“…All data regarding UASB effluent quality presented in Fig. 2 were obtained from UASB systems operating in developing countries ( Aiyuk et al, 2004 ; Amildon Ricardo et al, 2018 ; Antonio da Silva et al, 2021 ; Bhatti et al, 2014 ; Bressani-Ribeiro et al, 2021a ; Cardinali-Rezende et al, 2013 ; De Almeida et al, 2009 ; Espinosa et al, 2021 ; Gonçalves et al, 2020 ; Komolafe et al, 2021 ; Lopes et al, 2017 ; Luo et al, 2014 ; Marson et al, 2020 ; Oliveira and Von Sperling, 2008 ; Paniagua et al, 2020 ; Silva et al, 2021a ; Vassalle et al, 2020a , Vassalle et al, 2020 ). According to these studies, post-treatment systems following UASB reactors include aerated filter, anaerobic filter, trickling filter, facultative pond, maturation pond and, to a lesser extent, coagulation/flotation unit.…”