The simplest vermifiltration system is one which uses gravity... in one end and out the other.
Vermifiltration uses gravity to flow wastewater into the top, through the media and out the bottom.
Vermifilters can even be stacked directly on top of each other in towers. If the influent can go in at the top and out at the bottom, the stack can be as high as you like. The higher the stack is (or the more vermifilters in series), the better the level of treatment.
The key requirement for a gravity flow vermifilter system is that if the influent can be directly discharged into the vermifilter at the top, and the outlet can discharge to a soakage field or irrigation system, then no pumps are required.
This is not always the case though, such as where the land is flat and the wastewater flow is at or below ground level. In this case the wastewater needs to be raised into the inlet of the vermifilter, using a pump, that feeds into the top of a single pass or recirculating vermifilter.
Primary vermifilter feeding into two secondary vermifilters in series, all gravity flow.