I think the very popular Oxitop system is the easiest. Most wastewater laboratories have them.

https://www.xylemanalytics.com/en/general-product/id-1560/respirometric-bod-measuring-system-oxitop%C2%AE-i-is-6---wtw

The Best way to measure BOD is to use the methods in the book Titled "standard methods for the examination of water and wastewater".

Reads the attached file

Dear Shishita,

You can use activated sludge method to quantify the BOD of wastewater.

Hope it helps.