RU2320547C1 - Waste water treatment process - Google Patents

Abstract

FIELD: waste water treatment.

SUBSTANCE: invention is directed to reuse liquid wastes, in particular, to treat high-concentration waste water from alcohol plants processing grain-potato raw material. Waste water containing large amount of organic pollutants is subjected to primary settling to remove suspended substances and then cleaned in the first-step air tank wherein waste water is aerated for 0.72 of 24 h while maintaining activated sludge dose at the level of 4.2 g/L. Thereafter, waste water is cleaned in the second-step air tank wherein waste water is aerated for 1.13 of 24 h while maintaining activated sludge dose at the level of 2.8 g/L. Finally, waste water is fed to settler to remove activated sludge.

EFFECT: enhanced efficiency of treatment of waste waters from alcohol plants and considerably decreased amount of organic pollutants getting into surface aqueous reservoirs with food industry waste waters.

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Description

The present invention relates to the field of liquid waste disposal, in particular to the treatment of wastewater highly concentrated wastewater from distilleries that process grain and potato raw materials.

A known method of wastewater treatment of alcohol production by physico-chemical methods (see RF patent No. 2151172, 2000). It provides for the purification of contaminated wastewater of alcohol production with the removal of suspended, colloidal and dissolved mineral and organic impurities using coagulation, reverse osmosis and hot air blowing. However, this method has several disadvantages: the use of coagulants slightly reduces the BOD, the performance is limited when using reverse osmosis membranes, the operation of weapons is much more complicated, the energy intensity of the cleaning process is increased, and, as a result, the investment and operating costs are increased. It was found that organic impurities contained in highly concentrated wastewater can be removed using reverse osmosis membranes with a pore diameter of not more than 10-15 · 10 ^-10 m. Currently, organic pollution of wastewater, especially in the production of alcohol, is so great that special attention is paid to highly efficient methods of wastewater treatment under extreme loads on the treatment system.

The closest, in fact, is the wastewater treatment technology introduced at the Strusovsky distillery for the treatment of wastewater from a grain-processing plant (see the book Alcohol Technology, authors Marinichenko V.A., Smirnov V.A. et al. Moscow, 1981 city, pp. 404-406), including mechanical wastewater treatment followed by biological treatment in aeration tank. At this enterprise, effluents of the first category — heat-exchange waters — are sent to a pond, and then to a river. Industrial-polluted effluents of the second category are collected in a receiving well located on the territory of the plant, from which they flow by gravity to the treatment facilities. The mixture of all dirty effluents has the following physicochemical parameters: pH 7.6-7.8, transparency 2 cm, odor 3 points, suspended solids concentration 300-400 mg / l, BOD 250-680 mg / l, COD 340-850 mg O ₂ / L.

The technological scheme provides for mechanical and single-stage biological wastewater treatment. Coarse mechanical impurities are separated on a grate, then successively the wastewater enters the sand trap and primary sump to separate sand and coarse organic impurities. The precipitate from the sand trap is periodically removed to the sand pad for drying.

To prevent the growth of filamentous bacteria and the resulting swelling of activated sludge, the effluent is sent to a pre-aerator, to which excess activated sludge from the secondary sump is returned, and urgent water is aerated for 20 minutes. In this case, flocculation and adsorption of finely dispersed impurities by active sludge occur, which are secreted in the sump.

Sludge from sedimentation tanks is periodically removed to the sludge site. The clarified liquid enters the buffer tank, designed to stabilize the amount of effluent sent to the aeration tank, where the wastewater is subjected to biological treatment with activated sludge. The concentration of activated sludge is maintained at 3-3.5 g / l. The biological treatment effect is 96% for suspended solids and 95% for BOD ₅ .

The treated effluents enter the secondary sump, designed to stay in it for 2.5 hours. Activated sludge is removed from the sludge chambers of the sump using an airlift and fed to a pre-aerator and aeration tank.

