RU2672419C1 - Biofilm nitrification-contact denitrification system and method - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to the biofilm nitrification-contact denitrification system and method, in which environmentally acceptable technology is used, as well as water recovery technologies, and which provide the organic carbon, nitrogen and phosphorus thorough removal from wastewater. Biofilm nitrification-contact denitrification system (I) includes at least one wastewater receiver (II), through which the untreated sewage is supplied into the system, at least one selector tank (III), in which found in the sewage the precipitated organic matter mixes with the biomass, at least one intermediate clarifier (IV), in which solid organic substances are precipitated by means of bioflocculation, at least one biofilm aero tank (V), in which the nitrification process is carried out, at least one deoxygenation chamber (VI), which allows to reduce the dissolved oxygen high concentration that occurs in the biofilm aero tank (V), at least one contact denitrification reservoir (VII), in which the denitrification process is carried out, at least one aero tank (VIII), which allows to remove gaseous nitrogen released from the system as the result of the denitrification process and oxidize the residual ammonia nitrogen and / or dissolved organic matter in the wastewater, at least one secondary clarifier (IX), which allows to separate purified water from biomass, at least one purified water drain pipe (X), which is located at the secondary clarifier (IX) outlet, at least one aeration / displacement tank (XI), which allows to optimize the oxygen concentration in the aero tank (VIII) and biofilm aero tank (V) and ensure the oxygen uniform distribution, at least one excess sludge drain pipe (XII), through which generated in the system excess sludge is removed, at least one returnable sludge pipeline (XIII), which allows the deposited in the system sludge part returning to the selector tank (III) and its other part to the deoxygenation chamber (VI).EFFECT: invention enables the biofilm nitrification-contact denitrification system and method development, which provide for the organic carbon, nitrogen and phosphorus thorough removal from wastewater, eliminate necessary for denitrification the nitrates internal recycling, and allow to reduce the area occupied by the wastewater treatment plant, allow the use of almost all precipitated organic (biodegradable) substances in the denitrification process.8 cl, 2 dwg

Description

Technical field

The present invention relates to a system and method for biofilm nitrification-contact denitrification, which use environmentally friendly technology, as well as water recovery technologies, and which provide deep removal of organic carbon, nitrogen and phosphorus from wastewater.

BACKGROUND OF THE INVENTION

Nitrification is the oxidation of ammonia nitrogen in wastewater to nitrate nitrogen, which is an oxidized form of nitrogen in an aerobic environment, formed due to the activity of microorganisms. This process involves the oxidation of ammonia nitrogen to nitrite (NO ₂ ) by bacteria of the Nitromonas genus and the oxidation of nitrite to nitrate (NO ₃ ) ions by bacteria of the Nitrobacter genus. Denitrification is the conversion of oxidized forms of nitrogen (NO ₂ , NO ₃ ) to molecular nitrogen due to the activity of bacteria. Typically, nitrification and denitrification are carried out in monoil systems by selecting suitable process conditions in activated sludge systems.

In fluidized bed bioreactor (FBBR) systems, a reactor (typically plastic) is placed in the reactor to increase the capacity of activated sludge systems and to hold a larger volume of biomass in the reactor and thereby increase productivity without the need for additional volume. Typically, due to the introduction of such charges, a greater volume of biomass is retained in aerobic and / or anaerobic reactors. The load used for FBBR is added to single-core systems in which nitrification and denitrification processes occur together. The nitrification and denitrification processes are carried out using an attached biofilm growing on the loading surface.

Competition between the bacteria responsible for the nitrification and removal of organic carbon causes leaching of nitrifying bacteria due to the relatively low rate of their reproduction and growth. Since the bacteria that carry out the nitrification process are in the same environment with heterotrophic bacteria that remove organic carbon, they cause oxidation of organic carbon under aerobic conditions, resulting in a loss of denitrification ability. In particular, in urban wastewater, where the rate of nitrification is very low, this situation leads to a loss of nitrogen removal efficiency or the need to select large-volume reactors.

