Efficacy analysis of a field scale IFAS reactor under different aeration strategies applied at high aeration rates: A statistical comparative analysis for practical feasibility

Abstract

In the present research study, a field-scale integrated fixed-film activated sludge reactor treating municipal wastewater was examined under three cyclic aeration on/off periods (also known as intermittent aeration), applied at a aeration rate of 110 m3/h (capable to maintain bulk dissolved oxygen in the range of 4.5–5.0 mg/L). The whole experimental campaign was divided into four operational phases (continuous aeration followed by three aeration on/off cycles, expressed in terms of ratio of aeration on/off time, Period I: 150/30 min, Period II: 120/60 min, Period III: 90/60 min). Each experimental run was studied at a hydraulic retention time of 11.1 h and mixed liquor suspended solids concentrations as 2 ± 0.2 g/L. The treatment performance results showed that high rate assisted in achieving the desired performance under applied intermittent aeration conditions. Except nitrogen removal, other performance parameters such as chemical oxygen demand, biological oxygen demand, total suspended solids, ammonia nitrogen, and phosphorus were found to be least affected by on/off control applied in Period I and could cope up with Indian discharge standards. Whereas, Period II and III were not found to be appropriate with respect to desired performance. With respect to nutrient parameters, nitrogen and phosphorus removal rates were significantly deteriorated with increasing aeration off times. A statistical comparison of different operational phases, using analysis of variance and Turkey Post Hoc test, was also done to check the similarity/dissimilarity of applied strategies. The results revealed that period I and continuous aeration phase were quite similar in terms of all performance parameters.