RU2013382C1 - Sewage water cleaning method and device - Google Patents

Abstract

FIELD: cleaning of domestic and agricultural sewage waters. SUBSTANCE: method involves physical-chemical and biological cleaning of water by coagulation, settling, flotation, filtration and aeration. Aeration is conducted by blowing off ammonia or by streaming in two stages. At the first stage silt and water mixture is urged to be continuously circulated to provide maximum surface area of contact between water to be cleaned and air flow. At the second stage nozzle is introduced into water flow to facilitate nitrification of ammonia nitrogen on nozzle surface under the action of aerobic bacteria. Upon completion of aeration, nozzle is introduced into cleanable water flow and additional amount of water is poured in anaerobic conditions, with additional water being cleaned from organic contaminants only partially to provide nutrient medium for anaerobic bacteria, which facilitate denitrification of water after aerobic cleaning of water. Device has a succession of interconnected aerating reactors, which are positioned downstream of ammonia blow-off column. Each reactor has nozzle and circulation system. Terminating reactor has pipeline for supplying partially cleaned water from ammonia blow-off column to reactor. EFFECT: increased efficiency in cleaning sewage waters. 4 cl, 3 dwg, 2 tbl

Description

 The invention relates to physico-chemical and biological treatment of domestic and agricultural wastewater with a view to their use for technical water supply.

 A known method of wastewater treatment [1] of pig breeding complexes, including primary sedimentation, two-stage treatment in aeration tanks with intermediate secondary sedimentation and subsequent flotation. The method is feasible only in open tanks, which occupy a large territory and are a source of bad smell. In addition, the cleaning process in open tanks depends on seasonal and climatic variations. The duration of the process due to the limited surface area of contact of the treated water with air is quite large and is several days.

Closest to the claimed is a method of wastewater treatment, including coagulation, sedimentation, aeration, filtration and blowing of ammonia [2]. In this case, coagulation is carried out with a 10% solution of milk of lime until a pH of 11.5 - 11.7 is created. The sedimentation necessary for the deposition and separation of calcareous sediment lasts 1.5-2 hours. The need to prepare a solution of milk of lime of a certain concentration, the need for the delivery of reagents and the problems of their storage make inconvenience and complexity of the prototype method. Aeration with view to ammonia stripping is effected by passing through the cleaned water, heated to 90 wherein ^a, an appropriate quantity of air flow. After blowing, a recarbonization operation is necessary to remove calcium introduced during liming by precipitating it with carbon dioxide and neutralizing its hydroxide. The recarbonization operation does not provide complete purification and, at the same time, lengthens and complicates this process. The presence of residual impurities determines the next cleaning operation - filtering. In this case, expanded clay and anthracite are selected as the filtration material. Filtration channels formed by these materials, on the one hand, do not provide a high degree of separation of residual impurities from water, and, on the other hand, are the reason for the long duration of filtration: from 12 to 24 hours. In addition, the periodic clogging of these channels necessitates periodic water-air washing, for which the cleaning process has to be interrupted periodically.

 A known installation [2] for implementing this method. The installation contains a coagulator connected in series, a first settling tank, an ammonia stripping column, a recarbonization unit made in the form of two saturators and a second settling tank between them to remove calcium carbonate, and a filter in the form of a metal column filled with anthracite and expanded clay and equipped with a pump for air-water washing filter.

 Serially connected to the filter is a radiation neutralization unit containing an ionizing radiation source, in particular an electron accelerator of the ILU or ELV type. For each water treatment plant of this type, an accelerator with a capacity of 20 kW is required. The specificity of the specified ionizing source and its danger to human health greatly limit the possibilities of using the specified method and installation. In addition, the design of the filter does not allow to reduce the duration of the filtration and does not provide a sufficiently high degree of wastewater treatment, which, along with the settling tanks, in which the water should be for a long time and which also do not ensure the completeness of its purification, an ammonia stripping column that consumes all air spent on the installation, and saturators for recarbonization, consuming additionally supplied carbon dioxide and requiring additional time and energy costs - in total I do not allow t ensure high performance and efficient use of air, as well as increase the degree of water purification.

 The purpose of the invention is to increase the degree of purification of water and the use of air.

 In the method of wastewater treatment, including coagulation, settling, filtering and ammonia blowing, coagulation is carried out by electrocoagulation using iron electrodes, aeration is carried out by jet aeration after ammonia blowing in two stages, at the first of which the contact surface of the air with the water to be purified is created by the sludge-water mixture the distribution of which by volume is supported by recirculation. For repayment, air is used to blow off ammonia, and in the second stage, the surface is created by introducing a nozzle into the stream of purified water and forming a biofilm on its surface. The flow rates of air and water and the number of nozzles are selected so that the rates of biofilm formation and self-oxidation are equal. After aeration, water is passed under anaerobic conditions through a nozzle with a biofilm, and partially purified water is used as a carbon-containing substrate. The flow of water to be filtered at the time of clogging of the pores of the filtration channels is directed perpendicular to the direction of filtration.

