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.