As noted in a previous column, I have had questions about design, installation and maintenance of constructed wetland systems. The kind of system I am most familiar with is the subsurface flow constructed wetland. In this system, septic tank effluent is delivered to the head of the wetland into normal drainfield rock material. The best treatment results are obtained when flow is equalized to the wetland cell (bed). Effluent is delivered in timed dosing through a pressure distribution network in the rock.Both the wetland vegetation and the pea gravel substrate are involved in the treatment processes. In cold climates,
