1. A method for granulating sludge is characterized in that: in a continuous flow reactor with the lower inlet and the upper outlet, taking crushed anaerobic granular sludge as granulation crystal nuclei, and inoculating inoculated sludge with the same density as the granulation crystal nuclei; the preparation method of the inoculated sludge with the same density as the granulation crystal nucleus comprises the following steps: when low-concentration wastewater is treated, 200 plus 10000 meshes of zero-valent iron are added, and the density of sludge is adjusted by adding a flocculating agent until the density of the sludge is the same as that of the granulation crystal nucleus; when high-concentration wastewater is treated, adding the following components in a molar ratio of (0.1-10): (0.1-10) calcium chloride and sodium carbonate, and adding a flocculating agent to adjust the density of the sludge until the density of the sludge is the same as that of the granulation crystal nucleus.

2. The method for sludge granulation as claimed in claim 1, wherein: directly putting the crushed anaerobic granular sludge and the inoculated sludge into the reactor, and uniformly stirring the granulation crystal nucleus and the inoculated sludge.

3. The method for sludge granulation as claimed in claim 1, wherein: when low-concentration wastewater is treated, the concentration of the inoculated sludge is 2000-4000 mg/L and is 5-10 times of that of the granulation crystal nucleus.

4. The method for sludge granulation as claimed in claim 1, wherein: when high-concentration wastewater is treated, the concentration of the inoculated sludge is 4000-10000mg/L and is 10-100 times of that of the granulation crystal nucleus.

5. The method for sludge granulation as claimed in claim 1, wherein: the flocculating agent is selected from one or more of polyferric sulfate, polyferric chloride, polyaluminum sulfate and polyaluminum ferric sulfate.

6. The method for sludge granulation as claimed in claim 1, wherein: the method further comprises the step of increasing the viscosity of the sludge by adding 1-1000ppm PAM to prevent the separation of granulation crystal nuclei from the inoculated sludge during the operation of the reactor.

Background

Since the birth of the activated sludge process, the activated sludge process is increasingly widely used for sewage treatment. With the gradual increase of land cost, people have more and more eagerly demanded reactors with high load and small occupied area. And the appearance of sludge granulation technology well solves the problem. However, the formation of sludge granules is affected by many factors, including the growth and decay of microorganisms and the diffusion of substrates, which are very complicated, and this makes the sludge granulation process time-consuming, often taking several months, and if the object to be treated is low-concentration wastewater, it takes a longer time.

The nucleus hypothesis is about the mechanism of anaerobic granular sludge formation, which is believed to be similar to the crystallization process, wherein granular sludge is continuously developed on the basis of the nucleus, and mature granular sludge is finally formed. Anaerobic granular sludge has also been reported as a common crystal nucleus. However, compared with inoculated sludge, anaerobic granular sludge has higher density, and crystal nuclei and inoculated sludge are easy to generate layering phenomenon in the process of culturing granular sludge in a continuous flow reactor, thereby influencing the granulation effect of the reactor. A method for rapidly culturing aerobic granular sludge and a sequencing batch reactor (CN201710666785. X) disclose a method for accelerating sludge granulation by using anaerobic digestion sludge as crystal nucleus, but the method adopts a sequencing batch method for culturing granular sludge in order to better mix the crystal nucleus and flocculent sludge, and does not solve the requirement of realizing the granular sludge culture of a continuous flow reactor in engineering; a calcified anaerobic granular sludge secondary nucleation recycling method and a calcified anaerobic granular sludge secondary nucleation recycling system (CN 201811130287.4) disclose a calcified anaerobic granular sludge secondary nucleation recycling method, in order to uniformly mix inoculated sludge and crystal nucleus, an ex-situ pretreatment method is adopted, but a mechanical stirring method can damage sludge agglomeration, and the problem that the density of the crystal nucleus is different from that of the inoculated sludge is still not changed. The invention aims to enhance the polymerization capacity of crystal nucleus and flocculent sludge, improve the granulation capacity of low-concentration wastewater and shorten the formation time of granular sludge by increasing the density of the flocculent sludge.

Disclosure of Invention

Aiming at the problems of long sludge granulation time, poor density of added crystal nucleus and original sludge, easy loss of added medicament and the like, the invention provides a sludge granulation method by utilizing the prior reactor (cited in a patent ZL 201910487315.6) in combination with the background technology.

