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Biological reactors are the most energy-consuming facilities of conventional wastewater treatment plant (WWTP). Therefore, adjustment of aerators installation angles inside the aeration tank seems to be an effective way to ensure efficient biological performance. In this work, the biological treatment performance of Kermanshah's municipal WWTP (Kermanshah, Iran) was surveyed via varying angles of the aerators installation relative to the perpendicular. Two different aeration configurations in terms of installation angles of aerators, 30° and 45°, were considered. Effect of the aerators installation angles on variations of some operating and process parameters such as dissolved oxygen (DO), oxidation reduction potential (ORP), nitrogenous compounds, and phosphorus were pursued. From results, more DO and ORP amounts were found at the 30° angle compared to the 45° angle. However, changes trends in the DO and ORP amounts were similar at both angles. As the main conclusion, no prominent effect on remediation of carbon, nitrogenous compounds, and phosphorus was reported in these two angles. These results were justified by low influent organic loading, and also not to have appropriate conditions for nitrogen and phosphorus removal. In addition, in this study kinetic evaluation was conducted, and obtained findings were in a good agreement with literature. [ABSTRACT FROM AUTHOR]

Abstract A hybrid anaerobic activated sludge and rotating biological contactor (AnAS-RBC) reactor with sludge return was investigated for biological hydrogen production from molasses by a mixed culture of hydrogen-producing bacteria via a dark fermentation process. The pH was not controlled during the experiments. The effects of organic loading rate (OLR) and disk rotational speed (DRS) on process performance were studied using response surface methodology. Both OLR and DRS showed significant effects on all process responses. High levels of DRS were found favorable for efficient process. Optimal mixing of the bacterial culture contributed towards higher acetate production resulting in higher hydrogen production. The highest hydrogen production (168 mL/g COD) was achieved by applying OLR and DRS of 23 g/L.d and 30 rpm, respectively. In this study, the highest percentage of hydrogen in biogas produced was 87% in hydraulic retention time of 12 h. Highlights • Using a hybrid AnAS-RBC reactor for biohydrogen production from molasses. • Focusing on the effects of OLR and DRS, and delineating the mixing behavior. • The DRS exerted stronger effect than OLR on all process responses. [ABSTRACT FROM AUTHOR]

The biomass concentration of conventional activated sludge (CAS) process due to low sludge sedimentation in clarifiers is limited to 3000 mg/L. In this study, high-frequency ultrasound wave (1.8 MHz) was applied to enhance the CAS process performance using high Mixed Liquor Suspended Solid (MLSS) concentration. The study conducted using a pilot scale CAS bioreactor (with and without ultrasound) and their performance for treating a hospital wastewater were compared. Experimental conditions were designed based on a Central Composite Design (CCD). The sets of data analyzed, modeled and optimized using Response Surface Methodology (RSM). The effect of MLSS concentration 3000–8000 mg/L and hydraulic retention time (HRT) 2–8 h are considered as operating variables to investigate on process responses. The obtained results showed that high-frequency ultrasound was significantly decreased the sludge volume index (SVI) 50% and effluent turbidity about 88.5% at high MLSS. Also, observed that COD removal of both systems was nearly similar, as the maximum COD removal for sonicated and non-sonicated systems were 92 and 92.5% respectively. However, this study demonstrates that the ultrasound irradiation has not had any negative effect on the microbial activity. [ABSTRACT FROM AUTHOR]