Operation and management of anaerobic tower: 1. Issues to be noted in the operation and management of anaerobic biological treatment facilities;

(1) When the concentration of the treated wastewater is high (CODCr value greater than 5000mg/L), the reflux operation mode must be adopted, and the reflux ratio is determined according to the specific situation. Effective reflux can not only reduce the inflow concentration, but also increase the inflow volume, ensuring that the water flow distribution in the treatment facility is uniform and avoiding short flow phenomena. Reflux can also prevent severe fluctuations in the influent concentration and pH value inside the anaerobic reactor, allowing the anaerobic reaction to proceed smoothly. In other words, it can reduce the demand for alkalinity in anaerobic reactions and lower operating costs. Anaerobic reaction is a production process where the effluent temperature is higher than the inlet water temperature Therefore, when the temperature is low in winter, the temperature inside the reactor remains constant, allowing anaerobic microorganisms to operate at their optimal temperature as much as possible. (2) The temperature of general industrial wastewater is difficult to reach 35 ℃ and requires heating (especially in winter). Therefore, in order to save the energy required for heating, on the one hand, attention should be paid to insulation (including measures such as increasing the reflux rate) to prevent heat loss from the reactor as much as possible. On the other hand, the characteristic of high sludge concentration in the reactor should be fully utilized to increase the sludge concentration as much as possible and weaken the influence of temperature on anaerobic reactions. (3) Biogas should be discharged promptly and effectively. The anaerobic digestion process is inevitably accompanied by the production of biogas, which can stir and act on sludge, promoting the mixing and contact between sewage and sludge, which is its advantageous side. At the same time, the presence of biogas also plays a role similar to floating slag. When biogas overflows upwards, it brings some sludge to the liquid surface, resulting in the production of floating slag, an increase in suspended solids content in the effluent, and a deterioration of water quality. Therefore, gas baffles and gas collection hoods should be installed to extract biogas from the anaerobic digestion device, leaving sufficient sedimentation area near the effluent weir to ensure the quality of the effluent. (4) The sludge load should be appropriate. To maintain the balance of the three stages of anaerobic digestion, balance the generation and consumption of intermediate products such as volatile fatty acids, and prevent acid accumulation from causing a decrease in pH value, the influent organic load should not be too high, generally not 0.5kgCODcr/(kgMLSS · d). By increasing the sludge concentration inside the reactor, a relatively low sludge load can be maintained to achieve a higher volumetric load. Generally speaking, the volumetric load of anaerobic digestion equipment is above 5kg CODcr/(m3 · d), and even up to 50kg CODcr/(m3 · d). (5) When the concentration of suspended solids in the treated wastewater is high (generally above 1000mg/L), appropriate pretreatment such as sedimentation, filtration, or flotation should be carried out to reduce the suspended solids content in the influent and prevent clogging of the packing layer. Generally, the suspended solids in the influent of AF do not exceed 200mg/L, but if the suspended solids can be biodegraded and evenly dispersed in the sewage, they will have little adverse effect on AF. (6) To fully create an anaerobic environment. Anaerobic is a prerequisite for the normal activity of anaerobic microorganisms, while methanogens must operate efficiently in an absolutely anaerobic environment. Efforts should be made to avoid contact with air as much as possible during the process of sewage lifting into anaerobic digestion equipment and effluent reflux, in order to minimize the chance of contact with air. During the water flow process, it is advisable to avoid phenomena such as water drop and agitation. Control tanks, reflux tanks, etc. should be covered and sealed, and air lift pumps should not be used for sewage lifting. Anaerobic reaction structures are best subjected to airtight testing to ensure tightness and no leakage. 2. Control indicators of anaerobic bioreactor (1) oxidation-reduction potential: The method of measuring oxidation-reduction potential is used to determine whether multiple oxidation-reduction component systems in the anaerobic reactor are in equilibrium. Although this method has poor reliability, due to the simplicity of oxidation-reduction potential measurement and its combination with other monitoring indicators, it has certain guiding significance. (2) Concentration ratio of propionate and acetate: If the organic load of the anaerobic reactor exceeds the normal range, the concentration ratio of propionate and acetate will immediately increase before other operating parameters change. Therefore, the ratio of propionate and acetate concentrations can be used as a sensitive and reliable warning indicator for abnormal operation caused by anaerobic reactor overload. (3) Volatile acid VFA: Abnormal increase in volatile acids is the most effective indicator of inhibited metabolism of methane producing bacteria in anaerobic reactors. (4) Phenylacetic acid: Phenylacetic acid is an intermediate product produced by the degradation of large organic compounds such as aromatic amino acids and lignin. When treating wastewater containing such pollutants, the content of phenylacetic acid in the effluent of anaerobic treatment is a more sensitive indicator of the operating status of anaerobic reactors than volatile acids. (5) Methyl mercaptan: Methyl mercaptan has a unique odor that can be detected by smell even at the lowest levels. A sudden increase in the content of methyl mercaptan (sudden appearance or increase in odor) often indicates a sudden increase in the content of toxic chlorinated hydrocarbons in the influent. (6) Carbon monoxide CO: The production of CO is closely related to the production of methane. CO is insoluble in water and can be monitored online. There is a good correlation between the content of CO in the gas phase and the concentration of acetate in the liquid phase, and the change in CO content is also related to the inhibitory effects caused by heavy metals and organic toxicity. 3. Basic conditions for maintaining high efficiency in anaerobic bioreactors (1) Suitable pH value: In order for anaerobic processes to proceed smoothly, the pH value in the reactor must be between 6.5 and 8.2. (2) Adequate conventional nutrition: The concentration of nitrogen in the reactor must be within the range of 40-70mg/L to meet the needs, while maintaining lower concentrations of phosphorus and sulfides can meet the requirements. Methanobacteria have a specific need for sulfides and phosphorus, and their content must be ensured in the reactor. Sometimes, it is necessary to add phosphate fertilizer and sulfate to the influent. (3) Essential trace specific nutrients: There are many specialized nutrients that can activate methane bacteria, such as iron, cobalt, nickel, zinc, manganese, molybdenum, copper, and even selenium, boron, etc. Lack of one of them may seriously affect the entire biological treatment process. (4) Appropriate temperature: Anaerobic reactions generally operate under moderate temperature conditions of 30-37 ℃. (5) Adaptability to toxicity: It is necessary to complete the domestication of anaerobic microorganisms to adapt to toxic substances. (6) Adequate metabolic time: It is necessary to ensure both hydraulic retention time (HRT) and solid retention time (SRT) for anaerobic biological treatment. (7) Moderate carbon source: The organic matter from the influent should meet the carbon source requirements for heterotrophic methane bacteria for biosynthesis, while the dissolved CO2 in the reactor should meet the carbon source requirements for autotrophic methane bacteria. (8) The mass transfer of pollutants to microorganisms is good: The granular sludge in anaerobic bioreactors has good mass transfer ability in fluidized state, but excessive accumulation of biomass or excessive thickness of biofilm when using anaerobic biofilm method may cause mass transfer problems. It is necessary to regularly discharge the remaining biological sludge or increase the reflux ratio to reduce some mass transfer resistance.