CN110482835B - Method for rapidly preparing aerobic granular sludge - Google Patents

Abstract

The invention discloses a method for rapidly preparing aerobic granular sludge. The method comprises the following operation steps: (1) extracting sludge with higher biological activity; (2) carrying out ultrasonic pretreatment on the sludge; (3) Add flocculant to the sludge, and the addition amount is 1.5‰～3‰ of the dry solid mass of the sludge; (4) Add lignocellulose to the sludge, and the addition amount is 5% to 15% of the dry solid mass of the sludge. %; (5) Microbial exopolysaccharide was added to the sludge, and the addition amount was 1.5‰ to 3‰ of the dry solid mass of the sludge; (6) The sludge was centrifugally dehydrated and granulated to obtain aerobic granular sewage. mud. The aerobic granular sludge obtained by the present invention is put into the aeration tank as the core material for inoculating the granular sludge, the cultivation period is short, the system is stable, and it can be quickly utilized and practiced in engineering. Compared with traditional activated sludge, it has good settling performance and short settling time. At the same time, the added chemicals will not affect the activity of microorganisms in the sludge and improve the efficiency of the wastewater treatment system.

Description

A kind of method for rapidly preparing aerobic granular sludge

technical field

The invention belongs to the technical field of water treatment, in particular to a method for rapidly preparing aerobic granular sludge which is applied to wastewater treatment.

Background technique

With the rapid development of economy and society, and the acceleration of industrialization and urbanization, a large amount of toxic and harmful substances have accumulated in natural water bodies, and the freshwater resources that human beings depend on have been seriously polluted. This has led to a series of water ecological and environmental problems that need to be solved urgently. Among them, water eutrophication has become a major water environment problem that seriously threatens aquatic animals and plants, human health, and industrial and agricultural development. The main cause of water eutrophication is the excessive discharge of nitrogen and phosphorus in domestic sewage.

The existing water treatment methods have many problems, and most of them have certain limitations, such as long process flow, complex treatment process, large floor space, low treatment efficiency, and high operating cost. In view of the poor effect of simultaneous nitrogen and phosphorus removal in most biological treatments in sewage treatment plants, the aerobic granular sludge method is considered to be a promising advanced sewage biological treatment technology because of its economical and efficient characteristics. Aerobic granular sludge is a group composed of mutually aggregated, multi-species microorganisms and is considered to be a special kind of self-immobilizing special biofilm. The aerobic granular sludge has the characteristics of large specific gravity and biological density, which makes it have a fast settling speed, which is beneficial to the separation of sludge and water, reducing or eliminating the sludge secondary sedimentation tank, simplifying the process flow, and reducing the floor space and investment cost of the sewage treatment system. . Moreover, the high sludge concentration and volumetric load of aerobic granular sludge can withstand the impact of water quality fluctuations and high organic load, ensuring good effluent quality. In addition, the granular structure of aerobic granular sludge makes _O2 subject to mass transfer resistance during the transportation process, and it is divided into aerobic layer, anoxic layer and anaerobic layer in turn from outside to inside, providing suitable living space for different microorganisms , this unique hierarchical structure enables it to have high biodiversity and the potential to simultaneously degrade organic carbon, nitrogen and phosphorus.

Since 1992, dozens of papers have reported that the use of ultrasonic effects can improve sludge dewatering efficiency and biological treatment. Ultrasonic pretreatment destroys the good water retention of bacterial micelles and the bound water in cells, while maintaining larger sludge particles, which improves the sludge settling performance. The destroyed sludge can be used as endogenous carbon, saving or even replacing external carbon sources, and accelerating the formation of aerobic granular sludge nutrient channels.

In 1991, Mishima and Nakamura first obtained aerobic granular sludge in a continuous flow aerobic sludge bioreactor. Morgenroth et al. used the SBR reactor to cultivate aerobic granular sludge for the first time in 1997. By gradually shortening the hydraulic retention time and increasing the water exchange rate, and using a very short settling time (0-1min), it took 70 days to successfully achieve Aerobic sludge granulation. It shows that the formation time of aerobic granular sludge is too long. Most practices show that stable aerobic granular sludge takes 60 to 90 days to form, which is difficult to meet the start-up requirements for practical engineering applications.

