A comparative assessment of intensive and extensive wastewater treatment technologies for removing emerging contaminants in small communities.

Ecosystem pollution due to the lack of or inefficient wastewater treatment coverage in small communities is still a matter of great concern, even in developed countries. This study assesses the seasonal performance of 4 different full-scale wastewater technologies that have been used in small communities (<2000 population equivalent) for more than 10 years in terms of emerging contaminant (EC), chemical oxygen demand (COD), total suspended solids (TSS) and NH4-N removal efficiency. The studied technologies, which were selected due to their widespread use, included two intensive treatment systems (an extended aeration system (AS) and a rotating biological contactor (RBC)) and two extensive treatment systems (a constructed wetland (CW) and a waste stabilization pond (WSP)), all located in north-eastern Spain. The studied compounds belonged to the groups of pharmaceuticals, sunscreen compounds, fragrances, antiseptics, flame retardants, surfactants, pesticides and plasticizers. The 25 ECs occurred in wastewater at concentrations ranging from undetectable to 80 μg L(-1). The average removal efficiency was 42% for the CW, 62% for the AS, 63% for the RBC and 82% for the WSP. All the technologies except the WSP system showed seasonal variability in the removal of ECs. The ecotoxicological assessment study revealed that, whilst all the technologies were capable of decreasing the aquatic risk, only the WSP yielded no risk in both seasons.