Seyed Mahdi Ghasemi - Expert at Process Group, Toossab Consulting Engineers Company, Mashhad, Iran- Assistant supervisor, Research Center for Membrane and Separation Processes, Ferdowsi University of Mashhad, Mashhad, Iran
Poria Esmaeili - BSc Student, Department of Chemical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
Mahdi Pourafshari Chenar - Professor, Department of Chemical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

The A2O process is one of the conventional processes used for nutrient and BOD removal. This process is associated with issues such as high sludge production and low SRT during operation. Also, wastewater treatment plants (WWTP) overloading forces operators to produce more sludge in order to meet effluent quality standards. In this paper, enhancing conventional A2O to IFAS was investigated by simulation. GPS-X was used for modeling, simulation, and analyzing the process. The Integrated Fixed-film Activated Sludge (IFAS) process simultaneously consists of suspended sludge and attached biofilm. The enhancement was carried out through two scenarios using media with a filling factor of 50% and adding a new liquid line. Results showed that adding suspended media and the new liquid line (upgraded-A2O) reduced waste sludge by 15% and met the standards for wastewater quality. Also, IFAS showed a fourfold increase in SRT. IFAS can be applied as a better method of sludge stabilization and reduction. Although the IFAS and extended aeration processes operate similarly, IFAS involves high oxygen consumption at high SRT. Hence, economic evaluation is needed for both IFAS and upgraded-A2O. Based on the results, IFAS has 29% more energy consumption and 54% greater total operating costs Compared to upgraded-A2O. The total cost of wastewater for IFAS is 0.008 $/ (m3.d) less than that of upgraded-A2O.

A2O, GPS-X, Sludge Reduction, IFAS, Simulation