Avoiding clogging in constructed wetlands by using anaerobic digesters as pre-treatment

Abstract The main operational problem of subsurface flow constructed wetlands (CWs) is clogging of granular medium, a phenomenon related to the accumulation of different types of solids that lead to a reduction of the infiltration capacity of the gravel bed. It is generally accepted that the application of a good wastewater pre-treatment is essential for the long-term operation of subsurface flow CW. Anaerobic digesters (ADs) could help to the aim of clogging prevention. Two combined AD-CW treating either municipal or winery wastewater were designed and monitored for trough performance and efficiency parameters, solids accumulation and hydraulic conductivity, over a long term period. CW operated at high organic loading rates in terms of TCOD and BOD 5 while suspended solids loading rates and solids accumulation in CW were lower. In turn, CW maintained an adequate hydraulic conductivity and low rates of solids accumulation.