To ensure denitrification in conventional single-wire systems, high internal recycling (nitrate) ratios are required. Biological nitrogen removal in conventional systems requires 4-5-fold recycling of the input wastewater back to the anoxic reactor (the head of the bioreactor). This increases operating costs due to pumping costs. In addition, the oxidation of organic matter to CO ₂ under aerobic conditions also negatively affects the possibility of obtaining biogas from activated sludge by anaerobic digestion. In modern practice (in single-wire systems) it is impossible to separately control the processes of nitrification and denitrification, which is the main disadvantage. Nitrogen and phosphorus-containing fractions make it impossible to reuse water for irrigation.

The above problems have been overcome by the biofilm nitrification-contact denitrification system and method of the present invention.

Summary of the invention

The aim of the present invention is to provide a system and method for biofilm nitrification-contact denitrification, which provide a deep removal of organic carbon, nitrogen and phosphorus from wastewater.

Another objective of the present invention is the creation of a system and method for biofilm nitrification-contact denitrification, which eliminate the internal recycling of nitrates necessary for denitrification, and can reduce the area occupied by the wastewater treatment plant.

Another objective of the present invention is to provide a system and method for biofilm nitrification-contact denitrification, which allows the use of almost all precipitated organic (biodegradable) substances in the denitrification process.

DETAILED DESCRIPTION OF THE INVENTION

The system and method of biofilm nitrification-contact denitrification, designed to achieve the objectives of the present invention, are illustrated in the accompanying figures (Fig. 1 and Fig. 2), in which:

In FIG. 1 is a schematic view of a biofilm nitrification-contact denitrification system.

In FIG. 2 shows the steps of a biofilm nitrification-contact denitrification method.

The components shown in FIG. 1 are indicated by the following positions:

I. Biofilm nitrification-contact denitrification system

II. Sewage receiver

III. Selector tank

IV. Intermediate sump

V. Biofilm aeration tank

VI. Deoxygenation (DeOx) Chamber

VII. Contact Denitrification Reservoir

Viii. Aerotank

IX. Secondary sedimentation tank

X. Drain pipe of purified water

Xi. Aeration / mixing tank

XII. Drain pipe for waste sludge

Xiii. Return Sludge Pipeline

The method steps shown in FIG. 2, the following items correspond:

100. Contact denitrification method

101. Mixing the deposited organic matter with biomass in a selector tank (III),

102. The deposition of solid organic matter in the intermediate sump (IV) through biofloculation,

103. The implementation of the nitrification process in biofilm aeration tank (V),

104. Reducing the high concentration of dissolved oxygen in the deoxygenation chamber (VI),

105. The implementation of the denitrification process in the tank (VII) contact denitrification,

106. Oxidation of residual ammonia nitrogen and / or dissolved organic matter in wastewater in aeration tank (VIII),

107. The discharge of purified water into the secondary sump (IX) after separating it from the biomass,

108. Removing excess (excess) sludge formed in the system through a drain pipe (XII) for the removed excess sludge and delivering a part of it to the return sludge pipe (XIII).

The biofilm nitrification-contact denitrification system (I), which provides a deep level of nitrogen and phosphorus removal from wastewater, mainly includes:

- at least one wastewater receiver (II) through which untreated wastewater is supplied to the system,

- at least one selector tank (III), in which the deposited organic matter in wastewater is mixed with biomass,

at least one intermediate sump (IV) in which solid organic matter is precipitated by biofloculation,

- at least one biofilm aeration tank (V) in which the nitrification process is carried out,

- at least one deoxygenation chamber (VI), which allows to reduce the high concentration of dissolved oxygen that occurs in the biofilm aeration tank (V),

- at least one reservoir (VII) of contact denitrification, in which the denitrification process is carried out,

- at least one aeration tank (VIII), which allows you to remove gaseous nitrogen released as a result of the denitrification process from the system and oxidize residual ammonia nitrogen and / or dissolved organic matter in wastewater,

