The impact on microorganisms in activated sludge
-Inhibition of microbial activity: Difficult to degrade organic compounds such as phenols and polycyclic aromatic hydrocarbons can inhibit the activity of enzymes in microbial cells in activated sludge, leading to inhibition of physiological activities such as respiration and substance metabolism, and affecting the ability of activated sludge to remove pollutants.
-Changing the microbial community structure: Long term exposure to recalcitrant organic matter can cause changes in the microbial community structure in activated sludge. Microorganisms capable of degrading recalcitrant organic matter gradually become dominant populations, such as the Pseudomonas genus with special degradation capabilities, while the number of microorganisms sensitive to recalcitrant organic matter decreases or even disappears.
The impact on the settling performance of activated sludge
-Sludge swelling: Certain recalcitrant organic compounds can cause deterioration of the settling performance of activated sludge, leading to sludge swelling. For example, when the activated sludge process is used to treat wastewater containing a large amount of carbohydrates, it is easy to cause filamentous bacteria to swell the sludge, multiply in large numbers, loosen the sludge structure, deteriorate the settling performance, increase the sludge volume index (SVI), and make it difficult to separate sludge and water.
-Impact on sludge floc structure: Difficult to degrade organic matter may disrupt the structural stability of sludge flocs, causing them to become smaller and looser, and reducing the settling performance of sludge. Hydrophobic and difficult to degrade organic matter can alter the surface properties of sludge, reduce the interaction forces between sludge particles, and hinder the formation and stability of flocs.
The impact on the treatment efficiency of activated sludge
-Reduced treatment efficiency: The presence of recalcitrant organic matter can decrease the removal efficiency of pollutants in wastewater by activated sludge. Due to the difficulty of rapidly decomposing recalcitrant organic matter by microorganisms, the effluent's chemical oxygen demand (COD), biochemical oxygen demand (BOD), and other indicators increase, making it difficult to meet water quality standards.
-Increasing treatment costs: In order to improve the treatment efficiency of recalcitrant organic matter, it is necessary to increase treatment time, add additional chemicals, or adopt more complex treatment processes, which will increase the cost of activated sludge treatment of sewage, including energy consumption, chemical costs, and equipment maintenance costs.
The impact on the biological activity of activated sludge
-Reduce dehydrogenase activity: Dehydrogenase is an important indicator reflecting microbial activity. Difficult to degrade organic matter can reduce the activity of dehydrogenase in activated sludge, indicating a decrease in microbial metabolic activity and substrate utilization ability.
-Impact on respiration rate: Difficult to degrade organic matter can inhibit the respiration of activated sludge microorganisms, leading to a decrease in respiration rate and a weakened ability of microorganisms to obtain energy, thereby affecting their growth, reproduction, and ability to degrade pollutants.