Then the water is mixed in a mixer with chlorine water and sent to a contact tank, where the water is disinfected with chlorine. After holding in this apparatus for 30 minutes, the purified water is discharged into the river.

Water treated according to this technological scheme has the following indicators: pH 7.8-8.0, transparency 30 cm, odorless, suspended solids concentration 5-20 mg / l, BOD ₅ 8-20 mg O ₂ / l, COD 35- 40 mg O ₂ / L.

An analysis of this method shows that it is quite effective as applied only to wastewater, the quality indicators of which do not exceed the above. However, the use of such a treatment method in relation to highly concentrated wastewater with BOD values of more than 4000 mg O ₂ / l and COD more than 7000 mg O ₂ / l of distilleries does not give the expected treatment effect.

The technical task is to create a method of biological wastewater treatment of distilleries processing grain potato raw materials using a two-stage aerobic scheme and processing the resulting waste into feed products.

The technical result is an increase in the efficiency of wastewater treatment of distilleries, as well as a significant reduction in the amount of organic pollutants entering surface water bodies with wastewater from the food industry.

It is achieved by the fact that waste water containing a large amount of organic contaminants was subjected to initial sedimentation to remove suspended solids, fed to the first stage aeration tank, where it was aerated for 0.72 days, and a dose of activated sludge of 4.1 g / l was maintained; then fed to the sump to remove part of the activated sludge. Next, the water was fed into the second stage aeration tank, where it was aerated for 1.13 days and a dose of activated sludge of 2.8 g / l was maintained; then water was fed into the sump to remove activated sludge

One of the main indicators of the degree of harmfulness of wastewater discharged into water bodies is the need for oxygen to oxidize the organic substances contained in them. With a large number of effluents discharged into a reservoir with a low flow rate, these compounds are oxidized by atmospheric oxygen. All this has a negative effect on the oxygen balance of the water body, and, in general, affects the quality of water resources.

Example 1 of a specific implementation of the method.

The wastewater of the distillery was supplied to a two-stage biological treatment model plant with preliminary sedimentation. The experimental setup consisted of models of aeration tanks with pneumatic aeration up to 10 l and models of sludge separators in the form of vertical settlers. Additional aeration of wastewater contributed not only to the oxidation of wastewater, but also their biological treatment, since as a result of this, the vital activity of aerobic microorganisms that decompose organic compounds is intensified.

Water supply and circulation of activated sludge in the system was carried out using a multi-channel metering pump. The installation model was a technological scheme of a two-stage wastewater treatment. Each stage had its own sludge separator; therefore, at all stages operating under flowing conditions, a biocenosis of activated sludge microorganisms was formed, which was most adapted to incoming contaminants and used a multicomponent substrate for its life activity. This significantly intensified the biological treatment process. The species composition of microorganisms of activated sludge was determined by the qualitative and quantitative composition of organic wastewater pollution.

The wastewater treatment process was controlled by BOD _{5 of the} source and purified water, the dose of sludge, the ash content of the sludge, the concentration of dissolved oxygen, and the sludge index. The considered parameters were determined by standard methods.

The quality of the initial runoff had the following indicators: BOD 4500 mg / l, COD 9800 mg / l, suspended solids 180 mg / l.

The treatment option under consideration was characterized by the following features. The volumes of the first and second stages of purification were 8.6 and 13.6 l, respectively, the aeration time was 0.72 days and 1.13 days, the concentration of activated sludge in aeration tanks was maintained on average 4.1 g / l and 2.8 g / l . The wastewater flow rate in the model plant remained constant and amounted to 0.012 m ³ / day.

The specified cleaning mode allowed to achieve the following results. After the first stage of biological treatment, BOD of wastewater decreased by 70%, COD by 60%. At the output, the main indicators of BOD and COD were 45 mg O ₂ / L and 180 mg O ₂ / L, respectively. Other indicators of wastewater quality, such as nitrogen compounds, did not exceed the maximum permissible values.

The data obtained testified to the possibility of discharge into the city sewer for subsequent treatment and discharge into a water body.

