Organic Agriculture and Local Food

Green Building & Retrofitting

Appropriate Technology: Water
Whole Systems Approach to Water	Constructed Wetlands Treatment	Rainwater Harvesting	Lagoon and Tank Based Treatment

Future Optional Vertical Flow Reed Bed to Treat Septage

It may be beneficial in the future to consider a vertical flow reed bed to treat septage on site. The bed is a simple planted sand filter, installed inside an impermeable liner. Leachate is collected at the low point in the bed and flows to a nearby treatment constructed wetland.

The pores in the sand are kept open by the plant stems, shoots and roots. The plants improve de-watering by seeking out moisture, and by keeping the septage open to air. At the same time, roots remove both pore water and biological slime in the sand.

Sludge will accumulate over time in the bed. Continuous exposure of the sludge to air promotes the decomposition and oxidation of the sludge. The volumes of sludge will be reduced between 90 to 98%. The principal form of reduction is de-watering. Mineralization is also significant (Kim 1993, Nielsen 1993, Reed et al 1995).

The bed is designed with a freeboard, which allows the sludge to accumulate for many applications. It is unlikely the bed will need to be cleared in less than ten years. If and when clearing becomes necessary, the accumulated material is scraped off the surface of the bed. The treated sludge, which is now a stabilized composted material, is suitable for land application in the forest.

Experience with septage treatment beds is that there are odours generated during the loading of the bed, but within 15 minutes to an hour, obnoxious odours have been replaced by an earthy smell, similar to that of the soil and leaf litter in a forest floor. During the loading period, most of the odours are trapped by the leaves and plant stems. Most people cannot smell any door when 50 to 100 metres down wind. The bed would be sited among trees to further reduce the possibility of unpleasant door. No buildings should be within 100 metres of a septage treatment bed.