g ., IPC C02F 3/06, 3/12, published on 08.27.05).

The disadvantage of this method is the lack of the ability to remove from wastewater difficult to oxidize organic compounds - petroleum products, surfactants, etc., insufficiently high degree of purification from organic compounds due to the low duration of the biological treatment process and the possibility of accumulation of decay products in the bioreactor; the latter leads to rapid clogging of the membranes and the need for frequent washing.

A known method of biological wastewater treatment from organic compounds, nitrogen and phosphorus, the closest in purpose and technical essence to the claimed, consisting in treating it at the anaerobic stage with activated sludge to remove phosphates within 10 minutes - 4 hours, at the anoxic stage - for denitrification with recirculation of the denitrified sludge mixture to the previous anaerobic stage. At the first aerobic purification stage, water is saturated with oxygen, subjecting it to aeration, and the nitrogen-rich nitrate sludge mixture is recycled to the anoxic stage; this sludge mixture is essentially combined with the sludge mixture of the anaerobic stage for denitrification. At the second anoxic stage, a further denitrification process occurs with stirring of the purified water to form elemental nitrogen. The duration of both stages of anoxic treatment is 20-90 minutes.

At the second aerobic stage, along with water treatment by aeration, membrane separation of the purified water occurs with the separation of activated sludge and cleaning the membrane surface of its particles; The sludge mixture is recycled from the second aerobic treatment stage to the deaeration stage preceding the anaerobic treatment stage to reduce the oxygen concentration in the sludge mixture. The duration of both stages of aerobic treatment is 2-10 hours.

The next stage of purification provides for continuous dosing of powdered activated carbon (PAH) and monitoring of its concentration, treatment of the treated water is carried out with mixing with PAH at a concentration of 10-15 g / l to remove difficultly oxidized organic substances with membrane separation.

The purified water is subjected to disinfection (see US patent No. 6863818 B2 with prior. 11.02.03, publ. 08.03.05, IPC C02F 3/00).

The disadvantages of this method are:

- a low degree of removal of oxidized forms of nitrogen due to inhibition of the denitrification process at the anoxic stage, due to the supply of a sludge mixture enriched with oxygen from the first aerobic stage. An increase in the concentration of dissolved oxygen in the medium over 1.0 mg / l leads to a decrease in the denitrification rate by 2–4 times at concentrations of oxidized forms of nitrogen within the MPC for a fishery reservoir;

- a low degree of phosphorus removal due to deep glycolysis of organic compounds with the formation of low molecular weight acids, accompanied by a decrease in the pH of the sludge medium, due to the anaerobic process for a sufficiently long time - 4 hours; Moreover, at low pH, both the inhibition of the nitrification processes at the aerobic and denitrification stages at the anaerobic stage of purification and the denitrification process at the anoxic stage, due to the insufficient amount of readily oxidizable organic compounds, occur. Carrying out the anaerobic treatment process for 10 minutes does not provide glycolysis, the formation of low molecular weight fatty acids necessary for phosphate-accumulating microorganisms;

- the lack of the possibility of deep removal of difficultly oxidized organic compounds, for example, petroleum products, surfactants, phenols, etc. with the indicated process parameters and the sequence of anoxic and aerobic stages;

- the duration of the process, comprising 6.5-19.5 hours;

- the complexity of the process due to its multi-stage process - the presence of two stages of aerobic treatment with recirculation of the sludge mixture from the first stage to anoxic and two stages of anoxic processing;

- unreasonably high cost of the process both due to its multi-stage nature and due to the high consumption of activated carbon during its continuous supply, due to the low efficiency of purification from difficultly oxidized organic compounds at the stage of biological treatment.

According to data reproduced under comparable conditions, the content in purified water is: BOD 3.0–4.0 mg / L, total nitrogen 15.0–16.0 mg / L, including organic nitrogen 2.0–2.4 mg / l, ammonium nitrogen - 0.8-1.2 mg / l, nitrite nitrogen 0.02-0.08 mg / l, nitrate nitrogen 10.0-12.0 mg / l, phosphorus 0.3-0, 6 mg / l, petroleum products 0.1-0.3 mg / l, SAS 0.5-0.8 mg / l, phenols 0.005-0.01 mg / l, i.e. the quality of the treated wastewater does not meet the requirements for discharge into a fishery reservoir. The duration of wastewater treatment at all stages is 6.5-19.5 hours.

