CN114349290A - An enhanced phosphorus removal method based on MBBR sewage treatment process - Google Patents

Abstract

The invention relates to an enhanced phosphorus removal method based on MBBR sewage treatment process. After the sewage is treated in an anaerobic tank, an anoxic tank, an MBBR tank and a sedimentation tank in sequence, the obtained water is discharged, and a part of the obtained sedimentary sludge is directly returned to the anaerobic tank , part of it is sent to the hydrolysis and fermentation unit for processing, and the hydrolysis and fermentation mixed liquor is returned to the anaerobic tank to complete the process. Compared with the prior art, the present invention hydrolyzes and ferments the activated sludge generated in the process of domestic sewage, produces easily degradable organic matter (rbCOD) and volatile fatty acids (VFAs), and supplements the insufficiency of VFAs in the influent water, thereby improving the removal of sewage in the sewage plant. Phosphorus effect, reducing the demand for external carbon sources, reducing aeration energy consumption, and reducing the use of phosphorus removal agents.

Description

An enhanced phosphorus removal method based on MBBR sewage treatment process

technical field

The invention belongs to the technical field of sewage treatment, and relates to an enhanced phosphorus removal method based on an MBBR sewage treatment process.

Background technique

The main factor of water eutrophication is closely related to phosphorus in water body. With the development of society, the continuous use of agricultural fertilizers, the discharge of urban domestic sewage and industrial sewage into rivers, lakes, oceans and other water bodies, the phosphorus content in the water environment continues to rise, resulting in serious eutrophication of the water environment. bring great harm to the ecological environment.

With the increasing pressure of water environmental protection, energy conservation and emission reduction in my country, the requirements for effluent quality of sewage treatment plants are becoming more and more strict. However, in many areas of my country, there is a common problem of insufficient carbon sources in the influent of sewage plants, and poor denitrification and phosphorus removal is a common problem faced by the industry.

In order to solve the problem that N and P are difficult to handle due to insufficient carbon sources, the current method is to add organic carbon sources (such as methanol, sodium acetate, acetic acid, etc.) to supplement the soluble easily biodegradable organic matter (rbCOD) to achieve enhanced biological removal. Nitrogen and phosphorus removal. In addition, chemical phosphorus removal methods are usually used at home and abroad. For example, the metal salt phosphorus removal method needs to invest a large amount of chemical agents, resulting in a large amount of chemical sediment, causing secondary pollution and additionally increasing the cost of sludge disposal. In addition, there is a physical adsorption phosphorus removal method, but there are also problems such as high cost of use, saturation or clogging of the adsorbent, and difficulty in the regeneration of the adsorbent; the phosphorus removal method by membrane treatment, the problems of membrane fouling and enrichment treatment still need to be solved; natural The treatment method has the problems that the organic load per unit area is low, that is, the area is large, and the rate of natural treatment is relatively low, that is, the residence time of sewage is long.

Obviously, adding carbon sources, chemicals, adsorbents, etc., increases the operating costs of sewage plants and sludge disposal costs. It is difficult to continue to popularize and apply, and it goes against the concept of sustainable development.

At home and abroad, some studies have been carried out on the use of sludge hydrolysis and fermentation to supplement carbon sources, and some processes have also been developed and applied to engineering examples, but anaerobic fermentation of primary sludge is mostly used. Fermentation of primary sludge can produce higher concentrations of rbCOD and VFAs. However, due to the low overall quantity of primary sludge, instability, and lack of sufficient number of mixed bacteria with hydrolysis and fermentation functions, the hydrolysis rate of this process is low. Utilization is not high.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of enhanced phosphorus removal method based on MBBR sewage treatment process, in order to overcome the shortcoming of the difficulty of phosphorus removal in the current domestic sewage treatment process, adopting activated sludge hydrolysis and fermentation back to supplement the deficiency of influent VFAs to improve sewage Plant phosphorus removal effect.