- at least one secondary sump (IX), which allows you to separate the purified water from the biomass,

- at least one drain pipe (X) of purified water, which is located at the outlet of the secondary sump (IX),

- at least one tank (XI) for aeration / mixing, which allows you to optimize the oxygen concentration in the aeration tank (VIII) and biofilm aeration tank (V), and to ensure a uniform distribution of oxygen,

- at least one drain pipe (XII) for the removed excess (excess) sludge, through which the excess sludge formed in the system is removed,

- at least one pipe (XIII) of the return activated sludge, which allows you to return part of the sludge settled in the system to the selector tank (III), and another part of it to the deoxygenation chamber (VI).

In a preferred embodiment of the present invention, a charge is used to reduce the volume of biofilm aeration tank (V) and contact denitrification tank (VII). In addition, the complete mixing of the contents of the deoxygenation chamber (VI) and the reservoir (VII) of contact denitrification is carried out using mixers.

The volume of biofilm aeration tank (V) in which the nitrification process is carried out is selected depending on the specific surface (m ² surface / m ³ loading volume) and the specific value of the filler load on nitrogen (gram of nitrogen / m ² / day).

In a preferred embodiment of the present invention, in a biofilm aeration tank (V) in which the nitrification process is carried out, a fluidized bed bioreactor and / or a fixed bed bioreactor can be used.

To prevent obstruction of the process of nitrogen gas (N ₂ ) precipitation resulting from the denitrification process occurring in the contact denitrification tank (VII), an aeration tank (VIII) is introduced into the system to remove N ₂ gas from the system and oxidize the residual dissolved organic matter and ammonia nitrogen in wastewater.

In a preferred embodiment of the present invention, the secondary sump (IX), which allows the purified water to be separated from the biomass, is also in the form of a membrane bioreactor (MBR) to remove all suspended solids (biomass) from the wastewater. Due to this, a high degree of removal efficiency is achieved. In particular, in processes involving the purification / regeneration of water, the MBR system can also be incorporated into an existing system configuration.

In a preferred embodiment of the present invention, additional aeration tank (XIII) from the aeration tank (VIII) is connected to a deoxygenation chamber (VI) for removing residual nitrogen, which is converted into an oxidized form of nitrogen.

Method (100) of biofilm nitrification-contact denitrification, providing a deep level of nitrogen and phosphorus removal from wastewater, mainly includes the steps

- mixing (101) of the organic substances present in the wastewater with biomass in the selector tank (III),

- deposition (102) of solid organic substances in the intermediate sump (IV) by biofloculation,

- the implementation of the process (103) of nitrification in a biofilm aeration tank (V),

- reduce (104) the high concentration of dissolved oxygen generated in the biofilm aeration tank (V) in the deoxygenation chamber (VI),

- implementation (105) of the denitrification process in the reservoir (VII) of contact denitrification,

- oxidation (106) of residual dissolved organic matter and ammonia nitrogen in wastewater in aeration tank (VIII),

- discharge of water (107) treated in the secondary sump (IX), after separating it from the biomass,

- removal (108) of excess sludge formed in the system through a drain pipe (XII) for the excess sludge to be removed, and delivery of its remaining part to the return sludge return pipe (XIII).

The untreated wastewater is mixed with the stream leaving the return sludge pipe (XIII) in the selector tank (III). Therefore, to remove biological nitrogen (denitrification) and excess biological phosphorus in wastewater, an organic substance such as volatile fatty acid and fermentable organic substances are used.

Solid organic matter in wastewater that is mixed in a selector tank (III) with a sludge stream exiting the return activated sludge pipe (XIII) can be deposited with high efficiency in an intermediate sump (IV). The effectiveness of the deposition and residence time in the treatment plant can (alternatively) be controlled by the addition of chemicals. This is done so that the deposited (separable) organic substances can be separated to the maximum extent from wastewater and kept in an intermediate sump (IV).