The technical result of the proposed method for the biological treatment of wastewater from organic contaminants, nitrogen and phosphorus is to increase the degree of purification from nitrogen and phosphorus, expanding the range of removable difficultly oxidized organic compounds, simplifying and reducing the duration and cost of the process.

The technical result is achieved by the fact that in the method of biological wastewater treatment from organic compounds, nitrogen and phosphorus, comprising hydraulically communicated anaerobic, anoxic, aerobic treatment stages with activated sludge with membrane separation, a deaeration step preceding the anaerobic treatment step, a powder activated carbon treatment step with membrane separation, recirculation of the sludge mixture from the stage of aerobic treatment to the stage of deaeration and recirculation of the sludge mixture from the anoxic stage to anaerobic,

purified water after a successive anaerobic stage with a load of activated sludge according to BOD of 2.0-4.0 mg / g / h. and anoxic stage when the load on activated sludge on nitrogen 3,5-4,5 mg / g · h and BOD 8-13 mg / g · h. fed directly to the stage of aerobic treatment with membrane separation at a load of activated sludge for nitrogen 0.8-1.2 mg / g · h., for petroleum products 0.5-0.7 mg / g · h., for surfactant 0, 16-0.22 mg / g · h. and for phenols 0.18-0.25 mg / g · h., 80-90% of the recycled sludge mixture from the deaeration stage is sent to the anoxic treatment stage, PAH water treatment is carried out while maintaining the dissolved oxygen concentration to 4.0 mg / l per the supply of compressed air, maintaining the concentration of PAHs of 20-30 g / l with a one-time loading and loading on PAHs for oil products of 0.35-0.45 mg / g · h, for surfactants 0.06-0.07 mg / g · h and phenols 0.02-0.024 mg / g · h.

The method is as follows:

initial wastewater with the following indicators: BOD - 200-250 mg / l, total nitrogen - 30-35 mg / l, phosphorus - 3.0-4.0 mg / l, petroleum products - 10-15 mg / l, SAS - 4.0-5.0 mg / l, phenols 3.0-5.0 mg / l, suspended solids 120-150 mg / l, and the recirculated sludge mixture from the deaeration and anoxic stages is fed to the anaerobic purification stage. At the same time, at the deaeration stage, dissolved oxygen is removed, which inhibits the process at the subsequent anoxic stage, and at the anoxic stage, nitrate nitrogen is removed, the presence of which inhibits the process of biofuel removal of phosphorus.

At the anaerobic stage, in the absence of dissolved oxygen and nitrates, but in the presence of easily oxidizable organic compounds and a load of activated sludge of 2.0-4.0 mg / g · h on activated sludge, glycolysis of readily oxidizable substances is carried out until low molecular weight fatty acids are formed with the development of phosphate-accumulating microorganisms t .e. there is a process of deep biological removal of phosphorus up to 0.2 mg / l.

At this stage, when the load on activated sludge by BOD is below 2 mg / g · h. - 1.5 mg / g · h, the degree of purification of phosphorus increases slightly, but at the same time, the capital and operating costs increase and the amount of organic compounds required for the denitrification stage decreases (see table 1, p. 4).

When the load on activated sludge by BOD above 4.0 mg / g · h - 5.0 mg / g · h, there is a sharp deterioration in the degree of purification of water from phosphorus due to the low degree of glycolysis, and, consequently, the low concentration of the resulting low molecular weight fatty acids (see table 1, paragraph 5).

After completion of the anaerobic treatment, the sludge mixture is fed to the anoxic treatment stage, where up to 80-90% of the recirculated sludge mixture containing nitrates from the deaeration stage is supplied. The process of denitrification of nitrates at the anoxic stage to molecular nitrogen proceeds efficiently in the absence of dissolved oxygen, which is removed at the deaeration stage, in the presence of easily oxidizable organic compounds coming from the anaerobic stage, and with an activated sludge load of 8-13 mg / g · h by BOD and nitrogen 3.5-4.5 mg / g · h.

At this stage, when the load on activated sludge for BOD below 8.0 mg / g · h - 7.0 mg / g · h and nitrogen below 3.5 mg / g · h - 3.0 mg / g · h the degree of purification for nitrogen compounds, in particular nitrates, is increased, but at the same time, capital and operating costs increase (see table 1, p. 4).

