Minimal Organic Loading to a WWTP

Published on by in Technology

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! ​