Why are natural biological treatment processes often inadequate for large-scale wastewater treatment?

Natural biological treatment processes rely on the presence of sufficient bacteria and oxygen to effectively decompose organic matter in wastewater. In large-scale wastewater treatment operations, the volume and concentration of pollutants can exceed what these natural processes can handle.

When the influent contains excessive pollutants, the demand for oxygen increases significantly, and the existing bacterial populations might not be adequate to manage the high levels of contaminants. This imbalance can lead to incomplete treatment, as the bacteria may struggle to thrive and effectively break down the organic material under such stress.

Thus, the reliance on natural biological treatment methods can become inadequate in scenarios where the pollutant load is substantially high, as the system may not provide enough oxygen or support a sufficient bacterial population to manage the treatment requirements effectively.