When the load on activated sludge for BOD is more than 13.0 mg / g · h - 14.0 mg / g · h and for nitrogen over 4.5 mg / g · h - 5.0 mg / g · h, a sharp deterioration occurs purification of water from nitrogen compounds (see table 1, p. 5).

When a sludge mixture is recycled from the deaeration stage to the anoxic stage in an amount of less than 80%, the nitrate concentration in the anaerobic stage increases and the efficiency of phosphorus removal decreases; with an increase in the amount of recirculated sludge mixture above 90%, the degree of purification from phosphorus also decreases due to a decrease in the amount of activated sludge supplied to the anaerobic stage.

Next, the sludge mixture is fed to the aerobic stage with membrane separation (where oxygen is supplied), to oxidize the remaining organic compounds, including difficultly oxidized ones, and to carry out the nitrification process with a load of activated sludge on nitrogen of 0.8-1.2 mg / g h, for petroleum products 0.5-0.7 mg / g · h, for surfactants 0.16-0.22 mg / g · h and for phenols 0.18-0.25 mg / g · h.

At this stage, with activated sludge loads for nitrogen below 0.8 mg / g · h, - 0.7 mg / g · h, for petroleum products below 0.5 mg / g · h - 0.40 mg / g · h , for surfactants below 0.16 mg / g · h - 0.14 mg / g · h and for phenols below 0.18 mg / g · h - 0.12 mg / g · h, the degree of purification for nitrogen compounds increases slightly hardly oxidizable organic compounds, but at the same time capital and operating costs are unjustifiably increased (see table 1, p. 4).

With loads of activated sludge for nitrogen over 1.2 mg / g · h - 1.5 mg / g · h, for petroleum products over 0.7 mg / g · h - 0.9 mg / g · h, for surfactants over 0.22 mg / g · h - 0.4 mg / g · h and for phenols over 0.25 mg / g · h - 0.3 mg / g · h there is a sharp deterioration in the degree of purification of water from nitrogen compounds and hardly oxidizable organic compounds (see table 1, p. 5).

The duration of the aerobic stage is 2.5-4.5 hours.

Biologically purified water complies with the MPC standards for nitrogen and phosphorus compounds and has the following composition:

total nitrogen - 7.5-10.5 mg / l, incl. organic nitrogen - 1.1-1.23 mg / l, ammonium nitrogen - 0.25-0.39 mg / l, nitrate nitrogen - 6.0-9.0 mg / l, nitrite nitrogen - 0.018-0.02 mg / l, phosphorus - 0.18-0.2 mg / l, BOD - 2.0-3.0 mg / l, petroleum products - 0.4-0.6 mg / l, SAS - 0.2-0 5 mg / l, phenol - 0.06-0.08 mg / l.

Biologically purified water is separated from the activated sludge by membrane separation using hollow fiber membranes and sent to the PAH water treatment stage by mixing with membrane separation - the post-treatment stage. At this stage, the concentration of dissolved oxygen is maintained at 3.0-4.0 mg / l by supplying compressed air, the concentration of activated carbon is 20-30 g / l with a one-time loading and PAH load on oil products of 0.35-0.45 mg / g · h, for surfactants 0.06-0.07 mg / g · h and for phenols 0.02-0.024 mg / g · h.

At this stage, due to the combination of the above techniques, conditions are created for the oxidation of the organic compounds remaining in the water and the removal of difficultly oxidized organic compounds (see table 1, p.1-3).

When the PAH load for petroleum products is below 0.35 mg / g · h, 0.25 mg / g · h, for surfactants below 0.06 mg / g · h, 0.05 mg / g · h and for phenols below 0.02 mg / g · h - 0.015 mg / g · h the degree of purification from difficult-oxidizable organic compounds increases, but capital and operating costs unnecessarily increase (see table 1, p. 4).

When the load on PAHs for petroleum products is more than 0.45 mg / g · h, 0.6 mg / g · h, for surfactants over 0.07 mg / g · h, 0.08 mg / g · h, for phenols over 0.024 mg / g · h - 0.036 mg / g · h there is a decrease in the degree of purification from difficultly oxidized organic compounds (see table 1, p. 5).

