Odour impact of extensive wastewater technologies in small treatment plants

CENTA Experimental Centre focuses on the development, assessment, and dissemination of appropriate technologies for treating urban wastewater from small municipalities. Effluent from Carrión de los Céspedes (Seville, Spain) is treated using diverse systems, predominantly extensive processes. This study evaluated organic matter and macro-nutrient removal alongside odorous emissions, simultaneously. Collectively, the technologies implemented in CENTA met wastewater organic matter discharge thresholds, with the most significant odour emission rate (OER) detected in anaerobic lagoons I and II (ALI and ALII), a facultative lagoon (FL) and a septic tank (ST) (625.0 and 21.3, 66.3 and 23.0 ou E /s, respectively). Novel odour generation indices—OGI C (OER per unit of organic matter removal) and OGI CN (OER per combined organic matter and nitrogen removal)—were proposed. OGI C reached the highest individual values in free flow wetlands (FFW) and ALI (23,200 and 14,711 ou E /g O 2 , respectively), although this order reversed under OGI CN . In addition, a chemometric analysis carried out using two-dimensional principal components analysis (PCA) explained 60.29% of the total variance and successfully grouped the technologies under study.