2020 Volume 18 Issue 6 Pages 383-397
This study aims to assess the performance of five municipal wastewater treatment plants (MWWTPs) from different locations in Morocco using chemical analyses and bioassays. The toxicity assessments were based on the chronic algal growth inhibition using the green microalgae Pseudokirchneriella subcapitata and acute immobilization using the crustacean Daphnia magna. The physicochemical results show that the effluents were mainly polluted with organic and nitrogenous compounds as indicated by higher values of chemical oxygen demand (COD), biochemical oxygen demand (BOD), as well as total nitrogen (TN). The promotion of algal growth was detected in all raw samples, except MWWTP2, MWWTP3, and MWWTP4 influents, in which, the half maximal effective concentration after 72 hours (EC50-72 h) were 61.83% v/v, 53.4% v/v and 87.46% v/v, respectively. Meanwhile, all treated effluents stimulate the algal growth, except MWWTP2 effluent (EC50-72 h: 55.1% v/v). Furthermore, the untreated samples display immobilizations towards Daphnia magna. The EC50-48 h values were ranked from 7.30% v/v to 79.76% v/v. However, only two effluents from MWWTP1 and MWWTP2 exhibit acute toxicities (the EC50-48 h were 45.80% v/v and 41% v/v, respectively). The Spearman correlation coefficients indicate strong positive correspondences between EC50-48 h and COD (r = 0.840, p < 0.05), TN (r = 0.731, p < 0.05), total phosphorus (TP) (r = 0.730, p < 0.05), and PO43- (r = 0.792, p < 0.05).
