In industrial wastewater treatment engineering, the common methods for cultivating activated sludge (strains) are:

1. Inject clean water (and introduce domestic sewage) into the aerobic tank to a certain water level, and pay attention to the water temperature.

2. Start the fan, and blow according to the fan operation procedures.

3. Add the filtered concentrated manure water to the aerobic tank (when the manure water is insufficient, it can be supplemented by sludge in septic tanks and drainage ditches. ), so that the sludge concentration is not lower than 1000mg/L and BOD reaches a certain value.

4. If conditions permit, strains of activated sludge can be added to speed up the culture.

5. Aerate, stir, settle and drain the reaction tank according to the operation flow of activated sludge culture.

6. Observe the growth of activated sludge through microscopic examination and determination of sedimentation ratio and sludge concentration. Pay attention to the changes of online PH value and DO value, and adjust the process in time.

7. Determine the initial water quality and supernatant water quality in the drainage stage, and judge the activity of activated sludge and the situation of dominant bacteria according to the changes of the concentration values of NH3-N, BOD, COD, NO3- and NO2- in the influent and effluent, so as to adjust the dosage of influent, drainage, manure, NH4Cl, H3PO4 and CH3OH and the time distribution in the circulation.

8. Pay attention to the growth of activated sludge. When a large number of dense bacterial micelles are observed through microscopic examination, and protozoa (such as bell worms) can be observed, and the number increases rapidly from few, it shows that the sludge is mature and can be domesticated in production wastewater.

Domestication steps of activated sludge

1. Through analysis, confirm that all indicators of incoming water are within the allowable range, and prepare water.

2. Start to enter a small amount of production wastewater, the amount of which shall not exceed 20% of the treatment capacity before domestication. At the same time, fresh water, manure and NH4Cl are supplemented.

3. After better treatment, the consumption of production wastewater can be increased by no more than 10 ~ 20% at a time, while the consumption of NH4CL can be reduced. And continue to increase the production wastewater after microbial adaptation and consolidation until NH4Cl stops completely. At the same time, the indexes such as CODcr concentration in effluent were monitored, and the sludge characteristics of mixed liquor were observed. In the period of sludge domestication, the metabolites, namely the supernatant after sludge separation, should be discharged in time.

4. Continue to increase the consumption of production wastewater until it is fully loaded. In the full-load operation stage, due to the cultivation and maintenance of sufficient activated sludge with high concentration and high activity in the tank, the MLSS of the mixed liquor after aeration in the tank reached 5000mg/ 1. In this process, the dissolved oxygen is monitored synchronously, the operation of the aerator is controlled, and the sludge is examined by biological phase microscope.

Monitoring and control during commissioning

There are many factors that affect the treatment effect during commissioning, mainly including CODcr concentration, pH value, temperature and dissolved oxygen, so it is essential to monitor the whole system through sensory judgment and chemical analysis. According to the monitoring and analysis results, adjust the influencing factors to achieve the best results.

1, temperature

Temperature is the main environmental factor affecting the whole process, and all kinds of microorganisms grow in a specific temperature range. The temperature range of biochemical treatment is 10 ~ 40℃, and the optimum temperature is 20 ~ 30℃. Any microorganism can only survive in a certain temperature range, and can grow and reproduce in large quantities in a suitable temperature range. When cultivating sludge, it is necessary to put it under the most suitable temperature conditions to make microorganisms grow at the fastest speed. Too low or too high a temperature will slow down the metabolic rate and growth rate, and too high a temperature will kill microorganisms.

2.ph value

The life activities and substance metabolism of microorganisms are closely related to pH value. The optimum pH of most bacteria and protozoa is 6.5 ~ 7.5, and they grow and reproduce best in this environment, and the adaptive range of pH is 4 ~ 10. However, in the aeration system of activated sludge wastewater treatment, as the main body of activated sludge, the bacteria in the bacterial micelle can produce more viscous substances and form good flocs when the pH value is 6.5 ~ 8.5.

3. nutrients

Microorganisms in wastewater should constantly absorb nutrients, degrade complex macromolecular substances or high-energy compounds into simple low-molecular substances or low-energy compounds through catabolism (alienation), and release energy; Through anabolism (assimilation), the energy and substances provided by catabolism are transformed into their own cellular substances; At the same time, the generated metabolic waste is excreted.

Water, carbon source, nitrogen source, inorganic salts and growth factors are the conditions for microbial growth. Nitrogen source and phosphorus-containing inorganic salt should be supplemented in wastewater according to the ratio of BOD5∶N∶P= 100∶4∶ 1, so as to create good nutritional conditions for the culture of activated sludge.

4. Suspended substance SS

Sewage contains a lot of suspended solids. Most of the suspended solids have been removed by pretreatment, but some of them cannot be degraded. Scum layer will be formed during aeration, but it will not affect the sewage treatment of the system.

5. What does dissolved oxygen do?

Improved biochemical bacteria belong to aerobic. Oxygen has two effects on aerobic microorganisms: ① oxygen acts as the final electron acceptor in respiration; ② The biosynthesis of alcohols and unsaturated fatty acids needs oxygen. And only oxygen (called dissolved oxygen) microorganisms dissolved in water can be utilized.

In activated sludge culture, the supply of DO should be considered comprehensively according to the structure and concentration of activated sludge and the concentration of wastewater. Specifically, it is determined by observing the structure of activated sludge under a microscope, that is, the maturity, measuring the concentration of mixed liquid in the aeration tank and monitoring the change of CODCr in the supernatant of the aeration tank. According to the experience, DO should be controlled at 1 ~ 2 mg/L at the initial stage of culture, because the floc structure has not yet formed at this time, excessive oxygen supply enhances the metabolic activity of microorganisms, and the supply of nutrients is insufficient, which leads to the oxidation of sludge itself and the aging of sludge. In the mature period of sludge culture, DO should be increased to about 3 ~ 4 mg/L, so that microorganisms in sludge flocs can get enough DO and have good settling performance. During the whole culture process, DO should be gradually improved according to the sludge culture situation.

Special attention should be paid to DO not be too low, DO is insufficient, aerobic microorganisms can not get enough oxygen, the normal growth law will be affected, and the metabolic capacity will be reduced. At the same time, microorganisms that DO not require much will emerge as the times require, so that the normal cultivation process of biochemical bacteria will be destroyed.

6. MLSS concentration of mixed solution

Microorganism is the active part of biological sludge and the main body of organic matter metabolism, which plays a major role in biological treatment. The MLSS value of mixed sludge can roughly represent the number of active parts. Biological treatment of high concentration organic wastewater generally needs to maintain a high sludge concentration. During the commissioning and operation of this project, the range of MLSS is 4.4-5.6g/L, and the optimal value is about 4.8g/L. ..

7. The influent CODcr concentration and influent organic matter concentration have great influence on the treatment.

8. Microscopic examination of sludge.

Activated sludge is in different growth stages, and various microorganisms also show different proportions. Bacteria are responsible for decomposing the basic metabolism of organic matter, while protozoa (including metazoa) devour free bacteria. During the debugging and operation of sewage, there are many kinds of microorganisms, such as bacteria, green algae and other algae, protozoa and metazoa. Protozoa include solar worms, fiber worms and metazoa, and metazoa have nematodes. There are a large number of fixed ciliates in the mixed solution at the later stage of debugging, which shows that the effluent quality of the treatment system is good.

9. Sludge index SVI is about 80 1/mg in normal operation.