 Due to the activation of bacterial culture growth, both autotrophs, which intensify the processes of nitrification of ammonium nitrogen, and heterotrophs, which contribute to the denitrification and oxidation of carbon-containing substances, the processes at all stages of aerobic-anaerobic treatment are intensified by introducing iron ions into the purified water as an activator.

 At the first stage of aeration blasting, the formation of activated sludge is intensified, which, due to mixing by recirculation and blast aeration, forms a sludge-water mixture at the indicated stage, distributed by the recirculation stream throughout the entire volume of this zone and therefore providing accelerated water purification.

 At the second stage of water purification by jet aeration, due to the introduction of a nozzle into the stream of purified water and, thereby, the creation of a developed surface in it, in combination with the introduction of iron ions, favorable conditions have been created for the formation of a biofilm on it, which ensures the oxidation of organic contaminants and the complete nitrification of ammonium nitrogen moreover, the speed of the process and, therefore, the intensification and degree of water purification is determined by the thickness of the biofilm, since the amount of oxygen penetrating into the biofilm depends on it a. The thickness of the biofilm is determined by the rate of its growth and self-oxidation, which are maintained equal during the cleaning process and are determined by the number and specific surface of the nozzle and the flow rates of the treated water and aeration air, as well as the degree of initial water pollution.

 The nitrified ammonia nitrogen contained in the water after jet aeration is denitrified by a known anaerobic treatment in the presence of carbon-containing substances. The use of partially purified water ammonia stripping as the indicated substances is new. This ensures additional purification without additional reagents and, therefore, increasing the degree of purification of water in a simpler way than the prototype.

 At the filtration stage, a change in the direction of the flow of purified water when clogging the filtration pores from longitudinal to transverse to the pore channels provides both mechanical washing away of residual contaminants adhering to the filter walls and the absorption of residual liquid from the pores into the flow of purified water and, therefore, automatic removal of impurities . Due to this, the filtering operation does not require any special time or special measures for cleaning or replacing the filter and therefore provides additional intensification and simplification of the whole water treatment process as a whole.

 The proposed method can be carried out in an installation that contains a coagulator, sedimentation tank, filter, ammonia stripping column and a sludge collector and which, according to the claimed technical solution, is additionally equipped with an aerobic-anaerobic processing unit connected in series with the ammonia stripping column, made in the form of a series of connected reactors with built-in jet aerators, the first of which is made together with an ammonia stripping column and equipped with a recirculation system, and the rest are made with a coiled surface in the form of a nozzle for a biofilm, the last reactor being connected to the outlet of the ammonia stripping column.

 The filter is located in the upper part of the ammonia stripping column and is made in the form of horizontally arranged tubes with porous walls, the pores of which open into the drain of the specified column. The ends of the tubes are connected on one side with a nozzle connected through a pump and a flotator to an electrocoagulator, and on the other hand, with a valve that is sensitive to pressure increase and located on the drain line to the sludge collector.

 The installation allows you to combine electrocoagulation in the treatment of domestic and agricultural wastewater when using iron electrodes with jet aeration in the conditions of a developed contact surface of aeration air with purified water when using a stream of air directed to ammonia blowing for defoaming and automatic self-cleaning during filtration of filtration channels that intensifies and increases the degree of water purification and the degree of air usability. Achieving this goal is ensured by creating favorable conditions for the growth of bacterial culture in accordance with the properties inherent in the proposed method.

 The increase in plant productivity and the degree of water purification are due to the fact that automatic filter cleaning is provided during the operation of the installation, due to which the process of water purification as a whole is stabilized. In addition, the water purification process is further stabilized by the destruction of the foam from the first jet aerator, which is due to its integration with the ammonia blowing column, as well as the sequential placement of aerobic-anaerobic processing reactors along the flow of the purified water after the electrocoagulator and, thereby, providing the possibility of continuous introduction in the aeration zone of the activator resulting from electrocoagulation - iron ions, and a large contact surface of the treated water with aeration air, for which at the first stage of jet aeration, the recirculation system continuously ensures mixing of the sludge-water mixture and, thus, its distribution over the entire volume of the working space. The nozzle of the second stage reactors provides aerobic conditions for water treatment with the aeration system turned on, and the nozzle of the after-aeration treatment reactor in the absence of aeration and with the introduction of carbon-containing water creates anaerobic conditions for water purification, which is provided by the distinguishing features characterizing the location of the reactors with aerators, their type and form of execution, as well as the implementation and location of the filter.

