Horizontal subsurface flow constructed wetlands for tertiary treatment of dairy wastewater.

The aim of this work was to evaluate the efficiency of horizontal subsurface flow constructed wetlands (HSFCWs) planted with Typha domingensis and Phragmites australis in the final treatment of dairy wastewater. Ten microcosms-scale reactors simulating HSFCWs were arranged outdoors under a semi-transparent plastic roof. Five replicates were planted with T. domingensis and five with P. australis. In both cases, light expanded clay aggregate (LECA) 10/20 was used as a substrate. Real effluent with previous treatment was used. In order to evaluate contaminant removal efficiencies in each reactor, pH, electrical conductivity, suspended solids, ammonium, nitrate, nitrite, total phosphorus, and chemical oxygen demand (COD) were analyzed before and after treatment. HSFCWs planted with T. domingensis and P. australis were efficient for the final treatment of dairy wastewater. Removal efficiencies obtained in microcosms planted with both macrophytes were over 96% for ammonium and nitrite. Nitrate removal efficiency was 39%. COD decreased along the experiment near 75% for both treatments. High removal percentages for suspended solids (78.4-81.1%) were also achieved. However, systems planted with T. domingensis were significantly more efficient for total phosphorus removal (88.5%) than those planted with P. australis (71.6%).