Abstract. This study aims to determine the performance of the jet clarifier for turbidity removal and its mechanisms for proposing the optimal operating conditions and design criteria. The experiment were performed continuously using a pilot scale jet clarifier with the volume of 243 L. Effects of liquid flow rates, types of liquid phase, and sludge blanket heights on turbidity removal efficiency were investigated. Moreover, the residence time distribution (RTD) study was carried out to investigate the flow pattern. The results indicated that the jet clarifier can effectively reduce the turbidity of the synthetic water with the efficiency of 80% under the optimal condition. The RTD results suggested that the flow pattern in the jet clarifier corresponded to the design as the plug flow and mixed flow conditions were found in the coagulation and the flocculation/sedimentation zones, respectively. The presence of the sludge blanket can reduce the bypass and recirculated flows. Besides, the increase of flow rate resulted in the increase recirculation in the tank. It can be suggested that the jet clarifier can be used for removing turbidity in the water treatment. The hydrodynamic in the reactor, which relates to flow pattern in the reactor, is one among the important factors in a jet clarifier.

An enzyme-immobilized platform for biocatalysis was developed through 3D printing of a hydrogel ink comprising dimethacrylate-functionalized Pluronic F127 (F127-DMA) and sodium alginate (Alg) with laccase that can be done at ambient temperature, followed by UV-induced cross-linking. Laccase is an enzyme that can degrade azo dyes and various toxic organic pollutants. The fiber diameter, pore distance, and surface-to-volume ratio of the laccase-immobilized and 3D-printed hydrogel constructs were varied to determine their effects on the catalytic activity of the immobilized enzyme. Among the three geometrical designs investigated, the 3D-printed hydrogel constructs with flower-like geometry exhibited better catalytic performance than those with cubic and cylindrical geometries. Once tested against Orange II degradation in a flow-based format, they can be reused for up to four cycles. This research demonstrates that the developed hydrogel ink can be used to fabricate other enzyme-based catalytic platforms that can potentially increase their industrial usage in the future.

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Abstract. The objective of this study is to propose a prediction model for characterizing stabilized oily-wastewater that has been treated using Induced Air Flotation (IAF) and Modified Induced Air Flotation (MIAF), which is a combination of coagulation and flotation. Wastewater samples containing an anionic surfactant at the critical micelle concentration (CMC) were prepared as the stabilized oily-emulsion. The amount of oil as well as the amount removed was measured using COD. The study shows that the coagulant dosage (CAlum), interfacial area (a), and velocity gradient (G) are the important factors that affect flotation performance. Therefore, the proposed model is based on these parameters in terms of the CAlum and a/G ratio. The maximum removal efficiency and the reduction of the COD values can be predicted for any of the operating conditions. It was found that predicted oily wastewater efficiency and removal kinetic were compatible with those obtained from experiments. The discrepancy of 5% between the results from the prediction and the experiment can be found.