What is the typical F:M ratio range for an extended aeration process?

The typical Food to Microorganism (F:M) ratio range for an extended aeration process is generally around 0.2 to 0.5, but it can sometimes extend up to about 1.0 depending on specific operational conditions. Extended aeration systems are characterized by longer retention times and a lower F:M ratio, which promotes the growth of denser biomass.

In these processes, a lower F:M ratio helps to ensure thorough treatment of the wastewater, allowing for more complete degradation of organic matter and promoting stable operation of the biological treatment system. The low F:M is effective in encouraging the growth of microorganisms that can survive on lower food sources, leading to better treatment efficiency and lower sludge production.

In this scenario, while the choice providing a ratio of 0.05 to 0.15 is noted, it does not accurately represent the broader accepted range for effective operation of extended aeration systems, which usually supports better effluent quality at higher F:M values than those stated in that option. Therefore, the given ratio of 0.2 to 0.4 or possibly extending to around 0.5 is generally more typical in design and operational guidelines for extended aeration processes.