The most significant difference between summer and other seasons is the higher temperature, which can also cause changes in the production varieties of industrial enterprises due to seasonal variations, thereby affecting the quality and quantity of wastewater. The water consumption of urban residents in summer is also higher than in other seasons. Some characteristics of sewage treatment plants during summer operation, such as high temperatures, thunderstorms, etc.
The impact of these characteristics in summer on sewage treatment plants is multifaceted. Not only will it affect the physiology of microorganisms and the oxygenation performance of equipment, but it will also affect various reaction processes and the mental state of personnel in the sewage treatment process. Therefore, in operation management, attention should be paid to these characteristics and targeted solutions should be made.
The impact of high temperature on microbial activity
Water temperature has become a very important parameter due to its impact on chemical reactions, reaction rates, aquatic organisms, and suitability for perpetual use. The amount of oxygen dissolved in hot water is less than in cold water, and as the temperature increases, the rate of biochemical reactions also increases. Combined with the decrease in oxygen levels in surface water, summer months often lead to severe depletion of dissolved oxygen in river channels. When a large amount of hot water is discharged into natural receiving water bodies, this impact is exacerbated.
The optimal temperature range for bacterial activity is 25-35 ℃. Nowadays, many sewage treatments use cover deodorization measures, which lead to heat accumulation. When the temperature rises to 50 ℃, aerobic digestion and nitrification stop. Therefore, cooling measures such as water spraying should be taken.
One more thing, more than one friend has reported that after the aeration tank is covered, the nitrification efficiency actually deteriorates under high summer temperatures. If any friends have experienced this situation, they can also communicate with the Pollution Toho Community!
The effect of high temperature on dissolved oxygen in aeration tanks
Due to the high temperature in summer, oxygen is not easily dissolved in water. Therefore, the dissolved oxygen transferred from the same quality of air to water is relatively low, often resulting in insufficient oxygen supply.
It is reported that when the dissolved oxygen in the aeration tank is 2mg/L, the dissolved oxygen at the center point of the 500ram diameter floc is only 0.1mg/L, indicating that except for the microorganisms on the surface of the floc reaching a high dissolved oxygen level, most of the microorganisms inside are in a state of hypoxia. Therefore, when the sludge concentration in the aeration tank is high, such as 4g/L, the dissolved oxygen concentration should be controlled between 3-4mg/L.
Management of secondary sedimentation tank under high temperature
Due to the high temperature, the sedimentation rate of the layer decreases, and the secondary sedimentation tank is prone to mud overturning, resulting in an increase in SS in the effluent.
Under high temperature conditions, the metabolic capacity of microorganisms accelerates, and anaerobic or denitrification may occur in the secondary sedimentation tank, often producing gas and causing sludge to float up. Some algae also utilize nutrients in the water to generate algae on the surface of the secondary sedimentation tank, which affects the appearance. For this reason, sufficient oxygen supply should be ensured during summer operation, and if necessary, coagulants such as PAC should be added to improve the sedimentation performance of sludge.
Management of structures, pipelines, and equipment under high temperatures
High temperatures and thunderstorms in summer often cause equipment failures, thereby affecting the normal operation of the process. To ensure a smooth summer for the sewage treatment plant, measures should be taken for some key equipment, pipelines, and structures based on their characteristics in summer to prevent problems before they occur.
