Analyzing Flow Characteristics and Influence of Biological Growth on Dispersion in Aerated Submerged Fixed-Film Reactors (ASFFR)

The Aerated Fixed Activated Sludge System is one of the biological systems used to treat different types of wastewater containing organic substances. This paper presents the results of the preliminary phase of a study to determine the performance pattern of such a system treating petrochemical wastewater on a pilot scale. As the hydraulic characteristics of such systems are important factors affecting the behaviour, design and interpretation of data from the reactor, the hydraulic regime of the system was determined using a pulse input of Rhodamine B into the system. Various air supply and water flows were used as independent variables during the tracer study. Experimental data in 16 different conditions were collected and dispersion number (d/ul) in each condition was determined using a computer program which was developed in this research. Furthermore, the statistical patterns were used to evaluate the fit of data in each condition with the ideal completely-mixed model. The results showed that, in a wide range of air supply and water flows, the completely mixed condition is achievable in this system; biological growth of film at different hydraulic loading rates did not change the pattern of mixing significantly. The content of this article is so organized that the complete methodology and computative approaches for performing flow pattern characterization in water and wastewater treatment systems are easily available.

Keywords
fixed activated sludge, aerated submerged fixed-film reactors, hydraulic regime, dispersion number, mixing