The technical scheme of the invention is as follows:

granular sludge is cultured by using a continuous flow reactor, crushed granular sludge is used as granulation crystal nucleus for granulation of flocculent sludge, the sludge density of suspended sludge is increased, the problem of sludge loss or crystal nucleus deposition caused by different ascending flow rates due to the density difference of sludge in two states is prevented, and the granulation capability of low-concentration wastewater is enhanced. The specific method comprises the following steps:

crushing anaerobic granular sludge by using a centrifugal pump, and using the crushed anaerobic granular sludge as granulation crystal nuclei for sludge granulation;

inoculating aerobic activated sludge floc to the reactor, wherein the concentration of the inoculated sludge is 2000-10000mg/L, and the concentration of the sludge is 5-50 times of that of the granulation crystal nucleus;

if the reactor is used for treating low-concentration wastewater, 200 plus 10000 meshes of zero-valent iron are added into inoculated sludge, a flocculating agent is added to adjust the density of the sludge until the density of the sludge is the same as that of a granulation crystal nucleus, and rotational flow water distribution is utilized for uniformly mixing;

if the reactor is used for treating high-concentration wastewater, firstly adding calcium chloride into inoculated sludge, uniformly mixing by using rotational flow water distribution, then adding sodium carbonate, and adding a flocculating agent to adjust the density of the sludge until the density is the same as that of granulation crystal nuclei;

and finally, uniformly mixing the granulation crystal nucleus and the inoculated sludge, and adding 1-1000ppm of PAM to strengthen the mixing of the inoculated sludge and the granulation crystal nucleus.

The water treatment process of the reactor adopts a lower inlet and upper outlet immersion type. When the reactor operates, the water distributor rotates slowly to provide certain driving force for the disturbance of the sludge bed. Meanwhile, the state of rotational flow and water distribution provides enough hydraulic shearing force for the sludge, and the generation of granular sludge is strengthened.

The invention is further improved as follows: aiming at the problem that the density of crystal nucleus for promoting sludge granulation is poor when granular sludge is cultured by using a continuous flow reactor, the adding mode of the granulation crystal nucleus is changed, the connection between the granulation crystal nucleus and inoculated sludge is strengthened by adding a flocculating agent and a coagulant aid into the inoculated sludge, the density of the inoculated sludge is improved by adding zero-valent iron or calcium chloride/sodium carbonate and the flocculating agent, and the phenomenon that the granulation crystal nucleus and the inoculated sludge are layered in the running process of the continuous flow reactor is prevented.

The invention is characterized in that: a culture method of granular sludge is developed, so that the granular sludge is easier to form in the reactor, and the load of the reactor can be greatly improved. Meanwhile, when low-concentration wastewater is treated, the addition of the zero-valent iron is beneficial to promoting electron transfer, strengthening the reaction process, improving the reaction rate and saving the treatment cost of the low-concentration wastewater. Compared with the traditional suspended sludge reactor, the invention can greatly improve the sludge concentration of the reactor and the load of the reactor, reduce the occupied area of the reactor and save the investment cost. Compared with a granular sludge reactor, the reactor can take flocculent sludge as an inoculation object, and reduce granulation crystal nucleus loss, accelerate sludge granulation speed and reduce the starting cost of the reactor by improving the density of the inoculated sludge and strengthening the sludge cohesive force method. The invention provides technical support for the design of a high-load reactor.

Drawings

FIG. 1 is a schematic diagram of an anaerobic reactor for treating low concentration wastewater, which is cited in patent ZL 201910487315.

Reference numerals

1-central water inlet end; 2-a central water inlet pipe; 3-a reaction zone; 4-water distribution port; 5-water distribution pipe; 6-anaerobic sludge; 7-water outlet; 8-a water distributor; 9-edge water inlet end; 10-tangential water distribution port; 11-a three-phase separator; 12-a clarification zone; 13-air vent.

Detailed Description

The invention is further illustrated by way of example in the following figures:

the sludge pretreatment flow is shown in a figure I, and the pretreatment flow is described as follows:

crushing the granular sludge, measuring the density of the granular sludge, and standing for later use; the aerobic activated sludge floc is used for inoculating the reaction zone 3.

When low-concentration wastewater is treated, the concentration of inoculated sludge is 2000-4000 mg/L, and the concentration of the sludge is 5-10 times of that of the granulation crystal nucleus.

Adding 200 plus 10000-mesh zero-valent iron into inoculated sludge, enabling part of wastewater and a flocculating agent to enter a water distribution pipe 5 of a water distributor 8 through a central water inlet end 1 and a water inlet pipe 2, and then enabling the wastewater and the flocculating agent to flow into a reaction zone 3 through a water distribution port 4; the other part of the wastewater and the flocculating agent enter the reaction zone 3 from the edge water inlet end 9 through the tangential water distribution port 10, the flocculating agent is used for adjusting the sludge density to be the same as the crystal nucleus sludge density by utilizing the hydraulic shearing force, and the flocculating agent, the zero-valent iron and the inoculated sludge are uniformly mixed;

when high-concentration wastewater is treated, the concentration of inoculated sludge is 4000-10000mg/L, and the concentration of the sludge is 10-100 times of that of the granulation crystal nucleus. A part of the waste water and the calcium chloride enter a water distribution pipe 5 of a water distributor 8 through a water inlet pipe 2 from a central water inlet end 1 and then flow into a reaction zone 3 through a water distribution port 4, the other part of the waste water and the calcium chloride enter the reaction zone 3 through a tangential water distribution port 10 from an edge water inlet end 9, sodium carbonate (the molar ratio of the calcium chloride to the sodium carbonate is (0.1-10): (0.1-10)) is added after uniform mixing, and the mixture is uniformly stirred by the same method.