The duration of the process at the stage of water treatment PAHs with membrane separation is 1.7-2.0 hours.

Purified water from hardly oxidizable organic substances is separated from PAHs by membrane separation on hollow fiber membranes and sent to discharge into fishery reservoirs.

The total duration of the wastewater treatment from organic compounds, nitrogen and phosphorus is 5.0–9.0 hours.

Purified water has the following composition:

total nitrogen - 7.0-10.0 mg / l, incl. organic nitrogen - 0.59-0.732 mg / l, ammonium nitrogen - 0.25-0.39 mg / l, nitrate nitrogen - 6.0-9.0 mg / l, nitrite nitrogen - 0.018-0.02 mg / l, phosphorus - 0.18-0.2 mg / l, BOD - 1.0-1.5 mg / l, petroleum products - 0.03-0.05 mg / l, SAS - 0.03-0.05 mg / l, phenols - 0.0008-0.001 mg / l.

Data indicating the advantage of the claimed parameters of the method of wastewater treatment from organic compounds, nitrogen and phosphorus are shown in table 1.

Example 1

The initial waste water containing: BOD - 200 mg / l, total nitrogen - 30 mg / l, phosphorus - 3.0 mg / l, petroleum products - 10 mg / l, surfactant - 4.0 mg / l, phenol - 3, 0 mg / l, suspended solids - 120 mg / l together with the recirculated sludge mixture from the deaeration stage and the anoxic stage are fed to the anaerobic stage.

At the deaeration stage, dissolved oxygen is removed, which inhibits the process at the subsequent anoxic stage, and at the anoxic stage, nitrate nitrogen is removed, the presence of which inhibits the process of biological removal of phosphorus.

At the anaerobic stage, water treatment is carried out under a load of activated sludge according to BOD of 2.0 mg / g · h with stirring in the absence of dissolved and bound oxygen. The duration of the process at the anaerobic stage is 90 minutes.

Next, the resulting mixture is fed to the stage of anoxic treatment together with 80% recirculated sludge mixture from the deaeration stage for denitrification, which is carried out in the absence of dissolved oxygen when the activated sludge is loaded with 8.0 mg / g · h of BOD and 3.5 mg of nitrogen / gh The duration of the process at the anoxic stage is 1 hour.

Next, the resulting mixture is fed to the stage of aerobic treatment for the oxidation of difficultly oxidized organic compounds and nitrification, which is carried out at a load of activated sludge with nitrogen of 0.8 mg / g · h, of petroleum products of 0.5 mg / g · h, of surfactant 0.16 mg / g · h and phenolam 0.18 mg / g · h when oxygen is supplied. The duration of the process at the aerobic stage is 4.5 hours.

Biologically purified water has the following composition:

total nitrogen - 7.5 mg / l, incl. organic nitrogen - 1.232 mg / l, ammonium nitrogen - 0.25 mg / l, nitrate nitrogen - 6.0 mg / l, nitrite nitrogen - 0.018 mg / l, phosphorus - 0.18 mg / l, BOD - 2.0 mg / l, petroleum products - 0.4 mg / l, SAS - 0.2 mg / l, phenols - 0.06 mg / l.

Biologically purified water is fed to the PAH treatment stage with membrane separation with stirring — the stage of post-treatment of hardly oxidizable organic compounds. The process is conducted with a PAH load of 0.35 mg / g · h for petroleum products, 0.06 mg / g · h for surfactants and 0.02 mg / g · h for phenols, dissolved oxygen concentration 3.0 mg / l, activated coal 20 g / l with a one-time loading. The duration of the post-treatment process is 1.5 hours.

After purification, purified water has the following composition:

total nitrogen - 7.0 mg / l, incl. organic nitrogen - 0.732 mg / l, ammonium nitrogen - 0.25 mg / l, nitrate nitrogen - 6.0 mg / l, nitrite nitrogen - 0.018 mg / l, phosphorus - 0.18 mg / l, BOD - 1.0 mg / l, petroleum products - 0.03 mg / l, surfactants - 0.03 mg / l, phenols - 0.0008 mg / l.

