RU2439001C1 - Method of treating waste water - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used to treat household waste water or waste water with similar composition to household waste water, concentrated with organic contaminants. In order to realise the method, initial waste water undergoes mechanical treatment with extraction of dispersed mechanical impurities. The obtained water undergoes anaerobic treatment with content of dissolved oxygen not higher than 1 mg/l, followed by aerobic treatment using free-flowing sludge with concentration of 4-6 g/l with content of dissolve oxygen of 2-4 mg/l. After intermediate settling, the formed water-sludge mixture undergoes floatation in the presence of a bioreagent containing a culture of Zoogloea bacteria and Chlorella algae, immobilised on a metal support, followed by final settling. The obtained treated water is taken for decontamination. The residue after intermediate and final settling, which contains active sludge, is recirculated for anaerobic treatment. The excess active sludge undergoes aerobic stabilisation, followed by mechanical drying. The method is realised in a single block-modular structure, fitted with aeration, airlifting and recirculation systems.

EFFECT: invention enables to cut treatment time and volume of the formed residues, increase degree of purification of waste water from contaminants to the maximum allowable concentration set for water bodies for fishing purposes.

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Description

The invention relates to the field of wastewater treatment, in particular to methods of multi-stage biological treatment, and can be used for the treatment of household wastes concentrated in organic pollution and wastewater close to them.

Numerous wastewater treatment methods are known, including multistage anaerobic-aerobic treatment using both attached and suspended microflora.

A known method of deep biological treatment of wastewater from nitrogen of ammonium salts in an installation divided into four successively alternating anaerobic and aerobic zones, according to which 60% of the initial wastewater is directed to the first anaerobic zone, 40% to the third anaerobic zone, and the return activated sludge after settling recycle in the first and third zones in the ratio of 100% and 100%, respectively, of the volume received for wastewater treatment / RF Patent No. 2185338, C02F 3/30, 2002 /.

The disadvantages of this method are limited functionality, since it is aimed at wastewater treatment from nitrogen of ammonium salts and does not contribute to the removal of phosphates, as well as a significant amount of facilities on which it is implemented.

The known method of multi-stage wastewater treatment, according to which in the first stage the wastewater is aerated, in the second it is subjected to intermediate clarification, in the third stage it is finally aerated, and in the fourth stage it is additionally precipitated, while all the treatment steps are carried out in one basin separated by partitions to the corresponding zones, partitions are made with the possibility of movement in order to change the volume of zones. The method further includes a filtration step / Patent RF 2121981, C02F 3/00, 1998 /.

The disadvantages of this method are the low degree of wastewater treatment, which leads to the need to use an additional filtering stage, as well as the complexity of the design, due to the presence of movable partitions with outlet openings.

A known method of deep biological wastewater treatment in an installation divided into four series-connected zones using anaerobic and aerobic conditions, followed by separation of activated sludge and treated water by settling and removal of activated sludge and purified water, while wastewater treatment in the first two zones of the installation lead under anaerobic conditions with stirring using microflora attached to an inert loading material reinforced with metal, in the absence of dissolved acid sort in the first zone and the concentration of dissolved oxygen in the second zone, not exceeding 1.0 mg / l, the cleaning in the third and fourth zones is carried out under aerobic conditions, while the cleaning in the third zone is carried out using microflora attached to an inert loading material, when the concentration of dissolved oxygen is 2-3 mg / l, and the purification in the fourth zone is carried out using free-floating microflora while maintaining an excess of dissolved oxygen more than 4.0 mg / l, the purified water after settling is divided into two streams, one and which in an amount not less than 50% of the total amount of purified water is fed to the first zone and the second is directed to advanced treatment under aerobic conditions using microflora boot attached to an inert material / RF Patent No. 2225368, C02F 3/30, 2004 g. /.

The disadvantage of this method is the use at several stages of processing immobilized on an inert loading material microflora, which significantly increases the cost of the process due to the need for periodic regeneration of the load.

The technical result obtained from the use of the proposed method is to increase the degree of wastewater treatment from organic compounds, suspended solids, as well as nutrient compounds of nitrogen and phosphorus to the maximum permissible concentrations (MPC) established for fishery reservoirs, as well as reducing the processing time and volumes of precipitation formed.

The technical result is achieved due to the fact that in the method of wastewater treatment, the initial wastewater is subjected to preliminary mechanical treatment with the extraction of coarse and finely dispersed mechanical impurities, the wastewater purified from mechanical impurities is subjected to anaerobic treatment with a dissolved oxygen content of not more than 1 mg / l followed by aerobic processing using free-floating activated sludge with a concentration of 4-6 g / l with a dissolved oxygen content of 2-4 mg / l and an intermediate lag The water-sludge mixture formed during the intermediate sedimentation is flotated in the presence of a bioreagent containing cultures of bacteria Zoogloea and algae of the genus Chlorella immobilized on a metal carrier, followed by final sedimentation, after the final sedimentation, the purified water is sent for disinfection, and the residue after intermediate and sedimentation containing activated sludge is recycled for anaerobic treatment, and excess activated sludge is subjected to aerobic stabilization with following mechanical dewatering, the anaerobic and aerobic treatment, flotation, as well as intermediate and final sedimentation and aerobic stabilization is carried out in a single modular structure provided with aeration systems, airlifts and recycling.

