Iron-driven biological treatment system and process for domestic wastewater

Abstract

The application discloses a kind of based on iron driving domestic sewage biological treatment system and process, belong to sewage biological treatment field.Processing device includes the water inlet tank and two reaction pools connected in sequence by pipeline, two reaction pools are in sequence dissimilatory iron reduction reaction pool and Feammox reaction pool, two reaction pools are equipped with iron source dosing port and effluent weir, fill the sludge with iron reduction function in dissimilatory iron reduction reaction pool, fill the sludge with Feammox function in Feammox reaction pool.The application couples dissimilatory iron reduction, iron autotrophic ammonia oxidation and iron autotrophic denitrification technology, realizes the synchronous removal of organic matter, nitrogen, phosphorus in wastewater, and the processing cost is low, reduces the emission of greenhouse gas.

Description

Technical Field

[0001] This invention belongs to the field of biological wastewater treatment and relates to an iron-driven biological treatment system and process for domestic wastewater. Specifically, it relates to a biological wastewater treatment system and process that combines dissimilar iron reduction, Fe(III) / Fe(II) cycle-driven iron ammonia oxidation (Feammox) coupled with nitrate-type ferrous oxidation (NDFO), and adsorption crystallization phosphorus removal. Background Technology

[0002] Nitrogen and phosphorus pollution in water bodies is a global problem, while excessive discharge of organic matter makes the treatment of black and odorous water bodies an urgent issue. Currently, biological treatment processes are the preferred choice for large-scale wastewater treatment. Traditional domestic wastewater treatment relies on a two-stage process (nitrification-denitrification) to remove nitrogenous pollutants while simultaneously removing organic matter and phosphorus. However, nitrification requires additional aeration, increasing energy consumption, and insufficient carbon sources lead to incomplete denitrification. The introduction of additional organic matter increases the economic burden, and achieving both deep carbon control and deep denitrification is difficult. Furthermore, traditional treatment technologies result in high greenhouse gas emissions and large sludge treatment and disposal volumes. Compared to heterotrophic denitrification technologies, autotrophic denitrification avoids certain drawbacks. Feammox, as a novel denitrification technology, utilizes Fe... 3+ Oxidized NH4 + -N is N2, accompanied by some NO X – The generation of -N, and Fe 3+ Reduced to Fe 2+ At the same time, Fe 2+ It can react with NO in wastewater X – The -N reaction, known as nitrate-dependent ferrous oxidation (NDFO), is an iron-autotrophic denitrification technology. The coupling of these two processes can remove ammonia nitrogen and nitrate from wastewater, while simultaneously achieving Fe... 2+ and Fe 3+ The cycle. Besides pollutants like nitrogen, wastewater also contains a large amount of organic matter. Dissimilatory iron reduction is a process that couples carbon and iron, reducing Fe through the oxidation of organic matter. 3+ This leads to the formation of a series of Fe-containing mineralization processes in the extracellular environment. 2+ Minerals can be used to remove organic matter from wastewater through the dissimilar reduction process of iron. Meanwhile, iron is widely used in wastewater treatment as a highly efficient phosphorus removal material. Therefore, using iron to remove the three major pollutants from wastewater can lead to the development of a low-carbon, low-material-consumption wastewater treatment system.

[0003] Low C / N sewage is ubiquitous, especially in many rural areas, there are a large number of domestic sewage is discharged without treatment. Although the sewage treatment capacity is increasing year by year, but the rural domestic sewage treatment rate is still at a low level, domestic sewage is directly discharged or insufficiently treated, which becomes an important source of water pollution in rural areas, and brings great pressure to the rural ecological environment.

[0004] Unlike urban sewage treatment, the bottleneck of rural domestic sewage treatment is the limitation of economic conditions: traditional two-step denitrification technology requires high-energy aeration and additional organic matter, and brings problems such as excessive carbon emissions and sludge disposal, so it is not suitable for rural domestic sewage treatment. The treatment of rural domestic sewage should first choose autotrophic technology, and at the same time consider factors such as cost and operation mode, therefore, the development of low-carbon, low-material-consumption pollution reduction and denitrification and phosphorus removal technology is imminent for the treatment of rural domestic sewage. SUMMARY

[0005] In view of the high energy consumption and high cost of existing domestic sewage treatment, the purpose of the present application is to provide a domestic sewage biological treatment system and process based on iron driving, which is based on dissimilatory iron reduction, Fe(III) / Fe(II) cycle driven iron ammonia oxidation (Feammox) coupled with nitrate type ferrous oxide (NDFO) and adsorption crystallization phosphorus removal process, which can realize efficient removal of organic matter in sewage and fixation of carbon dioxide, autotrophic technology for deep denitrification and adsorption and crystallization of phosphate, simultaneous efficient removal of pollutants in sewage, has the advantages of easy operation and low cost, and is especially suitable for rural domestic sewage treatment. The purpose of the present application is realized by the following technical scheme.

