# Minimal Organic Loading to a WWTP

Hi everybody!

I am designing a 1000 PE WWTP for a Sea Resort. I assumed extended aeration process and volumetric loading of 0.25 kgBOD/m3.d and got the needed volume of aeration basin of 240 m3.

My question is: ** What is the minimal volumetric loading or F/M ratio necessary for the process to work, i.e. what is the minimal number of people that need to be in resort throughout the year in order for the process to be maintained? **

M&E book states that the typical design values for extended aeration are 0.1-0.3 kgBOD/m3.d. When I apply the lowest value of 0.1 to my 240 m3 basin I end up with the load from 400 PE, which is quite high, because I guess the Resort will not be 40% full in winter months.

I assume the values given in M&E are given for the highest loading. Same case in other books and standards that I use, they all make recommendations for the highest loading, and I haven't yet come across the data about the lowest possible loading needed for the biomass to survive and do its work.

I guess the best solution is to make multiple trains and shut down one of the trains in off-season.

Thank you in advance for your answers!