The crushed granular sludge is put into a reaction zone 3, wastewater and 1-1000ppm PAM partially enter a water distribution pipe 5 of a water distributor 8 through a central water inlet end 1 and a water inlet pipe 2, and then flow into the reaction zone 3 through a water distribution port 4; the other part of the wastewater enters the reaction zone 3 from the edge water inlet end 9 through the tangential water distribution port 10, and the broken granular sludge and the inoculated sludge are tightly connected by utilizing PAM through hydraulic stirring.

After the sludge pretreatment is finished, the reactor is formally started, the water distributor 8 rotates slowly under the action of an external driving force, and drives the sludge 6 to fully contact with the wastewater in the reactor and react with the wastewater together with the water flow of the tangential water distribution port 10; the sludge is washed by hydraulic shearing force generated by water distribution, and the formation of granular sludge is accelerated.

Example 1

The reactor is used for culturing denitrification granular sludge, wherein 1# is used as a control group to directly add crushed granular sludge for granular culture, 2# is used for pretreating sludge by using the method, zero-valent iron and polymeric ferric sulfate are added to improve the density of inoculated sludge, the concentration of the sludge is 4000 mg/L, the concentration of crystal nucleus sludge is 200 mg/L, the inlet water is municipal secondary sedimentation tank wastewater, the nitrogen content of nitrate is 10-15 mg/L, the COD of the inlet water is a compound carbon source of sodium acetate and methanol, the concentration is about 40-60 mg/L, the ascending flow rate of the 1# reactor is 3m/h, and the ascending flow rate of the 2# reactor is 5m/h, and is gradually increased to 10 m/h along with the operation of the reactor. In the operation process, the phenomena of flocculent sludge loss and particle granulation crystal nucleus deposition occur in the No. 1 reactor, the operation effect of the No. 2 reactor is obviously better than that of the No. 1 reactor, the sludge concentration of the No. 1 reactor is reduced to 2756 mg/L and the sludge concentration of the No. 2 reactor is increased to 8965 mg/L after the operation of the reactor is finished. The specific operating parameters are shown in table 1:

table 1 operational monitoring data for example 1

Example 2

Anaerobic granular sludge is cultured by using the reactor, wherein No. 1 is used as a control group to directly add crushed granular sludge for granular culture, No. 2 is used for pretreating sludge by using the method, the sludge density is improved by using calcium chloride, sodium carbonate and polyaluminium chloride, the concentration of inoculated sludge is 9000mg/L, the concentration of nucleus sludge is 2000 mg/L, the inlet water is starch wastewater, the COD of the inlet water is 9000mg/L +/-1000 mg/L, the ascending flow rate of the No. 1 reactor is 3m/h, the ascending flow rate of the No. 2 reactor is 5m/h, and the loads of the two reactors are increased to 8-10 m/h along with the granulation. The sludge loss phenomenon and the phenomenon of layering of crystal nucleus and inoculated sludge exist in the early stage of the No. 1 reactor, and the sludge of the No. 2 reactor is obviously superior to that of the No. 1 reactor in both sedimentation performance and granulation degree. Specific operating data are shown in table 2.

Table 2 operation monitoring data of example 2

Example 3

The reactor is used for culturing denitrification granular sludge, wherein 1# is used as a control group to be directly added with crushed granular sludge for granular culture, 2# is used for pretreating sludge by using the method, the sludge density is improved by using calcium chloride, sodium carbonate and polyaluminium chloride, the sludge concentration is 9000mg/L, the crystal nucleus sludge concentration is 500 mg/L, the inlet water is oxalic acid production wastewater, the nitrate nitrogen content is 800-1200 mg/L, the nitrite nitrogen concentration is 50-150 mg/L, the COD of the inlet water is 800-1000 mg/L, and a carbon source is compounded by using sodium acetate and methanol to ensure that the C/N =4, the ascending flow rate of the 1# reactor is 3m/h, and the ascending flow rate of the 2# reactor is 5m/h and is gradually increased to 10 m/h along with the operation of the reactor. In the operation process, the flow rate of the reactor No. 1 is increased to 1.5 m/h when a large amount of flocculent sludge is lost, the operation effect of the reactor No. 2 is obviously better than that of the reactor No. 1, the sludge concentration of the reactor No. 1 is reduced to 4369 mg/L and the sludge concentration of the reactor No. 2 is increased to 16359 mg/L after the operation of the reactor is finished. The specific operating parameters are shown in table 3:

table 3 operational monitoring data for example 3

The embodiment 1, the embodiment 2 and the embodiment 3 are respectively used for culturing the low-concentration denitrification granular sludge, the high-concentration denitrification granular sludge and the anaerobic granular sludge, the sludge granulation is completed rapidly by using the method of the invention, and flocculent sludge is well reserved in the early stage of granulation, so that the method has high industrial application value.