[0006] The primary aspect of the present application is to provide a domestic sewage biological treatment system based on iron driving, comprising a water inlet tank and two reaction tanks connected in sequence through a pipeline, the two reaction tanks are dissimilatory iron reduction reaction tank and iron ammonia oxidation reaction tank in sequence, and the two reaction tanks are each provided with an iron source adding port, a water inlet and a water outlet weir, the dissimilatory iron reduction reaction tank is filled with sludge containing iron-reducing bacteria, and the iron ammonia oxidation reaction tank is filled with sludge with iron ammonia oxidation function.

[0007] Further, the dissimilatory iron reduction reaction tank is provided with an aeration system, and the iron ammonia oxidation reaction tank is provided with a stirring system.

[0008] Further, if the C / N ratio in the effluent of the dissimilatory iron reduction reaction tank is greater than 2, an additional dissimilatory iron reduction tank is added to create a suitable low C / N ratio environment for subsequent iron ammonia oxidation.

[0009] Further, if the NH4 + -N>5 mg / L in the effluent of the iron ammonia oxidation reaction tank, an additional iron ammonia oxidation reaction tank is added to achieve standard removal of ammonia nitrogen.

[0010] Another aspect of the present application is to provide a ferric-driven domestic sewage biological treatment process, comprising the following steps:

[0011] S1, iron-reducing sludge containing iron-reducing function is put into the dissimilatory iron reduction tank, and iron source is filled, domestic sewage is introduced, and dissimilatory iron reduction process is started and fully reacted;

[0012] S2, iron ammonia oxidation sludge with iron ammonia oxidation function is filled into the iron ammonia oxidation reaction tank, iron source is added, effluent from the dissimilatory iron reduction tank is introduced into the iron ammonia oxidation reaction tank, iron ammonia oxidation process is started and fully reacted, and treated domestic sewage is discharged after full reaction.

[0013] Fe(III) oxide is driven by dissimilatory iron reduction (DIR) through iron-reducing bacteria (IRB), IRB uses extracellular Fe(III) as an electron acceptor to oxidize organic matter, and Fe(III) is reduced to Fe(II). Iron ammonia oxidation (Feammox) oxidizes ammonia nitrogen to N2, NO2 - , NO3 - , using Fe(III) as an electron acceptor; and nitrate-dependent ferrous oxidation (NDFO) reduces NO3 − to N2, NO2 - , NH4 + , using ferrous as an electron donor. The products of the two processes of NDFO and Feammox are mutual reactants, the effective coupling of the two processes can effectively remove nitrate and ammonia nitrogen simultaneously, achieve deep denitrification, and help the internal Fe(III) / Fe(II) cycle formed by ferrous oxidation in NDFO and trivalent iron reduction in Feammox, reducing the amount of iron salt added. Excessive organic matter will weaken the denitrification effect of Feammox, and after the organic matter in the sewage is effectively removed by the front-end dissimilatory iron reduction process, the subsequent denitrification process creates favorable autotrophic conditions, and the carbon dioxide generated by the dissimilatory iron reduction process can form ferrous carbonate precipitation with Fe(II), reducing greenhouse gas emissions and achieving carbon dioxide fixation; the iron salt in the three processes can effectively remove phosphate. The domestic sewage biological treatment process provided by the present application can provide a low-carbon, low-material-consumption solution for domestic sewage treatment through the coupling of the above processes, and the COD removal rate can reach more than 95%, and the ammonia nitrogen and phosphate removal rates can reach more than 90%.

