This living document will illustrate Standard Operating Procedures (SOPs) for sampling biofilm material from reverse osmosis (RO) membrane modules. The SOPs will empower the NAWI research community to apply omics tools (e.g., time-series metagenomic, meta-transcriptomic, metaproteomic and metabolomic workflows) to fundamentally understand biofilm formation with unprecedented resolution (e.g., the transition from innocuous to detrimental biofilm) and mitigate biofouling in water treatment and distribution systems.