The drawing shows a flow chart of the proposed wastewater treatment, where 1 is a sewage pumping station, 2 is the feed water for treatment, 3 is a mechanical grill, 4 is a storage averager, 5 is a sand trap, 6 is an anaerobic treatment zone, 7 is an aerobic zone treatment, 8 - intermediate sump, 9 - flotator with bioreagent 10, 11 - final sump, 12 - biological treatment unit, 13 - disinfection device, 14 - sludge containing activated sludge, 15 - recirculated activated sludge, 16 - excess activated sludge , 17 - aerobic stable Isator, 18 - device for mechanical dewatering of sediments.

The method is as follows.

From the sewage pumping station 1, the initial waste water is supplied 2 to the mechanical grid 3, where coarse particulate matter is retained. The wastewater purified from coarse impurities is accumulated in the drive averager 4 to average the flow rate of the wastewater supplied to biological treatment. From the averager-accumulator 4, the wastewater is fed into a sand trap 5, where it is cleaned from fine mechanical impurities, and then into the anaerobic treatment zone 6 of the biological treatment unit 12. In the anaerobic treatment zone 6, the wastewater purified from sand and coarse floating impurities is mixed with recirculated activated sludge 15 with a dissolved oxygen content of not more than 1 mg / l. In the presence of heterotrophic microorganisms, partial restoration of the oxidized forms of nitrogen, partial oxidation of the carbon component of organic substances, and partial consumption of phosphates occur. From the anaerobic treatment zone 6, the purified water is supplied to the aerobic treatment zone 7, in which free-floating activated sludge with a concentration of 4-6 g / l is used with a dissolved oxygen content of 2-4 mg / l. In the aerobic treatment zone 7, an increase in activated sludge biomass occurs and a selective species composition of autotrophic microorganisms is formed, with almost complete oxidation of ammonium nitrogen, as well as oxidation of the remaining part of organic nitrogen. Water sequentially purified under anaerobic and aerobic conditions using heterotrophic and autotrophic microorganisms, respectively, is separated in the intermediate sump 8 from activated sludge. The water-sludge mixture is fed to a flotator 9 equipped with a bioreagent 10, which is a metal carrier on which cultures of Zoogloea bacteria and Chlorella algae are immobilized. In flotator 9 in the presence of bioreagent 10, phosphate is removed. The bacterial culture Zoogloea is a bacterial component of bioreagent 10, and the culture of algae of the genus Chlorella is a microalgal component of bioreagent 10. Immobilization of both components on a metal carrier allows one to obtain a two-component bioreagent for removing phosphates.

The water-sludge mixture freed from phosphates is sent for final sedimentation to the sump 11, from which the purified water is sent for UV disinfection 13, and the settled activated sludge together with activated sludge after intermediate settling 14 is recycled 15 for anaerobic treatment, excess activated sludge 16 is subjected to anaerobic stabilization 17, and then served on a mechanical dehydration 18. Mechanical impurities can also be fed to a plant for mechanical dewatering of sediments from preliminary mechanical cleaning .

Anaerobic and aerobic treatment, flotation, as well as intermediate and final sedimentation and aerobic stabilization are carried out in a single block-modular design 12, equipped with aeration, airlift and recirculation systems. The use of biological treatment unit 12 provides the implementation of the proposed method for wastewater treatment in a single block module due to the constructive combination of all stages of the process, which makes the treatment plant more compact and less difficult to manage. Depending on climatic conditions, the biological treatment unit can be installed in the production room, in an open area, if necessary, with a lightweight shelter.

Examples of the method.

Example 1

Domestic wastewater with a flow rate of 400 m ³ / day or 16.6 m ³ / h, containing 213 mg / l of suspended solids, 124 mg / l of organic matter, 23 mg / l of ammonium nitrogen, 10 mg / l of phosphate is directed to cleaning according to the proposed technology with the following parameters at each stage of cleaning:

- mechanical cleaning on grids with 6 mm openings is due to the retention of coarse particulate matter. The content of suspended solids after the gratings was 174 mg / l, the cleaning efficiency at this stage is 18.3%;

- mechanical cleaning of fine impurities on sand traps. The content of suspended solids after sand traps was 64 mg / l, the cleaning efficiency at this stage was 36.7%;

- biological treatment with alternating anaerobic and aerobic conditions with free-floating sludge with its content of 4.8 g / l for 4.5 hours. The cleaning efficiency was 98% from organic substances and 98.6% from ammonia nitrogen.

The composition of biologically treated wastewater:

organic matter 2.9 mg / l, ammonium nitrogen 0.3 mg / l, phosphates 3.2 mg / l.