The object of the present invention can be realized through the following technical solutions:

An enhanced phosphorus removal method based on MBBR sewage treatment process. After the sewage is treated in an anaerobic tank, an anoxic tank, an MBBR tank and a sedimentation tank in sequence, the obtained water is discharged, and a part of the obtained sedimentary sludge is directly returned to the anaerobic tank, and the other part is sent to the anaerobic tank. It is processed in the hydrolysis and fermentation unit to obtain the hydrolysis and fermentation mixed liquor and then returned to the anaerobic tank, that is, it is completed.

Further, the total return ratio of the sedimented sludge is 30% to 80% Q, wherein Q is the amount of sewage inflow.

Further, the amount of sedimented sludge directly returned to the anaerobic tank is 20-79% Q, and the amount sent to the hydrolysis and fermentation unit is 1-20% Q.

A more preferred amount of sedimented sludge sent to the hydrolysis and fermentation unit is 4-7%Q.

Further, the hydrolysis fermentation unit includes a hydrolysis fermentation tank and a concentration tank connected in sequence, and part of the sedimented sludge is sent into the hydrolysis fermentation tank, and then, the mud and water are separated in the concentration tank to obtain the hydrolysis fermentation mixed solution and return to the anaerobic tank, Part of the obtained sludge is returned to the hydrolysis and fermentation tank, and the rest is discharged.

Further, the SRT of the sludge in the hydrolysis and fermentation tank is 3-7d, the pH is controlled to be 4-6, and the mud level during static precipitation in the hydrolysis-fermentation tank is 0.5-1.0m (because the hydrolysis and fermentation tank adopts intermittent aeration and stirring. Therefore, there is also a static precipitation cycle), and the operating sludge solid load rate of the thickening tank is 30 to 100 kg/(m ² .d).

More preferably, during the operation of the hydrolysis and fermentation tank, the mixed liquid in the tank is controlled by intermittent aeration and stirring to be in an alternating environment of "anoxia-anaerobic", and the stirring power density is 10-20kw/m ³ tank capacity. , At the same time, the operating range of the control redox potential ORP is -300 ~ +100mv.

Further, the hydrolysis yield of the sludge in the hydrolysis fermentation tank is 0.03-0.18gVFAs/gVSS, and the product is expressed as volatile fatty acids, VFAs; or the sludge hydrolysis yield in the hydrolysis fermentation tank is 0.08-0.35gSCOD/ gVSS, product is expressed as soluble COD, SCOD.

Further, the concentration of the sedimented sludge sent to the hydrolysis and fermentation tank is 5-12g/L, the average sludge concentration during operation in the hydrolysis-fermentation tank is 6-9g/L, and the sludge is returned from the concentration tank to the hydrolysis and fermentation tank. The concentration is 10～15g/L.

Further, part of the nitrification solution from the MBBR tank is sent to the sedimentation tank, and the rest is returned to the anoxic tank.

Compared with the prior art, the present invention can anaerobic hydrolyze the activated sludge produced by the sewage treatment plant itself to produce rapidly degradable organic matter rbCOD and VFAs, and effectively supplement the insufficiency of VFAs in the influent water; Rapid absorption to improve the removal capacity of P; to reduce additional carbon sources and chemical phosphorus removal agents to reduce costs; to reduce sludge production in sewage plants, and to reduce sludge treatment and disposal costs.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

In the following embodiments or examples, if there is no special description of the raw materials or processing techniques, it is indicated that they are all conventional commercially available raw materials or conventional processing techniques in the art.

In order to improve the phosphorus removal effect of the sewage plant, the present invention provides an enhanced phosphorus removal method based on the MBBR sewage treatment process. Referring to FIG. 1, the sewage is processed through an anaerobic tank, an anoxic tank, an MBBR tank and a sedimentation tank in sequence. After that, the obtained water is discharged, a part of the obtained sedimentary sludge is directly returned to the anaerobic tank, and a part is sent to the hydrolysis and fermentation unit for processing, and the hydrolysis and fermentation mixed liquor is returned to the anaerobic tank, which is completed.