[0014] The application provides a domestic sewage biological treatment process, which utilizes different valence state iron to remove three pollutants in sewage, realizes microbial-driven iron oxidation-reduction mediated dissimilatory iron reduction, Feammox and NDFO to remove carbon and nitrogen in the sewage, utilizes generated Fe(II) to fix carbon dioxide, reduces greenhouse gas emission, and utilizes adsorption and crystallization between iron salt and phosphate to remove phosphorus in the sewage. C / N in rural sewage is about 5-8, which will inhibit the effect of autotrophic denitrification technology. Therefore, in the front end, dissimilatory iron reduction microorganisms and a large amount of iron source filled in are utilized to efficiently remove organic matter in the sewage through dissimilatory iron reduction. After C / N is reduced, the sewage enters the Feammox tank, NH4 + N2 is generated through the Feammox process, Fe(III) is reduced to Fe(II), and part of the product NO3 - can be combined with residual organic matter in the sewage to generate N2 through heterotrophic denitrification, and Fe(II) generated through Feammox can also be combined with NO3 - to generate N 2， through the NDFO effect, so that deep removal of nitrogen is realized and Fe(II) / Fe(III) is recycled through the NDFO effect.

[0015] Further, the iron source in step S1 is iron ore or iron-containing waste sludge, and the dosage is 5-15 mmol / L; and the iron source in step S2 is ferrihydrite, and the dosage is 5-15 mmol / L.

[0016] Preferably, the main pollutants of the domestic sewage in step S1 include organic matter, NH4 + and PO4 3- , and the pH is 6-8.

[0017] Further, the hydraulic retention time of the domestic sewage in the dissimilatory iron reduction reaction tank in step S1 is 6-20 h, the C / N ratio of the effluent is less than 2, and the COD is less than 80 mg / L; and the hydraulic retention time of the domestic sewage in the iron ammonia oxidation reaction tank in step S2 is 6-20 h.

[0018] Further, the Fe 2+ concentration in the reaction tank is monitored regularly, when the Fe 2+ concentration in the dissimilatory iron reduction reaction tank accounts for more than 60%, Fe 2+ is intermittently aerated and oxidized, the addition of external iron is reduced, and the oxidation cycle of iron is realized; or the sewage in the dissimilatory iron reduction tank is discharged, the contact area between the top of the reaction tank and air is increased, and the oxidation cycle of iron is realized.

[0019] Further, the Fe 2+ concentration in the reaction tank is monitored regularly, when the Fe 2+When the concentration ratio is more than 60%, the continuous flow mode is adjusted to be operated in a sequencing batch mode, the stirring is turned on to make the sludge contact with air for oxidation of Fe 2+ After the end, the stirring is turned off, the water is discharged by standing and precipitation, and the continuous flow mode is operated.

[0020] Compared with the prior art, the present application has the following beneficial technical effects:

[0021] (1) The present application is suitable for domestic sewage treatment, and has simple treatment process and low cost. The dissimilatory iron reduction, iron autotrophic ammonia oxidation and iron autotrophic denitrification technology are coupled to realize the simultaneous removal of organic matter, nitrogen and phosphorus in the sewage.

[0022] (2) The dissimilatory iron reduction technology is used to remove the organic matter in the sewage efficiently, and provides suitable conditions for the application of Feammox to actual sewage treatment.

[0023] (2) The dissimilatory iron reduction is used to strengthen the subsequent denitrification process, so that the autotrophic denitrification technology can be completely applied to actual sewage treatment, the inhibition of organic matter is reduced or even eliminated, the best environment for the autotrophic denitrification technology is created, and the efficient denitrification of Feammox is ensured.

[0024] (3) The autotrophic technology does not need additional aeration in the ammonia oxidation stage, the generated nitrate does not need additional carbon source, and the added iron salt can be recycled. The subsequent autotrophic denitrification process does not need to consider the sludge treatment and disposal problem, and is beneficial to reduce the treatment cost.

[0025] (4) The iron added in the dissimilatory iron reduction tank is released from the added iron source Fe(III), and the regeneration of Fe(III) is realized by rapid oxidation of air, which reduces the cost consumption and ensures long-term efficient removal of pollutants. At the same time, the generated CO2 can be fixed by Fe(II) to form FeCO3 precipitation, which can reduce the emission of greenhouse gases. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a structure schematic diagram of a domestic sewage biological treatment system provided by the present application.

[0027] In the figure: 1 - water inlet tank; 2 - peristaltic pump; 3 - dissimilatory iron reduction reaction tank; 4 - sludge; 5 - iron source adding port; 6 - mechanical stirring; 7 - water outlet weir; 8 - iron ammonia oxidation reaction tank.

