Constructed wetlands for grey water treatment

A vertical flow and horizontal sub-surface flow wetland were compared with a novel system (the GROW green roof water recycling system) for treatment of low-organic strength domestic grey water for reuse. The vertical and horizontal flow wetlands were planted with Phragmites australis in a sand:soil:compost medium. The GROW system was planted with a variety of marginal plants selected for treatment and aesthetic characteristics. BOD removal did not differ significantly between the three systems which all consistently met USEPA standards for grey water for reuse. However, the GROW system was most effective at removal of suspended solids and turbidity (mean removal 91.2% and 98.2% respectively) and both GROW and VF were more effective at removing pathogens (4.2 and 4.8 log reduction of total coli-forms respectively) than the HF (2.7 log reduction).