In a preferred embodiment of the present invention, a coagulant is added, if necessary, to the sedimentation stage of the solid organic substances in the intermediate sump (IV) by biofloculation (102), in order to increase the efficiency and rate of phosphorus precipitation and removal.

After settling, the concentration of organics and suspended solids in the contents obtained from the intermediate sump (IV) is low, but the contents of ammonia and phosphorus are high. Wastewater with a high content of ammonia and phosphorus is sent to biofilm aeration tank (V), in which the process of oxidation of ammonia nitrogen (NH ₄ -N) to nitrite / nitrate nitrogen (NO ₂ -N, NO ₃ -N), which is mainly These are oxidized forms of nitrogen, known as the nitrification process. As a result, bacteria can multiply in biofilm aeration tank (V). In this aeration tank (V), the oxygen concentration can be controlled using the aeration / mixing tank (XI), in which a homogeneous reactor mixture can be obtained (if necessary, using mixers). At the output of the biofilm aeration tank (V) receive a stream of wastewater with a high content of phosphorus and oxidized forms of nitrogen (NO ₂ , NO ₃ ); so that, as a result, part of this stream, having a high content of nutrients (N, P), can be used for irrigation immediately after the post-treatment step (after control filtration, etc.).

More effective nitrogen removal can be achieved by denitrification of oxidized nitrogen obtained from biofilm aeration tank (V) using precipitated biomass and organic matter from an intermediate sump (IV). The denitrification process is carried out in a contact denitrification tank (VII).

Another preferred embodiment of the present invention is the stabilization and / or dewatering of the removed excess sludge generated in the system. Due to the properties of the sludge, biogas can be obtained as a result of the process of anaerobic digestion of the latter.

The system and method of biofilm nitrification-contact denitrification, corresponding to the present invention, provide many advantages to the technologies that are used in this field of technology. First of all, the present invention allows to accommodate a wastewater treatment plant in a smaller area. On the other hand, the present invention provides a spatial advantage in urban areas where the level of nitrification is low. The internal nitrate recycling necessary for denitrification is also eliminated.

The present invention allows the use of all the separated and precipitated organic matter in the denitrification process. Fermentable dissolved organic matter can be used in denitrification and in the process of enhanced biological phosphorus removal (EBPR).

The biofilm nitrification-contact denitrification system in accordance with the present invention allows separate control of the nitrification and denitrification processes and the full adjustment of processing processes requiring improvement.

In the process of denitrification, heterotrophic microorganisms require organic carbon. In the present invention, by optimizing the use of organic carbon necessary for denitrification, biogas can be obtained from excess organic carbon in the process by stabilizing anaerobic sludge. When using biogas in gas engines, heat and electric energy can be obtained.

In addition to all of the above, increasing the resistance of nitrification bacteria to low temperatures and toxic substances through biofilm processes is one of the main advantages of the present invention.

Claims (29)

