An integrated wastewater treatment system using a BAS reactor with biomass attached to tubular supports

This paper describes laboratory experiments aimed to develop a new wastewater treatment system as an alternative to a conventional domestic wastewater plant. A modified Biofilm Airlift Suspension reactor (BAS), with biomass attached to tubular supports, is proposed to address low organic loads (typical of domestic sewage) and low residence time (typical of compact reactors technology). Attached and suspended biomasses, coupled to the high dissolved oxygen (DO), allow high removal efficiencies (90% and 56% for COD and N–NH4+ removal respectively) and high effluent quality to be reached. The experimental activity, divided into three parts, demonstrates the good efficiency of the process, and the reduction of the removal kinetics for the high operating pressure used in the technology. The occurrence of simultaneous nitrification–denitrification (SND) was also observed. When compared with the conventional BAS system, the present treatment shows comparable removal efficiencies and higher specific removal rates (80 mg COD/g VSS and 2.60 mg N–NH4+/g VSS). The experimental results were coupled with the development of a numerical model to aid in designing a full-scale treatment plant in Italy.

► A BAS reactor with biomass attached to fixed pipes is proposed for civil sewage treatment. ► Effects of high pressures on suspended biomass are analyzed. ► Simultaneous nitrification–denitrification processes are taken into account. ► A comparison with conventional activate sludge treatment efficiency is carried out. ► Experimental and model results were used to design a full-scale plant.