Cultivation conditions and precautions for anaerobic reactor granular sludge

Anaerobic granular sludge is produced in high-load anaerobic reactors in high-concentration wastewater treatment systems for industries such as starch, starch sugar, citric acid, alcohol, and papermaking. EGSB 、 IC) Fresh granular sludge produced. The volumetric load, upflow velocity, and removal rate of the anaerobic reactor are all higher than 20kgCOD/(m ³˙ d) ，5m/h and 90%。

　　（ ) Factors to consider when cultivating granular sludge
　　1. Substrate
　　The cultivation of granular sludge first requires certain substrate requirements. Generally, in the substrate for cultivating granular sludge, COD:N:P=110~200:5:1. The substrates of organic waste liquid can be divided into carbohydrate-type and protein-type. In order to successfully cultivate granular sludge, N and P need to be added to carbohydrate-type wastewater. For protein-type wastewater, carbon sources such as glucose need to be added. N and P 。 ( such as glucose )。

　　2. Temperature
　　Anaerobic treatment of wastewater mainly relies on the life activities of microorganisms to achieve the treatment purpose. Different microorganisms require different temperature ranges for growth. A slight difference in temperature can cause an imbalance between the two main populations. Therefore, temperature is very important for the cultivation of granular sludge. Granular sludge at low temperature (15~25℃ ) 、mesophilic (30~40 ℃ ) and high temperature (50~60 ℃ ) have been successful. Generally, the cultivation time at high temperature is shorter than that at mesophilic temperature, but due to the high temperature NH3 The increased toxicity of the mixture with certain compounds will lead to certain limitations in its application. ; Mesophilic temperature is generally controlled at 35 ℃, under appropriate other conditions, 1~3 months, granular sludge can be successfully cultivated. ; There is less research on cultivating granular sludge at low temperatures, but literature reports that in experiments using low-temperature acclimatized granular sludge to treat low-concentration pharmaceutical wastewater, COD removal rate reached 90% ，and good results were obtained.

　　3、 pH value
　　Inside the reactor The pH value should be controlled within the suitable range for methanogens (6.8-7.2) 。Due to different properties of wastewater pH value, in order to ensure the stability of the value in the reactor and prevent the accumulation of acid and the inhibition of methanogens, chemical reagents such as pH value NaHCO3、Na2CO3、 Ca(OH)2 can be added to the wastewater.

（ ) Factors affecting granular sludge formation
　　1. Alkalinity
　　It is generally believed that the alkalinity in the influent water quality should generally be 1000mg/L (as CaCO3 calculated ) around, and for wastewater mainly composed of carbohydrates, influent alkalinity: COD >1:3 is necessary. Some scholars have shown that in the early stage of granular sludge cultivation, controlling the effluent alkalinity at 1000mg/L ( as CaCO3 calculated ) above can successfully cultivate granular sludge. After the granular sludge matures, the requirement for the alkalinity of the influent is not high. This is of positive significance for reducing treatment costs.

　　2. Trace elements and inert particles
　　Trace elements also play an important role in the good growth of microorganisms. Among them Fe， Co ， Ni ， Zn etc. are beneficial to improving sludge activity and promoting granular sludge formation.
　　In addition, inert particles, as the core for bacterial attachment, play a positive role in granulation. In addition, studies have shown that the addition of activated carbon can greatly shorten the granulation time of sludge ; after the addition of activated carbon, the granular sludge has a large particle size and makes the reactor run more stably.

　　3、 SO42-
　　About SO42- on the formation of granular sludge is still under discussion. Sam-Soon The extracellular polymeric substance hypothesis suggests that a high partial pressure of local hydrogen induces microorganisms to produce extracellular polymeric substances, leading to interactions between the bacterial surface and other components. Through electrostatic attraction of charged groups and bridging effects such as physical contact, a biofilm containing multiple components is formed, which is a necessary condition for the formation of granular sludge. However, in the presence of sulfate, the rapid utilization of hydrogen by sulfate-reducing bacteria prevents the reactor from establishing a high hydrogen partial pressure, thus hindering the formation of granular sludge. However, some domestic and foreign scholars have found that very thin filaments can be produced when treating wastewater containing high sulfate, which can serve as the original nucleus for the attachment of methanogenic filaments, thus initiating granule formation. ; Sulfides produced by sulfate reduction combine with some metal ions to form insoluble particles, which may become secondary nuclei for granular sludge growth.

　　4. Inoculum sludge and inoculation amount
　　Generally, there are no special requirements for inoculum sludge, but different inoculum sludge directly affects the speed of granular sludge formation. Therefore, ensuring good sludge settling performance, abundant anaerobic microbial species, and high activity is very beneficial to accelerating the formation of granular sludge.
　　Regarding the amount of inoculum sludge, some scholars believe that the anaerobic sludge inoculation amount is 11.5 kgVSS/m³ ( Calculated according to the volume of the reaction zone ) is suitable for rapidly cultivating anaerobic granular sludge.

　　5. Startup method
　　Using low-concentration influent combined with a startup method that gradually increases the hydraulic load is conducive to sludge granulation. This is because low-concentration influent can effectively avoid the excessive accumulation of inhibitory biochemical substances, while a higher hydraulic load can enhance the hydraulic screening effect.

　　6. Hydraulic load
　　Gradual increase. Too low a hydraulic load will lead to excessive growth of a large amount of dispersed sludge, affecting the sludge settling performance and even causing sludge bulking. However, an excessively high hydraulic load will shear the granular sludge and peel off the extracellular polysaccharide viscous layer of unaggregated cells, hindering adhesion and aggregation. Therefore, a smaller hydraulic load should be used in the initial stage (0.05-0.1m³ / ㎡• h) allows flocculent sludge to bond with each other and grow into groups, which is conducive to the formation of the initial body of granular sludge. When a certain amount of sludge appears, increase the hydraulic load to 0.25 m ³ / ㎡• h or more, which can wash away some flocculent sludge, allowing the denser granular sludge to settle to the bottom of the reactor and form a granular sludge layer. In order to achieve sludge granulation as quickly as possible, increasing the hydraulic load to 0.6m ³ / ㎡• h can wash away most of the flocculent sludge. However, the hydraulic load should not be increased too quickly; otherwise, the premature elimination of a large amount of flocculent sludge will lead to excessive sludge load and affect the stable operation of the reactor.