Liu et al. confirmed that adding 500mg/L of polyaluminum chloride can accelerate the formation process of aerobic granular sludge (from 17 days to 7 days). The particles formed in the reactor of aluminum chloride were smaller (2.7 mm). Moreover, polyaluminum chloride can significantly improve the sedimentation, compactness, mechanical strength and EPS secretion of aerobic granular sludge. However, the addition of PAC has little effect on COD and NH4 ⁺ -N treatment. It shows that although the addition of high molecular polymer accelerated the incubation time of aerobic granular sludge, the effect of sewage treatment did not change significantly, which increased the engineering cost.

Wan et al. improved the mechanism of the formation process of aerobic granular sludge from the perspective of calcium precipitation as a granular core: a variety of crystals formed an inorganic core in an alkaline environment for microorganisms to attach, and then these microorganisms secreted PS to gradually form the framework of aerobic granular sludge . Among them, the main functional bacteria attached to the inner core are Sphingomonas sp., Paracoccus sp. Sinorhizobium americanum strain and Flavobacterium sp., these bacteria will promote the synthesis of extracellular circulating diguanylate cyclase, and then accelerate the aerobic granular sludge formation and maturation. By changing the composition of aerobic granular sludge, the formation process of aerobic granular sludge is accelerated, but the process is complicated and difficult to achieve in practical applications.

Due to the unstable start-up time of aerobic granular sludge, it is one of the bottlenecks that limits the application and optimization of aerobic granular sludge. Due to certain factors, aerobic granular sludge has not been widely used in the world. In view of this problem, the inoculated sludge of spherical granulation of fresh aerobic dewatered sludge is developed to promote the granulation of aerobic sludge and further promote the formation of aerobic granular sludge, which is beneficial to the cultivation conditions of aerobic granular sludge. Optimization.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for rapidly preparing aerobic granular sludge with rapid granulation, short culture period and stable system.

The present invention solves the above-mentioned technical problems with the following technical solutions:

A method for rapidly preparing aerobic granular sludge of the present invention comprises the following operation steps:

(1) Extracting sludge with higher biological activity;

(2) carrying out ultrasonic pretreatment to the sludge of step (1);

(3) adding a flocculant to the sludge in step (2), stirring to make it fully mixed, and the amount of the flocculant added is 1.5‰-3‰ of the dry solid matter mass of the sludge;

(4) adding lignocellulose to the sludge in step (3), stirring to make it fully mixed, and the amount of lignocellulose added is 5%-15% of the dry solid mass of the sludge;

(5) adding microbial exopolysaccharide to the sludge in step (4), stirring to make it fully mixed, and the added amount of microbial exopolysaccharide is 1.5‰-3‰ of the dry solid mass of the sludge;

(6) The sludge in step (5) is centrifugally dehydrated and granulated to obtain aerobic granular sludge.

The sludge described in step (1) is secondary sedimentation tank sludge, excess sludge or sugar food industry sludge, and is screened to remove filamentous and large particulate matter, and the MLVSS/MLSS in the sludge is 0.75-0.8.

In the ultrasonic pretreatment described in step (2), the ultrasonic power used is 20-25Hz, and the pretreatment time is 30-50s.

The flocculant described in step (3) is one or more of polyferric sulfate, polyaluminum chloride and polyacrylamide.

The lignocellulose described in step (4) is one or more of bagasse cellulose, straw cellulose, wood cellulose, and bamboo cellulose, and the cellulose is dried and pulverized to a particle size of 0.425mm- 0.5mm.

The microbial extracellular polysaccharide described in step (5) is one of gellan gum, welan gum and xanthan gum.

In the centrifugal dewatering treatment in step (6), the rotational speed used is 3000-4000 r/min, the time is 15-25 min, and the moisture content of the sludge after dewatering treatment is 75%-80%.

The granulation treatment described in step (6) is realized by an extrusion granulator, and the dewatered sludge is extruded through a sieve plate with a pore diameter of 1.5mm-3mm, cut into columnar particles, and then rotated for 5-15min. After granulation, spherical aerobic granular sludge is obtained.

