From start-up to heavy clogging: performance evaluation of horizontal subsurface flow constructed wetlands during 10 years of operation.

The objective of this work is to evaluate the performance of two horizontal subsurface flow constructed wetlands, one planted with cattail (Typha latifolia) and the other unplanted. The distinguishing feature of this study is that it spans a period of more than 10 years, from start-up to a final operation with heavy clogging and full overland flow. For most of the time, starting in June 2007, the system received municipal sewage previously treated in an upflow anaerobic sludge blanket (UASB) reactor, but for one specific period, the pre-treatment was comprised of the UASB reactor and a trickling filter in series.

Difficulties and modifications in the use of available methods for hydraulic conductivity measurements in highly clogged horizontal subsurface flow constructed wetlands.

Despite the fact that several authors consider the available measurement methods of hydraulic conductivity (k) suitable for a good representation of the bed condition and clogging potential in horizontal subsurface flow constructed wetlands, others have questioned their adequacy. In this work, hydraulic conductivity measurements with conventional and modified methods were undertaken in two small full-scale units, one planted with cattail (Typha latifolia) and the other unplanted. Both units had already been operating for seven years and showed a high degree of clogging.