“…h X 2-7 : methane production (MP) (Vrecko et al, 2006) T g X 2-8 : net energy consumption (E) (Vrecko et al, 2006) M w . h X 2-9 : operating cost (Vrecko et al, 2006) -X 3-1 : overall bulking risk (Comas et al, 2008) days X 3-1,1 : low C/N bulking risk (Comas et al, 2008) days X 3-1,2 : low DO bulking risk (Comas et al, 2008) days X 3-1,3 : low F/M bulking risk (Comas et al, 2008) days X 3-2 : overall foaming risk (Comas et al, 2008) days X 3-2,1 : low FM foaming risk (Comas et al, 2008) days X 3-2,2 : high S s /X s foaming risk (Comas et al, 2008) days X 3-3 : rising sludge risk (Comas et al, 2008) days X 4-1 : TIV COD (Copp, 2002) days X 4-2 : TIV TSS (Copp, 2002) days X 4-3 : TIV BOD (Copp, 2002) days X 4-4 : TIV TN (Copp, 2002) days additional objectives are taken into account, specifically economical, technical and legal issues. Thus, the degree of satisfaction of the economical objectives was quantified by the following criteria: sludge production (X 2-1 ), aeration energy (X 2-2 ), pumping energy (X 2-3 ), carbon source (X 2-4 ), mixing energy (X 2-5 ), heating energy (X 2-6 ), methane production (X 2-7 ) and net energy consumption (X 2-8 ).…”