In a small package wastewater treatment plant, the operator should try to keep the dissolved oxygen in the aeration tank at approximately how many mg/L?

In a small package wastewater treatment plant, maintaining the dissolved oxygen levels in the aeration tank is crucial for the efficient functioning of the biological treatment process. The optimal dissolved oxygen concentration for aerobic conditions, where microorganisms can effectively break down organic matter, typically ranges from about 2.0 to 4.0 mg/L.

Choosing approximately 2.0 mg/L helps ensure that there is enough oxygen available for the aerobic bacteria without oversaturating the water with oxygen, which could lead to inefficiencies or even harm to the microbial community. At this level, the microorganisms are able to thrive and carry out their metabolic processes effectively, promoting optimal treatment of the wastewater.

While higher concentrations of dissolved oxygen can enhance treatment, they may not significantly improve the performance relative to the energy costs and aeration required to maintain those levels. Thus, setting the target around 2.0 mg/L strikes a balance between effective treatment and operational practicality in a small package treatment plant.