Compared with the prior art, the method of the present invention has the following beneficial effects:

(1) The present invention selects the sieved sludge with higher biological activity to ensure the diversity of the number and types of microorganisms in the sludge; after the sludge is ultrasonically pretreated, the sludge bacteria micelles are destroyed, so that the sludge has Better polymerizability and settling properties;

(2) The method of the present invention appropriately mixes pulverized lignocellulose, such as bagasse, sawdust, straw and bamboo fiber, etc., since cellulose is a biochemically degradable component, the stomata channels in the degraded granular sludge are favorable for oxygen In order to improve the internal porosity of the sludge, improve the oxygen mass transfer efficiency, improve the sludge activity, and accelerate the formation of aerobic granular sludge.

(3) The method of the present invention makes the formed sludge compared with traditional activated sludge by appropriately adding chemical flocculants, such as polyferric sulfate, polyaluminum chloride and cationic, anionic or nonionic polyacrylamide. It has good settling performance and saves settling time. At the same time, the addition of chemicals not only does not affect the biological activity of activated sludge, but also improves the efficiency of the wastewater treatment system.

(4) The method of the present invention appropriately adds microbial extracellular polysaccharides, such as cold gelatin, welan gum and xanthan gum, which can be used as degradable biological adhesives to bind activated sludge into agglomerates, and can be used as microbial culture medium The adsorbed microorganisms secrete a large amount of extracellular polymers, and quickly form aerobic granular sludge bacteria micelles.

(5) The method of the present invention processes the dewatered sludge into spherical aerobic granular sludge through granulation, and the granular sludge formed by physical granulation is more uniform in force and can withstand greater surface tension. The gas pool can withstand stronger high-pressure water flushing, aeration flushing, collision and cutting between sludges, etc.

Detailed ways

The technical solutions of the present invention are further described below in conjunction with specific examples, but are not limited to the following examples.

Example 1

(1) Activated sludge dehydration: extract 20g of sludge from the secondary sedimentation tank of the sewage treatment plant, remove filamentous and large particles through a sieve, and MLVSS/MLSS in the sludge = 0.8; Add anionic polyacrylamide with a sludge dry solid mass of 3‰, stir to make the sludge fully flocculate; then add bagasse cellulose with a sludge dry solid mass of 10%. After crushing and pretreatment until the particle size is 0.425mm-0.5mm, the cellulose and the sludge are fully mixed by stirring; then cold gelatinization with a dry solid mass of 2‰ of the sludge is added, and the sludge is fully glued by stirring; then Centrifugal dewatering at 3500r/min for 20min was used as the sludge for the test, and the sludge moisture content was 80%.

(2) Spherical granulation: using a granulator, extrude the sludge after the dehydration treatment in step (1) from a sieve plate with an aperture of 1.5 mm, and then place the obtained cylindrical sludge in a drum for 5 min of rotation After granulation, aerobic granular sludge with a particle diameter of 1.5 mm was produced.

The application shows that the physical granular sludge formed by dewatering and granulation is used as the inoculated sludge, which obviously improves the granulation speed of aerobic sludge. On the 25th day, the particle size of more than 90% of the inoculated physical granular sludge was greater than 0.2 mm, the removal rate of COD and ammonia nitrogen during the cultivation period was greater than 90%, and the removal rate of TN in the later period of cultivation was about 70%.

Example 2

(1) Activated sludge dehydration: extract 20g of industrial sludge produced during the treatment of sugar industry wastewater, remove filamentous and large particles through a sieve, and the MLVSS/MLSS in the sludge = 0.78; ultrasonic power 23kHz, ultrasonic time 40s After ultrasonic pretreatment, polyaluminum chloride with a dry solid mass of 2‰ of the sludge was added, and the sludge was fully flocculated by stirring; then straw cellulose with a dry solid mass of 15% was added, and the straw cellulose was dried at 105 °C in the early stage. Dry for 4 hours, then crush and pre-process to a particle size of 0.425mm-0.5mm, stir to fully mix the cellulose and the sludge; then add Welan gum with a dry solid mass of 3‰ of the sludge, and stir to make the sludge fully glued ; Then centrifugal dewatering at 4000r/min for 15min was used as the sludge used in the test, and the sludge moisture content was 78%.

(2) Spherical granulation: using a granulator, extrude the sludge after the dehydration treatment in step (1) from a sieve plate with an aperture of 2 mm, and then place the obtained cylindrical sludge granules in a drum for 10 min of rotation After granulation, aerobic granular sludge with a particle diameter of 2 mm was produced.