Example 2

The process is carried out analogously to example 1, with the following process parameters:

initial waste water containing: BOD - 225 mg / l, total nitrogen - 32.5 mg / l, phosphorus - 3.5 mg / l, petroleum products - 12.5 mg / l, surfactant - 4.5 mg / l, phenols - 4.0 mg / l, suspended solids - 125 mg / l together with the recirculated sludge mixture from the deaeration stage and the anoxic stage are fed to the anaerobic stage.

At the anaerobic stage, water treatment is carried out under a load of activated sludge according to BOD of 3.0 mg / g · h in the absence of dissolved and bound oxygen. The duration of the anaerobic treatment process is 1 hour.

At the stage of anoxic treatment, together with 85% of the recirculated sludge mixture, denitrification is carried out in the absence of dissolved oxygen at a BOD load of 10 mg / g · h and nitrogen 4.0 mg / g · h. The duration of the anoxic treatment process is 0.7 hours.

At the stage of aerobic treatment, the process is carried out under a load of activated sludge on nitrogen 1.0 mg / g · h, on BOD 5.0 mg / g · h, on petroleum products 0.6 mg / g · h, on surfactant 0.2 mg / g · h and phenolam 0.21 mg / g · h when oxygen is supplied. The duration of the aerobic treatment process is 3.0 hours.

Biologically purified water has the following composition:

total nitrogen - 9.5 mg / l, incl. organic nitrogen - 1.181 mg / l, ammonium nitrogen - 0.3 mg / l, nitrate nitrogen - 8.0 mg / l, nitrite nitrogen - 0.019 mg / l, phosphorus 0.19 mg / l, BOD - 2.5 mg / l, petroleum products - 0.5 mg / l; SPAS - 0.4 mg / l, phenols - 0.07 mg / l.

At the stage of PAH water treatment - aftertreatment - the process is carried out at a PAH load of 0.4 mg / g · h for petroleum products, 0.065 mg / g · h for surfactants and 0.022 mg / g · h for phenols, 3.5 mg / ml dissolved oxygen concentration l, activated carbon concentration of 25 g / l with a one-time loading. The duration of the post-treatment process is 1.8 hours.

After processing the PAH water - aftertreatment - purified water has the following composition:

total nitrogen - 9.0 mg / l, incl. organic nitrogen - 0.681 mg / l, ammonium nitrogen - 0.3 mg / l, nitrate nitrogen - 8.0 mg / l, nitrite nitrogen - 0.019 mg / l, phosphorus - 0.19 mg / l, BOD - 1.2 mg / l, petroleum products - 0.04 mg / l, SAS - 0.04 mg / l, phenols - 0.0009 mg / l.

Example 3

The process is carried out analogously to example 1, with the following process parameters:

initial waste water containing: BOD - 250 mg / l, total nitrogen - 35 mg / l, phosphorus 4.0 mg / l, petroleum products - 15 mg / l, surfactant - 5.0 mg / l, phenols - 5.0 mg / l, suspended solids - 125 mg / l together with the recirculated sludge mixture from the deaeration stage and the anoxic stage are fed to the anaerobic stage.

At the anaerobic stage, water treatment is carried out at a load of sludge according to BOD of 4 mg / g · h in the absence of dissolved and bound oxygen. The duration of the anaerobic treatment process is 0.5 hours.

At the stage of anoxic treatment, together with a 90% recirculated sludge mixture, denitrification is carried out in the absence of dissolved oxygen, with a sludge load of 13 mg / g · h in the BOD and 4.5 mg / g in nitrogen. The duration of the anoxic treatment process is 0.3 hours.

At the stage of aerobic treatment, the process is carried out under a load of activated sludge on nitrogen 1.2 mg / g · h, on petroleum products 0.7 mg / g · h, on surfactant 0.22 mg / g · h and phenol 0.25 mg / g · h when applying oxygen. The duration of the aerobic treatment process is 2.2 hours.

Biologically purified water has the following composition:

total nitrogen - 10.5 mg / l, including organic nitrogen - 1.09 mg / l, ammonium nitrogen - 0.39 mg / l, nitrate nitrogen - 9.0 mg / l, nitrite nitrogen - 0.02 mg / l, phosphorus - 0.2 mg / l, BOD - 3.0 mg / l, petroleum products - 0.6 mg / l, SAS - 0.5 mg / l, phenols - 0.08 mg / l.