 The method is as follows. The water to be cleaned is fed to the electrocoagulation zone, where under the influence of electric current and when using electrodes from iron, the latter transitions to an aqueous solution in the form of iron hydroxide cations. Some of these cations provide coagulation of suspended solids. Another part of the iron hydroxide ions falls into the subsequent purification zones. After coagulation, sedimentation and flotation follow. After flotation, the purified water is filtered and then ammonia is blown. After ammonia is blown off, water is aerated by jet aeration, for which it is first sent to the first stream aeration zone, where the formation of a sludge-water mixture occurs. Part of this mixture, with the aim of its continuous distribution throughout the entire working space of the first zone, is recycled, and the resulting foam is removed from the surface of the water with a stream of air directed to ammonia blowing. Then, the purified water is sent to the second aerobic treatment zone, where the nozzle is introduced into it in such an amount that, at given values of the flow rates of water and aeration air, the biofilm formation rate on the nozzle surface and its self-oxidation rate are equal. Continuously carry out jet aeration. After jet aeration, the water to be purified is passed through a nozzle with a biofilm under anaerobic conditions, and at this stage water treatment is introduced into the zone, which is only partially purified after ammonia has been blown off.

 In FIG. 1 shows a process diagram of an installation for implementing the proposed method; in FIG. 2 - node connection of the first reactor with a column of ammonia stripping; in FIG. 3 - filter with a partial tearing of the front wall and strapping.

 The installation comprises a coagulator, including an electrocoagulator 1, a foam collector 2, a thin-layer sump 3, an electroflotator 4, combined in one common housing 5 and equipped with drain valves 6, 7 and 8 with a drain line 9 and a line 10 for supplying purified water with a pump 11 to the input of the filter 12, equipped with a pressure-sensitive valve (not shown) from the opposite end inlet, actuating a valve on the drain line 13 into the column 14. A filter 12, which is a stack of tubular ultrafilters, is installed in the upper part of the column 14 and is equipped with a drain ohm 15. In its lower part, the column 14 is equipped with a pipe 16 connecting a fan 17 to the column. This lower part of the column 14 is integral with the reactor 18 (I), which is structurally placed under the column, serves as its base and is connected to it by pipes 19 and 20 , of which 19 serves as the junction of the column and the reactor, and is also equipped with a jet aerator 21 and a recirculation system in the form of a pipe 22 with a pump 23. The reactor 18 is connected by a pipe 24 to a sump 25, which has a drain line 26 and is connected to the reactor 28 with a jet aerator 29 and recycling system AI 30 with compressor 31. Reactor 28 (II) contains a nozzle 32. Reactors 33 (III) and 34 (IV) identical to it, equipped with identical recirculation systems 35 and 36 with pumps 37 and 38, are connected in series to reactor 28. Reactor 34 by pipe 39 is connected to a sump 40 having a drain line 41 at the bottom and a discharge pipe 42 provided with a pump 43 for connecting to a consumption system. Drain lines 9, 13, 26 and 41 are connected to a sludge collector 44 provided with a recirculation line 45 with a pump 46. The output of the column 14 is connected to the reactor 34 by a pipe 47.

 Installation works as follows.

 The purified water is continuously fed into the electrocoagulator 1 of the housing 5. The water separated here from the sediment as a result of electrocoagulation falls into a thin-layer sump 3, where it is separated into clarified water, sediment and foam. The foam is collected by the foam collector 2, and then the water is electroflotated in an electroflotator 4, from where the pump 11 delivers clarified water to the filter 12. When operating in the filtration mode, the valve on the drain line 13 is closed, the water to be purified passes through the walls of the tubular filters through filter channels that trap solid particles , and enters the drain 15. When the filter channels are blocked, the pressure inside the filter rises, as a result of this, a pressure-sensitive valve and a tear-off valve on line 13 are activated. the entire flow of the liquid being cleaned passes freely through the filter tangentially to the mouths of the filtration channels in the drain line 13 and into the sludge collector 44. In this case, particles that clog the filter channels are carried away by the flow of this liquid, the channels are released, the pressure in the filter drops, the shut-off valve closes the valve on the line 13, the filtering cycle is repeated, etc. Drain 15 directs the filtered water to the ammonia stripping column 14, equipped with a plane-parallel nozzle for countercurrent ammonia stripping from the water flowing down the nozzle from the upper parts of the column to the bottom. The pipe 20 delivers water from the column 14 to the reactor 18, where the pump 23 delivers air under the aerator 21 fender umbrella through the pipe 22, which in the form of a mass of bubbles floats to the surface and causes foam. The foam, which at the same time rises along the nozzle 19, is removed by a stream of air pumped by the fan 17 into the lower part of the column 14 tangentially. Here, the air pumped by the fan 17 is mixed with the air supplied by the aerator 21, and rises along the column 14 up along the surface of its nozzle. Water containing activated sludge generated in the reactor 18 enters the sump 25, which separates the water from the activated sludge. The nozzle 27 feeds water by gravity to the reactor 28 under the fender aerator 29, where the compressor 31 through the recirculation system 30 pumps air, which in the form of a mass of bubbles floats up along the surface of the nozzle 32. Reactor 33 (III) operates similarly. From the reactor 33, water enters the reactor 34 (IV), and part of the water from the outlet of the column 14 is supplied thereto by a pipe 47. The resulting water stream rises in the reactor 34 — with the recirculation system turned off and the pump 36, 38 — along the nozzle surface, covered with biofilm, and leaves the reactor 34 through pipes 39. The latter sends the purified water to the sump 40, from where the pump 43 feeds it through a pipe 42 to a consumption system, for example, to a farm manure removal system or for utilities. Sludge is removed through a drain line 41 into the sludge collector 44, where all the other drains and sediments enter through valves and drain lines 6, 7, 8, 9, 13 and 26.

