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. 2018 Jan 2;13(1):e0189867. doi: 10.1371/journal.pone.0189867

Fig 4. PCA analysis of ASs concentration and other physico-chemical indexes (data from winter) in influent (red circle, 1–10), secondary effluent (green square, 11–20) and effluent (blue diamond, 21–30).

Fig 4

Each object is a data vector of the 9 following variables: pH, DO, COD, NH4+-N, TN, ACE, CYC, SAC and SUC.