At the stage of PAH water treatment - aftertreatment - the process is carried out with a PAH load of 0.45 mg / g · h for petroleum products, 0.07 mg / g · h of surfactants and 0.024 mg / g · h of phenols, 4.0 mg of dissolved oxygen / l, activated carbon concentration of 2 g / l with a one-time loading. The duration of the post-treatment process is 2.0 hours.

After purification, purified water has the following composition:

total nitrogen - 10 mg / l, including organic nitrogen - 0.59 mg / l, ammonium nitrogen - 0.39 mg / l, nitrate nitrogen - 9.0 mg / l, nitrite nitrogen - 0.02 mg / l, BOD - 1.5 mg / l, phosphorus - 0.2 mg / l, petroleum products - 0.05 mg / l, SAS - 0.05 mg / l, phenols - 0.001 mg / l.

Data indicating the advantage of the proposed method in comparison with the known, are shown in table 2.

Only a combination of factors such as: the proposed sequence of hydraulically communicated stages, the implementation of the aerobic treatment process with membrane separation immediately after successive processes of deaeration, anaerobic and anoxic treatment with recirculation of the sludge mixture from the deaeration stage to the anoxic treatment stage, the selected parameters are reasonable: load on activated sludge , the amount of recycled activated sludge, the oxygen regime at each stage, allows us to solve the problem - increase l the degree of purification from nitrogen and phosphorus, to expand the range of difficultly oxidized organic compounds to be removed and to simplify and reduce the cost of the process both by eliminating the aerobic and anoxic stages with recycling the sludge mixture to the last from the aerobic stage, and by eliminating the introduction of additional fresh PAHs at the processing stage them.

The proposed method of water purification in comparison with the known provides:

- increasing the degree of purification for total nitrogen to 7-10 mg / l compared to 15-16 mg / l and for phosphorus to 0.18-0.2 mg / l compared to 0.3-0.6 mg / l;

- expanding the range of removed specific difficultly oxidized organic compounds and increasing the degree of purification from them, in particular by surfactant to 0.03-0.05 mg / l compared with 0.5-0.8 mg / l in the known method, as well as on phenols and petroleum products (see table 2);

- simplification, reduction of the duration of the process to 5.0-9.0 hours compared with 6.5-19.5 hours and cost reduction due to the proposed sequence of processing steps, their modes and parameters, the exclusion of one aerobic and one of the two anoxic stages , exclusion of the introduction of an additional amount of fresh powdered coal at the stage of processing PAHs - stage of post-treatment; the cost of the process is reduced by 1.5-2 times.

From table 1 it follows that the claimed parameters ensure the quality of purified water for compounds of nitrogen, phosphorus, BOD and hardly oxidizable organic compounds, the corresponding maximum concentration limit for discharge into fishery reservoirs, the exorbitant values lead to a deterioration of the required indicators or significant, 1.5- 2 times increase in capital and operating costs.

Claims (1)

A method of purifying water from organic compounds, nitrogen and phosphorus, including hydraulically communicated anaerobic, anoxic, aerobic stages of treatment with activated sludge with membrane separation, a deaeration stage, preceding anaerobic treatment stage, a stage of processing powdered activated carbon (PAH) with membrane separation, recirculation of the sludge mixture from the stage of aerobic treatment to the stage of deaeration and recirculation of the sludge mixture from the anoxic stage to anaerobic, characterized in that the water to be purified after successive the erobic stage when the load on activated sludge according to BOD is 2.0-4.0 mg / g · h and the anoxic stage when the load on activated sludge on nitrogen is 3.5-4.5 mg / g · h, according to BOD is 8-13 mg / g · h fed directly to the stage of aerobic treatment with membrane separation at a load of activated sludge for nitrogen 0.8-1.2 mg / g · h, for petroleum products 0.5-0.7 mg / g · h, for surfactant 0.16-0.22 mg / g · h and for phenols 0.18-0.25 mg / g · h, 80-90% of the recycled sludge mixture from the deaeration stage is sent to the anoxic treatment stage, PAH water treatment is carried out while maintaining dissolved oxygen concentration up to 4.0 mg / l per second em supply of compressed air, maintaining the concentration of PAHs of 20-30 g / l with a one-time loading and loading on PAHs for oil products of 0.35-0.45 mg / g · h, for surfactants 0.06-0.07 mg / g · h and phenols 0.02-0.024 mg / g · h.