[0028] Figure 2 is a principle schematic diagram of the present application. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention. Example 1

[0030] An iron-driven biological treatment system for domestic sewage, such as Figure 1 As shown, the system includes an inlet tank 1 and two reaction tanks connected sequentially by pipes. The two reaction tanks are, in sequence, a dissimilar iron reduction reaction tank 3 and an iron ammonia oxidation reaction tank 8. A peristaltic pump 2 is installed between the inlet tank 1 and the dissimilar iron reduction tank 3. Both reaction tanks are equipped with an iron source inlet 5 and an outlet weir 7. Sludge 4 containing iron-reducing bacteria is inoculated into the dissimilar iron reduction reaction tank 3, and sludge with iron ammonia oxidation function is filled into the iron ammonia oxidation reaction tank. The iron ammonia oxidation reaction tank 8 is equipped with a mechanical stirrer 6. Example 2

[0031] The process for treating domestic sewage using the system described in Example 1 is as follows: Figure 2 As shown, it includes the following steps.

[0032] (1) Preparation of simulated wastewater: Prepared with tap water, adding CH3COONa, NH4Cl, and KH2PO4. Adjust the pH of the influent to between 6 and 8 using 1 M HCl and NaOH. Control the influent COD to 300 mg / L; NH4... + 50 mg / L, PO4 3- The concentration is 5 mg / L.

[0033] (2) Anaerobic iron-containing sludge was inoculated in the dissimilar iron reduction tank, and iron ore was filled at the bottom of the reactor; the microorganisms required for the iron ammonia oxidation process were acclimated in the iron ammonia oxidation reactor with anaerobic ammonia oxidation granular sludge, and 10 mM prepared ferrohydrate was added. The volume ratio of the dissimilar iron reduction tank and the iron ammonia oxidation reactor was 1:11.

[0034] (3) The HRT of the dissimilar iron reduction tank is set to 18 h, and the HRT of the iron-ammonia oxidation reactor is set to 18 h. An upflow reactor is used, with wastewater flowing in from the bottom and having an overflow weir at the top. After flowing out, the wastewater enters the bottom of the next stage reactor, ensuring complete reaction. At the same time, the upflow reactor reduces the subsequent sedimentation stage of the effluent, eliminating the need for additional construction costs.

[0035] (4) After the wastewater enters the dissimilatory iron reduction tank, the iron ore added in the tank will slowly release a large amount of Fe(III), providing sufficient substrate for the dissimilatory iron reduction process, and the organic matter is rapidly consumed, so that the C / N in the wastewater is reduced to below 2. At the same time, the generated Fe(II) can not only fix the generated CO2, reducing the emission of greenhouse gases; but also participate in the crystallization process of phosphate to form phosphate minerals, such as vivianite, to realize the recovery of phosphorus, and Fe(III) can also realize the adsorption of phosphorus. The dissolved oxygen in the wastewater will also be completely consumed in this area, creating a more anaerobic environment for the subsequent process.

[0036] (5) After the C / N of the effluent of the dissimilatory iron reduction tank is reduced, the wastewater enters the iron ammonia oxidation reaction tank, and through the Feammox effect, NH4 + in the wastewater is oxidized to N2, and a small amount of NO3 – product is generated, and Fe(III) is reduced to Fe(II). The remaining organic matter and the generated Fe(II) remove NO3 – product, realize the cycle of Fe(II) / Fe(III), and consume the remaining organic matter. Fe(III) in the iron ammonia oxidation reaction tank can also participate in the dissimilatory iron reduction process, so that the organic matter in the wastewater is further removed in the reaction tank. Phosphate is also further removed through the combined action of adsorption and crystallization in this area.

[0037] (6) The iron concentration of the sludge in the two areas is regularly monitored. When the Fe(II) concentration in the dissimilatory iron reduction reaction tank accounts for more than 60%, intermittent aeration can be used to oxidize Fe(II), reduce the addition of external iron, and realize the oxidation cycle of iron; or the wastewater in the dissimilatory iron reduction tank can be discharged, and the contact area between the top of the reaction tank and the air can be increased to realize the oxidation cycle of iron. When the Fe(II) accounts for more than 60% in the iron ammonia oxidation reaction tank, the continuous flow can be changed to intermittent operation, the stirring is turned on to make the sludge contact with the air to oxidize Fe(II); after the end, the stirring is turned off, and the water is discharged after standing and sedimentation, and the continuous flow mode is operated.

