This is a nice concise description you found thseng.

In places like Haiti where people need not only clean water but
employment, the building and selling of biosand filters by
nationals has been a boon to local economies.

It may be possible to inoculate a filter using an existing filter's smutzedecke, as long as the same water source
is used by both filters. This might speed up the time it takes
for the bacterial disinfection action to start. Still might be
several days.

I remember hearing there is evidence that chemical eating bacterial grow and can remove oil and other man made materials.