Constructed wetland treatment of agricultural effluent from an anaerobic digester

A study to assess the effectiveness of hybrid constructed wetlands in the treatment of agro-zoo technical diluted digestate was carried out. Continued stirred tank reactor (128 L capacity) was used to produce the digestates to be treated. The hybrid CW platform had three units (two vertical subsurface flow and one horizontal subsurface flow) filled with river gravel and sand media. Two experiments were performed one with a 50 L/d inlet flow, and the second with an inlet flow four times higher (200 L/d). The hybrid CW was able to remove COD, nitrate, ammonia and phosphorous. Mean removals referred to the lower inlet flow (50 L/d) organic load, were 76% for COD, 86% for nitrate, 87% for ammonia and 87% for phosphorous. Mean removals referred to the higher inlet flow (stress conditions 200 L/d) organic load, were 88% for COD, 73% for nitrate, 98% for ammonia and 99% for phosphorous. (C) 2013 Elsevier B.V. All rights reserved.