In some specific embodiments, the total return ratio of the sedimented sludge is 30% to 80% Q, where Q is the amount of sewage inflow. Specifically, if the total sludge return ratio is designed to be (30% and 80%) Q (Q is the raw water inflow), the corresponding ratio of direct return to the front end of the anaerobic tank is (20-29%, 60-79%) )Q, the proportion of side reflux to the hydrolysis fermentation tank is (1~10%, 1~20%)Q

In a more specific embodiment, the amount of sedimented sludge directly returned to the anaerobic tank is 20-79% Q, and the amount sent to the hydrolysis and fermentation unit is 1-20% Q. A more preferred amount of sedimented sludge sent to the hydrolysis and fermentation unit is 4-7%Q.

In some specific embodiments, the hydrolysis and fermentation unit includes a hydrolysis fermentation tank and a concentration tank connected in sequence, and part of the sedimented sludge is sent into the hydrolysis fermentation tank, and then, the mud and water are separated in the concentration tank to obtain the hydrolysis fermentation mixed liquor Returning to the anaerobic tank, the obtained sludge is partially returned to the hydrolysis and fermentation tank, and the rest is discharged.

In a more specific embodiment, the SRT of the sludge in the hydrolysis and fermentation tank is 3 to 7d, the pH is controlled to be 4 to 6, and the mud level during static precipitation in the hydrolysis tank is 0.5 to 1.0m (due to the use of intermittent aeration and The way of stirring, therefore, there is also a static precipitation cycle), the operating sludge solid load rate of the thickening tank is 30 ~ 100kg/(m ² .d).

More preferably, during the operation of the hydrolysis and fermentation tank, the mixed liquid in the tank is controlled by intermittent aeration and stirring to be in an alternating environment of "anoxia-anaerobic" (generally, aeration is stopped every 5 hours, and the residence time is 0.5 -1.0h), the stirring power density is 10~20kw/m ³ tank capacity, and at the same time, the operating range of monitoring the redox potential ORP is -300~+100mv (by adjusting the sludge residence time, stirring and aeration means to control) . In addition, in order to prevent odor pollution, the hydrolysis fermentation tank is covered and sealed, and sent to the deodorization equipment through the setting of the exhaust pipe.

In a more specific embodiment, the hydrolysis yield of the sludge in the hydrolysis fermentation tank is 0.03～0.18gVFAs/gVSS, and the product is expressed as volatile fatty acids, VFAs; or the sludge hydrolysis yield in the hydrolysis fermentation tank is 0.08～ 0.35gSCOD/gVSS, the product is expressed as soluble COD, SCOD. Here, the hydrolysis products of sludge are mainly mixed acids such as acetic acid and propionic acid.

In a more specific embodiment, the concentration of the sedimented sludge sent to the hydrolysis and fermentation tank is 5-12g/L, and the average sludge concentration in the hydrolysis-fermentation tank during operation is 6-9g/L, which is returned from the concentration tank to the hydrolysis fermentation. The sludge concentration in the pool is 10-15g/L. In some specific embodiments, part of the nitrification solution from the MBBR tank is sent to the sedimentation tank, and the rest is returned to the anoxic tank.

The above embodiments may be implemented individually, or may be implemented in any two or more combinations.

The above embodiments will be described in more detail below with reference to specific embodiments.

Example 1:

As shown in Figure 1, an enhanced phosphorus removal method based on MBBR sewage treatment process includes the following steps: most of the sludge settled in the sedimentation tank is returned to the beginning of the biological tank, that is, the inlet end of the anaerobic tank, and a small part of the remaining The sludge enters the hydrolysis fermentation tank and the concentration tank in turn for hydrolysis and fermentation. The hydrolysis fermentation tank is equipped with an anchor stirrer (the stirring power density is about 15kw/ ^m3 tank capacity), and the complete mixing flow is adopted to realize the anaerobic hydrolysis and fermentation of the sludge. , The concentration tank adopts static gravity sedimentation, which mainly completes the separation of mud and water from the mixed liquid from the hydrolysis and fermentation tank. The mixed liquid rich in VFAs enters the anaerobic tank from the concentration tank; the concentrated sludge at the bottom of the concentration tank is returned to the hydrolysis and fermentation tank. The sludge can be circulated repeatedly in the hydrolysis fermentation tank and the concentration tank, which increases the sludge residence time, and the excess sludge is discharged through the discharge system.