A water-sludge mixture with a concentration of activated sludge of 4.8 g / l is sent for clarification for 2.5 hours, followed by flotation in the presence of a bioreagent containing cultures of bacteria Zoogloea and algae of the genus Chlorella immobilized on a metal carrier, and final clarification to exclude removal suspended solids with treated wastewater.

The composition of the treated and clarified wastewater: the content of organic substances in terms of BOD is ₅ 2.23 mgO ₂ / l, suspended solids 4.3 mg / l, ammonium nitrogen 0.3 mg / l, phosphates 0.2 mg / l, nitrites 0 , 02 mg / l, nitrates 9.1 mg / l, which corresponds to the established standards when dumping them into a fishery reservoir.

Bacterial contamination is practically absent in wastewater treated with a high dose of free-floating sludge. The treated wastewater is sent for disinfection by UV irradiation, however, the dose and intensity of exposure are minimal.

Example 2

Wastewater from a holiday village with a flow rate of 100 m ³ / day or 4.16 m ³ / h, containing 119 mg / l of suspended solids, 78 mg O ₂ / l of organic substances, 12 mg / l of ammonium nitrogen, 4.2 mg / l of phosphates are sent for purification according to the proposed technology with the following parameters at each stage of purification:

- mechanical cleaning on grids with 6 mm openings is due to the retention of coarse particulate matter. The content of suspended solids after the gratings was 104 mg / l, the cleaning efficiency at this stage is 12.6%;

- mechanical cleaning of fine impurities on sand traps. The content of suspended solids after sand traps was 49 mg / l, the cleaning efficiency at this stage was 52.8%;

- biological treatment with alternating anaerobic and aerobic conditions with free-floating sludge with its content of 5.6 g / l for 3.5 hours, intermediate sedimentation, biological treatment using bioreagent containing cultures of Zoogloea bacteria and algae of the genus Chlorella, immobilized on a metal carrier, and final flotation treatment with the removal of treated water and sludge.

The cleaning efficiency was 97.8% from organic substances, and 97.5% from ammonia nitrogen.

The composition of the treated wastewater:

organic substances 2.4 mgO ₂ / l, ammonium nitrogen 0.3 mg / l, phosphates 0.2 mg / l.

A water-sludge mixture with a concentration of activated sludge of 5.6 g / l is sent for clarification for 2.5 hours using intermediate sedimentation, flotation purification in the presence of a bioreagent containing cultures of Zoogloea bacteria and Chlorella algae immobilized on a metal carrier for cleaning from phosphates and final sedimentation.

The composition of purified and clarified wastewater: the content of organic substances in terms of BOD is ₅ 2.2 mgO ₂ / L, suspended solids 3 mg / L, ammonium nitrogen 0.3 mg / L, phosphates 0.2 mg / L, nitrites 0.02 mg / l, nitrates 9.1 mg / l, which corresponds to the established standards when dumping them into a fishery reservoir. Bacterial contamination is practically absent in wastewater treated with a high dose of free-floating sludge. The treated wastewater is sent for disinfection using UV irradiation, however, the dose and intensity of exposure are minimal.

The advantages of the proposed method of wastewater treatment:

- high cleaning efficiency and resistance to changes in composition, concentration of contaminants, runoff temperature;

- the compactness of structures based on the biological treatment process using a bioreagent;

- reliability of the process and equipment;

- a decrease of more than 10 times, or, in some cases, the complete exclusion of excess sludge, depending on the composition of the wastewater entering the treatment;

- low energy consumption due to the exclusion of the initial sedimentation of wastewater at the stage of mechanical treatment and additional systems of deep post-treatment at the final stage using feed materials and their washing systems;

- achievement of established standards for the discharge of treated wastewater into surface water bodies of fishery purpose.

Thus, the proposed method of wastewater treatment allows to increase the degree of wastewater treatment from organic compounds, suspended solids, and nutrient compounds of nitrogen and phosphorus to the maximum permissible concentrations (MPC) established for fishery reservoirs, as well as to reduce the treatment time and the volume of generated precipitation.

Claims (1)

A method of wastewater treatment, characterized in that the source wastewater is subjected to preliminary mechanical treatment with the extraction of coarse and finely divided mechanical impurities, the wastewater purified from mechanical impurities is subjected to anaerobic treatment with a dissolved oxygen content of not more than 1 mg / l followed by aerobic treatment using free-floating activated sludge with a concentration of 4-6 g / l with a dissolved oxygen content of 2-4 mg / l and intermediate sedimentation, formed in In the process of intermediate sedimentation, the water-sludge mixture is flotated in the presence of a bioreagent containing cultures of bacteria Zoogloea and algae of the genus Chlorella immobilized on a metal carrier, followed by final sedimentation, after the final sedimentation, the purified water is sent for disinfection, the precipitate after intermediate and final sedimentation, containing sludge is recycled for anaerobic treatment, and excess activated sludge is subjected to aerobic stabilization followed by mechanical treatment zvozhivaniem, wherein anaerobic and aerobic treatment, flotation, as well as intermediate and final sedimentation and aerobic stabilization is carried out in a single modular structure provided with aeration systems, airlifts and recycling.

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