The application shows that the physical granular sludge formed by dewatering and granulation is used as the inoculated sludge, which obviously improves the granulation speed of aerobic sludge. On the 20th day, the particle size of more than 90% of the inoculated physical granular sludge was greater than 0.2 mm, the removal rate of COD and ammonia nitrogen during the cultivation period was greater than 90%, and the removal rate of TN in the later period of cultivation was about 70%.

Example 3

(1) Activated sludge dehydration: extract 20g of excess sludge from the sewage treatment plant, remove filamentous and large particles through a sieve, MLVSS/MLSS in the sludge = 0.75; after ultrasonic pretreatment with ultrasonic power of 25 kHz and ultrasonic time of 30 s, Add polymeric ferric sulfate with a dry solid mass of 1.5‰ of the sludge, and stir to fully flocculate the sludge; then add bamboo cellulose with a dry solid mass of 5%. Pretreatment to a particle size of 0.425mm-0.5mm, stirring to fully mix the cellulose and sludge; then adding xanthan gum with a dry solid mass of 1.5‰ of the sludge, stirring to make the sludge fully glued; then at 3000r/min Centrifugal dehydration for 25min was used as the sludge used in the test, and the sludge moisture content was 75%.

(2) Spherical granulation: using a granulator, the sludge after the dehydration treatment in step (1) is extruded from a sieve plate with an aperture of 3 mm, and then the cylindrical sludge particles obtained are placed in a drum and rotated for 15 minutes. After granulation, aerobic granular sludge with a particle diameter of 3 mm was produced.

The application shows that the physical granular sludge formed by dewatering and granulation is used as the inoculated sludge, which obviously improves the granulation speed of aerobic sludge. On the 16th day, the particle size of more than 90% of the inoculated physical granular sludge was larger than 0.2 mm, the removal rate of COD and ammonia nitrogen during the cultivation period was greater than 90%, and the removal rate of TN in the later period of cultivation was about 70%.

Claims (4)

1. a method for rapidly preparing aerobic granular sludge, is characterized in that, comprises the following operation steps: (1) Extract sludge with high biological activity; (2) Ultrasonic pretreatment is performed on the sludge in step (1), the ultrasonic power used is 20-25 Hz, and the pretreatment time is 30-50 s; (3) Add flocculant to the sludge in step (2), stir to make it fully mixed, and the amount of flocculant added is 1.5‰-3‰ of the dry solid mass of the sludge; (4) Add lignocellulose to the sludge in step (3), stir to make it fully mixed, the amount of lignocellulose added is 5%-15% of the dry solid mass of the sludge; lignocellulose is bagasse fiber One or more of cellulose, straw cellulose, wood cellulose and bamboo cellulose, and the cellulose is dried and pulverized to a particle size of 0.425 mm-0.5 mm; (5) Adding microbial exopolysaccharide to the sludge in step (4), stirring to make it fully mixed, the added amount of microbial exopolysaccharide is 1.5‰-3‰ of the dry solid mass of the sludge; The polysaccharide is one of gellan gum, welan gum and xanthan gum; (6) The sludge in step (5) is centrifugally dehydrated and granulated to obtain aerobic granular sludge; the centrifugal dehydration treatment adopts a rotating speed of 3000-4000 r/min and a time of 15-25 min. The moisture content of the sludge after dehydration treatment is 75%-80%. 2 . The method for rapidly preparing aerobic granular sludge according to claim 1 , wherein the sludge described in step (1) is secondary sedimentation tank sludge, excess sludge or sugar-refining food industrial sludge, and 2 . Filamentous and large particulate matter are removed by sieving, and the MLVSS/MLSS in the sludge is 0.75-0.8. 3. The method for rapidly preparing aerobic granular sludge according to claim 1 or 2, wherein the flocculant in step (3) is one of polyferric sulfate, polyaluminum chloride and polyacrylamide or several. 4. The method for rapidly preparing aerobic granular sludge according to claim 1 or 2, wherein the granulation treatment in step (6) is realized by an extrusion granulator, and the dewatered sludge is passed through a pore size of Spherical aerobic granular sludge is obtained by extruding in a sieve plate of 1.5 mm-3 mm, cutting it into columnar granules, and then rotating granulation for 5-15 min.