COSTEL BUMBAC, ELENA ELISABETA MANEA, OLGA TIRON, VALERIU ROBERT BADESCU CORRELATION BETWEEN WASTEWATER TREATMENT PERFORMANCES AND SLUDGE CHARACTERISTICS The balance between biotechnological useful microorganisms species, as well as the aerobic sludge granules morphology influences the treatment plant performance. This paper presents an attempt to correlate the experimental results on wastewater treatment performance with aerobic granular sludge structural community. The experiments were conducted in two lab scale bioreactors operated in parallel at different retention times. Treatment performances achieved in both systems lead to an effluent that complies NTPA001 limits, both systems being able of simultaneous nitrification / denitrification and phosphorus removal. For qualitative and quantitative analysis of aerobic granular sludge specific microorganisms, DNA has been succeesfully isolated and purifyied from sludge samples, thus obtaining bacterial DNA extracts in concentrations of up to 56 ng/mL and 78% purity. The resulted DNA extracts were used for qPCR amplification. Amplification was carried out in the presence of a series of 10 pairs of primers for the detection / quantification of specific bacteria and genes involved in the treatment process: universal bacteria; Micotrix parvicella; Ammonia oxidizing archaea; Ammonium monooxigenase; Nitrobacter Sp.; nitrite reductase; N2O reductase; phosphorus accumulating microorganisms. The experimental results showed a qualitative and quantitative improvement of the sludge quality in terms of species distribution and share of biotechnologically useful bacteria.