Dealing with BOD (bacterial oxygen demand) in the black water system

We are getting ready to install the basic black water system.  Todd Banks pointed out that we need some kind of filtration system to deal with the BOD.  Steven Markovich concurred with the  need to deal with BOD.  Given that some filtration is key,  factors that we are considering are type of filtration, placement and its size.  Any filtration system needs to fit in a small portion of the lab or efficiently and transparently outside (commercialization seems to demand simplicity and economy).  Some things we are looking at are: sand filters after the septic tank like used for swimming pools.  pre-filtration that removes most solids (composting toilet, making fuel to burn, etc.), textile/carbon pre/post-filters and chemical treatments at various stages.  I'm leaning toward making a fuel with pre-filtered wastes (I remember how well it burned on shit-detail in the Army) that have been macerated and filter-pressed with a fuel mixture.  Paul Scalese and i have discussed the potential for sawdust or combinations of sawdust (e.g., he makes an interesting coal/sawdust  fuel bisquette that i bet could also be a filter) as a filtration medium and fuel.  i think that making the water as clean as posible before going to the septic tank makes sense.  This is an open topic; what do others think?