Wikipedia
A vermifilter (also called vermicomposting filters and vermicomposting digesters) is an aerobic treatment system that provides primary treatment of blackwater influent. Vermifiltration was first advocated by researchers at the University of Chile in 1992 as a low cost sustainable technology suitable for decentralised sewage treatment in rural areas. Vermifilters offer treatment performance similar to conventional decentralised wastewater treatment systems but with potentially higher hydraulic processing capacities.
Untreated blackwater enters an enclosed and ventilated environment above a bed of filter medium. Solids accumulate on the surface of the filter bed while liquid drains through the filter medium and is discharged from the digester. The solids (feces and toilet paper) are aerobically digested by composting worms into humus, thereby significantly reducing the volume. The liquid effluent is either discharged directly to a drain field or undergoes secondary treatment before being used for surface irrigation of soil.