1. A biofilm nitrification-contact denitrification system that removes organic carbon, nitrogen and phosphorus from wastewater, characterized in that it contains - at least one wastewater receiver (II) through which untreated wastewater is supplied to the system, - at least one selector tank (III) to which the wastewater receiver (II) is connected and in which the deposited organic matter in the wastewater is mixed with biomass, - at least one intermediate sump (IV), located after the selector tank (III), in which solids and biomass are deposited by biofloculation, - at least one biofilm aeration tank (V) into which a stream is sent from an intermediate sump (IV) and in which a nitrification process is carried out, the stream from which contains purified water enriched with nitrogen and phosphorus and is used for irrigation after the post-treatment stage, - at least one deoxygenation (DeOx) chamber (VI), which allows to reduce the high concentration of dissolved oxygen that occurs in the biofilm aeration tank (V), while full mixing in the DeOx chamber (VI) is provided by mixers, - at least one reservoir (VII) of contact denitrification, in which the denitrification process is carried out and into which oxidized nitrogen enters from the deoxygenation chamber (VI) and a sludge stream including precipitated biomass and solid organic matter from the intermediate settler (IV), while mixing in the tank (VII) contact denitrification is provided by mixers, - at least one aeration tank (VIII), which allows you to remove gaseous nitrogen released as a result of the denitrification process, and to oxidize residual ammonia nitrogen and deposited organic matter in wastewater, - at least one secondary sump (IX), which is connected to the aeration tank (VIII) and which allows you to separate the biomass from purified water, - at least one drain pipe (X) of purified water, which is located along the flow path from the secondary sump (IX), - at least one tank (XI) for aeration / mixing, which allows you to optimize the oxygen concentration in the aeration tank (VIII) and biofilm aeration tank (V) and to ensure a uniform distribution of oxygen, - at least one drain pipe (XII) for the removed excess sludge, which directs the excess sludge collected from the secondary sump (IX) and from the bottom of the intermediate sump (IV), to the stabilization and / or dewatering process, - at least one return sludge pipe (XIII) that connects both the drain pipe (XII) for the excess sludge to be removed and the selector tank (III), and the drain pipe (XII) and the deoxygenation chamber (VI) and which directs part of the deposited sludge back to the selector tank (III) and returns another part of the deposited sludge to the deoxygenation chamber (VI), - mixers that provide complete mixing in a deoxygenation (DeOx) chamber (VI) and a contact denitrification tank (VII). 2. The system (I) of biofilm nitrification-contact denitrification according to claim 1, characterized in that to reduce the volume of biofilm aeration tank (V) and reservoir (VII) of contact denitrification, a load is used, which depends on the specific area of the biofilm loading and which depends on the daily nitrogen load supplied to nitrification. 3. System (I) of biofilm nitrification-contact denitrification according to claim 1, characterized in that in the biofilm aeration tank (V) in which the nitrification process is carried out, a fluidized-bed bioreactor and / or fixed-bed bioreactor are used. 4. The system (I) of biofilm nitrification-contact denitrification according to claim 1, characterized in that the secondary sump (IX), which allows you to separate the purified water from the biomass, is made in the form of a membrane bioreactor (MBR). 5. The system (I) biofilm nitrification-contact denitrification according to claim 1, characterized in that it contains at least one internal return pipe that connects the aeration tank (VIII) with a deoxygenation chamber (VI) for denitrification of residual nitrogen, which is formed at the outlet aeration tank (VIII) and turns into an oxidized form of nitrogen. 6. The method (100) of biofilm nitrification-contact denitrification, carried out by system (I) according to claim 1, which ensures the removal of organic carbon, nitrogen and phosphorus from wastewater, characterized in stages - mixing (101) of the deposited organic substances present in the wastewater with biomass in the selector tank (III), - deposition (102) of solid organic substances in the intermediate sump (IV) by biofloculation, - implementation (103) of the nitrification process in a biofilm aeration tank (V), - reduce (104) the high concentration of dissolved oxygen in the deoxygenation chamber (VI), - implementation (105) of the denitrification process in the reservoir (VII) of contact denitrification, - oxidation (106) of residual ammonia nitrogen and / or dissolved organic matter in wastewater in aeration tank (VIII), - discharge (107) of water treated in the secondary sump (IX), after separating it from the biomass, - removal (108) of excess (removable) sludge formed in the system through a drain pipe (XII) for the excess sludge to be removed and its part to be delivered to the return sludge return pipe (XIII). 7. The method (100) of biofilm nitrification-contact denitrification according to claim 6, characterized in that at the stage of deposition of solid organic substances in the intermediate sump (IV) by means of bioflocculation (102), a coagulant is added to increase the sedimentation efficiency. 8. The method (100) of biofilm nitrification-contact denitrification according to claim 6, characterized in that the sludge removed through the drain pipe (XII) for the removed excess sludge is sent to stabilize and / or dewater the sludge.

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