> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/structural-practices/septic.str/bod_decay.md).

# bod\_decay

Biozone BOD coefficient is normalized by the volume of biomass in the formula.