Vermifilter

A vermifilter (also vermi-digester or lumbrifilter) is an aerobic treatment system, consisting of a biological reactor containing media that filters organic material from wastewater. The media also provides a habitat for aerobic bacteria and composting earthworms that purify the wastewater by removing pathogens and oxygen demand. The "trickling action" of the wastewater through the media dissolves oxygen into the wastewater, ensuring the treatment environment is aerobic for rapid decomposition of organic substances.

Vermifilters are most commonly used for sewage treatment and for agro-industrial wastewater treatment.^[1] Vermifilters can be used for primary, secondary and tertiary treatment of sewage, including blackwater and greywater in on-site systems and municipal wastewater in large centralised systems.

Vermifilters are used where wastewater requires treatment before being safely discharged into the environment. Treated effluent is disposed of to either surface or subsurface leach fields. Solid material (such as fecal matter and toilet paper) is retained, de-watered and digested by bacteria and earthworms into humus that is integrated into the filtration media. The liquid passes through the filtration media where the attached aerobic microorganisms biodegrade pathogens and other organic compounds, resulting in treated wastewater.

Vermifiltration is a low-cost aerobic wastewater treatment option.^[2] Because energy is not required for aeration, vermifilters can be considered "passive treatment" systems (pumps may be required if gravity flow is not possible). Another advantage is the high treatment efficiency given the low space requirement.