 Depending on the nature of the pollution and the degree of water pollution, all jet aerators or only a part of them can be used.

 From the collection of sludge 44, its contents are periodically discharged by a pump 46 and fed for further processing, for example, into organic fertilizers.

 The following are examples of specific implementation of the proposed method.

 PRI me R 1. Livestock wastewater with an initial content of suspended solids of 40,000 mg / l, COD 50,000 mg / l, BOD 20,000 mg / l are subjected to treatment.

After coagulation, sedimentation, flotation, filtration and ammonia stripping, the total nitrogen content was 2000 mg / l, BOD 3500 mg / l. Nozzle - drainage plastic tubes with a diameter of 20 mm. With a wastewater flow of 1.25 m ³ / h or 30 m ³ / day, the air flow rate was 10.0 kg / h with a nozzle surface of 2200 m ² / m ³ in reactor II and 314 m ² / m ³ in reactors III and IV and moreover, reactor IV is anaerobic in this case. Water at the outlet of the installation contains suspended solids 100 mg / l, COD 50 mg / l, BOD 25 mg / l, total nitrogen 0-1 mg / l.

 Analogously to example 1, the inventive installation was used for wastewater treatment of communal and livestock farms in different operating modes.

 In the table. 1 shows comparative data on the effectiveness of cleaning, and in table. 2 - characterization of nitrification identification processes.

 As can be seen from the table. 1, the degree of purification compared with the prototype is increased by such indicators as COD, MIC, and the nitrogen content is brought up to 100%. In addition, the limits of the initial concentrations of pollution in both domestic (communal) and livestock wastewater have been expanded.

 The data table. 2 show that the optimal specific surface area of the nozzle for the given values of air flow rate and plant productivity provides, in contrast to the prototype, the complete removal of nitrogen from wastewater. The ability to carry out the entire cleaning process in the proposed device without additional introduction of reagents simplifies the method of wastewater treatment.

Claims (4)

 1. A method of wastewater treatment, including coagulation, sedimentation, aeration, filtration and ammonia blowing, characterized in that, in order to increase the degree of water purification and air use, coagulation is carried out by electrocoagulation using iron electrodes, aeration is carried out by jet aeration after ammonia blowing in two stages, at the first of which the contact surface of the air with the water being purified is created by means of a sludge-water mixture, the distribution of which over the working volume is supported by recirculation, they use air directed to ammonia blowing for defoaming; in the second stage, this surface is created by introducing a nozzle into the stream of purified water and forming a biofilm on its surface, and the air and water flow rates and the number of nozzles are selected so that the rates of biofilm formation and self-oxidation are equal, and after aeration, water is passed under anaerobic conditions through a nozzle with a biofilm, and partially purified water is used as a carbon-containing substrate.  2. The method according to p. 1, characterized in that the flow of water to be filtered at the time of clogging of the pores of the filtration channels is directed perpendicular to the direction of filtration.  3. Installation for wastewater treatment, containing a coagulator, sedimentation tank, filter, ammonia stripping column and sludge collector, characterized in that, in order to increase the degree of water purification and air use, it is equipped with an aerobic-anaerobic device connected in series with the ammonia stripping column processing, made in the form of a series of series-connected reactors with built-in jet aerators, the first of which is connected to the ammonia stripping column and is equipped with a recirculation system, the rest are made with nozzle d I biofilm reactor and the latter is connected to the outlet of the ammonia stripping column.  4. Installation according to claim 3, characterized in that the filter installed in the upper part of the ammonia stripping column is made in the form of horizontally arranged tubes with porous walls, the pores of which are directed toward the discharge into the column, and the ends of the tubes are connected on one side to the coagulator and, on the other hand, with a collection of sludge.

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