System design

Low cost wastewater treatment for the world

System design requires an understanding of the site, the location of the dwelling, and where the treated effluent will be irrigated.


In this page:

System types

Three system types are described below:

Gravity flow vermifilter

Gravity flow vermifilters offer a simple method for high levels of treatment where there is fall between one reactor and the next reactor and the effluent field being irrigated. Gravity flow vermifilters achieve a lower level of treatment than recirculating vermifilters, but are simpler to construct and maintain. Pumps are required for recirculating vermifilters but no fall is required between vermifilters.

The example below shows a gravity flow vermifilter system with primary and secondary treatment:

This is the simplest system, which can gravity feed treated effluent to land or crops, so no pump is required. Multiple secondary vermifilter reactors can be employed in series. This design suits land with fall between the wastewater entry and treated water exit. Additional fall would be required for sufficient pressure for a bell siphon and irrigation lines.

However, an elevated site with sufficient fall is not always available, for example where the land is flat or the wastewater flow is at (or below) ground level. Where the effluent needs to be raised into the inlet of the vermifilter (or to the soakage field), a pump is required.

Single pass vermifilter

This uses a single pump, followed by gravity flow. The example below shows a single-pass vermifilter with primary and secondary treatment:

This system uses a pump to raise the primary-treated wastewater up into an elevated vermifilter, with the outlet elevated sufficiently to gravity discharge the treated wastewater to surface irrigation. The outlet should have sufficient head for a bell siphon to generate pressure on the irrigation lines for even distribution of water through the drippers. 

However, the recirculating vermifilter is perhaps the easiest design to match the level of treatment required with most land forms. 

Recirculating vermifilter

A recirculation pump passes wastewater through a vermifilter reactor multiple times. The example below shows a primary vermidigester followed by a secondary recirculating vermifilter:

The primary treated wastewater is pumped from the sump to the top of a secondary vermifilter and returns via gravity back to the sump. The sump overflows into a tank with a pressure pump and float switch, or alternatively gravity feeds using a bell siphon to surface irrigation.

Construction

Vermifilter.com have put together a section focussed on constructing off-grid solar vermifilter systems that treat wastewater to a standard suitable for surface irrigation of crops, pasture or trees: 

Vermifilter system construction