Raw Water Quality

The higher the organic matter content in raw water, the greater the oxygen consumption for microbial decomposition, metabolism and nitrification. When controlling dissolved oxygen, focus should be placed on fluctuations in influent flow rate and changes in influent organic matter content.

Activated Sludge Concentration

On the premise of satisfying pollutant removal and discharge standards, the activated sludge concentration should be reduced as much as possible to decrease aeration volume and power consumption. Avoid over-aeration at low concentrations to prevent sludge bulking and turbid effluent; high concentrations require a correspondingly high dissolved oxygen level to avoid hypoxia that inhibits treatment efficiency.

Sludge Settling Ratio

Over-aeration causes tiny air bubbles to attach to activated sludge flocs, leading to sludge floating and poor settling performance. Especially when sludge undergoes filamentous bulking, bubbles adhere more easily, resulting in a large amount of scum on the liquid surface, which must be avoided in actual operation.

pH Value

pH affects activated sludge concentration and microbial activity, thereby indirectly changing the dissolved oxygen level in wastewater. During treatment, the function of the regulating tank must be fully utilized, and water quality conditions should be monitored in coordination with discharging units. Appropriate reagents should be added promptly to neutralize abnormal pH.

Temperature

The saturated dissolved oxygen concentration in wastewater varies with temperature. Both low and high temperatures inhibit microbial activity and reduce treatment efficiency. For low-temperature environments in northern regions, underground, semi-underground or indoor treatment processes can be adopted; in hot weather, the regulating tank is used to control temperature and improve treatment performance.

Food-to-Microorganism Ratio (F/M)

Both excessively high and excessively low F/M ratios increase oxygen demand in wastewater. Energy saving can be achieved by adjusting the F/M ratio: on the basis of ensuring treatment efficiency, the F/M ratio should be increased as much as possible to reduce unnecessary aeration energy consumption.