[0038] (7) By running the Feammox reaction with low C / N, there is a small amount of iron loss in the effluent. If the operation mode is adjusted according to (6), the denitrification effect is still decreased, and a proper amount of Fe(OH)3 can be added to improve the denitrification effect.

[0039] After stable operation, the COD in the effluent of the iron ammonia oxidation reaction tank is below 10 mg / L, the NH4 + is below 5 mg / L, and the PO4 3- is below 0.5 mg / L.

[0040] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and that changes, modifications, substitutions and variations can be made by those skilled in the art without departing from the spirit and scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A biological treatment system for domestic sewage based on iron drive, characterized in that, The device comprises a water inlet tank and two reaction tanks connected in sequence through a pipeline, the two reaction tanks are in sequence a dissimilatory iron reduction reaction tank and an iron ammonia oxidation reaction tank, the two reaction tanks are each provided with an iron source feeding port, a water inlet and a water outlet weir, the dissimilatory iron reduction reaction tank is filled with sludge with iron reduction function, and the iron ammonia oxidation reaction tank is filled with sludge with iron ammonia oxidation function.

2. The domestic wastewater biological treatment system according to claim 1, characterized by The dissimilatory iron reduction reaction tank is provided with an aeration device, and the iron ammonia oxidation reaction tank is provided with a stirring device.

3. The domestic wastewater biological treatment system according to claim 1, characterized by If the C / N ratio of the effluent of the dissimilatory iron reduction reaction tank is greater than 2, an additional dissimilatory iron reduction tank is added.

4. The domestic wastewater biological treatment system according to claim 1, characterized by If the effluent of the iron ammonia oxidation reaction tank is NH4 + -N>5 mg / L, add an iron ammonia oxidation reaction tank.

5. Process for the treatment of domestic sewage by means of the biological treatment system of any one of claims 1 to 4, characterized in that, The method comprises the following steps: S1: feeding sludge with iron reduction function into the dissimilatory iron reduction reaction tank, filling the iron source, and feeding domestic sewage, and starting the dissimilatory iron reduction process for sufficient reaction; S2: filling the iron ammonia oxidation reaction tank with sludge with iron ammonia oxidation function, feeding the iron source, feeding the effluent of the dissimilatory iron reduction reaction tank into the iron ammonia oxidation reaction tank, starting the iron ammonia oxidation process for sufficient reaction, and discharging the treated domestic sewage after sufficient reaction.

6. The process of claim 5, wherein, In step S1, the iron source is iron ore or iron-containing waste sludge, and the feeding amount is 5-15 mmol / L; in step S2, the iron source is ferrihydrite, and the feeding amount is 5-15 mmol / L.

7. The process of claim 5, wherein, The main pollutants of the domestic sewage in step S1 include organic matter, NH4 + and PO4 3- , and the pH is 6 ~ 8.

8. The process of claim 5, wherein, In step S1, the hydraulic retention time of the domestic sewage in the dissimilatory iron reduction reaction tank is 6-20 h, the effluent C / N ratio is less than 2, and the COD is 80 mg / L or less; in step S2, the hydraulic retention time of the domestic sewage in the iron ammonia oxidation reaction tank is 6-20 h.

9. The process of claim 5, wherein, Periodically monitor the Fe in the reaction tank 2+ concentration, when the Fe 2+ concentration in the dissimilatory iron reduction reaction tank accounts for more than 60%, intermittent aeration oxidizes Fe 2+ , reduces the addition of exogenous iron, and realizes the oxidation cycle of iron.

10. The process of claim 5, wherein, Regularly monitor Fe in the reaction tank 2+ Concentration, when Fe in the iron reduction reaction tank 2+ When the concentration exceeds 60%, the wastewater from the iron reduction reaction tank is discharged, and the iron oxidation cycle is achieved by increasing the contact area between the top of the reaction tank and the air.

11. The process of claim 5, wherein, Periodically monitor the Fe in the reaction tank 2+ concentration, when the Fe 2+ concentration in the iron ammonia oxidation reaction tank accounts for more than 60%, adjust the continuous flow mode to the sequencing batch operation, start the stirring to make the sludge contact with the air to oxidize Fe 2+ ; after the end, turn off the stirring, and place it to precipitate to discharge the water, and change to the continuous flow mode operation.

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