Effect of coagulation-flocculation pre-treatment on the biological nitrogen removal by sequencing batch reactor

The present paper shows the results obtained through an experimental work aimed at studying the effects of a coagulation-flocculation pretreatment on the biological nitrogen removal carried out in a Sequencing Batch Reactor (SBR). A lab-scale SBR, working through a pre-denitrification followed by an aerated phase, was set in a full-scale continuous flow municipal wastewater treatment plant. Activated sludge from the oxidation tank was used as seed. A first experimental run was performed by feeding the SBR with the effluent from the traditional primary settle tank of the full-scale plant. Nitrification and denitrification rate removal measured agreed with the literature data, though the biomass yield was quite low. Validation and calibration of a mathematical model formulated for the nitrogen and carbon removal, was also performed by using the experimental data obtained; then the optimal operative cycle was selected. A second experimental run was made by feeding the biomass with the effluent from the coagulation-flocculation treatment. Since an incomplete denitrification was shown due to a lack of carbon source, the addition of methanol to the feed, as external source, was adopted. During each run, characterization of the influent and effluent from both reaction phases was made, along with the determination of the active biomass and the kinetic constants.