Hydraulic characteristics of integrated settler based biofilm reactor as onsite sanitation system

The present study identifies the hydraulic efficiency of a novel onsite sanitation system at variable hydraulic shock loading conditions. The system consisted of three chambers, each working as an up-flow anaerobic bioreactor, accommodated within a single unit. The hydraulic characteristics were identified with the help of residence time distribution (RTD) analysis by step feeding of lithium chloride (LiCl) solution into the system. The experiments were run at variable hydraulic loading conditions at different peak flow factors (PFF) of 1, 2, 4 and 6 while maintaining 24-h hydraulic retention time. As revealed in the RTD analysis, the biofilm reactor achieved a very good hydraulic efficiency that varied from 0.76 to 0.81 at PFF 1, 2 and 4. Although in the case of PFF6, it was comparatively low. It was noted that the dispersion number was always below 0.2 at variable hydraulic shock loading conditions under different PFFs, which indicated that the reactor behaved perfectly between mixed-flow and plug-flow reactor. The system was also able to achieve good pollutant removal efficiency for chemical oxygen demand (COD) and total suspended solids (TSS) under all PFFs, which was more than 68 and 75%, respectively.

Tracer Injection Simulations and RTD Analysis for the Flow in 3-Strands Steelmaking Tundish

Steel cleanliness in the continuous casting process can be improved by the enhancement of inclusion floatation via the flow control in tundish.The aim of this study is to define potential steel flow improvements in the 3-strands tundish of BSI (Bangkok Steel Industry) steelmaking shop. The numerical models of tundish without and with flow modifiers are simulated using the commercial computational fluid dynamics (CFD) software, ANSYS Fluent Workbench 14.0. The simulations of tracer injection using species transport model were performed. Flow characteristics were analyzed by RTD (residence time distribution) curves and the volumes fraction of three types of flow conditions. The results from this reseach shows how the current design of the flow modifiers improves some flow characteristics.

CFD analysis of sludge accumulation and hydraulic performance of a waste stabilization pond

Sludge management in waste stabilization ponds (WSPs) is essential for safeguarding the system performance. Sludge accumulation patterns in WSPs are strongly influenced by the pond hydrodynamics. CFD modeling was applied to study the relation between velocity profiles and sludge deposition during 10 years of operation of the Ucubamba WSP in Cuenca (Ecuador). One tracer experiment was performed and three sludge accumulation scenarios based on bathymetric surveys were simulated. A residence time distribution (RTD) analysis illustrated the decrease of residence times due to sludge deposition. Sludge accumulation rates were calculated. The influence of flow pattern on the sludge deposition was studied, enabling better planning of future pond operation and desludging.

Effect of Dam Design on the Fluid Flow in T-Shaped Continuous Casting Tundish

In the continuity casting technology of steel-manufacturing process, the tundish has two important functions: the preservation and distribution of molten metal and the reaction container able to perform float-out separation of nonmetallic inclusions. The residence time affects the effective removal of the nonmetallic inclusions. In this study, a T-shaped tundish with a submerged entry nozzle (SEN) and three strands was investigated for its ability to extend the residence time. Analysis conditions were the shape of the dam which was transformed to three cases. Fluid flow and non-metallic inclusion movement were also analyzed. The movement and removal of nonmetallic inclusions was determined by residence time distribution (RTD) analysis. As a result, the number of float-out, non-metallic inclusions was increased when the deviation of mean residence time was reduced.