Main design parameters: the design total sludge return ratio is 30%, the activated sludge concentration of the biological pool is 3000mg/L, the flow rate of the sludge back to the hydrolysis and fermentation tank is 10%, and the sludge concentration of the hydrolysis and fermentation tank is 12g/L, and the return flow from the concentration tank The sludge concentration in the hydrolysis and fermentation tank is about 15g/L, the SRT of the hydrolysis and fermentation tank is 5d, the pH is controlled to be 4-6, the mud level in the hydrolysis and fermentation tank is about 0.6-0.8m during static precipitation, and the solid load rate of the operating sludge is about It is 60kg/(m ² .d). The sludge hydrolysis yield is 0.15gVFAs/gVSS and 0.30gSCOD/gVSS; meanwhile, the operating range of the control redox potential ORP is -300～+100mv.

Enter the anaerobic zone or anoxic zone of the biological pool together with the pretreated sewage and another part of the activated sludge returned from the sedimentation tank (that is, corresponding to the anaerobic tank and the anoxic tank respectively) to strengthen the anaerobic phosphorus release;

In the biological tank, the sewage is degraded by anoxic, anaerobic and aerobic processes to achieve the removal of pollutants and the reduction of the concentration. The supernatant is discharged up to the standard;

The concentrated activated sludge is transported to the water inlet of the biological tank and the water inlet of the hydrolysis fermentation tank respectively through the sludge return pump, and the excess sludge produced by the system is processed by the sludge treatment and discharge process unit.

Example 2:

As shown in Figure 1, an enhanced phosphorus removal method based on MBBR sewage treatment process includes the following steps: most of the sludge settled in the sedimentation tank is returned to the beginning of the biological tank, and the remaining small part of the sludge enters the hydrolysis and fermentation tank in turn. The concentration tank is used for hydrolysis and fermentation. An anchor stirrer is installed in the hydrolysis and fermentation tank, and a complete mixing flow is used to realize the anaerobic hydrolysis and fermentation of the sludge. The mixed liquid rich in VFAs enters the beginning of the biological tank from the concentration tank; the concentrated sludge at the bottom of the concentration tank is then returned to the hydrolysis and fermentation tank, and the sludge can be repeatedly circulated in the hydrolysis fermentation tank and the concentration tank, which increases the sludge residence time, and the excess sludge. The sludge is discharged through the discharge system.

Main design parameters: the design total sludge return ratio is 80%, the activated sludge concentration of the biological pool is 2500mg/L, the flow rate of the sludge returned to the hydrolysis and fermentation tank is 20%, the sludge concentration of the hydrolysis and fermentation tank is 5g/L, and the hydrolysis and fermentation tank SRT= 4d; sludge hydrolysis yield is 0.12gVFAs/gVSS, 0.27gSCOD/gVSS;

Enter the anaerobic zone or anoxic zone of the biological pool together with the pretreated sewage and another part of the activated sludge returned from the sedimentation tank to strengthen the anaerobic phosphorus release;

In the biological tank, the sewage is degraded by anoxic, anaerobic and aerobic processes to achieve the removal of pollutants and the reduction of the concentration. The supernatant is discharged up to the standard;

The concentrated activated sludge is transported to the water inlet of the biological tank and the water inlet of the hydrolysis fermentation tank respectively through the sludge return pump, and the excess sludge produced by the system is processed by the sludge treatment and discharge process unit.

Example 3:

A sewage plant, sewage inflow indicators: COD 300mg/L, BOD 150mg/L, SS 150mg/L, TN 50mg/L, NH ₃ -N 30mg/L, TP 3mg/L.