Example 2

The wastewater of the distillery entered the two-stage biological treatment model plant with preliminary sedimentation. The experimental setup consisted of models of aeration tanks with pneumatic aeration up to 10 l and models of sludge separators in the form of vertical settlers. Additional aeration of wastewater contributed not only to the oxidation of wastewater, but also their biological treatment, since as a result of this, the vital activity of aerobic microorganisms that decompose organic compounds is intensified.

Water supply and circulation of activated sludge in the system was carried out using a multi-channel metering pump. The installation model was a technological scheme of a two-stage wastewater treatment. Each stage had its own sludge separator; therefore, at all stages operating under flowing conditions, a biocenosis of activated sludge microorganisms was formed, which was most adapted to incoming contaminants and used a multicomponent substrate for its life activity. This significantly intensified the biological treatment process. The species composition of microorganisms of activated sludge was determined by the qualitative and quantitative composition of organic wastewater pollution.

The wastewater treatment process was controlled by BOD _{5 of the} source and purified water, the dose of sludge, the ash content of the sludge, the concentration of dissolved oxygen, and the sludge index. The considered parameters were determined by standard methods.

The quality of the initial runoff had the following indicators: BOD 4500 mg / l, COD 9800 mg / l, suspended solids 180 mg / l.

The treatment option under consideration was characterized by the following features. The volumes of the first and second stages of purification were 13.6 and 8.6 l, respectively, the aeration time was 1.13 days and 0.72 days, the concentration of activated sludge in aeration tanks was maintained on average 4 g / l and 2.6 g / l. The wastewater flow rate in the model plant remained constant and amounted to 0.012 m ³ / day.

The specified cleaning mode allowed to achieve the following results. After the first stage of biological treatment, BOD of wastewater decreased by 90%, COD by 80%. At the output, the main indicators of BOD and COD were 21 mg O ₂ / L and 90 mg O ₂ / L, respectively. Other indicators of wastewater quality, such as nitrogen compounds, did not exceed the maximum permissible values.

The data obtained indicated the possibility of discharge into the water body without further treatment.

It is known that the biological treatment of concentrated wastewater of food enterprises is most reliably described by the equations of enzymatic reactions. The obtained experimental data allow us to analyze the process of two-stage biological wastewater treatment of distilleries in the absence of oxygen limitation of the process.

For the considered examples, the constants of the equations of enzymatic reactions were calculated. The calculation of constants was carried out on the basis of the analysis of data from two cleaning schemes. The obtained constants K _m and V _max are 132 mg / l and 50 mg / g hour for the first stage and 14.7 mg / l and 29.67 mg / g hour for the second stage, respectively.

The obtained values allow to optimize the wastewater treatment process of this production. In the process of research, the optimal treatment regimes were identified, namely, the residence time of wastewater in the first and second stages, comprising 29.37 hours and 6.86 hours, respectively. Calculated volumes of structures for the implementation of the scheme. The possibility of using excess activated sludge for feed purposes has been identified.

The experiment was conducted at the Astrakhan Distillery OJSC.

An analysis of experimentally obtained indicators and calculated optimization parameters of the treatment process show that two-stage treatment of highly concentrated wastewater is the simplest and less capital-intensive way of biological treatment of wastewater containing a large amount of organic pollutants.

Claims (1)

A method of wastewater treatment, including mechanical wastewater treatment followed by biological treatment in an aeration tank, characterized in that the waste water containing a large amount of organic impurities is subjected to primary sedimentation to remove suspended solids, purified in the first stage aeration tank, where the wastewater is aerated for 0.72 days, while maintaining a dose of activated sludge in an amount of 4.1 g / l, then wastewater is supplied to the sump, where part of the activated sludge is removed, then the wastewater is similarly treated in aeration tank II tupeni, where the wastewater is aerated for 1.13 days and a dose of activated sludge of 2.8 g / l is maintained, after which the wastewater is fed to a sump to remove activated sludge.