Environmental conditions
- Temperature: Temperature is an important factor affecting anaerobic fermentation. Different anaerobic fermentation processes have their appropriate temperature ranges. For example, the appropriate temperature for medium-temperature anaerobic fermentation is generally around 35°C, and the appropriate temperature for high-temperature anaerobic fermentation is generally around 55°C. Too high or too low temperature will affect the activity of microorganisms, and thus affect the fermentation effect, so the fermentation temperature needs to be strictly monitored and controlled.
- pH value: pH value is also one of the key parameters of anaerobic fermentation. Generally speaking, the appropriate pH value for anaerobic fermentation is between 6.5 and 7.5. Too high or too low pH value will inhibit the activity of microorganisms and cause abnormal fermentation process. During the fermentation process, the pH value may change due to the metabolism of microorganisms, so it needs to be monitored regularly and adjusted by adding acid-base regulators.
- Alkalinity: Alkalinity can reflect the buffering capacity of the fermentation system and is of great significance for maintaining the stability of the fermentation process. Generally, the alkalinity of the fermentation liquid is required to be within a certain range, such as 2000-5000 mg/L (measured in CaCO3). Low alkalinity may cause large fluctuations in the pH value of the fermentation liquid, affecting the growth and metabolism of microorganisms.
Material characteristics
- Organic matter content: Organic matter is the substrate of anaerobic fermentation, and its content directly affects the gas production rate and treatment effect of fermentation. Commonly used indicators of organic matter content include chemical oxygen demand (COD) and biochemical oxygen demand (BOD). During the fermentation process, it is necessary to regularly monitor the changes in the content of organic matter to understand the progress of fermentation and the treatment effect.
- Nutrients: Anaerobic fermentation microorganisms require certain nutrients for normal growth and metabolism, such as carbon sources, nitrogen sources, phosphorus sources, etc. Therefore, it is necessary to monitor the content of nutrients in the fermentation materials to ensure that they meet the needs of microorganisms. Generally speaking, the carbon-nitrogen ratio (C/N) of anaerobic fermentation is more suitable between 20-30.
- Toxic and harmful substances: Fermentation materials may contain some toxic and harmful substances, such as heavy metals, pesticide residues, etc. These substances will inhibit or poison microorganisms and affect the normal progress of fermentation. Therefore, it is necessary to monitor the toxic and harmful substances in the fermentation materials to ensure that their content is within the allowable range.
Microbial activity
- Microbial concentration: Microbial concentration is an important indicator reflecting the number of microorganisms in the fermentation system, which is generally determined by measuring sludge concentration or cell density. The level of microbial concentration directly affects the speed and efficiency of fermentation. It needs to be monitored regularly during the fermentation process and adjusted as needed.
- Microbial activity: Microbial activity refers to the metabolic capacity and growth and reproduction capacity of microorganisms. Commonly used monitoring methods include specific activity determination and enzyme activity determination. The level of microbial activity directly affects the fermentation effect, so it is necessary to monitor regularly and improve the activity of microorganisms by optimizing fermentation conditions.
Fermentation products
- Biogas production and composition: Biogas is one of the main products of anaerobic fermentation, and its production and composition are important indicators for measuring the fermentation effect. It is necessary to measure the production of biogas regularly and analyze the composition of biogas, such as methane content and carbon dioxide content, by methods such as gas chromatography. Generally speaking, the methane content in biogas from anaerobic fermentation should be between 50% and 70%.
- Properties of biogas slurry and biogas residue: Biogas slurry and biogas residue are two other products of anaerobic fermentation, and their properties also need to be monitored, such as pH value, organic matter content, nutrient content, etc. of biogas slurry, and moisture content, organic matter content, heavy metal content, etc. of biogas residue. These indicators are of great significance for the subsequent treatment and utilization of biogas slurry and biogas residue.