Due to the insufficient carbon source in the influent, the original MBBR process was modified by the method of Example 1. The main parameters were: the flow rate of the mud into the hydrolysis and fermentation tank was 10%, the SRT was 5 days, and the supernatant of the hydrolysis and fermentation tank entered the biological tank. In the anaerobic tank, the measured supernatant VFA concentration was 2170-3410 mg/L, TN was 93-117 mg/L, and TP was 19-24 mg/L. The operation after the transformation shows that the phosphorus removal effect of the sewage treatment plant has been significantly improved without adding external commercial carbon sources and phosphorus removal agents.

The original MBBR process (that is, omitting the side-stream activated sludge hydrolysis and fermentation tank) can also reach the effluent standard of Grade 1 B, but the effluent quality is unstable.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (10)

1. An enhanced phosphorus removal method based on an MBBR sewage treatment process is characterized in that sewage is treated by an anaerobic tank, an anoxic tank, an MBBR tank and a sedimentation tank in sequence, the obtained effluent is discharged, part of the obtained precipitated sludge directly returns to the anaerobic tank, and the other part of the obtained precipitated sludge is sent to a hydrolysis fermentation unit for treatment to obtain hydrolysis fermentation mixed liquid and then returns to the anaerobic tank, and the treatment is completed.

2. The method of claim 1, wherein the total reflux ratio of the precipitated sludge is 30-80% Q, wherein Q is the wastewater influent.

3. The method for enhanced phosphorus removal based on the MBBR sewage treatment process of claim 2, wherein the amount of the precipitated sludge directly returned to the anaerobic tank is 20-79% Q, and the amount of the precipitated sludge fed into the hydrolysis fermentation unit is 1-20% Q.

4. The method for enhanced phosphorus removal based on the MBBR sewage treatment process of claim 3, wherein the amount of the precipitated sludge fed into the hydrolysis fermentation unit is 4-7% Q.

5. The method of claim 1, wherein the hydrolysis fermentation unit comprises a hydrolysis fermentation tank and a concentration tank which are connected in sequence, part of the precipitated sludge is fed into the hydrolysis fermentation tank, then sludge-water separation is carried out in the concentration tank, the obtained hydrolysis fermentation mixed liquid is returned to an anaerobic tank, part of the obtained sludge flows back into the hydrolysis fermentation tank, and the rest of the obtained sludge is discharged.

6. According to claim 5The enhanced phosphorus removal method based on the MBBR sewage treatment process is characterized in that the SRT of the sludge age in the hydrolysis fermentation tank is 3-7 d, the pH is controlled to be 4-6, the sludge level in the hydrolysis fermentation tank is 0.5-1.0 m during static precipitation, and the solid load rate of the sludge running in the concentration tank is 30-100 kg/(m & lt m & gt)².d)。

7. The MBBR sewage treatment process-based enhanced phosphorus removal method of claim 6, wherein in the operation process of the hydrolysis fermentation tank, the mixed liquid in the tank is controlled to be in an anaerobic-anoxic-anaerobic alternative environment by adopting an intermittent aeration and stirring mode, and the stirring power density is 10-20 kw/m³The tank capacity is controlled, and meanwhile, the running range of the oxidation-reduction potential ORP is controlled to be-300 to +100 mv.

8. The method for enhanced phosphorus removal based on MBBR sewage treatment process of claim 5, wherein the hydrolysis yield of the sludge in the hydrolysis fermentation tank is 0.03-0.18 gVFAs/gVSS, and the product is expressed by Volatile Fatty Acids (VFAs); or the hydrolysis yield of the sludge in the hydrolysis fermentation tank is 0.08-0.35 g SCOD/gVSS, and the product is expressed by soluble COD (chemical oxygen demand).

9. The MBBR sewage treatment process-based enhanced phosphorus removal method of claim 5, wherein the concentration of the precipitated sludge fed into the hydrolysis fermentation tank is 5-12 g/L, the average sludge concentration during operation in the hydrolysis fermentation tank is 6-9 g/L, and the sludge concentration returned from the concentration tank to the hydrolysis fermentation tank is 10-15 g/L.

10. The method for enhanced phosphorus removal based on the MBBR sewage treatment process of claim 1, wherein part of the nitrified liquid from the MBBR tank is sent to the sedimentation tank, and the rest part is returned to the anoxic tank.

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